sugestions on slipjoint spring

[22H2]

I just finished heat treating and tempering a spring for a slip joint currently working on. After tempering the hardness tested in the high 30 rockwell c don't know what happened but I will need to correct. My question how do I re-heat treat or can I temper again to change hardness? I flashed tempered at 400 for two hours as soon as it came out and tempered at 1150 for two hours twice. any sugestions?

thanks

[son_of_bluegras]

Any further tempering without hardening first will only soften the steel further.

Knowing what steel you are using will help to answer your questions.

I've made a couple using 1095. For that steel 1150 would be way too hot for tempering. For 1095, if memory serves correctly, I tempered at 550 F.

ron

[Don Robinson]

I'm with Ron.

You annealed it.

We can't help you without know what steel it is.

[22H2]

sorry, it is ats 34

[22H2]

Don/Ron is it annealed enough to re heat treat? (ats 34)

[zerogee]

For ATS34 springs, one recommended process is to harden at 1900F and then do the spring temper (for 43-45RC, it's 1200F for 2 hrs (I'd only do it once, not twice) -- bring the temp down a bit if you want a bit harder springs). Don't mess about with the flash tempers in between -- though I wouldn't expect them to hurt anything other than making unnecessary work. I'm really wondering if your temperature control is hosing up -- by getting that soft it makes me think the temp got significantly above 1150F during your tempering - that or they never really hardened properly in the first place. I'd reharden, then check first to see if they actually hardened.

[22H2]

thanks zerogee, to re harden do I just go through the hardening cycle again or do I need to anneal first?

[Don Robinson]

Originally Posted by 22H2

Don/Ron is it annealed enough to re heat treat? (ats 34)

Yes, just start over.

From what i've gathered here, i think your problem was caused by the initial hardening. If you quenched from 1900, you were right at the edge of the proper temperature range, which is 1900 to 2000.

I just went out to the shop and checked my records. For ATS34 springs, this is the formula I've used with success:

1920 to 1950 for 30 minutes, prefer 1950.

Flash temper at 350 2 hrs.

cryo in dry ice overnight

Springs only now, temper at 1150 two hours

temper at 1150 again for 2 hrs.

result 49Rc

Without cryo, this should yield around 47-48Rc.

[22H2]

thanks Don, I will start over today

[zerogee]

Note that if you are *not* doing cryo, then the flash tempers are not needed.

[Don Robinson]

Originally Posted by zerogee

Note that if you are *not* doing cryo, then the flash tempers are not needed.

Sorry to disagree, but this isn't true.

If you don't have a second heat treat furnace in which to temper immediately after the quench, then you must flash temper in order to keep the built-up stresses from cracking the steel while you wait for your furnace to cool down to tempering temperature.

[zerogee]

Originally Posted by Don Robinson

Sorry to disagree, but this isn't true.

If you don't have a second heat treat furnace in which to temper immediately after the quench, then you must flash temper in order to keep the built-up stresses from cracking the steel while you wait for your furnace to cool down to tempering temperature.

Ah, well, in that case, sure.

[22H2]

ok re heat treated the spring 1925 for two hours, flash tempered for 1 hour at 350 and tempered at 1150 for two hour I got 42-43 on hardness. I would like to have at least 45-48 any sugestion. the spring seems to work well. just would feel better if it was harder.
thanks

[Kirby Bletcher]

When making springs I always find it easier to reach my target hardness by starting out with a lower temperature. Never heat treat anything at an suggested temperature until you have figured out a formula that works with you equipment. So if someone suggest a draw temp of 1125-1150 start at 1025 and check hardness. From there you can increasing in 25 or 50 degree intervals. It takes a little time but you only have to do it this way one time if you record every little detail on the way.

Kirby

[22H2]

thanks Kirby, If I understand correctly you think my temper may be to high? Would it hurt anything to temper the same part multiple times until I get the hardness correct moving up in temp with each temper? Once I find the right temp can I just start there the next time or will the multiple tempers change the formula some? sorry for all the questions just trying to get the best spring that I can.

Ted