A kind of al-zn-mg-cu ultrahigh-strength aluminum alloy and its rapid extrusion on-line quenching production method

Abstract

The invention discloses an Al-Zn-Mg-Cu ultrahigh strength aluminum alloy and a rapid extrusion online quenching production method thereof, and belongs to the technical field of aluminum alloy materials. The aluminum alloy disclosed by the invention comprises the following components in percentages by weight: 5.5wt% to 6.5wt% of Zn, 1.8wt% to 2.2wt% of Mg, 0.4wt% to 0.6wt% of Cu, 0.20wt% to 0.30wt%of Si, 0.10wt% to 0.15wt% of Mn, 0.02wt% to 0.06wt% of Cr, 0.03wt% to 0.05wt% of Ti, 0.02wt% to 0.03wt% of Zr, 0 to 0.12wt% of Fe and the balance of Al. An Al-Zn-Mg-Cu aluminum alloy cast ingot withhigh extrudability and low quenching sensitivity is obtained by reasonably controlling the component range and production technology of the alloy, the maximum extension speed of the alloy can reach 6m / min, online quenching can be realized, and in cooperation with the control for the technologies such as three-step aging, the ultrahigh strength aluminum alloy with the tensile strength of more than500 MPa is obtained.

Description

technical field [0001] The invention belongs to the technical field of aluminum alloy materials, and in particular relates to an Al-Zn-Mg-Cu ultra-high-strength aluminum alloy and a rapid extrusion on-line quenching production method thereof. Background technique [0002] Ultra-high-strength aluminum alloys such as 7075, 7050, etc., due to the high content of Zn, Mg, Cu, etc., have very poor extrudability, which is manifested in large deformation resistance and slow extrusion speed. The maximum extrusion speed is at At about 1m / min, cracking will occur when the speed is increased; at the same time, its quenching sensitivity is very high, which is manifested in its narrow solution temperature range, fast quenching and cooling speed requirements, and the extrusion speed cannot be increased, resulting in product extrusion. When extruding the front beam of the extruder, the temperature is already far below its solid solution temperature, so it is impossible to realize on-line qu...

AI Technical Summary

Problems solved by technology

[0002] Ultra-high-strength aluminum alloys such as 7075, 7050, etc., due to the high content of Zn, Mg, Cu, etc., have very poor extrudability, which is manifested in large deformation resistance and slow extrusion speed. The maximum extrusion speed is at At about 1m / min, cracking will occur when the speed is increased; at the same time, its quenching sensitivity is very high, which is manifested in its narrow solution temperature range, fast quenching and cooling speed requirements, and the extrusion speed cannot be increased, resulting in product extrusion. When extruding the front beam of the extruder, the temperature is already far below its solid solution temperature, so it is impossible to realize on-line quenching on the conventional production line. At present, there are some plans to install a heating and heat preservation device between the extruder and the on-line quenching device. In order to realize the on-line quenching of ultra-high-strength aluminum alloys such as 7075, but because the problems of high quenching sensitivity and poor extrudability of the alloy have not been fundamentally solved, the solid solution temperature range of the alloy used is very narrow, and the product in the extrusion process is It is difficult to control the temperature uniformity of the product when it is mobile, and it is difficult to control the temperature uniformity of the product, and it is easy to cause the product to be over-burned or solution quenched insufficiently. It is not yet possible to promote the use of large quantities of industrial

[0003] At present, aluminum alloys with good extrudability and low quenching sensitivity, such as 6063, 6005A, 7020, etc., which can be quickly extruded and realized on-line quenching, have low strength, and the tensile strength after aging does not exceed 450MPa, which cannot meet the requirements. Requirements for the use of ultra-high-strength, lightweight structural parts

[0004] After retrieval, Chinese patent, application number 201710240655.X, a manufacturing method of 6101 aluminum alloy profiles, the method produces high-strength aluminum alloy profiles through rapid extrusion and online quenching, which solves the problems of low production efficiency and yield Low problem, but the composition of this method is ordinary 6101 alloy, the content of Zn, Mg, Cu, etc. is very small, and the homogenization of the ingot has not been improved, and the final profile tensile strength is about 200MPa, which cannot meet the application of higher strength need

[0005] Chinese patent, application number 201410180442.9, a large-scale flat cast ingot of ultra-high-strength Al-Zn-Mg-Cu aluminum alloy and its manufacturing method. The method improves the manufacturing method and prepares large-sized, high-strength ingots without the need for pure aluminum bottoming. Flat cast ingots with high strength, no cracks and high casting success rate, but the content of main strengthening elements Zn, Mg and Cu in this method is high, especially the content of Cu, the alloy has high quenching sensitivity, and the secondary ingot used is homogenized The process cannot take into account the two aspects of rapid homogenization and control of deformation resistance, and the alloy has poor extrudability, resulting in the production of slab ingots that can only be rolled and offline solution quenching, and the final product cannot be produced by rapid extrusion and online quenching

[0006] Chinese patent, application number 201710518117.2, a preparation process of Al-Zn-Mg alloy profiles for high-speed EMU car bodies. This method adopts continuous solution quenching at the bottom of the roller and the aging of the plate-type three-stage aging furnace for aviation can greatly improve the production process. Heat treatment accuracy, at the same time, the method of gradient heating is adopted during extrusion to accurately control the temperature difference between the head and tail of the Al-Zn-Mg profile, and reduce the performance difference between the head, middle and tail of the Al-Zn-Mg alloy profile, thus ensuring the Al-Zn- The performance stability of the Mg profile, but the content of the main strengthening elements Zn, Mg, Cu in this method, especially the content of Cu is low, the homogenization of the ingot is not improved, the extrudability of the alloy is poor, the extrusion speed is low and requires Off-line solution quenching, although the three-stage aging process is adopted, the strength of the produced product is low, which cannot meet the application requirements of higher strength

[0007] Chinese patent, application number 201810134607.7, processing technology of 7075 aluminum alloy profiles and aluminum alloy profiles, this method reduces the extrusion molding die on the one hand by designing an inclined plane with a smooth transition, combined with the extrusion temperature and the distance entering the quenching equipment. The obstruction of metal flow can effectively prevent the surface of the profile from cracking. On the other hand, to ensure the mechanical properties of the product, the qualified rate of the obtained 7075 aluminum alloy profile reaches 80% and above, but this method uses the conventional 7075 alloy, and its main strengthening elements The contents of Zn, Mg and Cu, especially the high content of Cu, the homogeneity of the ingot has not been improved, the quenching sensitivity of the alloy is high, and the extrudability is poor, resulting in a very slow extrusion speed and unable to achieve fast extrusion

[0008] In summary, the ultra-high-strength aluminum alloys that can be mass-produced currently have the disadvantages of high quenching sensitivity and poor extrudability, resulting in low extrusion speed and the need for offline quenching, low production efficiency, long process flow, and high production costs. high

However, alloys with good quenching sensitivity and extrudability, which can be quickly extruded and quenched online, have too low strength to meet the application requirements of ultra-high strength.

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