Production Practice Study Of H08A Steel Smelted By Converter

Under the impact of the financial crisis, the steel industry so-called the lifeblood of national economy is involved in unprecedented predicament. In this paper, the H08A steel has been researched systematacially, according to the theoretical analysis and the actual production of the Top-Bottom blowing converter furnace in a company with the capacity of60t.The raw materials were as follows:the molten iron containing S lower than0.28%, steel crap and pig iron that meets national steelmaking standard. The optimal processing conditions were obtained through series of experiments. Firstly, the single slag method with large residues was used to remove sulfur in the converter furnace. Set the temperature of inverted furnace at about1655℃and the tapping temperature between1670℃and1690℃. Secondly, the ferromanganese and manganese silicon alloys with low carbon component were added to alloy during steel tapping. The aluminum conductor steel and calcium carbide were exploited for the deoxidation process. Then, calcium treatment was introduced by feeding in100-150m calcium iron and the oxygen content of molten steel was controlled within50-80ppm. After Blowing more than12minutes, the temperature would be control at1605℃～1620℃. Protective casting with ladle and tundish were executed for continuous casting. Regarding to tundish, the casting was conducted under the temperature of1560±10℃and the ratio of water in1.2～1.4L/kg. Lastly, in the process of smelting, the H08A steel was in-depth analyzed from the faces of the desulphurization, the terminal control, the order control of the impurities and the quality of the semifinished product.Through the research discovery:(1)The single slag method with large residues that was used to remove sulfur in the converter furnace satisfies composition design requirement with p<0.025%of H08A steel. With the decreasing of Si component, it is benefit to control the P content. That is to say, the rate of P removal is increasing. (2) Under the situation of the low C content in tapping steel, in other words, with the high O content, the inclusion can achieve the quality demand. Under the same continuous casting water distribution mechanism, the quality of the cast semifinished product satisfies the rolling demand, and the inclusion rank undulates between0.5and1.0.(3)The research also discovered that the more specific water amount of the continuous casting can create the semifinished product drop in quality. Under the specific water amount control in1.2～1.4L/kg and the tundish temperature control under1560±10℃the condition, can realize casts the semifinished product quality optimization.(4) It was also discovered that the excess water of the continuous casting ratio resulted in the lower quality of the semifinished product. When the temperature of the tundish was conducted at1560±10℃and the ratio of water in1.2～1.4L/kg, the quality of the semifinished product was optimized.In conclusion, the processes of the steelmaking include the bottom blowing argon technology, ladle calcium treatment processes, bulndle casting protect, tundish casting protect, mould electro-magnetic stirring, and so on, through adding the fine material into the furnace, optimizing smelting process, and improving the control level of the end-point of the converter. These processes solved the problem of the fluidity of molten steel, reduced the content of inclusions in steel, and reduced the cast billet times defect levels, which leaded the quality of the H08A steel superior to the national standard. The production technology of the H08A steel achieved the domestic advanced leve.