1 00:00:04,400 --> 00:00:07,760 Speaker 1: Welcome to text Stuff, a production from I Heart Radio. 2 00:00:12,160 --> 00:00:15,000 Speaker 1: Hey there, and welcome to tech Stuff. I'm your host, 3 00:00:15,160 --> 00:00:18,280 Speaker 1: Jonathan Strickland. I'm an executive producer with I Heart Radio 4 00:00:18,360 --> 00:00:21,440 Speaker 1: and I love all things tech and we are continuing 5 00:00:21,600 --> 00:00:25,840 Speaker 1: our episodes about iron and steel today. So in the 6 00:00:25,880 --> 00:00:29,000 Speaker 1: previous episode, I covered the history of our use of 7 00:00:29,040 --> 00:00:32,120 Speaker 1: iron and how we learned how to refine it into 8 00:00:32,159 --> 00:00:36,200 Speaker 1: something you know, actually useful. To go from hard stuff. 9 00:00:36,280 --> 00:00:39,839 Speaker 1: What's inside those rocks? We found two material we can 10 00:00:39,920 --> 00:00:43,040 Speaker 1: use to build things and or make weapons to poke 11 00:00:43,080 --> 00:00:47,360 Speaker 1: each other with. We talked about smelting and furnaces and 12 00:00:47,479 --> 00:00:51,600 Speaker 1: the refining processes, and we ended that episode with a 13 00:00:51,720 --> 00:00:56,320 Speaker 1: very brief explanation of what an electrical arc furnace is. Today, 14 00:00:56,320 --> 00:00:58,640 Speaker 1: we're going to start off by going into a bit 15 00:00:58,680 --> 00:01:02,640 Speaker 1: more detail about how the electrical arc furnace actually works 16 00:01:03,040 --> 00:01:05,720 Speaker 1: to refine iron, and then we'll move on to talk 17 00:01:05,800 --> 00:01:11,840 Speaker 1: about the different types of steel, including the famous Damascus steel. Now, 18 00:01:11,959 --> 00:01:15,600 Speaker 1: as I said in the previous episode, the electrical arc 19 00:01:15,640 --> 00:01:20,000 Speaker 1: furnace generates high temperatures through the creation of an electrical arc. 20 00:01:20,280 --> 00:01:24,160 Speaker 1: But that description isn't terribly satisfying, is it. How does 21 00:01:24,200 --> 00:01:28,160 Speaker 1: it create the electrical arc what makes it so hot? Well, 22 00:01:28,200 --> 00:01:31,880 Speaker 1: in that last episode I mentioned, Sir Humphrey Davy invented 23 00:01:31,920 --> 00:01:35,800 Speaker 1: the arc lamp using a pair of carbon electrodes. He 24 00:01:35,959 --> 00:01:39,480 Speaker 1: used a couple of thousand battery cells and connected one 25 00:01:39,520 --> 00:01:43,400 Speaker 1: electrode to the positive terminal and one to the negative terminal. 26 00:01:43,680 --> 00:01:47,760 Speaker 1: Then he brought these two electrodes in contact with one another. 27 00:01:48,400 --> 00:01:51,480 Speaker 1: This formed a circuit. So not only could electricity flow 28 00:01:51,560 --> 00:01:55,480 Speaker 1: through this completed path, but also the negative carbon electrode 29 00:01:55,520 --> 00:01:59,560 Speaker 1: began to attract particles from the positive carbon electrode. In 30 00:01:59,600 --> 00:02:04,600 Speaker 1: other words, material from the positively charged electrode was literally 31 00:02:04,720 --> 00:02:08,360 Speaker 1: moving over to the negatively charged one and pulling the 32 00:02:08,400 --> 00:02:13,200 Speaker 1: electrodes apart slowly allows an electrical arc to form between 33 00:02:13,240 --> 00:02:17,560 Speaker 1: the two electrodes. It seems like electricity is still traveling 34 00:02:17,760 --> 00:02:20,000 Speaker 1: between one and the other even though there is no 35 00:02:20,080 --> 00:02:24,799 Speaker 1: longer a physical path. So if it's seemingly passing through 36 00:02:24,800 --> 00:02:28,280 Speaker 1: the air itself, how is that even possible? Is there 37 00:02:28,320 --> 00:02:31,720 Speaker 1: an enormous difference in electric potential between the rods? Is 38 00:02:31,760 --> 00:02:35,800 Speaker 1: the voltage super high? Remember voltage is like water pressure, right, 39 00:02:35,840 --> 00:02:39,960 Speaker 1: It's how hard the current is being pushed through a circuit. 40 00:02:40,040 --> 00:02:43,160 Speaker 1: But no, that's not the case. The voltage doesn't have 41 00:02:43,240 --> 00:02:46,480 Speaker 1: to be super high, although typically we're talking about more 42 00:02:46,520 --> 00:02:50,200 Speaker 1: than forty five volts for arc lamps and sometimes more 43 00:02:50,240 --> 00:02:54,639 Speaker 1: than a hundred volts for electrical arc applications. But when 44 00:02:54,639 --> 00:02:57,480 Speaker 1: the two electrodes make contact with one another, there is 45 00:02:57,520 --> 00:03:00,320 Speaker 1: a lot of atomic movement at the point of contact. 46 00:03:00,600 --> 00:03:02,920 Speaker 1: Atomic movement means lots of stuff, but one thing we 47 00:03:02,960 --> 00:03:06,919 Speaker 1: can think about is heat. Hot atoms move around a lot, 48 00:03:07,320 --> 00:03:10,399 Speaker 1: cold atoms don't. In fact, there are some who say 49 00:03:10,440 --> 00:03:13,600 Speaker 1: that absolute zero or zero kelvin isn't just the bottom 50 00:03:13,680 --> 00:03:15,920 Speaker 1: end of how cold temperatures can get, but represents a 51 00:03:15,919 --> 00:03:20,360 Speaker 1: total lack of atomic movement. This heat is enough to 52 00:03:20,520 --> 00:03:25,400 Speaker 1: boil off some atoms from the solid carbon electrodes and 53 00:03:25,480 --> 00:03:29,240 Speaker 1: it forms a gas. That gas is still capable of 54 00:03:29,280 --> 00:03:32,760 Speaker 1: conducting an electric charge, and it does so. Thus you 55 00:03:32,840 --> 00:03:37,120 Speaker 1: get a plasma and ionized gas. So what we have 56 00:03:37,240 --> 00:03:41,000 Speaker 1: here is a plasma generator with a bright electrical arc 57 00:03:41,040 --> 00:03:43,960 Speaker 1: passing through it. There's a lot more science than this 58 00:03:44,080 --> 00:03:46,640 Speaker 1: that we could talk about, such as ionization and stuff, 59 00:03:46,640 --> 00:03:49,560 Speaker 1: but the important thing for us is that by bringing 60 00:03:49,600 --> 00:03:53,720 Speaker 1: these electrodes in contact with one another and then separating 61 00:03:53,760 --> 00:03:56,360 Speaker 1: them from each other slightly, you get a very hot, 62 00:03:56,640 --> 00:04:00,480 Speaker 1: very bright electrical arc. This would end up being basic 63 00:04:00,560 --> 00:04:06,000 Speaker 1: technology behind some of the earliest electric lights before incandescent bulbs. 64 00:04:06,040 --> 00:04:09,160 Speaker 1: They were used for street lighting and for movie projectors 65 00:04:09,160 --> 00:04:13,840 Speaker 1: and search lights. The light they produce is incredibly bright. 66 00:04:13,880 --> 00:04:16,080 Speaker 1: It's bright enough to hurt your eyes if you look 67 00:04:16,120 --> 00:04:20,040 Speaker 1: straight at it, and they also emit ultra violet light, 68 00:04:20,560 --> 00:04:22,839 Speaker 1: so you wouldn't want to look at them directly or 69 00:04:22,920 --> 00:04:27,960 Speaker 1: be around and unshielded electrical arc for a really long time. Fortunately, 70 00:04:28,560 --> 00:04:31,919 Speaker 1: good old playing glass doesn't allow ultra violet light to 71 00:04:31,920 --> 00:04:34,800 Speaker 1: pass through it, so with a glass lens you can 72 00:04:34,839 --> 00:04:39,600 Speaker 1: actually block that pesky UV radiation. Our lamps aren't that 73 00:04:39,680 --> 00:04:42,679 Speaker 1: common these days. I mean, there are still some out there, 74 00:04:42,760 --> 00:04:46,039 Speaker 1: but electrical arcs are still used for lots of stuff. 75 00:04:46,240 --> 00:04:48,520 Speaker 1: Old time listeners to the show might remember that one 76 00:04:48,520 --> 00:04:51,720 Speaker 1: of my first articles for the website how Stuff works 77 00:04:51,760 --> 00:04:56,520 Speaker 1: dot com was on a technology called plasma waste converters. 78 00:04:57,000 --> 00:04:59,880 Speaker 1: These facilities use a plasma torch, which is a sin 79 00:05:00,200 --> 00:05:02,640 Speaker 1: a variation of what I've already been talking about with 80 00:05:02,760 --> 00:05:09,719 Speaker 1: arc lamps, to gasify or to liquefy garbage. Essentially, anything 81 00:05:09,760 --> 00:05:14,640 Speaker 1: that's carbon based gets gasified. It's it's turned into gas. 82 00:05:15,040 --> 00:05:17,640 Speaker 1: Anything that's not carbon based gets heated up so much 83 00:05:17,680 --> 00:05:22,040 Speaker 1: that it becomes molten. Well, electrical arc furnaces use this 84 00:05:22,240 --> 00:05:26,760 Speaker 1: same basic technology in order to make steel. Your typical 85 00:05:26,839 --> 00:05:31,800 Speaker 1: electrical arc furnace has a cylindrical vessel, right This is 86 00:05:32,200 --> 00:05:36,279 Speaker 1: the base of the furnace. This is what holds the charge. 87 00:05:36,440 --> 00:05:39,960 Speaker 1: In other words, the raw material you're using. This vessel 88 00:05:40,279 --> 00:05:45,000 Speaker 1: has an interior lining of refractory material designed to reflect 89 00:05:45,040 --> 00:05:51,080 Speaker 1: heat back into the chamber. The melted material, called helpfully 90 00:05:51,120 --> 00:05:54,560 Speaker 1: the melt, will gather at the bottom of the furnace. 