What Are the Requirements for Low Pressure Casting?
1. Conditions required for low pressure casting: temperature
The temperature of the molten soup will be affected by the type and shape, but the overall difference will not be much. Whether the temperature is appropriate will directly affect the quality and appearance of the product, so the temperature should be controlled within a reasonable range. It should be noted that the mold temperature of low pressure casting cannot be ignored. From the perspective of molten metal solidification, the temperature distribution of the mold is mainly gradually reduced from the upward direction of the gate, but because this will prolong the casting cycle and affect the solidification speed, the gate temperature difference can be increased according to the actual situation to make the current situation can be changed.
2. Conditions required for low pressure casting: pressurization time and setting time
The pressurization time of low pressure casting mainly refers to the time it takes for the molten metal to solidify at the gate from filling. Boost time can be affected by a number of factors, which requires cylinder head time to be considered. The extension cord should be as long as possible, and the extension cord is mainly based on weight. Pressurization time is easily affected by temperature conditions. If the temperature is stable, the pressurization time will also be stable.
The solidification time of molten metal can be unstable due to changes in heat and decreases in temperature. Because the number of castings will continue to increase, the temperature will be very unstable, and the cross-sectional area of the gate will decrease, which will cause changes in the solidification time and cause internal defects in the quality of the castings. Therefore, great attention must be paid to the influence of temperature, gate, feed pipe and other factors on the soup system.
The solidification time of low pressure casting refers to the time from the completion of pressurization to the release of the product. After the casting is demolded, it is not really completed, but to ensure that the casting is not deformed and the quality of the casting is guaranteed. The time required for this part must be added to the time required for solidification. The solidification time will not be long, and it is related to the temperature, and the solidification speed will be faster than the pressurization time. In order to shorten the solidification time, the cooling rate can be increased.
3. Conditions required for low pressure casting: pressurized conditions
In order to ensure the filling effect, attention should be paid to adjusting the pressurization speed. Too fast or too slow will affect the filling effect and the quality of low pressure castings. Specifically, if the speed is slow, it will cause the problem of poor molten soup flow; if the speed is too fast, the product will be disturbed by gas and cause quality defects. Therefore, it is imperative to adjust the pressurization speed. Since the flow is affected by the difference in the shape of the runner, it is necessary to control the speed according to the actual situation.
In summary, low-pressure casting technology has great advantages and is the mainstream casting technology for aluminum alloy castings. Compared with other casting methods, the technology has a wide range of applications, high casting quality, high precision, good performance and high degree of automation. The low-pressure casting technology has a history of more than 100 years, and it is affecting the alloy casting industry with a good development trend.