A large-scale aluminum-based powder metallurgy ingot wide plate rolling method

Abstract

The application discloses a large-size aluminum-based powder metallurgy ingot blank wide plate rolling method, and adopts a synergic control process of forging square densification and secondary reversing rolling to couple the "densification" of free forging or closed die forging and the "widening" depth of reversing rolling. Through the total deformation of the square forging stage of greater than or equal to 50%, the internal porosity and interface defects of the powder metallurgy ingot blank are eliminated in advance, and a "crack-free foundation" is provided for the subsequent large-deformation widening of the reversing rolling. Meanwhile, the step-by-step widening of the reversing rolling reversely optimizes the microstructure uniformity of the square forging blank, solves the technical problems of the edge cracking and insufficient widening of the conventional square forging and rolling, and forms a closed-loop process of first densification, then widening and then finishing, instead of the traditional square forging and rolling.

Description

Technical Field

[0001] This invention relates to the field of powder metallurgy technology, specifically to a method for rolling large-format aluminum-based powder metallurgy ingots into wide plates. Background Technology

[0002] With the increasing demand for high-performance structural components in high-end fields such as aerospace and new energy equipment, the market demand for large-size (ingot diameter ≥ 500mm) and wide-width (plate width ≥ 2000mm) aluminum-based powder metallurgy plates continues to grow. Powder metallurgy aluminum-based plates possess advantages such as uniform composition, fine grains, and excellent mechanical properties. However, during the rolling process, they face numerous insurmountable technical challenges due to the intrinsic characteristics of powder metallurgy billets, inherent constraints of rolling equipment, and limitations in process adaptability, severely hindering their industrial production and large-scale application. (1) The intrinsic properties of the billet make the cold rolling process unsuitable. Compared to traditional cast ingots, powder metallurgy billets have inherent defects such as low initial density (typically only 80%–90%), weak interfacial bonding of powder particles, insufficient plasticity reserves, and susceptibility to micro-component segregation and microstructure gradients. When directly using cold rolling for wide-width rolling, the billets are prone to fatal defects such as cracking, delamination, and edge cracking. Moreover, during large deformation rolling, the probability of defect induction increases exponentially, and the yield of sheet metal is less than 30%. Therefore, the industry typically uses hot rolling for preparation.

[0003] (2) Existing hot rolling equipment conditions have rigid limitations. While the cold rolling industry has mature wide-width rolling mills, wide-width hot rolling mills suitable for powder metallurgy billets are generally lacking. On the one hand, wide-width hot rolling mills with ultra-long roll lengths have investment costs exceeding 100 million yuan, extremely high energy consumption, and scarce domestic production capacity. On the other hand, conventional hot rolling mills have limited roll length and opening, making it impossible to directly process large-sized powder metallurgy billets (billet diameter exceeding the maximum opening of the mill). Furthermore, the width extension of conventional unidirectional rolling is limited (width extension rate is usually only 20% to 30%), making it difficult to achieve the production of wide-width (≥2000mm) plates with existing equipment. Modifying the opening and roll length of existing mills would not only be costly and time-consuming but would also significantly reduce the versatility of the mills, making it extremely economically feasible.

[0004] To address the aforementioned problems in the prior art, prior art application number CN201210131206.9 discloses a method for preparing powder metallurgy plates using a unidirectional hot rolling process. Densification is achieved through multiple passes with small reductions. However, this method has high requirements for mill opening and roll length, making it unsuitable for producing wide plates on conventional equipment. Furthermore, the unidirectional rolling width is limited, failing to meet wide-width requirements. Additionally, prior art application number CN201210133031.5 describes a method for preparing large-size thin plates of niobium-titanium-aluminum-based powder metallurgy alloys. While addressing the high requirements for rolling equipment in large-size plate preparation, it does not involve forging densification or reversing rolling processes, representing an optimization of the conventional hot rolling route.

[0005] In summary, current rolling technology for large-format powder metallurgy ingots and wide-width plates still faces core technical challenges such as high equipment dependence, poor process adaptability, high plate defect rate, and low yield. There is an urgent need to develop a rolling process that can overcome the limitations of rolling mill equipment, adapt to the characteristics of large-format powder metallurgy ingots, and achieve coordinated control of densification and width expansion in order to address the shortcomings of existing technologies and promote the industrial application of large-format powder metallurgy wide-width plates. Summary of the Invention

[0006] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention employs a synergistic control process of forging densification and secondary reversing rolling, deeply coupling the "densification" of free forging or closed-die forging with the "breading" of reversing rolling. This solves the technical problems of easy edge cracking and insufficient breadth in conventional forging after rolling. Furthermore, through graded deformation and temperature control processes, it effectively solves the technical problems of easy cracking and uneven performance in the rolling of wide plates from large-size powder metallurgy ingots. Addressing the inherent limitations of conventional rolling mill roll length and opening, this invention achieves stable production of wide plates (width ≥ 2000 mm) without modifying the rolling mill rolls or increasing the opening, through a combined design of forging thickness reduction and two 90° reversing rolling processes. This significantly reduces the investment cost of ultra-wide rolling mills.

