Carbon Dioxide, CO², is an active gas when used with welding wire but at room temperature it is an inert gas. Form of a compound containing carbon monoxide and oxygen.
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CO², obtained by burning natural gas, oil, and coking coal. As for CO², obtained from the production of ammonia and fermented alcohol, it is 100% pure CO², gaseous and liquid. It is non-flammable, non-toxic, odorless and colorless. In addition, CO², is about 15 times heavier than air. Grades of CO², can be divided into several grades. According to the nature of the components and purity are:
*Food Grade
*Medical Grade
* Industrial Grade
and Welding Grade consists of the following details
Minimum Carbondioxide 99.5%
Moisture less than 100 ppm.
CO² through an arc is broken down into carbon monoxide and oxygen. The oxygen combines with the elements transported by the arc to form oxides. and floats above the melting pool in the form of slag and scale. Although CO², is an active oxidizing gas, the weld quality is perfect without porosity and flaws. CO², will be applied to steel welding and low alloy steel Because it is a gas that is easy to find, cheap, and has good weld quality. and easy to install The metallurgical efficiency of CO², is low because of the spatter loss which affects the total cost when welding with CO².
CO², Spray Transfer is not possible, but only Short Circuiting and Globular Transfer. The advantage of using CO² gas is high welding speed and high penetrating depth. High Spatter Using CO², for example, will result in a high oxide weld surface. Therefore, it is necessary to add elements to reduce oxygen. (Deoxidizing) a lot into the welding wire to prevent the welding surface from oxides. and achieve good mechanical properties as well When welding using argon mixed with CO, as a shielding gas, the properties are different from CO², only gas for applications requiring high impact resistance. A gas mixture of Argon and CO² is recommended.
Connecting CO², discharge to each tank should not exceed 25 C.F.H (12 L/min) flow rate from the tank. If the demand is exceeded, a Manifold system or Flow Meter should be used.
The type with Heater gives heat better. Because if the flow rate of CO², is too high, it will cause solidification of CO², clogging the Flowmeter or drawing CO², liquefied from the tank.
2 types of mixed gas
Argon + Oxygen
Argon mixed 0, a small amount produces a uniform arc. Increased welding wire fill rate, spray arc formation at low current (Transition Current), molten metal with good flow (Wetting) and beautiful weld shape. The metal water in the molten pond remains liquid for a long time in order to Metal water to flow to the TOE of the welding seam, which the above mentioned properties will help the weld seam not occur undercut and the seam will be flat.
Non-Ferrous Welding It has been reported by NASA that mixing 1% oxygen will cause
Uniform arc for extremely clean aluminum sheet welding
Argon-1% O² Shielding gas initially used in stainless steel ray transfer welding. The addition of 1% oxygen provides a uniform arc. Improved filling of welding wire rod metal and improved weld appearance
Argon-2% O²- Shielding gas used for welding wire carbon steel. Low-alloy steel and Spray Transfer stainless steel, but will provide better flow properties than the 1% O². The mechanical properties and corrosion resistance of the weld with 1% and 2% O². the same
Argon-5% 0.
– It is a shielding gas that mixes a lot of oxygen. to cause the flow of better metal water But it can also control the melting pool. It is commonly used to weld carbon steel. Adding more oxygen also increases the welding speed.
Argon-8-12% 0. – It is a very popular shielding gas in Germany. At present, 3% and 12% gas mixtures are used in the United States. For welding a single line of welds (Single pass) for the overlapped line of welds (Multi-pass) is also used. which must depend on the chemical alloying elements of the welding wire that is, the alloying elements must Compensate for the loss of elements in the metal reacting with the shielding gas. The advantage of this type of gas shield is to allow the flow of water. Good Metal and Low Spray Arc Current (Transition Current)
Argon-12-25% 0, is a very high-oxygen shielding gas. The advantage between 12% and 25% 0% mixing ratio is inconclusive. But the flow of metal water when The use of gas covering this type is very high. The weld will have slag or scale. Very thick weld face masking and difficult to remove. The integrity of a 25% mixed gas weld has little or no porosity. For overlapping welding, all slag or scale must be cleaned before welding.
