【作者】 方剑；

【导师】 袁泽喜；

【作者基本信息】 武汉科技大学 ， 材料学， 2008， 硕士

【摘要】 微合金非调质钢的研发与应用,简化了生产工艺流程,节约了能源,是现在工业的重要产品之一,具有广阔的发展前景。本文结合衡阳钢管有限公司生产的微合金非调质无缝钢管40Mn2V的生产实际,对其高温变形过程中的变形抗力和动态再结晶以及第二相析出情况进行了研究,为实际生产提供了可靠的理论依据。本文共设计了14个不同的变形条件,近似模拟40Mn2V钢管的实际生产变形过程。通过在Gleeble-1500热模拟试验机上,测得各变形条件下的真应力-应变曲线,来研究变形条件对变形抗力和动态再结晶的影响。结合显微组织观察和透射电镜观察,分析再结晶晶粒和原始晶粒的大小以及第二相析出情况。研究结果表明,40Mn2V钢的高温变形过程,是加工硬化和高温软化的综合作用过程,温度越高、变形速率越低,变形抗力越小。变形抗力σ的对数值lnσ随温度T和变形速率对数值lnε的增加,分别成线性减少和增加,变形抗力值σ与变形程度ε的成非线性关系。根据周纪华、胡克智提出的变形抗力模型公式,用Matlab软件对测得数据进行综合回归,拟合出了微合金非调质钢40Mn2V的变形抗力公式,拟合度R为0.9663,拟合较好。根据真应力-应变曲线,只有当变形量足够大时,才能发生和完成动态再结晶,温度越高、变形速率越低,动态再结晶越容易。根据经验公式和试验数据,求出40Mn2V钢的动态再结晶激活能Qd为382.2168KJ/mol,比低碳钢再结晶激活能287KJ/mol高出95.2KJ/mol。将Zener-Hollomen因子Z引入,简化了动态再结晶图,因子Z越小,动态再结晶越容易。因子Z越大,动态再结晶晶粒尺寸越小,细化效果越强。透射电镜观察表明,在800℃～950℃范围内有V和Ti的碳氮化合物析出,这些析出物不仅提高了变形抗力,且显著地提高了动态再结晶激活能,阻碍了动态再结晶行为。更多还原

【Abstract】 The research and application of microalloyed non-quenched and non-tempered steels simplified production process and saved energy, which is one of the most important product in modern industry and have great development space. In this paper, resistance of deformation, dynamic recrystallization and second-phase precipitation in high temperature deformation had been studied for microalloyed non-quenched and non-tempered seamless steel pipe 40Mn2V combining the actual production of Hengyang Steel Tube.Co.,Ltd., which had provided reliable theory data for actual production.Fourteen of deformation condition had been designed for approximatively simulating the actual production of steel tube 40Mn2v in this paper. Resistance of deformation and dynamic recrystallization had been researched according to true stress-strain curve in high temperature deformation tested by the Gleeble-1500 thermal simulation machine. The size of recrystal grain in deformation condition and original grain had been analyzed by microstructure observation, and the state of second-phase precipitation in high temperature deformation had been observed by TEM.The results show that the high temperature deformation process of steel 40Mn2V is a integrative process of work-hardening and high temperature softening, and the deformation resistance become smaller with higher temperature and lower deformation rate. The logarithm value lnσof deformation resistanceσlinearity reduce and increase respectively with the increasing of temperature T and deformation rate lnε, however the value of deformation resisitance and deformation degree comply to nonlinear relation. The fitting formula of deformation resistance of microalloyed non-quenched and non-tempered steel 40Mn2V had been gained by using Matlab soft to synthetically regress for the tested datas, according to the resistance of deformation model proposed by Jihua Zhou and Kezhi Hu, which fit degree is better for 0.9663. Only as the deformation degree is big enough, recrystallization behavior could occur and achieve, which become more easily with higher temperature and lower rate of deformation, according to the true stress-strain curve. The dynamic recrystallization activation energy Qd of microalloyed non-quenched and non-tempered steel 40Mn2V had been calculated for 382.2168KJ/mol by experiential formula and test datas, which is 95.2KJ/mol more than low carbon steel 287KJ/mol. As the Zener-Hollomen factor Z were adopted, it simplified the graph of dynamic recrystallization, which show that recrystallization behavior become more easily with smaller factor Z. There are smaller recrystal grain size and stronger effect of refinement with bigger factor Z. TEM observation show that the carbonitride of V and Ti precipitate in temperature range of 800℃～950℃, which not only strengthened the resistance of deformation, but also increased the dynamic recrystallization activation energy, and hampered dynamic recrystallization evidently.更多还原