Low-alkalinity synthetic slag for external refining of boiler tube steel

Abstract

The invention relates to a low-alkalinity synthetic slag for external refining of boiler tube steel, wherein CaO, Al2O3, MgO, SiO2 and CaF2 are used as basic components in the synthetic slag; the alkalinity range of the synthetic slag is controlled; and the synthetic slag comprises the following specific chemical compositions in percentage by weight: 48-55% of CaO, 18-25% of Al2O3, 6-8% of MgO, 14-18% of SiO2, 25% of CaF and smaller than 1% of MnO and FeO, wherein the alkalinity of the synthetic slag is 3-3.5. Compared with the traditional synthetic slag for external refining of boiler tube steel, the oxidbillity of refining slag is strictly controlled so that the content of MnO and FeO is smaller than 1%; the oxygen activity of liquid steel balanced with the synthetic slag is promoted to be decreased; and the total oxygen in the steel can be controlled between 12ppm and 15ppm. The alkalinity of the synthetic slag is kept between 3 and 3.5; and the refining slag keeps good melting, flowing, adsorption and desorption abilities of slag inclusion while having good deoxidating and desulphurizing abilities.

Description

technical field [0001] The invention belongs to the technical field of steelmaking, and specifically relates to a synthetic slag for refining outside a furnace, which is especially suitable for deoxidation and controlled removal of inclusions in molten steel for high-pressure boiler tube steel. Background technique [0002] With the continuous development of science and technology, the requirements for steel quality are becoming more and more stringent, forcing the steelmaking process and technology to be updated and developed continuously to produce clean steel and ultra-clean steel to improve the quality and performance of steel. For this reason, the accelerated progress of refining desulfurization, deoxidation, and inclusion control technology is required to meet the quality level of products. For the steel used for boiler tubes, because the high-pressure boiler tubes often work under high pressure and high temperature for a long time, the service conditions are relativel...

AI Technical Summary

Problems solved by technology

[0007] In the prior art, the widely used synthetic slag for the refining of molten steel for high-pressure boiler tubes does not strictly control the content of FeO+MnO in the refining synthetic slag, and the synthetic slag has high oxidation

The secondary oxidation is more serious and the slag has poor ability to absorb inclusions. The inclusions produced by the secondary oxidation have not been removed in time, and there are irregular Al in the slab. 2 o 3 Inclusions and a large number of sulfides, poor resistance to steam, hydrogen, alkali and other corrosion and oxidation resistance

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