Avoid direct contact between furnace gas and aluminum alloy liquid, try to keep the oxide film intact during smelting, avoid unnecessary stirring covering agent stored in the dryer, and keep it above the temperature before use. In the design of metal molds, adequate exhaust structure should be given, the gate system should be reasonably designed to avoid being involved in the gas, and the jitter plugs should be appropriately added to the areas where pinholes are likely to be generated. The mold must still be preheated and warmed to fit the mold. Controlling the gettering ability of liquid aluminum alloy The gettering ability of liquid aluminum alloy is mainly related to the chemical composition modification temperature and melting time of the alloy. The chemical composition of the door aluminum alloy is analyzed from the following aspects: First, as the content of silicon increases, the fluidity of the alloy increases accordingly, and the tendency of the metal to shrink and thermally crack is reduced, but the aluminum alloy liquid reduces the solubility of hydrogen during solidification, and the precipitation of a large amount of magnesium hydrogen can strengthen the aluminum alloy.
The mechanical properties of aluminum and aluminum can refine the structure of the alloy and improve the mechanical properties. However, the gettering capacity of aluminum alloys is also related to these elements. The effects of commonly used elements on the hydrogen content in aluminum are shown in the table. Calculate the selected charge according to the chemical composition and the burning of the relevant elements, and reasonably configure the charge to ensure that the chemical composition of the aluminum alloy after melting is qualified, and the harmful substances are within the allowed range, so as to control the aluminum alloy's air-absorbing capacity . The increase and decrease of hydrogen in the aluminum alloy have no effect and increase its structure and properties. But the modifying agent exacerbates the tendency of the alloy to get inhaled. When the silicon in the aluminum alloy solidifies, it promotes the decrease of the solubility of hydrogen in the aluminum alloy. At the same time, it increases the viscosity and surface tension of the aluminum alloy, so that a large amount of Hydrogen does not run out of the casting and does not form pinholes. Therefore, the dosage of the modifier should be reasonable, and the specific dosage should refer to the instructions of the manufacturer of the modifier. For example, if the salt modifier is used, the amount of the modifier is the alloy amount. The temperature is within the normal melting temperature range. The higher the temperature, The greater the solubility of hydrogen. Therefore, under the condition that the aluminum alloy liquid has sufficient filling capacity, the lower temperature should be taken as far as possible. After the degassing refining and modification treatment of the alloy liquid, the interval from the furnace to the pouring should be as short as possible, and the pouring can be completed as soon as possible within the time allowed by the process specification. The increase of the cooling speed of the mold of the mold will cause the gas to dissolve in the casting in a supersaturated manner without precipitation, and avoid pinholes. The wall thickness of the mold of the mold is the main factor that determines the cooling rate of the casting.
The wall thickness of the metal mold used can refer to the reference value of the metal mold for the wall thickness decay. Coating coating Coating on the metal mold can not only increase the service life of the mold, control the solidification speed of the casting, obtain the required metallographic structure, but also avoid direct contact with the air, reducing the tendency of the metal mold to get air. The thickness of the coating is usually shown in the table where pinholes are prone to occur, and the corresponding mold coating should be appropriately thinned. In the pouring operation, the opportunity for the oxidation and gettering of the aluminum alloy liquid should be avoided. For this reason, after drying and coating the coating spoon, it is best to heat it to red, and then pick up the alloy liquid, so as not to lower the temperature of the alloy liquid. The pouring spoon only removes the slag before pouring. The distance between the pouring spoon mouth and the metal-type external gate should be as short as possible, keep the external gate always in a full state, prevent jitter and interruption, and strive to avoid turning the spoon as much as possible during the pouring process. Back to increase vortex. Degassing treatment of aluminum alloy liquids At present, aluminum alloy wheel manufacturers generally degassing aluminum alloy liquids, usually adding a three-gas refining agent and then refining and degassing by the nitrogen pass method. Three gas refining agents generate three main gases, namely the following reactions with the aluminum alloy liquid. At the melting temperature, and as a gaseous substance, when it floats upward, it adsorbs solid impurities such as oxide slag and floats to the liquid surface, effectively reducing the aluminum alloy liquid. Content of hydrogen. Principle of the nitrogen flow method When nitrogen floats upward from the bottom of the alloy liquid in the form of bubbles, due to the pressure difference of hydrogen at cast bushing Manufacturers the interface of the bubbles, the hydrogen in the alloy liquid continuously enters the bubbles. When the bubbles rise to the liquid level, the hydrogen It also escapes into the atmosphere, and during the rise of the bubble, it also adsorbs other solid impurities of the oxide slag and floats to the liquid surface together. Nitrogen must pass through a filtering device equipped with a desiccant before passing through the alloy liquid.
The desiccant can be discolored silica gel or calcium chloride. The desiccant should be replaced frequently. When the aluminum alloy liquid passes through nitrogen, it should be caused by the alloy liquid boiling motorcycle technology process material host Zhang He on the technical conditions of motorcycle piston ring discussion Tian Wen Sandian Kui Wuhan Auto Parts Factory since the 1990s The rapid development of China's motorcycle piston ring industry has broken the pattern of several designated enterprises, and has also produced a considerable number of people who do not have a deep understanding of the technical conditions and performance of piston rings, but have made exaggerations in pursuit of sales benefits. Publicity and hype caused confusion in the judgment and testing of the quality of process technology products.
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