A fine-grained Cu-Ni-Si alloy material and its preparation method

Abstract

The present invention relates to the technical field of copper alloy materials, and discloses a method for preparing a fine-grained, high-performance Cu-Ni-Si alloy material. The present invention makes technical adjustments to the traditional preparation process, including: semi-continuous casting → hot rolling and online quenching → milling → pre-aging → cold rolling deformation → regression heat treatment → re-aging or a combination of re-aging and cold rolling deformation → surface cleaning → straightening. The fine-grained, high-performance Cu-Ni-Si alloy material and its preparation method provided by the present invention introduce second-phase particles through pre-aging to improve cold deformation energy storage, and obtain a fine-grained Cu-Ni-Si alloy with high strength, high conductivity, and high elongation through a high-temperature, short-time regression treatment combined with a re-aging process, thereby improving the conductivity and plastic toughness of the Cu-Ni-Si alloy plate and strip while ensuring the strength of the Cu-Ni-Si alloy.

Description

Technical Field

[0001] The present invention relates to the technical field of copper alloy materials, and in particular to a fine-grained Cu-Ni-Si alloy material and a preparation method thereof. Background Art

[0002] Copper alloys, with their high strength, excellent electrical and thermal conductivity, and good machinability, are the preferred material for manufacturing integrated circuit leadframes. In recent years, with the rapid development of information technology, the scale of integrated circuits has rapidly expanded, moving towards higher density and miniaturization. This has led to a continuous reduction in the wire diameter of leadframe pins, placing higher demands on the strength, electrical conductivity, and thermal conductivity of the materials used. Cu-Ni-Si alloys (Corson copper alloys) combine high strength with excellent electrical conductivity. For example, the Cu-Ni-Si-Mg alloy C70250 boasts a tensile strength of 750 MPa and an electrical conductivity of 40% IACS, making it a major development direction for copper alloys used in leadframes.

[0003] As a typical age-hardenable alloy, Cu-Ni-Si alloys are solution-quenched to form a supersaturated solid solution with fully dissolved solute atoms. The solute atoms are then precipitated as a nanoscale second phase through thermomechanical treatment, thereby hardening and purifying the matrix and achieving both high strength and electrical conductivity. The current production process for Cu-Ni-Si alloy sheets and strips typically consists of the following steps: semi-continuous casting → hot rolling → solution quenching → cold rolling → aging. In theory, this process can promote the precipitation of the δ-Ni2Si second phase and improve the overall properties of the Cu-Ni-Si alloy. However, in practice, this process presents several challenges: 1. For larger ingots or heavy coils weighing several tons, solution quenching results in inconsistent cooling rates inside and outside the ingot, ultimately leading to uneven material properties. This phenomenon is particularly pronounced for alloys with high nickel and silicon content, which are highly quench-sensitive. To overcome this problem, a "hot rolling-online quenching" approach is often used in industrial production to achieve a supersaturated solid solution. However, obtaining a fully solid-solution Cu-Ni-Si alloy requires a high hot rolling finish temperature and intense quenching, placing high demands on process design and equipment capabilities. The Cu-Ni-Si alloy obtained through the "solid solution → cold rolling → aging" process exhibits limited microstructure refinement, resulting in poor ductility and toughness, and weak bending resistance, failing to meet the requirements of high-end electronic conductor materials. The Cu-Ni-Si alloy treated in this process is prone to over-aging softening, and while maintaining strength, its electrical conductivity is generally below 50% IACS. Therefore, Cu-Ni-Si alloys prepared using traditional processes struggle to meet the development requirements of leadframe conductor materials. To obtain high-performance Cu-Ni-Si alloys, it is necessary to maximize the precipitation of nickel and silicon from the copper matrix without significantly softening the alloy through over-aging, thereby achieving high electrical conductivity, while also refining the alloy structure and improving the material's ductility and toughness. Summary of the Invention

[0004] The present invention provides a fine-grained Cu-Ni-Si alloy material and a preparation method thereof. Second-phase particles are introduced through pre-aging to improve cold deformation energy storage. A fine-grained Cu-Ni-Si alloy with high strength, high conductivity, and high elongation is obtained through a high-temperature short-time regression treatment combined with a re-aging process. The electrical conductivity and plastic toughness of the Cu-Ni-Si alloy plate and strip are improved while ensuring the strength of the Cu-Ni-Si alloy.

[0005] The present invention provides a preparation method of a fine-grained Cu-Ni-Si alloy material, which makes technical adjustments to the traditional preparation process, including: semi-continuous casting → hot rolling-online quenching → surface milling → pre-aging → cold rolling deformation → retrograde heat treatment → re-aging or a combination of re-aging and cold rolling deformation → surface cleaning → tension straightening.

