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The Five Major Technology Of Machining Automotive Aluminum Wheel Hub
Jan 10, 2018

the five major technology of machining Automotive aluminum wheel hub

Wheel hub, also known as the rim, is the drum-shaped tire inner support tire, the center of the shaft mounted on the metal parts.


The wheels are mainly divided into steel wheels and light alloy wheels according to the materials, while the light alloy wheels are mainly made of aluminum alloy and magnesium alloy. In today's automotive market, steel wheels are rare, and most models use aluminum wheels, light alloy wheels.


Aluminum alloy materials used to make aluminum wheels include A356, 6061, and the like. Among them, A356 aluminum wheels are cast a large number of selection. A356 aluminum alloy with small specific gravity, good erosion resistance and other characteristics, mainly by the aluminum, silicon, magnesium, iron, manganese, zinc, copper, titanium and other metal elements, aluminum accounted for about 92%, is a technology of mature aluminum alloy material.


Aluminum alloy wheels are more suitable for passenger cars than steel wheels. At present, the manufacturing process can be basically divided into three types. The first type is foundry. At present, most automobile manufacturers choose to use the casting process. The second is forging, and more for high-end sports cars, high-performance cars and high-end conversion market. The third is more special, is the MAT spinning technology put into use earlier by the Japanese Enkei company, at present this technology in the domestic application is not as good as the first two.


1, Gravity casting method

Gravity casting simply said that the main is to rely on the gravity of aluminum water to fill the mold, is a relatively early casting method.

The method has the advantages of low cost, simple process and high production efficiency. However, the inclusions in the casting process are easy to be entangled in the casting, and sometimes gas may be entrained to form stomatal defects. The hubs produced by gravity casting tend to have shrinkage cavities and poor internal quality. In addition, the fluidity limitations of aluminum fluids can also lead to low yields of molded hubs. Therefore, the automotive wheel manufacturing industry has rarely used the process.


2, Low-pressure casting method

Low-pressure casting is aluminum liquid filled under pressure in the mold, under pressure in the case of solidification crystallization process. Under the same conditions, the internal structure of the low-pressure cast hub is denser and stronger than gravity casting. In addition, low-pressure casting using pressure filling and replenishment, greatly simplifying the structure of water and pouring system, the liquid metal recovery rate of up to 90%. At present, low-pressure casting has become the preferred aluminum wheel production technology, the majority of domestic aluminum alloy wheel manufacturing enterprises have adopted this technology. However, low-pressure casting method also has its drawbacks: casting a longer time, feeding, mold change for a long time, equipment investment and more.


3, forging method

Hot forging → RM forging → Cold spinning → Heat treatment → Machine work → Shot blast → Surface finishing

Forging is a solid to solid change, through the beat, pressure, forging and other means to form the wheel hub, the process does not occur in the liquid phase change, are solid changes. Therefore, its mechanical properties than the cast to be high, with high strength, good corrosion resistance, the advantages of accurate size. Grain flow and stress direction, so the strength, toughness and fatigue strength are significantly better than the cast aluminum wheel hub. At the same time, forged aluminum wheel typical elongation of 12% to 17%, which can well absorb the road vibration and stress. In addition, the surface of the forged aluminum wheel holes, which has a good surface treatment.

However, the big disadvantage of forging aluminum wheels is that they have many manufacturing steps and the production cost is much higher than that of casting. Although the performance of the forged hub is better, auto makers still use mostly foundry wheels on most vehicles, with only a few luxury cars equipped with forged wheels. However, the leading domestic hub manufacturing company CITIC DICARD has successfully entered the passenger car forging wheel production line and the cost of forging the hub compressed to a thousand dollars, and has begun to serve as the primary hub of the domestic joint venture plant supply.


4, Squeeze casting method

Squeeze casting, also known as liquid forging, is a combination of casting and forging features in a single process - a certain amount of liquid metal poured directly into the open metal type, through the punch to a certain pressure on the liquid metal , So that filling, forming and crystallization solidification, and in the crystallization process to produce a certain amount of plastic deformation. Advantages: Filling smooth, metal directly under the pressure of crystallization solidification, so the casting will not produce porosity, shrinkage and shrinkage casting defects, and the organization of dense, low-pressure casting and mechanical properties of high investment and much lower than the low-pressure casting method. Disadvantages: As with traditional forged products, milling is required to complete the spokes. Japan has a considerable part of the automotive aluminum wheel extrusion die casting process, from pouring molten metal to take out the entire process of casting by the computer to control the degree of automation is very high. At present, all countries in the world regard squeeze casting as one of the directions for production of automobile aluminum wheel hubs.


5. Special molding: MAT spinning technology

MAT spinning technology earlier put into use by the Japanese company Enkei, strictly speaking, it should be considered a casting, referring to the overall cast in the rim after the use of special equipment to force the Department of rotary pressure treatment, Which makes the internal metal arrangement of the treated position changed. The specific dividing plane presents a fibrous structure with higher density than the normal cast product, so as to change the overall metal mechanics process. The quality, strength and extensibility of MAT wheels made with MAT spinning technology are close to forged wheels and are now easier to produce for forged wheels. In general, MAT spinning technology provides a relative guaranteed manufacturing cost of the hub while also enabling the cast hub to achieve the same weight and strength as a forged hub. Just immature domestic technology, higher cost, so few applications.


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