Method for smelting ultra-low carbon steel by low oxygen site in whole process

Abstract

The invention discloses a method for smelting ultra-low carbon steel by low oxygen site in the whole process. The ultra-low carbon steel comprises the chemical components of, by mass, no more than 0.0030% of C, 0.01% of Si, 0.08-0.18% of Mn, no more than 0.015% of P, no more than 0.010% of S and 0.015-0.055% of Al<sol>. The process of KR stirring desulfuration, a top-bottom combined blown converter, an RH vacuum refining furnace and a slab continuous casting machine is adopted for smelting production. According to the method, the mode of converter terminal low-oxygen and slag modification lowtotal iron, RH furnace low oxygen site deep decarbonization, continuous casting machine fully-protected argon sealing and tundish breathable block brick argon blowing is adopted, the total iron is controlled within 5% after slag modification, end-point oxygen after RH furnace deep decarbonization is controlled to be about 350 ppm, casting blank oxygen is controlled within 20 ppm, the zero-order ratio of inclusions reaches 97% or above, RH end-point carbon is controlled within 20 ppm, and the casting sequence of the continuous casting machine reaches 10 times. The castability and casting blankquality of ultra-low carbon steel such as DDQ-grade cold rolled steel are improved, the number of inclusions in the steel and the shape control level of the steel are improved, and the percent of passof steel blanks is effectively improved.

Description

technical field [0001] The invention belongs to the field of iron and steel metallurgy, and in particular relates to a method for smelting ultra-low carbon steel with low oxygen levels in the whole process. Background technique [0002] The market application range of steel products is becoming wider and wider, and the requirements for quality reliability, performance stability and special indicators have become more urgent. Taking the purity index of molten steel as the requirement, the quantity, shape and size distribution of non-metallic inclusions in the steel must be effectively controlled to avoid quality defects such as cracked edges, substandard properties, and cracks in the steel. The traditional smelting process based on the composition of molten steel obviously cannot meet the quality requirements of steel. [0003] With the R & D and production of DDQ grade deep drawing steel by steel mills, the number of molten steel inclusions, continuous casting castability, ...

AI Technical Summary

Problems solved by technology

Because this type of steel requires that the carbon content at the end point is generally controlled below 50ppm, or even lower, it makes the control of the system more difficult.

One is that the end point of converter smelting is difficult to control, and there are often cases of low carbon, high carbon and high oxygen accumulation in the converter. The carbon at the end point of the converter is about 0.03%, and the oxygen content reaches about 1000ppm, resulting in strong oxidation of the slag, and the total iron of the top slag of the ladle reaches more than 20%. , which brings difficulties to the modification of ladle top slag; second, for deep decarburization of the RH furnace, the oxygen content in the process is controlled at a high oxygen level, and the oxygen content in the station is controlled above 500-600ppm. After deep decarburization, the oxygen content is controlled at Above 450-500ppm, the high oxygen level control has a great impact on the quality of molten steel and the castability of continuous casting; the third is that the secondary oxidation of molten steel during the pouring process of the continuous casting machine amplifies this influence

Practice shows that the whole process of high oxygen level control causes many problems such as nodules at the continuous casting nozzle, pinholes under the skin of the slab, cracked edges of the rolled material, etc., and the qualified rate of the slab is low

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