Kemppi MinarcTig Evo 200 Operating Manual

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EN3.2 Manual metal arc welding (MMA)In Manual Metal Arc (MMA) welding the filler material is melted from the electrode to the weldpool. The rate of welding current is selected on the basis of the welding electrode size usedand welding position. The arc forms between the electrode tip and work piece. The meltingelectrode coating forms a gas and slag shield, which protects the molten metal in transferto the weld pool and during solidification. As the slag solidifies over the hot weld metal, itprevents weld metal oxidation. This slag coating is removed after welding e.g. with a chippinghammer. When removing the slag coating, ensure you protect your eyes and face with suitableequipment.For more info www.kemppi.com > Welding ABC.MMA welding electrodesIn MMA welding, the welding electrodes must be connected to the correct pole. Normally,the electrode holder is connected to the positive and the earthing cable to the negativeconnector.It is also important to properly adjust the welding current so that the filler material andcoating will melt properly and the welding is efficient. The table below presents the electrodesizes available with the MinarcTig Evo welding machine and the corresponding weldingcurrent values.MMA Electrodes and corresponding current settings rangeElectrode diameter 1.6 mm 2.0 mm 2.5 mm 3.25 mm 4.0 mmFe-Rutile 30–60 A 40–80 A 50–110 A 80–150 A 120–210Fe-Basic 30–55 A 50–80 A 80–110 A 110–150 A 140–2003.3 TIG weldingThe TIG process forms an arc between the tungsten electrode and the work piece. The arcmelts the work piece forming a molten weld pool. The arc and tungsten electrode mounted inthe TIG torch, are shielded by an inert shielding gas that is connected to, and flows through,the nozzle of the TIG torch. The gas required is Argon and the flow rate is approximately 8 to15 litres per minute. If necessary, suitable filler material is added to the weld pool to completethe weld joint. Filler wire is fed into the weld pool from the outside of the arc and gas shield.The filler wire and the welding current level are decided according to the base material typeand thickness, joint form and welding position. (Gas regulator, flow meter and pure argonshielding gas are not provided in this package.)TIG welding electrodes and gas nozzlesIn DC TIG welding we recommend the use of the WC20 (grey) type electrode, however othertypes are available.The welding electrode size (diameter) is selected depending on the welding current/power tobe used. An electrode with an insufficient diameter compared to the welding current will melt,while excessive electrode size will make it more difficult to ignite the arc.Generally speaking, a 1.6 mm tungsten electrode will cover currents up to 150 A, and 2.4 mmtungsten electrode up to 250 A DC current.Before use, grind the tungsten electrode to a sharp point at approximately 1.5 times thediameter of the electrode. If the electrode touches the work piece during welding, re-sharpenthe electrode.7© Kemppi Oy / 1201