In the rapid development of science and technology today, due to the special advantages of casting process, there is no other manufacturing process for some complex structure parts.Casting process is still the most economical and convenient metal forming process.With the integration of global economy and the increasingly close international cooperation and fierce competition, China's automobile foundry industry should give full play to its advantages in foundry resources and develop its own foundry industry.

1. Current situation of China's foundry industry

China is the largest casting production country in the world. According to the data, the output value of casting products in China accounts for about 1% of the national economy.In recent years, casting import and export trade has increased rapidly, casting output has reached about 9%.There are more than 20,000 foundries and 1.2 million foundry workers in China.The "Yangtze river delta" region accounts for 1/3 of the casting output in China, and the region is mainly dominated by private enterprises. The development of automobile and auto parts industry has strongly promoted the development of the casting industry.Wanfeng auto is the largest aluminum wheel manufacturer in Asia, with an annual output value of over 1 billion yuan and an export value of 6,000 us dollars.Kunshan fushihe machinery co., ltd. produces castings for automobile engines and braking systems, with an annual output of 40,000 tons and a sales revenue of 550 million yuan.East China taikesi is an advanced modern cylinder block casting production enterprise, with an annual output of 10 million pieces

Car cylinder block casting capacity.Shanxi is a large province of casting resources, rich in pig iron, coal, aluminum and magnesium, electricity, labor resources, so that shanxi's casting industry has a unique advantage, with 500 casting enterprises, 80% of the private enterprises.The annual output of shanxi international, hejin mountain and shanxi huaxiang reaches 40,000 t, 20,000 t and 120,000 t respectively.Faw group, hafei group and other key automobile enterprises in the "three northeastern provinces" have led to the growth of automobile casting output.Faw group foundry company, has formed 400,000 t casting production capacity.Liaoning north crankshaft co., LTD., will form a crankshaft production base with an annual output of 150,000 engines, 1 million crankshafts and an output value of 2 billion by the end of the "eleventh five-year plan"."Pearl river delta" die casting industry developed, there are more than 700 die casting enterprises, the annual output of 200,000 t.Dongfeng nissan, guangzhou Honda, guangzhou Toyota and parts enterprises have strongly driven the development of the die casting industry, car cylinder block, cylinder head die casting production increased year by year.

2. Status quo of foreign foundry industry

In recent years, the global casting industry keeps growing, the casting output in 2004 increased by 8.4% compared with the previous year, and China's casting production reached 22.42 million tons, ranking the first in the world, with an increase of 23.6% compared with the previous year.The output and growth rate of the world's top 10 casting producing countries are shown in table 1.As can be seen from table 1, China accounted for about 1/4 of global casting production in 2004.Brazil saw the fastest growth in casting production, at 25.8 per cent.Countries with double-digit growth rates include Brazil, China, Mexico and India, all developing countries.The casting growth rate in developed countries is generally low.U.S. casting production has fallen to no. 2 since 2000.In 2004, the total production of castings in the United States was 12.31 million tons, of which 35% were gray iron, 33% were ductile iron, 8.4% were cast steel and 16% were aluminum alloy.In terms of demand, the demand for ductile iron castings and aluminum castings is increasing.In 2003, imported castings accounted for 15% of the total demand, and the price of imported castings was 20% ~ 50% lower than that of domestic castings.In recent years, due to the high environmental requirements, high energy consumption and expensive labor, the foundries of ordinary automobile castings produced by large American automobile companies have closed down one after another and gradually shifted the casting production to China, India, Mexico, Brazil and other developing countries.Japan's foundry industry is stagnant and its workforce is shrinking.The total output of Japanese castings in 2004 was 6.39 million tons, among which gray iron parts accounted for 42%, ductile iron parts for 30%, steel castings for 4% and aluminum alloy parts for 21%.In terms of demand, the demand for ductile iron castings and aluminum castings is increasing.Japan's foundry industry has done a lot of work in technological innovation, such as the development of low expansion spherical foundry sand, high vibration damping cast iron materials, medium silicon nodular iron and other materials.Its vacuum die casting can be welding and heat treatment, semi - solid casting production for automotive aluminum wheel hub, improve the strength and elongation.Magnesium alloy die casting is further developed and replaces gravity casting, with improved performance and lower cost.

