Welding Mild and Stainless Steel

[jmoore]

I'm planning some modifications to my SD rack and thinking about using stainless bolts. I would be welding them to the mild steel, used on the rack. I'll be usining a 110 MIG with CO2/Argon mix. Is there anything special I should look out for or do?

 

[MUSKYMAN]

thats really a hard question to answer...not all stainless is the same, some grades such as 303 is damn near impossible to weld and will weaken and crack. some of the lower grades will no longer have corosion resistance after you weld it due to intergranular destabilization.

the prefered method to weld stainless will always be tig because it allows you to control the heat and localize the destabilization.

I would just use grade 8 hardware and keep it touched up with a rattle can if it were me.

 

[jmoore]

Most of the reading I've done says that the stainless melts quicker than the mild steel and that you really have to play with the heat. The bolts I'm using I got from Lowes so I'm sure sure of the grade of stainless. I did buy a few of both stainless and regular mild steel to play around with.

I was wanting to go with stainless to avoid corrison. Are you suggesting grade 8 because it's stronger or corrision reisitant?

 

[DeMak]

I wouldn't use either stainless or grade eight. The best weld is with the most simular metal. If you decide to to weld stainless, go with a filler metal that one grade higher than the bolt. You still may not be happy, as the two metal have different wetting properties and puddle control can be difficult as you weld around the head.

DeMak

 

[racerwad]

you can't weld dissimlar metals like mild steel and stainless. as someone mentioned, just use bolts.
stainless without a tig machine is too difficult. besides, as others have alluded to, there are other issues like pre and post treatment, etc.

grade 8, 5, whatever, addresses strength in various situations. they are coated with cad so they are fairly corrosion resistant. what are you trying to do?

a

 

[racerwad]

oh, and peep out www.weldingweb.com. this is the best site i've ever seen for welding, fab, machine work, etc.

a

 

[nvprospector]

You can weld stainless and mild steel. This is done quite abit using TIG, MIG and Oxyacetylene. You will need to use 309 stainless steel filler for this type of weld and don't forget to back up the weld seam with copper strips or welder's ceramic fiber paste to prevent contamination in the weld. If you do MIG, your gase should be Ar 2-5%/CO2 Gas.

These sites will give some basic info:
http://www.esabna.com/EUWeb/AWTC/Lesson5_18.htm
http://files.aws.org/wj/2006/02/wj200602/wj200602-46.pdf

But, my question is WHY? What you want to do is a really, BPITA. Just use bolts, it all works out for the better in the end.

racerwad, nice welding site. I really like the information it provides.

 

[jmoore]

But, my question is WHY? What you want to do is a really, BPITA. Just use bolts, it all works out for the better in the end.

racerwad, nice welding site. I really like the information it provides.

Thanks guys. The sites are great.

What I would like to do is make part of the top rail on my SD rack removeable. My idea was to cut the bottom of the vertical legs were they attach to the lower horizontal rails. I was thining about taking 1/2" bolts and puddle welding them inside the tubing so the theads were exposed. I would then drill holes in the lower rails so the bolts could go through. I would then attach the top assembly with wing nuts and washers.

I want to do this, so I can get my truck in the garage without having to remove the entire rack. Also, there are times when it would be good to have the top rails gone, like when I load up plywood.

thoughts?

 

[mikeyb]

i cut mine for the exact same reasons a few years ago. i found on onlinemetalsdotcom a section of tubing that had the same ID and the OD of the leg tubing and bonded them to the upper rack, after fishmouthing the tubing so it would "sit" on the rack still attached to the truck. then i ran carriage bolts from top to bottom and bolted the whole thing back on when needed.

funny thing is, i never really needed to bolt it back on and it just sat in the garage all the time. even funnier thing was i later decided i to just build a totally new rack, so even doing all that was useless work.

so that is my thought, anyway.

happy t-day.

 

[jmoore]

Mike,

that's an interesting solution! And might be stronger that what I'm considering.

When I bought my rack the top rail had been removed in the back. I kept it that way for awhile, but I found it difficult to keep gear secure back there without the side rails, so I had a local shop fab some for me. I'll have to take a look at mine and think about how you approached it.

Thanks!

 

[jmoore]

Mike,

I looked at my rack and I'm really beginning to like your idea better. I could cut a square notch on the top side of the rails to hold a 5" or so carriage bolt. I could use a smaller size bolt and not have to cut such a large hole in the bottom rail. I was also thinking about cutting down some 1" pipe to make it slide inside the vertical rails to hold them in place. Hmmmm. Thanks for the idea.

 

[mikeyb]

sure, glad it may make things easier for you! i reread my post and i was not totally clear on one thing, i found tubing with the same ID ~as~ the OD of the rack tubing. i figure you figured that out though...

good luck with your crafting!

 

[antichrist]

You can indeed weld stainless to mild steal. It's quite commonly done, particularly in the chemical piping field. You use stainless filler. It can be done with stick, TIG or MIG, I've used all three to do it. My experience is that the stainless from places like Lowes and HomeDepot are high carbon stainless and will corrode.