Aluminum profile extrusion grain size control method

Abstract

The present application relates to the field of aluminum profile production, and particularly relates to a grain size control method for extrusion forming of aluminum profile, which defines that the cross section of the aluminum profile has a hole as a base, functional legs extending around the hole, and the center of the hole is a base point, the distance from the base point to the side wall of the hole is L1, and the overall wall thickness of the aluminum profile is L2, and the forming of the aluminum profile comprises the following steps: a, casting an ingot, the ingot being a hollow structure, the wall thickness being controlled to be between (L1-L2) / 10 and (L1+L2) / 5, and the cross section of the ingot being circular or quasi-circular; b, placing the ingot into an extrusion die to be extruded by an extruder to obtain an aluminum alloy profile blank. The present application solves the problem of insufficient consistency of grain size after the extrusion forming of the existing aluminum profile.

Description

Technical Field

[0001] This invention relates to the field of aluminum profile production, specifically to a method for controlling the grain size of aluminum profiles during extrusion molding. Background Technology

[0002] Grain size is a measure of grain size, commonly expressed as the number of grains per unit volume (or unit area) or the average linear length (or diameter) of the grains. In industrial production, grain size grades are used to represent grain size. The principle is that during metal crystallization, each grain grows from a single nucleus. Therefore, grain size depends on the number of nuclei and the relative growth rate. The number of nuclei is expressed as the nucleation rate. A higher nucleation rate means more nuclei per unit volume, resulting in finer grains. A lower growth rate means more batches of nuclei are formed during growth, leading to a larger number of nuclei and thus finer grains. Conversely, a lower nucleation rate and a higher growth rate result in coarser grains. Therefore, grain size depends on the ratio of the nucleation rate (N) to the growth rate (G). The larger the ratio (N / G), the finer the grains.

[0003] In existing technologies, the main methods for controlling or improving the grain size of products mostly involve modifying liquid metal in conjunction with pre-processes such as vibration and stirring. For example, Chinese Patent CN 112680638 B describes a method for preparing high-efficiency aluminum profiles for shovel teeth, which includes the following steps: obtaining an aluminum alloy casting rod with an average grain size of less than 150 μm; extruding the aluminum alloy casting rod to obtain an aluminum profile with a uniform fine-grained structure and uniform internal hardness distribution in the cross-section.

[0004] Slowly cool the aluminum profile to obtain an aluminum profile for the shovel teeth;

[0005] The aluminum profile for the shovel teeth contains the following components by weight percentage: Mg ≤ 0.03%, Si 0.10%-0.15%, Fe ≤ 0.14%, Zn ≤ 0.03%, Ti 0.02%-0.03%, Mn ≤ 0.03%, Cr ≤ 0.03%, Cu ≤ 0.03%. The remainder is Al; wherein, the heating temperature of the die used for extruding the aluminum alloy casting is 400℃-420℃, the heating temperature of the aluminum alloy casting is 345℃-355℃ during extrusion, the main cylinder speed of the extruder used for extruding the aluminum alloy casting is 20mm / s, the discharge speed of the extruder used for extruding the aluminum alloy casting is greater than 13.5m / min, the discharge temperature of the extruder used for extruding the aluminum alloy casting is 420℃-445℃, and the specific method for slowly cooling the aluminum profile is as follows: first, turn off all cooling fans, including the fans on the cooling bed and all fans that can blow on the material, and after the aluminum profile cools to 150℃, directional air cooling can be used to cool the aluminum profile to below 50℃.

[0006] This control method has significant limitations. It involves many process steps and requires adjustments to parameters such as the content of internal materials, the temperature of the extrusion die, the die forming structure, the temperature of the cast rod, and the discharge speed of the extruder. The number of parameters that need to be considered is very large, and obtaining a product often requires repeated trials. Furthermore, within the same batch, instability in the value of a certain parameter can easily lead to insufficient product consistency. Summary of the Invention

[0007] Therefore, the present invention provides a method for controlling the grain size of aluminum profiles after extrusion molding, which solves the problem of insufficient grain size consistency after extrusion molding of existing aluminum profiles.

[0008] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0009] A method for controlling the grain size of aluminum profile extrusion molding, defining an aluminum profile cross-section with a hole serving as a base, functional supports extending from the periphery of the hole, with the center of the hole as the base point, the distance from the base point to the sidewall of the hole as L1, and the overall wall thickness of the aluminum profile as L2, characterized in that the forming of the aluminum profile includes the following steps:

[0010] a. Casting ingots, wherein the ingots are hollow structures with wall thickness controlled between (L1-L2) / 10 and (L1+L2) / 5, and the cross-section of the ingots is circular or near-circular.

