Low pressure casting aluminum wheel hub crack formation causes and improvement measures

Low-pressure casting Can achieve a high degree of mechanization and automation, increase productivity (10 ~ 15 type / h), it can also reduce many human factors that are detrimental to the production process, improve the rate of finished products, and greatly reduce the labor intensity of workers. However, the quality of low pressure casting by the process plan, process parameters, mold structure and manual operation and other factors, any design unreasonable or improper operation of the link may lead to low pressure casting defects. The generation of aluminum wheel cracks is an important factor that affects the production cost and productivity of enterprises. Therefore, it is particularly important to discuss the causes of cracks in low pressure casting aluminum wheels. Next, I will discuss with you in China low pressure casting plant casting aluminum Formation and elimination measures of cracks in automobile wheels.

What is a low-pressure cast wheel?

Low pressure casting wheels are manufactured by low pressure casting technology, which provides high density, high strength and good quality control. The process injects a liquid alloy into a mold at low pressure, where the alloy cools and solidifies. Low pressure casting produces wheels with high density, uniform structure, good strength and toughness, and is suitable for mass production.

The production process is divided into several steps: first, the liquid alloy is injected into a mold; next, the alloy is cooled and solidified; and finally, the wheel is completed through heat treatment, finishing and painting processes. This process reduces air bubbles and impurities, improves strength and precision, and enhances the safety of the wheel.

together withGravitational castingLow-pressure casting is more efficient and produces better product quality than low-pressure casting. Gravity casting relies on gravity to flow the metal, which can lead to uneven distribution, compromising quality and safety. Low-pressure casting controls the flow of aluminum alloy by applying pressure, ensuring wheel accuracy and strength.

As a result, low-pressure cast wheels are becoming increasingly important in automotive manufacturing, providing high efficiency, quality and safety.

Low Pressure Casting WheelsApplications and Uses

Automobile Industry
Low-pressure cast wheels are widely used in the automotive industry, especially for high-performance cars, electric vehicles and SUVs. commonly used materials include aluminum alloys (e.g. ADC12, A380) and magnesium alloys (e.g. AZ91D).
The process enables the manufacture of lightweight and strong wheels that improve vehicle handling, fuel efficiency and safety for high loads and high speeds.

Motorcycles & Bicycles
Low-pressure cast wheels are also available for motorcycles and high-end bicycles.
Wheels produced through this process provide high strength and durability for extreme riding and high speeds while remaining lightweight.

Commercial Vehicles and Heavy Duty Vehicles
Commercial vehicles, trucks and heavy-duty vehicles also use low-pressure cast wheels.
This process enhances the load-bearing capacity and toughness of the wheel hubs, ensuring stable operation of the vehicle under severe working conditions and improving safety and durability.

aerospace
Low-pressure casting technology also has applications in the aerospace sector, mainly for the manufacture of hubs for lightweight spacecraft and drones.
This process provides high-strength, low-weight components that meet aerospace's stringent requirements for precision and performance.

Low-pressure casting of aluminum wheel hub crack shape produced by the reason

The main factors affecting crack generation

For the same alloy, whether the wheel cracks or not often depends on the wheel construction, process parameters and mold temperature.

The effect of improper wheel structure design on wheel cracking

(1) Improperly sized inside fillets are the most common cause of thermal cracking in hubs, because the sharp corners of the hub generate high stresses when the hub cools. A small inner fillet can cause thermal cracking even if the shrinkage is good.

(2) Sudden changes in hub cross-section can lead to different cooling rates, which can generate large stresses even if the shrinkage is good, resulting in cracks or crazing of the hub after solidification.

Effect of unreasonable process parameters on wheel cracking

In low-pressure casting, due to too long holding time or too long liquid-raising pipe, the liquid in the liquid-raising pipe solidifies, and the wheel casting is subjected to a certain tensile force when ejecting, which leads to cold cracking of the wheel hub. Therefore, the design of reasonable pressure holding time and ascending liquid system is of great significance to reduce the cracking of wheel hub when ejecting.

Effect of Mold Temperature on Wheel Cracking

Low-pressure casting mold temperature determines the solidification mode of the alloy liquid, directly affects the casting's internal surface condition, is one of the main causes of dimensional deviation and deformation and other defects, also has a great impact on productivity. Mold temperature with casting quality, die casting cycle, die casting temperature and mold cooling method and change.

