The die-casting industry is highly dependent on the automobile industry, and the rise and fall or change of the automobile industry strongly impact the die-casting industry. This paper summarizes the impact of automotive industry changes on China’s casting industry. At present, the automobile industry is in a period of rapid change. The production and sales of new energy vehicles are soaring, changing the automobile industry’s pattern. The urgent need for new energy vehicles to reduce weight and improve efficiency has accelerated the application of structural parts and the highly integrated die-casting of body parts. The transformation of the automobile industry brings new business opportunities for die-casting but also puts forward new requirements and challenges for die-casting equipment and technology. In this revolution, the die-casting industry should take active actions, fully enhance its technical strength, and expand the market to maximize its benefits. Due to the destruction of the environment, global warming has become increasingly serious, which has posed a major threat to the earth’s ecology and human survival. Countries worldwide have expressed serious concern over global environmental deterioration and climate warming and have reached a consensus on environmental protection. Under the pressure of the environment, countries worldwide have formulated a series of energy-saving and emission-reduction policies, strictly limiting the CO2 emissions of automobiles and making “carbon peak and carbon neutrality” a national strategic goal. The strict implementation of the double carbon policy prompts OEMs to explore new ways and use new technologies, mainly reflected in new energy and lightweight. New energy mainly refers to unconventional vehicle fuel, such as electricity, solar energy and hydrogen energy. New energy vehicles use clean energy and new technology, new structure, higher efficiency, save energy and reduce CO2 emissions, to achieve the purpose of environmental protection. The effect of lightweight energy saving and emission reduction is obvious. When the vehicle weight is reduced by 10%, the energy consumption can be reduced by 6%~8%, and the emission can be reduced by 10%.
In addition, it can improve tire life and reduce acceleration time and braking distance. More importantly, lightweight can also increase the range of new energy vehicles and improve the driving performance of new energy vehicles. In this context, many countries or more automobile main engine factories announced the fuel vehicle ban schedule. Predictably, more stringent emission reduction regulations may accelerate the withdrawal of fuel cars from the market. To encourage the development of new energy vehicles, various countries have given strong promotion and policy support to new energy vehicles. The Chinese government has introduced a series of policies, such as a subsidy policy, carbon credits policy and license issuance, which have played a huge role in promoting the development of new energy vehicles. In recent years, OEMs have been transforming, and the rapid growth of new energy vehicles is changing the pattern of the automobile industry. To provide some ideas for the future development of the Chinese die-casting industry, this paper summarizes the influence of the automobile industry changes.
Changes in the automobile industry
The development of new energy vehicles is changing the auto industry landscape. Under the dual drive of government policy and market, the auto OEMs increase investment and research and development efforts, the performance of new energy vehicles has been significantly improved, and the sales of new energy vehicles have risen rapidly. Figure 1 shows the sales trend of new energy vehicles in China, Europe and North America in recent years; Figure 2 shows the sales and growth rate of new energy vehicles in China in recent years; Table 1 shows the penetration rate of new energy vehicles in China and other countries in recent years; Figure 3 shows the growth curve of the penetration rate of new energy vehicles in China.
Figure 1 Sales trend of new energy vehicles in China, Europe and North America
Figure 2 Sales volume and growth rate of new energy vehicles in China in recent years
Table 1 Penetration rate of new energy vehicles in China and other countries in recent years
Figure 3 Growth curve of the penetration rate of new energy vehicles in China
According to the regional market trend of new energy vehicles, China and Europe were accelerating upward in 2020. In 2021, the overall high level of the European new energy vehicle market is stable, while China’s new energy vehicle market continued to rise in 2021, and the trend in the year’s second half is the strongest. The new energy vehicle market in North America is relatively low but shows a small growth trend. By the end of 2021, the global sales of new energy passenger vehicles in a broad sense reached 9.37 million, among which the global sales of new energy vehicles in a narrow sense of plug-in hybrid, pure electric and fuel cell reached 6.23 million, up 118% year-on-year. New energy vehicle sales in China hit a record high of 3.52 million units, with a growth rate of 157.2 per cent. China’s new-energy passenger vehicle sales currently account for 53% of the global market share, and electric vehicles account for 61% of the market share. The penetration rate of new energy vehicles globally generally shows a rapid improvement trend and has reached 7% this year. Among them, the penetration rate of new energy vehicles in China has reached more than 12%, 22% in Germany, 69% in Norway and 4% in the United States. Although the world’s new energy development is not balanced, the upward trend is obvious. With the United States increasing the penetration of new energy, the world’s new energy vehicles into a new stage of strong development.
