A heat treatment method for 2A12 aluminum alloy plugs

Abstract

This invention relates to a heat treatment method for 2A12 aluminum alloy plugs, employing a solution treatment + annealing + stress-relief annealing approach. Solution treatment allows for complete recrystallization of the plug after rough machining, resulting in a more thorough dissolution of the strengthening phase and a homogeneous solid solution. Full annealing precipitates the strengthening phase from the solid solution, yielding numerous fine S(CuMgAl2) and (CuAl2) strengthening phase particles uniformly distributed on an α(Al) matrix, resulting in a uniform and fine microstructure. Simultaneously, stress-relief annealing eliminates the machining stress from finishing, thus relieving work hardening and stabilizing dimensions. This heat treatment process is applicable to the production of 2A12 aluminum alloy plugs from bars of different states and diameters, and provides better dimensional stability for the plugs.

Description

Technical Field

[0001] This invention relates to a heat treatment method for aluminum alloy plugs, specifically a heat treatment method for 2A12 aluminum alloy plugs. Background Technology

[0002] 2A12 aluminum alloy is a wrought aluminum alloy that can be strengthened, possessing good plasticity and machinability, and is one of the most widely used aluminum alloys. However, 2A12 aluminum alloy has many heat treatment states, including H112 (hot-formed), F (free-machining), O (annealed), T1 (high-temperature forming followed by natural cooling), T4 (solution + natural aging), and T6 (solution + artificial aging). The mechanical properties of different heat treatment states vary greatly. Furthermore, the mechanical properties of 2A12 aluminum alloys of different specifications also vary significantly under the same heat treatment state.

[0003] The 2A12 aluminum alloy hot-extruded bars used in the production of plugs vary in size and condition. In addition, the larger the diameter of the bar, the greater the difference in mechanical properties between the core and other parts. Plugs require a tensile strength distribution between 215MPa and 245MPa and an elongation at break between 14% and 20% after heat treatment. This leads to significant differences in the mechanical properties of plugs in different conditions but of the same specifications, as well as plugs in the same condition but of different specifications after heat treatment. Sometimes, the mechanical properties do not meet the requirements. Furthermore, the heat treatment process for aluminum alloy bars in different conditions and of different specifications is complex, requiring different heat treatments for each specification and condition.

[0004] Currently, the commonly used heat treatment method for 2A12 aluminum alloy plugs is a full annealing process of holding at 398℃ for 40 minutes and then furnace cooling. This process is only suitable for hot-extruded bars with a diameter not exceeding 150mm and heat treatment conditions of T4 (solution + natural aging) or T6 (solution + artificial aging). When the specifications exceed these limits or the condition is not T4 or T6, mechanical properties fail to meet the requirements after annealing using this process. In production, annealing is performed on 2A12 aluminum alloy plugs of different specifications in H112, F, O, T1, T4, and T6 states. For example, after annealing at 398℃, the tensile strength of 200mm diameter extruded bar in H112 state is distributed between 190MPa and 215MPa, which does not meet the requirements; the tensile strength of 250mm diameter extruded bar in F state is distributed between 180MPa and 225MPa after annealing at 398℃, which also does not meet the requirements; and the tensile strength of 40mm diameter extruded bar in O state is distributed between 180MPa and 190MPa after annealing at 398℃. The tensile strength of extruded bars in the T1 state with a diameter of 260mm, after annealing at 398℃, is between 195MPa and 245MPa, which does not meet the requirements. The tensile strength of extruded bars in the T4 and T6 states with a diameter of 200mm, after annealing at 398℃, is between 205MPa and 255MPa, which also does not meet the requirements. Only extruded bars in the T4 and T6 states with a diameter of 120mm, after annealing at 398℃, have a tensile strength between 220MPa and 245MPa and an elongation at break between 16.8% and 19.5%, which meets the requirements. Therefore, the different heat treatment states and specifications of the extruded bars used for 2A12 aluminum alloy plugs lead to significant differences in the mechanical properties after heat treatment, resulting in unqualified products. Furthermore, different heat treatment processes need to be explored for each specification and different states, thus these problems hinder the heat treatment production of plugs.

