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  • Suggestions for Welding a SS Turbo Header

    I am about to embark on a new project: Building a stainless header for a turbocharged motorcycle. I have been welding and fabricating for about 25 years, but I do not weled on a regular basis. I may go for a period of several weeks or longer where I weld at least something 3-4 times a week. then I may go for months without welding much at all. When I am in practice, I am decent, though not a professional by any means.

    This project will require me to learn a new skill, and that is welding stainless. So I am looking for some advice and tips to help me get up to speed on this as quickly as possible. All material will be 304SS. The header will be primarily constructed from schedule 10 (.109" thick) mandrel bends, with a 1/2" thick turbo flange. The exhaust pipe and wastegate will be done with .065" tubing.

    I will be using a Synchrowave 351, with a Weldcraft WF225 torch. We will start on the header itself first, (the .109" tubing) and I was planning to use 1/16" thoriated tungsten, .062" 308L rod, and argon as both the shielding and the back purge. Back purging is also something I have never done before, so any pointers would also be welcome on that as well.

    So what I am looking for is starting points on the welder settings or any recommendations on the actual equipment or consumables, and any relevant tips or advice for the actual welding process, the back purging, and any other advice that will generally make my life easier.

    Thanks in advance for any advice to come.

  • #2
    Since argon is heavier than air, fill your backpurge from the bottom, pushing the air out the top; like filling a swimming pool from the drain. Doesn't need a lot of pressure, just wait for the air to displace.

    That's all I got.
    RETIRED desk jockey.

    Hobby weldor with a little training.

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    • #3
      SS Headers

      Phil: Welcome to the Forum. Good questions. Practice on some scraps first, as expensive as SS is, it's still cheaper to mess up scraps.

      You're right on the border of 1/16"-3/32" filler metal for .109 (7/64") material.
      may want to have some 3/32" 308 rods handy, especially when you get to the turbo flange (which I'll cover shortly)

      Use a gas lens on SS. DC- amps starting @ 80-110 for butt welds, and a 1/4- 3/8" cup, argon flow @ 11 cfh.

      Are you using 304H (high temp SS) for this project? Two problems of welding austenitic SS are 1.) sensitization of the weld heat affected zone, and 2.) hot cracking of the weld metal.

      304H maintains strength at high temps, and has good scaling resistance.

      You don't need a sophisticated purge system, I've seen cardboard used.

      Unlike ferrous steels, heat travels slowly in SS. This is why control of carbide precipitation is important. You could be welding on a header/tube joint, but yet be able to touch the end of the header tube with your bare hand.

      Keep us posted, and good luck!

      Dave
      Last edited by davedarragh; 08-06-2009, 07:33 PM.
      "Bonne journe'e mes amis"

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      • #4
        I appreciate the responses.

        Some of the research I have done recommends that you butt-fit the tubes with no beveled edges, then fuse the tubes together with little or no rod. I selected the 1/16" rod size based on that. Any comments on that approach are certainly welcomed.

        I figured once I got to the 1/2" flange that I would need something bigger than 1/16", but I was going to wait until I had a little better idea of exactly what would be needed. And I will definitely be practicing first.

        When you mentioned 308H, are you referring to the type of rod? I have seen 308H, 308L, and 308LHS. I know the HS stands for high silicone, but I can't find any information regarding what the specific individual properties for each one are, or which of these would be the best choice for what I am doing. So if you have any further enlightenment on that, I would appreciate it.

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        • #5
          304h

          Originally posted by flyinphill View Post
          I appreciate the responses.

          Some of the research I have done recommends that you butt-fit the tubes with no beveled edges, then fuse the tubes together with little or no rod. I selected the 1/16" rod size based on that. Any comments on that approach are certainly welcomed.

          I figured once I got to the 1/2" flange that I would need something bigger than 1/16", but I was going to wait until I had a little better idea of exactly what would be needed. And I will definitely be practicing first.

          When you mentioned 308H, are you referring to the type of rod? I have seen 308H, 308L, and 308LHS. I know the HS stands for high silicone, but I can't find any information regarding what the specific individual properties for each one are, or which of these would be the best choice for what I am doing. So if you have any further enlightenment on that, I would appreciate it.
          Actually Phil, I mis-typed "304H" as the base metal. It's a high-temp "version" of 304 stainless.