[0006] Specific methods include:

[0007] (1) Semi-continuous casting: Prepare the raw materials. First, put pure copper into a medium frequency induction furnace to melt. When the temperature rises to 1350~1450℃, keep it warm and add pure silicon blocks. After the silicon melts, add pure nickel. After the melt is uniformly stirred by electromagnetic stirring, quickly add slag-making agent to stir and degas and remove slag. Then add covering agent to prevent oxidation. Control the melt temperature to maintain at 1200~1250℃. During casting, the melt is introduced into the crystallizer through the launder and pulled down to obtain a flat ingot.

[0008] (2) Hot rolling-online quenching: The flat ingot obtained in step (1) is cut off at the head and tail, and heated to 900-950°C, kept at this temperature for 60-240 minutes for homogenization, and then immediately hot rolled to a thickness of 12-18 mm, with a final rolling temperature of 680-780°C, and water quenched online to obtain a slab;

[0009] (3) Milling: The slab obtained in step (2) is subjected to milling treatment to remove oxides and defects on the surface of the slab;

[0010] (4) Pre-aging: The coil obtained in step (3) is heated to 580-620°C for pre-aging treatment, kept at this temperature for 5-24 hours, and then cooled naturally in the furnace for later use;

[0011] (5) Cold rolling deformation: cold rolling deformation is performed on the slab after the treatment in step (4), and the rolling deformation amount is greater than 70%;

[0012] (6) Retrograde heat treatment: heating the cold-rolled sheet obtained in step (5) to 800-850°C, keeping the temperature for 10 seconds to 5 minutes, and then water quenching;

[0013] (7) Re-aging or a combination of re-aging and cold deformation: heating the slab obtained in step (6) to 350-450°C, keeping the temperature for 4-16 hours, and performing re-aging treatment, followed by natural cooling to room temperature; or performing a combined thermomechanical treatment consisting of re-aging and cold rolling deformation on the slab obtained in step (6);

[0014] (8) Surface cleaning: Clean the surface of the sheet obtained in step (7) to remove the oxides generated during the aging process and obtain a bright surface;

[0015] (9) Straightening: The slab obtained in step (8) is straightened and straightened to obtain a Cu-Ni-Si alloy material.

[0016] Furthermore, the weight ratio of Ni element to Si element contained in the obtained Cu-Ni-Si alloy material is 4.1-4.2.

[0017] Furthermore, in step (1), the furnace, launder, crystallizer and bottom plate are fully dried before smelting; the pure copper, pure nickel and pure silicon materials used are cleaned and dried; and the composition of the melt alloy is tested and supplemented online before casting.

[0018] Furthermore, in step (2), the single-pass pressing amount is ≥15%, the total rolling amount is ≥70%, the rolling speed is 0.1~1m / s, the quenching cooling intensity is ≥20℃ / s, and the composition difference between the head and tail of the ingot is <2%.

[0019] Furthermore, a protective atmosphere is used in the treatment of step (4) to prevent oxidation of the alloy surface; after the pre-aging time is set, the Cu-Ni-Si alloy is in an over-aged state, and its Vickers hardness is less than 190HV.

[0020] Furthermore, in step (5), the alloy is subjected to large deformation cold rolling, the single cold rolling deformation is greater than 15%, and the cold rolling rate is greater than or equal to 0.1 m / s.

[0021] Furthermore, in step (6), the maximum heating temperature of the regression process is lower than the theoretical solution temperature of the Cu-Ni-Si alloy; the thickness of the alloy slab during the regression treatment is less than 1.5 mm; the alloy is protected by an inert gas to prevent oxidation, the material heating rate is greater than 100°C / min, and the quenching cooling intensity is ≥100°C / s.

[0022] Furthermore, in step (7), the material heating rate is 10~50℃ / min; the combined thermomechanical treatment includes the combination of: "cold rolling→aging", "aging→cold rolling", "cold rolling→aging→cold rolling→aging", and "aging→cold rolling→aging→cold rolling", wherein the aging temperature is 350~450℃, the aging time is 30~240min, and the cold rolling deformation is ≥50%, wherein the cold rolling deformation sacrifices the set elongation to obtain higher alloy strength.

[0023] The present invention also provides a fine-grained Cu-Ni-Si alloy material, which is prepared using the method for preparing the fine-grained Cu-Ni-Si alloy material as described above. The Cu-Ni-Si alloy material contains 3.0 to 6.0% by weight of Ni, 0.5 to 1.5% by weight of Si, and the balance is Cu and unavoidable impurity elements. The average grain size is less than 3 μm. When the tensile strength is 750 MPa, the elongation can reach 15%, and the electrical conductivity can reach 52% IACS.

[0024] The practical effects produced by the present invention include:

[0025] When the material's tensile strength (σb) reaches 750 MPa, its yield strength (σ0.2) reaches 680 MPa, its electrical conductivity reaches 52% IACS, its elongation (ε) reaches 15%, and its strip can be bent at 90° without cracking. These performance indicators exceed those of TM00 C70250 alloy (σb of 650 MPa, electrical conductivity of 40% IACS, and elongation of 6%). BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a process flow chart for preparing Cu-Ni-Si alloy in the present invention.

