More questions

[reefera4m]

Does anyone know the composition of the scale that forms during the various heating cycles (5160 steel if that makes a difference)?

The reason I ask is to understand if the amount of scale is any indication of carbon migration/loss. If not is there any way to determine the relative amount of carbon loss in each of the heating cycles?

If carbon is a component of scale then wouldn't repeating heating cycles, normalization, and hardening (heating/quenching) contribute to excessive carbon loss?

I don't question the benefit of multiple heating cycles but want to understand if this is a trade-off I should consider.

I'm particulary interested as I'm fairly new at forging and it takes me more than just a few forging cycles to shape my 5160 steel to the point where I'm satisfied with the shape (to save on grinding/sanding). I know that forging cycles contribute to carbon loss so I'm trying to weigh the trade-offs, less forging/more grinding to preserve caron or limiting the number of normalizing and hardening cycles I use. Again, I'm looking at this from the perspective of one who is not yet efficient at forging and yet willing to spend extra time forging to get the result I want to acheive.

Thanks

[Ray Rogers]

I'm not really an expert on the subject of carbon migration but I can make a few (possibly) intelligent comments on the subject.

First off, from what I've read, carbon migration happens very slowly - we're talking at a glacial pace. Yes, you lose carbon but that's mostly from a few thou off the surface. By the time you have ground your blade clean you should have removed the decarbed steel.

Second, the fewer heats required to shape your blade the better BUT over heating the steel is probably more damaging than extra heats. In the end, the extra heats make for bad grain growth but normalizing and such should bring it back in line.

The bottom line will be the testing you do on your new blade. In the end, the performance of the blade will tell you if you did enough things right or not. I know from experience that there is likely to be widely varying opinions on the subject of carbon migration and it's effects on the finished blade but, again, in the end it will be the results that YOU get that will tell you whether or not carbon migration, extra heats, or over heating actually was a problem for you ....

[Doug Lester]

Carbon being oxidised off the surface of the steel is not a big problem because that part of the blade is ground away while finishing. Carbon migration increases with temperature so it's a bigger problem at bright yellow (welding temperature) than at cherry red. This is another reason not to overheat your steel beside grain growth. Yes you can burn the carbon out of a piece of steel. Burning the carbon out of cast iron is part of the process of making steel. Burning the carbon out of a piece of steel is effected more by the temperature than the length of time. Smithing and heat treating is a matter of finding the right ballance.

Doug Lester

[reefera4m]

Thanks for the timely and excellant feedback. You're why I continue to to rely on this forum! Always great information!