Question: I need to weld a stainless steel grade 904L, 1.5-in. schedule-10 pipe to an SA-105 coupling. I am considering using ER385 filler. Is this the best TIG filler metal for this dissimilar material combination?

Answer: For most applications, ER385 can be used as long as the welder avoids high dilution, especially in GTA root pass. A tight root in this situation often results in a root pass that is over 80% dilution, and this may be brittle due to martensite formation in the root. To cope with this situation, open the root to create a gap of 0.12 to 0.16 inches to force the welding machine to use more filler metal.

Question: I have an older anvil dented through years of abuse and would like to repair the face and edges. What electrode and preheat will I need to do the job?

Answer: The first step is to identify the material you are dealing with — cast iron or cast steel. The next step is the cleaning and preparation (crack removal) of the surfaces to be repaired.

Once the material is prepared, preheat to 400° F for cast steel, or to 450° F for cast iron. These temperatures should be maintained during welding.

If the material is cast iron, put a butter layer of a high nickel electrode — 99% nickel is preferred. If the material is cast steel, this step can be bypassed.

The butter layer is followed by a build-up layer of high manganese-chromium filler material to produce an austenitic manganese deposit with good work-hardening characteristics. Lincoln Wearshield 15CrMn will work, as will similar filler materials produced by other manufacturers.

At this point, the weld should be slow-cooled, peened and dressed. Peening this filler material will work-harden the material, increase the surface hardness and yield a good surface that resists rounding-over or "mushrooming" during use.

Some articles recommend putting a harder, martensitic material over the austenitic manganese buildup to increase resistance to wear. This is an optional step and should be limited to a maximum of one or two passes. Two web sites that contain fairly detailed repair instructions are: www.metalsmith.org/pub/mtlsmith/V23.1/anvil-r.htm and www.metalwebnews.com/howto/anvil1/anvil2.html.

Question: I have heard the term "phase lock" used while troubleshooting a welding machine. What does the term mean?

Answer: The term Phase-Locked Loop (PLL), is a control algorithm traditionally used in radio receiver/ transmission equipment for signal synchronization. I have seen the term associated with ultrasonic welding and inspection systems as well as signal-based systems. This control scheme is a circuit that controls an oscillator to maintain a constant phase angle relative to a reference signal.

"Phase lock" is not a term I have run across associated with conventional welding machines used for SMAW, GTAW, SAW, FCAW or GMAW. If associated with conventional welding equipment, there may be confusion with the closed-loop control commonly used in these machines. This control compares the actual value or output from a welding machine to a preset or desired value and makes changes in the control circuit to minimize the error or difference.