The TIG class

[opjohnny]

I am on the 3rd full day of the TIG class I am takeing. I had a big ah ha experience last night. We are working stainless steel and every time I tried to add filler it was looking burnt. I was really struggling. I use the same booth/torch/lincoln every night so far. I took the torch apart and found half an o-ring was missing. Well the instructor took my tungsten and used his 20 years experience to sharpen it. He did a demo in my booth then I took over. What a difference! Wish he would sharpen mine all the time! I will post a picture.



John

 

[GHarman]

I am on the 3rd full day of the TIG class I am takeing. I had a big ah ha experience last night. We are working stainless steel and every time I tried to add filler it was looking burnt. I was really struggling. I use the same booth/torch/lincoln every night so far. I took the torch apart and found half an o-ring was missing. Well the instructor took my tungsten and used his 20 years experience to sharpen it. He did a demo in my booth then I took over. What a difference! Wish he would sharpen mine all the time! I will post a picture.



John

Looking forward to the pictures! GregH

 

[opjohnny]

Its my sons camera and I need to have him show me how to take closeups! I sure like how clean tig welding is. No sparks no fuss!

 

[GHarman]

OPJohnny, Glad you are getting some good experience. Any hole in an argon system will aspirate atmosphere. Your welds will turn black and the boss will try to blame you for running them to hot! Check your connections and eliminate any possibilities at your end.

I was working for a company that had a plant wide piped argon system as opposed to individual bottles at each welder. I was getting alot of black welds on stainless steel. I told the foreman that their system had a leak! He said I was running to hot and was reassigned. That weekend, the maintainence crew isolated the argon distribution piping, pressure tested it and found the leak. I was back on the job, Monday, with a sheepish apology from the foreman:-laf. GregH

 

[opjohnny]

I have 3 pictures the pretty stuff the instructor did with and without filler. The grey snakes were with the leaky torch.



John

 

[opjohnny]

I have a lot of room for improvement. Yours is a funny story about the argon system! Now I know what that looks like. I have been practicing at home on mild steel in my spare time. I wish I was ambidextrous and spent the money for no line bifocals for my safety glasses, the line messes with me.

 

[GHarman]

Being ambidextrous is all in your head. You practice with your off hand and think mirror image. When you think it you can do it. It does take practice. Bi- focals are a pain, but there are also reading glasses that may work as close work glasses. They are cheap and may or may not work for you. GregH

 

[champspa]

get him to show you how to walk the cup. it's easier than what your doing and free hand will come later.

 

[GHarman]

get him to show you how to walk the cup. it's easier than what your doing and free hand will come later.

Yep! Walkin the cup on a lap weld will simplify things alot. Course you still gotta learn that hand eye coordination process. On a flat surface, free hand with a little pinky finger drag, to steady yourself works wonders (watch the heat). When welding aluminum, for example, you cant walk the cup. You gotta freehand or drag your hand on a rest. A "finger stall" can be made from a popcicle stick taped to the little finger of your torch hand glove. There are a hundred ways to cheat:-laf, but only good welds count. The hand eye coordination will come with practice. GregH

 

[opjohnny]

I noticed I have been cooking the filler rod glove hand letting it get to close to the heat. I really enjoy the class though. I hope in May I can post some pictures of my work I can be proud of! Thanks for the input.

John

 

[opjohnny]

I am going to post a picture of some stainless I welded today. I am seeing some improvement but it is slow. I had a hose on the watercooled torch burst on me last night! Soaked me and my gloves so I had to call it a night.

 

[GHarman]

OPJohnny, Nice weld. Good color. Needs a little more filler metal. The legs of the fillet need not be wider than the thickness of your thinnest piece. I always setup my cooling lines to feed from the chiller to the torch head and bach down the power cable. That gives the greatest temperature drop where you need it, especially when welding aluminum. Feeding the coolant up the power cable to the tourch and back the tube only preheats the coolant before it hits the torch head. Dont lay your torch cables over your work. If there is a flaw in the casing, the high freq will find it, blowing out the side of your power cable. GregH

 

[DValentine]

Greg, what can you tell us about covering gas. I have been welding 9 chrome down here. Its some special stuff welded with + 92 wire. We are running TIG all the way out. I have not welded stainless tubes before this. My partner has, though. We have to purge, and the other night we were trying to purge up 20 foot to the weld. We didn't have good coverage. Yes the weld was black... but here is my question. It seemed that the bevel didn't break down very well... at all. My partner was looking me in and told me to go back over it. It wouldn't break down. So we cut it out, fixed the purge and the edges broke down fine, and the weld was clean. How does purge gas change the way the metal flows and breaks down? Just for others reading this, we are not in a shop environment, we are hanging off a scaffold 180 feet above the bottom of the boiler. I know argon is heaver than air and displaces it.

