Method for improving grain structure and impact energy of aluminum alloy forge piece

Abstract

The invention provides a method for improving grain structure and impact energy of an aluminum alloy forge piece, and belongs to the technical field of aluminum alloy preparation. The method comprises the steps of blank preparation, blank heating, free forging blank manufacturing, blank machining, blank heating, die forging, solid solution heat treatment and aging heat treatment. By adjusting the production process of the forge piece and regulating and controlling the grain distribution morphology of the forge piece and the distribution characteristics of the AlFeNi phase, the comprehensive performance of the alloy is improved under the condition that the impact energy is improved, and therefore the service performance of the forge piece is improved.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy preparation technology, and in particular to a method for improving the grain structure and impact energy of aluminum alloy forgings. Background Technology

[0002] For aluminum-copper alloys with microalloying elements such as Cr, Mn, and Ti, as well as those without rare earth elements, such as heat-resistant wrought aluminum alloys like 2618 and 2A70, abnormal grain growth often occurs during the production of aluminum alloy forgings, which seriously affects the tensile and fatigue properties of the forgings. At the same time, due to the presence of the micron-sized high-temperature stable phase AlFeNi, it is often difficult to improve the impact energy performance of such alloys. Summary of the Invention

[0003] In view of this, in order to solve the technical problem that there are often great difficulties in improving the impact performance of existing aluminum alloys, the present invention provides a method for improving the grain structure and impact performance of aluminum alloy forgings. By adjusting the production process of forgings, controlling the grain distribution morphology and AlFeNi phase distribution characteristics of forgings, the overall performance of the alloy is improved while improving impact performance, thereby improving the service performance of forgings.

[0004] To achieve the above objectives, the present invention provides the following technical solution: A method for improving the grain structure and impact energy of aluminum alloy forgings includes the following steps: Step (1), billet preparation: Remove the surface segregation layer from the homogenized ingot and saw it according to the size requirements of the forging; Step (2), billet heating: Heating the sawn billet; Step (3) Free forging billet: After the billet is kept warm, it is free forged. The billet making process is three-stage forging and three-stage drawing. The temperature at the bottom of the line should not be lower than 390℃. The forging speed should be controlled at 5-15mm / s, the forging ratio is 6-7, and the billet is cooled naturally after forging. Step (4), billet machining: The free-forged billet is surface machined; Step (5), billet heating: Heating the machined free forging billet; Step (6), Die forging: The heated blank is die forged, and the temperature after forging is not lower than 430℃. It is then naturally cooled after forging. Step (7), Solution heat treatment: The forging is subjected to solution heat treatment and quenching; Step (8) Aging heat treatment: The quenched die forging is subjected to aging heat treatment and then naturally cooled after being taken out of the furnace.

[0005] Compared with the prior art, the present invention has the following beneficial effects: (1) Grain structure morphology: The die forging produced by this process undergoes recrystallization changes due to the matching of plastic deformation process and solution heat treatment temperature. This results in the micro-grains and grain size in each deformation direction reaching grade 5.0 or above in GB / T 3246.1, and there are no abnormally large grains.

[0006] (2) Significantly improved impact energy: Compared with the comparative production process, the forgings produced by this production process, through the combined deformation of free forging billet and die forging deformation, not only ensure the consistency of fine grain structure of the forgings and increase the crack propagation path, but also increase the resistance to crack propagation by breaking and discontinuously distributing AlNiFe, thus significantly improving its room temperature impact energy KV2. Attached Figure Description

[0007] Figure 1 This is a comparison diagram of the grain size of Example 1 and Comparative Example 1 of the present invention.

[0008] Figure 2 This is a comparison diagram of the grain size of Example 2 and Comparative Example 2 of the present invention.

