Method for controlling inclusion in ultra-low carbon steel based on straight cylinder type vacuum refining device

Abstract

The invention discloses a method for controlling inclusion in ultra-low carbon steel based on a straight cylinder type vacuum refining device. The method comprises the following steps that a steel ladle is conveyed to a straight cylinder type vacuum refining station and jacked; a dipping pipe is inserted below the liquid level of molten steel by 50 mm, an argon blowing nozzle, on the same side asa steel ladle eccentric bottom blowing nozzle, of the semi-circumference of the wall of the dipping pipe is adjusted to blow argon strongly, and an argon blowing nozzle on the different size is adjusted to blow argon weakly; the dipping pipe is inserted below the liquid level of the molten steel by 200 mm, and the steel ladle is opened for eccentric bottom argon blowing; the dipping pipe is inserted below the liquid level of the molten steel by 400-500 mm, and rapidly pumped to the limit vacuum degree; the argon blowing flow is adjusted slightly until top slag is pushed to the weak blowing side of the wall of the dipping pipe to the minimum area; after decarbonization treatment is carried out, a molten steel sample is taken for oxygen fixation, then molten steel deoxidization treatment iscarried out, and CaO / Al2O3 in a top slag system is controlled to be equal to 1.2-2.0; and after air breaking, the steel ladle is opened. According to the method, Al2O3 inclusion generated by deep deoxidization is transformed into calcium aluminate low-melting-point inclusion, the amount of the Al2O3 inclusion in the continuous casting molten steel is reduced, thus the adhesion amount of the Al2O3inclusion on the wall of a water opening in the process of the molten steel poured into a crystallizer by passing through a tundish water opening is reduced, and occurrence of flow accumulation of thewater opening is avoided.

Description

technical field [0001] The invention relates to the technical field of steelmaking, in particular to a method for controlling inclusions in ultra-low carbon steel based on a straight cylinder type vacuum refining device. Background technique [0002] The size, quantity and type of inclusions in molten steel have a decisive impact on product quality. Therefore, an important way to improve the quality of steel products includes reducing the number of various inclusions in molten steel to the greatest extent, and harmlessly removing inclusions that cannot be removed. treatment. For high-quality steel with a carbon content below 0.03%, the control of inclusions in the steel is mainly achieved through LF furnace refining; during the LF furnace refining process, there is a slag reaction between the ladle top slag and molten steel: x[Me]+ y[O]=(Me x o y ), there is an inclusion reaction between molten steel and inclusions: x[Me]+y[O]=(Me x o y ), when the two reactions are clo...

AI Technical Summary

Problems solved by technology

Fe in reducing top slag above molten steel in RH vacuum chamber t The content of O is low and the alkalinity is high. During the RH refining process, the reducing top slag is relatively "stationary", the molten steel and the reducing top slag are basically not stirred and mixed, and the slag-gold reaction cannot proceed, so the reducing property in the vacuum chamber cannot be used. Top slag removes Al from molten steel 2 o 3 The inclusions are spheroidized and transformed into low-melting calcium-aluminate inclusions, and the solid Al in molten steel 2 o 3 The inclusions are easy to collide and grow into large-sized inclusions in the continuous casting process after RH vacuum refining. When the molten steel is poured into the crystallizer through the tundish nozzle 2 o 3 Inclusions are easy to stick to the nozzle wall, causing the nozzle to accumulate