Study Of Microstructure And Mechanical Properties Of Q235 Steel Welding Joint With Different Brazing Layer Thickness

In the actual production process there are a lot of axial or connected to the ring artifacts,connection area is large,using the traditional electrode arc welding or carbon dioxide gas shielded welding methods,such as it is difficult to make a one-off connection,the most commonly used welding method is overall brazing.In the soldering process,the size of the joint clearance for the formation of braze welding head and solder and influence the interaction of parent metal,in order to explore joint clearance on microstructure and mechanical properties of braze welding head,this paper adopts copper solder,in guarantee under the premise of all other things being equal,of Q235 steel by different joint clearance brazing,and obtain the braze welding head to micro characterization and mechanical performance test,the main conclusions are as follows:The results are as follows:(1)Q235 steel welding joint shape is better,no visible flaws,from top to bottom on both sides of the base in line with the combination of solder.Brazing seam organization for copper as-cast organization,grain is bulky,and at the interface between combined with parent metal brazing seam metal along the grain boundary permeability motherhood material inside,and parent metal small grains on the interface.(2)In the process of welding,exist the diffusion phenomenon of solder copper to the the parent metal,make the brazing seam and the parent metal to obtain good metallurgical combination and strengthen the interface,there are rich copper phase at the interfaces.(3)Tensile experiment results:the tensile strength of Q235 steel weld joint with brazing seam thickness of 0.08mm,0.5mm,1mm,2mm,3mm,4mm,7mm,9mm,12 mm,14mm,16mm,19mm were 359MPa,366MPa,362MPa,340MPa,329MPa,300 MPa,284MPa,283MPa,276MPa,273MPa,264MPa and 261 MPa.When brazing seam thickness less than 1 mm,welding joint strength is not lower than the parent metal,the thickness of the brazing seam is greater than 1 mm,with the increase of brazing seam thickness,the joint strength is reduced,and the falling rate gradually reduced.(4)Result of the impact tests show that the impact toughness of Q235 steel welded joint with brazing seam thickness of 0.08mm,0.5mm,1mm,2mm,3mm,4mm were 19.04J,28.30J,49.82J,74.01 J,74.49J,97.75J with the increase of the thickness of the weld,the impact toughness increased gradually.(5)Results of bending test show that the Q235 steel welded joint with brazing seam thickness of 0.08mm,0.5mm,1mm,2mm,3mm and 4mm after 90° bend test,after all did not break,the specimen after the experiment to observe from different point of view,no crack found exist,and the bending strength were 533MPa,515MPa,506 MPa,522MPa,520MPa,483MPa rectively.(6)The result of hardness near the Joint interface show that the hardness of parent metal is higher than weld joint and it is different because different organizations;Diffusion zone groups compared with the parent metal hardness increased slightly;Brazing seams with low hardness value basic in 70HV-80HV,and did not change significantly with different weld thickness.