Hand Tools Archive

Re: Voids in steel
Response To:
Re: Voids in steel ()

Patrick Chase
You need to re-read my post, carefully.

PM avoids *primary* carbide formation during casting. It doesn't prevent *secondary* carbide formation during austenitization (the hot dwell during hardening).

Fallkniven's SGPS steel contains 2% V, and would be expected to form Vanadium K2 [*] carbides during hardening, much like CPM-3V. It is simply impossible that any SiO2 sharpening medium could "fully sharpen" those secondary carbides, as the carbides are MUCH harder than the abrasive.

Secondary carbides tend to be small, but steels with significant amounts of V seem to develop larger ones than others, and certainly large enough to explain the "micro voids" you describe depending on how big "micro" is. It has been amply demonstrated that CPM-3V takes a lousy edge on SiO2 for basically that reason, and I don't see any reason why the Fallkniven steel would be much different.

Put simply, that steel is a "challenging" choice for your sharpening method. PM helps make higher-alloy steels "accessible" to people using common sharpening approaches but it's no panacea, particularly where Vanadium is involved.

Of course it's entirely possible that the voids in question aren't so "micro" and that Fallkniven simply overheated the weld and formed new primary carbides. It's impossible to know for sure without more information.

[*] K1 and K2 are different chemical compositions of secondary carbides, with K2 being harder. SGPS is well into the "K2 + austenite" portion of the Cr-C phase diagram at typical hardening temperatures.

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