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  • Making a joint look nice

    Lets start with the most inportant things first I have never mig welded SS before I have a customer who wants me to modify a hood for a commercial kitchen. I am assuming that when I weld it the heat from the weld will discolor the SS where the seam is. How can i get it back to its nice shiny SS finish that it started with or can I?

    My second question is welding SS realy and different than welding mild steal I mean aside from using SS wire and whats the best shielding gas to use?

  • #2
    Been a while since I welded Stainless with Mig, but here is what I can offer.

    Best gas will be Tri Mix (Ar, He variety). You will want to back gas the weld or use a flux (not for food use). The rainbow colors you'll see can be removed, polish as you would the rest of the material.

    As far as being harder than mild steel, a little. You will need to pay attention to your heat control to avoid warpage. Spend a little time thinking about your welds so you can apply heat evenly (think tightening lug nuts using star pattern). Avoid drafts and try to weld in an area that is 80 degrees. Pre heat may become necessary if material is thick, but that is no different than for mild steel.
    John

    Millermatic DVI
    Miller Plasma Extreme 375
    Brand Spank'n new Syncro 200

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    • #3
      SS welds slightly hotter than mild steel...this hood is prolly 14ga to maybe 11ga, so you're gonna hafta be quick in welding to keep from blowing holes...vertical down will help you there. Then you will need to hand finish the weld after with special sanding wheels, and prolly a Scotch Brite wheel, to match the surrounding finish. This is an art, and can be really messed up if you don't know what you're doing. I suggest Tri-Mix also.

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      • #4
        Mega,

        If you've never mig welded SS (stated), the first thing I'd do is get my hands on some similar material and practice, practice, and then practice some more. "Finishing" the welds is going to be the least of your problems.

        As Rocky has indicated, you're probably dealing with less than 14ga material. Warpage will be a major concern. Blowing through the base metal will also be a problem. Tri gas (90%Helium, 7.5%Argon, 2.5%CO2) as a covering gas and straight Argon for backing/purge is recommended.

        Not saying it can't be done with mig (for an experienced guy) but tig would be my choice. Especially if it's going to be in a commercial environment where the weld is visible. Tig would allow much more control of the heat.

        Based on your previous comments/questions, I kinda question whether this is a project you want to be taking on. Could do more damage than good.

        Good luck.
        SundownIII

        Syncrowave 250DX, Tigrunner
        Dynasty 200 DX w/CM 3
        MM 251 w/30 A SG
        HH 187 Mig
        XMT 304 w/714D Feeder & Optima Pulser
        Dialarc 250 w/HF 15-1
        Hypertherm PM 1250 Plasma
        Victor, Harris, and Smith O/A
        PC Dry Cut Saw and (just added) Wilton (7x12) BS
        Mil Mod 6370-21 Metal Cut Saw
        More grinders than hands (Makita & Dewalt)
        Grizzly 6"x48" Belt Sander
        Access to full fab shop w/CNC Plasma & Waterjet
        Gas mixers (Smith(2) and Thermco)
        Miller BWE and BWE Dig

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        • #5
          I think back gassing may not be possible for this type of job, but if the weld is not going to be visible from the back, you can use Solar B flux...it's also possible to weld it with out penetrating, and then a wire wheel while still hot does a good job. You will still have to run a scotch Brite wheel over it to match the finish, and it's the finish work that requires skill...You might want to go to a sheet metal shop that does kitchens and ask what they use.

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          • #6
            Originally posted by SundownIII View Post
            Mega,

            If you've never mig welded SS (stated), the first thing I'd do is get my hands on some similar material and practice, practice, and then practice some more. "Finishing" the welds is going to be the least of your problems.

            As Rocky has indicated, you're probably dealing with less than 14ga material. Warpage will be a major concern. Blowing through the base metal will also be a problem. Tri gas (90%Helium, 7.5%Argon, 2.5%CO2) as a covering gas and straight Argon for backing/purge is recommended.

