Machinery's Handbook, 31st Edition
1582 Gas Metal Arc Welding only an adjustment for voltage, which should be set initially at 31 volts, when using an argon + CO 2 mixture. GMAW Spray Transfer for Metal Thicknesses 1 ∕ 4 in. (6.4 mm) and Up.— The 0.45-in. (1.2-mm) diameter is the most cost-effective GMAW electrode for spray transfer welding of carbon, low-alloy, and stainless steels 1 ∕ 4 in. and thicker. A 7 ∕ 16 -in. (11.2-mm) single- pass, no-weave, fillet weld can be produced with this electrode. If larger single-pass welds are required, use of flux-cored electrodes should be considered.
Spray Contact Tip Setting and Electrode Stick-out
Ar Oxy Ar Oxy CO 2
Ar 15–20 CO 2
0.035 in. 0.9 mm
230
30
270
350
31
280
420
1 2 –5 8 in. (13 – 16 mm)
350 150
Contact Tip Recessed 1 8 in. (3.2 mm)
420 180
280 120
490
490 210
210 90
Ar 15–20 CO 2
31 280
560
560 240
140 60
630 270
630
70 30
700 300
33
0
700
ON OFF
300
34
Volts
350
Amps
Fig. 2. GMAW Spray Transfer Parameters with 0.035-inch (0.9-mm) Diameter Electrodes
A 400-amp power source is a practical cost-effective unit to use with the 0.045-in. diam eter electrode. Globular spray transfer, obtained at the ten o’clock position on the wire feed adjustment knob, starts at current levels of approximately 230 amps and requires a wire feed rate of approximately 210 in/min (90 mm/s). Most spray applications are carried out in the higher-energy, deeper-penetrating 270- to 380-amp range, or between twelve and two o’clock wire feed positions giving 350 to 490 in/min (150 to 210 mm/s). In this range, in which there is minimum weld spatter, the weld deposits are in the form of minute droplets and vaporized weld metal. The quadrants at the top in Fig. 3 show some typical settings for feed rate, voltage, and current, with different shielding gases. An ideal starting point with a 0.045-in. (1.2-mm) diameter electrode is to set the wire feed rate knob at the one o’clock position, or 420 in/min, at which rate the current drawn, depending on the power source used, should be about 320 to 350 amps. The best starting voltage for the 0.045-in. (1.2-mm) electrode is 30 volts. The arc length should then be set as indicated in Fig. 4. With current over 400 amps at 560 in/min, the 0.045-in. diameter electrode may produce a turbulent weld puddle and a digging arc, which can lead to lack of fusion, porosity, and cracks. GMAW Spray Transfer with 0.062-in. (1.6-mm) Diameter Electrodes.— Electrode wire of 0.062-in. (1.6-mm) diameter is the largest size in normal use and is often chosen for its high deposition rates. Due to the high-current requirements for the spray trans- fer mode, use of these thicker electrodes is generally restricted to metal thicknesses of 1 ∕ 2 in. (13 mm) and thicker. The high-current requirement reduces ease of welding. This electrode size is suitable for mechanized welding in which fillet welds greater than 3 ∕ 8 in. (9.6 mm) are required.
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