CN114369739B - Preparation method and device of lead-free graphite brass composite material - Google Patents
Preparation method and device of lead-free graphite brass composite material Download PDFInfo
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- CN114369739B CN114369739B CN202111525377.5A CN202111525377A CN114369739B CN 114369739 B CN114369739 B CN 114369739B CN 202111525377 A CN202111525377 A CN 202111525377A CN 114369739 B CN114369739 B CN 114369739B
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C1/00—Making non-ferrous alloys
- C22C1/04—Making non-ferrous alloys by powder metallurgy
- C22C1/05—Mixtures of metal powder with non-metallic powder
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/003—Apparatus, e.g. furnaces
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/02—Compacting only
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- B22—CASTING; POWDER METALLURGY
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- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/10—Sintering only
- B22F3/1003—Use of special medium during sintering, e.g. sintering aid
- B22F3/1007—Atmosphere
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- B22—CASTING; POWDER METALLURGY
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- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/10—Sintering only
- B22F3/1017—Multiple heating or additional steps
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/10—Sintering only
- B22F3/1035—Liquid phase sintering
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C9/00—Alloys based on copper
- C22C9/04—Alloys based on copper with zinc as the next major constituent
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
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Abstract
The preparation method and device of the lead-free graphite brass composite material provided by the disclosure comprise the following steps: uniformly mixing brass powder, graphite powder and a binder and pressing into a blank; and sintering the blank along the blank drawing direction, so that the blank sequentially forms a blank area, a sintering area and a casting blank area along the blank drawing direction, wherein the sintering area is kept at a first temperature, the casting blank area is kept at a second temperature, and gas in the sintering process overflows along the direction opposite to the blank drawing direction. The first temperature is a temperature at which the brass in the sintering zone is in a two-phase state of liquid and solid phases. The second temperature is a temperature at which the brass in the sintering zone changes from a liquid phase to a solid phase. The method can improve the density of the casting blank, lead graphite particles to be uniformly distributed on the brass matrix and lead the components of the casting blank to be more stable.
Description
Technical Field
The disclosure relates to the field of alloy materials and preparation thereof, in particular to a preparation method and a device of a lead-free graphite brass composite material.
Background
The lead brass has excellent cold and hot processing performance, cutting performance and wear resistance, can meet the machining requirements of parts in various shapes, and is widely applied to industries such as civil water supply systems, electronic appliances, automobiles, machine manufacturing and the like at present. However, when lead brass is used as a drinking water pipe fitting such as a faucet or a pipe joint, lead atoms are leached into water by the action of water substances; lead in the waste lead brass spare and accessory parts is easy to enter soil and seriously harms human health, so the application of the lead brass is increasingly limited. All countries in the world pay great attention to the pollution and harm caused by lead, and a series of restrictions on the application of lead-containing brass are put out in succession. According to the national diagnosis Foundation, JIS, DIN50930 and European Union, the standard for lead elution in the waterway must be lowered from 0.05mg/L to 0.01 mg/L. In recent years, the development and research of eco-friendly lead-free-cutting brass has been a research hotspot in the field of copper alloys. One of the methods for eliminating lead pollution is to find a proper brass material capable of replacing lead, namely lead-free brass, so that lead can be thoroughly eliminated, and excellent cutting performance and mechanical performance can be ensured. At present, researchers at home and abroad have successfully prepared the lead-free graphite brass by mainly adding graphite with excellent electric conduction and heat conduction properties to replace lead. In the cutting process, a lubricating film is formed on the newly-generated surface of the graphite which is continuously exposed, the newly-generated surface which appears instantly is covered, the friction between the front cutter face and chips and the friction between the rear cutter face and the contact surface of the workpiece are reduced, and the surface quality of the workpiece is favorably improved.
