Welding Gas

John - you wouldn't want to use anything other than argon (or possibly argon-helium mix) with aloominum. CO2 isn't inert, which is why MIG used with CO2 (steel) is technically "MAG" ie metal active gas. And for TIG you always use just argon or argon-helium. So generally I have an argon / 5% CO2 mix for my steel welding MIG (ie MAG) machine which never gets used for loominum and pure argon for my TIG which is used for both loominum and steel. 2 cylinders.

Running a MIG machine with loominum usually requires a spool gun as the wire gets stuck easily in a normal machine. It also doesn't like running in a gun that has traces of steel in it (contamination). Not worth the hassle anyway unless you are welding large numbers of loominum parts in production, which we don't.

CO is used to refine iron ore into iron i.e. carbon is more reactive than iron, so in steel welding the CO2 is inactive.

CO is less reactive than aluminium (which is why you need to use electrolysis or other fancy techniques to purify aluminium) and why it is not suitable as a shielding gas for it.

Neil

I was just repeating what a man from BOC said. I know no more but assume that as he said it some do use it for that. He also added that it's usually used for TIG. I just queried that pureshield was pure argon for tig welding. The site can seem a bit confusing in that respect.

John

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The bottle trolley looks pretty good. I just wheeled my son around on it. He weighs over 90kg.

The max bottle width at the bottom is 235mm, top more or less the same. No signs of rust inside the tubes. Nice big wheels.

The powder coating will get chipped off with use especially under the bottom platform. As it looks to be a keeper I may do something about that. Piece of thin al sheet or something.

It's possible to pay silly amounts for these things, including what may be the same model.

John

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I think there must be something wrong with one of your assertions there.

In electric welding CO2 is an *active* gas.

The energy in the plasma liberates one of the oxygen atoms from each CO2 molecule and the oxygen atom can then either bond with an iron or a carbon atom in the weld pool.

As I understand it the oxygen would prefer to bond with carbon. It is more mobile than the carbon in the weld pool which is at a lower energy. The oxygen forms carbon monoxide in the solidifying metal matrix, and becomes entrapped.

Porous welds are generally unwelcome so manufacturers add other more attractive elements into the feed-wire alloy, and avoid porosity.

In any case you know CO2 is active, when you weld with it; by the shower of sparks.

Edited to add;

I wonder if you were describing acetylene welding?

Complete combustion there (neither oxidising nor carburising) produces CO2 as a by-product of combustion, and since there is little ionisation, the CO2 can act to shield the weld pool.

Edited By Andy Ash on 17/01/2017 14:26:07

More from BOC via email. I now have an account number and my welcome pack will arrive shortly.

Also a note - my account is not set for direct debit and this will mean that a £2.40 transaction fee will be added to all invoices. Maybe the depot's can't accept payment with say a debit card? They attach a direct debit mandate form and a free post address to send it to. They also mention an original signature which I would have thought the bank would want anyway so why the docusign method.

What actually thought was that there would be some other way of setting up a direct debit and intended to do that if needed anyway.

Blue background on the dd form. Uses more of my laser ink than needed. Would in black and white too.

John

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Edited By Ajohnw on 17/01/2017 14:26:42

Hmm, if you say so. In which case, perhaps you could explain what MAG is and what gases you might use?

You might start with BOC's intro - "Adding oxygen and/or carbon dioxide to a shielding gas for MIG welding carbon steel increases its oxidation potential. In general, for a given welding wire, the higher the oxidation potential of a shielding gas, the lower the strength and toughness of the weld. This occurs because the oxygen and carbon dioxide in the shielding gas increase the number of oxide inclusions and reduce the level of materials such as manganese and silicon in the weld metal."

Merry

Very true! Ordinary experience might lead us to believe CO2 is inert, but experience as opposed to experiment is liable to mislead. I well remember Fire Training given in 1972 by a seasoned Fireman and his film showing what happens when you use the wrong type of fire extinguisher on a fire.

One of the more spectacular clips was of a CO2 extinguisher used on a magnesium fire. Magnesium burns white hot in Carbon Dioxide, no oxygen is needed. In it's own way CO2 hitting burning Magnesium was as spectacular as the fireball resulting from pouring water into a burning chip fryer.

