To study the continuous cooling transformation behavior of 4330V low alloy high strength steel, experiments were conducted at different cooling rates 0.05-30 ℃/s using a quenching dilatometer. Optical microscopy, field emission scanning electron microscopy, and microhardness tester were used to detect and analyze the microstructure and Vickers hardness of the material after phase transformation at different cooling rates, and the continuous cooling transformation (CCT) curve of its supercooled austenite was plotted. The results showed that when the cooling rate was 0.05-0.15 ℃/s, the microstructure was mainly bainite + ferrite, belonging to the high-temperature and medium-temperature two-phase composite transformation zone, and the hardness values were all below 450 HV; when the cooling rate was 0.2-1 ℃/s, the microstructure was mainly bainite + martensite, belonging to the medium-temperature and low-temperature two-phase composite transformation zone, and the hardness was between 472-577HV; when the cooling rate was greater than or equal to 3 ℃/s, the microstructure was fully martensitic, belonging to the low-temperature martensitic transformation zone, and the hardness values were all above 593 HV.
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