The traditional preparation methods of the lead-free graphite brass mainly comprise two methods, namely a cold pressing sintering method and a melt stirring method. The cold pressing sintering method is the earliest method for preparing the copper-based graphite composite material and mainly comprises the processes of powder mixing, pressing and forming, sintering, re-pressing and the like. The graphite brass prepared by the traditional cold pressing sintering method has the defects of more air holes, lower tensile strength and difficult meeting of the mechanical property. In order to reduce the pores of the graphite brass and increase the tensile strength, some researchers began to prepare copper-based graphite composite materials by a melt stirring method. The melt stirring method can be classified into a liquid stirring method and a semi-solid stirring method according to the state of the melt. The liquid stirring method is to gradually mix graphite particles in liquid matrix metal under mechanical stirring, and because the specific gravity phase difference of graphite and metal is large, graphite is easy to float on the surface of molten metal to generate segregation; the semi-solid stirring method is to reduce the viscosity of semi-solid melt containing certain solid phase under the action of high-speed shear stress, gradually add graphite particles, and prevent the particles from floating and sinking. However, during the preparation by the semi-solid stirring method, the floating segregation degree of the graphite particles is gradually reduced along with the increase of the solid fraction of the semi-solid slurry, but the rapid stirring easily causes a large amount of gas to be involved, so that air holes are easily formed in castings, and the mechanical property of the material is obviously reduced. In addition, graphite and metallic copper or zinc are easily exposed to air during stirring to cause oxidation reaction, thereby reducing the component stability of the finished product.
Disclosure of Invention
The present disclosure is directed to solving one of the problems set forth above.
Therefore, the preparation method of the lead-free graphite brass composite material capable of improving the mechanical property and the component stability of the material provided by the embodiment of the first aspect of the disclosure comprises the following steps:
uniformly mixing brass powder, graphite powder and a binder and pressing into a blank;
and sintering the blank along the blank drawing direction, so that the blank sequentially forms a blank area, a sintering area and a casting blank area along the blank drawing direction, wherein the sintering area is kept at a first temperature, the casting blank area is kept at a second temperature, and gas in the sintering process overflows along the direction opposite to the blank drawing direction.
The preparation method of the lead-free graphite brass composite material provided by the embodiment of the first aspect of the disclosure has the following characteristics and beneficial effects:
firstly, because the solid phase in the sintering zone (namely, the liquid/solid two-phase zone) can prevent graphite from floating and reduce graphite segregation, graphite and copper-based alloy delamination can be eliminated by controlling the first temperature (namely, the heating temperature) to ensure that graphite brass liquid and the solid phase (the solid phase and the liquid phase are both brass, but the concentrations of zinc elements in copper of the solid phase and the liquid phase are different) coexist in the sintering zone; secondly, the gas can escape directionally along the graphite brass pressed compact by adopting a directional sintering mode, so that the defect of air holes is reduced, and the problem of high porosity in the traditional sintering is solved; again, directional sintering reduces zinc evaporation from brass and results in greater compositional uniformity throughout the sample. The casting blank, the pressed blank and the crystallizer isolate a sintering area from the outside, can prevent and reduce the outward volatilization of zinc, because the directional sintering heat flow is unidirectionally dissipated along the throwing direction, the temperature distribution at the cross section of a sample in the sintering area is uniform, the volatilization amount of zinc is uniform at each position on the cross section, and the fluctuation of the zinc component on the cross section is small; finally, the sintering of the internal area of the graphite brass can avoid the oxidation reaction of graphite, copper or zinc which is easily exposed to the air in the stirring process of the traditional melt stirring method, and the component stability of the casting blank is increased.
In some embodiments, the first temperature is a temperature at which the brass in the sintering zone is in a two-phase state of liquid and solid phases.
In some embodiments, the first temperature is set between 950 ℃ and 1050 ℃.
In some embodiments, the second temperature is a temperature at which brass in the sintering zone changes from a liquid phase to a solid phase.
In some embodiments, the second temperature is set at 60 ℃ to 150 ℃.
In some embodiments, the blank is placed in a vacuum environment during sintering at a vacuum level of 10 deg.f -2 Pa～10 -3 Pa。
In some embodiments, the graphite powder is added in an amount of 0.5% to 3% by weight, the binder is added in an amount of 0.5% to 1.0% by weight, and the balance is brass powder.
In some embodiments, the binder is zinc stearate powder or epoxy resin.
