to temper or not?

[Rick1-2]

hey guys, after heat treating do you absolutely have to temper a knife or can you leave it just heat treated, the question is do all of you temper your knives and if you do whats the best temp and time.

thanks

 

[JeffreyFogleboch]

Yes you have to temper your knives. Untempered martensite (which is what you have after quenching) is very hard but will also be very brittle. You can easily break the knife if you drop it. Tempering temperature depends on steel type, application, and desired hardness. Tempering reduces hardness and increases toughness.


Sent from my iPhone using Tapatalk

 

[Stacy E. Apelt - Bladesmith]

The structure formed upon cooling after the quench is called brittle martensite. It is very hard and full of stresses. It can crack just suiting on the bench. Any stress or shock can make it break in half. Most makers have accidentally dropped a freshly quenched blade on the floor and watched it shatter like glass. When tempered, the structure changes slightly to tempered martensite. This structure becomes a little less hard, and is tougher and stronger. The second temper makes some other changes that make the blade even tougher. The temperature of the temper oven determines how much change is made. As a rule, most blade steel needs a temper at 400F to 450F to be usable as a knife blade.

Many new smiths and some back yard knifemakers say they don't temper the blade and it holds up fine. This is undoubtable caused by a very poor HT that only partially hardened the blade. This is not the best way to do it. Strive for full conversion to martensite and the temper to make it a bit less hard and tougher.

 

[Rick1-2]

wow great explanitions thanks

 

[Rick1-2]

jeffrey that knife is beautiful