91 00:05:55,000 --> 00:05:57,560 Speaker 1: And this is really dense stuff right now we're talking 92 00:05:57,560 --> 00:06:02,320 Speaker 1: about steel. So the slag, as in the other materials, 93 00:06:02,320 --> 00:06:05,600 Speaker 1: the impurities that were also part of the charge. Typically 94 00:06:05,600 --> 00:06:08,839 Speaker 1: it's stuff you don't want. Tends to float in a 95 00:06:08,960 --> 00:06:12,680 Speaker 1: layer above the steel melt, and it can be drawn 96 00:06:12,720 --> 00:06:16,760 Speaker 1: out through a slag door. At a certain height on 97 00:06:16,880 --> 00:06:20,480 Speaker 1: the chamber. Towards the bottom of the furnace is a 98 00:06:20,520 --> 00:06:23,520 Speaker 1: tap hole. It's kind of the drain for the furnace, 99 00:06:24,080 --> 00:06:28,120 Speaker 1: and this is the hole through which molten steel will flow. 100 00:06:28,560 --> 00:06:31,560 Speaker 1: And then it's collected in another vessel called the ladle. 101 00:06:31,680 --> 00:06:34,320 Speaker 1: So you have a ladle is essentially a special kind 102 00:06:34,360 --> 00:06:37,599 Speaker 1: of bucket that's underneath this tap hole. The open up 103 00:06:37,640 --> 00:06:39,840 Speaker 1: the tap hole and the molten steel comes out. And 104 00:06:39,920 --> 00:06:44,400 Speaker 1: typically these furnaces are mounted on platforms that have a 105 00:06:44,560 --> 00:06:48,760 Speaker 1: hydraulic lifting arm below them that can extend so it 106 00:06:48,880 --> 00:06:52,880 Speaker 1: tilts the entire furnace to get every last delicious drop 107 00:06:52,920 --> 00:06:56,680 Speaker 1: of molten steel out, although honestly they don't always take 108 00:06:56,760 --> 00:06:59,880 Speaker 1: every drop out. In fact, some furnaces specifically leave some 109 00:07:00,200 --> 00:07:05,279 Speaker 1: and steel behind to help with future UH steel production. 110 00:07:05,800 --> 00:07:09,720 Speaker 1: The furnace is removable lid, which is really more of 111 00:07:09,760 --> 00:07:13,720 Speaker 1: a roof because these things are usually several meters in diameter. 112 00:07:13,800 --> 00:07:19,800 Speaker 1: They're huge anyway. This removable lid typically has three electrodes 113 00:07:19,880 --> 00:07:24,680 Speaker 1: which extend down into the chamber. The electrodes make contact 114 00:07:24,800 --> 00:07:28,040 Speaker 1: with the charge and the furnace operator filips the switch 115 00:07:28,360 --> 00:07:32,320 Speaker 1: to send electricity through these electrodes. Current flows from the 116 00:07:32,360 --> 00:07:36,040 Speaker 1: electrodes to the charge. UH The electrodes are typically made 117 00:07:36,040 --> 00:07:38,880 Speaker 1: out of graphite, so a type of carbon, and the 118 00:07:38,920 --> 00:07:43,560 Speaker 1: electrodes just like the old carbon electrodes that Sir Humphrey 119 00:07:43,600 --> 00:07:47,760 Speaker 1: Davy used, they begin to ionize and they form a 120 00:07:47,760 --> 00:07:50,760 Speaker 1: plasma gas and that allows this electrical arc to form. 121 00:07:51,120 --> 00:07:53,880 Speaker 1: Power continues to go to the electrodes to perpetuate the 122 00:07:53,960 --> 00:07:58,400 Speaker 1: arc because in this case, this process does not depend 123 00:07:58,520 --> 00:08:03,000 Speaker 1: upon the chemical process oxidation, which was what was generating 124 00:08:03,040 --> 00:08:09,440 Speaker 1: heat with stuff like basic oxygen uh processes. Now, it's 125 00:08:09,480 --> 00:08:13,320 Speaker 1: not like electrical arc furnaces are the new norm. In fact, 126 00:08:13,360 --> 00:08:16,520 Speaker 1: they're responsible for only about a quarter of the world's 127 00:08:16,560 --> 00:08:19,440 Speaker 1: steel production. Most of the rest is still produced through 128 00:08:19,520 --> 00:08:24,680 Speaker 1: basic oxygen furnaces. And the steel that electrical arc furnaces 129 00:08:24,680 --> 00:08:29,360 Speaker 1: produces typically has a higher carbon content than the kind 130 00:08:29,560 --> 00:08:33,600 Speaker 1: that is produced by those other furnaces. And we have 131 00:08:33,679 --> 00:08:38,760 Speaker 1: to remember carbon content and steel affects the metals properties 132 00:08:39,080 --> 00:08:42,760 Speaker 1: like hardness and how malleable versus brittle it is and 133 00:08:43,000 --> 00:08:47,280 Speaker 1: the melting point for the metal. The more carbon, the 134 00:08:47,360 --> 00:08:49,400 Speaker 1: harder the surface of the metal tends to be, the 135 00:08:49,440 --> 00:08:52,000 Speaker 1: more brittle it will be, and the lower the melting 136 00:08:52,040 --> 00:08:55,960 Speaker 1: point will be. One drawback to electrical arc furnaces is 137 00:08:56,000 --> 00:08:59,559 Speaker 1: that they can introduce nitrogen into the steel alloy, and 138 00:08:59,640 --> 00:09:03,800 Speaker 1: nitrog can make steel more brittle. So to deal with 139 00:09:03,840 --> 00:09:07,000 Speaker 1: that the furnace operators can blow in other gases to 140 00:09:07,080 --> 00:09:11,319 Speaker 1: react with the nitrogen, thus neutralizing it, or carbon monoxide 141 00:09:11,960 --> 00:09:16,080 Speaker 1: can be used for this purpose or other other techniques 142 00:09:16,080 --> 00:09:19,080 Speaker 1: included shorter bursts of the electrical arc so you're not 143 00:09:19,160 --> 00:09:23,000 Speaker 1: producing so much nitrogen. Often electrical arc furnaces will use 144 00:09:23,120 --> 00:09:27,080 Speaker 1: scrap steel as part of the charge material, so the 145 00:09:27,120 --> 00:09:29,160 Speaker 1: input you're putting into the furnace in order to get 146 00:09:29,160 --> 00:09:32,640 Speaker 1: steel at the end, it might involve shredded or scrapped 147 00:09:32,679 --> 00:09:36,280 Speaker 1: steel from other stuff, but they can also bring in 148 00:09:36,920 --> 00:09:40,360 Speaker 1: things like iron from blast furnaces to it doesn't have 149 00:09:40,480 --> 00:09:44,440 Speaker 1: to be scrap steel, and it can involve other materials 150 00:09:44,440 --> 00:09:47,800 Speaker 1: as well. Scrap steel can contain other stuff in it, 151 00:09:47,840 --> 00:09:53,080 Speaker 1: typically referred to as residuals, stuff like nickel, copper, chromium, tin, 152 00:09:53,280 --> 00:09:55,600 Speaker 1: and other stuff which you may or may not actually 153 00:09:55,640 --> 00:09:57,959 Speaker 1: want in your final product, and you may have to 154 00:09:58,040 --> 00:10:01,880 Speaker 1: draw that off separately. And that's generally how electrical arc 155 00:10:01,920 --> 00:10:05,439 Speaker 1: furnaces work. It's a different approach, not just in technique 156 00:10:05,480 --> 00:10:08,400 Speaker 1: but in the actual physics involved, but the end result 157 00:10:08,520 --> 00:10:11,199 Speaker 1: is the production of steel. So let's talk a bit 158 00:10:11,240 --> 00:10:13,319 Speaker 1: about the different kinds of steel and what they all 159 00:10:13,360 --> 00:10:15,360 Speaker 1: do and what makes them different. But we're going to 160 00:10:15,440 --> 00:10:20,440 Speaker 1: start with a legendary type of steel, Damascus steel. And 161 00:10:20,520 --> 00:10:23,080 Speaker 1: to talk about this, we have to go way back 162 00:10:23,120 --> 00:10:26,960 Speaker 1: before anyone had ever considered using an electrical arc furnace. So, 163 00:10:27,080 --> 00:10:31,480 Speaker 1: beginning sometime around five Common era, sword makers in the 164 00:10:31,480 --> 00:10:35,679 Speaker 1: Middle East began to create weapons that were known for 165 00:10:35,840 --> 00:10:39,040 Speaker 1: their sharpness, for their durability, and for their beauty. They 166 00:10:39,040 --> 00:10:41,920 Speaker 1: could hold an edge really well, they stood up to 167 00:10:42,000 --> 00:10:45,360 Speaker 1: a lot of abuse, and they had these intricate wavy 168 00:10:45,440 --> 00:10:49,440 Speaker 1: patterns on the surface of the metal itself. And legend 169 00:10:49,480 --> 00:10:52,120 Speaker 1: stated that a sword made from that kind of steel 170 00:10:52,200 --> 00:10:55,160 Speaker 1: could be sharpened to the point where it could cut 171 00:10:55,240 --> 00:10:58,280 Speaker 1: a feather in half while the feathers floating in the air. 172 00:10:58,640 --> 00:11:01,600 Speaker 1: Or similarly, if you were to drop a silk scarf, 173 00:11:01,600 --> 00:11:03,880 Speaker 1: you could cut it in half before it hit the ground. 174 00:11:04,000 --> 00:11:07,760 Speaker 1: So sharp these these swords could be because of that 175 00:11:07,760 --> 00:11:13,880 Speaker 1: that incredible metal. But there's some complications to this story. First, 176 00:11:14,200 --> 00:11:18,040 Speaker 1: the legend also states that sword makers lost this ability 177 00:11:18,240 --> 00:11:22,120 Speaker 1: sometime in the eighteenth or nineteenth century, that the entire 178 00:11:22,480 --> 00:11:25,959 Speaker 1: method of producing weapons of this quality was lost to time. 179 00:11:26,720 --> 00:11:28,640 Speaker 1: It seemed as though people just forgot how to make 180 00:11:28,679 --> 00:11:31,840 Speaker 1: weapons this way, and sword makers could still make weapons. 181 00:11:31,920 --> 00:11:34,440 Speaker 1: In fact, they could still make weapons that had wavy 182 00:11:34,480 --> 00:11:37,200 Speaker 1: patterns in the metal. More on that in a second. 183 00:11:37,600 --> 00:11:41,160 Speaker 1: But they didn't possess the legendary hardness and edge holding 184 00:11:41,200 --> 00:11:45,880 Speaker 1: capabilities of those earlier weapons. So how did that knowledge 185 00:11:45,920 --> 00:11:49,439 Speaker 1: die out so suddenly? What was so special about the weapons? Well, 186 00:11:50,040 --> 00:11:54,760 Speaker 1: one reason this is so confusing is that name Damascus Steel. 