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Weld compatibility between Stainless and A36 steels

Weld compatibility between Stainless and A36 steels

Weld compatibility between Stainless and A36 steels

(OP)
Stainless steel exhaust hoods are to be welded to A36 structural angles using E70 welding rods. Is there an issue between these materials?

RE: Weld compatibility between Stainless and A36 steels

I think there are rods specifically for this- either 308 or 309, I forget which- one is used for stainless to stainless, other for stainless to carbon.

One issue is that you can have dissimilar metal corrosion, which would tend to corrode the carbon steel.  While I know this CAN happen, I've never heard or seen anything that predicts how fast this happens, or if it's a problem in a specific application.  And of course, you're contaminating your stainless steel, which reduces corrosion resistance of it.

RE: Weld compatibility between Stainless and A36 steels

Normally one would use 309 SS electrodes for a dissimilar (CS/SS) weld.  To overcome a potential field welding problem would be to Shop weld a CS tab/tabs to the hood with 309 SS and then use the E70 electrodes to field weld it to the support.  

You can get by with using E70 but there will be a time it will give you trouble.   

Comeback with more information as to alloy used for the hood and the configuration of support connection.

RE: Weld compatibility between Stainless and A36 steels

(OP)
To unclesyd, Stainless Steel series 430 and 18 guage thick, is being used for the two hoods.  Also what do the initials CS stand for? and give me an idea how strong these tabs are (i.e.,how much weight can these tabs support).  I had initially intended for  the welder to apply continuous fillet welds between the A36 structural angle frame and the hoods but now you have brought up the idea of using these tabs and I am curious.

RE: Weld compatibility between Stainless and A36 steels

Have you fabricated these hoods yet?  

In my opinion 430 SS isn't the best material for this application.  Normally if you weld 430 SS it will require an anneal procedure after welding.  Also 430 SS isn't very corrosion resistant, it gets an oxide quite similar to rust.
 

RE: Weld compatibility between Stainless and A36 steels

(OP)
No,the hoods have not yet been fabricated, however, I have nothing to do their fabrication.  My responsibility is to design a vertical frame system from which will be hanging a horizontal frame welded to the top of the hoods. This entire framework is to support the entire weights of the hoods, inlet and outlet ducts, blowers, fire extinguishing system. There will be lateral forces and since the two hoods would bear such forces , I decided instead to have this horizontal frame bear the brunt of such forces.

RE: Weld compatibility between Stainless and A36 steels

Can you bolt some stainless tabs onto the horizontal frame then weld the tabs to hood?

Barry1961

RE: Weld compatibility between Stainless and A36 steels

(OP)
I will discuss your recommendation with the steel frame fabricator Barry1961.

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