[0009] Figure 3 This is a comparison diagram of the grain size between Example 3 and Comparative Example 3 of the present invention. Detailed Implementation

[0010] This invention provides a method for improving the grain structure and impact energy of aluminum alloy forgings, comprising the following steps: Step (1), billet preparation: Remove the surface segregation layer from the homogenized ingot and saw it according to the forging size requirements. In this step (1), the ingot is an aluminum-copper alloy, such as 2A70 or 2618 ingot.

[0011] Step (2) Heating the billet: Heating the sawn billet, preferably the billet temperature should be controlled at 440~460℃, and the holding time should be 3~6h.

[0012] Step (3) Free forging billet: After the billet is kept warm, it is free forged. The preferred billet making process is three-stage forging and three-stage drawing. The offline temperature should not be lower than 390℃. The forging speed should be controlled at 5-15mm / s, the forging ratio is 6-7, and the billet is naturally cooled after forging.

[0013] Step (4) Billet machining: After free forging, the billet is machined on the surface, preferably to a depth of 3-5mm.

[0014] Step (5) Billet heating: Heat the machined free forging billet. The billet temperature should be controlled at 460~480℃ and the holding time should be 3~6h.

[0015] Step (6), Die forging: The heated blank is die forged, preferably at a forging speed of 3-8 mm / s, with an offline temperature of not less than 430℃, and then naturally cooled after forging; Step (7) Solution heat treatment: The forging is subjected to solution heat treatment at a temperature of 510-535℃ and a holding time of 1.5-4h. The quenching medium is preferably water and the water temperature is preferably 30-50℃.

[0016] Step (8) Aging heat treatment: The quenched die forging is subjected to aging heat treatment. The preferred aging heat treatment temperature is 180-200℃, the holding time is 16-22h, and it is obtained by natural cooling after being taken out of the furnace.

[0017] The technical solution of the present invention will be clearly and thoroughly described below with reference to specific embodiments.

[0018] Example 1 The ingot selected is 2A70, and its process is as follows: Step (1) Billet preparation: Remove the surface segregation layer from the homogenized 2A70 ingot and saw it according to the forging size requirements.

[0019] Step (2), billet heating: Heat the sawn billet. The billet temperature should be controlled at 460℃ and the holding time should be 6 hours.

[0020] Step (3) Free forging billet: After the billet is kept warm, it is free forged. The billet making process is three-stage forging and three-stage drawing. The offline temperature is 400℃. The forging speed should be controlled at 10mm / s. The forging ratio is 6. After forging, it is naturally cooled.

[0021] Step (4) Billet machining: After free forging, the billet is machined to a depth of 5mm.

[0022] Step (5) Billet heating: Heat the machined free forging billet. The billet temperature should be controlled at 460℃ and the holding time should be 3h.

[0023] Step (6), Die forging: The heated blank is die forged at a forging speed of 8 mm / s and a minimum temperature of 450°C. After forging, it is allowed to cool naturally. Step (7) Solution heat treatment: The forging is subjected to solution heat treatment at a temperature of 520℃ for 4 hours, followed by quenching. The quenching medium is water at a temperature of 50℃.

[0024] Step (8) Aging heat treatment: The quenched die forging is subjected to aging heat treatment at a temperature of 200℃ and a holding time of 16h. After being taken out of the furnace, it is naturally cooled to obtain the product.

[0025] Example 2 The ingot selected is 2A70, and its process is as follows: Step (1) Billet preparation: Remove the surface segregation layer from the homogenized 2A70 ingot and saw it according to the forging size requirements.

[0026] Step (2), billet heating: Heat the sawn billet. The billet temperature should be controlled at 440℃ and the holding time should be 3 hours.

[0027] Step (3) Free forging billet: After the billet is kept warm, it is free forged. The billet making process is three-stage forging and three-stage drawing. The offline temperature is 410℃. The forging speed should be controlled at 15mm / s. The forging ratio is 7. After forging, it is naturally cooled.

[0028] Step (4) Billet machining: After free forging, the billet is machined to a depth of 3mm.

