Q: What shielded metal arc welding electrode should I use to weld ASTM A487 Grade 6 Class A material? Can you give any suggestions regarding precautions when welding this material?

A: The ASTM A487 is a broad class of steel castings intended for pressure service. Specifically, ASTM A487 Grade 6 Class A references a material that is a manganese-nickel-chromium-molybdenum alloyed steel casting that undergoes an austenitizing heat treatment followed by an air cool to 500 degrees F., then water quench, and tempering at 1,100 degrees F. The listed minimum tensile strength is 115 ksi, and the minimum yield strength is 80 ksi. The question does not indicate if this is a casting repair or a joining application involving other materials, therefore a definitive recommendation is not possible. However, if the application requires a matching strength weld you may consider either an E12018 or E11018.

Within the ASTM A487 specification, a minimum preheat and interpass temperature of 300 degrees F. is required, and may need to be increased in the presence of a highly restrained joint. The part should be post weld stress relieved at 1,100 degrees F. Good low hydrogen practice must be followed and should include but not be limited to the following practices:

1. Proper surface preparation to remove hydrocarbon producing materials along with millscale and other harbingers of hydrogen.
2. Proper filler metal storage and exposure.
3. Proper preheat/interpass control. Preheat may need to be adjusted based on restraint and actual chemistry.

Q: I am considering using a 0.045 in. ER70S-3 for a job that I am producing in accordance with AWS D1.5 Bridge Code, and need to make welds in the 3G position on 1-in.-thick plate. I want to use a welding procedure of 26 V and 280 amps. Will this wire be suitable for the welding application?

A: For welding in accordance with AWS D1.5 Bridge Code, you will have to use a vertical up progression for welds in the 3G position. Welding in this position and progression with the gas metal arc process is best done with either short circuit or pulsed arc transfer. Short circuit transfer is allowed only by the engineer of record within this code, so that leaves pulsed arc transfer as the only viable process to use.

The welding condition you reference in your question, 26 V and 280 amps, would produce either a globular transfer or spray transfer depending on the shielding gas used, and neither of these transfer processes would be useable for the 3G position with a vertical up progression as you have listed.

Typically, to a weld like this with GMAW-P would be performed with a 0.045 in. diameter wire, a shielding gas with greater than 82 percent argon balance CO2 (or 95 percent argon, balance O2), and a wire feed speed in the 100 ipm to 180 ipm range. The typical range for the average voltage would be 19 V to 23 V, DC (+), and the average current would be in the range of 120 amps to 160 amps.

As far as using an ER70S-3 filler metal, it is adequate from a mechanical standpoint as long as you are using steel that is appropriate for an E70 filler metal as listed in Table 4.1 of AWS D1.5.

Further, you may find that an all position flux cored wire, such as an ER71T-1, is a more efficient solution for your application. That which is what most bridge fabricators use today.

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.