CN113278836B

CN113278836B - Method for preparing CuW/low-carbon steel heterogeneous bimetallic material

Info

Publication number: CN113278836B
Application number: CN202110440939.XA
Authority: CN
Inventors: 杨晓红; 刘永定; 梁淑华; 邹军涛; 肖鹏
Original assignee: Xian University of Technology
Current assignee: Xian University of Technology
Priority date: 2021-04-23
Filing date: 2021-04-23
Publication date: 2022-04-08
Anticipated expiration: 2041-04-23
Also published as: CN113278836A

Abstract

The invention discloses a method for preparing a CuW/low-carbon steel heterogeneous bimetallic material, which comprises the following steps: firstly, preparing Mn, Fe, Ni, Cr and Co powder by using a gas atomization method, accurately weighing each element according to a molar ratio, mixing, and pressing to obtain a high-entropy alloy billet; and performing solid-phase sintering on the prepared raw materials according to Cu/W, the high-entropy alloy billet and the low-carbon steel to obtain the CuW/low-carbon steel heterogeneous bimetallic material. The alloy prepared by the method has low cost, short sintering period and simple and easily realized process, and the high entropy effect of the high entropy alloy is utilized to inhibit the generation of intermetallic compounds between the CuW and the low carbon steel interface, so that the CuW/low carbon steel heterogeneous bimetallic material has good interface bonding strength and great development potential.

Description

Method for preparing CuW/low-carbon steel heterogeneous bimetallic material

Technical Field

The invention belongs to the technical field of heterogeneous bimetal connection, and relates to a method for preparing a CuW/low-carbon steel heterogeneous bimetal material.

Background

In high-voltage circuit breakers in high-voltage networks, the CuW alloy is often connected to steel as a structural part as a functional part, in order to reduce costs. At present, in actual engineering, a screw or a rivet is generally adopted to connect the CuW and the steel supporting clamp, although the connection can obtain good bonding strength, the heat conductivity of the CuW can be reduced, the heat dissipation of the CuW is not facilitated, and meanwhile, the connection also has the problems of larger component, more occupied space and the like. In addition, the brazing research on tungsten and steel in China shows that under the condition of not adding any activating element, an obvious and very thin discontinuous layer of metal oxide exists at the brazing interface of the tungsten base metal and the steel, so that the mechanical property of the whole material is reduced. The invention utilizes the high entropy effect of the high entropy alloy to inhibit the brittle metal compound generated by the joint surface of the CuW and the steel in the sintering process, and obtains good interface structure. The CuW/low-carbon steel integral material with good heat conductivity is prepared, and has very important engineering practical application value.

Disclosure of Invention

The invention aims to provide a method for preparing a CuW/low-carbon steel heterogeneous bimetallic material, which has the characteristics of preparing a CuW/low-carbon steel integral material with good interface bonding strength and good heat conductivity.

The technical scheme adopted by the invention is that the method for preparing the CuW/low-carbon steel heterogeneous bimetallic material is implemented according to the following steps:

step 1, preparing Fe, Ni, Co, Cr and Mn powder with the purity of 99.9%;

step 2, weighing the powder raw materials prepared in the step 1 according to the following element mole percentages: 5 to 30 percent of Mn, 5 to 30 percent of Fe, 5 to 30 percent of Ni, 5 to 30 percent of Cr and 5 to 30 percent of Co, wherein the sum of the mole percentages of the elements is 100 percent;

step 3, mixing the powder raw materials weighed in the step 2, and pressing the mixture into a high-entropy alloy billet by using a cold press;

step 4, pretreating the processed low-carbon steel and Cu/W alloy block materials;

and 5, sequentially stacking the CuW alloy block, the high-entropy alloy billet and the low-carbon steel obtained in the

steps

3 and 4 into a crucible from bottom to top, sintering the crucible in a vacuum furnace, and cooling to obtain the CuW/low-carbon steel heterogeneous bimetallic material.

The invention is also characterized in that:

step 1, preparing Fe, Ni, Co, Cr and Mn blocks into Fe, Ni, Co, Cr and Mn powder with the purity of 99.9% by adopting an air atomization method, wherein the particle sizes of the Fe, Ni, Co, Cr and Mn powder are 10-500 mu m.

And 3, mixing the powder by using balls and materials in a ratio of 1-40: 1, wherein the powder mixing time is 16-24 hours.

The pressure adopted in the step 3 is 100MPa to 500 MPa; the pressing time is 10-50 s.

