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采用热膨胀法结合金相-显微硬度法,在Gleeble-1500热模拟试验机上测定了弹簧钢55SiCrA的相变临界点Ac1、Ac3、Ar1、Ar3和Ms;同时测定了奥氏体在不同冷却速度下连续转变时的膨胀曲线,并绘制了动态连续冷却转变曲线(CCT图);通过FE-SEM研究了不同的冷却速度对显微组织形貌和珠光体片层间距的影响。结果表明:随着冷速的增加,珠光体片层间距减小,显微硬度值增大;弹簧钢55SiCrA线材控制冷却理想的冷速范围为0.5～1℃/s。
The critical phase transition points Ac1, Ac3, Ar1, Ar3 and Ms of the 55SiCrA spring steel were measured on the Gleeble-1500 thermal simulator by the method of thermal expansion combined with the metallographic-microhardness test. The effects of austenite at different cooling rates (CCT). The effects of different cooling rates on microstructure and pearlite lamella spacing were investigated by FE-SEM. The results show that with the increase of cooling rate, the spacing between the pearlite layers decreases and the microhardness increases. The ideal cooling speed range of the 55SiCrA wire is 0.5 ~ 1 ℃ / s.