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Istruzioni per l'uso Metabo, Modello MIG Welding Machines OMEGA 400 SEK/W

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Cast iron electrodes, for example, fall into this class. When buying Kb and So type electrodes make sure they are suitable for AC current. As far as the quality grades are concerned, a higher number indicates a better grade quality. For common low-carbon steels grades 7 - 9 are best suitable. The last letter of the code shown on the stick electrode indicates the coating thickness. d = light coating m = medium coating s = heavy coating 4.4.2.6 Arc Starting And Arc Burning Arc Strike Always start the arc in the welding groove. When the arc is stable weld over the arc strike and melt for good fusion, otherwise there is a risk of cracking. Arc starting open-circuit voltaqe Short-circuit voltage workinq voltage 3 to 5 V 20 to 30 V Arc Length The arc length “a”, that is the distance between the stick electrode and the work, should be: with stick electrodes of coating type R, RR, A, C = 1.0 x d with stick electrodes of coating type B = 0.5 x d Too long an arc reduces the penetration, increases the arc blow effect and, particularly with basic coated stick electrodes, causes a porous weld seam. 4.4.2.T Welding Positions According To DIN 1921 w w = gravity position h = horizontal position s = vertical-up position f = vertical-down position q = horizontal-vertical position ü = overhead position 4.4.3 Welding Hints Because of the multitude of and great differences in the important points for welding only the very basic operations for the most common electrodes for low-carbon steels, the Ti-type electrode, are introduced here. In the case that other electrodes have to be used, the electrode manufacturers supply upon request all relevant information for the type of special electrode to be used. Always make some trial welds on scrap material. Select electrode diameter and welding current as per Table 1). Attach earth clamp to work piece and place electrode into electrode holder as described earlier. Now hold the electrode tip approx. 2 cm / 3/4 inch above the starting point of your welding seam. Hold the welding visor in front of your face and draw the electrode with a short stroke along the groove. Through the welding shield you watch the arc, keeping it to a length of 1 to 1.5 times the electrode diameter. arc too long (Fig. 1) approx. 1 1.5 the electrode-0 (Fig. 2) The correct arc length is important for a good weld, because with too short or too long an arc both welding current and working voltage change. A low working voltage causes insufficient penetration. Too high or too low welding current gives a poor welding seam. Too long an arc does not sufficiently melt the parent material, resulting in high spatter losses. Also the air, with its detrimental substances like hydrogen and nitrogen, may get access to the weld pool. For a good weld the work angle of the electrode (or electrode inclination angle) is of substantial importance. The inclination should be 70° - 80° to the welding direction. With the work angle too steep slag will run under the weld pool, too flat an work angle causes the arc to spatter, in both cases the result is a porous, weak welding seam (see figure 3 - 5). wrong welding direction -► wrong welding direction -► (Fig. 3) (Fig. 4) (Fig. 5) The welder has to keep the arc at the same length, that is the electrode burn-off is compensated by feeding the electrode into the weld. At the same time the welder has to watch the weld pool for even penetration and width. Welding is always done from left to right (backhand welding). At the end of the welding seam the electrode can not simply be lifted or pulled from the weld, this creates porous end craters, which weaken the weld. To correctly terminate a weld the electrode is held for a short moment at the end of the weld seam, then lifted in an arc over the just laid weld. (Fig. 6) (Fig. 7) Remove slag only after it has cooled down and is no longer glowing. If an interrupted weld is to be continued, the slag at the end of the already finished weld must be removed. Then the arc can be started either in the groove or on the weld, as described earlier, and then moved to the end of the weld, which has to be thoroughly melted for good fusion. Welding is then continued normally. 4.4.4 Weld Types For Butt Welds the work piece edges should be bevelled to approx. 30°, which gives a groove angle of 60° (Fig. 8). The root opening between the two work pieces should be 2-3 mm. For Fillet Welds “a” is the throat width size. The throat width should be at least x 0.7 the plate thickness of the thinner plate. Other weld types: double-V-groove weld (x-weld) single-bevel-groove weld (y-weld) single-J-groove weld (J-weld) flange weld (Fig. 8) (Fig. 9) A joint weld must always have a good fusion at the root. wrong correct (Fig. 10) Let weld cool down in the ambient air, do not quench. (Fig. 11) 4.4.5 Weld Flaws And Possible Causes -Shown On Fillet Welds Weld Undercut Welding current to high Electrode work angle...