Study on connection and properties of green assembled building steel structures

In order to meet the research and industrialization application needs of green building integration technology and key technology of green building envelope structure in affordable housing projects, the effects of laser power and welding speed on the forming quality, microstructure and hardness of welded joints of heterogeneous steels with unequal thickness in steel structures were studied. The results showed that, for the front weld width, the influence of laser power on the back weld width is more obvious, and the influence of welding speed on the back weld width is greater than that of the front weld width. With the increase of laser power, coarse lath martensite and ferrite are formed in laser welded joints; with the increase of welding speed, heat input decreases, heat dissipation speed increases, grain growth time shortens, and grain refinement occurs. With the increase of laser power and welding speed, the tensile strength of laser welded joint has little change compared with base metal, but the elongation of welded joint is lower than that of base metal. With the increase of laser power, the fracture position of welded joint will shift from base metal to heat-affected softening zone. With the increase of welding speed, the fracture position of welded joint will shift from heat-affected softening zone to base metal. The suitable laser power for HC550/DP780 heterogeneous steel plate is 1.2 KW and the welding speed is 2400 mm/min. At this time, the welded joint has good welding forming quality, the hardness of weld zone is high and there is no softening point in heat affected zone.