Sintering furnace and cemented carbide sintering method based on the sintering furnace

Abstract

The present invention provides a sintering furnace and a cemented carbide sintering method based on the sintering furnace, which relates to the technical field of alloy sintering. Inside the furnace body of the sintering furnace, there is a sintering box with an electric auxiliary heating layer and a heat preservation layer wrapped around the periphery. At the same time, the sintering furnace is also provided with a microwave heating device, a vacuum device, a rapid cooling device and an inert gas filling device. Therefore, during sintering, simultaneous heating by electric auxiliary heating and microwave heating can be realized under vacuum conditions, effectively alleviating the problems of long heat preservation time, high sintering temperature and ineffective control of alloy grain growth in the existing electric heating vacuum sintering furnace, or the problem of poor sintering effect caused by the negative temperature gradient phenomenon due to the surface temperature of the alloy product being lower than the inside in the existing microwave sintering furnace.

Description

Technical Field

[0001] The present invention relates to the technical field of alloy sintering, and particularly to a sintering furnace and a cemented carbide sintering method based on the sintering furnace. Background Art

[0002] Cemented carbide is known as the "teeth of industry". China is a major producer and consumer of cemented carbide in the world, but 70% of the high-precision and high-performance CNC tools used in China's machining manufacturing rely on imports. Ultra-fine and nano-crystalline structured "dual-high" cemented carbide is required for modern processing industries and special fields, and it is also the only way for the development of cemented carbide enterprises.

[0003] However, currently, the traditional cemented carbide sintering equipment is a horizontal electric heating vacuum (pressurized) sintering furnace. This type of sintering furnace is a heat conduction type degreasing and sintering integrated furnace, and its heating method is to heat the surface of the material, forming a temperature difference between the inside and outside of the material. Heat transfer occurs due to the internal and external temperature gradients of the material, and the material is heated as a whole through heat transfer to balance the internal and external temperatures by "conductive heating". The sintering time is as long as more than 20 hours, and the holding time is long, the sintering temperature is high, the thermal efficiency is low, the sintering cost is high, and the growth of alloy grains cannot be effectively controlled.

[0004] In recent years, microwave heating sintering furnaces have become a research hotspot for alloy sintering furnaces. Microwave heating is a "transmission heating" method in which the material directly absorbs microwaves and its energy is consumed to increase the temperature. Microwaves penetrate the material instantaneously, enabling the material to absorb microwaves and be heated simultaneously inside and outside. It is a "volume heating method" without a heat transfer process, and has the advantages of uniform heating, low energy consumption, short sintering time, low sintering cost, uniform alloy particle size distribution, and no abnormal growth.

[0005] However, due to the sintering principle, the heating gradient of alloy products by microwave heating is different from that of traditional cemented carbide sintering furnaces. The heating process of traditional cemented carbide sintering furnaces is carried out by convection, conduction, and radiation methods, forming a temperature gradient with the edge temperature of the alloy product higher than the center temperature. However, for alloy products heated by microwave, due to the heat dissipation on the surface, a temperature gradient opposite to that of conventional sintering will be generated, that is, the temperature in the central region of the alloy product is high, and the temperature in the edge region is low. The heat dissipation on the surface of the alloy product makes the surface temperature of the alloy product lower than the inside, showing a negative temperature gradient phenomenon.

[0006] Due to the above negative temperature gradient phenomenon, the sintering effects of existing microwave sintering furnaces, such as the density, porosity, and internal structure of alloy products, are not ideal; the microwave sintering of cemented carbide has remained at the experimental furnace stage and has not yet entered industrial production.

[0007] In view of this, the present invention is specifically proposed. Summary of the Invention

[0008] The first object of the present invention is to provide a sintering furnace, which can realize simultaneous heating operation of electric auxiliary heating and microwave heating under vacuum conditions, effectively alleviating the problems of long heat preservation time, high sintering temperature, and ineffective control of alloy grain growth in existing electric heating vacuum sintering furnaces, or the problem of poor sintering effect caused by the negative temperature gradient phenomenon due to the surface temperature of alloy products being lower than the internal temperature in existing microwave sintering furnaces.

[0009] The second object of the present invention is to provide a cemented carbide sintering method based on the above sintering furnace. This method effectively solves the problem of negative temperature gradient where the temperature in the central region of the cemented carbide product is high and the temperature in the edge region is low during the microwave sintering process, making the temperature in each region of the furnace chamber basically the same; the cemented carbide products after sintering and being taken out of the furnace have a uniform hardness distribution, fine WC grains, and a more uniform microstructure.

