Stainless project

[Samurai Dave]

Backpurging? is that where you use a gas like Argon on the back of the weld while your welding it?? Have welded a few things out of stainless with TIG and a couple with SMAW, worked OK but didn't back purge either?? can you explain?? I have heard of it just not sure about it...Thanks

You are correct. Purging consists of replacing the air on the backside of a weld with argon. This can be as simple as taping cardboard to the back of the metal to form a channel to seal the area for argon. The main reason I have a flow meter with two seperate outlets is to purge with one (@ higher psi), while welding with the other.

Welds in stainless can be done successfully without purging, but the back side (of a butt weld) will have "cauliflower" growing out the backside. This is how the stainless steel reacts with the atmosphere, which is not pretty. It can be ground-down, but takes work. If you are welding a box, that inside corner where 3 side come together is expecially hard to fix with a grinder. Most of the time when the customer is paying a premium for stainless, they expect the welds to be not only strong, but cosmetically appealing as well.

[JonnyTIG]

Back purging stops the vegetable effect? Kudos on the mental imagery 'Sugaring' is the term I've learned, but not as descriptive as cauliflower.

If the stainless is 1/8" or thinner, and not requiring multiple passes, you can use a product called Solar Flux, type B. Paste it onto the back of the joint, and it will shield the root reinforcement the same as back purging, but only for a single pass. It is used for thin wall pipe or tubing, yet is versitle engough to use for cabinets and plate projects.

[Anti-GMAW]

Sugaring is carbide precipitation. It's accelarated when an inferior atmosphere is present (unpurged open roots, etc.). In certan stainless aplications nitrogen and/or nitrogen mixes are acceptible (particularly with GMAW).

[HMW]

I thought thats what I had read. Thanks for the explanantion. Now that I think about it what I have welded that was stainless was a barbecue grille grate, hammock stand made out of stainless square tubing and repaired some restaurant equipment. So I guess nothing thin and you couldn't see the back side. It would seem that back purging would be expensive, but have no choice i guess.

[youngwelder_154]

I was thinking hard about purging it but since it will be an open ends theres no way I can do it with out the help of another person. I have no one at the shop to help me so I'm thinking I'm just going to fuse the ends together since its just 16g I might need a little filler but other then that I think ill be good to go. Today I'm ready to start the welding of my project so wish me luck

[youngwelder_154]

I got my tool box fitted and welded together I just have to figure out how to use my camera to get the pictures on the computer I am very happy and happy at the results I got it may have warped a little but not enough to even complain about it was just on the side of the box. Hardly any burn through only at the parts that had a little but of a gap, Pictures will be on every soon I promise you!

[fun4now]

cool
did you back purge or use a paste or just wing it ??

[youngwelder_154]

I just went for it. I just told my self what is there to lose besides learning what and what not to do and I guess I just put all 100% confidence in myself and it worked...

[fun4now]

16gage with no back gassing ?? ou eather have some ugly inside seems or you dont have verry good penitration, i would take a good look at the strangth of the welds. melting filler onto the top is not a good weld. not trying to be a pain or a jerk, i just dont see a good solid weld on 16gage SS without back gassing or some ugly insides.

[youngwelder_154]

fun4now I agree I may not have 100% penetration but from what I was told there I should have just enough penetration, I looked at the back sides and it didn't look too bad. I have a couple of burn through pieces but other then that it really looked pretty good. I wish I could have perged it but no one was around to help do that I didn't think about using something to cover the whole area and just put the perge hose in that and tape it shut but for next time I do this I will make sure it is done better. I really only built this tool box for a fathers day present and my father isn't what you would call a gear head so it will suit him for what he will use it for. Also next time I will be building one I'm hoping that I can build it out of alluminum diamond plate so that will be something I'm going to be looking forward to building. But I will still be posting pictures of it very shortly I still have to find the camera and the installing disc.