OA welding thick square rods

"Timur Aydin" wrote: (clip) It takes

^^^^^^^^^^^^^^^^^^^^^^ I don't know about prices where you are, but I am willing to be that you could but a good used arc welder for less than the cost of the gases you will use if you continue. And the time--the weld should take seconds, not minutes.

Been awhile but in the UK my experience is that the tips are sized in cubic feet of acetylene per hour and a 6 would be small for that job, also the pressure seems low on the acetylene and high on the oxygen, usual to run both the same in my experience for welding. The acetylene flame without oxygen wants to burn with enough turbulence that it produces no soot so you could set you acetylene pressure for that and try the same pressure of oxygen and then set the flame to neutral burning condition for welding, you did say you had.

Popping I have experienced more on thicker welds and I think are just sparks getting into the tip and igniting the gas prior to it exiting the tip and don't seem to be an issue but makes you jump, overheating the tip causes the torch to scream and it should be removed and cooled, I've only experienced this when working with the tip in confined areas.

This seems odd -- I'd expect the two pressures to be the same. I also don't know how tip sizes vary between countries (I have a hazy recollection they aren't even standard within a country!)

Something is seriously wrong. You should be getting hot much, much faster than this. I don't know whether it's your tip, or if you don't have the torch turned up high enough, or if you don't really have a neutral flame (my biggest single error with OA is that by the time I think it's neutral, it's really too lean. Maybe you've got the opposite problem?). But you aren't getting anywhere near the heat on the joint you need to.

I'd be tracking down why things are so slow first, and then see if that's also causing the pop...

I wonder if you've got the valves on the torch turned high enough?

Hmm, never thought about this... The oxygen bottle fills for about 15 dollars and the acetylene bottle for 75 dollars. I will check the bottle capacity, but I am guessing it is 9 liters. I'll check and write...

I will try setting both oxygen and acetylene to 1 bar and try again.

You are definitely right about the jumps :) I am a newbie to OA welding, so my jumps are much more intense ...

I will try equal pressure. Given equal pressures, should I use more pressure for thicker pieces and less pressure for thinner pieces? or is it the opposite?

As far as I can see the flame stays neutral, but with the big tip that I am using, I am noticiing that the white cone in the flame is not nicely shaped. It seems to be two cones attached to each other, one cone being a little smaller. Here is one more observation: I normally keep the tip of the torch at a distance of 3 centimeters. If I go closer or if I increase the oxygen flow a little, the melting gets a little faster. But in this case I am a little worried about the pops, so I usually return to neutral flame and 3 cm distance.

Hmm, I have tried increasing the acetylene and oxygen. In fact, I maxed out the oxygen once. The flame didn't chance ! If I keep increasing the acetylene, it doesn't change the flame after some point either...

Timur

If your #6 tip is designated for "between 8mm and 14mm", that is a BIG tip. That rating is for a butt weld of a pair of large plates. Properly set up, that should melt the end off the bar in half a minute.

The popping is either a dirty tip or running too lean. The fact that you have to hold it so far away to avoid popping means you are not running it at any where near it's capacity. I've found that although the "perfect neutral flame" is when the outer cone coincides with the inner flame, I prefer it just a little bit richer to avoid oxidizing my base metal.

I'd set the pressures equal at around .3 bar. Light the torch, > Hi,

You leave the pressure the same, and use a different size tip for thick vs. thin.

That sounds like what it should look like -- here's an image I found of the three regions of the oxy flame:

3cm sounds like it might be too far away. you should have the middle cone in the link I posted up above on the workpiece.

The valves on the torch (not the pressure control back on the regulator) should both be at settings where adjusting either one makes a difference to the flame. As a starting point, you should only have the acetylene valve open 1/2 turn when you first strike the flame.

(yes, I know I suggested they might not be open enough a moment ago, but there's more information now that makes that guess seem wrong)

You mentioned being new to oxy-acetylene, and you're asking questions here instead of mentioning your instructor, so I'm inferring you're on your own. My guess based on my own tiny (I'm not a complete newby, but I am awfully close to it) experience is that I'd never have gotten anywhere without a *very* knowledgeable instructor (both an expert welder and somebody who'd seen all the newbymistakes before) looking over my shoulder.

MIG and fluxcore are much, much easier (what I own at home is a little Clarke MIG welder).

Unfortunately I don't have an instructor available. I am an electronics engineer and my entire knowledge about OA welding is based on research done on the internet. I think I know have fair knowledge about the safety precautions. I have performed the leak test after the initial setup. I also have flashback arrestors installed at both the regulators and the torch. The gas tubes are of a non-flammable type. I also have bought a relatively large acetylene tank (6 KG) so that I don't accidentally consume too much acetylene within 1 hour.

I am planning to sign up to a week long OA course that the local mechanical engineering association is giving, but it isn't certain when that will be.

I am proficient in soldering though (I can't say it helped me much with OA, but anyway)

Thanks for all the info. I will try your suggestions and let everybody know how it goes.

An instructor isn't necessarily required, I taught myself to do OA welding as the first welding process I ever did and didn't learn anything new when it was covered on a welding course. Main thing is getting a good guide to how to do it.

