Conventional forging
Forging is one of the early forming processes for aluminum wheel hubs. Forged aluminum wheel hub has the advantages of high strength, good corrosion resistance, accurate size and small processing volume. Generally, its weight is only equivalent to 1 / 2 or less of the steel wheel of the same size. The grain flow direction of forged aluminum hub is consistent with the stress direction, and its strength, toughness and fatigue strength are significantly better than that of cast aluminum hub.
At the same time, the performance has good reproducibility, and almost every hub has the same mechanical properties. The typical elongation of forged aluminum hub is 12% ~ 17%, so it can well absorb the vibration and stress of the road. Generally, the cast wheel hub has a relatively strong ability to withstand compressive force, but the ability to withstand impact, shear and tensile loads is far less than the forged aluminum wheel hub. Forged hubs have a higher strength to weight ratio.
In addition, the surface of forged aluminum wheel hub is free of pores, so it has good surface treatment ability, which can not only ensure uniform coating, reliable combination, but also good color. The biggest disadvantage of forged aluminum hub is that there are many production processes and the production cost is much higher than that of casting.
Casting forging method
It is a method of using the casting as a blank in the forging process and plastically processing it. As forging is the final forming process of parts, it can eliminate casting defects, improve the structure of products, greatly improve the mechanical properties of products compared with castings, and give full play to the advantages of casting technology in forming complex parts, so that the forging process of products with complex shapes is reduced, the material utilization rate is greatly improved, and the production cost is reduced.
The properties of aluminum wheel hub produced by casting and forging technology can fully meet the mechanical properties of forgings, but the production cost can be reduced by 30% compared with ordinary forgings. At present, this process has been successfully applied to batch production since September 1996, and has been adopted by many Japanese companies with good economic effect. At present, only a few enterprises in the mainland (mainly in Taiwan’s Liuhe system) are using this process, and the equipment and technology are from Bulgaria.
Semi solid die forging process
The so-called semi-solid die forging is a process that heats the semi-solid billet to a semi-solid state with about 50% of the volume of liquid phase and then forms it in one die forging to obtain the required finished parts close to the size. It is a brand-new process between solid forming and liquid forming.
Advantages of semi-solid die forging: the parts shrink less in the die, easy to near finish forming, and less machining; The semi-solid die forgings have smooth surface, dense internal structure, fine grain, and higher mechanical properties than die casting and squeeze casting; The forming is not easy to wrap up air, and the macro porosity and micro porosity are much less than those in the conventional casting; Low forming temperature and long die life.
In the past 10 years, semi-solid forming technology has been widely used abroad, and has gradually become a new field of competitive development in advanced industrial countries. It is called the new generation of metal forming technology in the 21st century by experts and scholars. It is expected that the main market of semi-solid forming will be the automobile industry for a long period of time, and the most successful and widely used aluminum alloy parts for automobiles.
Several aluminum alloy semi-solid die forging plants have been built in the United States. Among them, aemp company of the United States cooperated with superior industrial company to build the world’s first semi-solid die forging aluminum alloy automobile hub plant in Arkansas in 1992. Using semi-solid die forging instead of low-pressure casting to produce ZL101 Aluminum alloy wheel hub can not only reduce machining amount and improve productivity, but also improve mechanical properties and reduce quality.
Forging spinning
It is a relatively high-end forming process. At present, only about 10% of domestic enterprises adopt this process for production, and the products are mainly supplied to the domestic and foreign bus, truck and high-end car markets. The advantages are good internal quality, high product strength and light quality; The disadvantage is that the equipment cost is high, the spokes of the products manufactured by the traditional forging process can only be completed by milling, the metal utilization rate is low and the production efficiency is not high. Forging is divided into traditional forging and rolling forging. Rolling forging can directly forge the shape of spokes.