American Welding Society Forum
Any reference information on how much of a reduction in mechanical properties a weldment of 6061 in the T 6 condition would experience? This is a multi pass Mig application with Post Weld Heat Treat is not an option.
Specifically any data on the drop in HAZ yield point or any other information that provides an accurate correlation between hardness and yield (NOT TENSILE) strength for 6061 T6 material. If I can avoid approximations and guesstiments I will.
The question arises from the fact that welding on 6061 T6 results in softening of the base material, so how much does it degrade the base metal? How do you quantify this?
Any thoughts, personal convictions or opinions?
I think that you may have a hard time finding yield strength correlations for the HAZ vs original tensile strength. This is because there is no way to get a homogenious tensile sample made entierely of HAZ material with normal welding practice. A heterogenious sample for tensile testing (such as a transverse tensile) does not give relavent yield strength information. A tensile test made up of different strenght metals will break in the lowest strength area, but the values will typically be higher than if a homogeneous sample of the lowest strenght area was tested by itself. Fortunaltely, this is what happens in real life too, so the tests themseves are not invalid. The only way to get a sample of HAZ for yield strength testing (that I know about) would be to simulate the heat cycles on a gleeble machine. There may be research out there on this, but again, it does not represent real life situations, as any actual HAZ will always be surrounded by stronger weld metal and base metal. (assuming correct filler use). So HAZ data by itself may be of limited real world use??
A gleeble !
What a great idea.
I had the chance to play with one in university, now the only problem is that I do not have access to one in the " real world" :(
If you need this info bad enough to pay for it, I'm sure there are labs and universities around that would have the equipment. I would try EWI, Ohio State, Lehigh, and LeTourneau U (Longview Tx) for starters.
EWI Lab Services Group may be the best/easiest source for Geeble testing: http://www.ewi.org/labservices/standard.asp ...this link shows their Geeble capabilities. Universities tend to be a little harder to get use of their facilities.
What is a gleeble machine?
A gleeble is a machine that controls heating rates to produce simulated heat affected zones. It can precisely raise the temperature in a sample bar and thus allow for evaluation of phases or constitutes that develop in a specific temperature band.
Thanks for the info.
I have some data from an old publication that gives "Summary of data obtained in dissimilar alloy program from MIG weldments made at the department of metallurgical research, Kaiser Aluminum & Chemical Corporation".
This tabulates values of what the strengths of different alloy weld combinations are following welding, and in particular lists the "efficiency". In other words, the strength after welding compared with the strength before welding.
These values are however for a very particular welding set-up used during their testing. The values obtained will vary quite widely, depending on the heat input, as this will have an effect on the HAZ width, which has a bearing on the strength.
For 6061 - 6061 using a 4043 filler, the "efficiency" was 67%.
This sounds about right, based on a theoretical assessment, because one could expect that somewhere in the HAZ you would end up with a typically T4 heat treatment. Typically a T4 heat treatment would give you about 50% of the strength of a T6 heat treatment. If the HAZ is narrow, then 67% sound about right. If you were TIG welding this, you would probably end up closer to the 50%.
If you would like the full table, let me know and I can try to scan it in and e-mail it to you.
Alcotec has the best aluminum info I've found. I believe you will find what you're looking for there. Good luck, Scott.
I was just reading a WJ article "Determination of Mechanical and Fracture Properties of Laser Beam Welded Steel Joints" for the CTOD information, but it talks about flat microtensile specimens that were originally developed for property determination of HAZ for conventional multipass weld joints. The paper describes it a little bit, but the reference it gives for this is in German, so I have no idea what it is.
I can't answer your question specifically, but I can offer this. Control your interpass temp (not to exceed 250F). We went through a lot of research prior to qualifying GMAW on 6061-T6. Excessive interpass will definitely cause the tensile test to fail (out of spec low).
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