1 Current status of heat treatment industry

According to the investigation of the China Heat Treatment Industry Association in formulating the “Eleventh Five-Year Plan” of the national heat treatment industry, the heat treatment in China in 2003 summed up the following basic conditions:

(1) Total number of enterprises

There are about 15,000 heat treatment plants, branch factories, workshops, joint-stock companies and private heat treatment enterprises in the national all-round enterprises. Among them, 80% of the enterprises owned by the whole people have 12,000, and 20% are private and joint-stock enterprises, about 3,000. Due to the restructuring of state-owned SMEs in many parts of the Mainland, private enterprises in the cities of East China and South China are still emerging. Many foreign-funded enterprises are preparing to set up heat treatment plants in coastal cities. The total number of private and joint-stock enterprises will continue in the late 10th Five-Year Plan period. rise.

(2) Total number of heat treatment employees

According to the national 15,000 heat treatment plants, each with an average of 25 employees, the total number of employees nationwide is about 370,000. Among them, the proportion of enterprise technicians averaged 8%, about 370,000; the management staff was about 9%, about 33,000.

(3) Total number of heat treatment heating equipment

According to the number of enterprises accounting for 5% of the total number of enterprises in the country, the national heat treatment heating equipment (with a standard of 75kW) is about 150,000 units, and the installed capacity is 11×106kW.

(4) Heat treatment capacity

The average production capacity of each equipment is 100kw/h, the national average is 1.5 shifts, and the annual production capacity of 150,000 heating equipment is nearly 45×106t.

(5) Heat treatment energy consumption

The average utilization rate of heat treatment heating equipment is 30%, the national average is 1.5 shifts, and the actual annual heat treatment capacity of 150,000 sets of equipment is 13.5×106t, and the total power consumption is 9.9×109kW.h.

(6) Heat treatment annual turnover

In the survey, the average price of heat treatment was 2.30 yuan / kg. According to the actual annual output of 13.5×106t, the annual turnover of national heat treatment is about 31 billion yuan. If the average profit margin is 10%, the annual profit will be 3 billion yuan. The average value-added tax rate in the heat treatment industry is 12.5%, and the annual tax payment to the state is about 3.9 billion yuan.

2 Research, development and application of new technologies

(1) Progress in basic research in physical metallurgy

Combining the research of new engineering materials and the potential of existing materials, Shanghai Jiaotong University has developed the theory of metal phase transformation and the mechanism of strengthening and toughening, the microstructure, fine structure and pre-phase transformation mechanism of martensite and bainite. The phase change mechanism of shape memory alloys and superplastic alloys has been studied in depth. The computer simulation of controlling the temperature and stress fields of carburizing, nitriding and thermal processes is also a prominent aspect of Shanghai Jiaotong University's work since the 1980s.

Xi'an Jiaotong University has conducted a long-term research on the macroscopic properties, microstructure and interrelationship of materials according to the service conditions and failure modes of machine parts. Professor Zhou Huijiu proposed a small energy multiple impact theory to correct some criteria for material evaluation and selection. Combined with the application of low-carbon martensite in production, significant results have been achieved.

Over the years, under the leadership of Professor Lei Yanquan, Harbin Institute of Technology has insisted on the theory and practice of metal deformation strengthening. For the recrystallization of metal under certain temperature and deformation, there are many rebellious yarns between different tissues and properties after heat treatment. Important conclusions, and based on this, guided and developed a series of change heat treatment methods. A typical example of a deformation heat treatment application is the post-forging residual heat quenching of steam turbine blades and diesel engine connecting rods, which not only saves energy but also improves performance. Harbin Institute of Technology has also made outstanding achievements in metal matrix composites, duplex steels, copper-based and iron-based shape memory alloys and ceramic toughening, and ion plating and ion implantation of metals and alloys.

Beijing University of Science and Technology has carried out systematic research on the theory and practice of low-alloy high-strength steel and microalloyed steel, controlled rolling, the role of rare earth elements in amorphous materials in steel and the deposition of diamond thin films. The results obtained in the metallurgical industry application.

In particular, it is pointed out that the early non-diffusion shear mechanism of the bainite proposed by Professor Ke Jun and the diffusion-step mechanism of Alonson have become the tit-for-tat view of the court in the international arena. Xu Zuyao, Kang Mo Ni, Yu Degang and others have made outstanding contributions to the theory of bainite transformation and the development of bainitic steel and bainite isothermal treatment.

