1, Selection and Characteristics of Aluminum Alloy Body Materials
Aluminum alloys can be divided into two categories based on their alloy state and heat treatment characteristics: non heat treatable reinforced aluminum alloys and heat treatable reinforced aluminum alloys. Non heat treatable strengthened aluminum alloys mainly improve their strength through work hardening, while heat treatable strengthened aluminum alloys such as Al Cu (2 series), Al Mg Si (6 series), and Al Zn Mg (7 series) improve their strength through methods such as aging strengthening and precipitation strengthening. The tensile strength of 6-series aluminum alloy can usually reach over 350MPa, while 7-series aluminum alloy can reach over 500MPa, reaching the level of medium high strength steel, effectively solving the problem of low strength of commonly used aluminum alloys in automobiles.
However, these high-strength aluminum alloys have poor plasticity at room temperature and large rebound after forming, hence the emergence of hot forming technology. Hot forming technology overcomes the problems of poor formability and large rebound of aluminum alloys by plastic deformation at high temperatures and rapid quenching to fix their shape and strength.
2, Principles and Processes of Aluminum Alloy Hot Forming Technology
In the hot forming technology of aluminum alloys, the hot forming and cold die quenching (HFQ) technology for high-strength aluminum alloys has become the most widely used and focused key technology due to its advantages of low cost, low investment, and high efficiency. The HFQ process is a non isothermal forming process, and stamping and quenching are achieved simultaneously. This process mainly consists of material solution heat treatment, hot forming and quenching, aging treatment and other processes.
Specifically, during forming, the sheet metal is first heated to the solid solution temperature and kept at that temperature for a period of time, so that the solute atoms in the aluminum alloy are fully dissolved in the matrix to form a supersaturated solid solution. Then, quickly transfer the sheet metal into a cold mold that is maintained at room temperature through water cooling or other methods, and form, quench, and maintain pressure in a short period of time. This process can ensure that the microstructure of aluminum alloy sheets quickly becomes a supersaturated solid solution state during quenching, reducing material hardness, improving sheet formability, weakening stamping springback, and reducing the required equipment tonnage. Subsequent manual aging treatment of aluminum alloy parts taken out of the mold after forming quenching can significantly improve the strength of the formed parts.
3, Application and advantages of aluminum alloy hot forming technology
The application of aluminum alloy hot forming technology in automobile body mainly focuses on key parts such as A-pillar reinforcement plate, B-pillar reinforcement plate, floor reinforcement, door collision beam, and door inner panel. These parts are crucial for the strength and safety of the vehicle body, and aluminum alloy hot forming technology can precisely meet these requirements.
The main advantages of HFQ technology include:
Cost reduction: Achieving cost savings of over 20% in molds and stamping parts through component integration.
Weight reduction: High strength aluminum achieves a weight reduction of 20-50%, which helps improve the fuel efficiency and range of automobiles.
Almost no rebound: precise control of dimensional accuracy can be achieved in one molding process, improving the dimensional stability and reliability of the parts.
Maintain toughness: After hot forming, aluminum alloy parts still have good ductility and impact performance.
Component integration: lower product and mold costs, improved production efficiency.
Flexibility and sustainability in alloy selection: Standard alloy materials (6 series&7 series) are fully recyclable and meet environmental requirements.
High strength: After quenching, aluminum alloys 6 and 7 series obtain higher strength, meeting the demand for high-strength materials in automobiles.
4, The Development Status of Aluminum Alloy Hot Forming Technology at Home and Abroad
In major automotive production areas in Europe, China, and North America, there is a rapidly growing interest in the application of hot forming for automotive lightweighting, especially for electric vehicles, which creates a demand for new production lines for large-scale aluminum hot forming (HFQ). In 2016, Swedish AP&T company successfully delivered the world's first dedicated aluminum alloy hot forming production line based on HFQ technology, which can produce components with lighter weight, higher strength, more complex shapes, and higher dimensional stability. Subsequently, HFQ technology has been widely applied to high-end automotive brands such as Aston Martin and Lotus, and designed for multiple new global electric vehicle platforms.
In China, the application of aluminum alloy hot forming technology is slightly later than abroad, but significant progress has also been made in recent years. Some domestic enterprises have already mastered HFQ technology and are actively building the first domestic aluminum alloy hot forming production line. The construction of these production lines will strongly promote the development and application of domestic aluminum alloy hot forming technology.
