Welding disimilar SS

By sp09206 Date 09-26-2002 15:28

Can anyone tell me what the affect of welding disimilar stainless steels.
we are welding a small device made up from 301,304 and some 302. The welding process is tig (no filler metal) the joint is a internal butt weld.
The components are stacked together and staked into place, we then weld over the stake portion in a circle approx. 3/16 inch in diameter.
The stake of components are of (4) four different pieces the thinnest being .004 thick and the thickest is .030, the rest range from .015 to .010.
Does the use of different stainless steels have a affect on the melted metal joining, defects or does one harm the other.
We are inprocess of changing some to 304L for consistent weld blend and reduction of potential problems.
The weld must be leak free and withstand many cycles 300,000 to be exact.
Any help would be greatly appreciated, bet you would like to see this one.

Thanks
sp09206

By RBeldyk (**)

Date 09-26-2002 16:36

Alloy C Mn P S Si Cr Ni Mo Others
301 0.15 2.00 0.045 0.030 1.00 17.00 7.00 - -
302 0.15 2.00 0.045 0.030 1.00 18.00 9.00 - -
304 0.08 2.00 0.045 0.030 1.00 19.00 9.25 - -

As you will notice in the above the nominal chemical composition of these stainless steels are very simillar with a slight difference in Carbon. The differences in the Ni & Cr are really no existence, the difference are within normal tolerenace range of these elements.

These are typical 18-8 SS I would not expect any problems different then welding each individualy.

>The weld must be leak free and withstand many cycles 300,000 to be exact.

Determine what the Max and Min stress levels and use a goodman or S-N diagram to determine failure limits.

By Niekie3 (***)

Date 10-01-2002 20:19

Would agree with other respondent that welding will not be a major problem because they have very simmilar compositions. You must however remember that the non "L" grades will have a tendency to sensitize during welding. This will impede their corrosion resistance.

Usually it is also not a good idea to weld these materials autogenously. Usually a slightly over alloyed filler is used. This is however very much a factor of your component geometry and end use requirements of your weldment.

By steveho (*)

Date 10-01-2002 20:59

Why aren't they simply brazing it ?