187 00:11:55,040 --> 00:11:58,280 Speaker 1: It is a little bit misleading because it makes it 188 00:11:58,320 --> 00:12:01,800 Speaker 1: sound as though the steel for the legendary pieces of 189 00:12:02,080 --> 00:12:05,839 Speaker 1: arms and armor all came from Damascus. The city of 190 00:12:05,920 --> 00:12:10,280 Speaker 1: Damascus is in Syria, and that region does have iron mines, 191 00:12:10,840 --> 00:12:13,800 Speaker 1: But the steel they were using to make these particularly 192 00:12:13,800 --> 00:12:17,800 Speaker 1: strong weapons probably didn't come from the Middle East, at 193 00:12:17,840 --> 00:12:22,480 Speaker 1: least not most of it. Most of it came from India. See, 194 00:12:22,760 --> 00:12:27,480 Speaker 1: Damascus was an incredibly important trade city in the Middle Ages. 195 00:12:27,600 --> 00:12:31,320 Speaker 1: All sorts of merchants passed through that city trading goods, 196 00:12:31,440 --> 00:12:35,000 Speaker 1: and some of those goods included steel forged from iron 197 00:12:35,080 --> 00:12:37,959 Speaker 1: that had been mined far away in India and then 198 00:12:38,000 --> 00:12:41,480 Speaker 1: refined into steel in India. So they were actually bringing 199 00:12:41,760 --> 00:12:47,040 Speaker 1: steel ingots, or more fittingly, steel cakes to Damascus, and 200 00:12:47,120 --> 00:12:50,840 Speaker 1: this particular type of steel is more accurately called woots 201 00:12:50,880 --> 00:12:55,480 Speaker 1: steel w O O t Z. This steal happened to 202 00:12:55,480 --> 00:13:00,000 Speaker 1: have a low concentration of an impurity that gave Damascus 203 00:13:00,200 --> 00:13:06,760 Speaker 1: steel that particularly vibrant, wavy pattern and strength. It was vanadium. 204 00:13:06,800 --> 00:13:09,880 Speaker 1: As it turns out, there is a mine in Jordan's 205 00:13:10,120 --> 00:13:13,400 Speaker 1: that also produces iron ore with a similar amount of 206 00:13:13,480 --> 00:13:18,200 Speaker 1: vanadium in it, So at least some Damascus steel may 207 00:13:18,200 --> 00:13:21,760 Speaker 1: have originally come from the Middle East, with most of 208 00:13:21,760 --> 00:13:25,360 Speaker 1: the rest being imported from India. The process for making 209 00:13:25,360 --> 00:13:29,679 Speaker 1: the steel itself involved smelting iron ore using a bloomery, 210 00:13:30,320 --> 00:13:32,760 Speaker 1: which remember it doesn't melt the iron, it just heats 211 00:13:32,760 --> 00:13:36,080 Speaker 1: it up to a glowing, hot, spongy mass that you 212 00:13:36,120 --> 00:13:39,080 Speaker 1: didn't have to work with a hammer. But then after 213 00:13:39,160 --> 00:13:41,800 Speaker 1: the iron bloom, which is what you call the lump 214 00:13:42,360 --> 00:13:45,000 Speaker 1: that you create at the end of the bloomery process, 215 00:13:45,040 --> 00:13:48,080 Speaker 1: after the iron bloom cooled, then they would crush it 216 00:13:48,200 --> 00:13:51,800 Speaker 1: up and put the little pieces of the iron bloom 217 00:13:51,840 --> 00:13:55,760 Speaker 1: into a crucible. And along with that iron bloom they 218 00:13:55,760 --> 00:14:00,320 Speaker 1: would put some green leaves, uh some crushed glass, and 219 00:14:00,520 --> 00:14:03,600 Speaker 1: maybe some charcoal in there. Before they would seal the 220 00:14:03,640 --> 00:14:07,240 Speaker 1: crucible up so it's completely sealed, and they would then 221 00:14:07,320 --> 00:14:10,800 Speaker 1: put that into a furnace. And because the crucible sealed, 222 00:14:10,880 --> 00:14:16,040 Speaker 1: no oxygen gets into this process, so combustion cannot happen. Remember, 223 00:14:16,080 --> 00:14:20,000 Speaker 1: for combustion to happen, you need heat, you need fuel, 224 00:14:20,200 --> 00:14:24,360 Speaker 1: and you need an oxidizer. It doesn't combust the material 225 00:14:24,400 --> 00:14:27,960 Speaker 1: inside heats up to very high temperatures. The leaves release 226 00:14:28,080 --> 00:14:31,280 Speaker 1: hydrogen as they heat up, which facilitates the absorption of 227 00:14:31,360 --> 00:14:35,880 Speaker 1: carbon into the iron. And as iron absorbs carbon, the 228 00:14:35,960 --> 00:14:39,400 Speaker 1: melting point for the iron decreases, and that allowed these 229 00:14:39,560 --> 00:14:42,960 Speaker 1: ancient blacksmiths to actually work with molten iron. They weren't 230 00:14:43,040 --> 00:14:45,680 Speaker 1: just heating up a lump anymore. Now the iron was 231 00:14:45,760 --> 00:14:51,080 Speaker 1: melting into a molten liquid. The glass also melts, becoming 232 00:14:51,480 --> 00:14:54,760 Speaker 1: a cap over the iron. Because the glass is less 233 00:14:54,800 --> 00:14:57,480 Speaker 1: dense than the iron, it floats on top. That further 234 00:14:57,560 --> 00:15:00,720 Speaker 1: protected the iron from being exposed to the air prematurely. 235 00:15:01,240 --> 00:15:03,800 Speaker 1: And the charcoal serves not just as a source of 236 00:15:03,840 --> 00:15:06,080 Speaker 1: some carbon, but also as a way to neutralize any 237 00:15:06,120 --> 00:15:09,520 Speaker 1: oxygen that was being released in the process. The result 238 00:15:10,000 --> 00:15:14,120 Speaker 1: was an ingot or cake of high carbon steel. A 239 00:15:14,200 --> 00:15:17,560 Speaker 1: skilled blacksmith would take that steel, and through a long 240 00:15:17,720 --> 00:15:21,640 Speaker 1: process of reheating the steel and cooling it, would then 241 00:15:21,680 --> 00:15:25,240 Speaker 1: prepare it for forging. Forging would involve heating the metal 242 00:15:25,600 --> 00:15:28,520 Speaker 1: enough so that it would become malleable when struck with 243 00:15:28,560 --> 00:15:32,480 Speaker 1: a hammer, and these are all dependent on specific temperature ranges. 244 00:15:33,040 --> 00:15:36,240 Speaker 1: So the blacksmith would get that metal hot enough, put 245 00:15:36,280 --> 00:15:39,160 Speaker 1: it into on an anivil, work it with a hammer, 246 00:15:39,280 --> 00:15:42,360 Speaker 1: work the metal into a long sword blank, for example, 247 00:15:42,920 --> 00:15:46,920 Speaker 1: which would then be further worked into the sword itself, 248 00:15:47,200 --> 00:15:50,880 Speaker 1: and the steel's composition, combined with the sword maker's technique, 249 00:15:51,280 --> 00:15:54,240 Speaker 1: is what would create those intricate patterns on the blades. 250 00:15:54,360 --> 00:15:57,560 Speaker 1: The patterns were made in part because the vanadium was 251 00:15:57,720 --> 00:16:02,200 Speaker 1: in that iron and carbides or the carbon compounds, and 252 00:16:02,240 --> 00:16:05,080 Speaker 1: the blade itself provided the strength and hardness needed to 253 00:16:05,120 --> 00:16:09,760 Speaker 1: create very sharp, durable weapons. But then there's another way 254 00:16:09,760 --> 00:16:12,120 Speaker 1: of creating those patterns. I alluded to it earlier. It's 255 00:16:12,120 --> 00:16:16,760 Speaker 1: called pattern folding. This is a totally different technique, and 256 00:16:16,800 --> 00:16:21,320 Speaker 1: the patterns in pattern folded weapons are not exactly identical 257 00:16:21,480 --> 00:16:24,760 Speaker 1: to those of true Damascus steel, but they are still 258 00:16:24,840 --> 00:16:27,520 Speaker 1: very pretty, so they were kind of sought after. But 259 00:16:27,600 --> 00:16:30,240 Speaker 1: this is a technique in which a blacksmith would take 260 00:16:30,280 --> 00:16:35,240 Speaker 1: iron from different blooms. Thus, these different chunks of iron 261 00:16:35,320 --> 00:16:39,040 Speaker 1: have different concentrations of carbon in them, so some of 262 00:16:39,080 --> 00:16:41,880 Speaker 1: them may be low carbon, some of them may be 263 00:16:42,040 --> 00:16:46,000 Speaker 1: high carbon. And they would hammer out these various pieces 264 00:16:46,040 --> 00:16:49,280 Speaker 1: of iron into strips. They would heat these strips up 265 00:16:49,320 --> 00:16:53,200 Speaker 1: together so they would reach this very high temperature, and 266 00:16:53,240 --> 00:16:57,480 Speaker 1: then would start to hammer those together to weld these 267 00:16:57,520 --> 00:17:00,760 Speaker 1: different layers of metal together. Are so you've got these 268 00:17:00,760 --> 00:17:05,120 Speaker 1: different concentrations of carbon in different strips of iron all 269 00:17:05,240 --> 00:17:09,320 Speaker 1: getting welded together, and they would fold it and weld 270 00:17:09,400 --> 00:17:13,399 Speaker 1: it again, folded and welded again, and this would create 271 00:17:13,800 --> 00:17:16,560 Speaker 1: that sort of pattern. Look, because you're actually looking at 272 00:17:16,640 --> 00:17:21,680 Speaker 1: different concentrations of carbon in iron, it's that's what's causing 273 00:17:21,720 --> 00:17:24,960 Speaker 1: the pattern. It's not the nature of the iron itself. 