3. Development direction of automobile casting technology

Automobile technology is developing towards lightweight, numerical and environmental protection.According to relevant data, a 10% reduction in the dead weight of a car can reduce fuel consumption by 5.5%, improve fuel economy by 3%-5%, and reduce emissions by about 10%.There are two main ways to reduce the weight of castings.One is the use of aluminum, magnesium and other non-ferroalloy castings, the United States in 2003 statistics have 2/3 of the aluminum castings used in cars, each car up to 107 kg.Second, reduce casting wall thickness, design multi-part combination casting, produce thin-wall high-strength composite casting, and reduce machining allowance to produce near-final casting.With the rapid development of automobile technology, rapid mold making technology, computer simulation, 3d modeling and numerical control technology are required to shorten the preparation period of casting production and reduce the risk of new product development.Clean production and waste recycling are the development trend of foundry industry, and reducing energy consumption is the theme of its sustainable development.China's automobile foundry industry must follow the path of high efficiency, energy saving, material saving, environmental protection and green foundry, because the state and society require strict control of large energy consumption and large pollution in the automobile foundry industry, so as to improve the labor environment of employees in hot, dirty and tiring labor-intensive industries.

4. Development trend of automobile casting technology

There are many development trends of automobile casting technology at home and abroad, and only a brief introduction of casting technology and development trend in mass production line of automobile industry is given.

4.1 sand mold casting technology

After manual compaction of a shock + compaction compaction, high pressure + microseismic compaction, air impact compaction, static compaction several stages of development.The essence of static pressure molding technology is "pre-compaction + compaction in air", which has the following advantages: clear profile of the casting mold, high and uniform surface hardness, small draft Angle, high utilization rate of the mold plate, small wear of process equipment, low surface roughness of the casting mold, and low waste rate of the casting mold.Therefore, it is the latest and most advanced molding technology, and has become today's mainstream compaction process.At present, high pressure molding and single air impact molding have been gradually replaced by static pressure molding, the original high pressure molding line and air impact molding line host has been gradually updated to static pressure molding host, new foundry are preferred to use static pressure molding technology.At present, the more famous manufacturers of static pressure molding equipment abroad include German KW company, HWS company and Italian savelili company.Most of the domestic automobile foundry manufacturers choose the equipment manufactured by HWS company or KW company, such as faw foundry company, dongfeng automobile foundry, Shanghai shengdeman foundry company, east China taikesi, shanxi sanlian, guangxi yuchai, wuxi diesel engine factory and so on.

4.2 near-net technology

(1) lost foam casting process

Lost foam casting is also called gasification mold casting, solid mold casting and cavity free casting.The process, with a dimensional accuracy of up to 0.2mm and surface roughness of up to Ra5 m ~ Ra6 m, is known as "21st century casting technology" and "casting green engineering" in the casting industry.The technology is dry sand without binder and vacuum pumping.According to the statistics in 2003, there are 150 enterprises in China using this process to produce three kinds of castings, such as box body, pipe parts and valve body, heat-resistant and wear-resisting alloy steel, with a total output of more than 100,000 t.The domestic automobile foundry, some USES the domestic foundry production line: some USES the simple production line or the single machine production;Some adopt the foreign introduction casting production line production.In 1993, faw group corporation introduced the vibration table for modeling from fukang company of the United States to produce the pre-foaming machine and molding machine for EPS model and other equipment to produce automobile air inlet pipes.Changsha engine general factory introduces automatic casting line from Italy to produce aluminum alloy cylinder block and cylinder head casting.Hefei forklift group produces complex box castings with 4 sections of foam modules bonded into a whole. The dimensional accuracy can reach ct7-ct8, and the products are exported to the United States.Chengdu chenggang group produces loader gearbox with 8 pieces of foam modules bonded into a whole process. The casting quality is up to 320 kg. Compared with sand mold casting, the blank weight is reduced by 15%, and the yield is more than 95%.In recent years, epc technology has developed greatly in the United States. General motors has invested and built 6 epc casting production lines to mass produce aluminum alloy cylinder block and cylinder head castings.In the future, a large number of rapid moulding technology and simulation technology will be used in this process to shorten the production preparation cycle and realize the rapid production of castings.The future direction of development is bound to be good quality, complex, precision, long life of high-grade mold.The technology level of the mould material, forming technology, coating technology and tooling equipment should be improved, so that EPS casting can get a wider development prospect.

