Composition design of CaO-Al2O3 series low reactivity continuous casting molding flux for high titanium steel
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摘要: 高钛钢连铸过程采用传统的CaO-SiO2-Al2O3连铸保护渣会发生剧烈的钢渣界面反应,影响连铸顺行。为减弱钢渣界面反应,设计了高钛钢低反应性连铸保护渣,通过钢渣界面热力学计算,确定CaO-Al2O3基保护渣的可行性,使用Factsage热力学软件计算低反应性保护渣成分范围,对拟定的三组保护渣采用旋转黏度测试仪和全自动炉渣熔点熔速测定仪测量其黏度和熔点,并对新开发的适合连铸生产的保护渣采用VSgr-60-2000型真空气氛压力烧结炉进行钢渣界面反应试验。结果表明,开发的高钛钢专用CaO-Al2O3系低反应性保护渣渣中CaO/Al2O3为1.1,配加10%CaF2、7%MgO、5%Na2O、3%K2O、13%B2O3以及5%SiO2,黏度为0.413 Pa·s,熔点为1106 ℃,钢渣界面反应试验后,钢中Ti含量降低0.03个百分点,保护渣中TiO2含量增加0.002个百分点,界面反应微弱。新开发的保护渣极大程度抑制了钢渣界面反应的进行。Abstract: In the continuous casting process of high-titanium steel, the traditional CaO-SiO2-Al2O3 mold slag will produce a violent steel/slag interface reaction, which will affect the continuous casting process stability. In order to weaken the interface reaction of steel/slag, a low reactivity mold flux for casting high titanium steel had been designed and the feasibility of CaO-Al2O3 based mold flux had been determined through the thermodynamic calculation of the steel slag interface by using Factsage thermodynamic software to calculate the composition range of the low reactivity mold flux. The viscosity and melting point of the three groups of mold slag were measured by rotary viscosity tester and automatic slag melting point and melting rate tester, and the newly developed mold slag suitable for continuous casting production was tested by VSgr-60-2000 vacuum atmosphere pressure sintering furnace. The CaO/Al2O3 in newly developed mold flux at 1.1, with addition of 10%CaF2, 7%MgO, 5%Na2O, 3%K2O, 13%B2O3 and 5%SiO2, its viscosity measured by viscometer is 0.413 Pa·s, and the melting point is 1106 ℃. After the steel/slag interface reaction test, the Ti content in the steel decreases by 0.03%, and the TiO2 content in the mold slag increases by 0.002%, and the interface reaction is weak. The newly developed mold slag can extremely suppress the progress of the interfacial reaction of steel/slag.
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表 1 高钛钢专用保护渣成分可选取范围
Table 1. The selectable composition range of special mold flux for high titanium steel
CaO/Al2O3 w/% SiO2 MgO Na2O CaF2 B2O3 K2O BaO 1.1 5 0~7 0~5 0~25 12~17 0~3 0~16 表 2 保护渣的拟定成分
Table 2. The composition designs of mold flux
% 编号 CaO Al2O3 SiO2 MgO Na2O CaF2 B2O3 K2O BaO N0 21 20 5 7 5 10 13 3 16 N1 31 28 5 7 2 5 13 1 8 N2 20 18 5 4 2 18 17 1 16 表 3 保护渣熔点、黏度测试结果
Table 3. Mold melting point and viscosity test results
编号 熔点/℃ 黏度/(Pa·s) 试验值 平均 试验值 平均 N0 1098, 1108, 1112 1106 0.415, 0.410, 0.413 0.413 N1 1207, 1201, 1212 1207 0.605, 0.610, 0.608 0.608 N2 1199, 1187, 1192 1193 0.796, 0.808, 0.803 0.802 表 4 界面反应前后钢种S4的成分分析
Table 4. Composition analysis of S4 steel after interfacial reaction
% C Mn Si Als Cr Ni Mo Ti 反应前 0.11 2.62 1.60 1.23 0.41 1.43 0.34 2.02 反应后 0.11 2.54 1.58 1.01 0.40 1.36 0.34 1.99 表 5 界面反应前后N0保护渣的成分分析
Table 5. Composition analysis of N0 mold flux after interface reaction
% 编号 CaO Al2O3 SiO2 MgO Na2O CaF2 B2O3 K2O TiO2 BaO N0 21 20 5 7 5 10 13 3 — 16 反应后 19.87 21.3 4.98 6.89 4.16 — 15.68 10.25 0.002 15.58 -
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