With the development of automotive industry, the market development of automotive cold bending profile forming machine is driven one after another. Fuel economy, low carbon emission and higher safety put forward new requirements and challenges for automotive body lightweight, and promoted the steady growth of application of advanced high-strength steel in body design and manufacturing.
Advanced high strength steel, especially ultra-high strength steel, brings new challenges in production and application technology due to the changes in microstructure and macro mechanical properties. It is of great significance to make full use of the properties of advanced high-strength steel by adopting reasonable part design and applicable processing methods.
Rolling forming adopts multi-stage progressive bending forming, which can obtain smaller bending radius compared with stamping forming, and can form various parts with open or closed complex cross-section, with better rigidity of parts; at the same time, through multi-stage deformation for springback compensation, it is easier to control springback and obtain good forming accuracy, and the surface quality of parts is good. As a suitable forming technology, roll forming is an important forming method of advanced high strength steel plate. Its technological advantages, especially for the complex cross-section shape, high production efficiency, low cost of mass production, have been widely used in automotive, construction and other fields.
When ultra-high strength steel is used in roll forming, due to the high strength of materials, the traditional process parameters and design experience can not meet the application requirements of advanced high strength steel roll forming. At present, the technical difficulty is that the plasticity of high-strength steel plate is reduced due to the addition of alloy elements or the application of temperature control technology. During the roll forming process, the sharp corner of the roll forming parts is prone to crack; the rebound of high-strength steel is serious, and the head and tail of the open roll forming parts are more serious, which makes the size accuracy of products difficult to control, the loading difficulty of parts is increased, and waste products are produced The rate is rising. It has become an urgent task to study the key technology of roll forming of advanced high-strength steel to provide technical support for the large-scale roll forming application of advanced high-strength steel.
The following is an example of threshold stiffener of ultra-high strength steel used in an automotive. The process technology research and sample development of the typical parts of the open-ended asymmetric roll forming are carried out. The Springback Control and pre punching distortion that affect the roll forming of the advanced high-strength steel are studied by using the analytical and finite element simulation, and the optimal design process parameters are obtained. The mechanism of the longitudinal bending, lateral bending and torsional defects of the asymmetric roll forming is analyzed, and the solutions are given The roll forming process of ultra-high strength steel was tested, and the typical samples meeting the requirements of dimensional accuracy were manufactured. This study provides the technical conditions for the mass industrial application of advanced high strength steel.
Advanced high strength steel material and its properties
Advanced high-strength steel mainly includes dual phase steel (DP), transformation induced plastic steel (trip), dual phase steel (CP) and martensitic steel (MS), etc. this kind of steel achieves high strength through transformation structure strengthening, with the strength range of 500mpa-1500mpa (usually called ultra-high strength steel with tensile strength over 700MPa).
