Development and trend of automobile casting technology

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

1. Status quo of foundry industry in China

China is the world's largest casting production country, according to the information, China's casting product output value in the national economy accounts for about 1%.In recent years, the import and export trade of casting has increased rapidly, and the output of casting has reached about 9%.China has more than 20,000 foundries and 1.2 million employees in the foundry industry.The casting output of "Yangtze river delta" region accounts for 1/3 of the whole country, and the region is mainly dominated by private enterprises. The development of automobile and auto parts industry strongly promotes the development of casting industry.Wanfeng auto is the largest aluminum alloy wheel enterprise in Asia, with an annual output value of more than 1 billion yuan and an export value of us $6,000.Kunshan Fuji and machinery co., LTD produces automobile engine and brake system castings with an annual output of 40,000 t and sales revenue of 550 million yuan.East China tekexi is an advanced modern production enterprise of cylinder block casting with an annual output of 10 million pieces

Car cylinder block casting capacity.Shanxi is a big province of casting resources, with abundant pig iron, coal, aluminum and magnesium, electric power, labor resources, making shanxi's casting industry has unique advantages, with 500 casting enterprises, 80% of which are private enterprises.The annual output of shanxi international, hejin shanlian and shanxi huaxiang reached 40,000t, 20,000t and 120,000t respectively."Northeast three provinces" faw group, hafei group and other backbone automobile enterprises led the growth of automobile casting output.Faw group casting company, has formed a production capacity of 400,000 t casting.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 11th five-year plan."Pearl river delta" die casting industry developed, there are more than 700 die casting enterprises, annual output of 200,000 t.Dongfeng nissan, guangzhou Honda, guangzhou Toyota and parts enterprises strongly promoted the development of the die casting industry, the car cylinder block, cylinder head die casting output increased year by year.

2. Status quo of foreign foundry industry

In recent years, the global casting industry continues to grow. In 2004, the casting output increased by 8.4% over the previous year, and China produced 22.42 million tons of casting, ranking the first in the world, with an increase of 23.6% over the previous year.The output and growth rates of the top ten global casting producers are shown in table 1.As can be seen from table 1, China's casting production in 2004 accounted for about 1/4 of the global casting production.Brazil saw the fastest growth in casting production, reaching 25.8%.Countries with double-digit growth rates include Brazil, China, Mexico and India, all developing countries.The growth rate of castings in developed countries is generally lower.Since 2000, American casting production has fallen to the second place.In 2004, the total casting production in the United States was 12.31 million t, among which gray iron accounted for 35%, ductile iron 33%, steel 8.4% and aluminum alloy 16%.In terms of demand, the demand for ductile iron casting and aluminum casting is increasing.In 2003, imported castings accounted for 15% of the total demand, and the cost of imported castings was 20% ~ 50% lower than that in the United States.In recent years, due to the high requirements for casting environmental protection, high energy consumption, high labor cost and other reasons, the large American automobile companies have closed down the foundry manufacturing ordinary automobile castings, and gradually shifted the production of castings to China, India, Mexico, Brazil and other developing countries.Japan's foundry industry is in recession and its workforce is shrinking.The total casting output of Japan in 2004 was 6.39 million t, among which gray iron accounted for 42%, nodular iron 30%, steel 4% and aluminum alloy 21%.In terms of demand, the demand for ductile iron casting and aluminum casting is increasing.The Japanese foundry industry has done a lot of work in the field of technological innovation, such as the development of low expansion casting sand, high vibration absorption cast iron, heat resistant nodular iron and other materials.Its vacuum die casting casting can be welded and heat treated, semi-solid casting production for automotive aluminum hub, improve the strength and elongation.Magnesium alloy die casting has been further developed and replaced by gravity casting.

