第6期 黎先浩等:CSP生产600MPa级低碳贝氏体钢的相变 .707. 该工艺经涟钢CSP线生产8O00余吨商业材,钢板 试样冲击吸收功Aw、韧脆转变温度FATT50和180° 碳当量CE(美国金属学会推荐公式)、裂纹敏感指数 弯曲实验结果见表3,可见钢板具有高强韧和良好 Pm、屈服强度Rpo.2、抗拉强度Rm、伸长率A、小试 的成形、焊接性能 样(5mm×10mm×55mm)一40℃夏比V型缺口 表3CSP线生产6O0MPa级低碳贝氏体钢性能指标 Table 3 Properties of 600 MPa grade low carbon bainite steel produced by CSP 类别 CE P R 0.2/MPa R/MPa A/%A.(-40℃)小 FATT30/℃180弯曲(d=3a) 最大值 0.44 0.178 670 775 20 84 最小值 0.46 0.160 590 730 17 72 平均值 0.45 0.169 620 755 18 75 60 合格 properties of HSLA steds.Scand J Metall.1980.9(2):83 4 结论 [4]Hulka K.Gray J M.High temperature processing of line pipe (1)由于加入了合金元素Nb、Ti和Mo等,提 stees//Niobium.Science and Technology:Proceedings of the 高了过冷奥氏体的稳定性,抑制了多边形铁素体形 International Symposium Niobium 2001.Bridgeville.2001:587 [5]Kazukuni H.Toshiyuki H.Keniti A.New extremely low carbon 成,在冷却速度大于10℃s时,静态CCT和动态 bainitic high-strength steel bar having excellent machinability and CCT都不发生先共析铁素体转变,室温组织为贝氏 toughness produced by TPCP technology.Kawasaki Steel Tech 体,使得钢具有较高的强度 Rep,2002(47):35 (2)冷却速度小于7℃s1时,室温组织为铁素 [6]He X L.Shang C J.Yang S W,et al.High performance low car- 体十贝氏体十退化的珠光体的复合组织,随冷却速 bon bainitic steel refinement principle and application.Heat Treat Met,2007,32(12):1 度增加,组织中贝氏体组分迅速增多,硬度大幅增 (贺信菜,尚成嘉,杨善武,等。高性能低碳贝氏体钢的组织 加:在7~20℃s范围内,室温组织主要为粒状贝 细化技术及其应用.金属热处理,2007,32(12):1) 氏体并逐渐细化,硬度增加平缓;超过20℃s一1后, [7]Shang C J.Wang X M.Yang S W,et al.Microstructure refine- 除粒状贝氏体外,板条贝氏体组分增多,硬度增幅 ment of high strength low carbon bainitic steel.Acta Metall Sin, 较大 2003,39(10):1019 (尚成嘉,王学敏,杨善武,等.高强度低碳贝氏体钢的工艺 (③)变形降低了奥氏体稳定性,动态CCT曲线 与组织细化.金属学报,2003,39(10):1019) 相对于静态CCT明显向左上方移动,高温转变的开 [8]Hu L J,Shang C J,Wang X M.et al.Effect of relaxation pro- 始温度为800℃,终了温度为700℃,相对静态CCT cess and cooling rate on intermediate phase transformation struc- 均升高了约50℃;动态CCT中温转变的开始温度 ture refinement.JUniv Sei Technol Beijing.2004,26(3):260 为610~668℃,终了温度为520~551℃,相对静态 (胡良均,尚成嘉,王学敏,等,弛豫一析出一控制相变技术中 CCT分别升高了约130℃和90℃. 冷却速度对组织的影响.北京科技大学学报,2004,26(3): 260) (4)在CSP技术条件下生产6O0MPa级低碳贝 [9]Kang Y L.Fu J.Liu D L,et al.Control of Microstructure and 氏体钢的较优工艺是热轧后入水温度为800℃左 Properties of Steel Produced by TSCR.Beijing:Metallurgical In- 右,冷却速度应控制在25~30℃s1,卷取温度约 dustry Press,2006 550℃.该工艺在涟钢CSP线上已成功实现商业化 (康永林,傅杰,柳得橹,等.薄板坯连铸连轧的组织性能控 生产 制.北京:冶金工业出版社,2006) [10]Jun HJ,Kang JS.Seo D H.et al.Effects of deformation and boron 参考文献 on microstructure and continous cooling transformation inlow carbon [1]Weng Y Q.Wang G D.Wang X H.et al.Ultrafine Grained HSLA steels.Mater Sci Eng A.2006.422(1/2):157 Steel:Theory and Controlled Technology of Microstructure Re- [11]Lis A K.Lis J.Effect of hot deformation and cooling rate on finement of Steel.Beijing:Metallurgical Industry Press.2003 phase transformations in low carbon HN5MVNb bainitic steel. (翁字庆,王国栋,王新华,等.超细晶钢:钢的组织细化理论 Mater Sci Forum,2007.539/543:4620 与控制技术.北京:治金工业出版社,2003) [12]Shanmugam S.Ramisetti N K.Misra R DK.et al.Effect of cool- [2]Rodrigues P C M.Pereloma E V,Santoc D B.Mechanical prop- ing rate on the microstructure and mechanical properties of Nbmi- erties of an HSLA bainitic steel subjected to controlled rolling with croalloyed steels.Mater Sci Eng A.2007.460/461:335 accelerated rolling.Mater Sci Eng.2000.283:136 [13]Singh S B.Bhadeshia H K D H.Estimation of hainite plate thick- [3]Morrison W B.Relationship between thermo mechanical treatment and ness in low-alloy steels.Mater Sci Eng A.1998.245(1):72该工艺经涟钢 CSP 线生产8000余吨商业材钢板 碳当量 CE(美国金属学会推荐公式)、裂纹敏感指数 Pcm、屈服强度 Rp0∙2、抗拉强度 Rm、伸长率 A、小试 样(5mm×10mm×55mm) -40℃夏比 V 型缺口 试样冲击吸收功 Akv、韧脆转变温度 FATT50和180° 弯曲实验结果见表3.