O1 and Soak Times

[samuraistuart]

I remember that study also. The one with extended O-1 soak times that amounted to hours upon hours. But I also remember a much higher temp (but at the same time 1515 rings a bell....if that makes any sense). Different alloy carbides dissolve at different rates. Iron and carbon dissolved relatively low. 1350-1414+. Then proeutectoid cementite. Then the chromium bond carbides. Then the tungsten bond carbides. And then the vanadium bond carbides. All at increasing heats. And as long as you stay below the temps at which these carbides dissolve, then grain growth should not occur, even with really extended soak times.

That’s why O-1 can be soaked at 1700f+ for extended periods without grain growth. That temp is not hot enough to dissolve the tungsten and vanadium carbide. Because tungsten begins dissolving at a much higher temp than 1700f, and vanadium even higher.