274 00:17:25,760 --> 00:17:29,920 Speaker 1: And because you were using this approach where you're hammering 275 00:17:29,960 --> 00:17:33,680 Speaker 1: it out and you're never melting the iron, you couldn't 276 00:17:33,680 --> 00:17:37,119 Speaker 1: get as pure a version of steel as you would 277 00:17:37,119 --> 00:17:40,879 Speaker 1: with the crucible. The crucible would allow all the slag 278 00:17:41,000 --> 00:17:43,159 Speaker 1: to rise to the top of the crucible. You know, 279 00:17:43,200 --> 00:17:45,679 Speaker 1: everything turns into liquid, so you could just pour the 280 00:17:45,720 --> 00:17:50,600 Speaker 1: slag off, but you couldn't do that with this approach 281 00:17:50,600 --> 00:17:54,119 Speaker 1: because you never melted the iron, so you had to 282 00:17:54,119 --> 00:17:56,119 Speaker 1: work it with a hammer, and it would never be 283 00:17:56,160 --> 00:18:00,040 Speaker 1: as pure as true Damascus steel would, so you and 284 00:18:00,240 --> 00:18:04,480 Speaker 1: not get a weapon of the same quality as one 285 00:18:04,560 --> 00:18:07,080 Speaker 1: that was a true Damascus steel sword made by an 286 00:18:07,119 --> 00:18:12,520 Speaker 1: actual master sword maker. Damascus steel, the real stuff died 287 00:18:12,520 --> 00:18:16,959 Speaker 1: out largely because industrialization brought about mass production and steel, 288 00:18:17,400 --> 00:18:21,120 Speaker 1: and that lowered the demand for the more artisan approach 289 00:18:21,640 --> 00:18:25,080 Speaker 1: and the process of working the steel, which included very 290 00:18:25,080 --> 00:18:28,320 Speaker 1: many steps. It was typically passed down through oral tradition, 291 00:18:28,440 --> 00:18:31,919 Speaker 1: not written down anywhere, so it was gradually forgotten because 292 00:18:32,280 --> 00:18:34,600 Speaker 1: there was no call to make that steal, so no 293 00:18:34,640 --> 00:18:39,520 Speaker 1: one was passing down that knowledge. More recently, modern blacksmiths 294 00:18:39,560 --> 00:18:42,720 Speaker 1: have been working with different approaches to replicate the forging 295 00:18:42,800 --> 00:18:47,240 Speaker 1: of Damascus steel, largely based on some very educated guesses 296 00:18:47,280 --> 00:18:49,439 Speaker 1: as to how it must have happened, and they've made 297 00:18:49,480 --> 00:18:52,000 Speaker 1: a lot of progress, largely through trial and error. But 298 00:18:52,160 --> 00:18:54,960 Speaker 1: it all starts with having the right type of steal 299 00:18:55,480 --> 00:18:59,040 Speaker 1: from the right type of iron ore. When we come back, 300 00:18:59,359 --> 00:19:02,800 Speaker 1: we're gonna talk about some modern classifications of steel and 301 00:19:02,840 --> 00:19:05,879 Speaker 1: what that all means. But first, let's take a quick break. 302 00:19:13,480 --> 00:19:18,399 Speaker 1: So how many types of steel are there? Well, golly, 303 00:19:18,520 --> 00:19:21,399 Speaker 1: that really depends upon whom you ask. I know that 304 00:19:21,720 --> 00:19:24,480 Speaker 1: is a lame answer, but it's true. Some people will 305 00:19:24,560 --> 00:19:29,440 Speaker 1: divide steel into four broad categories. Uh. Those broad categories 306 00:19:29,440 --> 00:19:34,840 Speaker 1: could be plane, carbon steel, alloy steel, tool steel, and 307 00:19:34,960 --> 00:19:39,600 Speaker 1: stainless steel. Some say alloy steel and low alloy steel 308 00:19:39,840 --> 00:19:43,520 Speaker 1: instead of tool steel. And the reason why you get 309 00:19:43,560 --> 00:19:46,399 Speaker 1: all these different terms for the same basic stuff is 310 00:19:46,440 --> 00:19:49,240 Speaker 1: because it all depends on your point of view. It's 311 00:19:49,280 --> 00:19:53,199 Speaker 1: just like what obi Wan said. The site mead Metals 312 00:19:53,240 --> 00:19:59,040 Speaker 1: classifies steel into carbon, alloy, stainless, and tool. But Thomas, 313 00:19:59,160 --> 00:20:02,560 Speaker 1: which is an industrial sourcing company, so it's a company 314 00:20:02,560 --> 00:20:06,640 Speaker 1: that helps manufacturing companies find sources for the raw materials 315 00:20:06,640 --> 00:20:11,200 Speaker 1: they need, they classify it as carbon alloy, low alloy, 316 00:20:11,320 --> 00:20:16,080 Speaker 1: and stainless. Uh. Meanwhile, the home Stratosphere site breaks it 317 00:20:16,119 --> 00:20:19,920 Speaker 1: down to twenty six different types. And then you have 318 00:20:20,119 --> 00:20:24,520 Speaker 1: various standards associations like s a E International s a 319 00:20:24,600 --> 00:20:28,600 Speaker 1: E originally stood for Society of Automotive Engineers or the 320 00:20:28,600 --> 00:20:32,120 Speaker 1: American Iron and Steel Institute or ai s I. Those 321 00:20:32,119 --> 00:20:34,159 Speaker 1: are just two in the United States. You also have 322 00:20:34,280 --> 00:20:37,360 Speaker 1: other ones in other countries, like British standards in the UK. 323 00:20:37,600 --> 00:20:43,040 Speaker 1: You have International Organization for Standardization lots of these different groups, 324 00:20:43,080 --> 00:20:47,440 Speaker 1: and they have thousands of different grades for steel. So 325 00:20:47,480 --> 00:20:49,920 Speaker 1: what does this tell us, Well, it tells us there's 326 00:20:49,960 --> 00:20:53,199 Speaker 1: an incredible amount of variability in the different types of 327 00:20:53,200 --> 00:20:56,320 Speaker 1: steel people have made over the years, and that creating 328 00:20:56,359 --> 00:21:00,280 Speaker 1: standards is tricky. If your standard is Lucy goosey and 329 00:21:00,720 --> 00:21:04,119 Speaker 1: each grade of steel covers a fairly wide range of 330 00:21:04,200 --> 00:21:08,720 Speaker 1: qualities like hardness or flexibility, or percentage of carbon or 331 00:21:08,760 --> 00:21:11,600 Speaker 1: percentage of other alloys, you really end up with some 332 00:21:11,680 --> 00:21:15,520 Speaker 1: real problems. So let's say that you've got a standardization 333 00:21:15,720 --> 00:21:19,680 Speaker 1: system where you've got pretty wide grades to cover a 334 00:21:20,160 --> 00:21:26,080 Speaker 1: spectrum of steel. But you're in charge of making steel girders, 335 00:21:26,160 --> 00:21:29,080 Speaker 1: and so you're looking for a specific grade of steel, 336 00:21:29,480 --> 00:21:32,240 Speaker 1: and the problem is that because it covers a spectrum, 337 00:21:32,280 --> 00:21:35,160 Speaker 1: some of the girders you make might be stronger than others. 338 00:21:35,200 --> 00:21:39,280 Speaker 1: Some might be better at standing up to really strong 339 00:21:39,359 --> 00:21:42,960 Speaker 1: compression forces, and others are not. And that ain't great. 340 00:21:43,280 --> 00:21:49,480 Speaker 1: You really want all that steel to be of similar hardness, 341 00:21:49,560 --> 00:21:53,040 Speaker 1: similar strength. You really need it all to be consistent. 342 00:21:53,480 --> 00:21:56,720 Speaker 1: So it really is necessary to break down steel into 343 00:21:56,800 --> 00:21:59,800 Speaker 1: thousands of grades so that when it comes to actually 344 00:21:59,840 --> 00:22:03,480 Speaker 1: manufacturing and selling the stuff, companies can make sure they 345 00:22:03,480 --> 00:22:06,840 Speaker 1: are getting the raw materials they need to do whatever 346 00:22:07,000 --> 00:22:10,520 Speaker 1: the job necessary is. But the downside is there's no 347 00:22:10,560 --> 00:22:13,000 Speaker 1: way for me to do an episode about every single 348 00:22:13,080 --> 00:22:16,520 Speaker 1: grade of steel, as it would be a billion hours long, 349 00:22:16,760 --> 00:22:20,840 Speaker 1: and a lot of it would just be repeating seemingly 350 00:22:20,960 --> 00:22:25,879 Speaker 1: arbitrary designations between two very similar but technically distinct types 351 00:22:25,920 --> 00:22:29,399 Speaker 1: of steel, and that is just too much. But I 352 00:22:29,440 --> 00:22:32,600 Speaker 1: will go over some of the classification strategies though, and 353 00:22:32,640 --> 00:22:35,600 Speaker 1: what it all means. So let's start with some of 354 00:22:35,640 --> 00:22:39,560 Speaker 1: the broader categories and we can drill down from there. Uh. 355 00:22:39,560 --> 00:22:44,680 Speaker 1: And we're gonna go with carbon steel first. Now quickly, 356 00:22:45,359 --> 00:22:47,600 Speaker 1: just as a reminder, we're gonna be talking about carbon 357 00:22:47,680 --> 00:22:52,159 Speaker 1: steel and alloy steel. Things like that steel itself is 358 00:22:52,240 --> 00:22:56,399 Speaker 1: an alloy, so that makes these designations confusing, right, And 359 00:22:56,560 --> 00:23:00,600 Speaker 1: more than that, steel is an alloy of iron and carbon, 360 00:23:01,000 --> 00:23:03,040 Speaker 1: so that makes it even more confusing. Why do you 361 00:23:03,080 --> 00:23:06,680 Speaker 1: have carbon steel versus alloy steel? I mean, if all 362 00:23:06,680 --> 00:23:09,280 Speaker 1: steel has carbon in it, and if all steel is 363 00:23:09,320 --> 00:23:14,120 Speaker 1: an alloy, what do those designations even mean well, all 364 00:23:14,160 --> 00:23:17,760 Speaker 1: of these steels are still alloys, and all of them 365 00:23:17,800 --> 00:23:20,400 Speaker 1: still have carbon in them, But what really differentiates them 366 00:23:20,440 --> 00:23:24,800 Speaker 1: is how much carbon each type of steel contains, and 367 00:23:25,320 --> 00:23:28,080 Speaker 1: whether or not the steel has a significant amount of 368 00:23:28,240 --> 00:23:32,200 Speaker 1: other stuff in it besides iron and carbon. Other factors 369 00:23:32,240 --> 00:23:35,720 Speaker 1: also make a difference, such as how slowly or rapidly 370 00:23:35,800 --> 00:23:39,080 Speaker 1: the steel cools in the manufacturing process, or how long 371 00:23:39,119 --> 00:23:42,320 Speaker 1: the steel has been held at specific temperatures, or whether 372 00:23:42,359 --> 00:23:46,360 Speaker 1: it's been heat treated. These processes all have their own names. 