1． Automobile manufacturing industry
(1) Typical multinational industry
As equipment for all walks of life, as a means of transportation, and as a durable consumer product for families, automobiles have a history of only a hundred years. But there are now more than 600 million cars in the world, with an average of less than 10 people per car. Developed countries such as the United States are developing rapidly on the wheel of automobiles. The rapid advancement of information technology has brought the world into the information age, with each other becoming more closely connected and the earth appearing much smaller. Economic globalization is no longer a prediction by scholars, but a reality. The WTO provides a common "game" plan for globalized economic exchanges. More and more countries feel that the status of their own economies is closely related to the prosperity of the global economy.
The Asian financial crisis a few years ago affected most countries. The economic prosperity of the United States for several consecutive years has enabled many countries to take advantage of the situation for development. Now the U.S. economic growth rate has dropped significantly, and its negative impact will also be global.
As a typical multinational industry - automobile manufacturing industry; it plays an important role in the formation of economic globalization. The automobile industry not only makes large-scale overseas investments, but also cross-border mergers and acquisitions in recent years. Strong alliances are common, and multinational companies have been formed one after another. For example, the "Daimler-Chrysler" multinational company that shocked the world came into being a few years ago. And born. The purpose of forming a multinational company is to achieve maximum sharing of resources, complementary advantages and low-cost economies of scale. When the U.S. economy gradually entered recession, Daimler-Chrysler, a multinational company located on the other side of the ocean in Germany, had to announce that it would lay off 26,000 people in the next three years. Naturally, multinational companies were the first to be affected by the cross-border impact. Obviously, as a typical multinational industry, the organization of global automobile manufacturing is undergoing fundamental changes. In line with the pace of globalization in automobile manufacturing and sales, the global procurement system for automobile parts is also further developing. Faced with the new competitive situation formed by the growing liberalization of trade and investment, it is difficult to develop a country's automobile industry in a closed state without the general pattern of division of labor in the global automobile industry. Technology introduction and persistent localization efforts can play a role in substituting imports when the domestic market is well protected. However, due to the advantages of economies of scale on a global scale, this cannot be achieved in any country's internal market. Therefore, as a typical transnational industry, the automobile industry of each country should be integrated into the division of labor system of the global automobile industry as much as possible, and continuously improve its international competitiveness by participating in global competition.
(2) China’s automobile industry has attracted much attention
Whether from the perspective of the trend of economic globalization or the characteristics of the automobile industry as a typical multinational industry, the development of China’s automobile industry Survival and development are inseparable from domestic and foreign automobile demand markets and the direction of world automobile development.
Regardless of the United States or the European Union, during the negotiations on my country's accession to the WTO, one of the main points of contention with China was the terms related to automobiles. As large-scale restructuring and mergers in the automobile industry continue, it is expected that by 2005 there will be a pattern of 5-6 large multinational groups controlling the global automobile industry. Therefore, developed countries regard China, the only remaining potential market for automobiles with the largest potential market in the world, as a battleground for their global automobile development strategy. They are very concerned about the Chinese automobile industry and they promote their development through direct investment and international trade. competitive strategy.
China's automobile manufacturing industry started with trucks. The scale of general-purpose medium and heavy-duty trucks has ranked among the top in the world, and is more suitable for China's national conditions and needs. While cars started late and are not large in scale, multinational companies are optimistic about China, the world's largest potential car market. This refers to China's car market, especially the family car market, and the comparative advantage of trucks in the Chinese automobile industry. The huge market potential of cars has attracted great attention from all walks of life in China.
The automobile industry has a high degree of industrial correlation, a strong driving force for the economy, and has ripple benefits and guiding effects on the entire national economy. It is inevitable that it will be highly valued by all parties.
China's truck manufacturing industry has economic scale and a relatively complete domestic marketing system. As long as it adheres to independent and open development, China's FAW and Second Automobile Works are likely to become the first or second largest truck manufacturers in Asia. , and the car industry has great development potential. According to analysis, when the annual household income in our country reaches more than 80,000-100,000 yuan, the family demand for cars will increase significantly.
