Pressure casting
high pressure die casting
[Edit Paragraph]First, the overview
Pressure casting (referred to as die casting) of the essence of the high-pressure action, so that the liquid or semi-liquid metal at a high rate of filling the cavity of the die casting mold, and under pressure Molding and solidification and obtain the casting method.
1, die casting characteristics
High pressure and high speed filling die casting mold is the two main characteristics of die casting. It is commonly used injection pressure is from thousands to tens of thousands of kPa, and even as high as 2 × 105 kPa. filling speed of about 10 ~ 50m / s, and in some cases even up to 100m / s or more. Filling time is very short, generally in the range of 0.01 ~ 0.2s. Compared with other casting methods, die casting has the following three advantages:
1. good product quality
casting dimensional accuracy is high, generally equivalent to 6 ~ 7, and even up to level 4; Surface finish is good, generally equivalent to 5 ~ 8; Strength and hardness is high, the strength of the general than the sand casting to improve the 25 ~ 30%, but elongation is reduced by about 70%; Stable dimensions, interchangeable good; Can die casting thin-walled complexity, the size of the casting, the size of the casting, the size of the casting is stable. Can die casting thin-walled complex castings. For example, the current zinc alloy die casting minimum wall thickness of up to 0.3mm; aluminum alloy castings up to 0.5mm; minimum casting hole diameter of 0.7mm; the minimum pitch of 0.75mm.
2. High productivity
machine productivity, such as the domestic J ⅲ3 horizontal cold air die casting machine average eight hours can die casting 600 ~ 700 times, small hot room die casting machine average Every eight hours can die casting 3000 ~ 7000 times; die casting long life, a die casting type, die casting bell alloy, life up to hundreds of thousands of times, or even millions of times; easy to realize mechanization and automation.
3. Excellent economic results
Due to the die casting size is accurate, the table flood clean and other advantages. Generally no longer mechanical processing and direct use, or processing is very small, so both improve the utilization of metal, but also reduces a large number of processing equipment and man-hours; casting price is easy; can be used in a combination of die-casting to other metal or non-metallic materials. Both save assembly labor time and save metal.
Although there are many advantages of die casting, but there are also some shortcomings, yet to be resolved. Such as:
1). Die casting due to the liquid metal filling cavity speed is high, the flow state is not stable, so the use of general die casting method, the casting is easy to produce porosity, can not be heat treatment;
2). For the concave complex castings, die casting is more difficult;
3). High melting point alloys (such as copper, ferrous metals), die casting mold life is lower;
4). Not suitable for small batch production, the main reason is the high cost of manufacturing die casting type, die casting machine production efficiency, small batch production is not economical.
2, die casting application scope and development trend
Die casting is one of the most advanced metal molding method, is to realize less chip, no chip effective way, the application is very wide, the development is very fast. At present, the die-casting alloy is no longer limited to non-ferrous metals of zinc, aluminum, magnesium and copper, and also gradually expand to die-casting cast iron and cast steel parts.
The size and weight of the die casting, depending on the power of the die casting machine. Due to the increasing power of the die-casting machine, casting shape size can be from a few millimeters to 1 ~ 2m; Weight can be from a few grams to tens of kilograms. Foreign countries can die-casting diameter of 2m, weight of 50kg aluminum castings. Die casting is no longer limited to the automobile industry and instrumentation industry, gradually expanding to other industrial sectors, such as agricultural machinery, machine tool industry, electronics industry, national defense industry, computers, medical equipment, clocks and watches, cameras and daily-use hardware and so on dozens of industries. In the die-casting technology and the emergence of vacuum die-casting, oxygen die-casting, fine speed density die-casting and the application of soluble cores and other new technologies.