A method for preparing aluminum alloy without coarse grains

Abstract

The present invention relates to a method for preparing an aluminum alloy without coarse grains, comprising the following steps: setting a temperature gradient: setting a temperature gradient in the longitudinal and radial directions of an aluminum alloy cast rod; setting an extrusion direction: facing the front high-temperature end of the aluminum alloy cast rod to an extrusion die, and the rear low-temperature end to an extrusion pad; setting an extrusion speed: setting the extrusion speed such that the extrusion speed of the front section of the aluminum alloy cast rod is greater than the extrusion speed of the rear section; extrusion and cooling: performing extrusion according to the temperature gradient, extrusion direction, and speed set in the above steps, cooling the extrusion die throughout the extrusion process through a cooling unit, and adjusting the extrusion die temperature to a temperature lower than that of each position of the aluminum alloy rod. The present invention solves the problem of coarse grains generated after aluminum alloy extrusion, particularly the problem of obvious coarse grains at the end of the extrusion, while significantly increasing the extrusion speed without generating coarse grains. The surface quality of the aluminum alloy is significantly improved, thereby having the advantages of improving production efficiency, yield, and quality.

Description

Technical Field

[0001] The invention belongs to the technical field of aluminum alloy preparation, and in particular relates to a method for preparing an aluminum alloy without coarse grains. Background Art

[0002] 6000 series aluminum alloys, characterized by high strength, excellent formability, and good corrosion resistance, are considered one of the most promising aluminum alloys and play a key role in lightweighting automobiles. Due to their high strength, excellent weldability, and corrosion resistance, 6000 series aluminum alloys are widely used in transportation and structural engineering. While ensuring product quality, increasing aluminum alloy extrusion speeds is the most economical way to meet the growing market demand for aluminum alloys. (Positive) During the extrusion process, the surface of the ingot experiences severe deformation and intense friction with the extrusion barrel, resulting in significantly higher strain, deformation speed, and deformation temperature at the surface than in the center. The surface structure absorbs a significant amount of deformation energy, thereby lowering its recrystallization temperature. Furthermore, under severe deformation conditions, the intense friction between the die and the deformed metal surface generates significant heat, causing dynamic recrystallization at the surface, resulting in aluminum alloy products with a coarse-grained layer.

[0003] Therefore, the aluminum alloy prepared by the prior art has the disadvantages of low production efficiency, low yield and poor quality. Summary of the Invention

[0004] In order to solve the technical problems existing in the background technology, the present invention provides a method for preparing an aluminum alloy without coarse grains.

[0005] The technical solution of the present invention is to provide a method for preparing an aluminum alloy without coarse grains, which is specifically carried out by the following steps:

[0006] S1: Setting temperature gradients: Setting temperature gradients in the longitudinal and radial directions of the aluminum alloy cast rod, wherein the temperature gradient in the longitudinal direction of the aluminum alloy cast rod is set to be high in the front section and low in the rear section, and the temperature gradient in the radial direction of the aluminum alloy cast rod is set to be high in the core layer and low in the surface layer;

[0007] S2 sets the extrusion direction: the front high-temperature end of the aluminum alloy casting rod faces the extrusion die, and the rear low-temperature end faces the extrusion pad;

[0008] S3 sets the extrusion speed: the extrusion speed is set according to the principle that the extrusion speed of the front section of the aluminum alloy casting rod is greater than the extrusion speed of the rear section;

[0009] S4 Extrusion and cooling: Extrusion is performed according to the temperature gradient, extrusion direction and speed of the aluminum alloy bar set in the above steps. The extrusion die is cooled throughout the extrusion process. The temperature of the extrusion die is adjusted to be lower than the temperature at each position of the aluminum alloy bar and kept stable.

[0010] Preferably, the temperature gradient in the longitudinal direction of S1 is set to 10 to 50°C, and the temperature gradient in the radial direction of S1 is set to 10 to 50°C.

[0011] Preferably, the surface temperature of the front section of the aluminum alloy casting rod in S1 is 480±10°C, and the core temperature is 510±10°C, and the surface temperature of the rear section of the casting rod is 450±10°C, and the core temperature is 480±10°C.

