Lightweight of Magnesium alloy

 Lightweight and smart car has become the global automotive technology development trend. In recent years, with the global pressure on energy-saving and emission reduction and development trends, all countries have formulated strict standards for fuel consumption of passenger vehicles, which put more stringent requirements on fuel consumption and corresponding CO2 emissions of passenger vehicles. More is the development trend of the world's cars. Especially in China, the fuel consumption of automobiles will drop more obviously than that of other countries by 2020, and the pressure of fuel emission will be greater. Reducing the weight of vehicle is the most effective way to reduce the weight of vehicles.

 

 

Lightweight car is the car "downsizing", to ensure stable and enhance performance, based on the energy-saving design of the various components, continue to optimize the model. Experiments show that if the car vehicle weight is reduced by 10%, the fuel efficiency can be increased by 6% -8%; vehicle weight can be reduced by 1% and the fuel consumption can be reduced by 0.7%; for every 100kg reduction of vehicle weight, the fuel consumption per hundred kilometers can be reduced by 0.3-0.6 Rise.

 

Lightweight car trend

In 2016, Professor Ouyang Ming from Tsinghua University announced the content of roadmap for energy-saving and new energy vehicles on behalf of the Strategic Advisory Committee on Energy-saving and New Energy Vehicles development. This roadmap proposes the development of light-weight technologies and is mainly divided into three stages Achieve annual car weight loss.
 
The first phase is from 2016 to 2020, achieving a weight reduction of 10% over that of 2015. Focus on the development of ultra-high-strength steel and advanced high-strength steel technology, including the development of material properties, lightweight design methods, molding technology, welding technology and test evaluation methods to achieve high-strength steel in the automotive application ratio reached 50% Sheet metal stamping technology research and practice in the body, the connection of different materials technology.
 
The second phase is from 2021 to 2025, achieving a weight reduction of 20% over that of 2015. The third generation of automotive steel and aluminum alloy technology as the main line, to achieve a variety of materials such as steel and aluminum mixed body, aluminum body a wide range of applications, to achieve aluminum alloy cover and aluminum alloy parts production and industrial applications, at the same time Increase the production of magnesium alloy and carbon fiber composite parts manufacturing technology development, increase the proportion of magnesium alloy and carbon fiber parts, aluminum cycling amount to 350kg.
 
The third phase is from 2026 to 2030, achieving a weight reduction of 35% over that of 2015. Focus on the development of magnesium alloy and carbon fiber composite materials technology to solve the magnesium alloy and composite materials recycling problems, to achieve a wide range of hybrid carbon fiber composite body and carbon fiber components, breaking the complex parts forming technology and the connection of different parts technology. Bicycle with magnesium alloy to 45kg, the use of carbon fiber accounts for 5% of the car.
 
According to the statistics, in 2016, the amount of bicycle magnesium alloy produced in China is only 7.3kg, which is still a huge gap from the target of 45kg for bicycle magnesium alloy in 2030. The magnesium alloy has a vast market for light-weight automotive applications in the future, with unlimited potential.

 

Magnesium alloy performance and advantages

Low density
The density of die-cast magnesium alloy is only 2/3 of aluminum alloy and 1/4 of steel, the specific strength and specific stiffness are better than steel and aluminum alloy, much higher than engineering plastic, so die-casting magnesium alloy is a good one in many Lightweight structural materials that can compete with these materials in applications.
 
Vibration absorption is good
For example, at a stress level of 35 MPa, the attenuation coefficient of magnesium alloy AZ91D is 25% and that of aluminum alloy A380 is only 1%. At 100 MPa stress levels, AZ91D, AM60 and AS41 magnesium alloys are 53%, 72% and 70% respectively, while aluminum alloy A380 is only 4%.
 
High dimensional stability
The magnesium alloy die-casting due to changes in ambient temperature and time caused by the size of the unstable decrease.
 
High thermal conductivity
Magnesium alloy thermal conductivity (60 ~ 70W / m-1 K-1), second only to aluminum alloy (about 100 ~ 70W m-1 K-1), so good thermal diffusivity.
 
Non-magnetic, can be used for electromagnetic shielding.
 
Good wear resistance
Magnesium alloy also has a good damping coefficient, damping than aluminum and cast iron, the shell can reduce noise for the seat, the hub can reduce vibration and improve the car's safety and comfort. As the lightest engineered material, magnesium alloy is not only the most suitable material for casting auto parts, but also the most effective light weight for automobiles. It has the advantages of light weight, strong shock absorption, good casting performance, high automatization capacity and high die life Quantitative material.
 
Magnesium alloy automotive die casting industry status quo
Lightweight development of the car, so that the demand for magnesium alloy and other light alloy castings increased year by year. Since 1990, magnesium for automobiles has been growing rapidly at an average annual rate of 20%. Magnesium alloys have become an important area for the development of automotive materials technology. Die-cast magnesium alloy with its recyclability and less no cutting technology, advanced, especially for circular economy and energy-saving low-carbon and cleaner production requirements in the car to the development of lightweight process dominates. Major auto parts manufacturers to actively grasp the timing of development, have invested in magnesium alloy automotive die-casting production R & D to. According to the "China magnesium alloy automotive die casting industry analysis report" data show that in 2015, China magnesium alloy automotive die casting industry demand reached 14.9 million tons, an increase of 23.12%. At present, the domestic and foreign automobile enterprises are devoted to studying the body parts (about 30%), engine (about 18%), transmission system (about 15%), walking system (about 16%), wheel 5%) and other magnesium alloy or steel parts.
 
