Reason analysis on uncoiling and peeling of oxide scale of Q235B hot rolled strip
PAN Hongtao1, ZHANG Zhao2
1. Technical Center of Jiuquan Iron and Steel Group Co., Ltd.,Jiayuguan 735100,China; 2. Carbon Steel Sheet Plant of Jiuquan Iron and Steel Group Co., Ltd.,Jiayuguan 735100,China
Abstract:The oxide scale of Q235B hot rolled strip (especially for the specification with thickness more than 10 mm) is uncoiled and peeled seriously, which pollutes the working environment and affects the welding quality of welded pipe. In order to find out the cause, three specifications of Q235B hot rolled strip, i.e., 9.45 mm, 11.45 mm, and 16.2 mm, were selected. X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDS) were employed for the qualitative analysis of phase structure of oxide scale, the quantitative analysis by full spectrum fitting without standard sample, the characterization of microstructure and morphology, and the composition analysis of micro regions. The results showed that Fe3O4, Fe2O3 and FeO were the main three-phase structure in the oxide scale of three specifications of Q235B hot rolled strip (9.45 mm, 11.45 mm, and 16.2 mm). The phase of 2FeO·SiO2 (iron olivine) was not observed, and Si existed in the form of SiO2. The microstructure of oxide scale crack indicated that the stress state in oxide skin changed with the increase of strip steel thickness. The internal stress in oxide scale of 9.45 mm hot rolled strip was compressive stress, the internal stress in oxide scale of 11.45 mm hot rolled strip was tensile stress, and the internal stress in oxide scale of 16.2 mm hot rolled strip represented in both tensile stress and compressive stress. In addition, there were microstructure defects such as gas holes, cracks, pores, and slag entrapment in the oxide scale of all three specification of Q235B hot rolled strips. These defects essentially formed the crack source of large-area peeling of the oxide scale in the uncoiled state. The inclusion of refractories would cause the pores to fail to close. The oxide skin was loosely combined with the steel matrix, and easy to peel off.
潘红涛, 张昭. Q235B热轧带钢氧化皮开卷易剥落原因分析[J]. 冶金分析, 2023, 43(3): 91-96.
PAN Hongtao, ZHANG Zhao. Reason analysis on uncoiling and peeling of oxide scale of Q235B hot rolled strip. , 2023, 43(3): 91-96.
[1] 孙彬,郝明欣,齐建军,等.我国钢材氧化皮控制技术的研究进展[J].中国材料进展,2019,38(7):689-716. SUN Bin,HAO Mingxin,QI Jianjun,et al.Research progress on oxide scale control technology of steel in China[J].Materials China,2019,38(7):689-716. [2] Lucía Suárez,Yvan Houbaert,Xavier Vanden Eynde,et al.High temperature deformation of oxide scale[J].Corrosion Science,2009,51(2):309-315. [3] 曾令民,汪万林,陆美文.X射线全谱图拟合定量相分析铁矿石[J].广西科学院学报,2010,26(3):291-294. ZENG Lingmin,WANG Wanlin,LU Meiwen.X-ray quantitative analysis of iron ore using Rietveld refinement method[J].Journal of Guangxi Academy of Sciences,2010,26(3):291-294. [4] 王博,李铸铁,战东平,等.高氮耐候钢锈层的电化学与物相表征[J].冶金分析,2018,38(4):11-15. WANG Bo,LI Zhutie,ZHAN Dongping,et al.Electrochemical and phase characterization of rust layer on high nitrogen weathering steel[J].Metallurgical Analysis,2018,38(4):11-15. [5] 刘振宇,于洋,郭晓波,等.板带热连轧中氧化铁皮的控制技术[J].轧钢,2009,26(1):5-9. LIU Zhenyu,YU Yang,GUO Xiaobo,et al.Techniques of oxide scales control during hot strip rolling[J].Steel Rolling,2009,26(1):5-9. [6] 于洋,王畅,王林,等.热轧板带生产中氧化的基本特点及麻点缺陷的成因与控制[J].轧钢,2021,38(5):1-11,17. YU Yang,WANG Chang,WANG Lin,et al.Basic characteristics of oxidation and formation mechanism and control of salt and pepper defects in hot rolled strip production [J].Steel Rolling,2021,38(5):1-11,17. [7] 朱立.钢材热镀锌[M].北京:化学工业出版社,2006:48-50. [8] 吴园园,张珂,洪慧敏.硅钢高温氧化铁皮的显微结构表征[J].冶金分析,2014,34(10):25-31. WU Yuanyuan,ZHANG Ke,HONG Huimin,et al.Characterization of the microstructure of high temerature oxide scale on silicon steel[J].Metallurgical Analysis,2014,34(10):25-31. [9] 迟景灏,甘永年.连铸保护渣[M].沈阳:东北大学出版社,1993:3-12. [10] 叶东东,陈建钧,王忠建.不同应力状态下带钢的破鳞机理[J].钢铁研究学报,2016,28(1):64-70. YE Dongdong,CHEN Jianjun,WANG Zhongjian.Spalling mechanisms of oxide scale of strip under different stress states[J]Journal of Iron and Steel Research,2016,28(1):64-70.