Mo levels in Cr-Mo steel to mimise temper embrittlement 2

[Gem1]

I'm looking for information about the affects of molybdenum content on low alloy Cr-Mo steels, in relation to temper embrittlement. I've been trying to determine at what Mo content you could say that the likelihood of temper embrittlement was relatively low. Some digging suggests that 0.5% might be effective, but I haven't seen much work to back this up. Can anyone provide any insight or references?

Thanks.

 

[metengr]

I believe 0.75% mass content of Mo will significantly reduce temper embrittlement in Cr-Mo steels. More information on this subject could be found in the "Physical Metallurgy Handbook" by Sinha.

 

[TVP]

Minimizing the P content is the real key. Conventional Cr-Mo steels with ~ 0.25% Mo can have low or minimal susceptibility to temper embrittlement if the P content is reduced to 0.010% or less. I think that there have been some articles in ISIJ International (a Japanese journal published in English) that were on this subject. A Google Scholar search should fine them and others. Here is a link to the ISIJ website, where you can freely download any article except for the most recent 12 months, which requires a subscription:

http://www.jstage.jst.go.jp/browse/isijinternational/_vols

 

[Gem1]

Thank-you for the input. That's a particularly handy link TVP, thanks for the tip.

 

[metengr]

You also might want to review the API technical document below regarding fabrication of standard Cr-Mo steels for the petrochemical industry. For standard Cr-Mo alloys endorsed by ASME/API where you can't necessarily adjust Mo content from standard specification, it does support reduction of elements like P and S, but also residual elements and recommended melting practice and heat treatment to reduce susceptibility to TE or creep embrittlement in service.

http://committees.api.org/standards/cre/sccm/ballots/docs/Ballot934DFinalDraftJuly20.pdf