[0011] b. Place the ingot into the extrusion die and extrude it through an extruder to obtain aluminum alloy profiles;

[0012] The extrusion die includes a die pad, an upper die, and a die sleeve for fixing. A cooling system is provided on the outside of the die sleeve. The die pad has a pad hole in the center, and the upper die has an extrusion hole in the center corresponding to the pad hole. The extrusion hole has a core that fits and passes through the pad hole. The output end of the core and the extrusion hole is the working part for forming aluminum profiles. The upper die at the rear end of the working part is a hollow part for maintaining the size stability of the aluminum profile. The inner wall of the core and the extrusion hole is the pre-forming area of ​​the ingot. The radial dimension of the core located in the pre-forming area gradually decreases from the pad hole side to the working part side, and the radial dimension of the extrusion hole at the corresponding position is set accordingly.

[0013] c. The extruded aluminum alloy profiles are subjected to online water mist quenching treatment at the extrusion die exit;

[0014] d. The quenched aluminum alloy profile is stretched and straightened, and then artificially aged to obtain the aluminum profile.

[0015] Preferably, the cooling system includes a first cooling component for cooling the aluminum profile at the output end of the working part and a second cooling component for cooling the extrusion die. The first cooling component acts on the empty blade part, and the second cooling component acts between the upper die and the die pad.

[0016] Preferably, the periphery of the hollow blade portion is provided with a cooling channel for the entry of liquid nitrogen from the first cooling assembly.

[0017] Preferably, the thickness of the preformed area gradually decreases from the mold pad side to the working part side.

[0018] Preferably, the thickness of the preformed area is constant.

[0019] Preferably, in step a above, the aluminum alloy raw materials are prepared according to the following weight ratio to produce the ingot: Si 1.35-1.45%, Fe 0.21%, Cu 0.05%, Mn 0.44-0.48%, Mg 0.50-0.55%, Cr 0.09%, Zn 0.05%, Ti 0.02%, with other individual impurities ≤0.05%, total impurities ≤0.15%, and the balance being Al. The prepared aluminum alloy raw materials are added to a melting furnace, mixed evenly, and melted into liquid aluminum alloy. The liquid aluminum alloy is then cast into an ingot.

[0020] By adopting the aforementioned technical solution, the beneficial effects of the present invention are:

[0021] In this technical solution, the specific control of the grain size of the aluminum profile is designed based on the cross-sectional shape of the aluminum profile. During the ingot forming process, the aluminum profile is pre-treated according to its cross-section to make it hollow and limit its thickness. The thickness is determined by the hole in the center of the aluminum profile and the material required for the corresponding side support. During the extrusion forming process, compared with the traditional solid ingot, the change of the internal fine grain structure during extrusion can be reduced, ensuring its uniformity and thus ensuring that the hardness of the aluminum profile can be relatively uniformly distributed. At this time, the influence of the forming structure of the mold on the grain size is greatly reduced, and the main control methods can be concentrated on adjusting the supercooling of the profile and the modification treatment. This method can form a relatively stable control system for the grain size of the aluminum profile, thereby improving the quality consistency of the produced aluminum profile. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the cross-section of the aluminum profile in an embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram of the cross-sectional structure of the ingot in an embodiment of the present invention;

[0024] Figure 3 This is a schematic cross-sectional view of the extrusion die in an embodiment of the present invention;

[0025] Figure 4 This is a schematic diagram of the cooling channel structure in an embodiment of the present invention.

[0026] Reference numerals: 100, hole; 101, support leg; 200, ingot; 201, protrusion; 1, mold pad; 2, upper mold; 21, extrusion hole; 211, working part; 212, preforming area; 213, empty blade part; 22, core part; 3, mold sleeve; 4a, first cooling assembly; 4b, second cooling assembly; 41, nozzle; 42, hose; 43, liquid nitrogen cylinder; 44, cooling channel; 441, liquid inlet channel; 442, annular groove; 443, liquid outlet channel. Detailed Implementation

[0027] The following will describe in detail the implementation of the present invention with reference to specific embodiments, so that the process of how the present invention uses technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly. Example

[0028] refer to Figure 1 , Figure 2 and Figure 3A method for controlling the grain size of aluminum profile extrusion molding, defining an aluminum profile cross-section having a hole 100 as a base, functional supports 101 extending from the periphery of the hole 100, with the center of the hole 100 as the base point, the distance from the base point to the sidewall of the hole 100 being L1, and the overall wall thickness of the aluminum profile being L2, characterized in that the forming of the aluminum profile includes the following steps:

[0029] a. Casting ingot 200, wherein the ingot 200 is a hollow structure, and its wall thickness is controlled between (L1-L2) / 10 and (L1+L2) / 5. The cross-section of the ingot 200 is circular or near-circular, and depending on the position of the support leg 101, its cross-section has a thicker protrusion 201.

