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低过热度、低温度梯度是提高连铸坯等轴晶率的两个重要技术措施,复式结晶器上部由于实现了弱冷,因此可以用于降低钢凝固前沿的温度梯度,达到抑制柱状晶生长、扩大等轴晶区的目的,进而提高铸坯的内部质量。为了降低复式结晶器上段的热流,在结晶器铜板表面喷涂了隔热涂层,检测了涂层的导热系数及其热震性能。在此基础上,建立了带涂层的复式结晶器传热模型,分析并计算了涂层成分、孔隙度及厚度对复式结晶器上段热阻的影响。结果表明,含20%ZrO2和含30%ZrO2镍基涂层的导热系数分别为8.2W/(m·K)和13.9W/(m·K);600℃下两种涂层的抗热震次数均在50次以上;采用厚度为1.5mm的含20%ZrO2的镍基涂层可以使复式结晶器上段热流密度降低到传统结晶器的一半。
Low superheat and low temperature gradient are two important technical measures to increase the equiaxed grain rate of continuous casting billets. The upper part of the double crystallizer can be used to reduce the temperature gradient at the front of the solidification of the steel and inhibit the growth of columnar grains , Expanding the purpose of equiaxed zone, thereby increasing the internal quality of slab. In order to reduce the heat flux in the upper section of the double crystallizer, a thermal barrier coating was sprayed on the surface of the copper mold, and the thermal conductivity and thermal shock resistance of the coating were tested. On this basis, the heat transfer model of coated double-crystallizer was established, and the influence of coating composition, porosity and thickness on the thermal resistance of the upper section of the double-crystallizer was analyzed and calculated. The results show that the thermal conductivities of the coatings containing 20% ZrO2 and 30% ZrO2 are 8.2W / (m · K) and 13.9W / (m · K), respectively. The thermal shock resistance of the two coatings at 600 ℃ The number of times are more than 50 times; the thickness of 1.5mm with 20% ZrO2 nickel-based coating can make the upper section of the dual-stage crystallizer heat flux density is reduced to half of the traditional mold.