Editor's Note: The first part of Barton's Q&A column is a response to a question Dave answered in May. We usually use such letters in a separate part of the magazine, but this response from Steve Sparkowich was so detailed that we decided use it in this month's column. Thanks, Steve!

Re. Welding zirconium in “Welding zirconium requires care and attention.” (Welding Magazine, May 2008, Page 30.) This is an area our company has experience in and I have several comments:

Ideally, dedicated austenitic stainless steel brushes, such as 304SS, will be used to prepare the area of the weld joint plus the region 1 in. to 2 in. around the weld. Any surfaces that will exceed 600 deg. F during the welding process should be brushed.

A final cleaning with pure acetone or electronic grade MEK is preferred immediately prior to welding.

Rather than using a pointed tip on the tungsten alloy electrode, the end should be blunted after grinding so that the sharp point does not break off into the weld metal.

UNS R60704 is no longer commercially produced, and obtaining ER Zr3 weld wire would be difficult today.

After completion of welding using the “dip & dab” technique, the wire should not be taken out from under the flowing torch gas until it cools below 600 deg. F to 700 deg. F. Otherwise, the end of the weld wire needs to be clipped off before re-use.

We recently published an extensive welding guide for TIG welding of zirconium that can be found at: www.wahchang.com/pages/products/data/pdf/DS_ZircadyneZrWelding_080121.pdf.

Also, we offer one-day and three-day titanium and zirconium GTAW welding seminars several times per year. Details on upcoming events can be found at: www.wahchang.com.

Steve Sparkowich, P.E., ATI Wah Chang — Technical Services, Albany, Ore.

Q: I am a contractor looking for recommendations on welding chrome moly SA335 P5 to SA335 P22 pipe. In my contract documents, the customer cites AWS D10.8 which I am not familiar with, can you help?

A: AWS D10.8 is titled “Recommended Practices for Welding of Chromium - Molybdenum Steel Piping and Tubing.” The current edition is dated 1996.

As the name implies this document furnishes recommendations related for welding these materials. In particular, the issue of welding dissimilar ferritic grades of materials is addressed.

The following are recommendations that you may find helpful:

1. To weld SA335 P5 to SA335 P22 pipe you should match the lower alloy of the two materials. In this case, the SA335 P22, which is nominally 2.25 percent chromium and 1 percent molybdenum, provides the basis for the consumable selection which would be E8018-B3L or E9018-B3.

2. Preheat shall be appropriate for the higher of the two alloys which is the SA335 P5. That means you need to have a minimum preheat and interpass temperature of 400 deg. F.

3. The issue of back purging depends on the corrosive service of the pipe. Purging is recommended for materials greater than 4 percent chromium, which is applicable in this case given the nominal 5 percent chromium in the SA335 P5 pipe.

4. Post weld heat treatment shall be appropriate for the higher of the two alloys being joined. In this case, the post weld heat treatment must to be appropriate for the SA335 P5 material; 1300 deg. F. to 1400 deg. F at 1 hr. per in. of thickness.

The time for post weld heat treatment may vary based on other applicable codes, particularly for materials exceeding 4 percent chromium which is applicable given the level of chromium in the SA335 P5 pipe. You should check other applicable codes — such as ASME B31.3 to see if it is applicable or if it is specified by contract documents — for further guidance.

Any time you are dealing with these types of alloys, diffusible hydrogen is critical, therefore strict low hydrogen practice shall be observed, which include but may not be limited to:

Clean base materials. No rust, oil, mill scale, dirt, grease or any other hydrocarbon producing materials shall be present.

Electrodes must be from new; hermetically sealed containers, or must have been properly stored and documented in an approved fashion to minimize the chance of hydrogen pickup.

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.

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