[0005] Therefore, it is imperative to seek a heat treatment method that is highly efficient, has stable mechanical properties, and meets the requirements of most 2A12 aluminum alloy hot extruded bars. Summary of the Invention

[0006] Technical problems to be solved

[0007] To avoid the shortcomings of existing technologies, this invention proposes a heat treatment method for 2A12 aluminum alloy plugs, providing a heat treatment method for 2A12 aluminum alloy plugs that is efficient, has stable mechanical properties, and has a simple heat treatment process.

[0008] Technical solution

[0009] A heat treatment method for a 2A12 aluminum alloy plug, characterized by the following steps:

[0010] Step 1: Perform a solution treatment on the rough-machined plug to allow the plug to recrystallize completely after rough machining, fully dissolve the strengthening phase in the 2A12 aluminum alloy, and obtain a homogeneous solid solution.

[0011] Step 2: Perform full annealing on the plug after solution treatment to precipitate the strengthening phase in the solid solution, so that fine S(CuMgAl2) and (CuAl2) strengthening phase particles are uniformly distributed on the α(Al) matrix;

[0012] Step 3: The finished plug is subjected to stress annealing to eliminate work hardening and residual stress, thus maintaining structural stability.

[0013] The solution treatment involves: solidifying the rough-machined plug, heating it to 495℃~500℃, holding it at that temperature for 50min~70min, and then removing it from the furnace and water-cooling it to room temperature.

[0014] The complete annealing process involves heating the solution-treated plug to 400℃~410℃, holding it at that temperature for 60 minutes, and then cooling it in the furnace at a rate not exceeding 25℃ per hour until it reaches below 260℃ before being removed from the furnace and air-cooled.

[0015] The stress-relief annealing process involves heating to 200℃~260℃, holding at that temperature for 100min~120min, and then air-cooling the product after removal from the furnace.

[0016] The process parameters are as follows: during solution treatment, heat to 498°C, hold for 60 minutes, and then water-cool to room temperature after removal from the furnace; during complete annealing, heat to 400°C, hold for 60 minutes, and then cool with the furnace at a rate not exceeding 25°C per hour to below 260°C before air cooling; during stress-relief annealing, heat to 200°C, hold for 120 minutes, and then air cool after removal from the furnace.

[0017] The plug is made of H112 material with a diameter of 200mm. After treatment, the tensile strength of the plug is distributed between 230MPa and 235MPa, the elongation after fracture is between 16.8% and 19.0%, and the roundness of the plug opening is 0.05mm.

[0018] The plug, after being treated with F-state plug with a diameter of 250mm, has a tensile strength distribution between 225MPa and 235MPa, an elongation after fracture between 16.0% and 19.2%, and a roundness of 0.06mm at the plug opening.

[0019] The plug, after being treated with an O-state plug with a diameter of 40mm, has a tensile strength distribution between 225MPa and 230MPa, an elongation after fracture between 16.5% and 18.7%, and a roundness of 0.02mm at the plug opening.

[0020] The plug, after being treated with a T1 state plug with a diameter of 260mm, has a tensile strength distribution between 225MPa and 235MPa, an elongation after fracture between 16.8% and 19.3%, and a roundness of 0.05mm at the plug opening.

[0021] The plugs are treated with T4 conditions of 120mm and 200mm diameter, respectively. The tensile strength of the 120mm diameter plug is distributed between 230MPa and 235MPa, the elongation after fracture is between 16.3% and 18.7%, and the roundness of the plug opening is 0.03mm; the tensile strength of the 200mm diameter plug is distributed between 225MPa and 235MPa, the elongation after fracture is between 15.8% and 19.1%, and the roundness of the plug opening is 0.06mm.

