Welding Tips and Tricks

Not weld porosity, but porosity in cheap stainless castings. The parts in question are for pumps and cannot leak, we pressure test them and sometimes find porosity, usually pinholes where water can seep through. My problem as the welder is how to weld over it. The second the metal turns molten the trapped water or casting sand expands and bubbles and pops through the weld and make it like swiss cheese and contaminates the tungsten. I can't grind all the way through the porosity because its either all the way through the part or sometimes I blow compressed air into it and it comes out on the inside of the part but 4 inches away around the corner, grinding the whole part in half to get to it isn't really a good idea. Is there another process I can use or something to get a weld cap over the opening so it just doesn't leak anymore?

Heat the area with oxy torch till dull red and let cool. Won't hurt it and it will drive the moisture sway. Then stick weld over it with 312 rods.

Coldman wrote:Heat the area with oxy torch till dull red and let cool. Won't hurt it and it will drive the moisture sway. Then stick weld over it with 312 rods.

Why 312? I don't have those.

By the way the castings are either 316L or CA6NM which I normally use 308L for.

Is 312 compatible with those?

You can use 316 for 316 castings and 308 for the other.
312 is an excellent rod for repairs and dissimilar metals. Very tolerant of difficult situations and super easy to run, flows like butter. Fully compatible for your materials. Expensive but worth it to have on hand. They can be bought in small quantities. You won't be disappointed. Can be bought in tig wire too, but I'm recommending the repair be done MMA (stick), say 3/32" rods. You have the issue of air contaminating the back of the tig weld through porosity, 312 stick will tolerate this situation better. I used to repair refrigeration valve castings that failed pressure test straight out of the foundry (back in the day when we still manufactured valves here in the backside of the world). All done with stick.

Coldman wrote:You can use 316 for 316 castings and 308 for the other.
312 is an excellent rod for repairs and dissimilar metals. Very tolerant of difficult situations and super easy to run, flows like butter. Fully compatible for your materials. Expensive but worth it to have on hand. They can be bought in small quantities. You won't be disappointed. Can be bought in tig wire too, but I'm recommending the repair be done MMA (stick), say 3/32" rods. You have the issue of air contaminating the back of the tig weld through porosity, 312 stick will tolerate this situation better. I used to repair refrigeration valve castings that failed pressure test straight out of the foundry (back in the day when we still manufactured valves here in the backside of the world). All done with stick.

Thanks, I'll order some and give it a try. In the mean time would 316L stick be better than trying to TIG?

Yes, certainly.

By the way don't just put a tack over a pin hole. Put a 1" long bead over it. If there are multiple pin holes close by, pad the area.

Coldman wrote:By the way don't just put a tack over a pin hole. Put a 1" long bead over it. If there are multiple pin holes close by, pad the area.

Thanks that is what I do, a bead with the hole in the middle where possible. I tried your advice today, dull red with a torch and used 316L stick electrode instead of TIG and it worked real nice. Thanks! Now if only I could figure out how to weld porosity in Bronze castings haha

Delasangre wrote:Now if only I could figure out how to weld porosity in Bronze castings haha

Well....

http://www.stratawelding.com/shop/Speci ... trode.html

http://www.gedikwelding.com/product/bronze-electrode

https://www.alcaminc.com/bronze-brass.html

http://www.stoodyind.com/Catalogs/FISC/ ... tpg353.pdf

I'd say there are some options

Bye, Arno.

Arno wrote:

Delasangre wrote:Now if only I could figure out how to weld porosity in Bronze castings haha

Well....

http://www.stratawelding.com/shop/Speci ... trode.html

http://www.gedikwelding.com/product/bronze-electrode

https://www.alcaminc.com/bronze-brass.html

http://www.stoodyind.com/Catalogs/FISC/ ... tpg353.pdf

I'd say there are some options

Bye, Arno.

I have bronze TIG wire and the previous welder before me said he could do it no problem, he showed me a pulse setting he liked and everything. I have never gotten it to work well if at all. Problem is the bronze with the porosity is I am usually welding on less than 1/8" thick wall of the parts and on top of that I have to grind out the porosity. I struggle to find the perfect sweet spot on AMPs too, if I set it too low it doesn't melt the base material, if I set too high it melts and falls through the other side. It feels like the sweet spot is like a 5 AMP zone somewhere above 200A on a 3/32 electrode.

On the one I tried and failed yesterday I ground away all visible porosity and struck the arc but it sputtered and spit like I forgot to turn on the gas which I didn't forget. There was nasty black and white residue on around the area, and the bronze I laid down had bubble and holes in it. It seemed like when I ground out the visible porosity the metal just a hairs distance further was like swiss cheese still.

Have another go with his settings but this time don't strike the arc on the casting. Lay your filler flat and melt it with the arc. There will be enough heat transferred to the casting for the filler to fuse. Keep the arc on the filler and walk over it.

If your using brazing rod with tig you don’t want to be melting the base metal. (Brazing doesn’t melt the base metal). If you do your welding then the benefits of the brazing rod become not a benefit.