Fluorine-free mold flux for continuous casting of zirconium-containing medium carbon steel

Abstract

The invention discloses a fluoride-free mould flux for continuous casting of zirconium-containing medium-carbon steel. The mould flux is composed of, by mass, 35%-45% of CaO, 30%-35% of SiO2, 2%-5% of Al2O3, 1%-3% of MgO, 6%-10% of B2O3, 10%-15% of (Na2O+Li2O) and 1%-3% of ZrO2, wherein the ratio of (Na2O+Li2O+ZrO2) to B2O3 is greater than or equal to 1.3 and smaller than or equal to 2. The fluoride-free mould flux is excellent in crystallization property, the crystallized phase is calcium borate silicate, and meanwhile ZrO2 is added so as to facilitate precipitation of the calcium borate silicate, refine grains of the calcium borate silicate and enhance the stability of the calcium borate silicate. The mould flux contains no fluoride, solves the problem of fluorine pollution in the continuous casting process, and can greatly reduce treatment cost of continuous casting cooling water and the corrosion speed of a casting machine.

Description

technical field [0001] The invention belongs to the field of iron and steel smelting and continuous casting, and relates to the preparation and stabilization technology of fluorine-free protective slag for continuous casting of zirconium-containing medium carbon steel and a new type of lance spar crystal mineral phase replacement. Background technique [0002] Continuous casting technology is one of the key technologies to optimize the modern iron and steel industry. The continuous casting mold mold slag plays an important role in the continuous casting process, such as heat insulation, preventing secondary oxidation of molten steel, absorbing non-metallic inclusions, lubricating the billet shell, and controlling heat transfer. Among them, the lubrication and heat transfer functions are the most important, which play an extremely important role in improving the surface quality of the slab and ensuring the smooth progress of the continuous casting process. At present, the prop...

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Problems solved by technology

[0006] The main problems faced in the non-fluoridation process of medium-carbon mold flux are: 1. How to ensure the stability of the viscosity-temperature characteristics under high temperature conditions after the mold flux is free of fluoride; 2. How to precipitate under the condition of fluorine-free Close crystals to ensure effective control of heat transfer during solidification

The results show that after adding titanium, the mold flux will precipitate CaOSiO 2 TiO 2 Mineral phase, the incubation time of this mineral phase is very long at high temperature, the crystallization ability is much lower than that of commercial fluorine-containing slag, and the ability of mold slag to control heat transfer is weak

At the same time, the addition of Ti is easy to form TiN and Ti(C,N) at high temperature, and the probability of viscous breakout is greatly increased

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