Mild Steel housing welded with SS rod??

MiniBuggyBuild · Mon Feb 17, 2014 12:44 pm

I am building two mini buggies. (Single seat, long trav suspension, sport bike motors). There is a rear end housing that has mounts for double A Arm suspension and there is a center section containing the sprocket brake and axles.

I have access to a TIG Machine and bottomless SS rod. I have welded this housing solid and have had one person mention that was a bad idea to use SS on a MS housing. What are your thoughts? This should not have a lot of stress on it and (hopefully) shouldn't be hitting the ground. I believe for the most part this will have little torsion or bending.

What about cold and hot weather? Will the metals expand at different rates and crack?

Hoping for good news!

noddybrian · Mon Feb 17, 2014 2:55 pm

You'll get more expert replies - but in laymans terms I don't see this as a big problem depending on the stainless alloy used - I think the caution from other people is because stainless has a bad reputation for cracking - but there are many reasons why this may happen - suppose your center section is mild steel ( if your using motorcycle parts it's probably not ) and the tubing is some other alloy maybe chrome moly or something else - the go to filler I would use is 309 L as this will successfully take to differing low alloy / carbon steel - it's not usually prone to cracking if the joint is suited to the application - I have'nt researched current Tig filler composition in this alloy but in the past if using arc rods of this type then you looked out for ones that were stabilized with Niobium which helped with cracking & corrosion related issues ( all of which you could read up on if interested ).

Bottom line - in my limited personal experience 309L should work - but if joining tubular parts that flex with vehicle movement the design of the frame & joints will have more effect on how well it holds together than choice of filler rod - but whatever rod using Tig should give you better control & quality of the welds over say Mig.

MiniBuggyBuild · Mon Feb 17, 2014 4:26 pm

Yes the pieces are mild steel. They are laser cut.

Also I am using 316L will this have any difference to the 309L?

MinnesotaDave · Mon Feb 17, 2014 4:45 pm

You should do a search of what the rods are for before you use them actually.

http://www.lincolnelectric.com/en-us/su ... etail.aspx

That link is very basic, there is a lot more information out there to read up on.

MiniBuggyBuild · Mon Feb 17, 2014 5:24 pm

Bummer! So if I'm reading correctly I should probably scrap this housing? I'd hate to do this but I'd also hate to cut it out of a finished chassis on down the line if it develops problems.

Is there any testing I can do on these welds? I think I saw a dye test in another post. Will that be accurate?
And is it any benefit or downfall that the housing is fully welded vs every few inches knowing I have 316L in MS?

Superiorwelding · Mon Feb 17, 2014 6:06 pm

MiniBuggyBuild,
One thing to remember is always use the higher grade of the two metals for filler. In this case if they are both mild steel ER70S-2 is the way to go. If you are going to use SS filler use 309. Will the 316L hold, maybe, but it is better to do it correctly than have to do it over. I see no need or benefit in using the 316L filler.
Here are some videos on using 309.
http://www.weldingtipsandtricks.com/tig-weld-steel.html
http://www.youtube.com/watch?v=knSoRX8RB9g

Also the die test will only show you cracks, porosity, leaks etc in your welds. Unless you suspect the welds already being bad, you will not need to die check it.

Can you get some pictures up?

noddybrian · Mon Feb 17, 2014 6:10 pm

I'm sure Otto or someone else with more stainless experience will chime in on this one - but I'd not have used 316 of choice - however all may not be lost ! - a picture or two of the actual part will help others give you better advice & it maybe that the welds / engineering of this piece make it 20 times stronger than it needed to be - the thing with making stuff from scratch of your own design - sometimes the part you worried most about turns out to be fine & some other part will fail that you never thought of - often only time will tell - as to the dye test - it will tell you only if the part is cracked now - it can't predict what may happen in the future ! either way - if you knew the parts to be regular mild steel why not use ER70 S2 or similar ?- best of luck with your project - interested to some pictures as it progresses if possible.

MiniBuggyBuild · Mon Feb 17, 2014 6:57 pm

Thank you all so much for your responses.... Here are a couple pictures. I hope all is not lost!

MinnesotaDave · Mon Feb 17, 2014 7:31 pm

Heck, it's done already and it's not for on the roads. I'd run it

Just use correct fillers next time man

Superiorwelding · Mon Feb 17, 2014 7:39 pm

I think you are good to go. That is a lot of weld to fail! Looks good by the way.

Mon Feb 17, 2014 7:50 pm

Well, apparently this does not include cast parts, so you may be fine.

316 welds well for 304 and 316 steels, and will do an acceptible job for most mild steels, but, in general, I would use a 70- or 80- series mild steel rod for those welds. I would be willing to use 309, for it's compatibility with mild steel. It's actually fairly common in industrial welding to use 309 on carbon steel, as the properties of the weld are more resistant to corrosion than heat-affected mild steel.

With what you're building, I'd think you won't be getting a "call back" on this anytime soon, especially with the quality and "over-engineering" I see.

I'd run with it, myself...

Steve S

MiniBuggyBuild · Mon Feb 17, 2014 8:07 pm

Thank you for the kind words!

So is the consensus that I should have used a more appropriate filler vs what we have laying around? And that this will stay together for me?

What if, on my second housing (already tacked, as well as a few full welds with 316L) I used e70s6(2?) on the rest. Is it better or worse to have two different fillers?

Mon Feb 17, 2014 8:18 pm

MiniBuggyBuild wrote:Thank you for the kind words!

So is the consensus that I should have used a more appropriate filler vs what we have laying around? And that this will stay together for me?

What if, on my second housing (already tacked, as well as a few full welds with 316L) I used e70s6(2?) on the rest. Is it better or worse to have two different fillers?

I believe your first piece will likely be fine. It's overbuilt for its purpose, and the weld quality seems high (though I have only the photos to go on... If you have a trusted friend who is a qualified welder, get a second set of eyes on it, just to see little things you may not. It's hard to QC your own work).

I'd weld the whole thing out with ER70S-2, and not worry at all about the tacks and existing welds in 316.

Just an opinion, though... Your mileage may vary.

Steve S

Superiorwelding · Mon Feb 17, 2014 8:28 pm

Otto Nobedder wrote:
MiniBuggyBuild wrote:Thank you for the kind words!

So is the consensus that I should have used a more appropriate filler vs what we have laying around? And that this will stay together for me?

What if, on my second housing (already tacked, as well as a few full welds with 316L) I used e70s6(2?) on the rest. Is it better or worse to have two different fillers?
I believe your first piece will likely be fine. It's overbuilt for its purpose, and the weld quality seems high (though I have only the photos to go on... If you have a trusted friend who is a qualified welder, get a second set of eyes on it, just to see little things you may not. It's hard to QC your own work).

I'd weld the whole thing out with ER70S-2, and not worry at all about the tacks and existing welds in 316.

Just an opinion, though... Your mileage may vary.

Steve S

I second Steve.

MiniBuggyBuild · Mon Feb 17, 2014 8:43 pm

Otto, I think I will take that advice and roll with it, ER70S2 it is.

Thanks again everyone for quick responses. It looks like a crisis averted and huge lesson learned.

noddybrian · Tue Feb 18, 2014 4:47 am

That's for a lightweight motorcycle engined small buggy ? well having seen it I would'nt imagine the weld strength to be a problem ! it looks more like part of a rock truck ! I'd agree with the others here & use it - but next time use a more suitable filler - after all the correct one is also the cheapest in this case .