Help with tiging stainless steel.

[con_fuse9]

Looks like you are getting there. A couple of last things.

1) the wirebrush you use should be (must be) stainless. If its carbon steel, the carbon will interact with the base metal. So, dedicated, stainless steel wire brush. (you didn't mention what type you used)

2) Welding near the ends is always difficult because heat has no where to go. At the end you need to taper off on the pedal. In your case, at a couple spots you heated it to the point where you made it all the way though. You will contaminate on the back side (which often can and will show up on the front)

Your going to have to come up with a plan to protect the backside. Stainless is very very sensitive. To give you an idea, I was welding on .035 304. With the post flow set to 'auto'. Weld amps about 30 (35 on the dial), so I think it was 3 seconds of post flow. As I finished the weld, I move the torch back a little as the arc cut off. I could hear the gas and in about 3 seconds I could here the gas snap off. Within about one second after that (almost instantly), I heard a little crackle and if you can imagine the area covered by the torch as a clock, in the 2-3 O'clock position a tiny, about 2 mm long ridge appeared.... precipitation of chromium carbides. Its like it snapped out of the metal. BTW, that was with a No 7 cup and about 13cfh. Never before have I seen that kind of contamination on the front side. I'm now running a solid 15 cfh and the post flow set to 6 seconds.

3) When I finish welding, I always have to resist the urge to move the torch away to see what I've accomplished - back the torch up a little and let the post flow keep the last area bathed in argon. I like to set the pre-flow at 2 seconds, just because it helps calm me down (that's probably the wrong term - not like I'm hyper). The idea is its a precision, calm process. No panic. Calm breathing. etc. I don't always remember that.

4) 304 stainless can be quenched. Its actually how you anneal (make it softer) and it actually can improve the resistance to corrosion. Its my understanding that some commercial kitchen guys actually use a wet rag. On thin gauge, an air compressor will do. It will lock in whatever warping though. BTW on .035, anything more than about 1/2 bead and you have serious warping. Even at 1/2" you can see it. I clamp it down tight and try to fusion weld with about a staple's worth of gap. So you can cool it down between welds. No worries.

[usmcruz]

To the above post, Id like to add that quenching thin stainless with a wet rag will cause warpage not lock it in. In the same breath it will also take some warp out if you quench it in the right spot.

[con_fuse9]

To the above post, Id like to add that quenching thin stainless with a wet rag will cause warpage not lock it in. In the same breath it will also take some warp out if you quench it in the right spot.

If you could elaborate. I'm trying to find out as much info as possible on this. When I have time I'll probably start a new thread on this.

[Dipsomaniac]

Alright I tried it again... this time with a bit more success.

Here's all the info I think you guys would require.

1/8th Stainless flat bar
3/32 308 filler rod
1/16 Tungsten Lanthanated
# 8 Gas Lens
14 CFM
120 Amps

308 is a low temp filler, so now this begs the question. What type of stainless steel are you trying to weld on?

[usmcruz]

If you could elaborate. I'm trying to find out as much info as possible on this. When I have time I'll probably start a new thread on this.

The fitters in the shipyard showed this neat little trick. They heat up the area with a torch, and lets say for training sake that this symbol here is a bow ( , you would apply a wet rag to the left side of the bow right in the middle to take out the bo to make it look like this | . Its that simple. After working with thin stainless and sheetmetal you get a feel for where to apply the heat and cool. Like I said, its a neat little trick, and gets your piece back to normal, but once a piece bows it will never be the same again, but you can get it so its not that visible.

[HAWK]

inconsisent travel speed

I looked at your practice welds. Not bad. It seems like you have an issue with keeping a steady travel speed with the torch. Check the colors of the weld as it progresses. Compare these colors with the color/temperature progressions the Miller engineer listed. I think you will see what I am referring to.

[Maggie]

I am learning this process and I am having this same problem with the color. My question is, though it has been stated that once the stainless turns grey it has little to no corrosion resistance, is it still strong as far as from a breakage perspective? I have to do an onsite repair of a piece made using a MIG machine, but my only option is my TIG because it runs on 115 and that is all that is available...

[Dipsomaniac]

I am learning this process and I am having this same problem with the color. My question is, though it has been stated that once the stainless turns grey it has little to no corrosion resistance, is it still strong as far as from a breakage perspective? I have to do an onsite repair of a piece made using a MIG machine, but my only option is my TIG because it runs on 115 and that is all that is available...

That would depend on if it is Martensitic, Ferritic, or Austenitic stainless steel.

Martensitic stainless is subjected to becoming brittle at the affected areas but if you over heat Austenitic stainless steel and rapidly cool it, that actually softens the affected area...

[Maggie]

That would depend on if it is Martensitic, Ferritic, or Austenitic stainless steel.

