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Case vs Pack Hardening for the carburization of rr spikes


DaveTheBrave

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I am pretty new to forging and I wanted to know how well each of these methods of carburization would work to turn a rail spike into suitable steel for blades. I find that there isn't much out there for me to read up on to get better answers on the topic. The answers I do get are usually are "these are both methods of carburization" or variations in favor of one or the other. I figured that if anything could help me, it would be experience. What do you guys think?

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Both methods generally only affect a thin surface layer and so if done to a spike would scale off during forging and if done to the forged but not finished knife would be ground off in finishing and if done to the finished knife would provide a high carbon steel edge until you sharpened through it.

  So I would say: NEITHER, it's not a good alloy for knives.  (You could try making blister steel from it; but the grain growth would probably weaken it greatly and the fuel cost of keeping it at temp for days would be high.)

 

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Welcome aboard Dave, glad to have you. If you put your general location in the header you'll have a better chance of hooking up with members living within visiting distance. 

Packing is only applicable to wrought iron where hammer refining drives more slag out resulting in a harder product. Low carbon steel doesn't "pack," there isn't any slag to begin with.

Case hardening only effects to a couple few thousandths of an inch depth.

RR spikes do NOT have a high enough carbon content to harden. The alloy was formulated specifically NOT TO HARDEN. Having RR spikes snapping because they've work hardened is a B A D thing. Think trains derailing on a daily basis because they won't hold gauge for the spikes snapping. 

The ONLY way to make a real knife as in takes ad holds an edge from a RR spike is to weld a high carbon steel bit to it and proceed. 

Frosty The Lucky.

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Actually pack carburizing is different from "edge packing" and is a known and used industrial process:

"Pack carburizing is a process in which carbon monoxide derived from a solid compound decomposes at the metal surface into nascent carbon and carbon dioxide. ... The three types of furnaces most commonly used for pack carburizing are the box, car-bottom, and pit types."   ASM handbook

I remember it as Ric Furrer was using pack carburizing material for making blister steel in his "3 Methods of Making Steel" demo at Quad-State one year.

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