Stainless steel is more popular compared to other metals due to its valuable characteristics such as resistance to different kinds of liquid, chemical and gaseous corrosion. It is well-known for its robust and long-lasting properties. In view of this fact, an attempt has been made to discuss the latest advanced technology for welding stainless steel.
By A.K.Vaish, M.K. Mukherjee, J.Krishnan, B. J. Chauhan, S. D. Kahar, Ankit Bhojani and K.M. Bhaisaheb
The stainless steel welding process varies depending on the thickness and finish of the material as well as the use of the finished product. Latest developed welding technologies include advanced arc welding, laser welding, tailor welded blanks, electron beam welding and robotic welding.
Advanced arc welding
In this process, electric current is used to create an electric arc between the materials and an electrode. By applying heat, the filler metal placed between
the joints of the two materials is melted. It solidifies after cooling, forming a metallurgical bond. This weld potentially has the same strength as that of the component metals. Welds produced by this process are very resistant to corrosion and cracking, even after a long period of time. Gas metal arc welding is a gas shielded metal arc welding process which uses high heat of an electric arc between continuously fed, consumable electrode wire and the material to be welded.
Laser welding
This is a unique type of welding. It uses an extremely high-powered laser light to instantly melt metals and weld them together. Laser welding provides slightly better weld penetration depths and increased weld speeds in most of the austenitic stainless steels due to their lower thermal conductivity in comparison to low carbon steels.
Different variables of laser beam welding are laser power, welding speed, defocusing distance and type of shielding gas. They have an important effect on heat flow and fluid flow in the weld pool and in turn affect penetration depth, shape and the final solidification structure of the fusion zone. Both the shape and microstructure of the fusion zone considerably influence the properties of the weldment. Lasering is three to ten times faster than MIG and even faster compared to TIG. It can weld relatively thick joints that may require multiple passes with MIG or TIG.
Tailor welded blanks
This is a new technology, which has mostly been adopted in the automotive industry in recent years. As a result, the car weight can be greatly reduced, considerably improving its fuel economy. Tailor welded blanks are made from individual sheets of steel of different thickness, strength and coating which are joined together by laser welding. These tailor welded blanks are currently being used for body side frames, door inner panels, motor compartment rails, centre pillar inner panels and wheel house/shock tower panels.
Electron beam welding
Electron beam welding of stainless steels is readily performed with good results even in very deep welds. During this welding, high energy electrons are fired into the material to create heat resulting in welds of very high quality. The remarkably high depth to width ratio permits electron beam welding to join configurations not possible with other means. With the heat input being low and the heat affected zone having limited extent, the mechanical properties of steel are not damaged and no further heat treatment is required.
Robotic welding
This technique removes the welder from an unpleasant and even dangerous environment, lowers cost and improves quality. A variety of robots can suit stainless steel welding needs. Compared to manual welding, robotic welding is faster and has higher productivity. The welding cost per piece decreases since the welding robot can produce more welded parts than its human counterpart. Automated machining can perform the same welding process for extended periods of time with a minimum of manpower. The advantages of robotic welding vary from process to process but common benefits generally include improved weld quality, increased productivity, reduced weld costs, and increased repeatable consistency of welding.
