American Welding Society Forum
Posted this question on the Miller board, the guys there suggested I ask here.
"Mig or Tig, which is stronger?
I'm looking for hard facts, not opinions about what type of welding is stronger and/or better. Mig or Tig. Engineering data would be fine, but some sort of tangible evidence is what I'm looking for. Material would be either M.S. or S.S. approx. 1/8 thick."
If anybody can provide some cold hard facts, that would be great.
Hello Masta: Recently here on the Forum this question was posed. Do a search and look at the results. A whole lot of people responded.
For 1/8 inch mild steel or stainless steel I would consider the tensile strength of the filler metal and base metal and apply it to the process of choice. This is a case of 6 or 1/2 dozen.
Regards, Donnie Mann
Neither is stronger. Both use EXACTLY the same wire in many cases.
Each process has advantages and disadvantages.
For GTAW welding 304 SS the wire often used is ER308L, for GMAW the wire is ER308L.
The deposited weld metal strengths are the same. When properly applied both processes make sound welds.
Here is a response to this question I have already made. http://www.weldinginspectionsvcs.com/processopinions.htm . I think it was on this forum.
Have a nice day
I would have to agree with Gerald and Donnie, there are advantages and disadvantages to each process. The choice of filler material and joint design have more to do with the strength, of the joint, than the process. The same goes for inspection methods, they each have a niche' that they fit into.
I second the opinions of Gerald, Donnie, and John. The process is not the determining factor for defining the strength of the weld metal, which is what I assume you mean when you say, “Which is stronger”. Factors that affect weld metal mechanical properties (i.e., Tensile strength, Yield strength, and CVN data) are filler metal type, welding parameters, joint design for butt welds, and the effective throat size of a fillet weld. In the case of the filler metal, strength is going to be either the tensile strength of the wire or the yield strength. When working with ASME or AWS it will be tensile strength, work for the Navy is usually based on yield strength of the filler metal. If you need facts or proof of this, many welding books detail this. Some that come to mind are the welding handbooks, and ASM Handbook Vol. 6. In most of these books you will find that fillet welds and butt welds have there own calculations for determining allowable stress on a weld but each calculation will use the weld metal tensile strength in some fashion or another.
In some cases, I have seen where the process may affect CVN data but this is between FCAW and the GMAW process. However, I do not believe that it is a processes issue more than a filler metal issue.
Through my growing up years I have heard acetaline torch welds are superior on steel becouse the heat afected zone is heated and cooled much slower.Is there any merit to that?I posed this on the same post in the Miller board.Note;when I heard this no one was migging or tigging,stick was it.
Actually, I believe that the opposite is true. Since the welding travel speed is low, the process produces slower rates of heating and the total heat input per unit length will be high. This combination will produce a very large HAZ and produce more distortion, but more importantly, it will produce a slower cooling rate. The slower cooling rate will produce a larger grain structure in the solidified weld metal, which will actually lower the strength of the weld metal. This will also reduce the Yield strength – UTS ratio.
With the arc welding processes, SMAW, GMAW, GTAW the weld metal grain structures tend to be finer which produces higher Yield strength – UTS ratio and therefore a higher strength weld metal when compared to OAW. This is because the arc welding processes tend to produce rapid heating and therefore higher cooling rates.
Hi M Squared!
I agree with you, but what about the 'annealing' effects of oxy-fuel welding on ferric steels?
Let me start by admitting that my information was unreliable at best.Its interesting what you say about the grain size.What I was led to believe is that the gain gets scrambled when hot and stays that way when cooled rapidly,where as slow cooling allows the grain to straiten out.
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