1 00:00:04,400 --> 00:00:07,760 Speaker 1: Welcome to text Uff, a production from my Heart Radio. 2 00:00:12,039 --> 00:00:14,840 Speaker 1: Hey there, and welcome to text Stuff. I'm your host, 3 00:00:15,000 --> 00:00:17,840 Speaker 1: John than Strickland. I'm an executive producer with I Heart 4 00:00:17,960 --> 00:00:22,000 Speaker 1: Radio and I love all things tech and tech stuff. 5 00:00:22,040 --> 00:00:26,000 Speaker 1: Listener Nick contacted me on Twitter and asked if I 6 00:00:26,079 --> 00:00:28,720 Speaker 1: might do an episode to talk about the different kinds 7 00:00:28,760 --> 00:00:32,320 Speaker 1: of steel, in the different grades of steel, and what 8 00:00:32,440 --> 00:00:35,680 Speaker 1: makes one different from the next. Now. I have talked 9 00:00:35,720 --> 00:00:39,239 Speaker 1: about steel a little bit in previous episodes, but it 10 00:00:39,320 --> 00:00:43,040 Speaker 1: was always in relation to some other topic. For example, 11 00:00:43,360 --> 00:00:45,839 Speaker 1: I did a couple of episodes with my friend Ariel 12 00:00:45,960 --> 00:00:49,320 Speaker 1: about swords, and that included some stuff on steel. But 13 00:00:49,840 --> 00:00:52,360 Speaker 1: I really want to dedicate a couple of episodes to 14 00:00:52,440 --> 00:00:55,760 Speaker 1: this metal and why we have so many different classifications 15 00:00:55,760 --> 00:00:59,120 Speaker 1: of it and what this classifications actually mean. But first 16 00:00:59,680 --> 00:01:02,240 Speaker 1: let's get to some definitions and history. In fact, that's 17 00:01:02,280 --> 00:01:04,840 Speaker 1: what this episode is going to be about, is sort 18 00:01:04,840 --> 00:01:10,320 Speaker 1: of the history of steel making in general, because it's 19 00:01:10,360 --> 00:01:14,880 Speaker 1: complicated stuff. And in the next episode will conclude with 20 00:01:15,000 --> 00:01:17,840 Speaker 1: the history part and move on to the different types 21 00:01:17,880 --> 00:01:20,600 Speaker 1: of steel. Now, if you take a look at the 22 00:01:20,720 --> 00:01:25,240 Speaker 1: periodic table of elements, you'll notice that steel is not 23 00:01:25,560 --> 00:01:29,240 Speaker 1: on it. And that's because steel isn't an element, it's 24 00:01:29,240 --> 00:01:33,120 Speaker 1: an alloy, and alloy is a metal created from the 25 00:01:33,160 --> 00:01:38,840 Speaker 1: combination of at least two metallic elements. And technically steel 26 00:01:39,040 --> 00:01:42,319 Speaker 1: is an alloy of iron and carbon. But here's where 27 00:01:42,360 --> 00:01:45,479 Speaker 1: it gets really confusing. All the iron we work with, 28 00:01:45,880 --> 00:01:49,520 Speaker 1: the iron that's in our stuff like iron nails and stuff, 29 00:01:49,640 --> 00:01:52,400 Speaker 1: all of that is really an alloy of iron and carbon. 30 00:01:52,920 --> 00:01:55,080 Speaker 1: So this means that these episodes are really going to 31 00:01:55,120 --> 00:01:58,120 Speaker 1: be not just about steel, but iron and how we 32 00:01:58,200 --> 00:02:01,400 Speaker 1: learned how to work with iron. Now you might wonder 33 00:02:01,800 --> 00:02:05,280 Speaker 1: why you'd bother making an alloy in the first place. 34 00:02:05,480 --> 00:02:08,560 Speaker 1: Why would you not just use pure iron? Wouldn't that 35 00:02:08,560 --> 00:02:12,959 Speaker 1: be easier? Well, it's because alloys can have different, more 36 00:02:13,120 --> 00:02:18,440 Speaker 1: beneficial properties than the individual elements that combine together to 37 00:02:18,639 --> 00:02:22,280 Speaker 1: make that alloy. So, in general, the reason we make 38 00:02:22,320 --> 00:02:25,720 Speaker 1: alloys at all is to create materials that are stronger 39 00:02:25,880 --> 00:02:30,040 Speaker 1: or lighter, or more resistant to corrosion or some other 40 00:02:30,120 --> 00:02:34,040 Speaker 1: positive quality or combination thereof, compared to the metals we 41 00:02:34,160 --> 00:02:36,720 Speaker 1: use to create the alloy. In the first place. Steel 42 00:02:37,160 --> 00:02:40,679 Speaker 1: is superior to iron in many ways, which we will 43 00:02:40,760 --> 00:02:44,160 Speaker 1: get into. But to really understand the development of steel, 44 00:02:44,480 --> 00:02:46,640 Speaker 1: we have to take a closer look at the history 45 00:02:46,720 --> 00:02:50,880 Speaker 1: of meta allergy in general. So for thousands of years, 46 00:02:51,000 --> 00:02:55,000 Speaker 1: humanity relied primarily upon stone as a material for tools 47 00:02:55,040 --> 00:02:58,400 Speaker 1: and weapons. And we have a name for this age, 48 00:02:58,840 --> 00:03:01,519 Speaker 1: the flint stones. No way, I'm sorry, I just meant 49 00:03:01,520 --> 00:03:04,280 Speaker 1: the Stone Age. But we can further divide the Stone 50 00:03:04,280 --> 00:03:08,160 Speaker 1: Age into the Paleolithic or Old Stone Age, you know 51 00:03:08,160 --> 00:03:10,799 Speaker 1: when everyone was listening to that, you know, real crappy music, 52 00:03:11,120 --> 00:03:14,840 Speaker 1: and Neolithic or New Stone Age, which is what all 53 00:03:14,840 --> 00:03:20,160 Speaker 1: the kids were listening to. Stone is plentiful. It's hard stuff, right, 54 00:03:20,240 --> 00:03:22,800 Speaker 1: It's durable. Depending upon the type of stone, you could 55 00:03:22,800 --> 00:03:25,880 Speaker 1: fashion it into sharp edges, and you could polish it up. 56 00:03:25,880 --> 00:03:30,000 Speaker 1: You could make stuff like axes and spears, and so 57 00:03:30,040 --> 00:03:33,200 Speaker 1: the ancestors of humans were using stone tools as far 58 00:03:33,320 --> 00:03:37,640 Speaker 1: back as three million years ago, not earlier. I mentioned 59 00:03:37,800 --> 00:03:40,840 Speaker 1: for thousands of years. But that wasn't to d emphasize 60 00:03:40,840 --> 00:03:43,120 Speaker 1: how long we relied on stone, but rather just as 61 00:03:43,160 --> 00:03:45,200 Speaker 1: a nod to how tricky it is to apply the 62 00:03:45,240 --> 00:03:50,440 Speaker 1: word humans, because we're talking about you know, ancestors of 63 00:03:50,520 --> 00:03:53,560 Speaker 1: humans as well. While stone could get the job done, 64 00:03:53,640 --> 00:03:57,800 Speaker 1: it wasn't necessarily the best material for most jobs. It 65 00:03:57,920 --> 00:04:00,600 Speaker 1: was brittle and heavy, and you could find yourself with 66 00:04:00,640 --> 00:04:03,520 Speaker 1: a tool that had edges that were not as sharp 67 00:04:03,600 --> 00:04:06,720 Speaker 1: after a few uses, or one that would break in 68 00:04:06,720 --> 00:04:10,520 Speaker 1: a relatively short amount of time. Also, when we talk 69 00:04:10,600 --> 00:04:14,240 Speaker 1: about stuff like the Stone Age and the Bronze Age 70 00:04:14,240 --> 00:04:16,120 Speaker 1: and the Iron Age, we have to remember that these 71 00:04:16,240 --> 00:04:20,320 Speaker 1: terms describe very broad eras that didn't actually have a 72 00:04:20,360 --> 00:04:25,920 Speaker 1: definitive beginning and end. Some regions moved towards metallurgy much 73 00:04:25,960 --> 00:04:30,080 Speaker 1: earlier than others, sometimes by as much as two thousand years. 74 00:04:30,440 --> 00:04:32,160 Speaker 1: So I just don't want any of you thinking that, 75 00:04:32,440 --> 00:04:34,440 Speaker 1: you know, a person went to bed on a Wednesday 76 00:04:34,560 --> 00:04:36,560 Speaker 1: night when it was the Stone Age, and then they 77 00:04:36,560 --> 00:04:39,119 Speaker 1: woke up Thursday morning and it was suddenly the Bronze Age. 78 00:04:39,560 --> 00:04:43,520 Speaker 1: It's a little more subtle than that. Generally speaking, we 79 00:04:43,600 --> 00:04:46,359 Speaker 1: think of the Bronze Age as beginning around three thousand 80 00:04:46,400 --> 00:04:49,280 Speaker 1: b c E, and we think of it as ending 81 00:04:49,320 --> 00:04:52,560 Speaker 1: as well. That depends on where you lived. If you 82 00:04:52,600 --> 00:04:56,320 Speaker 1: lived in Mesopotamia, it ended sometime around twelve hundred b C. 83 00:04:56,760 --> 00:04:58,800 Speaker 1: But if you were in Northern Europe you had to 84 00:04:58,800 --> 00:05:01,120 Speaker 1: wait a little longer. It was closer to six hundred 85 00:05:01,160 --> 00:05:04,760 Speaker 1: b c. E. Generally, the onset of the Bronze Age 86 00:05:04,839 --> 00:05:08,680 Speaker 1: was brought about by trade, so the knowledge of how 87 00:05:08,800 --> 00:05:13,440 Speaker 1: to produce bronze spread outward from the Mesopotamian area for 88 00:05:13,480 --> 00:05:16,599 Speaker 1: the most part, so cultures first began to learn how 89 00:05:16,640 --> 00:05:20,960 Speaker 1: to work with copper, and at first copper was fairly scarce. 90 00:05:21,000 --> 00:05:24,240 Speaker 1: It just wasn't as readily available as different types of stone. 