Ramp to Pre-Heat Slowly -

R

rlinger

Joined
Mar 29, 2002
Messages
4,591
Well I think I just learned another basic about heat treating. It may be a fluke but I did not get any warp this time after soaking a S30V blade at 1960 F for 25 minutes and quenching. I usually have to straighten a tang and sometimes a blade section. This time I ramped to pre-heat at a rate that took about 2 1/2 hours to reach pre-heat temperature. This allows the steel to expand more uniformly. At pre-heat I believe the steel expands and at austenitizing it tends to contract (one reason for pre-heating; to prevent the two from occuring simultaniously).

For this blade I ramped at a rate of 650 F per hour to a pre-heat of 1550 F. After holding at pre-heat for 7 minutes I ramped at maximum oven speed to austenitizing temperature. This is a rather thin blade of 7 5/8 in. OAL and expected some warp but got none :). In the future I will ramp to pre-heat even more slowly.

RL
 
As always - thanks for the info. I'm all over that one. Sounds good.

Steve
 
Steve, also look for stress relieving annealed specs on your data sheets. You can do this after grinding and before heat treating. You can hold at relief temp and then oven or still air cool.

In addition we can stress relieve after finish grinding (grinding performed after HT) with a temper of about 25 to 50 degrees F lower than final temper.

RL
 
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