The melting of high-temperature alloy steel castings involves several key points that require attention. First is the selection and preparation of raw materials. High-quality raw materials must be selected to ensure that their chemical composition meets the requirements. For some critical elements, such as chromium, nickel, and molybdenum, their content must be accurately controlled. The surface of the raw materials should be clean and free of oil, rust, and other impurities to avoid affecting the quality of the molten steel. Before melting, the raw materials should be pre-treated, such as drying and removing scale.
Regarding melting equipment, a suitable melting furnace must be selected. Commonly used melting furnaces include electric arc furnaces and induction furnaces. Electric arc furnaces have the advantages of fast melting speed and precise control of the steel liquid composition, but they have higher energy consumption; induction furnaces have fast heating speed, good steel liquid quality, and relatively lower energy consumption. The appropriate melting furnace should be selected based on the production scale and quality requirements of the castings. During the melting process, the melting temperature must be strictly controlled. High-temperature alloy steels generally have high melting points, requiring high melting temperatures to ensure the fluidity and homogeneity of the molten steel. However, excessively high temperatures will increase the burning loss of alloy elements in the molten steel, reducing the quality of the molten steel.
Therefore, the melting temperature should be reasonably determined based on the composition of the alloy steel and the characteristics of the melting equipment. At the same time, the heating rate and holding time should be controlled to ensure that the molten steel is fully melted and homogenized. Deoxidation and degassing are also important steps. The molten steel contains a certain amount of oxygen and gases, which will affect the quality of the castings. During the melting process, deoxidizers should be added for deoxidation; commonly used deoxidizers include aluminum, silicon, and manganese. Simultaneously, appropriate methods should be used for degassing, such as vacuum treatment and argon blowing, to reduce the gas content in the molten steel and reduce defects such as pores in the castings. During the alloying process, alloy elements must be added accurately.