可见钢板具有高强韧和良好 的成形、焊接性能. 表3 CSP 线生产600MPa 级低碳贝氏体钢性能指标 Table3 Properties of 600MPa grade low carbon bainite steel produced by CSP 类别 CE Pcm Rp0∙2/MPa Rm/MPa A/% A kv(-40℃)/J FATT50/℃ 180°弯曲( d=3a) 最大值 0∙44 0∙178 670 775 20 84 - - 最小值 0∙46 0∙160 590 730 17 72 - - 平均值 0∙45 0∙169 620 755 18 75 60 合格 4 结论 (1) 由于加入了合金元素 Nb、Ti 和 Mo 等提 高了过冷奥氏体的稳定性抑制了多边形铁素体形 成在冷却速度大于10℃·s -1时静态 CCT 和动态 CCT 都不发生先共析铁素体转变室温组织为贝氏 体使得钢具有较高的强度. (2) 冷却速度小于7℃·s -1时室温组织为铁素 体+贝氏体+退化的珠光体的复合组织随冷却速 度增加组织中贝氏体组分迅速增多硬度大幅增 加;在7~20℃·s -1范围内室温组织主要为粒状贝 氏体并逐渐细化硬度增加平缓;超过20℃·s -1后 除粒状贝氏体外板条贝氏体组分增多硬度增幅 较大. (3) 变形降低了奥氏体稳定性动态 CCT 曲线 相对于静态 CCT 明显向左上方移动高温转变的开 始温度为800℃终了温度为700℃相对静态 CCT 均升高了约50℃;动态 CCT 中温转变的开始温度 为610~668℃终了温度为520~551℃相对静态 CCT 分别升高了约130℃和90℃. (4) 在 CSP 技术条件下生产600MPa 级低碳贝 氏体钢的较优工艺是热轧后入水温度为800℃左 右冷却速度应控制在25~30℃·s -1卷取温度约 550℃.该工艺在涟钢 CSP 线上已成功实现商业化 生产. 参 考 文 献 [1] Weng Y QWang G DWang X Het al.Ultrafine Grained Steel:Theory and Controlled Technology of Microstructure Refinement of Steel.Beijing:Metallurgical Industry Press2003 (翁宇庆王国栋王新华等.超细晶钢:钢的组织细化理论 与控制技术.北京:冶金工业出版社2003) [2] Rodrigues P C MPereloma E VSantoc D B.Mechanical properties of an HSLA bainitic steel subjected to controlled rolling with accelerated rolling.Mater Sci Eng2000283:136 [3] Morrison W B.Relationship between thermo mechanical treatment and properties of HSLA steels.Scand J Metall19809(2):83 [4] Hulka KGray J M.High temperature processing of line-pipe steels∥ NiobiumScience and Technology:Proceedings of the International Symposium Niobium2001.Bridgeville2001:587 [5] Kazukuni HToshiyuki HKeniti A.New extremely low carbon bainitic high-strength steel bar having excellent machinability and toughness produced by TPCP technology.Kawasaki Steel Tech Rep2002(47):35 [6] He X LShang C JYang S Wet al.High performance low carbon bainitic stee-l refinement principle and application.Heat T reat Met200732(12):1 (贺信莱尚成嘉杨善武等.高性能低碳贝氏体钢的组织 细化技术及其应用.金属热处理200732(12):1) [7] Shang C JWang X MYang S Wet al.Microstructure refinement of high strength low carbon bainitic steel.Acta Metall Sin 200339(10):1019 (尚成嘉王学敏杨善武等.高强度低碳贝氏体钢的工艺 与组织细化.金属学报200339(10):1019) [8] Hu L JShang C JWang X Met al.Effect of relaxation process and cooling rate on intermediate phase transformation structure refinement.J Univ Sci Technol Beijing200426(3):260 (胡良均尚成嘉王学敏等.弛豫-析出-控制相变技术中 冷却速度对组织的影响.北京科技大学学报200426(3): 260) [9] Kang Y LFu JLiu D Let al.Control of Microstructure and Properties of Steel Produced by TSCR.Beijing:Metallurgical Industry Press2006 (康永林傅杰柳得橹等.薄板坯连铸连轧的组织性能控 制.北京:冶金工业出版社2006) [10] Jun H JKang J SSeo D Het al.Effects of deformation and boron on microstructure and continuous cooling transformation in low carbon HSLA steels.Mater Sci Eng A2006422(1/2):157 [11] Lis A KLis J.Effect of hot deformation and cooling rate on phase transformations in low carbon HN5MVNb bainitic steel. Mater Sci Forum2007539/543:4620 [12] Shanmugam SRamisetti N KMisra R D Ket al.Effect of cooling rate on the microstructure and mechanical properties of Nb-microalloyed steels.Mater Sci Eng A2007460/461:335 [13] Singh S BBhadeshia H K D H.Estimation of bainite plate-thickness in low-alloy steels.Mater Sci Eng A1998245(1):72 第6期 黎先浩等: CSP 生产600MPa 级低碳贝氏体钢的相变 ·707·