A low-oxygen high-temperature sintered oxygen-free copper ingot and production method

Abstract

The present application relates to the technical field of oxygen-free copper ingot production, specifically a low-oxygen, high-temperature sintered oxygen-free copper ingot and a production method. The ingot has an elongation of more than 45% after sintering and is used to manufacture thick-walled heat pipes with a wall thickness of ≥0.4 mm. The heat pipe has a fine and uniform grain structure after sintering, which can avoid grain boundary cracking and leakage during the forming process. The present invention adds a specific proportion of Ni-Nb intermediate alloy during the preparation process of the copper ingot, and utilizes the characteristics of the Nb element's atomic radius being larger than copper and having a higher melting point to inhibit the excessive growth of copper grains during the sintering process, thereby obtaining a fine and uniform grain structure, significantly improving the elongation of the copper ingot, improving the material's forming performance, and ensuring the uniform distribution of the Ni-Nb alloy element in the copper matrix; it can effectively solve the quality problems of existing thick-walled heat pipes such as bending leakage, flattening depression, and cracking that are prone to occur during the forming process.

Description

Technical Field

[0001] The present application relates to the technical field of oxygen-free copper ingot production, and specifically to a low-oxygen, high-temperature sintered oxygen-free copper ingot and a production method. Background Art

[0002] Heat pipes are highly efficient heat transfer components widely used in devices requiring efficient heat conduction and dissipation, such as computer CPU coolers, laptop computers, and various industrial and electronic devices. They operate based on the principle of phase-change heat transfer, where the internal working medium absorbs heat in the evaporation stage, transforms into vapor, and then moves to the condensation stage, releasing heat and returning to liquid.

[0003] In existing technology, thick-walled heat pipes are primarily made of pure copper. However, during the high-temperature sintering process, pure copper tends to develop coarse and unevenly sized grains. This uneven grain structure leads to uneven forces acting on different grains during subsequent forming processes (such as bending and flattening), which can easily lead to quality issues such as cracking and leakage at grain boundaries. This poses significant risks to product use and can cause serious economic losses.

[0004] This is because different grains are heated unevenly during the sintering process, resulting in inconsistent grain growth rates. This uneven grain growth is particularly pronounced in existing pure copper pipes, posing a significant risk to subsequent use. Effectively controlling copper grain growth during high-temperature sintering has become a key technical challenge in addressing the quality issues associated with thick-walled heat pipes. Summary of the Invention

[0005] The technical problem to be solved by this application is to overcome the existing defects and provide a low-oxygen, high-temperature sintering oxygen-free copper ingot and production method, so as to solve the technical problem that the existing pure copper material is prone to coarse and uneven grains during high-temperature sintering, thereby avoiding quality problems such as bending, leakage, flattening, and cracking of thick-walled heat pipes during the subsequent forming process, and can effectively solve the problems in the background technology.

[0006] To achieve the above objectives, this application provides the following technical solutions:

[0007] A method for producing a low-oxygen, high-temperature-resistant, sintered oxygen-free copper ingot comprises the following steps:

[0008] S1) Ingredients: Use Grade A electrolytic copper plates, adding 3500 kg per heat. Before adding the copper plates, add 0.15 kg of Ni-Nb master alloy per heat into the furnace. The Ni-Nb master alloy has a Nb content of 33.8-37.8% by weight, with the remainder being Ni.

[0009] S2) Melting: Melting is carried out in an induction furnace at a temperature of 1140-1220°C. After all the copper plates are melted, the next step of refining is carried out;

[0010] S3) Refining: Deoxidize, degas, and purify the copper liquid by adding 0.2 kg of P-Cu (phosphorus content of 14%) and 0.3 kg of B-Cu (B content of 5%) per heat for deoxidation and degassing;

[0011] S4) Standing: Allow the slag produced by refining to float out due to the density difference with the copper liquid. The standing time is 15-25 minutes.

[0012] S5) Slag removal: Use graphite tools to remove the charcoal and slag covering the surface of the copper liquid. At the same time, add calcined charcoal and evenly cover the surface of the copper liquid to a thickness of not less than 200mm.

