Dephosphorizing and steelmaking method of medium-high-phosphorous semisteel by top-blown converter

Abstract

The invention provides a dephosphorizing and steelmaking method of medium-high-phosphorous semisteel by a top-blown converter. The method comprises the following steps of: adding remained slag, splashed slag and a slag forming agent in semisteel containing 0.25-0.80% of phosphorous to prepare 2.8-4.0 high-alkalinity furnace slag in the top-blown converter; carrying out appropriate lance height control and temperature control by adopting the top-blown oxygen supply intensity of 2.90-3.30m<3> per ton of the steel per minute, wherein the content of the phosphorous in the steel when replacing the steel is less than or equal to 0.12%, controlling the C / P is more than or equal to 10, the early dephosphorization rate is more than or equal to 80% and optimally 95%; and adding a semisteel slag forming agent and active lime after replacing the slag, slagging and melting again so as to reduce the content of the phosphorous from <=0.12% to a range required by conventional steel grade and guarantee the product quality. The method provided by the invention has the advantages that an original device does not need reformation, the dephosphorization rate is high, the influence on the melting period and the productivity of the converter is little, the application of large reserves of low-cost high-phosphorous ores can be expanded by iron making, and the production cost is reduced.

Description

technical field [0001] The invention relates to the technical field of iron and steel smelting, in particular to a method for steelmaking in a top-blown converter using vanadium-extracted medium-high phosphorus semi-steel as the main raw material. Background technique [0002] Foreign advanced molten iron dephosphorization processes mainly include Nippon Steel’s LD-0RP method and MURC method, JFE’s LD-NRP method, Sumitomo Metal’s SRP method, Kobe Steel’s H furnace, and domestic advanced dephosphorization processes mainly include Baosteel’s BRP method, Anshan Iron and Steel Co., Ltd. has also conducted a lot of research on the converter dephosphorization process. The characteristics of the hot metal dephosphorization process can be summarized as follows: (1) The process methods can be divided into two types: "double method" and "double slag method". (2) The P content of molten iron before treatment is generally below 0.150%. (3) "Double-link method" and "double-slag method"...

AI Technical Summary

Problems solved by technology

[0005] 1) The "double-link method" is mainly aimed at the smelting of ultra-low phosphorus steel for medium and low phosphorus hot metal, which is not suitable for the high phosphorus resources of vanadium and titanium, the structure of low-end products and the characteristics of process equipment (top-blown converter, oxygen lance does not have powder spraying devices, etc.), it is impossible to realize the comprehensive utilization of vanadium resources in iron, and it seriously affects the production capacity of converter equipment.

[0006] 2) There are many process constraints such as high cost of pre-dephosphorization of molten iron, large amount of foreseeable slag, insufficient ladle reaction space, large temperature drop of molten iron, difficulty in removing slag, and serious sticking to the tank

[0007] 3) The P content of molten iron before traditional double slag treatment is generally below 0.150%, and the basicity of slag is controlled below 2.5, which makes it difficult to combine a large amount of phosphorus in molten iron; the temperature control is relatively low, around 1350°C, which is not conducive to the early stage of top-blown converter slag; and the comprehensive utilization of vanadium resources in iron cannot be realized