Research On Secondary Cooling Technology Of Quality Steel During Billet Continuous Casting

At present, low-carbon steel and general-carbon steel take a main part in the billet continuous casting steel. Due to the immaturity of the continuous casting technology for quality steel and high grade steel, especially the middle and high carbon-steel, therefore, the continuous casting for these steel will dominate the continuous casting technology development in the future.Secondary cooling technology is critical in the continuous casting process. The disadvantages such as surface crack, inner crack, strand drum, center separate and center crack, have closely association with secondary cooling process. Thus, optimizing and controlling secondary cooling technology play an important role in improving the yield of continuous casting and the strand quality.The billet continuous casting in a certain factory changed from casting general-steel to casting quality steel through technology innovation. According to the requirement, continuous casting mainly produces high carbon steel, alloyed steel, spring steel, easy-cutting steel, tyre steel besides a little part of general steel and low-alloyed steel. The casting category contains all the grade steels which are hard to produce in strand continuous casting. In this article, the thermo-conduct mathematics model of continuous casting machine for the quality steel is established, in which the boundary condition of secondary cooling water and air-spraying area are amended by measuring strand surface temperature and solidification shell at the spot. Meanwhile, the problem of the too low temperature in the mode foot caused by fast cooling is sovled by modifying thermo-conduct condition and different-segregated equation. In addition, the effective spaying coefficiency is utilized to optimizing secondary cooling process in model calculation. Considering the low temperature in strand foot and and thermo-size of the strand, the nozzles are arranged to ensure slow cooling of strand in casting speed direction.A new secondary cooling water-distribution model is put forward through the research of secondary cooling numerical emulation for the quality strand. The new water-distribution model takes several more factors besides the casting speed into consideration, such as the over-thermo steel, the chemical element of the casting steel and the temperature of secondary cooling water.On account of too many kinds of quality steel and the large span of the component, the steels are classified into several categoris. The secondary cooling system for each class is determined by choosing typical steel and applying it into the category. However, the value of K in the water-distribution model can be adjusted to determine the secondary cooling system for the different steel in the same category.The designed secondary cooling system was applied in practice in October 2007. The results show that the secondary cooling structure of the casting machine, the arrangement of nozzles in each area and the new secondary cooling water model are reasonably designed. Consequently, the proposed secondary cooling system can greatly deduce the strand crack and protect the strand quality.