Stainless Castings

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So, I've been doing some welding on stainless steel castings at my new job.  I'll start by saying the castings are from China to save me a lot of words.  Anyways, I'm welding plugs in them and I'm having problems with pores in the steel opening up along the edges of the weld.  After doing the weld, the weld doesn't leak, but everything else on the casting does.  This is TIG, argon, 2% thoriated, and so on...  Any pointers or just scrap the parts?  I think they're expensive.
Reply:So the piece itself is leaking from porosity in the casting?  If it needs to be waterproof, then i'd scrap it.  That sounds like it is no good.
Reply:It's part of an air valve, it just leaks air which isn't that big of a deal.
Reply:Not sure if it would help, but maybe try cooling the casting slower? It sounds as if it could be a rather dangerous situation, if after welding the casting is cracking, pressurized air can do a lot of damage.  60PSI will pot a a soda can through a wall! (thats 1/2" sheetrock, 1/2" plywood and 3/4" worth of ceder shingles, and yes I know this from first hand experience).
Reply:I'll start by saying the castings are from China to save me a lot of words
Reply:They make em out of old beer cans.David Real world weldin.  When I grow up I want to be a tig weldor.
Reply:Originally Posted by David RThey make em out of old beer cans.David
Reply:It's a new grade of SS...  LOL
Reply:Maybe he meant the big cans, you know, kegs.  As for a new grade, it's supposed to be 316L, but... you never know.
Reply:Originally Posted by Me!Not sure if it would help, but maybe try cooling the casting slower? It sounds as if it could be a rather dangerous situation, if after welding the casting is cracking, pressurized air can do a lot of damage.  60PSI will pot a a soda can through a wall! (thats 1/2" sheetrock, 1/2" plywood and 3/4" worth of ceder shingles, and yes I know this from first hand experience).
Reply:How big and what type of stainless are these castings? One thing I can think of that may help is if size and composition will permit is a preheat. Stainless has very low thermal conductivty and a high coeffecient of expansion. What this means is that there may be a lot of movement going on around the weld. Welds are always held in tension due to plastic deformation of the material from expansion during welding. As the weld cools it will contract and try to pull away from the base metal. If a preheat is used it may lower the difference in temperatures between the basemetal and weld metal enough that it may not stress the heat affected zone at the edges of the weld. If the casting is an austenitic stainless, a preheat of 200 degrees shouldn't hurt it. Contolling distortion through preheat is a common practice in industry. If the parts are just going to get scrapped anyway then it's worth a try.Last edited by reddoggoose; 08-15-2007 at 10:33 PM.Arguing with a Welding Engineer is like wrestling with a pig... after a while you realize the pig likes it
Reply:Just out of curiousity has any body pressure check any of these castings before welding. If that's possible. If there's a production problem there is nothing you could do to change it.
Reply:Don't you just hate days like that...lol. New job huh, hope this isn't an indicator of the way Puchasing works. Anyway, I've seen that junk and it's no fun. The casting had to be purchased within a certain set of specs. That stuff usually just barely meets the minimum spec. All you can do is try to get them to x-ray some of the bare castings before anyone works on them. If they don't meet the minimum then your company can go through the hassle of reinbursment for repairs required (charge-back). Odds are they do meet spec and you'll just have to work them until you get lucky and don't have a blow-back.Anything worth doing is worth doing RIGHT
Reply:Maybe also try an electrode with more ductility. I don't know what composition you are welding, but if possible an ER308LSi has an elongation of 42%.Arguing with a Welding Engineer is like wrestling with a pig... after a while you realize the pig likes it
Reply:If these castings are like the ones I've seen then what he has is a bunch of voids and pockets of sand and some gas. The Chinese seem to either have a hard time keeping the binder correct or just plain use junk binder. Seems that when the hot pour enters the sand mold the binder just doesn't hold the internal surfaces together as it's designed to do. What that does is send the mold sand and binder throughout the casting causing the afore mentioned problems. He probably also is finding head shatter in those areas as well. They must really sell this stuff on the cheap because it's unbelievable that the they can continue to sell the junk with the rework costs involved after shipping it over here.Anything worth doing is worth doing RIGHT