Methods for preventing and reducing welding deformation of wear-resistant steel plates
1. Do not weld too much
The more metal filled in the weld will produce a larger deformation force. The correct size of the weld can not only obtain smaller welding deformation, but also save welding material and time. The amount of welding metal filling the weld should be minimal, and the weld should be flat or slightly convex, and excessive welding metal will not increase strength. On the contrary, it will increase the shrinkage force and increase the welding deformation.
2, intermittent weld
Another way to reduce the amount of weld filling is to use more intermittent welding. For example, when welding high-strength plates, intermittent welding can reduce the amount of weld filling by 75%, while also ensuring the required strength.
3, reduce the weld bead
Welding with thick wire and fewer passes is less deformed than welding with thin wire and more passes. In multiple passes, the shrinkage caused by each pass accumulatively increases the total weld shrinkage. It can be seen from the figure that the welding process with fewer passes and thick electrode is better than the welding process with more passes and thin electrode.
4, anti-deformation technology
The parts are bent or tilted in the opposite direction of the welding deformation before welding (except for overhead welding or vertical welding). The preset amount of reverse deformation needs to be determined by test. Prebending, presetting, or prearching welded parts is a simple way to use reverse mechanical forces to offset welding stress. When the workpiece is preset, a deformation occurs that causes the workpiece to be opposite to the weld contraction stress. The pre-deformation and post-deformation cancel each other, making the welding workpiece an ideal plane.
5. Welding sequence
According to the structure of the workpiece, a reasonable assembly sequence is determined, so that the structure of the workpiece shrinks in the same position. Double-sided groove is opened in the workpiece and the shaft, multi-layer welding is adopted, and the double-sided welding sequence is determined. Intermittent welding is used in fillet welds, and the contraction in the first weld is balanced by the contraction in the second weld. The fixture can hold the workpiece in the desired position, increasing rigidity and reducing welding deformation. This method is widely used in the welding of small workpieces or small components, due to the increase of welding stress, only suitable for low carbon steel structure with good plasticity.
6. Remove shrinkage force after welding
Tapping is a method of counteracting the contraction force of the weld, as is welding cooling. Tapping will cause the weld to extend and become thinner, thus removing stress (elastic deformation). However, when using this method, it must be noted that the root of the weld cannot be knocked, and cracks may occur when knocked. In general, tapping cannot be used on the cover weld.
7, reduce welding time
Welding produces heat and cooling, and it also takes time to transfer heat. Therefore, the time factor also affects the deformation. Usually, it is desirable to complete the welding as soon as possible before the large workpiece is heated and expanded. The welding process, such as the type and size of the electrode, welding current, welding speed, etc., affects the degree of shrinkage and deformation of the welding workpiece. The use of mechanized welding equipment reduces the welding time and the amount of deformation caused by heat.
