Low-oxygen high-temperature-sintering-resistant oxygen-free copper cast ingot and production method

Abstract

The invention relates to the technical field of oxygen-free copper cast ingot production, in particular to a low-oxygen high-temperature-sintering-resistant oxygen-free copper cast ingot and a production method, the elongation rate of the cast ingot after sintering reaches 45% or above, the cast ingot is used for manufacturing a thick-wall heat pipe with the wall thickness larger than or equal to 0.4 mm, and the heat pipe has a fine and uniform grain structure after being sintered; according to the method, Ni-Nb intermediate alloy with a specific proportion is added in the preparation process of the copper cast ingot, the characteristic that the atomic radius of the Nb element is larger than that of copper and the Nb element has a high melting point is utilized, overgrowth of copper grains can be restrained in the sintering process of the copper cast ingot, and therefore a fine and uniform grain structure is obtained; the elongation of a copper ingot is remarkably improved, the forming performance of the material is improved, and it is ensured that Ni-Nb alloy elements are evenly distributed in a copper matrix; and the quality problems of bending leakage, flattening sinking, cracking and the like easily occurring in the forming process of an existing thick-wall heat pipe can be effectively solved.

Description

Technical Field

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

[0002] A heat pipe is an efficient heat conduction element, which is widely used in devices that require efficient heat conduction and dissipation, such as the CPU radiator of a computer, the interior of a laptop computer, and various industrial and electronic devices. It works based on the principle of phase change heat transfer. The working medium inside absorbs heat in the evaporation section and turns into steam, and then moves to the condensation section to release heat and turn back into liquid to achieve rapid heat transfer.

[0003] In the prior art, thick-walled heat pipes are mainly made of pure copper materials. However, during the high-temperature sintering process, the pure copper material is prone to the phenomenon of large and uneven grain size. This non-uniformity of the grain structure causes quality problems such as cracking and leakage at the grain boundaries during subsequent forming processes (such as bending and flattening), which brings great risks to the use of the product and causes serious economic losses.

[0004] This is because during the sintering process, different grains are heated unevenly, resulting in inconsistent grain growth rates. In existing pure copper pipes, this non-uniformity of grain growth is particularly obvious, bringing great risks to subsequent use. Effectively controlling the grain growth of copper materials under high-temperature sintering conditions has become a key technical challenge to solve the quality problems of thick-walled heat pipes. Summary of the Invention

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

[0006] To achieve the above object, the present application provides the following technical solution: A production method of a low-oxygen high-temperature resistant sintered oxygen-free copper ingot, specifically including the following steps:

[0007] S1) Batching: Use A-grade electrolytic copper plates, with an addition amount of 3500 tons per furnace. At the same time, before adding the copper plates, proportion 0.15 kg of Ni-Nb master alloy per furnace and add it into the furnace. The weight content of Nb in the Ni-Nb master alloy is 33.8 - 37.8%, and the rest is Ni element;

[0008] S2) Melting: Use an induction furnace for melting, with a melting temperature of 1140 - 1220 °C. After all the copper plates are melted, proceed to the next refining treatment;

[0009] S3) Refining: Deoxidize, degas and purify the copper liquid. The method is to add 0.2 kg of P-Cu (weight content of phosphorus is 14%) and 0.3 kg of B-Cu (weight content of B is 5%) for each furnace charge to carry out deoxidation and degassing operations;

[0010] S4) Standing: Let the slag phase generated by refining float out by using the density difference with the copper liquid, and the standing time is 15 - 25 min;

[0011] S5) Skimming the slag: Use a graphite tool to fish out the covering charcoal and slag phase on the surface of the copper liquid, and at the same time add calcined charcoal and evenly cover it on the surface of the copper liquid, with the covering thickness not less than 200 mm;

[0012] S6) Casting: Cast a copper ingot with an outer diameter of 320 mm by vertical semi - continuous casting process. The casting temperature is 1170 - 1180 °C, and keep argon protection in the furnace during casting, with the flow rate of 20 - 400 L / min.

[0013] As a preferred technical solution of this application, it also includes the cooling process in the casting step. The cooling process includes: the initial small - water cooling water flow rate is 40 - 60 L / min; after stabilization, the casting cooling water flow rate is 120 - 140 L / min; the cooling water flow rate from the end of casting to the stop of casting is 120 L / min.

[0014] As a preferred technical solution of this application, it also includes the casting speed in the casting step. The casting speed includes: the initial casting speed is 15 - 20 mm / min; the stable casting speed is not greater than 60 mm / min; the casting speed from the end of casting to the stop of casting is 25 mm / min.

[0015] As a preferred technical solution of this application, the added Ni - Nb master alloy controls the Nb element content in the final ingot to be 15 - 25 ppm.