91 00:05:24,640 --> 00:05:28,080 Speaker 1: But ancient people's developed mining and metallergy and created all 92 00:05:28,160 --> 00:05:30,840 Speaker 1: sorts of stuff out of copper. But copper is not 93 00:05:31,080 --> 00:05:34,400 Speaker 1: that great for tools. It's not terribly durable, it doesn't 94 00:05:34,400 --> 00:05:37,800 Speaker 1: hold an edge very well. But by adding some tin 95 00:05:38,480 --> 00:05:42,520 Speaker 1: to the copper t I N tin, mellergists could create 96 00:05:42,560 --> 00:05:47,799 Speaker 1: a much stronger alloy bronze. This material made much better 97 00:05:47,880 --> 00:05:51,880 Speaker 1: tools and weapons. Iron is even stronger, but the high 98 00:05:51,920 --> 00:05:54,760 Speaker 1: melting point of iron meant that the tools humans had 99 00:05:54,800 --> 00:05:59,400 Speaker 1: for me allergy weren't sufficient to make iron. The pods 100 00:05:59,520 --> 00:06:03,120 Speaker 1: used to melt copper and tin couldn't withstand the temperatures 101 00:06:03,120 --> 00:06:06,560 Speaker 1: you would need in order to smelt iron from iron. 102 00:06:06,560 --> 00:06:11,520 Speaker 1: Ore the word smelt means to extract metal from ore, 103 00:06:11,839 --> 00:06:15,000 Speaker 1: and or is a solid rock or sediment that contains 104 00:06:15,040 --> 00:06:18,040 Speaker 1: one or more metals or minerals in it, So smelting 105 00:06:18,120 --> 00:06:21,880 Speaker 1: is really about separating the metal from all the other 106 00:06:21,960 --> 00:06:24,560 Speaker 1: stuff that's in that rock so that you can work 107 00:06:24,600 --> 00:06:26,440 Speaker 1: with the metal. One of the things you had to 108 00:06:26,480 --> 00:06:30,680 Speaker 1: deal with was iron oxide, which forms on the surface 109 00:06:30,720 --> 00:06:33,120 Speaker 1: of iron exposed to air. Also, I should mention that 110 00:06:33,200 --> 00:06:36,719 Speaker 1: iron oxide is actually an imprecise term, or rather it's 111 00:06:36,720 --> 00:06:40,120 Speaker 1: a term for a bunch of different chemical compounds made 112 00:06:40,160 --> 00:06:43,279 Speaker 1: up of iron and oxygen, and the iron oxide we 113 00:06:43,400 --> 00:06:47,920 Speaker 1: know of as rust is just one form of that. Gradually, 114 00:06:48,040 --> 00:06:50,640 Speaker 1: humans figured out how to build more robust forges and 115 00:06:50,680 --> 00:06:52,839 Speaker 1: they could heat up or enough so that they could 116 00:06:52,839 --> 00:06:55,919 Speaker 1: actually smelt iron, but it took some more time for 117 00:06:56,000 --> 00:07:00,120 Speaker 1: anyone to really be able to reliably create steel. An 118 00:07:00,120 --> 00:07:05,720 Speaker 1: exception was meteoric iron as an iron from space. Some 119 00:07:05,839 --> 00:07:09,840 Speaker 1: meteorites contained alloys of iron and nickel, and the process 120 00:07:09,840 --> 00:07:13,560 Speaker 1: of entering the Earth's atmosphere created enough heat to do 121 00:07:14,080 --> 00:07:17,360 Speaker 1: essentially the smelting work for us. But this wasn't exactly 122 00:07:17,560 --> 00:07:20,840 Speaker 1: plentiful stuff, so it's mostly used in small ornaments and 123 00:07:20,880 --> 00:07:23,520 Speaker 1: things like that until we got more up to speed, 124 00:07:23,600 --> 00:07:27,000 Speaker 1: like you might be say an Egyptian pharaoh with a 125 00:07:27,080 --> 00:07:31,600 Speaker 1: meteoric iron dagger buried with you next to a gold dagger, 126 00:07:31,640 --> 00:07:34,560 Speaker 1: because that's how valuable these things were. One of the 127 00:07:34,640 --> 00:07:37,320 Speaker 1: things about iron that made it harder to work with 128 00:07:37,480 --> 00:07:40,840 Speaker 1: is that it does oxidize rapidly upon contact with the air. 129 00:07:41,320 --> 00:07:45,160 Speaker 1: Oxidization is a process in which a substance like an atom, 130 00:07:45,200 --> 00:07:49,200 Speaker 1: an ion, or a molecule loses electrons in a chemical reaction. 131 00:07:49,600 --> 00:07:53,440 Speaker 1: Now this does not necessarily involve oxygen, but oxygen is 132 00:07:53,480 --> 00:07:59,640 Speaker 1: a pretty effective electron thief. Iron oxidizes pretty quickly. Oxidation 133 00:07:59,840 --> 00:08:04,800 Speaker 1: is an exothermic reaction. Now that means that as a 134 00:08:04,840 --> 00:08:08,040 Speaker 1: byproduct of this reaction there is a release of heat. 135 00:08:08,520 --> 00:08:12,080 Speaker 1: So you can actually see the effects of oxidation on iron. 136 00:08:12,520 --> 00:08:15,480 Speaker 1: It is what causes iron to rust. So iron in 137 00:08:15,520 --> 00:08:18,080 Speaker 1: the presence of oxygen and water is going to rust. 138 00:08:18,800 --> 00:08:22,120 Speaker 1: But even iron that's not actively rusting will have a 139 00:08:22,240 --> 00:08:25,320 Speaker 1: layer of iron oxide on the surface of the iron itself. 140 00:08:26,040 --> 00:08:30,120 Speaker 1: The process of oxidation is also pretty darn fast. If 141 00:08:30,160 --> 00:08:33,760 Speaker 1: you were to expose a very small speck of iron 142 00:08:33,920 --> 00:08:37,120 Speaker 1: to the air, it would oxidize and heat up and 143 00:08:37,160 --> 00:08:39,920 Speaker 1: you would see a spark. So if you've got a 144 00:08:39,920 --> 00:08:42,679 Speaker 1: lot of iron that's in a lump, you're gonna have 145 00:08:42,720 --> 00:08:46,080 Speaker 1: more volume compared to surface area. Right, You've got more 146 00:08:46,120 --> 00:08:51,000 Speaker 1: iron in the lump than is exposed on the surface, 147 00:08:51,360 --> 00:08:53,920 Speaker 1: just because of the size. This is all about volume, 148 00:08:54,160 --> 00:08:56,679 Speaker 1: and only the surface of the iron is oxidizing with 149 00:08:56,720 --> 00:08:58,320 Speaker 1: the air because you know, the rest of the iron 150 00:08:58,520 --> 00:09:03,079 Speaker 1: is shielded from the it's inside the lump. The heat 151 00:09:03,400 --> 00:09:07,440 Speaker 1: from that oxidizing reaction, the oxidation will be able to 152 00:09:07,480 --> 00:09:10,319 Speaker 1: dissipate into the rest of the lump of iron. Again, 153 00:09:10,320 --> 00:09:13,240 Speaker 1: you've got that big volume of iron, so the heat 154 00:09:13,280 --> 00:09:16,960 Speaker 1: from that process doesn't really amount too much in the 155 00:09:17,000 --> 00:09:20,040 Speaker 1: grand scheme of the lump. But if you have a tiny, 156 00:09:20,080 --> 00:09:23,680 Speaker 1: tiny speck of iron, well, now the ratio of surface 157 00:09:23,720 --> 00:09:27,120 Speaker 1: area to volume has totally changed. There's very little volume 158 00:09:27,120 --> 00:09:30,480 Speaker 1: in a tiny piece of iron. The surface will still 159 00:09:30,480 --> 00:09:34,199 Speaker 1: react to oxygen, and there isn't so much iron inside 160 00:09:34,440 --> 00:09:37,440 Speaker 1: the spec for the heat to dissipate so effectively. So 161 00:09:37,480 --> 00:09:41,080 Speaker 1: the spec gets really hot, hot enough to glow. When 162 00:09:41,080 --> 00:09:43,800 Speaker 1: someone uses a power grinder on iron and you see 163 00:09:43,800 --> 00:09:47,319 Speaker 1: sparks fly, or they're using flint and steel, those sparks 164 00:09:47,320 --> 00:09:50,600 Speaker 1: are tiny specks of iron oxidizing at a super fast rate. 165 00:09:51,320 --> 00:09:54,480 Speaker 1: Iron oxide isn't the stuff we want, right, we want iron, 166 00:09:54,760 --> 00:09:58,920 Speaker 1: So smelting helps us remove iron oxide and get iron instead. 167 00:09:59,040 --> 00:10:01,400 Speaker 1: It goes through the set type of reaction we call 168 00:10:01,480 --> 00:10:05,640 Speaker 1: this one reduction. Smelting also helps separate the iron from 169 00:10:05,720 --> 00:10:10,840 Speaker 1: other impurities that could be in the ore, stuff like sulfur, phosphorous, silicon, 170 00:10:11,480 --> 00:10:16,040 Speaker 1: things like that. Now, as far as the actual smelting process, that, 171 00:10:16,400 --> 00:10:19,360 Speaker 1: as we will learn, evolved a great deal over time. 172 00:10:19,880 --> 00:10:24,760 Speaker 1: The earliest furnaces used to smelt iron, we're called bloomer eyes. 173 00:10:25,320 --> 00:10:28,640 Speaker 1: There's some great videos on YouTube that show how these 174 00:10:28,640 --> 00:10:32,400 Speaker 1: bloomers worked. I highly recommend you guys go on YouTube 175 00:10:32,440 --> 00:10:35,480 Speaker 1: and look up bloomery b l o O m e 176 00:10:35,679 --> 00:10:40,520 Speaker 1: r Y because these videos are equal parts fascinating and terrifying. 177 00:10:40,679 --> 00:10:44,880 Speaker 1: So typically, you would build a chimney like structure and 178 00:10:44,920 --> 00:10:47,640 Speaker 1: you would use something like clay to make it. So 179 00:10:48,120 --> 00:10:52,800 Speaker 1: imagine a a stack a chimney made of clay. You 180 00:10:52,840 --> 00:10:55,280 Speaker 1: would have a little section in the very front that 181 00:10:55,320 --> 00:10:57,080 Speaker 1: would be cut out like a door, but you would 182 00:10:57,120 --> 00:11:00,439 Speaker 1: have a a piece of clay that fit into that. 183 00:11:00,960 --> 00:11:03,360 Speaker 1: You would have at least one hole cut in the 184 00:11:03,400 --> 00:11:06,320 Speaker 1: side of the chimney called a two year, and this 185 00:11:06,360 --> 00:11:09,360 Speaker 1: would allow for more air circulation to go into the 186 00:11:09,440 --> 00:11:13,640 Speaker 1: chamber of the bloomery. If you blue air into it, 187 00:11:13,679 --> 00:11:16,839 Speaker 1: you would increase the temperature of the burn. So you 188 00:11:16,920 --> 00:11:21,800 Speaker 1: would possibly have bellows attached to this, either operated by 189 00:11:21,880 --> 00:11:25,760 Speaker 1: hand or later by having a water wheel turning a 190 00:11:25,800 --> 00:11:29,600 Speaker 1: cam that would allow these bellows to open and close 191 00:11:29,640 --> 00:11:33,200 Speaker 1: and thus blow air into the bloomery, or you might 192 00:11:33,280 --> 00:11:36,360 Speaker 1: just be dependent upon the wind, which wouldn't be the 193 00:11:36,400 --> 00:11:39,720 Speaker 1: most efficient way to make this stuff. You'd also typically 194 00:11:39,760 --> 00:11:42,880 Speaker 1: have a hole towards the very bottom of the chimney 195 00:11:42,960 --> 00:11:45,840 Speaker 1: that would allow you to draw off slag. This would 196 00:11:45,840 --> 00:11:49,960 Speaker 1: be the the hot melted mixture of impurities, and you 197 00:11:50,120 --> 00:11:53,720 Speaker 1: don't have to worry about melting off the iron having 198 00:11:53,720 --> 00:11:56,960 Speaker 1: the iron pour out along with the slag, because that's 199 00:11:56,960 --> 00:11:59,560 Speaker 1: just not going to happen. We're not talking about temperatures 200 00:11:59,640 --> 00:12:04,400 Speaker 1: high enough to melt iron at this point. Conversely, the 201 00:12:04,600 --> 00:12:08,160 Speaker 1: entire bloomery, if you didn't have this way of tapping 202 00:12:08,200 --> 00:12:10,960 Speaker 1: it so that you can put get slag out, you 203 00:12:11,040 --> 00:12:14,480 Speaker 1: might even have to push it over, which sounds incredibly 204 00:12:14,520 --> 00:12:17,319 Speaker 1: dangerous to me, and then allow the molten slag to 205 00:12:17,320 --> 00:12:20,880 Speaker 1: to pour out the top of it. Now, slag typically 206 00:12:20,960 --> 00:12:23,440 Speaker 1: contains a little bit of iron in it as well, 207 00:12:23,800 --> 00:12:25,920 Speaker 1: but for the most part you're talking about all the 208 00:12:25,960 --> 00:12:29,280 Speaker 1: other stuff that you wanted to remove, leaving as much 209 00:12:29,280 --> 00:12:31,840 Speaker 1: of the iron behind as possible. So you might have 210 00:12:31,960 --> 00:12:34,640 Speaker 1: little chunks of iron in the slag, and thus you 211 00:12:34,720 --> 00:12:37,160 Speaker 1: might want to keep the slag just in case has 212 00:12:37,200 --> 00:12:39,520 Speaker 1: any iron in it in order to use in a 213 00:12:39,600 --> 00:12:44,360 Speaker 1: future burn. But to facilitate the removal of slag, forgers 214 00:12:44,480 --> 00:12:47,040 Speaker 1: or you know, smith's or metal or just however you 215 00:12:47,040 --> 00:12:50,120 Speaker 1: want to call them, would typically add in a substance 216 00:12:50,400 --> 00:12:53,600 Speaker 1: with a relatively low melting point that could help siphon 217 00:12:53,640 --> 00:12:56,640 Speaker 1: out some of the impurities. That would act almost like 218 00:12:56,679 --> 00:12:58,880 Speaker 1: a lubricant, if you can think of it that way, 219 00:12:59,400 --> 00:13:02,400 Speaker 1: The bind with things and and be liquid in order 220 00:13:02,440 --> 00:13:05,360 Speaker 1: to help coax more of those impurities to flow out. 221 00:13:05,480 --> 00:13:09,440 Speaker 1: The stuff is called collectively flux, and flux can be 222 00:13:09,520 --> 00:13:12,440 Speaker 1: made up of lots of different stuff, including sand or 223 00:13:12,480 --> 00:13:17,240 Speaker 1: silica or limestone, but with ancient bloomer eyes, often the 224 00:13:17,280 --> 00:13:20,559 Speaker 1: flux came from the material used to build the bloomery itself. 