Stainless Steel oxy-acetilene welding, how-to?

[lwmar]

Hello,

Please explain me how to do oxy-acetylene welding of stainless steel, I used the right flux which is only for it, but I couldn't do it, where I applied the torch it looks like coal.

Thanks
Regards

Marcelo

[chadford]

Here is some good info

http://www.cut-like-plasma.com/info_...less_steel.htm

[jakeru]

Solar Flux "B" works great. Mix into a paste (with something like isoypropyl alcohol), and apply (with a small brush) to the front, inside, and back side of parent metal joint, AND you might as well put some on your filler rod for good measure. It should weld nicely, with a very fluid puddle. (I actually think it welds more nicely than mild steel without any flux.) Use a standard (neutral, maybe slightly rich/excess acetylene as you want to stay away from oxidizing) flame.

Afterwards, plan on some removal of the flux residue, which will be hard an "glass like" where it got converted from heat. Flux that has not been heated sufficiently to "melt", will easily wipe / brush / wash away. Supposedly, a stainless steel passivation acid mixture can remove the glass-like solar flux residue, although I have not tried it for myself. (Solar flux literature recommends Bradford Derustit "wonder gel" product.) This has nitric acid in it, so may not be very easy to get a hold of.

I have used a stainless steel cup brush applied by HEAVY pressure and power by a large (7") angle grinder. In the process of removing the oxidation and flux, the power wire brush will kind of "smear" the surface of the stainless however. Also it will not be able to reach deep down into a crevise where the brush can not access.

The process isn't suitable for food grade or other applications, where the flux, or the flux residue itself could cause any problems. I have welded up a couple complete automotive mandrel bent exhaust systems with it however, works great.

Best of luck

[SeanMurphy265]

Tin Man Tech is a good resource for oxy fuel welding. He also has a youtube channel. I don't even think this guy owns a tig, he is all about oxy fuel welding.
http://www.tinmantech.com/

[Steve]

Hello,

Please explain me how to do oxy-acetylene welding of stainless steel, I used the right flux which is only for it, but I couldn't do it, where I applied the torch it looks like coal.

Thanks
Regards

Marcelo

When gas welding stainless steel, you need to run a carburizing flame....which is running more acetylene than a neutral flame. If you run a neutral flame as used for regular steel, you will get black soot all over. Stainless steel is almost as difficult to weld as aluminum. But once you get the hang of it, it becomes just like anything else.

[Trip59]

Can't comment on the welding part, but for passivation of stainless, check out these folks http://www.citrisurf.com/ Excellent product, excellent folks to deal with, ask questions of, etc. and it's a piece of cake to get and deal with (compared to nitric and other passivation agents). Dilute it out and wash it down the drain of your choice too!

[Steve]

By now you've probably figured it out. But for those who want to know.......

You need to use a carburizing flame....you run more acetylene and the inner cone is longer than normal. What I am thinking it does is prevents oxygen from getting to the weld due to too much oxygen being used in the process.

Here is a link to the AWS and is a powerpoint presentation on oxygen acetylene and the different flames and what they are used for.

www.aws.org/educators/Library/0000/000631.ppt

Once you get it down it will be just like welding anything else. It just takes a little bit of knowledge and some practice.

[jakeru]

A neutral, edging slight on the rich side (but just so any "regulator hiccups" don't go lean) is what I have used.

Here is what a book I have sitting on my bookshelf, "The oxy-acetylene welding handbook", copyright 1960 union carbide corporation, says about the topic in chapter 18 "Welding chromium and Chromium-nickel steels", p. 238:

"Flame Adjustment
A neutral flame is preferred for welding the chromium steels. Chromium readily oxidizes so that the use of an oxidizing flame would result in a lowering of the corrosion resistance because some chromium would be burned out. On the other hand, the use of an excess acetylene flame would increase the amount of carbon in the weld, which also would be undesirable. If difficulty is experienced in maintaining a strictly neutral flame, a slight excess acetylene feather is preferred to avoid any possibility of the flame going over into the oxidizing side. The neutral flame protects the molten weld metal from reactive welding gases and from the atmosphere. The proper adjustment of the flame is important in maintaining the chromium content and in promoting sound welds."

I recall if you weld lean or without adequate flux coverage, 304 stainless can rapidly "bubble", indicating extreme porosity and brittleness in the bubbled region. That is pretty bad news and if you see it happening, stop and fix something so it doesn't keep happening. It could be making your flame more rich, or it could be adding more flux coverage, or it could be not making something so hot where it doesn't need to be so hot.


Here is something I stumbled across to get you in the mood. A stainless steel shift linkage I fabricated many years ago, and even used for a while on my race car, I fabricated out of 304 stainless steel and oxy-acetylene welded. This part has never been painted or cleaned, aside from maybe wiped with a paper towel.