[0029] Step (5) Billet heating: Heat the machined free forging billet. The billet temperature should be controlled at 480℃ and the holding time should be 6h.

[0030] Step (6), Die forging: The heated blank is die forged at a forging speed of 3 mm / s and a minimum temperature of 455℃. After forging, it is allowed to cool naturally. Step (7) Solution heat treatment: The forging is subjected to solution heat treatment at a temperature of 510℃ for 3 hours, followed by quenching. The quenching medium is water, and the water temperature is preferably 30℃.

[0031] Step (8) Aging heat treatment: The quenched die forging is subjected to aging heat treatment at a temperature of 180℃ and a holding time of 22h. After being taken out of the furnace, it is naturally cooled to obtain the final product.

[0032] Example 3 The ingot selected is 2A70, and its process is as follows: Step (1) Billet preparation: Remove the surface segregation layer from the homogenized 2A70 ingot and saw it according to the forging size requirements.

[0033] Step (2), billet heating: Heat the sawn billet. The billet temperature should be controlled at 450℃ and the holding time should be 4 hours.

[0034] Step (3) Free forging billet: After the billet is kept warm, it is free forged. The billet making process is three-stage forging and three-stage drawing. The offline temperature is 415℃. The forging speed should be controlled at 5mm / s. The forging ratio is 6. After forging, it is naturally cooled.

[0035] Step (4) Billet machining: After free forging, the billet is machined to a depth of 5mm.

[0036] Step (5) Billet heating: Heat the machined free forging billet. The billet temperature should be controlled at 470℃ and the holding time should be 5h.

[0037] Step (6), Die forging: The heated blank is die forged at a forging speed of 6 mm / s and a minimum temperature of 460℃. After forging, it is allowed to cool naturally. Step (7) Solution heat treatment: The forging is subjected to solution heat treatment at a temperature of 535℃ and a holding time of 1.5h. It is then quenched with water at a temperature of 40℃.

[0038] Step (8) Aging heat treatment: The quenched die forging is subjected to aging heat treatment at a temperature of 190℃ and a holding time of 20h. After being taken out of the furnace, it is naturally cooled to obtain the product.

[0039] Comparative Example 1 Similar to Example 1, 2A70 ingots are selected, the difference being: Step (3) Free forging billet: After the billet is kept warm, it is free forged. The billet making process is two upsetting and two drawing. The lower temperature is 380℃. The forging speed should be controlled at 8mm / s. The forging ratio is 6. After forging, it is naturally cooled.

[0040] Step (6), Die forging: The heated blank is die forged at a forging speed of 7 mm / s and a minimum temperature of 420℃. After forging, it is allowed to cool naturally. Step (7) Solution heat treatment: The forging is subjected to solution heat treatment at a temperature of 550℃ for 3 hours, followed by quenching. The quenching medium is water at a temperature of 40℃.

[0041] Step (8) Aging heat treatment: The quenched die forging is subjected to aging heat treatment at a temperature of 210℃ and a holding time of 20h. After being taken out of the furnace, it is naturally cooled to obtain the product.

[0042] Comparative Example 2 Similar to Example 2, 2A70 ingots are selected, the difference being: Step (3) Free forging billet: After the billet is kept warm, it is free forged. The billet making process is two upsetting and two drawing. The lower temperature is 385℃. The forging speed should be controlled at 8mm / s. The forging ratio is 7. After forging, it is naturally cooled.

[0043] Step (6), Die forging: The heated blank is die forged at a forging speed of 7 mm / s and a line temperature of 420℃. After forging, it is naturally cooled.

[0044] Comparative Example 3 Similar to Example 3, 2A70 ingots are selected, the difference being: Step (7) Solution heat treatment: The forging is subjected to solution heat treatment at a temperature of 500℃ and a holding time of 2.5h. It is then quenched with water at a temperature of 30℃.

