Silver solder for SS wire?

[TomP]

Originally Posted by Douglas

Tom , that information you just described, tells me that you are knowledgable about ss and monel fabrication.

There is a piece of information on welding ss , that I hope you can clarify .

I have been told that when welding ss, some of the chromium and nickle are boiled away, from the molton puddle, vaporized as it were, and that changes the alloy balance percentage to somewhat less than the mil spec ,,,,, ie 18 - 8 , might be less, of a percentage, at the finished weld.

I have been also told that using a filler rod, higher in content (richer) of chrome and nickle, likely will replace that boiled away "lost" chrome and nickle , thus keeping the alloy percentages more near the mill spec.

Is there any truth to these ideas of enrichening a weld ?

Douglas

Douglas,

It is all about the filler that is used. Some filler rods can cover a wide range of specifications, while other are type specific. Generally speaking, one will want to use a filler rod that is exactly, or as close to, specification of the material being welded. Though this does not always hold completely true. Take 4130 tubing for example: With what I just said, one would think to grab a 4130 filler rod and go happily down the road...but this is not the case. Although there are several good filler materials, ER80S-D2, is one you should consider. This filler material is capable of producing welds that approximate the strength of 4130. ER-70S-2 is an acceptable alternative to ER80S-D2, as is ER70S-6, although the weld strength will be slightly lower.
Now, back to your original question of specification. Yes. The filler material, when diluted with the parent material, will typically undermatch the 4130. However, with the proper joint design (such as cluster or gusset, for example), the cross-sectional area and linear inches of weld can compensate for the reduced weld deposit strength.
There is a slight loss...but the bottom line is in the knowledge base and skill of the welder and the joint design.
Though stainless steel is far more forgiving than welding aluminum with it many different alloys, one still needs to determine the base metal alloy type and select the correct filler alloy.
I will refer you to the American Welding Society (AWS) AWS B2.1-BMG:2005 standard and qualifications for base metal grouping for further study.

Tom