Heat treatment of 3" dia. 4130 1

[mwpe1985]

What is the recommended temperatures and times for Heat treatment of 3" dia. 4130- 6 in length?

 

[Lyrl]

What type of treatment (stress relieve, through harden, case harden, etc.) are you looking at?

Also, what hardness or mechanical requirements must be met on the final product?

 

[mwpe1985]

We are through hardening. We have tried a few different trials. 1600 for 2 hours. Oil quench and checking before drawing. We are getting 15 to 20 Rockwell.

 

[redpicker]

What are your objectives? What hardness are you aiming for? Do you have tensile requirements? Impact requirements?

I am not surprised at getting 15/20 HRC as-quenched since you are probably dealing with an as-rolled piece of stock. Have you considered rough-machining?

 

[gruntguru]

6" length has two machined faces at least.

je suis charlie

 

[mwpe1985]

The part has close tolerances so we are heat treated material first. We need 38-40 Rc. We never had this much trouble with 4130. Oven is Delta dual chamber and is in AS 9100 Calibration. We think our problem is in quenching. We use Houghton-Quench K. Anyone had any problems with Houghton?

 

[AidanMc]

AMS 2759/1 recommends austenitizing 4130 at 1575F and quenching in oil, water, or polymer so you're not too far off. We've successfully used Houtghton-Quench K on other parts so I would be somewhat surprised if that is the problem. What face are you checking the hardness on? Have you sectioned a part and examined the microstructure? My first guess is that you have significant decarburization and that is affecting the results. This could be diagnosed with a cross section of the bar.

Aidan McAllister
Metallurgical Engineer

 

[mwpe1985]

Aidan,

We had good with quenching in water. Current Rc. is 55Rc. To get 35 Rc. what draw temp. do you suggest. Our 2759 says 1200 for 4hours. Old school charts tell us 880 for 2 hours.

 

[metengr]

For 4130 steel fully hardened from quenching the tempering temperature that would provide the closest to 35 HRC (your earlier post you stated 38 to 40 HRC?)would be 870 +/- 25 deg F for 2 hours minimum, based on ASM Handbook - Heat Treating. Because of the diameter of the bar, I would hold for 3 hours at this temperature. If you need 38-40 HRC, you would lower the tempering temperature to around 800 deg F.

 

[AidanMc]

Based on an as-quenched hardness of 55 HRC, it looks like 2759/1 says that you should be tempering about 1000°F to get that hardness level. Soak should be 2.25-4.5 hours.

Do you have any kind of oil analysis for the Houghton-Quench K? I curious what could've gone wrong with it to cause such a large difference in results.

Aidan McAllister
Metallurgical Engineer

 

[redpicker]

Yes, water quenching is preferable, particularly if you have a simple shape, such as a solid cylinder.

We need 38-40 Rc.

To get 35 Rc. what draw temp. do you suggest.

I'm confused.

I wouldn't use 1200F, but the 4 hour cycle is fine, I think I'd try 1100F for tempering, maybe even 1080F. It it better to be on the hard side so you can correct it with a second tempering operation than to be too soft and have to start over from the start. After tempering, measure the hardness again and go up about 10 degrees for every rockwell point you need to drop. That is, if you are 45 HRC after tempering at 1080F, but you were aiming for 40 HRC, retemper at 50 degrees higher, or 1130F for another 4 hours.

You might want to consider standing these on end for quenching, particularly if you are getting some distortion. A length to diameter ratio of 2 isn't that bad, but if you had longer parts or smaller diameter, you could end up with banana-shaped parts.

 

[mwpe1985]

WE are going to draw at 900 for 4 hours, and check. Thanks to all that have responded. I'll post the result.

 

[mwpe1985]

We got 35.5 Rc. @ 900 FOR 3 HOURS
Thanks again to all

 

[priyam07]

Make sure to stay around the 900F tempering temperature and fast cool after it, slow cooling might induce low toughness by temper embrittlement!

 

[EdStainless]

I agree with Sravii, I am not a fan of 900F if toughness matters at all.
Look up some temper curves that have impact toughness data on them.

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P.E. Metallurgy, Plymouth Tube