[0027] Figure 2 This is the metallographic structure diagram of the Cu-Ni-Si alloy after regression-re-aging treatment in the present invention.

[0028] Figure 3 Schematic diagram of a transmission electron microscope bright field image of the Cu-Ni-Si alloy after regression-re-aging treatment in the present invention.

[0029] Figure 4 Schematic diagram of the tensile properties curve of the Cu-Ni-Si alloy after regression-re-aging treatment in the present invention.

[0030] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0031] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0032] The present invention designs and develops a method for preparing a fine-grained Cu-Ni-Si alloy material. The Cu-Ni-Si alloy prepared according to the method can meet the performance requirements of conductor materials for large-scale and miniaturized integrated circuit lead frames. The alloy has excellent comprehensive properties and is suitable for large-scale industrial production. Example

[0033] like Figure 1 As shown, this embodiment provides a method for preparing a fine-grained Cu-Ni-Si alloy material, comprising:

[0034] (1) Semi-continuous casting: Prepare raw materials according to the weight percentage of pure copper, pure silicon and pure nickel, which is Cu92.4~95.2%, Si0.8~1.6% and Ni4~6%. After drying and dust removal, put the pure copper into a medium frequency induction furnace for melting. When the temperature rises to 1400℃, keep it warm for 10 minutes, and add pure silicon blocks and pure nickel blocks. After the melt is uniformly stirred by electromagnetic stirring, quickly add slag-making agent to stir, degas and remove slag, and add covering agent to prevent oxidation. Then the melt temperature is controlled at 1200℃, and the ingot blank is obtained by downward drawing.

[0035] (2) Hot rolling-online quenching: The flat ingot obtained in step (1) is cut off at the head and tail, heated to 950°C, kept at this temperature for 120 minutes for homogenization, and then hot rolled; wherein the single-pass reduction amount is 25%, the total reduction amount is 80%, the strain rate is 0.5 m / s, the final rolling temperature is 700°C, and the temperature is cooled by water quenching to obtain a 15 mm thick slab, which is then coiled for standby use.

[0036] (3) Milling and trimming: The rolled plate obtained in step (2) is milled and trimmed to remove oxides and defects on the surface of the slab. Double-surface milling is performed with a single-side depth of 1 mm and double-side removal with a single-side width of 4 mm.

[0037] (4) Pre-aging: Place the coil obtained in step (3) in a bell-shaped furnace, pass nitrogen protection, heat to 580°C at a rate of 10°C / min, and keep warm for 8 hours. Cool naturally in the furnace and set aside.

[0038] (5) Cold rolling deformation: The slab after the treatment in step (4) is subjected to cold rolling deformation, with a single-pass deformation amount of 20%, a total deformation amount of 95%, and a strain rate of 1 m / s.

[0039] (6) Retrograde heat treatment: The cold-rolled sheet obtained in step (5) is heated to 800°C, protected by nitrogen, and the sheet is retained in the furnace for 3 minutes; after being taken out of the furnace, it is quickly water-quenched and cooled.

[0040] (7) Second aging: The slab obtained in step (6) was placed in a bell-shaped furnace, protected by nitrogen, and heated to 450°C at a rate of 10°C / min, kept at this temperature for 12 hours, and subjected to secondary aging treatment. The slab was then naturally cooled to room temperature in the furnace.

[0041] (8) Surface cleaning: The sheet material obtained in step (7) is cleaned to remove impurities and oxides produced during the aging process and obtain a bright surface.

[0042] (9) Straightening: The sheet obtained in step (8) is straightened and straightened to obtain a flat and bright sheet surface. The obtained Cu-Ni-Si alloy has a tensile strength of 700 MPa, a conductivity of 55% IACS, an elongation of 18%, and does not crack when bent at 90° or folded at 180°. Example

[0043] like Figure 1-4 As shown, this embodiment provides a method for preparing a fine-grained Cu-Ni-Si alloy material, comprising:

[0044] (1) Semi-continuous casting: Prepare raw materials according to the weight percentage of pure copper, pure silicon and pure nickel, Cu93~96%, Si1~1.3%, Ni5~5.5%. After drying and dust removal, put the pure copper into a medium frequency induction furnace for melting. When the temperature rises to 1400℃, keep it warm for 10 minutes, and add pure silicon blocks and pure nickel blocks. After the melt is uniformly stirred by electromagnetic stirring, quickly add slag-making agent to stir and degas and remove slag, and add covering agent to prevent oxidation. Then the melt temperature is controlled at 1200℃, and the ingot blank is obtained by the down-drawing method.

[0045] (2) Hot rolling-online quenching: The flat ingot obtained in step (1) is cut off at the head and tail, heated to 920°C, kept at this temperature for 180 minutes for homogenization, and then hot rolled; wherein the single pass reduction is 20%, the total reduction is 78%, the strain rate is 0.5 m / s, the final rolling temperature is 680°C, and the temperature is lowered by water quenching to obtain a 18 mm thick slab, which is then coiled for later use;

[0046] (3) Milling and trimming: The rolled plate obtained in step (2) is milled and trimmed to remove oxides and defects on the surface of the slab. Double-surface milling is performed with a single-side depth of 1 mm and double-side removal with a single-side width of 4 mm.