[0007] (II) Technical Solution To achieve the above objectives, the present invention provides the following technical solution: a method for rolling large-format aluminum-based powder metallurgy ingot billets into wide plates, comprising the following steps: S1: Forging and densification, which involves forging an ingot into a square billet through free forging or closed die forging. S2: One-time rolling, the square billet is parallel to the length direction and is fed into the rolling mill for longitudinal rough rolling; S3: One-time reversing rolling, the thick plate rolled in one step is removed from the rolling mill, rotated 90° as a whole, so that the original width direction becomes the rolling direction, and then fed back into the rolling mill for transverse rolling to widen it. S4: Secondary reversing rolling, the plate after the first reversing rolling is rotated 90° again to restore the original longitudinal rolling direction, and then the final finishing rolling is performed to obtain a wide plate.

[0008] Preferably, the densification of the forging is carried out by high-temperature slow forging, with a forging strain rate of 0.05–0.5 s. —1 Furthermore, the initial forging temperature for densification is 0.70–0.90°C. m Final forging temperature ≥ 0.60t m , where t m The melting point temperature (°C) of the powder metallurgy ingot material.

[0009] Preferably, the total deformation during the forging densification stage is ≥50%.

[0010] Preferably, the primary rolling, primary reversing rolling, and secondary reversing rolling are all low-temperature fast rolling, with a rolling strain rate of 0.5–10 s. —1 .

[0011] Preferably, the initial rolling temperature for the first rolling is 0.70–0.85°C. m Final rolling temperature ≥ 0.65t m .

[0012] Preferably, the initial rolling temperature for the first reversing rolling is 0.65–0.80 t. m Final rolling temperature ≥ 0.60t m .

[0013] Preferably, the initial rolling temperature for the secondary reversing rolling is 0.60–0.75 t. m Final rolling temperature ≥ 0.50t m .

[0014] Preferably, the single-pass reduction of the first rolling is 8% to 20%, and the total reduction is 35% to 60%; the single-pass reduction of the first reversing rolling is 8% to 20%; the single-pass reduction of the second reversing rolling is 5% to 15%; and the cumulative total reduction is not less than 90% based on the thickness of the billet at the first rolling inlet.

[0015] Preferably, the diameter of the powder metallurgy ingot is ≥500mm, and the width of the wide plate is ≥2000mm.

[0016] (III) Beneficial Effects Compared with the prior art, the present invention provides a method for rolling large-format aluminum-based powder metallurgy ingot billets into wide plates, which has the following beneficial effects: This invention employs a synergistic control process of forging densification and secondary reversing rolling, deeply coupling the "densification" of free forging or closed-die forging with the "breading" of reversing rolling. By achieving a total deformation of ≥50% in the forging stage, internal porosity and interface defects in the powder metallurgy ingot are eliminated beforehand, providing a "crack-free foundation" for the large deformation and breading of subsequent reversing rolling. The total reduction in the first rolling stage is controlled between 35% and 60%. If the deformation is too low, microcracks or even through-cracks are easily generated on the edges and surface of the plate during the subsequent two reversing rolling processes, resulting in low final plate density. If the total reduction in the first rolling stage is too high, although the density can be further improved, the limited plasticity reserve of the powder metallurgy slab means that excessive single-stage deformation will lead to intensified work hardening, a significant increase in edge cracking rate, and difficulty in plate shape control. The subsequent step-by-step widening of the reversing rolling optimizes the uniformity of the microstructure of the forged billet, solving the technical problems of easy edge cracking and insufficient widening in conventional post-forging rolling. It forms a closed-loop process of "first densification, then widening, and then finishing", rather than the traditional post-forging rolling. This invention solves the technical problems of easy cracking and uneven performance in the rolling of large-size powder metallurgy ingot billets by using a graded deformation and temperature control system, employing high-temperature slow forging in the forging stage to avoid cracking of powder billets, and low-temperature fast rolling in the reversing rolling stage. This ensures maximum width expansion and suppresses the generation of nano / micron-level porosity defects. This invention addresses the inherent limitations of conventional rolling mill roll length and opening. Through a combination of forging thickness reduction and two 90° reversal rolling processes, it achieves stable production of wide plates (width ≥ 2000 mm) without modifying the rolling mill rolls or increasing the opening, significantly reducing the investment cost of ultra-wide rolling mills. Attached Figure Description

