Asking for the right heat treatment
Asking for the right heat treatment
(OP)
I am fabricating a rear sway bar for a race car. I was planning on using 4130 steel tubing, but have the option of using 4140 or 4340 if that would be more appropriate.
Based on my stress calculations for a tube under torsion, I need to have a yield point of 167,500 psi. 4130 in the normalized condition has a yield point of 75,000 psi.
What steel would work the best for this application, which is a tube in pure torsion under cyclic loading, and needs to remain ductile to avoid fatigue issues.
What do I specify to the heat treatment company to obtain the required yield point.
Based on my stress calculations for a tube under torsion, I need to have a yield point of 167,500 psi. 4130 in the normalized condition has a yield point of 75,000 psi.
What steel would work the best for this application, which is a tube in pure torsion under cyclic loading, and needs to remain ductile to avoid fatigue issues.
What do I specify to the heat treatment company to obtain the required yield point.





RE: Asking for the right heat treatment
The heat treatment for 4340 is:
Oil quench from 1475°F
Temper two times at 1000°F
This should give you a Y.S. of 166,000-169,000 psi with no problem. As you have a tube you could get a Y.S. of 163,000 psi if you temper at 1100°F with a lot better properties.
RE: Asking for the right heat treatment
Where 4340 has its advantage over 4140 is in thick sections, something over ~1 1/2-2" thick (solid).
RE: Asking for the right heat treatment
Does this affect what you guys have discussed?
Thanks for all the help.
RE: Asking for the right heat treatment
RE: Asking for the right heat treatment
Just buy it in the SA (solution annealed) condition. After you do the low temp. HT be sure to shot-peen the OD surface. MIC (Metal Improvement Co.) is one company with shops all over that can do this work-there are probably others.
RE: Asking for the right heat treatment
What kind of properties are they achieving with these numbers, and what do you expect they used for the heat treatment process.
They are assuming a 5 degree max twist on pavement, where I am on dirt and expect to be in the range of 7 to 10 degrees of twist at one end.
I could drop down from a 1.25" dia. bar to maybe a solid or 0.25" wall 1" dia. bar, which would lower my max stress.
RE: Asking for the right heat treatment
Now, the big shops probably use a heat treater who is able to avoid decarb.-probably by using a special furnace with a protective atmosphere.
But for your application I'd see about the avail. of either the 17-4 or 17-7. Costs more up front, but avoids HT problems later.
RE: Asking for the right heat treatment
Don't use a solid bar if weight is a problem-most of the strength is near the OD. If weight isn't a concern, then solid is easier to find and work with.
RE: Asking for the right heat treatment
I can buy 4130 tubing all day in any length and size.
The local heat treat company has some concerns about water quenching a thin walled tube of 4130, and wants to try and oil quench it.
What kind of results can I obtain from this? It looks like I am going to have to just use 4130, and hope for the best.
As a clarification to Metalguy, I am welding steel arms to the ends of the tube, not bending the bar into a shape as you mentioned that I could do with 17-4 or 17-7 PH.
Thanks again.
RE: Asking for the right heat treatment
4140 thin wall tubing used to readily available from the suppliers to the air craft industry. I guess the race car builders switching from 4140 to 4130 for better welding qualities lessened the demand.
I still like 4340 as a shaft material, torsional or otherwise. We had much better luck with than 4140 as shaft material. It welds better than 4140 but not as good as 4130. Is the thin wall tube available in 4340?
We found 17/4 PH needed to treated to at least H1150 to have any endurance as shafting material, especially if there were any stress risers. We had hundreds of 17/4 PH shafts. The old ARMCO Research Group finally admitted this after several years of probing. I haven’t had as much experience with 17-7 PH except as a spring material.
RE: Asking for the right heat treatment
Also, different heats of 4130 will give widely different response to HT-at least the quenching part. What you want is to find a supplier who can give you a tube that has the Cr, Mo and Mn all near the high side of the limits. Also ask for AQ (aircraft quality) which will help your fatigue life. Finally, how does your heat treater plan to avoid. decarb?
RE: Asking for the right heat treatment
http://www.factorysteel.com