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Anti-fatigue manufacturing technology and aero engine bearing

2019-4-26
Bearings are one of the key components of an aero engine, and its life has a significant impact on the overall life of the aero engine. For a long time, the life of China's aero-engines is not long, the interval between overhauls is relatively short, and it has a lot to do with the short life of aero-engine bearings. What level has China's aviation engine bearing technology been developed to? Today, we combine the technological progress made in this technical field in recent years, and separately sort out the technical level of domestic aero-engine bearings in terms of materials, processes, and manufacturing theory.
The first is the material, the most important raw material for the manufacture of bearings is the bearing steel. Bearing steel is one of the most technically demanding steel grades in steel products. It is called the “king of steel” and is a special steel used to make bearing balls, rollers and bearing rings. Bearings are usually the most central operating components in mechanical equipment and work conditions are very harsh. This requires the bearing steel to have high fatigue strength, high hardness, good wear resistance and strong rust resistance. The manufacturing capacity and quality of bearings and bearing steel directly affect the manufacturing capacity and industrialization level of a country.
Good bearings are inseparable from good bearing steel. The key indicator for evaluating the quality of bearing steel is the uniformity and purity of the material. Purity affects the fatigue life of the bearing, and the uniformity is related to the deformation and tissue uniformity of the bearing after heat treatment. The oxygen content is an important indicator. The lower the oxygen content, the less the oxide inclusions, the higher the purity, the longer the fatigue life of the bearing steel and the longer the service life of the bearing. At present, the world's advanced level of bearing steel can control the oxygen content in the range of ≤ 5ppm. The bearing steel produced by Xingcheng Special Steel in China can fully meet this standard. In November 2017, when the China Iron and Steel Association organized an evaluation of Xingcheng Special Steel's scientific research results, it believed that the metallurgical quality and performance level of Xingcheng Special Steel's high-end bearing steel reached the international leading level.
For bearings, the service life is basically determined by the fatigue life of the bearing steel. As early as 2009, Xingcheng Bearing Steel's fatigue life has surpassed that of its Japanese counterparts. Japanese users have also done similar follow-up evaluations, and the conclusions are the same. Xingcheng Special Steel has cooperated with German users to develop pure bearing steel and provided samples for it in 2016. After two years of fatigue life testing, Xingcheng Bearing Steel has a fatigue life of up to 1150 hours. It is a European bearing. 2.5 times that of steel. ”
China has long been a major producer of bearing steel. Statistics show that in 2017, China's major bearing steel producers produced 3.0146 million tons of crude steel. The top three bearing steel productions were: Xingcheng Special Steel, Xinye Steel and Bengang Special Steel. These three companies accounted for China. 51% of total bearing steel production. China can not only manufacture high-end bearing steel, but also can export a large amount. Taking Xingcheng Special Steel as an example, in 2017, it produced 965,000 tons of bearing steel, and 630,000 tons were supplied to world-renowned bearing enterprises such as Sweden SKF, Germany SCHAEFFLER, Japan NSK, NTN. It has been ranked first in the world in bearing steel production and sales for 8 consecutive years.
After the material is finished, let's look at the processing technology of the bearing. Let me talk about the machining process of the bearing. In 2016, Shandong Huayun Electromechanical Technology Co., Ltd. and Zhao Zhenye, academician of the Chinese Academy of Engineering, jointly achieved technological breakthroughs in the use of aerospace engine bearings processed by Huayun's Haoke Energy Technology, and the service life reached 22 times that of FAG Aerospace Bearings in Germany. FAG is part of the Schaeffler Group of Germany and is the world's top manufacturer of aerospace engine bearings.
Haoke Energy Technology is a processing technology invented by Zhao Xianhua, the chairman of Shandong Huayun Electromechanical Technology Co., Ltd., which can realize the nano-grain of metal surface. It is a new product after the machining process such as turning, milling, planing and grinding. New machining process. The composite material of the activation energy and the impact energy can be used to process the metal parts, and the surface quality of the mirror surface can be obtained, and the surface modification of the parts can be realized. The metal material fatigue life is increased by 100 times, the surface microhardness is increased by 20%, the wear resistance is increased by 50%, and the corrosion resistance is increased by 50%. It is a very good processing technology to solve the problem of stress concentration in material processing.
Say the machining process and then the heat treatment process. The machining process of the bearing, especially the heat treatment process, directly affects the overall performance of the aero-engine bearing. The carburizing heat treatment process is one of the key technologies to greatly improve the surface hardness, fatigue strength and wear strength of mechanical parts. It is widely used in the surface hardening treatment of key components such as gears, drive shafts and bearings, and upgrades high-end machinery and Quality improvement plays an important role.
At present, the most prominent problem in the metal carburizing heat treatment in China is that the surface quality is not relevant. Although foreign countries have advanced equipment and technology to solve the above problems, they are expensive and technically blocked. Recently, Dr. Wang Yujie, a major in material processing engineering at Northeastern University, led the entrepreneurial team to develop a new low-pressure vacuum carburizing heat treatment process in China, which achieved precise control of the steel carbide layer for aerospace engine bearings. This new heat treatment process enables higher-end aerospace bearing steels to achieve higher strength, better surface hardness, fatigue strength, wear strength, longevity and better overall performance. It has been approved by China Aerospace Harbin Bearing Co., Ltd.
The heat treatment process developed by Wang Yujie and his team has been used for key components such as aerospace bearings and gears, robot RV reducer cycloidal wheels, and high-speed seals for high-speed rails. Breaking the strict technical blockade abroad, these foreign monopoly products have achieved domestic independent manufacturing and greatly reduced costs. At present, the team of Wang Yujie has established cooperative relations with Shenyang Liming, Dongan Engine, Harbin Bearing Co., Ltd., etc., and will promote the market-oriented mass production of the second and third generation aviation engine bearings and gear carburizing steel through low-pressure vacuum carburizing technology. .