Martensitic stainless is subjected to becoming brittle at the affected areas but if you over heat Austenitic stainless steel and rapidly cool it, that actually softens the affected area...

Oh, okay. Well it is all 308, is there a way to tell the difference? What is the difference in those classifications?

[Dipsomaniac]

Oh, okay. Well it is all 308, is there a way to tell the difference? What is the difference in those classifications?

308 is an austenitic stainless steel that is very stable throughout the entire welding process.

Take a look at this link for the classification.

http://ajh-knives.com/metals-ss.html

[Maggie]

Thanks for the advice, I just got back from the repair job. Luckily the break was not in the place where I thought it might be but a much easier spot to repair. My co-workers went a little to far when grinding the welds smooth on the first go around and didn't leave much actual wall thinkness! Yeesh. Anyways, I think I'll post some pictures of my stainless beads in this thread so you all can give me some feedback on what I am doing wrong.

[turbo38t]

I've heard some people mention how hard aluminum is to weld but in reality I found stainless to be more difficult to get a "proper" weld. Aluminum is rather simple as long as you can move fast and steady enough. Stainless is like someone said earlier.....it doesn't take much in either direction to make a too hot or too cold weld. And being that the welds are so much smaller than with aluminum applying the proper amount of filler is key as well. I've only messed with .065 stainless plate and 1.5"x .065" stainless square tube but TOO MUCH HEAT is most likely the culprit. Dave

[grizzquad]

Hi, Check out this website, and I think you will get some very helpful information and videos.
www.weldingtipsandtricks.com

Good Luck, Steve

[Hillbilly69]

SS Tig

Welding without filler is different than with filler

The addition of filler cools the puddle Therefore requiring either higher Amps for the same travel speed or Slower travel speed at the same Amps......??? Think about it you're trying to melt a lot more SS per inch of weld.

Usually you do not want to slow down cause your heat inputs will get too high.
When adding filler increase your amperage!

Believe it or not sometimes you need to increase your amperage to reduce your heat inputs (You lower your heat by getting a quicker puddle and travelling faster).

I would say the gray color is slightly overheated chrome (Burnt chrome) from travelling too slow because you are waiting on the puddle. Bump up your Amps by 5-10 when using filler.

Usually the biggest problem with overheated SS is Carbide precipitation next to the HAZ that will crack when in service.

Make sure to back purge with Argon or use Solar Flux.

[mooseye]

Dude,
You need to stop worrying about color. It is a side effect.
Lay your wire in the groove and turn the heat up a little. You will be able to weld over the wire in effect duplicating a pass with no wire. You have to increase the amperage to compensate for the added heat sink (the filler). You should not have to move the filler much at all if the heat and travel speed are correct.
Try this and see if the color doesn't come on its own. It only means that your are getting even atmospherical contamination. Stainless is silver not red, salmon, ect...
Those colors are caused by the gasses in the atmosphere reacting with the haz. No cup can keep it all out but if all things are right you get the same color on the entire bead. No color at all other than original material color would be the best possible.

edit When I say weld over the wire, I don't mean spread it like peanut butter. You should have a puddle in the base metal groove and the filler should melt away and flow into this puddle as you walk the cup along the groove. If you don't walk the cup you can accomplish the same thing freehand with a controled motion. Just make sure you are filling the puddle and leaving no undercut due to lack of filler. If you have excessive undercut use a larger filler or slightly more angle on the filler rod.

Alright I tried it again... this time with a bit more success.

Here's all the info I think you guys would require.

1/8th Stainless flat bar
3/32 308 filler rod
1/16 Tungsten Lanthanated
# 8 Gas Lens
14 CFM
120 Amps

-Before starting I cleaned both sides of the flat bar with a wire wheel attached to a drill. The wire wheel is only used on stainless.
-I cleaned all pieces with acetone before staring, including the bench.
-I used a brand new set of tig cloves

It appears I did a bit better. The two things that I know I changed from tyring this yesterday was I believe I have the heat a bit higher then I did, and the other thing which I believe was a lot of the fix was I kept the filler in contact with the base metal. Basically never moving the filler rod and just melting it in as I went.

That last step I mentioned is a major difference from what I was doing with aluminum. Aluminium I was always puddle, dip, move, puddle, dip, move. It appears if I tried to dip and move with stainless it turns grey.

Anyways this is by no means perfect. Please ignore the pin holes and all the inconsistency. I was strictly focusing on not pulling the rod out away from the material.

Please any suggestions you may have is much appreciated. Please keep in mind I'm a rookie when it comes to this so I'm sucking all this stuff in like a sponge.

It was extremely hard to take pics of these but I tried my best.

Bottom right in this picture is where I started, used no filler rod just to see if things were looking correct. I then moved on adding filler from there. Each length there's three seperate attempts. Each time trying I tried to change my control just a little bit. Settings all stayed the same.





Last attempt I just used no filler rod again.


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