Friction stir welding-braze welding composite welding method for dissimilar metal bonding structure

Abstract

A friction stir welding-braze welding composite welding method for a dissimilar metal bonding structure is provided. The operation process of the method is as follows: before welding, a material with low hardness is placed on the upper layer, a material with high hardness is placed on the lower layer, and a soft solder with a low melting point, such as pure Zn or a Zn-matrix solder, is placed between two plates; a stirring head which rotates at a high speed is inserted into the metal in the upper layer, a stirring pin enters the metal in the lower layer, and the solder which is clamped between two types of metal is melted by stirring friction heat; and finally excess melted solder is extruded under the pressure action of a shaft shoulder, the purification of the interface is realized, diffusion bonding is formed, and the purpose of welding is achieved. According to the method, composite welding seams can be obtained; the effective bonding width of the bonding structure can be increased; stress concentration and the interface effect of the bonding interface are reduced; and the service performance of joints is improved.

Description

technical field [0001] The invention belongs to the field of metal welding, and relates to a composite welding method for simultaneously realizing friction stir welding connection and brazing connection of dissimilar metal overlapping structures. Background technique [0002] Dissimilar metal welded joints are widely used in many fields because they have the properties of two metals and have the effect of complementing each other's advantages and avoiding weaknesses. For example, in the field of automobile industry, the use of aluminum / steel bimetallic joints can greatly reduce the weight of the structure on the premise of ensuring the bearing capacity of the joints, laying a foundation for reducing the weight of the body and reducing fuel consumption. Studies have shown that when the weight of the car Every 25% reduction can save 50% of fuel consumption; in the field of aviation industry, "reducing weight and increasing thrust-to-weight ratio" has become an important design...

AI Technical Summary

Problems solved by technology

However, when the friction stir welding is used to weld the lap structure, the effective load-bearing thickness of the interface will be reduced due to the interface migration at the lap interface

At the same time, the existence of the unwelded area at the lap interface is similar to the crack tip in the weld, and stress concentration is easily generated there during the load-bearing process, resulting in cracking; the structure serving in the corrosive medium is easily immersed by the corrosive liquid, and Due to surface adsorption, the corrosive liquid accumulates and is difficult to remove, resulting in localized corrosion and failure of the structure

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