【作者】 宋清华；

【导师】 王伯健；

【作者基本信息】 西安建筑科技大学 ， 材料加工工程， 2007， 硕士

【摘要】 本文主要研究了65Mn和SWRH82B珠光体钢丝在剧烈冷拉塑性变形条件下，其力学性能及内部组织的演变规律，系统探讨了：①65Mn和SWRH82B珠光体钢丝剧烈冷拉塑性变形的拉拔工艺和配模规律；②剧烈冷拉塑性变形对65Mn和SWRH82B珠光体钢丝力学性能的影响及抗拉强度与硬度之间的关系；③65Mn和SWRH82B剧烈冷拉塑性变形的强化机制；④剧烈冷拉塑性变形对65Mn和SWRH82B珠光体钢丝显微组织演变的影响；⑤剧烈冷拉塑性变形珠光体钢丝渗碳体溶解的热力学和动力学条件。研究结果表明：(1)采用合理的拉拔速度、润滑条件和配模方法可以实现65Mn和SWRH82B珠光体钢丝的剧烈冷拉塑性变形，真应变量分别可达到3.0和5.0以上。(2)随着冷拔塑性加工量的增大，65Mn和SWRH82B珠光体钢丝抗拉强度和硬度显著提高，与强化机制有着密切联系，强度最大可以达到3730MPa和2712MPa。(3)随着冷拔塑性加工量的增大，65Mn和SWRH82B珠光体钢丝的组织逐步细化，珠光体片间距不断减小，珠光体团发生转动、取向逐渐与拉伸轴方向趋于一致，渗碳体片经历了拉伸、扭曲变形、减薄、颈缩和断裂等塑性变形从而碎化、细化；变形量较大时，渗碳体发生大量溶解。伴随着65Mn和SWRH82B珠光体钢丝中渗碳体的大量溶解，其抗拉强度和硬度出现一定波动。(4)最后，通过热力学和动力学分析，提出剧烈冷拉塑性变形珠光体钢丝中渗碳体强制溶解的驱动力主要取决于三个因素：一是由于渗碳体的减薄以及渗碳体相的不稳定性；二是渗碳体界面处的位错密度以及位错与渗碳体接触区域不断增大的缘故；三是铁素体中的碳原子与位错的结合焓超过了碳原子与渗碳体中铁原子的结合焓，也是渗碳体发生溶解的原因之一。更多还原

【Abstract】 Microstructure and mechanical properties evolution of 65Mn and SWRH82B heavily cold drawn pearlite steel wires were mainly studied in this paper. The investigation involves: (1) The drawing processes and mold distribution rules of 65Mn and SWRH82B heavily cold drawn pearlite steel wires; (2) Effect of heavily cold drawn plastic deformation on mechanical properties of 65Mn and SWRH82B pearlite steel wires, and the relationship between tensile strength and hardness; (3) The strengthening mechanism of heavily cold drawn plastic deformation of 65Mn and SWRH82B pearlite steel wires; (4) Effect of heavily cold drawn plastic deformation on microstructure of 65Mn and SWRH82B pearlite steel wires; (5) The thermodynamics and dynamics conditions of cementite dissolution in heavily cold drawn pearlite steel wires.The results show that:(1) Heavily cold drawn plastic deformation of 65Mn and SWRH82B pearlite steel wires could be realized with reasonable drawing velocity, lubrication condition and mold distribution mode. And the true strains of 65Mn and SWRH82B pearlite steel wires were respectively above 3.0 and 5.0.(2) The tensile strength and hardness of 65Mn and SWRH82B pearlite steel wires remarkably increased with cold drawn plastic deformation, and that was tied up with the strengthening mechanism of heavily cold drawn plastic deformation. The most tensile strength could respectively reach 3730MPa and 2712MPa.(3) The microstructure of 65Mn and SWRH82B pearlite steel wires can be refined gradually with cold drawn plastic deformation. Interlamellar spacing of pearlite reduced by degrees in the drawing processes. The pearlite groups rotated and tropisms tended to be consistent with the direction of the drawing axis. The lamellar cementite was broken and refined after deformations of cutting, bending and drawing, and the dissolution of cementite occurred severely with heavily cold drawn plastic deformation. The tensile strength and hardness appeared fluctuant changes because of cementite dissolution in heavily cold drawn pearlite steel wires.(4) In the end, the drive of cementite dissolution in heavily cold drawn pearlite steel wires mainly depended on three factors from thermodynamic and kinetic analysis: the first factor was the lamellar cementite thinning and instability; the second factor was the increase of dislocation density and the contact area between cemmentite and dislocations which were located mainly at the interface; the third one was the binding enthalpy of carbon and dislocation in ferrite exceeded the binding enthalpy of carbon and iron atoms in cementite, and that was one reason of cementite dissolution.更多还原