From the heat transfer point of view, increasing the mold temperature can reduce the intensity of heat transfer between the metal and the mold and extend the flow time. It has also been shown that increasing the mold temperature can also slightly reduce the interfacial tension between the liquid metal and the casting. As the mold temperature increases, the filling time decreases slightly, i.e., the filling capacity increases with the mold temperature. Therefore, an appropriate increase in mold temperature is conducive to stress reduction. If the mold temperature is too low, the casting is cooled too quickly in the metal type, the casting solidification speed of each part of the casting is different, the casting cooling is not uniform, resulting in thermal stress and deformation, leading to the finished casting thermal cracks, residual stress and residual deformation, high mold temperature is not conducive to the organization of the small crystalline, the liquid metal is easy to absorb and contraction, increase the casting to produce porosity, shrinkage and shrinkage defects. In order to unify this contradiction, the mold temperature can be increased appropriately in the absence of casting defects. In order to unify this contradiction, the mold temperature can be appropriately increased in the absence of casting defects. The general wheel crack site is in the spoke or the inner wall of the wheel.

Improvement measures

(1) Reasonable design of the liquid-raising system. Due to too long holding time or too long lift tube, the liquid in the lift tube solidifies, and the wheel casting is subjected to a certain tensile force when it is ejected, which leads to cold cracking of the wheel hub. Therefore, a reasonably designed liquid-raising system is of great significance in reducing the cracking tendency. Liquid-raising system refers to the liquid metal channel that enters the cavity from the crucible, including liquid-raising pipe, insulation sleeve and casting pouring system. The dimensions of these components directly affect the distance between the liquid level in the crucible and the gate in the casting. The longer the distance is, the faster the liquid metal cools during pouring, which can easily lead to early solidification of the liquid-raising tube channel. So be careful:
① Shorten the distance between the liquid level in the crucible and the gate in the casting. This distance involves equipment, process, mold and other aspects, so it should be considered comprehensively and should be shortened.
②Improve the thermal insulation sleeve. Appropriately increase the inner diameter of the insulation sleeve, expand the thickness of the insulation layer, the use of aluminum silicate fiber felt and other materials with good thermal insulation properties as a thermal insulation sleeve.
(iii) Increase the diameter of the ascending tube appropriately. To prevent early solidification of the ascending tube, the diameter of the ascending tube should be increased appropriately.
(2) Design reasonable hub structure. When designing the hub structure, the sharp angle structure and the sudden change of cross section should be avoided, and the structure with rounded corners or uniform thickness should be used.
(3) The temperature of the mold should be increased appropriately without casting defects.

Choosing the right low pressure casting wheel plant

Low pressure casting is a simple and commonly used casting process, but it also requires knowledge and experience in the industry, so outsourcing to the right service provider like us is a better approach.

It is a wise decision to choose Hersin as the cooperation factory for low pressure casting wheel, because Hersin has more than 20 years experience in aluminum casting with low pressure casting, gravity casting and high casting technology.

Frequently Asked Questions and Answers

1. What are the advantages of low-pressure cast wheels?
High strength, uniform metal structure, lighter weight and better safety.

2. What is the difference between a low-pressure cast wheel and a conventional cast wheel?
Low-pressure casting wheels ensure a more uniformly dense wheel by applying low-pressure injected metal, which reduces porosity and cracks and improves strength and precision.

3. What materials are commonly used for low-pressure casting hubs?
Commonly used materials include aluminum alloys (e.g., ADC12, A380) and magnesium alloys (e.g., AZ91D), which have lightweight and high-strength characteristics.

4. Why are low-pressure cast wheels suitable for high-performance vehicles?
Lightweight and strong, low-pressure cast wheels improve vehicle handling, acceleration and fuel efficiency, making them particularly suitable for sporty cars and electric vehicles.

5. What are the disadvantages of low-pressure cast wheels?
The low-pressure casting process is relatively complex, with longer production cycles and higher costs than traditional casting methods.

6. How can the quality of low-pressure cast wheels be improved?
The quality of the wheels can be improved through precise control of temperature, pressure and cooling rates, optimized mold design and removal of impurities.

7. What types of vehicles are low-pressure cast wheels suitable for?
Low pressure casting wheels are widely used in high performance cars, sports cars, electric vehicles, commercial vehicles and heavy duty vehicles.

8. What is the production process for a low-pressure cast wheel?
The production process includes steps such as melting the alloy, low-pressure injection into the mold, cooling and curing, subsequent heat treatment and surface treatment.