轴承钢GCr15SiMn相变和组织的热模拟研究

发布时间：2018-03-30 16:23

  本文选题：轴承钢GCr15SiMn　切入点：CCT曲线　出处：《江苏大学》2017年硕士论文

【摘要】：轴承被誉为工业的心脏,随着现代工业的突飞猛进,对轴承钢的要求越来越严格。本文以轴承钢GCr15SiMn为对象,基于控轧控冷的工艺,采用热模拟实验方法,系统研究了轴承钢生产过程中的相变和组织演变规律,并采用轧后两阶段冷却工艺有效降低了网状碳化物的级别。论文的主要研究内容与结果如下:(1)轴承钢GCr15SiMn在连续冷却过程中,珠光体析出温度区间为600~700℃。随冷速的增加,相变温度降低,室温组织中珠光体量减少,马氏体量增加;和静态相比,动态变形会提高珠光体相变温度,使珠光体相变温度沿CCT曲线向左上方移动;变形会促进珠光体转变量增加,并使组织明显细化;完全发生珠光体相变的临界冷却速度由静态2℃/s提高到动态变形3℃/s;变形使马氏体相变温度由204℃降低到166℃。(2)以0.3℃/s冷却时,二次碳化物沿晶界大量析出、聚集,形成彼此相连的网状碳化物,随冷速的增加,碳化物的析出逐渐减少;相比于静态,动态变形会促进二次碳化物的析出,使明显抑制网状碳化物生成的临界冷速由静态3℃/s提高到5℃/s,但由于冷速较高,室温组织中均有马氏体组织产生。(3)随冷速的增加,试验钢显微硬度不断提高,当冷速小于2℃/s时,与静态相比,变形促进了再结晶的发生,细化了晶粒,显微硬度更大;冷速增大到2℃/s及以上时,静态组织中领先生成了马氏体,显微硬度大幅增加,冷速相同时,高于变形条件下的显微硬度。(4)变形速率和变形量对网状碳化物的析出无明显影响;终轧温度越低,对碳化物网状破碎作用越强,但温度越低对轧机要求越高,易使轧机断辊;相比于变形速率、变形量、终轧温度,轧后冷速对轴承钢GCr15SiMn组织形貌的影响显著,轧后冷速的增加,二次碳化物的析出减弱明显,碳化物厚度减小,能有效的抑制网碳,但高冷速下,室温组织中会产生大量的马氏体组织。(5)结合实际生产,终轧后采用分段冷却的工艺,在高温阶段,快速穿过二次碳化物大量析出温度范围,快冷到合理的终冷温度,随后缓冷至室温,奥氏体充分发生珠光体相变,在抑制网状碳化物析出的同时避免产生马氏体。快冷阶段的冷速与终冷温度是该工艺的关键,快冷冷速增大到5℃/s冷却到610℃时,随后以1℃/s缓冷至室温,可有效地抑制网状碳化物的形成,获得理想的珠光体组织。
[Abstract]:Bearing is known as the heart of industry. With the rapid development of modern industry, the requirement of bearing steel becomes more and more strict.In this paper, based on the controlled rolling and controlled cooling process, the phase transformation and microstructure evolution of bearing steel during production are systematically studied by means of thermal simulation experiment based on GCr15SiMn.The two-stage cooling process after rolling can effectively reduce the grade of reticulated carbides.With the increase of cooling rate, the transformation temperature decreases, the amount of pearlite decreases and the amount of martensite increases at room temperature, compared with static state, the dynamic deformation will increase the transformation temperature of pearlite, and make the temperature of pearlite phase transition move along the CCT curve to the upper left.Deformation will increase the amount of pearlite transformation and make the microstructure thinning obviously.When the critical cooling rate of pearlite phase transformation is increased from static 2 鈩，

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