Molybdenum-copper alloy with high molybdenum content and preparation method thereof
Technical Field
The invention relates to a refractory metal powder metallurgy technology, in particular to a molybdenum-copper alloy with high molybdenum content and a preparation method thereof.
Background
The research of Mo-Cu composite materials starts in the twenty-second thirty years of the twentieth century, and mainly focuses on industrially developed countries such as Germany, Japanese, American and English. In the 60 s of the 20 th century, the former soviet union studied molybdenum-copper materials as constant expansion alloys with certain expansion coefficients, and studied the influence of the copper content in the alloys on the expansion coefficients of the materials. The research on Mo-Cu composite materials in China is that the Mo-Cu composite materials are produced only in 1956 after new China is established, and the thermal expansion coefficient of Mo-Cu is researched in the last 70 th century to be applied as a constant expansion alloy and be considered as a heat-resistant material. In recent years, with the development of large-scale integrated circuits and high-power electronic devices, molybdenum-copper materials are beginning to be used as electronic packaging and heat sink materials on a large scale.
The infiltration method is to press molybdenum powder or molybdenum powder mixed with a small amount of copper powder into a blank, then presintering, then overlapping the infiltration copper and the presintering blank, and sintering at a temperature higher than the melting point of copper in a reducing atmosphere or vacuum to enable the infiltration copper to infiltrate into a molybdenum skeleton under the action of capillary force. The molybdenum-copper composite material with high molybdenum skeleton strength and strong material corrosion resistance can be obtained by sintering and solution infiltration step by step.
The infiltration method has the advantages of higher density, good sintering performance and ideal heat and electric conductivity. But also has the disadvantages that (1) the high sintering temperature can cause the aggregation and growth of molybdenum particles to form a coarse uneven structure; (2) liquid phase copper is infiltrated only by capillary force, and if the channel in the molybdenum skeleton is uneven, the defects of copper agglomeration, insufficient infiltration, closed hole and the like are easily caused.
Disclosure of Invention
Aiming at the defects and defects of the prior art, the invention aims to provide a preparation method of a molybdenum-copper alloy with high molybdenum content, which overcomes the defects of high cost, low efficiency and large product quality fluctuation of the existing preparation method.
The invention also aims to provide the molybdenum-copper alloy with high molybdenum content, which has uniform structure, high compactness and good performance consistency, and solves the problems that the conventional molybdenum-copper alloy with high molybdenum content has non-uniform structure and difficult performance guarantee.
The technical scheme adopted by the invention for solving the technical problem is as follows:
a preparation method of a molybdenum-copper alloy with high molybdenum content comprises the following steps:
molybdenum powder treatment: carrying out airflow crushing on molybdenum powder to obtain agglomeration-free molybdenum powder;
spray granulation, namely adding water and a binder into the agglomeration-free molybdenum powder, stirring to obtain uniform slurry, and preparing the uniform slurry into spherical molybdenum powder by adopting a spray granulation method;
an automatic pressing step: carrying out automatic pressing molding on the spherical molybdenum powder to obtain a pressed compact;
rubber discharging: removing the binder in the green compact to obtain a blank;
copper infiltration: and carrying out copper infiltration treatment on the blank to obtain the molybdenum-copper alloy.
In the above method for preparing a molybdenum-copper alloy with a high molybdenum content, as a preferred embodiment, in the molybdenum powder treatment step, the fisher particle size of the molybdenum powder is 4.0 μm to 7.0 μm, and the bulk density is 1.2g/cm to 1.7g/cm3. The molybdenum powder used in the invention can ensure the compactness of the prepared product, thereby having better performance.
In the above method for preparing a molybdenum-copper alloy with a high molybdenum content, as a preferred embodiment, in the step of spray granulation, the amount of water added is 10% to 30% of the mass of the agglomeration-free molybdenum powder; the addition amount of the binder is 2-4% of the mass of the agglomeration-free molybdenum powder; preferably, in the spray granulation method, the diameter of a nozzle used in spray granulation is 0.6mm to 0.8mm, the pressure (pressure) applied to the slurry is 1200KPa to 1400KPa, the drying temperature is 150 ℃ to 180 ℃, and the diameter of the spherical molybdenum powder is 20 μm to 50 μm.
