Stainless MIG or TIG ??

[KC1]

Which process would be the best for 304 stainless sheet 16 ga. If Mig what gas and wire would you use? This will be used as duct work a Medical facility.

[aametalmaster]

308 wire and a tig if it has to look good. If its burried in a wall than mig...Bob

[Paul Seaman]

I am going to add if the process is to be mig the Gas is Tri-mix or I think I have heard it referred to as Stargon. I have used this on thicker material tubing in 308 and it did very well. My best suggestion is having to do with the quanity of work to be done if Tig is possible and there is not a tremendous amount to be done then its better appearance and simplier. if there is alot to be done the mig is definently the call in my book.

Good luck,
Paul

[aametalmaster]

Gas link...Bob
http://www.praxair.com/praxair.nsf/7...5?OpenDocument

[Bodybagger]

You'll spend a fraction of the time if you MIG weld it. If you take the time to get all your parameters set up good, the appearance will be quite acceptable.

One other thing... 304 is spec'd for corrosive environments. A weld on 304 can look like silk and have terrible corrosion resistance, and vice versa. If it's in a hospital, good chance this is going to be an exhaust duct for an autoclave or lab fume hood. Some autoclaves do not use steam, but rather use a gas. Generally ethylene oxide. They use these for sterilizing things that would melt in a steam autoclave, such as stethescopes.

This gas is explosive, toxic (if it wasn't, it probably wouldn't kill germs very good), and carcinogenic. A leak of any size is intolerable.

Find out the application and safety concerns for corrosion and leaks. If it's mission critical, like a gas sterilizer exhaust, you'll probably want to TIG weld it. If it's an overbuilt AC duct, MIG weld it.

[griff01]

I am going to add if the process is to be mig the Gas is Tri-mix or I think I have heard it referred to as Stargon. I have used this on thicker material tubing in 308 and it did very well. My best suggestion is having to do with the quanity of work to be done if Tig is possible and there is not a tremendous amount to be done then its better appearance and simplier. if there is alot to be done the mig is definently the call in my book.

Good luck,
Paul

Not stargon. Stargon is a tri-mix but it is not the same as the tri-mix for SS. Stargon is designated for mild steel. I have not used stargon in years so my memory is fuzzy on the percentages but the gases are Argon, co2 and oxygen.

The tri-mix for stainless is 90% helium/7.5%argon/2.5% co2 (or 2.5% oxy). I am certain you would not use the helium tri-mix on 16g as it is very hot. I am using a bottle a week right now on stainless piping. The helium mix is HOT.

Your LWS can verify which gas/wire combination is correct. If they cannot or will not, you need to find a new LWS.

Griff

[bigo]

I use the 90hel, 7.5ar, 2.5 co2 daily on 16ga on up,on a daily basis, I also run the .045 wire but smaller would be much nicer. get everything set perfect from a good ground to a good tip and clean nozzle ,andclean work you should be fine. ive used straight argon on the thin stuff and its not as easy and seems like spatter city compared to the trimix.

[bvweld]

I use the 90hel, 7.5ar, 2.5 co2 daily on 16ga on up,on a daily basis, I also run the .045 wire but smaller would be much nicer. get everything set perfect from a good ground to a good tip and clean nozzle ,andclean work you should be fine. ive used straight argon on the thin stuff and its not as easy and seems like spatter city compared to the trimix.

Another vote with the TRI MIX for mig. No problems on 16ga. s.s. duct work Would not recommend straight argon for mig use.

[bvweld]

You'll spend a fraction of the time if you MIG weld it. If you take the time to get all your parameters set up good, the appearance will be quite acceptable.

One other thing... 304 is spec'd for corrosive environments. A weld on 304 can look like silk and have terrible corrosion resistance, and vice versa. If it's in a hospital, good chance this is going to be an exhaust duct for an autoclave or lab fume hood. Some autoclaves do not use steam, but rather use a gas. Generally ethylene oxide. They use these for sterilizing things that would melt in a steam autoclave, such as stethescopes.

This gas is explosive, toxic (if it wasn't, it probably wouldn't kill germs very good), and carcinogenic. A leak of any size is intolerable.

Find out the application and safety concerns for corrosion and leaks. If it's mission critical, like a gas sterilizer exhaust, you'll probably want to TIG weld it. If it's an overbuilt AC duct, MIG weld it.

BB sumed it up well. Since it is in a medical facility,might be a good idea to find out a few more details so you won't have any surprises and can decide how best to proceed. I have welded a few feet of duct,some only had to pass a visual inspection, some were tested with pressure. If it has a pin hole they can detect it. Good luck on your job

[KC1]

Thanks everyone for the replies the duct work is for exhaust on the kitchen hoods. The hoods are equipped with a steam cleaner so the duct will have to be water tight. The appearance of the weld is not a priority it is in the ceiling and will not be seen.