AISI 4140 1

[deaconp]

Can anybody tell me is it acheivable to obtain heat treated AISI 4140. lookin to acheive 130,000 yield with a hardness of 34 Rockwell C. The bar stock forged to shape with a 5.750" ID and a 8" OD.

This is not Nace required so would an Rockwell C of 36 be acceptable?

Cheers for any help available

 

[metengr]

For a forged hollow of this size, you can order it from a steel distribution center and probably have it heat treated as a separate operation - quenched and tempered. According to the hardenability curve in my reference material, the AISI Type 4140 should be able to achieve a hardness of 45 HRc at 1" depth.

For heat treatment, the austenitizing temperature should be 1600 deg F and held for 1 hour per inch of wall thickness. Liquid (no water) quench and temper at 900 deg F for 1 hour to assure a minimum yield of 131 Ksi. The hardness will be in the range of 33-36 HRc.