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Aluminum Workshop: Acceptable tensile sample failure

Q: We are fabricating components from ½-in.-thick 5083-H131 armor plate using robotic GMAW and 5183 filler metal. The tensile samples are failing at 41 KSI during welding procedure qualification. My customer says this is unacceptable and that the tensile samples should fail at 46 KSI or higher. What am I doing wrong?

A: You aren’t doing anything wrong. The 41-KSI value you are seeing is normal and acceptable. Your customer has fallen into a classic trap. He thinks that because the 5083-H131 plate has a tensile strength of 46 KSI, the weld should too. Unfortunately, this isn’t the way it works. All of the 5XXX alloys, including 5083, are not heat-treatable. They can be hardened by cold work. The H131 temper is a cold-worked temper. In this case, cold working has raised the tensile strength of the 5083 from the 40 KSI of the annealed material to 46 KSI.

However, during welding, the heat-affected zones (HAZs) are annealed back to the O temper state. This is true for all 5XXX alloys. There is nothing that can be done to get the HAZs back up to the cold-worked temper. No matter what temper you start with, you end up with annealed O temper in the HAZs.

Your customer is demanding that the weld test out to the 46 KSI of the parent plate. It can’t be done. If you look up the mechanical properties of 5083-O, you will find that a minimum tensile strength of 40 KSI is required. This is what you are seeing, and it is perfectly acceptable.

All of the welding fabrication codes that I am familiar with (AWS D1.2, ASME, etc.) acknowledge this. I encourage you to look at Table 3.2 of AWS D1.2-2003. You will find that, depending on product form, the minimum tensile strength for 5083 welds is 38 to 40 KSI. For plate of all thicknesses, it is 40 KSI.

About the Author
Aluminum Consulting Inc.

Frank Armao

President

Aluminum Consulting Inc.

440-479-0239

Frank Armao was an active member of the AWS D1 Committee, chairman of the AWS D1 Aluminum Subcommittee, and member of the Aluminum Association Committee on Welding and Joining. He also was the author of The WELDER's "Aluminum Workshop" column from 2001 to 2020.