American Welding Society Forum
I am getting ready to under go a quite large project involving welding together 20" diameter roll formed 316L stainless. There will be a large number of these welded together utilizing a 60 degree bevel with a 1/8" back up bar (If TIG is used) The material is 1/4" thick and will require a full pen weld with minimal build up as it will have to be ground and polished to a #4 finish when completed. We are currently looking at using circumfrencial automatic welding equipment utilizing either TIG or GMAW-FCAW. All welding will be done in position (3G) What I need help with is this:
1. Do I use TIG or GMAW-FCAW?
2. Once I establish which process to use if it is TIG what should my essential variables be? i.e. voltage, amperege, what type of tungsten, polarity? You get the point. I have an idea here just looking for more input.
3. Anyone know of a supplier who makes good equipment for this particular process who will be willing to help me through this.
4. If I do use TIG will the weld be prequalified or will I have to qualify the procedure?
5.Is there a better joint configuration to use?
I appreciate you input, if you guys can help me out and bump this every once in awhile I would appreciate this. This is a very important job and I want to be on the ball when I present my WPS's!
Have you checked into the cold feed TIG machines out there yet? They are a wire fed TIG. Might not be bad for an automated process. I looked into them for a project where I'm the tech - CWI, but it wouldn't work for what I was doing. The FCAW stainless is a good choice also. I guess it all boils down to what your facility is used to using. How long will these things be when you are done? I assume your 3G will be in the upward progression. Oh, make sure your vertical seams are staggered.
As for a supplier, Try big blue, (MILLER) They can surely help in that department. AWS D1.6 does have some prequalified joint details, see if any apply to what you are doing. Check section 3, part G, prequalified tubular joint details. 30 Deg. should be fine for the Mat. thickness you discribed (1/4"). If I helped you, OORAH. If I only suceeded in confusing you, sorry. I'm sure you will get responses from people out there that might be better informed then I.
I hope you made the right choice and did some R&D for whatever process you are using. My choice for getting started fast? GTAW. Automated circ. seams are a breeze with this process & equipment. You can cut your bevelling out completely if you work your R&D. We do full penetration into a gas purged copper backing bar on 3/8" plate with the edges as sheared (0 bevelling) and butted tight. The method does need a second filler pass. You may be able to add the filler on 1/4" and still succeed. For long term production you would be better off working the GMAW process because it can be the cheapest and achieve good results. The bead profile can be controlled with modern pulse equipment and R&D on the procedure. Good luck. I'm curious as to where you go with the choice and how it pans out.
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