Stainless steel welding process

 　　Curved metal, charcoal colored welds, and a sense of frustration; These are some things that may happen when welding stainless steel. Although it contains elements similar to carbon steel, stainless steel adds alloying elements such as chromium and molybdenum, and presents completely different challenges when fusing two or more stainless steels instead of carbon steel. The oxygen around the stainless steel melt pool must be maintained at an absolute minimum level. The behavior of the molten pool is different from that of aluminum or carbon steel. The thermal conductivity of stainless steel is much smaller, which makes deformation and heat input a significant problem. Although there are many considerations when welding stainless steel, one of the most important decisions to make is which welding process to use.

　　Stainless steel welding process

　　Below, we will discuss the most popular welding processes used for stainless steel.

　　Metal Inert Gas (MIG) welding/Gas Metal arc welding (GMAW)

　　MIG welding, or more formally gas shielded metal arc welding, is one of the more popular methods of welding stainless steel. There are many similarities between MIG welding of stainless steel and welding of carbon steel. No special driving rollers are required, and the polarity remains unchanged. However, the composition of the protective gas is usually different. When welding stainless steel, the allowable amount of oxygen is low, so the O2 or CO2 level should be maintained at around 2% or lower. It is common to use a three mixed shielding gas containing argon, helium, and carbon dioxide or oxygen when MIG welding stainless steel. Due to the need for corrosion resistance in welds and base materials, stainless steel welding wires must be used. In addition, to prevent cracking, the filler wire and base stainless steel should be low-carbon versions or contain stabilizers such as tantalum or niobium. The use of pulse welding waveforms can also help users weld stainless steel more successfully.

　　Tungsten inert gas (TIG) welding/tungsten gas shielded welding (GTAW)

　　TIG welding, more formally known as tungsten gas shielded welding, is another process commonly used for welding stainless steel. This process also has similarities when used for welding carbon steel and stainless steel. Both materials require direct current electrode negativity (DCEN). Usually, almost 100% argon or helium gas is used as a shielding gas. Like MIG welding, TIG welding requires stainless steel filler metal to prevent the formation of welds that are prone to corrosion. Low carbon or stable grade stainless steel should be used as filler metal, and base metals should also be low carbon or stable. Deformation may be a major issue when welding stainless steel, so maintaining a certain driving speed and low heat input is crucial when TIG welding stainless steel.

　　Flux cored arc welding

　　Generally, the welding process using flux is not the best choice for welding stainless steel. Nevertheless, stainless steel can be welded using the cored process. Special gas mixtures are required. Compared with flux cored arc welding, gas shielded flux cored arc welding is usually a better process for welding stainless steel, because it relies more on flux than the latter to protect the weld metal from the atmosphere.

　　Metal core arc welding

　　The better cored welding alternative to self shielded flux cored arc welding and gas shielded flux cored arc welding is metal cored arc welding. This is mainly because metal core arc welding does not rely on flux at all. Although the metal core of the filling material does have certain types of deoxidizers, it is mainly filled with powdered metal to increase deposition. Through proper shielding gas and wire feeding system, metal core arc welding can be used for high-quality welding on stainless steel. In most cases, high quality stainless steel welding through metal core arc welding requires pulse waveform or spraying transmission arc.

　　Laser beam welding (LBW)

　　Laser beam welding is often used to connect stainless steel together at very fast travel speeds and very low heat input. When using laser welding, attention must be paid to avoiding porosity and cracking. By optimizing the shielding gas and welding parameters to reduce the amount of oxygen, cracks and pores can be avoided. Laser beam welding is never manually performed, therefore, if laser beam welding is chosen as the process for welding stainless steel, automation is necessary.

　　Other welding processes used on stainless steel

　　The above process may be the most common process used for welding stainless steel. There are many other unpopular processes in the industry that can be used for welding stainless steel. They include plasma arc welding (PAW), electron beam welding (EBW), shielded metal arc welding (SMAW), friction stir welding (FSW) and resistance welding (RW). This list is not exhaustive, and there are more welding processes that can be used to weld stainless steel with varying degrees of success.