3. Development direction of automobile casting technology

Automobile technology is developing towards lightweight, numerical and environmental protection.According to relevant data reports, for every 10% reduction in vehicle weight, fuel consumption can be reduced by 5.5%, fuel economy can be improved by 3-5%, and emissions can be reduced by about 10%.There are two main ways of casting lightweight.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.The other is to reduce the casting wall thickness, design multi-part composite casting, produce thin-wall high-strength composite casting, reduce the machining allowance, and produce near-final casting.With the rapid development of automobile technology, in order to shorten the preparation period of casting production and reduce the risk of new product development, rapid molding technology, computer simulation, 3d modeling and numerical control technology are required.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 casting industry must take the road of high efficiency, energy saving, material saving, environmental protection and green casting, because the state and society require strict control of the large energy consumption and pollution of automobile casting industry, in order to improve the hot, dirty and tiring labor intensive industry employees' working environment.

4. Development trend of automobile casting technology

There are many developing trends of automobile casting technology at home and abroad. Now we only introduce some casting technology and developing trends in mass production line of automobile industry.

4.1 sand mold casting and forming technology

After manual compaction, one-shock + compaction → high pressure + microseismic compaction → air impact compaction → static compaction, several development stages of the model are presented.The essence of static pressure molding technology is "pre-compacting in air + compacting", which has the following advantages: clear cast profile, high surface hardness and uniformity, small drawing inclination, high utilization rate of mold plate, small wear and tear of process equipment, low surface roughness of mold, low waste rate of mold.Therefore, it is the latest and most advanced molding technology, and has become the mainstream of today's compact technology.At present, the high-pressure modeling and single air impact modeling have been gradually replaced by static pressure modeling, the original high-pressure modeling line and the main machine of gas impact modeling line have been gradually updated to static pressure modeling main machine, new foundries are preferred to adopt static pressure modeling technology.At present, the more famous foreign manufacturers of static pressure molding equipment have Germany KW company, HWS company and Italy sawei company.Domestic automobile casting manufacturers mostly choose the equipment made by HWS company or KW company, such as faw casting company, dongfeng automobile casting factory, Shanghai shengdeman casting company, east China taixi, shanxi sanlian, guangxi yuchai, wuxi diesel engine factory, etc.

4.2 near-netting technology

(1) epc forming process

Lost mold casting is also known as gasification mold casting, solid mold casting, non - cavity casting.The size accuracy of the process is up to 0.2 mm, and the surface roughness is up to Ra5 ~ Ra6 muon.The process adopts dry sand without binder and vacuum extraction.According to the statistics in 2003, 150 enterprises in China used this technology to produce three kinds of castings, such as box type, pipe fitting and valve body type, heat-resisting and wear-resisting alloy steel type, with a total output of more than 100,000 t.Domestic automobile foundry, some use domestic casting production line: some use simple production line or single machine production;Some adopt the foreign introduction casting production line production.Faw group co., LTD. Introduced shaker shaker from fukang company in 1993 to produce EPS mould pre-foaming machine and molding machine, and produce automobile intake pipe.Changsha engine general factory from Italy to introduce automatic casting line production aluminum alloy cylinder block, cylinder head casting.Hefei forklift group produces complex box castings with the process of bonding 4 sections of foam mould into a whole, with the dimensional accuracy up to ct7-ct8. The products are exported to the United States.Chengdu chengtong group, with 8 pieces of foam die bonding into a whole process to produce the loader transmission, casting quality up to 320 kg, compared with sand casting, blank weight reduction of 15%, the yield of more than 95%.In recent years, lost mold process has developed greatly in the United States. General motors invested and built 6 lost mold casting production lines to mass produce aluminum alloy cylinder block and cylinder head castings.In the future, the technology of rapid mould making and simulation will be widely used to shorten the production preparation period and realize the rapid production of casting.The future direction of development must be good quality, complex, precision, long life of high-grade mold.To improve the technical level of the mould material, forming process, coating technology and tooling equipment of this technology, so that EPS casting can have a broader development prospect.

