高强度低温用结构钢高温变形行为及热处理工艺研究

发布时间：2018-06-03 15:12

  本文选题：高强度低温用结构钢 + 高温变形行为　； 参考：《南京航空航天大学》2017年硕士论文

【摘要】：随着钢铁材料在高寒地区应用的快速发展,人们对其低温韧性和安全性提出了更高的要求,采用控轧控冷及多元微合金化工艺开发的高强度低温用结构钢具有良好强韧性、强塑性匹配。因此,低温用结构钢的研发和生产成为世界上各大钢铁制造商的重要发展方向。本文采用光学显微镜(OM)、扫描电镜(SEM)、透射电镜(TEM)及附带的能谱仪(EDS)、拉伸试验、冲击试验等手段,以宝山钢铁股份有限公司开发的高强度低温用热轧态结构钢板为研究对象,在研究无Co钢板的高温变形行为、热处理组织和力学性能的基础上,研究加入微量Co(0.1wt%)对高强度低温用热轧态结构钢板的高温变形行为、热处理组织和力学性能的影响规律。采用Gleeble 3800热模拟试验机,测定了无Co高强度低温用结构钢的CCT曲线,并分析了变形温度为850~1200℃,应变速率为5s-1条件下变形温度对其热压缩变形组织与动态再结晶行为的影响。结果表明:无Co高强度低温用结构钢的相变临界点Ac1=723.9℃,Ac3=810.1℃,Ms=390℃,淬火临界冷却速度约为15℃/s。在850~1200℃下压缩变形时无Co高强度低温用结构钢的真应力-真应变曲线具有动态回复型流变曲线特征。随变形温度由850℃升高到1100℃,细小等轴再结晶晶粒尺寸由50μm减小至9μm,动态再结晶分数(X)由67.4%增加至100%。研究了(800、920、950℃)正火×60min+20%冷变形+650℃×60min高温回火复合形变热处理工艺对无Co高强度低温用结构钢组织及力学性能的影响,结果表明:正火态复合形变热处理试样较热轧态冷变形回火试样强度稍有降低而低温韧性得到显著改善,随着正火温度的升高,强度先升高后降低,低温韧性呈持续降低的趋势。800℃两相区正火态复合形变热处理试样组织为铁素体和回火粒状贝氏体,具有最佳强韧性匹配,屈服强度和抗拉强度分别为637MPa、706MPa,-20℃和-50℃下的冲击吸收能量分别达到63J和40J。以韧性断裂方式及弯曲、扭折的二次裂纹扩展路径为特征的800℃两相区正火态复合形变热处理试样展现出良好的低温韧性。研究了Co含量为0.1%的高强度低温用结构钢850~1200℃温度下压缩变形时的高温变形行为及复合形变热处理(800℃两相区淬火×60min+20%冷变形+650℃高温回火×60min)态试样低温韧性的影响。结果表明:加入0.1%Co能够增加试验钢在同等变形温度下的流变应力并延迟动态再结晶的发生,变形温度为850℃时,真应变为0.9的无Co和0.1%Co试样的X值分别为67.4%和43.9%,当变形温度升高至1100℃时,X均增加到100%。0.1%Co添加后试验钢回火索氏体中渗碳体的数量增加,平均尺寸却在减小,屈服强度由756MPa增加至787MPa,-20℃和-50℃下的低温冲击吸收能量由69J、41J增加到102J、65J,塑韧性呈现显著提高。
[Abstract]:With the rapid development of the application of iron and steel materials in high and cold regions, the low temperature toughness and safety of steel materials have been put forward higher requirements. The high strength low temperature structural steel developed by controlled rolling and controlled cooling and multi element microalloying process has good strength and toughness. Strong plastic matching. Therefore, the research and production of low-temperature structural steel has become an important development direction of major steel manufacturers in the world. In this paper, optical microscope, scanning electron microscope (SEM), transmission electron microscope (TEM) and attached energy spectrometer (EDSU), tensile test and impact test were used to study hot rolled structural steel plate with high strength and low temperature developed by Baoshan Iron and Steel Co., Ltd. On the basis of studying the high temperature deformation behavior, heat treatment structure and mechanical properties of Co free steel plate, the effects of adding a small amount of Co 0. 1 wt) on the high strength low temperature hot rolled structural steel plate at high temperature deformation behavior, heat treatment structure and mechanical properties were studied. The CCT curves of Co free high strength low temperature structural steel were measured by Gleeble 3800 thermal simulator. The effect of deformation temperature on the hot compression deformation microstructure and dynamic recrystallization behavior was analyzed under the condition of 850,1200 鈩，

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