Local constant-temperature preheating stirring friction welding method

Abstract

The invention discloses a local constant-temperature preheating stirring friction welding method. The method comprises the following steps of placing a heating piece on the upper surface of a weld seam of a to-be-welded workpiece, and meanwhile placing a heating piece on the lower surface of the weld seam of the to-be-welded workpiece, and then clamping and fixing the to-be-welded workpiece; and uniformly preheating local welding seam to a predetermined temperature through the heating pieces on the upper and lower surfaces, and finally completing the welding of the to-be-welded workpiece through using the stirring friction welding method. During the welding process, the position of the heating piece on the lower surface is fixed, and meanwhile the heating piece on the upper surface keeps adistance with a stirring head and moves forward along with the stirring head, wherein both speeds of the heating piece and the stirring head are kept to be consistent, thus ensuring that the distancefrom the heating piece on the upper surface to the stirring head is unchanged; and in addition, the temperature field distribution of a welding joint can be controlled through adjusting the preheating temperature, position and range of the heating pieces on the upper and lower surfaces, and deformation rate distribution of the weld joint can be further adjusted. According to the local constant-temperature preheating stirring friction welding method, the distribution of deformation temperature and deformation rate of a joint material can be adjusted and controlled, and therefore the welding operation is simple, convenient and flexible.

Description

technical field [0001] The invention belongs to the field of welding technology, in particular to a local constant temperature preheating friction stir welding method. Background technique [0002] Friction stir welding is a solid-state welding technology. During welding, the joint metal will undergo strong plastic deformation accompanied by strong recrystallization, so the joint grains are very fine. Since this welding method does not solidify the molten pool during the welding process, the joints will not produce defects such as pores, thermal cracks, and segregation, and the performance of the welded joints is very excellent. In the friction stir welding process, the heat source comes from the frictional heat and plastic deformation heat between the stirring head and the workpiece. The heat production is low, the workpiece temperature is low, and the material deformation resistance is high. Therefore, when welding high melting point metals or thick plates, the stirring he...

AI Technical Summary

Problems solved by technology

However, auxiliary heat sources such as lasers, acetylene flames, and plasma arcs mostly act on the upper surface of the workpiece to be welded, while the bottom is not effectively preheated. The temperature difference between the top and the top of the weld leads to a huge difference in the microstructure and mechanical properties of the top and bottom of the welded joint, and the joint is also prone to welding defects; when resistance and high frequency are used as auxiliary heat sources, the stirring head, welding platform, Fixtures must be specially insulated to prevent electric shock, and the welding process is cumbersome; some researchers fix the workpiece to be welded on a controllable heating device, preheat the entire workpiece to a predetermined temperature, and then use friction stir welding technology to achieve Connection of workpieces

Obviously, this preheating method is only suitable for heating smaller workpieces, and cannot be achieved for large workpieces.

It can be seen that there are still many problems in the current auxiliary heat friction stir welding technology, and the preheating effect or preheating operation process is not ideal.

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