The turbo I am using has a cast steel downpipe section which is a press fit in the turbine housing. There is a ring of sorts that holds it in place. In fabricating the rest of the downpipe I need to weld to this cast section. I tacked it in numerous locations around the circumference before running small beads 180* apart from each other. Well, after several beads I heard a crack and noticed a nice fault line had formed across approx. 1.5" of bead.
What's the correct procedure for welding exhaust tubing to cast steel?
Do I need to heat the cast first? I assume it's the temp. variations that are causing it to crack? Is the tubing cooling too quickly compared to the cast steel?
I don't want this bitch to crack apart when I install it and put it through a heat cycle or two.
Help!

 

im an illiterate ------.
lmao


yeah, weak penitration & bad prep. Yes, pre-heat it.

 

^-Cast steel my friend, probably to mild steel tubing.

Probably just not getting good enough penetration. Are you mig'ing or tig'ing? Probably has more to do with differences in wall thickness of the two pieces your welding (I'm guess the cast piece is quite a bit thicker, so it retains more heat).

*Disclaimer: I don't know ---- about welding.

 

I'll try heating it first. Actually it was prepped fairly well. I took a wire wheel to both pieces and then wiped them off with acetone.
I was using the second to highest amp output the welder has to offer. It's a Lincoln 135 and I'm sporting the fluxcore goodness. The cast piece is much thicker than the mild steel tubing. I didn't want to turn the amperage up all the way because I feel certain it will blow right through the tubing.

 

Push the weld from the cast into the tubing. This will keep from blowing out the mild steel and it will also help keep the cast hot.

 

Take every little advantage you can.
lmao!

 

last time i welded cast to mild, i started by cleaning the cast contact area with a grinder (better penetration than wire wheel prep), then fired up the oxy/acet and heated the ---- out of the cast. fit up the pieces and puddled the weld deep as i could on the cast and just "washed" the puddle up the edge of the mild piece. that was my root pass with 6011 or 13. let it cool a little so i didn't blow through and put a cover pass of 7018 on top. looked good and was strong but i was using stick weld. when i did it with flux core i turned up the amps and welded pretty much the same way except i didn't change spools of wire. never cracked but the welds looked like pigeon ----.

 

I suppose I'll grind, heat, and add some pidgeon ---- of my own
Thanks fellas!