[0010] A sintering furnace provided by the present invention includes a furnace body with a hollow cavity, a sintering device, a microwave heating device, a vacuum device, and a rapid cooling device;

[0011] Among them, the sintering device includes a sintering box disposed inside the furnace body for placing sintering materials, and an electric auxiliary heating layer and a heat preservation layer sequentially coated around the sintering box;

[0012] The microwave heating device is a microwave magnetron, and the microwave magnetrons are arranged on the top and both sides of the furnace body and are evenly and cross - distributed;

[0013] The vacuum pipeline is connected to the inside of the furnace body to provide a vacuum environment inside the furnace body.

[0014] Furthermore, the sintering box is mainly made of alumina, polycrystalline mullite, silicon nitride ceramics or graphite materials, preferably fiberboard;

[0015] Preferably, the electric auxiliary heating layer is mainly made of carbon fiber, carbon composite material, silicon carbide or graphite materials;

[0016] Preferably, the heat preservation layer is mainly made of alumina, mullite, zirconium fiber and graphite carbon fiber materials, preferably graphite carbon fiber materials;

[0017] Furthermore, the furnace body includes a furnace door, a pneumatic switch and a cooling water jacket.

[0018] Furthermore, the microwave heating device includes a plurality of microwave magnetrons for conducting microwaves into the furnace body.

[0019] Furthermore, the sintering furnace further includes a wax collection pipeline, which is connected to the inside of the furnace body and is used to discharge paraffin when paraffin is used as a forming agent for sintering;

[0020] Preferably, the sintering furnace further includes an inflation pipeline for inflating inert gas;

[0021] Preferably, the sintering furnace further includes a rapid cooling device, which includes an inert gas inlet at the top of the furnace body, an internal circulating water condenser and a motor fan at the tail of the furnace body, and a circulating water cooling jacket installed around the whole furnace body.

[0022] Preferably, the sintering furnace further includes a temperature measuring device, preferably a thermocouple.

[0023] Furthermore, the sintering furnace further includes a control system, which is electrically connected to the furnace body, the sintering device, the microwave heating device, and the vacuum pipeline in an electrical signal.

[0024] A cemented carbide sintering method based on the above sintering furnace provided by the present invention, the method includes the following steps:

[0025] Place the alloy green compact to be sintered in the sintering box of the above sintering furnace; under the condition of simultaneous heating by the microwave heating device and the electric auxiliary heating layer, perform degreasing treatment, deoxidation and degassing treatment, sintering treatment and cooling treatment in sequence to obtain cemented carbide.

[0026] Furthermore, the sintering conditions for the degreasing treatment at least satisfy at least one of the following:

[0027] Vacuum degree 10 - 20 Pa, temperature 450 - 550 °C, heating-up time 10 - 30 min, heating-up speed 5 - 10 °C / min;

[0028] Preferably, the sintering conditions for the deoxidation and degassing treatment at least satisfy at least one of the following:

[0029] Vacuum degree 5 - 10 Pa, temperature 850 - 1200 °C, heating-up time 15 - 30 min, heating-up speed 10 - 20 °C / min;

[0030] Preferably, the sintering conditions for the sintering treatment at least satisfy at least one of the following:

[0031] Vacuum degree 1 - 10, sintering temperature 1370 - 1400 °C, holding time 20 - 30 min.

[0032] Furthermore, the method includes the following steps:

[0033] (a), Degreasing treatment: Place the alloy green compact to be sintered in the sintering box of the above sintering furnace, under a vacuum degree of 10 - 20 Pa, heat up to 450 - 550 °C at a heating-up speed of 5 - 10 °C / min, and then hold for 10 - 30 min to obtain a degreased blank;

[0034] (b), Deoxidation and degassing treatment: The degreased alloy is heated from room temperature to 830 - 850 °C at a heating rate of 10 - 20 °C / min under a vacuum of 5 - 10 Pa, held for 5 - 10 min, and then further heated to 1150 - 1200 °C at a heating rate of 10 - 20 °C / min and held for 10 - 20 min to obtain a billet after deoxidation and degassing;

[0035] (c), Sintering treatment: The billet after deoxidation and degassing is heated from room temperature to 1370 - 1400 °C at a heating rate of 10 - 20 °C / min under a vacuum of 1 - 10 Pa, then held for 20 - 30 min to obtain a sintered alloy;

[0036] (d), Cooling treatment: The sintered alloy is cooled to 1150 - 1200 °C under a vacuum of 10 - 20 Pa, and then in an atmosphere of protective gas, a rapid cooling device is started to cool the furnace temperature to 100 °C - room temperature to obtain a cemented carbide;

[0037] The sintering heating in the steps (a) degreasing treatment, (b) deoxidation and degassing treatment, and (c) sintering treatment is carried out under the condition of simultaneous heating by a microwave heating device and an electric auxiliary heating layer.

