Aluminum wheel hub 8 typical production process, casting and forging is the core!
Wheel hub, alias wheel rim, that is, the inner contour of the tire is used to support the tire barrel-shaped, the center of the assembly in the shaft parts. Common automotive wheel hubs are steel wheel hubs and aluminum alloy wheel hubs. Steel wheels have high strength and are commonly used in large heavy-duty vehicles; however, steel wheels are heavy and have a single shape, which is not in line with today's low-carbon and fashionable concepts, and are gradually being replaced by aluminum alloy wheels. At present, the original wheels of passenger cars on the market are basically aluminum alloy wheels.
Aluminum alloy wheel production process mainly has the following kinds:
- Gravity casting
Metal-type gravity casting refers to a casting method in which the liquid metal fills the metal casting by gravity under normal pressure to obtain castings, which is also an ancient casting method. Due to the liquid metal in the metal casting cooling speed, and thus castings than sand casting organization dense, the method of simple processes, high production efficiency, less investment in equipment, lower production costs, suitable for small and medium-scale production. But this method of production of aluminum wheel hub internal quality is poor, shrinkage shrinkage is serious, pouring process of oxide film and slag and other inclusions are easy to roll into the casting, and sometimes also rolled into the gas and the formation of porosity defects, at the same time, the liquid metal yield is also low. Most of the vehicle manufacturers have now rejected the process of production of wheels, aluminum wheel manufacturing industry has gradually been marginalized trend.
- Low-pressure casting
Low-pressure casting is the casting on top of a closed furnace, the cavity of the following with a tube (called liquid tube) and the liquid metal in the furnace chamber connected. If the liquid metal in the furnace is added to the surface of the liquid metal with the pressure of air, the liquid metal will flow into the cavity from the rising liquid pipe. After the liquid metal solidifies, the compressed air in the furnace chamber is released and the unsolidified metal flows back into the furnace from the lift tube. Control the pressure and speed of the air flowing into the furnace chamber, you can control the speed and pressure of the metal flowing into the cavity, and can let the metal crystallize and solidify under pressure. This process is characterized by castings crystallized under pressure, dense organization, good mechanical properties, high metal utilization.
- Squeeze casting method
Squeeze casting, also known as liquid forging, is a set of casting and forging features in one of the new process, the process is a certain amount of liquid metal directly into the open metal type, through the punch to a certain pressure on the liquid metal, so that it is filled, shaped and crystallization of solidification, and in the process of crystallization to produce a certain amount of plastic deformation. Squeeze casting filling smooth, no turbulence and not rolled gas, metal crystallization and solidification directly under pressure, so the casting will not produce porosity, shrinkage and loosening and other casting defects, and the organization of dense, grain refinement, mechanical properties than the low-pressure casting parts high. Products are close to the excellent mechanical properties of forgings, but also precision castings of a precision molding of high efficiency, high precision, and investment is much lower than the low-pressure casting method. The disadvantage is that the liquid die forging products and traditional forging products, the same need for milling to complete the spoke molding.
- Casting spin
Casting spinning is divided into "low-pressure casting + spinning" and "gravity casting + spinning" two kinds of technology. At present, Korean car companies on the aluminum wheel molding process has a comprehensive use of "low-pressure casting + spinning" trend, other car systems also have part of the product demand for this process, the process is cast spinning process in the mainstream process, to do the OEM products most of the enterprises are used in this process; at the same time, there are a small number of enterprises to do the overseas retail market Using "gravity casting + spinning" process, theoretically speaking, this process is feasible, it really combines the strengths of the two processes of gravity casting and spinning together, the quality of the product has been improved, but due to the blanks are produced by gravity casting process, so the economics of this process is very bad, the production cost is very high. In short, the cast and spun product, because the spoke part is cast out, it has the same advantages and disadvantages as the casting process produced products; and the rim part is spun out, so the air tightness is better. Casting spinning products can theoretically reduce weight, but the practical application of the effect is not obvious.
5.Conventional forging
Forging is one of the earlier forming processes for aluminum wheels. Forged aluminum wheel with high strength, good corrosion resistance, precise size, small amount of processing and other advantages, the general situation of its weight is only equivalent to the same size steel wheel 1/2 or lower. Forged aluminum wheel grain flow direction and the direction of the force is the same, its strength, toughness and fatigue strength are significantly better than cast aluminum wheel. At the same time, the properties are very reproducible, with almost every hub having the same mechanical properties. Forged aluminum wheels have a typical elongation of 12% to 17%, which makes them very good at absorbing road vibration and stress. Typically cast wheels are quite capable of withstanding compressive forces, but are far less capable of withstanding impact, shear and tensile loads than forged aluminum wheels. Forged wheels have a higher strength-to-weight ratio. In addition, the surface of forged aluminum wheels without air holes, and therefore has a very good surface treatment capabilities, not only to ensure uniformity of the coating, the combination of firm, and color is also good. The biggest disadvantage of forged aluminum wheel is that the production process is more, the production cost is much higher than the casting.
- Casting forging method
It is the casting as a forging process billet use, the plastic processing method. As a result of the forging process as the final shape of the parts, so you can eliminate casting defects, improve the organizational structure of the product, so that the mechanical properties of the product than the casting is greatly improved, and at the same time give full play to the casting process in the forming of complex pieces of the advantages of the complex shape of the product forging process to reduce the material utilization rate greatly improved, lower production costs. With casting and forging technology to produce aluminum wheels, its performance can fully meet the mechanical properties of forgings index, but the production cost can be 30% lower than ordinary forging parts. At present, the process since September 1996 successfully applied to mass production, has been used by a number of Japanese companies, the economic results are good. At present, only a few enterprises in mainland China (mainly in Taiwan, six and system) in the use of this process, equipment and technology from Bulgaria.
- Semi-solid die forging process
The so-called semi-solid die forging, that is, semi-solid billet heated to about 50% of the volume of the liquid phase of the semi-solid state after a die forging, to obtain the required size close to the finished part of the process, which is a between the solid state forming and liquid molding between the new process.
Advantages of semi-solid die forging: parts in the mold shrinkage is small, easy to form near the end of the shape, reduce the amount of machining; semi-solid die forging surface smooth, dense internal organization, fine grain, mechanical properties higher than the die casting and extrusion casting parts; molding is not easy to wrap the gas, macroporosity and microscopic porosity is much less than in conventional castings; forming temperature is low, long die life.
- Forging spinning
Comparison of high-end molding process, at present only about 10% of domestic enterprises to use the process for production, products are mainly supplied to domestic and foreign buses, trucks and high-end car market. Advantages are good intrinsic product quality, product strength and high quality light; disadvantage is the high cost of equipment, traditional forging process manufacturing products spoke shape can only be completed by milling, metal utilization rate is low and production efficiency is not high. Forging is divided into traditional forging and milling forging, milling forging can be directly forged spoke molding.