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View Full Version : What is the proper way to weld on the High Strength Alloy Steel (HSLA) C4 K member ?



55 Rescue Dog
03-10-2016, 03:28 PM
I was wondering, what is the proper procedure for MIG welding mild steel, to HSLA steel {dissimilar metals), like the C4 K member is made of? To prevent cracking, is it necessary to pre-heat the heat affected zone, before welding, and cool at a certain rate? And, how do you accomplish that?

Rick_L
03-10-2016, 04:04 PM
I know Chevynut welds on them. Seems like I saw where Newman wouldn't, or avoided certain areas.

I don't know what alloy they use. I have used HSLA alloys in my work. There are some precautions, and choice of filler wire is critical if you think you need weld strength as high as the parent alloy. Usually the use of a lower strength wire such as ER70S6 or ER70S2 is just fine.

Preheating or slow cooling is usually only necessary with thick sections which we don't have here.

The other thing is if you're welding HSLA to mild steel, the joint can only be as strong as mild steel anyway.

This parallels what most do with chrome moly alloys. You weld them with lower strength filler and get a more ductile joint. You rely on joint design and weld area to get a strong weld joint - not just strong weld material.

I'm sure Chevynut will voice an opinion, but I expect he'll agree in general.

NickP
03-10-2016, 08:37 PM
With the three that I have either used, modified or otherwise, were TIG welded rather than MIG. No issues as of yet. Clean the metal regardless completely. There is an e-coating of sorts and regardless of the welding process used, it needs to be spotless. If you have a local source that can hot tank it, even better. That will remove all of the grease and oil residue trapped inside that will play havoc with any weld process.