Research On Stress Relief Mechanism By Peening Roll After Surfacing Welding And Welding With Trailing Peening System

As a key part of mill, roll has been consumpted significantly in the process of rolling. Surfacing welding technology has been widely used to repair roll in recent years. The roll has a long life and more effective characteristics after repair, so that through the repair of used roller, saving the cost of production. But the welding residual stress had made a serious impact on the performance of repaired roll, the form of failures include spalling and crack. The craft of weling with trailing peening can improve the performance of roll repairing by: effectively eliminate the existence of residual stress in roll, improve fatigue strength of roll surface chilled layer and reduce non-uniform and micro-defects in the material of roll surface chilled layer.Electromagnetic hammer device is the key component which to achieve with hammering, including parameter detection module, hammering parameters control circuit, implementation part.Different welding wire and specimen are selected in the test, orifice method is adopted to measure stress value. First of all, single factor analysis of hammering force, hammering temperature, hammering frequency and size of hammer on the impact of residual stress; followed by Microstructure analysis and comparison of test samples by optical microscope and scanning electron microscopy; Finally, the use of orthogonal test to the welding with trailing peening process parameters were optimized.Through the test concluded that: (1) Electromagnetic trailing peening system for welding roll is developed, experiments show that a good run. (2) In the different norms to deal with the hammer, the weld residual stress has been reduced to varying degrees, the largest amplitude is found on welding seam, the farther away from welding seam, to reduce the stress of the smaller amplitude. (3) From the weld structure can be seen: hammer can be refined grains and increase the weld strength of the weld and to improve hardness. (4) Through range analysis of orthogonal test The optimal program of welding with trailing peening process is obtained; through a multiple regression analysis to verify that resulted in residual stress and a mathematical model is built between residual stress and peening parameters. (5) The test with the optimal program on the material of roll concluded that welding with trailing peening process can be essential to reduce the surfacing weld residual stress significantly and improve its microstructure.