Shielding gas

I had find many products about gas shielding welding from some websites such as

	DIY Inverter DC Tig Welder (Tig-160s; Tig-200s; 250s) 1. Advanced inverter technology, high working frequency, reduced size and weight, easy to carry. Welding Electrode Holder Welding Electrode Holder Good durabilityHigh conductivityComplete prevention of electric shockEasy to repair and replace parts

And you can see more from ac dc welder Tig Welding Machine hobart mig welder exhaust pipe tip battery spot welder Wire Feed Welding Gas Machine Welding flux wire welding hydraulic welded cylinders
Shielding gases are inert or semi-inert gases that are commonly used in several welding processes, most notably gas metal arc welding and gas tungsten arc welding. Their purpose is to protect the weld area from atmospheric gases, such as oxygen, nitrogen, carbon dioxide, and water vapour. Depending on the materials being welded, these atmospheric gases can reduce the quality of the weld or make the welding process more difficult to use. Other arc welding processes use other methods of protecting the weld from the atmosphere as well shielded metal arc welding, for example, uses an electrode covered in a flux that produces carbon dioxide when consumed, a semi-inert gas that is an acceptable shielding gas for welding steel.
Contents
1 Common shielding gases
2 Properties of shielding gases
3 Applications
4 See also
5 References
//
Common shielding gases
Shielding gases fall into two categories姊歯ert or semi-inert. Only two of the noble gases, helium and argon, are cost effective enough to be used in welding. These inert gases are used in gas tungsten arc welding, and also in gas metal arc welding for the welding of non-ferrous materials. Semi-inert shielding gases, or active shield gases, include carbon dioxide, oxygen, nitrogen, and hydrogen. Most of these gases, in large quantities, would damage the weld, but when used in small, controlled quantities, can improve weld characteristics.
Properties of shielding gases
The important properties of shielding gases are their thermal conductivity and heat transfer properties, their density relative to air, and how easy they undergo ionization. Gases heavier than air (e.g. argon) blanket the weld and require lower flow rates than gases lighter than air (e.g. helium). Heat transfer is important for heating the weld around the arc. Ionizability influences how easy the arc starts, and how high voltage is required. Shielding gases can be used pure, or as a blend of two or three gases. [1] [2]
Helium is lighter than air; larger flow rates are required. It is an inert gas, not reacting with the molten metals. Its thermal conductivity is high. It is not easy to ionize, requiring higher voltage to start the arc. Other gases are often added. Blends of helium with addition of 5-10% of argon and 2-5% of carbon dioxide can be used for welding of stainless steel. In comparison with argon, helium provides more energy-rich but less stable arc. Helium and carbon dioxide were the first shielding gases used, since the beginning of World War 2.
Argon is heavier than air; lower flow rates are needed to blanket the weld. It is an inert gas, not reacting with the molten metals. It has low thermal conductivity. It ionizes easily. It is often used as pure when welding aluminium and other nonferrous metals, though other gases can be added. A blend of argon with 25-50% of helium is used for some nonferrous metals, as helium improves heat transfer into the base material and makes the molten metal more fluid. An oxidizing component (oxygen, carbon dioxide) is usually added to stabilize the arc for welding of steels; without it the arc control can be difficult as the arc tends to stray. In industrial gas business it is known as "the big A".
Carbon dioxide has good heat transfer properties; it dissociates in the weld and recombines in contact with the colder metal. Due to the presence of dissociated oxygen, the weld zone has oxidizing properties, producing more slag. Carbon dioxide can be used as pure, or in a mixture with argon as 5 to 25%. Increasing percentage of carbon dioxide increases width and depth of the weld penetration. For welding of stainless steels where carbon content control is required, an argon-helium blend with 1-2% of carbon dioxide can be used. "Trimix" blends of argon-oxygen-carbon dioxide are more common in United Kingdom, while argon-carbon dioxide blends are more common in the USA. In comparison with argon-carbon dioxide mixture, for steel welding, pure carbon dioxide increases spatter and the arc is less stable. [3] Pure carbon dioxide provides deep weld penetration and is very cheap. [4]
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. 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.
Nitrogen is used for welding of some stainless steels. It increases the weld penetration and enhances arc stability. It however can cause porosity in carbon steels. Argon-carbon dioxide-nitrogen blends can be used. Pure nitrogen is also used, or can be blended with 10% of hydrogen, depending on application. Blends with nitrogen content are used to weld nitrogen-containing alloys (up to...(and so on)

	AC / DC Welder (Super416, Super518) 1. Advanced inverter techenology, light, smart & efficient.

You can also see some feature products :

hot air welder welding spare parts SMD Rework Station Plastic Welding Machine MIG Welding Wire led super flux aluminium welding wire DC ARC Welder Stainless Wire Welding aluminum machine welding Aluminum Welding Wire ac/dc arc welder DIY Tig Welder Gun Spot Welding gas shielding welding Laser Spot Welding Solder And Flux ARC Machine Welding Artificial Nail Tip Pipe Fitting Welding Machine Tig Welding