A method for denitrification of high-speed steel molten steel for rolls

Abstract

The invention discloses a roller high-speed steel molten steel tapping denitrification method, and is characterized in that in a tapping process, pre-prepared synthetic slag with the amount of 5-15 kg / t steel is added along with stream, wherein the synthetic slag comprises the chemical composition by the weight percentage: 10-30% of CaO, 30-50% of SiO2, 5-15% of FexOy, 5-20% of Al2O3, 1-8% of C, 5-10% of Re (Y), and inevitable impurities; nitrogen in the molten steel is carried out by CO2 or CO bubbles generated from a reaction of metallic oxide in the synthetic slag with [C] in molten steel and a reaction of C in the synthetic slag with O2 in air and is discharged into an atmospheric layer, rare-earth nitrides generated from a reaction of rare-earth metal elements in the synthetic slag with [N] go into molten slag to be removed, and the [N] content in the molten steel is reduced. The method significantly reduces the [N] content in the molten steel and improves the metallurgical quality of a roller.

Description

technical field [0001] The invention relates to the technical field of denitrification in steelmaking technology, in particular to a tapping denitrification method for high-speed steel for rolls that can significantly reduce the [N] content in molten steel and improve the metallurgical quality of products. Background technique [0002] At present, too high nitrogen content in cast high-speed steel rolls is considered harmful. When the nitrogen content in the steel exceeds 100ppm, subcutaneous pores and microporosity will occur on the roll; The occurrence of fire brittleness and age hardening reduces the plastic toughness of the roll material; when the nitrogen content is too high, "blue brittleness" is prone to occur during the heat treatment and use of the roll, reducing the impact toughness of the roll material; when the nitrogen content is too high, the high-speed steel Ti, V, etc. in the material and nitrogen produce brittle nitrides that seriously affect the high-temper...

AI Technical Summary

Problems solved by technology

[0002] At present, too high nitrogen content in cast high-speed steel rolls is considered harmful. When the nitrogen content in the steel exceeds 100ppm, subcutaneous pores and microporosity will occur on the roll; The occurrence of fire brittleness and age hardening reduces the plastic toughness of the roll material; when the nitrogen content is too high, "blue brittleness" is prone to occur during the heat treatment and use of the roll, reducing the impact toughness of the roll material; when the nitrogen content is too high, the high-speed steel Ti, V, etc. in the material and nitrogen produce brittle nitrides that seriously affect the high-temperature strength and high-temperature plasticity of high-speed steel materials.

The commonly used denitrification methods in steelmaking are vacuum denitrification and stirring denitrification. The denitrification devices used in these methods (such as VD furnace, VOD furnace, LF furnace RH degassing device, bottom blowing argon device, etc.) are complex and expensive. Large, complicated operation, high operating cost and less than ideal effect, such as Chinese patent 02111478.1 discloses a refining denitrification method for molten steel, the refining denitrification device for molten steel involved in this invention application consists of a vacuum system, a DC pulse power supply, Composed of working gas and glow plasma generation system, its working feature is to form a glow plasma of argon-hydrogen mixed gas above the molten steel by means of a DC pulse electric field, and the nitrogen in the molten steel reacts with the glow plasma and escapes into an ion state Nitrogen and react with the working gas, and finally form nitrogen and ammonia, these gases are extracted by the vacuum system extraction device to achieve the purpose of denitrification, this denitrification method is not only complicated in equipment, large in equipment investment, complex in operation and high in operating costs, And the working gas hydrogen that uses easily causes the shortcomings such as the secondary hydrogen pollution of molten steel, discloses a kind of method for denitrification of molten steel in converter tapping process as Chinese patent CN102277467A, it is characterized in that, in the converter tapping process successively pours nitrogen into molten steel ladle Add carbonate, coke and metal aluminum, use the dynamics and thermodynamics of molten steel during tapping to decompose it or prompt it to react with oxygen in molten steel to generate CO 2 Or CO bubbles, because [N] in molten steel is easily adsorbed on the surface of the bubbles, with the CO 2 Or [N] is removed by the floating discharge of CO bubbles, and its components are added sequentially according to the weight ratio. This method is extremely difficult to control the decomposition rate of carbonate, causing violent boiling of molten steel and splashing of molten slag, causing safety hazards in production