225 00:13:20,640 --> 00:13:23,920 Speaker 1: It would just be leached out of the interior of 226 00:13:23,960 --> 00:13:27,599 Speaker 1: the bloomery and become part of the mixture, so you 227 00:13:27,640 --> 00:13:30,960 Speaker 1: didn't necessarily have to add more in the process of 228 00:13:31,000 --> 00:13:35,760 Speaker 1: smelting and refining iron. This way is laborious. It involves 229 00:13:35,760 --> 00:13:38,880 Speaker 1: getting the furnace really hot with a layer of charcoal 230 00:13:38,960 --> 00:13:42,600 Speaker 1: at the base of the furnace. Then you add more 231 00:13:42,720 --> 00:13:45,880 Speaker 1: charcoal to heat up the entirety of the furnace, and 232 00:13:45,920 --> 00:13:48,680 Speaker 1: then you start adding in equal amounts of iron ore 233 00:13:48,760 --> 00:13:52,280 Speaker 1: and charcoal every few minutes, and you alternate between them, um, 234 00:13:52,559 --> 00:13:54,640 Speaker 1: but you add them both at around the same time. 235 00:13:54,720 --> 00:13:57,319 Speaker 1: So you do, all right, let's put in a kilogram 236 00:13:57,360 --> 00:14:00,720 Speaker 1: of iron ore and a kilogram of charcoal, and then 237 00:14:00,800 --> 00:14:03,160 Speaker 1: after a few minutes another kilogram of iron or and 238 00:14:03,200 --> 00:14:06,040 Speaker 1: another kilogram of charcoal. You have to keep doing this 239 00:14:06,160 --> 00:14:08,880 Speaker 1: over and over and over again every few minutes for 240 00:14:09,000 --> 00:14:12,240 Speaker 1: several hours. So these bloomerys couldn't get hot enough, as 241 00:14:12,280 --> 00:14:15,760 Speaker 1: I said, to actually melt the iron ore outright. Instead, 242 00:14:16,040 --> 00:14:20,040 Speaker 1: you would produce what was called a bloom thus bloomery. 243 00:14:20,080 --> 00:14:23,840 Speaker 1: This would be a mass of hot iron and kind 244 00:14:23,840 --> 00:14:26,640 Speaker 1: of you know, charcoal. Mixt year, the iron doesn't get 245 00:14:26,680 --> 00:14:29,040 Speaker 1: hot enough to really melt, but it's hard enough to 246 00:14:29,080 --> 00:14:33,000 Speaker 1: be kind of a spongy looking material that was somewhat 247 00:14:33,040 --> 00:14:35,240 Speaker 1: malleable if you were to pull it out of the 248 00:14:35,240 --> 00:14:37,960 Speaker 1: bloom moraine then hit it with a hammer. Managing this 249 00:14:38,040 --> 00:14:40,760 Speaker 1: process is tricky because not only do you have to 250 00:14:41,000 --> 00:14:44,600 Speaker 1: maintain that high level of heat, you also have to 251 00:14:44,600 --> 00:14:47,440 Speaker 1: make sure that the two year remains clear of material. 252 00:14:47,520 --> 00:14:50,840 Speaker 1: Remember that's the air channel, where air is either blowing 253 00:14:50,840 --> 00:14:53,240 Speaker 1: in from the wind or you're forcing it in through 254 00:14:53,320 --> 00:14:56,560 Speaker 1: something like a bellows. A lot of stuff can go 255 00:14:56,640 --> 00:15:00,360 Speaker 1: wrong in this process, and even when everything goes corre directly, 256 00:15:00,400 --> 00:15:03,080 Speaker 1: you might not end up with a great amount of iron, 257 00:15:03,200 --> 00:15:06,720 Speaker 1: depending upon the quality of the ore itself. Once the 258 00:15:06,760 --> 00:15:11,080 Speaker 1: process is done, it's time to retrieve the iron bloom. 259 00:15:11,120 --> 00:15:14,280 Speaker 1: So you've tapped out the slag, You've let the slag 260 00:15:14,360 --> 00:15:19,000 Speaker 1: run out. You pull the door off the furnace, assuming 261 00:15:19,040 --> 00:15:21,880 Speaker 1: that or the bloomery, assuming that the bloomery has a door. 262 00:15:21,920 --> 00:15:24,640 Speaker 1: You might even just break the bloomery open. Often these 263 00:15:24,640 --> 00:15:28,680 Speaker 1: were just one use devices. You would construct one every 264 00:15:28,680 --> 00:15:31,200 Speaker 1: time you want to do one of these, and uh 265 00:15:31,560 --> 00:15:34,400 Speaker 1: you might have to break it apart anyway, because sometimes 266 00:15:34,400 --> 00:15:37,280 Speaker 1: the iron bloom would be too large to fit through 267 00:15:37,320 --> 00:15:40,080 Speaker 1: the door in the first place. Now the bloom will 268 00:15:40,120 --> 00:15:44,960 Speaker 1: have absorbed some charcoal would be incorporated into it. Charcoal 269 00:15:44,960 --> 00:15:48,080 Speaker 1: has a very high carbon content, and at higher temperatures, 270 00:15:48,440 --> 00:15:52,520 Speaker 1: iron absorbs some of that carbon. This also lowers the 271 00:15:52,520 --> 00:15:55,280 Speaker 1: melting point for iron a little bit, and that will 272 00:15:55,280 --> 00:15:58,920 Speaker 1: become important later on. The charcoal needs to burn really 273 00:15:59,080 --> 00:16:02,440 Speaker 1: thoroughly for of this process to really work, Otherwise you'll 274 00:16:02,440 --> 00:16:05,200 Speaker 1: get chunks of charcoal that are too large, and you'll 275 00:16:05,280 --> 00:16:07,600 Speaker 1: end up with iron that might have big chunks of 276 00:16:07,800 --> 00:16:10,360 Speaker 1: unburned charcoal embedded in it, which is going to be 277 00:16:10,600 --> 00:16:12,800 Speaker 1: harder to get rid of. But if the coals are 278 00:16:12,800 --> 00:16:16,520 Speaker 1: the right size, the iron will absorb some carbon, but 279 00:16:16,720 --> 00:16:19,560 Speaker 1: not all of it obviously. So now you've got a 280 00:16:19,640 --> 00:16:22,840 Speaker 1: big old, porous lump of red hot iron with some 281 00:16:22,920 --> 00:16:26,800 Speaker 1: carbon and maybe some charcoal. You've got some other stuff, 282 00:16:26,840 --> 00:16:29,480 Speaker 1: and it some slag is still inside that, because again 283 00:16:29,480 --> 00:16:33,800 Speaker 1: it's spongey, it's porous, so there will be slag contained 284 00:16:34,000 --> 00:16:38,160 Speaker 1: inside this red hot bloom of iron. So what do 285 00:16:38,200 --> 00:16:40,480 Speaker 1: you do then, Well, that stage the iron still isn't 286 00:16:40,560 --> 00:16:44,440 Speaker 1: terribly useful, so you would have to reheat the mass 287 00:16:44,480 --> 00:16:46,960 Speaker 1: so that it's malleable. You know, get it hot enough 288 00:16:47,000 --> 00:16:49,040 Speaker 1: so that you can work it. Then you put it 289 00:16:49,040 --> 00:16:52,600 Speaker 1: on an anvil and you start beating that iron bloom 290 00:16:52,640 --> 00:16:56,520 Speaker 1: with a hammer. This compresses the mass. It forces the 291 00:16:56,600 --> 00:17:00,720 Speaker 1: molten slag out of the lump to the surface of 292 00:17:00,760 --> 00:17:03,880 Speaker 1: the iron. So remember I said it's like a sponge, 293 00:17:03,880 --> 00:17:07,280 Speaker 1: it's porous. This is kind of like squeezing out a sponge. 294 00:17:07,520 --> 00:17:11,359 Speaker 1: If you have a sponge that's absolutely saturated with water 295 00:17:11,760 --> 00:17:14,520 Speaker 1: and you start to squeeze it, you force the water out. 296 00:17:14,760 --> 00:17:18,800 Speaker 1: That's kind of what's happening when a blacksmith starts hammering 297 00:17:18,880 --> 00:17:22,400 Speaker 1: an iron bloom with a hammer. You're forcing that slag 298 00:17:22,480 --> 00:17:25,399 Speaker 1: out to the surface. You can watch videos of blacksmiths 299 00:17:25,440 --> 00:17:28,560 Speaker 1: doing this process on YouTube. Again, it's fascinating. You're gonna 300 00:17:28,600 --> 00:17:32,679 Speaker 1: see this sort of glowing orange mass of iron. But 301 00:17:32,760 --> 00:17:35,720 Speaker 1: it will start to grow darker as it's getting hammered, 302 00:17:35,760 --> 00:17:38,400 Speaker 1: not just because it's cooling off. I mean that is happening, 303 00:17:38,440 --> 00:17:41,280 Speaker 1: but it's also growing darker because the slag is being 304 00:17:41,320 --> 00:17:44,640 Speaker 1: forced towards the surface of the mass. So smith's need 305 00:17:44,720 --> 00:17:47,880 Speaker 1: to hammer out the mass folded back in on itself 306 00:17:48,280 --> 00:17:51,800 Speaker 1: and repeat this process over and over. Reheating it, hammering 307 00:17:51,800 --> 00:17:55,240 Speaker 1: it out, folding it back on itself, welding it to itself, 308 00:17:55,280 --> 00:17:59,920 Speaker 1: reheating it, hammering it out. This takes a lot of time, 309 00:18:00,600 --> 00:18:04,199 Speaker 1: and you'll see that typically a relatively large bloom that 310 00:18:04,280 --> 00:18:07,320 Speaker 1: you'll get out of a bloomery will ultimately reduce to 311 00:18:07,359 --> 00:18:10,680 Speaker 1: a much smaller size once the smith has hammered out 312 00:18:11,040 --> 00:18:14,080 Speaker 1: most of that slag, what is left is typically a 313 00:18:14,119 --> 00:18:17,680 Speaker 1: hammered piece that is mostly iron with a very low 314 00:18:17,760 --> 00:18:22,280 Speaker 1: carbon content less than point zero eight percent carbon compared 315 00:18:22,320 --> 00:18:25,719 Speaker 1: to iron, and some other impurities are in there too. 316 00:18:26,080 --> 00:18:28,520 Speaker 1: Because the smith had to work the mass by hand 317 00:18:28,560 --> 00:18:32,440 Speaker 1: to produce this, we call it wrought iron w r 318 00:18:32,560 --> 00:18:37,120 Speaker 1: o U g h T iron. That means worked iron. 319 00:18:37,640 --> 00:18:39,560 Speaker 1: That we had to do work on it in order 320 00:18:39,560 --> 00:18:41,879 Speaker 1: to make it this way. So once in a while, 321 00:18:42,280 --> 00:18:45,480 Speaker 1: using this method of bloomery's you could produce steel. It 322 00:18:45,520 --> 00:18:48,960 Speaker 1: wasn't necessarily predictable. You weren't necessarily going to be able 323 00:18:49,040 --> 00:18:51,919 Speaker 1: to do it time and time again, but it did happen, 324 00:18:52,119 --> 00:18:56,320 Speaker 1: and you'd be really happy whenever it did. Sometimes, however, 325 00:18:56,359 --> 00:19:00,880 Speaker 1: that steel would be particularly hard but brittle. Gradually, mill 326 00:19:01,000 --> 00:19:04,320 Speaker 1: Or just learned that by plunging very hot steel. We're 327 00:19:04,320 --> 00:19:08,680 Speaker 1: talking about steel. This around nine degrees celsius into water. 