[0047] (4) Pre-aging: Place the coil obtained in step (3) in a bell-shaped furnace, pass nitrogen protection, heat to 600°C at a rate of 10°C / min, and keep warm for 8 hours. Cool naturally in the furnace and then set aside;

[0048] (5) Cold rolling deformation: The slab after the treatment in step (4) is subjected to cold rolling deformation, with a single-pass deformation of 15%, a total deformation of 80%, and a strain rate of 1 m / s;

[0049] (6) Retrograde heat treatment: the cold-rolled sheet obtained in step (5) is unfolded and passed through an air cushion furnace with nitrogen protection to prevent oxidation of the sheet; the air cushion furnace temperature is 800°C, and the sheet is retained between the inlet and outlet of the air cushion furnace for 3 minutes; after being taken out of the furnace, it is quickly water quenched and cooled;

[0050] (7) Second aging: The slab obtained in step (6) is placed in a bell-shaped furnace, protected by nitrogen, and heated to 450°C at a rate of 15°C / min, kept at this temperature for 10 hours, and subjected to a secondary aging treatment, and then naturally cooled to room temperature in the furnace;

[0051] (8) Surface cleaning: Clean the surface of the sheet obtained in step (7) to remove impurities and oxides produced during the aging process and obtain a bright surface;

[0052] (9) Straightening: The sheet obtained in step (8) is straightened and straightened to obtain a flat and bright sheet surface. The resulting Cu-Ni-Si alloy has a tensile strength of 750 MPa, a conductivity of 52% IACS, an elongation of 15%, and does not crack when bent at 90° or folded at 180°. Example

[0053] like Figure 1 As shown, this embodiment provides a method for preparing a fine-grained Cu-Ni-Si alloy material, comprising:

[0054] (1) Semi-continuous casting: Prepare raw materials according to the weight percentage of pure copper, pure silicon and pure nickel, Cu93~94%, Si1~1.2% and Ni5~5.5%. After drying and dust removal, put the pure copper into a medium frequency induction furnace for melting. When the temperature rises to 1400℃, keep it warm for 5 minutes, and add pure silicon blocks and pure nickel blocks. After the melt is uniformly stirred by electromagnetic stirring, quickly add slag-making agent to stir and degas and remove slag, and add covering agent to prevent oxidation. Then the melt temperature is controlled at 1200℃, and the ingot blank is obtained by the down-drawing method.

[0055] (2) Hot rolling-online quenching: The flat ingot obtained in step (1) is cut off at the head and tail, heated to 900°C, kept at this temperature for 120 minutes for homogenization, and then hot rolled; wherein the single pass reduction is 25%, the total reduction is 80%, the strain rate is 0.5 m / s, the final rolling temperature is 700°C, and the temperature is lowered by water quenching to obtain a 15 mm thick slab, which is then coiled for later use;

[0056] (3) Milling and trimming: The rolled plate obtained in step (2) is milled and trimmed to remove oxides and defects on the surface of the slab. Double-surface milling is performed with a single-side depth of 1 mm and double-side removal with a single-side width of 4 mm.

[0057] (4) Pre-aging: Place the coil obtained in step (3) in a bell furnace, heat it to 550°C at a rate of 10°C / min, and keep it at this temperature for 10 hours. Cool it naturally in the furnace and then set aside;

[0058] (5) Cold rolling deformation: The slab after the treatment in step (4) is subjected to cold rolling deformation, with a single-pass deformation of 25%, a total deformation of 90%, and a strain rate of 1 m / s;

[0059] (6) Retrograde heat treatment: the cold-rolled sheet obtained in step (5) is unfolded and passed through an air cushion furnace with nitrogen protection to prevent oxidation of the sheet; the air cushion furnace temperature is 850°C, and the sheet is retained between the inlet and outlet of the air cushion furnace for 2 minutes; after being taken out of the furnace, it is quickly water quenched and cooled;

[0060] (7) Second aging: The slab obtained in step (6) is placed in a bell-shaped furnace, protected by nitrogen, and heated to 450°C at a rate of 10°C / min, kept at this temperature for 16 hours, and subjected to a secondary aging treatment, and then naturally cooled to room temperature in the furnace;

[0061] (8) Surface cleaning: Clean the surface of the sheet obtained in step (7) to remove impurities and oxides produced during the aging process and obtain a bright surface;

[0062] (9) Straightening: The sheet obtained in step (8) is straightened and straightened to obtain a flat and bright sheet surface. The obtained Cu-Ni-Si alloy has a tensile strength of 670 MPa, a conductivity of 65% IACS, an elongation of 26%, and does not crack when bent at 90° or folded at 180°. Example

[0063] like Figure 1 As shown, this embodiment provides a method for preparing a fine-grained Cu-Ni-Si alloy material, comprising:

[0064] (1) Semi-continuous casting: Prepare raw materials according to the weight percentage of pure copper, pure silicon and pure nickel, Cu93~94%, Si1~1.2% and Ni5~5.5%. After drying and dust removal, put the pure copper into a medium frequency induction furnace for melting. When the temperature rises to 1400℃, keep it warm for 5 minutes, and add pure silicon blocks and pure nickel blocks. After the melt is uniformly stirred by electromagnetic stirring, quickly add slag-making agent to stir and degas and remove slag, and add covering agent to prevent oxidation. Then the melt temperature is controlled at 1200℃, and the ingot blank is obtained by the down-drawing method.

