Aluminum alloy metal casting process and equipment

1. Overview

The aluminum alloy casting method is widely used because of its high productivity, clean working environment, smooth surface of the casting, and dense internal tissues. Especially in automobile engine parts, many industrialized countries such as Japan, the United States, Britain, Germany, and Italy adopt metal-type gravity casting methods to produce automobile engine aluminum cylinders, aluminum cylinder heads, and aluminum pistons. In recent years, many manufacturers in China have also introduced advanced metal-type equipment or home-made equipment to produce aluminum castings for automobile engine cylinder heads, intake pipes, and pistons. Metal-type cast aluminum technology is also widely used in aviation, aerospace, high-voltage electrical appliances, electrical machinery and instrumentation and other industries. Compared with other casting methods (die casting, low pressure casting, sand casting, etc.), aluminum alloy casting has the following advantages:

1) The overall quality of the geometry and the metallographic structure is good.

2) The lower pressure and high pressure casting process is flexible and can produce more complex castings.

3) It is more conducive to mass production and achieves a high degree of automation and simplification of maintenance; Under the same production scale, compared with high and low pressure castings, the one-time investment of casting equipment and metal type tooling is lower.

2. Aluminum Alloy Mold Casting Technology

(1) Metal-type casting process design of aluminum alloy pieces The key to the design of metal-type casting process is the determination of the casting position of the casting, the design of the pouring system, and the control and adjustment of the mold working temperature.

l) Casting position. It is directly related to the number of metal cores and parting surfaces, the location of molten metal introduction, the degree of exhaust patency, and the complexity of the metal structure, etc., to determine the ease of metal processing and operation and the cooling temperature distribution of the castings. , And then affect the casting production efficiency, dimensional accuracy and other internal and external quality. Therefore, casting position is an important part of the casting process design.

2) Pouring system. Casting pouring system design determines the internal and external quality of the casting. The tumbling system should have slagging, venting and feeding functions, and at the same time, it should ensure a reasonable solidification and cooling temperature field of the casting. In addition to empirically estimating the correct and reasonable rigging system, computer-based numerical simulation can directly predict the temperature field of the solidification process of the casting and show that the casting may produce dangerous parts of shrinkage (holes), thus guiding the process design and adjusting the pouring. Measures temperature field and eliminates casting defects, such as system structure and size, metal structure, control of cooling rate or adjustment of paint layer thickness, such as the use of bottom-injection castings for automotive engine aluminum cylinder heads, albeit taken in the upper setting almost exceeded It is also difficult to adjust the temperature field for a reasonable sequence of solidification for the large riser weight and the forced cooling of the bottom of the casting, and it is difficult to eliminate the shrinkage defects caused by overheating around the bottom inner gate. A factory to introduce the French Sifa aluminum alloy metal casting machine is the use of this tumbling system, the production process is not stable. One-hundred percent of cylinder heads need to be infiltrated. If the cylinder head is severed, even if it is impregnated, it will not meet the requirements of pressure resistance. However, aluminum liquid is injected directly from the feeder and the aluminum liquid is purified by the ceramic filter and then entered into the cavity to ensure reasonable castings. The cooling gradient, that is, the bottom-up sequential solidification method eliminates the shrinkage defect and significantly increases the cylinder head yield. The Foseco company in the United Kingdom had conducted detailed studies and comparative test work on two casting methods and called the latter the DYPUR method. This method makes the model simple and compact, saves liquid aluminum, and has high casting yield. Using this method, even if there is a small amount of inclusion defects due to the high drop of molten aluminum, the mechanical properties and airtightness of the castings have little effect. Of course, in addition to taking into account the solidification temperature field of the casting, the opening position, structure and size of the pouring system must also take into account the complexity of the type, whether the metal liquid filling is stable, whether it has the function of slag slag and exhaust gas.

3) Metallic working temperature. Also, the metal type working temperature and the temperature difference of each part play an important role in the cooling temperature field of the casting. Forced water cooling and air cooling on metal-type local overheating areas is to ensure that the area maintains a normal operating temperature, improves production efficiency, eliminates overheating, and ensures a normal cooling temperature field. The more advanced and effective method for metal type working temperature control is to control the cooling water outlet temperature, and the outlet temperature is adjusted by the cooling circulating water circulation speed. Metals such as Fata of Italy and Sifa of France have advanced water and air cooling devices. In addition, for the local thick hot junctions, metal inserts with high thermal conductivity or high heat storage capacity can be embedded or the coating layer thickness and coating type can be adjusted to ensure that the castings form a reasonable cooling temperature gradient, eliminating local shrinkage (hole) defects. .

(2) Metal Alloy Design and Material

1) Metallic design and manufacturing. Good metal-type design and manufacturing techniques are the key to satisfying process design and adapting to high-volume, high-quality casting production. The metal type design mainly includes a metal type structure, an exhaust system, a locking mechanism, a cooling system, a connection mechanism, and a casting ejecting mechanism. Reasonable casting process and metal type design can only be realized through advanced metal processing manufacturing technology.

2) Metallic materials. Materials suitable for the production of metal types should have sufficient high temperature strength, certain thermal and thermal fatigue strength, and sufficient strength and toughness. In general, domestic cast iron, cast steel and copper alloys are used as metal alloy die materials, with an average life span of 10,000 to 50,000 times. Developed countries generally adopt the AISI classification H-13, which is equivalent to domestic 4CrMoVSi steel. This kind of steel has higher thermal strength and hardness, and also has higher wear resistance and toughness. Using it as a mold, its casting size is stable and its die life is long, generally more than 100,000 times. Of course, the life of the mold is not only related to the material, but also related to the mold structure, the material of the casting alloy, the operation and management, and other factors.

3. Aluminum Alloy Mold Casting Equipment and Automation

(1) Metal mold casting equipment Metal mold casting machines can be classified into special metal mold casting machines and general metal mold casting machines according to their uses. According to power, they can be divided into manual, pneumatic, electric and hydraulic metal mold casting machines. Some foreign foundry equipment factories have developed many special metal casting machines according to the requirements of products and users, such as aluminum cylinder heads, aluminum cylinders, aluminum pistons, aluminum intake manifolds and other metal casting machines. The famous metal casting machines for aluminum alloys are Fata of Italy and Sifa of France. In recent years, more than 20 manufacturers in China have gradually introduced aluminum alloy metal casting machines and technology from abroad to support the production of automobile aluminum alloy castings at home and abroad. The Shanghai Automotive Non-ferrous Foundry General Plant introduced the Fata metal casting machine to produce the aluminum cylinder head of the Santana car engine, and the FAW light engine plant introduced the Sifa equipment to produce the CA488 car engine cylinder head.

(2) Metal Forming Automatic Production Line