In the above method for producing a molybdenum-copper alloy with a high molybdenum content, as a preferred embodiment, in the automatic pressing step, the automatic pressing is performed using a fully automatic molding press; preferably, the pressure of the automatic pressing is 50 tons to 80 tons (such as 55 tons, 60 tons, 65 tons, 70 tons and 75 tons) and the frequency is 10Hz to 20Hz (such as 12Hz, 14Hz, 16Hz and 18Hz), the cost is increased due to the excessive pressure, the strength of the pressed blank is low due to the small pressure, and edges and corners are easy to fall off; if the frequency is too high, the pressure is insufficient, and if the frequency is too low, the efficiency is reduced; when the pressure of the automatic pressing is 50-60 tons (such as 52 tons, 54 tons, 56 tons and 58 tons), the adopted full-automatic molding press is a 0PC-60TG type full-automatic powder press manufactured by Nanjing Dongtian precision machinery Co., Ltd; when the pressure of the automatic pressing is 60-80 tons, the structure of the used full-automatic molding press is the same as that of the full-automatic powder press of the 0PC-60TG model; the spherical molybdenum powder can ensure that the condition of uneven pressure distribution can not occur even if a large unidirectional pressure is used for pressing, thereby avoiding composition segregation. The invention adopts a spray granulation method to prepare the spherical molybdenum powder, the press forming property is good, and the density required by the molybdenum skeleton can be achieved through automatic pressing. In the above method for preparing a low molybdenum content molybdenum-copper alloy, as a preferred embodiment, in the step of binder removal, the step of binder removal (binder removal) is performed in a pusher furnace, and more preferably, the atmosphere in the pusher furnace is hydrogen, wherein the reducing atmosphere provided by hydrogen can ensure that molybdenum-copper is not oxidized, and if vacuum and nitrogen are used, the cost is increased, and the effect of preventing oxidation is not as good as that of the hydrogen of the present invention; the temperature of the boat pushing furnace is 500-700 ℃ (such as 520 ℃, 540 ℃, 560 ℃, 580 ℃, 600 ℃, 620 ℃, 640 ℃, 660 ℃, 680 ℃), and the speed is 5-10 Hz (such as 6Hz, 7Hz, 8Hz, 9 Hz); the glue discharging time is 2-4 hours, and the glue discharging time is 500-700 ℃. If the temperature of the boat pushing furnace is too low, the glue (namely the binder) is not easy to volatilize, and if the temperature is too high, energy is wasted; if the speed of the boat pushing furnace is too high, the glue discharging is not thorough, and if the speed is too low, the cost is increased.
In the above method for preparing a high molybdenum content molybdenum-copper alloy, as a preferred embodiment, in the step of infiltrating copper, the copper used in the infiltrating copper treatment is an oxygen-free copper plate, and the purity of the oxygen-free copper plate is greater than 99.95%; preferably, the oxygen-free copper plate accounts for 13-70% of the blank (such as 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%); wherein a copper plate is placed under the blank. Preferably, the copper infiltration treatment is performed in a push boat furnace, the atmosphere in the push boat furnace is hydrogen, and the reducing atmosphere provided by the hydrogen can ensure that the molybdenum and the copper are not oxidized, so that the copper infiltration furnace has good wettability, the compactness of the material is ensured, the cost is increased if vacuum and nitrogen are used, and the effect of preventing oxidation is not as good as that of the hydrogen in the invention; the temperature of the pusher furnace is 1200-1250 ℃ (such as 1210 ℃, 1220 ℃, 1230 ℃ and 1240 ℃) and the speed is 20 Hz-30 Hz (such as 22Hz, 24Hz, 26Hz and 28 Hz); the copper impregnation time is 40 minutes to 1 hour (for example, 45 minutes, 50 minutes, 55 minutes, the copper impregnation time is 1200 ℃ to 1250 ℃). Copper leakage can occur when the temperature is too high, and energy is wasted; the fluidity of copper is insufficient when the temperature is too low, and the phenomenon of insufficient infiltration occurs; too fast copper infiltration is insufficient, infiltration is not full, and material density is reduced; too slow a speed may result in copper leakage and may reduce efficiency.
In the above method for preparing the high molybdenum content molybdenum-copper alloy, as a preferred embodiment, the molybdenum content in the high molybdenum content molybdenum-copper alloy is 60% to 90% (e.g. 65%, 70%, 75%, 80%, 85%). Molybdenum-copper alloys with lower molybdenum content do not have a molybdenum skeleton and are therefore not suitable for preparation using the process of the present invention.
The molybdenum-copper alloy with high molybdenum content is prepared by the preparation method of the molybdenum-copper alloy with high molybdenum content.
