Temper Embrittlement Screening tests 2

[codeeng]

Could anyone point me the right direction to read up on this subject. Specifically on pressure vessels fabricated in 2 1/4 Cr 1.0 Mo material.

 

[metengr]

The simplest method for estimating the susceptibility of Cr-Mo steels to temper embrittlement is by calculation using the so-called, X or J-Factor equations. These equations provide a numerical value that equates to the susceptibility of temper embrittlement based on certain elements present in the steel. The X-factor equation is used for weld deposits, the J-factor for wrought material. For more information on these equations, see the web site below

http://www.exocor.ca/products/low_alloy_steels/embrittlement.php

There is plenty of information on the subject of temper embrittlement. The one reference I have found that provides a comprehensive evaluation on the subject is the book
“Physical Metallurgy Handbook" by Anil Sinha. He provides excellent technical information on the causes, influence of variables, and characteristics of temper embrittlement in low alloy steels.

 

[Carburize]

To actually physically check if a particular heat of steel is susceptible, charpy impact tests can be very useful - see Metals Handbook Volume 4 "Tempering"

 

[TVP]

Excellent information from both metengr & Carburize. FYI, Metals Handbook Volume 4 Heat Treating is now called ASM Handbook Volume 4 Heat Treating. ASM Handbook Volume 1 Properties and Selection: Irons, Steels, and High-Performance Alloys also has some good information on temper embrittlement. You can obtain both ASM Handbooks and Sinha's book from ASM International by using the following link:

http://www.asminternational.org/Template.cfm?Section=Bookstore&NavMenuID=18

 

[codeeng]

Thank you all
For my specific application I have a 2 1/4 Cr 1.0 Mo vessel operating at 520F and we have specified J and X factors <100 and <15 respectively. Would you consider additional step-cooling tests to be an overkill ?

 

[metengr]

Yes, especially at your operating temp of 520 deg F.

 

[PAN]

codeeng,
Please advise me about the specific reason to use Cr-Mo Steel in this temperature. Normally, I always use carbon steel for this operating temperature.

 

[codeeng]

Material selection per API-941 based on thickness and Hydrogen partial pressure.

 

[PAN]

Refer to API RP 581 Appendix G and API RP 571, temper embrittlement of 2.25Cr-1Mo steel should not occur at 520 F. Do we need step-cooling tests for this case? Please comment.