On the whole the professional didn't care much for CO2 extinguishers; he said they are usually too small to put a proper fire out and most amateurs forget the instructions and give themselves frostbite.

Generally his message was to concentrate on fire prevention rather than fire fighting. In the event of a fire his advice was "sound the alarm, clear the building, and get out as fast as you can." The speed at which a fire can spread is amazing - sometimes you only have seconds.

The other thing I remember vividly was the Fireman's scathing opinion of smokers and his emphatic use of "industrial language". Apparently they're a bunch of ******* junkies who can't be trusted not to ******* light up whilst looking for a ******* gas leak.

Much more effective than the web based fire training I did the year I retired!

Dave

Edited By SillyOldDuffer on 17/01/2017 16:13:37

A bit or trivia - Neon is more noble than argon. More so than helium too, or thought to be.

Left me wondering if neon could be used for welding. The breakdown voltages vary too.

A link to a table

https://en.wikipedia.org/wiki/Dielectric_gas

John

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Edited By Ajohnw on 17/01/2017 16:35:39

I wondered what the wiki had to say on the subject quote

It is one of the most commonly used compressed gases for pneumatic (pressurized gas) systems in portable pressure tools. Carbon dioxide is also used as an atmosphere for welding, although in the welding arc, it reacts to oxidize most metals. Use in the automotive industry is common despite significant evidence that welds made in carbon dioxide are more brittle than those made in more inert atmospheres, and that such weld joints deteriorate over time because of the formation of carbonic acid.^{[citation needed]} It is used as a welding gas primarily because it is much less expensive than more inert gases such as argon or helium.^{[citation needed]} When used for MIG welding, CO₂ use is sometimes referred to as MAG welding, for Metal Active Gas, as CO₂ can react at these high temperatures. It tends to produce a hotter puddle than truly inert atmospheres, improving the flow characteristics. Although, this may be due to atmospheric reactions occurring at the puddle site. This is usually the opposite of the desired effect when welding, as it tends to embrittle the site, but may not be a problem for general mild steel welding, where ultimate ductility is not a major concern.

John

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Just a quick update on Chorley Bottle Gas Ltd. Talking to Steve (the owner) yesterday (while collecting a 25L Argon 5% Mix) and he assures me that the prices on his website are inclusive of VAT. He is able to offer Pure Argon, Argon 5% Mix, Oxygen and Nitrogen in 10L, 20L 25L and 50L bottles. All bottles have a deposit of just £50 and gas costs are:

Pure Argon:

10L - £30.00 (2200Ltr Capacity)

20L - £55.00 (4400Ltr)

25L - £68.75 (5500Ltr)

50L - £100.00 (11000Ltr)

Argon 5% Mix, Oxygen and Nitrogen:

10L - £25.00 (A-2200Ltr, O-2100Ltr, N-1900Ltr)

20L - £50.00 (A-4400Ltr, O-4200Ltr, N-3800Ltr)

25L - £62.50 (A-5500Ltr, O-5250Ltr, N-4750Ltr)

50L - £90.00 (A-11000Ltr, O-10500Ltr, N-11000Ltr)

Chorley Bottle Gas are able to deliver in a large part of Lancashire free of charge.

Gas-UK are also offering Acetylene in 10Ltr bottles with a deposit of £100.00 and a fill charge of 82.80 having a capacity of 1780Ltrs.

Hope this helps

Nishka

BOC for 20L, Y sized cylinder gas £47.97, rent £75.72. I've added vat. That 230bar though so 5m^3. I've seen several where they contain 4m^3 plus a bit more. I came across one rental deal where the fill was 300bar and the regulator is fitted but the deposit was a couple of hundred and the fill charge very high even accounting for near 30% more of it.

John

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Edited By Ajohnw on 17/01/2017 23:55:24

This is an old thread and originally concerned oxy acetylene cylinders. It now seems to deal with tig and mig welding.

Can anyone tell me if there is a current cheaper source for oxy-acetylene gases other than BOC? I have finally had enough of their rather greedy pricings.

Thanks,

Andrew.

As said in thte post above!

Nishka