Special Issue on Progress in Welding Processes
Welding is one of the most versatile joining methods for constructing products and structures in nearly all industrial fields. Arc has been widely used as a cheap heat source for welding since carbon arc fusion welding was first applied to join Pb plates in about 1880. New welding technologies have been developed according to social needs or changes since 1960. Therefore, half-automated welding, automatic welding and highefficient welding have been developed for saving man-power and afterward full automation. First, tandem one-side SAW (submerged arc welding), high-speed rotational arc, high-heat input SAW, tandem wire MAG, etc. have been introduced as highly efficient welding processes. On the other hand, as gas-shielding arc welding processes, CO2 gas, MAG, man-power saving automatic welding, the use of a flux-cored wire, AC MIG, MIG with two wires, laser-arc hybrid welding, CMT process have been developed and most widely employed in the industries in conjunction with an advance in the welding heat sources from thyristor to inverter and nowadays digital inverter. Furthermore, robotization has been developed from spot welding robot to squire robot, multi-axes GAM robot, mobile robot, portable many-axes robot and 7 axes robot together with the development in welding sensors such as probe sensor, one-touch sensor, magnetic sensor, arc sensor, laser-slit light sensor, stereo CCD, etc. Recently, novel arc sources are not developed, but deep weld penetration and geometry are controllably obtained in TIG welding by active flux pasted on the plate surface, good use of an active gas and narrow oxidation treatment. Clean MIG process for steels is also developed by use of a unique solid-wire of double layers with different melting temperatures, and different hybrid heat sources of plasma and GMA or laser and MIG. Hybrid welding processes with CO2 laser and MAG, disk laser and MAG, fiber laser and CO2 arc or MAG has recently been applied in the shipbuilding industry. I thank the authors for their generous cooperation to the publication of new development in the welding technologies.