[0030] b. Place the ingot 200 into the extrusion die and extrude it through an extrusion press to obtain an aluminum alloy profile;

[0031] The extrusion die includes a die pad 1, an upper die 2, and a die sleeve 3 for fixing. A cooling system is provided on the outside of the die sleeve 3. The die pad 1 has a center hole, and the upper die 2 has a center extrusion hole 21 corresponding to the center hole. A core 22, adapted to and passing through the center hole, is located at the center of the extrusion hole 21. The output end of the core 22 and the extrusion hole 21 forms a working section 211 for aluminum profile forming. The upper die 2 at the rear end of the working section 211 is a hollow section 213 for maintaining the size stability of the aluminum profile. The inner wall of the core 22 and the extrusion hole 21 forms a pre-forming area 212 of the ingot 200. The radial dimension of the core 22 located in the pre-forming area 212 gradually decreases from the center hole side towards the working section 211 side, and the radial dimension of the corresponding extrusion hole 21 is set accordingly. The shape of the working section 211 is adapted to the cross-section of the aluminum profile to be formed, and the extrusion hole 21 is determined according to different product sizes. Specifically:

[0032] When the required thickness of the aluminum profile is thin or ultra-thin, the thickness of the pre-forming area 212 gradually decreases from the die pad 1 side to the working part 211 side. This allows the thickness to gradually decrease as the size of the extrusion orifice 21 changes during the extrusion process. Consequently, at the working part 211 position, the wall thickness of the ingot 200 forms a more reasonable thickness, preventing significant thickness changes during the forming of the working part 211. The extrusion process of the ingot 200 is gradual and uniform, reducing the amount of change in the internal fine grain structure.

[0033] When the required thickness of the aluminum profile is of a general size, and there are few functional support legs 101 around the aluminum profile, and the dimensional difference between the wall thickness of the ingot 200 and the wall thickness of the aluminum profile is small, the thickness of the preforming area 212 is constant. In this case, the specific forming is no different from the traditional extrusion die structure, and the forming is directly performed at the working part 211. Figure 3 The middle part is this structure;

[0034] c. Perform on-line water mist quenching treatment on the extruded aluminum alloy profile at the exit of the extrusion die;

[0035] d. Stretch and straighten the quenched aluminum alloy profile and perform artificial aging to obtain an aluminum profile. In this technical solution, the specific control of the formed grain size of the aluminum profile is designed according to the cross-sectional shape of the aluminum profile. During the forming process of the ingot 200, it is pretreated according to the cross-section of the aluminum profile to make it a hollow structure and limit its thickness. The thickness is determined according to the materials required for the hole 100 in the center of the aluminum profile and the supporting feet 101 on the corresponding sides. During the extrusion forming process, compared with the traditional solid ingot 200, it can reduce the change of the internal fine grain structure during the extrusion process, ensure its uniform state, and further ensure that the hardness of the aluminum profile can be relatively evenly distributed; at this time, the influence of the forming structure of the die on the grain size is greatly reduced, and the main control method can be concentrated on adjusting the supercooling degree of the profile, modification treatment, etc. This method can form a relatively stable control system for the control of the formed grain size of the aluminum profile, and then improve the quality consistency of the produced aluminum profile.

[0036] Structurally, the cooling system includes a first cooling component 4a for cooling the aluminum profile at the output end of the working part 211 and a second cooling component 4b for cooling the extrusion die. The first cooling component 4a acts on the empty knife part 213, and the second cooling component 4b acts between the upper die 2 and the die pad 1; wherein, both the first cooling component 4a and the second cooling component 4b include a nozzle 41, a hose 42 for output, a liquid nitrogen cylinder 43, and structures such as solenoid valves, safety valves, pressure gauges, and pressure regulators that are matched with the liquid nitrogen cylinder 43; the installation and connection structures of the nozzle 41 and the hose 42 can be referred to the prior application CN111346937B of the applicant;

[0037] Specifically, a cooling channel 44 for the coolant nitrogen in the first cooling component 4a to enter is opened on the periphery of the empty knife part 213. Refer to Figure 4 , wherein the cooling channel 44 includes a liquid inlet channel 441 extending radially in the empty knife part 213, an annular groove 442 extending around the empty knife part 213, and a liquid outlet channel 443 extending inward from the annular groove 442; the liquid inlet channel 441 is connected to the nozzle 41, and the coolant nitrogen enters inward therefrom and is annularly output towards the aluminum profile by the annular groove 442 to achieve the purpose of rapid cooling to increase the supercooling degree; while the second cooling component 4b can adjust the production temperature of the extrusion die during production to ensure production efficiency.

