Stress relieving

I would think so. You should be able to tell with X-Ray photography or some other means of seeing deformities in the crystal structure.

What are these springs used for? Mattresses? Racing springs for F1 cars?

Not sure that 300 degrees is significant "stress relief" I have seen 400 450 degree temper used for very low carbon alloys,after mock carburizing.

I would think that at 300 degrees you are actually just strain aging, and possibly protecting the materials yield point.

Around 600 degrees, you can encounter blue brittleness.

Personally, I never stress relieved below 800 degrees for my commercial bar lines.typically .40 C carbon and alloys.

milo "all degrees F of course"

I've tempered molybdenum steel at 350° in a conventional oven.

I'm sure that you did, but how did you measure that the material's properties actually/significantly changed? Lower BHN, test yield with extensometer, or slap test?

milo

First, guide book told me to use that temperature. Second, compared with moly steel that wasn't treated in the oven, was significantly harder and more brittle.

However, I could have done a lot more testing... Oh, it's a fair cop!!!

Clearly worked for you on your scale.

Temperature is well below those in common commercial use.

Pragmatics always seem to overrule professional standards/codes.

"but it worked" always carries the day.

milo

Just FYI, It was one of the alloys I was using to make knife blades with. I had basically three tests I would put edged pieces through.

1. Did it bend if flexed.
2. How well did it hold an edge.
3. How deeply would it bite into a block of brass.

You'll need to stress relieve them afterward anyway. Coiling the rod put stress in the material which pre-stress relieve cannot take it out.

Coiling them when they're hot may remove stress relieve afterward.

Pineapple

I really don't understand what's going on here. I thought springs only became springs after they have been formed and then hardened and then tempered. How do you form something out of hardened and tempered steel? Surely stress relieving after forming can at best undo the very temper the thing depends on, otherwise have no effect at all?

Shhhh!

Next thing you'll be asking if the stress relief temperature has to be above the tempering temperature to have an effect, and then where will we be?

People love to put fire on steel, and your line of thinking will surely put a damper on that.

We had a continuous wire drawing line where we welded coils of steel together to run continuously, but the welds had to be "quenched " with a wet rag; then "stress relieved"with a low resistance current. this was low carbon low residual steel. took aminimum of 8 minutes a coil weld;

I started a second shift with new untrained operators, we ran the welds as soon as we chipped off the weld flash. Good old superstitious union thinking and ignorance of metallurgy-RIP.

People love to add fire to steel, and you cant convince them otherwise, especially in my case where that got them some "bench time."

milo

(in a whisper)... Sorry!

(PS 'Guest' was me.....Sorry!)