welding stainless

Got a little job to weld some bolts to a clamp rail for a stepside truck bed . Shop is supplying the materials including the machine , SS wire , and C25 shield gas . Alloys are unknown ... I'm mostly wondering if the C25 is going to be a problem . These are being welded to the underside , so weld appearance is not critical . Top surface will be repolished after welding , do we need to passivate first ? This is for a friend who runs a car resto business , his guys have been dancing around this project for a while now .

Reply to
Terry Coombs
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C25 will be a problem. You need to use pure argon. Make sure that none of the SS is 303. Eric

Reply to
etpm

Added carbon ? This might be the only option we have , unless I use my MIG with flux core mild steel . He's planning on me using his equipment . Maybe this is why his guys have been avoiding this project .

Reply to
Terry Coombs

Carbon is problematic in stainless steel welds whether added by a gas mix containing CO2 or already there from using unknown alloys which are unlikely to be low carbon. Unless you use all low carbon materials and add no additional carbon, stainless steel weldments need to be solution annealed after welding in order not to be sensitive to intergranular corrosion, which is particularly bad in the presence of chlorides (road salt). The job as you stated it is a recipe for future failure of the weld or adjacent HAZ. Becoming familiar with the details of corrosion sensitization of stainless steel is a really good idea for anyone considering welding stainless.

Reply to
Glen Walpert

I told him there's more to it than just spool up a roll of SS wire and weld away ... I'll explain what the potential problems are , how we can control them , and let him decide . It may be that he does have some argon . Most of the work they do there is for "toys" , I doubt this truck will see road salt . Whether it will or not , this should be done right .

Reply to
Terry Coombs

Do not forget that stainless deforms due to heat. Weld with that in mind.

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Reply to
Ignoramus26586

C25 gas is OK, but it will leave a heavy grey oxide layer. In industry we run tri-mix gasses for stainless. Argon-CO2-Helium, or Argon-CO2-Oxygen. You can rent a cylinder from your gas supplier.

You will have to increase your voltage, compared to steel, because the stainless wire is a terrible conductor of weld current.

Reply to
Ernie Leimkuhler

My thanks to all who responded . I did a little web searching , and as you say , this one should be OK done with 75/25 . It's a relatively low-stress application , the truck is going to be a show-toy , and it's gotta get done today . One thing I did see , I only get one pass . Probably because of that oxide layer . Upping my amps , I'd probably not have caught that one until I buggered up a weld ... y'all wish me luck !

Reply to
Terry Coombs

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