Getting proper heat tint with GMAW of Austenitic SS

By cdubbs714 Date 09-27-2017 19:20

Good Day everyone. I am working at a new company and my experience with GMAW SS is light. Our welders struggle to get a good appearance on their welds. We weld sheet metal, typically 7-10 gauge sheet. The welds usually have the darker gray "crust" on them...not quite sugared. I have one or two welders who can get it right and get good colors. However, I cannot get other welders to duplicate the results by replicating their settings.

I have inherited WPSs that use a tri-mix 90Ar7.5He2.5CO2. This is a high energy gas so I decided to bring in 98Ar/2CO2. The results were okay at best. Once we got good colors the toes were not wetted out and it looked "cold".

Considering our parts are short arc-on time parts and cleaning each joint is not feasible, what else is left to try? What should we be doing to get good color and avoiding the grayed out welds? Training is not being effective, as we are fighting decades of habits.

Any ideas????

By Maggs47 (**)

Date 09-27-2017 23:10

If training is not effective BECAUSE of decades of bad habits, job postings might get it done. If the people won't change, then change the people. That being said, first make sure you're not throwing good welders out because of a faulty process.

By fschweighardt (***)

Date 09-28-2017 12:51

This is 7 ga. 97/3 Ar/CO2

By cdubbs714 Date 09-28-2017 13:01

Penetration looks good, but what did the face of the weld look like? Good heat tint colors/no coloring, any graying?

By fschweighardt (***)

Date 09-28-2017 13:33

Added a face pic. Its not shiny chrome, but its pretty good. I think I gave it a lick with a brush.
Maybe 350 IPM, 26V? .045 wire.

By Lawrence (*****)

Date 09-28-2017 15:27

7-10 gage in most cases is plenty thick enough for spray transfer, so the 98/2 Ar/Co2 is a good choice in my opinion.

I think we also really need to define exactly what you want and mean by "proper heat tint"

If the work is structural, pretty much anything other than what most folks call "sugared" is arguably proper.   But I get it... You want nice looking welds.... But getting them consistently may take some process control for GMAW to make a shiny weld face.

GMAWP is way better than short circuiting transfer in almost every situation and better than traditional spray transfer on base metals in the range you state. GMAWP will give a lower overall heat input than spray which helps with color.

The oxide tint is ALWAYS a function of the temperature of the weld face when the gas coverage is withdrawn... So gun angle, gas flow, nozzle size, travel speed are all much bigger factors than type of gas in my opinion....

If the welds are short as you say.... How short?    Could the operator have a small postflow timer setting and then hold the gun over the small weld for a defined time period?

Gun angle... If the operator has the gun with a very slight push angle 5-10 degrees push (close to perpendicular to the work) the gas coverage stays on the weld for a significantly longer period than if a greater push angle is used... This can have a big effect on the color of short welds.

Nozzle size.. A 5/8" nozzle will offer a much better coverage zone than a 1/2" nozzle... This is not the time to be stingy with gas flow eh?

Gas flow..   Too much flow, Just like excessive push angles cause a venturi effect, sucking in atmospheric oxygen and nitrogen that increases the tint....

These are a few things the shop floor leader needs to observe for every operator and look for consistency...   Who is doing it right... And why its right...

By yojimbo (***)

Date 09-30-2017 16:51

Could pre-cleaning the base metal haz zone thoroughly prior to welding improve better color tint?

By Lawrence (*****)

Date 09-30-2017 20:30

Ha !

I suppose that depends on how contaminated the base metal is before you pre-clean it

By 803056

Date 09-30-2017 17:23

Any shielding gas containing oxygen is going to discolor. If you want a nice silver weld, stick with inert gas, i.e. argon and use a trailing nozzle to ensure the weld is protected from atmospheric gases until it is cooled and no longer reacts to oxygen in the air. The weld face will look "humped up" because there is no oxygen (in the shielding gas) to change the characteristics of the surface tension. Better yet, stick with GTAW and use argon shielding gas with a trailing gas nozzle. You will experience a reduction in deposition rate, but the welds will not discolor if the trailing nozzle is employed.

Al

By kcd616

Date 09-30-2017 23:55

Agreed

sincerely,
Kent

By 803056

Date 10-01-2017 13:41

Good morning Kent. How's the world treating you?

I find it's a dog eat dog world and my ass feels like a Milk Bone Dog Biscuit! (To quote "Norm" from Cheers)

Al :yell:

By kcd616

Date 10-02-2017 03:31

my health is what is
but everything else is great
I have to ask Alfred about my membership
I have some questions, he can answer
we will talk later
on a different thread
got another kid going for his CWI
might ask for more pointers :wink:

sincerely,
Kent
btw: hope your doing well my friend :cool:

By 803056

Date 10-02-2017 12:08

Tell him to study before attending the seminar. He is planning to attend a seminar before taking the examine isn't he?

Good to hear you are doing fine.

Al

By kcd616

Date 10-02-2017 12:26

Al,
he is attending the seminar
the whole week
just like the kid
and want the best for him
so I ask the best :cool:

sincerely,
Kent
btw: hope you and your family are doing good my friend

By 803056

Date 10-03-2017 02:04

Sounds like the young fella has found a mentor.

Al