Q: I need advice on doing a weld procedure for A335 P1 stainless steel to 2205 duplex stainless steel. This is strictly for external fillet welds. Composition is not important, only mechanicals. The preferred processes are stick electrode and gas metal arc welding.

A: The materials you have specified, A335 P1 is essentially mild steel with nominally 0.50 percent molybdenum and the duplex stainless steel, 2205, is a 22 percent chromium, 5 percent nickel, 3.0 percent molybdenum with controlled additions of nitrogen.

An electrode that should work well is ER309/ER309L filler that is available in stick electrode and wire forms.

This recommendation is based on the assumption that there will be a total of 30 percent dilution from the parent materials, 15 percent from A335 P1 and the 2205.

The estimated chromium equivalent is 20.7 percent and the nickel equivalent is 12.5 percent based on the WRC1992 diagram, and should produce an estimated 12 to 15 ferrite number in the weld metal.

All of this indicates that the 309L filler should produce a weld containing adequate ferrite to avoid centerline cracking and to remain austenitic, which will produce good toughness.

Estimating mechanicals is difficult but, based on the estimated weld composition, the weld should be in the 85Ksi range for ultimate tensile strength and 35Ksi for yield strength.

Given the estimated mechanicals of the weld, the resultant strength should be equal to or should exceed the A335 P1 material which is listed as 55 Ksi minimum for ultimate tensile strength and 30 Ksi minimum yield strength.

Q: We are trying to weld SAE 12L14 hexagon rod to a threaded rod that is an ASTM A193 B7 steel rod. We are experiencing failures in which the hexagon rod is breaking off.

We are using GTAW (TiG) welding, and have tried a couple different fillers with no improvement. Can you make a recommendation?

A: The cracking you are experiencing is predictable and should be expected. The SAE 12L14 hexagon rod has a composition as follows:

Carbon (C)	0.15 percent (maximum).
Manganese (Mn)	0.85 percent to 1.15 percent.
Phosphorus (P)	0.04 percent to 0.09 percent.
Sulfur (S)	0.26 percent to 0.35 percent.
Lead (Pb)	0.15 percent to 0.35 percent.

The SAE 12L14 material by itself is un-weldable based on the levels of both sulfur and lead. Both of these elements produce low melting point materials that will be forced to the center of the weld during solidification to create a hot cracking situation.

The actual cracking may change location based on relative thicknesses of the parts and the joint design, but will most certainly occur.

The ASTM A193 B7 rod essentially is equivalent to an SAE 4140. It is hardenable and prone to heat affected zone cracking, which is likely to occur next to the toe of the weld along the fusion line, if proper procedures are not followed.

Essentially, you have two components, one that is un-weldable and the other that requires care to prevent cracking. The result is that you are getting cracking.

My recommendation would be to consider alternate materials, at least replace the SAE 12L14 if you want to stay with a process such as GTAW or consider brazing as an alternative joining process.

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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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