(2) investment casting process

The automobile investment casting technology has developed rapidly in our country, and the near-net casting technology can be used to produce non-surplus casting products.The investment casting process includes water glass shell making process, compound shell making process and silica sol shell making process.Automotive products materials are carbon steel, alloy steel, non - ferrous alloy and ductile iron.Abroad have high alloy steel, superalloy material.Domestic smelting equipment using ordinary, fast if furnace;Foreign vacuum furnace, rotary furnace, high - frequency furnace technology.Surface roughness up to Ra1.6 m, dimensional accuracy up to CT4, minimum wall thickness up to 0.5 ~ 1.5mm.Europe, the United States, Japan and other countries began to pay attention to the application and expansion of casting in the automotive industry.The market demand of automobile investment casting is also growing rapidly in China. In 2003, the output of investment casting was 600,000 t and the output value reached 11 billion yuan.Dongfeng automobile precision casting co., ltd. adopts the silicon sol + water glass composite shell making process to produce high technical content and high value-added products, and designs and manufactures the original castings, forgings, machining and multiple assembly structures into an integral precision casting, which significantly reduces the manufacturing cost.

The future development trend of investment casting process is that the casting products are more and more close to the parts and components.The degree of complexity and quality of component products are getting higher and higher, the means of research and development are getting stronger and stronger, and professional cooperation begins to emerge. The application of CAD, CAM and CAE has become the main technology of component product development.As the leader of China's investment casting industry, the investment casting enterprises of dongfeng motor corporation and faw group corporation are sure to develop rapidly with strong r&d strength and advanced technology.

4.3 core manufacturing technology

At present, there are three core-making processes for automobile casting at home and abroad. The main processes commonly adopted in modern automobile casting are hot core box core-making, shell core core-making, and cold core box core-making, etc., while the traditional grease or oil sands core-making has been eliminated.Cold core box technology has two characteristics: one is the hardening speed, high initial strength, high productivity;The second is the high dimensional accuracy of the sand core, which can meet the production of thin-walled high-strength casting sand core.Therefore, the core - making technology has a tendency of cold - core box technology.Faw foundry co., LTD., dongfeng motor foundry co., LTD., Shanghai shengdeman foundry co., LTD., east China taikesi co., LTD., shanxi international foundry co., LTD., etc.The modern advanced 110L cold core box core making machine is shown in figure 1.

The most advanced Core manufacturing technology is the Core manufacturing center combining Key Core and cold Core box technologies. The whole Core shooting, Core taking, burr dressing, positioning and combination of multiple cores into one, coating, drying and other processes are completed automatically with one or more Core manufacturing machines and mechanical hands.The famous core manufacturing center manufacturers abroad include LORMENDl company of Spain, Laempe company of Germany, Hottinger company and FA company of Italy.Dongfeng motor foundry co., LTD., faw foundry co., LTD., Shanghai shengdeman foundry co., LTD., east China taikesi, Shanghai diesel engine co., LTD., luotuo no.2 railway, weichai, jiangxi isuzu co., LTD., etc., all adopt the core technology of cold core box.

4.4 cast iron smelting technology

At present, domestic and foreign cast iron smelting technology has two main ways: one is the use of large hot air dust removal cupola and power frequency insulation furnace double melting process;Second, intermediate frequency induction furnace melting technology.The intermediate frequency furnace technology produced by inder and piler in the United States starts to receive more and more attention. The technology is becoming more and more mature, and its advantages of cleanness, environmental protection, energy saving, high efficiency and safety are prominent, which is the future development direction.

Therefore, cast iron is gradually transformed from power frequency furnace melting to intermediate frequency furnace melting with high efficiency and energy saving.1. Adopting the intermediate frequency furnace and heat preservation furnace technology produced by inda company and piler company, automobile foundry company and dongfeng motor company have developed and applied spherifying agent, inoculating agent, vermicularizing agent and various other additive products, forming commercialized, standardized, standardized and serialized products.Cast iron inoculating machine with photoelectric control.The SINTER CASTZ technique, which combines the newly developed wire feeding spheroidization method with the modern detection technology, is an advantageous technique for the spheroidization and vermicularization of cast iron, and has been increasingly applied.Foreign metal charge after crushing, purification, weighing, greatly improve the melting efficiency and quality of molten iron.Domestic foundries such as tianjin Toyota, tianjin qimeida and suzhou qimeida have adopted crushing process for furnace charge.

