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采用热模拟试验研究了形变温度和冷速对SWRCH35K冷镦钢组织和硬度的影响。结果表明,形变温度低于750℃,部分珠光体发生了球化,硬度明显降低;当形变温度在700℃左右,珠光体明显球化,硬度达到最低;形变后冷速越慢,珠光体球化越明显,其硬度也越低。通过工艺调整,适当降低精轧温度及冷却强度,生产出SWRCH35K热轧盘条,抗拉强度约为560MPa,面缩率大于55%,表面硬度低于82HRB。经用户使用,该盘条能实现免球化退火生产8.8级标准件。
The effects of deformation temperature and cooling rate on microstructure and hardness of SWRCH35K cold heading steel were investigated by means of thermal simulation. The results show that when the deformation temperature is lower than 750 ℃, part of the pearlite is spheroidized and its hardness is obviously decreased. When the deformation temperature is about 700 ℃, the pearlite is obviously spheroidized and the hardness is the lowest. The more obvious the lower the hardness. Through the process adjustment, the finish rolling temperature and the cooling intensity are properly reduced to produce the SWRCH35K hot rolled wire rod, the tensile strength is about 560MPa, the reduction ratio is more than 55% and the surface hardness is less than 82HRB. By the user, the rod can achieve the ball-free annealing production of 8.8 standard parts.