328 00:19:09,040 --> 00:19:13,480 Speaker 1: The cool steel's surface becomes extremely hard and brittle. But 329 00:19:14,160 --> 00:19:16,880 Speaker 1: by reheating that steel to a temperature of around four 330 00:19:16,920 --> 00:19:20,760 Speaker 1: hundred degrees celsius, in a process that was later called tempering, 331 00:19:21,119 --> 00:19:24,199 Speaker 1: the material will become less brittle but still retain a 332 00:19:24,200 --> 00:19:28,760 Speaker 1: lot of its hardness. So you would hear these terms 333 00:19:28,800 --> 00:19:32,879 Speaker 1: by blacksmith talking about tempered steel. That's what they're referring to. 334 00:19:33,680 --> 00:19:36,520 Speaker 1: But here's the thing. The process for making steel was 335 00:19:36,640 --> 00:19:40,000 Speaker 1: imprecise and dependent on so many factors, including the quality 336 00:19:40,040 --> 00:19:42,919 Speaker 1: of the ore being used to smelt the iron and 337 00:19:42,960 --> 00:19:45,920 Speaker 1: the process to create the actual steel. It was hard 338 00:19:45,960 --> 00:19:48,840 Speaker 1: to dial into the specific ratios you need to go 339 00:19:48,920 --> 00:19:53,080 Speaker 1: from iron to steal in those times. So the concentration 340 00:19:53,119 --> 00:19:56,080 Speaker 1: of carbon really determines what kind of metal you end 341 00:19:56,160 --> 00:19:58,359 Speaker 1: up with. If you don't have enough carbon, you end 342 00:19:58,440 --> 00:20:01,960 Speaker 1: up with wrought iron. If you have too much carbon, 343 00:20:02,000 --> 00:20:05,960 Speaker 1: you end up with cast iron, two very different extremes. 344 00:20:06,359 --> 00:20:07,920 Speaker 1: It's got to be just right, and for a couple 345 00:20:07,960 --> 00:20:10,040 Speaker 1: of thousand years, that was pretty hard to do. Now, 346 00:20:10,040 --> 00:20:11,760 Speaker 1: when we come back, I'll talk a bit about how 347 00:20:11,840 --> 00:20:15,760 Speaker 1: humans figured out more effective ways to produce iron and steel. 348 00:20:16,000 --> 00:20:25,919 Speaker 1: But first, let's take a quick break. We've looked at 349 00:20:25,960 --> 00:20:28,920 Speaker 1: the oldest method of smelting iron with bloomers, and a 350 00:20:28,960 --> 00:20:32,480 Speaker 1: bloomery gets the job done, but it's not terribly efficient. 351 00:20:32,720 --> 00:20:35,119 Speaker 1: You have to pour in a lot of labor and 352 00:20:35,200 --> 00:20:38,440 Speaker 1: a lot of iron ore and a lot of charcoal 353 00:20:38,840 --> 00:20:41,840 Speaker 1: to get any results, and the bloom you produce still 354 00:20:41,880 --> 00:20:43,960 Speaker 1: needs a lot of work to turn it into iron 355 00:20:44,000 --> 00:20:46,359 Speaker 1: that can be put to any good use. So what 356 00:20:46,520 --> 00:20:48,720 Speaker 1: was really needed was a better way to reduce the 357 00:20:48,800 --> 00:20:52,800 Speaker 1: iron oxide and iron ore to iron, and one of 358 00:20:52,840 --> 00:20:54,920 Speaker 1: the best ways to do that is to produce even 359 00:20:55,000 --> 00:20:58,200 Speaker 1: higher amounts of heat. Now let's think about this chemically. 360 00:20:58,440 --> 00:21:01,359 Speaker 1: I've mentioned that the oxidizing reaction is exothermic, but I 361 00:21:01,359 --> 00:21:03,239 Speaker 1: haven't really talked about what's going on here at an 362 00:21:03,280 --> 00:21:07,679 Speaker 1: atomic level. So with iron oxide, you've got iron and 363 00:21:07,760 --> 00:21:12,199 Speaker 1: oxygen effectively bond with one another within a furnace. The 364 00:21:12,280 --> 00:21:15,439 Speaker 1: intense heat and the presence of carbon allows for the 365 00:21:15,560 --> 00:21:20,439 Speaker 1: separation of oxygen from iron. The oxygen instead bonds with 366 00:21:20,560 --> 00:21:24,520 Speaker 1: the carbon forming carbon monoxide, which is an odorless and 367 00:21:24,720 --> 00:21:28,440 Speaker 1: toxic gas. The carbon monoxide is happy to take on 368 00:21:28,480 --> 00:21:32,120 Speaker 1: another oxygen atom as well, So at temperatures around six 369 00:21:32,359 --> 00:21:35,240 Speaker 1: D nine D degrees celsius in a furnace, you'll end 370 00:21:35,320 --> 00:21:38,439 Speaker 1: up with iron and carbon dioxide as well, not just 371 00:21:38,520 --> 00:21:43,280 Speaker 1: carbon monoxide but carbon dioxide. The bloomers just weren't going 372 00:21:43,320 --> 00:21:45,320 Speaker 1: to get the job done. They weren't going to get 373 00:21:45,320 --> 00:21:48,080 Speaker 1: to those temperatures. So that brings us to the blast furnace. 374 00:21:48,720 --> 00:21:51,800 Speaker 1: The bloomery produces a hot of lump iron. It gets 375 00:21:51,880 --> 00:21:54,520 Speaker 1: hot enough to glow and it's malleable at that temperature, 376 00:21:54,520 --> 00:21:58,200 Speaker 1: but it's not hot enough to melt. Blast furnaces can 377 00:21:58,240 --> 00:22:00,879 Speaker 1: reach higher temperatures high end, so that you're not just 378 00:22:01,000 --> 00:22:05,440 Speaker 1: reducing iron oxide to iron plus carbon monoxide or carbon dioxide. 379 00:22:05,800 --> 00:22:08,920 Speaker 1: You're also getting a hot enough chamber so that you 380 00:22:08,960 --> 00:22:14,719 Speaker 1: can melt the iron completely. You get molten iron liquid metal. 381 00:22:15,359 --> 00:22:18,480 Speaker 1: So how is this possible? Well, first, blast furnaces are 382 00:22:18,680 --> 00:22:21,680 Speaker 1: much bigger than bloomery's. They tend to have a chimney 383 00:22:21,720 --> 00:22:24,720 Speaker 1: like structure, much like your typical bloomery, but instead of 384 00:22:24,720 --> 00:22:26,879 Speaker 1: being made out of clay, they're usually made out of 385 00:22:26,920 --> 00:22:30,399 Speaker 1: several layers of brick that form the chimney. Sometimes with 386 00:22:30,480 --> 00:22:34,439 Speaker 1: other materials to provide both stability and often away for 387 00:22:34,560 --> 00:22:37,720 Speaker 1: heat to dissipate. They can be a couple of stories tall, 388 00:22:37,880 --> 00:22:40,520 Speaker 1: whereas a bloomery might only be a couple of meters tall, 389 00:22:40,640 --> 00:22:43,280 Speaker 1: maybe three or four meters for the really big ones, 390 00:22:44,440 --> 00:22:47,560 Speaker 1: and like a bloomery, blast furnaces have two years through 391 00:22:47,600 --> 00:22:51,080 Speaker 1: which pumped air can enter into the furnace. The pumps 392 00:22:51,200 --> 00:22:54,159 Speaker 1: or bellows could be operated by hand, but later on 393 00:22:54,200 --> 00:22:57,800 Speaker 1: it was far more convenient to locate a furnace next 394 00:22:57,840 --> 00:23:01,000 Speaker 1: to a source of flowing water and then use a 395 00:23:01,000 --> 00:23:03,920 Speaker 1: water wheel to provide the power needed to pump the bellows. 396 00:23:04,000 --> 00:23:07,680 Speaker 1: You are in effect blasting the combustion in the furnace 397 00:23:07,840 --> 00:23:11,879 Speaker 1: with air. Thus you have a blast furnace. Unlike people, 398 00:23:12,119 --> 00:23:14,000 Speaker 1: the water doesn't need to take a break, and the 399 00:23:14,000 --> 00:23:17,440 Speaker 1: furnace could be kept at a high consistent temperature, assuming 400 00:23:17,480 --> 00:23:21,200 Speaker 1: it was being fed with fuel regularly like a bloomery. 401 00:23:21,280 --> 00:23:24,840 Speaker 1: Metal orgists would feed a blast furnace by pouring iron 402 00:23:24,880 --> 00:23:28,639 Speaker 1: ore fuel and flux down into a chimney like furnace 403 00:23:28,720 --> 00:23:31,680 Speaker 1: from the top of it. A description of a typical 404 00:23:31,680 --> 00:23:34,760 Speaker 1: blast furnace says that to charge a furnace that is 405 00:23:34,800 --> 00:23:39,200 Speaker 1: to prepare it for the process of smelting iron. First, 406 00:23:39,280 --> 00:23:43,840 Speaker 1: workers called fillers would empty around twenty baskets of charcoal 407 00:23:43,960 --> 00:23:46,760 Speaker 1: into the furnace through the top. The bottom of the 408 00:23:46,760 --> 00:23:49,400 Speaker 1: furnace would be lit, and so you would have combustion 409 00:23:49,480 --> 00:23:54,000 Speaker 1: going on inside the furnace, and the hot gases created 410 00:23:54,160 --> 00:23:58,080 Speaker 1: from that combustion would start heating up the charcoal that 411 00:23:58,200 --> 00:24:01,320 Speaker 1: was further up the stack. Soon the heat would reach 412 00:24:01,359 --> 00:24:03,639 Speaker 1: a stage where the heat of rising gas would be 413 00:24:03,760 --> 00:24:07,840 Speaker 1: enough for the whole smelting process would start as soon 414 00:24:07,880 --> 00:24:10,639 Speaker 1: as you start pouring charges in through the top, and 415 00:24:10,680 --> 00:24:14,760 Speaker 1: a charge at this point is that mixture of iron ore, 416 00:24:15,640 --> 00:24:19,639 Speaker 1: charcoal and flux. So after they get this started with 417 00:24:19,760 --> 00:24:22,720 Speaker 1: those twenty baskets full of charcoal, they would add in 418 00:24:22,760 --> 00:24:26,280 Speaker 1: around oh, I don't know, seven hundred pounds of iron ore, 419 00:24:26,800 --> 00:24:30,719 Speaker 1: followed by limestone. So within half an hour the charge 420 00:24:30,840 --> 00:24:34,080 Speaker 1: level would have sunk down by about ten ft. So 421 00:24:34,160 --> 00:24:38,360 Speaker 1: you're looking at this chimney that was effectively full of material. 