[0022] Beneficial effects

[0023] This invention proposes a heat treatment method for 2A12 aluminum alloy plugs. For 2A12 aluminum alloy plugs, the requirements of low strength and high plasticity at room temperature are to be met. Traditional heat treatment methods only use full annealing for 2A12 aluminum alloy plugs. Due to the different heat treatment states and specifications of the extruded bars used, the mechanical properties of the plugs after full annealing vary greatly, and there are also problems of non-compliance.

[0024] The heat treatment method for 2A12 aluminum alloy plugs provided by this invention employs a solution treatment + annealing + stress-relief annealing approach. First, solution treatment allows for complete recrystallization of the plug after rough machining, resulting in a more thorough dissolution of the strengthening phase and a homogeneous solid solution. Then, full annealing precipitates the strengthening phase from the solid solution, yielding a large number of fine S(CuMgAl2) and (CuAl2) strengthening phase particles uniformly distributed on the α(Al) matrix, resulting in a uniform and fine microstructure. Finally, stress-relief annealing eliminates the machining stress from finishing, thus relieving work hardening and stabilizing dimensions.

[0025] The method of this invention differs from the traditional full annealing heat treatment process in that: traditional full annealing is only applicable to bar stock with a diameter of no more than 150mm in T4 and T6 states, and is not suitable for large-diameter bars or bars in different states. However, through the heat treatment process of solution treatment + full annealing + stress-relief annealing, a homogeneous solid solution can be obtained first. Full annealing on the basis of the solid solution ensures that the strengthening phase particles are evenly and finely distributed on the matrix, resulting in a homogeneous overall microstructure and thus a more uniform distribution of mechanical properties. Simultaneously, stress-relief annealing of the finished plug eliminates work hardening and residual stress, resulting in better dimensional stability of the plug and preventing deformation during placement. Furthermore, this heat treatment process is applicable to the production of 2A12 aluminum alloy plugs from bars of different states and diameters. Detailed Implementation

[0026] The present invention will now be further described with reference to the embodiments:

[0027] This invention provides a heat treatment method for 2A12 aluminum alloy plugs, comprising the following steps:

[0028] 1) Solution treatment: Solvent the rough-machined plug, heat to 495℃~500℃, hold for 50min~70min, remove from the furnace and water cool to room temperature;

[0029] 2) Full annealing: Heat the solution-treated plug to 400℃~410℃, hold for 60 minutes, and then cool it in the furnace at a rate of no more than 25℃ per hour to below 260℃ before air cooling.

[0030] 3) Stress-relief annealing: The finished plug is stress-relief annealed by heating to 200℃~260℃, holding for 100min~120min, and then air-cooled after removal from the furnace.

[0031] The present invention provides several heat treatment methods for rough machining of 2A12 aluminum alloy extruded bars of different shapes into plug blanks. The heat treatment process is simple and solves the problems of unqualified mechanical properties of 2A12 aluminum alloy plugs with different heat treatment states and different diameter bars.

[0032] Example 1:

[0033] The heat treatment method for a 2A12 aluminum alloy plug described in this embodiment is carried out according to the following steps: a 200mm diameter H112 extruded bar is rough-machined into a plug blank, held at 498℃ for 60 minutes, removed from the furnace and water-cooled to room temperature, then the solution-treated plug blank is heated to 400℃ and held for 60 minutes, then cooled in the furnace at a rate not exceeding 25℃ per hour to below 260℃ and air-cooled; then the finished plug is held at 200℃ for 120 minutes and air-cooled.

[0034] In Example 1, the tensile strength of the heat-treated plug was between 230 MPa and 235 MPa, the elongation after fracture was between 16.8% and 19.0%, and the roundness of the plug opening was 0.05 mm.

[0035] Comparative Experiment 1:

[0036] The H112 extruded bar stock with a diameter of 200mm was processed into a plug, held at 398℃ for 40 minutes, and then cooled in the furnace to below 280℃ before being air-cooled.

