A highly efficient method of thermal stress bending with non-thinning and grain refinement

Abstract

Thickness thinning is one of the processing defects that tend to occur in traditional stamping or mechanical bending of plate (tube). In the field of high mechanical performance requirements (such as pressure vessel), the thinning phenomenon can not be ignored. Thermal stress forming has excellent characteristics of forming without thinning, but the forming angle of the method is small, thus limiting the promotion and application of the process in the field of forming. To solve the problem, an applying baffles method (ABM) to both ends of workpiece based on thermal stress forming is proposed. A coupled thermodynamic model about ABM is developed, and the bending angle and deformation mechanism are investigated. Finally, the grain size and thickness of the deformed region are observed. The results show that ABM can increase the bending angle by 14.26 times compared with the traditional method. The bending angle of ABM is determined by both the temperature difference and the baffle, and the baffle plays a major role. Compared with the traditional method, ABM can obtain smaller grain size and increase the microhardness by 1.39 times. ABM can increase the thickness of the upper surface by 121 μm and the thickness of the lower surface by 47 μm. For upper surface thickening, ABM is 9.31 times greater than the traditional method. This thickening will effectively avoid thinning problems in stamping (mechanical bending). This method can make thermal stress forming a high-quality process in the forming field.