The gears of automobile and tractor are the basic parts with large quantity and wide range. In 1972, China produced 3.7 million automobile gears, 7 million tractor gears, 10.7 million in total, of which 90% are cylindrical gears and 2.5% are large spiral bevel gears, which consume about 70000 tons of steel (mainly low-carbon alloy steel) every year. In 1975, China’s planned output of auto tractor gears reached 24 million pieces (including accessories), with 150000 tons, and 50% of spare parts. The gear industry is developing rapidly. However, due to the short service life of gears in China, although the output has increased substantially, it still cannot meet the requirements of the national plan.
At present, there are about 90 specialized factories producing automobile and tractor gears in China, and there are more than 80 small and medium-sized gear factories. The output of these gear factories will remain between 100000 and 400000 in 75 years. Therefore, in order to meet the needs of the rapid development of the national economy, in addition to further mining production capacity and increasing output, the most effective measure is to find quantity from improving quality, starting from improving the life of gears, so that one gear can be used for several gears.
Gear material and processing technology:
At present, the materials for gears in China are generally lscrmnti; 2MR mnmo; 25c-i-mntibre; zscrtiwa; 12cit discussion a; 20mnt sacrifice; 25mntmr. And more than 95% of the gears are still machined. The basic technological process of the cylindrical gears is: die forging – Drilling – hole pulling – turning – gear hobbing (shaping) – gear shaving or cold extrusion – heat treatment – gear Qi. Automobile, tractor gear heat treatment Qi tooth.
Most of the gears of automobile and tractor are carburized and quenched with low carbon alloy steel, and a few are cyanidated. Solid carburizing is still used in agricultural machinery plants in general counties. In addition to Changchun No.1 Automobile Factory, Luoyang Tractor Factory and Sichuan Yingjiang gear factory, which adopt the more modern controlled atmosphere carburizing furnace, most of the gear factories still adopt the well type gas carburizing furnace in the 1940s of the Soviet Union to conduct gas carburizing and cyanate liquid carburizing by dropping kerosene. The equipment is old, the technology is backward, and the quality is very unstable.
The accuracy requirements of the gears of automobile and tractor are generally between 6 and 8 grades. The gear accuracy of car is higher than that of tractor. From the aspect of cold working, the accuracy of gear hobbing machine and the quality of hob are poor, resulting in low accuracy of gear profile. In terms of materials, there are many kinds of gear materials, and the hardening performance of the materials is not stable. Therefore, there is a large deformation after heat treatment, and there is no ideal finishing process after heat treatment, so the ability of Qi gear to correct the error is very poor. Therefore, the qualified rate of finished gear is low, the gear noise is large and the service life is low. The service life of foreign automobile gears is generally more than 200000 kilometers, and that of tractor gears is 500. More than hours. In China, the life span of automobile tractor gears is not stable. The low ones are only several hundred kilometers and dozens of hours, and the high ones are only tens of thousands of kilometers and hundreds to thousands of hours. The average service life of Jiefang Truckis less than 100000 km. It is reported that the service life of British truck gearbox is 500000 km.
The problem of quality is a political problem and a route problem. Finding out the quantity from the quality, starting from improving the service life of gears, and changing the backward state of our domestic gears. At present, it is an important measure to do well in gear heat treatment.