High-quality 6-series aluminum alloy extrusion casting blank and preparation method thereof

Abstract

The invention discloses a high-quality 6-series aluminum alloy extrusion casting blank and a preparation method thereof. The preparation method comprises the following steps of performing primary cooling treatment, bath treatment and subsequent cooling treatment on a 6-series aluminum alloy ingot subjected to homogenization heat treatment in sequence. Compared with a traditional uniform casting blank in actual production, the prepared casting blank has the advantages that a large number of dispersed micron-sized precipitated phases are distributed in a matrix, the structure can not only effectively reduce the extrusion deformation resistance of a cast ingot, improve the surface quality of an extruded product, but also improve the online quenching solid solubility of the extruded product, so that a good tissue basis is provided for later aging treatment. Finally, the high-quality extrusion casting blank capable of improving the extrusion performance and improving the final aging strength is finally obtained.

Description

technical field [0001] The invention belongs to the field of aluminum alloy materials, and in particular relates to a high-quality 6-series aluminum alloy extruded billet and a preparation method thereof. Background technique [0002] As an important member of deformed aluminum alloys, 6 series aluminum alloys are widely used as extrusion parts. The microstructure has a crucial influence on the extrusion process performance, surface quality and final mechanical properties of the cast slab: if the subsequent cooling treatment of homogenization causes excessive solid solution of alloying elements in the aluminum matrix, significant solid solution The strengthening effect will lead to high hardness of the slab, making it difficult to extrude and deform; if the subsequent cooling treatment after homogenization causes excessive precipitation of alloying elements and the formation of coarse Mg 2 Si phase, the solid solution strengthening effect basically disappears, and the stren...

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Problems solved by technology

The microstructure has a crucial influence on the extrusion process performance, surface quality and final mechanical properties of the cast slab: if the subsequent cooling treatment of homogenization causes excessive solid solution of alloying elements in the aluminum matrix, significant solid solution The strengthening effect will lead to high hardness of the slab, making it difficult to extrude and deform; if the subsequent cooling treatment after homogenization causes excessive precipitation of alloying elements and the formation of coarse Mg 2 Si phase, the solid solution strengthening effect basically disappears, and the strengthening effect of the coarse second phase is also very limited. At this time, although the overall hardness of the ingot material is greatly reduced, which is conducive to reducing the resistance to extrusion deformation, these coarse precipitated phases It is difficult to dissolve quickly during the extrusion process, and a large amount remains after online quenching, so it cannot participate in precipitation strengthening in the later aging process

In addition, the existence of these coarse precipitates is easy to produce many surface quality defects during extrusion, and what is more serious is that these coarse precipitates will also locally melt and cause cracking at higher extrusion temperatures

In actual production, the effect of conventional cooling treatment is not ideal, and it is often difficult to obtain timely cooling and cooling treatment for the slab after homogenization heat treatment, which leads to the precipitation of a large amount of coarse Mg in the ingot 2 Si, this billet material cannot guarantee final aging strength, good surface quality and high extrusion speed

[0003] In the existing technology, in order to solve the problem of slow cooling response, water mist is directly sprayed on the billet just out of the furnace after homogenization. Although this method can obtain the effect of rapid cooling, it will cause serious quenching stress and even cause deformation and cracking of the ingot. There are also technologies that improve the strength of aluminum alloys through their corresponding schemes, but do not make special requirements for the cooling of the ingot after homogenization. In order to solve the problem of low solid solubility of the matrix after thermal deformation, a separate solution heat treatment is carried out. This solid solution link increases energy consumption and production costs; some ingots are homogenized and then adopted a three-stage cooling method, hoping to achieve the purpose of accelerating the cooling of high-temperature ingots without producing quenching stress and dimensional deformation. However, the cooling strength of the method used is limited, and a large number of production data show that the size of the precipitated phase in the matrix is ​​still large and cannot be completely dissolved during the extrusion process, so there is still a lot of room for improvement in the aging strength of the final product

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