The preparation device of the lead-free graphite brass composite material based on the preparation method provided by the embodiment of the second aspect of the disclosure comprises:
the crystallizer is provided with a gas outlet and is arranged in the sintering furnace and used for accommodating blanks, and gas in the sintering process overflows from the gas outlet;
a heater disposed outside of the crystallizer for providing a first temperature to the sintering zone of the billet;
a cooler disposed outside the mold for providing a second temperature to the strand region of the billet;
a heat shield disposed between the heater and the cold zone vessel; and
a driver for moving the crystallizer and the cooler in a direction of drawing.
In some embodiments, the power of the heater is controlled to be 10 KW-15 KW, and the frequency of the heater is controlled to be 6000 HZ-8000 HZ; controlling the power of the cooler to be 5 KW-10 KW, and controlling the pressure in the cooler to be 0.1 MPa-0.2 MPa.
Drawings
Fig. 1 is a schematic diagram illustrating the principle and structure of a method for preparing a lead-free graphite brass composite material according to an embodiment of the present disclosure.
Fig. 2 is an experimental comparison diagram, in which (a) is an electron microscope diagram of a sintered sample prepared by the preparation method provided in the example of the present disclosure, and (b) is an electron microscope diagram of a sintered sample prepared by a conventional sintering method.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.
On the contrary, this application is intended to cover any alternatives, modifications, equivalents, and alternatives that may be included within the spirit and scope of the application as defined by the appended claims. Furthermore, in the following detailed description of the present application, certain specific details are set forth in order to provide a better understanding of the present application. It will be apparent to one skilled in the art that the present application may be practiced without these specific details.
The invention aims to prepare the lead-free graphite brass by adopting a novel method of regionally oriented liquid phase sintering. The zone directional sintering method integrates the characteristics of traditional sintering and directional solidification, and the working principle of the zone directional sintering method is similar to that of directional solidification. The preparation process can be described as follows: referring to fig. 1, a method for preparing a lead-free graphite brass composite material provided in an embodiment of the first aspect of the present disclosure includes:
uniformly mixing brass powder, graphite powder and a binder and pressing into a blank;
and sintering the blank along the blank drawing direction, so that the blank sequentially forms a blank area, a sintering area and a casting blank area along the blank drawing direction, wherein the sintering area is kept at a first temperature, the casting blank area is kept at a second temperature, and gas in the sintering process overflows along the direction opposite to the blank drawing direction.
In some embodiments, the first temperature is set between 950 ℃ and 1050 ℃ for bringing the brass in the sintering zone into a two-phase state of liquid and solid.
In some embodiments, the second temperature is set to 60-150 ℃ for solidifying the brass liquid phase in the casting blank area, meanwhile, a small amount of brass solid phase in the brass liquid phase can prevent graphite particles from floating upwards, and gas generated during solidification can be fully discharged upwards, so that the excellent effects of improving the density of the casting blank and uniformly distributing the graphite particles in the brass matrix are achieved.
In some embodiments, the blank is placed in a vacuum environment during sintering at a vacuum level of 10 deg.f -2 Pa～10 -3 Pa。
In some embodiments, the blank is made by the steps of:
mixing graphite powder, brass powder and a binder to obtain mixed powder, wherein the particle size of the graphite powder is 20-80 um, the particle size of the brass powder is 50-150 um, the binder is zinc stearate powder or epoxy resin, the graphite powder is added according to 0.5-3% (accounting for the whole volume ratio, the same below) of the total amount, the binder is added according to 0.5-1.0% of the total weight, and the balance is the brass powder, and the brass powder can be selected from any one or a mixture of more of brass H60, brass H62, brass H65, brass H68, brass H70, brass H75, brass H80, brass H85 and brass H90;
adding the mixed powder into a ball milling tank for ball milling to enable the powder to be mixed more uniformly, and enabling part of brass alloy metal particles to wrap graphite particles under the impact of milling balls to finally obtain an ideal ball milling mixed material, wherein the ball milling speed is 200-400 r/min, the ball-to-material ratio is 10-20: 1, and the ball milling time is 6-10 hours;
the ball-milling mixed material is filled into the ball mill with the aperture of
Pressing and forming the blank in a mould to obtain a blank, wherein the compressive stress is 600-800 MPa, and the pressure maintaining time is 10-15 min; the length of the obtained blank is 80-120 mm. 2-4 blanks are loaded into the container with the diameter of
The alumina ceramic tube is put into a sintering furnace for directional sintering. During sintering, the withdrawal rate is controlled to be 0.5 mm/min-1.2 mm/min.