At present, the number of households nationwide with an annual income of more than 90,000 yuan has reached about 7 million, and by 2005, the number will reach more than 40 million. By then, even if only 5% of households buy cars, the annual demand for cars will reach 2 million units. Last year, a sample survey was conducted in seven major cities across the country. About 70% of households expressed their intention to purchase a car in the next five years. In 2000, my country's total automobile sales were 2.08 million, of which only 610,000 were sedans, accounting for about 30% of the total automobile sales. More than 70% are cars. The potential demand for cars in my country is huge.
In the 10th Five-Year Plan formulated by our government, it has been clearly stated: to develop economical cars, support the transformation of key automobile industries, encourage cars to enter households, and improve the manufacturing of automobiles and key parts level, we must actively develop high-efficiency, energy-saving, low-emission vehicle engines and hybrid power systems.
Of course, how to promote the potential huge market to become a realistic big market requires long-term unremitting efforts. Currently, we are vigorously standardizing the automobile consumption environment and usage environment. In order to meet the ever-changing diversification of cars, , personalized needs, car manufacturing companies are also formulating development strategies and medium- and long-term plans, further expanding international strategic cooperation, and accelerating the development of various cars that meet the different needs of different users in China. The entire Chinese automobile industry, including trucks, cars and other passenger cars and commercial vehicles, will surely undergo the test of fierce competition and large-scale restructuring in a transnational industry such as the automobile industry after joining the WTO and no longer receiving special government protection. , and to become part of the global automobile industry, it is possible for the Chinese automobile industry to become a strong player in the manufacturing link, but it will take a longer time to make great progress in the product development link and marketing link.
2. Overview of China’s automotive casting industry
1. Young industry
Generally speaking, as an ancient foundry country with thousands of years of casting history, China's automobile casting industry has only a history of more than 40 years. Such a young Chinese automobile casting industry is basically in the A self-sufficient foundry affiliated with the main engine factory established under the planned economic system. This is also because the automobile industry itself is an emerging infant industry in China, and the ability and level of the whole society to cooperate in supplying goods to the automobile industry were extremely limited at that time. Therefore, the "big but complete, small but complete" approach of the automobile foundry was also a last resort. Automobile castings are more complex than those in traditional industries, have higher quality requirements, and faster delivery times. Therefore, casting equipment and facilities with a certain level of higher productivity must be used, and the capital investment is also higher. However, since it is affiliated to the OEM and is not the main specialty of the OEM, the actual investment that can be arranged is very limited. Even if some foreign equipment is introduced, due to limited funds, only some of the main equipment can be introduced, and there is no ability to introduce a full set of equipment. This results in the technical level of the professional casting factory being lower than that of the mechanical processing, assembly and other professional factories that are also affiliated with the main engine factory. It is backward and has low production efficiency, which often becomes the "bottleneck" that restricts the main engine. After struggling through the initial stage, China's automobile casting industry is facing the increasingly higher requirements for castings from its users - the automobile industry. It is also facing the society's The foundry industry has increasingly stringent requirements. In order to achieve sustainable development strategies, automobiles must achieve energy conservation and environmental protection goals. Therefore, automobiles must strive to improve fuel economy and strictly control emissions to achieve such goals. Self-weight is an important measure. In order to reduce the self-weight of automobiles, automobile castings must be lightweight and precise. The requirements for lightweight and precision of automobile castings have set the level of casting technology, equipment and molds for automobile iron castings in my country. The improvement in the level of casting raw and auxiliary materials has created huge pressure. However, my country's automotive aluminum casting has only just begun with the rise of the car industry in recent years, which shows that my country's automotive magnesium casting has almost started from scratch. The pressure is huge. On the other hand, society can no longer forgive the foundry industry, a large energy consumer and polluter, for letting it go. The protection of resources and the protection of the environment have become the common sense of everyone. There is no choice for the road of high efficiency, energy saving, material saving and environmental protection. The young Chinese automobile casting industry has a long way to go.