422 00:24:38,840 --> 00:24:41,480 Speaker 1: Now that material has sunk in ten ft because of 423 00:24:41,520 --> 00:24:45,399 Speaker 1: that combustion and and the conversion of these solids into 424 00:24:45,480 --> 00:24:49,640 Speaker 1: gases and slag. So then you would add in more 425 00:24:49,680 --> 00:24:52,880 Speaker 1: iron ore, more charcoal, more limestone, and then a bit 426 00:24:52,920 --> 00:24:54,879 Speaker 1: more iron ore at the end, and you repeat that 427 00:24:54,960 --> 00:24:59,520 Speaker 1: process every so often as the furnace burns down, working 428 00:24:59,520 --> 00:25:02,399 Speaker 1: in shive to keep the furnace working the entire time. 429 00:25:02,720 --> 00:25:04,479 Speaker 1: You know, you have to keep on going because if 430 00:25:04,520 --> 00:25:07,320 Speaker 1: you lose this, if you let the furnace go cold, 431 00:25:07,760 --> 00:25:11,119 Speaker 1: then that's a whole thing and you have to start 432 00:25:11,160 --> 00:25:14,280 Speaker 1: all over. Essentially. Inside the furnace, you've got a few 433 00:25:14,320 --> 00:25:16,800 Speaker 1: different areas. So if we were looking at a cross 434 00:25:16,840 --> 00:25:18,840 Speaker 1: section of a furnace at the very base, we would 435 00:25:18,840 --> 00:25:21,560 Speaker 1: see a section that's called the crucible. This is the 436 00:25:21,560 --> 00:25:25,439 Speaker 1: bottom interior part of the furnace. This is where the 437 00:25:25,480 --> 00:25:29,240 Speaker 1: molten iron will eventually collect more on that in a second. 438 00:25:29,600 --> 00:25:32,800 Speaker 1: Above the crucible is an area called the bosch b 439 00:25:33,000 --> 00:25:36,400 Speaker 1: O s H. This is where the furnace temperatures get 440 00:25:36,480 --> 00:25:40,520 Speaker 1: hot enough to reduce iron oxide and ultimately melt iron 441 00:25:40,640 --> 00:25:44,399 Speaker 1: into molten iron. Above the bosch, you've got the stack, 442 00:25:44,480 --> 00:25:47,920 Speaker 1: which is where all your charges are. The intense heat 443 00:25:47,960 --> 00:25:51,679 Speaker 1: in the furnace increases as you get lower down into it, 444 00:25:51,720 --> 00:25:54,600 Speaker 1: allowing for this chemical reaction for iron oxide to reduce 445 00:25:54,680 --> 00:25:57,879 Speaker 1: to iron and as iron got hotter, it melts, and 446 00:25:57,920 --> 00:26:01,040 Speaker 1: because it's so heavy, it's so dense, it sinks to 447 00:26:01,080 --> 00:26:03,520 Speaker 1: the very bottom of the blast furnace. Because just because 448 00:26:03,520 --> 00:26:06,720 Speaker 1: the iron has gone from solid to liquid doesn't mean 449 00:26:06,760 --> 00:26:10,800 Speaker 1: it's no longer dense. It still is. And the slag 450 00:26:11,200 --> 00:26:13,560 Speaker 1: that is all the impurities that were in the iron 451 00:26:13,560 --> 00:26:16,280 Speaker 1: ore plus stuff like the flux that you're adding in 452 00:26:16,840 --> 00:26:20,320 Speaker 1: UH typically again in the form of limestone, would float 453 00:26:20,640 --> 00:26:24,280 Speaker 1: on top of the layer of iron because it's it's 454 00:26:24,320 --> 00:26:26,639 Speaker 1: not as dense. So it's kind of like when you 455 00:26:26,720 --> 00:26:30,119 Speaker 1: mix water and oil together, the denser material is going 456 00:26:30,160 --> 00:26:33,600 Speaker 1: to be at the bottom, right, So taps near the 457 00:26:33,640 --> 00:26:36,719 Speaker 1: base of the furnace. These are pipes that lead into 458 00:26:36,800 --> 00:26:40,480 Speaker 1: the furnace would allow mel or just to tap off 459 00:26:40,600 --> 00:26:43,840 Speaker 1: the slag and also to drain out the molten iron. 460 00:26:44,440 --> 00:26:48,440 Speaker 1: Now that molten iron would typically follow a channel from 461 00:26:48,520 --> 00:26:52,200 Speaker 1: the tap and go down the channel and flow into 462 00:26:52,280 --> 00:26:55,320 Speaker 1: molds on either side of the channel. So while a 463 00:26:55,359 --> 00:26:58,439 Speaker 1: blacksmith would have to work a bloom for ages and 464 00:26:58,440 --> 00:27:00,760 Speaker 1: a bloomery in order to turn it into a bar, 465 00:27:01,240 --> 00:27:05,320 Speaker 1: a blast furnace produces liquid iron that then flows into 466 00:27:05,359 --> 00:27:09,520 Speaker 1: molds and just cools into bars big labor saver there 467 00:27:09,600 --> 00:27:13,000 Speaker 1: right well. In addition, while blue Morays use charcoal as 468 00:27:13,040 --> 00:27:17,399 Speaker 1: a fuel of choice and blast furnaces, once charcoal became 469 00:27:17,480 --> 00:27:21,240 Speaker 1: scarce because people were cutting down all the forests, they 470 00:27:21,280 --> 00:27:25,520 Speaker 1: started to move toward coke. Now, I don't mean the 471 00:27:25,560 --> 00:27:29,320 Speaker 1: soft drink instead, I mean the carbon rich fuel that 472 00:27:29,359 --> 00:27:33,000 Speaker 1: we produce by heating either oil or coal in a 473 00:27:33,119 --> 00:27:36,320 Speaker 1: chamber that doesn't have air in it. Now, if you 474 00:27:36,359 --> 00:27:39,440 Speaker 1: don't have air in a chamber and you add heat, 475 00:27:39,760 --> 00:27:43,800 Speaker 1: you cannot have combustion. Combustion or fire needs three things, right. 476 00:27:43,840 --> 00:27:47,480 Speaker 1: You need fuel, you need heat, and you need an oxidizer, 477 00:27:48,600 --> 00:27:51,639 Speaker 1: of which oxygen is one. But if you're burning something 478 00:27:51,720 --> 00:27:53,800 Speaker 1: or heating something in a chamber that has no air, 479 00:27:54,240 --> 00:27:57,280 Speaker 1: you can't really burn it. You can only heat it up. 480 00:27:57,359 --> 00:27:59,920 Speaker 1: And in this case you can convert stuff like coal 481 00:28:00,119 --> 00:28:04,000 Speaker 1: or oil into coke. The higher temperatures inside a blast 482 00:28:04,040 --> 00:28:07,400 Speaker 1: furnace would allow the iron inside it to absorb more 483 00:28:07,560 --> 00:28:11,080 Speaker 1: carbon than you would find in a bloomery. I think 484 00:28:11,080 --> 00:28:13,240 Speaker 1: of it kind of like how I think of how 485 00:28:13,240 --> 00:28:16,800 Speaker 1: sugar will dissolve into hot tea much more readily than 486 00:28:16,960 --> 00:28:20,399 Speaker 1: it would in cold tea. Chemically, we're not talking about 487 00:28:20,400 --> 00:28:23,400 Speaker 1: identical processes here. I don't want to make you think 488 00:28:23,400 --> 00:28:25,280 Speaker 1: that it's exactly the same thing. It's just sort of 489 00:28:25,280 --> 00:28:28,080 Speaker 1: an analogy I use. Also, it's a reminder that if 490 00:28:28,080 --> 00:28:30,280 Speaker 1: you want to make sweet ice tea, you don't do 491 00:28:30,320 --> 00:28:32,560 Speaker 1: it by dumping sugar in a cold glass of tea. 492 00:28:32,600 --> 00:28:36,000 Speaker 1: Don't don't try that stuff around me. I'm from the South, 493 00:28:36,520 --> 00:28:38,920 Speaker 1: but this is tech stuff, not simple syrup stuff. So 494 00:28:38,920 --> 00:28:42,200 Speaker 1: I'll get back on topic whether the blast furnace is 495 00:28:42,320 --> 00:28:45,600 Speaker 1: using charcoal or coke as a fuel. In the end, 496 00:28:45,640 --> 00:28:48,320 Speaker 1: you produce molten iron which can be tapped to run 497 00:28:48,320 --> 00:28:51,920 Speaker 1: into that channel and it splits off into those molds 498 00:28:52,320 --> 00:28:55,280 Speaker 1: down the length of the channel, forming bars of iron. 499 00:28:55,760 --> 00:28:59,200 Speaker 1: Somewhere along the way, someone thought that this channel with 500 00:28:59,400 --> 00:29:02,440 Speaker 1: the mold that split off to either side kind of 501 00:29:02,480 --> 00:29:06,040 Speaker 1: looked a bit like a sow, as in a female 502 00:29:06,160 --> 00:29:10,120 Speaker 1: pig suckling her piglets. And so the name for this 503 00:29:10,160 --> 00:29:13,840 Speaker 1: type of iron is called pig iron. If you've ever 504 00:29:13,880 --> 00:29:16,280 Speaker 1: heard of pig iron, this is where he gets his name. 505 00:29:16,320 --> 00:29:19,120 Speaker 1: He gets his name because of those channels that ran 506 00:29:19,240 --> 00:29:22,800 Speaker 1: from the blast furnace and split off into these molds 507 00:29:22,840 --> 00:29:27,080 Speaker 1: for pig iron. Bars. Pig iron typically isn't an end 508 00:29:27,120 --> 00:29:30,520 Speaker 1: goal in of itself. It's a starting point for metalworking. 