[0012] Preferably, the extrusion speed of the front section is 8.0±1.0 mm / s, and the extrusion speed of the back section is 6.0±1.0 mm / s.

[0013] Preferably, in the cooling step S4, the extrusion die is cooled by spraying or injecting liquid nitrogen.

[0014] Preferably, the method further comprises S5 liquid nitrogen releasing: releasing liquid nitrogen from an outlet of the extrusion die.

[0015] Preferably, during the extrusion process in step S4, the mold is cooled to 420±10°C.

[0016] Compared with the prior art, the present invention provides a method for preparing a coarse-grained aluminum alloy, which has the following beneficial effects: by setting temperature gradients in the longitudinal and radial directions of the aluminum alloy cast rod, the temperature gradient in the longitudinal direction of the aluminum alloy cast rod is high in the front section and low in the rear section, and the temperature gradient in the radial direction of the aluminum alloy cast rod is high in the core layer and low in the surface layer; the high-temperature end of the front section of the aluminum alloy cast rod faces the extrusion die, and the low-temperature end of the rear section faces the extrusion pad; the extrusion speed is set according to the extrusion speed of the front section of the aluminum alloy cast rod being greater than the extrusion speed of the rear section; the aluminum alloy rod is extruded according to the temperature gradient, extrusion direction and speed set in the above steps, and the extrusion die is cooled throughout the extrusion process by a cooling unit, and the temperature of the extrusion die is adjusted to be lower than the temperature of each position of the aluminum alloy rod, so as to prevent the friction heating of the extrusion die.

[0017] The present invention sets the temperature gradient in the longitudinal and radial directions of the cast rod, and coordinates the mold temperature and the extrusion speed, so that the overall temperature of the aluminum alloy rod and the extrusion outlet temperature are kept stable, thereby solving the problem of coarse crystals generated after the aluminum alloy is extruded, especially solving the problem of obvious coarse crystals at the extrusion tail. At the same time, the extrusion speed is greatly increased without generating coarse crystals, and the surface quality of the aluminum alloy is significantly improved. During the entire extrusion process, efficient production of aluminum alloy with no coarse crystals, high strength, high surface quality and high consistency is achieved, which has the advantages of improving production efficiency, yield rate and quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a diagram of the surface structure of an aluminum alloy prepared according to existing technology.

[0019] Figure 2 FIG. 4 is a diagram showing the surface structure of an aluminum alloy prepared according to the second embodiment of the present invention. DETAILED DESCRIPTION

[0020] The specific implementation of the present invention is described in detail below with reference to specific embodiments.

[0021] The present invention provides a method for preparing an aluminum alloy without coarse grains, which is specifically carried out by the following steps:

[0022] S1 sets the temperature gradient: through the heating induction furnace, the temperature gradient is set in the length direction and radial direction of the aluminum alloy cast rod, the temperature gradient in the length direction of the aluminum alloy cast rod is set to be high in the front section and low in the rear section, the temperature gradient in the radial direction of the aluminum alloy cast rod is set to be high in the core layer and low in the surface layer, the temperature gradient in the length direction of S1 is set to 10 to 50°C, and the temperature gradient in the radial direction of S1 is set to 10 to 50°C. In view of the fact that during the extrusion process of the aluminum alloy cast rod, the rear section and the surface layer of the cast rod have a larger temperature increase than the front section and the core layer, by setting this temperature gradient, the temperature of each point of the aluminum alloy cast rod remains basically consistent and relatively stable.

[0023] S2 sets the extrusion direction: the high-temperature end of the front section of the aluminum alloy cast rod faces the extrusion die, and the low-temperature end of the rear section faces the extrusion pad. When the front section of the aluminum alloy cast rod enters the extrusion die, the temperature between the cast rod and the extrusion die rises due to friction and extrusion, and the heat is further transferred to the rear section. The extrusion direction of the aluminum alloy cast rod is set accordingly to keep the temperature of the front and rear sections consistent;

[0024] S3 sets the extrusion speed: The extrusion speed is set according to the principle that the extrusion speed of the front section of the aluminum alloy casting rod is greater than that of the rear section. When the front section of the aluminum alloy casting rod enters the extrusion die, the temperature between the casting rod and the extrusion die rises due to friction and extrusion, and the heat is further transferred to the rear section. Based on this, the extrusion speed of the aluminum alloy casting rod is set to extend the cooling time of the rear section in the extrusion die so that its temperature is consistent with that of the front section.