According to the amount of bicycle magnesium alloy used in our country, the market capacity of magnesium alloy automotive die-casting industry in our country will reach 229,000 tons by 2017, and the market capacity will reach 660,000 tons by 2022, with an average annual compound growth rate of 23.5%.
 
The global low volume of magnesium for motorcycles, magnesium alloy automotive demand expansion potential. For a long time, lightweight materials such as high-strength steel, aluminum alloy and engineering plastic have been widely used in various fields of automobile and auto parts manufacturing. Magnesium alloy has not been widely promoted and used for various reasons. Magnesium alloy is mainly used in dashboard Bracket, Steering Bracket, Engine Cover, Steering Wheel, Seat Bracket, Interior Door, Transmission Case, etc. At present, each car in North America uses 3.8kg of magnesium alloy and 9.3kg in Japan. The use of magnesium alloy per car in Europe PASSAT and Audi A4 achieves 14kg, while the average domestic car consumes only 1.5kg.
 
Magnesium alloy in the automotive light of the specific application
 
Car interior construction
Although the corrosion resistance of magnesium alloy is poor, the anticorrosion is not the main consideration for the internal structure of the automobile. Therefore, the magnesium alloy has been widely used in automobile interior construction, especially in the dashboard and steering structure. It is reported that the first magnesium alloy instrument panel props by the General Motors in 1961 die-casting production, than the same parts produced using zinc alloy die-saving 4kg material. Over the past ten years, using magnesium alloy die-casting dashboard pillar made great progress.
 
Magnesium alloy on the seat The application began in Germany in the 1990's, primarily with Mercedes-Benz's seat construction with SLBs using magnesium die-cast in the SL Roadster. Similar to the application of magnesium alloy on the dashboard, in recent years, the seat made of magnesium alloy has undergone a significantly improved process. Now using the thinnest magnesium alloy seat structure can reach 2mm, greatly reducing the weight. Although other materials such as high-strength steel, aluminum, composites and the like are also used, experts predict that the future of magnesium alloys will be a key material for lightweight and cost-effective automotive seat components.
 
Body
Magnesium alloys are limited in body applications but have also been used by OEMs. GM introduced the entire magnesium-alloy die-cast roof frame when it introduced the C-5 Corvette in 1997. In addition, magnesium alloys are used in the retractable hardtop convertible roof and top frame of the Cadillac XLR Convertible. Ford F -150 Trucks and SUVs also use coated magnesium castings as brackets for heat sinks. In Europe, Volkswagen and Mercedes-Benz have pioneered the application of thin-walled magnesium alloy castings in body panels.
 
Chassis
Currently, cast or forged magnesium alloy wheels have been used in many high-priced racing or high-performance sports cars. However, the relatively high cost and potential corrosion problems of magnesium alloy wheels prevent their use in mass production vehicles.
 
The future, lightweight and low-cost magnesium alloy chassis components, such as wheels, engine suspension and control arm and other parts of the production will rely on the magnesium alloy casting process greatly improved, has been developed in aluminum alloy wheels and chassis components Casting process can be successfully adapted to magnesium alloy after modification. In addition, the development of low-cost, corrosion-resistant layers and new magnesium alloys with fatigue and high impact strength will also accelerate the use of magnesium alloys on the chassis.
 
Powertrain
Most of the powertrain castings such as engine block, cylinder head, gearbox, oil pan, etc. are made of aluminum alloy. At present, North American pickups and SUVs have magnesium alloy transmissions, and Volkswagen and Audi's magnesium alloy manual transmissions are also mass-produced in Europe and China.
 
At present, effective tests have been made on dynamometer tests of magnesium-enhanced engine prototypes, which means that more magnesium alloys will be used in power systems in the future.
 
Magnesium alloy in the promotion of the main challenges
Poor corrosion resistance, high cost and high scrap rate is the popularity of "stumbling block" magnesium alloy.
 
Magnesium alloy manufacturing auto parts do exist high cost of casting, reject rate is high, there are potential safety problems. Du Fangci, a consultant of China Association of Automobile Manufacturers, said that magnesium is a very lively element and its corrosion resistance is very poor. The technological capability of our country in respect of the corrosion resistance of magnesium alloy parts is somewhat worse. In addition magnesium in the process of processing, prone to combustion and explosion, there are safety issues. Production site needs strict management to ensure safety in production.
 
As the process of urbanization accelerates, energy becomes more and more in short supply, environmental pollution is more and more serious, and energy conservation and emission reduction have become important events concerning the national economy and the people's livelihood. Whether it is traditional cars, or emerging new energy vehicles are very lightweight body design, in order to achieve the purpose of energy saving.
 
Automotive magnesium alloy boom, magnesium alloy die-casting process is becoming more mature, expanding the scope of applications, large-scale magnesium alloy die-casting car parts will promote the process of lightweight car.
 
 

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