Die casting technology of 4.5 aluminum alloy cylinder block and cylinder head

Aluminum alloy is the fastest and most widely used light metal in automobiles, because the performance of aluminum alloy itself has reached the requirements of light weight, high strength and corrosion resistance.Initially, aluminum alloys were used only for parts that were not impacted.Later, through the strengthening of alloying elements, the strength of aluminum alloy is greatly improved. Because of its light weight, good heat dissipation and other characteristics, it can meet the requirements of engine piston, cylinder block and cylinder head working in harsh environment.The core technology of die casting of aluminum alloy cylinder block and cylinder head can improve the quality control of material such as purification, refining, refining and metamorphism, so as to make the quality of aluminum casting consistent and stable.With the development of China's automobile industry, especially the rapid increase of household cars and auto parts export volume increase, automobile aluminum casting will have a great growth.The total production of castings in China in 2003 was 19.87 million tons, of which 1.17 million tons were aluminum and magnesium alloys, accounting for 5.8% of the total production.Toyota hopes to increase aluminum cylinder blocks to 50 percent in the next two years from 35 percent now.Nissan plans to use aluminum for 70 percent of gasoline engine cars by 2010, and for nearly 100 percent of cylinder heads and transmission cases.As early as 1994, Honda motor company replaced all the gasoline engine cylinder blocks with aluminum ones.Non-ferrous metals such as aluminum alloy cylinder block and cylinder head are mostly used in die-casting (including vacuum die-casting), low-pressure die-casting, high-pressure die-casting, metal mold gravity casting and semi-solid die-casting forming technology with great development prospects.The aluminum die-casting workshop of dongfeng Honda engine company and dongfeng nissan engine company adopts the 2500t die-casting machine to produce aluminum cylinder block, and has realized localization.There are two main types of aluminum cylinder head forming technology, one is the gravity casting technology represented by Europe and America, Shanghai pilberg, nanjing teksi and other companies choose Italy fata company gravity casting machine to produce aluminum cylinder head;The second is the low-pressure casting process represented by Japan and South Korea. The aluminum die-casting workshop of dongfeng nissan engine branch, guangdong zhaoqing casting company, and tianjin Toyota casting company all use the low-pressure casting machines of Japan Shinto to produce aluminum cylinder heads.

4.6 magnesium alloy forming technology

The specific strength and stiffness of magnesium alloy are higher than that of steel and aluminum alloy, and much higher than that of engineering plastics.Magnesium alloys also have high temperature resistance, corrosion resistance and creep resistance.Magnesium is currently the lightest metal used in the automotive industry. It is one-third lighter than aluminum, three-quarters lighter than steel, and one-fifth lighter than nonmetallic plastics.Therefore, magnesium alloy is an ideal material for automobile to reduce the quality. Magnesium alloy die-casting can replace some complex structural parts, such as dozens of steel parts of the dashboard framework, which are made by stamping and welding, with a mass of about 10 kg. If it is changed to magnesium alloy die-casting, the mass is only 4 kg and the production cost is greatly reduced.With the continuous development of magnesium alloys and new materials and the improvement of processing technology, magnesium alloys will continue to expand and grow steadily in the automotive market.Magnesium alloy production is given priority to with die casting forming technology, has been the focus of attention of automobile industry, magnesium alloy die casting demand accounted for 80% of its auto industry demand for magnesium alloy, mg alloy die casting in the automotive materials, in addition to meet the high temperature resistance and creep resistance, must also give full consideration to the design, processing, surface treatment and relevant die casting forming technology.Because of die casting magnesium alloy casting can be prominent advantage. Casting wall thickness can reach 1 ~ 1.5 mm, draft 1 ° - 2 ° slope while the magnesium alloy casting is still focus on the pressure die casting, but still face of die casting magnesium alloy performance and cost.Therefore, a new process - semi - solid magnesium alloy processing technology appears.The technology has been mainly used in the production of integrated magnesium, aluminum alloy castings.The magnesium alloy die casting production in Europe and America is increasing by 25% every year.Audi A6 car transmission case is a magnesium alloy die casting with a mass of only 14.2 kg. Audi first used magnesium casting for the dashboard framework.Ford motor company reduced the seat mass from 4 kg to 1 kg by replacing the steel frame with a magnesium alloy.Ford is working on magnesium alloys for cylinder blocks.Mitsubishi of Japan has teamed up with the Australian ministry of science and technology to develop an ultra-lightweight magnesium alloy engine with a mass of just 7.5kg.BMW has started mass production of its six-cylinder magnesium alloy cylinder block.The United States general production magnesium die casting intake manifold.Renault has produced magnesium alloy wheel castings.Dongfeng automobile foundry has mass produced magnesium alloy die castings. At present, dongfeng automobile and faw foundry are developing and undertaking key scientific and technological projects of the ministry of science and technology, such as transmission case, gear chamber cover, valve chamber cover, steering wheel frame and other magnesium alloy die castings.Shanghai gantong automobile accessories co., LTD. Takes the lead in the production of magnesium alloy car gearbox die casting.In recent years, China has also established a number of large foreign magnesium die-casting enterprises, such as Shanghai magnesium, suzhou GF and other companies.

