Abstract
Forming technology of aluminum and zinc alloys is an important method of shaped structures. It not only simplifies complicated structures such as ribbons, but also improves the performance of materials. In recent years, with the rapid development of the automotive, aerospace and shipbuilding industries, the demand for aluminum-zinc alloys formed parts has been increasing. At present, the common forming methods for aluminum and zinc alloys include extrusion, die casting and forging. Among them, hot extrusion forming of aluminum-zinc alloys has attracted much attention and has become a popular technology for producing structural parts in the aluminum and zinc alloy industry.
1 Introduction
Aluminum and zinc are two of the most widely used engineering materials in modern society. They have the advantages of low density, good corrosion resistance and good mechanical properties. As important alloying elements for aluminum and zinc alloys, Mg and Zn provide more strength and lower work hardening rate than pure aluminum and zinc, and also enhance corrosion resistance [1]. Therefore, aluminum and zinc alloys are widely used in the automotive, aerospace and shipbuilding industries, and have become an important material for manufacturing parts and components with complex 3D shapes and good mechanical properties. The traditional forming method of aluminum and zinc alloys is mostly realized through methods such as die casting and forging [2], which can meet many of the requirements in terms of shape, but cannot meet the requirements of materials with higher preferences. Hot extrusion is an efficient forming process for manufacturing complex shaped parts and components, and is widely used in aluminum and zinc alloys to manufacture parts with complex shapes and good mechanical properties.
2 Classification and characteristics of aluminum-zinc alloy extrusion systems
2.1 Classification of aluminum-zinc alloy extrusion systems
At present, the commonly used aluminum-zinc alloy extrusion system mainly includes two types, namely the continuous extrusion system and the forward extrusion system.
The continuous extrusion system is mainly composed of α-type and β-type pressure box, extruder screw and die. This system generally uses a reciprocating horizontal extrusion machine, which is also called a hot coreless extrusion press, to extrude the profile. The molten material is continuously injected into the pressure chamber with a plunger in the pressure box. The plunger is driven by the motor and pushes the material forward. The material is extruded from the extrusion, cooling and heeling die with the action of the oil pressure in the pressure chamber and the extrusion pressure generated by the extruder screw.
The forward extrusion system is mainly composed of Z-type pressure box, extruder, vertical extrusion machine and die. This system mainly relies on the pressure produced by the extruder screw in the pressure box to push the molten material forward, and the molten material is extruded from the extrusion, cooling and shrinking die under the action of pressure.
2.2 Characteristics of aluminum-zinc alloy extrusion systems
The aluminum-zinc alloy extrusion system has the advantages of high extrusion capacity, good economy, simple product shape and wide application range. The production speed of conventional single-roll continuous extrusion is 20 ~ 40mm/s. Its production capacity can reach 1000 ~ 3000 tons/year, which is very suitable for the production of large and medium-sized aluminum and zinc alloy products (including container parts, automotive parts, construction materials, etc.).
In addition, the aluminum-zinc alloy extrusion system has the characteristics of short manufacturing cycle, low cost and convenient maintenance. The process of aluminum-zinc alloy production is complex, and the electric control system of the extrusion process can carry out automatic adjustment and control according to the requirements of the shape and performance of the parts being produced.
3 Hot extrusion forming process of aluminum and zinc alloys
The hot extrusion process of aluminum and zinc alloys mainly consists of extrusion, cooling and shaping, as shown in Figure 1.
First of all, the aluminum and zinc alloys are heated to the required temperature in a furnace, then cut and sent to an accumulator or buffer to reduce the damage to finished products and increase the precision of the part. The heated aluminum and zinc alloys are then injected into the pressure box, where a plunger or screw is driven by the motor to push the material forward. The material is extruded from the die with the help of a PLC electric control system and hydraulic system. The cooling and heeling state of the extruded material can be adjusted according to the needs, and finally the required shape, size and performance can be obtained.
Figure 1 Schematic diagram of aluminum-zinc alloy extrusion process
4 Discussion
From the above analysis, it can be seen that hot extrusion of aluminum-zinc alloys is not only an effective method for the manufacturing of parts with complex shapes and good mechanical properties, but also a process with short manufacturing cycle and low cost. At present, many first-class aluminum-zinc alloy shaping enterprises in the world adopt this technology, which has achieved good results.
However, in the process of hot extrusion, there will be some problems such as uneven tube wall thickness and non-uniform microstructure, forming defects, etc. In order to solve these problems, increasing the number of passes of extrusion or using multiple pass tandem extrusion should be adopted to make the grain structure of the product more uniform and improve the surface quality of the product. In addition, reasonable design of the extrusion die and process parameters can improve the forming quality of the product.
5 Conclusions
In this paper, the forming technology of aluminum and zinc alloys is discussed in brief. Aluminum and zinc alloys are widely used in many fields because of their excellent performance. Hot extrusion forming technology has become a popular manufacturing process because of its advantages of high extrusion rate, good economy and simple product shape. The continuous and forward extrusion systems are commonly used in aluminum-zinc alloy extrusion. This hot extrusion process consists of extrusion, cooling and shaping steps. However, some problems may be encountered in the extrusion process, such as uneven wall thickness, non-uniform microstructure and forming defects. In order to solve these problems, it is necessary to adopt reasonable process parameters and die design, and increase the number of passes of extrusion.
References
[1] S. Paul, Understanding Aluminium Alloys and their Uses of Manufacture, Butterworth-Heinemann, Oxford, 2003.
[2] J.-L. Chen, Magnesium alloy castings, Materials Science and Engineering: A, vol. 391, no. 1-2, pp. 35-45, 2005.
