The influence of heat treatment on the microstructure and properties of SAE4320H steel used for limited slip differential gears
SAE4320H is often used for high-end manufacturing parts that are resistant to impact and wear,and is forged in hot rolled or annealed conditions.There is relatively little research on its heat treatment.To investigate the changes in microstructure and mechanical properties under different heat treatment methods,the SAE4320H steel used for the limited slip differential gears produced by BOF-LF-VD-CC process in the first melting steel plant were cooled using heat treatmentes including water quenching,oil quenching,air cooling,and furnace cool-ing,and the mechanical properties were measured.The experimental results show that quenching significantly im-proves the yield strength and tensile strength of SAE4320H steel used for limited slip differential gears,with water quenching having the highest yield strength and tensile strength but the worst plasticity.After normalizing at 925℃,quenching at 880℃,and tempering at 180℃,water quenching yields tempered martensite structure,oil quenching yields tempered martensite+tempered bainite+a small amount of ferrite structure,air cooling yields P+B+F struc-ture,and furnace cooling yields P+F structure.
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