Welding Gases
Acetylene | Air | Argon | Carbon Dioxide(CO2) | Helium
Hydrogen | Nitrogen | Oxygen | Propane
Carbon Dioxide (CO2)
Carbon Dioxide (CO2) is a non-flammable, colorless, odorless gas which exhibits an acidic taste. It is found in air at concentrations of about 0.03%. Carbon dioxide may exist simultaneously as a solid, liquid, and gas at a temperature of -69.9 degrees F (-56.6 degrees C) and a pressure of 60.4 psig (416 kPa). At a temperature of -110 degrees F (-79 degrees C) and atmospheric pressure, carbon dioxide solidifies forming "dry ice" at a density of 97.4 pounds per cubic foot. Because of its low concentration in the atmosphere, air is not a suitable feedstock for carbon dioxide production. Rather, carbon dioxide is obtained for by-product streams from various manufacturing processes, such as the combustion of coal and natural gas. Bulk quantities of carbon dioxide are usually stored and shipped as liquid under elevated pressure and refrigeration.
Although not truly inert, carbon dioxide is nonreactive with many materials and is often used for inerting purposes, such as blanketing and purging of tanks and reactors. Mixed with argon at various levels, carbon dioxide is valuable as a shielding gas in the arc welding process. In this application carbon dioxide is the best shielding gas because of its high heat conductivity and its ability to oxidize ferrous metals. Argon mixed with carbon dioxide usually increases penetration of the weld in most metals.
Carbon dioxide is also used as the source of bubbles in soft drinks and other carbonated beverages. It is used to fill certain types of fire extinguishers that rely on its inert properties, density, and low temperature when released from high pressure storage. In addition to its "inert" properties, carbon dioxide as dry ice is used to freeze a variety of foods.
| DOT Information | ||
| DOT Name: | Carbon Dioxide, Liquefied | |
| DOT Hazard Class: | Nonflammable Gas | |
| DOT Label: | Nonflammable Gas | |
| DOT ID No.: | UN1013 | |
| CAS No.: | 624-64-6 | |
| Valve Outlet: | CGA 320, CGA 960 Pin-indexed | |
| Physical State in High Pressure Cylinder: Liquid under own vapor pressure | ||
| Fire Potential: | Non-Flammable | |
| Major Hazards: | Asphyxiant, High Pressure Inhalation | |
Physical Properties of Carbon Dioxide |
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| Formula: | CO2 | |
| Molecular Weight: | 44.01 lb/mol | |
| Specific Volume at 70°F and 1 atm: | 8.74 ft3/lb (0.42 m3/kg) | |
| Specific Heat: | 8.92 BTU/lbmol-deg F@ 70 deg. F | |
| Specific Gravity: | 1.555 | |
| Gas Density: | .1144 lb/ ft3 @ 70 deg. F. 14.7 PSIA | |
| Psat @ 70 deg F: | 852.8 psia | |
| Liquid Density @ 70 deg F: | 47.64 lb/ft3 | |
| Boiling Point | ||
| Temperature: | -109.2 deg. F (-79 deg. C) | |
Critical Point |
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| Temperature: | 87.9 deg. F | |
| Pressure: | 1070.6 PSIA | |
| Triple Point | ||
| Temperature: | -69.9 deg. F | |
| Pressure: | 75.13 PSIA | |
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