welding 316S to 317L compatible?

[alyeska]

Is there any problem welding 317L to 316S? This is for a 95,000 gallon fish oil tank where we are trying to use both grades of material, and I am concerned about the compatibility, as the consequences of an oil spill of this size are substantial (I am on the coastline of the Bering Sea) Thank you for any and all input.

 

[Metalguy]

I'm sure McGuire will be along here soon, but what are you planning to use for the filler metal?

 

[Rich2001]

The Type 317L Stainless is Molydbenum-bearing austentic steel with an increase amount of nickel. (Generally improved corrosion resistance.)

As per welding 317L to 316 using 317L /ER317L filler the formation of intergranualar carbides is likely to occur. Therefore a soluntion anneal is required after welding to restores its' intergranular corrosion resistance. A typical solution anneal would be 1900/2100F (1040/1150C) for one hour thickness followed by a rapid quench (water quench if possible).

To possible eliminate the solution anneal, you might want to use a stabilized grade 347 (stabilized w/ Columbium) or 321 (stabilzed w/ titanium) to avoid carbide precipitation. Basically , these elements titanium and Columbium have a preferentially ties up the carbon so that chromium carbides are not formed.

 

[GRoberts]

Obviously, solution annealing a 95,000 gallon tank is out of the question. I am wondering, is the stainless steel for the fish oil, or the salt from being near the ocean? If intergranular corrosion is a concern, the easiest thing to do would be to switch to 316L material. If you cannot accept the strength reduction, specify a dual certified material (316 & 316L) so you will have the strength and low carbon. Metallurgically though, there is no problem with welding the two materials together. You could use either the 316 or 317 filler metal.

 

[stanweld]

The 317L is more resistant to pitting corrosion in Chloride environments than the 316. Is the tank currently 316 SS? Why are you mixing the 2 alloys?

The two materials are readily weldable but sensitization of the 316 is inevitable, although there are techniques to mitigate sensitization.