Microstructure and Properties of Laser Surface Treated CO2 Gas Shielded Welded High Strength Wear Resistant B-HARD360CFA Steel
Z. Zhang, J-N. Li, Y. Tian, J-W. Shi and F-X. Li
The high strength wear resistant B-HARD360CFA steel under quenching + tempering condition was welded by the CO2 gas shielded welding and laser surface treated with a fibre laser with the varied process parameters. The microstructure and properties of the welded joints have been studied by using a scanning electron microscope (SEM), a high resolution electron transmission microscope (HRTEM) and tensile testing. The temper martensite was observed in weld joint under the action of the different welding heat input, occurring temper softening in the heat affected zone (HAZ) after CO2 gas shielded welding, which affected the microstructure performance of the weld joints. The mechanical properties of welded joint were relatively stable when the welding heat input value was 10.4 kJ/cm. The amorphous and nanocrystalline phases can be formed in the weld zone after a laser treatment, enhancing the tensile strength by fine grain strengthening. This study will play an important role in improving the actual performance in the productions of the high strength wear resistant steel.
Keywords: Fibre laser, CO2 gas shielded welding machine, B-HARD360CFA steel, surface treatment, high strength, wear resistance, tensile strength, microstructure, martensite