AlN对高铝钢用CaO-SiO_(2)基保护渣性能的影响

Effect of AlN on properties of CaO-SiO_(2) based mold fluxes for high-Al steel

铝以合金元素加入到钢中,可细化晶粒、抑制低碳钢的时效现象,实现钢的耐腐蚀性、耐热性等性能的良好结合,同时又可满足新一代汽车钢对汽车安全性以及轻量化的需求。然而,当钢液中w([Al])过高时,钢液凝固前生成的AlN在结晶器内不断上浮至钢渣界面与保护渣作用,导致保护渣成分的改变和性能的恶化,进而影响连铸的顺行和铸坯表面质量。采用FactSage7.2热力学软件对高铝钢水中AlN的生成热力学进行了计算,利用半球点熔化温度测试仪、旋转黏度计测试分析了向传统CaO-SiO_(2)基保护渣中添加质量分数为2%、4%、6%、8%的AlN后保护渣黏度、熔化温度和转折温度的变化情况,并对添加AlN后的渣样进行了XRD物相检测。研究结果表明,随着钢中w([Al])和w([N])的增加,AlN的生成温度提高,生成总量增加。当AlN添加的质量分数从0增加到8%时,保护渣黏度和熔化温度均呈升高趋势,每添加质量分数为1%的AlN,黏度增大约0.032 Pa·s,熔化温度升高约13.5℃。当AlN添加质量分数为2%时,保护渣转折温度从1002℃下降到980℃;当AlN添加质量分数大于2%后,转折温度逐渐升高至8%AlN时的1117℃。随着AlN添加量的增加,在冷凝过程中传统CaO-SiO_(2)保护渣中枪晶石析出量逐渐减少,当AlN添加质量分数为8%时,渣样中物相以CaF;为主。

Al added to steel as alloying elements can not only refine grain size,inhibit aging phenomenon of low carbon steel,achieve a good combination of corrosion resistance,heat resistance and other properties of steel,but also to meet the new generation of automotive steel for automotive safety and lightweight requirements.However,when w([Al])in molten steel is too high,the AlN generated before the solidification of molten steel rises to the interface of steel and reacts with the mold fluxes in the mold,which leads to changes in the composition and deterioration in properties of the mold fluxes,thus affecting the alignment of continuous casting and the surface quality of billet.FactSage7.2 thermodynamic software was used to calculate the formation thermodynamics of AlN in high-Al molten steel,the change of viscosity,melting temperature and break temperature of traditional CaO-SiO_(2)based mold fluxes after adding mass fraction of 2%,4%,6%and 8%AlN was analyzed by hemisphere point melting temperature tester and rotary viscometer,and the slag samples after adding AlN were tested by XRD.The results show that with the increase of w([Al])and w([N])in steel,the formation temperature of AlN increases and the total formation amount of AlN increases.When the amount of AlN increases from 0 to 8%,both the viscosity and melting temperature of mold fluxes increase.The viscosity increased about 0.032 Pa·s and the melting temperature increased about 13.5℃with each added mass fraction of 1%AlN.When the mass fraction of AlN was 2%,the break temperature decreased from 1002℃to 980℃.When the mass fraction of AlN was more than 2%,the break temperature gradually increased to 1117℃at 8%AlN.With the increase of AlN content,the amount of cuspidine precipitation in the traditional CaO-SiO_(2)mold fluxes decreases gradually in the process of condensation.When the AlN content is 8%,the main phase in the slag sample is CaF;.