不同钛含量的钢与Al_(2)O_(3)和MgAl_(2)O_(4)界面润湿行为

Interface wettability between steel with various contents of titanium and Al_(2)O_(3)and MgAl_(2)O_(4)

高温下钢液中会生成大量的非金属夹杂物,对钢的浇铸工艺和钢产品性能产生不利影响。通过研究高钛钢与夹杂物的界面润湿行为,以期为高钛钢成分设计以及夹杂物的控制研究提供理论依据。以不同钛含量的钢样品以及Al_(2)O_(3)和MgAl_(2)O_(4)为研究对象,采用改进后的座滴法进行高温润湿试验得到表观接触角;通过电子探针对样品界面的微观形貌和元素进行表征,并结合热力学计算对钢与夹杂物的界面润湿行为进行解释。当钢中钛质量分数分别为0.01%、0.31%和0.68%时,Al_(2)O_(3)/钢润湿系统的表观接触角分别为96°、90°和112°,润湿后的样品界面均匀,无新反应相的存在和明显的元素富集。MgAl_(2)O_(4)/钢润湿系统的表观接触角分别为113°、106°和130°;低钛含量(w(Ti)=0.01%)时,界面无反应相生成,高钛含量时,界面存在不连续的反应层,为MgS、MgO、Ti4S2C2和MgAl_(2)O_(4)的混合物。研究表明,钛含量增多会导致钢液表面张力降低,界面接触角减小,但当钢中钛质量分数达到0.68%时,钢中夹带的大量TiN颗粒会使熔融钢液黏度增大,钢液滴在基片上的铺展受阻,其影响远大于表面张力的降低。因此,随着钢中钛含量的提高,两种系统的表观接触均呈现先减小后增大的趋势。高温下的熔融钢液是一个非常复杂的混合物体系,目前,针对钢样和夹杂物的润湿体系,主要通过接触角、界面微观形貌以及是否有新的产物生成来评价。因此,在后续的研究中,针对高钛钢与夹杂物基片界面润湿体系的评价方法还有待进一步探究与完善。

Non-metallic inclusions will be formed in molten steel at high temperature,which will adversely affect the casting process of steel and the properties of steel products.In order to to provide some theoretical and experimental basis for the design,preparation and application of high titanium steel by studying the interfacial wetting behavior between high titanium steel and inclusions.Three kinds of steel samples with different titanium content and typical inclusions(Al_(2)O_(3)and MgAl_(2)O_(4))were taken as research objects,and the high-temperature wetting experiments were carried out by a modified sessile drop method,and the apparent contact angles between solidified steel samples and inclusion substrates were obtained.After the experiments,the interface morphology and elements of the samples were characterized by electron probe microanalyzer,and the interface wetting behavior between steels and inclusions was explained by thermodynamic calculation.The main results are as follows.When the mass percent of titanium in steel was 0.01%,0.31%and 0.68%respectively,for the Al_(2)O_(3)/steel wetting system,the apparent contact angles were 96°,90°and 112°,respectively,and the interface between solidified steels and substrates was uniform with no new reaction phase and obvious element enrichment were found.For MgAl_(2)O_(4)/steel wetting system,the apparent contact angles were 113°,106°and 130°,respectively,and no reaction phase was found at the interface between steel with low titanium content(w(Ti)=0.01%),but a discontinuous chemical reaction layer existed at the interface between steels with high titanium content and substrates,which may be a mixture of MgS,MgO,Ti4S2C2and MgAl_(2)O_(4).Research showed that the decrease of the apparent contact angle was due to the decrease of the surface tension of molten steel caused by the addition of titanium content.However,when the titanium content in steel reached 0.68%,many TiN particles entrained in the steel leaded to the increase the viscosity of molten steel and then hindered its spreading.The effect of viscosity on the apparent contact angle was much greater than that of surface tension.Therefore,the apparent contact angles of both systems decreased and then increased obviously with the increase of titanium content.Molten steel at high temperature is a very complex mixture system.At present,the wettability between steel and inclusions is mainly evaluated by contact angle,interface morphology and chemical reaction.Therefore,the evaluation method of interface wetting system between high-Ti steel and inclusions needs to be further explored and improved in the future research.