Large cast iron platform

How to Install Large Cast Iron Platforms and Heavy Machinery Equipment
Control of Primary Austenite Dendrites in Large Cast Iron Platforms: Many factors influence the number and morphology of primary austenite dendrites in large cast iron platforms, such as the chemical composition and temperature of the original molten iron, the cooling rate of the molten iron in the mold, the effect of undercooling, etc. The carbon equivalent of cast iron is an important factor affecting the number of primary austenite dendrites in large cast iron platforms. As the carbon equivalent increases, the eutectic transformation becomes a critical part of the solidification process. Although primary austenite precipitates in both hypoeutectic and hypereutectic cast irons, the eutectic transformation does not rely on austenite nucleation and crystallization. Instead, it begins with graphite nucleation independently in the molten iron of eutectic composition on the primary austenite dendrites.

For sand cores, by extending the core curing time of large cast iron platforms by 10 seconds and increasing the curing temperature by 10°C, the sand cores can be better cured. Since the coating on sand cores is dried by the residual heat of the core, it cannot ensure complete drying of the coating. However, due to the simple structure of the sand core, the coated core is tempered after brushing, and to avoid secondary curing deformation during the tempering process of large cast iron platform sand cores, the temperature is set at 180°C. Additionally, after the sand cores for large cast iron platforms are made, they are not brushed with coating but are instead fully immersed, tempered, and dried after cooling. Verification results show that the rate of internal and external sand adhesion is basically reduced to around 10%.
Large cast iron platforms are cast using green sand molding processes, with sand cores made using coated sand technology. The scrap rate of castings due to sand adhesion is as high as 30%, and 10% of the sand-adhered castings are severely affected and cannot be cleaned, leading to scrapping. The sand-adhered areas of scrapped castings include both internal cavities and external surfaces. Conventional methods such as recoating and increasing coal dust content have failed to improve the sand adhesion situation. The large cast iron platform maintains a value between 0.0.015. Based on this understanding, it is thought that if the original molten iron is treated with an inoculant containing sulfur and oxygen after spheroidization, it should yield good results. This idea was confirmed by research from European counterparts years ago. Using inoculants containing sulfur and oxygen can increase the spheroidization rate of large cast iron platforms, increase the number of graphite spheres, and reduce the size of graphite spheres, thereby improving the quality of ductile iron castings.
After increasing the molding pressure, spraying alcohol-based coatings on the outer molds of large cast iron platforms has been incorporated into the process. At the same time, training for operators has been strengthened to ensure operational quality. When water-based coatings were applied to the entire sand core, it was found that although internal sand adhesion in castings was resolved, the scrap rate due to porosity in large cast iron platforms increased significantly. Therefore, the brushing method is not feasible. The structure, to some extent, determines the gating system of the castings, which has been verified in mold trials. Reducing the gas generation of molding sand and sand cores. Since the coal dust content in the workshop's large cast iron platform sand has no room for reduction.
Sand adhesion in large cast iron platforms can be broadly categorized into mechanical sand adhesion, chemical sand adhesion, damaging sand adhesion, and thermal sand adhesion. Mechanical sand adhesion, also known as metal penetration sand adhesion, occurs when molten metal penetrates the gaps between sand grains on the mold surface through capillary or gas-phase penetration, forming an adhesive layer of metal and sand grains mechanically mixed on the surface of the large cast iron platform. The comparison and variation of two forces determine the tendency for sand adhesion: one force promotes the penetration of molten metal into the sand mold pores, and another force resists penetration. The penetration driving force, which promotes the penetration of molten metal into the sand mold pores, mainly includes the dynamic and static pressure of the mold. The penetration resistance, which prevents the penetration of molten metal into the sand mold pores, primarily consists of two factors: the resistance of the sand mold pores and the back pressure of gas in the sand mold pores.