Op, good for you, taking a class. You will be happy looking at your pictures, as you improve. Sometimes it seems like a guy goes backwards or gets stuck in a rut. Then there is a huge gain, leaping forward and a guy feels like he is getting somewhere. Keep going...

Dave

 

[GHarman]

Dave, Are you using purge dams? Stainless Steel needs more purge flow than Carbon Steel. The volume of the pipe has to be calculated and a prepurge allowed that will fill up the pipe, from the bottom past the weld joint for at least a foot on a vertical rise. I have used masking tape and Stainless Steel sheet metal wrapped around the joint to contain the purge gas till you are ready to tack and weld. This is necessary to retain purge gas and eliminate aspiration of atmosphere. Purge rate(Cu. Ft. per hr or minute) x volume of pipe to be purged. This could be between purge dams (Disolvable) or a complete rise or run of pipe. Vent at the top. Insufficient purge flow and a wide open joint that allows purge gas to be blown out may be a cause. A leaking hose or connection may cause an impure purge? A Stainless Steel sheet metal collar, about 3 or 4" wide, rolled in the shape of an exagerated C could be fabricated. This could be snapped on, over the weld joint and slid around as you progress with the weld root until you have a shielded purge. You would have to secure it with something that will not contaminate the heat affected zone, a tack maybe. It'll keep the wind out of the equation. This is just a SWAG, as I am not on your job, just some thoughts. Dont be in a hurry during your purge. An Oxygen meter may be useful to test the purge gas that escapes at the vent? Hope this is helpful. GregH

 

[GHarman]

Hey Dave, Can you get us some pictures? GregH

 

[DValentine]

Yeah, we are stuffing the tube ahead of the weld. Where we can't get the purge line in the end of the tubes, we use a needle and stuff both sides of the weld. I wish I could get some pictures but the lighting is horrible and it is hard, with all the panels in the boiler, where we are working it is hard to get a perspective.

I was wondering how the lack of oxygen propagates the weld. I understand that we need to get the oxygen, but it seems to affect how the metal mixes and welds. We are welding on weird stuff. It has not been used in a boiler application before. We can't cut corners or stuff does not work. We are feathering our tacks, running 3/32 in a 1/8 gap, leaving a feather edge on the tubes-no land. It is weird stuff. It will not reconsume if you have to go back and heat it up. We have found that you have to grind out the weld metal and start over. The inside of the puddle doesn't move, it dribbles. We have done both horizontal and vertical welds. It has been an education. When running the purge hose in the bottom of a tube we usually can get enough purge so we don't have to tape it. We just have to back down the gas flow when closing up the weld or it will blow the backing gas out of the torch.

Not trying to hijack the thread. I have just spent the last 2 months TIGing more than I ever have in my career.

Dave

 

[opjohnny]

Dave no offense taken here about the thread. You have a difficult job going on there. Thanks for the positive words about the welding. I really enjoy it. I dont have to do it for a living and I know that would take the fun out of it.



John

 

[GHarman]

Dave , GOOD Questions and Practical applications. You are doing the work and that is what learning is all about. Not all welding is done on a bench. Just the easy stuff fer us oldtimers, and new learners.



The presence of oxygen at the weld allows for metal oxides to form, which prevents the metal from wetting and flowing. Sometimes there are other issues, like dirty base metal, both externally and metallurgically. There can be problems with compatability of filler metal. Where you are having problems with the base metal flowing at the root, is that on the new piece(s) or is it where you are welding replacement tubes (new) to the existing tube? Are these Stainless Steel tubes? What alloy? There are some specs. that do call for a specific O2 content in the purge or cover gasses. Are you preheating? GregH

 

[GHarman]

PS, Having Helium added to the cover gas increases the ionization potential of you cover gas (at the torch) and provides more heat input. This should be done in the shop to prove it before you try it in the boiler.

Were you able to prove your existing process in the shop before you went into the boiler? GregH

 

[GHarman]

Dave, After some further thought on this, your 9% Chrome tube is not my area of expertise, so I asked a real expert. He suggested several things, both are subject to your W. P. S. . Slow down on the root, weld it in sections and make sure you are breaking down both sides of the bevel lead using ER-90S B3 wire. Let it cool some and procede with another section, dont get it to hot. Before you close it up, peek through the remaining root opening and do a visual. If it looks good, then close it up. There may be to much heat being used. Take your time. X-ray the root. You can run a hot pass, if needed, carefully, in sections. Watch the heat. Then the big change is; fill and cap with 8018-B3 or 9018 B3 H4R SMAW rod. He suggested that you may be getting it to hot. Remember to maintain the preheat temperature! What is the wall thickness?

Hope this is helpful. GregH