[0065] (2) Hot rolling-online quenching: The flat ingot obtained in step (1) is cut off at the head and tail, heated to 900°C, kept at this temperature for 120 minutes for homogenization, and then hot rolled; wherein the single pass reduction is 25%, the total reduction is 80%, the strain rate is 0.5 m / s, the final rolling temperature is 700°C, and the temperature is lowered by water quenching to obtain a 15 mm thick slab, which is then coiled for later use;

[0066] (3) Milling and trimming: The rolled plate obtained in step (2) is milled and trimmed to remove oxides and defects on the surface of the slab. Double-surface milling is performed with a single-side depth of 1 mm and double-side removal with a single-side width of 4 mm.

[0067] (4) Pre-aging: Place the coil obtained in step (3) in a bell furnace, heat it to 550°C at a rate of 10°C / min, and keep it at this temperature for 10 hours. Cool it naturally in the furnace and then set aside;

[0068] (5) Cold rolling deformation: The slab after the treatment in step (4) is subjected to cold rolling deformation, with a single-pass deformation of 25%, a total deformation of 90%, and a strain rate of 1 m / s;

[0069] (6) Retrograde heat treatment: the cold-rolled sheet obtained in step (5) is unfolded and passed through an air cushion furnace with nitrogen protection to prevent oxidation of the sheet; the air cushion furnace temperature is 850°C, and the sheet is retained between the inlet and outlet of the air cushion furnace for 2 minutes; after being taken out of the furnace, it is quickly water quenched and cooled;

[0070] (7) Second aging: The slab obtained in step (6) is placed in a bell-shaped furnace, protected by nitrogen, and heated to 450°C at a rate of 10°C / min, kept at this temperature for 16 hours, and subjected to a secondary aging treatment, and then naturally cooled to room temperature in the furnace;

[0071] (8) Cold rolling again: the slab obtained in step (7) is subjected to secondary finishing rolling, with a cold rolling deformation of 50%, a single-pass deformation of 10%, and a strain rate of 1 m / s;

[0072] (9) Surface cleaning: Clean the surface of the sheet obtained in step (8) to remove impurities and oxides produced during the aging process and obtain a bright surface;

[0073] (10) Straightening: The sheet obtained in step (9) is straightened and straightened to obtain a flat and bright sheet surface. The obtained Cu-Ni-Si alloy has a tensile strength of 790 MPa, a conductivity of 50% IACS, an elongation of 7%, and does not crack when bent at 90° or folded at 180°. Example

[0074] like Figure 1 As shown, this embodiment provides a method for preparing a fine-grained Cu-Ni-Si alloy material, comprising:

[0075] (1) Semi-continuous casting: Prepare raw materials according to the weight percentage of pure copper, pure silicon and pure nickel, Cu93~94%, Si1~1.2% and Ni5~5.5%. After drying and dust removal, put the pure copper into a medium frequency induction furnace for melting. When the temperature rises to 1400℃, keep it warm for 5 minutes, and add pure silicon blocks and pure nickel blocks. After the melt is uniformly stirred by electromagnetic stirring, quickly add slag-making agent to stir and degas and remove slag, and add covering agent to prevent oxidation. Then the melt temperature is controlled at 1200℃, and the ingot blank is obtained by the down-drawing method.

[0076] (2) Hot rolling-online quenching: The flat ingot obtained in step (1) is cut off at the head and tail, heated to 900°C, kept at this temperature for 120 minutes for homogenization, and then hot rolled; wherein the single pass reduction is 25%, the total reduction is 80%, the strain rate is 0.5 m / s, the final rolling temperature is 700°C, and the temperature is lowered by water quenching to obtain a 15 mm thick slab, which is then coiled for later use;

[0077] (3) Milling and trimming: The rolled plate obtained in step (2) is milled and trimmed to remove oxides and defects on the surface of the slab. Double-surface milling is performed with a single-side depth of 1 mm and double-side removal with a single-side width of 4 mm.