[0038] In this embodiment, in step a above, ingot 200 is prepared by preparing aluminum alloy raw materials according to the following weight ratio: Si 1.35-1.45%, Fe 0.21%, Cu 0.05%, Mn 0.44-0.48%, Mg 0.50-0.55%, Cr 0.09%, Zn 0.05%, Ti 0.02%, with other individual impurities ≤0.05%, total impurities ≤0.15%, and the balance being Al. The prepared aluminum alloy raw materials are added to a melting furnace, mixed evenly, and melted into liquid aluminum alloy. The liquid aluminum alloy is then cast into ingot 200. By adding Ti, Zn, and other components, the aluminum metal is modified, thereby adjusting the grain structure. The values ​​of each raw material can be adjusted according to experiments and requirements, and can be within this range. With this design, the unevenness of deformation during material forming is significantly improved, the grain size distribution of the material is more uniform, and the strength and hardness after processing are significantly improved, making it particularly suitable for aluminum alloy products with ultra-thin walls.

[0039] Although the invention has been specifically shown and described in conjunction with preferred embodiments, those skilled in the art should understand that various changes in form and detail may be made to the invention without departing from the spirit and scope of the invention as defined in the appended claims, all of which shall be within the scope of protection of the invention.

Claims

1. A method for controlling the grain size of extruded aluminum profiles, wherein the cross-section of the aluminum profile has a hole (100) as a base, functional supports (101) extending from the periphery of the hole (100), the center of the hole (100) is taken as the base point, the distance from the base point to the sidewall of the hole (100) is L1, and the overall wall thickness of the aluminum profile is L2, characterized in that, The forming of aluminum profiles includes the following steps: a. Casting ingot (200), the ingot (200) is a hollow structure, its wall thickness is controlled between (L1-L2) / 10 and (L1+L2) / 5, the cross-section of the ingot (200) is circular or near-circular, and its cross-section has a protrusion (201) depending on the position of the support (101). b. Place the ingot (200) into the extrusion die and extrude it through an extruder to obtain an aluminum alloy profile billet; The extrusion die includes a die pad (1), an upper die (2), and a die sleeve (3) for fixing. A cooling system is provided on the outside of the die sleeve (3). The die pad (1) has a pad hole in the center. The upper die (2) has an extrusion hole (21) in the center corresponding to the pad hole. The extrusion hole (21) has a core (22) in the center that is adapted to it and passes through the pad hole. The output end of the core (22) and the extrusion hole (21) is the working part (211) for aluminum profile forming. The upper die (2) at the rear end of the working part (211) is a hollow part (213) for maintaining the size stability of the aluminum profile. The inner wall of the core (22) and the extrusion hole (21) is the pre-forming area (212) of the ingot (200). The radial dimension of the core (22) located in the pre-forming area (212) gradually decreases from the pad hole side to the working part (211) side. The radial dimension of the extrusion hole (21) at the corresponding position is set accordingly. c. The extruded aluminum alloy profiles are subjected to online water mist quenching treatment at the extrusion die exit; d. The quenched aluminum alloy profile is stretched and straightened, and then artificially aged to obtain the aluminum profile.

2. The method for controlling the grain size of aluminum profiles in extrusion molding according to claim 1, characterized in that: The cooling system includes a first cooling component (4a) for cooling the aluminum profile at the output end of the working part (211) and a second cooling component (4b) for cooling the extrusion die. The first cooling component (4a) acts on the empty blade part (213), and the second cooling component (4b) acts between the upper die (2) and the die pad (1).

3. The method for controlling the grain size of aluminum profiles in extrusion molding according to claim 2, characterized in that: The hollow blade section (213) has a cooling channel (44) on its periphery for the entry of liquid nitrogen from the first cooling assembly (4a).

4. The method for controlling the grain size of aluminum profiles in extrusion molding according to claim 1, characterized in that: The thickness of the preformed area (212) gradually decreases from the mold pad (1) side to the working part (211) side.

5. The method for controlling the grain size of aluminum profiles in extrusion molding according to claim 1, characterized in that: The thickness of the preformed area (212) is constant.

6. A method for controlling the grain size of aluminum profiles during extrusion molding according to any one of claims 1-5, characterized in that: In step a above, the aluminum alloy raw materials for ingot (200) are prepared according to the following weight ratio: Si 1.35-1.45%, Fe 0.21%, Cu 0.05%, Mn 0.44-0.48%, Mg 0.50-0.55%, Cr 0.09%, Zn 0.05%, Ti 0.02%, with other individual impurities ≤0.05%, total impurities ≤0.15%, and the balance being Al. The prepared aluminum alloy raw materials are added to the melting furnace, mixed evenly, and melted into liquid aluminum alloy. The liquid aluminum alloy is then cast into ingot (200).

Images