The appearance of blisters on the surface of Brass Accessories will seriously affect its quality and performance. It is of great significance to deeply explore its causes and seek preventive measures from a microscopic level.
First, from the perspective of raw materials. During the smelting process of brass, if the raw material purity is not high and contains more impurities, such as oxides and sulfides, these impurities cannot be evenly integrated into the brass matrix during the solidification process, and tiny cavities will be formed, which will then develop into blisters. For example, when the iron oxide content in the raw material exceeds the standard, it will not react completely with other elements during high-temperature smelting, and it will separate when cooled, causing local defects. Moreover, if the gas content is not properly controlled during smelting, such as hydrogen, the solubility of gases in the brass liquid decreases with the decrease of temperature. If the gas escapes, it will form pores in the solidified brass, which will become the source of blisters.
Secondly, in the casting process. If the casting speed is too fast, a large amount of air will be entrained in the brass liquid when it flows in the cavity. This air is wrapped in the metal liquid and forms blisters after solidification. At the same time, if the permeability of the mold is poor, the gas in the cavity cannot be discharged smoothly, which will also promote the formation of sand holes. From the microstructural analysis, uneven casting speed will cause the solidification order of brass liquid in different parts of the cavity to be disordered, and the first solidified part will hinder the discharge of gas from the later solidified part, causing gas to gather and form sand holes.
In addition, the quality of the mold also affects the formation of sand holes. When the mold surface is rough or damaged, during the injection of brass liquid, it is easy for the metal liquid to adhere to the mold defects and cannot completely fill the cavity, thus forming sand holes. At the microscopic level, tiny protrusions or cracks on the mold surface will destroy the flow integrity of the brass liquid, hinder the flow of local metal liquid, and form sand hole-like defects after cooling.
In order to prevent sand holes on the surface of Brass Accessories, in the selection of raw materials, the purity of the raw materials should be strictly controlled, and refining and impurity removal should be carried out to reduce the gas content. In terms of casting technology, it is necessary to reasonably control the casting speed and optimize the mold design to improve the permeability. For the mold, its surface should be smooth and undamaged, and it should be maintained and inspected regularly. By deeply understanding the formation mechanism of sand holes at the microscopic level and taking targeted preventive measures, the quality of Brass Accessories can be effectively improved, the scrap rate caused by sand holes can be reduced, and production efficiency and product reliability can be improved.
