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Building "7050" for C919- Record of Independent Development of Aluminum Materials for Domestic Large Aircraft

Update time:2023-06-12 16:35:07Number of clicks:0次
On May 28th, the domestically produced large aircraft C919, which took off from Shanghai, landed smoothly at Capital Airport, marking the first successful commercial flight with passengers.

West Aluminum - West Aluminum Industry Telecom: On May 28th, the domestically produced large aircraft C919, which took off from Shanghai, landed smoothly at Capital Airport, marking the first successful commercial flight with passengers.

At that moment, Southwest Aluminum Industry (Group) Co., Ltd. (hereinafter referred to as Southwest Aluminum) of China Aluminum Group, located far away in Chongqing, was in full swing - over 50% of the aluminum used in C919 came from this enterprise.

Since the establishment of the C919 project, Southwest Aluminum has undertaken the research and production task of domestically produced aluminum materials for large aircraft. Through independent innovation, they have overcome the difficulty of "from scratch" and continuously improved the independent guarantee rate of domestic civil aircraft aluminum materials.

Starting from scratch and targeting the third-generation advanced aluminum alloy

In the history of world aviation development, there is a saying that "one generation of aircraft, one generation of materials".

Large passenger aircraft are considered the "jewel of modern industrial crown", and material performance is the primary factor determining aircraft performance. To manufacture domestically produced large aircraft, it is necessary to achieve material autonomy and control.

Aluminum alloy materials account for 65% of the main materials used in manufacturing commercial aircraft. The most important international third-generation advanced aluminum alloy, 7050 aluminum alloy thick plate, is known as "one of the most difficult aluminum alloys to cast in the industry". Previously, China could not independently produce it.

"The '7050' is widely used in the manufacturing of key load-bearing parts such as aircraft wing beams, ribs, fuselage frames, wallboards, and is an indispensable key material." Zhou Hua, deputy chief engineer and project leader of the Southwest Aluminum Technology Center, told the Science and Technology Daily that the key production technology of 7050 aluminum alloy thick plates has always been regarded as a core technology secret by developed countries and has been strictly blocked, Imported materials are not only priced at over 100000 yuan per ton, but are also often restricted from foreign purchases

Without any experience to learn from, we started completely from scratch, "Yang Rongdong, the director of Southwest Aluminum Technology Center with gray hair, recalled his time with great emotion.

In 2005, Southwest Aluminum Corporation and some universities formed a joint research and production team; At the same time, professional technical personnel in the fields of melting, rolling, forging, and testing are also selected from within the enterprise to form a project team. They began systematic research on industrial preparation techniques from the preparation of large-sized 7050 aluminum alloy ingots, thick plate rolling, heat treatment, and other aspects.

At that time, everyone was holding back a strong desire to develop the third-generation advanced aviation aluminum alloy! "Yang Rongdong said.

Breaking the "curse" of ingot cracking after a hundred failures

7050 aluminum alloy thick plate has high strength, toughness, fatigue resistance, and damage resistance, which is an unprecedented test for the purity of raw materials and casting technology. At that time, the equipment and tooling of the Southwest Aluminum melting and casting plant were relatively backward, and the "7050" large-sized ingot forming was the first "roadblock" encountered by the team.

New materials require high strength, and the first challenge during casting is the tendency to crack, "said Chen Xinmin, the supervising engineer. During that time, project team members stood by the furnace 24 hours from the beginning of casting, waiting for the final shape after smelting.

Tn general, minor cracking does not affect the use of aluminum alloys, but civil aviation materials do not. The latter requires higher safety requirements, not only passing airworthiness certification, but also meeting various standards for all types of materials, with a service life of about 15 years.

At that time, I was most afraid of hearing a 'bang' sound. It was the cracking of the ingot, "Zhou Hua said. At first, there was no pilot production line, and all the tests were directly completed on the production line of the enterprise. A furnace of raw materials was worth four to five million yuan, and cracking meant that all were scrapped.

During that period, ingot cracking occurred frequently, with the melting and casting plant stacking thousands of tons of cracked ingots, resulting in losses of up to tens of millions of yuan. Everyone was both distressed and anxious, suppressing their anxiety while groping to adjust their parameters. The project team members live and eat in the office for several months. According to the job division, some continuously calculate and adjust the concentration ratio of the alloy, while others improve the temperature and cooling method of the furnace

At that time, I didn't feel tired at all, just thinking about how to overcome this difficult problem, "Zhou Hua said.

After hundreds of failures, the project team finally broke the "curse" of ingot cracking through continuous optimization of alloy composition and proportion. The first formed ingot was born in December 2005.

From "Following" to "Merging" Civil Aircraft Aluminum Materials Going Abroad

The problem of ingot forming was solved, and another major challenge that followed was placed in front of the project team.

In 2008, the project advanced in depth and successively produced qualified 60mm and 80mm thick plates. However, during the trial production of 100mm, 120mm, and 150mm thick ultra-thick plates, the fatigue performance and high tensile performance of the products frequently failed to meet the standards. Project research is like stepping into a 'black hole'.

After repeated comprehensive dissection and analysis of the samples, the project team innovatively proposed new insights into the relationship between material structure and performance, "said Wang Zheng'an, the chief engineer and then deputy director of the technical quality department.

Afterwards, the project team went through multiple failed verifications in terms of billet specifications, rolling processes, and parameter control, and finally formed a mature process plan in 2009, producing qualified ultra-thick plates.

In 2015, after breaking through a series of key technologies such as large-scale ingot preparation, strong deformation rolling, strengthening and toughening heat treatment, and residual stress control, Southwest Aluminum developed the largest cross-section 7050 aluminum alloy ultra wide and ultra thick pre stretched plate in China, established a complete industrial manufacturing technology system for 7050 aluminum alloy pre stretched plate, and achieved industrial production of full thickness products ranging from 6.0mm to 203mm, And it has been applied on a large scale in multiple key models of equipment in China's aerospace industry.

Since 2017, Chinalco Group and COMAC have jointly identified 21 key main structural aluminum materials and collaborated with domestic advantageous teams to carry out systematic research; Southwest Aluminum has become the first qualified supplier of domestically produced aluminum materials for large aircraft in China. As of now, it has provided over 600 aluminum alloy materials in 30 specifications for C919.

In addition to supporting the domestic aviation market, Southwest Aluminum's civil aircraft aluminum products have already gone abroad. On May 23, Chinalco Southwest Aluminum, Boeing Company and AVIC International signed a forging project agreement in Chongqing to provide forgings for Boeing 787 Dreamliner.

Compared to internationally advanced aluminum material enterprises, we used to be 'running with', but now we have reached the stage of 'running together', striving to become a 'leader' in the industry in the future, "said Li Yong, Secretary of the Party Committee and Chairman of Southwest Aluminum, The 20th National Congress of the Communist Party of China proposed to accelerate the construction of a strong manufacturing and aerospace country. Southwest Aluminum will resolutely fulfill its mission as a 'leader, main force, and leader', and play a 'pillar' role in serving the national strategy


(Chongqing Xialu Xinda Aluminum Industry Co., Ltd. Publicity Department collates contributions)


Source: Network

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