Preliminary melting type continuous casting crystallizer protecting slag and preparation thereof

Abstract

The invention belongs to the field of auxiliary materials for smelting steel, in particular to a covering slag for a pre-melting continuous casting crystallizer. The weight percentage components of the covering slag are as follows: 31 to 36 percent of SiO2, 30 to 35 percent of CaO, 2 to 5 percent of MgO, not more than 1.5 percent of Fe2O3, 2 to 5 percent of Al2O3, 8 to 11 percent of Na2O, 5 to 8 percent of F, 0.8 to 1.5 percent of Li2O, 3 to 6 percent of C and the rest are unavoidable impurities. The covering slag has a good liquidity and spreadability, can uniformly cover the surface of molten steel, has no piling phenomenon, and has the advantages of active slag surface, uniform melting and no caking phenomenon. The invention has a better insulating performance and has no cold steel agglomerated on the liquid surface; can ensure a casting blank to be fully lubricated so as to realize a high pulling rate; has a stable performance after absorbing the impurities and can realize stable and smooth continuous manufacture; avoids the steel leakage phenomenon, improves the casting blank quality and can lead the longitudinal crack of a plate blank and the angle part cross crack to be reduced by more than two third averagely; the invention has a low cost and is convenient for popularizing.

Description

(1) Technical field [0001] The invention belongs to the field of steelmaking auxiliary materials, and in particular relates to a pre-melting continuous casting mold powder and a preparation method thereof. (2) Background technology [0002] Continuous casting mold powder is an important material in continuous casting production and a necessary means to produce defect-free slabs. Continuous casting mold slag has five functions in the crystallizer: to isolate the air and prevent the secondary oxidation of molten steel; to insulate and keep heat to prevent partial condensation on the surface of molten steel; to purify the interface of molten steel and absorb floating inclusions in the steel; to lubricate the surface of the cast slab to reduce the resistance of casting ; Improve solidification heat transfer between slab and mold. The performance of continuous casting mold flux directly affects the surface quality and internal quality of the slab and even the yield of steel. ...

AI Technical Summary

Problems solved by technology

The reasons for the deterioration of the billet quality are as follows: ① Due to the high casting speed, the amount of molten steel injected into the mold per unit time is large, and the mold has a small buffering effect on the high-speed steel flow due to its small volume, so that the molten steel in the mold Intensified fluctuations in the surface of the meniscus are likely to be involved in slag and inclusions; intensified fluctuations in the meniscus often cause defects such as cracks, pits, inclusions, and pores in the billet, and at the same time make it difficult to maintain the slag layer on the molten steel surface of the mold; During the process, the temperature field distribution of the wall of the slab crystallizer is uneven (especially near the nozzle), and the thickness of the solidified slab shell is uneven under the strong erosion of the stream, which is easy to cause cracks in the slab

[0004] However, for the production of wide-slab steel plates by high-speed continuous casting, due to the large width-thickness ratio of slab continuous casting, the contact area between molten steel per ton of steel and the wall of the crystallizer is large, and the cooling rate of molten steel is faster than that of other types of slabs. The solidification speed of molten steel is fast, and the liquid surface temperature of the mold is low, resulting in poor melting conditions of mold slag, which may easily cause defects such as slag inclusions and wrinkled skins on the surface and subcutaneous of the casting slab; Larger tensile stress, this tensile stress is also one of the main reasons for longitudinal cracking of slabs, with the increase of slab width, the occurrence rate of longitudinal cracks tends to increase

[0005] Due to the above problems in the production of wide slabs by high-speed continuous casting, higher requirements are placed on the performance of mold flux. At present, some imported mold flux can solve the above problems, but the cost of imported mold flux is high, and it is not suitable for large-scale promotion.