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 of the tight supply of raw materials for the production of endothermic gas, natural gas and liquefied petroleum gas, and the large use of methanol, 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.
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