2. Several typical automobile castings. (1) Cylinder block
The most important and complex casting on the car is located in the heart of the car - the engine. In order to prevent the car from having "heart disease", the quality of the main castings on the engine is particularly important.
The cylinder block is the largest and most complex casting on the engine. Its wall thickness is often less than 3mm at its thinnest part. Most of it is cast with high-strength gray cast iron, and vermicular graphite castings are also used. Due to the progress in lightweighting of automobiles, aluminum alloys are used. More and more, some foreign automobile manufacturers have even begun to consider using magnesium alloy to cast cylinder blocks. The casting methods used in the production of cylinder blocks vary depending on the material and the conditions of each factory. There are many options, including air blast molding in green sand molding, static pressure molding, high-pressure multi-contact molding, boxless extrusion molding, and shock compression molding. wait. For the cast aluminum cylinder block, die casting and low-pressure casting are used. Foreign countries also use lost foam casting, squeeze casting (pre-embedded cylinder liner with aluminum-based composite material), and semi-solid casting, etc., and sand casting (such as DISA modeling process).
At present, for cylinders made of casting materials, green sand modeling is still the most widely used, especially the emergence of static pressure or air blast modeling that tightens the air flow, which shows many advantages. -Low energy consumption, low noise, less pollution, high efficiency and reliable operation. Recently, foreign equipment manufacturers have continued to improve their molding machines. There have been air ram and compaction, air flow gain and air ram compaction, static pressure and compaction, active multi-contact compaction, forming extrusion, compaction, etc. Improve the method to make the hardness of the sand mold more uniform. With the development of high-power semiconductor components, computers, and microelectronics technology, electric servo systems are used to replace the hydraulic and pneumatic drives commonly used in molding lines, which further speeds up the pace of the molding line, greatly improves operational reliability, and significantly simplifies the The hydraulic control system reduces the maintenance workload accordingly. If the molding line adopts a double-cylinder shakeout machine, the castings and pouring risers can be pre-cleaned while the sand is shaken out. The pouring of the molding line often restricts the operating rate of the entire line, so automatic pouring equipment should be used. Some manufacturers use air pressure ladle and contact pouring processes, which are beneficial to saving molten iron, ensuring quality and protecting the sand box. During the pouring process, flow incubation is often used, and some use a combination of in-mold incubation and filtration.
The cylinder block is the casting with the most sand cores. In addition to the thin and complex water jacket sand core, which is made by cold box core making, hot core box core making or shell core making according to different conditions of each factory, other sand cores - including crankcase sand core, cylinder barrel and top end Sand cores, front and rear end face sand cores, etc. are mostly made using cold core boxes to ensure dimensional accuracy and energy saving. Cold core boxes are increasingly used. Cold box core making mostly uses the ISOCURE triethylamine hardening method (recently, the United States has developed a more advanced ISOMAX), and the SO2 method hardening has its advantages. The core making method of warm core box combines the advantages of energy saving and environmental protection, so it is necessary to strengthen the sealing and ventilation of the core making unit. The development and application of non-toxic, pollution-free and environmentally friendly resin binders is even more important. In order to improve the quality of the inner surface of the casting and the cleanliness of the inner cavity, the sand core should be coated. Replacing alcohol-based paint with water-based paint is beneficial in preventing pollution. Microwave drying after coating is energy-saving and efficient. Using the Key-core process, the process holes opened on the sand core are used to fill and solidify the sand twice, so that multiple sand cores are combined into one integrated sand core, and then the entire sand core is coated and dried. In this way, the dimensional accuracy of the casting can be greatly improved. The overall size error can be <0.3mm. The computer-controlled "core making center" can automate the entire core making process. There are many sand cores in the cylinder. In order to reduce the impact of core sand on the performance of the molding sand and strengthen environmental protection, core sand regeneration and reuse should be vigorously promoted, especially thermal regeneration, which can increase the high-temperature expansion rate of quartz sand after roasting and phase change. The use of recycled sand to make cores can better ensure the quality of castings than new quartz sand. The use of recycled sand also reduces production costs.