(2) investment casting forming process

Automobile investment casting technology has made great progress in China, and the near-net casting technology can be used to produce a lot of casting products.The precision casting technology includes sodium silicate shell technology, composite shell technology and silica sol shell technology.Automobile product material has carbon steel, alloy steel, nonferrous alloy and nodular cast iron.Foreign high alloy steel, super alloy materials.Smelting equipment domestic use of ordinary, fast intermediate frequency furnace;Foreign use of vacuum furnace, converter, high frequency furnace technology.The surface roughness of the shell can reach ra1.6m, the size accuracy can reach CT4, and the minimum wall thickness can reach 0.5 ~ 1.5mm.Europe, the United States, Japan and other countries began to pay attention to the application and expansion of precision castings in the automobile industry.The market demand of automobile precision castings in China is also in rapid growth and development. In 2003, the output of precision castings was 600,000 t, with an output value of 11 billion yuan.Dongfeng automobile precision casting co., LTD. Adopts the composite shell making process of silica sol + water glass to produce products with high technical content and high added value. The original castings, forgings, machining and multiple assembly structures are designed and manufactured into a whole precision casting, which significantly reduces the manufacturing cost.

The future development trend of investment casting is that the casting products are more and more close to the parts and components.The complexity and quality of parts and components are getting higher and higher, the research and development methods are getting stronger and stronger, and professional collaboration is emerging. The application of CAD, CAM and CAE has become the main technology of parts and components product development.As the leader in China's precision casting industry, the precision casting enterprises of dongfeng motor company and faw group will surely develop rapidly with strong r&d strength and advanced technology.

4.3 core making technology

At present, there are three kinds of core-making processes in automobile casting at home and abroad. In modern automobile casting, the main technologies often used in parallel are hot core core, shell core core, cold core core, etc. Traditional grease or oil sand core has been eliminated.Cold core box technology has two characteristics: one is the hardening speed, high initial strength, high productivity;Second, the sand core has high dimensional accuracy, which can meet the requirement of producing thin wall and high strength castings.Therefore, the core making technology has the tendency of cold core box technology.Faw casting co., LTD., dongfeng automobile foundry, Shanghai saindeman casting co., LTD., east China taixi, shanxi international casting co., LTD.The modern advanced 110L cold box core making machine is shown in figure 1.

The most advanced Core making process is the Core making center combined with Key Core and cold Core box technology. The whole Core shooting, Core taking, burr dressing, positioning and combination of multiple cores, coating, drying and other processes are all completed automatically with one or more Core making machines and manipulator.The more famous core production centers abroad are LORMENDl company of Spain, Laempe company of Germany and Hottinger company, FA company of Italy and so on.Dongfeng automobile foundry, faw casting co., LTD., Shanghai sainderman casting co., LTD., east China taixi, Shanghai diesel engine, luotou no. 2 railway, weichai, jiangxi isuzu, etc. All adopt the technology of cold core box core making.

4.4 cast iron smelting technology

At present, there are two main ways of cast iron smelting technology at home and abroad.Second, adopt medium frequency induction furnace melting technology.The intermediate frequency furnace technology produced by inda company and piler company in the United States has begun to receive more and more attention. This technology is becoming more and more mature, and its advantages of cleanness, environmental protection, energy saving, high efficiency and safety are prominent. It is the future development direction.

Therefore, cast iron is gradually transferred from the former frequency furnace melting to the use of efficient and energy-saving medium frequency furnace melting.1. The technology of intermediate frequency furnace and heat preservation furnace produced by inda company and piler company has been developed and applied in spherification agent, inoculation agent, vermicularizing agent and various other additive products, forming commercialization, standardization, normalization and serialization.Cast iron inoculating machine with photoelectric control is widely used.The newly developed method of silk feeding spheroidization and SINTER CASTZ technique, which is combined with modern detection technology, is a very advantageous technology for spheroidization and vermicular treatment of cast iron.Foreign metal charge after crushing, purification, weighing, greatly improve the melting efficiency and quality of molten iron.Tianjin Toyota, tianjin qinmeida, suzhou qinmeida and other foundries in China have adopted crushing treatment technology for furnace burden.

