Method for inhibiting cracks of aluminum alloy self-piercing rivet joint

Abstract

The invention relates to a riveting method for inhibiting cracks of an aluminum alloy self-piercing rivet joint. The method comprises the steps that a cast aluminum component is preheated, SPR riveting with the cast aluminum located below is conducted on a steel plate or other high-extensibility materials, and the method is completed. Compared with the prior art, the cast aluminum component is preheated before riveting to further improve the plasticity deformation capability of the cast aluminum component, surface eutectic silicon segregation and the like of the cast aluminum component can beimproved and eliminated to allow the organization of the cast aluminum component to be more uniform, the formation of riveting cracks is inhibited, and therefore the service life of the joint is prolonged.

Description

technical field [0001] The invention belongs to the technical field of metal treatment and relates to a method for suppressing cracks in aluminum alloy self-piercing riveting joints. Background technique [0002] The design of multi-material hybrid body has become the most important means of lightweighting the body, but the traditional technology is difficult to meet the mixed connection of multiple materials, which makes the assembly of lightweight multi-material hybrid body a huge challenge. The SPR (Self-Piercing Riveting) self-piercing riveting process proposed by the British Henrob Company, which does not penetrate the lower layer, is a mechanical connection method. Due to its extremely low heat input, it can effectively avoid the interface hard and brittle phase caused by thermal connection. Problems such as joint softening are widely used in the manufacture of automobile bodies. [0003] The SPR process pierces the upper plate through a semi-hollow rivet and expands ...

AI Technical Summary

Problems solved by technology

[0004] With the wide application of aluminum alloy materials in the body, the proportion of aluminum alloy plates, profiles and castings is increasing, and the application of steel-aluminum mixed structures is increasing. However, for materials with low elongation such as cast aluminum, SPR connection There are some problems, mainly manifested in the plastic deformation process of SPR processing, especially when the steel plate is on top and low-elongation materials (cast aluminum, etc.) Cracks are likely to occur inside or at the bottom of the joint of the lower plate of the elongation material; the crack phenomenon of cast aluminum and other low elongation materials during SPR processing seriously reduces the quality of the joint and leaves hidden dangers for the subsequent safe service of the joint, especially affecting to the fatigue properties of joints

[0005] In order to solve the crack phenomenon of low-elongation materials in the SPR process, patent CN103796773A proposes to perform heat treatment on 7000 series aluminum alloy plates within 120 minutes before manufacturing the joint, and / or during at least part of the time during the joint, so that Temporarily reduce the tensile strength of the joint area of ​​the workpiece. This method is only suitable for AA7000 series aluminum alloy sheets, and the time requirements for the process are too high, and the operability of the actual production process is poor; patent CN104611652A proposes a yield strength of at least 200MPa And the heat treatment technology of the 6xxx series aluminum alloy plates with the r / t (bendability) ratio of up to 0.4, this method is only applicable to the AA6XXX series aluminum alloy plates, and does not provide specific SPR connection process and method; CN101495253A provides Laser heating of low-elongation materials to improve the formability of materials, but the cost of heating by laser is high, and it is difficult to apply on a large scale

[0006] For the SPR connection of steel-aluminum structure, especially the crack problem in the joint of steel-cast aluminum SPR connection, the current research mainly focuses on the initiation and propagation mechanism of fatigue cracks during the fatigue test process, and the cracks generated during the SPR riveting process Research on the production mechanism and its inhibition method has not seen any published related patents, nor has there been any published reports on the specific technical implementation process

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