[0038] Furthermore, when paraffin is used as a forming agent for sintering, the step (a) degreasing treatment is carried out in an atmosphere of protective gas;

[0039] Preferably, when paraffin is used as a forming agent for sintering, the step (a) degreasing treatment includes the following steps:

[0040] The green compact of the alloy to be sintered is placed in the sintering box of the above sintering furnace, and under an atmosphere of protective gas, the pressure in the furnace is controlled to be 8 - 12 Kpa; then it is heated from room temperature to 450 - 550 °C at a heating rate of 5 - 10 °C / min and held for 10 - 30 min to obtain a degreased alloy; during the degreasing process, paraffin is discharged from the furnace body through a wax collection pipeline.

[0041] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0042] The sintering furnace provided by the present invention has a sintering box with an electric auxiliary heating layer and a heat insulation layer wrapped around the periphery inside the furnace body, and at the same time, the sintering furnace is also provided with a microwave heating device and a vacuum device. Therefore, during sintering, it can achieve simultaneous heating work of electric auxiliary heating and microwave heating under vacuum conditions, effectively alleviating the problems of long heat preservation time, high sintering temperature, and ineffective control of alloy grain growth in the existing electric heating vacuum sintering furnace, or the problem of poor sintering effect caused by the negative temperature gradient phenomenon due to the surface temperature of the alloy product being lower than the inside in the existing microwave sintering furnace.

[0043] The cemented carbide sintering method based on the above-mentioned sintering furnace provided by the present invention first places the green compact to be sintered in the sintering box of the above-mentioned sintering furnace, and then, under the condition of simultaneous heating by the microwave heating device and the electric auxiliary heating layer, successively performs degreasing treatment, deoxidation and degassing treatment, sintering treatment and cooling treatment to obtain cemented carbide. Through the simultaneous heating of the microwave heating device and the electric auxiliary heating layer, the above-mentioned sintering method effectively solves the problem of negative temperature gradient where the temperature in the central area of the cemented carbide product is high and the temperature in the edge area is low during the microwave sintering process, making the temperature in each area of the furnace chamber basically the same; the cemented carbide products after sintering out of the furnace have a uniform hardness distribution, a microscopic tissue structure with fine and more uniform WC grains, no abnormal grain growth, high density, few internal pores, and the pore shape is rounder than that of traditional sintering, with better ductility and toughness, and the cobalt phase is evenly distributed, forming a good network structure, and the comprehensive performance is excellent. At the same time, the entire sintering process takes a short time, which is 1 / 5 to 1 / 3 of the traditional heating vacuum sintering time, with high production efficiency, low energy consumption and energy saving. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0045] Figure 1 It is a schematic diagram of the overall structure of the sintering furnace provided in Embodiment 1 of the present invention;

[0046] Figure 2 It is a schematic cross-sectional structure diagram of the sintering furnace provided in Embodiment 1 of the present invention;

[0047] Figure 3 It is a schematic diagram of the overall structure of the sintering furnace provided in Embodiment 4 of the present invention.

[0048] Reference numerals: 1 - furnace body; 2 - sintering device; 3 - microwave heating device; 4 - vacuum pipeline; 21 - sintering box; 22 - electric auxiliary heating layer; 23 - heat preservation layer; 11 - furnace door; 12 - pneumatic switch; 13 - cooling water jacket; 5 - wax collection pipeline; 6 - gas charging pipeline; 7 - rapid cooling device; 8 - temperature measuring device. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0049] The technical solution of the present invention will be clearly and completely described below in conjunction with embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0050] According to one aspect of the present invention, a sintering furnace includes a furnace body 1 with a hollow cavity, a sintering device 2, a microwave heating device 3, and a vacuum pipeline 4.

[0051] Among them, the sintering device 2 includes a sintering box 21 disposed inside the furnace body 1 for placing sintering materials, and an electric auxiliary heating layer 22 and a heat insulation layer 23 sequentially coated around the sintering box 21.

[0052] The microwave heating device 3 is disposed at the top and both sides of the furnace body 1 and is evenly and cross - distributed.

[0053] The vacuum pipeline 4 is connected to the inside of the furnace body 1 to provide a vacuum environment inside the furnace body 1.

[0054] For the sintering furnace provided by the present invention, a sintering box 21 with an electric auxiliary heating layer 22 and a heat insulation layer 23 coated around it is disposed inside the furnace body 1 of the sintering furnace. At the same time, the sintering furnace is also provided with a microwave heating device 3 and a vacuum pipeline 4. Therefore, during sintering, simultaneous heating of electric auxiliary heating and microwave heating can be realized under vacuum conditions, effectively alleviating the problems of long heat preservation time, high sintering temperature, and ineffective control of alloy grain growth in existing electric - heating vacuum sintering furnaces, or the problem of poor sintering effect caused by the negative temperature gradient phenomenon due to the surface temperature of alloy products being lower than the inside in existing microwave sintering furnaces.

[0055] In a preferred embodiment of the present invention, the sintering box 21 is mainly made of alumina, polycrystalline mullite, silicon nitride ceramics, or graphite materials, preferably fiberboard.

