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Heat storage temperature, heat storage density, heat storage stability and the cost of heat storage are the breakthroughs for further development of heat storage materials. In this study, a new type of sensible heat storage material was prepared by using low-cost steel slag as the main component, and at the same time, an effective way of recycling steel slag was provided. The stabilizable shaped steel slag powder was obtained by high temperature pretreatment, and the optimal high temperature pretreatment temperature was found to be 850 °C. Through the analysis of the effects of different pretreatment steel slag content and different sintering temperatures on the organization and properties of heat storage materials, it was found that a large number of elemental migration and oxide solid solution phenomena occur during the sintering process, and the melting of low melting point solid solution occurs during the high temperature treatment process. The steel slag heat storage material has the best performance when the content of pretreated steel slag is 60 wt% and the sintering temperature is 1200 °C. Its compressive strength is stabilized at about 80 MPa, thermal conductivity is 1.13 W/(m·K), and thermal density is 1222.168 J/g in the range of 50–1000 °C. More importantly, it has excellent thermal cycle stability. After 300 thermal cycles, the shape of the samples remains unchanged, and the samples retained 94.4 % of the compressive strength, 98.8 % of the thermal conductivity and the thermal density was almost unchanged. In addition, the cost of the sample was only $0.58/kWh. The results indicate that this study provides a novel low-cost method for the preparation of steel slag sensible heat storage materials, which has high potential for application in heat storage systems.

•The model of Na2CO3-K2CO3eutectic salt was established in this paper, which can accurately calculate the thermophysical properties of Na2CO3-K2CO3eutectic salt.•The thermophysical properties of Na2CO3-K2CO3eutectic salt during solid-liquid transition were calculated by the above model.•The local microstructure of Na2CO3-K2CO3eutectic salt in solid and liquid state was obtained.