Shielded Metal Arc Welding Machinery's Handbook, 31st Edition
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Table 15. Characteristics of AWS Electrodes for SMAW Welding Standard Description Table 15. (Continued) Characteristics of AWS Electrodes for SMAW Welding
AWS E7018 CSA E48018 BS E5154B11026(H) DIN E5154B(R)10 JIS D5016 AWS 7024 CSA E48024 BS E5122RR13034 DIN E5122RR11 JIS D4324
An iron-powder, low-hydrogen, all-position electrode. Excellent for rigid, highly stressed structures of low- to medium-carbon steel. Can also be used for welding mild and high-strength steels, high-carbon steels, and alloy steels. Polarity AC or DC + reverse polarity. An iron-powder electrode with low hydrogen, usable in all positions. Excellent for high-amperage, large, fillet welds in flat and horizontal positions. Polarity AC or DC, + or − .
AWS E7028 CSA E48028
BS E514B12036(H) DIN E5143B(R)12 JIS D5026 An iron-powder, low-hydrogen electrode suitable for horizontal fillets and grooved flat position welding. Higher deposition rates. More cost-effective than the AWS E7018 electrode. Polarity AC or DC + reverse polarity. The E7024 electrode is suggested for horizontal fillet welds. For 10-gage (0.135-in, 3.4- mm) material, try the 1 ∕ 8 -in. (3.2-mm) diameter electrode; for above 10-gage to 3 ∕ 16 -in. (5- mm) material, try the 5 ∕ 32 -in. (4-mm) diameter electrode. For plate of 3 ∕ 16 - to 1 ∕ 4 -in. thick ness, try the 3 ∕ 16 -in. size, and for plate thicker than 1 ∕ 4 in., try the 1 ∕ 4 -in. (6.4-mm) electrode. Gas Tungsten Arc Welding Often called TIG (for tungsten inert gas) welding, gas tungsten arc welding (GTAW) uses a nonconsumable tungsten electrode with a gas shield, and was, until the development of plasma arc welding (PAW), the most versatile of all common manual welding processes. Plasma arc welding is a modified GTAW process. In contrast to GTAW, plasma arc welding has less sensitivity to arc length variations, superior low-current arc stability, greater poten- tial tungsten life, and the capability for single-pass, full-penetration welds on thick sections. In examining a potential welding application, the three primary considerations are: achieving a quality weld, ease of welding, and cost. Selecting the optimum weld process becomes more complex as sophisticated electronic technology is applied to conventional welding equipment and consumable electrodes. Rapid advances in gas metal arc and PAW welding power source technology, and the development of many new flux-cored elec trodes, have made selection of the optimum welding process or weld consumable more difficult. When several manual welding processes are available, the logical approach in considering GTAW for production welding is to first examine whether the job can be welded by gas metal arc or flux-cored methods. GTAW Welding Current.— A major benefit offered by GTAW, compared with GMAW, FCAW, or SMAW, is the highly concentrated, spatter-free, inert heat from the tungsten arc, which is beneficial for many applications. The GTAW process can use any of three types of welding current, including direct-current straight polarity, electrode negative (DC − ), direct-current reverse polarity, electrode positive (DC+), and alternating current with high frequency for arc stabilization (ACHF). Each of the different current types pro vides benefits that can be used for a specific application. GTAW Direct-Current Straight Polarity (DC−): The most common GTAW current is straight polarity, where the electrode is connected to the negative terminal on the power source and the ground is connected to the positive terminal. Gas tungsten arc welding is used with inert gases such as argon, and argon + helium to weld most metals. During a DC − straight-polarity weld, electrons flow from the negative tungsten electrode tip and pass through the electric field in the arc plasma to the positive workpiece, as shown in Fig. 8.
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