mig welding stainless steel

Date 04-10-2006 04:24

Hello smyths, I would make the suggestion that the .030 wire is a good choice for the application that you have described here. I would consider tacking the boxes such that the tacks would act as the termination points for all of your one inch stitch welds, then I would try to make all of your welds in the vertical down position, turning the box so as to make all of the welds vertical down. Prior to doing the welding I would get some scrap and practice making these vertical down welds as hot as is reasonable without experiencing burn through. Whenever you are making a cold start with the wire make sure that you have clipped a new end on the wire, as long as you are going from one weld to the next without any lag time you shouldn't have to reclip the wire, but if you stop for very long, I would suggest reclipping. One question here, are you using a formed piece and capping the ends? If not you might want to consider this approach as it will cut down on warpage and distortion and also minimize the welding required to make these boxes. It will also be much more cost effective in the long run and look much better. Best of luck and Regards, aevald

By smyths

Date 04-10-2006 04:37

Aevald,
Thank you for the prompt reply. I almost made the boxes using the formed approach, but last minute made them out of five pieces. Oh well.
Yes, I am welding vertical down. My machine (inside panel) recommends about 17 or 18 volts for 16 ga. stainless. This seems cold to me. I like to crank the volts when welding stainless, and try to move quicker. Almost like a contrived pulse technique. What do you think? This gives me a wetter, flatter bead. The noise from the weld is more like a hiss, and less like a splatter or sizzle; furthermore, the wire immediately bites. I generally clip the ends, but when I run hot, I find I don't have to clip every time, if at all. I was also considering going to .023 wire. Thoughts? Do you have a gut on the right voltage?

Thanks again.

By aevald

Date 04-10-2006 07:12

Hello again smyths, when you talk about the numbers, they are great starting places and points of reference for future use,, as long as you are talking about using the same machine and all of the same peripherals. You talked about the sound that the arc made and I would agree that I like the hiss sound better, also consider the way that the puddle looks and try to keep a mental picture of this stored away in the old brain. The only way that you can truly use numbers to describe welding parameters is if you have calibrated electrical measuring equipment to verify them. When you go from one machine to the next, numbers are just reasonable starting places to work from. Personally I would avoid the .023 wire because it is more likely to give you feeding problems. You may want to consider using some form of a heat sink while you are making the long welded seams, this will help to minimize the distortion that will occur, a couple of copper or aluminum bars clamped to the outside of the corners should help. I would suspect that 19 to 20 volts might be a little closer to home for a setting, however, run some test pieces to verify for yourself. Best of luck and Regards, aevald

By TimGary (****)

Date 04-10-2006 11:13

I would suggest using 98% Argon / 2% O2 for sheilding gas. This will help the bead wet better on the edges.
(if you're not already...)

Tim

By - Date 04-10-2006 12:25

Tim,
Good suggestion. I would also recommend using a high silicon filler (308LSi) because the higher silicon has better wetting action and virtually eliminates the spatter that is so noticable in MIG welding.

Chuck

By 357max

Date 04-10-2006 14:02

Use the 0.023-25" diameter wire and use the vee knurled drive rolls. If you are welding with the short circuit metal transfer the gas should be the tri-mix 90% helium, 7 1/2% argon and 2 1/2% carbon dioxide. Or something similar with the high helium mix. If you are able to, add an inductor/stabilizer. Refer to the Miller GMAW Gas Metal Arc Welding book stock number #151 682 and page 41 and 42. "...wrap certain number of turns of the work cable around a chunk of iron or an iron pipe." An old tapped/jack plug or moveable shunt type of AC buzz box welder works quite good also. Tape off the primary cord so it doesn't get plugged into a power outlet/receptacle. Connect the work lead from the MM 250 to the work lead of the buzz box and use the electrode lead for the other end of the work lead and change the electrode holder to a work clamp. First set the wire feed speed to get the penetration desired, then set the voltage to flatten the weld. Then leaving those controls set; Increase/Decrease the "output" setting of the buzz box to fine tune the arc.

By TimGary (****)

Date 04-10-2006 14:14

357max,

???
You've confused the crap out of me...
Would you please expand on why you recommended what you did?

Thanks,
Tim

By 357max

Date 04-10-2006 16:24

With two drive roll systems the vee knurled drive rolls give very consistent feeding when feeding the "slippery" wires like stainless steel. Just minimum pressure with just enough to imprint a light grip impression of the vee knurled rolls. The hard part is just enough and not too much. Should mention to make certain that the liner supports the wire. If 0.023 wire is used; use the 0.023 - 0.030 liner. One liner size does not fit all wire diameters. Short circuit metal transfer with Argon/2% Oxygen proves a bit sluggish for my liking, therefore Trimix 90% helium, 7 1/2 argon and 2 1/2% carbon dioxide is preferred.

