A method for improving the surface quality of boron-containing steel continuous casting slab

Abstract

The invention belongs to the field of metallurgy technology, and relates to a method for improving the surface quality of boron-containing steel continuous casting slabs, including: (1) smelting process: controlling the timing and amount of titanium alloy addition; (2) continuous casting process: controlling continuous Casting machine casting speed, while low-carbon boron-containing steel adopts high-viscosity mold powder and low-carbon steel secondary cooling process, medium-high carbon boron-containing steel adopts low-viscosity mold powder and medium-high carbon steel secondary cooling process; (3 ) Heating process: the end temperature of the second heating section ≥ 1160°C, the slab exit temperature ≤ 1210°C, the first heating section heats up rapidly, the second heating section and the soaking section heat up slowly; (4) Rolling process: control the slab rolling temperature . The invention improves the yield of Ti and avoids the hazard of Ti oxides; the cooling rate is controlled in the whole process, which can not only achieve hot delivery and hot charging, save energy and reduce consumption, but also increase production without any equipment modification and cost investment , The qualified rate of continuous casting slab surface quality is ≥99.8%.

Description

technical field [0001] The invention belongs to the technical field of metallurgy, and in particular relates to a method for improving the surface quality of boron-containing steel continuous casting slabs. Background technique [0002] Boron is a rich element in China, and its total reserves rank fifth in the world. As a microalloying element, boron has a very high effect of promoting hardenability. Under the same addition condition, its effect of promoting hardenability is more than 100 times that of other alloying elements. It is widely used in steel to replace chromium, nickel, etc. rare alloying elements. In recent years, with the in-depth understanding of the mechanism of microalloying boron in steel, boron has been widely used in other steels. For example, adding boron to thin slab continuous casting and rolling production of cold-rolled base material can reduce the yield strength of hot-rolled strip steel, reduce cold-rolling rolling force, improve roll life, and r...

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Problems solved by technology

[0005] Nitrogen fixation by adding Ti element: The amount of Ti added in the prior art can only be added based on experience, and quantitative and precise addition cannot be achieved; in addition, because Ti element is particularly active and easily oxidized, if the timing and method of adding Ti element are inappropriate, not only The Ti element is oxidized, and the yield is low, and the oxidized oxide of the Ti element forms inclusions in the steel, pollutes the molten steel, causes high production costs, and damages the quality of the slab

[0006] Weak cooling as much as possible to increase the surface temperature of the slab: the measures adopted by the weak cooling in the prior art are mainly, one is to excessively reduce the water volume of the crystallizer or increase the temperature of the cooling water, which will lead to a thinning of the shell thickness of the mold exiting the mold, resulting in a Increase the possibility of steel breakout after the crystallizer, which will bring serious consequences to production

The second is to reduce the amount of secondary cooling water as much as possible and use mold powder with high alkalinity, high solidification temperature, and low viscosity. However, if the amount of secondary cooling water is too low, firstly, the cooling of the slab is not enough, and the strength of the slab shell will be difficult to resist the hydrostatic pressure. Various quality and production hazards such as subcutaneous cracks caused by bulging and bulging, crystallizer liquid level fluctuations, etc.; secondly, the continuous casting machine equipment cooling is not enough and the temperature is too high, which greatly reduces the service life of the equipment and increases the failure rate of the equipment; Thirdly, although the mold flux with high alkalinity, high solidification temperature and low viscosity has poor heat transfer and realizes weak cooling of the mold, the viscosity of the mold flux is low, and molten steel is very easy to entangle slag, resulting in quality defects in product slag entrainment, and High alkalinity and high solidification temperature will lead to poor lubrication of mold slag

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