[0037] The tensile strength of the heat-treated plugs in the comparative test ranged from 190 MPa to 215 MPa, the elongation after fracture ranged from 14.5% to 19.0%, and the roundness of the plug opening was 0.15 mm.

[0038] Example 2: The heat treatment method for a 2A12 aluminum alloy plug described in this example is carried out according to the following steps: a 250mm diameter F-state extruded bar is rough-machined into a plug blank, held at 498℃ for 60 minutes, removed from the furnace and water-cooled to room temperature, then the solution-treated plug blank is heated to 400℃ and held for 60 minutes, then cooled in the furnace at a rate not exceeding 25℃ per hour to below 260℃ and air-cooled; then the finished plug is held at 200℃ for 120 minutes and air-cooled.

[0039] In Example 2, the tensile strength after heat treatment was between 225 MPa and 235 MPa, the elongation after fracture was between 16.0% and 19.2%, and the roundness of the plug opening was 0.06 mm.

[0040] Comparative Experiment 2:

[0041] The F-state extruded bar with a diameter of 250mm was processed into a plug, held at 398℃ for 40 minutes, and then cooled in the furnace to below 280℃ before being air-cooled.

[0042] The tensile strength of the heat-treated plugs in the comparative test ranged from 180 MPa to 225 MPa, the elongation after fracture ranged from 15.8% to 19.8%, and the roundness of the plug opening was 0.18 mm.

[0043] Example 3: The heat treatment method for a 2A12 aluminum alloy plug described in this example is carried out according to the following steps: a 40mm diameter O-state extruded bar is rough-machined into a plug blank, held at 498℃ for 60 minutes, removed from the furnace and water-cooled to room temperature, then the solution-treated plug blank is heated to 400℃ and held for 60 minutes, then cooled in the furnace at a rate not exceeding 25℃ per hour to below 260℃ and air-cooled; then the finished plug is held at 200℃ for 120 minutes and air-cooled.

[0044] In Example 3, the tensile strength after heat treatment was between 225 MPa and 230 MPa, the elongation after fracture was between 16.5% and 18.7%, and the roundness of the plug opening was 0.02 mm.

[0045] Comparative Experiment 3:

[0046] The 40mm diameter O-state extruded bar is processed into a plug, held at 398℃ for 40 minutes, and then cooled in the furnace to below 280℃ before being air-cooled.

[0047] The tensile strength of the heat-treated plugs in the comparative test ranged from 180MPa to 195MPa, the elongation after fracture ranged from 18.8% to 21.5%, and the roundness of the plug opening was 0.08mm.

[0048] Example 4:

[0049] The heat treatment method for a 2A12 aluminum alloy plug as described in this embodiment is carried out according to the following steps: a 260mm diameter T1 state extruded bar is rough-machined into a plug blank, held at 498℃ for 60 minutes, removed from the furnace and water-cooled to room temperature, then the solution-treated plug blank is heated to 400℃ and held for 60 minutes, then cooled in the furnace at a cooling rate of no more than 25℃ per hour to below 260℃ and air-cooled; then the finished plug is held at 200℃ for 120 minutes and removed from the furnace and air-cooled.

[0050] In Example 4, the tensile strength after heat treatment was between 225 MPa and 235 MPa, the elongation after fracture was between 16.8% and 19.3%, and the roundness of the plug opening was 0.05 mm.

[0051] Comparative Experiment 4:

[0052] T1 state extruded bar stock with a diameter of 260mm was processed into a plug, held at 398℃ for 40 minutes, and then cooled in the furnace to below 280℃ before being air-cooled.

[0053] The tensile strength of the heat-treated plugs in the comparative test ranged from 195 MPa to 245 MPa, the elongation after fracture ranged from 14.2% to 20.5%, and the roundness of the plug opening was 0.22 mm.