By 357max

Date 04-11-2006 14:55

Forgot the explanation for using Inductance/Stabilizer; first the basics: wire feed speed determines the amperage which determines/influences the penetration, voltage controls the bead contour; more voltage - flatter welds. But with the combination of volts and amps which is watts or energy stainless steel can be easily "burned". To fine tune the arc to flatten the weld deposit and reduce the spatter, additional Inductance can be added without appreciable energy increase. Some machines have fixed increased inductance by having two output terminals for the positive terminal, one would be a low inductance/stabilizer and the other would be a high inductance/stabilizer. The miller cp300 or their deltaweld machines would be an example. If you have a machine with high/low inductance/stabilizer taps, disconnect the input power and open the machine and see inside what the inductance/stabilizer device looks like.
Other machines notably mig inverters have "arc control" which is a variable inductance control.
If the machine being used does not have an adjustable inductance control the original post describes what can be done to fine tune the short circuit mig arc with a "homemade" inductance control.
So Try It; set a very good wirefeed speed/amps and voltage short circuit arc and add or decrease just the inductance/stabilizer.
And as always a good test is worth a thousand opinions.

By TimGary (****)

Date 04-11-2006 15:37

"Now I see!" said the blind man...
Nice trick. I'll try that sometime.

Tim

By - Date 04-10-2006 14:48

"knurled vee" drive rollers are necessary for FCAW welding. Not necessary for GMAW. The tri-mix gas will work, but a much more economically gas mixture is the 98%Ar-2%O2. Please refer to the Avesta Welding Manual for gas mixture recommendations for GMAW welding in the short circuit mode of transfer or spray mode of transfer. Both can be used with 98-2.

By smyths

Date 04-10-2006 15:02

Thank you all for the information. This forum is fantastic.
I think today I will pick up some wire with the higher silicon content. I also have a feeling that the .023 might wet out better. I have to really bend the gun cable a bit when inside the boxes, so perhaps the .023 will want to follow the bends better. Although, my one complaint about this MM250X has always been the wire feeding. The cable has to be VERY straight.

I have been using the Tri-mix, but I have 100% Argon on hand. Can I use this, or does it have to be 98-2 O2?

The welds are on the inside and will not be seen. My main concern is to have nice wet out/penetration and minimal warpage and of course no burn through.

A while back, the guys at the welding store suggested a flux core wire to be used in tandem with a shielding gas. They swore by it, but it costs a small fortune. Anyone used this before?

Thanks again.

By jwright650 (*****)

Date 04-10-2006 16:00

I think you'll find the flux core digging a lttle deeper(more penetration) than the solid wire, so if burn through is a concern......
John Wright

By agong

Date 04-10-2006 16:17

You have to use 98%Ar+2%O2, this will give you better wetting and more arc stability. As I mentioned from your posts above, you only need to change shield gas then you will be there. You don't have to change wire size to 0.023'' (lower efficiency, more cost). Use short circuit transfer.
Good luck!

By - Date 04-10-2006 17:20

I agree totally...

Chuck

By smyths

Date 04-10-2006 20:49

Back at it today, and things are going much better. I'm still using the tri-mix and .030 wire. I just finessed my settings a bit more and made a better effort. I'd like to get the 98-2 tomorrow and will note any difference. My suppliers did not have any hi-sil wire in stock; no biggie.
20 bucks a pound.

Thanks to all for the information.

By - Date 04-10-2006 21:23

Smyths,
$20.00 a pound??? No way...Tell me where you are located and I will give you a source (distributor) where you can buy it at 1/3 that cost. There should be no cost increase over regular L grade wire. Example, 308L and 308LSi should be the same price. And, it is no where near $20.00 lb. Not even close..

By smyths

Date 04-11-2006 04:08

I am in San Diego, California. I used the Si wire some years back, and it was good.
Since then, it is never stocked, and I never think to order in advance. I would greatly appreciate a good lead, as the prices I've been quoted are ridiculous.

Thank you.

By - Date 04-11-2006 13:00

Try contacting the local Airgas welding distributor. I cannot speak for any other manufacturer, but the Avesta LSi wire will be a LOT less than the $20.00/lb you mentioned....probably around 1/3 that price. If you want to e-mail me, I will give you the name of the Avesta rep in California.

Chuck

By lewis edwards (*)

Date 04-10-2006 23:02

You probably have a weld with a 3/16" leg size and the plate is 1/16" thick . You don't need much heat you need to move fast .When you move the gun forward at a fast pace and a ball formes on the wire then your wire speed is to slow . When you move fast and yo feel the wire push back then the wire speed is too high . I use a quick forward and back osilation . forward to the outside edge of your puddle an back to blend in . You should have ripplels about 1/8" apart . Vertica down is the only way to go . I would also weld the whole seam with out stopping . When you do stop run the bead ahead to a small stringer then stop that will alow you to start back a little on your weave to seal your stop-start better . You must use a short stick-out of 1/4" to 3/8" past the "tip" . If you have a slip-on nossel push it on all the way to expose the tip or smash the end of it into an oval shape to fit tight into the corner . You can also cut two notches into the sides to allow yourself to get closer into the corner .

By smyths

Date 04-11-2006 04:13

I did exactly that today... I tapered my nozzle to get the tip closer. I think I'm running about 20 Volts and 200 ipm wire speed. Vertical down with the weave is how I like to do it, with the same technique that you described. I find that the weld flattens out nicely, although I often feel I'm spending too much time blending the puddle, which puts heat into the material.

I guess the materials going to move no matter what. I just hope I can keep the finish looking good with some old fashioned elbow grease.

Thanks again.

By TimGary (****)

Date 04-11-2006 11:35

Have you considered using a chill bar or heat sink on the backside?

Tim