1. Historical review In the 1960s, U.S. Carbon Corporation introduced the UCON (PAG) series of synthetic quenching agents, which can be used as an alternative to oil for the quenching and solution treatment of iron and non-ferrous alloys. A series of other types of synthetic quenching agent products were subsequently introduced. (11) High, medium, power frequency and super-audio and ultra-high frequency, ultra-high frequency pulse induction heating surface heat treatment process is widely used. Various static solid-state circuit high-frequency, high-power power supplies have been successively introduced, and fully automatic program-controlled multi-station quenching machine tools and automatic loading and unloading robots or robots have obtained industrial applications. (12) In the 1980s, the oxygen probe gradually replaced the infrared sensor for the gas potential control of the furnace gas and the computer simulation adaptive control, non-destructive testing technology, and robotic loading and unloading, so that the car parts of the mass production were carburized, quenched, cleaned, The whole process of tempering and quality inspection is automated and unmanned. (13) In the 1990s, European companies such as Ipsen International, ALD and ECM introduced cycle furnaces and semi-continuous production lines for low-pressure carburizing, low-pressure ion carburizing and high-pressure gas quenching to improve efficiency, improve quality, reduce distortion and protect the environment. Contributions provide a prospect for the heat treatment of the automotive industry. In the past 20 years, a large number of new heat treatment technologies have emerged, which has accumulated a large amount of technical reserves for the development of machine manufacturing, the improvement of mechanical product quality, and the technical transformation of heat treatment enterprises, providing a broad prospect for the progress of heat treatment production technology. Throughout the development of heat treatment technology at home and abroad, the starting point of its overall strategy can be roughly summarized into five aspects. The first is the endurable development, the second is the improvement of product quality, the third is energy saving, the fourth is to achieve accurate production, and finally the efficiency (effcient process). Technologies), low production costs. The English words in all five aspects are E, so it is called the 5E strategy. Next page Foot Measuring Gauge,Kids Foot Measuring Device,Shoe Measuring Devices,Toddler Foot Measuring Baby Yucheng Weisite Measuring Tools Co., Ltd , https://www.wsttools.com
Since the Russian metallurgist DK Chernov discovered in 1868 that the steel had a structural transformation during heating and cooling, F1 Osmond determined the phase transition temperature of the steel and the state diagram of the alloy by thermal analysis. Heat treatment has evolved from craftsmanship to science and technology for only a hundred years. In this history, both the physical metallurgy theory and the practical production technology, which are the basis of heat treatment, have made brilliant achievements. The most commendable theoretical contributions are: 1E.C. Bellin, P. Mela and Willel's systematic research on the phase transformation mechanism of steel and Duraluminium in the 1920s and 1930s. 2P. Debye, GV Wolff, WG Braig, etc. A series of studies on the crystal structure of metal alloys and their phases by X-ray injection since the 1920s. 3G.V. Kujumov and Saxe accurately measured the coherent features of the crystal changes of low carbon martensitic transformation and established the crystal KS relationship of the famous martensitic transformation. 4 The discovery of the defects of metal crystal dislocation structure and the conclusion of its influence on the strength make the physical metallurgy theory develop to a more microscopic and more quantitative depth, explain the mechanism of the heat treatment and toughening effect of metal materials, and inspire a series of new heat treatments. The development of technology, especially various types of new processes of deformation heat treatment. 5 Ke Jun and Alonson respectively proposed two tit-for-tat views of the non-diffusion-shear and diffusion-step mechanism of bainite transformation. Xu Zuyao, Kang Moman, Yu Degang and others in the research and development of bainite phase transition theory Bainitic steel has made outstanding contributions. This article is worth reviewing in the development of practical production technology: in 1890, the United Kingdom first published a patent for the preparation of a non-combustible atmosphere furnace, which was used for the bright heat treatment of metals. A. Fuli of Germany applied for it in 1921. Patent for ammonia nitriding in a pit furnace. 