            Not saying it can't be done with mig (for an experienced guy) but tig would be my choice. Especially if it's going to be in a commercial environment where the weld is visible. Tig would allow much more control of the heat.

            Based on your previous comments/questions, I kinda question whether this is a project you want to be taking on. Could do more damage than good.

            Good luck.
            As far as this being a project that I may not want to take on because I could do more harm than good I've been welding for years and make my living welding and before welding I was doing sheet metal fab. I can weld gauge steel and not blow holes. All I said before was that I have never mig welded SS before. I have tig welded it lots before but I don't have one available for this job. If I wanted to tig weld it I probably wouldn't have ask for advice on mig welding

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            • #7
              Try to make your welds vertical down. This will keep you from piling up too much metal. Also you need metal to metal fits...no gaps.

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              • #8
                Why no gap if it were mild steel I would put about a 1/16" gap? Is it no gap because its on ss?

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                • #9
                  Less heat in the joint...
                  intimate fit makes for good fusion....IMO
                  Some people require more attention than others.....Like a LOST DOG and strangers holding out biscuits....

                  Dynasty 350
                  Hobart Beta Mig 200
                  Twenty seven Hammers
                  Three Crow Bars
                  One English Springer Dog



                  A Big Rock

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                  • #10
                    Years ago i used to weld T-tops for boats , after welding the immediate area had some blueing , try this >>
                    keep your ground lead attached ,turn your amp control to 5-10 amps, take a copper electrode clamp in your stinger tape a piece of guase to the end ,dip the end in muratic acid and "wipe" the blue areas, worked for us but it may still need some polishing,,,,, be very careful welding 14-18 guage material >>> tough to do with a stick ! if you got Tig you will be much happier.
                    RJL

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                    • #11
                      Originally posted by Mega Arc 5040DD View Post
                      Lets start with the most inportant things first I have never mig welded SS before I have a customer who wants me to modify a hood for a commercial kitchen. I am assuming that when I weld it the heat from the weld will discolor the SS where the seam is. How can i get it back to its nice shiny SS finish that it started with or can I?
                      At work we use a three or sometimes 4 step process to re-grain the stainless steel we weld on, (mainly kitchen stuff).

                      One key is to always grind in the direction of the grain even when taking down excessive weld material, which may be an issue when using MIG rather than TIG. We use TIG for the jobs and here's what we do.

                      1. Grind weld down so the end result is flush with the counter with an 80 grit flapper disk on a 4.5 inch angle grinder.
                      2. Re-grain with zirconium grinding belt in direction of grain
                      3. Then a flap wheel
                      4 Than a clean wheel or something similar to scotch brite.

                      See this site for the materials or to get a visual.

                      http://www.csunitec.com/sand/hollowcore.html

                      We use a linear grinding machine like on the top of this page...

                      http://www.csunitec.com/sand/surfacefinishing.html


                      Hope that helps. - you should be able to make it look like there's never even been a weld, it takes a light hand with some finesse.

                      Regards,

                      Alexander

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                      • #12
                        Great post, Alex...I have used those fleece wheels...they make a mess, but they do a fine job. They sort of disintegrate while being used.

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                        • #13
                          Originally posted by Mega Arc 5040DD View Post
                          Why no gap if it were mild steel I would put about a 1/16" gap? Is it no gap because its on ss?
                          When you do vert down welds, the puddle tends to build up and want to run ahead...if the fit is tight it will run down perfect, any gap will open a hole that will extremely difficult to fix.

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                          • #14
                            Thanks Rocky,

                            I spent all day re-graining stainless steel sub bases. (when the gussets were welded in on the inside it caused some distortion on the outside of the sub bases.)

                            I should say that re-graining on used kitchen gear can be tough, since when you're done re-graining it may look better than the rest of the counter tops or overheads because those have become dull through time and scratching. At that point there's a way to make it look "old" like the rest of the counter by using a scotch brite pad by hand in random motion to mimic the rest of the "used"/"scratched" counter.

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