Research On Nonmetallic Inclusions Of Continuous Casting Board Produced By Weiyuan Steel Company

The characters of the inclusions in the molten steel affect the quality of the steel directly. Therefore, it is one of the key tasks of making steel to reduce inclusion. Now the status of inclusions in the casting board which are produced by Weiyuan steel making company are not known clearly. In order to learn the level of clean in the molten steel and influence of various procedure on removing of inclusions, improve the properties and competition of present production, provide theory and experiment gist with ameliorative of steel making procedure ,in this paper, first the inclusions of the Q195 steel continuous cast slab and Q235 casting billet are researched including the type, form, quantity, size and distribution of the inclusions made by LD→Ar injection treatment →CC of Weiyuan Iron and Steel Company. Then the effect of removing inclusions by various process are be made experiment and analyzed and discussed. According to the experiment and the theory analysis, the results are as follow: (1) the inclusions of Q195 casting slab: 1) The nonmetal inclusions are mostly spherical, the thimbleful is regular forms such as triangle. 2)The size is mainly smaller than 10 μm, accounting for more than 85%, 10⁵0 μm is over 10%, larger than 50 μm that is litter is only 0.19%. 3) The inclusions rely mainly on oxide inclusion and other inclusions less. Most of the inclusions are silicate of silicon aluminum, little are large-scale complex inclusions that is mainly Al2O3 in the center or some surrounded by a layer of silicate of silicon aluminum. A little of complex inclusions consist of sulfide. 4) On thickness the inclusions gather in the place of 1/4 from surface; on width the inclusions gather at 1/4 from surface too, the distribution of other positions is more even. 5) Single-phase inclusions contain roughly 27%Al₂O₃, 36%SiO₂, 7%CaO, 10%FeO, 14%MnO, a small quantity of TiO₂ and sulfide. The center of complex inclusion contains 66%Al₂O₃, 47%SiO₂, 12%CaO and a small quantity of oxide of Ti and Mg. 6)The inclusion mainly sources from deoxidation production and solidification, but the composition of furnace lining is found in individual inclusions. 7)The grade of inclusion is average 1.58(thin series) and 0.61(thick series);thin series is 2.55 grade and thick series is 1.14 grade in the strict district. (2) the inclusions of Q235 casting billet 1) The nonmetal inclusions are mostly spherical, the thimbleful is dendritic inclusion. 2) The size is mainly smaller than 10 μm, accounting for more than 87.43%, 10⁵0 μm is over 11.6%, larger than 50 μm that is litter is only 0.97%, and also larger than 200 μm is found. 3) The inclusions rely mainly on oxide inclusion and other inclusions less. Most of the inclusions are silicate of silicon aluminum, little are large-scale complex inclusions that the center and periphery both are silicate of silicon aluminum in which the material composition is different . 4) The inclusions gather in the place of 1/4 and 1/3 from surface, the distribution of other positions is more even. 5) Single-phase inclusions contain roughly 33%Al2O3, 38%SiO2, 6.7%CaO, and a small quantity of oxide of Mn. The center of complex inclusion contains 20%Al2O3, 41%SiO2, 3%CaO and a small quantity of oxide of Mn, and the periphery contains 20%Al2O3, 43%SiO2, 3%CaO and a small quantity of oxide of Mn. 6) The inclusion mainly sources from deoxidation production, secondary oxide and solidification. 7) The grade of inclusion is average 1.27(thin series) and 0.8(thick series);thin series is 2.03 grade and thick series is 1.16 grade in the strict district. (3) suggestion 1) ameliorate oxide system. 2) The effect of present wire feeding to liquid steel is not distinct. And so it is ought to adjust wire feeding technique, ensure the concert of the speed ,place and temperature of liquid steel and the depth of melting pool etc. 3) It is should improving the metallurgy effect of covering ladle stuff. 4) The effect of present blowing argon to remove inclusion is instability. It is needed to adjust technique parameter of blowing argon and achieve the optimal effect of removing inclusion by blowing argon. 5) As for casting slab, there is parent effect of reducing inclusion in ladle. As for casting billet, it is necessary to change protective casting.6) It is essential to strength the protection on the liquid steel and eliminate or decrease to the best the reveal of liquid steel in various tache during steel making.