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Causes and preventive measures of laser welding deformation stress?

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Causes and preventive measures of laser welding deformation stress?

Causes and preventive measures of laser welding deformation stress?

The basic forms of laser welding deformation include shrinkage deformation, angular deformation, bending deformation, wave deformation and twisting deformation. During the welding process, the uneven heating and cooling of the welding part is the root cause of welding stress and deformation. Reduce welding stress and Deformation process measures mainly include:


1. Reserve shrinkage deformation According to theoretical calculation and practical experience, shrinkage allowance should be considered in advance during welding preparation and welding processing, so that the welded workpiece can reach the required shape and size.


2. The anti-deformation method pre-estimates the direction and size of structural welding deformation based on theoretical calculations and practical experience, and then gives a preset deformation in the opposite direction and equal in size during welding assembly to offset the deformation after welding.


3. Rigid fixing method: When welding, rigidly fix the weldment, and remove the rigid fixation after the weldment is cooled to room temperature after welding, which can effectively prevent corner deformation and wave deformation. This method will increase welding stress and is only suitable for plasticity Good mild steel construction.


4. Choose a reasonable welding sequence to make the weld shrink freely as much as possible. When welding structural parts with many welds, you should first weld the staggered short welds, and then weld the straight long welds to prevent cracks at the welds , if the welding seam is long, the step-by-step reflow method and skip welding method can be used to make the temperature distribution more uniform, thereby reducing welding stress and deformation.


5. Hammer welding method: During the cooling process of the weld seam, the weld seam is hammered evenly and quickly with a small ball hammer, so that the metal produces plastic extension and deformation, and offsets part of the welding shrinkage deformation, thereby reducing welding stress and deformation.


6. Before welding with the "stress reduction zone" method, heat the area near the welded part (called the stress reduction zone) to make it elongate. When cooling after welding, the heating zone will shrink with the weld seam, which can effectively reduce the welding stress and deformation.


7. The purpose of preheating before welding and slow cooling after welding is to reduce the temperature difference between the weld zone and other parts of the weldment, reduce the cooling rate of the weld zone, and cool the weldment evenly, thereby reducing welding stress and deformation .


What are the disadvantages of laser welding processing?


(1) The welding position of the laser welding process should be very precise and needs to be within the focus range of the laser beam;


(2) When the weldment needs fixtures, it is necessary to ensure that the position of the weldment is aligned with the welding spot that the laser beam will hit;


(3) For workpieces with limited weldable thickness and penetration thickness much greater than 19mm, it is not suitable to use laser welding on the production line;


(4) The laser will change the weldability of materials with high reflectivity and high thermal conductivity such as aluminum, copper and their alloys;


(5) When performing high-energy laser beam welding, it is necessary to use a plasma controller to drive off the ionized gas around the molten pool to ensure the reproduction of the weld;


(6) The energy conversion efficiency is too low, usually lower than 10%;


(7) Rapid solidification of the weld bead may cause porosity and embrittlement;


(8) Expensive equipment;

The above is the content of "Causes and preventive measures of laser welding deformation stress?" I hope it can be useful to everyone.




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