[0056] As a preferred embodiment, the above - mentioned sintering box 21 is made of polycrystalline mullite plus graphite.

[0057] In a preferred embodiment of the present invention, the electric auxiliary heating layer 22 is mainly made of carbon fiber, carbon composite materials, silicon carbide, or graphite materials.

[0058] As a preferred embodiment, the above - mentioned electric auxiliary heating layer 22 is made of carbon fiber plus graphite.

[0059] In a preferred embodiment of the present invention, the heat insulation layer 23 is mainly made of alumina, mullite, zirconium fiber, and graphite carbon fiber materials, preferably graphite carbon fiber materials.

[0060] As a preferred embodiment, the above-mentioned heat insulation layer 23 is made of graphite carbon fiber and polycrystalline mullite fiber.

[0061] In a preferred embodiment of the present invention, the furnace body 1 includes a furnace door 11, a pneumatic switch 12 and a cooling water jacket 13.

[0062] As a preferred embodiment, the above-mentioned furnace door 11, pneumatic switch 12 and cooling water jacket 13, the whole body of the furnace body 1 is equipped with a circulating water cooling jacket to protect each flange, the seal of the furnace door 11, the valve seal and the cooling of the furnace body 1. When the rapid cooling device 7 is started, it helps to cool down quickly.

[0063] In a preferred embodiment of the present invention, the microwave heating device 3 includes a plurality of microwave magnetrons for conducting microwaves into the furnace body 1.

[0064] As a preferred embodiment, the above-mentioned microwave heating device 3, the magnetrons are arranged at the top and both sides of the furnace body 1 and are evenly and cross-distributed.

[0065] In a preferred embodiment of the present invention, the sintering furnace further includes a wax collection pipeline 5, which is connected to the inside of the furnace body 1 and is used to discharge paraffin when paraffin is used as a forming agent for sintering;

[0066] In a preferred embodiment of the present invention, the sintering furnace further includes an inflation pipeline 6 for inflating inert gas;

[0067] In a preferred embodiment of the present invention, the rapid cooling device 7 includes an inert gas inlet at the top of the furnace body 1, a built-in circulating water condenser and a motor fan at the tail of the furnace body 1, and a circulating water cooling jacket is installed on the whole body of the furnace body 1.

[0068] In a preferred embodiment of the present invention, the sintering furnace further includes a temperature measuring device 8, preferably a tungsten-rhenium thermocouple.

[0069] In a preferred embodiment of the present invention, the sintering furnace further includes a control system: executing process programs, starting and stopping each device, etc. The control system is electrically connected to the furnace body 1, the sintering device 2, the microwave heating device 3 and the vacuum pipeline 4.

[0070] According to one aspect of the present invention, a cemented carbide sintering method based on the above-mentioned sintering furnace, the method includes the following steps:

[0071] Place the alloy green compact to be sintered in the sintering box 21 of the above-mentioned sintering furnace;

[0072] Under the condition of simultaneous heating by the microwave heating device 3 and the electric auxiliary heating layer 22, a debinding treatment, a deoxidation and degassing treatment, a sintering treatment, and a cooling treatment are sequentially performed to obtain cemented carbide.

[0073] The cemented carbide sintering method based on the above sintering furnace provided by the present invention first places the alloy green compact to be sintered in the sintering box 21 of the above sintering furnace, and then, under the condition of simultaneous heating by the microwave heating device 3 and the electric auxiliary heating layer 22, a debinding treatment, a deoxidation and degassing treatment, a sintering treatment, and a cooling treatment are sequentially performed to obtain cemented carbide. Through the simultaneous heating of the microwave heating device 3 and the electric auxiliary heating layer 22, the above sintering method effectively solves the problem of negative temperature gradient where the temperature in the central region of the cemented carbide product is high and the temperature in the edge region is low during the microwave sintering process, making the temperature in each region of the furnace chamber basically the same; the cemented carbide product after sintering has a uniform hardness distribution, a fine and more uniform microstructure of WC grains, no abnormal grain growth, high density, few internal pores, a rounder pore shape than that of traditional sintering, better ductility and toughness, and a uniform distribution of the cobalt phase, forming a good network structure, with excellent comprehensive performance. At the same time, the entire sintering process takes a short time, which is 1 / 5 to 1 / 3 of the time of traditional heating vacuum sintering, with high production efficiency, low energy consumption, and energy conservation.

[0074] In a preferred embodiment of the present invention, the sintering conditions for the debinding treatment satisfy at least one of the following:

[0075] Vacuum degree 10 - 20 Pa, temperature 450 - 550 °C, heating-up time 10 - 30 min, heating-up speed 5 - 10 °C / min;

[0076] As a preferred embodiment, the sintering conditions for the above debinding treatment are: heating-up time 15 min, heating-up speed 7 °C / min.

