weld repair chaplet in cast iron/ductile iron

[Tmoose]

we are having some big castings made in ductile iron. To support some large internal cores the foundry prefers to use steel "chaplets" that pass thru the casting wall and protrude to the inside and outside. The chaplets are ground off and weld repairs are made. Welding this material has sometimes proven difficult without cracking, and even when the welds are sound the effect on metallurgy is always suspect. The operating stress is completley unknown, so objecting to welding on that level lacks teeth (as does NOT objecting).

Is there some other method of core support?

 

[btrueblood]

Well...why weld repair, is the surface after grinding that ugly (would a more careful hand on the grinder eliminate the "problem")? Why do the chaplets have to protrude into the core and mold walls - can they not be engineered to have flat (or contoured) faying surfaces to bear directly on the surface of the core and mold? Is there concern that the chaplets will move due to molten metal flow, and could that be mitigated by a controlled, slower pour, or multiple gates/runners, or...?

Finally, there are some foundries that weld ductile iron on a regular basis (from what I have read this requires very close control over the DI chemistry) - you may want to find one and move your operation there for this part. We have a local foundry that welds their ductile iron on a regular basis, and with ordinary steel wire MIG...I tried to find out how they do it, but they keep their cards very close to their vests. If only they were small enough to do some of our more "special" designs.

 

[1gibson]

Peening while cooling can prevent the cracking, that's a nice trick to have up your sleeve.

 

[arunmrao]

Without knowing much about the core profile, I shall risk a few comments.Some of these, I am sure, you will have tried.

Is the core simply supported or cantilever type.
Can you make the core print deeper to anchor the core well.
Are reinforcement rods able to support the core.

Have you changed the core binder to obtain higher strengths and finally

Have you tried shaped graphite blocks as chaplets ?

I'm just one step away from being rich, all I need now is money.
( read somewhere on the internet)

 

[Tmoose]

thanks for the suggestions.

Dan T