[0078] (4) Pre-aging: Place the coil obtained in step (3) in a bell furnace, heat it to 550°C at a rate of 10°C / min, and keep it at this temperature for 10 hours. Cool it naturally in the furnace and then set aside;

[0079] (5) Cold rolling deformation: The slab after the treatment in step (4) is subjected to cold rolling deformation, with a single-pass deformation of 25%, a total deformation of 90%, and a strain rate of 1 m / s;

[0080] (6) Retrograde heat treatment: the cold-rolled sheet obtained in step (5) is unfolded and passed through an air cushion furnace with nitrogen protection to prevent oxidation of the sheet; the air cushion furnace temperature is 850°C, and the sheet is retained between the inlet and outlet of the air cushion furnace for 2 minutes; after being taken out of the furnace, it is quickly water quenched and cooled;

[0081] (7) Cold rolling again: The slab obtained in step (6) is subjected to finish rolling again at room temperature, with a rolling deformation of 70%, a single-pass deformation of 10%, and a strain rate of 1 m / s;

[0082] (8) Second aging: The slab obtained in step (7) was placed in a bell-shaped furnace, protected by nitrogen, and heated to 400°C at a rate of 10°C / min, kept at this temperature for 4 hours, and subjected to a secondary aging treatment, and then naturally cooled to room temperature in the furnace;

[0083] (9) Surface cleaning: Clean the surface of the sheet obtained in step (8) to remove impurities and oxides produced during the aging process and obtain a bright surface;

[0084] (10) Straightening: The sheet obtained in step (9) is straightened and straightened to obtain a flat and bright sheet surface. The obtained Cu-Ni-Si alloy has a tensile strength of 780 MPa, a conductivity of 55% IACS, an elongation of 10%, and does not crack when bent at 90° or folded at 180°. Example

[0085] like Figure 1 As shown, this embodiment provides a method for preparing a fine-grained Cu-Ni-Si alloy material, comprising:

[0086] (1) Semi-continuous casting: Prepare raw materials according to the weight percentage of pure copper, pure silicon and pure nickel, Cu93~94%, Si1~1.2% and Ni5~5.5%. After drying and dust removal, put the pure copper into a medium frequency induction furnace for melting. When the temperature rises to 1400℃, keep it warm for 5 minutes, and add pure silicon blocks and pure nickel blocks. After the melt is uniformly stirred by electromagnetic stirring, quickly add slag-making agent to stir and degas and remove slag, and add covering agent to prevent oxidation. Then the melt temperature is controlled at 1200℃, and the ingot blank is obtained by the down-drawing method.

[0087] (2) Hot rolling-online quenching: The flat ingot obtained in step (1) is cut off at the head and tail, heated to 900°C, kept at this temperature for 120 minutes for homogenization, and then hot rolled; wherein the single pass reduction is 25%, the total reduction is 80%, the strain rate is 0.5 m / s, the final rolling temperature is 700°C, and the temperature is lowered by water quenching to obtain a 15 mm thick slab, which is then coiled for later use;

[0088] (3) Milling and trimming: The rolled plate obtained in step (2) is milled and trimmed to remove oxides and defects on the surface of the slab. Double-surface milling is performed with a single-side depth of 1 mm and double-side removal with a single-side width of 4 mm.

[0089] (4) Pre-aging: Place the coil obtained in step (3) in a bell furnace, heat it to 550°C at a rate of 10°C / min, and keep it at this temperature for 10 hours. Cool it naturally in the furnace and then set aside;

[0090] (5) Cold rolling deformation: The slab after the treatment in step (4) is subjected to cold rolling deformation, with a single-pass deformation of 25%, a total deformation of 90%, and a strain rate of 1 m / s;

[0091] (6) Retrograde heat treatment: the cold-rolled sheet obtained in step (5) is unfolded and passed through an air cushion furnace with nitrogen protection to prevent oxidation of the sheet; the air cushion furnace temperature is 850°C, and the sheet is retained between the inlet and outlet of the air cushion furnace for 2 minutes; after being taken out of the furnace, it is quickly water quenched and cooled;

[0092] (7) Second aging: The slab obtained in step (6) is placed in a bell-shaped furnace, protected by nitrogen, and heated to 450°C at a rate of 10°C / min, kept at this temperature for 16 hours, and subjected to a secondary aging treatment, and then naturally cooled to room temperature in the furnace;

[0093] (8) Cold rolling again: The slab obtained in step (7) is subjected to finish rolling again at room temperature, with a rolling deformation of 50%, a single-pass deformation of 10%, and a strain rate of 1 m / s;

[0094] (9) Three-stage aging: The slab obtained in step (8) was placed in a bell-shaped furnace, protected by nitrogen, and heated to 375°C at a rate of 10°C / min, kept at this temperature for 8 hours, and subjected to three-stage aging treatment, and then naturally cooled to room temperature in the furnace;

[0095] (10) Three-pass cold rolling: The slab obtained in step (9) is subjected to finish rolling again at room temperature, with a rolling deformation of 50%, a single-pass deformation of 10%, and a strain rate of 1 m / s;

[0096] (11) Surface cleaning: Clean the surface of the sheet obtained in step (10) to remove impurities and oxides produced during the aging process and obtain a bright surface;

[0097] (12) Straightening: The sheet obtained in step (11) is straightened and straightened to obtain a flat and bright sheet surface. The obtained Cu-Ni-Si alloy has a tensile strength of 860 MPa, a conductivity of 55% IACS, an elongation of 3%, and does not crack when bent at 90° or folded at 180°.

