pipeweld porosity

By Blacksmith Date 01-10-2007 14:08

I recently had a problem tig welding schedule 80 black pipe to forged fittings. This is 3/4 pipe for 10 psi propane. Anyway I was just getting random porosity, It did not seem to matter how well i prepped. Almost seemed like just heating the steel brought gas up. I looked on the web to see if others had this problem and found a site that I have since lost that suggested using a cover pass with 7014. Anycomments and sugggestions? Oh yes tried grinding out the pockets and rewelding (tig) with the same results.

By MDG Custom Weld (***)

Date 01-10-2007 14:15

I had a similar problem with forged fittings. The end result was the density of the forgings was low and they were saturated with oils. The carbon content was also very high. We baked the fittings at 400f for an hour (or longer depending on size) to "cook out" the tramp oils. Once we did that, they welded fine. If you are preheating the fittings and they smoke much more than you would normally see, they have something in them that's causing the porosity.

By jwright650 (*****)

Date 01-10-2007 14:18

I'm probably mentioning some things that you already know, but here goes anyway....random problems are tough to find sometimes....

check the sheilding gas lines/fittings for leaks, including the torch?

check gas flow pressures?... too low not enough coverage or too high causing turbulance

contamination on materials, oil, paint, coatings..be sure the material prep equipment hasn't been used on something greasy ot has paint lodged in the grit on the grinding disc...ect...?

contamination of filler?

shielding gas itself?