4.5 die casting technology of aluminum alloy cylinder body and cylinder head

Aluminum alloy is the fastest and most widely used light metal in automobile, because the performance of aluminum alloy itself has reached the requirements of light quality, high strength and corrosion resistance.Initially, aluminum was used only for parts that were not subject to impact.Later, through the strengthening of alloy elements, the strength of aluminum alloy is greatly improved, due to the light weight, good heat dissipation and other characteristics, can meet the requirements of the engine piston, cylinder block, cylinder head in the harsh environment.The core technology of aluminum alloy cylinder body and cylinder head die casting can improve the quality control of materials such as purification, refining, refining and deterioration, so that the quality of aluminum casting can reach consistency and stability.With the development of China's automobile industry, especially the rapid increase of family cars and the increase of automobile parts exports, automobile aluminum casting will have a great growth.The total casting production in China in 2003 was 19.87 million t, among which the aluminum magnesium alloy was 1.17 million t, accounting for 5.8% of the total production.Toyota hopes to increase its aluminum cylinder block from 35 percent to 50 percent in the next two years.Nissan plans to use aluminum in 70 percent of its gasoline engine cars by 2010, and nearly 100 percent of its cylinder heads and transmission cases.Back in 1994, Honda motor company replaced all gasoline engine blocks with aluminum blocks.Aluminum alloy cylinder block, cylinder head and other non-ferrous metals are mostly used die casting (including vacuum die casting), low pressure die casting, high pressure die casting, metal mold gravity casting and very promising semi-solid die casting forming technology.The aluminum die casting workshop of dongfeng Honda engine company and dongfeng nissan engine company adopts 2500t die casting machine to produce aluminum cylinder block and realizes localization.There are mainly two kinds of aluminum cylinder head forming process, one is the gravity casting forming process represented by Europe and the United States, Shanghai pilberg, nanjing taixi and other companies choose Italian fata company gravity casting machine production aluminum cylinder head;Second, the low pressure casting and forming process represented by Japan and South Korea, dongfeng nissan engine branch aluminum die-casting workshop, guangdong zhaoqing casting company, tianjin Toyota casting company all choose the low pressure casting machine of Japanese new east and other companies to produce aluminum cylinder head.