Compared with the prior art, the invention has the following positive effects:
(1) the invention discloses a preparation method of a molybdenum-copper alloy with high molybdenum content.
(2) The invention uses a spray granulation method to obtain spherical molybdenum powder. Firstly, the spherical powder obtained by using the spray granulation method has good fluidity, can be used in an automatic molding press, and improves the production efficiency and the consistency of alloy performance. Then, the spherical molybdenum powder obtained by using the spray granulation method has good compression molding performance, and the condition of uneven pressure distribution can not occur even if the spherical molybdenum powder is compressed by using larger one-way pressure, thereby avoiding component segregation.
(3) According to the invention, the molybdenum-copper green compacts are pressed by using the automatic forming press, so that the production efficiency and the product performance consistency are improved. The automatic forming press can provide great pressure, it is higher to obtain density, organize even pressed compact, consequently, need not very high temperature shrink skeleton, and even passageway provides stable capillary force, infiltration power is big, thereby make the infiltration temperature reduce (conventional infiltration temperature is 1350 ~ 1400 ℃, because the pressed compact is inhomogeneous, capillary force is inhomogeneous during the infiltration, need the mobility of higher temperature increase copper to accomplish the infiltration), allowable deviation is big (the infiltration temperature is allowed to fluctuate in 30 ℃ of the scope and the infiltration effect is not influenced), infiltration power is big, the time is short.
(4) The method has the glue discharging process, firstly, the colloid (binder) in the pressed compact is removed, simultaneously, the effect of removing impurities in the alloy is achieved, and the problems that the wettability of copper and a framework is poor and the infiltration is not full due to the impurities in the infiltration process can be avoided; in addition, when the colloid is removed, the smoothness of the channel in the molybdenum skeleton can be ensured, and the occurrence of closed pores is avoided.
(5) The invention uses the push boat furnace for infiltration, automatically moves the boat, has good alloy performance consistency, low sintering temperature (the infiltration plays a part of sintering role), short time and improves the production efficiency.
(6) The method fully considers the defects of agglomeration, pores, closed pores, uneven structure and the like possibly occurring in the molybdenum-copper alloy with high molybdenum content, and can prepare the molybdenum-copper alloy with uniform structure and high density and high molybdenum content.
(7) The invention overcomes the defects of low efficiency, complex production process, large product quality fluctuation and the like of the existing preparation process; the method can improve the production efficiency, and the molybdenum-copper alloy produced by the method has good consistency of performance and high yield.
Drawings
For a more clear description of the invention, reference is made herein to the accompanying drawings, which form a further part hereof. Wherein:
fig. 1 is a metallographic photograph of the Mo90Cu10 alloy prepared in example 1 after surface polishing, in which the bright portions are molybdenum and the dark portions are copper.
Detailed Description
In order to highlight the objects, technical solutions and advantages of the present invention, the present invention is further illustrated by the following examples, which are illustrative of the present invention and not limiting.
Example 1 preparation of a Mo90Cu10 alloy, comprising the steps of:
1. molybdenum powder treatment
Prepared with a Fisher-size of 7.0 μm and a bulk density of 1.7g/cm3And crushing the molybdenum powder by using an airflow crusher to obtain the molybdenum powder after airflow crushing.
2. Spray granulation
And (3) taking the molybdenum powder obtained after the airflow crushing in the step (1), adding water and PEG20000 binder, and mixing to obtain slurry. Wherein: the water addition amount is 25 percent of the total mass of the molybdenum powder after the airflow crushing; the addition amount of the binder is 4 percent of the total mass of the molybdenum powder after the airflow crushing. The slurry is dried under the protective atmosphere of nitrogen, the diameter of a spray nozzle is 0.8mm, the pressure of the slurry is 1400KPa, the drying temperature is 180 ℃, and spherical molybdenum powder with the diameter of 40-50 mu m is obtained.
3. Press forming
And (3) pressing the spherical molybdenum powder prepared in the step (3) by using an automatic pressing machine, wherein the pressure of the automatic pressing machine is 80 tons, and the speed is 10Hz, so that a pressed compact is obtained. The automatic molding press is a modification of a 0PC-60TG type full-automatic powder press manufactured by Nanjing Dongtian precision machinery Co., Ltd, and can provide 80 tons of pressure. The profiling process of the profiling of the automatic profiling machine is as follows: 1 adding spherical molybdenum-copper powder into a feeding bin; 2, the spherical molybdenum copper powder in the feeding bin flows into a die through a pipeline under the action of gravity; 3, pressing by a machine (an automatic molding press) according to the set speed and pressure, wherein 10 pieces of pressure are pressed every minute (the pressurization time of each single piece is 2s, the pressure maintaining time is 2s, and the pressure relief and unloading time is 2s (the unloading time is the time in the automatic demolding process)), and the pressure is 80 t; 4, automatically demoulding; 5 circulation 2-4 process.