[0017] Figure 1 This is a flowchart of a method for rolling wide plates from large-size aluminum-based powder metallurgy ingots according to the present invention. Detailed Implementation

[0018] To better understand the purpose, structure, and function of this invention, and to overcome the limitations of rolling mill equipment, adapt to the characteristics of large-size powder metallurgy ingots, and achieve coordinated control of densification and width expansion, a method for rolling wide plates of large-size powder metallurgy ingots according to this invention will be described in further detail.

[0019] Example 1: Reference Figure 1 This invention discloses a method for rolling large-format powder metallurgy ingots into wide plates. A carbon nanotube-reinforced 2024 aluminum alloy (CNT / 2024) powder metallurgy ingot with a diameter of 700 mm and a height of 500 mm is selected. The CNT / 2024 powder metallurgy ingot is prepared by atomizing 2024 aluminum alloy powder and carbon nanotubes with a volume fraction of 2% through variable speed ball milling, cold isostatic pressing and vacuum sintering.

[0020] S1: Densification of forged billets, by heating powder metallurgy ingots to 0.85t m (t) m Using 2024 aluminum alloy (melting point 635℃), closed-die forging was performed at a forging strain rate of 0.5 s⁻¹ to forge a square billet. The total deformation was controlled at 50%, and the final forging temperature was not lower than 0.63 t. m .

[0021] S2: One-time rolling, heating the forged square billet to 0.78t. m The material is fed into the rolling mill along its length for longitudinal roughing, with a single-pass reduction controlled at 12%–16%, a total reduction of 40%, and a final rolling temperature of not less than 0.66t. m The rolling strain rate is 4 s⁻¹.

[0022] S3: Single-direction rolling, rotating the thick plate after one rolling by 90° to change the original width direction to the rolling direction, and heating to 0.68t. m Lateral rolling is performed to widen the surface, with a single-pass reduction controlled at 10%–12%, a total reduction of 60%, and a final rolling temperature not lower than 0.61t. m The rolling strain rate is 5 s⁻¹.

[0023] S4: Secondary reversing rolling, the plate after the first reversing rolling is rotated 90° again to restore the original longitudinal rolling direction, and heated to 0.62t. m The final rolling is then carried out, with the single-pass reduction controlled at 8%–10%, the total reduction at 83.3%, and the final rolling temperature not lower than 0.52t. m The rolling strain rate is 6 s⁻¹.

[0024] The thicknesses of the slabs exiting each of the S1-S2-S3-S4 processes are 250mm, 150mm, 60mm, and 10mm, respectively. Based on an initial slab thickness of 250mm, the cumulative total reduction during rolling is 96%. After rolling using the above method, a 10mm thick plate with a width of 2150mm is obtained, with no cracks, edge cracks, or delamination defects on the plate surface. Testing shows that the density of the rolled plate reaches over 99.5%, the room temperature tensile strength of the T6 temper plate reaches 580MPa, and the elongation remains above 8%, exhibiting excellent strength-plasticity balance.

[0025] Example 2: A method for rolling large-format aluminum-based powder metallurgy ingot billets into wide plates, comprising the following steps: A 1% CNT / 6061 powder metallurgy ingot billet with a diameter of 800 mm and a height of 480 mm is selected and finally rolled into a wide plate with a width of 2200 mm. S1: Forging densification, the ingot is forged into a square billet through free forging or closed die forging, wherein the forging densification is carried out by high-temperature slow forging with a forging strain rate of 0.25 s. —1 Furthermore, the initial forging temperature for densification is 0.80t. m The final forging temperature is 0.68t. m , where t m The melting point of the material is approximately 650℃. Specifically, the total deformation amount in the forging densification stage is 50%, which eliminates the internal porosity and interface defects of the powder metallurgy ingot in advance, providing a crack-free basis for the large deformation expansion in the subsequent reversing rolling.