[0077] In a preferred embodiment of the present invention, the sintering conditions for the deoxidation and degassing treatment satisfy at least one of the following:

[0078] Vacuum degree 5 - 10 Pa, temperature 850 - 1200 °C, heating-up time 15 - 30 min, heating-up speed 10 - 20 °C / min;

[0079] As a preferred embodiment, the sintering conditions for the above deoxidation and degassing treatment are: heating-up time 25 min, heating-up speed 14 °C / min.

[0080] In a preferred embodiment of the present invention, the sintering conditions for the sintering treatment satisfy at least one of the following:

[0081] The degree of vacuum is 1 - 10 Pa, the sintering temperature is 1370 - 1400 °C, and the heat preservation time is 20 - 30 min.

[0082] As a preferred embodiment, the sintering conditions for the above sintering treatment: the heat preservation time is 20 min.

[0083] In a preferred embodiment of the present invention, the method comprises the following steps:

[0084] (a), degreasing treatment: placing the green compact of the alloy to be sintered in the sintering box 21 of the above sintering furnace, heating it from room temperature to 450 - 550 °C at a heating rate of 5 - 10 °C / min under a degree of vacuum of 10 - 20 Pa, and then keeping it warm for 10 - 30 min to obtain the green compact after degreasing treatment;

[0085] (b), deoxidation and degassing treatment: heating the degreased alloy from room temperature to 830 - 850 °C at a heating rate of 10 - 20 °C / min under a degree of vacuum of 5 - 10 Pa, keeping it warm for 5 - 10 min, and then continuing to heat it from room temperature to 1150 - 1200 °C at a heating rate of 10 - 20 °C / min and keeping it warm for 10 - 20 min to obtain the green compact after deoxidation and degassing treatment;

[0086] (c), sintering treatment: heating the alloy after deoxidation and degassing from room temperature to 1370 - 1400 °C at a heating rate of 10 - 20 °C / min under a degree of vacuum of 1 - 10 Pa, and then keeping it warm for 20 - 30 min to obtain the sintered alloy;

[0087] (d), cooling treatment: cooling the sintered alloy from room temperature to 1150 - 1200 °C under a degree of vacuum of 10 - 20 Pa, and then starting the rapid cooling device 7 to cool the furnace temperature to 100 °C - room temperature in the atmosphere of the protective gas to obtain the cemented carbide;

[0088] The sintering heating in the steps (a) degreasing treatment, (b) deoxidation and degassing treatment, and (c) sintering treatment is carried out under the condition of simultaneous heating of the microwave heating device 3 and the electric auxiliary heating layer 22.

[0089] In a preferred embodiment of the present invention, when paraffin is used as the molding agent for sintering, the step (a) degreasing treatment is carried out in the atmosphere of the protective gas;

[0090] Preferably, when paraffin is used as the molding agent for sintering, the step (a) degreasing treatment comprises the following steps:

[0091] Place the green compact of the alloy to be sintered in the sintering box 21 of the above sintering furnace. Under the atmosphere of a protective gas, control the pressure in the furnace to be 8 - 12 Kpa; then heat it at a heating rate of 5 - 10 °C / min to 450 - 550 °C and hold for 10 - 30 min to obtain the degreased alloy; during the degreasing process, the paraffin wax is discharged from the furnace body 1 through the wax collection pipeline 5.

[0092] The technical solution of the present invention will be further described below in conjunction with embodiments.

[0093] Embodiment 1

[0094] As Figure 1 、 Figure 2 shown, a sintering furnace, the sintering furnace includes a furnace body 1 with a hollow cavity, a sintering device 2, a microwave heating device 3 and a vacuum pipeline 4;

[0095] Among them, the sintering device 2 includes a sintering box 21 arranged inside the furnace body 1 for placing sintering materials, and an electric auxiliary heating layer 22 and a heat preservation layer 23 sequentially coated around the sintering box 21.

[0096] For the sintering furnace provided by the present invention, the sintering box 21 with an electric auxiliary heating layer 22 and a heat preservation layer 23 coated around is arranged inside the furnace body 1 of the sintering furnace. At the same time, the sintering furnace is also provided with a microwave heating device 3 and a vacuum pipeline 4. Therefore, during sintering, simultaneous heating work of electric auxiliary heating and microwave heating can be realized under vacuum conditions, effectively alleviating the problems of long heat preservation time, high sintering temperature, and ineffective control of alloy grain growth in the existing electric heating vacuum sintering furnace, or the problem of poor sintering effect caused by the negative temperature gradient phenomenon due to the surface temperature of the alloy product being lower than the inside in the existing microwave sintering furnace.