509 00:29:30,720 --> 00:29:33,800 Speaker 1: So the production of pig iron is really about taking 510 00:29:33,800 --> 00:29:36,520 Speaker 1: the stuff that comes out of the ground, whether from 511 00:29:36,600 --> 00:29:40,280 Speaker 1: bogs or mines or whatever, and separating the metal from 512 00:29:40,480 --> 00:29:42,440 Speaker 1: most of the other stuff it's stuck to. But pig 513 00:29:42,440 --> 00:29:44,719 Speaker 1: iron still has a lot of impurities in it and 514 00:29:44,880 --> 00:29:49,959 Speaker 1: way too much carbon for most uses. Remember, carbon hardens iron, 515 00:29:50,040 --> 00:29:53,040 Speaker 1: but it also makes it way more brittle. Often pig 516 00:29:53,080 --> 00:29:56,120 Speaker 1: iron has too many impurities and too high a carbon 517 00:29:56,200 --> 00:30:00,600 Speaker 1: content to be used as cast iron. Cast iron has 518 00:30:00,640 --> 00:30:04,320 Speaker 1: between two point one and four carbon in it, and 519 00:30:04,360 --> 00:30:07,800 Speaker 1: pig iron can have more than that. It also can 520 00:30:07,840 --> 00:30:13,160 Speaker 1: contain other impurities like manganese, sulfur, silicon, and phosphorus, and 521 00:30:13,200 --> 00:30:17,520 Speaker 1: those things affect the qualities of iron as well. If 522 00:30:17,520 --> 00:30:20,520 Speaker 1: there are high levels of impurities, iron workers will heat 523 00:30:20,560 --> 00:30:23,160 Speaker 1: the pig iron in another type of furnace quite similar 524 00:30:23,200 --> 00:30:26,480 Speaker 1: to a blast furnace, and adding other components to help 525 00:30:26,560 --> 00:30:30,080 Speaker 1: remove some of those impurities, to combine and form another 526 00:30:30,120 --> 00:30:32,600 Speaker 1: form of slag, and to tap that slag and move 527 00:30:32,640 --> 00:30:39,040 Speaker 1: the carbon percentage lower. In the same process, liquid cast iron, 528 00:30:39,360 --> 00:30:43,479 Speaker 1: which is you know that high carbon content iron with 529 00:30:43,520 --> 00:30:47,320 Speaker 1: fewer impurities than your general pig iron is liquid. Cast 530 00:30:47,360 --> 00:30:50,920 Speaker 1: iron can be poured into casts to form stuff, thus 531 00:30:50,920 --> 00:30:53,080 Speaker 1: its name. So if you want to make a cast 532 00:30:53,120 --> 00:30:56,920 Speaker 1: iron skillet, first you had created cast out of something 533 00:30:57,280 --> 00:31:02,280 Speaker 1: like sand, so you would carve out the shape of 534 00:31:02,560 --> 00:31:06,880 Speaker 1: a cast iron skillet that way. It's essentially a skillet 535 00:31:06,920 --> 00:31:10,600 Speaker 1: shaped cavity inside a sand block. And then you would 536 00:31:10,600 --> 00:31:15,880 Speaker 1: pour molten cast iron into that sand block, and you 537 00:31:15,880 --> 00:31:18,760 Speaker 1: would allow it to cool inside the sand block and set. 538 00:31:19,280 --> 00:31:22,280 Speaker 1: After doing so, you can break the cast open and 539 00:31:22,320 --> 00:31:25,280 Speaker 1: you've got yourself a cast iron skillet, though you'd still 540 00:31:25,320 --> 00:31:27,600 Speaker 1: have to do a few more steps to treat it 541 00:31:27,760 --> 00:31:30,960 Speaker 1: before you could actually use it as a skillet. But 542 00:31:31,000 --> 00:31:32,800 Speaker 1: the big problem with this type of iron is that 543 00:31:32,920 --> 00:31:36,760 Speaker 1: once it has cooled, you can't easily heat it up 544 00:31:36,800 --> 00:31:39,480 Speaker 1: and work it again, meaning shape it. You can't really, 545 00:31:39,960 --> 00:31:43,840 Speaker 1: you know, heat it up and hammer it and knock 546 00:31:43,880 --> 00:31:45,920 Speaker 1: it into a new shape. The iron is just too 547 00:31:45,920 --> 00:31:50,280 Speaker 1: brittle wrought iron, which has a much lower percentage of carbon. 548 00:31:50,600 --> 00:31:53,280 Speaker 1: In fact, wrought iron typically has less carbon in it 549 00:31:53,320 --> 00:31:58,200 Speaker 1: than steel does. It is much more easily worked if reheated, 550 00:31:58,320 --> 00:32:01,480 Speaker 1: so there needed to be a pro says to refine 551 00:32:01,560 --> 00:32:03,920 Speaker 1: pig iron to get rid of some of that carbon 552 00:32:04,000 --> 00:32:06,400 Speaker 1: and some of the other impurities if you wanted to 553 00:32:06,440 --> 00:32:11,280 Speaker 1: make wrought iron or steel on a much more efficient 554 00:32:11,560 --> 00:32:15,240 Speaker 1: sort of mass production kind of basis. Because as it stands, 555 00:32:15,680 --> 00:32:18,720 Speaker 1: you could make cast iron pretty easily, but wrought iron 556 00:32:18,800 --> 00:32:21,720 Speaker 1: was still hard to do. You were typically still using 557 00:32:21,720 --> 00:32:26,400 Speaker 1: bloomer eas and those just didn't produce on very large scales. 558 00:32:27,360 --> 00:32:30,600 Speaker 1: One advancement in iron working that made this possible was 559 00:32:30,640 --> 00:32:35,680 Speaker 1: the development of special forges called fineries and chaferies, each 560 00:32:35,720 --> 00:32:39,120 Speaker 1: of which did something special. So the finery forge was 561 00:32:39,200 --> 00:32:42,520 Speaker 1: where a finer this is the person working at the forge, 562 00:32:42,680 --> 00:32:45,720 Speaker 1: would take pig iron and they would put it into 563 00:32:45,840 --> 00:32:51,520 Speaker 1: a smallish furnace. The finer would use bellows, usually water 564 00:32:51,680 --> 00:32:55,000 Speaker 1: powered bellows, to blast more air on the pig iron 565 00:32:55,120 --> 00:32:58,480 Speaker 1: as it was being reheated inside this furnace. This would 566 00:32:58,480 --> 00:33:02,960 Speaker 1: cause an oxidation reaction. It would remove some of the carbon, 567 00:33:03,160 --> 00:33:06,560 Speaker 1: which would vent out as carbon monoxide. It would combine 568 00:33:07,120 --> 00:33:10,000 Speaker 1: with the oxygen that was being blown into the furnace, 569 00:33:10,920 --> 00:33:14,440 Speaker 1: or you might even get carbon dioxide, and this would 570 00:33:14,480 --> 00:33:18,800 Speaker 1: leave more pure iron behind. So you're kind of leaching 571 00:33:18,960 --> 00:33:22,240 Speaker 1: out some of the carbon of the pig iron, bringing 572 00:33:22,240 --> 00:33:24,840 Speaker 1: it closer to the type of iron you would find 573 00:33:24,880 --> 00:33:28,760 Speaker 1: in a bloom in a bloomery from centuries earlier, and 574 00:33:28,840 --> 00:33:33,040 Speaker 1: this was typically called a half bloom. The finer would 575 00:33:33,040 --> 00:33:36,320 Speaker 1: then remove this half bloom and then another forgeman would 576 00:33:36,320 --> 00:33:38,800 Speaker 1: take the half bloom and place it on an anvil 577 00:33:39,320 --> 00:33:43,360 Speaker 1: under a water powered trip hammer. What the heck is 578 00:33:43,400 --> 00:33:47,000 Speaker 1: a trip hammer. Well, imagine you've got a lever, okay, 579 00:33:47,120 --> 00:33:49,479 Speaker 1: like a see saw, but you don't have the pivot 580 00:33:49,520 --> 00:33:52,280 Speaker 1: in the middle of this lever. It's closer to one 581 00:33:52,320 --> 00:33:54,680 Speaker 1: side than the other. So on the long end of 582 00:33:54,680 --> 00:33:57,160 Speaker 1: the lever, which would typically be in the down position 583 00:33:57,160 --> 00:34:00,480 Speaker 1: because it's heavier, you have the hammer, and on the 584 00:34:00,640 --> 00:34:05,080 Speaker 1: short end you have that connected close to a cam. 585 00:34:05,280 --> 00:34:08,279 Speaker 1: Cam is a wheel in this case, it's got some 586 00:34:08,320 --> 00:34:12,120 Speaker 1: projections on it and those projections can make contact with 587 00:34:12,239 --> 00:34:14,680 Speaker 1: the short end of the lever. So as the wheel turns, 588 00:34:15,000 --> 00:34:17,359 Speaker 1: it pushes down on that short end of the lever 589 00:34:17,760 --> 00:34:20,600 Speaker 1: and it starts to lift the other side. So the 590 00:34:20,640 --> 00:34:24,000 Speaker 1: hammer goes up in the air. But as the cam 591 00:34:24,040 --> 00:34:27,080 Speaker 1: continues to rotate, it eventually rotates to a point where 592 00:34:27,480 --> 00:34:31,160 Speaker 1: it loses contact with the short end of the lever. 593 00:34:31,480 --> 00:34:34,520 Speaker 1: It's like if you were to push down on a 594 00:34:34,600 --> 00:34:37,920 Speaker 1: seesaw and then pull your hand away very quickly. So 595 00:34:37,960 --> 00:34:40,719 Speaker 1: the trip hammer starts to strike the half bloom and 596 00:34:40,760 --> 00:34:43,880 Speaker 1: does so several times, pushing out impurities that are otherwise 597 00:34:43,920 --> 00:34:47,040 Speaker 1: trapped inside the iron, just as the blacksmith would with 598 00:34:47,160 --> 00:34:50,320 Speaker 1: the bloom from a Bloomery. The process has to happen 599 00:34:50,400 --> 00:34:53,480 Speaker 1: several times, so the half bloom has to be reheated 600 00:34:53,520 --> 00:34:56,160 Speaker 1: and then hammered again and again until it can finally 601 00:34:56,160 --> 00:34:59,919 Speaker 1: be forged into a bar of wrought iron called an 602 00:35:00,040 --> 00:35:04,040 Speaker 1: and coney. The end coney would then be put into 603 00:35:04,160 --> 00:35:08,839 Speaker 1: the chaffery. Chaffery is a hearth style furnace, and the 604 00:35:08,880 --> 00:35:13,040 Speaker 1: bars would undergo reheating before being hammered out into de 605 00:35:13,120 --> 00:35:16,279 Speaker 1: carbonized iron. While this would bring us back to a 606 00:35:16,320 --> 00:35:19,600 Speaker 1: similar kind of iron produced by Bloomery's, the process was 607 00:35:19,719 --> 00:35:23,120 Speaker 1: still more efficient from a labor standpoint, particularly with the 608 00:35:23,200 --> 00:35:25,640 Speaker 1: use of water power, so you could do it faster 609 00:35:25,760 --> 00:35:27,239 Speaker 1: than you would if you were to use the old 610 00:35:27,239 --> 00:35:30,279 Speaker 1: Bloomery method. When we come back, we'll move on to 611 00:35:30,440 --> 00:35:33,319 Speaker 1: some other developments in iron and steel production. But first 612 00:35:33,360 --> 00:35:44,879 Speaker 1: let's take another quick break. We've talked a lot about iron, 613 00:35:44,920 --> 00:35:47,080 Speaker 1: and by wie, I mean i've talked a lot about iron. 614 00:35:47,120 --> 00:35:50,080 Speaker 1: What about steel? So, steel has a carbon content that 615 00:35:50,160 --> 00:35:54,600 Speaker 1: typically puts it between wrought iron and cast iron. Wrought 616 00:35:54,640 --> 00:35:59,040 Speaker 1: iron generally has less carbon than steel. Cast iron has 617 00:35:59,200 --> 00:36:03,280 Speaker 1: more carbon than steel. The carbon content and steel affects 618 00:36:03,320 --> 00:36:06,120 Speaker 1: the steel's weight, hardness, and melting point, as well as 619 00:36:06,160 --> 00:36:10,839 Speaker 1: it's malleability versus brittleness. But if pig iron has too 620 00:36:10,920 --> 00:36:13,800 Speaker 1: much carbon in it and wrought iron has too little 621 00:36:13,840 --> 00:36:17,240 Speaker 1: iron in it, how do you make steel? Well? Typically, 622 00:36:17,239 --> 00:36:20,320 Speaker 1: in days of your you'd have to take wrought iron billets. 