4. Blank discharging
And (3) putting the pressed blank prepared in the step (3) into a pusher furnace to discharge the glue, wherein the atmosphere is hydrogen, the temperature is 700 ℃, the speed is 5Hz, and the glue discharging time is 4 hours, so that a blank is obtained.
5. Copper infiltration
Weighing 13% of blank mass of oxygen-free copper plate (the oxygen-free copper plate is slightly excessive, so that residual copper is remained after infiltration to ensure infiltration) and the blank after glue removal, and putting the blank into a pusher furnace for copper infiltration at the temperature of 1250 ℃, the speed of 20Hz, the time of 4 hours and the copper infiltration time of 1 hour.
FIG. 1 is a metallographic photograph of the Mo90Cu10 alloy produced by the method after surface polishing, wherein the bright part is molybdenum and the dark part is copper. As can be seen from the metallographic phase, the Mo90Cu10 alloy produced by the method has no closed pores, no agglomeration and no tissue unevenness.
The Mo90Cu10 alloy with phi 15 x 8mm produced by the method has the yield of 500kg in one week and the density of 99 percent, 5 finished products are sampled and inspected, and the results are shown in the following table 1:
numbering
|
Diameter/mm
|
Height/mm
|
Density/g cm-3 |
1
|
15.01
|
8.00
|
9.97
|
2
|
15.00
|
8.00
|
9.97
|
3
|
14.99
|
8.02
|
9.96
|
4
|
15.00
|
8.00
|
9.97
|
5
|
15.00
|
8.00
|
9.97 |
As can be seen from the results in Table 1, the molybdenum-copper alloy prepared by the invention has the effects of uniform structure, high efficiency, good performance consistency, high yield and the like.
Example 2 preparation of Mo75Cu25 alloy
1. Molybdenum powder treatment
Prepared with a Fisher size of 5.0 μm and a bulk density of 1.5g/cm3And crushing the left and right molybdenum powder by using an airflow crusher.
2. Spray granulation
And (3) crushing molybdenum powder by using the airflow prepared in the step (1), adding water and PEG20000 binder, and mixing to obtain slurry. Wherein: the water addition amount is 20 percent of the total mass of the molybdenum powder after the airflow crushing; the addition amount of the binder is 3 percent of the total mass of the molybdenum powder after the airflow crushing. And (3) under the protective atmosphere of nitrogen, spraying the slurry with the diameter of 0.7mm by using a spray nozzle, controlling the pressure of the slurry to be 1300KPa and the drying temperature to be 165 ℃, and drying to obtain spherical molybdenum powder with the diameter of 30-40 mu m.
3. Press forming
And (3) pressing the spherical molybdenum powder prepared in the step (3) by using an automatic press, wherein the pressure is 65 tons, and the speed is 15Hz, so that a pressed compact is obtained. The automatic molding press is a modification of a 0PC-60TG type full-automatic powder press manufactured by Nanjing Dongtian precision machinery, Inc., and can provide 65t of pressure. The profiling process of the profiling of the automatic profiling machine is as follows: 1 adding spherical molybdenum-copper powder into a feeding bin; 2, the spherical molybdenum copper powder in the feeding bin flows into a die through a pipeline under the action of gravity; 3, pressing by a machine (an automatic molding press) according to the set speed and pressure, wherein 15 pieces are pressed every minute (the pressing time of each single piece is 1.5s, the pressure maintaining time is 1.5s, and the pressure relief and unloading time is 1s (the unloading time is the time in the automatic demolding process)), and the pressure is 65 t; 4, automatically demoulding; 5 circulation 2-4 process.
4. Blank discharging
And (3) putting the pressed blank prepared in the step (3) into a pusher furnace to discharge the glue, wherein the atmosphere is hydrogen, the temperature is 600 ℃, the speed is 7Hz, and the glue discharging time is 3 hours to obtain a blank.
5. Copper infiltration
Weighing an oxygen-free copper plate accounting for 36% of the mass of the blank and the blank after glue removal, and putting the blank into a pusher furnace for copper infiltration under the atmosphere of hydrogen at 1220 ℃, at the speed of 25Hz and for 50 minutes.
