【作者】 张娜；

【导师】 姜周华；

【作者基本信息】 东北大学 ， 钢铁冶金， 2008， 硕士

【摘要】 近年来,不锈钢因其具有耐腐蚀,高温下耐氧化,低温时延展性好等良好的性能,被广泛的应用于国民经济各个部门。钢中夹杂物的组成、大小、数量、形态和分布对钢性能的影响起了决定性作用,一直以来大量的研究人员从各种理论出发找寻控制夹杂物的方法。对于奥氏体不锈钢,从应用比较广泛的304奥氏体不锈钢中夹杂物的控制方面进行研究,模拟不锈钢工业冶炼中的AOD工位,采用常规的硅做终脱氧剂,选择CaO-SiO2-Al2O3-MgO-CaF2五元渣系,以碱度变化为依据变换渣系成分,考察不同碱度渣系对钢液中夹杂物的影响。从每次实验的精炼过程来看,夹杂物的形貌由条状变为球状,夹杂物的平均尺寸、总个数、总面积基本是逐渐减少的,最后组成是以SiO2为主的复合型夹杂物,说明精炼渣对304不锈钢中夹杂物的控制至关重要。从三炉高供氧条件实验的对比中看,随精炼渣碱度(R)的增大,钢中全氧含量降低,夹杂物的总数、总面积和平均半径减小。说明高碱度渣对304不锈钢中的脱氧产物吸附以及对细小夹杂物的生成有利。从实验结果分析来看,精炼渣的碱度R≥2时,更利于生成细小的夹杂物,同时考虑到还原后期脱硫的问题,故生产中应选择碱度R≥2的精炼渣系。对于430铁素体不锈钢,模拟现场不锈钢冶炼中的AOD工位,采用常规的铝做终脱氧剂,选择CaO-SiO2-Al2O3-MgO-CaF2五元渣系和无硅渣系,通过考察渣中Al2O3和CaF2含量的变化来考察不同成分配比对钢液中夹杂物的组成、形态、大小的影响。除此之外,考察无硅渣系对钢液中夹杂物的组成、形态、大小的影响,初步查明精炼渣成分的变化对不锈钢液中夹杂物生成、长大及排除的影响。从每次实验的精炼过程来看,夹杂物的平均尺寸、总个数、总面积基本是逐渐减少的。前三炉五元渣系精炼后得到的是球形硅酸盐复合夹杂物,无硅渣系精炼后得到的是近似球形的Al2O3-MgO夹杂。从430不锈钢五元渣系精炼结果分析来看,更易于生成细小夹杂物的渣系为R=3,Al2O3=30%的精炼渣系。更多还原

【Abstract】 Recent years, for the excellent properties of corrosion resistance, oxidation resistance at high temperature, better ductibility at low temperature etc, the stainless steel is extensively used in many departments of the National Economy. The composition, size, quantities, shape and distribution of inclusions in steel are main factors which determined the properties of steel, and lots of researchers studied on inclusions by different kinds of the theories and tried to find the methods to control inclusions.The 304 austenitic stainless steel which is used widely was researched, and the AOD metallurgy process which is always used for stainless steel smelting industry was simulated. The typical FeSi was choosed as the deoxidizer, and the composition of slag is CaO-SiO2-Al2O3-MgO-CaF2. The influence of different refining slag basicity on nonmetallic inclusion compositions was studied.From the refining process of every experiment, the shapes of inclusions were changed from strip to globosity, and the average size, the quantities, the total area of inclusions are gradually decreased, and the final compositions of inclusions are compound inclusions mainly consisted of SiO2. All these indicated that it is very important to control the inclusions in 304 stainless steel by refining slag.From comparing the results of the first three experiments under the high oxygen supply condition, with the increasing of refining slag basicity, the total oxygen content is decreased, the average size, the quantities, and the total area of inclusions are also decreased. All these indicated that the high basicity refining slag can accelerate the adsorption of deoxidization product, which has the advantage of forming small size inclusions. Comparing the results, we can conclude that the size of inclusions is smaller when the refining slag R≥2。Comparing the following four experiments under low oxygen supply condition, with the increasing of refining slag basicity, the total oxygen content is also decreased, the average size, the quantities, and the total area of inclusions are decreased.The 430 ferritic stainless steel which is used widely was also researched, and the AOD metallurgy process which is always used for stainless steel smelting industry was simulated. The oxygen content of 430 stainless steel melt was controlled by aluminum deoxidation, the composition of slag was CaO-SiO2-Al2O3-MgO-CaF2. Also, the refining slag without SiO2 was used. The compositions of slags were controlled primarily according to the basicity and the ratio of Al2O3 and CaF2 of which, the influence of different refining slag on nonmetallic inclusion compositions were studied to 430 stainless steels.From the refining process of every experiment, the average size, the quantities, the total area of inclusions are gradually decreased. The final compositions of inclusions are mainly consisted of SiO2 in the first three experiments using refining slag bearing SiO2. Global Al2O3-MgO was got in the final sample refined using slag without SiO2.Comparing the results of the slags bearing SiO2, the much smaller inclusions is easily got for the slag of R=3, Al2O3=30%.更多还原