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Welding stress refers to the stress generated during welding of welded parts, the internal stress generated during welding and the change of weldment shape and size. The uneven temperature field, local plastic deformation and the resulting organization with different specific volume during welding are the root causes of welding stress and deformation. When the welding temperature field does not disappear, The stress and deformation in the weldment are called transient welding stress, and the stress and deformation after the disappearance of temperature field are called welding residual stress. In the absence of external force, the welding stress is balanced in the weldment. The welding stress and deformation will affect the function and appearance of the weldment under certain conditions. The impact of welding residual stress on the structure and components:
The initial stress on the cross section before the member bears the load is the welding residual stress. During use, the member overlaps with the stress caused by other loads, resulting in the redistribution of residual stress and secondary deformation, reducing the structural stiffness and stability. Under the action of temperature and medium, it will affect the structural fatigue strength, resistance to stress corrosion cracking Resistance to brittle fracture and high temperature creep cracking.
Elimination method of welding stress
At present, vibration aging, thermal aging and houckner Pt aging are adopted.
Vibration aging
It is a common method to eliminate the internal residual stress. When the vector of internal residual stress and vibration stress exceeds the yield strength of the material, a small amount of plastic deformation will occur, which will relax and reduce the internal stress of the material.
Thermal aging
Heat the workpiece to the elastic-plastic transition temperature and keep it for a certain time to relax the stress, and then slowly cool down, so that the workpiece is in a low stress state after cooling. If the process parameters are improperly selected or not operated according to reasonable process specifications in heating, insulation and cooling, the stress cannot be eliminated, but will increase.
Hawk energy aging
At present, it is a method to completely eliminate welding residual stress and produce ideal stress. The fatigue strength can be increased by 50% - 120%, the fatigue life can be prolonged by 5-100 times, the corrosion resistance can be increased by about 400%, the treatment process is simple, and the effect is stable and reliable.
It is not limited by the material, shape, structure, thickness, weight and site of the workpiece, especially in the construction site and welding process. It is more flexible and convenient to eliminate the welding stress. The pits and undercuts at the weld toe can be treated into a smooth geometric transition, reduce the stress concentration factor, remove the microcracks and slag at the weld toe, and prevent the formation of cracks.
It is suitable for welding, welding repair and stress relief treatment of large components. It is environmentally friendly, energy-saving, safe and pollution-free. It is flexible and convenient to use on the construction site.
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