Gear precision forging is an advanced manufacturing technology with high
quality, high efficiency and low consumption, which is widely used in the mass
production of automotive tooth parts. With the advancement of precision forging
technology and precision mold manufacturing technology, the production of
automobile gears and tooth-shaped parts has increasingly adopted precision
forging. At present, the total mass of precision forgings used in an ordinary
car abroad has reached (40-45) Kg, of which the total mass of tooth-shaped parts
is more than 10Kg. The quality of a single piece of precision forged gear can
reach more than 1Kg, and the tooth profile accuracy can reach (DIN) level 7.
With the lightening of automobiles and the enhancement of people's awareness of
environmental protection, the automobile gear manufacturing industry will use
more precision forging technology.
The precision forging of bevel gears was first seen in the Bayer factory in Germany in the 1950s, and was widely used in companies such as Thyssen (1). In the 1970s, my country's Shanghai Automobile Gear Factory, etc., adopted hot precision forging technology and successfully carried out precision forging production of bevel gears. In the environment of great socialist collaboration at that time, the precision forging technology of bevel gears was quickly promoted and applied in the gear industry.
The application and development of this technology benefited from two advanced technologies at the time: the electrical discharge machining technology of the mold and the blank induction heating technology. The electric discharge machining, which is first quenched and then processed, avoids the tooth profile error caused by the quenching deformation of the mold; the rapid heating of the intermediate frequency induction heating solves the oxidation and decarburization of the gear blank during the heating process. The application of the above two technologies makes the forging shape Bevel gear tooth surface meets the requirements of no cutting processing.
The forging equipment of bevel gear generally uses hot die forging presses abroad. But in China in the 1960s and 1970s, hot die forging presses were very expensive equipment. Therefore, the forging equipment commonly used by domestic enterprises is a double-disc friction press. This equipment has simple structure and low price, and soon became the main equipment for gear precision forging. But the friction press technology is outdated, it is difficult to control the hitting accuracy, and the energy efficiency is low. With the emergence of high-energy screw presses and electric screw presses, backward friction presses tend to be replaced.
For mass-produced automobile planetary and differential gears, the mature precision forging forming technology is the hot precision forging process technology known as "one fire, two forging". After the hot forged gear is formed by hot forging and trimming, the waste heat of the forging is used for thermal finishing. The usual design principle is to design the forming mold and the finishing mold to be exactly the same size, so that the finishing mold can be used as a forming mold when it is close to the limit of mold change, so that the service life of the gear mold can be maximized.
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