[0013] S6) Casting: A copper ingot with an outer diameter of 320 mm was cast using a vertical semi-continuous casting process at a casting temperature of 1170-1180° C. During the casting process, argon gas was kept in the furnace for protection at a flow rate of 20-400 L / min.

[0014] As an optimal technical solution of the present application, the cooling process in the casting step includes: the initial small water cooling water flow rate is 40-60L / min; the casting cooling water flow rate after stabilization is 120-140L / min; the cooling water flow rate from the end of casting to the casting stop stage is 120L / min.

[0015] As a preferred technical solution of the present application, the casting speed in the casting step includes: the initial casting speed is 15-20 mm / min; the stable casting speed is not more than 60 mm / min; the casting speed from the end of casting to the casting stop stage is 25 mm / min.

[0016] As a preferred technical solution of the present application, the melting point of the Ni-Nb master alloy is close to the melting temperature of the copper liquid, and the melting point is 1280°C-1300°C.

[0017] As a preferred technical solution of the present application, the atomic radius of the Ni element is 126 pm, and it is infinitely miscible with the copper element, and serves as a companion element to assist the dissolution of the Nb element.

[0018] A low-oxygen, high-temperature-resistant, sintered oxygen-free copper ingot, wherein the elongation of the ingot after sintering reaches more than 45%.

[0019] As an optimal technical solution of the present application, it is used to manufacture thick-walled heat pipes with a wall thickness of ≥0.4 mm.

[0020] As a preferred technical solution of the present application, the heat pipe has a fine and uniform grain structure after sintering, which can avoid grain boundary cracking and leakage during the molding process.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] The present invention solves the problem that elemental Nb is difficult to dissolve in copper liquid due to its high melting point by adding a trace alloying element Nb during the casting process and using Ni as a companion element to prepare a Ni-Nb master alloy, thereby improving product performance as follows:

[0023] 1. Effectively refines the grain structure and improves material properties: Due to its large atomic radius and high melting point, Nb forms a barrier between copper unit cells, effectively inhibiting excessive copper grain growth during high-temperature sintering. Metallographic analysis shows that copper ingots with Nb addition exhibit a fine and uniform grain structure after sintering, significantly superior to pure copper without Nb addition.

[0024] 2. Significantly Improved Elongation, Enhanced Ductility and Toughness: Tests in the examples show that copper ingots with an appropriate amount of Nb (15-21.4 ppm) added to them achieve an elongation of 46.3%-48.1% after sintering, significantly exceeding the 28.7% achieved by pure copper in the comparative example. This invention effectively enhances the plasticity and processing properties of copper, making it more suitable for applications requiring high ductility, such as heat pipe mother tubes.

[0025] 3. Optimizing alloy addition methods to achieve stable industrial production: Using a Ni-Nb master alloy for addition not only lowers the alloy's melting point, enabling smooth dissolution in molten copper, but also improves the uniformity of alloy element distribution. Combined with precisely controlled melting, refining, settling, slagging, and casting process parameters, this ensures stability and repeatability for large-scale industrial production.

[0026] 4. Good crack resistance and processing adaptability: The comparative sample showed obvious cracking in the bending test, while the sample of the embodiment of the present invention showed excellent crack resistance, which further verified its excellent mechanical properties and processing adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the metallographic structure diagram of the Ni-Nb-free alloy in Example 4;

[0028] Figure 2 This is the cracking diagram of the heat pipe without Ni-Nb alloy after bending;

[0029] Figure 3 The metallographic structure diagram of the Ni-Nb alloy in Example 1;

[0030] Figure 4 The metallographic structure diagram of the Ni-Nb alloy in Example 2;

[0031] Figure 5 This is the metallographic structure diagram of the Ni-Nb alloy in Example 3. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0033] The present invention analyzes the mechanism of copper grain growth and adds trace alloying elements during the casting process to inhibit excessive growth of copper grains during high-temperature sintering. Specifically, the present invention selects Nb as the main additive element for the following reasons:

[0034] 1) The atomic radius of Nb (146 pm) is larger than that of copper (128 pm), and it can exist between copper unit cells;

[0035] 2) Nb element has a high melting point (2468℃), which is much higher than the sintering temperature of copper. As a high melting point substance, it can effectively hinder the growth of copper grains during sintering.

