Problems and development trend of casting technology in automobile industry

Although the amount of magnesium used in automobile industry is increasing, its application in automobile is still limited. At present, the main material in the automobile industry is still steel, followed by aluminum. There are several reasons why magnesium alloy has not been widely used in automobile industry.

a. Magnesium alloy has poor corrosion resistance, high temperature creep and low strength. In addition, its low temperature working ability and yield limit are limited [5]. High performance magnesium alloy needs to be researched and developed. At present, the basic data accumulation of magnesium alloy is not enough, there is no systematic mechanical property test, and there is not enough data in corrosion, thermal expansion and mold design, which makes the design of automobile parts more difficult and costs more.

b. With the rapid development of magnesium alloy, the new casting technology, technical personnel and equipment are insufficient. In recent years, a series of new casting technologies have been developed, such as vacuum pressure casting technology, oxygen filling pressure casting technology, squeeze casting technology, etc., which have greatly improved the properties of magnesium alloy. For example, the continuous casting and rolling technology of magnesium alloy has a good application prospect. At present, most of the domestic research is still in the laboratory, and there is little industrial production. In addition, these new technologies belong to the confidential technology of automobile manufacturers, which can not be widely used in the field of automobile. Magnesium alloy casting is a system engineering, which integrates design, manufacturing and research. It needs more comprehensive knowledge, experience and research and development ability of magnesium alloy casting workers. The new casting technology needs new equipment to match with it, so as to produce better castings and expand the application range of magnesium alloy. However, the investment and operation cost of the new equipment is high, so the existing equipment can be improved to reduce its production cost and production cycle, and finally expand the application of magnesium alloy in the automobile industry.

The North American magnesium strategic alliance plans to reach an average mass of 158 kg by 2020. According to the current average mass of 3 kg of magnesium for automobile and the annual growth rate of 20%, there is still a big gap between China and North America by 2020. To narrow this gap, the main development directions in the future are:

a. Improve the material properties of magnesium alloy. The corrosion resistance of magnesium alloy is poor. For the parts of automobile chassis and walking system exposed to the outside, especially in coastal areas, they should meet the requirements of the use environment for corrosion resistance. The research on high corrosion resistant magnesium alloy has become an important direction of magnesium alloy development [20]; currently widely used commercial magnesium alloy, such as AZ91D, due to the decomposition and softening of precipitates when working at a temperature above 120 ℃, The existing magnesium alloy is difficult to meet the use requirements for the high performance gearbox and crankcase whose working temperature is over 130 ℃. The development and application of high heat-resistant magnesium alloy is an important field in the application of magnesium alloy in the automobile industry in the future. At the same time of lightening automobile parts, its safety and reliability are very important. Important interior parts such as steering wheel, steering wheel column, seat frame and door frame, in addition to meeting the requirements of formability, more importantly, the material should have high strength and toughness, The alloy of AM60 and AM50, which can reduce vibration and keep the parts from fracture when being hit by heavy blows, has better plasticity, but lower strength, and the casting fluidity and corrosion resistance are not ideal. The magnesium alloy with higher strength and toughness and excellent casting fluidity should be developed vigorously.

b. New casting technology, high skilled personnel and new equipment will become the three elements of the development of magnesium alloy casting.