Effect of heating temperature on the mechanical properties and microstructures of X80M pipeline steels
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摘要: 研究了不同加热温度对厚壁X80M管线钢原始奥氏体晶粒、组织、析出相及力学性能的影响。结果表明,加热温度对厚规格X80M管线钢的落锤性能影响较大。随着加热温度逐渐升高,奥氏体晶粒不断粗化,当加热温度≤1210 ℃时,原始奥氏体晶粒细小,奥氏体晶粒的平均尺寸为35 μm。原始奥氏体晶粒越细小,在后续轧制和冷却过程中越能促进针状铁素体和粒状贝氏体的形核,即显著改善钢板的低温韧性。此外,加热温度越高,铸坯中合金元素的固溶量越多,能促进20 nm以下的NbC析出相的形成,但会导致晶粒粗化和组织中针状铁素体及粒状贝氏体比例减少。因此,控制加热温度在1210 ℃以下,保证针状铁素体(AF)和粒状贝氏体(GB)比例在60%以上时,可显著改善厚规格X80M管线钢的落锤性能。Abstract: The effects of heating temperatures on the prior austenite grain size, microstructure and mechanical properties of X80M pipeline steels with a large wall thickness were investigated in this paper. The results showed that the heating temperature has a great effect on the drop weight tear test (DWTT) properties of X80M pipeline steels. The austenite grains continued to coarsen with enhancing the heating temperatures. The average austenite grain size was within 35 μm by controlling the heating temperature below 1210 ℃. The finer prior austenite grains provide more nucleation sites of acicular ferrite (AF) and granular bainite (GB), and improve the low temperature toughness of steel plates during the subsequent rolling and cooling processes. Moreover, the higher solution degree of alloy elements in the casting blank promotes the formation of finer NbC precipitates with the sizes less than 20 nm by increasing heating temperature. It also leads to the grain coarsening and the decrease of AF and GB proportions in the microstructure. Therefore, the DWTT properties of X80M pipeline steels with the large wall thickness can obviously be improved by controlling the heating temperatures below 1210 ℃ and ensuring the acicular ferrite (AF) and granular bainite (GB) phase contents more than 60%.
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表 1 厚壁X80M管线钢的主要化学成分
Table 1. Main chemical composition of thick-wall X80M pipeline steel
% C Si Mn P S Al Nb+Ti Cr+Cu+Mo+Ni ≤0.05 0.2 1.7 ≤0.10 ≤0.002 0.030 0.07~0.11 0.61~0.75 表 2 不同加热温度下X80M管线钢力学性能对比
Table 2. Mechanical properties of X80M pipeline steel at different heating temperatures
加热温度/ ℃ Rp 0.2/MPa Rm/MPa −20 ℃下的
Akv2/J−15 ℃下的
DWTT/%1150 535 650 352 93 1180 542 661 330 88 1210 546 668 316 85 1240 560 683 301 70 -
[1] Wang Zhiyong, Li Shaopo, Li Qun, et al. Research on development of low-cost X80 pipeline steel[J]. China Metallurgy, 2016,26(11):64−68. (王志勇, 李少坡, 李群, 等. 经济型X80管线钢的研制开发[J]. 中国冶金, 2016,26(11):64−68. doi: 10.13228/j.boyuan.issn1006-9356.20160067WANG Zhi-yong, LI Shao-po, LI Qun, et al. Research on Development of Low-cost X80 pipeline steel[J]. China Metallurgy, 2016, 26(11): 64-68. doi: 10.13228/j.boyuan.issn1006-9356.20160067 [2] Tsuyama S, Nakamichi H, Yamada K, et al. Effects of distribution and the formation process of MA on deformation and toughness of high strength linepipe steel[J]. ISIJ International, 2013,53:317. doi: 10.2355/isijinternational.53.317 [3] Zhai Dongyu, Du Haijun, Wu Junping, et al. Development of X80M hot-rolled steel plate for LSAW pipe[J]. Iron Steel Vanadium Titanium, 2021,42(1):131−138. (翟冬雨, 杜海军, 吴俊平, 等. X80M 直缝埋弧焊管用热轧钢板开发[J]. 