[0097] In this embodiment, the sintering box 21 is mainly made of fiberboard material, the electric auxiliary heating layer 22 is mainly made of carbon fiber plus graphite material; the heat preservation layer 23 is mainly made of graphite carbon fiber material;

[0098] As Figure 1 shown, in this embodiment, the furnace body 1 includes a furnace door 11, a pneumatic switch 12 and a cooling water jacket 13. The whole furnace body 1 is equipped with a circulating water cooling jacket around to protect each flange, the furnace door 11 seal, the valve seal and cool down the furnace body 1. When the fast cooling device 7 is started, it helps to cool down quickly.

[0099] In this embodiment, the microwave heating device 3 includes a plurality of microwave magnetrons arranged on the furnace body 1 for conducting microwaves into the furnace body 1. The magnetrons are arranged on the top and both sides of the furnace body 1 and are evenly and cross - distributed.

[0100] See Figure 1 and Figure 2, in this embodiment, the vacuum pipeline 4 is connected to the inside of the furnace body 1 to provide a vacuum environment inside the furnace body 1.

[0101] In this embodiment, the sintering furnace further includes an inflation pipeline 6, a rapid cooling device 7 and a temperature measuring device 8. Among them, the inflation pipeline 6 is used to inflate inert gas; the rapid cooling device 7 includes an inert gas inlet at the top of the furnace body 1, an internal circulating water condenser and a motor fan at the tail of the furnace body 1, and a circulating water cooling jacket is arranged around the entire furnace body 1; the temperature measuring device 8 is a tungsten-rhenium thermocouple.

[0102] In this embodiment, the sintering furnace further includes a control system, and the control system is electrically connected to the furnace body 1, the sintering device 2, the microwave heating device 3 and the vacuum pipeline 4 for controlling the operation of the above-mentioned devices.

[0103] When the sintering furnace of this embodiment is used for hard alloy sintering, the specific method is as follows:

[0104] (a) Debinding treatment: Place the green compact of the alloy to be sintered in the sintering box 21 of the sintering furnace of this embodiment, close the furnace door 11, turn on the pneumatic switch 12 and the cooling water jacket 13, and at the same time, through the vacuum pipeline 4, make the vacuum degree in the furnace 10-20 Pa, and then heat it up to 500 °C at a heating rate of 8 °C / min, and then keep it warm for 20 min to obtain the green compact after debinding treatment;

[0105] (b) Deoxidation and degassing treatment: Heat the alloy after debinding treatment to 850 °C at a heating rate of 10-20 °C / min under a vacuum degree of 5-10 Pa, keep it warm for 10 min, and then continue to heat it up to 1200 °C at a heating rate of 15 °C / min and keep it warm for 15 min to obtain the green compact after deoxidation and degassing treatment;

[0106] (c) Sintering treatment: Heat the alloy after deoxidation and degassing treatment to 1370 °C at a heating rate of 15 °C / min under a vacuum degree of 1-10 Pa, and then keep it warm for 25 min to obtain the sintered alloy;

[0107] (d) Cooling treatment: Under a vacuum degree of 10-20 Pa, cool the sintered alloy to 1200 °C, and then start the rapid cooling device 7 in the atmosphere of the protective gas to cool the furnace temperature to 100 °C - room temperature to obtain the hard alloy;

[0108] In this embodiment, the sintering heating in the steps (a) debinding treatment, (b) deoxidation and degassing treatment, and (c) sintering treatment is carried out under the condition of simultaneous heating of the microwave heating device 3 and the electric auxiliary heating layer 22.

[0109] Embodiment 2

[0110] A method for sintering hard alloy, the method includes the following steps:

[0111] (a) Degreasing treatment: The alloy green sheet to be sintered is placed in the sintering box 21 of the sintering furnace of Example 1, the furnace door 11 is closed, the pneumatic switch 12 and the cooling water jacket 13 are turned on, and the vacuum degree in the furnace is set to 10-20 Pa through the vacuum pipe 4, and then the temperature is raised to 450° C. at a heating rate of 5° C. / min, and then kept at this temperature for 10 min to obtain a green sheet after degreasing treatment;

[0112] (b) Deoxidation and degassing treatment: the alloy after degreasing treatment is heated to 830°C at a heating rate of 10°C / min under a vacuum degree of 5-10Pa, and kept at this temperature for 5min, and then continued to be heated to 1200°C at a heating rate of 10°C / min, and kept at this temperature for 10min, to obtain a deoxidized and degassed blank;

[0113] (c) Sintering treatment: the deoxidized and degassed alloy is heated to 1380°C at a heating rate of 10°C / min under a vacuum degree of 1-10 Pa, and then kept at this temperature for 20 minutes to sinter the alloy;

[0114] (d) Cooling treatment: Cooling the sintered alloy to 1200° C. under a vacuum degree of 10 to 20 Pa, and then starting the rapid cooling device 7 to lower the furnace temperature to 100° C. to room temperature in an atmosphere of protective gas to obtain a cemented carbide;

[0115] The degreasing treatment in step (a), the deoxidation and degassing treatment in step (b), and the sintering heating in step (c) are all carried out under the condition that the microwave heating device 3 and the electric auxiliary heating layer 22 are heated simultaneously.