For the molding sand used in cylinder modeling, the sand mixing equipment includes roller type, balance wheel type, blade type and other sand mixers. Some manufacturers use double-disc roller-type continuous sand mixers, and some use counter-flow rotor-type sand mixers, which have high sand mixing efficiency. At the same time, they are equipped with molding sand performance online controllers to ensure the quality of sand mixing. In the molding sand system, there are also old sand magnetic separation equipment, sand block crushing equipment and screening equipment, and old sand cooling equipment to ensure the quality of reused old sand. At the same time, new sand, coal powder, bentonite and other added materials are accurately quantified and fed according to the proportion determined by the process, and the amount of water added is adjusted at any time based on real-time control data to ensure the performance of the molding sand. There are also closed-loop real-time control of the performance of the entire system of molding sand or online expert system control of molding sand quality calculation. It should be noted that the molding sand system has a large turnover of molding sand and is highly inert. The adjustment of molding sand performance should be judged based on trends and predictive adjustment measures should be adopted to ensure the quality stability of the molding sand system.
In order to protect the environment, regeneration of old sand and comprehensive utilization of waste sand should be carried out.
For cylinders made of cast iron, most of the smelting equipment used is a dual-smelting furnace-induction furnace, and some use a dual-smelting induction furnace-induction furnace. The use of electric arc furnaces as holding furnaces is decreasing, while the use of variable frequency induction furnaces as holding furnaces is increasing. In order to save energy and protect the environment, a water-cooled hot air dust removal cupola should be used in the cupola. The hot air may increase the temperature, quality and melting rate of the molten iron. It is necessary to replace metallurgical coke with cast coke with high calorific value to increase the temperature of molten iron, ensure the quality of molten iron, and improve melting efficiency. Pre-purification of the charge is necessary. The melting process of the cupola furnace can be controlled by a distributed control system such as a microcomputer. The detection of molten iron in the cupola furnace uses a thermometer, a carbon equivalent detector, a direct-reading spectrometer for chemical composition, etc. Clean, long-life refractory materials are beneficial to improving cupola lining life and environmental protection. The comprehensive utilization of waste slag from cupola furnace smelting is beneficial to reducing emissions and pollution.
After removing the pouring and riser, the cylinder castings are ground on all surfaces on the cleaning line, and then cleaned in the squirrel-cage shot blasting chamber. For various types of cylinders, a clamp-type high-efficiency shot blasting machine should be used for shot blasting. Then manually finish the cylinder one by one and blow out the residue in the inner cavity of the water jacket. After dimensional inspection, air tightness test, positioning point milling and final inspection, painting or other anti-rust treatment will be carried out to become a qualified cylinder casting required by the user.
(2) Cylinder head
The cylinder head is also a complex and critical casting in the automobile. The combustion chamber, air intake and exhaust port of the engine are all located on the cylinder head. The material of the cylinder head can be high-strength gray cast iron or compacted graphite cast iron, but the most widely used one is aluminum alloy cylinder head, and magnesium alloy cylinder head has also begun to be used abroad. There are many casting methods for cylinder heads, such as: sand casting, metal gravity casting, low-pressure casting. Foreign countries also include lost foam casting, die casting (using Douler sand core, etc.) and emerging semi-solid casting.
Let’s take the metal gravity cast aluminum cylinder head as an example. The shape of the cylinder head is formed by a metal mold. A computer can be used to automatically control the mold temperature of the metal mold. Part of the inner cavity is formed by a sand core. The manufacturing process of the sand core is basically the same as the core making process of the cylinder body mentioned above. The main reason is that the core sand sticks. Binders and sand core coatings are different.
