Gas in Arc welding

Gases used in arc welding processes are the shielding gases. Shielding gases used in arc welding are argon, helium, and carbon dioxide. The gases have a remarkable effect on the overall performance of the welding system. The main function of these gases is to protect the weld pool from adverse reactions with atmospheric gases. Oxygen, nitrogen and water vapour present in ambient air can cause weld contamination. Weld shielding, always involves removal of potentially reactive gases from the vicinity of the weld, preventing the detrimental effects on the molten metal of the surrounding atmosphere. Shielding gases also stabilizes the arc and enhances the metal transfer mode in arc welding processes. The shielding gas interacts with the base and filler metal and changes basic mechanical properties of the weld area, such as strength, toughness, hardness and corrosion resistance. Shielding gases moreover have important effects on the formation of the weld bead and the penetration pattern. The usage of shielding gases can lead to different penetration and weld bead profiles. However, apart from all these important effects, the gases have to be handled with care. These gases that stored in compressed gas cylinders are potentially hazardous because of the possibility of a sudden release of gas by removal or breaking off of the valve. High-pressure gas escaping from such a cylinder causes it to be like a rocket which may smash into people and properties. In storage, transport and operation of compressed gas cylinders it is imperative to observe the following rules: Whether in use or stored, the cylinders should be kept vertical and secured so as to avoid falling by means of chains and clamps. To open cylinder valves hammers and wrenches must not be used. The proper trolley should be used for moving cylinders from one point to another in the workshop. The cylinder should never be carried on shoulders because in case it falls it can not only injure the person but may also explode. Compressed gas should not be exposed to sunlight or heat as this may lead to an increase in the pressure leading to an explosion. The temperature of the gas cylinder should not be allowed to exceed 54 oC. Cylinder valve must be opened gradually with proper care otherwise it may damage the regulator diaphragm. Cylinders must have caps during storage and transport.