4.7 semi-solid die casting technology

Semisolid technology originated in the United States, the United States this technology has been basically mature and in the world's leading position.The technology has been called the most promising material forming technology of the 21st century.Plax takes the lead in transforming this technology into productivity. The raw size of aluminum alloy automobile brake master pump body produced by plax is close to the size of parts, and the processing amount accounts for 13% of the casting quality, and the machining allowance of the same metal mold casting accounts for 40% of the casting quality.Since the 1980s, Europe and other countries have done a lot of research and application work in the application of semi-solid state.Italy was one of the first countries to use semi-solid processing technology, which stampal-saa USES to make gearbox covers and rocker arms for Ford.Currently, Japan's Speed Star Wheel company has used this technology to produce aluminum alloy Wheel hub castings weighing about 5 kg.China's semi-solid metal processing technology started late in the late 1970s.Compared with foreign countries, the research of semi-solid metal forming technology in China is still very backward.In view of the current research situation in China, the development trend of this technology is that the metal thixotropic technology has been basically mature, while the rheological forming technology develops slowly.Therefore, more researchers will turn to the study of rheological forming theory and application in the future.At present, semi-solid metal forming technology is mainly used in the forming of low melting point metals such as aluminum, magnesium, lead, and so on.At present, scholars at home and abroad have developed numerical simulation software for semi-solid forming process, but there are still some shortcomings, which need to strengthen the application of computer technology.

4.8 cast iron material

(1) thin-walled high-strength gray cast iron technology

The total production of castings in China in 2003 was 1.87 million tons, of which 10.49 million tons were gray cast iron, accounting for 53% of the total production.Gray cast iron is widely used in automobile because of its low cost and good casting performance.With the requirement of lightweight automotive technology, the growth and development of gray cast iron will be affected, so its development trend is to strengthen the development and application of thin-walled high-strength cylinder block, cylinder head casting technology.The difficulty of thin-walled high-strength cylinder block and cylinder head casting technology is to make the hardness difference of the body section with the thinest wall thickness of only 3-5 mm <40HBS, and the microstructure is fine and even.There are high technical requirements for the metallographic structure such as the hardness, pearlescent volume, carbides content and graphite form of the cylinder block and cylinder head castings of car engine and high-power diesel engine.For example, the cylinder block and cylinder head of high-power diesel engine require the body hardness of 1 70 ~ 228 HBS and 179 ~ 235HBS respectively, with high strength and size requirements, and the surface roughness Ra<50 PM.The material grade of gray cast iron is constantly improving. HT300 has been used in the production of cylinder block and cylinder head. Some products may reach HT350.Domestic automobile foundries have done a lot of work in material technology, smelting technology, molding technology, core-making technology, mould manufacturing technology, testing technology and so on.

(2) vermicular cast iron technology

Vermicular cast iron has the strength of nodular cast iron, and similar anti-vibration, thermal conductivity and casting performance compared with gray cast iron. It has good plastic and heat-resistant fatigue performance, which can solve the thermal fatigue crack problem of high-power cylinder head.Ferrite body vermicular iron working temperature can reach 700 ℃;High silicon-molybdenum vermicular iron working temperature is 870 ℃.Vermicular cast iron will not replace nodular cast iron nor gray cast iron.The huge potential market of vermicular graphite cast iron is automobile industry, and its main products are engine cylinder block and high-power diesel engine cylinder head.As car lightweight and than power (power/volume), the working temperature of cylinder block and cylinder head is higher and higher, many parts of the working temperature over 200 ℃, the temperature, the strength of the alloy dropped substantially, and vermicular iron law has great advantage.It will be the only advanced automotive engine material that can meet the technical, environmental and performance requirements.Because vermicular cast iron has the characteristics of high strength and thin wall, it can reduce the quality.Opel's research showed that the same engine block with vermicular iron, the original 7 mm wall thickness can be reduced to 3 mm, casting quality can be reduced by 25%.