And step 4, specifically, placing the processed low-carbon steel and Cu/W alloy block materials into a beaker containing alcohol, then placing the beaker into a KQ-50DE type numerical control ultrasonic cleaner for cleaning, and respectively filling the cleaned beaker into sample bags for later use after drying.

The cleaning time is 20-30 minutes.

The sintering in the step 5 is specifically that the temperature is increased to 800-1000 ℃ at the temperature increasing speed of 10-25 ℃/min, the temperature is maintained for 20-40 min, then the temperature is increased to 1200-1500 ℃ at the temperature increasing speed of 10-25 ℃/min, and the temperature is maintained for 2-5 hours.

The cooling in the step 5 is specifically to cool to room temperature at 3-10 ℃/min.

The invention has the beneficial effects that: the method for preparing the CuW/low-carbon steel heterogeneous bimetallic material has the advantages that the cost of raw materials for preparing the high-entropy alloy is low, the whole preparation process is simple and easy to realize, the sintering period is short, the high-entropy effect of the high-entropy alloy can effectively reduce the formation of CuW/low-carbon steel interface metal compounds, and the CuW/low-carbon steel heterogeneous bimetallic composite material obtained by sintering has good interface bonding strength and good heat conductivity.

Drawings

FIG. 1 is a flow chart of the method of the present invention for preparing a CuW/low carbon steel heterogeneous bimetallic material;

FIG. 2 is a scatter plot of the experimental strength of the standard tensile bars of the materials of examples 1 to 4 of the present invention;

FIG. 3 is an SEM image of the interface of the CuW/low-carbon steel heterogeneous bimetallic material prepared by the method.

Detailed Description

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

The invention discloses a method for preparing a CuW/low-carbon steel heterogeneous bimetallic material, which is implemented according to the following steps as shown in figure 1:

step 1, preparing Fe, Ni, Co, Cr and Mn blocks into Fe, Ni, Co, Cr and Mn powder with the purity of 99.9% by adopting an air atomization method, wherein the grain sizes of the Fe, Ni, Co, Cr and Mn powder are 10-500 mu m;

step 2, respectively weighing the powder raw materials prepared in the step 1 by using an electronic balance with the precision of 0.001g according to the following element mole percentages: 5 to 30 percent of Mn, 5 to 30 percent of Fe, 5 to 30 percent of Ni, 5 to 30 percent of Cr and 5 to 30 percent of Co, wherein the sum of the mole percentages of the elements is 100 percent;

step 3, mixing the powder raw materials weighed in the step 2, wherein the ball-to-material ratio of the mixed powder is 1-40: 1, the powder mixing time is 16-24 hours, and then pressing the mixed powder into a high-entropy alloy billet by using a cold press, wherein the pressure for pressing is 100-500 MPa; the pressing time is 10-50 s;

step 4, pretreating the processed low-carbon steel and Cu/W alloy block materials, specifically, putting the processed low-carbon steel and Cu/W alloy block materials into a beaker, pouring alcohol into the beaker, stopping when the two block materials are completely immersed by the alcohol, then putting the beaker into a KQ-50DE type numerical control ultrasonic cleaner for cleaning for 20-30 minutes, and respectively putting the beaker into sample bags for later use after drying;

step 5, sequentially stacking the CuW alloy block, the high-entropy alloy billet and the low-carbon steel obtained in the step 3 and the step 4 into a crucible from bottom to top, placing the crucible into a sample chamber of a vacuum furnace, vacuumizing the sample chamber in the atmosphere protection vacuum furnace, and when the vacuum degree reaches 1 multiplied by 10^-2Pa～1×10^-3And when Pa is needed, filling high-purity hydrogen into the sample chamber to normal pressure, and sintering under the protection of the atmosphere, wherein the sintering is specifically carried out by firstly heating to 800-1000 ℃ at the heating rate of 10-25 ℃/min, preserving the heat for 20-40 min, then heating to 1200-1500 ℃ at the heating rate of 10-25 ℃/min, preserving the heat for 2-3 h, and cooling to room temperature at 3-10 ℃/min to obtain the CuW/low-carbon steel heterogeneous bimetallic material.

The invention relates to a method for preparing a CuW/low-carbon steel heterogeneous bimetallic material, which comprises the following steps:

the function of step 1 is

Adopts gas atomization powder preparation, and the principle is as follows: the alloy liquid is broken into fine droplets by a fast moving fluid (atomizing medium) and finally condensed into solid powder.

In the step 2, the principle is as follows: the formation of intermetallic compounds at the joint interface is inhibited by utilizing the high entropy effect of the high entropy alloy, and a single solid solution is formed at the interface after sintering, so that the strength and the plasticity of the joint surface of the CuW/low carbon steel heterogeneous bimetallic material are improved.

