Mig Stainless to Mild ?

[deepblue175plus]

Hello All,

Im new to this forum but have ventured into forums in the past. Its nice for someone like me who always seems to be getting myself into the unknown. Well, here is my current delima. I have a broken tonge on my boat trailer so being the do-it-yourselfer, I went out and baught a Lincoln SP-175-Plus Mig welder. On my first test project (mig cart) I have put a stainless plate on the 3/4" mild steel square tubing frame. Welding the tubular frame was a breeze (thaught i was a pro). Then came the humbling stainless plate. The bead was ugly to say the least (black pits, the works). I never thaught about them being dissimilar because they were both magnetic until reading the threads. Alot of the threads mention 309 wire. As far as i have seen thru searching, the only wires available for the Mig mild steel aplications and it is SuperArc™ L-56 mild steel. I was using the .35 wire 75/25 mix. I was using proper technique, correct working gap and so on but could not fine tune the amp/wire speed to produce anything close to being acceptable. No where in the recommended setting does the Lincoln differentiate between mild and stainless settings (that i have seen). Is it just that hard to weld dissimilar metal, stainless to mild? Please fire away, Im ready to learn the way. Thanks all and I really did read all threads that addressed this (seems to have confused me more i think (lol).

[Rocky D]

Welcome to the forum, Deep....you should be able to weld a stainless plate to mild steel tubing fine...this sounds like there's another culprit you may have overlooked. I'm thinking that maybe what you thought was stainless, was chrome plated steel. That will give you the results you describe. Was the puddle acting violent while you were welding it? maybe zinc plated, but that would give you splatter and globs of zinc all over. A picture would be good to help diagnose. Are you sure you had the gas on? It's easy to forget. Tell us more.

[deepblue175plus]

Thanks Rocky for your post. Do you know that it very well could have been zinc plated (never thaught of that). Also, when i welded the casters to the bottom i had kind of the same results and after your post, Im thinking crome plated on them. Just to let ya know, the gas was on. Welding is new for me so i have a planned check list i go over in my head everytime before pulling the trigger. I have pictures of the finished product and now that you mentioned it, I should have taken pictures of the process, it would be a good learning tool. I think when i get home i will start a lessons learned folder on my pc. Lets say for sake of confusion that these items were plated. What can i do to properly bond the 2 together with an acceptable appearance? Im on the rig here in Singapore till the end of the month or I would send you a picture. Im actually quite impressed with the final product.