373 00:23:46,600 --> 00:23:50,040 Speaker 1: To cool steel quickly is to quench it, which typically 374 00:23:50,119 --> 00:23:54,080 Speaker 1: hardens steel. A sword maker might quench a sword to 375 00:23:54,160 --> 00:23:57,520 Speaker 1: give the exterior a harder surface while the interior, which 376 00:23:57,800 --> 00:24:00,600 Speaker 1: will cool more slowly because it's not being bosed to 377 00:24:00,720 --> 00:24:03,960 Speaker 1: the water, retains a more flexible core. As a result, 378 00:24:04,680 --> 00:24:07,800 Speaker 1: to avoid making a sword to brittle, the sword maker 379 00:24:07,920 --> 00:24:11,600 Speaker 1: would temper the blade. That involves heating the sword back 380 00:24:11,680 --> 00:24:15,040 Speaker 1: up again, but below the critical temperature at which the 381 00:24:15,080 --> 00:24:18,080 Speaker 1: sword maker would you know, heat the blade in order 382 00:24:18,119 --> 00:24:20,520 Speaker 1: to work it. So it's not as hot that it 383 00:24:20,520 --> 00:24:24,960 Speaker 1: would be malleable, but it's hotter than it had been. 384 00:24:25,359 --> 00:24:28,960 Speaker 1: So it gets really complicated, right, and it's all about 385 00:24:29,240 --> 00:24:33,240 Speaker 1: creating the right crystalline structure for steel, and I'll get 386 00:24:33,280 --> 00:24:36,840 Speaker 1: more into that towards the end of this episode. For now, 387 00:24:36,920 --> 00:24:39,960 Speaker 1: let's take a closer look at some of those categories. 388 00:24:40,000 --> 00:24:43,679 Speaker 1: So carbon steel that is mostly iron and carbon with 389 00:24:43,720 --> 00:24:47,719 Speaker 1: only trace amounts of other elements in the mix. It's 390 00:24:47,760 --> 00:24:50,720 Speaker 1: also by far the most common type of steel produced 391 00:24:50,760 --> 00:24:53,560 Speaker 1: around the world. And we can also break down carbon 392 00:24:53,680 --> 00:24:58,920 Speaker 1: steel into three large subcategories. Low carbon steel sometimes also 393 00:24:59,040 --> 00:25:03,399 Speaker 1: called mile steel, this can contain up to point three 394 00:25:03,520 --> 00:25:08,160 Speaker 1: percent carbon. Then you've got medium carbon steels, this contains 395 00:25:08,200 --> 00:25:12,040 Speaker 1: between point three and point six percent carbon. And then 396 00:25:12,080 --> 00:25:15,200 Speaker 1: you get high carbon steels, which have more than point 397 00:25:15,280 --> 00:25:19,560 Speaker 1: six percent carbon, typically not much more than one percent. 398 00:25:20,000 --> 00:25:22,080 Speaker 1: You might go up as high as two point five 399 00:25:22,080 --> 00:25:26,080 Speaker 1: percent for some types, but beyond that is unusual, not 400 00:25:26,680 --> 00:25:31,000 Speaker 1: unheard of, but unusual. So even within these subcategories, you 401 00:25:31,080 --> 00:25:35,240 Speaker 1: see there is variation. Right, low carbon or mild steel 402 00:25:35,400 --> 00:25:38,000 Speaker 1: is the easiest to work and shape all of the 403 00:25:38,080 --> 00:25:42,359 Speaker 1: three subcategories because it doesn't have as much carbon in it. Remember, 404 00:25:42,560 --> 00:25:46,480 Speaker 1: you add carbon, the the steel becomes harder. That also 405 00:25:46,520 --> 00:25:50,640 Speaker 1: means it's harder to shape. Now, low carbon steel has 406 00:25:50,720 --> 00:25:54,320 Speaker 1: high ductility, which I haven't really talked about. Ductility is 407 00:25:54,320 --> 00:25:58,280 Speaker 1: the ability of a material to be plastically deformed under 408 00:25:58,359 --> 00:26:03,600 Speaker 1: ten style stresses without fracturing. Tensile stresses are those placed 409 00:26:03,600 --> 00:26:07,119 Speaker 1: on a material that tends to elongate the material. I 410 00:26:07,160 --> 00:26:09,800 Speaker 1: think of it as a kind of tug of war 411 00:26:10,119 --> 00:26:13,560 Speaker 1: kind of stress. Right, You've got people pulling on either 412 00:26:13,680 --> 00:26:17,159 Speaker 1: end of a rope, those are ten sile stresses on 413 00:26:17,359 --> 00:26:22,119 Speaker 1: that rope a pulling stress. Deforming means to change shape, 414 00:26:22,200 --> 00:26:26,560 Speaker 1: so a material with high ductility will stretch, becoming thinner 415 00:26:26,720 --> 00:26:30,320 Speaker 1: without breaking apart. And that also means that low carbon 416 00:26:30,359 --> 00:26:34,879 Speaker 1: steel can be drawn into wires. This involves passing the 417 00:26:34,880 --> 00:26:37,320 Speaker 1: steel through a series of dyes, and these are kind 418 00:26:37,320 --> 00:26:39,479 Speaker 1: of like metal blocks that have a hole in the 419 00:26:39,480 --> 00:26:42,240 Speaker 1: middle of them. And the hole is of a diameter 420 00:26:42,359 --> 00:26:45,000 Speaker 1: that's slightly smaller than what the steel is that you're 421 00:26:45,000 --> 00:26:48,399 Speaker 1: passing through it. So you narrow the end of the 422 00:26:48,480 --> 00:26:51,359 Speaker 1: steel so it'll go through this hole. You connect it 423 00:26:51,400 --> 00:26:55,840 Speaker 1: to some really powerful machine that pulls that steal through 424 00:26:56,320 --> 00:26:59,760 Speaker 1: and the steel elongates. Rather than gets more dense and 425 00:27:00,160 --> 00:27:03,080 Speaker 1: keeps the same density, it just it elongates and gets thinner. 426 00:27:03,760 --> 00:27:06,680 Speaker 1: And you do this several times, and each time you're 427 00:27:06,680 --> 00:27:10,159 Speaker 1: doing it, you're typically going a little smaller with the 428 00:27:10,160 --> 00:27:14,320 Speaker 1: following dye, and you eventually create wire this way, and 429 00:27:14,400 --> 00:27:16,399 Speaker 1: you do this until you reach the gauge or a 430 00:27:16,440 --> 00:27:19,960 Speaker 1: thickness of the wire that you want to produce. Besides wire, 431 00:27:20,040 --> 00:27:22,439 Speaker 1: low carbon steel can be used to make stuff like 432 00:27:22,520 --> 00:27:27,760 Speaker 1: pipes or automobile body parts, and some construction materials. They're 433 00:27:27,800 --> 00:27:32,720 Speaker 1: also used in processes that require machining or welding. Then 434 00:27:32,760 --> 00:27:36,480 Speaker 1: we move to medium carbon steels. These are less ductile, 435 00:27:36,760 --> 00:27:41,160 Speaker 1: but they are also more hard than low carbon steels. 436 00:27:41,160 --> 00:27:44,680 Speaker 1: They have greater hardness. They're often used for gear parts 437 00:27:44,720 --> 00:27:48,320 Speaker 1: like crank shafts and axles and stuff like that, or 438 00:27:48,560 --> 00:27:53,200 Speaker 1: in machinery parts where hardness is an important requirement. When 439 00:27:53,200 --> 00:27:56,399 Speaker 1: you get to the upper ranges of medium carbon steel, 440 00:27:56,480 --> 00:28:00,280 Speaker 1: meaning you're getting closer to high carbon steel, and you're 441 00:28:00,280 --> 00:28:02,080 Speaker 1: working with a metal strong enough to be used in 442 00:28:02,119 --> 00:28:05,520 Speaker 1: tools like screw drivers and pliers and that kind of thing. 443 00:28:06,000 --> 00:28:09,040 Speaker 1: So keep in mind, like I said earlier, each of 444 00:28:09,040 --> 00:28:12,880 Speaker 1: these types of steel has a range within it. They're 445 00:28:12,880 --> 00:28:15,960 Speaker 1: not all equal. But moving on up we get onto 446 00:28:16,040 --> 00:28:18,960 Speaker 1: high carbon steel, we get into the territory of the 447 00:28:19,080 --> 00:28:22,800 Speaker 1: hardest of the carbon steels. It's also the least ductal 448 00:28:22,920 --> 00:28:26,040 Speaker 1: and least malleable, meaning it's the most brittle and and 449 00:28:26,080 --> 00:28:29,479 Speaker 1: it's the most difficult to shape. This stuff can be 450 00:28:29,600 --> 00:28:34,840 Speaker 1: used for rails, for wear resistant plates, for high strength bars, 451 00:28:34,880 --> 00:28:36,879 Speaker 1: and that kind of thing. It's also sometimes used in 452 00:28:36,920 --> 00:28:40,920 Speaker 1: the production of knives. It's hardness makes it really valuable 453 00:28:40,920 --> 00:28:43,920 Speaker 1: for that purpose. They're even processes that can produce steels 454 00:28:43,920 --> 00:28:46,840 Speaker 1: with a really high carbon content around two and a 455 00:28:46,880 --> 00:28:49,960 Speaker 1: half percent. Remember, everything we've talked about from this point 456 00:28:50,120 --> 00:28:52,920 Speaker 1: has been steel with a carbon content of around one 457 00:28:52,960 --> 00:28:56,200 Speaker 1: percent or less. These knives can be sharpened to a 458 00:28:56,320 --> 00:28:59,080 Speaker 1: very fine edge, but they will lose that edge fairly 459 00:28:59,160 --> 00:29:02,680 Speaker 1: quickly over time and require sharpening. But high carbon steel 460 00:29:02,760 --> 00:29:06,960 Speaker 1: also has a very low resistance to corrosion, so if 461 00:29:06,960 --> 00:29:10,360 Speaker 1: you get high carbon steel near water, it can rust 462 00:29:10,400 --> 00:29:13,480 Speaker 1: pretty quickly. So while you can find cutlery made of 463 00:29:13,560 --> 00:29:17,280 Speaker 1: high carbon steel, it's far more common to encounter knives 464 00:29:17,320 --> 00:29:19,960 Speaker 1: and silverware made out of a different kind of steel, 465 00:29:20,320 --> 00:29:23,640 Speaker 1: and that is stainless steel. All right, how about we 466 00:29:23,640 --> 00:29:26,280 Speaker 1: shift over to stainless steel for a few minutes. We 467 00:29:26,320 --> 00:29:29,719 Speaker 1: already know that stainless steel has carbon in it, otherwise 468 00:29:29,720 --> 00:29:33,160 Speaker 1: it wouldn't be steel. But what makes it stainless, Well, 469 00:29:33,360 --> 00:29:37,520 Speaker 1: stainless is a type of alloy steel And