Abstract
Fiber laser welding of dissimilar materials between AISI316L austenitic stainless steel and EH36 ship steels were conducted. Then the effects of welding speed on microstructure and mechanical characterization of the welded joint were investigated. Optical microscopy, Scanning Electron Microscopy (SEM), and X-ray Diffraction (XRD) were used to analyze the microstructure. Microhardness testing, transverse tensile strength, and impact tests at the temperature of −40 °C were performed to study the mechanical properties. The martensite phase formed due to the rapid cooling rate during laser welding and low Creq/Nieq ratio. The coarse martensite grains in the center seam are transformed to finer martensite grains as the welding speed increases resulting in the higher cooling rate. The microhardness of joints was about 350 HV0.3, which was twice that of the base metal because of the formation of the martensite phase. When the welding speed was 0.6 m/min, fewer defects were found, and tensile testing indicated overmatching of the weld metal relative to the base metal. In addition, the joints also exhibited better ductility and impact toughness.
Highlights
The modern shipbuilding industry has exacting requirements for tonnage and speed of a ship.High strength and good corrosion resistance are vital for a ship due to the abominable working conditions
The fiber laser beam traveled along the center of the welding bead, and the 316L stainless steel and the EH36 steel were simultaneously irradiated by the fiber laser beam
The top sunken at a low welding speed, as the welding speed increases, the top surface becomes convex and surface is slightly sunken at a low welding speed, as the welding speed increases, the top surface narrower
Summary
High strength and good corrosion resistance are vital for a ship due to the abominable working conditions. As a type of important high strength low alloy (HSLA) structure steel, EH36 ship steel has attracted a lot of research for the advantages of low carbon, low alloy, and high strength [1,2,3,4,5,6,7,8,9]. The stainless steel is a good choice to deal with this problem for its high toughness and corrosion resistance, except for its high cost [10,11,12,13]. When considering performance and economy advantages compared with a single material, welding of dissimilar metals (like HSLA steel and stainless steel) in shipbuilding provides greater flexibility for the designer and engineer.
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