基于材料性能优化的模具钢成形磨削热损伤控制基础理论与试验研究

As a special measuring tool, thread gauge is used to integrate inspecting the machining quality of special thread joint which used in deep oil well pipe (more than 3000m), the safety production of oil-gas well is directly affected by the machining quality of thread gauge. Spiral tooth, up to IT3～IT4 level of dimensional accuracy, fatigue resistance performance (up to 20000 cycle time) under severe service condition, all of these requirements have close relation with the heat treatment and forming grinding processes which used in the machining of thread gauge. However, in the final grinding of thread gauge, surface defects on tooth such as forming grinding burn on the flange, macrocrack, microcrack and dimensionally out of tolerance were often happened. These defects would significantly reduce the abrasion resistance and service life of the gauge, durability of these products was only one tenth of imported gauges. In order to solve this situation, based on favorable usability and service properties of the gauge, this topic proposed a method to optimize the heat treatment of die steel which is the workpiece material and grinding process in parallel. Studies involve quantitative description of the relationship between heat treatment of die steel and its grinding performance, Convolution and reconstruction of a new numerical model for temperature calculation in forming grinding, system design and application of intermittent superabrasive grinding wheel which has complex surface structure and optimized surface topography. At last, the bottlenecks in high efficiency forming grinding of thread gauge could be solved by developing these new manufacturing techniques. The research contents in this topic provide an important theoretical basis for the domestication of thread gauge manufacturing technology and also are crucial support for the replication of imported products. This is also very important for ensuring the safety in national gas and oil production.

用于深层油井(三千米以上)管柱螺纹接头质量综合校验的专用量具，螺纹量规直接影响了油气井长期服役的安全性能。螺旋齿形结构，IT3-IT4级尺寸精度，极端服役环境下抗疲劳性能与量规的成形磨削工艺和材料热处理密切相关。其中，成形磨削烧伤、宏观与网状裂纹、尺寸超差等齿面缺陷已成为制约量规高效成形磨削的瓶颈问题，严重降低了产品的使用寿命，仅为进口量规的1/10。为此，本项目提出采用基于量规的使役性能需求，来驱动量规材料模具钢的热处理和磨削加工工艺优化的方法。通过开展定量描述模具钢热处理与磨削加工性能之间的关系、卷积重构复杂成形磨削加工温度场的数值计算模型、设计和应用具有复杂型面和砂轮表面形貌优化的断续超硬磨料砂轮等研究，解决量规高效成形磨削的瓶颈问题。本研究为实现螺纹量规制造技术国产化，替代国外进口产品这个目标提供了重要理论依据与工艺基础支撑，对保证国家油气井安全生产具有重要的战略意义。

本项目针对制约非API螺纹量规高效成形磨削的瓶颈问题，即螺纹量规磨削烧伤与磨削裂纹，基于螺纹量规的使役性能需求，实现了量规材料的热处理工艺和磨削参数优化。通过开展不同热处理状态螺纹量规材料的磨削性能研究，定量化描述了量规材料热处理与磨削加工性能之间的关系。通过增加两次冷处理和回火处理，量规材料中网状碳化物大量消除，碳化物级别在2级以内，残余奥氏体含量在4%以内，马氏体更加细化且均匀分布，此时量规材料具有良好的磨削加工性能。通过磨削弧区内直角三角形热源分布以及一维导热过程的简化，并基于平面连续磨削温度的理论分析，构建了成形磨削温度的数值计算模型，并设计了成形磨削温度的试验测试方法。由于成形磨削过程中同时存在平面和斜平面两个磨削热源，二者之间存在耦合作用，从而导致平面与斜平面交界处的温升急剧增加，极易引起磨削烧伤，而且不同磨削深度下的温升急剧增加的区域宽度为0.1mm～0.3mm。最后，对具有复杂型面和砂轮表面形貌优化的断续结构超硬磨料砂轮进行了详细的结构设计和制备，并结合优化的磨削加工工艺，采用改进后的超硬磨料砂轮，解决了非API螺纹量规的高效成形磨削问题。在采用优化的加工工艺技术后，零件加工时间由原18小时缩短至9小时，加工效率提升了50%；非API螺纹量规的使用寿命由优化加工工艺前的最低2000次提升至16000～17000次，从而替代了国外同类进口产品。本项目的研究成果也有望在其它模具钢类材料成形磨削加工领域中获得广泛的应用。