The Study On Relationship Between The Microstructure And Impact Performance Of High Strength Steel Laser-arc Hybrid Welding

Along with high-strength steel requirements of the times and the advancement of technology in our lives, the low-alloy high strength steel with excellent performance has been popularized in industry, and has been more widely used in welded structures. The laser-arc hybrid which is the emerging technology of the laser welding technologies has strong competitiveness and broad application market at home and abroad. But, opposed to some developed countries, our country is relatively backward in this area. This article adopts the method of laser-arc hybrid welding, the microstructure and impact properties of welding low-alloy high strength steel are studied.1.Using the laser-arc hybrid to weld the low-alloy high strength quenched and tempered steel under the laboratory conditions,and making a introduction about the laboratory provided equipments. Based on further analysis of high strength steel microstructure and Vickers hardness, the performance of low-alloy high strength steel were studied and analyzed after the impact test, preparing for follow-up studies. The Vickers hardness of welded joint was analyzed and microstructure morphology of the specimen was observed by optical microscopy and scanning electron microscope. Hardness of the base metal was at about 400 HV, the hardness had the tend to decrease near the center of the weld zone, and was the lowest in the softening zone, its width is about 0.6mm and the other zones were substantial. Microstructure morphology was observed by optical microscopy and scanning electron microscope and found: all is the lath marten site from a position near the base to a position near the fusion line. The analysis of the sample by X-ray diffraction showed that: the weld zone, the heat-affected zone or matrix organization is marten site. The analysis of the weld zone by EDS analysis, finds: the main elements of the weld zone, including Mn, Cr, Ni, do not change. That means, the composition of weld zone is more consistent and the hardness does not change.2. Impact test was carried out on the compound high strength steel joint welded, it is concluded that the impact fracture distribution in the weld zone, heat affected zone, heat affected zone and the parent metal interface, and the impact fracture were associated with impact energy: When the impact energy of 19.6J, the brittleness second phase particles broke to produce crack formation and toughening nests; When the impact energy of 20.1J, the macroscopic fracture, crack propagation along a flat surface. When the impact energy of 32.2J, the macro fracture rugged, increased the crack propagation resistance, so its impact is higher.