The function of step 3 is

Adopt powder mixer to mix the powder of weighing well, its advantage lies in: the materials are thoroughly mixed and a certain mechanical bonding (cold welding) is achieved, which makes a certain preparation for the subsequent high temperature sintering.

The cold press is adopted to press the mixed powder into a compact, and the advantages of realizing certain mechanical combination of the powder, being convenient for controlling the dosage and controlling the thickness of the alloy sheet layer are achieved.

The function of step 4 is

A KQ-50DE type numerical control ultrasonic cleaner is adopted to remove oil stains and various dirt on the surfaces of CuW alloy blocks and low-carbon steel in the turning process, so that the influence of the dirt on subsequent sintering is prevented.

The effect of step 5 is

Adopts hydrogen atmosphere protection, and has the advantages that: the method prevents the metal oxide generated by the oxidation of the connecting interface of the material in the sintering process from influencing the wettability of copper at the interface, and simultaneously inhibits the diffusion of the high-entropy alloy at the interface.

The invention realizes the connection of the heterogeneous material copper-tungsten alloy and the steel by introducing the multicomponent high-entropy alloy FeCoNiCrMn, and has the following advantages:

the five elements of Fe, Mn, Ni, Cr and Co are in the subgroup of the fourth period in the periodic table, and the elements are adjacent in position and have close atomic radii, so that the method is one of the necessary conditions for forming the simple solid solution alloy on the joint surface.

Secondly, the lattice distortion of each element under the microscale can inhibit the formation of brittle intermetallic compound phases at the interface and promote the interface to form simple face-centered cubic solid solution or body-centered cubic solid solution.

Thirdly, each component of the high-entropy alloy has higher melting point, and the slow diffusion effect is achieved because the temperature is far lower than the melting point of each component during solid-phase sintering, so that the dissolution and erosion of alloy elements to the Cu-W alloy can be avoided.

Example 1

step 2, respectively weighing the powder raw materials prepared in the step 1 by using an electronic balance with the precision of 0.001g according to the following element mole percentages: 20 percent of Mn, 15 percent of Ni, 20 percent of Cr, 20 percent of Co and the balance of Fe, wherein the sum of the mole percentages of the above elements is 100 percent;

step 3, mixing the powder raw materials weighed in the step 2, wherein the ball-to-material ratio of the powder mixing is 20:1, the powder mixing time is 24 hours, and then pressing the powder into a high-entropy alloy compact by using a cold press, wherein the pressure for pressing is 260 MPa; the pressing time is 30 s;

step 4, pretreating the processed low-carbon steel and Cu/W alloy block materials, specifically, putting the processed low-carbon steel and Cu/W alloy block materials into a beaker, pouring alcohol into the beaker, stopping when the two block materials are completely immersed by the alcohol, then putting the beaker into a KQ-50DE type numerical control ultrasonic cleaner for cleaning for 20 minutes, and respectively putting the beaker into sample bags for later use after drying;

step 5, sequentially stacking the CuW alloy block, the high-entropy alloy billet and the low-carbon steel obtained in the step 3 and the step 4 into a crucible from bottom to top, placing the crucible into a sample chamber of a vacuum furnace, vacuumizing the sample chamber in the atmosphere protection vacuum furnace, and when the vacuum degree reaches 1 multiplied by 10^-2And when Pa is needed, filling high-purity hydrogen into the sample chamber to normal pressure, and performing protective sintering in the atmosphere. The process comprises the following steps: raising the temperature to 1000 ℃ at a speed of 20 ℃/min, preserving the heat for 30min, raising the temperature to 1380 ℃ at a speed of 15 ℃/min, preserving the heat for 3 h, and cooling to room temperature at a speed of 4 ℃/min.

Example 2

step 2, respectively weighing the powder raw materials prepared in the step 1 by using an electronic balance with the precision of 0.001g according to the following element mole percentages: 20 percent of Mn, 20 percent of Ni, 20 percent of Cr, 20 percent of Co and the balance of Fe, wherein the sum of the mole percentages of the above elements is 100 percent;

3, mixing the powder raw materials weighed in the step 2, wherein the ball-to-material ratio of the powder mixing is 1-40: 1, the powder mixing time is 24 hours, and then pressing the powder into a high-entropy alloy billet by using a cold press, wherein the pressure for pressing is 260 MPa; the pressing time is 30 s;

step 5, sequentially stacking the CuW alloy block, the high-entropy alloy billet and the low-carbon steel obtained in the step 3 and the step 4 into a crucible from bottom to top, placing the crucible into a sample chamber of a vacuum furnace, vacuumizing the sample chamber in the atmosphere protection vacuum furnace, and when the vacuum degree reaches 1 multiplied by 10^-2And when Pa is needed, filling high-purity hydrogen into the sample chamber to normal pressure, and performing protective sintering in the atmosphere. The process is that the temperature is raised to 1000 ℃ at 20 ℃/min under the protection of atmosphere, the temperature is preserved for 30min, then the temperature is raised to 1330 ℃ at 15 ℃/min, the temperature is preserved for 3 h, and then the temperature is cooled to the room temperature at 4 ℃/min.

