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Method for preventing aluminum alloy overlap welding grain boundary liquefying cracks through friction stir processing

A technology of friction stir and liquefaction cracking, applied in the field of material processing, can solve the problems of reducing production efficiency and complicated process, and achieve the effects of improved crack resistance, low consumption frequency and low cost

Active Publication Date: 2017-09-12
NORTHEASTERN UNIV
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But above-mentioned method technology is loaded down with trivial details, reduces production efficiency

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  • Method for preventing aluminum alloy overlap welding grain boundary liquefying cracks through friction stir processing
  • Method for preventing aluminum alloy overlap welding grain boundary liquefying cracks through friction stir processing
  • Method for preventing aluminum alloy overlap welding grain boundary liquefying cracks through friction stir processing

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[0031] Specific embodiments of the present invention will be described in detail below in conjunction with technical solutions and accompanying drawings.

[0032] For 20mm and 9mm thick 7N01-T4 aluminum alloy plates, MIG fillet welding is performed, of which the 20mm plate is the reinforcing plate and the 9mm plate is the bottom plate. During the inspection of MIG fillet weld joints, it was found that there were crack defects in the heat-affected zone of the 20mm thick reinforcing plate near the weld. It is believed that the main reason is that the eutectic MgZn with low melting point is distributed on the grain boundary of this position. 2 phase, and there is a large welding tensile stress at this position. So the 20mm thick 7N01-T4 aluminum alloy plate was subjected to friction stir processing and MIG fillet welding. The surface of the 7N01-T4 aluminum alloy plate is mechanically polished to produce a metallic luster, and the workpiece is fixed on the friction stir process...

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Abstract

The invention discloses a method for preventing aluminum alloy overlap welding grain boundary liquefying cracks through friction stir processing. Before fusion welding is adopted for conducting overlap welding on an aluminum alloy thick plate, preprocessing of friction stir processing is conducted on the end face of the thick plate participating in weld joint forming, due to the fact that a preprocessed part is subjected to friction heat and a severe plastic deformation effect, completely dynamic recrystallization happens to fibril-shaped crystal grains, fine isometric crystals are formed, low-melting-point eutectic phases at the crystal boundary position are distributed in a dispersed manner, and the capability for resisting crystal boundary liquefying cracks of the part is improved. A friction stir processing head is mainly composed of three parts including a clamping handle, a shaft shoulder and a stirring needle. The stirring head is made of martensitic stainless steel or tool steel. According to friction stir processing parameters, the number of revolutions of the friction stir head ranges from 500 r / min to 2000 r / min, the traveling speed ranges from 20 mm / min to 100 mm / min, and the inclination angle of the stirring needle ranges from 0 degree to 5 degrees. Friction stir processing is conducted on the four machining faces, in the thickness direction, of the plate in sequence, and therefore an overlap welding plate good in cracking resisting performance is obtained.

Description

technical field [0001] The invention relates to the technical field of material processing, and relates to a method for preventing liquefaction cracks in aluminum alloy lap welding grain boundaries through friction stir processing. Background technique [0002] Due to the advantages of low density, high strength, good plasticity, corrosion resistance and easy forming, aluminum alloy has been widely used in aerospace, transportation, machinery manufacturing and other fields. Especially in recent years, the concept of lightweight and environmentally friendly high-speed trains and automobiles has been proposed, and various lightweight aluminum alloy welded structural parts have been widely used. However, aluminum alloy fusion welding is prone to defects such as pores, cracks and deformation. At present, the friction stir welding process for thin aluminum alloy is relatively mature, which avoids the common defects of fusion welding. However, the friction stir welding of thick ...

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Application Information

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IPC IPC(8): B23K20/12B23K20/22B23K20/24B23K20/26
CPCB23K20/122B23K20/22B23K20/24B23K20/26
Inventor 何长树张志强李颖田妮
Owner NORTHEASTERN UNIV
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