differential quench vs differential temper

"Del Cecchi" wrote

Same with old-timey swordsmiths; san-mai japanese blades, old time ax heads, some celtic swords- take a piece of 'tool-steel' and encase it in a softer steel soas to form the body of the implement with the edge presented.

Chas

That one's pretty simple, as nobody's specifying bainite in the back. Same applies to all the other examples of welded-bit tooling others have put forward - high-carbon welded to low carbon - not the bainite you were asking for in the back.

Bandsaw blades, IIRC, are generally laser or electron-beam welding of a high-carbon edge to a low carbon back in a very automated process - similar approach to the heat treat (that's often induction, as far as I recall, but might also be done with a laser depending on the setup & tooling of a particular production line).

If you could put up with the HAZ and had a precise, high-power laser or electron-beam setup you could weld bainite to martensite, but I don't think you'd like the properties of the HAZ even if it was small, which is why I suggested a press-fit earlier.

Interesting. I recently purchased a band saw blade from a custom blade shop that was supposed to be "bi-metal". When I asked them for specifics I was told it wasn't really bi-metal but differentially hardened.

GA

Looking back through my copy of "Metallurgy theory and practice" I think the edge would only have to be kept below Ms (temp at which martinsite begins to form). So a setup which keeps the edge below around 450 F while the spine is at 500 F or better (exact temps and time held there would depend on alloy). Still difficult to do but perhaps a copper tube with water flowing through it in contact with the edge while the whole blade is in an oven at

Sorry if some of you thought this thread was dead, but it takes a while for my brain to mull over new info.

ron

Sounds really good to me! :)

Cool one Ron. :)

Contact between the cooler/coolant and the freshly quenched part is the only real tricky part of that?

Something metal that'll mold itself to the part like copper or silver that can be re-shaped when needed or something that's liquid-and-magnetic like that stuff they put inside loudspeaker gaps ...but can handle the temperatures.

No such thing as a dead thread, they just idle, only takes one more post to it and it's running all over creation again. :)

Same with everyone.

If thinking didn't take time, a chess game would only take seconds.

Alvin in AZ

Laminate a core with sides which air cool to bainite and do a shallow edge quench. Or do a full bainite and reheat the edge, just *really* shallow (as in 1/8" high) through induction or similar and requench.

An elementary question, Gentlemen, if you please:

Why not simply treat the whole blade to bainite and then, after quenching, coat all but about .25" with something like "Handy-Jig"

Or the other way 'round: treat the whole blade for martensite then coat the edge and retreat for bainite.

If I'm missing something, I'd appreciate being enlightened.