Welding 17-4PH to 304L

admin

We have some parts we call "piggyback tiles" which consist of a small precision cast 17-4PH "holder" with a tungsten carbide wear plate soldered onto it.  These piggyback tile assemblies are then welded onto 304L auger flighting to form a hard face to push material.  Our current spec developed several years ago calls for 1/16" GTAW ER630 filler material to be used.  Electrical specs are straight DC 130-150 Amps @ 18-20 Volts.We are getting unacceptable breakage on the T/C that is soldered onto the 17-4PH holder.  We believe there is too much heat being added during the welding of the tile assemblies onto the 304L blades.  The breakage is occuring during cool down and it is usually tiles adjacent to the weld that break, not the one that is being welded.  Do you have any advice?
Reply:The Problem is there are different thermal expansions between the SS, the solder and the T/C. If you could find away to use a heat sink to remove the heat. I would say cool the part after welding an inch of weld, but then you could form a brittle Martinsitic structure in your PH SS. So the best thing you could do is solder the T/C after the Gtaw welding operation, or find a way to use a heat sink. Those are you best bets.
Reply:When welding difficult stainless parts we had some luck wrapping them in asbestos blankets to let the piece slow cool.