tempering slng questions

[Ethan B. A. Jackson]

hi

ummm i dont want to sound like a complete idiot but what does this mean "and triple draw at 400F". Geoff was talking about tempering and im clueless to how long tripple draw is.

[MrBaz]

hi

ummm i dont want to sound like a complete idiot but what does this mean "and triple draw at 400F". Geoff was talking about tempering and im clueless to how long tripple draw is.

 

 

After quenching some steels, they build up a LOT of stress. You want to relieve that stress from the blade so it doesn't crack.

To do this, we 'temper' the blade in an oven at 400*F for one hour increments three times.

 

The process is as follows:

Heat treat the steel

Nearly immediately afterward, temper it in a 400*F oven for one hour

After one hour take the blade out and cool down till it's cool enough to hold without burning yourself.

Put back in oven at 400*F for another hour.

Repeat until it has been in the oven 3 times, one hour each.

Edited June 22, 2008 by MrBaz

[Geoff Keyes]

I usually do tempering in 4-6 hour increments, but in essence that is correct.

 

Geoff

[Ethan B. A. Jackson]

thank you

 

happy dance, happy dance

[MrBaz]

I usually do tempering in 4-6 hour increments, but in essence that is correct.

 

Geoff

 

 

Mind if I ask what steel? I've heard varying times for different steels. The above is what seems pretty common with 1095.

[Guest Kyle Hershey]

And the temperature will vary depending on what the knife may be used for. If I make a small bird and trout knife, sometimes i just boil it in water for the heat treat, It only reaches 212'f, and the blades usually come out well over 60 R.C. It will eat the diamonds of a diamond hone, but when it gets sharp, it's like a surgical instrument. Just dont drop it!

[Doug Lester]

One explanation of the reason behind the tripple temper is that allowing the steel to come down to near room temperature and repeating the tempering allows the retained austenite to convert to ferite and carbides. If the retained austenite, which normally doesn't exist until over about 1400 degrees, is allowed to remain in the steel it will eventually convert to martensite (the steel crystal form that helps make it hard) and actually make the blade harder and more brittle than you want it. The higher the carbon content in the steel is the more likely that there will be retained austenite after quenching. Three cycles is usually enough to get rid of it.

 

Doug Lester

[kb0fhp]

A good rule of thumb is one hour per inch of thickness, 2 hour minimum. The second temper I would do at the same temperature or slightly lower - say 25F. The third temper is the same sort of thing.

[Ethan B. A. Jackson]

so (sorry geoff for asking twice ) what would be the recomended tempering for a 5160 steel knife that is 3/8 an inch thick and needs to hold a fairly sharp edge.

[Robert Mayo]

If properly heat threated and you temper at 400 degrees you should have around rc60.