摘要:
进行了利用磨削热替代高频感应热对微合金非调质钢48MnV试样表面强化,将磨削加工与表面强化复合为一体的可行性研究。给出了磨削强化温度预估数学模型;采用白刚玉砂轮在MMD7125平面磨床上进行了工艺试验,采用分块试件夹丝半人工热电偶测温技术获得了不同用量条件下的磨削强化温度变化曲线;利用HSX-1000型全自动显微硬度测试仪测定了磨削强化层的显微硬度;利用MM-6金相显微镜和数码相机拍摄了强化层的金相组织形貌照片,对强化机理进行了探讨。研究结果表明:预估温度与实测温度基本吻合,该模型可用于磨削强化温度的预估;通过磨削参数的优化,可以获得磨削强化所要求的温升速度、最高温度、温度作用时间和冷却速度;获得了与高频感应淬火相似的强化层组织,完全硬化区组织为细小针状马氏体;与高频感应淬火组织形成机理不同的是,由于磨削应力场的作用,完全硬化区表面层的马氏体组织比中间层细小。
Abstract:
An experimental study is carried out to prove that the grinding heat instead of high-frequency induction heat should be utilized to harden the surface of 48MnV microalloyed steel parts, through which the grinding process and surface hardening technique should be integrated. The mathematical model of grinding temperature is also established, and the changes in grinding temperature and cooling rate are measured. Furthermore, the grinding effect, hardening effect and the forming mechanism of grinding-hardening layers are investigated. The experimental results show that： 1 ) the estimated temperature is quite close to the measured temperature; hence the mathematical model can be utilized to optimize the processing parameters of the 48MnV microalloyed steel parts; 2) satisfactory grinding-hardening temperature and cooling rate can be achieved with the optimized processing parameters; 3) the grinding-hardening layer, the fine needlelike martensite in an entirely hardened zone, the martensite and ferrite in a transitional region have similar microstructures with those acquired with the high-frequency induction technique; 4) different from the forming mechanism of the high-frequency induction hardened layer, a higher grinding-hardening temperature is needed to compensate for shortertime austenitization; 5) because of the from surface to inside thermo-mechanical loading caused by grinding, the morphology of martensite changes from fine to thicker, then to finer, other than from thick to fine.
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