Preview Bending Workpiece

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Preview bend the workpiece. In a production environment to eliminate the warping often use pre-reverse bending the workpiece. This method is used to overcome the angular deformation during welding of butt and lap joints. When welding sheets of small width with V-shaped edges partitioned them have not in one plane and at an angle in the direction opposite to the expected deformation. Sheets of large width can be installed with pre-bending of the welded edges.

Field joints with fixed plates welded with the recommended pre-folded edges, which is achieved by means of jacks or special devices. To prevent deformation "of the plane," T-or I-sections produce elastic or plastic deformation zone. In order to eliminate the longitudinal strain "in plane" with welded H beams used devices, which bent the beam in the direction opposite to the expected deformation. Preview reverse bend can be created by work hardening the edges and sides of beams, or heating up temperature 700 750 C. An effective measure to prevent buckling of the walls in the I-beam, caused by welding belt joints – build with pre-tension of the wall. To do this, use the assembly stands with the jack device. Increase the stiffness of thin plates in welded structures in order to reduce the strain can be achieved by embossing. With the press on thin sheets of pre-squeezed patterns of rigidity, or corrugations.

Decrease welding stresses can be achieved by pre-stretching or compression of the workpiece along the weld. Cooling of the workpiece. If additional cooling weld areas in which there are plastic deformation, shrinking, which leads to a reduction of residual stress and strain. Zana distribution of maximum temperatures and the size of plastic deformations in cooling and without it. If additional cooling sections of plastic deformation are smaller than when welding under normal conditions. However, refrigeration is not applicable for all materials. When welding hardenable steels method of artificial cooling is not applicable because it can lead to brittle hardening structures. Effect of heating the workpiece. In a preliminary or concomitant heating decreases the temperature difference between adjacent sections of the welded joint, thanks to this somewhat reduced voltage. Found that when welding steel heated to a temperature of 200 'with a residual voltage Compared with welding without heating is reduced by 30%. At higher temperatures, heating the positive effect may be even greater. Noticeable effect on the voltage has concomitant heating. When welding is possible to conduct both general and local heating associated. The total heating is prescribed for welding parts of small size or non-plastics materials such as iron. When the local heating of heated area width 40 50 mm on both side of the seam. Heating only the welded edges does not give a noticeable effect. Temperature of preheating depends on the chemical composition and thickness of the metal, as well as rigidity. With increasing content carbon and alloying elements, metal thickness and rigidity required heating to higher temperatures.

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