Protective slag for continuous casting medium thick plate of low alloy high strength steel

Abstract

The protecting slag for continuously cast medium and thick plate of low alloy high strength steel consists of carbon black 0.5-2.0 wt%, graphite 4-10 wt%, Na2O 4-12 wt%, F- 1-7 wt%, Al2O3 2-7 wt%, Fe2O3 1-3 wt%, crystallization controlling agent 7-20 wt%, Li2O 0-2 wt%, except CaO and SiO2, where the weight ratio CaO / SiO2 is 0.90-1.05. The crystallization controlling agent in the protecting slag is component capable of promoting the crystal separation of the molten protecting slag during condensation without deteriorating the lubricant characteristic seriously. The protecting slag of the present invention used in protecting continuously cast medium and thick plate of low alloy high strength steel, can raise the plate product quality and has no influence on the normal delivery of cast blank.

Description

technical field [0001] The invention relates to a mold slag for a continuous casting crystallizer for steelmaking, in particular to a mold slag for continuous casting of a medium-thick plate of low-alloy high-strength steel. Background technique [0002] The two major tasks in the development of modern continuous casting technology are to expand the variety of continuous casting production and to realize high-efficiency production characterized by high casting speed, and to further reduce energy consumption through hot casting, red casting and direct rolling. In these continuous casting processes using mold slag pouring in the plunger nozzle, the mold slag plays a pivotal role, and it has an important impact on the surface and subcutaneous quality of the slab and the smooth flow of the continuous casting process. like figure 1 As shown, the mold slag forms a double-layer, three-layer or multi-layer slag layer structure on the molten steel surface of the mold to cover the mo...

AI Technical Summary

Problems solved by technology

However, the mold slag film with many crystals, especially the mold slag film with high crystallization temperature, has a poor lubricating effect on the casting slab, and it is easy to make the low-alloy high-strength steel casting slab with low high-temperature plasticity suffer from large frictional resistance in the middle and lower part of the mold. Intergranular cracks and microcracks occur in weak areas such as slab vibration marks

In order to reduce the loss caused by the scrapping of the steel plate due to micro-cracks, mold flux with good vitrification characteristics is forced to be used in production to enhance the lubrication of the slab, but the longitudinal cracks on the surface of the slab are aggravated, and the slab needs to be cleaned off the production line, which not only increases the processing cost , and it is impossible to organize the hot and red delivery of the slab, which seriously reduces the productivity

Therefore, for the continuous casting of low-alloy high-strength steel, how to coordinate the contradiction between lubrication and heat transfer control through mold slag, so as to produce continuous casting slabs without crack defects on the surface and under the skin, is still an unsatisfactory problem before the present invention. solved problem

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