[0026] S2: One-time rolling, the square billet is fed into the rolling mill for longitudinal rough rolling parallel to its length direction, using low-temperature fast rolling, with an initial rolling temperature of 0.80t. m The final rolling temperature is 0.70t. m The single-pass reduction is 12%–15%, and the total reduction is 55%. S3: Single-direction rolling. The thick plate rolled in the previous stage is removed from the mill, rotated 90° to change the original width direction to the rolling direction, and then fed back into the mill for transverse rolling widening. Low-temperature fast rolling is used, with an initial rolling temperature of 0.70t. m The final rolling temperature is 0.65t. m The single-pass reduction is 12%–15%, and the total reduction is 55.6%. S4: Secondary reversing rolling. The sheet material after the first reversing rolling is rotated 90° again to restore the original longitudinal rolling direction, and then subjected to final finishing rolling to obtain wide sheet material. Low-temperature fast rolling is used, with an initial rolling temperature of 0.68t. m The final rolling temperature is 0.60t. m The single-pass reduction is 8% to 10%, and the total reduction is 83.3%.

[0027] Specifically, the thicknesses of the slabs exiting each of the S1-S2-S3-S4 processes are 240mm, 108mm, 48mm, and 8mm, respectively. Based on an initial slab thickness of 240mm, the cumulative total reduction during rolling is 96.7%. After rolling using the above method, an 8mm thick sheet with a width of 2250mm is obtained, with no surface cracks, edge cracks, or delamination defects. Testing shows that the density of the rolled sheet reaches over 99.6%, the room temperature tensile strength of the T6 temper sheet reaches 410MPa, and the elongation remains above 12%.

[0028] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. A method for rolling large-format aluminum-based powder metallurgy ingot billets into wide-width plates, characterized in that, Includes the following steps: S1: Forging and densification, which involves forging an ingot into a square billet through free forging or closed die forging. S2: One-time rolling, the square billet is parallel to the length direction and is fed into the rolling mill for longitudinal rough rolling; S3: One-time reversing rolling, the thick plate rolled in one step is removed from the rolling mill, rotated 90° as a whole, so that the original width direction becomes the rolling direction, and then fed back into the rolling mill for transverse rolling to widen it. S4: Secondary reversing rolling, the plate after the first reversing rolling is rotated 90° again to restore the original longitudinal rolling direction, and then the final finishing rolling is performed to obtain a wide plate.

2. The method for rolling large-format aluminum-based powder metallurgy ingots into wide plates according to claim 1, characterized in that, The densification of the forged material is achieved through high-temperature slow forging, with a forging strain rate of 0.05–0.5 s⁻¹. —1 Furthermore, the initial forging temperature for densification is 0.70–0.90°C. m Final forging temperature ≥ 0.60t m , where t m The melting point temperature (°C) of the powder metallurgy ingot material.

3. The method for rolling large-format aluminum-based powder metallurgy ingots into wide plates according to claim 1, characterized in that, The total deformation during the densification stage of the forging process is ≥50%.

4. The method for rolling large-format aluminum-based powder metallurgy ingot billets into wide plates according to claim 1, characterized in that, The primary rolling, primary reversing rolling, and secondary reversing rolling are all low-temperature fast rolling processes with a rolling strain rate of 0.5–10 s⁻¹. —1 .

5. The method for rolling large-format aluminum-based powder metallurgy ingots into wide plates according to claim 4, characterized in that, The initial rolling temperature for the first rolling process is 0.70–0.85°C. m Final rolling temperature ≥ 0.65t m .

6. The method for rolling large-format aluminum-based powder metallurgy ingots into wide plates according to claim 4, characterized in that, The initial rolling temperature for the first reversing rolling is 0.65–0.80°C. m Final rolling temperature ≥ 0.60t m .

7. The method for rolling large-format aluminum-based powder metallurgy ingots into wide plates according to claim 4, characterized in that, The initial rolling temperature for the secondary reversing rolling is 0.60–0.75°C. m Final rolling temperature ≥ 0.50t m .

8. The method for rolling large-format aluminum-based powder metallurgy ingots into wide plates according to claim 1, characterized in that, The single-pass reduction of the first rolling is 8% to 20%, and the total reduction is 35% to 60%; the single-pass reduction of the first reversing rolling is 8% to 20%; the single-pass reduction of the second reversing rolling is 5% to 15%; based on the thickness of the billet at the first rolling inlet, the cumulative total reduction is not less than 90%.

9. A method for rolling large-format aluminum-based powder metallurgy ingots into wide plates according to claim 1, characterized in that, The diameter of the powder metallurgy ingot is ≥500mm, and the width of the wide plate is ≥2000mm.

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