[0098] The present invention also provides a fine-grained Cu-Ni-Si alloy material, which is prepared using the method for preparing the fine-grained Cu-Ni-Si alloy material as described above. The Cu-Ni-Si alloy material contains 3.0 to 6.0% by weight of Ni, 0.5 to 1.5% by weight of Si, and the balance is Cu and unavoidable impurity elements. The average grain size is less than 3 μm. When the tensile strength is 750 MPa, the elongation can reach 15%, and the electrical conductivity can reach 52% IACS.

[0099] The difference between the present invention and the traditional process is:

[0100] The present invention adds steps such as pre-aging treatment, large deformation cold rolling, high-temperature short-time regression treatment and re-aging treatment; the present invention introduces second-phase particles through pre-aging and fully utilizes their pinning effect on grain boundaries to hinder the occurrence of recrystallization, so that the material has higher strength and better electrical conductivity; the present invention, under the premise of fully considering the capacity of production equipment and based on the characteristics of the material itself under different process conditions, designs a new process combination and process parameters that are easy to achieve in practice, which is conducive to realizing large-scale industrial production.

[0101] The present invention is accomplished based on such recognition:

[0102] First, for the ingots obtained by semi-continuous casting, the present invention reduces the requirements for the final rolling temperature and cooling intensity of the hot rolling online quenching. The theoretical solid solution temperature of Cu-Ni-Si alloy is relatively high. When the nickel content is ≥3.0%, the solid solution temperature needs to exceed 850°C. For large ingots, there are actually more hot rolling passes, and the ingot inevitably cools during the hot rolling process. As the thickness of the ingot decreases, its length stretches and elongates, making it difficult to return to the furnace and reheat again. The thickness of the slab after hot rolling is generally 12~18mm. These factors make it difficult to ensure that the ideal supersaturated solid solution is obtained in the final rolling temperature and cooling intensity of the online quenching process. Therefore, relaxing the process requirements for hot rolling online quenching is more in line with production practice; on the other hand, the precipitation of a portion of Ni2Si second phase during hot rolling is beneficial to suppressing the occurrence of discontinuous precipitation during the pre-aging process.

[0103] Secondly, the present invention incorporates a pre-aging process that exceeds the aging state before cold deformation. Introducing second-phase particles before cold rolling fully utilizes the interaction between dislocations and the second-phase particles, resulting in more uniform deformation, higher dislocation density, and a denser and smaller substructure, such as dislocation cells. Furthermore, the second-phase particles hinder recovery and recrystallization processes in the copper matrix, contributing to higher deformation energy storage and finer grains. Long-term aging of Cu-Ni-Si alloys at high temperatures (>400°C) can cause overaging due to the ripening of the second-phase particles, leading to a significant drop in hardness from its peak value. Given that higher material hardness places greater demands on cold rolling mill capacity, setting the pre-aging process to the overaging state not only preserves some of the second phase's contribution to cold deformation, but also fully utilizes the overaging softening phenomenon, reducing the requirements on cold rolling equipment capacity. Furthermore, the overaging state allows ample time for uniform heating of the material, facilitating practical operation.

[0104] The present invention introduces the "regression-re-aging" process widely used in aluminum alloys to obtain fine-grained Cu-Ni-Si alloys with good comprehensive performance. The thickness of the slab becomes thinner after cold rolling deformation. During the regression process, the material is quickly heated to below the solid solution temperature and kept warm for a short time. At this time, the deformation stored energy is partially released, some second-phase particles dissolve back, causing the solid solubility of the copper matrix to increase, while other second-phase particles continue to grow and act as obstacle particles to prevent the growth of recrystallized grains. Partial recrystallization occurs in the material as a whole, effectively obtaining fine grains. Thinner cold-rolled slabs can be heated and cooled rapidly, which is beneficial for obtaining smaller grain size and higher supersaturated solid solubility. In the subsequent re-aging process, the remaining deformation stored energy continues to be released, combined with the supersaturated solid solubility to drive the re-precipitation of the Ni2Si second phase, and the electrical conductivity and hardness of the material increase. Compared to traditional processes, the alloy's initial electrical conductivity is higher because some second-phase particles have already precipitated before aging. Furthermore, the material retains some deformation energy after the regression process, which promotes the precipitation of the Ni2Si second phase. Furthermore, the remaining second-phase particles in the regression process continue to hinder recrystallization, delaying the alloy's over-aging softening during re-aging. This ensures that the alloy maintains good electrical conductivity while achieving high strength.

[0105] Therefore, under the premise that the process parameters are achievable, the present invention proposes a combined process condition, which can ensure that the Cu-Ni-Si alloy has higher strength while obtaining higher conductivity, finer grain size and higher elongation than the traditional process.