[0025] S4 Extrusion and Cooling: Extrusion is performed according to the temperature gradient, extrusion direction, and speed set in the above steps. The extrusion die is cooled throughout the extrusion process, and the die temperature is adjusted to be lower than the temperature at all locations on the aluminum alloy bar and maintained stable to prevent frictional heat rise in the die, thereby maintaining a stable overall temperature of the aluminum alloy bar and the extrusion outlet temperature. By setting the temperature gradient along the length and radial direction of the cast bar, and by synergizing the die temperature with the extrusion speed, efficient production of aluminum alloys with no coarse grains, high strength, high surface quality, and high consistency is achieved throughout the extrusion process.

[0026] Preferably, the surface temperature of the aluminum alloy casting rod in S1 is 480±10°C at the front end and 510±10°C at the core, and the surface temperature of the casting rod at the rear end is 450±10°C and 480±10°C at the core. The extrusion speed at the front end is 8.0±1.0 mm / s, and the extrusion speed at the rear end is 6.0±1.0 mm / s.

[0027] In the cooling step S4, the extrusion die is cooled by spraying or injecting liquid nitrogen. Liquid nitrogen cooling the extrusion die increases the extrusion speed, improves the die life, and improves the surface quality of the profile. Preferably, the die is cooled to 420±10°C during the extrusion process in step S4.

[0028] Furthermore, the method provided by the present invention also includes S5 liquid nitrogen release: releasing liquid nitrogen from the extrusion die outlet to cool the extrusion die and the metal in the deformation zone by taking away the deformation heat. At the same time, the extrusion die outlet is controlled by nitrogen gas, which not only reduces the oxidation of aluminum, but also reduces the adhesion and accumulation of aluminum oxide. Therefore, the cooling effect generated by the release of liquid nitrogen from the extrusion die outlet improves the surface quality of the aluminum alloy product, can greatly increase the extrusion speed, and stabilize the extrusion outlet temperature at 520±10°C.

[0029] Three embodiments are now listed according to the method provided by the present invention, as follows:

[0030] First embodiment:

[0031] A method for preparing a coarse-grain-free aluminum alloy comprises the following steps:

[0032] S1 sets the temperature gradient: the temperature gradient is set in the longitudinal and radial directions of the aluminum alloy casting rod. The surface temperature of the front section of the casting rod is set to 480℃, the core temperature is set to 500℃, the surface temperature of the rear section of the casting rod is set to 460℃, the core temperature is set to 470℃, and the surface temperature of the casting rod is 10℃ lower than the core temperature.

[0033] S2 sets the extrusion direction: the front high-temperature end of the aluminum alloy casting rod faces the extrusion die, and the rear low-temperature end faces the extrusion pad;

[0034] S3 sets the extrusion speed: the extrusion speed of the first half of the aluminum alloy casting rod is set to 8.0 mm / s, and the extrusion speed of the second half is set to 6.0 mm / s.

[0035] S4 extrusion and cooling: The aluminum alloy bar is extruded according to the temperature gradient, extrusion direction and speed set in the above steps. Liquid nitrogen is used to cool the extrusion die throughout the extrusion process. The extrusion die temperature is set to 420°C and kept stable.

[0036] Second embodiment:

[0037] A method for preparing a coarse-grain-free aluminum alloy comprises the following steps:

[0038] S1 sets the temperature gradient: Set the temperature gradient in the longitudinal and radial directions of the aluminum alloy casting rod. The surface temperature of the front section of the casting rod is set to 480℃, the core temperature is set to 500℃, the surface temperature of the rear section of the casting rod is set to 450℃, the core temperature is set to 480℃, and the surface temperature of the casting rod is 30℃ lower than the core temperature.

[0039] S2 sets the extrusion direction: the front high-temperature end of the aluminum alloy casting rod faces the extrusion die, and the rear low-temperature end faces the extrusion pad;

[0040] S3 sets the extrusion speed: the extrusion speed of the first half of the aluminum alloy casting rod is set to 8.0 mm / s, and the extrusion speed of the second half is set to 6.0 mm / s.

