CuMnC composite material, hot-pressing sintering preparation method and application thereof

Abstract

The application discloses a CuMnC composite material, a hot-pressing sintering preparation method and application thereof. A solid solution treatment and hot-pressing sintering synergistic process is adopted, that is, Cu, Mn and C powders are ball-milled and mixed under argon protection, and then subjected to solid solution treatment at 800±10 DEG C for 2h and water quenching, followed by aging treatment at 300±20 DEG C for 4-5h and furnace cooling; then, the temperature is raised to 800±10 DEG C at a speed of 90±5 DEG C / min, and the hot-pressing sintering is carried out at a pressure of 30±2 MPa for 15±1 min, and then the furnace is cooled. The material prepared by the process has a density of greater than or equal to 98%, a porosity of less than 2%, a hardness of 115-120 HV, an electrical conductivity of 4.2-5.7% IACS, and a wear coefficient of 0.65-0.72. Through the synergistic effect of carbon content control and solid solution treatment, the electrical conductivity is maintained at a high carbon content of 0.34 wt.% for the first time, and no noble metal is added, and the raw material cost is reduced by more than 50%. The application is suitable for parts requiring high strength and high conductivity, such as rail transit pantograph, electronic packaging heat dissipation substrates and the like.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of metal alloy materials, in particular to a high-strength and high-conductivity CuMnC composite material prepared through a hot-pressing sintering process, which is suitable for the fields of power transmission, electronic packaging and aerospace. BACKGROUND

[0002] The main strengthening phases of the CuMnC composite material are carbide phases, solid solution phases of manganese and intermetallic compound phases. The traditional preparation method (such as the casting method and the conventional hot-pressing sintering) of the alloy has significant defects, which seriously affects its industrial application, and has the following main problems: the Cu-Mn alloy has high tensile strength, the introduction of carbon can refine the grains and improve the strength, and the traditional casting method is easy to cause carbon segregation and form an uneven microstructure. In addition, when casting under atmospheric conditions, the oxidation loss rate of manganese is more than 15 wt.%, which makes it difficult to control the composition and requires additional manganese addition, increasing the cost. Hot-pressing sintering is introduced into the preparation of the CuMnC composite material, and its core advantages include high density, low temperature and high efficiency, and composition uniformity. Casting under atmospheric conditions will cause great loss and make it difficult to accurately control the carbon content. Therefore, it is more suitable for hot-pressing sintering preparation.

[0003] The hot-pressing sintering furnace is a process for high-density materials, which can simultaneously apply high temperature and pressure, effectively promote the diffusion and rearrangement of powder particles, and fully close the pores between copper, manganese and carbon powder particles, thereby significantly improving the density of the alloy. Since the mid-1970s, sintered ore has been the main raw material for blast furnaces at home and abroad. In 1862, Sobolevsky first obtained platinum by using the method of normal temperature pressure sintering, and after 1930, hot pressing developed more quickly and was mainly applied to large-sized hard alloy products, refractory compounds and modern ceramics. The basic principle of hot-pressing sintering is to promote the material transmission of powder particles under the combined action of high temperature and pressure, so as to realize the densification of the powder and the improvement of the performance of the material, thereby improving the comprehensive performance of the material. However, in the prior art, when the carbon content is more than 0.2 wt.%, the electrical conductivity decreases sharply (WANG Zhen, GAN Chunlei, LI Feng, et al. Effect of Zr Content on Microstructure and Properties of Commercial Pure Aluminum [J]. Materials Research and Application, 2022, 16 (2): 253-261.), and although high-end processes can improve the density, the cost of equipment is higher than that of hot-pressing sintering, the production cycle is prolonged, and it is difficult to be industrialized and popularized.

[0004] In summary, the existing technology in the preparation process of CuMnC composite material has the following key problems to be solved, including: the traditional casting method has carbon segregation and manganese burning loss problems, resulting in uneven material composition and unstable performance; the density of the alloy prepared by conventional molding sintering is insufficient, the porosity is too high, and the mechanical properties of the material are affected; the existing process is difficult to balance the contradiction between high carbon content and high electrical conductivity; the high-density preparation process is too high in cost, and it is difficult to meet the needs of industrial production. SUMMARY

[0005] The purpose of the present application is to solve the problem that the existing copper-based composite material cannot balance the electrical conductivity, strength and wear resistance. The present application provides a preparation method and application of CuMnC composite material. The preparation method is simple and easy to implement, and the copper-based composite material prepared by the method has high strength and high wear resistance.

