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Up Topic Welding Industry / General Welding Discussion / prequalified wps use for steel pile welding
- - By gm hdec Date 04-13-2017 10:45
We have Prequalified WPS accordance with AWS D1.1 approved by the client.
During welding of steel piles, they do not allow to weld steel piles by this prequalified WPS.
so can we do steel piles welding with prequalified WPS?
Parent - - By 803056 (*****) Date 04-13-2017 13:46 Edited 04-13-2017 16:37
Not if the material specification for piling is not listed by AWS D1.1.

What is the base metal specification for your piling? The specification for pipe pilings allows nearly anything to be used as long as the minimum tensile strength requirement is met. Often the piling is pipe that failed to meet the piping specification, so it is sold as piling. I had some that had a chemistry equivalent to an AISI 4140!

The project was funded by the state, so the contractor was required to qualify the WPS and the welders. The contractor refused to use preheat and welded the joint using E7018 without the benefit of an electrode oven. "We'll weld it like we always do!" All four guided bends failed, all the tensile test specimens failed, and all five CVN specimens broke in the single digits at 50 degrees F.

Long story short, it was the inspector's fault. "We never had to qualify a WPS before the inspector showed up!"

The contractor was an idiot, the state inspector that identified the problem knew what he was talking about. However, if the contractor had an inkling of what he was doing, I would be out of business. The less they know, the more I make!

God Bless America!!

Parent - By 803056 (*****) Date 04-15-2017 13:56 Edited 04-15-2017 14:00
I just did a quick search for the material specification ASTM A252 and my recollection appears to be correct. The specification only controls the minimum yield and tensile strength of the pipe, that is, there are no maximum values. The only control on chemistry is phosphorus and that is 0.05%, slightly higher than we like to see for ease of welding.

As I mentioned in my previous response, the chemistry is not controlled, so there is no assurance of ease of welding. The carbon equivalency is not assured since the chemistry is not specified. The chemistry can vary considerably from one lot to the next. Thus one lot could be rolled from ASTM A36 plate and welded longitudinally, but due to variations in wall thickness, chemistry, roundness, etc. it is not deliverable as welded pipe, so they sell it as piling. The next lot could be extruded pipe with a chemistry that is similar to a high strength low alloy steel such as 4130, 4140, etc., however, because there is an issue with the exact chemistry or manufacturing process, cannot be sold as drill casing for the petro industry. It does meet the minimum strength requirements for piling, so rather than scrap it, it is sold as piling. The weldability; more difficult due to the need for; high preheat, alloy filler metal, and post weld heat treatment if the welds are to ductile. 

Prequalified base metals listed in AWS D1.1 have controlled chemistry and mechanical properties that assure ease of welding. High strength low alloy steels that are quenched and tempered are permitted, but must be qualified by testing per section 4 of the structural welding code. Those same controls are not part of the piling material specification, thus ease of welding is not assured. Thus, piling Is not prequalified unless the material test reports states that the materials supplied meet several different material specifications, one of which is a prequalified base metal listed in AWS D1.1.

Your piling could be welded using a prequalified WPS if the material test report states the piling meets ASTM A252, ASTM A36, ASTM A53, or ASTM A106. Examples: in the case of the seam welded pipe, it could be made out of A36 plate and meets the requirements A53, or in the case of A106, it could be seamless pipe. In all three cases the pipe supplied could meet ASTM A252. Because A36, A53, and A106 are listed, the piling can be welded with a prequalified WPS. If the material certification only lists ASTM A252, all bets are off for all the reasons given.

Up Topic Welding Industry / General Welding Discussion / prequalified wps use for steel pile welding

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