Strict control of heat treatment quality
The increasingly strict control of product quality is one of the main features of the development of modern heat treatment technology. This is the result of the increasingly precise research of metallurgical laws, the long-term progress of testing sensing technology and instrument manufacturing, and the inevitable result of the popularization and application of electronic computers. The progress made by China in this respect is mainly reflected in the following aspects.1) The automation process of the process adopts the sequencer or microprocessor to realize the automatic production process of charging, heating, cooling, cleaning, tempering, unloading and other processes according to the requirements of the heat treatment process. Some cars, tractors, bearings, Large-volume production companies such as fasteners are put into use. Large-scale continuous carburizing, quenching, tempering production lines and sealed multi-purpose furnace production lines in the automotive industry mostly use microprocessor-controlled automation. There are also many successful experiences in program control operations with sequencers or microcomputers on vacuum heat treatment equipment.
2) Strict control of process parameters Strict control of heat treatment process parameters such as time, temperature, furnace gas withdrawal and pressure, concentration of quenching medium, impurities and cooling rate (degree of agitation) can maintain stable high quality of the workpiece. The surface quality of the workpiece, the surface and core hardness, the infiltration element concentration and gradient of the layer, and the depth of the layer can be effectively controlled. In China, due to the popularity of thyristor temperature control and PID instrumentation, the temperature control accuracy of general heat treatment resistance furnace (800 ~ 1000 °C) can reach ± ​​5 ° C, or even ± 2 ° C. The infrared gas analyzer and the computer can control the gas pressure of the CO2, CO, and CH4 furnaces in the furnace gas to achieve an accuracy of ±0.02. At present, the temperature control technology of thyristors has reached a considerable popularity, and controllers of various specifications are available on the market. Attempts by some universities, research institutes and enterprises to develop digital models based on process parameters and quality relationships with computers have been successful, and some of the results have been applied in production.
3) Strict quality management Through the quality management conducted by the heat treatment industry association, the company has passed the training of enterprises, standardized enterprise selection activities and quality inspectors. At the beginning of this century, the production management and quality management level of heat treatment enterprises have been significantly improved. Most enterprises pay attention to improving the quality inspection conditions. Except for state-owned enterprises, most private enterprises have purchased metallographic microscopes, hardness testers, magnetic particle flaw detectors, and a few enterprises are also equipped with spectroscopes and quantitative metallographic microscopes. The technical workers of the two types of enterprises and most of the surveyed enterprises have been trained and certified to work, and established various management systems such as heat treatment process cards, process cards, inspection procedures, quality archives, and actively implement heat treatment quality management standards and Determination of the effective heating zone of the heat treatment furnace and various process standards. Due to the strict regulations of these process conditions, the standardization of process operations, and the improvement of the quality of employees, the quality dispersion of heat treatment parts of these enterprises has been gradually reduced, and the qualification rate of products has increased to over 98%. By the end of 2003, nearly 1,000 enterprises have passed ISO9000 certification. , accounting for 6% of the total number of enterprises in the whole industry, accounting for about 20% of the total number of enterprises with a turnover of more than 5 million yuan.
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