welding 4130 chrome molly to mild steel tubing 2

[ipcrus]

What steps do I take to weld 4130 c/m with a wall of .225 to
mild steel with a wall of .190 ? C/M starts out as .375 wall
turned down to .228 wall in 6" of a 24" tube with a.003 press
fit into a tube of mild steel with a ID of 2.700 Depth of fit
is 6 " . This will be TIG welded.... What filler rod would
work best... elongation...dilution.... etc...
Thanks for you help....

 

[weldtek]

As you probably know ER80S-D2 is commonly used for type 4130 material, and it should work for your dissimilar joint too, but, you could probably use ER70S-2. For the thicknesses you describe preheat probably isn't necessary, but, I'd suggest you warm it up to 200F and slow cool. You may wan't to post this question on the welding, or metallurgy forums.

 

[unclesyd]

I concur with Weldtek that either electrode will work. I would tend toward the ER70S-2 as this was the standard electrode we used for a very similar setup. One other thing not normally considered is complete the weld once started, not normally a problem

The slow cooling can be accomplished by quickly wrapping in a fiberglass blanket or if you have many to do rig up a box filled with Vermiculite or Pearlite to stick the weldment in after welding.

Note:
The old fashion way was to stick it in bucket of lime or wrap in Asbestos cloth.