2 hour tempers
- Thread starter Danimal
- Start date
PMARTINKNIVES
Well-Known Member
The "2 hour" thing is to allow the steel to reach the tempering temperature evenly and allow the material time to relax, doing it twice makes sure it happens. There are more scientific ways to explain this but that's the jest of it.
Peter
Peter
samuraistuart
Well-Known Member
It is more than just "proper" to do two or more tempers. The first temper, along with the stress relief function, forms super super small carbides called Hagg and Eta carbides. The second temper converts any RA over to carbides and ferrite. The third temper (only when using the upper tempering temperatures) metastable carbides are replaced with stable cementite. Two tempers are needed. Three, not so much.
J. Doyle
Dealer - Purveyor
That would depend HUGELY on several factors, not the least of which are steel type and knife type and it's intended use.
It's too broad of a question to give a good answer.
J. Doyle
Dealer - Purveyor
Kevin Cashen has some good info on his site and you can search the forums, especially mentioning a certain steel and find some info.
Very important: There are usually numbers that refer to specific industry specs for certain steels under absolutely ideal conditions. And it usually isn't knife blades they're talking about. You should never take those as gospel. Rather, you use them to get you into a ballpark. The best thing to do for a particular steel is take the average temp range and start 25 degrees lower. Do some cutting tests and see how the knife holds up then walk your tempers up in increments slowly if needed.
You should always test tempering temps based on your methods in your shop. If person 'X' tells you that 1095 should be tempered at 'xyz' degrees F. doesn't mean that your shop and your equipment will yield that same number. And it might not be the right number for your methods.
Very important: There are usually numbers that refer to specific industry specs for certain steels under absolutely ideal conditions. And it usually isn't knife blades they're talking about. You should never take those as gospel. Rather, you use them to get you into a ballpark. The best thing to do for a particular steel is take the average temp range and start 25 degrees lower. Do some cutting tests and see how the knife holds up then walk your tempers up in increments slowly if needed.
You should always test tempering temps based on your methods in your shop. If person 'X' tells you that 1095 should be tempered at 'xyz' degrees F. doesn't mean that your shop and your equipment will yield that same number. And it might not be the right number for your methods.
scott.livesey
Dealer - Purveyor
check right here in this part of the forum. look up the steel you are using and you can find recommendations for tempering.
CliffStamp
Member
While these reactions can happen, they are more to do with the temperature used vs the number of tempering cycles. The only reason that multiple tempers can have a different effect is that there is more than just tempering, there is the quenching after the temper. For example if during the tempering there is precipitation of alloy, which happens in a number of ranges, the austenite can then have different Ms and Mf points and thus when it cools after the tempering it behaves very different than it cooled in the original quench where it had a different composition. In an extreme case, this could cause martensite to form from the austenite in the first temper in the cooling which then requires the second temper to temper that to prevent a blade having untempered martensite.