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 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 aittank 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. Hardfacing alloys contain as base elements typically iron, nickel, or cobalt, to which metallurgists add varying amounts of carbon, chromium, molybdenum, tungsten, silicon, manganese, vanadium, and boron. To raise hardness, the primary property for wear resistance, alloy designers add elements that either form hard constituents (carbides, borides, or Laves phase), or that strengthen the matrix by going into solid solution. Carbon content determines toughness and abrasion resistance--as carbon rises, abrasion resistance increases and toughness drops. Chromium forms carbides, increases corrosion resistance, and adds high-temperature strength. Tungsten, a potent carbide former, also boosts high temperature strength, as does cobalt. Tougheners include nickel and manganese. Boron forms hard wear-resistance borides. Electrodes come 3 to 24 in. long, 0.01 to 0.25-in. diameter. Colored markings--bands or dots--indicate composition: aittank pure tungsten, aittank green; 1-percent thoriated, yellow; 2 percent thoriated. red; ceriated, orange; lanthanted, black.Filler metal GIAW aittank does not usually requite addition of fillet metal, but filler is commonly added aittank when base-metal thickness is greater than 1/8 in. Finer metal for low-carbon (to 0.15 C) and mild (0.15 m 0.29 C) steels are described in AWS A5.2; for carbon steel in A5.18; and for low-alloy steels in A5.28 Flux. AWS specifications A5.17 and A5.23 describe fluxes for saw. AWS designation of fluxes precedes that of the wire when identifying a combination for a welding procedure. For example, the designation F7A2-EM12K indicates a flux (F) that will provide, with a given wire designation, tensile strength of 70,000 Psi (7), in the as-welded condition (A), and impact properties of 20 ft lb at -20 F (2). A designation containing a P rather indicates the flux properties after postweld heat treatment. 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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