[0041] S4 extrusion and cooling: The aluminum alloy bar is extruded according to the temperature gradient, extrusion direction and speed set in the above steps. Liquid nitrogen is used to cool the extrusion die throughout the extrusion process. The extrusion die temperature is set to 420°C and kept stable.

[0042] Third embodiment:

[0043] A method for preparing a coarse-grain-free aluminum alloy comprises the following steps:

[0044] S1 sets the temperature gradient: the temperature gradient is set in the longitudinal and radial directions of the aluminum alloy casting rod. The surface temperature of the front section of the casting rod is set to 480℃, the core temperature is set to 500℃, the surface temperature of the rear section of the casting rod is set to 440℃, the core temperature is set to 490℃, and the surface temperature of the casting rod is 50℃ lower than the core temperature;

[0045] S2 sets the extrusion direction: the front high-temperature end of the aluminum alloy casting rod faces the extrusion die, and the rear low-temperature end faces the extrusion pad;

[0046] S3 sets the extrusion speed: the extrusion speed of the first half of the aluminum alloy casting rod is set to 8.0 mm / s, and the extrusion speed of the second half is set to 6.0 mm / s.

[0047] S4 extrusion and cooling: The aluminum alloy bar is extruded according to the temperature gradient, extrusion direction and speed set in the above steps. Liquid nitrogen is used to cool the extrusion die throughout the extrusion process. The extrusion die temperature is set to 420°C and kept stable.

[0048] like Figure 1 As shown, the aluminum alloy surface prepared according to the prior art has a ring-shaped coarse grain area, such as Figure 2As shown in the figure, the aluminum alloy prepared according to the second embodiment of the present invention has no coarse grains on its surface. This shows that, through the above-mentioned technical means, the present invention solves the problem of coarse grains generated in extruded aluminum alloys, especially the problem of obvious coarse grains in the latter stage of extrusion. While significantly increasing the extrusion speed, coarse grains are not generated, and the surface quality is significantly improved, achieving the technical effect of improving production efficiency, yield rate, and quality.

Claims

1. A method for preparing a coarse-grain-free aluminum alloy, characterized in that: The method is specifically carried out according to the following steps: S1: Setting temperature gradients: Setting temperature gradients in the longitudinal and radial directions of the aluminum alloy cast rod, wherein the temperature gradient in the longitudinal direction of the aluminum alloy cast rod is set to be high in the front section and low in the rear section, and the temperature gradient in the radial direction of the aluminum alloy cast rod is set to be high in the core layer and low in the surface layer; S2 sets the extrusion direction: the front high-temperature end of the aluminum alloy casting rod faces the extrusion die, and the rear low-temperature end faces the extrusion pad; S3 sets the extrusion speed: the extrusion speed is set according to the principle that the extrusion speed of the front section of the aluminum alloy casting rod is greater than the extrusion speed of the rear section; S4 Extrusion and cooling: Extrusion is performed according to the temperature gradient, extrusion direction and speed of the aluminum alloy bar set in the above steps. The extrusion die is cooled throughout the extrusion process to adjust the temperature of the extrusion die to be lower than the temperature at each position of the aluminum alloy bar and keep it stable; The surface temperature of the front section of the aluminum alloy casting rod in S1 is 480±10°C, the core temperature is 510±10°C, and the surface temperature of the rear section of the casting rod is 450±10°C, the core temperature is 480±10°C; The extrusion speed of the front section is 8.0±1.0 mm / s, and the extrusion speed of the back section is 6.0±1.0 mm / s; In the cooling step S4, the extrusion die is cooled by spraying or injecting liquid nitrogen; During the extrusion process in step S4, the mold temperature is lowered to 420±10°C.

2. The method for preparing a coarse-grain-free aluminum alloy according to claim 1, wherein: The temperature gradient in the longitudinal direction of the S1 is set to 10 to 50°C, and the temperature gradient in the radial direction of the S1 is set to 10 to 50°C.

3. The method for preparing a coarse-grain-free aluminum alloy according to claim 1, wherein: The method further comprises S5 liquid nitrogen releasing: releasing liquid nitrogen from an outlet of the extrusion die.

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