Welder Qualification Test for Pulse-Mig

[weldtek]

Due to some non-fusion problems I've experienced with pulse mig, I'm contemplating implementing a 'special' qualification test for welders using that process. I'm thinking about a mockup to simulate a nozzle attachment weld where the welder would have to make a circular weld, as in production. If anyone has any ideas I'd appreciate your input.

 

[metengr]

weldtek;
I would agree with your suggestion; lack of fusion is problematic with GMAW and can only be dealt with by practice. Simulation of a production weld joint is an excellent approach.

 

[WPSGuy]

Weldtek the skill of welders now days, has gone way down. I agree. Give them a 6-G test and make them run the root up-hill.
Also I would check to make sure your welders are welding per the WPS parameters.

 

[gtaw]

As an outside inspector, I would ask to see the welding procedure specification and then verify the welders are working within the parameters. Once that has been verified and there was still an issue with incomplete fusion, I would look at training the welders.

I would also verify all the welders were using the same welding power supply, i.e. same model nummber, program number, and manufacturer. Every manufacturer has a different scheme of what makes a good pulsing unit. Every model of a pulse (from the same manufacture) also varies. The bottom line is you can't use a WPS intended to be used with Manufacturer A's model X, program V with Manufacturer B model Q, program V. They will be different and they will yield different results even if the meters on the power supply tell you they are the same.

The only way to truly monitor what the machine is doing (again we're talking about pulse GMAW) is to hook them up to an oscilloscopy and monitor the wave forms.



Best regards - Al

 

[pipewelder1999]

Wouldn't the below statement be a contractual requirement. The Boiler and Pressure code has not addressed some of these "requirements" as of yet that I am aware of. Though what you indicate is a good idea, it would be a problem to bind on a fabricator/contractor.

would also verify all the welders were using the same welding power supply, i.e. same model nummber, program number, and manufacturer. Every manufacturer has a different scheme of what makes a good pulsing unit. Every model of a pulse (from the same manufacture) also varies. The bottom line is you can't use a WPS intended to be used with Manufacturer A's model X, program V with Manufacturer B model Q, program V. They will be different and they will yield different results even if the meters on the power supply tell you they are the same.


Gerald Austin
Iuka, Mississippi

http://www.weldinginspectionsvcs.com

 

[gtaw]

I agree with you that some of the codes haven't addressed some of the variable I've listed. I don't believe all the code bodies have adequately addressed GMAW-P especially the new programmable inverter systems.

The older conventional power supplies were very rudimentary in their capabilities. They either pulsed at a rate of 60 or 120 pulses per second. The "welder" had to dial in parameters such as frequency, duration, peak and background amperage, etc. Pretty basic stuff that could be transferred from one machine to another, from one manufacturer to another.

That is not the case with the new programed inverter power supplies. With the meters supplied, the welder can not and does not know what the pulsing parameters are. The canned program for pulsing with model "A" is not the same as the canned program pulsing parameters supplied with the model "B" power supply. In some cases a program uses constant voltage and a different program from another manufacturer uses constant current.

The only way you will get consistent results is if the welders are using the similar parameters and the easiest way to achieve that is to have the welders use power supplies from the same manufacturer, the same model of power supply with the same "canned" program.

My comment; "I would also verify all the welders were using the same welding power supply, i.e. same model number, program number, and manufacturer" is not stating that it is a code requirement. I am saying that I would check those items to eliminate as many variables possible to simplify resolving the problems "Weldtek" is experiencing. If the machines are not the source of the problem, you can look at other varibles, such as welder skills or the adequacy of the WPS as sources of the problem.

If each welder is using a different power supply manufactured by different companies, the solution becomes more complex because "One WPS" doesn't fit all when it comes to using GMAW-P with programed parameters.

I've said it before and I'll say it again, it is easy to write a WPS that meets the "code", but is of little use to the welder. I try to keep in mind it is the welder that needs the WPS and I try to keep in mind what information is useful to the welder. The "code" lists the minimum requirements, the consultant's responsibility is to write a WPS that is usable (by the welder) and also meets the code requirements.

Best regards - Al

 

[pipewelder1999]

The synergenic machines that I have been involved with in the past were also difficult to even find out what parameters you were using.

The non-fusion that I observed was very similar to that resulting from GMAW short circuit. This was all on Nickel Alloys and it made me very un-trusting of the promise. Even among the same model machines similar settings resulted in very different characteristics. This may have been unique to that brand.

Heat input calculatiosn were also difficult.

Thanks for the feedback.

Gerald Austin
Iuka, Mississippi

http://www.weldinginspectionsvcs.com