Undermatching filler metal - AWS D1.1 and ASME IX

[warrior1987]

Hi Everybody,

I have a question regarding the use of undermatching filler metal in the qualification of welding procedures under AWS D1.1.

I understand that it is permissible to use undermatching filler metal if the engineer agrees to it or if it is acceptable for the application.

However, generally speaking, the requirement for the tensile test is that the ultimate tensile strength must exceed the minimum tensile strength of the base metal.

So, I don't understand how it is possible to use undermatching filler metal when, during the qualification of a welding procedure, the tensile test requirement might not pass.

For example, if you are welding a base metal with a tensile strength of 100 KSI using a filler metal with a tensile strength of 80 KSI, how does this meet the AWS D1.1 requirements? My question is about complete joint penetrations groove welds in tension aplicattions.

Is there any specific section in AWS D1.1 that explains this? M

In comparison, ASME Section IX QW-153 (Acceptance Criteria — Tension Tests) states:
“(c) the minimum specified tensile strength of the weld metal when the applicable Section provides for the use of weld metal having lower room temperature strength than the base metal.”

For me, it is clear that ASME permits the use of undermatching filler metal, but I'm not sure if AWS D1.1 does.

Thank you for your time!

 

[r6155]

You are confused.
In your example, the test must break greater than 80 ksi in the weld.
See QW-153.1 (c)

Regards)

 

[EdStainless]

And are you talking about specification minimum strength or actual strength?

 

[warrior1987]

Thank you for your response.

r6155, I undestand the stament i'm asme ix qw-153. But in AWS D1.1. for me it is no clear. But if you can use undermatching filler metal, what it is the acceptance criteria for tensile test?

EdStainless, Im talking about specification minimum strength.

 

[r6155]

AWS D1.1 is clear. See Table 4.3

Regards

 

[warrior1987]

Thanks, R6155,

Yes, but Table 4.3 does not allow undermatched filler metal for complete joint penetration groove welds in tension applications.

So, is it possible to use undermatched filler metal for these applications when your design allows design stresses below the minimum specified strength?

Suppose the design stress is 70 ksi, your filler metal has a minimum specified strength of 80 ksi, and the base metal has a minimum specified strength of 100 ksi.

In this case, I would qualify a WPS with undermatched filler metal. However, the tension test results will be less than the minimum specified strength of the base metal.

I couldn’t find anything in AWS D1.1 that permits this. I have the engineering team’s approval, and I believe it’s acceptable. However, I’m concerned that the auditor may not accept the qualification based on the tensile test results.

 

[r6155]

It seems to be a game with your "suppose".
I don't have any more time.

 

[warrior1987]

Ok, thank you for your time