[0016] As a preferred technical solution of this 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 this application, the atomic radius of the Ni element is 126 pm, and it is in an infinitely miscible state with the copper element, and serves as an accompanying element to assist the dissolution of the Nb element.

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

[0019] As a preferred technical solution of this application, it is used to manufacture thick - wall heat pipes with a wall thickness ≥ 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 forming process.

[0021] Compared with the prior art, the beneficial effects of the present application are as follows:

[0022] In the present invention, by adding a trace amount of alloy element Nb during the casting process and using Ni as a companion element to prepare a Ni-Nb master alloy, the problem that elemental Nb is difficult to dissolve in the copper melt due to its too high melting point is solved, and the product performance is improved, specifically as follows:

[0023] 1. Effectively refine the grain structure and improve the material properties: Due to its large atomic radius and high melting point characteristics, the Nb element forms an obstacle between the copper unit cells, effectively inhibiting the excessive growth of copper grains during the high-temperature sintering process. The metallographic analysis results show that the copper ingot after adding Nb presents a fine and uniform grain structure after sintering, which is significantly better than the pure copper material without addition.

[0024] 2. Significantly improve the elongation rate and enhance the ductility and toughness of the material: It can be known from the test of the examples that the elongation rate of the copper ingot added with an appropriate amount of Nb element (15 - 21.4 ppm) can reach 46.3% - 48.1% after sintering, which is much higher than 28.7% of the pure copper material in the comparative example. The present invention effectively improves the plasticity and processing performance of the copper material, making it more suitable for applications with higher ductility requirements such as the heat pipe mother tube.

[0025] 3. Optimize the alloy addition method and achieve stable industrial production: Adding in the form of Ni-Nb master alloy not only reduces the melting point of the alloy, enabling it to be smoothly dissolved in the copper melt, but also improves the uniformity of the distribution of alloy elements. Combining with precisely controlled melting, refining, standing, slag skimming and casting process parameters, the stability and repeatability of large-scale industrial production are ensured.

[0026] 4. Good crack resistance and processing adaptability: Obvious cracking occurred in the bending test of the comparative example samples, while the samples of the examples of the present invention showed excellent crack resistance, further verifying their excellent mechanical properties and processing adaptability. Description of the Drawings

[0027] Figure 1 It is the metallographic structure diagram of the heat pipe without Ni-Nb alloy in Example 4;

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

[0029] Figure 3 It is the metallographic structure diagram of the heat pipe with Ni-Nb alloy in Example 1;

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

[0031] Figure 5 It is the metallographic structure diagram of the Ni-Nb alloy in Example 3. Detailed implementation manners

[0032] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

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

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

[0035] 2) The Nb element has a relatively high melting point (2468 °C), 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, due to the too high melting point of pure Nb, which is much higher than the casting temperature of pure copper (1180 - 1200 °C), if the elemental Nb is directly added during the casting process, it cannot be effectively dissolved. Therefore, the present invention selects Ni as the accompanying element to prepare the Ni-Nb master alloy. The reasons for choosing Ni are as follows:

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

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

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

[0040] Example 1

[0041] A production method of a low-oxygen and high-temperature resistant sintered oxygen-free copper ingot is as follows:

[0042] S1) Batching: Use A-grade electrolytic copper plates, with an addition amount of 3500 tons per furnace. At the same time, before adding the copper plates, proportion 0.15 kg of Ni-Nb master alloy (the weight content of Nb is 35%) per furnace and add it into the furnace.

[0043] S2) Melting: Use an induction furnace for melting, and control the melting temperature at 1180 °C. After all the copper plates are melted, proceed to the next refining process.

[0044] S3) Refining: Deoxidize, degas and purify the copper liquid. The method is to add 0.2 kg of P-Cu (the weight content of phosphorus is 14%) and 0.3 kg of B-Cu (the weight content of B is 5%) per furnace for deoxidation and degassing operations.

[0045] S4) Standing: Make the slag phase produced by refining float out by using the density difference with the copper liquid, and the standing time is 20 min.

[0046] S5) Skimming: Use graphite tools to fish out the covering charcoal and slag phase on the surface of the copper liquid, and at the same time add calcined charcoal and evenly cover it on the surface of the copper liquid, with a covering thickness of 250 mm.

[0047] S6) Casting: Cast a copper ingot with an outer diameter of 320 mm by vertical semi-continuous casting process. The casting temperature is 1175 °C. The cooling water volume process is as follows: The initial small water cooling water flow rate is 50 L / min; after stabilization, the casting cooling water flow rate is 130 L / min; the cooling water flow rate from the end of casting to the stop of casting is 120 L / min. The casting speed is: the initial casting speed is 18 mm / min; the stable casting speed is 55 mm / min; the casting speed from the end of casting to the stop of casting is 25 mm / min. During the whole casting process, the furnace is protected by argon gas with a flow rate of 200 L / min.