[0036] However, since the melting point of pure Nb is too high, much higher than the casting temperature of pure copper (1180-1200℃), if the elemental Nb is directly added during the casting process, it cannot be effectively dissolved. Therefore, the present invention selects Ni as a concomitant element to prepare a Ni-Nb master alloy. The reasons for selecting Ni are:

[0037] 1) The atomic radius of Ni (126 pm) is close to that of copper, and its properties are infinitely miscible with copper;

[0038] 2) By preparing a Ni-Nb alloy with an appropriate composition ratio, the melting point can be lowered to be close to the casting temperature of copper, so that it can be smoothly dissolved in the copper liquid.

[0039] By searching the Ni-Nb alloy phase diagram, the present invention selects the element content corresponding to 1290°C near the eutectic line (close to the melting temperature of copper alloy) as the preferred ratio, that is, the Nb content is between 33.8-37.8%, and the rest is Ni. Example 1

[0040] A method for producing a low-oxygen, high-temperature-resistant sintered oxygen-free copper ingot, comprising the following steps:

[0041] S1) Ingredients: Use Grade A electrolytic copper plates, adding 3500 kg per heat. Before adding the copper plates, add 0.15 kg of Ni-Nb master alloy (Nb weight content is 35%) per heat into the furnace;

[0042] S2) Melting: Melting is carried out in an induction furnace with the melting temperature controlled at 1180°C. After all the copper plates are melted, the next step of refining is carried out;

[0043] S3) Refining: Deoxidizing, degassing and purifying the copper liquid by adding 0.2 kg of P-Cu (phosphorus content is 14% by weight) and 0.3 kg of B-Cu (B content is 5% by weight) per heat for deoxidation and degassing;

[0044] S4) standing: the slag produced by the refining is allowed to float out by utilizing the density difference with the copper liquid, and the standing time is 20 minutes;

[0045] S5) Slag removal: Use graphite tools to remove the charcoal and slag covering the surface of the copper liquid, and add calcined charcoal and evenly cover the surface of the copper liquid to a thickness of 250mm;

[0046] S6) Casting: Copper ingots with an outer diameter of 320 mm were cast using a vertical semi-continuous casting process at a casting temperature of 1175°C. The cooling water flow rate was as follows: 50 L / min for the initial run; 130 L / min for the stabilization phase; and 120 L / min for the final casting phase until the casting was stopped. Casting speeds were as follows: 18 mm / min for the initial run; 55 mm / min for the stabilization phase; and 25 mm / min for the final casting phase until the casting was stopped. The furnace was protected by argon gas at a flow rate of 200 L / min throughout the casting process.

[0047] The Nb content of the copper ingot prepared according to the above process is about 15 ppm (calculated as: 0.15 kg × 35% ÷ 3500 kg × 10^6 = 15 ppm). The ingot is then made into a heat pipe mother tube with a specification of 10 × 1 mm and sintered.

[0048] The grain structure was observed by metallographic analysis, such as Figure 3 As shown in the figure, it can be seen that the grains are small and uniform. The elongation test result is 46.3%, which is much higher than the 28.7% of the pure copper material in the control group. Example 2

[0049] A method for producing a low-oxygen, high-temperature-resistant sintered oxygen-free copper ingot, comprising the following steps:

[0050] S1) Ingredients: Use Grade A electrolytic copper plates, adding 3500 kg per heat. Before adding the copper plates, add 0.18 kg of Ni-Nb master alloy (Nb weight content is 36%) per heat into the furnace;

[0051] S2) Melting: Melting is carried out in an induction furnace with the melting temperature controlled at 1170°C. After all the copper plates are melted, the next step of refining is carried out;

[0052] S3) Refining: Deoxidizing, degassing and purifying the copper liquid by adding 0.22 kg of P-Cu (phosphorus content is 14% by weight) and 0.32 kg of B-Cu (B content is 5% by weight) per heat for deoxidation and degassing;

[0053] S4) standing: the slag produced by the refining is allowed to float out by utilizing the density difference with the copper liquid, and the standing time is 18 minutes;

