Frozen forming method for large tailored plate aluminum alloy component

Abstract

A frozen forming method for a large-size thin-walled aluminum alloy component using an aluminum alloy tailor-welded plate is described. An aluminum alloy tailor-welded plate is cooled to a temperature with a cryogenic fluid medium, and temperature of a weld zone is regulated to be lower than that of a base metal zone; and the component is fabricated by a tool integrally with aluminum alloy tailor-welded plate, by placing aluminum alloy tailor-welded plate onto tool; assembling tool and filling with cryogenic fluid medium so temperature of tool is −150 to −196 degrees Celsius; and apply pressure to deform the aluminum alloy tailor-welded plate when temperature of a weld zone reaches −150 degrees Celsius to −196 degrees Celsius, thereby facilitating forming the aluminum alloy tailor-welded plate to a designed shape of the aluminum alloy component; and disassembling the tool, and taking out the aluminum alloy component.

Description

TECHNICAL FIELD[0001]The present invention relates to the technical field of sheet metal forming, and in particular to a forming method at cryogenic temperature for a large-size component using an aluminum alloy tailor-welded plate.BACKGROUND ART[0002]Aluminum alloy, featuring excellent specific strength, specific stiffness and corrosion resistance, has been one of primary structural materials for aerospace equipment such as a rocket and an aircraft. The aluminum alloy accounts for about 80% of the structural mass of a carrier rocket and above 50% of the structural mass of a civil aircraft. With the development of a new generation of large rockets and aircrafts, an urgent need emerges for large-sized integral structure comprising aluminum alloy thin-walled components to meet their requirements for higher reliability, longer lifespan and lighter weight.[0003]An existing technical roadmap for manufacturing aluminum alloy thin-walled component was presented as “sheet metal forming sepa...

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Benefits of technology

[0020]Compared with the prior art, the present invention has some beneficial effects which include the following aspects: 1) The cracking problem caused by a high degree of deformation in the weld zone can be avoided by utilizing the feature that the plasticity and the strength of the weld zone are higher than the plasticity and the strength of the base metal zone, which is caused by the temperature difference on the aluminum alloy tailor-welded plate at cryogenic temperature; 2) The microstructure damages can be avoided and restored to original microstructure status after forming of aluminum alloy tailor-welded component by the frozen forming method. As a result, the microstructure and mechanical properties of the aluminum alloy tailor-welded component are minimally changed by the forming at the cryogenic temperature range; and 3) Frozen lubricating layers are formed at working surfaces between the tailor-welded plate and the tool, which can reduce friction force and forming force during flowing of the plate, as well as the tonnage and cost of forming equipment.

Problems solved by technology

The prior art has the main problems that a relatively high degree of distortion is caused after welding, and an even greater distortion is caused after the heat treatment.

What's more, the integral thin-walled component can't be subjected to shape correction after forming and welding, and the prior art method usually leads to lower precision and a failure to meet the use requirements.

However, there are some insuperable difficulties for forming the larger-sized aluminum alloy thin-walled integral component by an existing conventional cold forming (forming at room temperature) technology and a hot forming (forming at elevated temperature) technology.

As to the cold forming technology, a larger-sized thin-walled tailor blank is prone to wrinkle and a FSW weld joint is prone to crack when a conventional deep drawing technique is adopted, thus both the wrinkling and cracking defects exist and can't be overcome.

However, the forming force of a component with the diameter of 5 m reaches 800 MN, and the cost and risk of super-large fluid high pressure forming equipment are extremely high when sheet hydroforming technique is adopted.

As to the hot forming technology, the FSW weld joint is softened in heating status, and the cracking problem can't be solved for the lower strength caused by softened weld joint in the forming process.

Furthermore, there are very difficult to control the microstructure and mechanical properties of the formed component in the hot forming process.

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