The hub, the alias rim, that is, the barrel inner shape of the tire inner frame for supporting the tire, and the center assembly on the shaft. Common automotive wheels have steel wheels and aluminum alloy wheels. Steel wheels have high strength and are often used in large trucks. However, steel wheels are heavy in weight and single in shape, which does not meet the current low carbon and fashionable concept and is gradually being replaced by aluminum alloy wheels. At present, the original wheel hubs of passenger cars on the market are basically aluminum alloy wheels.
The production process of aluminum alloy wheels mainly has the following types:
1 Gravity casting Metal gravity casting refers to a casting method in which a liquid metal is filled with a metal mold by gravity to obtain a casting under normal pressure, which is also an ancient casting method. Because the metal liquid cools faster in the metal mold, the casting is denser than the sand casting structure. The process is simple, the production efficiency is high, the equipment investment is low, and the production cost is low, which is suitable for small and medium scale production. However, the internal quality of the aluminum wheel hub produced by this method is poor, and the shrinkage hole shrinkage is serious. In the pouring process, the inclusions such as oxide film and slag are easily caught in the casting, and sometimes the gas is caught in the gas to form the pore defect, and the liquid liquid is collected. The yield is also low. Most automakers have now rejected the wheels produced by the process and are gradually marginalized in the aluminum wheel manufacturing industry.
2 Low-pressure casting Low-pressure casting is to place the mold on a closed furnace. The bottom of the cavity is connected to the metal liquid in the furnace by a tube (called a riser tube). If pressurized air is added to the metal surface of the furnace, the molten metal will flow from the riser into the cavity. After the molten metal is solidified, the compressed air in the furnace is released, and the unsolidified metal flows back from the riser to the furnace. By controlling the pressure and velocity of the air flowing into the furnace, it is possible to control the speed and pressure of the metal flowing into the cavity and allow the metal to solidify under pressure. The characteristic of this process is that the casting is crystallized under pressure, the structure is compact, the mechanical properties are good, and the metal utilization rate is high.
The low-pressure casting process is currently quite mature in mainland China and is suitable for production management. It has been recognized by all OEMs as the mainstream process of aluminum alloy wheel manufacturing in China. The products are mainly sold to OEMs and overseas retail markets.
The aluminum alloy wheel hub manufactured by the low-pressure casting process, because the spokes are finally cooled and solidified, the spokes of some special modeling hubs are prone to quality problems such as shrinkage, and the rim portion has better strength due to the earliest crystallization.
3 Squeeze Casting Squeeze Casting, also known as liquid die forging, is a new process that combines the characteristics of casting and forging. The process involves pouring a certain amount of metal liquid directly into the open metal mold through the punch. It acts on the liquid metal with a certain pressure to fill, shape and crystal solidify, and produces a certain amount of plastic deformation during the crystallization process. Squeeze casting filling is stable, no turbulent flow and no wrapping gas, the metal crystallizes directly under pressure, so the casting does not produce casting defects such as pores, shrinkage and shrinkage, and the structure is dense, grain refinement, mechanical properties Higher than low pressure castings. The product has excellent mechanical properties close to forgings, high efficiency and high precision for precision forming of precision castings, and the investment is much lower than that of low pressure casting. The disadvantage is that liquid forged products, like traditional forged products, require milling to complete the spoke shape.