Development of foundry technology in China

On the whole, the academic research in the field of foundry in China is not backward, and many of the research results are at the advanced level in the world, but few of them are converted into the actual productivity. The high level of domestic casting production technology is limited to a few key enterprises. The overall technical level of the industry is backward, the quality of castings is low, the consumption of materials and energy is high, the economic benefit is poor, the working conditions are bad, and the pollution is serious. Specifically, the pattern is still processed by hand or simple machinery; there is a large gap between the socialization, specialization and commercialization of the production and supply of casting raw and auxiliary materials, which is far from meeting the needs of new process and new technology development in terms of variety quality; the production level and quality of casting alloy materials are low; the production management is backward; the process design is mostly based on personal experience, and the application of computer technology is few; The basic conditions of casting technology and equipment are poor; the proportion of manual operation in the production process is high, and the technical quality of field workers is low; only a few large-scale automobile and internal combustion engine group foundry adopt advanced molding and core-making technology, most of the foundry enterprises still use shock molding machine or even manual molding, and the core-making is mainly composed of tung oil, resin, clay and other binder sand. Most investment casting plants mainly use water glass as shell; low-pressure casting can only produce non-ferrous or cast iron small and medium-sized parts, not steel castings; EPC technology is only used to stabilize the production of exhaust pipe, shell and other castings, the productivity is below 30 mold / h, and the casting size accuracy and surface roughness level are low; although a relatively complete casting industry standard system has been established, most enterprises passively implement the standard, Most of the enterprise standards are lower than GB (national standard) and ISO (International Standard), and some enterprises have a scrap rate of up to 30%; the quality and market awareness are not strong, and only a few specialized foundry enterprises have passed the ISO 9000 certification. The research on quality management combined with the characteristics of foundry enterprises is very weak.

In recent years, some advanced smelting equipments have been developed and popularized, and the temperature and comprehensive quality of molten metal have been improved. For example, the external hot blast cupola has been applied, but only a few of them have been used. Only 1% of them use foundry coke. Some foundry non-ferrous alloy plants still use the backward smelting technology such as fuel oil and coke crucible furnace. Cupola electric furnace dual process is only used in a few batch production lines. A few large and medium-sized arc furnaces adopt the technology of ultra-high power (600-700 KVA / T).

AOD, VOD and other refining equipment and technologies have been introduced to improve the internal quality of high-grade alloy cast steel. The refining technology is used to improve the purity and performance of the ultra-low carbon high strength and toughness martensitic stainless steel. The yield strength ratio of 0Cr16Ni5Mo and cr13ni5mo cast martensitic stainless steel increased from 0.70-0.75 to 0.85-0.90, the strength increased by 30% – 60% and the hardness increased by 20% – 50% on the basis of maintaining the original toughness.

It is widely used in domestic products rich in rare-earth resources, such as nodular cast iron treated with rare-earth magnesium, which is used in automobiles, diesel engines and other products; medium carbon low alloy steel and rare-earth heat-resistant steel are used in machinery and metallurgical equipment; a series of inoculants, spheroidizers and vermicularizers made in China are preliminarily formed, which promotes the quality of iron castings.

The application of high-strength and high elastic modulus gray iron in machine tool casting and high-strength thin-wall gray iron casting technology makes the hardness difference of the body section of the cylinder block and cylinder head casting with the thinnest thickness of 4-6 mm less than hb30, and the structure is uniform and dense. The surface laser strengthening technology of gray cast iron is used in production. The application of artificial intelligence technology in the performance prediction of gray cast iron. Vermicular graphite cast iron has been used in automobile exhaust pipe and cylinder head of high horsepower diesel engine. The service life of automobile exhaust pipe is increased by 4 ~ 5 times. The service life of V-Ti wear-resistant cast iron is increased by 1 ~ 2 times when it is used in machine tool guide rail, cylinder liner and piston ring. High, medium and low chromium wear-resistant cast iron is used in grinding ball, lining plate, impurity pump and bimetal composite roller, and its service life is improved. The application of filtration technology in the assembly line production of high-strength thin-walled castings such as cylinder block and cylinder head reduces the defects of slag inclusion and porosity, and improves the internal quality of castings.

The domestic horizontal continuous casting production line has been put into the market, and it can produce Φ 30 ~ 250mm round and square, rectangular or special section gray cast iron and nodular cast iron sections of corresponding size. Compared with the sand mold, the performance of the product is improved by 1-2 grades, the utilization rate of molten iron is increased to over 95%, energy saving is 30%, material saving is 30% – 50%, and the qualified rate of rough machining is over 95%.

The cast iron pipe industry has introduced 10 sets of centrifugal casting equipment for medium-sized ductile iron pipes with diameter less than 1000 mm.

Progress has been made in the research of metal matrix composites. Short fiber, external particle reinforcement and in-situ particle reinforcement have achieved results, but few industrial applications have been realized.

In some key industries, direct reading spectrograph and thermal analyzer are used in the main foundry. The composition of molten metal is effectively controlled in front of the furnace, and the quality of castings is controlled by ultrasonic testing.

With the strengthening of environmental protection law enforcement, the foundry industry began to pay attention to environmental protection technology. Shenyang Foundry Research Institute has developed large row distance double layer blast cupola and blast furnace dehumidification technology; China has initially built a foundry coke production base, forming a batch scale. A series of achievements have been made in the treatment of casting dust and poison, sewage purification, waste residue utilization, etc., and many kinds of casting environmental protection equipment have been developed (such as dust cover of vibration sand remover, mobile vacuum cleaner, dust purification device, sewage purification and recycling system, dry and wet recycling technology and equipment for casting old sand, composite material technology and equipment for making waste plastic from casting waste sand and slag, etc.).

Commercial CAE software has been put on the market. Some large and medium-sized foundry enterprises began to use computer technology to control the composition, temperature and productivity of the molten metal. Chengdu University of science and technology developed online control system for sand processing, Tsinghua University and other universities developed computer-aided sand mold control system software, and Huazhong University of science and technology successfully developed commercial casting CAE software.

With the rapid development of Internet in foundry industry, some foundry enterprises are active in online e-commerce activities, for example, some foundry mould factories have realized remote design and manufacturing.

Although the research of foundry expert system started late, it has made rapid progress. The expert system of sand quality management, the expert system of casting defect analysis, the expert system of self hardening sand quality analysis, the expert system of die-casting process parameter design and defect diagnosis, etc. Robots and manipulators have been used in sand dropping, casting cleaning, die casting and investment casting.