With the increasing people's living standards, the performance requirements of various products has gradually increased, specifically to the motor vehicle, is required to have a comfortable, safe and energy-saving performance, which reflects the specific energy-saving engineering applications, is required Lightweight vehicle, and lightweight vehicle research is a focus of the heat exchange system, lightweight.
The light weight and reliability of the pipe material used in the heat exchanger itself is the focus of future research. Welded pipe material replaced by aluminum tube is the future trend of the field of heat exchangers, and the use of high-frequency induction welding pipe production methods greatly improve the efficiency of production, significantly reducing production costs for the industry's large-scale commercial applications solid foundation.
Despite the number of pipe production in China has been in the forefront of the world's pipe industry, but the pipe production technology, welding varieties and product quality there are still many shortcomings, high-quality welded pipe but also a large number of imports to meet the demand. In order to ensure the quality of welded pipe welding, the welding process must be strictly grasp the welding parameters of the selection and control of its change. Welding process is a complex process of many factors, including electromagnetic conversion, energy conversion, melting and solidification of welding materials, phase transformation, welding residual stress and structural deformation. Welding quality depends on the quality of welded joints, welded joints are composed of two parts, namely the weld and heat affected zone, during which a transition zone, known as the fusion zone. A large number of failure events prove that welding heat affected zone, especially fusion zone and coarse grain zone, is the most dangerous part of structural brittle failure.
Therefore, how to improve the structure and performance of welding heat affected zone and improve the reliability and reliability of welded joint Has become an important issue in the field of welding. Traditional welding process methods often rely on a large number of debugging work and workers’ long-term practical experience to sum up, its reliability and lack of theoretical, with the external conditions change significantly, limiting its economic application of large-scale and Promotion.
At the same time, with the development of science and technology, especially computer technology and finite element analysis, more and more scholars and engineers in welding field use computer numerical simulation method to study the welding process. Through the finite element analysis method to establish the appropriate mathematical model can directly find the welding parameters (such as voltage, current, frequency, time, V-shaped angle) and the relationship between the welding temperature field and stress field, sufficient test to verify the mathematical model Accuracy and reliability, which can be established to support the theoretical model of production applications.
In the 1950s, high-frequency welding technology in the United States first developed rapidly, in 1951 for the first time induction coil used in pipe production, and in 1954 published a “high-frequency induction welding process, " the patent has been studying high-frequency welding heat The relationship between the width of the affected zone and the strength of the welded joint, and the relationship between the welding parameters and the welding temperature and residual stress distribution.