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mytqik
Joined: 26 Jun 2004
Posts: 127
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quote:
Originally posted by Team Hell Bent!:
Are welding goggles as good as a mask cos they are a little more compact and easyer to use?
Well the goggles you refer to are for oxy/fuel welding. They are generally around a shade 5-6 lense & are solely for the oxy/fuel process.
The mask is the *only* option. Apart from having a lense that is around 11-13, they also stop all the nasty UV rays damaging your face, causing skin burn & possibly skin cancer.
If you can afford it I would highly recomend the purchase of a self darkening helment. These units normally have a larger window to see through making the welding process for beginners easier. Once turned on they are about a shade 3, which allows you to see fairly well, but also allows you to use other power tools (grinders etc) without having to take the welding helment off & put on your safety glasses.
Once an arc is struck by the welder the lense automatically darkens in a millisecond & you have a shade suitable for arc/mig welding. The cheap units are only fixed shade & battery powered, then the more you spend the more options you get eg: solar powered & lense shade adjustment.
quote:
Originally posted by Timothy Forde:
ok just wondering can you weld ali with a oxy?
In a word: no. Aluminium exibits a strange behavour in that its oxide coating which naturally forms with contact with oxygen actually has a higher melting point than its parent metal. The melting point of Al is about 550C but the ALO2 oxide melts at 1300C. Eg if you heat a piece of aluminium until is it cherry red, you will notice that the outside does not melt, however the metal has lost all strength. It actuallys melts from inside out.
Therefore to weld Al you need to remove this oxide layer. This is done by reversing the polarity of the welding process, so the arc actually goes from the workpiece to the handpiece. As the ALO2 is not conductive but the AL is the arc must pass through the ALO2 coating. This "shatters" the oxide coating & allows the AL to be welded. This process is best performed by an AC TIG, or a MIG & maybe an ARC welder if you have the right rods. However it is the least successful method.
The reversing of the polarity also help in that al of the heat is now generated in the hand piece. As AL has such a low melting point, the less heat induced into it the better the weld. People welding thicker sections of AL with a TIG will actually use a water cooled torch.
As the oxy/fuel welding relies on heat. not electrical current it can not weld AL. The only option would be to braze the AL together if you only have oxy/fuel equipment.
Hope this helps.
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Thu Sep 09, 2004 9:21 pm |
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mytqik
Joined: 26 Jun 2004
Posts: 127
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Nick,
You mentioned the build up of carbon?? I am therefore assuming you are talking about welding steel, as there is no carbon at all in the aluminium welding process. Pitting is usuaaly casused by two things:
1. There are contaiminats in the weld pool. This is usually caused by by not cleaning the surface of the workpiece before welding. A rub with a good quality stainless steel wire brush should fix this
2. Not enough gas flow. The gas is present to sheild the molten weld pool from the atmosphere. If not enough inert gas is present during the welding process, atmospheric air ie oxygen can come in contact with the molten weld. When hot/molten steel comes in contact with oxygen, it oxidises rapidly. This is the same property that allows steel to be oxy/fuel cut, but aluminium can't.
Nick, hope this helps. If you can take some photos of the welds you are refering too, I may be able to offer a more detailed answer. Also can you provide some more detials, ie material thickness, electrode thickness, amp settings, gas flow setting & gas type, is the electrode on the positive or negative etc. Cheers.
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Fri Sep 10, 2004 1:51 pm |
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