[0116] Example 3

[0117] A cemented carbide sintering method, the method comprising the following steps:

[0118] (a) Degreasing treatment: The alloy pressed green sheet to be sintered is placed in the sintering box 21 of the sintering furnace of Example 1, the furnace door 11 is closed, the pneumatic switch 12 and the cooling water jacket 13 are turned on, and at the same time, the vacuum degree in the furnace is made to be 10-20 Pa through the vacuum pipe 4, and then the temperature is increased to 550° C. at a heating rate of 10° C. / min, and then kept warm for 30 min to obtain a green sheet after degreasing treatment;

[0119] (b) Deoxidation and degassing treatment: the alloy after degreasing treatment is heated to 850°C at a heating rate of 20°C / min under a vacuum degree of 5-10Pa, and kept at this temperature for 8min, and then continued to be heated to 1200°C at a heating rate of 20°C / min, and kept at this temperature for 20min to obtain a deoxidized and degassed blank;

[0120] (c), Sintering treatment: The alloy after deoxidation and degassing is heated in a vacuum of 1 - 10 Pa at a heating rate of 20 °C / min to 1400 °C, then held for 30 min to obtain the sintered alloy;

[0121] (d), Cooling treatment: In a vacuum of 10 - 20 Pa, the sintered alloy is cooled to 1200 °C, and then in an atmosphere of protective gas, the rapid cooling device 7 is started to cool the furnace temperature to 100 °C - room temperature to obtain the cemented carbide;

[0122] The degreasing treatment in step (a), the deoxidation and degassing treatment in step (b), and the sintering heating in step (c) are all carried out under the condition of simultaneous heating of the microwave heating device 3 and the electric auxiliary heating layer 22.

[0123] Example 4

[0124] As Figure 3 shown, a sintering furnace, except that the sintering furnace further includes a wax collecting pipe 5, the rest is the same as in Example 1;

[0125] Among them, the wax collecting pipe 5 is communicated with the sintering box 21 inside the furnace body 1, and is used to discharge the paraffin when paraffin is used as a molding agent for sintering;

[0126] When the sintering furnace of this embodiment is used for sintering cemented carbide, the specific method is as follows:

[0127] (a), Degreasing treatment: Place the green compact of the alloy to be sintered in the sintering box 21 of the sintering furnace of this embodiment, and under the atmosphere of protective gas, control the pressure inside the furnace to be 8 - 12 Kpa; then heat at a heating rate of 5 - 10 °C / min to 450 - 550 °C and hold for 10 - 30 min to obtain the alloy after degreasing treatment; during the degreasing process, the paraffin is discharged from the furnace body 1 through the wax collecting pipe 5.

[0128] In this embodiment, the deoxidation and degassing treatment in step (b), the sintering treatment in step (c), and the cooling treatment in step (d) are the same as in Example 1;

[0129] In this embodiment, the degreasing treatment in step (a), the deoxidation and degassing treatment in step (b), and the sintering heating in step (c) are all carried out under the condition of simultaneous heating of the microwave heating device 3 and the electric auxiliary heating layer 22.

[0130] Comparative Example 1

[0131] In this comparative example, except that the degreasing treatment in step (a), the deoxidation and degassing treatment in step (b), and the sintering heating in step (c) are all carried out under the condition of heating by the electric auxiliary heating layer 22 (without turning on the microwave heating device 3), the rest is the same as in Example 4.

[0132] Comparative Example 2

[0133] This comparative example is the same as Example 4, except that the sintering temperature increase in the degreasing treatment in step (a), the deoxidation and degassing treatment in step (b), and the sintering treatment in step (c) are all carried out under the condition of heating in the microwave heating device 3 (without turning on the electric auxiliary heating layer 22).

[0134] Effect Example 1

[0135] To show that it is possible to achieve simultaneous heating of electric auxiliary heating and microwave heating under vacuum conditions, effectively alleviating the problems of long heat preservation time, high sintering temperature, and ineffective control of alloy grain growth in existing electric heating vacuum sintering furnaces, the sintering methods of Example 4, Comparative Example 1, and Comparative Example 2 are now used to sinter the to-be-sintered YG10 ultra-fine alloy compact, and the sintered cemented carbide is tested. The specific results are as follows:

[0136]

[0137] In summary, the sintering furnace provided by the present invention can achieve simultaneous heating of electric auxiliary heating and microwave heating under vacuum conditions during sintering, effectively alleviating the problems of long heat preservation time, high sintering temperature, and ineffective control of alloy grain growth in existing electric heating vacuum sintering furnaces, or the problem of poor sintering effect caused by the negative temperature gradient phenomenon due to the surface temperature of the alloy product being lower than the inside in existing microwave sintering furnaces.