[0048] The content of Nb element in the copper ingot prepared according to the above process is about 15 ppm (calculation method: 0.15 kg × 35% ÷ 3500 tons × 10^6 = 15 ppm). Prepare this ingot into a heat pipe mother tube with a specification of Φ10 × 1 mm and conduct sintering treatment.

[0049] Through metallographic analysis, observe its grain structure, as Figure 3 shown, it can be seen that the grains are fine and uniform. The elongation test result is 46.3%, which is much higher than 28.7% of the pure copper material in the control group.

[0050] Example 2

[0051] A production method of low-oxygen high-temperature resistant sintered oxygen-free copper ingot is as follows:

[0052] S1) Batching: Use A-grade electrolytic copper plates, with an addition amount of 3500 tons per furnace. At the same time, before adding the copper plates, proportion 0.18 kg of Ni-Nb master alloy (the weight content of Nb is 36%) per furnace and add it into the furnace;

[0053] S2) Melting: Use an induction furnace for melting, control the melting temperature at 1170 °C. After all the copper plates are melted, proceed to the next refining process;

[0054] S3) Refining: Deoxidize, degas and purify the copper liquid. The method is to add 0.22 kg of P-Cu (the weight content of phosphorus is 14%) and 0.32 kg of B-Cu (the weight content of B is 5%) per furnace for deoxidation and degassing operations;

[0055] S4) Standing: Make the slag phase produced by refining float out by using the density difference with the copper liquid, and the standing time is 18 min;

[0056] S5) Skimming: Use graphite tools to fish out the covering charcoal and slag phase on the surface of the copper liquid. At the same time, add calcined charcoal and evenly cover it on the surface of the copper liquid, with a covering thickness of 230 mm;

[0057] S6) Casting: Cast a copper ingot with an outer diameter of 320 mm by vertical semi-continuous casting process. The casting temperature is 1175 °C. The cooling water volume process is as follows: The initial small water cooling water flow rate is 45 L / min; After stabilization, the casting cooling water flow rate is 125 L / min; The cooling water flow rate from the end of casting to the stop of casting is 120 L / min. The casting speed is: The initial casting speed is 17 mm / min; The stable casting speed is 50 mm / min; The casting speed from the end of casting to the stop of casting is 25 mm / min. During the whole casting process, the furnace is protected by argon gas with a flow rate of 180 L / min.

[0058] The content of Nb element in the copper ingot prepared according to the above process is about 18.5 ppm (calculation method: 0.18 kg × 36% ÷ 3500 tons × 10^6 = 18.5 ppm). Prepare the ingot into a heat pipe mother tube with a specification of Φ12 × 1.2 mm and conduct sintering treatment.

[0059] Through metallographic analysis, observe its grain structure, as Figure 4 shown, it can be seen that the grains are fine and uniform. The elongation test result is 47.8%.

[0060] Example 3

[0061] A production method of low-oxygen high-temperature resistant sintered oxygen-free copper ingot is as follows:

[0062] S1) Ingredients: Use Grade A electrolytic copper plates, with an addition amount of 3500 tons per furnace. At the same time, before adding the copper plates, proportion 0.20 kg of Ni-Nb master alloy (the weight content of Nb is 37.5%) per furnace and add it into the furnace.

[0063] S2) Melting: Use an induction furnace for melting, control the melting temperature at 1190 °C. After all the copper plates are melted, proceed to the next refining process.

[0064] S3) Refining: Deoxidize, degas and purify the molten copper. The method is to add 0.25 kg of P-Cu (the weight content of phosphorus is 14%) and 0.35 kg of B-Cu (the weight content of B is 5%) per furnace for deoxidation and degassing operations.

[0065] S4) Standing: Make the slag phase produced by refining float out by using the density difference with the molten copper, and the standing time is 22 min.

[0066] S5) Skimming: Use a graphite tool to fish out the covering charcoal and slag phase on the surface of the molten copper, and at the same time add calcined charcoal and evenly cover it on the surface of the molten copper, with a covering thickness of 260 mm.

[0067] S6) Casting: Cast copper ingots with an outer diameter of 320 mm by vertical semi-continuous casting process. The casting temperature is 1180 °C. The cooling water volume process is as follows: The initial small water cooling water flow rate is 55 L / min; after stabilization, the casting cooling water flow rate is 135 L / min; the cooling water flow rate from the end of casting to the stop of casting is 120 L / min. The casting speed is: the initial casting speed is 19 mm / min; the stable casting speed is 58 mm / min; the casting speed from the end of casting to the stop of casting is 25 mm / min. During the whole casting process, the furnace is protected by argon, and the flow rate is 250 L / min.