[0054] S5) Slag removal: Use graphite tools to remove the charcoal and slag covering the surface of the copper liquid, and add calcined charcoal and evenly cover the surface of the copper liquid to a thickness of 230 mm;

[0055] S6) Casting: Copper ingots with an outer diameter of 320 mm were cast using a vertical semi-continuous casting process at a casting temperature of 1175°C. The cooling water flow rate was as follows: 45 L / min for the initial run; 125 L / min after stabilization; and 120 L / min from the end of the casting process to the end of the casting process. The casting speeds were: 17 mm / min for the initial run, 50 mm / min for the steady state run, and 25 mm / min from the end of the casting process to the end of the casting process. The furnace was protected by argon gas at a flow rate of 180 L / min throughout the casting process.

[0056] The Nb content of the copper ingot prepared according to the above process is approximately 18.5 ppm (calculated as: 0.18 kg × 36% ÷ 3500 kg × 10^6 = 18.5 ppm). The ingot is then made into a heat pipe mother tube with a specification of Φ12 × 1.2 mm and sintered.

[0057] The grain structure was observed by metallographic analysis, such as Figure 4 As shown in the figure, it can be seen that the grains are small and uniform. The elongation test result is 47.8%. Example 3

[0058] A method for producing a low-oxygen, high-temperature-resistant sintered oxygen-free copper ingot, comprising the following steps:

[0059] S1) Ingredients: Use Grade A electrolytic copper plates, adding 3500 kg per heat. Before adding the copper plates, add 0.20 kg of Ni-Nb master alloy (Nb weight content is 37.5%) per heat into the furnace;

[0060] S2) Melting: Melting is carried out in an induction furnace with the melting temperature controlled at 1190°C. After all the copper plates are melted, the next step of refining is carried out;

[0061] S3) Refining: Deoxidizing, degassing and purifying the copper liquid by adding 0.25 kg of P-Cu (phosphorus content is 14% by weight) and 0.35 kg of B-Cu (B content is 5% by weight) per heat for deoxidation and degassing;

[0062] S4) standing: the slag produced by the refining is allowed to float out by utilizing the density difference with the copper liquid, and the standing time is 22 minutes;

[0063] S5) Slag removal: Use graphite tools to remove the charcoal and slag covering the surface of the copper liquid, and add calcined charcoal and evenly cover the surface of the copper liquid to a thickness of 260 mm;

[0064] S6) Casting: Copper ingots with an outer diameter of 320 mm were cast using a vertical semi-continuous casting process at a casting temperature of 1180°C. The cooling water flow rate was as follows: 55 L / min at the initial low-flow stage; 135 L / min after stabilization; and 120 L / min from the end of casting to the end of casting. Casting speeds were as follows: 19 mm / min at the initial stage; 58 mm / min at the steady-state stage; and 25 mm / min from the end of casting to the end of casting. Throughout the casting process, the furnace was protected by argon gas at a flow rate of 250 L / min.

[0065] The Nb content of the copper ingot prepared according to the above process is approximately 21.4 ppm (calculated as: 0.20 kg × 37.5% ÷ 3500 kg × 10^6 = 21.4 ppm). The ingot is then made into a heat pipe mother tube with a specification of Φ15 × 1.5 mm and sintered.

[0066] The grain structure was observed by metallographic analysis, such as Figure 5 As shown in the figure, it can be seen that the grains are small and uniform. The elongation test result is 48.1%.

[0067] Comparative Example 4

[0068] In order to verify the technical effect of the present invention, a set of comparative examples was set up, using the same equipment and operating conditions to prepare pure copper ingots without adding any Ni-Nb master alloy, and the other process parameters were the same as those in Example 1.

[0069] The pure copper ingot of the comparative example was prepared into a heat pipe mother tube with a specification of Φ10×1mm. After sintering under the same conditions, its grain structure was observed by metallographic analysis. Figure 1 As shown in the figure, it can be seen that the grains are coarse and uneven in size. The elongation test result is only 28.7%, which is much lower than the test result in the embodiment of the present invention. In addition, it was observed through the bending test that Figure 2 As shown, the comparative sample is prone to cracking during the bending process.