623 00:36:20,560 --> 00:36:22,799 Speaker 1: You can think of those as just iron bars for 624 00:36:22,840 --> 00:36:26,000 Speaker 1: simplicity sake, and you would put them in clay pots 625 00:36:26,000 --> 00:36:30,160 Speaker 1: along with some charcoal. So layer of iron bars, layer 626 00:36:30,160 --> 00:36:32,920 Speaker 1: of charcoal, layer of iron bars, layer of charcoal all 627 00:36:32,960 --> 00:36:35,800 Speaker 1: the way to the top. And then you would close 628 00:36:35,920 --> 00:36:39,080 Speaker 1: these clay pots so that they were essentially airtight, and 629 00:36:39,120 --> 00:36:43,080 Speaker 1: you put them into a large kiln called a cementation furnace. 630 00:36:43,680 --> 00:36:45,920 Speaker 1: You would fire up the kiln and it would heat 631 00:36:46,000 --> 00:36:48,560 Speaker 1: up all the clay pots filled with these mixtures of 632 00:36:48,600 --> 00:36:51,920 Speaker 1: iron and charcoal, and it would cause the heated iron 633 00:36:52,000 --> 00:36:55,240 Speaker 1: to absorb some of the carbon that was in that charcoal. 634 00:36:55,680 --> 00:36:58,359 Speaker 1: And in case you're keeping track, yes, we've talked about 635 00:36:58,360 --> 00:37:02,239 Speaker 1: a process in which you add carbon to iron oxide 636 00:37:02,520 --> 00:37:05,440 Speaker 1: and you get a high carbon iron called pig iron. 637 00:37:06,040 --> 00:37:08,600 Speaker 1: You then refine that in a finery and a chaffery 638 00:37:08,719 --> 00:37:12,280 Speaker 1: to produce a low carbon type of iron called wrought iron. 639 00:37:12,760 --> 00:37:15,160 Speaker 1: And then you use the wrought iron and add carbon 640 00:37:15,200 --> 00:37:18,480 Speaker 1: back into it in order to get steel, which does 641 00:37:18,520 --> 00:37:22,440 Speaker 1: sound pretty crazy, right, like a very laborious process to 642 00:37:22,480 --> 00:37:26,799 Speaker 1: go from iron ore to steal. To make it even 643 00:37:26,880 --> 00:37:31,120 Speaker 1: more complicated, this kiln heating process was typically done multiple times, 644 00:37:31,239 --> 00:37:35,000 Speaker 1: with the iron reforged after heating and then put back 645 00:37:35,040 --> 00:37:39,360 Speaker 1: into pots with charcoal. Again, this was to ensure homogeneity 646 00:37:39,440 --> 00:37:42,879 Speaker 1: throughout the metal. You wanted that carbon to be distributed 647 00:37:43,000 --> 00:37:45,680 Speaker 1: evenly throughout the iron as much as possible so that 648 00:37:45,760 --> 00:37:50,680 Speaker 1: you would have really consistent iron. During the heating process, 649 00:37:50,760 --> 00:37:53,680 Speaker 1: one of the byproducts was once again carbon monoxide. The 650 00:37:53,719 --> 00:37:57,200 Speaker 1: forming of carbon monoxide gas would cause blisters to form 651 00:37:57,360 --> 00:38:00,359 Speaker 1: on the surface of the metal inside these pots, so 652 00:38:00,400 --> 00:38:03,920 Speaker 1: we came to call this type of metal blister steel. 653 00:38:04,560 --> 00:38:09,520 Speaker 1: We call this process a carburization process, which means to 654 00:38:09,600 --> 00:38:12,680 Speaker 1: use a heat treatment process in which iron is absorbing 655 00:38:12,760 --> 00:38:15,600 Speaker 1: carbon in order to become steel, or you might use 656 00:38:15,640 --> 00:38:17,879 Speaker 1: it with steel itself in order to make a more 657 00:38:18,000 --> 00:38:21,440 Speaker 1: high carbon form of steel. So if you want to 658 00:38:21,480 --> 00:38:24,400 Speaker 1: make steel around this time, it either involved a decent 659 00:38:24,400 --> 00:38:26,680 Speaker 1: amount of luck so that you were using a bloomery 660 00:38:26,680 --> 00:38:29,080 Speaker 1: and the iron bloom you produce just happen to have 661 00:38:29,120 --> 00:38:31,920 Speaker 1: the right amount of carbon and lack of impurities in 662 00:38:31,960 --> 00:38:35,040 Speaker 1: it to qualify as steel, or you need to go 663 00:38:35,080 --> 00:38:38,879 Speaker 1: through a series of refinement processes from smelting or into 664 00:38:38,880 --> 00:38:42,120 Speaker 1: pig iron, to refining the pig iron wrought iron, to 665 00:38:42,239 --> 00:38:45,279 Speaker 1: refining the wrought iron and too steel and making wrought 666 00:38:45,320 --> 00:38:48,239 Speaker 1: iron this way took a long time too. Then a 667 00:38:48,280 --> 00:38:54,160 Speaker 1: fellow named Henry Court came along in sevent four. Court 668 00:38:54,239 --> 00:38:56,759 Speaker 1: found that by heating pig iron in a furnace at 669 00:38:56,760 --> 00:38:59,719 Speaker 1: temperatures high enough to melt it, because remember pig iron 670 00:38:59,800 --> 00:39:02,400 Speaker 1: has a lower melting point than other kinds of iron, 671 00:39:02,920 --> 00:39:05,920 Speaker 1: and then by stirring this mixture in the presence of 672 00:39:05,960 --> 00:39:10,759 Speaker 1: oxidizing substances, he could produce wrought iron much more efficiently 673 00:39:10,880 --> 00:39:15,239 Speaker 1: than the old finery forge process. This new process was 674 00:39:15,280 --> 00:39:18,399 Speaker 1: called puddling, or since I'm from the South, I'm gonna 675 00:39:18,440 --> 00:39:22,120 Speaker 1: call it pudlin. This process was one in which the 676 00:39:22,160 --> 00:39:25,040 Speaker 1: iron wouldn't actually be in contact with the fuel, and 677 00:39:25,120 --> 00:39:28,359 Speaker 1: most of the other versions you're putting the iron ore 678 00:39:28,400 --> 00:39:31,000 Speaker 1: in the same chamber where the fuel is burning. Not 679 00:39:31,080 --> 00:39:34,359 Speaker 1: with puddling, the puddler what that's what they were called, 680 00:39:34,440 --> 00:39:37,400 Speaker 1: would use these really long iron tools to reach into 681 00:39:37,800 --> 00:39:42,680 Speaker 1: the furnace bed and violently stir the semi molten pig iron, 682 00:39:43,160 --> 00:39:46,680 Speaker 1: and the stirring action would help separate the iron from 683 00:39:46,760 --> 00:39:50,880 Speaker 1: the impurities, and in the process of oxidizers, it would 684 00:39:50,880 --> 00:39:55,200 Speaker 1: really help create that separation. This was done repeatedly with 685 00:39:55,400 --> 00:40:00,239 Speaker 1: the puddler eventually removing this ball of refined iron from 686 00:40:00,280 --> 00:40:03,440 Speaker 1: the furnace using really long tools. And the key thing 687 00:40:03,480 --> 00:40:08,000 Speaker 1: about this process is that even with the constant stirring 688 00:40:08,120 --> 00:40:10,720 Speaker 1: and vigorous stirring of the puddler, it was much faster 689 00:40:10,960 --> 00:40:13,480 Speaker 1: than using a finery where you were putting those pots 690 00:40:14,000 --> 00:40:17,200 Speaker 1: inside a furnace over and over again, and you could 691 00:40:17,200 --> 00:40:20,359 Speaker 1: produce wrought iron relatively fast, and it would become one 692 00:40:20,360 --> 00:40:24,400 Speaker 1: of the important contributors towards the Industrial Revolution as a result, 693 00:40:24,440 --> 00:40:29,920 Speaker 1: because wrought iron was desperately needed for big construction jobs, 694 00:40:29,960 --> 00:40:35,840 Speaker 1: you know, like building railroads. Still, steel production was more limited, 695 00:40:35,920 --> 00:40:37,640 Speaker 1: with most of it being made in the form of 696 00:40:37,680 --> 00:40:43,160 Speaker 1: blister steel. An Englishman named Benjamin Huntsman further refined steelmaking 697 00:40:43,280 --> 00:40:47,080 Speaker 1: by taking blister steel and melting it inside clay crucibles 698 00:40:47,120 --> 00:40:52,000 Speaker 1: and incredibly hot furnaces reaching temperatures around six degrees celsius 699 00:40:52,000 --> 00:40:56,120 Speaker 1: it's about twenty degrees fahrenheit, and then the molten steel 700 00:40:56,200 --> 00:40:59,719 Speaker 1: could be poured into casts, much like cast iron could be, 701 00:40:59,760 --> 00:41:02,840 Speaker 1: but with the benefits of steel. The next big development 702 00:41:02,840 --> 00:41:05,560 Speaker 1: in steel production came in eighteen fifty six thanks to 703 00:41:05,640 --> 00:41:09,719 Speaker 1: English inventor Henry Bessemer. Now to be totally fair, Bessemer 704 00:41:09,800 --> 00:41:11,960 Speaker 1: was one of a few people to suss this out. 705 00:41:12,160 --> 00:41:15,359 Speaker 1: There was also an American named William Kelly who came 706 00:41:15,440 --> 00:41:19,239 Speaker 1: up with the general same idea independently. Bessemer was trying 707 00:41:19,280 --> 00:41:21,880 Speaker 1: to find a means to produce steel and greater quantities 708 00:41:21,920 --> 00:41:25,279 Speaker 1: and at lower expense. His approach, which he called the 709 00:41:25,320 --> 00:41:31,120 Speaker 1: manufacture of iron without fuel, sounds kind of terrifying, honestly. First, 710 00:41:31,440 --> 00:41:35,320 Speaker 1: you take molten pig iron yikes. So when a process 711 00:41:35,400 --> 00:41:38,359 Speaker 1: begins with molten hot metal, you know you're getting into 712 00:41:38,360 --> 00:41:43,520 Speaker 1: some hardcore engineering. But next you blow oxygen through the 713 00:41:43,600 --> 00:41:47,600 Speaker 1: molten iron mix. The oxygen reacts with the impurities in 714 00:41:47,760 --> 00:41:51,440 Speaker 1: the pig iron and effectively creates oxides that end up 715 00:41:51,480 --> 00:41:54,360 Speaker 1: as slag, and the slag just gets tapped off separately 716 00:41:54,400 --> 00:41:59,160 Speaker 1: from the iron itself. The oxidizing reactions were exothermic, so 717 00:41:59,200 --> 00:42:02,360 Speaker 1: they generated eat that provided heat that could be harnessed 718 00:42:02,440 --> 00:42:06,320 Speaker 1: to keep this iron from solidifying, so the reaction would 719 00:42:06,320 --> 00:42:10,560 Speaker 1: help sustain itself this way, the result was the rapid 720 00:42:10,600 --> 00:42:15,759 Speaker 1: production of steel, very low carbon steel. Other inventors and 721 00:42:15,840 --> 00:42:18,439 Speaker 1: middle are just figured out that by adding some other 722 00:42:18,560 --> 00:42:23,040 Speaker 1: stuff like manganese, iron and carbon into the mix. So yes, 723 00:42:23,080 --> 00:42:26,120 Speaker 1: once again we are adding carbon, the carbon content of 724 00:42:26,120 --> 00:42:29,760 Speaker 1: the steel could be increased while remaining impurities like sulfur 725 00:42:29,920 --> 00:42:33,520 Speaker 1: could be neutralized. The resulting steel was a much more 726 00:42:33,600 --> 00:42:37,200 Speaker 1: pure version than the typical kind produced in older methods, 727 00:42:37,280 --> 00:42:40,640 Speaker 1: and it could be made quickly and cheaply. For the 728 00:42:40,640 --> 00:42:43,520 Speaker 1: first time in history, steel was easy enough to manufacture 729 00:42:43,600 --> 00:42:46,160 Speaker 1: to make it a viable material for stuff like construction. 