440 MPa级新型高强度烘烤硬化钢的组织与性能  

Microstructure and properties of a new 440 MPa grade high strength bake hardening steel

作　　者：惠亚军 潘辉 肖宝亮 吴科敏 李晓林 张大伟 HUI Ya-jun;PAN Hui;XIAO Bao-liang;WU Ke-min;LI Xiao-lin;ZHANG Da-wei(Sheet Metal Research Institute,Technology Institute of Shougang Group Co.,Ltd.,Beijing 100043,China;Beijing Key Laboratory of Green Recyclable Process for Iron and Steel Production,Beijing 100043,China;Manufacturing Department,Qian＇an Iron and Steel Company of Shougang Group Co.,Ltd.,Tangshan 064404,Hebei,China)

机构地区：[1]首钢集团有限公司技术研究院薄板所,北京100043 [2]绿色可循环钢铁流程北京市重点实验室,北京100043 [3]首钢股份公司迁安钢铁公司制造部,河北唐山064404

出　　处：《钢铁》2018年第10期79-84,89,共7页Iron and Steel

摘　　要：为了开发440 MPa级新型高强度热轧烘烤硬化钢,采用OM和TEM等仪器对其组织与性能进行了分析,研究了其强化机制与烘烤硬化机理。结果表明,显微组织为铁素体与少量珠光体的混合组织,随着氮质量分数增加与卷取温度的下降,铁素体晶粒变得更加细小;低氮钢在630与600℃卷取温度下铁素体晶粒平均尺寸分别为8.34与7.89μm,细晶强化对屈服强度的贡献值分别为190与196 MPa;高氮钢在630与600℃卷取温度下铁素体晶粒尺寸分别为6.93与6.71μm,细晶强化对屈服强度的贡献值分别为209与212 MPa。烘烤硬化处理后屈服强度与抗拉强度均呈现出上升的规律,在相同的预应变量下,晶粒尺寸越小,氮质量分数越高,抗拉强度上升值越大;高氮钢在10%预应变下BHT（bake hardening,tensile strength increase）值均在70 MPa以上,抗拉强度达到500 MPa以上,主要是由于预应变导入的位错在烘烤处理时变得坚固,并在塑性变形时促进了位错扩大再生。In order to develop a new 440 MPa grade high strength bake hardening steel, the microstructure, properties, strengthening mechanism and bake hardening mechanism were investigated by utilizing optical microscope （OM） and transmission electron microscopy （TEM）. The results showed that the microstructure was composed of ferrite and a small amount of pearlite. With the increase of mass percent of N and the decrease of coiling temperature, the ferrite would be refined. The ferrite grain sizes of the low N steel were 8.34 and 7.89 μm when coiling at 630 and 600 ℃, respectively. The contribution of fine grain strengthening to yield strength was 190 and 196 MPa, respectively. The ferrite grain sizes of the high N steel were 6.93 and 6.71 μm when coiling at 630 and 600 ℃, respectively. The contribution of fine grain strengthening to yield strength was 209 and 212 MPa, respectively. Both the yield strength and tensile strength exhibited an ascending tendency after bake hardening treatment. The smaller of the grain size and the higher of the mass percent of N was, the larger value of the tensile strength was. The BHT values of the high mass percent of N steel at 10% prestrain were all above 70 MPa and the tensile strength reached over 500 MPa, which mainly because the dislocations introduced by prestrain become firm during the baking treatment and promote dislocation enlargement and reborn during plastic deformation.

关 键 词：440 MPA 烘烤硬化钢 卷取温度 氮元素 强化机制 

分 类 号：TG142.1[一般工业技术—材料科学与工程]