welding of different grades of pipeline steel

[nipra03]

Hi,
I want to know the impact of welding different grades of carbon steel e.g. API 5L X52 to X65 or X42 to X52.
For strength purpsoes I understand the common practice is to consider the weaker steel for the complete assembly, but my question is more from the metallurgical and weldability point.
How much difference in grade is considered acceptable before questions are raised regarding weld procedures & metallurgy of the joint.
We are having to do this due to material availability.

 

[BigInch]

I've always limited different yield strengths to no more than 10,000 psi
GrB to 42 OK
GrB to 52 no
42 to 52 OK
42 to 60 no
52 to 60 OK
52 to 65 no

Learn from the mistakes of others. You don't have time to make them all yourself.

 

[SJones]

Qualifying the welding procedure with the dissimilar grades would give a pretty definitive answer. If API Std 1104 is the welding specification, the welding engineer would start with the indicated grouping of material grades and should then review the differences in chemistry, heat treatment condition etc and the expected service conditions to make the call.

Steve Jones
Corrosion Management Consultant

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

All answers are personal opinions only and are in no way connected with any employer.