HT question

[SteelSlaver]

I have been wondering how much over heat it takes to have a real effect on a steel. Lets say I have 2 pieces made from 5160 and I heat one to 1525 and hold for 15 and quench, the other I take to 1550 before an identical quench. How much effect will the 25f have on the grain. Small or profound. How much overheating does it take to have a real noticeable effect. 10f, 25f. 50f, 100f. On the same hand how about under 10, 25. I would think a bit under would be more detremental than a bit over. I make every effort to hit the manufactures recommended temp. But I have noticed minor changes when I replace thermocouple or pid and am curious. Yes I could take and start a test, but, I was wondering if someone had some real data. Plus how would I really have a accurate test if my oven was off say 10f. How much would you expect this to change from one steel to the next? Thanks for any input. Recommended method for assuring your ovens 1500 is 1500 besides the melting cones as per ceramics. This is a nagging voice in my head. Thanks Jim

 

[Larrin]

5160 has enough alloy in it where the grain size difference will be small if you vary by as much as 50F. If you're getting 100F over then you should start to worry, but as long as you are pretty close to the recommended austenitizing temperature, you have more important things to worry about than the final grain size, it won't vary as much as retained austenite, final hardness, amount of carbide dissolved, etc.