Fiber laser welding of AISI 304 stainless steel plates

Compared with conventional lasers, fiber laser welding is characterized by high melting efficiency, deferent keyhole modes and power density characteristics, which could affect the heat and melt flow of the molten pool during welding. The objective of the present work was to study the fiber laser weldability of 5 mm thick AISI 304 austenitic stainless steel plates; therefore, bead-on-plate welding was exploited on AISI 304 stainless steel plates with different laser powers, welding speeds, defocused distances with different types of shielding gas and their effects on the weld zone geometry and properties and final solidification microstructure at room temperature. Laser power, welding speed and defocused distance have a great effect on the bead appearance and weld zone shape while almost no significant effect on both the type of microstructure and mechanical properties of welds. The microstructure of all laser welds was always austenitic including about 3-5 % ferrite. However, the lower the laser power and/or the higher the welding speed, the finer solidification structure, primary ferrite or mixed-mode solidification resulted in crack-free welds. (author)