HEAT TREAT Recipe 4140 3

[JIMNOWAK]

The Material is 4140 steel, 1.50 thick about 50 lbs each.
The target is to heat treated to Rc 32/38.

We are planning on quenching with water. Can anyone help with a Recipe?

 

[TVP]

Austenitize at 845-870 C (1550-1600 F). Rule of thumb is 1 hour minimum or 15-20 minutes for every 25 mm (1 inch) of thickness. Quenching is usually into oil, not water, due to the likelihood of cracking and distortion. If you definitely plan to use water quenching then the austenitizing temperature can be reduced to 815-845 C (1500-1550 F). Temper around 540 C (1000 F).

 

[redpicker]

I'd be very careful about water quenching 4140. It can be done, but it takes a lot of experience as well as luck to avoid cracking it. With a section thickness of 1.5 inches and 50 Lbs in weight, you better hope you have a lot of experience becasue I don't think you'll have very much luck.

Seriously, though, you'll be better off finding an oil quench for these parts. If oil just cannot be used, consider polymer. As a last resort, I think I'd try a high-volume fan blowing on the load (with the parts carefully spaced to maximize cooling) before I used a water bath.

Also, some steel mills like to spheriodize anneal 4140. This can be slow to austenitize, meaning that you might want to use the high-end of the austenitizing range (1600 F) to get consistent results.

rp