Calcium treatment method under special steelmaking process

Abstract

The invention relates to a calcium treatment method implemented under a special steelmaking process. The calcium treatment method is characterized by comprising the following steps: carrying out desulfurization in a molten iron pretreatment process, namely, blowing CaO+Mg powder to desulfurize the molten iron until the sulfur content is 0.0018 to 0.0022 percent, and slagging off after the desulfurization; controlling the oxygen content at an end point of a converter within 650ppm in an converter process; ensuring the vacuum degree to be less than or equal to 300Pa in the RH (Ruhrstahl Heraeus) process, and maintaining the vacuum degree for 10 to 30 minutes; and secondarily returning the molten iron subjected to RH treatment to an LF (Ladle Furnace), adjusting the temperature, slagging after the RH treatment is completed, then conducting the calcium treatment, ensuring the feeding speed of a calcium line to be 180 to 200m/min, ensuring the feeding quantity of steel to be 1.4m/t, and controlling the bottom-blowing flow rate at 50 to 100 NL/min. By adopting the method, the impurities can be gradually converted from primary silicon manganate to calcium aluminosilicate, so that the quantity of the impurities per unit area of a steel plate can be remarkably reduced and is reduced from 87 to 100/mm<2> to 12 to 25/mm<2>. After the RH vacuum and calcium treatment, the type of the impurities is changed, and a product is deviated to the side of CaO-CaS; the size of the impurities in a tundish is relatively small, the impurities with the size being less than 10 micrometers account for 99.61 percent, and the impurity with the size being more than 30 micrometers is not found. By adopting the method, the molten steel purity and the steel plate flaw detection qualification rate can be improved, the calcium yield is stabilized at 20 percent or more, and the economic benefit is obvious.

Description

technical field [0001] The invention relates to a steelmaking process, in particular to a calcium treatment method under a special steelmaking process, and belongs to the technical field of metal smelting processes. Background technique [0002] The steelmaking production process usually includes molten iron pretreatment process, converter process, refining process, and continuous casting process; in the refining process, calcium treatment technology is used to deform the sulfide inclusions and oxide inclusions in molten steel. The brittle Al with high melting point in steel can be made by calcium treatment technology 2 o 3 The inclusions are denatured into low-melting calcium-aluminate inclusions with high calcium content, which are easy to float and remove, improve the purity of molten steel, and prevent nodulation and blockage at the nozzle; at the same time, the formation of CaS inhibits the production and aggregation of MnS, reducing the impact of large MnS inclusions ...

AI Technical Summary

Problems solved by technology

The above patents disclose the calcium treatment method under normal process conditions, but the calcium treatment effect is related to the process parameters of the calcium wire feeding, such as molten steel temperature, argon blowing flow rate, feeding amount and other paramete