[0054] Example 5:

[0055] The heat treatment method for 2A12 aluminum alloy plugs described in this embodiment is carried out according to the following steps: T4 state extruded bars with diameters of 120mm and 200mm are rough-machined into plug blanks, held at 498℃ for 60 minutes, removed from the furnace and water-cooled to room temperature, then the solution-treated plug blanks are heated to 400℃ and held for 60 minutes, then cooled in the furnace at a cooling rate of no more than 25℃ per hour to below 260℃ and air-cooled; then the finished plugs are held at 200℃ for 120 minutes and air-cooled.

[0056] In Example 5, the tensile strength of the heat-treated 120mm diameter plug was distributed between 230MPa and 235MPa, the elongation after fracture was between 16.3% and 18.7%, and the roundness of the plug opening was 0.03mm; the tensile strength of the 200mm diameter plug was distributed between 225MPa and 235MPa, the elongation after fracture was between 15.8% and 19.1%, and the roundness of the plug opening was 0.06mm.

[0057] Comparative Experiment 5:

[0058] T6 extruded bars with diameters of 120mm and 200mm were processed into plugs, held at 398℃ for 40 minutes, and then cooled in the furnace to below 280℃ before being air-cooled.

[0059] In the comparative test, the tensile strength of the heat-treated plug with a diameter of 120 mm ranged from 215 MPa to 245 MPa, the elongation after fracture ranged from 16.0% to 19.8%, and the roundness of the plug opening was 0.05 mm; the tensile strength of the heat-treated plug with a diameter of 200 mm ranged from 205 MPa to 255 MPa, the elongation after fracture ranged from 14.5% to 20.5%, and the roundness of the plug opening was 0.18 mm.

[0060] Analysis of the implementation effects of the present invention:

[0061] Compared with comparative experiments one through five, the heat-treated caps in examples one through five exhibited more uniform distribution of tensile strength and elongation at break, less cap deformation, and the heat treatment process was suitable for production of extruded bars in different states and diameters. In contrast, the comparative experiments, which targeted caps for extruded bars in different states and diameters, showed problems with unsatisfactory tensile strength and elongation at break after heat treatment, indicating significant limitations and large cap deformation.

[0062] Furthermore, in the above embodiments, the process parameters used are as follows: solution treatment: heating to 498°C, holding for 60 minutes, then water cooling to room temperature; complete annealing: heating to 400°C, holding for 60 minutes, then furnace cooling at a rate not exceeding 25°C per hour to below 260°C, followed by air cooling; stress-relief annealing: heating to 200°C, holding for 120 minutes, then air cooling. Various morphologies are also provided.

[0063] The range of process parameters given in the invention description also applies to bars of different states and diameters, namely:

[0064] Solution treatment: Heat to 495℃~500℃, hold for 50min~70min, then remove from the furnace and cool to room temperature with water;

[0065] Full annealing: Heat to 400℃~410℃, hold for 60 minutes, and cool in the furnace at a rate of no more than 25℃ per hour to below 260℃ before air cooling.

[0066] Stress-relief annealing: Heat to 200℃~260℃, hold for 100min~120min, then air cool after removal from the furnace.

[0067] The difference lies in the slightly different tensile strength distribution, elongation after fracture, and roundness of the plug opening compared to the specific embodiment. However, unlike the 2A12 aluminum alloy plug heat treatment using only full annealing, the plug heat-treated by this invention, through a heat treatment process of solution treatment + full annealing + stress-relief annealing, can preferentially obtain a uniform solid solution. Full annealing on the solid solution basis ensures that the reinforcing phase particles are evenly and finely distributed on the matrix, resulting in a more uniform overall microstructure and thus a more uniform distribution of mechanical properties. Simultaneously, stress-relief annealing of the finished plug eliminates work hardening and residual stress, resulting in better dimensional stability and preventing deformation during placement. This invention improves the tensile strength distribution, elongation after fracture, and roundness of the plug opening.

