Current situation of casting technology development in China

On the whole, the academic research in the field of casting in China is not lagging behind.Domestic precision foundry production technology is limited to a small number of backbone enterprises, the industry as a whole technical level is backward, casting quality is low, material and energy consumption is high, economic benefits are poor, labor conditions are bad, pollution is serious.Specific performance in, appearance is still manual or simple machinery for mold processing;The socialization, specialization and commercialization of the production and supply of foundry raw and auxiliary materials are far from meeting the needs of the development of new technology in terms of variety quality.The production level and quality of casting alloy materials are low;Backward production management;Process design based on personal experience, less computer technology application;Poor basic conditions of casting technology and equipment;The production process manual operation proportion is high, the site worker technical quality is low;Only a few large automobile, internal combustion engine group foundry using advanced molding core-making process, most of the casting enterprises still use shaker molding machine or even manual modeling, core-making to tung oil, fat and clay and other binder sand.Most of the investment casting factories are mainly made of water glass shell.Low pressure casting can only produce non-iron or cast iron small and medium parts, not steel casting parts.With EPC technology, only the exhaust pipe, shell and other castings are put into production stably. The productivity is below type 30 / h, and the casting size accuracy and surface roughness are low.Although a relatively complete casting industry standard system has been built, most enterprises passively implement the standard, and the enterprise standard is mostly lower than GB(national standard) and ISO(international standard), and the rejection rate of some enterprises is as high as 30%.Quality and market awareness is not strong, only a few professional casting enterprises through 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 equipment has been developed and popularized, which has improved the temperature and comprehensive quality of metal liquid.Some non-ferroalloy foundry still use fuel oil, coke crucible furnace and other backward smelting technology.Cupola - electric furnace dual process only in a few batch production line can be used.A small number of large and medium-sized electric arc furnaces adopt ultra-high power (600 ~ 700kVA/t) technology.

AOD, VOD and other refining equipment and technology began to introduce, improve the inherent quality of high-grade alloy cast steel.The purity and performance of super low carbon and high strength martensite stainless steel are improved by refining technology.On the basis of maintaining the original toughness, the flexural strength ratio of 0Crl6Ni5Mo and Crl3Ni5Mo 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%.

It is widely used in domestic rare earth resources, such as rare earth magnesium treated ductile iron in automobile, diesel engine and other products.Rare earth medium carbon low alloy cast steel and rare earth heat resistant steel have been applied in mechanical and metallurgical equipment.A series of domestic inoculants, spheroidizing agents and vermicularizing agents were preliminarily formed, which promoted the improvement of cast iron quality. 

High strength and high elastic modulus gray cast iron is used in machine tool castings, and the application of high strength thin-walled gray cast iron casting technology makes the section hardness difference of cylinder body and cylinder head casting body with the thinest wall thickness up to 4-16mm less than HB30, and the structure is uniform and dense.The surface laser hardening technology of gray cast iron is used in production.Application of artificial intelligence technology in grey cast iron performance prediction.Vermicular graphite cast iron has been applied to automobile exhaust pipe and cylinder head of high-horsepower diesel engine, and the service life of automobile exhaust pipe has been improved 4-5 times.Vanadium-titanium wear-resistant cast iron is applied to guide rail, cylinder liner and piston ring of machine tools, and the service life is increased 1 ~ 2 times.High, medium and low chromium wear-resistant cast iron can be used on grinding ball, lining plate, impurity pump and bimetallic compound roll.The filter technology is applied in the production line of high-strength thin-wall castings such as cylinder block and cylinder head.

The domestic horizontal continuous casting production line is put into the market, which can produce gray cast iron and nodular cast iron profiles with the diameter of 30 ~ 250mm circle and the corresponding sizes of square, rectangular or special-shaped sections.Compared with sand mold, the performance can be improved by 1 ~ 2 brands, the utilization rate of molten iron can be improved to above 95%, energy saving 30%, material saving 30% to 50%, and the qualified rate of blank processing can reach above 95%.

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

The research on metal matrix composites has made progress, and the research on staple fiber, external particle reinforcement and in-situ particle reinforcement has achieved some results, but few industrial applications have been realized.Direct reading spectrometer and thermal analyzer are adopted in some key industries' backbone foundries to effectively control the metal liquid composition in front of the furnace, and ultrasonic wave and other detection methods are used to control the casting quality.

Law enforcement of environmental protection is increasingly strengthened, forcing the foundry industry to pay attention to environmental protection technology.Shenyang foundry research institute has developed the large-row double-layer air supply cupola and the dehumidification air supply technology of cupola.The foundry coke production base was initially built in China and the batch scale was formed.Casting ChenDu governance, water purification, waste residue use and so on a series of achievements, and develop a variety of casting environmental equipment (such as vibration shakeout machine dust hood, portable vacuum cleaner, smoke purification device, sewage purification cycle reuse system, dry wet reclamation technology and equipment of casting sand, foundry waste sand, slag waste plastics composite technology and equipment, etc.).

Commercial CAE software has been listed.Some large and medium-sized foundry enterprises began to use computer technology in smelting, metal liquid composition, temperature and productivity control.Chengdu university of science and technology developed an online control system for sand processing, tsinghua university and others developed computer-aided sand mold control system software, and huazhong university of science and technology successfully developed commercial casting CAE software.

The Internet of casting industry develops fast, some casting enterprises are active in online e-commerce activities, such as some casting mold factories to achieve remote design and remote manufacturing.

Although the research of foundry expert system started late, it has made rapid progress.It has introduced sand quality management expert system, casting defect analysis expert system, self-hardening sand quality analysis expert system, die casting process parameter design and defect diagnosis expert system.Manipulator, robot in falling sand, casting cleaning, die casting and investment casting production began to apply.