WPS Qualification

By vicmag Date 05-25-2017 21:22

Hi everyone,

I have a couple of cuestions. I work as a Design Engineer. Currently we are mostly working with A36 steel as base metal and we use an ER70S-6 electrode, with GMAW process and 100% CO2 as shielding gas. We have qualified WPS for all the joints that we need with those two materials (A36 and ER70S-6).
For a new prototype we're working on, we want to test a new high streng steel (yield strength: 700 MPa and ultimate tensile: 1000 MPa). We ran a CAE analysis on our model and we found out that our structure will be working around 500-550 MPa. So we decided to test a new electrode (ER80S-D2). We chose this one because according to AWS A5.28, with that electrode, we won't have to change the shielding gas.
We have a CWI in our Quality Department, and he told us that he wont be able to qualify new WPS' if the ultimate tensile strength of the new steel (1000 MPa, around 145 ksi) is greater than the electrode's (in this case ER80S-D2).
We don't wan't to make the process more expensive and we think that this electrode would be more than enough.
I couldn't find anything that states that the strength of the electrode must be greater than the steel to validate a WPS.
Is this statement true??
Whether this is true or not, in what code can I find this information??

Appreciate your time.

Cheers!

By 803056

Date 05-26-2017 03:23

Are you working to a specific welding standard, i.e. AWS D1.1, ASME, API, etc.?

If D1.1:2015 is the governing standard, table 2.3 addresses the allowable stress for different load conditions and whether a matching filler metal must be used.

Al

By pipewelder_1999 (****)

Date 05-26-2017 11:40

There are statements in codes indicating that the tensile tests used when qualifying a procedure should fail in the base metal or at a specific load. Your inspector may have that in his/her mind as prohibiting the use of lower strength filler metals.

Those statements usually allow for failures in the weld metal when lower strength filler metals are used provided the filler metal requirements were met.

Without knowing the code, there is nothing I can refer you to.

If you find the code that applies. Look under the applicable section for qualification for procedures. The required tests (Tensiles, Bends etc...) will be referenced and should point you to the acceptance criteria.

Additionally, there may be statements in design portions of the codes allowing use of lower strength filler metals (A common practice).

In some cases there are even advantages to using the lower strength filler metals.

By welderbrent (*****)

Date 05-26-2017 13:50

You have not really given us the amount nor kind of information we need to give you guidance to answer your final question: "in what code can I find this information?" Not a clue.

It is dependent upon the use of your product (will mean the difference between D1.1 and D14 or others), the Engineers General Notes and Contract Documents that general state what the applicable working code is for Procedures, Qualification, Fabrication, and Inspection, what the thickness of your materials is (will mean the difference between D1.1 or D1.3 or others) and so much more.

I am guessing you are using GMAW to either Short Circuiting or Globular since you are using CO2 and have a qualified WPS (so, a PQR?).

As such, with a change in electrode class and increased material strength, you may not be able to stay with the CO2.

Meantime, the upgrade to a material with a 145ksi puts it way out of the class for being within the scope of D1.1.

Not sure what your CWI is trying to apply, you can use any electrode you want and have it tested. It only needs to meet either the customer strength and testing requirements or your company requirements established for your product. Unless you definitely fit under a specific code, as in the case of D1.1 for Pre-Qualified WPS's, then you would need to meet all of the Clause 3 requirements which you probably won't with the suspected welding parameters you are using.

But, Clause 4 of D1.1 is there to allow use of ALMOST anything you choose. It just has to pass the prescribed tests and be accepted by the engineer of the customer or for your product.

He Is In Control, Have a Great Day, Brent