[0068] Therefore, it can be seen that the 2A12 aluminum alloy plugs heat-treated by the method of the present invention have a more uniform distribution of tensile strength and elongation after fracture, less plug deformation, better product consistency and stability, and the heat treatment process can meet the production of extruded bars of different states and diameters, and can be widely used in the production of 2A12 aluminum alloy plugs.

Claims

1. A heat treatment method for a 2A12 aluminum alloy plug, characterized in that... The steps are as follows: Step 1: Perform a solution treatment on the rough-machined plug to allow the plug to recrystallize completely after rough machining, fully dissolve the strengthening phase in the 2A12 aluminum alloy, and obtain a homogeneous solid solution. The solution treatment involves: solidifying the rough-machined plug, heating it to 495℃~500℃, holding it at that temperature for 50min~70min, and then removing it from the furnace and water-cooling it to room temperature. Step 2: Perform full annealing on the plug after solution treatment to precipitate the strengthening phase in the solid solution, so that fine S (CuMgAl2) and CuAl2 strengthening phase particles are uniformly distributed on the α-Al matrix; The complete annealing process involves heating the solution-treated plug to 400℃~410℃, holding it at that temperature for 60 minutes, and then cooling it in the furnace at a rate not exceeding 25℃ per hour until it reaches below 260℃ before being removed from the furnace and air-cooled. Step 3: The finished plug is subjected to stress-relief annealing to eliminate work hardening and residual stress, thus maintaining structural stability; The stress-relief annealing process involves heating to 200℃~260℃, holding at that temperature for 100min~120min, and then air-cooling the product after removal from the furnace.

2. The heat treatment method for the 2A12 aluminum alloy plug according to claim 1, characterized in that: For solution treatment, heat to 498℃, hold for 60 minutes, and then water-cool to room temperature after removal from the furnace. For complete annealing, heat to 400℃, hold for 60 minutes, and then cool with the furnace at a rate not exceeding 25℃ per hour to below 260℃ before air-cooling. For stress-relief annealing, heat to 200℃, hold for 120 minutes, and then air-cool after removal from the furnace.

3. The heat treatment method for the 2A12 aluminum alloy plug according to claim 2, characterized in that: The plug is made from H112 extruded bar stock with a diameter of 200mm. The tensile strength of the plug is distributed between 230MPa and 235MPa, the elongation after fracture is between 16.8% and 19.0%, and the roundness of the plug opening is 0.05mm.

4. The heat treatment method for the 2A12 aluminum alloy plug according to claim 2, characterized in that: The plug is made of F-state extruded bar stock with a diameter of 250mm. After processing, the tensile strength is distributed between 225MPa and 235MPa, the elongation after fracture is between 16.0% and 19.2%, and the roundness of the plug opening is 0.06mm.

5. The heat treatment method for the 2A12 aluminum alloy plug according to claim 2, characterized in that: The plug is made from O-state extruded bar stock with a diameter of 40mm. After processing, the tensile strength is distributed between 225MPa and 230MPa, the elongation after fracture is between 16.5% and 18.7%, and the roundness of the plug opening is 0.02mm.

6. The heat treatment method for the 2A12 aluminum alloy plug according to claim 2, characterized in that: The plug is made of T1 state extruded bar stock with a diameter of 260mm. After processing, the tensile strength is distributed between 225 MPa and 235 MPa, the elongation after fracture is between 16.8% and 19.3%, and the roundness of the plug opening is 0.05mm.

7. The heat treatment method for the 2A12 aluminum alloy plug according to claim 2, characterized in that: The plugs are made from T4 extruded bars with diameters of 120 mm and 200 mm, respectively. The tensile strength of the 120 mm diameter plug is between 230 MPa and 235 MPa, the elongation after fracture is between 16.3% and 18.7%, and the roundness of the plug opening is 0.03 mm. The tensile strength of the 200 mm diameter plug is between 225 MPa and 235 MPa, the elongation after fracture is between 15.8% and 19.1%, and the roundness of the plug opening is 0.06 mm.