[0006] To achieve the above purpose, the technical scheme adopted by the present application is as follows: a CuMnC composite material has the following components and proportions: 0.1wt.%≤C≤0.34wt.%, 10wt.%≤Mn≤13wt.%, and the balance is Cu; and according to the Mn-C phase diagram, four different C contents represent the polymorphic transformation points of Mn at different temperatures, and the melting point of Mn content is 11% in the Cu-Mn phase diagram, which is lower than the highest melting point of Cu.

[0007] Further, the effect of C is better in the following range: 0.1wt.%≤C≤0.34wt.%.

[0008] Further, the effect of Mn is better in the following range: 10wt.%≤Mn≤12wt.%.

[0009] Further, the weight ratio of C and Mn is (0-3.5):100; more preferably, the weight ratio is (0.7-3.1):100.

[0010] Further, the porosity of the CuMnC composite material is ≤2%, the hardness is ≥115HV, the electrical conductivity is ≥3.4%IACS, and the wear coefficient is ≤0.72. The preparation efficiency is high, and it can meet different processing needs.

[0011] Another aspect of the present application is to protect the preparation method of the CuMnC composite material, which specifically includes the following steps:

[0012] a. Weigh the raw materials 0.1wt.%≤C powder≤0.34wt.%, 10wt.%≤Mn powder≤13wt.% and the balance is Cu powder according to the following proportions;

[0013] b. Ball milling in inert gas environment, ball-to-powder ratio 8-12:1, rotation speed 80-150 r / min, time 4±2 h, to ensure uniform embedding of Mn and C on the surface of Cu powder.

[0014] c. Filling the uniformly mixed powder into a mold, filling density ≥ 60%.

[0015] d. Vacuum treatment to an absolute pressure less than 20 Pa, creating an inert atmosphere.

[0016] e. Solution treatment of the obtained blank at the solid solubility limit temperature of Mn in Cu, followed by aging treatment, the aging treatment temperature and time being selected to cause C element to precipitate from the matrix, to finally prepare high-performance Cu-Mn-C composite material.

[0017] Further, the C content is 0.2-0.3 wt.%, and the Mn content is 11-12 wt.%. Further, the electrical conductivity of the material is ≥ 3.5% IACS, and the wear coefficient is as low as 0.65-0.72 (8N load, 300 mm / min).

[0018] Further, the raw materials are Cu powder (purity ≥ 99.85%), Mn powder (purity ≥ 99.8%), and C powder (purity ≥ 99.9%);

[0019] Further, in step b, an argon-protected planetary ball mill is selected, the ball-to-powder ratio is 10:1, the rotation speed is 120±10 r / min, and the ball milling time is 4 h, to achieve uniform dispersion of Mn and C powder in the Cu matrix.

[0020] Further, in step d, after vacuuming to below 20 Pa, high-purity argon is filled to 0.05 MPa, and the atmosphere is replaced 3 times.

[0021] Further, in step e, the solid solubility limit temperature is 800±10℃, and the holding time is 2-3 h, to allow sufficient solid solubility of Mn and optimal distribution of C element, and the cooling method is water quenching.

[0022] Further, in step e, the aging limit temperature is 300±20℃, and the holding time is 4-5 h, to allow sufficient precipitation of C element from the matrix, and the cooling method is furnace cooling.

[0023] Further, after the solution and aging treatment in step e, hot-press sintering is performed: heating to 800±10℃ at 90±5℃ / min, holding at 30±2 MPa for 15±1 min; the process temperature is strictly controlled below the melting point of copper (1083℃), effectively inhibiting the volatilization loss of manganese element. The hot-pressing pressure can be implemented in the range of 10-32 MPa, preferably 30±2 MPa.

[0024] Further, in step e, the cooling in the furnace is to below 150-200℃.

[0025] Another aspect of the present application is to protect the CuMnC composite material to have a wide application prospect in the field of precision manufacturing, aerospace and nuclear energy, etc. which have high requirements on material performance.

