WEBVTT - How Case Hardening Works

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<v Speaker 1>today at m o z y dot com. Welcome to

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<v Speaker 1>brain Stuff from how Stuff works dot com where smart Happens.

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<v Speaker 1>Hi Marshall Brain with today's question, what does case harden mean?

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<v Speaker 1>When it's stamped on a piece of metal? Steel is

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<v Speaker 1>an amazing substance. By mixing in different elements and heating

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<v Speaker 1>and cooling it in different ways, you can create surprisingly

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<v Speaker 1>different properties. Some steels are easily bent, while others are

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<v Speaker 1>so brittle that they shatter some rust, and others don't.

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<v Speaker 1>The huge variety of steels means that they work in

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<v Speaker 1>many different situations. Everything from a surgical scalpel to a

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<v Speaker 1>skyscraper's massive metal frame can be made of steel. The

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<v Speaker 1>idea behind case hardening is to have two different types

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<v Speaker 1>of steel in this same piece. During manufacturing, what you

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<v Speaker 1>would like is a relatively soft steel that's easy to

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<v Speaker 1>bend into machine for a lock shank. However, a soft

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<v Speaker 1>steel is not good because it's easy to cut with

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<v Speaker 1>a metal saw, so after the piece is formed, you

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<v Speaker 1>harden it to make it very difficult to cut. Case

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<v Speaker 1>hardened steel is usually formed by diffusing carbon or nitrogen

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<v Speaker 1>into the outer layer of the steel at very high temperature.

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<v Speaker 1>The carbon combines with the steel to make it nearly

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<v Speaker 1>glass like and its hardness. The core of the metal

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<v Speaker 1>stays soft. This gives you a piece of metal that

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<v Speaker 1>cannot be cut with a saw, but also will not shatter.

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