Research On Electromagnetic Heating Strengthening And Its Mechanical Property Of Welded Joints

Welding has been widely used in each of industrial fields because this technique is easy, effective and simple operation, however the crack is easily generated due to the unfavourable feature of welding. Today,at home and abroad the questions how to eliminate cracks are concentrated in the improvement of welding procedure and welding equipment, but the motheds about how to prevent cracks spreading is hardly dicussed. The thermal electromagnetic crack preventing process is a new crack arrest way, it has a positive meaning to apply this technique to welding fields because this mothed can make the crack arrested and improve mechanical property of welded joints better. This article take theoretical analysis, numerical simulation and experiment research to study crack arrest by electromagnetic heating in welded metals.On the foundation of theoretical analysis about metal structures with a elliptical embedding crack, by the differential calculus way the temperature field is deduced during the pulse current discharge. Meanwhile taking a specific example to calculate the temperature curve at the crack tip and its rule with the distance changing.The numerical simulations on welding temperature field and stress field during the16Mn welding process and45#,16Mn welding process are done by using Ansys software, at the same time the reason why crack is generated in the two welded joints is analysed. In order to prevent the elliptical embedding crack and edge crack spreading, this technique is applied to them, then its temperature field, residual stress field and strain field are simulated. Based on the above mentioned analysis, it proves that the technique is effective to improving welded joint’s mechanical property.Adopting machining processes, the16Mn welding piece with embedded crack and the45#,16Mn welded joint with edge crack is made. Later the two kind of welded joint are strengthened in the home-made ZL-2pulse current discharge device and making use of ultrasonic flaw detector detect the change of residual stress before and after pulse current discharge. Using WDW3100microcomputer control electronic universal test machine and impact testing machine to test the two kind welded joint’s mechanical property before and after pulse current discharge. Meanwhile the research on how to influence crack arrest result with different voltage and different crack length is finished.as well the macro-micro fracture and microstructure are observed and analysed before and after pulse current dischargeOn the foundation of analysis of welding technique, this article proves that the electromagnetic thermal crack arrest technique is effective to improve welded joint’s mechanical property by the way of theoretical analysis, numerical simulation and experimental research. And it can lay the foundation for applying this technique to welding field.