Strict control of heat treatment quality

Increasingly strict control of product quality is one of the main characteristics of the development of modern heat treatment technology. This is the inevitable result of the more and more precise research on the laws of metallurgy, the great progress in testing and sensing technology and instrument manufacturing, and the popularization and application of electronic computers. The progress my country has made in this area is mainly manifested in the following aspects.

1) The automatic operation of the technological process adopts a sequencer or a microprocessor to realize the automatic production process of loading, heating, cooling, cleaning, tempering, and unloading according to the requirements of the heat treatment process. The automatic production process has been used in some automobiles, tractors, bearings, Fasteners and other mass production enterprises are put into use. The large-scale continuous carburizing, quenching and tempering production lines and the sealing multi-purpose furnace production lines in the automobile industry mostly adopt automatic operations controlled by a microprocessor. There are also many successful experiences in using sequencer or microcomputer program control operations on vacuum heat treatment equipment.

2) Strict control of process parameters. Strict control of heat treatment process parameters, such as time, temperature, furnace gas tolerance and pressure, concentration of quenching medium, impurities and cooling speed (degree of agitation), can maintain a stable high quality of the workpiece. The surface quality of the workpiece, the hardness of the surface and the core, the concentration and gradient of the infiltration elements of the infiltration layer, and the depth of the infiltration layer can all be effectively controlled. In my country, due to the popularization of thyristor temperature control and PID meters, the temperature control accuracy of general heat treatment resistance furnaces (800~1000℃) can reach ±5℃, or even ±2℃.

Using infrared gas analyzer and computer can control factors such as CO2, CO, CH4 in the furnace gas and even the accuracy of ±0.02. At present, thyristor temperature control technology has reached a fairly popular level, and controllers of various specifications are available in the market. Some universities, research institutes and enterprises have developed successful attempts to directly control products with computers based on digital models based on process parameters and quality relationships, and some of the results have been applied in production.

3) Strict quality management. Through the quality management of trustworthy enterprises, standardized enterprise selection activities and training of quality inspectors carried out by the Heat Treatment Industry Association, the production management and quality management level of heat treatment enterprises has been significantly improved at the beginning of this century. Most companies attach importance to improving quality inspection conditions.

Except for state-owned enterprises, most private companies have purchased metallographic microscopes, hardness testers, and magnetic particle flaw detectors. A few companies are also equipped with spectroscopic mirrors and quantitative metallographic microscopes; The technical workers of the two types of enterprises and most of the enterprises under investigation have been trained and licensed to work. They have established heat treatment process cards, process cards, inspection procedures, quality files and other management systems in production, and actively implemented heat treatment quality management standards and Measurement of effective heating zone of 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 dispersion of the quality of heat-treated parts of these companies has gradually decreased, and the first pass rate of products has increased to more than 98%. By the end of 2003, nearly 1,000 companies have passed ISO9000 certification. , Accounting for 6% of the total number of enterprises in the industry, accounting for about 20% of the total number of enterprises with a turnover of more than 5 million yuan.