Question for RFR

[kiko hawaii]

When welding ss 304 tubing, are the welds supposed to penetrate all the way inside the tube? Or am I using too much amps, or too slow with the tig torch? I'm new to welding specially tig, but I want to learn and make my own exhaust sys. pls. help, thanks.

[Matt@RFR]

I happen to know that you're using 1/16" filler. That's too big. I'd use .035 filler for sure on .065" wall tube...especially on stainless.

Stainless doesn't like the kind of heat that mild steel can handle and still produce a sound weld. With stainless, if your welds are coming out a flat grey, you're too hot, which means that the welds, and the surrounding metal are brittle. And when talking about headers, that's certain death. The welds should be silver (good luck), light gold/orange, or blue and purple... and shiny. The further you get away from silver, the more corosion resistance you lose.

Blue and dark purple are signs that you're right on the edge, heat wise, or it could be that you don't have good enough gas coverage. Using smaller filler will let you run colder and still get a nice weld profile (flat to convex is good, concave is BAD!)

Cleanliness is also a big deal with stainless. You need to degrease every joint before you put any tacks on, as well as grind or sand the material. The problem with stainless is that it won't allways show you if there was contamination in the joint...until it cracks. Stainless moves around so much in response to heat that it takes very little to create enough of a stress riser to cause problems. And if you ever hear a "pop!" as your new weld is cooling, you know what just happened. :(

As an example, when I first started (MIG) welding stainless, I was shown this to make sure I knew what was about to happen, and to fixture for it: My Foreman took a piece of stainless flat bar about 1/8"x1", maybe 4' long, and ran a weld right down the middle of the 2" leg the entire length. By the time he was done with the weld, the starting end was almost at a 45º.

I also built some big water purification deals that were comprised of a ton of formed stainless angle...probably 30'L x 10'W x 12'T that, when welded and at room temperature, the 30' had shrunk 3/4".

Well! Back to your question.... :)

The one thing you need to do especially when welding thin stainless tubing, is purge (back gas). Tape up both ends of the total tube with that blue 3M painters tape (it doesn't melt), and poke about a 1/4" hole in one end. In the other end, insert a seperate Argon line, flowing at 30-50cfh for the first couple seconds, and then around 5 cfh for the weld. Argon is heavier than air, so try to have the Argon come in on the downhill side and fill up the tube, pushing the air out of the up hill hole. When done well, the inside of the weld will look exactly like the outside. Literally. You'll also get better color this way.

Purging is necessary for anything even semi-critical with stainless, not just headers.

Try this:

40 - 50 amps
15cfh through #7 or bigger cup and gas lens
.040 - 1/16 tungsten
Pulse would be fine, but not necessary
5cfh purge

You're shooting for silver to gold color, with a convex profile on BOTH sides. :)

[68protouring454]

hey matt i gotta get you a pin and a hat!! you da man
jake

[kiko hawaii]

Thanks Matt, what Ive just read was really enligthening.I'll try your suggestions, if it's not gonna improved then I know it's me. I was using a 1/16 tungsten and a # 5 cup (60 amps) as suggested by the welding place where I bought my supplies ( Miller ). But this time I'll try using the same tungsten ( 1/16 ) with a #7 cup & .035 filler and back purging and see how it goes. Thanks again.

[Matt@RFR]

You're welcome. :)

I'm not sure what your technique is, but if you're trying to spread your "coins" (where you dip the filler in the puddle) out, don't. Stainless likes you to dip the filler quickly between each deposit. It has a cooling effect on the puddle, and you'll have a better chance at convexity on both sides.

It's hard to explain...I'll see if I can do a weld like we've been talking about this weekend and post pictures.

[68protouring454]

hey matt any chance to ge a weld on some stainless??
jake

[Matt@RFR]

My second argon bottle is empty and I don't have a Y fitting to split off of one bottle. Sorry, but it'll have to wait a couple days.

Calm down Jake, go get stuck in a snow drift or something.... :lmao:

[Matt@RFR]

Well, it's not a great example, but you'll get the idea. Look at the file names for explanation of each picture.