4.6 magnesium alloy forming technology

The specific strength and specific stiffness of magnesium alloy is higher than that of steel and aluminum alloy, and much higher than that of engineering plastics.Magnesium alloy also has high temperature resistance, corrosion resistance and creep resistance.Magnesium is currently the lightest metal used in the automotive industry. It is 1/3 lighter than aluminum, 3/4 lighter than steel, and 1/5 lighter than nonmetallic plastic.Therefore, magnesium alloy is an ideal material for automobile to reduce the quality. Magnesium alloy die-casting parts can replace some complex structural parts, such as the panel framework of dozens of steel parts after stamping and welding, with a mass of about 10 kg. If changed to magnesium alloy die-casting parts, the quality is only 4 kg at one time, and the production cost is greatly reduced.With the continuous development of new magnesium alloy materials and the improvement of processing technology, magnesium alloy in the automotive market will continue to expand and continue to grow steadily.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.Due to the prominent advantages of the castability of die-casting magnesium alloy, the casting wall thickness can reach 1 ~ 1.5mm, and the die-drawing inclination is 1°-2°. Although the emphasis of magnesium alloy casting is still on pressure die-casting, the performance and cost of die-casting magnesium alloy are still faced.Therefore, a new process - magnesium alloy semi - solid processing technology appeared.The technology has been mainly used in the production of integrated magnesium and aluminum alloy castings.Magnesium alloy abroad has a broad application prospect in automobile. The production of magnesium alloy die casting in Europe and the United States is increasing at a rate of 25% per year.The transmission shell of Audi A6 car is a magnesium alloy die casting with a mass of only 14.2kg. Audi first used the magnesium casting for the dashboard skeleton.Ford motor company USES magnesium alloy to make seat frames instead of steel, reducing the weight of seats from 4 kg to 1 kg.Ford is working on making cylinder blocks with magnesium alloy.Japan's mitsubishi corporation and Australia's department of science and technology have teamed up to develop an ultralight magnesium alloy engine with a mass of just 7.5kg.BMW in-line six magnesium alloy cylinders have been put into mass production.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 science and technology projects of the Ministry of Science and Technology, such as transmission shell, gear housing cover, valve housing cover, steering wheel frame and other magnesium alloy die castings.Shanghai gantong automobile accessories co., LTD takes the lead in producing magnesium alloy gearbox shell die casting for cars.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, where the technology has been basically mature and in a leading position in the world.This technology is called the most promising material forming technology of the 21st century.Alumax takes the lead in transforming this technology into productivity. The blank size of the total brake pump body of aluminum alloy automobile is close to the size of parts. The processing amount accounts for 13% of the casting quality, and the processing allowance of the same metal type casting accounts for 40% of the casting quality.Since the 1980s, Europe and other countries have done a lot of research and application in semi-solid state applications.Italy is one of the first countries to use semisolid processing technology, which stampal-saa USES to make gearbox covers and rocker arms for Ford motor company.Japan's Speed Star Wheel already USES the technology to produce aluminum alloy Wheel castings weighing about 5 kg.Semi-solid metal processing technology in China started late, in the late 1970s.Compared with foreign countries, the research of semi-solid metal forming technology in China is still very backward.According to the current research situation in China, the development trend of this technology is that the metal thixoforming technology has been basically mature, while the rheological forming technology has been developing slowly.Therefore, in the future, more researchers will turn to the study of rheological forming theory and application.At present, semi-solid metal forming technology is mainly applied to the forming of low melting point metals such as aluminum, magnesium, lead, etc.At present, scholars at home and abroad have developed numerical simulation software for semisolid 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 casting production in China in 2003 was 1.87 million t, among which the gray cast iron was 10.49 million t, accounting for 53% of the total production.The great application of gray cast iron in automobile is due to its low cost and good casting performance.With the requirement of lightweight automobile technology, the growth and development of gray cast iron will be affected to some extent, so its development trend is to strengthen the development and application of thin-walled high-strength cylinder block and cylinder head casting technology.The difficulty of thin-walled high-strength cylinder block and cylinder head casting 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 uniform.The hardness, pearlite volume, carbide content, graphite form and other metallographic structure of automobile cylinder block and high-power diesel engine cylinder block and cylinder head casting have high technical requirements.For example, the body hardness of the cylinder block and head of high-power diesel engine is required to be 1 70 ~ 228 HBS and 179 ~ 235HBS respectively, with high strength and size requirements and surface roughness Ra<50 PM.The grade of grey cast iron material is constantly improving, HT300 has been used in the production of cylinder block and cylinder head, some products may reach HT350.Domestic automobile foundry in the material process, smelting process, molding process, core process, mold manufacturing process, detection technology and other aspects have done a lot of work, and these technologies are applied in the car cylinder block and high-power diesel engine cylinder block, cylinder head and other castings.

(2) vermicular graphite cast iron technology

Vermicular graphite cast iron has the strength of nodular graphite cast iron and similar anti-vibration, heat conduction and casting properties compared with gray cast iron.The working temperature of vermicular iron in ferrite body can reach 700℃.The working temperature of high silicon molybdenum vermicular iron can reach 870℃.Vermicular cast iron will not replace nodular cast iron nor gray cast iron.The great potential market of vermicular graphite cast iron is automobile industry, whose main products are engine block and high-power diesel engine head.With the increase of the automobile lightweight and specific power (power/displacement), the working temperature of the cylinder block and cylinder head is getting higher and higher, the working temperature of many parts exceeds 200℃, under this temperature, the strength of aluminum alloy drops substantially, and vermicular iron has a great advantage.It will be the only advanced automobile engine material that can meet the requirements of technology, environmental protection and performance.Because vermicular graphite cast iron has the characteristics of high strength and thin wall, it can reduce the quality.Opel's research shows that the same power engine cylinder block with vermicular iron can reduce the wall thickness from 7 mm to 3 mm and reduce the casting quality by 25%.

