Basic Knowledge of Shield Metal Arc Welding Process

Basic Knowledge of Shield Metal Arc Welding Process

Shield Metal Arc Welding (SMAW) is a welding process by using the coating electrode that can make shielding gas when it burned. An electric arc is caused between a consumable electrode and the work piece at the joint line. The base metal is melted and the weld created with the manual feed of the electrode along the weld and downwards as the electrode is being consumed. Simultaneously, a flux on the outside of the electrode melts covering the weld pool and generates a gas shielding it from the atmosphere and preventing oxidation. The shielding gas that produced from coating electrode use to protect the molten weld metals so that not interact with the atmosphere especially oxygen.

Base on the schematic picture, Shield Metal Arc Welding has three main parts. There are power and control unit, electrode holder as a negative pole and work piece or base metals as a positive pole. Firstly, power unit also is called welding machine which is used to setting and control the power source especially adjusting electrical voltage. Usually, welding machine is portable equipment that can be moved from a place to anothers places. SMAW welding machine have many types depends on the fabricant of the machine. Secondly, Electrode holder is equipment uses to hold the electrode and the same time it as negative pole to produces electric arc. Electrode holder is connected to welding machine by using a cable as long as needed. The holder is made from a material that has a good heat resistance, because the welding operator must be safe from high temperature does produced by electrical arc. The holder also must be can strong keep to the electrode, but easly to remove and replace the new electrode during the welding process. The last part is a workpiece, that the metals will be joined. Same with the electrode holder, it is connected to welding machine by using a cable as long as electrode cable and often using C claim at others point to catch the work piece. Work piece is as positive pole to produces electric arc.

During the welding process, electric arc causes high temperature condititon upper the melting point of the electrode and base metals. Then both of them melt in together become new unity is called weld metal. During the welding process also the electrode flux coating will burned down and produce much gases will be protect electric arc and molten weld metals. It gases is dangerous if it go into respiration of people, so that the welder must be use a masker during welding process. The molten weld metal occurred a quickly cooling that the temperature extremely decrease in short time. Causing high cooling rate, molten weld metal will become solid state weld metals and the burned flux will become a slag that covering the weld metal. Then, the slag uncover by using a special hammer, so that the weld metal can visible to check.

There are important things must be pay attention during the welding process. Firstly, the angle position between electrode and work piece, according to best experience is 45O until 60O. Secondly, the distance between tip of electrode and work piece, according to welding theory is about 1-2 diameter of electrode in used and the welder must be take care about it during the welding process. Because if longer distance will produce many spatter and opposite that if the distance too short then electric arc will be stop. So, it is needed the good skill of welder to do well. The last important thing is weld metal must be cleaned well before continued the welding process in term of replacing the electrode when the electrode go short during the welding process.

In brief, SMAW welding process is simple process by using the coating electrode. Welder should be understand well about basic knowledge of welding process so that they can do the process well.