The range of vermicular treatment of vermicular graphite cast iron is very narrow.The engine cylinder bodies of BMW, daimler-chrysler and duff abroad are produced with vermicular graphite cast iron.Ford, in partnersahip with Sinter, produced 100,000 cylinders a year in Brazil in 1999.German Halberg foundry has been producing V8 vermin iron cylinder block for audi since 1991. The wall thickness is 3.5mm and the cylinder block mass of 147kw is only 74kg.In may, 1984, the foundry of dongfeng motor company officially mass produced vermicular graphite cast iron exhaust pipe on the assembly line, becoming the first factory in China to mass produce vermicular graphite cast iron on the assembly line.In the early 1990s, the vermicular iron gearbox and the exhaust pipe of Shanghai Volkswagen santana car were developed successively.Wuxi diesel engine branch of faw foundry company started mass production of vermicular iron cylinder heads in 1980s.Shanghai sundmann foundry co., LTD. Produces medium silicon molybdenum vermicular iron exhaust pipes for Shanghai Volkswagen.

(3) ductile iron technology

Ductile iron is still developing in the automotive market due to its high strength, high toughness and low price.At the same time, many standards of ductile iron have been formulated. Advanced technologies that adapt to the mass production of ductile iron on the assembly line have been developed, such as ladle shaking, pneumatic desulfurization, spheroidization of mould inner and cover, various instantaneous inoculation, audio frequency, ultrasonic and thermal analysis and detection technologies.Currently, ductile iron production accounted for more than 25% of the total production of castings in the industrialized countries, and the ductile iron production in the United States accounted for 33% of the total production of castings in 2003.The development trend of ductile iron product technology in automobile foundry industry is as follows.

First, truck and car crankshafts with pearlite cast state, high strength (qt700-2, qt740-3), ferrite cast state, automobile exhaust pipe and chassis casting with high elongation (qt400-18, qt440-10).Higher brands qt800-2 and qt900-2 are also under development.

The second is security castings. The material and technical conditions for the production of car steering knuckles in the as-cast state are very strict, requiring zero casting defects and 100% non-destructive testing. At present, there are three automatic testing technologies for production.

Third, heat-resistant ductile iron parts, namely high silicon-molybdenum, medium silicon-molybdenum and high nickel ductile iron, the exhaust pipe parts produced by this material have good high temperature resistance performance: at present, the domestic automobile company foundry has produced medium silicon-molybdenum ferrite ductile iron exhaust pipe parts.

Fourthly, the austempered ductile iron has become the focus of casting industry due to its unique material properties. It is a material with great potential for development and application, mainly used in the production of crankshaft and other products.

In addition, the automobile foundry has produced ductile iron cold - excited camshaft.

4.9 casting process computer application technology

With the rapid development of automotive casting technology, rapid prototyping technology, computer simulation, 3d modeling and numerical control technology are widely used to shorten the production preparation period and reduce the risk of new product development.Rapid prototyping technology has been widely used in foundry production.It can be used to make phenolic resin shell and shell core, and can be used to assemble sand mold.After receiving 3d CAD data from customers, foreign companies can provide castings within 3 weeks at the soonest according to different product structures.The simulation molding process is becoming one of the foreland fields of international automobile foundry. Tsinghua university and Shinto industry of Japan have simulated the compaction process of wet molding sand.It is worth noting that the core process is being simulated by aachen university and tsinghua university in Germany.The integrated design and development of cad-cam-cae in domestic automobile casting industry has been fully applied. In particular, the virtual technology of CAE solidification simulation, Magma and China casting software were applied to simulate and analyze the mold filling, solidification temperature field and flow field of the new product, so as to predict and analyze the shortcomings of the casting.The casting expert system has been further applied, such as sand quality management, casting defect analysis, die casting process parameter design and defect diagnosis.

4.10 casting detection technology

Casting detection technology is the key to ensure casting quality.Casting dimension check, common check fixture, card board, special check fixture.For the complex parts such as cylinder block and cylinder head, the dimension of the castings is measured automatically by a three-coordinate instrument and the wall thickness of the castings is measured by an ultrasonic instrument.Nondestructive testing (NDT) technology is widely used, and fluorescence magnetic powder is often used to detect surface cracks of important parts.The spheroidization rate of ductile iron was detected by ultrasonic or audio frequency.Eddy current method is used to detect the matrix structure (pearlite content) of the casting.In order to meet the testing requirements of important parts, the above three testing instruments can be combined into an automatic testing line.Defects of shrinkage cavity and porosity in casting were detected by X-ray. 100% ductile iron steering knuckle casting by Honda used X-ray inspection: quality of inner cavity of casting was detected by industrial endoscope, and air tightness leakage was detected.Chemical composition test, vacuum direct reading spectrometer and carbon sulfur meter in front of the furnace, the furnace after widely applied on the quality of molten iron. Trace elements and gas elements attention to analysis of N, O, H: before the furnace rapid thermal analysis is widely used, rapid prediction of cast iron carbon equivalent, inoculation effect, matrix structure and mechanical properties.