The reaction mechanism of the preparation method of the lead-free graphite brass composite material provided by the embodiment of the first aspect of the disclosure is as follows:
according to the preparation method of the lead-free graphite brass composite material provided by the embodiment of the first aspect of the disclosure, the lead-free graphite brass is prepared by adopting a region-oriented liquid phase sintering method, the region-oriented liquid phase sintering method integrates the characteristics of traditional sintering and directional solidification, and the working principle of the method is similar to directional solidification, and specifically:
in the directional sintering process, when the temperature of a sintering area is controlled between a liquid phase region and a solid phase region of brass, the liquid phase and the solid phase exist in the sintering area, and the solid phase in the two-phase region can prevent light graphite particles from floating upwards, so that the graphite particles are uniformly distributed in a brass matrix. Because the heating area and the cooling area are fixed at certain positions, the pressed compact can pass through the sintering area in the process of moving from top to bottom, and therefore the effect of uniformly distributing graphite particles of the whole blank is achieved.
The preparation method of the lead-free graphite brass composite material provided by the embodiment of the first aspect of the disclosure has the following advantages:
firstly, because the solid phase in the sintering zone (namely, the liquid/solid two-phase zone) can prevent graphite from floating and reduce graphite segregation, the graphite and copper-based alloy delamination can be eliminated by controlling the first temperature (namely, the heating temperature) to ensure that the graphite brass liquid and the solid phase (the solid phase is a substance in which a small amount of Zn atoms are dissolved into a large amount of Cu atoms) coexist in the sintering zone; secondly, the gas can escape directionally along the graphite brass pressed compact by adopting a directional sintering mode, so that the defect of air holes is reduced, and the problem of high porosity in the traditional sintering is solved; again, directional sintering can reduce zinc volatilization from brass and the composition is more uniform throughout the sample. The casting blank, the pressed compact and the crystallizer isolate a sintering area from the outside, and can block and reduce the outward volatilization of zinc. Furthermore, because the directional sintering heat flow is unidirectionally dissipated along the blank drawing direction, the temperature distribution at the cross section of the sample in the sintering area is uniform, and the zinc volatilization amount is uniform at each position on the cross section, so that the zinc component fluctuation on the cross section is small; finally, the sintering of the internal area of the graphite brass can avoid the oxidation reaction of graphite, copper or zinc which is easily exposed to the air in the stirring process of the traditional melt stirring method, and the component stability of the casting blank is increased.
Various embodiments of the method for preparing the lead-free graphite brass composite material provided by the first aspect of the disclosure are described below:
example 1
The preparation method of this example includes the following steps:
1. preparing and mixing materials: graphite powder, brass powder and zinc stearate powder are mixed, wherein the particle size of the graphite powder is 20um, the particle size of the brass (H60) powder is 80um, the graphite powder is added according to 0.5 percent (accounting for the whole volume ratio, the same below) of the total amount, and the zinc stearate is added according to 0.5 percent of the total weight. In this embodiment, graphite powder, brass powder, and zinc stearate powder are respectively loaded into a v-type mixer to be uniformly mixed, so as to obtain mixed powder.
2. Ball milling: adding the mixed powder into a ball milling tank, and mechanically milling and mixing the mixed powder in a planetary ball mill (a microcomputer planetary ball mill with the model of MITR-YXQM-2L is adopted in the embodiment) to obtain a ball milled mixture, wherein the ball milling tank is made of polytetrafluoroethylene, the grinding balls are made of zirconia, the ball milling speed is 350r/min, the ball-to-material ratio is 10:1, and the ball milling time is 8 hours.
3. And (3) green compact forming: the ball-milling mixed material is filled into a container with the aperture of
And pressing and molding the blank on a material testing machine (the embodiment adopts a universal material testing machine with the model of WEW-300B) by using a pressure head, wherein the pressure stress is 600MPa, and the pressure maintaining time is 10min, so that a blank is obtained, and the length of the obtained blank is 120 mm.