[0068] The content of Nb element in the copper ingot prepared according to the above process is about 21.4 ppm (calculation method: 0.20 kg × 37.5% ÷ 3500 tons × 10^6 = 21.4 ppm). Prepare this ingot into a heat pipe mother tube with a specification of Φ15 × 1.5 mm and conduct sintering treatment.

[0069] Observe its grain structure through metallographic analysis, as Figure 5 shown, it can be seen that the grains are fine and uniform. The elongation test result is 48.1%.

[0070] Comparative Example 4

[0071] To verify the technical effects of the present invention, a set of comparative examples was set up. Using the same equipment and operating conditions, pure copper ingots were prepared without adding any Ni-Nb master alloy, and other process parameters were the same as those in Example 1.

[0072] The pure copper ingots of this comparative example were made into heat pipe mother tubes with a specification of Φ10×1 mm. After sintering treatment under the same conditions, their grain structures were observed by metallographic analysis. As Figure 1 shown, it can be seen that the grains are coarse and uneven in size. The elongation test result was only 28.7%, which is much lower than the test results in the examples of the present invention. In addition, through the bending test, it was observed that, as Figure 2 shown, the comparative sample was prone to cracking during the bending process.

[0073] Table 1 shows the comparison of process parameters and test results of each example and comparative example:

[0074] Sample number Addition amount of Ni-Nb alloy (kg) Nb content (ppm) Melting temperature (°C) Elongation rate (%) Grain structure Example 1 0.15 15.0 1180 46.3 Fine and uniform Example 2 0.18 18.5 1170 47.8 Fine and uniform Example 3 0.20 21.4 1190 48.1 Fine and uniform Example 4 0 0 1180 28.7 Coarse and non-uniform

[0075] From the comparison results in Table 1, it can be seen that by adding an appropriate amount of Ni-Nb master alloy to the present invention, the copper ingots contain a specific content of Nb element, which can effectively improve the grain structure of the copper material after high-temperature sintering, making it remain fine and uniform, thereby significantly increasing the elongation of the material. Especially when the content of Nb element is in the range of 15-25 ppm, the elongation of the copper material can reach more than 45%, which is much higher than 28.7% of the pure copper material.

[0076] Although the embodiments of the present application have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present application. The scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A production method of a low-oxygen high-temperature resistant sintered oxygen-free copper ingot, characterized in that, Specifically, it includes the following steps: S1) Batching: Use Class A electrolytic copper plates, with an addition amount of 3500 tons per furnace. At the same time, before adding the copper plates, proportion 0.15 kg of Ni-Nb master alloy per furnace and add it into the furnace. The weight content of Nb in the Ni-Nb master alloy is 33.8 - 37.8%, and the rest is Ni element; S2) Melting: Use an induction furnace for melting, with a melting temperature of 1140 - 1220 °C. After all the copper plates are melted, proceed to the next refining process; S3) Refining: Deoxidize, degas and purify the copper liquid. The method is to add 0.2 kg of P-Cu and 0.3 kg of B-Cu per furnace for deoxidation and degassing operations; S4) Standing: Make the slag phase generated by refining float out by using the density difference with the copper liquid, and the standing time is 15 - 25 min; S5) Skimming: Use a graphite tool to fish out the covering charcoal and slag phase on the surface of the copper liquid, and at the same time add calcined charcoal and evenly cover it on the surface of the copper liquid, with a covering thickness of not less than 200 mm; S6) Casting: Cast copper ingots with an outer diameter of 320 mm by a vertical semi-continuous casting process, with a casting temperature of 1170 - 1180 °C. Keep the furnace under argon protection during casting, with a flow rate of 20 - 400 L / min.

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

3. The production method of an oxygen-free copper ingot with low oxygen and high temperature resistance sintering according to claim 1, characterized in that, It also includes the casting speed in the casting step. The casting speed includes: the starting casting speed is 15 - 20 mm / min; the stable casting speed is not greater than 60 mm / min; the casting speed from the end of casting to the stop of casting is 25 mm / min.

4. The production method of an oxygen-free copper ingot with low oxygen and high temperature resistance sintering according to claim 1, characterized in that, The added Ni-Nb master alloy controls the Nb element content in the final ingot to be 15 - 25 ppm.

5. The production method of an oxygen-free copper ingot with low oxygen and high temperature resistance sintering according to claim 1, characterized in that, 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.

6. The production method of an oxygen-free copper ingot with low oxygen and high temperature resistance sintering according to claim 1, characterized in that, The atomic radius of the Ni element is 126 pm, and it is in an infinitely miscible state with the copper element, and serves as a companion element to assist the dissolution of the Nb element.

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

8. A low-oxygen high-temperature resistant sintered oxygen-free copper ingot according to claim 7, characterized in that, For manufacturing thick-walled heat pipes with a wall thickness ≥ 0.4 mm.

9. A low-oxygen high-temperature resistant sintered oxygen-free copper ingot according to claim 8, 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 forming process.

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