[0045] Step (8) Aging heat treatment: The quenched die forging is subjected to aging heat treatment at a temperature of 170℃ and a holding time of 23h. After being taken out of the furnace, it is naturally cooled to obtain the product.

[0046] The room temperature impact energy and grain size of Examples 1-3 and Comparative Examples 1-3 were tested using the Charpy pendulum impact test and optical (metallographic) microscopy-linear intercept measurement method. The grain size test results are as follows: Figure 1-3 As shown, compared with Comparative Examples 1-3, the forgings produced by the present invention, through the matching of the plastic deformation process and the solution heat treatment temperature, cause the grains of the forgings to undergo recrystallization changes, so that the micro-grains and grain size in each deformation direction can reach up to grade 9.0, which is far greater than the grain size of Comparative Examples 1-3.

[0047] The test results of the room temperature impact energy KV2 (J) are shown in Table 1 below: Table 1 Test results of Examples 1-3 and Comparative Examples 1-3

[0048] As shown in Table 1, compared with Comparative Examples 1-3, the forgings produced by the present invention, through the combined deformation of free forging billet and die forging deformation, not only ensure the consistency of fine grain structure of the forging and increase the crack propagation path, but also increase the resistance to crack propagation by breaking and discontinuously distributing AlNiFe, thus significantly improving its room temperature impact energy KV2.

[0049] The above description is merely a preferred embodiment of the present invention. However, the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for improving the grain structure and impact energy of aluminum alloy forgings, characterized in that, Includes the following steps: Step (1), billet preparation: Remove the surface segregation layer from the homogenized ingot and saw it according to the size requirements of the forging; Step (2), billet heating: Heating the sawn billet; Step (3) Free forging billet: After the billet is kept warm, it is free forged. The billet making process is three-stage forging and three-stage drawing. The temperature at the bottom of the line should not be lower than 390℃. The forging speed should be controlled at 5-15mm / s, the forging ratio is 6-7, and the billet is cooled naturally after forging. Step (4), billet machining: The free-forged billet is surface machined; Step (5), billet heating: Heating the machined free forging billet; Step (6), Die forging: The heated blank is die forged, and the temperature after forging is not lower than 430℃. It is then naturally cooled after forging. Step (7), Solution heat treatment: The forging is subjected to solution heat treatment and quenching; Step (8) Aging heat treatment: The quenched die forging is subjected to aging heat treatment and then naturally cooled after being taken out of the furnace.

2. The method for improving the grain structure and impact energy of aluminum alloy forgings according to claim 1, characterized in that, In step (2), the billet heating temperature should be controlled at 440~460℃ and the holding time should be 3~6h.

3. The method for improving the grain structure and impact energy of aluminum alloy forgings according to claim 1, characterized in that, In step (4), the machining depth is 3-5mm.

4. The method for improving the grain structure and impact energy of aluminum alloy forgings according to claim 1, characterized in that, In step (5), the billet temperature is controlled at 460~480℃ and the holding time is 3~6h.

5. The method for improving the grain structure and impact energy of aluminum alloy forgings according to claim 1, characterized in that, In step (6), the forging speed is 3-8 mm / s.

6. The method for improving the grain structure and impact energy of aluminum alloy forgings according to claim 1, characterized in that, In step (7), the quenching medium is water.

7. The method for improving the grain structure and impact energy of aluminum alloy forgings according to claim 6, characterized in that, The water temperature is 30-50℃.

8. The method for improving the grain structure and impact energy of aluminum alloy forgings according to claim 1, characterized in that, Step (7): The solution heat treatment temperature is 510-535℃, and the holding time is 1.5-4h.

9. The method for improving the grain structure and impact energy of aluminum alloy forgings according to claim 1, characterized in that, In step (8), the aging heat treatment temperature is 180-200℃ and the holding time is 16-22h.

10. A method for improving the grain structure and impact energy of aluminum alloy forgings according to any one of claims 1-9, characterized in that, In step (1), the ingot is an aluminum-copper alloy.

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