[0026] Further, the application includes the electrical contact components in the rail transit system, the parts of high-efficiency motors and generators, the integrated circuit elements of electronic information industry, and the heat dissipation and conductive elements in the field of electronic packaging industry.

[0027] Compared with the prior art, the present application has the following beneficial effects:

[0028] (1) The CuMnC composite material prepared by the method of the present application has:

[0029] The density is ≥98% (relative density), the porosity is <2%, and the density is reduced by 5% compared with conventional sintering;

[0030] The hardness is 115-120HV, which is increased by 25%-30% compared with the same composition material prepared by traditional melting and casting method;

[0031] The electrical conductivity is maintained at 4.2-5.7% IACS, which is increased by more than 20% compared with the material without solid solution and aging treatment under the same carbon content;

[0032] The wear coefficient is as low as 0.65-0.72 (8N load, 300mm / min), which is reduced by 14.3% compared with commercial alloys.

[0033] (2) The process of the present application has the following industrialization advantages:

[0034] The hot-pressing sintering cycle is <30 minutes, which is shortened by more than 30% compared with the hot isostatic pressing (HIP) process;

[0035] The comprehensive cost is reduced by 25%, mainly due to:

[0036] a) Avoiding manganese burning loss in melting and casting method (saving raw material cost by 10-30%);

[0037] b) Using conventional graphite mold (reducing cost by 30-50% compared with HIP special mold).

[0038] (3) Synergistic effect of technical scheme: through the synergistic effect of carbon content control (0.1-0.34wt.%) and 800℃ solid solution and aging treatment, the following is realized for the first time: maintaining electrical conductivity under high carbon content (breaking through the existing technology of 0.2wt.% C conductivity drop bottleneck); and without adding noble metals (such as Ag, Re, etc.), the raw material cost is reduced by more than 50%. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 Microstructure of Cu-11wt.% Mn-0.34wt.% C after 800℃ solution and aging heat treatment. It can be seen from the figure that the grains are uniformly distributed after solution heat treatment. DETAILED DESCRIPTION

[0040] In the following examples, unless otherwise specified, the Cu powder (purity ≥ 99.85%), Mn powder (purity ≥ 99.8%), and C powder (purity ≥ 99.9%) used are standard commercial products, and the hot-pressing sintering furnace is a conventional laboratory equipment. The present application is further illustrated by the following examples:

[0041] Example 1

[0042] This example discloses a preparation of Cu-11wt.% Mn-0.34wt.% C composite material, comprising the following steps:

[0043] (1) Prepare and sinter the CuMnC composite material raw material, wherein the CuMnC composite material contains 88.66wt% of Cu powder (purity ≥ 99.85%), 11wt% of Mn powder (purity ≥ 99.8%), and 0.34wt% of C powder (purity ≥ 99.9%), and 5 different components of CuMnC powder are proportioned according to a certain ratio.

[0044] (2) In the hot-pressing sintering furnace, after vacuumizing, the graphite mold filled with CuMnC powder is placed into the furnace, a thermocouple is inserted into the mold, the hydraulic lifting is turned on, the furnace door is closed and the four valves are tightened.

[0045] (3) The obtained blank is subjected to solution and aging treatment at the solid solution limit temperature of Mn element in Cu. The solution treatment is carried out at 800℃ for 2h and water quenching, followed by aging treatment at 300℃ for 5h and furnace cooling, so that the C element is fully precipitated from the matrix. The microstructure after treatment is shown in Figure 1 Finally, a high-performance Cu-Mn-C composite material is prepared.

[0046] After detection, the hardness of the Cu-11wt.% Mn-0.34wt.% C composite material prepared in this example is 122.8HV, the electrical conductivity is 5.731%IACS, and the average friction and wear coefficient under 8N pressure and 300mm / min sliding speed for 30min of friction is 0.6584.

[0047] Example 2

[0048] This example provides a preparation of Cu-11wt.% Mn-0.3wt.% C composite material, and the preparation method is basically the same as that of Example 1, except that the content of C element is 0.3wt.%.

[0049] The hardness is 119.1 HV, the conductivity is 5.464% IACS, and the average friction and wear coefficient is 0.7286 under friction for 30 min at a sliding speed of 300 mm / min under a pressure of 8 N.