The number of new energy vehicles in China has reached 7.84 million, accounting for 2.60% of the total vehicles, an increase of 59.25% compared with the previous year. Among them, the number of pure electric vehicles is 6.4 million, accounting for 81.63% of the total number of new energy vehicles. In 2021, 2.95 million new energy vehicles were registered in China, accounting for 11.25 per cent of the total number of newly registered vehicles, an increase of 1.78 million vehicles compared with the previous year, an increase of more than 151 per cent. At the same time, some institutions predict that in 2022 China’s new energy vehicle sales will reach more than 5 million units, a year-on-year growth of 42%, and the market penetration is expected to exceed 18%. Automobile belongs to durable consumer goods, in line with the “S” curve development law.
Some scholars have pointed out that if the development of an emerging industry conforms to the development law of the “S” curve when the market share exceeds 10%, positive internal impetus and continuous improvement of cost performance will be formed. Then the industry will grow at a fast speed. From this experience, global vehicle electrification has broken through a critical point and entered a steep growth period. New energy vehicles have gradually transformed from government-driven, market-driven and government-driven to a market-driven stage. Data such as sales figures and growth trends show that new energy vehicles already have strong market capabilities. It can be predicted that in the next few years, the production and sales of new energy vehicles will be enough to change the pattern of the automobile industry.
Promote the die-casting industry
Accelerate and improve the application of aluminium alloy structural parts
Replacing traditional fuel vehicles with new energy vehicles requires major technological breakthroughs, one of which is to increase the range. At present, it seems that the key to breaking through this dilemma is to develop high-energy batteries or other new energy sources and, secondly, lightweight vehicles. In the lightweight process of traditional fuel vehicles, die casting plays an important role with a series of advantages such as good forming, rib structure, high integration, easy handling and high efficiency. It replaces many ferrous metal castings and expands the application scope of die casting. Entering the stage of new energy vehicles, the requirements for lightweight are more prominent and urgent. New energy vehicles promote the lightweight process and the application of die-casting structural parts.
Aluminium alloy dies castings are mainly used in automobiles, machinery, electronics, communications, instruments, household appliances and other fields, among which auto parts account for the largest proportion, accounting for about 70%. The automobile industry is the pillar industry of the die-casting industry, and there is a significant positive correlation between the output of die-casting and automobiles. The trend of the output of die casting and the output of automobiles in recent years is shown in Figure 4. Due to the continuous increase of automobile production, the production of die casting has increased, and the increment of more than 10% for more than ten consecutive years. As can be seen from Figure 4, the increment of die casting is composed of two parts. The increase in automobile production drives one part, and the other part is driven by the increase in the consumption of automobile bicycle die casting. One of the important reasons for the increase in the consumption of bicycle die casting is the development of new energy vehicles in recent years, which accelerates the application of structural parts. Especially in 2020, in the case of declining car sales, the production of die-casting increased. The main reason should also be that the number of structural parts greatly contributed. The upward trend will be more obvious in 2021, indicating that new energy vehicles have a significant impetus to applying structural parts.
