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

Mo levels in Cr-Mo steel to mimise temper embrittlement

Mo levels in Cr-Mo steel to mimise temper embrittlement

(OP)
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.

RE: Mo levels in Cr-Mo steel to mimise temper embrittlement

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.

RE: Mo levels in Cr-Mo steel to mimise temper embrittlement

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

 

RE: Mo levels in Cr-Mo steel to mimise temper embrittlement

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

RE: Mo levels in Cr-Mo steel to mimise temper embrittlement

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

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