钢铁钒钛, 2021,42(1):131−138.ZHAI Dong-yu, DU Hai-jun, WU Jun-ping, et al. Development of X80 M hot-rolled steel plate for LSAW pipe[J]. Iron Steel Vanadium Titanium, 2021, 42(1): 131-138 [4] Bott I, Souza L, Teixeira J, et al. High-strength steel development for pipelines: A brazilian perspective[J]. Metallurgical and Materials Transaction A, 2005, 36: 443-454. [5] Kang M, Kim H, Lee S. Effect of dynamic strain hardening exponent on abnormal cleavage fracture occurring during drop weight tear test of API X70 and X80 linepile steels[J]. Metall. Mater. Trans A, 2014,45(2):68. [6] Zheng Lei, Fu Junyan. Recent development of high performance pipeline steel[J]. Iron and Steel, 2006,41(10):1−10. (郑磊, 付俊岩. 高等级管线钢的发展现状[J]. 钢铁, 2006,41(10):1−10. doi: 10.3321/j.issn:0449-749X.2006.10.001ZGENG Lei, FU Jun-yan. Recent Development of High Performance Pipeline Steel[J]. Iron and Steel, 2006, 41(10): 1-10. doi: 10.3321/j.issn:0449-749X.2006.10.001 [7] Tian Y, Li Q, Wang Z D, et al. Effects of ultra fast cooling on microstructure and mechanical properties of pipeline steels[J]. J Mater. Eng. Perform, 2015, 24: 3307-3314. [8] Hong Liang, Zuo Xiurong, Ji Yinglun, et al. Fracture behavior of thick X80 pipeline steel plates at −25 ℃[J]. Chinese Journal of Materials Research, 2018,32(1):33−41. (洪良, 左秀荣, 姬颍伦, 等. 厚规格X80管线钢低温断裂行为研究[J]. 材料研究学报, 2018,32(1):33−41.HONG Liang, ZUO Xiu-rong, JI Ying-lun, et al. Fracture behavior of thick X80 pipeline steel plates at −25 ℃[J]. Chinese Journal of Materials Research, 2018, 32(1): 33-41. [9] Shao Chunjuan, Zhen Fan, Zhang Jiming, et al. Effect of sample thinning on DWTT property of heavy wall X80 steel[J]. Journal of Iron and Steel Research, 2020,32(6):497−504. (邵春娟, 镇凡, 张继明, 等. 试样减薄对大壁厚 X80 级管线钢落锤性能的影响[J]. 钢铁研究学报, 2020,32(6):497−504.SHAO Chun-juan, ZHEN Fan, ZHANG Ji-ming, et al. Effect of sample thinning on DWTT property of heavy wall X80 steel[J]. Journal of Iron and Steel Research, 2020, 32(6): 497-504. [10] Zhang Shuai, Ren Yi, Wang Shuang, et al. Effect of hot-rolling process on recrystallization and microstructure of X80-grade steel for thick-walled pipeline[J]. Shanghai Metals, 2018,40(6):55−59. (张帅, 任毅, 王爽, 等. 热轧工艺对X80级厚壁管线用钢再结晶和微观组织的影响[J]. 上海金属, 2018,40(6):55−59.ZHANG Shuai, REN Yi, WANG Shuang, et al. Effect of hot-rolling process on recrystallization and microstructure of X80-grade steel for thick-walled pipeline[J]. Shanghai Metals, 2018, 40(6): 55-59. [11] Zhang Haozhen, Zhang Chuanguo, Sun Leilei. Effect of microstructure on DWTT properties of thick-walled high strength pipeline steels[J]. Hot Working Technology, 2021,50(24):25−31. (张豪臻, 章传国, 孙磊磊. 显微组织对厚规格高强度管线钢DWTT性能的影响[J]. 热加工工艺, 2021,50(24):25−31. doi: 10.14158/j.cnki.1001-3814.20201046ZHANG Hao-zhen, ZHANG Chuang-guo, SUN Lei-lei. Effect of microstructure on DWTT properties of thick-walled high strength pipeline steels[J]. Hot Working Technology, 2021, 50(24): 25-31. doi: 10.14158/j.cnki.1001-3814.20201046