Green casting technology

"Green casting" is to make casting products from the design, manufacture, packaging, transportation, use to scrap the whole life cycle of the product, the negative impact on the environment is the minimum, the resource efficiency is the highest.Casting industry has always been considered as a high energy consumption, high pollution industry, to constantly develop new energy saving, clean, low emission, low pollution casting materials for production and use.For resins, ways should be found to reduce the content of free formaldehyde and free phenol and other harmful substances;Gradually increase the application of cold core box technology, in order to reduce the impact of resin sand on the environment, achieve standard emissions: reduce the hot core box, shell core sand curing temperature, the core process from the hot core box method to the core box method, to save energy.The automobile foundries in China consume nearly 10 million tons of new sand every year, and the pollution caused by the discharge of old sand and the large consumption of new sand resources cannot bear the heavy burden, so the recycling technology of old sand is imperative.In advanced industrial countries, the discharge of waste sand is reduced to less than 10%, and the recycling technology of old sand is widely used in Europe, Japan and other regions.Harbin dong 'an automobile engine company introduced Italian thermal process regeneration equipment, which has been applied in production.Faw foundry company introduced Japanese technology, combined with thermal regeneration and mechanical regeneration, processing core sand and mold, core sand mixed sand has been applied in production.At present, dongfeng motor company is also accelerating the development and application of old sand recycling technology.Increase the utilization of scrap and return charge to reduce the consumption of new pig iron and aluminum resources.The automobile foundry industry faces the circular economy foundry technology, must take the circular economy 3R as the industry standard, namely by reduces, the Reuse, the Recycle carries on the work.

5. Problems faced by China's automobile foundry industry

In the process of transforming from planned economy to market economy, China's automobile foundry industry has gone through four stages: initial stage, stable stage, development stage and mature stage.However, we must have a clear understanding of the historical responsibility of automotive foundry industry and the reality gap with developed countries, firmly grasp the development trend of domestic and foreign foundry technology, timely and appropriate use of advanced foundry technology, the implementation of the sustainable development strategy of the foundry industry, the current automotive foundry owners have the following problems.

The average scale of foundry enterprises is far from that of economy and foreign countries.Although China's casting output has been ranked first in the world for five consecutive years, there are a number of large and medium-sized enterprises with high output, but most of the casting enterprises are small in scale.In terms of the whole foundry industry, its current situation is still scattered foundries (with more than 20,000 foundries), with a large number of employees (as many as 1.2 million), and low efficiency (the average foundry is only 500 t/ year), which is only 1/9-1/4 of the industrial developed countries such as the United States, Japan, Germany, France and Italy.

Foundry enterprise whole technology equipment level and foreign than have bigger difference.There is a big gap in the level of technology and equipment among enterprises. The level of technology and equipment in individual production workshops of a few enterprises has approached or reached the international advanced level, but the overall level is not high.According to statistics, China has imported more than 210 automatic molding lines from abroad, there are more than 250 domestic modeling production lines, these production lines are mainly concentrated in the automotive internal combustion engine parts of the mass production enterprises.

There is a big gap between the r&d and innovation ability of China's casting enterprises and that of foreign countries.According to statistics, there are more than 30 major casting inventions in the world, none of which are made in China.Only a few casting products with high technical content, high added value, independent intellectual property rights and international reputation are produced in China. However, it costs some money to import casting products with high technical requirements in industrial production every year.

High labor intensity, high energy consumption, high resource consumption and high environmental pollution are common in China's foundry enterprises.Casting is a labor-intensive industry, some domestic enterprises in the production process, such as the melting process of feeding, pouring process of artificial pouring, casting sand removal process of handling without equipment, so the labor intensity of manual operation is very large.Casting is a big energy consuming country, and one of the reasons for the high cost of casting is that the energy consumption of casting is too high.The foundry industry is also a major environmental polluter. It is estimated that the annual SO and other waste gas emissions are about 165m3, with 900,000 t of dust, 18 million ~ 22.5 million t of waste sand and 5.3 million t of waste residue.