730 00:42:46,800 --> 00:42:50,200 Speaker 1: The one impurity that the original Bessemer converter wasn't really 731 00:42:50,200 --> 00:42:53,600 Speaker 1: good at removing was phosphorus, which was unfortunate as that 732 00:42:53,719 --> 00:42:57,160 Speaker 1: stuff was fairly common in the iron ore of Europe. 733 00:42:57,840 --> 00:43:01,840 Speaker 1: Sydney Gilchrist Thomas invented the variation of the Bessemer converter 734 00:43:02,160 --> 00:43:06,880 Speaker 1: that incorporated limestone that helped strip phosphorus from the iron mix. 735 00:43:07,440 --> 00:43:10,359 Speaker 1: And it did have one other problem this approach, which 736 00:43:10,400 --> 00:43:13,200 Speaker 1: is that the original converters would introduce small amounts of 737 00:43:13,320 --> 00:43:18,319 Speaker 1: nitrogen into the iron ore, thus introducing an impurity making 738 00:43:18,360 --> 00:43:21,040 Speaker 1: the iron a little more brittle. This was hard to 739 00:43:21,080 --> 00:43:24,000 Speaker 1: correct for it was hard to get a pure source 740 00:43:24,040 --> 00:43:26,960 Speaker 1: of oxygen at this point in history. In the mid 741 00:43:27,080 --> 00:43:32,040 Speaker 1: nineteenth century, William or Wilhelm Siemens, who was German but 742 00:43:32,560 --> 00:43:35,160 Speaker 1: was living in Englands or right back to Old Blighty, 743 00:43:35,280 --> 00:43:38,279 Speaker 1: tried something new that would create an alternative to the 744 00:43:38,320 --> 00:43:41,880 Speaker 1: Bessemer converter. He rigged up a furnace so that the 745 00:43:42,120 --> 00:43:46,440 Speaker 1: escaping hot gases from the furnace would heat up a 746 00:43:46,640 --> 00:43:50,440 Speaker 1: chamber filled with a lattice of bricks so the bricks 747 00:43:50,440 --> 00:43:54,000 Speaker 1: would absorb this heat. Then he would change the flow 748 00:43:54,040 --> 00:43:57,160 Speaker 1: of air so that the incoming air used to feed 749 00:43:57,200 --> 00:44:01,040 Speaker 1: the furnace would first pass through these bricks lattices, and 750 00:44:01,080 --> 00:44:04,439 Speaker 1: that would preheat the incoming air and you would get 751 00:44:04,560 --> 00:44:08,120 Speaker 1: hotter furnace temperatures as a result, So it was essentially 752 00:44:08,120 --> 00:44:11,680 Speaker 1: creating a hot blower versus a cold blower. Unlike the 753 00:44:11,680 --> 00:44:15,920 Speaker 1: best of our process, Wilhelm's furnace, called an open hearth furnace, 754 00:44:16,560 --> 00:44:20,000 Speaker 1: was slow. But while it wasn't as fast as a 755 00:44:20,120 --> 00:44:23,960 Speaker 1: Bessemer converter, it allowed for far more precision when you 756 00:44:23,960 --> 00:44:27,360 Speaker 1: were making the steel, so the quality control was much better. 757 00:44:27,600 --> 00:44:30,879 Speaker 1: The end product was molten steel, so you could even 758 00:44:31,000 --> 00:44:35,399 Speaker 1: cast that into ingots right away. The open hearth furnaces 759 00:44:35,560 --> 00:44:39,359 Speaker 1: could take steel scraps as a charge, thus cutting down 760 00:44:39,360 --> 00:44:41,879 Speaker 1: on waste. So let's say you make some steel it's 761 00:44:41,920 --> 00:44:44,080 Speaker 1: not as good quality as you would like. You could 762 00:44:44,080 --> 00:44:46,080 Speaker 1: put it in an open hearth furnace and it could 763 00:44:46,080 --> 00:44:48,319 Speaker 1: be used as a charge to create your next batch 764 00:44:48,320 --> 00:44:50,920 Speaker 1: of steel that could be better. It could also process 765 00:44:51,000 --> 00:44:53,760 Speaker 1: pig iron. It became a popular method of steel making 766 00:44:53,840 --> 00:44:57,520 Speaker 1: for a century. Alright, we're getting into the home stretch 767 00:44:57,800 --> 00:45:02,720 Speaker 1: of this steel making episode. In night, a Swiss inventor 768 00:45:02,880 --> 00:45:06,640 Speaker 1: named Robert Durer improved upon the Bestimer converter from a 769 00:45:06,719 --> 00:45:11,400 Speaker 1: century earlier. He invented a process called basic oxygen steel making. 770 00:45:11,960 --> 00:45:15,840 Speaker 1: It's not using basic oxygen, it does use a highly 771 00:45:16,000 --> 00:45:20,320 Speaker 1: pure form of oxygen. Rather, the term basic actually refers 772 00:45:20,320 --> 00:45:23,880 Speaker 1: to the use of chemically base materials, again for the 773 00:45:23,920 --> 00:45:27,600 Speaker 1: purposes of removing impurities that are in pig iron. Like 774 00:45:27,640 --> 00:45:32,560 Speaker 1: the Bestimer process, basic oxygen steel making forces oxygen through 775 00:45:32,680 --> 00:45:36,719 Speaker 1: molten pig iron, but the process is totally wicked. So 776 00:45:37,080 --> 00:45:39,719 Speaker 1: imagine you've got a big container that's lined with a 777 00:45:39,760 --> 00:45:43,680 Speaker 1: refractory material, meaning it it reflects heat back into the 778 00:45:43,760 --> 00:45:48,400 Speaker 1: chamber itself. This container is called the ladle. Inside the ladle, 779 00:45:48,640 --> 00:45:53,680 Speaker 1: you pour molten pig iron. Suspended over the pig iron 780 00:45:53,800 --> 00:45:57,360 Speaker 1: inside the ladle is what is called an oxygen lance. 781 00:45:57,800 --> 00:46:02,799 Speaker 1: So imagine a pipe through which ultra pure oxygen can 782 00:46:02,920 --> 00:46:07,480 Speaker 1: blast out, hitting the molten pig iron at supersonic speeds. 783 00:46:08,160 --> 00:46:11,360 Speaker 1: The lance itself has to be actively cool to typically 784 00:46:11,440 --> 00:46:15,800 Speaker 1: water cooled, to keep it from overheating from the intense 785 00:46:15,800 --> 00:46:18,880 Speaker 1: heat from this furnace. The oxygen reacts with the impurities, 786 00:46:18,920 --> 00:46:22,600 Speaker 1: thus you get oxidation and it creates heat through that reaction, 787 00:46:22,920 --> 00:46:25,680 Speaker 1: and the heat sustains the temperature needed to keep the 788 00:46:25,719 --> 00:46:29,800 Speaker 1: furnace in action, it becomes sustaining. So in many ways, 789 00:46:29,880 --> 00:46:32,600 Speaker 1: it's a more advanced version of the best Americ converter. 790 00:46:33,400 --> 00:46:36,480 Speaker 1: And this became a new method for making steel efficiently, 791 00:46:36,520 --> 00:46:39,560 Speaker 1: with fewer impurities and at a faster rate than open 792 00:46:39,600 --> 00:46:43,520 Speaker 1: hearth furnaces. All right, we've got one more method to 793 00:46:43,640 --> 00:46:46,200 Speaker 1: talk about, or at least to introduce, and we'll really 794 00:46:46,239 --> 00:46:48,399 Speaker 1: talk about it more in the next episode, and then 795 00:46:48,400 --> 00:46:51,200 Speaker 1: we'll also explore about all the different types of steel 796 00:46:51,480 --> 00:46:53,680 Speaker 1: like Nick had asked. So, the final type of furnace 797 00:46:53,680 --> 00:46:56,520 Speaker 1: I need to mention here is the electric arc furnace, 798 00:46:56,719 --> 00:47:00,160 Speaker 1: and it heats up the materials inside the furnace the 799 00:47:00,280 --> 00:47:04,480 Speaker 1: charge through an electric arc rather than by burning some 800 00:47:04,520 --> 00:47:07,759 Speaker 1: sort of fuel. Back in the early nineteenth century, Sir 801 00:47:07,880 --> 00:47:12,320 Speaker 1: Humphrey Davy created an electric arc between two carbon electrodes. 802 00:47:12,520 --> 00:47:15,759 Speaker 1: In fact, we had electric arc lamps before we had 803 00:47:15,800 --> 00:47:19,120 Speaker 1: the incandescent light bulb, and these things were terrifying too. 804 00:47:19,239 --> 00:47:22,120 Speaker 1: They generate a light by by creating this electric arc 805 00:47:22,160 --> 00:47:25,759 Speaker 1: between two electrodes, very high voltage electric arc. And it 806 00:47:25,760 --> 00:47:27,879 Speaker 1: didn't take very long before someone thought, huh, I wonder 807 00:47:27,920 --> 00:47:30,640 Speaker 1: if there's enough energy in that electric arc to you know, 808 00:47:31,040 --> 00:47:34,480 Speaker 1: melt metal like iron. This is the same basic technology 809 00:47:34,520 --> 00:47:38,560 Speaker 1: that would go into electric arc welders. While using an 810 00:47:38,560 --> 00:47:43,520 Speaker 1: electric arc was effective early on, it was also inefficient 811 00:47:43,560 --> 00:47:46,359 Speaker 1: and expensive, which made it less viable as a means 812 00:47:46,400 --> 00:47:49,160 Speaker 1: of mass producing steel. And there's a lot more of 813 00:47:49,160 --> 00:47:50,759 Speaker 1: tech to go into with that, but I think that's 814 00:47:50,880 --> 00:47:53,839 Speaker 1: enough for today's episode. In our next episode, we'll pick 815 00:47:53,880 --> 00:47:57,080 Speaker 1: back up with electric arc furnaces, talk about how they 816 00:47:57,160 --> 00:47:59,560 Speaker 1: really work, and then finally we'll talk about the different 817 00:47:59,560 --> 00:48:03,680 Speaker 1: classications of steel and what they all mean, including maybe 818 00:48:03,760 --> 00:48:08,920 Speaker 1: a discussion about Damascus steel, because that stuff is largely misunderstood, 819 00:48:09,120 --> 00:48:11,799 Speaker 1: so we'll cover that in the next episode. Two. Uh. 820 00:48:11,840 --> 00:48:13,879 Speaker 1: If you guys have suggestions for things I should cover 821 00:48:13,920 --> 00:48:16,600 Speaker 1: in future episodes of tech Stuff, let me know. Send 822 00:48:16,600 --> 00:48:19,560 Speaker 1: me a message on Twitter or Facebook. The handle for 823 00:48:19,600 --> 00:48:22,840 Speaker 1: both is tech Stuff hs W, and I'll talk to 824 00:48:22,880 --> 00:48:31,160 Speaker 1: you again really soon. Text Stuff is an I Heart 825 00:48:31,239 --> 00:48:34,959 Speaker 1: Radio production. For more podcasts from I Heart Radio, visit 826 00:48:35,000 --> 00:48:38,120 Speaker 1: the i Heart Radio app, Apple Podcasts, or wherever you 827 00:48:38,160 --> 00:48:39,520 Speaker 1: listen to your favorite shows.