Present situation and Development Countermeasures of foundry technology in China
Casting is one of the most important methods of metal forming, which is the basis of hot working. The casting history is as long as the history of Chinese civilization. Our ancestors made the exquisite bronze ware like Sanxingdui more than 4000 years ago. Its technical level is amazing. However, in modern times, as the world's largest casting output country, China's casting level lags behind the developed countries.
General situation of foundry industry in China
Since 2000, China's casting output has surpassed that of the United States and has been ranked first in the world for six consecutive years, among which 22.42 million tons were in 2004 and 26 million tons were estimated in 2005. The annual output value of castings exceeded 250 billion yuan, accounting for 1 / 4 of the total output of the world, and has become the world foundry production base. According to the output statistics of major casting countries in the world in 2004, the top ten casting producing countries can be divided into two categories. One is developing countries, although the output is large, but the added value of castings is low, there are many small enterprises, a large number of employees, and the proportion of ferrous metals is large. The other is developed countries, such as Japan, the United States and Europe, which mainly produce high value-added castings with high technology.
In developed countries, casting technology is advanced, product quality is good, production efficiency is high, environmental pollution is small, and raw and auxiliary materials have formed series. Europe has established a multinational service system, the production of mechanization, automation, intelligence. Technical standards are strictly implemented in the production process, and the reject rate of castings is about 2% - 5%. It is important to use information technology to improve the level of casting process design. Software is widely used to simulate the filling and solidification process and optimize the design process.
In terms of batch production and labor productivity, Europe, the United States and Japan have great advantages. Japan's labor productivity is 140 tons of castings per capita, while China's is estimated to be about 20 tons, a difference of seven times. The labor cost in China is less than US $1 / hour, which is dozens of times higher than that in developed countries, so it has advantages to export castings. However, in recent years, the price of materials has soared, which makes the advantage of casting materials cost disappeared. In terms of product quality and grade, we are far behind developed countries. In recent years, China's casting export has increased, but the export only accounts for 97% of China's total output, accounting for less than 8% of the world casting market circulation. The overall growth rate is slow, showing poor quality and low price. For a long time, the export of castings to low-grade products, all kinds of pipe fittings, radiators, Kitchenware and Bathware accounted for 36%. Although some export castings can meet the international standards, there is still a long way to meet the European and American customer standards.
In China, foundry industry is an important industry related to the national economy and people's livelihood. It is the foundation of the pillar industries such as automobile, petrochemical, steel, electric power, shipbuilding, textile and equipment manufacturing. It is an important part of the manufacturing industry. In machinery and equipment, castings account for a high proportion of the whole machine weight, with internal combustion engines accounting for 80%, tractors accounting for 50% - 80%, hydraulic parts and pump machinery accounting for 50% - 60%. Almost all the key parts of the automobile are cast; the metallurgical, mining, power station and other major equipment rely on large castings and forgings, and the quality of castings directly affects the quality and performance of the whole machine.
China's foundry enterprises are mainly distributed in the East, and the output in the west is less. At present, there are about 24000 foundry enterprises and more than 1.2 million employees in China. From the perspective of industrial structure, there are not only casting branches or workshops subordinate to main engine production plants, but also professional foundry plants, as well as a large number of township foundries. In terms of scale and level, there are not only large foundry plants with advanced technology and high degree of mechanization, but also some advanced foundry plants in heavy industry, automobile industry and aviation industry, as well as small foundry plants with backward technology, simple equipment and manual operation, with an annual output of more than 100 tons of castings.
Problems existing in China's foundry industry
The technical level of China's foundry industry is about 20 years behind that of developed countries, which can not meet the needs of rapid development of national economy. Backward technology, obsolete equipment, high consumption of energy and raw materials, serious environmental pollution and poor working environment of workers have become the consensus of the industry.
The specific performance is as follows:
(1) The technology level is low and the casting quality is poor
① The machining allowance of casting is large. Due to the lack of scientific design guidance, it is difficult for process designers to control the deformation problem by experience. The machining allowance of casting is generally 1-3 times larger than that in foreign countries. Large machining allowance, serious energy consumption and raw material consumption of castings, long processing cycle and low production efficiency have become the bottleneck restricting the development of the industry.
② The segregation and inclusion defects of large castings are serious. After solidification of large steel castings and ingots, there are macro segregation and coarse grains in the riser root and the thick section of castings.
③ The problem of casting crack is serious.
④ The design of gating system is unreasonable. Due to improper design, there are defects such as air entrainment and inclusion, resulting in low yield and qualified rate of castings.
⑤ Simulation software is not widely used. Casting process simulation is a necessary part of casting production. In foreign countries, if there is no computer simulation technology, no order can be obtained. The computer simulation of foundry industry in China started earlier. Although the development ability of the core calculation part is strong, the overall software packaging ability is poor, which leads to the mature commercial software development far behind the developed countries. A considerable number of casting enterprises are deterred from the computer simulation technology and lack of trust. At present, although this situation has been improved, there are few enterprises that have purchased foundry simulation software to play its role. Therefore, it is urgent to train employees on software application.
⑥ The production capacity of ordinary castings is surplus, and the manufacturing of high-precision castings is still difficult