Please provide your recommendation on whether to use weld filler metal 16-8-2 or ER308H on stainless steel flue gas pipe made of ASTM A240-304H, and used in elevated temperature service to 1425 degrees F at 60 psig. Which weld filler metals have the demonstrated high temperature performance and creep resistance?
Both 16-8-2 and 308H have appropriate high temperature properties for 304H base metal. However the E308H-16 covered electrodes should be more available.

What SMAW and GTAW filler material is recommended for welding A335 P5? This is a P5B material but with 5 percent chromium and 0.5 percent molybdenum.
For welding SA335 P5 material you are correct. It is ASME P5B, and for SMAW is E8015-B6 or E8018-B6. For GTAW, the recommended electrode is ER80S-B6.

We are a steel-plate-tank building company that has just started building stainless steel tanks. We have been questioned by an inspector at our current jobsite as to whether or not we are allowed to use air carbon arc gouging for weld removal and back gouging stainless steel. This has always been standard practice for back gouging our steel tanks and we are looking for supporting information to support this practice with stainless steel. Can you help us with some documentation?
The Welding Handbook, Eighth Edition, Volume 4, Pages 325 to 326, discusses air carbon arc gouging of stainless. It indicates that, when properly done, air carbon arc gouging is an acceptable practice. However, if it is improperly done, air carbon arc gouging can leave a very thin layer of carburized material. If this occurs, the carburized material should be removed by grinding prior to welding.

I am working on different welding jobs at a large chemical plant. One job we are working on is replacing 6 in., schedule 120 Inconel pipe in a cracker unit. The engineer from the plant for which we are doing the welding is telling us to use plant nitrogen to purge the pipe. I disagreed with this practice, and informed them the best purge gas would be argon. We are Gas Tungsten Arc welding with an argon shielding gas on our rigs, using the appropriate Inconel filler metal. I need some help with welding procedures for this application because it does not seem to flow good with nitrogen purge gas, and generally does not look clean.
Using nitrogen as a purge gas for Inconel is a poor choice. The idea of using a purge gas is to provide an inert environment for both the base metal and the weld metal in the area of the weld. Nitrogen is not an inert gas with respect to Inconel materials. Commonly, there are elements such as niobium, titanium and aluminum that are part of the Inconel alloy system which are potent nitride formers. What you will see if you use nitrogen as your purge gas is a scaly, rough surface and difficulty with in wetting which is, by your description, what you are experiencing. Argon is the best purging gas for your Inconel application and will correct your problems.

I have a TIG welding machine, and I am going to weld a 304 stainless steel waste gate coupler to standard exhaust pipe. I have welded dissimilar metals to stainless steel before but never to an exhaust, any suggestions?
You do not reference what material you are using for the standard exhaust system. In either case, if the standard exhaust system you are welding the 304L stainless steel waste gate to is a mild steel or a 409 stainless, you can use either an ER309L or ER307 filler metal.

This column is sponsored by Penton and the Lincoln Electric Co., Cleveland. Dave Barton is a senior welding engineer in the Application Engineering Group of The Lincoln Electric Co. He oversees welding procedure development for both new technology and existing products, performs failure analyses for customers, and serves as a consultant on welding application problems. Barton has been with Lincoln Electric for 21 years. Send your questions for Mr. Barton in care of WDF by e-mail to: askdav@penton.com