Q: If a weld between two pieces of steel is deemed unacceptable, is it acceptable to grind both pieces of steel flush and reapply the weld? More to the point, is the base steel still good for welding after it already has been welded? This is assuming that temperatures of the steel have not exceeded normal temperatures during welding.

A: Generally, as long as this is a weldable grade of steel and has been properly welded but, due to an unforeseen circumstance, a defect was generated in the weld, the parent material should still be weldable.

The part’s fitness for service after the repair may be another issue that would require more detailed information. This may be covered more clearly in your contract documents or purchase agreement between you and your customer.

To do the repair, first the defect in the weld metal should be removed to sound material with an appropriate removal process. Acceptable processes for removal can range from air carbon arc gouging to grinding, as you have indicated. The part then should be re-welded with an appropriate process. Depending on the code you are welding in accord with, you may have to have a qualified welding procedure and personnel for the repair.

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

A: For most applications, ER385 can be used.

However, you should avoid high dilution, especially in a gas tungsten arc root pass.

If such a root pass is to be done, you should open the root so that there is a gap of 3 mm to 4 mm (0.118 in. to 0.157 in.), forcing the welder to use a lot of filler metal.

A tight root in this situation often results in a root pass that is more than 80 percent dilution, and this would be likely to be brittle due to martensite formation in the root.

Q: I want to know if you can weld the type of cast aluminum that most Asian automobile wheels are made from. I want to cut a lip off the edge of one rim, and weld it to another. Is this possible? And, if so, what do I need to do this?

A: You should give up on this one.

The wheel casting is heat treated to obtain higher strength and you have no way to do this.

That means your weld and its heat affected zone will be significantly weaker than the rest of the cast wheel, perhaps to the point of being dangerous. If I were you, I’d buy a new wheel.

Q: What would be the best electrode for welding AR400 under 1in."? It needs to be highly abrasive resistant.

A: Joining electrodes are seldom good for abrasion and for a good reason, they would crack.

For a situation in which you need to join AR400 to itself or to a mild steel support, a good, low hydrogen, 70 ksi material is appropriate.

After welding, the weld can be overlaid with a material that would be wear resistant and designed to resist the wear from the media in question.

Depending on the application, there are several different levels of chromium carbide materials that would yield dramatically improved wear life, and provide better wear life than the AR400 material.

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: askdave@penton.com