Study on the effect of laser welding rate on Q235 weld quality

Q235 low-carbon steel is widely used in construction, bridges, machinery manufacturing and other fields because of its good plasticity and weldability. To explore the optimized application of laser welding technology in Q235 steel processing, this study used an EEF-LWM-1500 welding machine and systematically investigated the effect of different welding speeds on the joint quality of Q235 steel under the condition of a constant laser power of 1200 W. The weld quality was systematically evaluated through multiple characterization methods, including metallographic microscopy, scanning electron microscopy, tensile testing, microhardness measurement, electrochemical corrosion tests, and friction-wear experiments. Experimental results indicated that a welding speed of 120 mm/min caused burn-through in the steel plate, while increasing the speed to 240 mm/min achieved good joint formability. Notably, the heat-affected zone gradually decreased with higher welding speeds. The hardness and tensile strength of the laser-welded zone both exceeded those of the base material. Specifically, the average hardness of the weld zone peaked at 177.56 HV when the welding speed was 500 mm/min. Below this speed, hardness increased with rising welding speed, while it tended to decrease above 500 mm/min. Tensile strength showed a similar trend, with the highest value of 424.98 MPa and the lowest value of 421.94 MPa. Electrochemical corrosion tests revealed that the welded joint at 500 mm/min exhibited the smallest self-corrosion current density (1.41×10⁻ 5 A/cm 2 ) and the largest capacitive arc radius, confirming optimal corrosion resistance. This study identifies that the optimal laser welding speed for Q235 steel is 500 mm/min, which provides important technical references for improving the welding quality and production efficiency of Q235 steel in practical production and expanding its application scope.