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Archive for March, 2014

An interesting project has come to our shop that is leading to a new welding procedure. The project is a simple stainless steel pressure vessel, 6” diameter pipe, 0.432” wall approximately 18” long. While this seems overly simple it has led me to investigate the welding options we have qualified for stainless in our shop. We have stainless hardwire, flux core, stick, and TIG procedures but which one to use? Flux core fills very fast, hardwire is clean and neat, TIG has an artistic look when done right but is slower then hardwire and flux core. Stick welding is smoky and unless the welder is REALLY good it just doesn’t look as nice as the others. I’m beginning to think multiple processes. If we hardwire the root then no backing gas is required (meaning we don’t have to purge the inside of the vessel to remove any oxygen exposure on the back side of the weld) then we can fill the majority of the weld joint with either spray arc hardwire or flux core and finish with TIG. We get a solid, quick welded joint that looks like art! But I don’t have a weld procedure that includes three different welding processes. Do I need to break out some stainless steel scrap and weld up a coupon using the three selected processes and have it tested? Conveniently, I do not. Because I have Procedure Qualification Reports (PQR’s) for all three processes I can write a new procedure using the existing PQR’s. I can take the information from each PQR and implement a new procedure that includes all three processes. Each process must be noted on the new weld procedure and the essential variables must also be noted. One other item to be sure to review, the thickness of the additive PQR’s must yield the thickness range required for the intended joint. Maintaining documentation of all our welding processes and procedures makes this an easy accomplishment, an accomplishment that allows us to utilize our knowledge and history to go forward. If you like the way a certain welding process looks but have been told it costs too much or takes too much time, give us a call. We’ll help you find a happy medium that yields beautiful welding and cost effectiveness.

TIG Cover Pass

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