          Dave
          "Bonne journe'e mes amis"

          Comment


          • #6
            Originally posted by davedarragh View Post
            Phil: Welcome to the Forum. Good questions. Practice on some scraps first, as expensive as SS is, it's still cheaper to mess up scraps.

            You're right on the border of 1/16"-3/32" filler metal for .109 (7/64") material.
            may want to have some 3/32" 308 rods handy, especially when you get to the turbo flange (which I'll cover shortly)

            Use a gas lens on SS. DC- amps starting @ 80-110 for butt welds, and a 1/4- 3/8" cup, argon flow @ 11 cfh.

            Are you using 304H (high temp SS) for this project? Two problems of welding austenitic SS are 1.) sensitization of the weld heat affected zone, and 2.) hot cracking of the weld metal.

            304H maintains strength at high temps, and has good scaling resistance.

            You don't need a sophisticated purge system, I've seen cardboard used.

            Unlike ferrous steels, heat travels slowly in SS. This is why control of carbide precipitation is important. You could be welding on a header/tube joint, but yet be able to touch the end of the header tube with your bare hand.

            Keep us posted, and good luck!

            Dave
            I weld LOTS of stainless butt welds and I hardly ever weld over 75 amps. Keep a sharp tungsten and a good purge. I personally feel alot of folks over think the purge , masking tape works well and is cheap.
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            • #7
              Originally posted by flyinphill View Post
              I appreciate the responses.

              Some of the research I have done recommends that you butt-fit the tubes with no beveled edges, then fuse the tubes together with little or no rod. I selected the 1/16" rod size based on that. Any comments on that approach are certainly welcomed.

              I figured once I got to the 1/2" flange that I would need something bigger than 1/16", but I was going to wait until I had a little better idea of exactly what would be needed. And I will definitely be practicing first.

              When you mentioned 308H, are you referring to the type of rod? I have seen 308H, 308L, and 308LHS. I know the HS stands for high silicone, but I can't find any information regarding what the specific individual properties for each one are, or which of these would be the best choice for what I am doing. So if you have any further enlightenment on that, I would appreciate it.
              I'd stick to the 1/16" filler . It consumes faster thus letting you move faster which reduces the heat affected zone.Don't cook your stainless by trying to use to big of filler , seen it a thousand times.
              Dynasty 200DX "Blue Lightning"
              Bernard 3500ss water-cooler
              Rockwell vertical mill
              Beverly Shear B-3
              Beverly Shear JR
              Home-made English wheel
              Milwaukee Porta-band
              " Sawz-all
              Tennsmith 36" stomp shear
              Fixer upper 1968 Redface Lincoln sa200
              Powcon 300st

              Comment


              • #8
                Originally posted by davedarragh View Post
                Actually Phil, I mis-typed "304H" as the base metal. It's a high-temp "version" of 304 stainless.

                Dave
                Now I understand what you were asking. To answer you, I don't know. The mandrel bends are coming from a company that makes them specifically for turbo header applications. It is a 304 alloy, but beyond that, I just can't answer. The material is so thick that cracking is not usually an issue.

                So is 308L the correct filler for this application?

                Comment


                • #9
                  "er"

                  Phil: Yes, ER308/308L cut length TIG rods will be just fine.

                  If you were using SMAW, E308-16/E308H-16 would provide improved high temperature strength.

                  304 Austenitic Stainless Steel is commonly referred to as "18-8" steels.

                  18.0-20.0% Chromium and 8.0-10.5% Nickel

                  The differences in 304H is a 0.04-0.10% Carbon content, where as "304" has a nominal 0.08% Carbon composition.

                  304L, 304LN has a 0.03 carbon content.

                  When you get your "pieces," send me the UNS Number (Unified Numbering System for alloyed metals) and I can tell you exactly what you have.

                  That way you can tell the guys; "yeah, I got this 304H SS, just for headers."

                  If nothing else, sounds impressive!

                  Good luck, stay in touch, like to see some pics when you're done.

