A rim is a barrel shaped metal part of the inner rim of a tire that supports the tire and is centered on a shaft.
Two, according to the material classification
The wheel ring is mainly divided into iron wheel ring and light alloy wheel ring according to the material.In today's car market, iron wheel ring is not seen, most models are used aluminum alloy wheel ring, aluminum wheels.
Aluminum alloy materials used in the manufacture of aluminum wheel ring include A356, 6061, etc.Among them, A356 is cast aluminum wheel ring a lot of choice.A356 aluminum alloy has the characteristics of small specific gravity and good corrosion resistance. It is mainly composed of aluminum, silicon, magnesium, iron, manganese, zinc, copper, titanium and other metal elements. Aluminum accounts for about 92%.
Production technology of aluminum alloy wheel ring
Aluminum alloy wheel ring is more suitable for passenger vehicles than steel wheel ring, the current manufacturing process can be divided into three basic, the first is casting, most of the car manufacturers have chosen to use casting process.The second is forging, which is mainly used for high-end sports cars, high-performance cars and high-end modification market.The third is the MAT spinning technology, which was first put into use by Enkei company in Japan. At present, the application of MAT spinning technology in China is less than the former two.
1. Gravity casting method
Gravity casting is a relatively early casting method, which mainly depends on the gravity of aluminum water to fill the mold.
The method has the advantages of low cost, simple process and high production efficiency. However, inclusions in pouring process are easy to be involved in the casting, and sometimes they will be involved in the gas, forming the blowhole defect.The wheel ring produced by gravity casting is easy to produce shrinkage cavity and porosity and the internal quality is poor. In addition, the limitation of the flow of aluminum liquid may lead to the low yield of the complex shaped wheel hub.As a result, the automobile rim manufacturing industry has rarely used this process.
2. Low pressure casting method
Low pressure casting is a process in which molten aluminum is filled into a mold under pressure and solidified and crystallized under pressure.In the same case, the inner structure of low-pressure casting hub is more compact and stronger than that of gravity casting.In addition, the low pressure casting makes use of pressure filling and replenishment to greatly simplify the structure of the pouring system, so that the metal liquid recovery rate can reach 90%.At present, low pressure casting has become the first selection process for aluminum wheel ring production.However, the low pressure casting method also has its disadvantages: casting time is long, feeding, mold change time is long, equipment investment and so on.
3. Forging method
Hot forging →RM forging → Cold spinning → Heat treatment → Machine work → Shot blast → Surface finish
Forging is the change from solid to solid, through the means of beating, pressing, forging to form hub style, this process will not occur liquid changes, are solid changes.Therefore, its mechanical properties are higher than casting, with high strength, good corrosion resistance, size precision and other advantages.The grain flow is consistent with the direction of stress, so the strength, toughness and fatigue strength are significantly better than the cast aluminum ring.At the same time, the typical elongation of the forged aluminum hub is 12%~17%, so it can well absorb the vibration and stress of the road.
In addition, the forged aluminum wheel ring surface without pores, so it has a good surface treatment capacity.
However, the * great disadvantage of forging aluminum wheel ring is that the production process is much more, the production cost is much higher than the casting.Although forged rims have better performance, car manufacturers still mainly use forged rims in most vehicles, and only a few luxury cars are equipped with forged rims.However, citic daika, the leading domestic wheel ring manufacturing enterprise, has successfully entered the passenger car forging wheel ring production line and reduced the cost of forging wheel ring to 1000 yuan, and has begun to supply domestic joint ventures as the original wheel ring.
4. Extrusion casting method
Squeeze casting is also known as liquid die forging, which is the approach of integrating characteristics of casting and forging, to a certain amount of liquid metal poured into the open metal mold directly, through the punch at a certain pressure on the liquid metal, make the filling, solidification and crystallization, and produce a certain amount of plastic deformation in the process of crystallization.Advantages: the mold filling is stable, the metal crystallizes and solidifies directly under pressure, so the casting will not produce porosity, shrinkage cavity and shrinkage porosity and other casting defects, and the organization is dense, the mechanical properties are higher than the low-pressure casting and the investment is much lower than the low-pressure casting method.Disadvantages: as with traditional forging products, the need for milling processing to complete the spokes modeling.In Japan, a considerable number of automobile aluminum hubs are produced by extrusion casting process. The whole process from pouring liquid metal to taking out the castings is controlled by computers with a high degree of automation.At present, extrusion casting is one of the production directions of automobile aluminum wheel ring in the world.
5, special molding: spinning technology
Spinning technology take the lead in put into use in Japan, strictly speaking should also be cast in a, refers to the reuse after rim integral cast type special equipment for mechanical rotating pressure processing, metal processing position is inside the molecular arrangement change, concrete face segmentation compared with general casting products present higher density fibrous, which changes the overall mechanics of metal process.The quality, strength, elongation and other characteristics of the ring made by spinning technology are close to that of the forged ring, and it is easier to produce for the forged ring.In general, MAT spinning technology can not only relatively guarantee the manufacturing cost of hub, but also make the cast wheel ring create a similar weight and strength as the forged wheel ring.Just domestic technology is not mature, the cost is high, so the application is not much.