Casting enterprise engineering and technical personnel and technical workers serious fault, r & d personnel shortage.Due to the poor environment, high labor intensity and low pay of personnel in foundry industry, some engineering and technical personnel and technical workers are lost.Many people who work on the casting line have not received systematic training and cannot meet the requirements of modern production.With the decrease of casting major in colleges and universities in China, the shortage of casting technical talents, especially senior technical talents with innovation ability, will be more serious in the future.

6. Countermeasures and Suggestions for China's automobile foundry industry

Automobile foundry industry faces some new opportunities and challenges.Foreign industrial developed countries will gradually transfer casting products to developing countries, which provides us with opportunities.But at the same time, automobile technology requirements, customer requirements for casting products, national requirements for environmental laws and regulations, foundry enterprises themselves are more and more stringent requirements.These have posed higher challenges to foundry enterprises.Facing the opportunities and challenges, how to transform China from a great foundry country into a great foundry country, the countermeasures and Suggestions are as follows.

The foundry enterprises should develop towards the specialization direction and further enhance the specialization level which is beneficial to the market competition.We must energetically develop commercialized and specialized production.Further improve expand the advantage of the professional development of the enterprise, to produce the similar size, wall thickness, material quality, complexity of castings, which can increase production batch, further improve the economies of scale, reduce degree of difficulty of management of raw materials, production process at the same time, product quality, to improve the efficiency improved accordingly.Specialization is not simply centralized integration, nor is it to build large factories.The principle of specialization is to set up a large number of small professional foundry enterprises with the advantages of capable personnel, easy operation, quick decision-making speed and strong strain capacity.

Casting enterprises should take improving casting product quality and reducing production cost as the eternal theme.Our casting quality has a big gap with the foreign ratio, such as casting size accuracy, surface roughness than foreign heterodyne 1 ~ 2 grade;There are great differences in the stability and consistency of castings.The defective rate of complex castings in China is about 10%, while that in foreign countries is less than 5%.In this way, a large number of main and auxiliary raw materials, energy consumption and labor costs are wasted, which increases the cost of casting production.Therefore, enterprises must greatly reduce energy consumption and raw material consumption, efforts to pay attention to environmental protection and labor security work.Foundry enterprises should stress the main line of quality management, establish a quality assurance system, and constantly improve the quality of operation.At the same time, enterprises should establish and improve a high level of product quality standards.The view of quality should be extended from various indexes of castings to the comprehensive reflection of customers' physical quality, service quality, price and delivery time.

Foundry enterprises should pay close attention to technological development and technical structure adjustment.In the way of technology development, enterprises should make full use of domestic resources in all aspects, and adopt the way of joint tackling key problems and benefit sharing to carry out technology development.Enterprises are both competitors and partners, so enterprises must strengthen cooperation in technology development if they want to achieve faster development.Enterprises should fully mobilize their own technical strength, and establish an enterprise-centered relationship platform combining production, learning and research.It is necessary to transform the traditional casting technology with high and new technology, adopt advanced technology appropriately and timely, and combine the improvement of technology and benefit.Such as the use of high efficiency, energy saving, environmental protection, safety smelting, molding, core-making, cleaning, sand and other equipment;Adopting advanced parallel development technology, computer aided design, process simulation optimization technology, rapid sample trial production technology, etc.

Foundry enterprises should accelerate the adjustment of market and product structure.Automobile foundry enterprises can no longer be attached to large automobile factories, but should become independent casting product manufacturers and suppliers, facing not only the domestic market, but also the global market.Become a real international, domestic OEM suppliers.The foreign big automobile manufacturing company implements the global purchase, the foundry which originally depends on the big automobile factory has become the independent, the specialized foundry enterprise.It is necessary to increase the proportion of complex castings, high technical content and high value-added castings, and improve the efficiency of enterprises.The deep processing of casting blank should be greatly developed to further increase the added value of casting.Develop and cultivate the enterprise's characteristic products, make them become famous brand products, increase the intangible assets for the enterprise.

Foundry enterprises should continue to strengthen education and training.It is necessary to train professionals in foundry, and enterprises should establish an incentive mechanism for retaining employees emotionally, professionally and financially, so as to mobilize the enthusiasm of scientific and technological personnel and make more contributions to the technological progress and development of the enterprise.Strengthen the technical and professional ethics training of the staff and workers, improve the technical and labor quality of the whole industry staff and workers.