[0106] It should be noted that, in this document, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, apparatus, article, or method comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, apparatus, article, or method. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, apparatus, article, or method comprising the element.

[0107] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the contents of the present invention description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing a fine-grained Cu-Ni-Si alloy material, characterized in that: include: (1) Semi-continuous casting: Prepare the raw materials. First, put pure copper into a medium frequency induction furnace to melt. When the temperature rises to 1350~1450℃, keep it warm and add pure silicon blocks. After the silicon melts, add pure nickel. After the melt is uniformly stirred by electromagnetic stirring, quickly add slag-making agent to stir and degas and remove slag. Then add covering agent to prevent oxidation. Control the melt temperature to maintain at 1200~1250℃. During casting, the melt is introduced into the crystallizer through the launder and the ingot is obtained by pulling it downward. (2) Hot rolling-online quenching: the ingot obtained in step (1) is cut off at the head and tail, and heated to 900-950°C, kept at this temperature for 60-240 min for homogenization, and then immediately hot rolled to a thickness of 12-18 mm, with a final rolling temperature of 680-780°C, and water quenched online to obtain a slab, which is then coiled for standby use; wherein the single-pass reduction is ≥15%, the total rolling amount is ≥70%, the rolling speed is 0.1-1 m / s, the quenching cooling intensity is ≥20°C / s, and the composition difference between the head and tail of the ingot is <2%; (3) Milling: The rolled plate obtained in step (2) is subjected to milling treatment to remove oxides and defects on the surface of the slab; (4) Pre-aging: The coil obtained in step (3) is heated to 580-620°C for pre-aging treatment, kept at this temperature for 5-24 hours, and then cooled naturally with the furnace for standby use; A protective atmosphere is used to prevent oxidation of the alloy surface. After a set time of pre-aging, the Cu-Ni-Si alloy is in an over-aged state, and its Vickers hardness is less than 190HV. (5) Cold rolling deformation: cold rolling deformation is performed on the coil after the treatment in step (4), and the rolling deformation amount is greater than 70%; (6) Retrograde heat treatment: the cold-rolled slab obtained in step (5) is heated to 800-850°C, kept at this temperature for 10 seconds to 5 minutes, and then subjected to water quenching treatment; the maximum heating temperature during the retrograde process is lower than the theoretical solution temperature of the Cu-Ni-Si alloy; the thickness of the alloy slab during the retrograde treatment is less than 1.5 mm; the alloy is protected by an inert gas to prevent oxidation, the material heating rate is greater than 100°C / min, and the quenching cooling intensity is ≥100°C / s; (7) Re-aging or a combination of re-aging and cold deformation: heating the slab obtained in step (6) to 350-450°C, keeping the temperature for 4-16 hours, and performing re-aging treatment, followed by natural cooling to room temperature; or performing a combined thermomechanical treatment consisting of re-aging and cold rolling deformation on the slab obtained in step (6); The material heating rate is 10-50°C / min; the combined thermomechanical treatment includes a combination of "cold rolling → aging", "aging → cold rolling", "cold rolling → aging → cold rolling → aging", and "aging → cold rolling → aging → cold rolling", wherein the aging temperature is 350-450°C, the aging time is 30-240 minutes, and the cold rolling deformation is ≥50%, wherein the cold rolling deformation sacrifices the set elongation to obtain higher alloy strength; (8) Surface cleaning: Clean the surface of the slab obtained in step (7) to remove oxides generated during the aging process and obtain a bright surface; (9) Straightening: The slab obtained in step (8) is straightened and straightened to obtain a Cu-Ni-Si alloy material.

2. The method for preparing a fine-grained Cu-Ni-Si alloy material according to claim 1, characterized in that: The weight ratio of Ni element to Si element contained in the obtained Cu-Ni-Si alloy material is 4.1-4.

2.

3. The method for preparing a fine-grained Cu-Ni-Si alloy material according to claim 1, characterized in that: In step (1), the furnace, launder, crystallizer and bottom plate are fully dried before smelting; the pure copper, pure nickel and pure silicon materials used are cleaned and dried; and the composition of the melt alloy is tested and supplemented online before casting.

4. The method for preparing a fine-grained Cu-Ni-Si alloy material according to claim 1, characterized in that: In step (5), the alloy is subjected to large deformation cold rolling, where the single cold rolling deformation is greater than 15% and the cold rolling rate is greater than or equal to 0.1 m / s.

5. A fine-grained Cu-Ni-Si alloy material, characterized in that: The Cu-Ni-Si alloy material prepared by the preparation method of the fine-grained Cu-Ni-Si alloy material according to any one of claims 1 to 4 contains 3.0 to 6.0% by weight of Ni, 0.5 to 1.5% by weight of Si, and the balance is Cu and unavoidable impurity elements, and has an average grain size of less than 3 μm. When the tensile strength is 750 MPa, the elongation is 15%, and the electrical conductivity is 52% IACS.

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