2P.P. Anosov advocated the gas carburization method in 1837, and after 100 years (1935), the Likhov Automobile Factory of the former Soviet Union had the first tank type with kerosene cracking gas. Continuous carburizing furnace; solid carburizing and liquid carburizing with cyanide salts were gradually replaced until the 1950s. 3 In the 1940s, GV Voroggin of the former Soviet Union gradually applied induction heating technology to steelmaking, forging heating and surface hardening heat treatment. The carbon potential controlled carburization with LiCl dew point meter appeared in the late 1940s. 5 Ion nitriding was patented in Germany in the 1930s, and KlÊckner developed commercial equipment in the late 1950s and pushed it into industrial applications. In the early 1960s, H. Weiss of Switzerland invented the CARBOMAAG drip controllable carburizing method in a pit furnace. In the mid-1960s, controlled carburization using an endothermic gas (carrier gas), methane or propane (for enriched gas) and CO2 infrared measurement and control of the carbon potential of the furnace gas was promoted in the automotive industry. At the same time, the first generation of cold-walled vacuum heating oil quenching furnaces and vacuum carburizing furnaces were introduced. Developed in the 1950s, the salt bath nitrocarburizing, known as the Tenifer or Tufftride trade name, promoted in the 1960s, shortening the nitriding cycle from tens of hours to 1 h to 2 h, which can significantly improve the fatigue resistance and resistance of the transmission parts. Grinding and anti-seizure ability; due to low processing temperature (<580 °C), the workpiece distortion is small, the disadvantage is that the cyanide salt used and the waste salt wastewater need to be properly disposed. 9 In order to avoid the use of highly toxic cyanide salts, gas nitrocarburizing of NH3 endothermic gas (Nikotrier) and NH3 CO2 (Nitroc) in a well or box furnace at 570 °C was developed in the late 1960s. The method was subsequently widely used in parts such as automobile crankshafts and low-load gears. Polymeric polymer solutions began to be used as quenching agents in the 1950s. The earliest used polymer is polyvinyl alcohol (PVA), which is used as a spray-cooling quenching of induction heating parts at a concentration of 0.1% to 0.3%. Its cooling capacity is between water and oil, and it is non-flammable and non-polluting.
2 Overall development strategy for heat treatment
2.1 Sustainable development strategy
In 1992, the United Nations Conference on Human Environment and Development in Rio de Janeiro presented the Global 21st Century Action Programme on “Promoting global sustainable development through global partnerships on the basis of equity.†At the World Summit on Sustainable Development in September 2002, Premier Zhu referred to this issue as "the harmony between mankind and nature, and the promotion of environment and development." This makes sustainable development the first principle that any country in the world must follow in its various economic construction activities. In the connotation of sustainable development, the environment is first, followed by the effective use and regeneration of resources. Heat treatment is a process closely related to the environment and resources. The production materials and surplus materials may be the root causes of pollution. The principle of avoiding pollution should be prevention first and governance second. Therefore, the primary consideration for the development of advanced heat treatment technology is the clean and safe production technology, the safe selection and use of production materials, and the avoidance of the formation of harmful residual materials. For the harmful substances that must be produced, there must be advanced and harmless treatment methods to meet the national safety discharge standards.
The potential for efficient use, conservation, and reuse of fuel, electricity, water, and oil resources for heat treatment is enormous. The energy of the heat treatment heating equipment must be reasonably selected according to the place and the time, and the thermal efficiency of the heating equipment has a great room for improvement. The waste heat of the fuel product must be fully utilized, and a large amount of cooling water must be recycled and cleaned from the surface of the workpiece. Grease should be classified and recovered, and the quenched oil that has failed should be collected for re-use or used as a refining. In short, the efficient use and recycling of resources is an important part of the sustainable development strategy of the heat treatment industry. Now people's understanding of the importance of this issue is far from reaching the level of understanding of the environment. The current national leaders and many people of insight are fully aware that the solution to this problem cannot be based on preaching. It is time to legislate and formulate regulations. Fortunately, China's environmental protection law has been introduced, and the International Standardization Committee has also proposed environmental protection requirements for ISO14000. Some enterprises in China have passed ISO14000 certification.
2.2 Continuous improvement of product quality
After China's accession to the WTO, the economy is in line with international standards, providing incentives for enterprises and increasing pressure, creating both opportunities and severe challenges. The establishment of Sino-foreign joint ventures and the influx of foreign-owned enterprises have caused fierce market competition for domestic manufacturing products. This competition is manifested in product quality, price and after-sales service, but the core is product quality.