(2) Progress in heat treatment production technology

——Advances in carburizing technology

Carburizing is one of the most widely used processes in the automotive tractor industry. In the 1950s, the transition from solid carburizing to the infiltration of liquid penetrant into the well furnace was achieved, which improved product quality and improved work efficiency. After the successful development of the LiCl dew point meter in the early 1960s, the controlled carburization of methanol and acetone was first realized on the well type carburizing furnace. After mastering the preparation method of the endothermic atmosphere and successfully developing the sealed carburizing furnace, the carbon potential control of the sealed carburizing furnace was realized by the dew point meter. In the late 1960s, a successful infrared carbon dioxide analyzer was developed. In order to improve the accuracy of carbon potential control, infrared instruments were promoted in the 1970s, mainly for drip-type carburizing of pit furnaces. At present, controlled carburization using methanol and kerosene has reached a fairly popular level. Especially in the late 1970s and early 1980s, a large number of drip-type sealed carburizing furnaces and a variety of microprocessor-programmable controller carbon potential controllers were introduced, and they were widely used in sealed multi-purpose furnaces.

Due to the instillation of methanol and kerosene into the furnace, the carbon monoxide component in the furnace gas is unstable, and the methane content is also 1% to 2%. The single factor control of the carbon dioxide infrared detector alone achieves a control accuracy of ±0.05%. To this end, research has developed instruments and methods for multi-factor carbon potential control of carbon dioxide, carbon monoxide and methane.

Because the raw materials for the preparation of endothermic gas, natural gas and liquefied petroleum gas, are tightly supplied, and methanol is used in large quantities, the production cost is high, forcing industrial production to find another way out. The emergence of carbon molecular sieve pressure swing adsorption nitrogen (PSA) technology has created conditions to solve this problem. In the early 1980s, the successful domestic carbon molecular sieve system was successfully developed. Subsequent synthetic carburization with a nitrogen-based atmosphere, methanol and ethyl acetate (or kerosene) emerged. At the same time, atmospheric oxygen (oxygen potential) measurement, control technology and instruments were introduced. At present, the method of carburizing using a nitrogen-based synthesis atmosphere and a gas control technology of an oxygen probe, and a method of controlling a carbon potential and a depth of a layer by a microprocessor have been widely used in production. Individual plants have also introduced equipment and processes for the Supercarb direct carburizing process. At present, controllable carburizing, carbonitriding, and nitrocarburizing technologies in the automotive, motorcycle, construction machinery, bearing, gear, and fastener industries have reached considerable popularity.

Since the 1980s, local equipment manufacturers have been able to produce series of sealed multi-purpose furnaces, push rod continuous furnace carburizing, quenching, cleaning, tempering production lines and mesh belt furnace production lines. The production and supply of carbon potential and process automation control systems are also available. Since the 1990s, internationally renowned equipment manufacturers have established joint ventures and wholly-owned production plants in China, providing advanced equipment with high reliability and acceptable price for heat treatment enterprises. To this end, it has also stimulated the improvement of the manufacturing level of local equipment manufacturers, creating favorable conditions for the privately-owned, joint-stock heat treatment processing enterprises and state-owned large factories in the past ten years.

—— Popularization of vacuum heat treatment technology

In the 1970s, oil- and gas-quenched cold-wall vacuum heat treatment furnaces were developed. In the 1980s, they were mass-produced in series. At present, local manufacturing companies have been able to provide vacuum heating, oil and gas quenching furnaces, low pressure carburizing furnaces, 1 MPa (10 bar) high pressure gas quenching furnaces, vacuum sintering furnaces, and brazing furnaces. The maximum temperature of vacuum quenching and high pressure gas quenching furnace can reach 1350 °C, and the vacuum sintering furnace can reach up to 1800 °C. The output of various types of furnaces and furnaces is more than 200. In recent years, the development of the aviation industry and the mold industry has a large demand for vacuum heat treatment furnaces, vacuum brazing furnaces, especially vacuum heating high pressure gas quenching furnaces, which has promoted the prosperity of the vacuum equipment manufacturing industry. The combination of low-pressure carburizing and high-pressure gas quenching technology provides a new way for the life extension, distortion reduction (variation) and noise reduction of vehicle gears, and the development of semi-continuous production lines embodying this advanced technology is the mass production of automotive gears. Technical modifications to heat treatment offer the possibility. At the beginning of the new century, several domestic and diesel gear manufacturers have introduced such equipment and production lines.