Vermicular graphite cast iron has a narrow range of vermicularizing treatment.Foreign BMW automobile company, daimler-chrysler automobile company and duff company produce vermicular graphite cast iron for engine block.Ford, in partnership with Sinter, produced 100,000 cylinders a year in Brazil in 1999.The German Halberg foundry has been producing V8 vermicular iron cylinder block for audi since 1991. The wall thickness is 3.5mm and the weight of 147kw cylinder block is only 74kg.The foundry of dongfeng motor company formally produced vermicular cast iron exhaust pipes on the assembly line in May 1984, becoming the first factory in China to mass produce vermicular cast iron products on the assembly line.In the early 1990s, the vermicular transmission shell and exhaust pipe of Shanghai Volkswagen santana car were developed successfully.Wuxi diesel engine branch of faw foundry company started mass production of vermicular iron cylinder heads in the 1980s.Shanghai senderman casting co., LTD. Produces medium silicon molybdenum vermicular iron exhaust pipes for Shanghai Volkswagen.

(3) ductile iron technology

Because of its high strength, high toughness and low price, ductile iron still has a great development in the automobile market.The output of ductile iron in our country is also growing continuously, with the annual output of 2003 accounting for 24% of the total output. At the same time, many standards of ductile iron have been formulated, and advanced technologies suitable for mass production of ductile iron on the assembly line have been developed, such as shaking bag, pneumatic desulfurization, type inner and cover balling, various instantaneous inoculation, audio, ultrasonic and thermal analysis and detection technologies.At present, the production of ductile iron in the developed countries accounts for more than 25% of the total casting production, and the production of ductile iron in the United States accounted for 33% of the total casting production in 2003.The development trend of ductile iron product technology in automobile casting industry includes the following four aspects.

One is cast pearlite, high strength (qt700-2, qt740-3) truck and car crankshaft, cast ferrite, high elongation (qt400-18, qt440-10) automobile exhaust pipe and bridge shell chassis casting.Higher qt800-2 and qt900-2 are also in development and application.

The second is the security casting, casting production of car steering knuckle material technical conditions are very strict, the casting requirements of zero defects, 100% non-destructive testing, there are three automatic testing technology used in production.

Third, the heat-resisting ductile iron, namely high-silicomolybdenum, medium-silicomolybdenum and high-nickel ductile iron, the exhaust pipe produced by this material has a very good high-temperature resistance performance: at present, the foundry of domestic automobile companies has produced the cast silicomolybdenum ductile iron exhaust pipe.

Fourth, austenite ductile iron, the special material properties of the material has become the focus of the casting industry, this is a kind of material with great potential for development and application, mainly used in the production of crankshaft and other products.

In addition to the above, the automobile foundry has produced the cast ductile iron chilled camshaft.

4.9 casting process computer application technology

With the rapid development of automobile casting technology, rapid prototyping technology, computer simulation, 3d modeling and numerical control technology have been widely applied to shorten the production preparation period of casting and reduce the risk of new product development.The application of rapid prototyping technology in casting production has made great progress.In addition to the moulds for new products and wax moulds for investment casting, it can also be used to make phenolic resin shell mould and shell core, which can be directly used to assemble sand mould.After receiving 3d CAD data from customers, foreign companies can provide castings to customers within 3 weeks according to different product structures.Simulation molding process is becoming one of the frontiers of international automobile casting, tsinghua university, Japan's new east industry and other green sand compaction process simulation.It is worth noting that Germany aachen university and tsinghua university are conducting data simulation of the core-shooting process.The integrated design and development of cad-cam-cae in automobile casting industry in China has been fully applied, especially the virtual technology of CAE solidification simulation. The Magma and sinocasting software are applied to simulate and analyze the mold filling, solidification temperature field and flow field of the casting of new products, so as to predict and analyze the shortcomings of the casting.The casting expert system is further applied, such as sand quality management, casting defect analysis, die casting process parameter design and defect diagnosis.