[0050] Example 3

[0051] This example provides a preparation method of a Cu-11wt.% Mn-0.21wt.% C composite material, which is basically the same as that of Example 1, except that the content of the C element is 0.21wt.%.

[0052] The hardness is 118.4 HV, the conductivity is 5.243% IACS, and the average friction and wear coefficient is 0.8302 under friction for 30 min at a sliding speed of 300 mm / min under a pressure of 8 N.

[0053] Example 4

[0054] This example provides a preparation method of a Cu-11wt.% Mn-0.1wt.% C composite material, which is basically the same as that of Example 1, except that the content of the C element is 0.1wt.%.

[0055] The hardness is 107.2 HV, the conductivity is 4.632% IACS, and the average friction and wear coefficient is 0.9492 under friction for 30 min at a sliding speed of 300 mm / min under a pressure of 8 N.

[0056] Comparative Example 1

[0057] This example provides a preparation method of a Cu-11wt.% Mn-0wt.% C composite material, which is basically the same as that of Example 1, except that the composite material does not contain carbon.

[0058] The hardness is 103.3 HV, the conductivity is 4.213% IACS, and the average friction and wear coefficient is 0.9634 under friction for 30 min at a sliding speed of 300 mm / min under a pressure of 8 N.

[0059] Comparative Example 2

[0060] This example provides a preparation method of a Cu-11wt.% Mn-0.34wt.% C composite material, which is basically the same as that of Example 1, except that the composite material is prepared by solid solution heat treatment.

[0061] After the solid solution heat treatment, the grains are uniformly distributed. The hardness is 125.1 HV, the conductivity is 5.351% IACS, and the average friction and wear coefficient is 0.6493 under friction for 30 min at a sliding speed of 300 mm / min under a pressure of 8 N.

[0062] Comparative Example 3

[0063] This example provides a preparation of Cu-11wt.%Mn-0.34wt.%C composite material, which is prepared by the same method as that of Example 1, except that the Mn powder is oxidized during the preparation of the composite material.

[0064] It is detected that the microstructure has larger grains, and the grains are unevenly distributed. The hardness is 113.6HV, the electrical conductivity is 3.021%IACS, and the average friction and wear coefficient is 0.7692 after friction for 30min at a sliding speed of 300mm / min under a pressure of 8N.

[0065] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A CuMnC composite material having the following components and proportions: 0.1wt.%≤C≤0.34wt.%, 10wt.%≤Mn≤12wt.%, with the balance being Cu; the CuMnC composite material having a porosity ≤2%, a hardness ≥115HV, an electrical conductivity ≥3.4%IACS, and a wear coefficient ≤0.

72.

2. The hot-pressing sintering preparation method of CuMnC composite material as described in claim 1, characterized in that: Includes the following steps: a. Weigh the raw materials according to the following proportions: 0.1 wt.% ≤ C powder ≤ 0.34 wt.%, 10 wt.% ≤ Mn powder ≤ 12 wt.%, with the remainder being Cu powder; b. Ball milling shall be carried out in an inert gas environment, with a ball-to-material ratio of 8~12:1, a rotation speed of 80~150 r / min, and a time of 4±2 h; c. Fill the mold with the uniformly mixed powder, ensuring a filling density of ≥60%; d. Vacuum treatment until the absolute pressure is less than 20 Pa to create an inert atmosphere; e. A high-performance Cu-Mn-C composite material is prepared by solution aging treatment of the obtained green body at the solution limit temperature of Mn in Cu; the solution limit temperature is 800±10℃, the holding time is 2~3 h, and the cooling method is water quenching; the aging limit temperature is 300±20℃, the holding time is 4~5 h, and the cooling method is furnace cooling.

3. The method according to claim 2, characterized in that: After solution aging in step e, hot pressing sintering is performed: the temperature is increased to 800±10℃ at 90±5℃ / min, and the pressure is maintained at 30±2MPa for 15±1min.

4. The application of the CuMnC composite material as described in claim 1 in precision manufacturing, aerospace and nuclear energy fields.

5. The application according to claim 4, characterized in that: This includes applications in electrical contact components in rail transit systems, parts for high-efficiency motors and generators, integrated circuit components in the electronics and information industry, and heat dissipation and conductive components in the electronic packaging industry.

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