Effect of Na2O on properties of ultra-high basicity continuous casting mold fluxes
PAN Wei-jie1,2, LI Min1,2, ZHU Li-long3, HE Sheng-ping1,2
1. College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China; 2. Chongqing Key Laboratory of Vanadium-Titanium Metallurgy and Advanced Materials, Chongqing University, Chongqing 400044, China; 3. Chongqing University of Science and Technology, Chongqing 401331, China
Abstract:During the continuous casting of peritectic steel, defects of longitudinal cracks of casting strands frequently appear. Production practice shows that mold fluxes with strong crystallinity can effectively reduce the occurrence of longitudinal cracks, but it will deteriorate the lubrication function of mold fluxes. In recent years, the ultra-high basicity continuous casting mold fluxes have the characteristics of low initial crystallization temperature and fast crystallization rate, which can successfully balance the contradiction between lubrication and heat transfer in the continuous casting of peritectic steel. However, there are few studies on the effects of related components on the crystallization properties of the ultrahigh basicity mold slag, and the corresponding structural characteristics are also rarely reported. Na2O is a common component element in mold fluxes and plays an important role in adjusting the properties of mold fluxes. The effect and mechanism of Na2O content on the melting flow characteristics and solidification and crystallization properties of continuous casting mold fluxes at ultra-high basicity(R=1.75) was analyzed by hemispherical point melting temperature tester, rotational viscometer and high temperature in-situ crystallization performance tester. The results showed that the viscosity (1 300 ℃) of mold fluxes,melting temperature,break temperature and crystallization temperature all decreased with the increase of Na2O content,while the crystallization rate first decreased and then increased,and the crystallization rate was the lowest when mass percent of Na2O was 6%. In addition,it is found that the main precipitates in the ultra-high basicity mold flux were gun spar(Ca4Si2F2O7). With the further increase of Na2O content,the new crystalline phases CaF2 and Na2CaSiO4F appeared in the mold flux.
潘伟杰, 李民, 朱礼龙, 何生平. Na2O对超高碱度连铸保护渣性能的影响[J]. 钢铁, 2022, 57(1): 93-101.
PAN Wei-jie, LI Min, ZHU Li-long, HE Sheng-ping. Effect of Na2O on properties of ultra-high basicity continuous casting mold fluxes[J]. Iron and Steel, 2022, 57(1): 93-101.
[1] Hideko Nakada,Kazuhiro Nagata. Crystallization of CaO-SiO2-TiO2 slag as a candidate for fluorine free mold flux[J]. ISIJ International,2006,46(3):441. [2] LONG Xiao,HE Sheng-ping,WANG Qian,et al. Development of ultrahigh-basicity mold fluxes for peritectic steel continuous casting[C]//TMS 2017 Annual Meeting and Exhibition;Symposium on Materials Processing. San Diego(US):[s.n.],2017. [3] 曹磊. 包晶钢连铸坯表面纵裂与保护渣性能选择[J]. 钢铁,2015,50(2):38.(CAO Lei. Surface longitudinal crack of slab and property of mold slag for continuous casting of peritectic steel[J]. Iron and Steel,2015,50(2):38.) [4] 江中块,蔡兆镇,牛振宇,等. 1 650板坯压下过程热/力学行为及压下工艺优化[J]. 中国冶金,2017,27(7):22.(JIANG Zhong-kuai,CAI Zhao-zhen,NIU Zhen-yu,et al. Thermo-mechanical behavior of 1 650 slab during soft reduction and optimization of soft reduction process[J]. China Metallurgy,2017,27(7):22.) [5] 李玉娣,张发斌. 包晶钢板坯纵裂纹分析及保护渣优化[J]. 连铸,2021,46(2):57.(LI Yu-di,ZHANG Fa-bin. Analysis of longitudinal cracks and optimization of mold flux for peritectic steel slab[J]. Continuous Casting,2021,46(2):57.) [6] LONG Xiao,WANG Qian,HE Sheng-ping. Chris pistorius. structure evolution of slag films of ultrahigh-basicity mold flux during solidification[J]. Metallurgical and Materials Transactions B,2017,48(4):1. [7] 龙潇,何生平,王谦.包晶钢连铸保护渣固渣膜粗糙度影响因素[J]. 钢铁研究学报,2017,29(7):551.(LONG Xiao,HE Sheng-ping,WANG Qian. Factors influencing roughness of solidified mold flux film for peritectic steel continuous casting[J]. Journal of Iron and Steel Research,2017,29(7):551.)、 [8] 朱礼龙,何生平,毛敬华,等. 特厚板连铸保护渣系列规划[J]. 钢铁,2016,51(3),44.(ZHU Li-long,HE Sheng-ping,MAO Jing-hua,et al. Systematization of mold fluxes for ultra-thick slab continuous casting[J]. Iron and Steel,2016,51(3):44.) [9] 华江峰,杨军,操瑞宏,等. 16MnD-R钢板坯保护渣成分与性能[J]. 上海金属,2016,38(5):59.(HUA Jiang-feng,YANG Jun,CAO Rui-hong,et al. Study on compositions and properties of the mold powder for 16MnD-R steel slab[J]. Shanghai Metals,2016,38(5):59.) [10] 龙潇. 包晶钢连铸保护渣渣膜凝固结构特征研究[D]. 重庆:重庆大学,2018.(LONG Xiao. Study on Structure Characteristics of Solid Slag Films of Mold Fluxes for Peritectic Steel Continuous Casting[D]. Chongqing:Chongqing University,2018.) [11] 朱礼龙. 包晶钢用超高碱度保护渣的理论研究和应用[D]. 重庆:重庆大学,2018.(ZHU Li-long. Theoretical Research and Application of Ultrahigh-basicity Mold Fluxes for Peritectic Steel[D]. Chongqing:Chongqing University,2018.) [12] WANG H,TANG P,WEN G H,et al. Effect of Na2O on crystallisation behaviour and heat transfer of high Al steel mould fluxes[J]. Ironmaking and Steelmaking,2007,38(5):369. [13] YANG Chang-lin,WEN Guang-hua,SUN Qi-hao,et al. Evolution of temperature and solid slag film during solidification of mold fluxes[J]. Metallurgical and Materials Transactions B,2017,48(2):1292. [14] LU Bo-xun,CHEN Kun,WANG Wan-lin,et al. Effects of Li2O and Na2O on the crystallization behavior of lime-alumina-based mold flux for casting high-Al steels[J]. Metallurgical and Materials Transactions B,2014,45(4):1496. [15] Miyuki Hayashi,Takashi Watanabe,Hideko Nakada,et al. Effect of Na2O on crystallization of mould fluxes for continuous casting of steel[J]. ISIJ International,2006,46(12):1805. [16] 李至荣. 高锰高铝钢保护渣反应性控制及熔渣基本结构性能研究[D]. 重庆:重庆大学,2019. (LI Zhi-rong. Research on Reactivity Control and Basic Structure Properties of Mold Flux for High-Mn High-Al Steel[D]. Chongqing:Chongqing University,2019.) [17] ZHU Li-Long,WANG Qian,WANG Qiang-qiang,et al. The relationship between crystallization and break temperature of mould flux[J]. Ironmaking and Steelmaking,2019,46(9):865. [18] ZHU Li-Long,WANG Qian,WANG Qiang-qiang,et al. In situ observation of crystallization of mold slag using a digital optical microscope in an infrared furnace[J]. Journal of the American Ceramic Society,2019,102(1):104. [19] ZHANG Shao-da,LI Min,ZHU Li-Long,et al. Effect of substituting Na2O for SiO2 on the non-isothermal crystallization behavior of CaO-BaO-Al2O3based mold fluxes for casting high Al steels[J]. Ceramics International,2019,45(9):11296.