Low Pressure Die Casting Principles and Applications

What is low pressure die casting?

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Aluminum low pressure die casting (LPDC) is to make liquid metal under pressure to complete filling cavity and solidification process two get casting a casting method. Due to the existence of a certain pressure but far lower than the pressure of high-pressure die casting (the highest pressure is only for high-pressure die casting 1%), low pressure die casting pressure range in (20 ~ 60kPa), with its role in the pressure is small and slow, but also be able to manufacture a more complex internal hollow products (the hollow part of the need for the sand core subsequent to the removal of the so-called low-pressure sand casting), and the principle of its role is closer to the Aluminum casting, so it is also called aluminum low-pressure casting.

Low pressure die casting processIn the impermeable crucible, through the pipe into the compressed dry gas, the molten aluminum liquid under the action of gas pressure, along the rising liquid pipe (crucible middle pipe) through the mold gate smoothly into the cavity, keep the gas pressure on the liquid surface of the crucible, maintain a certain period of time pressure, such as low-pressure mold cavity solidification of the product, and then lifting the crucible on the liquid surface of the gas pressure, so that the liquid rising liquid pipe in the un-solidified metal Then the gas pressure on the liquid surface in the crucible is lifted, so that the unsolidified metal in the liquid ascending tube flows back to the crucible, and the low-pressure aluminum castings are taken out by opening the mold through the low pressure casting machine. As the casting direction of low pressure casting is against gravity casting, it is also called anti-gravity low pressure casting.

History of Low Pressure Casting

At the beginning of the twentieth century, there have been countries one after another began to study the low-pressure casting process, the United Kingdom E.H. Lake is the first registered on the aluminum alloy low-pressure casting patents of the company, the French first in the aluminum alloy casting production in the promotion and use.

After the outbreak of the Second World War, the aviation military industry and other manufacturing industries have further development, should be low-pressure casting process is widely used in high requirements of the aviation engine system aluminum alloy parts, high-volume production of aluminum alloy castings, North America using aluminum alloy low-pressure casting technology is widely used in the manufacture of automotive parts, motor shells and other castings. In this way, the low-pressure casting process quickly spread to the field of general machinery, textile machinery, instrumentation and commercial products.

China began to study low-pressure casting from the 1950s, but the development has been relatively slow. With the development of the automobile industry, and the adoption of a large number of new technologies, at the end of the last century and the beginning of this century, low-pressure casting in China has been the rapid development of domestic low-pressure casting machine function and performance, and the use of the stability and reliability of the machine has been close to or reached the international advanced level, is used in a large number of automobile wheel hubs, automobile cylinder heads and other castings production.

Low pressure die casting mold material selection

Low pressure die casting mold is also known as low pressure permanent mold, the use of metal cavity manufacturing molds, can be used to turn the sand mold (ductile iron), mold steel mold (p20, #45, H13 and other heat-resistant mold steel), production. Different molds have different mold life, ordinary sand mold life is about 2000-5000 mold, modulation of #45 life can be done 5000-10000 + mold, ordinary have done a vacuum heat treatment of h13 can reach 30000 mold life. The better ones can even reach 50,000 molds or even 100,000 molds.

Advantages and disadvantages of low pressure die casting

Advantages of low-pressure casting

• 1, low-pressure die-casting aluminum liquid flow rate is slow, debris involved in less, by changing the pressure rate, the molten soup by laminar flow to fill.
• 2、Using the bottom injection type charging, the metal liquid charging is smooth, no splash phenomenon, can avoid the involvement of gas and the scouring of the wall and core, and improve the qualification rate of the castings.
• 3, low-pressure die-casting machine manufacturer production of aluminum alloy products under pressure crystallization, low-pressure die-casting product organization dense, clear contours, surface finish, high mechanical properties, for the casting of large thin-walled parts is particularly advantageous.
• 4, can change the low-pressure casting process pressurization rate, molten soup by laminar flow for filling.
• 5, low-pressure aluminum casting materials are widely used.

Disadvantages of low pressure die casting

• 1, low production efficiency, more gravity die casting, high pressure die casting compared. High-pressure die casting > gravity die casting > low-pressure die casting
• 2. Long casting cycle, poor productivity. In order to maintain directional solidification and molten soup mobility, the mold temperature is high and the solidification speed is slow.
• 3, close to the gate low pressure die casting aluminum organization is coarse, the mechanical properties of the lower surface is not high, need a comprehensive and close management (temperature, pressure, etc.).
• 4, mold cost is high, low-pressure casting mold for metal mold life non-sand casting one-time casting, known as "low-pressure permanent mold casting".
• 5, equipment costs are high. Low-pressure casting machine prices relative to the gravity casting machine, sand casting is not a small investment.

Low pressure cast aluminum material selection

Low pressure casting is mainly used in the field of non-ferrous alloy casting, common aluminum alloy, magnesium alloy and other light alloy castings. One of the most widely used aluminum alloy, usually we speak of low pressure die casting refers to aluminum alloy low pressure casting. Common aluminum alloy materials are.

1. aluminum-silicon alloy: Usually si content in 11% or so, to aluminum silicon as the main raw material while adding a small amount of while adding a small amount of copper, iron, nickel to improve strength, is a low-pressure casting of the more common materials.
2. aluminum-copper alloy: Copper-aluminum alloy is very much a relatively hard aluminum alloy, usually made of 3% copper, is the earliest cast aluminum alloy used in industry. Its main performance is characterized by high mechanical properties at room temperature and high temperature, simple casting process, good cutting and machining performance, excellent heat resistance.
3. magnesium aluminum alloy: Aluminum-magnesium alloys have good strength, hardness and heat resistance, making them ideal for the manufacture of high-quality components. At the same time, because aluminum-magnesium alloys also have good weldability and corrosion resistance, they are also suitable for the manufacture of parts with high color and surface quality requirements.
4. Aluminum-magnesium-silicon alloy: This alloy also offers good strength and stiffness, as well as excellent heat resistance and mechanical properties. Aluminum-magnesium-silicon alloys are an ideal material choice in the manufacture of high-quality components and industrial equipment. It is most widely used in low-pressure casting applications, with A380 and A356 aluminum alloys being the most common in low-pressure casting applications.

Scope of Application

The application range of low-pressure casting is quite wide, especially suitable for the fields which have high requirements on the quality of castings. Especially in the developed manufacturing industry in China, in order to be able to provide customers with more, cheap and good aluminum alloy castings, OEM, ODM, batch customized aluminum alloy products. Aluminum low pressure casting plant will be used in.

Frequently Asked Questions (FAQs)

Is aluminum low pressure die casting the same as high pressure die casting? What's the difference?

Aluminum low pressure die casting is a kind of slow casting way, and high pressure die casting is a kind of high speed and high pressure casting way, although all are pressure casting a form but, high pressure die casting products are more brittle, low pressure casting products performance is closer to gravity casting (low pressure die casting also known as antigravity casting) can be heat treatment, aluminum should be more extensive. High-pressure die casting production efficiency, speed, low-pressure casting efficiency is relatively low more slow.

Is low pressure die casting suitable for mass production?

Suitable, although the low pressure die casting efficiency relative to the high pressure die casting is lower but also can reach (24 hours 200 molds -300 molds), much higher than the sand casting, high degree of automation, high use of aluminum, high product stability.

Compared with gravity casting low-pressure casting product qualification rate is higher?

Yes, although it is called low-pressure die casting, but its flow rate is slow, the pressure is small closer to the gravity casting, but its automation is high, the pressure (20~60kPa) is lower than the die casting but greater than the gravity, so the product production is more stable.