FIG. 4 Trend of die casting output and automobile output
The production technology of automotive structural parts has made great progress. After the initial batch of structural parts, such as the A-column and shock absorber tower, it has expanded to structural parts with a relatively difficult process, such as the rear side beam and subframe. The specific structural parts are shown in Figure 5. The damping tower was originally composed of 10 parts, which were integrated into one piece after production by the die-casting process. The rear longitudinal beam was originally composed of 18 parts integrated into one piece after die casting. The subframe die-casting process is difficult; before, most of the low-pressure or gravity processes changed to die casting, shape and size accurate, thin wall thickness, and weight reduction, greatly improving production efficiency. The performance of castings, such as the hanging arm and the rear longitudinal beam, is relatively high, and heat treatment is generally required. Currently, vacuum die casting is used to ensure the heat treatment and weldability of the casting.
Figure 5. Typical structure
2.2 Application of conversion Die casting The consumption of some die-casting parts in traditional fuel vehicles and new energy vehicles has changed. The consumption of die casting has increased or decreased, and the change mainly comes from the power and transmission systems. In the fuel car, the power and transmission system, including the engine cylinder block, gearbox, and clutch housing, such as this part of the die casting consumption is relatively large, and the engine has about 16 die casting. The transmission system has about 8 die casting. But in an electric vehicle, there are about four die castings for the drive system and about two for the driveline. Compared with the traditional fuel car, the electric vehicle has less application in the power system and transmission system. However, the power and transmission system of hybrid electric vehicles in new energy vehicles includes both fuel and electric systems, and the consumption of die casting has increased. If ICEE (die casting machine clamping force (cycle time) is used to represent the application index, size and quantity factors of die castings), then the application index of die castings for fuel cars, electric cars and hybrid cars is shown in FIG. 6.
Figure 6 three models of electric power and transmission system of die casting application index while the dosage of the die casting in terms of power and transmission system is reduced, but in SanDian systems, increasing the dosage of die casting can partially compensate for power and reduce the dosage of the drive system for die casting, the typical application is the battery bracket, as shown in figure 7. As electric vehicles continue to increase, the average amount of aluminium used in battery cases and motor casings will increase rapidly, with the amount of aluminium used in battery cases accounting for nearly two-thirds of the average increase in future aluminium consumption. To increase the battery capacity, the size of the current onboard battery is larger, and the battery carrier is larger. Some models are up to 2 m in length. Most die-casting machines used are above 4 000 t, and the maximum can reach the requirements of ten thousand tons. In addition, the die-casting process produces the electric casing, end cover, rotor and junction box shell, which makes up for the amount of die-casting parts, as shown in Figure 8.
FIG. 7 Various battery carriers
FIG. 8 Die casting of electric vehicle drive system
If the use of dual motor drive, the amount of die casting is more powerful to compensate.
Promoting Integrated die Casting Technology Under the multiple pressures of weight reduction, efficiency improvement and cost reduction, Tesla proposed the integrated body-forming casting method in 2019. The rear body of Model Y was produced by integrated forming and die-casting, which integrated more than 70 parts originally required by multiple processes into one, reduced assembly and welding procedures, reduced the weight by about 30% and reduced the manufacturing cost by about 40%. After integrated die-casting, the body weight of Model Y is only 66 kg, which is 10-20 kg lighter than the same part of the smaller Model 3, as shown in Figure 9. The CTC version of Tesla Model Y4680 will apply 2-3 large die castings to replace the entire vehicle body composed of 370 parts, which will further reduce the weight by 10% and increase the subsequent mileage by 14%. There are also die-casting manufacturers planning or implementing integrated die-casting automobile chassis or skateboard automobile chassis, as shown in Figure 10 and Figure 11. If the all-aluminium die-cast body is adopted, the weight will be 200~250 kg, while the weight of the steel body of the same grade will be 350~450 kg, reducing the weight by about 150~200 kg.
