Manufacturing method of 7000-series aluminum alloy section for vehicular bodies

Abstract

The invention discloses a manufacturing method of a 7000-series aluminum alloy section for vehicular bodies. The 7000-series aluminum alloy section comprises alloy elements including, by mass, 0.145%-0.155% of Si, 0.145%-0.155% of Fe, 0.09%-0.11% of Cu, 0.045%-0.055% of Mn, 0.58%-0.8% of Mg, 0.019%-0.021% of Cr, 5.5%-5.8% of Zn, 0.15%-0.19% of Zr, 0.028%-0.031% of Ti and the balance aluminum, wherein other single element content is smaller than or equal to 0.045%, other element total content is smaller than or equal to 0.15%, and a Zn / Mg ratio is controlled to be 7-10. The manufacturing method includes procedures of smelting, purification, casting for rod forming, homogeneous annealing, extruding, stretching, natural aging, manual aging treatment and the like, great static collision effects of materials can be achieved, the 7000-series aluminum alloy section is especially suitable for manufacturing of aluminum alloy energy absorption boxes and longitudinal beams for vehicular bumper systems, and comprehensive requirements of light weight of the vehicular bodies and energy absorption in low-speed and high-speed collision can be met.

Description

technical field [0001] The invention relates to the design of alloy components of 7000 series aluminum alloy profiles and the manufacturing processes of smelting, purification, casting into rods, annealing, extrusion, stretching, etc., and is especially suitable for manufacturing aluminum alloy energy-absorbing boxes and Longitudinal beams can meet the comprehensive requirements of lightweight body, low-speed and high-speed collision energy absorption. Background technique [0002] 7000 series (Al-Zn-Mg) aluminum alloy profiles are widely used in aerospace, high-speed rail and high-end automobile manufacturing and other fields. The production of such aluminum alloy profiles generally includes: melting, homogenization, extrusion, natural aging and artificial aging heat treatment. [0003] The 7000 series aluminum alloy will form a relatively coarse grain structure and a coarse eutectic structure during the casting process. The reasons for the formation of the coarse grain st...

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Problems solved by technology

[0003] The 7000 series aluminum alloy will form a relatively coarse grain structure and a coarse eutectic structure during the casting process. The reasons for the formation of the coarse grain structure are generally divided into two categories: (1) The casting temperature is too high, resulting in the formation of nucleation particles in the solution Smaller, resulting from uneven online refinement; (2) Insufficient cooling intensity causes the formed grains to grow at a certain temperature; the coarse eutectic structure is mostly caused by deep liquid pockets and insufficient cooling intensity The grain boundary forms a relatively coarse eutectic structure, and the eutectic structure is difficult to completely eliminate during the homogenization process, which is unfavorable to the crushing performance, impact toughness, corrosion performance and fatigue performance of the extruded profile in the later stage

[0011] (3) The casting process parameters are unreasonable, the casting temperature is too high, and the cooling intensity is not enough, resulting in a relatively coarse grain structure in the middle part of the cast aluminum rod, more eutectic structure and large-grained inclusion phases, and material denaturation in later processing Afterwards, the performance uniformity is reduced, and the fatigue life is reduced;

[0012] (4) The homogenization process is unreasonable. The domestic production of this type of alloy cast rod mostly adopts a single-stage or two-stage homogenization heat treatment process. The furnace conditions cannot achieve the gradient temperature rise conditions, which leads to the inability to precipitate the particles that prevent the recrystallization of the grains. The phase cannot be dissolved back;

[0013] (5) The extrusion process parameters are unreasonable, the extrusion temperature is too low, resulting in a sharp decrease in die life; the extrusion temperature is too high, the material outlet temperature exceeds its solidus temperature, prone to overburning, and the overall performance is drastically reduced, which cannot be realized Corrosion resistance over the lifetime of automotive alloys;

[0014] (6) The design of the extrusion die is unreasonable, the design inlet of the extrusion die is too small, and it is difficult to extrude the profile; the design of the extrusion die is too large, and the comprehensive performance of the profile is poor; the position of each section of the extrusion profile cannot achieve isothermal extrusion As a result, the overall performance of the profile is not high, and the difference is large, which is not conducive to the later processing and molding and the overall performance of the final part;

[0015] (7) The heat treatment process is unreasonable. The later heat treatment process can be performed in T6 / T7 and other types. Most manufacturers do not know or even understand the process, resulting in their materials failing to meet the final requirements of automotive alloys; in the case of identical performance , the impact toughness, welding performance and bending performance are quite different

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