In recent years, China's shipbuilding and ocean engineering manufacturing industry has developed rapidly, and high strength, high toughness, easy weldability, and corrosion resistance have become the development direction of steel for shipbuilding and ocean engineering. Welding is a key link in hull manufacturing, and it has become the first choice for shipbuilding companies to use high-energy-input welding to improve shipbuilding efficiency. However, the increase of welding line energy leads to severe grain coarsening, local softening and embrittlement of EH40 marine steel plate welding heat affected zone, and its low-temperature impact toughness deteriorates, which seriously threatens the safe use of hull steel.
Oxide metallurgy is to induce the nucleation and growth of intragranular ferrite during the solidification, thermal processing and welding process of the molten steel through the ultrafine and uniformly distributed oxide inclusions in the EH40 marine steel plate, forming an interwoven and interlocking structure, so that the EH40 marine steel plate Has good toughness, high strength and excellent weldability. Using the EH40 marine steel plate produced by oxide metallurgy technology as the research basis, the multi-element micro-alloy system is used to smelt the steel for high-energy welding. The 35 mm thick high-strength steel plate is under the welding line energy of 120 kJ/em, from the fusion line on the upper surface The average impact energy in the heat-affected zone at 2 mm at -40 ℃ is 274 J.
Using metallographic microscope and scanning electron microscope to study the microstructure characteristics of the welding heat-affected zone, the results show that the microstructure in EH40 marine steel plate is mainly composed of polygonal ferrite and pearlite, and the sizes of various grains range from 5 to 25 um mostly. Systematically observe the microstructure of each area in the welding heat-affected zone of the sample, and explore the microstructure distribution in each area.
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