大过冷工艺下珠光体钢微观组织参量与力学性能及加工硬化的联系
发布时间：2019-05-13 12:10
【摘要】：本文以SWRS82B珠光体钢为研究对象,首先采用膨胀法和金相法绘制了实验SWRS82B珠光体钢等温转变TTT曲线,研究了珠光体转变动力学相关内容;其次,结合SWRS82B珠光体钢等温转变TTT和连续冷却CCT曲线,设定对比实验,利用DIL-805A/D动静态相变仪进行了精确的热处理,研究了大过冷工艺的可行性;最后,采用盐浴等温等温工艺替代了传统铅浴工艺,进行了盐浴大过冷实验,通过OM、SEM及TEM组织形貌观察,MTS Landmark拉伸性能试验,Image tool软件测量显微组织(晶粒)尺寸,Origin软件绘图分析,SPSS软件线性回归分析等手段,全面系统研究了不同大过冷工艺参数下珠光体亚结构组织及力学性能的变化,建立了珠光体微观组织参量与力学性能及加工硬化指数之间的经验性方程,并分析了三者之间的联系,得到了以下主要结论:1)与传统等温处理相比,大过冷新工艺能明显提高珠光体形核率,当相对(瞬时)过冷度增加250时,珠光体(形核)体积提高了近50%,说明了大过冷工艺具有可行性。2)过冷温度越低,过冷度增大,瞬时形核率提高,团尺寸明显细化,且易出现纳米级渗碳体。随过冷时间增加,团尺寸和片层间距均增大,铁素体和渗碳体两相界面位错密度下降;而随过冷时间进一步延长,团尺寸和片层间距又开始减小,珠光体亚结构组织连续性变好,且出现少量下贝氏体组织。3)过冷温度为300℃,过冷时间为3 s时,珠光体团尺寸和片层间距最小,分别为2.39μm和62.11 nm,且部分区域出现了55 nm左右的纳米级渗碳体。力学性能主要受片层间距和团尺寸影响,但具体还受纳米级渗碳体、位错、亚结构组织连续性以及下贝氏体等影响。4)大过冷工艺为300℃-3 s-550℃时,珠光体亚结构组织最细小,综合力学性能较好,考虑到冷拉拔线材钢丝的原材料以全珠光体钢最佳,排除贝氏体相影响,并结合实际生产应用,大过冷最优工艺参数为300℃-3 s-550℃。5)珠光体微观组织参量(晶粒尺寸)与力学性能及加工硬化指数的经验性方程表明:抗拉强度和形变硬化指数主要受片层间距影响,同时受团尺寸影响较大,几乎不受晶粒尺寸影响;断面收缩率主要受团尺寸影响,较少受晶粒尺寸影响,基本不受片层间距影响。
[Abstract]:In this paper, SWRS82B pearlite steel is taken as the research object. Firstly, the isothermic transformation TTT curve of experimental SWRS82B pearlite steel is drawn by expansion method and metallographic method, and the related contents of pearlite transformation kinetics are studied. Secondly, combining the isotherm transformation TTT curve and continuous cooling CCT curve of SWRS82B pearlite steel, the comparative experiment is set, and the precise heat treatment is carried out by using DIL-805A/D dynamic and static phase transformation instrument, and the feasibility of large supercooling process is studied. Finally, the salt bath isotherm process was used instead of the traditional lead bath process, and the salt bath supercooling experiment was carried out. The microstructure (grain) size was measured by, MTS Landmark tensile property test, Image tool software through OM,SEM and TEM microstructure observation. The changes of pearlite substructure and mechanical properties under different supercooling process parameters were studied comprehensively and systematically by means of Origin software drawing analysis and SPSS software linear regression analysis. The empirical equation between microstructure parameters, mechanical properties and work hardening index of pearlite is established, and the relationship between them is analyzed. The main conclusions are as follows: 1) compared with traditional isotherm treatment, The new supercooling process can obviously improve the nucleation rate of pearlite. When the relative (instantaneous) undercooling degree increases by 250, the volume of pearlite (nucleation) increases by nearly 50%, which shows that the high supercooling process is feasible. 2) the lower the supercooling temperature, With the increase of undercooling, the instantaneous nucleation rate is increased, the cluster size is obviously refined, and nanometer cementite is easy to appear. With the increase of undercooling time, the cluster size and lamellar spacing increase, and the dislocation density at the interface between ferrite and cementite decreases. However, with the further prolongation of supercooling time, the cluster size and lamellar spacing began to decrease again, and the continuity of pearlite substructure became better, and a small amount of lower bainitic structure appeared. 3) when the undercooling temperature was 300 鈩，
本文编号：2475857
[Abstract]:In this paper, SWRS82B pearlite steel is taken as the research object. Firstly, the isothermic transformation TTT curve of experimental SWRS82B pearlite steel is drawn by expansion method and metallographic method, and the related contents of pearlite transformation kinetics are studied. Secondly, combining the isotherm transformation TTT curve and continuous cooling CCT curve of SWRS82B pearlite steel, the comparative experiment is set, and the precise heat treatment is carried out by using DIL-805A/D dynamic and static phase transformation instrument, and the feasibility of large supercooling process is studied. Finally, the salt bath isotherm process was used instead of the traditional lead bath process, and the salt bath supercooling experiment was carried out. The microstructure (grain) size was measured by, MTS Landmark tensile property test, Image tool software through OM,SEM and TEM microstructure observation. The changes of pearlite substructure and mechanical properties under different supercooling process parameters were studied comprehensively and systematically by means of Origin software drawing analysis and SPSS software linear regression analysis. The empirical equation between microstructure parameters, mechanical properties and work hardening index of pearlite is established, and the relationship between them is analyzed. The main conclusions are as follows: 1) compared with traditional isotherm treatment, The new supercooling process can obviously improve the nucleation rate of pearlite. When the relative (instantaneous) undercooling degree increases by 250, the volume of pearlite (nucleation) increases by nearly 50%, which shows that the high supercooling process is feasible. 2) the lower the supercooling temperature, With the increase of undercooling, the instantaneous nucleation rate is increased, the cluster size is obviously refined, and nanometer cementite is easy to appear. With the increase of undercooling time, the cluster size and lamellar spacing increase, and the dislocation density at the interface between ferrite and cementite decreases. However, with the further prolongation of supercooling time, the cluster size and lamellar spacing began to decrease again, and the continuity of pearlite substructure became better, and a small amount of lower bainitic structure appeared. 3) when the undercooling temperature was 300 鈩，
本文编号：2475857
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