[0138] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some 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 invention.

Claims

1. A sintering method for cemented carbide, characterized in that, The sintering furnace of the sintering method includes a furnace body with a hollow cavity, a sintering device, a microwave heating device, a vacuum device, and a rapid cooling device; Among them, the sintering device includes a sintering box disposed inside the furnace body for placing sintering materials, and an electric auxiliary heating layer and a heat preservation layer sequentially coated around the sintering box; The microwave heating device is a microwave magnetron, and the microwave magnetrons are arranged at the top and both sides of the furnace body and are evenly and cross - distributed; The sintering method of the cemented carbide includes the following steps: (a) Degreasing treatment: Place the green compact of the alloy to be sintered in the sintering box of the sintering furnace. Under a vacuum of 10 - 20 Pa, heat it at a heating rate of 5 - 10 °C / min to 450 - 550 °C, and then keep it warm for 10 - 30 min to obtain the degreased blank; (b) Deoxidation and degassing treatment: For the degreased alloy, under a vacuum of 5 - 10 Pa, heat it at a heating rate of 10 - 20 °C / min to 830 - 850 °C, keep it warm for 5 - 10 min, and then continue to heat it at a heating rate of 10 - 20 °C / min to 1150 - 1200 °C, keep it warm for 10 - 20 min to obtain the deoxidized and degassed blank; (c) Sintering treatment: For the deoxidized and degassed blank, under a vacuum of 1 - 10 Pa, heat it at a heating rate of 10 - 20 °C / min to 1370 - 1400 °C, and then keep it warm for 20 - 30 min to obtain the sintered alloy; (d) Cooling treatment: Under a vacuum of 10 - 20 Pa, cool the sintered alloy to 1150 - 1200 °C, and then in the atmosphere of a protective gas, start the rapid cooling device to cool the furnace temperature to 100 °C - room temperature to obtain the cemented carbide; The sintering heating in the steps (a) degreasing treatment, (b) deoxidation and degassing treatment, and (c) sintering treatment is carried out under the condition of simultaneous heating by the microwave heating device and the electric auxiliary heating layer.

2. The sintering method of cemented carbide according to claim 1, wherein When paraffin is used as the molding agent for sintering, the step (a) degreasing treatment is carried out in the atmosphere of a protective gas.

3. The sintering method of cemented carbide according to claim 1, characterized in that, When paraffin is used as the molding agent for sintering, the step (a) degreasing treatment includes the following steps: Place the green compact of the alloy to be sintered in the sintering box of the sintering furnace. In the atmosphere of a protective gas, control the pressure inside the furnace to be 8 - 12 Kpa; then heat it at a heating rate of 5 - 10 °C / min to 450 - 550 °C, keep it warm for 10 - 30 min to obtain the degreased blank; during the degreasing process, the paraffin is discharged from the furnace body through the wax collection pipeline.

4. The sintering method of cemented carbide according to claim 1, characterized in that, The vacuum device is a vacuum pipeline, and the vacuum pipeline is connected to the inside of the furnace body to provide a vacuum environment for the furnace body.

5. The sintering method of cemented carbide according to claim 1, characterized in that, The sintering box is mainly made of alumina, polycrystalline mullite, silicon nitride ceramics or graphite materials; And / or, the electric auxiliary heating layer is mainly made of carbon fiber, carbon composite materials, silicon carbide or graphite materials; And / or, the heat preservation layer is mainly made of alumina, mullite, zirconium fiber and graphite carbon fiber materials.

6. The sintering method of cemented carbide according to claim 1, characterized in that, The furnace body includes a furnace door, a pneumatic switch and a circulating water cooling jacket.

7. The sintering method of cemented carbide according to claim 1, characterized in that, The microwave heating device includes a plurality of microwave magnetrons for conducting microwaves into the furnace body.

8. The sintering method of cemented carbide according to claim 1, characterized in that, The sintering furnace further includes a wax collection pipeline, which is connected to the interior of the furnace body and is used to discharge paraffin wax when paraffin wax is used as a forming agent for sintering. And / or, the sintering furnace further includes an inflation pipeline for inflating inert gas. And / or, the sintering furnace further includes a rapid cooling device, which includes an inert gas inflation inlet at the top of the furnace body, an internal circulating water condenser and a motor fan at the tail of the furnace body, and a circulating water cooling jacket around the entire furnace body. And / or, the sintering furnace further includes a temperature measuring device.

9. The sintering method of cemented carbide according to claim 1, characterized in that, The sintering furnace further includes a control system, which is electrically connected to the furnace body, the sintering device, the microwave heating device and the vacuum pipeline.

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