Abstract
The process of laser welding of sheets of HSLA (high-strength low-alloy steel), DP600 (dual-phase steel) and TRIP steels was investigated. A weld was successfully made in a double-sided hot-dip galvanized sheet with a thickness of 0.78–0.81 mm using a laser power of 2 kW per pass without any pretreatment of the weld zone. Microstructure studies revealed the presence of martensitic and ferritic phases in the weld zone, which could be associated with a high rate of its cooling. This made it possible to obtain good strength of the weld, while maintaining sufficient ductility. A relationship between the microstructural features and mechanical properties of welds made in the investigated steels has been established. The highest hardness was found in the alloying region of steels due to the formation of martensite. The hardness test results showed a very narrow soft zone in the heat affected zone (HAZ) adjacent to the weld interface, which does not affect the tensile strength of the weld. The ultimate tensile strength of welds for HSLA steel was 340–450 MPa, for DP600 steel: 580–670 MPa, for TRIP steel: ~700 MPa, respectively, exceeding the strength of base steels.
Highlights
Laser welding technology is used in various sectors
It can be observed that samples C showed five measurements for each sheet type
It can be observed that samples C showed maximum load-bearing values, where the following average value of YS maximum values,tensile wherestrength) the following value of 4YS
Summary
Laser welding technology is used in various sectors. The laser welding thermal cycle is usually faster than conventional arc technologies, leading to smaller weld widths and heat affected zones. Laser technologies in conjunction with robotization enabling 5-dimensional movement to make the greatest development mainly in the automotive industry where they are most often used for engraving, heat treatment of materials (hardening), cutting and especially welding. Nowadays, car manufacturers such as Audi, Mercedes, BMW, Volvo, Volkswagen, and Škoda use laser technology to increase productivity, product quality and competitiveness [1]. One of the most effective measures to reduce fuel consumption and minimize air pollution is decreasing the weight of vehicles, while maintaining the high level of strength, reliability, and safety. It is known that decreasing the car weight by 10%, as a rule, reduces gas consumption by about 5% [2]
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