Reduce sand hole and air hole defects of large steel castings

How to overcome the shortcomings of quartz sand and significantly reduce the sand holes and pores of large and medium-sized steel castings?

The first way: calcine quartz sand (raw sand) above 870 ℃ to make α A transformation of quartz into β One scale quartz, after volume expansion β A scale quartz cooled to room temperature and then changed back α A quartz, and at this time α— Quartz has expanded its molecular structure α First, the volume of quartz sand after roasting expands, and the expanded volume is retained after cooling to room temperature. In this regard, the research unit has done special research. Jinan casting and Forging Machinery Research Institute also applied for the patent technology of raw sand roasting and developed raw sand roasting equipment. The application of roasted sand has also developed from the field of coated sand to the field of sand mold casting. Due to the increase of cost and other reasons, the scope of use was small in previous years. In recent years, the research on the technology of roasted sand has been deepened, and the production process and equipment of roasted sand have been updated, which has laid a foundation for the comprehensive promotion of this technology.

Zhang Caiyuan, senior engineer of Jinan casting and Forging Machinery Research Institute, elaborated in detail on the research on roasting quartz sand and its application – casting technology 204, the research on roasting raw sand and changing the properties of silica sand – Chinese casting equipment and technology 19 9, etc.

The second way: maximize the pouring speed, reduce the radiation time of molten steel to the cavity surface (especially the upper surface) during the pouring process, and pour the parting surface (i.e. the body pouring is completed) before the temperature of quartz sand on the cavity surface is heated to 370 ℃ (i.e. before the volume expands sharply). How to master this degree? Provide you with a time data for reference: the pouring time of the body shall be controlled within 30 seconds, and at least within 60 seconds. If it is controlled within 60 seconds, it is not surprising that a large number of sand holes and pores appear. Moreover, with the further extension of the pouring time of the body, the severity of sand hole and pore defects also intensifies.

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