Hardness before Temper- ATS34

Mark Behnke

Well-Known Member
What would be considered the the full rockwell C hardness before tempering?

The only numbers I can find are after temper.

At 1900* for 30 min. I got 52-54RC. so I went to 1925* for 15 min. and got RC61-62 plate quenched both times.

I have a small 120V oven that struggles at these temps. so looking for minimum temp. and time but max hardness before temper is priority.

The optimal as tempered numbers are a mater of opinion, but I don't think the max hardness before temper is, correct me if that's wrong.

Thanks for help on this.

Mark
 
62 would be about as expected at 1925 without cryo, but I'd increase soak to 30 min at least for better consistency.

I would expect more from your 1900 profile -as a matter of fact, would expect as quenched to be more or less equal to your 1925 profile or even 1950.

Have to ask if its possible that a burr influenced your 1900 Rockwell readings?

Rob!
 
Hi Rob

Thanks for your response,

I did several tests on 3 different coupons, 2 different runs, and checked my tester with a 63 and 48 RC test blocks and they both came in within 1/2 point.

Not sure how cryo would come to play, I'm wondering if it's getting as hard as possible and what that RC number would be.

Another thing is oven temp controller and thermocouple could be giving false temperature.

I'll try again and give it a 30min. soak and see what i get.

Mark
 
Sounds like you've covered the hardness testing bases. Cryo does come into effect with ATS34. We routinely get 63.5 with cryo and 62 is tough without. Of course, those numbers are subject to both precision and accuracy assumptions, but the spread is what I'm trying to illustrate. ATS has an American identical twin (almost) in 154CM. The datasheet for 154CM is more helpful to me than anything I've seen published by Hitachi or Admiral for ATS34. I don't think you'll get much better than 62 without cryo.

If you can't do cryo, you may get a little extra martensite conversion by using a third temper, but the returns diminish.

Rob!
 
Thanks Rob

I'll increase my time and temp. see if the 61-62 RC will increase then work on the temper and consistent repeatable results, then maybe cryo.

Mark
 
Increased the temp. to 1950* and held for 15 min.

Rc 60-61

The coupon size is 1/2"X 1 1/4"x 3/16"

I can't temper accurately because the temper oven needs a digital control that I have on order.

Does anyone test before temper?
 
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Rob This answers a lot of questions and helps explain some of my previous numbers.


I assumed with no basis that there would be at least 3or4 point drop from as quenched HRC to tempered HRC and an as quenched of 63 would be needed. I had tempered in a oven without digital controls and the chart would explain a high heat, in that case.

The chart shows that you can achieve 1 point difference from quenched to tempered.

I feel I can now sort this out and develop a recipe that works.

Thank You very much.
Mark
 
Sometimes final characteristics just don't reflect what you'd intuitively expect. I'm heat treating a blade right now that austenizes at 2200F. It came off the quench plates at RHC63. It came out of cryo at RHC68. Its first temper at 1025F took it RHC70 (target hardness for this blade) and it still has two tempers to go. Whoda thunk :les:

Of course, this is a completely different alloy than you are using but demonstrates the extremes of how weird heat treat can get.

Rob!
 
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