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Spray-arc

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Re: Spray-arc

Postby welderkid556 » Wed Jun 12, 2013 2:09 am

i am confused with the whole idea of people adding oxygen to tank mixtures, doesnt that contaminate welds just as if wind is to blow away the shield? i have never seen any mixture in my area include oxygen. all we can get is argon,co2, helium for welding. but for cutting we can get full tanks of oxygen. i have always been taught that if ANY oxygen gets into the weld it will contaminate the puddle and your done, it causes porosity, snail trails if useing flux core and massive popping and crackleing and none of it sounds good. so please explain what you mean by adding oxygen to a gas cylinder for welding.
thank you for the replies
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Re: Spray-arc

Postby Alexa » Wed Jun 12, 2013 9:19 am

welderkid556 wrote:i am confused with the whole idea of people adding oxygen to tank mixtures, doesnt that contaminate welds just as if wind is to blow away the shield? i have never seen any mixture in my area include oxygen. all we can get is argon,co2, helium for welding. but for cutting we can get full tanks of oxygen. i have always been taught that if ANY oxygen gets into the weld it will contaminate the puddle and your done, it causes porosity, snail trails if useing flux core and massive popping and crackleing and none of it sounds good. so please explain what you mean by adding oxygen to a gas cylinder for welding. thank you for the replies


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Welderkid556.

I found this paragraph for you from Wikipedia.

"... Oxygen is used in small amounts as an addition to other gases; typically as 2–5% addition to argon. It enhances arc stability and reduces the surface tension of the molten metal, increasing wetting of the solid metal. It is used for spray transfer welding of mild carbon steels, low alloy and stainless steels. Its presence increases the amount of slag. Argon-oxygen (Ar-O2) blends are often being replaced with argon-carbon dioxide ones. Argon-carbon dioxide-oxygen blends are also used. Oxygen causes oxidation of the weld, so it is not suitable for welding aluminium, magnesium, copper, and some exotic metals. Increased oxygen makes the shielding gas oxidize the electrode, which can lead to porosity in the deposit if the electrode does not contain sufficient deoxidizers. Excessive oxygen, especially when used in application for which it is not prescribed, can lead to brittleness in the heat affected zone. Argon-oxygen blends with 1–2% oxygen are used for austenitic stainless steel where argon-CO2 can not be used due to required low content of carbon in the weld; the weld has a tough oxide coating and may require cleaning. ..."

source: http://en.wikipedia.org/wiki/Shielding_gas

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Re: Spray-arc

Postby Otto Nobedder » Wed Jun 12, 2013 6:35 pm

Rediron881, a member here, regularly TIGs heavy stainless to vacuum-tight standards with a mix containing mostly argon with 2% O2. If I recall, there's a third gas at 3%, but I'm not sure. I'll have to dig up that topic and refresh my memory.

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Re: Spray-arc

Postby Otto Nobedder » Wed Jun 12, 2013 6:38 pm

My mistake...

It's 98% AR, 2% HYDROGEN!

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Re: Spray-arc

Postby welderkid556 » Thu Jun 13, 2013 12:35 am

correct me if im wrong but isnt hydrogen highly unstable, the same reason why automobile companies wont use hydrogen to power the automobiles instead of gas. by compressing that into a gas cylinder would make the risk even higher if something was to happen inside of a shop? say if something happened to the compressed gas cylinder? im not saying the mixture wouldnt work i would just be concerned about having any form of hydrogen in or anywhere near our shop.
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Re: Spray-arc

Postby Alexa » Thu Jun 13, 2013 1:47 am

welderkid556 wrote:correct me if im wrong but isnt hydrogen highly unstable, the same reason why automobile companies wont use hydrogen to power the automobiles instead of gas. by compressing that into a gas cylinder would make the risk even higher if something was to happen inside of a shop? say if something happened to the compressed gas cylinder? im not saying the mixture wouldnt work i would just be concerned about having any form of hydrogen in or anywhere near our shop.


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Welderkid556.

Found this brief information concerning the safety of hydrogen on page 62 of the following link.
http://www.awssection.org/uploads/longi ... Manual.pdf

"... HYDROGEN DANGER

Hydrogen is a flammable gas. A mixture of hydrogen with oxygen or air in a confined area will explode if ignited by a spark,
flame, or other source of ignition. A hydrogen flame is virtually invisible in well-lighted areas. Hydrogen as a liquid or cold gas may cause severe frostbite to the eyes or skin. Do not touch frosted pipes or valves.

Always use a pressure-reducing regulator when withdrawing gaseous hydrogen from a cylinder or other high-pressure source.
Take every precaution against hydrogen leaks. Escaping hydrogen cannot be detected by sight, smell, or taste. Because of its lightness, it has a tendency to accumulate beneath roofs and in the upper portions of other confined areas.

Do not mix hydrogen with other gases from separate cylinders. Always purchase hydrogen blends ready-mixed. ..."

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Re: Spray-arc

Postby noddybrian » Thu Jun 13, 2013 7:14 am

In the UK hydrogen in cylinders is available & although it's not commonly used yet BOC are unable to provide acetylene here since both bottling plants suffered incidents they are having to buy in acetylene from Air Liquide in France & although their part of the same group they state they are going to phase out acetylene completely & it's suggested that hydrogen will replace it for oxy - fuel cutting / welding. This is not a new idea - a long time ago I'd used hydrogen for cutting underwater - don't think they still do as there is oxy arc / thermic lanse & probably other methods now.

Sorry to side track this post but when oxy / acet was easy to obtain & cheap a company made a thing called H2O-2000 ( or something like it ) basically just a big mains powered HHO generator which was grossly over priced & never caugh on - but with the supply issues & cost of gas now does anyone know if there is anything like it still around - if so has anyone tried it - was it any good - or better yet does anyone know how big the plate stack was in it as it would not be rocket science to make one.
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Re: Spray-arc

Postby welderkid556 » Thu Jun 13, 2013 4:54 pm

i thought hydrogen was pretty flammable lol. ive used accetline for cutting but i use propane now and it works just fine for cutting steel, just today i cut a peice of 1/4 inch steel and it cut right through it with no problem, but im sure it would cut through half inch and possibly even 3/4 inch steel. i may have to try it but i know propane seems to get the steel pretty hot before you can blast through the steel. it seems with accetline its a more mellow way to cut steel and doesnt take half as much heat. over in the UK can you get ahold of propane or have they gotten rid of propane aswell as accetline?
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Re: Spray-arc

Postby noddybrian » Thu Jun 13, 2013 6:15 pm

Sure - you can get propane here - alot of people use it - more for heating than cutting - ir's obviously not as hot or concentrated a flame as with acetylene but is adequate for most free hand cutting - never seen a profiler use it though - cuts are never as clean - it's also alot slower getting initial heat into the job & you will use more oxygen per similar amount of cut. acetylene is currently still available but as it's having to be imported the price is awefull. not sure what maximum thickness for hand held cutting is - obvioulsy it's in proportion to nozzle size & cutting pressure, but I routinely cut upto 4" by hand - when cutting any amount over say 1" though I usually swap to a longer torch as the amount of hot metal & general heat from the job gets a bit much - depending on the job I use 12" necked torch for small odd jobs & easier control then I have 24" & 36" torches in regular 90degree 45 degree & a straight one I keep mostly for cuttting sheet piles in situe.
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Re: Spray-arc

Postby Otto Nobedder » Thu Jun 13, 2013 7:33 pm

I once worked at a plastics manufacturer, and used a hydrogen-oxygen torch on a regular basis.

I now work almost exclusively in the LIQUID hydrogen transport industry.

It's safer than you think.

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