FIG. 9 Integrated die-casting of Model Y body rear parts
FIG. 10 Integrated die-casting frame
Figure 11. The integrated die-casting scheme of skateboard chassis greatly simplifies the manufacturing process, eliminates the accumulated errors caused by the connection of a large number of parts, improves the manufacturing accuracy, saves a lot of time cost, equipment cost and labour costs, and greatly reduces the manufacturing cost of the whole vehicle. The technical advantages of integrated die casting, such as weight reduction, efficient manufacturing and cost reduction, have attracted great attention from various OEMs. Some people believe that integrated die-casting technology is revolutionary in the automobile manufacturing industry and will become a trend in future automobile manufacturing. Many OEMs say they will follow up on the integrated die-casting technology or have entered the implementation stage. Integrated die-casting provides a new method for main machine factories to manufacture automobiles and provides opportunities for auto parts die-casting enterprises. Many auto parts die-casting enterprises actively cooperate with OEMs to jointly develop integrated technology, increase investment and financing intensity, expand production capacity, accelerate the layout of integrated die casting, and strive to gain market share in integrated die casting. Industry insiders estimate that in 2025, the sales volume of models equipped with integrated die casting is expected to rise to 3.03 million, and the market space for integrated die casting will be increased from 900 million yuan in 2021 to about 27 billion yuan in 2025. The market space is huge. At present, the integrated forming die casting is mainly used in new energy vehicles to reduce body weight, reduce energy consumption and improve the driving range. The industry believes that the market share of new energy vehicles will increase to 50 per cent by 2030. If large integrated die casting permeates to fuel models, the application prospect of super large integrated die casting is very considerable.
It should be noted that integrated die casting increases the overall weight of die casting and significantly impacts the weight increment of die casting. However, the number of die castings may be reduced because the integrated die casting has a higher degree of integration, which may combine several adjacent die castings, such as the rear side beam, shock absorber tower or chassis longitudinal parts, into one piece as shown in Figure 12. Therefore, the production of this type of die-casting enterprises should respond in advance.
FIG. 12 High integration of integrated die casting
There is no strict definition of the tonnage of the die casting machine, which belongs to the super large die casting machine in the professional field. It is generally considered that the die casting machine which can die cast the large integrated parts of the body is considered the super large die casting machine, and the clamping force is more than 6 000 t. The weight of the die-casting parts of the integrated body can generally reach more than 60 kg, and the pouring weight can reach more than 100 kg. The size is about 1 700 mm× 1 500 mm×800 mm, which is beyond the limit of the die-casting products. Under this background, the manufacture of super large die casting machines becomes inevitable. Large-scale integrated die casting has opened the era of super large die casting machines. In just 3 years since the concept of integrated die casting was put forward, die casting machine manufacturing enterprises have developed rapidly, and 6 000 t super large die casting machine has been used to produce integrated die casting of automobile parts. The 8 000 t and 9 000 t super large die casting machines have entered the market and can form the production capacity in a short time. The 15 000 t die casting machines have also entered the research and design stage. FIG. 13 shows the 9 000 t die-casting machines. The recognition of integrated die casting by auto OEMs will further popularize integrated die casting, and the demand for large die-casting machines will enter the normal demand and continue to exist.
Developing new energy vehicles brings new business opportunities to the die-casting industry, but the die-casting industry faces some problems and challenges.