[0070] Table 1 is a comparison of the process parameters and test results of each embodiment and comparative example:

[0071] Sample number Ni-Nb alloy addition amount (kg) Nb content (ppm) Melting temperature (℃) Elongation (%) Grain structure Example 1 0.15 15.0 1180 46.3 Small and uniform Example 2 0.18 18.5 1170 47.8 Small and uniform Example 3 0.20 21.4 1190 48.1 Small and uniform Example 4 0 0 1180 28.7 Coarse and uneven

[0072] The comparison results in Table 1 demonstrate that the present invention, by adding an appropriate amount of Ni-Nb master alloy to achieve a specific Nb content in the copper ingot, effectively improves the copper material's grain structure after high-temperature sintering, maintaining a fine and uniform grain structure and significantly increasing the material's elongation. Specifically, when the Nb content is within the range of 15-25 ppm, the copper material's elongation reaches over 45%, significantly exceeding the 28.7% of pure copper.

[0073] Although the embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for producing a low-oxygen, high-temperature sintered oxygen-free copper ingot, characterized in that: The specific steps include: S1) Ingredients: Use Grade A electrolytic copper plates, adding 3500 kg per heat. Before adding the copper plates, add 0.15 kg of Ni-Nb master alloy per heat into the furnace. The Ni-Nb master alloy has a Nb content of 33.8-37.8% by weight, with the remainder being Ni. S2) Melting: Melting is carried out in an induction furnace at a temperature of 1140-1220°C. After all the copper plates are melted, the next step of refining is carried out; S3) Refining: Deoxidize, degas, and purify the copper liquid by adding 0.2 kg of P-Cu and 0.3 kg of B-Cu per heat for deoxidation and degassing; S4) Standing: Allow the slag produced by refining to float out due to the density difference with the copper liquid. The standing time is 15-25 minutes. S5) Slag removal: Use graphite tools to remove the charcoal and slag covering the surface of the copper liquid. At the same time, add calcined charcoal and evenly cover the surface of the copper liquid to a thickness of not less than 200mm. S6) Casting: A copper ingot with an outer diameter of 320 mm is cast using a vertical semi-continuous casting process at a casting temperature of 1170-1180° C. During the casting process, the furnace is protected by argon gas at a flow rate of 20-400 L / min.

2. The method for producing a low-oxygen, high-temperature-resistant, sintered oxygen-free copper ingot according to claim 1, characterized in that: It also includes a cooling process in the casting step, which includes: an initial small water cooling water flow rate of 40-60L / min; a casting cooling water flow rate of 120-140L / min after stabilization; and a cooling water flow rate of 120L / min from the end of casting to the casting stop stage.

3. The method for producing a low-oxygen, high-temperature-resistant, sintered oxygen-free copper ingot according to claim 1, characterized in that: The method also includes a casting speed in the casting step, wherein the casting speed includes: an initial casting speed of 15-20 mm / min; a stable casting speed of no more than 60 mm / min; and a casting speed of 25 mm / min from the end of casting to the casting stop stage.

4. The method for producing a low-oxygen, high-temperature-resistant, sintered oxygen-free copper ingot according to claim 1, wherein: The melting point of the Ni-Nb master alloy is close to the melting temperature of copper liquid, and the melting point is 1280°C-1300°C.

5. The method for producing a low-oxygen, high-temperature-resistant, sintered oxygen-free copper ingot according to claim 1, characterized in that: The atomic radius of the Ni element is 126 pm, and it is infinitely miscible with the copper element, and acts as a companion element to assist the dissolution of the Nb element.

6. A low-oxygen, high-temperature sintered oxygen-free copper ingot, characterized in that: The low-oxygen, high-temperature-resistant, sintered oxygen-free copper ingot produced by the method according to any one of claims 1 to 5 has an elongation of more than 45% after sintering.

7. The low-oxygen, high-temperature-resistant, sintered oxygen-free copper ingot according to claim 6, characterized in that: Used to manufacture thick-walled heat pipes with a wall thickness of ≥0.4mm.

8. The low-oxygen, high-temperature-resistant, sintered oxygen-free copper ingot according to claim 7, characterized in that: The heat pipe has a fine and uniform grain structure after sintering, which can avoid grain boundary cracking and leakage during the molding process.

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