again, yes, 470 00:29:37,840 --> 00:29:40,200 Speaker 1: steel all on its own is an alloy with iron 471 00:29:40,240 --> 00:29:43,360 Speaker 1: and carbon, but in this case we're talking about alloy 472 00:29:43,440 --> 00:29:46,800 Speaker 1: with another metal added to it. So what is our 473 00:29:47,240 --> 00:29:52,720 Speaker 1: addition to our favorite iron carbon combo. Well, it's chromium, 474 00:29:52,760 --> 00:29:55,280 Speaker 1: and that typically ends up making up between ten and 475 00:29:55,400 --> 00:30:00,320 Speaker 1: twenty percent of the overall composition of stainless steel. Other 476 00:30:00,480 --> 00:30:03,320 Speaker 1: metals and materials are typically in that alloy as well, 477 00:30:03,360 --> 00:30:07,760 Speaker 1: including nickel, and then you get stainless steel. And chromium 478 00:30:08,040 --> 00:30:12,320 Speaker 1: is a hard, brittle metal. It's also incredibly resistant to corrosion, 479 00:30:12,640 --> 00:30:16,200 Speaker 1: and it's specifically that property that comes in awfully handy 480 00:30:16,240 --> 00:30:21,880 Speaker 1: when you're producing a steel alloy. Stainless steel resists corrosive effects, 481 00:30:21,880 --> 00:30:24,120 Speaker 1: and so there are types of stainless steel that are 482 00:30:24,120 --> 00:30:28,000 Speaker 1: really handy for stuff like cutlery or containers that hold 483 00:30:28,040 --> 00:30:31,880 Speaker 1: corrosive materials. It's also pretty strong stuff, or at least 484 00:30:31,920 --> 00:30:35,360 Speaker 1: it can be, because there are different types of stainless steel, 485 00:30:35,600 --> 00:30:38,959 Speaker 1: just as there are different types of carbon steel, and 486 00:30:39,000 --> 00:30:42,280 Speaker 1: the grades of stainless steel depend on many factors, not 487 00:30:42,400 --> 00:30:45,479 Speaker 1: just how much carbon and chromium are in the alloy, 488 00:30:45,720 --> 00:30:50,560 Speaker 1: but also stuff like nickel, copper, silicon, aluminum, and even 489 00:30:50,640 --> 00:30:53,480 Speaker 1: the process of making the steel itself. All of these 490 00:30:53,520 --> 00:30:57,200 Speaker 1: can affect the various aspects of the stainless steel, including 491 00:30:57,240 --> 00:31:01,800 Speaker 1: its hardness, its resistance to corrosion, its heat resistance, and more. 492 00:31:02,680 --> 00:31:06,160 Speaker 1: There are lots of different steel alloys, and each creates 493 00:31:06,160 --> 00:31:09,040 Speaker 1: a different kind of steel with properties that are sought 494 00:31:09,080 --> 00:31:13,160 Speaker 1: after for specific applications. Steel that works great for one 495 00:31:13,200 --> 00:31:16,600 Speaker 1: purpose might not be ideal for another. But luckily, because 496 00:31:16,640 --> 00:31:19,680 Speaker 1: metallurgists have a lot of time on their hands, I mean, 497 00:31:19,720 --> 00:31:22,840 Speaker 1: they've done so much work experimenting with different alloys that 498 00:31:22,960 --> 00:31:25,120 Speaker 1: we can produce a lot of different kinds of steel, 499 00:31:25,760 --> 00:31:28,120 Speaker 1: and there's probably a kind that's going to be ideal 500 00:31:28,160 --> 00:31:30,440 Speaker 1: for whatever purpose you have in minds let's go over 501 00:31:30,480 --> 00:31:34,680 Speaker 1: a few of them. Tungsten is a dull silver metal 502 00:31:35,000 --> 00:31:39,280 Speaker 1: sometimes it's called wolfram that one of tungsten's properties is 503 00:31:39,360 --> 00:31:42,680 Speaker 1: a very high melting point. So if you make an 504 00:31:42,720 --> 00:31:47,400 Speaker 1: alloy of steel with tungsten and you get toungusten steel, 505 00:31:47,480 --> 00:31:50,720 Speaker 1: you get a really tough, hard metal that can withstand 506 00:31:51,080 --> 00:31:55,040 Speaker 1: incredible temperatures, and for that reason, engineers rely on tungsten 507 00:31:55,120 --> 00:31:58,160 Speaker 1: steel for stuff like rocket engine nozzles. I mean, you 508 00:31:58,160 --> 00:32:00,920 Speaker 1: don't want your engine melting off your launch vehicle when 509 00:32:00,920 --> 00:32:03,920 Speaker 1: you're headed off to space. After all. Tungsten steel is 510 00:32:03,920 --> 00:32:07,080 Speaker 1: a go to for applications that involve high temperatures, but 511 00:32:07,120 --> 00:32:10,080 Speaker 1: it may also be combined with other metals like nickel 512 00:32:10,280 --> 00:32:14,680 Speaker 1: or iron for the production of turbine blades. Nickel steel 513 00:32:14,960 --> 00:32:17,920 Speaker 1: is another alloy and is a pretty common one. It's 514 00:32:17,920 --> 00:32:20,840 Speaker 1: one of the alloys that works best for heat treated steel, 515 00:32:20,960 --> 00:32:23,800 Speaker 1: as it decreases the amount of distortion in the steel 516 00:32:23,920 --> 00:32:26,640 Speaker 1: when it has been quenched, you know, when it's been 517 00:32:26,640 --> 00:32:31,120 Speaker 1: cooled very quickly. That also boosts steels strength while not 518 00:32:31,280 --> 00:32:35,200 Speaker 1: trading off on ductility, so you can get very strong steel. 519 00:32:35,360 --> 00:32:39,960 Speaker 1: There's still ductal Like chromium, nickel resists corrosion. It's one 520 00:32:40,000 --> 00:32:43,040 Speaker 1: of the reasons why it's frequently a component in stainless steel. 521 00:32:43,720 --> 00:32:47,719 Speaker 1: Then there's manganese. Manganese steel typically has between eleven and 522 00:32:47,760 --> 00:32:51,840 Speaker 1: fourteen percent manganese in it. Manganese steel is quite hard 523 00:32:51,960 --> 00:32:54,800 Speaker 1: and it resists where and tear. It's frequently used in 524 00:32:54,880 --> 00:32:58,120 Speaker 1: railway tracks and heavy duty applications that encounter lots of 525 00:32:58,160 --> 00:33:02,400 Speaker 1: mechanical forces, like parts for rock crushers, for example, or 526 00:33:02,440 --> 00:33:07,200 Speaker 1: cement mixers and you know other seriously tough machines. Next, 527 00:33:07,280 --> 00:33:11,000 Speaker 1: we come to a medal we mentioned earlier in this episode, vanadium. 528 00:33:11,240 --> 00:33:15,240 Speaker 1: Vanadium steel is resistant to corrosion. It's also got some 529 00:33:15,320 --> 00:33:19,360 Speaker 1: shock absorption qualities. It's used in the automobile industry and 530 00:33:19,440 --> 00:33:22,880 Speaker 1: parts meant to distribute shock and vibration. It's also a 531 00:33:22,880 --> 00:33:27,200 Speaker 1: common material in pipes and tubes, mint for carrying corrosive chemicals, 532 00:33:27,240 --> 00:33:30,400 Speaker 1: and it is often used as a bonding material to 533 00:33:30,560 --> 00:33:35,080 Speaker 1: bring steel and titanium into b f F territory. Get 534 00:33:35,120 --> 00:33:38,440 Speaker 1: your titanium steel. I've got more to say on different 535 00:33:38,440 --> 00:33:40,760 Speaker 1: types of steel, but Gali, I need to steal myself 536 00:33:40,840 --> 00:33:42,959 Speaker 1: with some tea. My voice is giving out. We'll be 537 00:33:43,080 --> 00:33:53,080 Speaker 1: right back. In the last section, when I was talking 538 00:33:53,080 --> 00:33:57,200 Speaker 1: about stainless steel, I mentioned chromium. But making matters more 539 00:33:57,240 --> 00:34:01,280 Speaker 1: confusing is that there are chromium steel alloys that are 540 00:34:01,320 --> 00:34:05,760 Speaker 1: not stainless steel. In addition to corrosion resistance, chromium can 541 00:34:05,800 --> 00:34:09,080 Speaker 1: give steel a boost in high temperature strength, and it's 542 00:34:09,120 --> 00:34:13,399 Speaker 1: also a more elastic alloy with greater tensile strength. It's 543 00:34:13,480 --> 00:34:17,040 Speaker 1: used in automobile manufacturing and frequently is the steel that 544 00:34:17,080 --> 00:34:23,040 Speaker 1: you find for safes. Sometimes chromium and vanadium while tag 545 00:34:23,080 --> 00:34:26,960 Speaker 1: team with steel and create a chromium vanadium steel alloy, 546 00:34:27,280 --> 00:34:30,440 Speaker 1: and this alloy has got high tensile strength, and it's 547 00:34:30,440 --> 00:34:33,680 Speaker 1: suitable for stuff like vehicular frames and gears, that kind 548 00:34:33,680 --> 00:34:37,600 Speaker 1: of thing. Aluminium steel there's another alloy that I need 549 00:34:37,640 --> 00:34:40,560 Speaker 1: to touch on, So that is a thing. Aluminium boosts 550 00:34:40,600 --> 00:34:45,359 Speaker 1: steel's ability to reflect heat, and aluminium is much much 551 00:34:45,480 --> 00:34:49,319 Speaker 1: lighter than steel, So an aluminium steel alloy results in 552 00:34:49,360 --> 00:34:52,480 Speaker 1: a type of steel that's lighter than most other kinds, 553 00:34:52,840 --> 00:34:55,400 Speaker 1: and it's used in all sorts of applications, from packaging 554 00:34:55,520 --> 00:35:00,239 Speaker 1: to energy production to the automotive industry. Cobalt steel, like 555 00:35:00,360 --> 00:35:03,400 Speaker 1: nickel steel, is tough and stands up well too high temperatures. 