Quality Issues in Shielding Metal Arc Welding Process

As you know, SMAW is the most popular welding process that it is used in mechanical work. So that, this article will be talking about several thing related with the quality issues in SMAW welding process. There are especially in process, inspection welding result, electrode in use and work piece material.

About details of SMAW welding process you can see in other article in this link (SMAW welding process). One of qualities process in SMAW is moderate to high quality welds with moderate, but acceptable levels of distortion can be produced. Another thing about it is quality and consistency of weld related to skill of welder to maintain correct arc length and burn-off rate. So that, welder skill is one of important things must be considered particularly on large fabrication. Jigs and fixtures also needed to keep joints rigid during welding and subsequent cooling to reduce distortion of work piece or using backing strips can be used for avoiding excess penetration, but at added cost and increased setup times. Besides, there are any ways to get quality process in SMAW welding that are pre-heating of work piece can reduce porosity and hydrogen cracking or weld ideally left to cool to room temperature before the slag removed. Welder operator should be maintenances the welding current during welding process with a stable power supply. The last thing should be to know in quality issue of process is that fabrication tolerances typically in SMAW about 1 mm.

Quality issues in Shielding Metal Arc Welding Process

The important thing must know to control the overall welding result is inspection. Firstly, the things must be inspections are joint edge and surface preparation. Contaminates must be removed from the weld area to avoid porosity and inclusions after each pass. Then, the welding parameter must be carefully check to make sure that parameter match with type of electrode, material type of work piece and welding position in used. Another one is that a heat affected zone always present. Some stress relieving may be required for restoration of materials original physical properties. It should be decided to solve that problem will be using the pre-heat or post weld heat treatment. The last thing should be to know in quality issue of inspection is that access for weld inspection important, e.g. NDT (Nondestructive Test).

Electrode is significant consumable that determine the quality of welding result. Before in use, the electrodes must be dry and free from oil and grease to prevent weld contamination. Low hydrogen electrodes should be used when welding high carbon steels to reduce chance of hydrogen cracking. The protective slag can help the weld to keep its shape during positional welding. Besides, it can alter composition of weld by addition of alloying elements in the electrode. Addition of de-oxidants in the flux minimizes carbon loss, which reduces weld strength. The last is small thing about utilizing of electrodes, but must be pay good attention that when the electrode’s length reduced to approximately 50 mm it should be replaced.

Work piece material or called base metal should be well treated on before, during and after welding process. Before welding process be done, engineer or welder must know about the ‘weldability’ of the material used. Weldability of the material important and combines many of the basic properties that govern the ease with which a material can be welded and the quality of the finished weld, i.e. porosity and cracking. Material composition (alloying elements, grain structure and impurities) and physical properties (thermal conductivity, specific heat and thermal expansion) are some important attributes which determine weldability. During the welding process, arc deflection can sometimes occur with DC supplies, especially in magnetized metals. The work piece may need demagnetizing or the return cable repositioned. And after the welding process, surface finish of weld fair to good. Weld spatter often covers the surface.

Finally, best quality in welding process of SMAW can be reached when many matters about process, inspection welding result, electrode in use and work piece material are well treated.