Reverberatory furnaces can be used to melt aluminum alloys, but they suffer from serious oxidation and outgassing, large burning losses, difficult temperature control, waste of energy, and environmental pollution. When an induction furnace is used, the churning of aluminum water in the furnace is beneficial to the uniformity of the ingredients. However, the magnetic field of the induction furnace interferes with the thermometer, and the maintenance of the induction furnace is difficult. Worthy of widespread adoption is the continuous high-efficiency gas furnace, which can achieve charge preheating, continuous melting, uniform composition, precise temperature control, energy saving, and is suitable for mass production. It should be noted that the furnace charge must be clean. In addition to using ordinary aluminum liquid refining and deterioration treatment methods, an aluminum alloy flux injection comprehensive treatment device can be used to complete refining, deterioration, and grain refinement in one step. The traditional pouring method of the cylinder head is bottom pouring, which facilitates smooth filling of molten aluminum. Nowadays, the top injection type is mostly used, which cooperates with the cooling system of the mold, which is more conducive to the formation of sequential solidification, thereby significantly improving the density of the casting. During the pouring process, the exhaust of the mold must be smooth, and automatic pouring is often used - including single machine type, double unit type and multi-unit in-line type. The multi-station turntable pouring machine is suitable for mass production, but the investment is large. Multi-unit rotary pouring machines require less investment. When using long-acting strontium modifier, it is better to use a quantitative insulation pouring furnace. On-site inspection of the quality of aluminum liquid mostly uses hydrogen tester and direct reading spectrometer. The maintenance of metal molds is very important. You can regularly spray small particles of dry ice to remove the scale on the molds. This method is simple and easy and does not pollute the environment.
After the poured aluminum cylinder head castings are sawed off on the cleaning line, the pouring, risers, milled planes, and leakage tests are often roughed and milled to position the points before being sent to the user.
Many manufacturers use low-pressure cast aluminum cylinder heads. The use of electromagnetic pump low-pressure casting technology can improve the metallographic structure and mechanical properties of the casting material.
(3) Transmission housing
Truck transmission housings are mostly made of gray cast iron, and some are also made of vermicular graphite cast iron. Sand casting is commonly used. The car gearbox housing is a typical large-scale, complex thin-walled housing casting. The material is mostly aluminum alloy. The use of magnesium alloy is increasing, and the die-casting process is generally used. In order to improve the quality of die castings, low-speed and medium-pressure filling die-casting, double-injection punch die-casting, vacuum die-casting, oxygenated die-casting, etc. can be used.
Spraying, pouring and picking up parts in die-casting production are all automatic, and there are online detection devices to correct the die-casting machine and casting forming conditions.
The melting and refining of the aluminum alloy used in the gearbox housing is basically the same as the aluminum cylinder head mentioned above. Injection parameters have a great influence on the pores of die castings and must be adjusted reasonably. Adopt closed injection end time control system. Flash-free die casting is possible. The quality of die castings can be tested by X-ray flaw detection, ultrasonic testing, etc. The ductility and toughness of the die-casting mold material are very important to prevent hot cracking and cracking of the die-casting mold. Improve the working condition of the mold. Good operation and maintenance will help extend the service life of the die-casting mold. The semi-solid magnesium alloy injection molding technology recently developed abroad can make the filling of magnesium alloy smooth and non-turbulent, prevent hydrogen from being involved, and avoid alloy-mold reactions. It is a composite process of injection molding and die-casting.
(4) Intake manifold
The irregular and variable cross-section shape of the intake cavity of the intake manifold has always been a problem for the automotive casting industry. In recent years, the development of engine electronic injection technology has made the intake manifold more complex. Therefore, it is natural that many manufacturers choose the lost foam process as the casting method for the intake manifold. The intake manifolds used in trucks are mostly made of gray cast iron and are commonly cast in sand molds. The intake manifold of a car is made of aluminum alloy, and the casting methods used include lost foam casting and metal gravity casting.
The lost foam process is used to cast the aluminum intake manifold. The melting and refining process is the same as the aluminum alloy melting and refining of the cylinder head mentioned earlier in this article. Small-sized EPS beads should be used to ensure pre-foaming and molding. The gluing of molding molds must be carried out according to process regulations. The coating process of the assembled lost foam pattern is very important. It is necessary to control the performance and coating thickness of the coating. This is critical to the elimination of pyrolysis products of the pattern during pouring, the filling speed of the aluminum liquid and the quality of the lost foam casting. After the paint is dried, it is filled with dry sand and can be poured after being compacted. After eliminating the riser, the obtained lost foam intake manifold casting should also be inspected for leakage. If there is leakage, the leakage can be repaired by impregnation according to the contract.