556 00:35:03,600 --> 00:35:07,480 Speaker 1: It's frequently used to produce high speed cutting tools. Cobalt 557 00:35:07,480 --> 00:35:10,839 Speaker 1: steel is also ferro magnetic, and uh oh, that reminds me. 558 00:35:11,480 --> 00:35:13,680 Speaker 1: One of the things I haven't really talked about much 559 00:35:13,800 --> 00:35:18,719 Speaker 1: in these episodes is magnetism. With certain temperatures, iron is 560 00:35:18,800 --> 00:35:22,480 Speaker 1: ferro magnetic. Now those temperatures involved pretty much all the 561 00:35:22,520 --> 00:35:25,719 Speaker 1: temperatures that you and I would ever experience. If we 562 00:35:25,719 --> 00:35:29,000 Speaker 1: were to experience the temperatures above which iron no longer 563 00:35:29,000 --> 00:35:33,520 Speaker 1: as ferro magnetic, we would be in trouble. See those 564 00:35:33,600 --> 00:35:37,120 Speaker 1: high temperatures beyond what is called the Curi point, iron 565 00:35:37,360 --> 00:35:40,759 Speaker 1: isn't nearly as faro magnetic. It will react weakly to 566 00:35:40,880 --> 00:35:45,760 Speaker 1: magnetic fields. Now that temperature is pretty high. We're talking 567 00:35:45,840 --> 00:35:50,440 Speaker 1: seven seventy degrees celsius for pure iron, but other stuff 568 00:35:50,480 --> 00:35:53,480 Speaker 1: can affect the cury point for steel, and some alloys 569 00:35:53,520 --> 00:35:57,799 Speaker 1: are downright diamagnetic, which means they're not magnetic at all. 570 00:35:58,360 --> 00:36:00,840 Speaker 1: To get into why something can sometime as be magnetic 571 00:36:00,920 --> 00:36:04,400 Speaker 1: and at other temperatures it's not as magnetic, and in 572 00:36:04,440 --> 00:36:07,400 Speaker 1: certain alloys it's not magnetic at all would require a 573 00:36:07,400 --> 00:36:11,000 Speaker 1: full blown dive into quantum physics and the crystalline structure 574 00:36:11,040 --> 00:36:13,719 Speaker 1: of iron, and I'm just not prepared to get into that. 575 00:36:14,200 --> 00:36:16,399 Speaker 1: I ain't got enough coffee in this house to take 576 00:36:16,440 --> 00:36:18,799 Speaker 1: care of that. But the important thing to remember is 577 00:36:18,800 --> 00:36:22,200 Speaker 1: that steals magnetic nature depends heavily on which alloy you're 578 00:36:22,239 --> 00:36:25,239 Speaker 1: talking about. One alloy that is on the high end 579 00:36:25,400 --> 00:36:29,640 Speaker 1: for magnetic force is silicon steel. This stuff is used 580 00:36:29,680 --> 00:36:36,280 Speaker 1: in lots of electromagnetic components, stuff like electrical transformers, relays, motors, 581 00:36:36,320 --> 00:36:39,400 Speaker 1: that kind of thing. If you've got a steel permanent magnet, 582 00:36:39,800 --> 00:36:43,960 Speaker 1: chances are it's made out of silicon steel alloy. Now 583 00:36:44,000 --> 00:36:45,799 Speaker 1: it's time for you to cross your fingers for me, 584 00:36:45,920 --> 00:36:48,080 Speaker 1: because it's time for me to attempt to say the 585 00:36:48,120 --> 00:36:53,480 Speaker 1: word molybdenum. Adding molybdenum to steal and making an alloy 586 00:36:53,800 --> 00:36:57,960 Speaker 1: improves steels well debility as well as its toughness. It's 587 00:36:58,000 --> 00:37:01,120 Speaker 1: also more resistant to corrosion, and it is a common 588 00:37:01,160 --> 00:37:05,040 Speaker 1: material for structural steel, particularly around what would otherwise be 589 00:37:05,160 --> 00:37:08,760 Speaker 1: really corrosive environments, like anything having to do with the ocean. 590 00:37:08,840 --> 00:37:12,440 Speaker 1: So if you were building, say, uh, like an oil 591 00:37:12,560 --> 00:37:16,560 Speaker 1: drilling rig out on the ocean, you're probably using molybdenum 592 00:37:16,760 --> 00:37:19,799 Speaker 1: in your steel alloy. And that's pretty much it for 593 00:37:19,880 --> 00:37:21,880 Speaker 1: the major alloys. Now, keep in mind, each of the 594 00:37:21,960 --> 00:37:24,759 Speaker 1: kinds I mentioned have their own grades of steel, and 595 00:37:24,760 --> 00:37:27,120 Speaker 1: the qualities I mentioned are are general in nature. So 596 00:37:27,800 --> 00:37:31,880 Speaker 1: while one maybe harder than steel typically is you know, 597 00:37:31,960 --> 00:37:35,520 Speaker 1: just carbon steel, the grade to which it is harder 598 00:37:35,600 --> 00:37:39,200 Speaker 1: is dependent upon multiple factors. I guess I should really 599 00:37:39,239 --> 00:37:43,400 Speaker 1: briefly go over tool steels. These are also alloy steels, 600 00:37:43,640 --> 00:37:45,799 Speaker 1: but of course they get their own designation and their 601 00:37:45,840 --> 00:37:50,120 Speaker 1: own subcategories because categorizing stuff is hard, and these steels 602 00:37:50,160 --> 00:37:53,960 Speaker 1: typically include a larger amount of materials like vanadium and 603 00:37:54,080 --> 00:37:57,120 Speaker 1: tongue sten. These have greater resistance to wear and tear. 604 00:37:57,640 --> 00:38:02,000 Speaker 1: They have increased hardness and toughness over typical alloys, and 605 00:38:02,120 --> 00:38:05,759 Speaker 1: tool steels typically have a carbon content between point five 606 00:38:06,320 --> 00:38:08,680 Speaker 1: and one percent. They put us put them closer to 607 00:38:08,680 --> 00:38:12,680 Speaker 1: the high carbon steel category. You can break this down 608 00:38:12,840 --> 00:38:19,400 Speaker 1: into six subcategories, cold work, hot work, shock resistant, water hardening, 609 00:38:19,600 --> 00:38:22,640 Speaker 1: and dealer's choice. No way, I'm sorry, I'm I'm in 610 00:38:22,719 --> 00:38:25,640 Speaker 1: special purpose. The names give you a big hand about 611 00:38:25,640 --> 00:38:28,160 Speaker 1: what's going on here. Some of these steel types are 612 00:38:28,239 --> 00:38:31,520 Speaker 1: best if you need to work within very hot or 613 00:38:31,719 --> 00:38:36,560 Speaker 1: very cold materials or environments. Water hardened steel is a 614 00:38:36,600 --> 00:38:39,840 Speaker 1: type that is water quenched when produced, and it's pretty 615 00:38:39,840 --> 00:38:42,120 Speaker 1: similar to high carbon steel in a lot of ways. 616 00:38:42,560 --> 00:38:46,439 Speaker 1: But that's kind of the down and dirty approach to 617 00:38:46,440 --> 00:38:50,239 Speaker 1: tool steel. But what is it about steel grades? What's 618 00:38:50,280 --> 00:38:52,680 Speaker 1: the story there? Well, it helps if we focus on 619 00:38:52,680 --> 00:38:56,680 Speaker 1: one set of standards and explain from there. So for 620 00:38:56,719 --> 00:38:59,120 Speaker 1: the purposes of this podcast, we're gonna go with the 621 00:38:59,440 --> 00:39:04,439 Speaker 1: s a E steel grade designations. This system grew out 622 00:39:04,560 --> 00:39:08,520 Speaker 1: from the nineteen forties as various engineers and drafts people 623 00:39:08,680 --> 00:39:12,520 Speaker 1: and architects and metallurgists and all these folks were getting 624 00:39:12,520 --> 00:39:15,200 Speaker 1: together and trying to catalog all the different types of 625 00:39:15,239 --> 00:39:20,160 Speaker 1: steel and the specific qualities to those specific types, including 626 00:39:20,160 --> 00:39:23,360 Speaker 1: the differences within a specific group of steel. And the 627 00:39:23,520 --> 00:39:27,440 Speaker 1: s a E system uses a four digit code to 628 00:39:27,600 --> 00:39:30,360 Speaker 1: designate steel so that you really know what you're dealing 629 00:39:30,400 --> 00:39:33,680 Speaker 1: with the first two digits of that four digit code 630 00:39:33,840 --> 00:39:38,080 Speaker 1: tells you which alloying element is present in the steel 631 00:39:38,239 --> 00:39:42,880 Speaker 1: and to what degree. The first digit indicates the alloying element, 632 00:39:42,960 --> 00:39:46,719 Speaker 1: the second indicates the presence of major elements. So here's 633 00:39:46,719 --> 00:39:50,160 Speaker 1: how the first digits shake out. If the first digit 634 00:39:50,239 --> 00:39:52,800 Speaker 1: in that four digit code is a one, then the 635 00:39:52,840 --> 00:39:55,760 Speaker 1: type of steel that's being talked about is a carbon steel, 636 00:39:56,400 --> 00:40:00,760 Speaker 1: so there are no other major trace elements in that steel, 637 00:40:00,960 --> 00:40:04,720 Speaker 1: or at least not beyond trace amounts. If the first 638 00:40:04,920 --> 00:40:07,520 Speaker 1: number is a two, then you're talking about a nickel 639 00:40:07,600 --> 00:40:12,480 Speaker 1: steel alloy. Three would be nickel chromium steel, four is 640 00:40:12,560 --> 00:40:18,640 Speaker 1: molybdenum steel, five is chromium steel, six is chromium vanadium steel, 641 00:40:19,000 --> 00:40:23,800 Speaker 1: seven is tungsten steel, eight is nickel chromium vanadium steel, 642 00:40:24,320 --> 00:40:30,320 Speaker 1: and nine is silicon manganese steel. So that first digit 643 00:40:30,360 --> 00:40:32,640 Speaker 1: tells you a lot, and then the last two digits 644 00:40:32,680 --> 00:40:35,520 Speaker 1: in that four digit code tell you how much carbon 645 00:40:36,040 --> 00:40:38,160 Speaker 1: is in the steel, and it's all in point zero 646 00:40:38,239 --> 00:40:42,360 Speaker 1: one increments. So if you saw a code that said 647 00:40:42,480 --> 00:40:46,680 Speaker 1: ten forty two steel, that would mean you've got carbon 648 00:40:46,760 --> 00:40:51,440 Speaker 1: steel with a carbon percentage of point for two, so 649 00:40:51,480 --> 00:40:54,360 Speaker 1: you would have a type of medium carbon steel in 650 00:40:54,440 --> 00:40:58,120 Speaker 1: other words. But sometimes these four digit codes go and 651 00:40:58,160 --> 00:41:00,640 Speaker 1: make things more confusing. They throw a le are in there, 652 00:41:01,000 --> 00:41:05,080 Speaker 1: so you might see something like twelve L fourteen, So 653 00:41:05,160 --> 00:41:08,279 Speaker 1: what the heck does that mean? If the twelve means 654 00:41:08,280 --> 00:41:11,080 Speaker 1: it's a carbon based steel with some other element in it, 655 00:41:11,160 --> 00:41:15,920 Speaker 1: and fourteen tells you there's point one four carbon in it, 656 00:41:16,080 --> 00:41:19,239 Speaker 1: was the L. The letter L indicates the addition of 657 00:41:19,320 --> 00:41:23,280 Speaker 1: some other material to the steel alloy. L specifically refers 658 00:41:23,320 --> 00:41:26,480 Speaker 1: to lead, so adding lead to the alloy would improve 659 00:41:26,560 --> 00:41:29,759 Speaker 1: the machine ability of the steel. The letter B is 660 00:41:29,800 --> 00:41:31,719 Speaker 1: a similar thing, it could appear in the middle of 661 00:41:31,719 --> 00:41:36,040 Speaker 1: a code, but B stands for boron that improves steel's hardness. 