Advanced heat treatment technology

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The advancement of technological levels has also led to continuous improvements in metal heat treatment techniques. Traditional heat treatment methods cause certain environmental pollution and pose threats to human health. Modern technology has been used to improve these heat treatment techniques, and we will now share with you the most advanced heat treatment methods available today. 1. Controlled Atmosphere Heat Treatment
Controlled atmosphere heat treatment is primarily used to prevent oxidation and decarburization, while also enabling precise control over carburizing and nitriding processes. It began to be used in industrial production at the end of the 1980s, and has since become widely applied today. Domestic and foreign equipment manufacturers have newly launched controllable-atmosphere heat treatment furnaces of various grades and with diverse functions, tailored to the characteristics of the Chinese market. Large-scale models such as Epson’s sealed box-type multi-purpose furnaces, as well as Fengdong’s fully automatic and intelligent sealed box-type multi-purpose furnace production lines, can not only handle processes like carburizing and carbonitriding, but also enable various heat treatment techniques such as bright quenching and bright annealing. It is possible to carry out a series of tasks such as computer-aided design, production management, logistics management, on-site control, quality management, and process management. At the same time, it has changed the previous “dirty, messy, and poor” condition of the heat treatment workshop, replacing it with a neat and tidy environment. Of course, these production lines are expensive and suitable for mass production, such as in the automotive industry. Domestic manufacturers, in close alignment with customer needs, have developed a variety of controlled atmosphere furnaces that offer reasonable prices, diverse designs, and excellent performance. It is generally capable of optimizing process parameters, predicting and precisely controlling the distribution of carbon concentration, thereby achieving an ideal concentration profile and case structure. It supports computer-based management, features a simple menu design, and offers a user-friendly interface. II. Vacuum Heat Treatment Vacuum heat treatment is a new type of heat treatment technique that combines vacuum technology with heat treatment techniques. The vacuum environment in which vacuum heat treatment takes place refers to an atmosphere with a pressure lower than one atmosphere, including low vacuum, medium vacuum, high vacuum, and ultra-high vacuum. In fact, vacuum heat treatment also falls under the category of atmosphere-controlled heat treatment. The application and development of vacuum heat treatment technology have been further improved and promoted. It features no oxidation or decarburization, a clean and shiny surface of the workpiece after quenching, high wear resistance, no pollution, and a high degree of automation. Heat treatment techniques such as vacuum annealing, vacuum degassing, vacuum oil quenching, vacuum water quenching, vacuum hardening, vacuum tempering, and vacuum carburizing are widely used in industrial production. In recent years, with the advent of high-pressure gas quenching vacuum furnaces, the vacuum quenching of high-speed steel tools has become a reality. There are many manufacturers of vacuum furnaces, including domestic or joint-venture companies such as Ipsen, France’s ECM Industrial Furnaces, and G-M Company. There are also many well-known domestic manufacturers; examples include the “Great Wall” series by China Aerospace Science and Technology Corporation, and the WZ series of vacuum furnaces produced by the Beijing Research Institute of Mechanical and Electrical Engineering. These products boast a high level of technological sophistication, excellent performance, and competitive pricing in the domestic market. Vacuum heat treatment is set to become one of the most widely used and dominant technologies in heat treatment workshops. III. Induction heat treatment and ion nitriding heat treatment technologies. Induction heat treatment is widely used in industries such as the automotive industry, construction machinery, and petrochemicals, thanks to its advantages of high efficiency, energy savings, cleanliness, and flexibility. Nearly 40% of automotive parts can be subjected to induction heat treatment, such as crankshafts, gears, universal joints, half-shafts, etc. With induction heating, fully or semi-automatic production lines can be established for processing many products, thereby improving the stability of product quality, reducing labor intensity, and enhancing the working environment. The fastest-growing sector in China is induction heating power supplies; the old-style electronic oscillation tubes have fulfilled their historical role, and they have been replaced by all-transistor designs. A microcomputer-controlled transistor regulator is used for power supply regulation, offering convenient and precise control while **reducing** interference from grid harmonics. The solid-state high-frequency heating devices developed in recent years have obvious advantages. They no longer require expensive, fragile, and energy-intensive electron tubes, as well as ancillary components such as anode step-up transformers, anode water jackets, and filament voltage stabilizers. Instead, they utilize MOSFET power electronic devices. As a result, they consume one-third less electricity and half as much water. Similarly, quenching machines equipped with heating power sources have also made great progress. This is reflected in: ① a significant increase in the number of manufacturers of machine tools; previously, it was Tianjin No. 9 Machine Tool Factory that held a monopoly in this area. ②The precision, stability, and degree of automation of quenching machines have been greatly improved. ③The technical level of targeted and specialized quenching machines is put to good use. Ion nitriding technology is characterized by a clean surface of the treated parts, excellent corrosion resistance, minimal deformation, and high wear resistance. Compared to gas nitriding, it has advantages such as shorter cycle time, higher efficiency, and less pollution. In recent years, ion nitriding has seen rapid development. In particular, the advent of pulsed power supplies for ion nitriding furnaces has made it possible to separate the physical parameters of discharge (voltage, current, gas pressure) from the temperature control parameters (pulse width). It enhances the adjustability of the process, facilitating the selection and precise control of process parameters. IV. Quenching media and cooling techniques. An ideal quenching medium should possess the following characteristics: ① Mass-type: rapid cooling during the high-temperature phase and slow cooling during the low-temperature phase. That is, eliminating cracks and reducing quenching deformation. ②Environmentally friendly: No emission of toxic or harmful smoke and gases; non-flammable; easy to clean after quenching of workpieces; non-corrosive to equipment; does not irritate or burn the skin. ③Stable type: The properties of the workpiece remain uniform and stable after quenching; the medium itself maintains stable properties over a certain period of time. ④Economy version: high quality at a good price, low energy consumption. In recent years, quenching media have developed very rapidly. The performance of quenching oils has improved, and research and application of organic polymer quenching media have seen unprecedented development. Abroad, there are the American companies Goodfulton and Derunbao, as well as the British company PB Petroleum. In China, there are companies such as Beijing Huali Fine Chemicals Company and Nanjing Kerun Fine Chemicals Company. V. Adoption of new surface strengthening technologies and promotion of heat treatment in nitrogen-based atmospheres. Existing methods for treating tool surfaces are limited to outdated techniques such as steam treatment and oxynitriding; generally, these can only extend the tool life by 30%–50%. Since the 1980s, our country has independently developed as well as introduced from abroad the QPQ salt bath composite treatment technology and the PVD titanium oxide physical coating technology. The former can steadily increase tool life by 2 to 3 times; it features simple equipment and low costs, making it particularly suitable for ordinary cutting tools. The latter can increase tool life by 3 to 5 times, and is suitable for various precision and expensive gear cutting tools. A nitrogen-based atmosphere is used for protective heat treatment and chemical heat treatment; it enables oxidation-free decarburization during heat treatment and helps to avoid nitrogen embrittlement. Chemical heat treatment in a nitrogen-based atmosphere can reduce defects such as internal oxidation, thereby improving the quality of the chemical heat treatment.