Requirements for CO2 shielding gas for gas shielded welding
Industrial CO2 is in liquid state, and it gasifies at room temperature. Water in liquid CO2 can dissolve water with a mass fraction of about 0.05%. This moisture evaporates with CO2 during the welding process, and water vapor is mixed into the CO2 gas and enters the welding zone together. The main harmful impurities in CO2 gas are moisture and nitrogen. Nitrogen is generally less in content, and the most harmful is moisture. With the increase of moisture in the CO2 gas, the hydrogen content in the weld also increases, and porosity may also occur in severe cases. The purity of CO2 for welding should be greater than 99.5%.
方面 The production of CO2 gas shielded welding protective gas mainly depends on the by-products of lime kiln manufacturers, chemical companies and brewing companies in various regions. If the water content of CO2 gas is high, the following measures can be taken:
1) Put the new gas bottle upside down for 1 to 2 hours, then open the valve to drain the free state water deposited in the lower part. Depending on the water content in the bottle, it can be drained 2 to 3 times, every 30 minutes. After draining, place the cylinder upright
2) Before using the gas cylinder, the gas cylinder must be deflated for 2 ~ 3min before using the gas. Because this part of the gas usually contains more air and moisture, these air and moisture are mainly mixed into the bottle when it is filled.
3) High pressure dryer and low pressure dryer are set in the gas path to further reduce the moisture in the CO2 gas. Generally use silica gel or dehydrated copper sulfate as the dryer. The used dryer can be reused after drying.
4) When the air pressure in the bottle drops to 980kPa, it is no longer used.