4. Directional sintering: 2 are made of
The cylindrical formed blank is put into an alumina ceramic tube with the diameter of 13mm and put into a directional sintering furnace, and then the furnace door is closed. Starting vacuum-pumping systemThe system is operated by a mechanical pump to vacuumize for 30min, and then a molecular pump is started to operate for 35min to ensure that the vacuum degree is 10 -2 Pa. Starting a heating system, adjusting the heating power to 12KW and the heating frequency to 7000HZ until the temperature of a sintering area reaches 1020 ℃; the cooler is started, the cooling power is adjusted to be 5.5KW, and the pressure in the cooler is 0.1MPa until the temperature of the casting blank area reaches 92 ℃. Starting a stepless speed changer to carry out directional sintering drawing, wherein the drawing speed is 0.8 mm/min.
Example 2
The preparation method of this example includes the following steps:
1. preparing and mixing materials: graphite powder, brass powder and epoxy resin powder are mixed, wherein the particle size of the graphite powder is 40um, the particle size of brass (H90) is 100um, the graphite powder is added according to 1.5 percent of the total weight, and the epoxy resin powder is added according to 1.0 percent of the total weight. In this embodiment, graphite powder, brass powder, and epoxy resin powder are respectively loaded into a v-type mixer to be uniformly mixed, so as to obtain mixed powder.
2. Ball milling: adding the mixed powder into a ball milling tank, and mechanically milling and mixing the mixed powder in a planetary ball mill (a microcomputer planetary ball mill with the model of MITR-YXQM-2L is adopted in the embodiment) with the ball milling tank made of polytetrafluoroethylene, the ball milling tank made of zirconia, the ball milling speed of 350r/min, the ball-material ratio of 15:1 and the ball milling time of 8h to obtain the ball-milled mixed material.
3. And (3) green compact forming: the ball-milling mixed material is filled into the ball mill with the aperture of
And pressing the die hole by using a pressure head on a material testing machine (the embodiment adopts a universal material testing machine with the model of WEW-300B) to form a blank, wherein the pressure stress is 700MPa, and the pressure maintaining time is 15min, and the length of the obtained blank is 100 mm.
4. Directional sintering: 3 cylindrical molding blanks with the diameter of 14mm are loaded into an alumina ceramic tube with the diameter of 15mm, and the furnace door is closed after the alumina ceramic tube is placed into a directional sintering furnace. Starting the vacuum-pumping system, starting the mechanical pump to operate for 30min, starting the molecular pump to operate for 40min to make the vacuum degree 0.8 × 10 -2 Pa. OpenerMoving a heater, adjusting the heating power to be 15KW and the heating frequency to be 6000HZ until the temperature of the sintering area reaches 1035 ℃; the cooler was started at 7.5KW and the pressure in the cooler was 0.15MPa until the temperature in the casting zone reached 84 ℃. Starting a stepless speed changer to carry out directional sintering drawing, wherein the drawing speed is 0.6 mm/min.
And (3) validity verification:
in order to verify the effectiveness of the preparation method of the lead-free graphite brass composite material provided in the first aspect of the present disclosure, the sintered samples prepared by the above-mentioned example 1 and the existing conventional powder sintering method (influence of sintering temperature on the structure and performance of lead-free graphite brass, university of Nanchang (Gongchang's school edition), 2014, volume 36, phase 4: 373-377) are compared, see fig. 2, where (a) is an electron microscope image of the sintered sample prepared in the example 1 of the present disclosure, and (b) is an electron microscope image of the sintered sample prepared in the conventional method, and as can be seen from (a) in fig. 2, the graphite particles prepared in the example 1 of the present disclosure do not have an agglomeration phenomenon, and are uniformly distributed on a brass matrix, and the size of the graphite particles is about 10 um. This shows that after ball milling for 8h at a ball milling speed of 350r/min, the raw graphite particles are crushed and refined under the impact of the milling balls. Meanwhile, no obvious pores appear in the brass matrix. As shown in fig. 2 (b), the lead-free graphite brass prepared by the conventional method has uneven graphite particle distribution, obvious agglomeration phenomenon and more pores in the brass grain boundary. Therefore, the method provided by the embodiment of the disclosure can prepare the lead-free graphite brass with the excellent structure, in which the graphite particles are uniformly distributed and have no obvious pores, and has obvious advantages compared with the lead-free graphite brass prepared by the traditional method.