                  Dave
                  "Bonne journe'e mes amis"

                  Comment


                  • #10
                    Has anyone used anything other than thoriated for stainless? I am probably not exposed to the thorium frequently enough for it to be a health issue. But then again, why take an unnecessary chance.

                    Some of the stuff I have read indicates that ceriated is a good choice for DC applications. And also I have read that lanthanated can be used for basically everything. Do any of you have any experience with these other types of tungsten?

                    Comment


                    • #11
                      I use ceriated for most of the SS I weld, it seems to hold a point better for me.
                      One tip I've found on SS tubing is to tack in at least four places and move around a lot to cut down on warping, esp on .065 and thinner.
                      Hope this helps.

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                      • #12
                        That actually brings up something else I am curious about. When tacking these tubes together, is it necessary to back purge the tubes? Or is the limited amount of contamination that would occur acceptable in this application?

                        Comment


                        • #13
                          That really depends on how much penetration you have and how much filler you use. On the .120 tubes if you make a light tack with heavy filler so as not to get full penetration then you can get by with out back purging.
                          When I'm fitting up header tubes I prefer to use backing rings and a marker, then when everything looks good, back purge, tack, double check everything, then weld away.

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                          • #14
                            Originally posted by flyinphill View Post
                            That actually brings up something else I am curious about. When tacking these tubes together, is it necessary to back purge the tubes? Or is the limited amount of contamination that would occur acceptable in this application?
                            If you want it right you need to purge even when tacking. At my job anytime I forget to purge I cut the joint no questions and start over. This is on stainless butt welds that get x-rayed.
                            Dynasty 200DX "Blue Lightning"
                            Bernard 3500ss water-cooler
                            Rockwell vertical mill
                            Beverly Shear B-3
                            Beverly Shear JR
                            Home-made English wheel
                            Milwaukee Porta-band
                            " Sawz-all
                            Tennsmith 36" stomp shear
                            Fixer upper 1968 Redface Lincoln sa200
                            Powcon 300st

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                            • #15
                              Time for an update.

                              I am putting together the stuff to purge today, but I went ahead and tried a weld yesterday without the purge just to see where I was at. I butted 2 pieces together, with no chamfer, and tried to weld part of the seam by just fusing them together. It worked OK, but it doesn't seem to have enough penetration. Looking inside of the tube there are only a couple of areas where the metal just started to melt on the inside, and there is no penetration of the weld all the way through. I tried some different techniques, different heat, adding rod at different rates. etc. and nothing really gave me what I am looking for.

                              Now I don't really know if a full-penetration weld is needed or even adviseable on tubing this thick. But if I do need a full penetration, I am not sure where to make a change to what I did already. I could try to turn up the heat (it was just under 100 amps, maybe 95 by the dial) but I would be surprised if that will do the trick. I was moving pretty fast pushing the puddle, so maybe slowing down the speed would allow more time for penetration. Or maybe the combination of slower with more heat will do it.

                              But it seems to me that the best way is going to be to bevel the tubes before welding, and use some filler rod. Butting unbeveled ends and fusing may work with .065" tube, but I can't see it working with .109". Maybe it will and I just need to experiment some more. This, however, brings up a new problem with the weld turning gray when I add more than just a minute amount of filler.

                              Another issue I see is that it doesn't seem as if I am getting sufficient shielding. I did discover that when I stop the weld and let off the pedal I need to hold the torch with the post-flow still gassing in place until the metal stops glowing. When I do this, I get a perfect circle the size and shape of the cup where the weld is shiny and a blueish-gold color. But behind this area the weld has started to turn a little gray. Not nearly as bad as some of the pictures of other beginners, but it is obviously continuing to stay hot enough to oxidize too long after the torch and its shielding has moved past that area. So what should I try here? A bigger cup, more CFH, or maybe slowing down the travel rate will help this also.

                              Take a look at these 2 pics. The one from the outside is an area where I ran with no filler, just fusing the parts. The inside picture is the same area of tubing, showing where the heat was just getting through the material. This is the only area this happened, and it had no penetration anywhere that I used filler. Also note the color in the first pic. It is not as easy to see as in person, but you can just make out the circle where the cup was left post-flowing over a cooling weld.

                              So any thoughts?
                              Attached Files

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