(5) Exhaust manifold
Due to the high exhaust temperature of automobile engines, the exhaust manifold material is basically gray cast iron, ductile iron or vermicular graphite. cast iron. The exhaust manifold is also a thin-walled casting with a complex shape. Most of them are sand casting, and some also use lost foam casting. Let’s take a sand-cast exhaust manifold made of ductile iron as an example. Its shape and core-making process are basically the same as the cylinder shape and core-making process mentioned above.
In terms of ductile iron melting, many manufacturers use cupola furnace-induction furnace dual melting. In order to ensure the quality of ductile iron, in addition to using pig iron for ductile iron and casting coke, the molten iron coming out of the cupola should also be desulfurized. Nitrogen porous plug bottom-blown desulfurization bags are often used for continuous desulfurization, and moisture-resistant and explosion-proof granular Desulfurizer. The spheroidizing process is mostly covered by the covering method. Recently, the cored wire method from the metallurgical industry has been introduced into the foundry industry as the spheroidizing process. This is beneficial to improving the absorption rate of spheroidized alloys, stabilizing spheroidizing quality, reducing costs and reducing environmental pollution. Most of the incubation methods are flow incubation, some use in-mold spheroidization and in-mold inoculation, and some use bead-shaped spheroidizing agents, which can prolong the failure time of the spheroidizing agent, and can add spheroidizing agents at any time to ensure The spheroidized state of molten iron. There are also new processes abroad that use desulfurization-spheroidization-inoculation in one go, which can reduce the consumption of magnesium and inoculation, increase the spheroidization rate, and save energy. Carbon equivalent detection, rapid carbon and sulfur determination and rapid metallographic analysis in front of the furnace are very important for controlling the quality of ductile iron hot metal.
The exhaust manifold is an as-cast ductile iron casting and does not require heat treatment. The ultrasonic method can be used to detect the spheroidization rate of ductile iron castings.
Because compacted graphite iron has good thermal fatigue resistance, it is very suitable for the production of exhaust manifolds. Strict chemical composition control and good vermicularizing agents are the keys to stable production of vermicular iron castings.
(6) Crankshaft and camshaft
Crankshaft and camshaft are typical automobile shaft castings, which require both toughness, fatigue resistance and friction pair parts. Thick-section automotive castings with wear-resistant surfaces capable of high-speed rotation. The material used is mostly ductile iron. Including Aubert ductile iron. The camshaft material is sometimes alloy cast iron, chilled cast iron or alloy steel. The modeling methods used, in addition to various sand casting methods, are many using shell molds (including iron molds covered with sand). Some also use self-hardening sand molding and lost foam casting.
(7) Piston
The top of the piston is part of the engine combustion chamber. The cylindrical surface of the piston makes high-speed reciprocating motion through the piston ring close to the inner wall of the cylinder barrel. Pistons are key automotive castings that create engine power. Its material is aluminum alloy, including fiber reinforced composite aluminum alloy. Casting methods include metal gravity casting, low pressure casting, squeeze casting, etc.
(8) Wheel hub
The wheel hub is a rotary motion automotive casting, and the material of the car wheel hub is aluminum alloy. There are several casting methods - low pressure casting, squeeze casting (including rotary vertical extrusion), metal mold gravity casting, differential pressure casting, etc.
Of course, there are many types of castings on cars, so I won’t list them all. In recent years, many foreign car castings have begun to use magnesium alloys to meet the requirements of lightweight vehicles. These magnesium alloy castings include: clutch housing, transmission housing, transmission upper cover, engine hood cover, steering wheel frame, seat frame, instrument panel frame, door inner panel, rim, steering bracket, brake bracket, valve bracket, etc., and even There are also cylinder heads and cylinder blocks.
3. The rising aluminum and magnesium casting industry