【作者】 王刚；

【导师】 周建新；

【作者基本信息】 华中科技大学 ， 材料加工工程， 2014， 硕士

【摘要】 铸钢件淬火过程是一个同时有温度变化、组织转变以及应力应变产生的复杂过程。铸钢件淬火工艺是否合适直接决定了铸钢件的性能是否能够满足使用要求。然而通过实验方式来确定铸钢件淬火工艺是否正确合适，需要大量的人力、物力以及时间成本，而且每一次实验都只能针对某一种特定成分、特定工艺条件下的铸钢件淬火过程进行研究。因此，采用计算机数值模拟技术对铸钢件淬火过程的温度变化进行计算，对淬火组织和性能进行快速预测，探讨不同淬火工艺对铸钢件组织和性能的影响以及寻求最为合适的铸钢件淬火工艺方式，对改善铸钢件产品质量具有非常重要的现实意义。本文首先研究了铸钢件淬火过程中的热量传递原理，基于热传导方程，构建了铸钢件淬火过程中的温度场计算模型。计算模型考虑了铸钢件淬火过程中的相变潜热，以及不同冷却介质换热系数和铸钢件材质物性参数随温度变化对铸钢件淬火温度的影响。以梅尼尔-卡西预测模型为基础，提出了一种对铸钢件淬火组织及性能进行预测的方法。并根据温度场求解算法，提出了一种铸钢件淬火冷却过程中700℃的计算方法。基于铸钢件淬火过程中的温度场计算算法及组织和硬度预测方法，开发出了可应用于铸钢件淬火过程的数值模拟及组织性能预测系统。其次，本文针对三维阶梯件实例，系统的分析了淬火冷却过程中铸钢件的热物性参数、淬火冷却介质的换热系数变化对铸钢件淬火过程温度变化及组织性能的影响。重点模拟分析了阶梯件在水、L-AN22全损耗系统用油、10%NaCl水溶液三种冷却介质中的温度场结果以及组织性能预测结果。模拟预测结果基本符合文献中提到的三种冷却介质换热系数变化规律。然后，以实际零件起重机制动轮为算例，分析了水冷、油冷、水淬油冷三种不同工艺下制动轮的瞬态温度场结果及马氏体、贝氏体、珠光体-铁素体和硬度的分布情况。结果表明，采用水淬油冷的工艺不仅可以使制动轮表面获得很高的硬度，提高制动轮的耐磨性能，还可以保证制动轮心部具有较强的韧性，具备一定的抗冲击性。更多还原

【Abstract】 Steel casting quenching process is a complex process which with temperature changes,organizational change and stress and strain, it is an important method to improve theperformance of steel casting after moulding by casting. The quenching process directly decidethe performance of steel casting whether meet the requirements. But adopts experimentalmethod to determine the appropriate correctness of steel quenching process, need a lot ofmanpower and material resources and time cost. And every experiment can only study a steelcasting quenching process with a particular component under specific process. Therefore,using the numerical simulation to caculate the temperature changes of steel castingquenching process, predict microstructure and performance and discuss the influence ofdifferent quenching process on the microstructure and mechanical properties of steelcasting and to seek the most appropriate way of steel quenching process has veryimportant practical significance.This thesis firstly studied the heat transfer principle in the process of steel quenchingprocess. Based on the heat conduction equation, a three dimensional mathematical model isestablished for the temperature field. This mathematical model consider the latent heat of steelcasting quenching process, the change of heat transfer coefficient of different cooling mediumand physical parameters of steel casting. Finite difference method is used to develop thecomputer program for calculating the temperature field of steel casting quenching process.One prediction method the Maynier’s model for forcasting the microstructure andmechanical properties of steel casting is put forward. Developed the system for thenumerical simulation of steel casting quenching process and prediction of microstructureand mechanical properties.Secondly, focusing on the ladder parts case study, the systematic analysis of influence ofthermal physical parameters of steel casting and the change of heat transfer coefficient ofdifferent cooling medium to the temperature field and microstructure and mechanical properties of steel casting after quenching are discussed. Importantly anlysisd thetemperature field and prediction results when steel casting cooling in the water, L-AN22total loss system oil and10%NaCl aqueous solution. The analysis results are conform tothe describtion of cooling capacity of three kinds cooling medium referred in otherthesis.Lastly, focusing on the brake wheel of crane case study, analysised the temperaturefield and the distribution of martensite, bainite, ferrite-pearlite and hardness in brake wheelafter quenching in water, oil, and water-cooling then oil quenching. We can known fromthe results that water-cooling then oil quenching not only can improve the hardness ofbrake wheel surface, but also can ensure that toughness of the center of brake wheel.更多还原