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Welding SS 316 with 7018 DC rod.


oleman
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Our old Gillig bus has lots of heavy chassis parts and mounting brackets  made from stainless steel.

You welder guys think I can get away with just using the 7018 DC rod, or should I locate some SS rod to be sure of a good weld?

 

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Probably would get away with it but two things; Is someones life depending on it and  the future repair will be a night mare to get done right. Do It right the first time is an easy choice.

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22 minutes ago, VacDaddyt said:

Probably would get away with it but two things; Is someones life depending on it and  the future repair will be a night mare to get done right. Do It right the first time is an easy choice.

That's also my thinking.  What I am after is a trailer hitch.  The rear chassis rails are SS.  Would never weld to a truck chassis or mix SS and regular steel brackets. The bolt to chassis part of the hitch has to be stainless   but logically the the rest of the hitch would be regular steel so the SS flanges would need to be bolted to SS chassis and welded to regular steel tube for the hitch cross tube.  Want a 5T hitch to flat tow a 6900# Suburban 4X4 behind the bus.

The local muffler MIGS all the stainless pipes with normal wire but MIG is not 7018.

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 Quoted from my daughter who is a welder; "Yes you could can do it that way, but you really need to do SS with SS. It will look better and save you problems in the future if any occur. In all seriousness, if you have questions this early in the process you need to take it some where and have them look at it and talk with them and get their thoughts and ideas on your project. "

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The food & chemical processing equipment I used to work for did lots and lots and lots of welding, 90% was SS to SS, and about 9+% mild steel to mild steel and there were a few pieces they welded SS to mild steel. They always used SS rod or wire for that.

Never heard of a vehicle with a stainless steel frame.  Maybe that's something more companies should do.  Some of the really old UPS package cars had aluminum sheet in the bodies and as a general rule those eventually rusted.  The first "Stainless Steel Car" was built by Ford in 1934/1936 with Alleganie Ludlum Steel company.

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16 hours ago, oleman said:

That's also my thinking.  What I am after is a trailer hitch.  The rear chassis rails are SS.  Would never weld to a truck chassis or mix SS and regular steel brackets. The bolt to chassis part of the hitch has to be stainless   but logically the the rest of the hitch would be regular steel so the SS flanges would need to be bolted to SS chassis and welded to regular steel tube for the hitch cross tube.  Want a 5T hitch to flat tow a 6900# Suburban 4X4 behind the bus.

The local muffler MIGS all the stainless pipes with normal wire but MIG is not 7018.

So... you’re welding stainless brackets to the frame then bolting or welding your hitch to these brackets?

Why not just build your hitch to bolt to the frame and be done? 

 

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309 or maybe 316. Pita for vertical, if you have to weld up probably have to tack and tack or stack tacks. Practice some before you start something that matters, if you would run a 7018 at 125 amps then run a 309 around 90. Using stainless rods will be best if potential for corrosion as well as strength.

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On 11/4/2019 at 3:00 PM, oleman said:

 The bolt to chassis part of the hitch has to be stainless   but logically the the rest of the hitch would be regular steel 

Just a question, as alluded to before, why not build a steel hitch and then bolt it to the SS frame. Is there a corrosion or dissimilar metals issue? 

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Since it's not life or death if we get off topic, I'll say that I'm not a welder but I do ok around the farm. I tried to build a step frame  out of stainless angle iron once (because I had a lot of it .25 x2" and I thought it would look nice) and then I capped it with treads made of regular steel diamond plate and while working on the second tread I heard a loud Snap, and the first tread jumped off of the frame.  7018 rod. 12-15 1" beads all cracked Near the stainless, but not away from the stainless. I would have said physically impossible.   I jumped.   I deducted that welding the mixed materials was a no-no

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Im confused. If the brackets next to frame have to be stainless , why then is it ok to make the rest out of mild steel? You still have a stainless to reg steel transition....

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11 hours ago, stronger800 said:

Since it's not life or death if we get off topic, I'll say that I'm not a welder but I do ok around the farm. I tried to build a step frame  out of stainless angle iron once (because I had a lot of it .25 x2" and I thought it would look nice) and then I capped it with treads made of regular steel diamond plate and while working on the second tread I heard a loud Snap, and the first tread jumped off of the frame.  7018 rod. 12-15 1" beads all cracked Near the stainless, but not away from the stainless. I would have said physically impossible.   I jumped.   I deducted that welding the mixed materials was a no-no

I’m not going to argue with these welders on here, they certainly don’t think it’s a good idea so I’ll take it at that. Why, damned if I know but I’m assuming it’s something about the metal alloys not being compatible enough to provide any strength.

However, why not just build a hitch and bolt it to the stainless steel frame? You still need a barrier between the two to stop or minimize corrosion issues, we use plastic at work when we do this with stainless steel bolts. 

Hopefully these guys will be kind enough to educate the non educated people here on the reason why ?

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3 minutes ago, stronger800 said:

So does placing stainless against regular steel result in more corrosion at the joint face than say just regular  steel against regular steel? How is that possible.? I use plastic to isolate steel from aluminum sometmes though. 

It can produce galvanic action that corrodes the metal at a higher rate. In essence you have made a battery.

 

 Kind of like asking if your tractor is big enough to pull a disk so wide, there are a lot more variables so maybe 

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2 hours ago, iowaboy1965 said:

Im confused. If the brackets next to frame have to be stainless , why then is it ok to make the rest out of mild steel? You still have a stainless to reg steel transition....

In a dissimilar metal joint in a corrosive situation  something has to be sacrificial.  If you use mild steel bolts to bolt on a stainless bracket to stainless steel the bolts have a very short life. No part of the frame is to be sacrificial but the trailer hitch could be to save money on construction therefor the ends that attach to the SS frame must be SS and  must also be attached to the mild steel hitch.  My gut feeling  is to use SS brackets to the bolted to the frame and also bolt them to the hitch and keep an eye on the joints.

I am not a metal worker by trade but got a lot of good experience working on and around USN war ships for 20 of my younger years.  The ships in the 60's would have an aluminum superstructure above the  main deck  and steel below the main deck the  whole aluminum to steel seam would be separated by a plastic membrane and attached with bronze alloy rivets so the joint never allowed the steel to meet aluminum.  They used a new technology in the early 70's where they produced a "welding strip" made from fusing an aluminum alloy to steel alloy at a molecular level so it became one "strange" metal piece (the official mfg method description, was that a sheet of aluminum was placed on top of a sheet of steel and they used high explosives to create enough force to meld the materials together, personally I think it had something to do with  a nuclear reaction).  They never let that metal out of their sight so I was never able to capture  a sample section. It  had an aluminum side and a steel side, the joint was made by welding the aluminum side to the aluminum superstructure and the steel side to the steel hull.  Don't know if that technique was successful over many years of ship use because I left that ship and ship service in 1983.

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Chances are it would be fine for a very long time. How ever anything sacrificial as part of a hitch used to pull a 6000# suburban in todays litigation happy world makes me wonder if in the long run a hitch made wholly of stainless might be cheap after all....

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