The integrated die casting of automotive structural parts cannot be separated from the super large die casting machine. The super large die casting machine has just started, is in the leading-in period of development, and has not reached the mature stage, so there are bound to be many problems to be solved. Firstly, the overall structure should be further optimized to improve the rigidity and strength of the machine structure, improve the scientific rationality of the design, and ensure the stability of the machine’s overall structure. The mass of moving parts in the injection system of a super large die-casting machine increases significantly, and the dynamic response characteristics of the injection process will be greatly affected. To meet the forming requirements of large integrated castings, the injection performance should be improved, and the technical parameters such as injection speed, injection pressure and dynamic response speed should be further improved. The size of the parts of the super large die-casting machine increases, and the processing and manufacturing difficulty increases. A template can be more than 100 tons, using ductile iron integral casting forming, and need an exquisite casting process to ensure good periodization to meet the performance requirements. Secondly, the need for large processing equipment can achieve the required processing accuracy. At present, the most prominent problem is reducing the failure rate of the equipment and improving the stability of equipment operation and uptime of equipment. 3.2 Large integrated die casting technology and process The size and complexity of large integrated castings have increased significantly, leading to a significant increase in the difficulty of the die-casting process. Currently, the pouring weight of integrated body parts is up to 100 kg, and the filling time and forming process are prolonged, so it is very important to control the die-casting process. Ideal filling and forming process control, including filling speed control, forming pressure control, mold temperature control, product front-end and end performance consistency control, mechanical properties (tensile strength, yield, elongation, bending Angle, etc.), and pass rate control, are dependent on the continuous improvement of die casting technology and process. Currently, the pass rate of large integrated die casting is about 40%~60%, the pass rate is low, and the production cost is high. The price of integrated die casting will not always be high, and the production efficiency must be improved by reducing the rejection rate. Only through the continuous exploration and improvement of die-casting technology can the pass rate be improved. 3.3 Large-scale integrated die-casting mold is very important to the success of die-casting and has been considered the key process equipment of die-casting production. The super large mold has reached a leap in size, and there is no experience to follow in the design of super large mold at home and abroad. The wall thickness of ultra-large integrated die castings varies greatly, the structure is complex, the filling distance is long, the flow path changes a lot, the gating system design is difficult to meet various requirements, and the ideal filling process and solidification process is even more difficult to achieve. Mould in the premise of meeting the requirements of die casting, at the same time, consider the durability of the mould. The durability of the mould directly affects the production cost. The die-locking force of the integrated die-casting machine is larger, the stress applied to the mold is larger, and the possibility of damage to the mold is increased. The impact effect of integrated die casting on the mould is greater; the working conditions are bad, affected by various stresses, and may lead to premature cracking failure of the mold, so the mold design and materials and heat treatment requirements are higher. The thermal management of die casting becomes more and more important in the process of large-scale integrated die casting. However, due to the large-scale die casting, the thermal control of die casting becomes more difficult. Good cooling/heating system design is a prerequisite for effectively controlling mold temperature in production. Mould temperature control greatly influences the quality of integrated die casting. Too high or too low a temperature will cause casting defects. 3.4 Alloy materials of integrated die casting large-scale integrated die casting belongs to the structural parts of the automobile body. To ensure the car’s driving safety, the mechanical properties of the car’s structural parts are required to be high. The toughness-related structural parts generally require tensile strength ≥180 MPa, and elongation ≥10%; For strength-related structural parts, tensile strength ≥210 MPa and elongation ≥7% are generally required. To achieve the required mechanical properties, it is common practice to heat treat the die casting. Because of its large size, thin wall and complex structure, it isn’t easy to heat treat the integrated body parts. Improper treatment will lead to casting deformation, surface bubbles and other problems, which may lead to casting scrap. Secondly, heat treatment of large integrated castings requires large heat treatment furnaces and additional castings fixed supports, which greatly increases the cost of castings. Therefore, the innovation of alloy materials is needed to develop heat-treatment-free aluminium alloy materials; that is, the required alloy structure and mechanical properties can be obtained in the cast state. Previous studies have shown that the new integrated die-casting aluminium alloy without heat treatment can improve the overall mechanical properties by 20%-30%, which can meet the collision requirements. After die casting, heat treatment is not needed, and the next process can be directly entered, saving time more than 6 h and eliminating heat treatment equipment and tooling. Although some progress has been made in the development of heat-free alloys, there is still much work to be done. 3.5 Large-scale integrated die casting peripheral equipment Large-scale integrated die casting eliminates the possibility of manual operation. All operations in the die casting unit must be completed by automatic peripheral equipment, including spraying, pouring, parts taking, edge cutting, cleaning and other processes. Relevant enterprises must develop peripheral equipment suitable for large-scale integrated die casting as soon as possible to effectively organize production, shorten cycle time and improve production efficiency. 