4.10 casting inspection technology

Casting inspection technology is a key means to ensure casting quality.Casting size inspection, there are commonly used inspection fixture, clamp, special inspection fixture.For the complicated parts such as cylinder block and cylinder head, the dimension of the casting is measured automatically with the three-coordinate instrument and the wall thickness of the casting is detected with the ultrasonic instrument.The application of NDT technology is more and more extensive. Fluorescent magnetic powder is often used to detect surface cracks of important parts.The spheroidization rate of nodular iron was detected by ultrasonic or audio.The matrix structure (pearlite content) of the casting was detected by eddy current.In order to meet the testing requirements of important parts, the above three testing instruments can be combined into an automatic testing line.The defects of shrinkage cavity and porosity in the casting were detected by X-ray, and 100% of ductile iron steering knuckle castings were detected by X-ray by Honda of Japan.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 minimize the negative impact on the environment and achieve the highest resource efficiency in the whole life cycle of casting products from design, manufacturing, packaging, transportation, use to scrap disposal.Casting industry has always been considered as an industry with high energy consumption and high pollution. It is necessary to continuously develop new casting materials with energy saving, clean, low emission and low pollution for production and use.For resin, to reduce the content of free formaldehyde and free phenol and other harmful substances;Gradually increase the application of cold core box technology, to reduce the impact of resin sand on the environment, to achieve standard emissions: reduce the solidification temperature of hot core box, shell core sand, core process from hot core box method to warm core box method, to save energy.China's automobile foundry consumes nearly 10 million tons of new sand every year, and the pollution from the old sand and the large amount of new sand resources are unbearable. Therefore, the recycling technology of the old sand is imperative.The waste sand emission in advanced industrial countries has been reduced to less than 10%, and the old sand recycling technology has been widely used in Europe, Japan and other regions.Harbin dong 'an automobile engine co., LTD. Has introduced thermal regeneration equipment from Italy and applied it in production.Faw casting co., LTD. Introduced Japanese technology, combined thermal and mechanical regeneration, processing core sand and core sand mixed sand has been applied in production.At present, dongfeng motor company is also accelerating the development and application of old sand regeneration technology.Increase the utilization of scrap and return charge to reduce the consumption of new pig iron and aluminum resources.The casting technology oriented to circular economy in automobile casting industry should take circular economy 3R as the industry criterion, namely to carry out the work with Reduce, Reuse and Recycle.

5. Problems faced by China's automobile foundry industry

During the transition from "planned economy" to "market economy", China's automobile foundry industry has experienced four stages of starting, stability, development and maturity, and has made remarkable achievements.However, we must have a clear understanding of the historical responsibility of automobile casting industry and the gap with the reality of developed countries, firmly grasp the development trend of domestic and foreign casting technology, timely and appropriately adopt advanced casting technology, the implementation of the sustainable development strategy of the foundry industry, the current automobile casting owners have the following problems.

The average scale of foundry enterprises is quite different from that of 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 casting industry, its current situation is still scattered factories (more than 20,000 founders), with more employees (up to 1.2 million) and low benefits (casting per plant is only 500 t/ year), which is only equivalent to 1/9-1/4 of the industrial developed countries such as the United States, Japan, Germany, France and Italy.

The overall technical equipment level of foundry enterprises is quite different from that of foreign countries.The technical equipment level difference between enterprises is big, the technical equipment level of 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 also more than 250 domestic molding production lines, these production lines are mainly concentrated in the mass production enterprises of automobile internal combustion engine parts.

