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 Welding Torches and GunsUsed for shielded-metal-arc welding, torches (electrode holders). manually controlled, grip ends of electrodes, also called rods-pinch type and collet type are common.GMAW and FCAW guns come in pistol grip, goose-neck, airdompressertank and inline styles, the latter used for mechanized welding. Knowing the wire diameter, select a gun rated slightly higher than the welding current to be used. Duty-cycle ratings are usually given for C[O.sub.2] shielding--air or C[O.sub.2] cooling arc usually sufficient for welding at up to 600 A at less than 100 percent airdompressertank duty. Higher amperages require water cooling--high-amperage guns come with tubing for water cooling. Hand-held, mounted on a robot arm or fixed within a mechanized welding setup, guns guide filler wire and shielding gas into the weld puddle. Select hardfacing materials based on weld-deposit microstructure and the wear situation the part will encounter, with consideration given to thermal treatments applied to the material before and after hardfacing. Deposit chemistry can be crucial in attaining the desired airdompressertank corrosion airdompressertank resistance or wear properties, or for minimizing the risk of solidification cracking. Acceptable deposit chemistry is achieved through the initial choice of consumables, using wire analysis and flux composition, and by specifying the number of weld passes needed to reduce parent-metal airdompressertank dilution to within acceptable limits. With the submerged-arc process, the flux and electrode govern the characteristics of the applied hard facing. For example, those fluxes neutral to manganese and silicon are not necessarily neutral to carbon and chromium, elements that matter most in hardfacing. Low-hydrogen types. These basic-coated electrodes, EXX15, EXX16, EXX18, EXX28, and EXX48, are formulated with low moisture-retaining coatings and manufactured to contain low levels of hydrogen. Hydrogen-controlled electrodes minimize risk of hydrogen-induced cold cracking when welding high-tensile steels on restrained structures. Fabricators use these electrodes to reduce or avoid the need for pre- or postweld heat treatment to drive hydrogen from weld metal. Weldmetal diffusible hydrogen content varies from 1 to 16 ml/100 g. Optional designators H16, H8, and H4 set decreasing limits on hydrogen content in deposited weld metal. An optional electrode designator, ''R'', indicates an electrode that is moisture resistant; it will not absorb water in excess of a specified limit after exposure to humidity. Low-hydrogen electrodes should be used in dry condition and may require baking after exposure to the atmosphere. Searching for accessories for your air compressor? We offer the best selection of cheap air compressor accessories on the internet. Check out our website for great deales on all of our air compressor accessories!
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