Example 3

step 2, respectively weighing the powder raw materials prepared in the step 1 by using an electronic balance with the precision of 0.001g according to the following element mole percentages: 20 percent of Mn, 25 percent of Ni, 20 percent of Cr, 20 percent of Co and the balance of Fe, wherein the sum of the mole percentages of the above elements is 100 percent;

3, mixing the powder raw materials weighed in the step 2, wherein the ball-to-material ratio of the powder mixing is 40:1, the powder mixing time is 24 hours, and then pressing the powder into a high-entropy alloy compact by using a cold press, wherein the pressure for pressing is 260 MPa; the pressing time is 30 s;

step 5, sequentially stacking the CuW alloy block, the high-entropy alloy billet and the low-carbon steel obtained in the step 3 and the step 4 into a crucible from bottom to top, placing the crucible into a sample chamber of a vacuum furnace, vacuumizing the sample chamber in the atmosphere protection vacuum furnace, and when the vacuum degree reaches 1 multiplied by 10^-2And when Pa is needed, filling high-purity hydrogen into the sample chamber to normal pressure, and performing protective sintering in the atmosphere. The process is that the temperature is raised to 1000 ℃ at 20 ℃/min under the protection of atmosphere, the temperature is preserved for 30min, then the temperature is raised to 1280 ℃ at 15 ℃/min, the temperature is preserved for 3 h, and then the temperature is cooled to the room temperature at 4 ℃/min.

Example 4

step 5, sequentially stacking the CuW alloy block, the high-entropy alloy billet and the low-carbon steel obtained in the step 3 and the step 4 into a crucible from bottom to top, placing the crucible into a sample chamber of a vacuum furnace, vacuumizing the sample chamber in the atmosphere protection vacuum furnace, and when the vacuum degree reaches 1 multiplied by 10^-2And when Pa is needed, filling high-purity hydrogen into the sample chamber to normal pressure, and performing protective sintering in the atmosphere. The process is that the temperature is raised to 1000 ℃ at 20 ℃/min under the protection of atmosphere, the temperature is preserved for 30min, then the temperature is raised to 1250 ℃ at 15 ℃/min, the temperature is preserved for 3 h, and then the temperature is cooled to the room temperature at 4 ℃/min.

A tensile strength tester is used for testing the tensile strength of the standard sample prepared in the embodiment 1-4 of the invention, and the strength results of the tensile test bar are shown in table 1;

TABLE 1 Strength results for tensile bars

Example 1	Example 2	Example 3	Example 4
				212MPa	201MPa	196MPa	180MPa

At present, two methods are mainly used for connecting the Cu-W alloy and the low-carbon steel, namely, mechanical combination of riveting and threaded connection; secondly, metallurgical bonding mainly by welding. The joint of the two materials of the former has a bulky structure and poor thermal conductivity. The strength of the latter joint surface can only reach about 110MPa, and the strength requirement is difficult to meet. The strength of the combined surface of the CuW/low-carbon steel heterogeneous bimetallic material obtained by the invention can reach 212MPa to the maximum extent, and the strength is obviously improved.

FIG. 2 is a graph showing the strength change scattering of Table 1, in which the interface bonding strength of the material is decreased as the maximum sintering temperature is decreased in examples 1 to 4. The higher the temperature, the better the interface element diffusion, and the strength of the material is obviously improved.

FIG. 3 is an SEM picture of the bonding interface of the materials of example 1, and it can be seen from FIG. 3 that the high-entropy alloy interlayer can be fully dissolved and diffused into the heterogeneous materials at the two sides of the interface, the high-entropy alloy interlayer has better fusion with the heterogeneous materials at the two sides of the interface, no unmelted substance remains on the interface, and metallurgical diffusion and dissolution occur on the Cu-W/low-carbon steel interface, so that the two phases of Cu and W which are originally not dissolved with each other are metallurgically bonded at the Cu-W phase interface.

Claims

1. A method for preparing a CuW/low-carbon steel heterogeneous bimetallic material is characterized by comprising the following steps: