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The welded steel pipe has won praises for its uniform wall thickness and low price. So, can seamless Steel Pipes be replaced by welded steel pipes? The answer: NO
There are some reasons
1) HAZ is very fragile
Although it is rare now that the mechanical properties of the weld seam exceed the base metal itself, the weakest part of the welded steel pipe is not the weld seam, not the base metal, but the heat-affected zone of the weld. This place is the most vulnerable.
2)The limited upper wall thickness of the welded steel pipe
Most thick-walled steel pipes can only be seamless steel pipes instead of Welded Pipes
3)The H2S resistance of welded pipes is far worse than that of seamless pipes.
The requirements for seamless pipes on NACE MR0175 are: the S content must not exceed 0.010%. However, the requirements for Steel Plates and welded pipes are particularly strict: S must not exceed 0.003%. Although strict requirements are imposed on the steel plate, it can pass the HIC test, but the welding seam has to pass the test, which is still a very difficult problem. Not only must we choose the good welding material, but also the skilled welding process.