Due to the high requirements of surface quality and distortion of the mold, vacuum high pressure gas quenching has almost become an irreplaceable technology for mold heat treatment. At present, in the coastal areas of South China and East China, a small-scale private heat treatment processing enterprise has at least one vacuum heating high-pressure gas quenching furnace of 0.4 MPa (maximum of 6). In the cutting tool industry, the wide application of CNC and machining centers strongly demands that the tools have high quality and long life. The environmental protection of the city also imposes stricter requirements on heat treatment. Vacuum heating and high-pressure gas quenching have become the substitutes for heat treatment of high-speed steel tools. The preferred process for bath heating and quenching.

—— Wide application of induction heating

Induction heating technology is widely used in the automotive, tractor, and engine industries. There are more than 200 types in automobile manufacturing. Nearly 50% of the weights are induction hardened, such as crankshaft, half shaft, camshaft, brake cam, steering knuckle, shifting guide slot, valve adjusting bolt, intake and exhaust valve end. Head, ball head, etc. Among them, Dongfeng Motor Corporation's semi-axial transverse magnetic field heating and quenching is the most representative advanced technology. The rectangular inductor with transverse magnetic field realizes one-time heating and quenching of the semi-axis surface and the rounded corner, which improves the production efficiency by several times and the bending-torsion fatigue strength of the half-axis by 10 times. The semi-axis induction hardening automatic production line with fault alarm, diagnosis function and automatic control by computer has been put into production for many years. The induction heat treatment of China's automobile industry has reached the international advanced level.

China's inductive power supply manufacturers since the introduction of SIT (static induction transistor), 1GBT (insulated gate bipolar transistor) and MOSFET (metal oxide semiconductor field effect transistor) all solid-state transistor power supply since the 1990s, the old-fashioned tube high-frequency power supply and machine The intermediate frequency generator set has been gradually replaced by the transistor power supply. The new power supply produced by the local enterprise can basically meet the power and frequency requirements of the user enterprise. The induction hardening machine develops the induction quenching device with identification parts, control power, automatic adjustment of process parameters, fault display, alarm and diagnosis in the direction of flexibility, automation and intelligence. It is also gradually applied in the production of automobile industry.

——The potential of chemical heat treatment is brought into play

In addition to carburizing, carbonitriding chemical heat treatment, especially the chemical heat treatment of steel in the ferrite state, it is characterized by small distortion of the workpiece, improve the wear resistance and friction reduction of machine parts, improve fatigue resistance and corrosion resistance. It has obvious effects on anti-seizure ability and energy saving. Since the 1960s, the Mechanical Science Research Institute of the Ministry of Machinery has successfully developed the nitrogen bath and the nitriding (soft nitriding) of the salt bath and the non-toxic raw material nitrocarburizing, and since the application in production, it has successively developed the carbon, boron and boron triads. Seepage, ammonia + endothermic atmosphere, ammonia + air, ammonia + carbon dioxide gas nitrocarburizing and nitrogen oxynitridation and low cyanide bath nitriding, polishing, oxidation QPQ technology and LT salt bath nitrocarburizing Automobiles, motorcycles, textile machinery, machine tools, tooling, fasteners, instrumentation, weapons and other industries have been widely used. Because of its good effect, low cost, simple process and low toxicity, it is especially favored by foreign-invested enterprises and export-oriented products enterprises listed above.

Although the process cycle of gas nitriding is long, the hardness of the layer is high, the wear resistance of the parts is improved, and the distortion of the workpiece is small, which is widely used in precision parts of machine tools. Professor Pan Jiansheng of Shanghai Jiaotong University conducted a systematic study on controlling nitriding technology in the 1980s. Through the precise control of the ammonia decomposition rate (H2), the expected nitrogen content of the steel layer and the ideal microstructure can be obtained and promoted and applied in production. In the 1970s, Shandong University of Technology (now the School of Materials Engineering of Shandong University) and Jiangsu Machinery Research Institute (now the Institute of Casting and Forging Heat Treatment) developed a solid boronizing method and a granular boronizing agent that can obtain a single-phase Fe2B layer with low brittleness. commodity. The Wuhan Institute of Materials Protection also developed a borax salt bath metal infiltration technology (similar to the Japanese TD method). Both have fully exploited the potential of chemical heat treatment in improving the life of metallurgy, mining machine parts and molds.

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