What to bring on a job...

Well... I got my u know what handed to me today... A guy called me about welding a vent hood and ductwork in a restaurant Wednesday night. It was in Memphis where I lived until this time last year. I told him that I moved two hours away and no longer worked in Memphis. He went on to say that he could not get in touch with his normal guy, and he had to get the job done. The city inspector is coming by Friday afternoon. I told him for X amount of cash for gas and X amount per hour; he then quoted a number and that sounded good to me. I asked him to send me some pics before I left. He said stainless steel vent hood so I loaded up my tig welder and left for the 2 hour drive to Memphis. I never got any pics...

Here is where things get a little rough... The vent hood is stainless steel, but the ductwork is 16 gauge sheet metal, mild steel. He wanted the stainless steel vent hood welded to the mild steel ductwork, and the ductwork is welded to a piece of galvanised sheet metal connected to the roof vent.

I asked the guy why the different types of metal, because I assumed everything would be stainless steel. The guy replied that it is built to code, and he does them all the time. He also said the guy that normally does it uses a mig welder with flux core wire.

I left my mig welder at home.....

Needless to say I was on top of the vent hood attempting to tig weld stainless to mild steel with 308L tig rod... It did not go well... I picked up some 1/16 7018 rods and it worked a lot better. the vent hood and duct work had 1 inch gaps on two sides, so you can imagine how well it looked.

I learned a lesson today... If you own it then bring it to the job site with you!

My question is how are you suppose to weld something like this and it be right?

Things can get dicey … when it comes to dietary … 308 is what you would think is proper but I’ve seen people do strange things … at the hospital where I work they only have a big Miller wire feed. I don’t work in the engineering department but I probably should be. I’ve seen them weld stainless to mild steel using mild steel wire a bunch of times … sometimes they get away with it, sometimes they don’t. One time I saw one of the engineers who claimed he used to work as a welding inspector (sure he did …lmao) rolling the MIG unit over to the scullery to weld up the inside of the dishwasher and I noticed he had steel mix gas … I told him he could get away with it but asked what kind of wire he was using. He told me “whatever’s on the machine” I popped it open and saw it was .030 mild steel and advised him since he was welding the inside of the unit where it’s wet all the time and the machine was dietary stainless this was not a good combination … I then told him what he should be using … he just shrugged and said “oh it’ll be fine” … I walked away shaking my head. He made the “repair” … two days later … it broke again. Amazing … simply amazing. I don’t know if there is an answer to your question because I’ve seen people get away with things that are just plain wrong … I guess you just have to fade back and punt.

309L is designed for joining steel to stainless. For the galvanized, stick would have been best, and 6013 would have worked.

I had some 309l, but it would have been impossible for me to tig weld. I'm one of these people that need to be in a good position when I'm tig welding. Originally I was told it would be on the ground, I would weld it and then we would hang everything.

What I'm having a hard time wrapping my head around is the code part. This guy is very legit, he had all is permits, and does some work for the local government. I heard him talking with someone on the phone, and he told them he could not start his job because the guy did not have a card at the inspectors office, and he could not get a permit. He said he never worked without a permit.

I'm baffled that this even code.

On a good note he told me if I wanted to do another one on Saturday I can. He pays good and pays in cash!

They make 309l in stick. Get lincoln red baron. It's the best to weld with. You got to use about 20% lower heat, and keep it moving, but it looks as good or better than any 7018 and the weld will not corrode (easily). Weld no more than about 1/2 rod at a time or it will overheat...The slag is literally molten lime, and I have a nasty burn scar on my thigh from it, but it will work great...just watch the drips. Having dissimilar metals isn't something unusual. The main contact area is all they worry about SS. In fact, hoods often are galvanized only....at least around here, and definitely the duct work is. SS is expensive and reserved for the most expensive applications. IF food isn't in direct contact with the metal, SS isn't usually required. Welding the galvanized is a little iffy though....You need to spray some cold galvanized coating on it when you finish though.

Quote:

---

Originally Posted by performance

309L is designed for joining steel to stainless. For the galvanized, stick would have been best, and 6013 would have worked.

---

This is why I love this forum ... every time I go here I learn something ... I knew about the 6013 but the 309L is new to me ... I'm ganna put it in my notes folder.

Jobs like this make me want a MTS unit with a 20' mig gun, 20' tig torch, and 100' of cable for stick.

Sean, not to derail and throw off your thread here...
But since it's in discussion.
I've used 309L extensively, especially when I was getting my technical training at school. Had to pass all positions with it with stick. We used 3/8" plates and coupons, as well as on pipe, if memory serves. For me it was no problem.
The 309L is used in many pipe welding operations and areas where there is corrosive, or abrasive material flowing through a steel pipe or fitting like a steam pressure valve. The joint will wear much faster typically, and it offers great corrosion resistance.

One thing about it, is that the slag is heavy. I most cases, the slag is so heavy that improper rod manipulation will send slag scooting in front of the puddle...and into the weld. Another issue is, that the slag is so heavy and gobby, (is that a word?) that you can't even see the profile of the bead much under it. It usually looks much worse on top before the slag is broken off, than the actual weld underneath. In other words, looking at the cooled slag tells little about the weld itself.

BUT and this is a BIG BUT....it will drive you crazy, because the rods are extremely picky to amps. No two guys seem to weld the rod at the same exact amps, but ALL seem to be affected by the slightest change up or down in amps. An amp or two hot, will look like you are shaking the left over water out of the end of the water hose....an amp or two low will just stick the rod, and turn it white hot in a half second. Get it tuned in...and wow! what a difference. The lincolns are the most tolerant that I know of.

Warning: These welds hold heat for a very long time, by comparison. The slag when it chips loose (or flies off itself) likes to find the soft and exposed parts of your body, particularly your face, especially your lips....This molten lime slag is as bad as it comes. It's not hard to get it off, but it shatters sometimes like broken, cheap glass and goes flying.

With all that said, it makes a beautiful weld that you can be proud of, IF you practice with it.

i use 309 or 312 filler rod works well to weld for carbon steel to stainless

Wow. I'm not a pro welder just a hobby musclecar/hot rod builder but I learned a lot in this discussion. Sometimes exhaust is steel to stainless also so good tips.. Thanks for all the info!

never could figure out have stainless steel pipe but carbon steel flanges . if not sure what metal it is 312 usaly works all the time when using filler rod

Cash is king... in a deal like that though, if it had any structural anything, I personally would have walked. I got a feeling in my gut as I was reading your post, seen too many deals start out that way and end horrible.

Cool that you got it to work, some great problem solving on the spot.

With TIG, wouldn't you want to buzz the galvanization clear so as not to have it gas in the puddle?

If I weld on galvanised metal I grind it off, or as much as I can. That makes a BIG difference!