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Case Hardening Experiments Mod-Up

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vtsteam:
The piece was heated to cherry red, and then plunged and stirred in the sugar. Lots of smoke and flames, etc.as before. The piece was well coated when done:

vtsteam:
The piece was then rolled in tool wrap several tight turns, the end folded over, and the remainder wrapped again to the end:

vtsteam:
The whole was heated to bright cherry red and held there for three minutes. Then plunged in cold water. The sugar coating hd further carbonized, but it did not burn off as it would in air:

vtsteam:
The test piece wouldn't scratch the piece C (unhardened control) in this state, so I reheated it to cherry red and plunged it again in cold water. It did after that scratch piece C, showing that it did case harden to some degree using sugar without air.



The X shaped marks are the scratches from the case hardened rod.

You can also see in this photo how deeply piece A cut into the Control piece in the earlier samples experiment -- it left the notch on the left side of the photo.

Testing the sugar case hardened threaded rod against hardened pieces A and S showed it wasn't as hard as either. Neither could be scratched with it.

That's an end to my sugar testing for now.

Lew_Merrick_PE:
VTSteam & All,

Have you ever tried to work a piece of LC steel that was flame cut?  During that (flame cut) process the carbon in the steel migrates from within the part to the cut edge/surface and becomes quite hard.  That can be one of the effects you are seeing.

Carburizing, on the other hand, is the migration of carbon from the pack into the part.  This process most readily occurs when the part is heated to (and held) slightly above the Curie Point (which is the temperature causes a change in the crystal structure of the iron/steel such that it is no longer significantly affected by magnetic fields).  [Samurai blacksmiths used this technique to make the high-carbon steel for laminating their blades.]  It is known as a Time-Temperature-Transformation in metallurgy texts.

Heat Treating steel (and some other metals) is two processes:  (1) Hardening, and (2) Tempering.  Case Hardening (LC) steel is also two processes:  (1) Carburizing, and (2) Hardening.  The difference is that in case hardening the two may be combined into a single operation.

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