662 00:41:36,560 --> 00:41:39,279 Speaker 1: Other letters might be found at the very front of 663 00:41:39,320 --> 00:41:41,640 Speaker 1: the code. So if you see the letter M, that 664 00:41:41,760 --> 00:41:45,040 Speaker 1: stands for merchant quality, meaning the steel is suitable for 665 00:41:45,120 --> 00:41:49,040 Speaker 1: non critical parts of machinery or structures. The letter E 666 00:41:49,280 --> 00:41:51,800 Speaker 1: before a code would indicate that the steel is suitable 667 00:41:51,800 --> 00:41:55,920 Speaker 1: for electric furnaces. If the code has the letter H 668 00:41:56,080 --> 00:41:58,840 Speaker 1: at the end, that would mean the steel meets harden 669 00:41:58,920 --> 00:42:03,600 Speaker 1: ability limits. And then you have other coding systems entirely, 670 00:42:03,760 --> 00:42:06,759 Speaker 1: so that works for S A E. But the AI 671 00:42:07,080 --> 00:42:10,520 Speaker 1: S I coding system also includes three digit designations for 672 00:42:10,680 --> 00:42:14,960 Speaker 1: different classifications of stainless steel, and the first digit in 673 00:42:15,040 --> 00:42:18,480 Speaker 1: those three digits ranges between two and five. You don't 674 00:42:18,520 --> 00:42:21,359 Speaker 1: have any one hundred series, but two hundred to five 675 00:42:21,440 --> 00:42:26,680 Speaker 1: hundred series that indicates whether the stainless steel is forritic, austinitic, 676 00:42:26,960 --> 00:42:32,120 Speaker 1: or martensitic. So what is that? What? Well? It all 677 00:42:32,160 --> 00:42:34,800 Speaker 1: has to do with that crystalline structure of stainless steel, 678 00:42:35,280 --> 00:42:38,760 Speaker 1: which in turn will dictate certain properties of that steel. 679 00:42:38,920 --> 00:42:42,840 Speaker 1: And I've avoided talking about this because it's hard to 680 00:42:42,880 --> 00:42:47,120 Speaker 1: talk about, but here we go. So crystals only form 681 00:42:47,160 --> 00:42:52,760 Speaker 1: as molten steel or molten iron cools. As the material cools, 682 00:42:52,880 --> 00:42:56,520 Speaker 1: it's lidifies, and it forms a type of lattice that's 683 00:42:56,560 --> 00:43:00,120 Speaker 1: the crystalline structure. Now that that lattice includes a very 684 00:43:00,160 --> 00:43:03,280 Speaker 1: small amount of carbon, and we're talking about just point 685 00:43:03,480 --> 00:43:07,640 Speaker 1: zero to five or less, we call it fairte. And 686 00:43:07,719 --> 00:43:11,359 Speaker 1: fairite has a cubic body crystal structure, and there's an 687 00:43:11,400 --> 00:43:14,279 Speaker 1: iron atom at the center of this crystal that has 688 00:43:14,400 --> 00:43:17,120 Speaker 1: one iron atom at each corner. There's just not much 689 00:43:17,239 --> 00:43:21,200 Speaker 1: room for carbon to fit in there. Ferretic steel is 690 00:43:21,719 --> 00:43:25,919 Speaker 1: susceptible to corrosion. It's not particularly strong or particularly hard, 691 00:43:25,920 --> 00:43:30,000 Speaker 1: so it's not really used very much. Austinitic steel contains 692 00:43:30,040 --> 00:43:33,680 Speaker 1: a form of iron called austinite, and this has a 693 00:43:33,719 --> 00:43:37,760 Speaker 1: different crystalline structure. It's slightly more conducive to absorbing carbon. 694 00:43:38,239 --> 00:43:41,799 Speaker 1: So to make austinite you have to heat faeryte up 695 00:43:41,800 --> 00:43:45,719 Speaker 1: to really high temperatures like n twelve degrees celsius, at 696 00:43:45,760 --> 00:43:49,799 Speaker 1: which point the crystalline structure shifts. But it doesn't break 697 00:43:49,800 --> 00:43:52,880 Speaker 1: apart and become molten. It doesn't liquefy. You're still solid. 698 00:43:52,960 --> 00:43:56,640 Speaker 1: It's just the crystal structure changes and at that temperature 699 00:43:56,960 --> 00:44:00,840 Speaker 1: the steel can absorb more carbon, but needs additional additives 700 00:44:00,880 --> 00:44:04,280 Speaker 1: like manganese and nickel in order to maintain that crystalline 701 00:44:04,320 --> 00:44:07,759 Speaker 1: structure when it starts to cool down. This type of 702 00:44:07,760 --> 00:44:10,960 Speaker 1: stainless steel is much more resistant to corrosion, and it's 703 00:44:11,040 --> 00:44:15,880 Speaker 1: used in stuff like stainless steel, screws, Martin sidic stainless 704 00:44:16,000 --> 00:44:19,400 Speaker 1: steel has Martin site in it, and that clears everything 705 00:44:19,480 --> 00:44:23,200 Speaker 1: up right. So Martin site is another form of crystallized iron, 706 00:44:23,520 --> 00:44:27,400 Speaker 1: and you create it by taking austinite. You heat up 707 00:44:27,440 --> 00:44:31,760 Speaker 1: the austinite, then you cool it rapidly through quenching. So 708 00:44:32,000 --> 00:44:35,480 Speaker 1: when you do this, when the austinite cools down very 709 00:44:35,560 --> 00:44:40,800 Speaker 1: quickly relatively speaking, it prevents those carbon atoms from getting 710 00:44:40,800 --> 00:44:44,120 Speaker 1: the boot from the austinite. Right, Because remember I said 711 00:44:44,160 --> 00:44:46,400 Speaker 1: that you had to add in stuff or for austinite 712 00:44:46,400 --> 00:44:49,399 Speaker 1: to maintain that crystalline structure. One other thing you could 713 00:44:49,400 --> 00:44:52,800 Speaker 1: do is cool it really fast, and then you prevent 714 00:44:53,040 --> 00:44:56,320 Speaker 1: the austinite from converting back into fairite. There are a 715 00:44:56,360 --> 00:45:00,000 Speaker 1: lot of other differences between these types austinitics. Stainless steels 716 00:45:00,080 --> 00:45:03,840 Speaker 1: can't be heat treated, for example, but Martin Siddik stainless 717 00:45:03,840 --> 00:45:07,040 Speaker 1: steel can be. This also means that the different types 718 00:45:07,080 --> 00:45:10,680 Speaker 1: of stainless steel are good for different applications. There's so 719 00:45:10,760 --> 00:45:13,600 Speaker 1: much more we could go into, including stuff like prolite, 720 00:45:13,600 --> 00:45:15,799 Speaker 1: which is important with some of those Damascus blades I 721 00:45:15,800 --> 00:45:18,680 Speaker 1: talked about in the beginning of this episode, but it 722 00:45:18,719 --> 00:45:21,880 Speaker 1: really gets fairly far out of the realm of tech stuff. 723 00:45:22,480 --> 00:45:24,839 Speaker 1: The interesting thing I find about steel is that there 724 00:45:24,840 --> 00:45:27,080 Speaker 1: really are so many different kinds of it, and all 725 00:45:27,120 --> 00:45:29,400 Speaker 1: of them have different qualities that make them great for 726 00:45:29,520 --> 00:45:33,840 Speaker 1: certain and sometimes incredibly specific applications. I have a greater 727 00:45:33,880 --> 00:45:36,640 Speaker 1: appreciation for that now. It's about way more than just 728 00:45:37,000 --> 00:45:40,200 Speaker 1: heating up a lump of metal until it's glowing and 729 00:45:40,200 --> 00:45:44,200 Speaker 1: then whacking at it with the hamlets. Far more nuanced 730 00:45:44,320 --> 00:45:49,040 Speaker 1: than that, and that ends our discussion about iron and 731 00:45:49,160 --> 00:45:53,560 Speaker 1: steel and why there are so many different grades. I mean, honestly, 732 00:45:53,560 --> 00:45:58,719 Speaker 1: it's because these different variations of steel have different enough 733 00:45:58,760 --> 00:46:01,480 Speaker 1: properties that you got to be aware of it before 734 00:46:01,520 --> 00:46:04,080 Speaker 1: you start buying it in bulk and using it to 735 00:46:04,160 --> 00:46:07,879 Speaker 1: create stuff you would hate to create or to order 736 00:46:08,000 --> 00:46:10,920 Speaker 1: steal that is hard to work with. For example, if 737 00:46:10,920 --> 00:46:13,080 Speaker 1: you wanted to have something that was really easy to 738 00:46:13,200 --> 00:46:16,560 Speaker 1: mold into different shapes. You'd really be stuck there. So 739 00:46:16,880 --> 00:46:20,600 Speaker 1: the gradations are important. They're just difficult to really get 740 00:46:20,640 --> 00:46:24,799 Speaker 1: your mind wrapped around. If you guys have any suggestions 741 00:46:24,840 --> 00:46:27,560 Speaker 1: for future topics that I should cover here on tech Stuff, 742 00:46:27,600 --> 00:46:30,360 Speaker 1: reach out to me on Twitter or Facebook. To handle 743 00:46:30,400 --> 00:46:32,880 Speaker 1: for both of those is text Stuff H s W, 744 00:46:33,440 --> 00:46:41,600 Speaker 1: and I'll talk to you again really soon. Text Stuff 745 00:46:41,719 --> 00:46:44,879 Speaker 1: is an I Heart Radio production. For more podcasts from 746 00:46:44,880 --> 00:46:48,640 Speaker 1: my Heart Radio, visit the i Heart Radio app, Apple Podcasts, 747 00:46:48,760 --> 00:46:50,760 Speaker 1: or wherever you listen to your favorite shows.