Linepipe Chemical Properties Deviation 1

[ek4putr4]

Dear All,

We have a linepipe specification (API 5L X-65 PSL2 LSAW)that requiring max chemical composition %wt as follow:
C:0.16, Mn:1.3, Si:0.45, P:0.015, S:0.003, V:0.08, Nb:0.05, Ti:0.04, Cr:0.2, Mo:0.1, Ni:0.35, Cu:0.4, Al:0.05, N:0.012, B:0.0005, Ca:0.006, CE:0.39, PCM:0.21

Unfortunately, the only MFR available can only supply material with following deviation:
C<=0.1, Mn<=1.6, Cr<=0.25, Mo<0.25

My question is whether this deviation will result in major properties changes? If not major, is it still acceptable? If not acceptable, what is the acceptance range?

Regards,
ekaputra

 

[SJones]

The 'MFR' appears to believe that carbon is the most influential element in the material and its reduction outweighs any counteracting effects of the minor increases in the other constituents (which is probably true). Looking at the specified requirements, the pipe appears destined for H2S service and, if the correct testing requirements have been specified, any compositional deviations can be validated. The only problem will be if you have a separate pipeline welding contractor who has bid the job on the basis of the specified chemistry. If you now present pipe with a different chemistry don't be surprised to receive a claim!

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdoweb/

 

[ek4putr4]

You are correct. The pipe is intended for sour service.
My preference is to maintain the requirement of C & Mn and allow deviation in Cr & Mo. My question is whether higher Cr & Mo have major impact to the final strength?

 

[SJones]

The supplier is drastically reducing the carbon content for which you should be thankful! Having done that compensation needs to be made by additions of other elements: managanese for solid solution strengthening; Cr and Mo for transformation product control. Strength will not be an issue, nor (over)hardenability, so I would hazard a guess that the supplier is focusing on HIC and toughness factors. The carbon and managanese issues are straightforward and going to 1.6 mass % Mn should not be a stumbling block. Your treatment of Cr and Mo needs to be taken in the context of the proposed amounts of the other alloying elements.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[ek4putr4]

Does it means I should accept the less carbon content but higher Mn as a better option?