The preparation device of the lead-free graphite brass composite material provided by the embodiment of the second aspect of the disclosure, referring to fig. 1, comprises:
the crystallizer is provided with a gas outlet and is arranged in the sintering furnace for accommodating the blank, and gas in the sintering process overflows from the gas outlet;
the heater is arranged outside the crystallizer and used for providing a first temperature for a sintering area of the blank;
the cold area device is arranged outside the crystallizer and is used for providing a second temperature for a casting blank area of the blank;
a heat insulation plate arranged between the heater and the cold area device; and
and the driver is used for moving the crystallizer and the cooler along the throwing direction.
The crystallizer is generally made of aluminum oxide, in the process of blank drawing, the heater is kept stationary, the cooler and the crystallizer are kept relatively stationary, namely, the cooler also moves along the direction of blank drawing. The heat shield is used to isolate the heating zone from the cooling zone to create a temperature gradient in the sintering zone.
In some embodiments, the heater power is 10-15 KW and the heater frequency is 6000-8000 HZ during sintering.
In some embodiments, the power of the cooler is 5-10 KW during sintering, and the pressure in the cooler is controlled to be 0.1-0.2 MPa.
In the description herein, reference to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the application. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Moreover, various embodiments or examples and features of various embodiments or examples described in this specification can be combined and combined by one skilled in the art without being mutually inconsistent.
Although examples of the present invention have been shown and described above, it should be understood that the above examples are illustrative and not to be construed as limiting the present invention, and that changes, modifications, substitutions and alterations can be made in the above examples by those of ordinary skill in the art without departing from the scope of the present invention.
Claims (8)
1. A preparation method of a lead-free graphite brass composite material is characterized by comprising the following steps:
uniformly mixing brass powder, graphite powder and a binder and pressing into a blank;
sintering the blank along a blank drawing direction to enable the blank to sequentially form a blank area, a sintering area and a casting blank area along the blank drawing direction, wherein the sintering area is kept at a first temperature, the casting blank area is kept at a second temperature, and gas in the sintering process overflows in the direction opposite to the blank drawing direction; the first temperature is a temperature at which the brass in the sintering zone is in a two-phase state of liquid phase and solid phase, and the second temperature is a temperature at which the brass in the sintering zone changes from liquid phase to solid phase.
2. The method of claim 1, wherein the first temperature is set at 950 ℃ to 1050 ℃.
3. The method of claim 1, wherein the second temperature is set at 60 ℃ to 150 ℃.
4. The method of claim 1, wherein the blank is placed in a vacuum environment during the sintering process, wherein the vacuum is 10 ° f -2 Pa～10 -3 Pa。
5. The method according to claim 1, wherein the graphite powder is added in an amount of 0.5 to 3% by weight, the binder is added in an amount of 0.5 to 1.0% by weight, and the balance is brass powder.
6. The method as claimed in claim 1, wherein the binder is zinc stearate powder or epoxy resin.
7. A preparation device of the lead-free graphite brass composite material based on the preparation method of any one of claims 1 to 6, characterized by comprising:
the crystallizer is provided with a gas outlet and is arranged in the sintering furnace and used for accommodating blanks, and gas in the sintering process overflows from the gas outlet;
a heater disposed outside of the crystallizer for providing a first temperature to the sintering zone of the billet;
a cooler disposed outside the mold for providing a second temperature to the strand region of the billet;
a heat insulating plate interposed between the heater and the cooler; and
a driver for moving the crystallizer and the cooler in a direction of drawing.
8. The manufacturing apparatus according to claim 7, wherein the heater is controlled to have a power of 10kW to 15kW and a frequency of 6000Hz to 8000 Hz; controlling the power of the cooler to be 5 kW-10 kW, and controlling the pressure in the cooler to be 0.1 MPa-0.2 MPa.
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| CN202111525377.5A CN114369739B (en) | 2021-12-14 | 2021-12-14 | Preparation method and device of lead-free graphite brass composite material |
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| CN202111525377.5A CN114369739B (en) | 2021-12-14 | 2021-12-14 | Preparation method and device of lead-free graphite brass composite material |
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