The Mo75Cu25 alloy produced by the method has the density of 99 percent, 5 finished products are selected and inspected, the diameter range is 15.00 +/-0.01 mm, the height range is 8.00 +/-0.02 mm, and the density can reach 9.79g/cm3。
Example 3 preparation of Mo60Cu40 alloy
1. Molybdenum powder treatment
Prepared such that the Fisher's particle size is 4.0 μm and the apparent density is 1.2g/cm3And crushing the left and right molybdenum powder by using an airflow crusher to obtain the molybdenum powder after airflow crushing.
2. Spray granulation
And (3) crushing molybdenum powder by using the airflow prepared in the step (1), adding water and PEG20000 binder, and mixing to obtain slurry. Wherein: the water addition amount is 15 percent of the total mass of the molybdenum powder after the airflow crushing; the addition amount of the binder is 2 percent of the total mass of the molybdenum powder after the airflow crushing. And (3) under the protective atmosphere of nitrogen, spraying the slurry with the diameter of 0.6mm by a spray nozzle, controlling the pressure of the slurry to be 1200KPa, and drying at 150 ℃ to obtain spherical molybdenum powder with the diameter of 20-30 mu m, thus obtaining a pressed compact.
3. Press forming
The spherical molybdenum powder prepared in the step 3 is pressed by an automatic press, the pressure is 50 tons, and the speed is 20Hz, so that a pressed compact is obtained; wherein, the automatic molding press is a full-automatic powder press with a model number of 0PC-60TG produced by Nanjing Dongtian precision machinery Limited, and the molding process of the automatic molding press specifically comprises the following steps: 1 adding spherical molybdenum-copper powder into a feeding bin; 2, the spherical molybdenum copper powder in the feeding bin flows into a die through a pipeline under the action of gravity; 3, pressing by a machine (an automatic molding press) according to the set speed and pressure, wherein 20 pieces of the product are pressed every minute (the pressurization time of each single piece is 1s, the pressure maintaining time is 1s, the pressure relief and unloading time is 1s), and the pressure is 50 t; 4, automatically demoulding; 5 circulation 2-4 process.
4. Blank discharging
And (3) putting the pressed blank prepared in the step (3) into a pusher furnace to discharge the glue, wherein the atmosphere is hydrogen, the temperature is 500 ℃, the speed is 10Hz, and the glue discharging time is 2 hours, so that a blank is obtained.
5. Copper infiltration
Weighing an oxygen-free copper plate accounting for 70% of the mass of the blank and the blank after glue removal, and putting the blank into a pusher furnace for copper infiltration under the atmosphere of hydrogen at 1200 ℃, at the speed of 30Hz and for 40 minutes.
The Mo60Cu40 alloy produced by the method has the density of 99 percent, 5 finished products are selected and inspected, the diameter range is 15.00 +/-0.01 mm, the height range is 8.00 +/-0.02 mm, and the density can reach 9.65g/cm3。
Comparative example 1 phi 15 x 8mm Mo90Cu10 prepared by the prior art method
The existing preparation method of Mo90Cu10 comprises the following steps: 1 weighing molybdenum powder and batching (dry mixing) the molybdenum powder in a mixer for 12 hours; 2, mixing glue (glycerol alcohol (the volume ratio of the glycerol alcohol to the glycerol alcohol is 2:5)) and stirring uniformly; 3, manually pressing and molding by using a Y41-40C hydraulic press produced by a fertilizer-mixing forging machine tool factory (specifically, manually weighing the powder, manually filling the weighed powder into a die, manually pressurizing to 10 t-12 t, maintaining the pressure for about 1s, and manually demolding); 4, degumming, wherein the degumming temperature is 700 ℃ and the degumming time is 4 hours; 5, skeleton sintering, specifically: keeping the temperature at 1600 ℃ for 1.5 hours; 6, copper infiltration, specifically: the temperature is kept at 1350 ℃ for 2 hours, and the density of Mo90Cu10 produced by the existing Mo90Cu10 method is 97%.
Comparing inventive example 1 with comparative example 1, the comparison results are shown in table 2 below:
TABLE 2
From the comparison of example 1 (inventive process) with comparative example 1 (prior art process) in table 1 above, it can be seen that: the method has the effects of high efficiency, high compactness, uniform tissue, good consistency, high yield and the like; the method has low sintering temperature and short sintering time, and can still obtain materials with high density.