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大型水轮发电机组镜板制造是制约我国水电装备国产化的瓶颈之一。某700 MW级国产化机组镜板采用25CrMo4材料锻造而成,保证镜板面的硬度均匀性是其主要技术难点之一。本文采用热模拟锻造及热处理实验,深入研究了锻造温度、应变量、应变速率、回火温度和淬火深度对25CrMo4的微观组织及硬度均匀性的影响。结果表明:锻造时,在高温下采用大变形速率有利于细化晶粒,而混晶可能导致镜板面硬度超差;热处理时,回火温度和淬火深度对硬度的影响明显,只有镜板面上各点回火温度波动小于40℃,淬火深度的差异小于30mm时,硬度差才可能满足小于30HB的要求。
Manufacture of large hydrogenerator plate is one of the bottlenecks restricting the localization of hydropower equipment in our country. A domestication unit 700 MW-level mirror plate made of forged 25CrMo4 material to ensure that the mirror surface hardness uniformity is one of the main technical difficulties. In this paper, the effects of forging temperature, strain, strain rate, tempering temperature and quenching depth on the microstructure and hardness uniformity of 25CrMo4 were investigated by means of thermal simulation forging and heat treatment. The results show that the large deformation rate at high temperature is favorable for the grain refinement during the forging process, while the mixed crystal may lead to over-hardness of the mirror plate surface. The influence of the tempering temperature and the quenching depth on the hardness is obvious during the forging process, Surface temperature tempering temperature fluctuations of less than 40 ℃, the difference between the depth of quenching is less than 30mm, the hardness difference may be less than 30HB requirements.