- 2" x .065" 304 Round Tube

- Degreased with Simple Green, prepped with a 3M hand pad

- 35 amps, 1/16" tungsten, .035" 304L filler, 15cfh with 15 seconds post flow, no pulse, #8 cup

The fillet was to make sure I could still weld. :banghead:

[kiko hawaii]

hey matt, that looks really cool,,, it looks like a robot or a computer machine did it,,,, by the way did you used a gas lens? i did try your suggestions but my welds are not even close to yours,,, my amps are in the higher side too,,,, also i can't find any .035 filler rod here in honolulu
i ended up using .035 ear308lsi mig wire,,,, thanks,,, kiko :worship:

[Matt@RFR]

Thanks for the compliment!

The only time I don't use a gas lens is if I have to get into a super tight spot.

Nothin' wrong with using MIG wire! I use .023" sometimes. If you have to do it again, cut your pieces however long you want them, then clamp one end of the wire in a vise, and put a set of safety wire pliers on the other end. Twist (roughly 2-3 pulls on the pliers), and voila! Straight TIG filler.

The weld I posted is on the hot side. I didn't bevel the tubing enough. Put a bevel about half the distance of the tubes' wall or alittle more, and you can run colder (25-30 amps?) and still get good penetration.

How does the inside of your welds look?

[myclone]

The welds should be silver (good luck), light gold/orange, or blue and purple... and shiny. The further you get away from silver, the more corosion resistance you lose.

Blue and dark purple are signs that you're right on the edge, heat wise, or it could be that you don't have good enough gas coverage. Using smaller filler will let you run colder and still get a nice weld profile (flat to convex is good, concave is BAD!)

You're shooting for silver to gold color, with a convex profile on BOTH sides.

Excellent info... At the production plant I work at they have a nice (IMO) Syncrowave 350LX TIG that I have been trying to teach myself how to weld 304 SS on which has been a frustrating experience at times. The above helps tremendously since I really didnt know if what I was doing was structurally sound or not even though the pieces were well attached to each other when I was done making a pass. A big "thanks" :icon996:

[Matt@RFR]

Mr. Clone, (Can I call you My? :) )

Yeah, the Synchro 250's and 350's are timeless. Rock solid machines, especially on DC.

The hardest part for me when I was learning TIG stainless was not running too hot. It takes a very short arc and good eyes! Your beads should be smaller than you probably expect. Same with Chrome Moly.

So, are you ready to post up some pictures of your welds?

[myclone]

This is the only pics I have and its the last bead I ran after several 12hr nights of practice (I work night shift). Anything I did previously looked pretty scary so I didnt bother taking pics at the time. Tubing is 304 .065" wall, filler was ~.060", back purged with 100% argon. The biggest issue Im having is trying to get my heat/speed correct to get a good weld but not get any sugaring on the inside.
https://static1.pt-content.com/images/noimg.gif

Same weld but this is the inside of the tubing.
https://static1.pt-content.com/images/noimg.gif

Go easy on me since the only welding I had performed previously was self tought MIG welding when I was in the body shop business :) .

[Matt@RFR]

If I'm seeing that right, there's a light line (joint), and a couple spots of grey on the right side, which is penetration/sugar, right?

If so, your purge is not even close. You should have as good, if not better, gas coverage inside the tube than outside.

Get your hands on some .035" filler. You'll never look back!

How far from the work do you have your tungsten?

When you do more practicing, take a picture of the outside before you wire brush it.

[myclone]

If I'm seeing that right, there's a light line (joint), and a couple spots of grey on the right side, which is penetration/sugar, right?

Yeah just a couple of little dots of sugaring on the inside. I hate to say it but I was actually proud of that weld considering how much sugaring I was getting before. It was scary trust me.


If so, your purge is not even close. You should have as good, if not better, gas coverage inside the tube than outside.

After reading your previous post Im going to change my back purging technique since I wasnt purging the tubing nearly long enough or with enough gas flow.


Get your hands on some .035" filler. You'll never look back!

Will do since I was using what we had on hand at the plant. All of the welding that is done is on thick material compared to exh tubing so Ill pick up some smaller filler and give it a try.


How far from the work do you have your tungsten?

Im working on the "proper" distance from the work piece and generally I try to hold it as close as possible but since Im a noob Im constantly dipping the tungsten in the puddle by accident. I need more practice on technique but until I come across good info I really dont know what Im doing wrong. I cant ask the welding guys at the plant since they all work day shift not to mention they dont like non welders in their shop (they're funny that way).


When you do more practicing, take a picture of the outside before you wire brush it.

Will do and thanks again for the info.