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Tig Stainless steel back purge
Posted: Sat Mar 07, 2020 9:38 am
by mainemetalman
- block1.jpg (80.74 KiB) Viewed 2044 times
Just wanted to share this with you guys. I have been making maple syrup evaporator pans and tig welding the corners. The outside welds look great but the back has some sugaring and doesnt look so well. It also tends to rust a little bit. Ive been thinking of ways to eliminate this. I always use cooling blocks on the inside and outside which helped out a lot but I still wasnt happy. After a couple house on a milling machine this is what I came up with and it works very well. Only issue I have with my first time using it was the front of the weld wasnt coming out as good as the back. Im running 12 CFH both front and back, wasnt sure if I should lower the back side? Here are some pictures. Thanks!
Re: Tig Stainless steel back purge
Posted: Sat Mar 07, 2020 4:21 pm
by Coldman
Excellent solution for your needs. It will stand you out from your competition with increased quality too.
Really well done!
Have you tried pulsing to improve outside corner finish?
Re: Tig Stainless steel back purge
Posted: Sat Mar 07, 2020 9:59 pm
by Simclardy
Your photo is the inside? Do you have a shot of the outside? On outside joints i find it hard to get good gas coverage i would try cutting back on the back and turning up on the front.
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Re: Tig Stainless steel back purge
Posted: Sat Mar 07, 2020 11:21 pm
by cj737
For an inside purge, you really don't need a lot of gas, just enough to fill the volume.
For your purge block, I made something similar but did not use "holes". Instead, I milled off the chamfer until I had a complete slit for full coverage. With holes, you'll get lapses in coverage.
For stainless welds, I default to a Furick #12 cup, 25-30 CFH whether the joint is flat, outside, or inside.
Re: Tig Stainless steel back purge
Posted: Sun Mar 08, 2020 8:53 am
by Bill Beauregard
GH Grimm in Rutland VT went from soldering all their joints to TIG. They bought two huge Lincoln TIG machines and a wall full of purge blocks for each shape they purge. You might take a piece of square stock, or heavy aluminum angle. Grind to the radius of your joint. Cut "worm tracks" where you want gas. Bore in from the worm tracks to the other side, and thread for a gas fitting.
Clamp in place, it'll serve as a chill block also.
I've had limited success with SOLAR FLUX. Mix a paste, spread it on the back side.
Willie
Re: Tig Stainless steel back purge
Posted: Sun Apr 05, 2020 8:51 am
by Bill Beauregard
I believe you need a bit more gas.
I'm a big fan of gas lens. Use your biggest cup, as little stick out as possible.
Strive to hold torch at equal angle to both faces of an outside corner.
Where you can, bend the corner & join with a butt weld.
Re: Tig Stainless steel back purge
Posted: Mon Apr 06, 2020 10:02 am
by snoeproe
Not that I tig much stainless anymore but, when I needed back purge I usually used solarB flux. I still have some around for such cases as this. As long as you can clean the area afterwords.