3.6 Competition intensifies the changes in the automobile industry, making many enterprises see the development opportunities of large-scale integrated die casting. Enterprises in the industry actively raise funds to buy super large die casting machines early to carry out the layout of large integrated die casting. This opportunity has also attracted companies from other industries to enter the field of large-scale integrated die casting to gain development and interest in this field. There is also a trend for auto OEMs to produce integrated die castings independently. There are new auto manufacturers like Tesla that directly set up die-casting workshops to supply integrated large-scale die castings by themselves. The size of the integrated die casting is large, the wall is thin, and it is easy to produce deformation. It needs a stable transport bracket and is unsuitable for long-distance transportation. The automobile main engine factory has strong advantages in entering the field of die-casting integration. The integrated die-casting workshop is built in parallel with workshops such as stamping, welding and electric driving for painting. After necessary processing, it can directly enter the automobile assembly workshop, shorten the transfer distance of parts and increase loading efficiency. If too many new enterprises exist, it will intensify the industry’s competition trend, and enterprises should be prepared to face the competition. 3.7 Risks and opportunities coexist
New energy vehicles bring new development opportunities for the die-casting industry and promote the rapid development of the industry. However, we should also recognize that while bringing opportunities, there are risks or uncertainties. Affected by the epidemic and some other factors, the global core shortage and other conditions repeatedly affect the global automotive industry’s prosperity. Die casting is highly dependent on the automobile industry. If this effect brings a downward trend to the automobile industry, it will affect the die-casting terminal enterprises.
Raw material price rises, also bring adverse effects to die-casting enterprises. Since 2021, the price of aluminium ingots has soared, with the highest price exceeding 22,000 yuan/ton, increasing by more than 50%. Continuous high or volatile aluminium prices may bring systemic risks but also cause difficulties for downstream enterprises and increase the burden. Integrated die casting was proposed and realized by Tesla, and other auto OEMs actively followed up. Suppose the promotion of automobile and enterprise integrated die casting is not as expected, or the integrated die casting is affected by other factors. In that case, the development of integrated die-casting will be delayed. Attention should also be paid to whether changes in subsidy policies for new energy vehicles and the implementation of dual carbon targets will affect the development of new energy vehicles. The war between Russia and Ukraine is likely to impact the global economy, and the impact on the energy, raw materials and auto sectors remains to be seen. Natural disasters or financial market turmoil could disrupt supply chains or hurt consumer markets, which could eventually spill over into the die-casting market
The continuous and rapid development of China’s auto industry provides a huge space for the development of the die-casting industry. Changes in the automotive industry are becoming a new driving force for the development of the die-casting industry. Under the new situation, our country’s die-casting industry should seize the opportunity of the great development of automobiles and lightweight to improve production and technology and expand the market of automobile die-casting parts. Die-casting enterprises should strengthen cooperation with automobile factories to explore and develop die-casting resources to increase the amount of aluminium used in bicycles. Further play to the advantages of technological progress, continue to strengthen the research and development and application of high vacuum process, mold thermal management, efficient spraying, high-performance alloy, large mould design and manufacturing and other new technologies, improve the comprehensive technical level of die casting, improve the quality of die casting, improve the competitive ability to die casting process.
Further strengthen the high efficiency, intelligence, and excellent performance of ultra-large die-casting equipment manufacturing for the integration of die casting to provide strong equipment support. Die-casting enterprises should actively transform to Industry 4.0 and green and low-carbon upgrading to promote the high-quality development of die-casting enterprises. In the face of new trends, we should follow the trend and take advantage of new opportunities. China dies casting depends on continuous technological progress, on the positive progress of the whole industry, seizing the opportunity will in the great reform of the automobile industry to obtain greater dividends.