Tempering and metalurgy

[samuraistuart]

Is it necessary to quench in water after the temper? If so, what does it do?

Hoss

It is most certainly NOT necessary to quench in water after a temper. What does it do...for me? Allows me to get right into the next temper. Usually my initial temper is much lower (350f) than my final target temper, and I try to get in in there as soon as it has cooled to room temp from quench. By quenching the tempered blade in water, it cools down fast so that I can handle it and remove any scale/decarb layer, if I want to monitor tempering colors on the following temper. It may have some metallurgical benefit, it may not. I have my doubts that it does anything beneficial or detrimental. Just a convenience thing for me.

 

[Stacy E. Apelt - Bladesmith]

Stuart is right in that the difference isn't probably detectable. Is there a difference - Yes. Can you tell - NO.

It does speed things up considerably. I just take the blade out of the oven, hold under the running tap for a few seconds, dry off, and stick right back in the oven. Maybe 30 seconds between temper cycles.

 

[Stacy E. Apelt - Bladesmith]

Verhoeven's written work can hurt your head but as a teacher he was much more down to earth. He brought in Beck's beer to class to show us how grain growth works by watching the bubbles grow together. Brilliant stuff. On the tempering side, you are simply moving carbon atoms into a happier place in the steel. The trapped carbon atoms are what cause hardness to begin with so the tempering energy just allows them the ability to move to this less stressed state. Yes, you have conditioning of the martensite too which causes the need for more than one temper but the mechanism is the same. If you temper with enough energy to form carbides you are into another mechanism all together outside of tempering and shouldn't be confused with it except for the fact the precipitated carbides may stress the structure enough to cause a hardness bump (secondary hardening). With heat treatable alloys it's all about the carbon. It's the reason all the fun things happen.

NYMet (Ed?) - can you send me an email. sapelt@cox.net