CO₂ Laser Hybrid Welding Of A 600MPa Low-alloyed High Strength Steel For Shipbuilding

As a typical low-alloy high-strength steel, 10CrNi3MoV has a good overall performance, and be widely used in the construction of special ships and vessels. Accordingly, the requirements on the welding is also higher. In this paper, a CO₂ laser hybrid weld method was used to do research on T-joint 10CrNi3MoV steel.With the optimization of welding process, the 14mm thick T-joint were welded successfully, then tested the mechanical properties and analyzed the microstructure of the specimens, and a satisfactory result has been achieved. First, basic research of the laser hybrid welding process on the general CCS-B T-shaped shipbuilding steel was carried out.The study includes Laser-MIG hybrid welding parameters'influence on formation of weld and the impact of weld penetration, parameters is as follows: laser incidence angle, laser power, welding speed, wire feed speed ,different fit-up gaps ,these welding process parameters, and ultimately established a basical process parameters on the CCS-B steel T-joint welding. T-joint CCS-B steel was welded under the previous process parameters, and got the concave showing , good macro-observation lap welded joints. Made the microstructure analysis and microhardness testing, the test results met the welding standards.Second, made a careful weld process research of 10NiCr3MoV under the CCS-B hybrid welding process parameters. First of all studied influence on the weld formation in the different heights of the incident laser; then made the analysis on the effect of weld composition with different protection gas to determine the 25% He +75% Ar gas mixture; figured out the better wires through the comparison of weld organizations and pull extension; finally did the comparison on welding test results of preheating taken in room temperature and 90℃preheating ,draw off the conclusion that preheating has an important influence on weld quality . The results showed that welded joint coarse grain area is thick high-carbon martensite, fine grain zone is mainly martensite with a small amount of granular bainite, the weld itself contained ferrite granular bainite + martensite. Microhardness analysis showed that the joint maximum hardness is located in coarse grain zone, weld metal hardness is about 360HV. Tensile tests showed that weld strength is higher than the base metal strength, which strength is 670MPa, the impact of performance test results show that the impact toughness at room temperature is 60J. Welding test results meet the requirement.