In the SMAW welding process, there are three types or types of welding machines, namely AC, DC and AC/DC welding machines. All types of welding machines have their respective advantages and disadvantages, if you need two types of welding machines you can buy AC/DC welding machines. For SMAW welding machines with DC current are further divided into two polarities, namely the DCEP (Positive Direct Current Electrode) and DCEN (Negative Direct Current Electrode) polarity.
Straight polarity – DCSP
In straight polarity the workpiece is connected to the positive (+) position of the welding machine and the electrode is connected to the negative (-) position of the welding machine. With a negatively charged electrode, the current moves from the workpiece to the electrode, 2/3 of the heat generated is released to the workpiece and 1/3 is released to the electrode. The heat concentration of the base metal results in deep penetration of the weld.
Thus in a straight polarity the electrons move from the electrode and strike the parent metal at high speed so that deep penetration can occur. Because the electrode does not collide with electrons, the electrode temperature is relatively not too high, therefore with a straight polarity large current can be used. DCSP is used with high melting temperatures of the base metal, for slow welding speeds and for narrow beads.
Reverse polarity – DCRP
Whereas in reverse polarity (DCRP) the workpiece is connected to the negative (-) position of the welding machine and the electrode is connected to the positive (+) position of the welding machine. The current moves from the electrode to the workpiece where 2/3 of the heat is completely dissipated at the electrode and 1/3 “” is released to the base metal.
In reverse polarity the electrode becomes very hot, so that the electric current that can be flowed is low. For the same electrode size in reverse polarity, only 1/10 of the straight polarity current can flow. If the current is too large, the tip of the electrode will also melt and will change the composition of the resulting liquid metal. Concentration of heat will produce shallow seepage, with high average weld metal deposition and produce good welds on sheet metal. DCRP is specifically used for the flat position because the metal does not get too hot.