The high demands of product quality are both pressure and power. It can drive the technical transformation of heat treatment and equipment renewal, which will make a big difference in the quality and life of machine parts. The equipment renewal of heat treatment enterprises has brought business opportunities to the equipment manufacturing industry. However, due to the low level of technology and poor reliability, domestic heat treatment equipment is also facing fierce competition in the opening up situation, which has caused many domestic heat treatment equipment manufacturers to be on the brink of collapse. It is also imperative to improve the quality and reliability of heat treatment equipment. At the same time, if the quality and reliability of equipment components, pumps, valves, electrical components, instruments, furnace materials, etc. cannot be greatly improved, the level of heat treatment equipment cannot be a big breakthrough, and it must compete. Continue to eat and lose. To improve product quality, we must strengthen the product quality management, strengthen the ISO9000 series of certifications, and carefully implement the heat treatment standards and the quality standards of the heat treatment parts in the production process. Product quality has quickly reached a new level.
2.3 Effective use of energy
Heat treatment is a major energy consumer in the machine manufacturing process. Its power consumption is generally 20% to 30% of machinery manufacturing companies. According to the survey in the 1990s, the annual energy consumption for heat treatment in the country is about 8.6 billion kWh, accounting for about 1% of the total power generation. In 1996, the total amount of heat treatment in the United States was 5.9 billion kWh, which was only 68% of China's electricity consumption. The cost of heat treatment for machinery factories in China accounts for about 40% of the production cost. It can be seen that the rational selection of heat treatment energy, effective and economical use of energy is also one of the important starting points for the development and transformation of heat treatment production technology. Electricity is secondary energy, and thermal power plants need only about 9196kJ of heat energy, and the efficiency of power generation is 30% to 40%. If the thermal efficiency of the heat treatment furnace can reach 80%, the comprehensive thermal efficiency is only 24% to 32% based on the primary energy utilization rate. The use of natural gas combustion furnaces, combined with the combustion of preheated flue gas, the comprehensive thermal efficiency of 60% to 65% is very easy to achieve. Therefore, in areas where natural gas is used, it is advantageous to use a furnace instead of a part of the electric resistance furnace.
In addition to the advanced technology, advanced heating equipment is an important indicator for energy conservation. The heat treatment furnace should have the least heat loss, the minimum lining heat storage, and the waste heat should be fully utilized. The furnace should have a high-efficiency burner or radiant tube, and a reasonable combustion system. Reasonable selection of the process has great potential for energy saving and can achieve significant results with minimal input. Shortening the heating time, lowering the heating temperature, replacing the overall heat treatment with surface heat treatment, simplifying the process, and rationally selecting the workpiece materials are all good energy-saving measures. The key lies in the energy-saving awareness of the technicians in the production posts. The rational organization of production and strict management of energy are also one of the fundamental measures for energy conservation. Increasing the heat treatment equipment load and maintaining continuous production are very important for energy saving. In this sense, specialized production is a very advantageous way.
2.4 Accurate production process
Modern physics and metallurgy theory can almost understand the microstructure, properties, chemical composition, and even the instantaneous changes of the atomic state of the metal during the heat treatment, so that the accurate and sensitive sensing control system can be used to accurately control the quality of the heat treatment product. 100% pass rate. Precisely guaranteeing the production conditions on the equipment, such as furnace temperature uniformity, heating and cooling rate, and the chemical composition of the workpiece material and the range of the hardenability zone, can achieve the same product quality in different heats and different parts of the same heat. Reproducibility, so that the product's organizational performance, distortion and other quality dispersion degree to zero, truly achieve precision production.
2.5 Efficient production technology
Increasing labor productivity, reducing production costs, and maximizing economic benefits are always the goals of heat treatment production and all companies. An important prerequisite for achieving high production efficiency is the mass production of a single variety. Under the conditions of large-scale and large-scale production, the use of production process automation, quality online information, process parameters and quality effects simulation and adaptive control can maximize production efficiency and achieve unmanned operation, which can also be completely Eliminate human factors and ensure low dispersion of product quality. The heat treatment process that shortens the production cycle not only saves energy but also increases production efficiency. Improve equipment reliability and reduce failure rate, which can reduce the number of repairs and reduce the auxiliary time. The use of flexible equipment and multi-purpose equipment production lines in multi-variety and small-volume production methods can also increase production efficiency. Of course, in the specializing in heat treatment processing enterprises, the optimal management of production planning, reasonable production organization, and keeping equipment at full capacity are effective measures to ensure high production efficiency.