Regarding pressures the recommendations for the equipment I use give lower pressures for the smaller tips and the pressure increases with increasing tip size. If you have or can get the details from your torch maker the pressures should be given.

Yes, based on the equipment pictures I have seen on the internet, this tip is really huge. There are two more sizes above this, the #7 (15 - 20 mm) and #7 (20 - 30 mm) and nothing more... I'm not sure, but the jet hole looks close to 3mm in diameter.

Ok, I will try reducing the oxygen to 0.3 bar and open the torch valves more. Yes, the hissing sound that this tip is making is almost unbearable :O I need to stop the damn thing every now and then...

Timur

OK, the oxygen tank is 6 liters and the acetylene tank is 6 Kg

Timur

Here is "my standard way" of setting up oxy-acetylene welding kit:

You do not need gauges to set the pressures of the acetylene and oxygen. Learn to set pressures without needing pressure gauges.

I set the acetylene and oxygen pressures at the regulators just a bit higher than needed, so that control on the valves in the torch, restricting back the flow just a bit -gives sensitive fine control over big valve turn. And a bit of "head-room" if you do need that bit more heat.

First you set the acetylene pressure. Set the acetylene regulator pressure very low, open up the torch valve fully, light the flame and turn up the regulator watching the acetylene flame grow. The pressure is just right when the acetylene flame just stops smoking. Turn the acetylene pressure up at the regulator a little bit more so the acetylene flame is now a bit "forced" and roaring, then restrain back the acetylene flow to the correct just-smoke-free flame with the torch acetylene valve ( closing the torch valve to some degree).

Then set the oxygen pressure. You have also set the oxygen regulator pressure low. Turn the oxygen valve in the torch full on. Turn up the regulator oxygen pressure until you get a neutral flame with the perfectly formed inner cone. Turn up the oxygen a bit more turning the flame oxidising. Then restrain back the oxygen flow with the torch valve until you have a neutral flame gain.

And you are now ready to weld.

When you relight the torch, all you have to do is spin the acetylene valve to full open lighting as you do so then trim back to the smoke-free flame, then spin the oxygen valve full open then trim back to the neutral flame. Holding the torch in one hand and spinning the valves with the fingers of that same hand you should can have the flame set and ready for welding within 1 second.

See what happens with these setting then you should be able to get much more accurate help if you are still having problems.

#6 is a big nozzle! Never used bigger than a #4, so cannot tell you what a #6 should be able to do...

Richard Smith

"Richard Smith" wrote: (clip) I set the acetylene and oxygen pressures at the regulators just a bit

^^^^^^^^^^^^^^^^^^^^^ I am not an expert, but I learned by asking questions of an expert. Your method is the one he taught me, and it has worked well for the last 55 years. You can tell it's right by looking at the flame, regardless of what is on a chart or on a gauge.

It is expensive to weld stuff thicker than sheet with oxy acetylene. It also turns so much metal red that the working in making the square shape is lost and the metal is more flexible where it was red. Here the tanks are talked about in scfm which is a how much volume it holds in cubic feet at 40 psi. Just a liter measurement without a designation of at what pressure isn't particularly informative. It does sound as if you have a small oxygen tank.

As for the tip numbering system some use the amount of acetylene or acetylene equivalent if alternate fuel used per hour. some use the suggested pressure for the tip. Quoting the number drill size of the hole in the end bypasses that problem. Most set ups should use approximately the same pressures however some will use greatly higher oxygen and quite low fuel.

Fran

True, but it helps. had a shade tree / farm mechanic show me how to patch thin sheet & moderate thickness metal with a torch and clothes hanger for rod over 20 years ago. He actually showed me how to adjust and do it with a cutting tip first by adjusting the flame. He told me that it to know how to do it with the wrong equipment because sometimes you just don't have the right stuff in the truck, and every minute you sit idle its costing money.

Anyway, without the ten minutes of guidance he gave me I might still not know how to do that.

Bob La Londe

Richard Smith wrote: > Then set the oxygen pressure. You have also set the oxygen regulator

Thanks for the detailed description :)

I have tried this procedure with a #3 tip. The "just smoke free" acetylene flame amounts to about 0.3 bar pressure on the acetylene regulator. But when I open the oxygen using the regulator, the neutral flame is achieved at about 2.5 bar oxygen pressure. So oxygen and acetylene area nowhere near equal pressure... Also, the flame has a really loud hissing.

I will try this with the #6 tip also and then will try welding the 10 mm square rods.

Really loud flame ALWAYS ALWAYS means an oxidizing flame. Is your acetylene valve on the torch opened way up? If not, try opening it more.

GWE

Yes the torch valve is open at max. I used the regulator valve to adjust the just smoke free flame. The acetylene tank valve is open about 1 or

1.5 turns. With this setup, the acetylene input pressure is 10 bars and the output pressure is 0.3 bar.

The oxygen tank valve is open only a quarter turn. I open the torch oxygen valve to the max and the use the regulator valve to adjust the neutral flame. When I am at neutral, the input pressure is about 170 bar and the output pressure is 2.5 bar.

Timur