The r & d and innovation ability of China's foundry enterprises is quite different from that of foreign countries.According to statistics, there are more than 30 major casting inventions in the world, none of which is Chinese.Only a few casting products with high technology content, high added value, independent intellectual property rights and international reputation are produced in China.

High labor intensity, high energy consumption, high resource consumption and high environmental pollution are common in foundry enterprises in China.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, castings in the process of sand removal handling without equipment, so manual operation labor intensity is very large.Casting is a big energy consumer. One of the reasons for the high cost of casting is the high energy consumption of casting. The average energy consumption of China is about twice or more than that of developed countries.The foundry industry is also a major environmental polluter. It is estimated that the annual emissions of SO and other gases are about 165m3, 900,000 tons of dust, 18 million to 22.5 million tons of waste sand and 5.3 million tons of waste residue.

Casting enterprise engineering technical personnel and technical workers serious fault, research and development personnel shortage.Due to the casting industry's poor environment, high labor intensity and low pay, some engineering and technical personnel and skilled workers drain.But in the foundry production line work related personnel many are not through the system training, can not meet the requirements of modern production.With the decrease of casting specialty in colleges and universities in China, the shortage of casting technical talents in the future, especially senior technical talents with innovative ability, will be more serious.

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 the casting products to developing countries, for us to provide opportunities.But at the same time, the requirements of automobile technology, the requirements of customers on casting products, the requirements of the state on environmental protection laws and regulations, and the requirements of casting enterprises themselves are increasingly strict.These again put forward higher challenge to foundry enterprise.Facing the opportunities and challenges, the countermeasures and Suggestions are as follows.

Foundry enterprises should develop towards specialization and further improve the specialization level which is conducive to market competition.We will vigorously develop commercial 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 a simple centralized integration, nor is it to build a large factory.The principle of specialization is to set up a large number of personnel, smooth operation, decision-making speed and strong flexibility advantages of professional small casting enterprises.

Casting enterprises should take improving casting product quality and reducing production cost as the eternal theme.There is a big gap between the quality of our casting and that of foreign countries, such as the size accuracy and surface roughness of the casting is 1 ~ 2.The stability and consistency of castings vary greatly.The defect rate of complex castings in China is about 10%, while the defect rate of complex castings in foreign countries is less than 5%.This wastes a lot of main and auxiliary raw materials, energy consumption and labor cost, which increases the production cost of the casting.Therefore, enterprises must reduce energy consumption and raw material consumption, and strive to do a good job in environmental protection and labor security.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 the high level of product quality standards.The concept of quality should be extended from various indexes of castings to the integrated reflection of customers' physical quality, service quality, price and delivery time.

Foundry enterprises should speed up the development of technology and the adjustment of technical structure.In the way of technology development, enterprises should make full use of domestic resources, adopt joint research and benefit sharing to develop technology.Enterprises are both competitors and partners. Therefore, enterprises must strengthen cooperation in technology development if they want to develop faster.Enterprises should fully mobilize their own technical forces, to establish an enterprise - centered production, learning, research relationship platform.High and new technology should be used to transform the traditional casting technology, and advanced technology should be adopted timely and appropriately.Such as the use of high efficiency, energy saving, environmental protection, safety smelting, modeling, core making, cleaning, sand and other equipment;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 big automobile factories, but should become independent manufacturers and suppliers of casting products, facing not only the domestic market, but also the global market.To become a true international and domestic OEM supplier.Foreign big car manufacturing companies to implement global procurement, the original attached to the big car factory foundry has become an independent, professional casting enterprises.It is necessary to increase the proportion of complex casting, high technology content and high value-added casting and improve the benefit of enterprises.The further processing of casting blank should be developed and the added value of casting should be increased.Develop and cultivate the characteristic product of this enterprise, make it become famous brand product, increase intangible assets for the enterprise.

Foundry enterprises should continue to strengthen education and training.It is necessary to train professional talents in casting, establish an incentive mechanism for retaining people with affection, career and salary, arouse 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 improve the technical and labor quality of the staff and workers in the whole industry.