I'm currently trying to figure out whether or not we can flame-harden a steel wheel which was supplied with a lower hardness than expected. I'm worried, however, that flame-hardening can either deform the wheel or change its size somehow, especially given that a flame-hardening job has never been done in the company before.

The wheels are about 13" in diameter and about 6" in thick. They have a few metal details and inner holes, which I'm not exceedingly worried about since other wheels on the same machine will have different designs. The wheel will roll on a plate, although I do not know the hardness of the plate at the moment.

Ideally, I would like to flame harden the wheels from 160 Br to 400 Br, to bring it up to the design specifications, although I would be content taking it up to 300 Br, which is the hardness of some previous wheels we have tested from the same machine.

What considerations should I take before attempting to set up the flame-hardening? I have quite a few wheels to spare in case the job goes wrong, but I would also like to know if there is some quantitative analysis that should be done before starting.

  • $\begingroup$ Getting an even heat ... $\endgroup$
    – Solar Mike
    Oct 17 '17 at 22:21
  • $\begingroup$ To what surface depth does the metal need to be hardened? Also, why do this in-house? $\endgroup$
    – user6335
    Oct 18 '17 at 9:52
  • $\begingroup$ A thickness of about 2-3 mm should be enough, if possible. There are no local places we know of that will do this job for us, and we're too time-constrained to send them internationally. $\endgroup$ Oct 18 '17 at 16:45
  • $\begingroup$ Could you consider a slightly smaller wheel with a "hardened band" that is shrink-fitted to provide the hardened surface? Think of the wooden wagon wheels with a metal surface... $\endgroup$
    – Solar Mike
    Oct 20 '17 at 6:29

With 13" diameter and 6" thickness they are VERY "stocky" to flame harden. It would require very high heat flux to heat the surface before the whole wheel is hot. Like 20 oxy-acetylene tips on a 6" wide burner. The goal is to heat the surface to 1600F while the bulk is no hotter than 500F so that you get a conduction quench. Induction heating would work - not for amateurs. Alternative would be carburizing to some depth and quenching; presumably the low carbon core would not harden. I have assumed this is a low carbon steel like AISI 1020.

  • $\begingroup$ Unfortunately, the suppliers have yet to give us the carbon content used, although we should be able to get that soon. We might have to go with this solution, although we are worried about the fluid used. Will certain oils catch fire, or is there a particular volume of oil we should use for quenching? Thanks for the help.. $\endgroup$ Oct 18 '17 at 16:51
  • $\begingroup$ To properly carburize and quench harden you would need to know : C, Mn, Si ,Cr ,Mo, Ni, at least.. You can quench in water if Carbon is less than about 0.26. A local heat-treat shop or consultant may say higher C is okay. Burning oil is not a problem with the "right" oil .I can only guess than about 500 gallons of oil would be needed for a 200 pound wheel. As the hot part is pulled out, residual oil will likely burn ; the facility should be able to tolerate that. A practical answer is to use what you have as-is, and add new requirements if needed, to the next wheel purchase. $\endgroup$ Oct 18 '17 at 19:18

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