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Cr-Mo steel temper embrittlement

Cr-Mo steel temper embrittlement

Cr-Mo steel temper embrittlement

(OP)
For High pressure system in my current project we use 2.25Cr-Mo steel piping and heat exchangers.
The client has a strict specification for 2.25Cr-Mo equipment. this coveres chemical restrictions, J-factors and temperembrittlement testing.

For the steam piping however no reference to this spec. is made.
My question is: How do I specify the seamless piping?

I would think it is also prone to the same principles of temper embrittlement.

RE: Cr-Mo steel temper embrittlement

The specification for seamless piping would be in accordance with an international recognized standard specification, like ASTM or ASME or European standards like DIN or EN.

The actual chemical composition ranges for the pipe material are listed in these specifications. The concern for temper or more likely thermal embrittlement are the presence of tramp elements in the steel, such as Pb, Sb, Sn, As, etc. If these tramp elements are kept out of the steel, the risk of embrittlement is very low.

Keep in mind one important point regarding Cr-Mo piping in elevated temperature service - it may suffer from some degree of thermal embrittlement, over time. However, if the operating temperature of the piping system is in the upper shelf region of the notch toughness curve, there is no concern for brittle fracture in service.

Typically, the upper shelf region for these materials is at or above 400 deg F. One other cautionary statement regarding embrittlement of aged materials is that once the piping is installed, in-service pressure tests using water must be avoided. This would assure no exposure to brittle fracture for materials that either suffer from thermal embrittlement or have low toughness because of steel making practice.
 

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