Process for improving sintering qualification of boron carbide flat plate

Abstract

The invention discloses a process for improving boron carbide plate sintering qualification, and belongs to the technical field of boron carbide ceramic sintering, and the technical scheme is characterized in that the process comprises the following steps: step 1, raw material preparation: grinding a boron carbide raw material into boron carbide powder in a sand mill, adding a caking agent, a plasticizer, a dispersing agent and a defoaming agent, and mixing and stirring to obtain a raw material; 2, discharging: adding a sintering aid into the prepared raw materials, putting the raw materials into a mold, and introducing inert gas into the mold; and 3, sintering is conducted, specifically, the mold is put into a hot-pressing sintering furnace to be sintered, the temperature rising time is prolonged by 300-600 DEG C during sintering, and pre-pressing is conducted for 100 T when sintering is conducted at the temperature of 1800 DEG C. The craft ceramic product is high in sintering qualification rate, high in compactness and high in stability.

Description

Technical Field

[0001] The invention relates to the technical field of boron carbide ceramic sintering, in particular to a process for improving the sintering lattice of boron carbide plates. Background Art

[0002] Boron carbide ceramics are widely used in cutting tools, abrasives, bulletproof materials, high temperature resistant parts and other fields due to their excellent hardness, wear resistance, corrosion resistance and high temperature stability. In the preparation process of boron carbide ceramics, sintering is a crucial link. In the existing boron carbide flat plate sintering process, the air inside the mold and the green body is not completely removed during the sintering process, which is prone to defects such as pores and cracks. In addition, the exhaust and debinding time is too fast, resulting in residual air, volatile gases and vaporized glue causing impact damage to the green body, resulting in poor quality of sintered ceramics and low pass rate. In view of this, a process for improving the sintering qualification of boron carbide flat plates is proposed. Summary of the invention

[0003] In view of the problems existing in the prior art, the object of the present invention is to provide a process for improving the sintering quality of boron carbide plates, so that the sintering qualification rate of ceramic products is high, the density is high and the stability is strong.

[0004] The above technical purpose of the present invention is achieved through the following technical scheme: a process for improving the sintering quality of boron carbide plates, comprising the following steps: step 1: raw material preparation, grinding the boron carbide raw material in a sand mill to obtain boron carbide powder, and adding a binder, a plasticizer, a dispersant, and a defoaming agent to mix and stir to obtain the raw material; step 2: discharging, adding a sintering aid to the prepared raw material and then putting it into a mold, and passing an inert gas into the mold; step 3: sintering, putting the mold into a hot pressing sintering furnace for sintering, extending the heating time of 300°C-600°C during sintering, and pre-pressing 100T when sintering at 1800°C.

[0005] In some embodiments, in step three, when sintering at 1500° C., the temperature is kept constant for half an hour.

[0006] In some embodiments, the mold includes a cover plate and a receiving groove, a pressure plate and a lifting member are arranged inside the cover plate, and the lifting member is slidably connected with the cover plate, a placement area, a bearing member and a heat preservation area are arranged inside the receiving groove, a transmission pipe is arranged on one side of the placement area and the heat preservation area in the receiving groove, and a temporary storage area is arranged on the other side, the transmission pipe connects the cover plate and the heat preservation area, an air transmission hole is opened in the heat preservation area, and the cover plate is connected with the temporary storage area.

[0007] In some embodiments, the lifting member includes a pressure plate, a U-shaped plate is fixedly connected to the pressure plate, a storage area is arranged between the pressure plate and the U-shaped plate, a sliding groove is arranged between the pressure plate and the cover plate, a vent is arranged on the U-shaped plate, and the surface of the vent is covered with a polyimide film. In some embodiments, bending portions are provided at both ends of the cover plate, each of the bending portions is provided with a connecting hole, the connecting holes are respectively connected to the transmission pipe and the temporary storage area, and the bending portions are in contact with the pressing plate.

[0008] In some embodiments, the support member includes a support screw, an internal thread column is screwed onto the support screw, a top of the internal thread column is rotatably connected to a support plate, and boron carbide sintering raw material is placed on the support plate.

[0009] In some embodiments, edges of the bending portion contacting the pressing plate are all provided with arcuate portions.

[0010] In some embodiments, a gas transmission channel is provided in the temporary storage area, the bottom of the gas transmission channel is connected to a gas storage tank, an L-shaped plate and a horizontal plate are provided in the gas storage tank, a pad is provided between the end of the L-shaped plate and the horizontal plate, the pad is made of polyimide, and the gas storage tank is provided with a gas outlet above the L-shaped plate.

[0011] In summary, the present invention has the following beneficial effects: The present invention introduces inert gas into the mold, gradually removes air impurities in the mold as the temperature rises during the sintering process, and at the same time prolongs the heating time of 300°C-600°C during the sintering process, cooperates with the existing exhaust system to increase the debinding and exhaust time, prevents the impact damage of debinding on the green body, reduces the generation of defects such as pores and cracks during the sintering process, and improves the qualified rate of products; and keeps the temperature unchanged for half an hour when sintering at 1500°C, so that the green body is not affected by temperature when shrinking, and pre-presses 100T when sintering at 1800°C, further enhancing the compactness and performance stability of the product; the entire mold is provided with a lifting piece, a transmission pipe and a temporary storage area, and the various structures cooperate with each other, so that the flow of the inert gas is more reasonable, and the air and impurities can be better driven to the temporary storage area and discharged, further improving the sintering qualified rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a schematic diagram of the overall structure of the mold of the present invention; Figure 2 is a cross-sectional view of the mold of the present invention; Figure 3 It is a partial enlarged view of the mold of the present invention; Figure 4 It is a structural schematic diagram of the mold temporary storage area of ​​the present invention.

[0013] In the figure: 1. cover plate; 11. pressure plate; 12. U-shaped plate; 13. storage area; 14. sliding groove; 15. bending part; 16. ventilation hole; 2. accommodating groove; 21. placement area; 22. insulation area; 23. transmission pipe; 24. temporary storage area; 241. gas transmission channel; 242. gas storage tank; 243. L-shaped plate; 244. cross plate; 245. cushion block; 246. gas outlet; 3. bearing member; 31. support screw; 32. internal thread column; 33. bearing plate; 4. gas transmission hole. DETAILED DESCRIPTION

[0014] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0015] See also Figure 1-4 A process for improving the sintering quality of boron carbide plates includes the following steps: Step 1: raw material preparation, grinding the boron carbide raw material in a sand mill to obtain boron carbide powder, and adding a binder, a plasticizer, a dispersant, and a defoaming agent to mix and stir to obtain a raw material; Step 2: Discharging the material, adding the prepared raw material to the sintering aid and then placing it into the mold, and passing inert gas into the mold; Step 3: Sintering: Place the mold into a hot pressing sintering furnace for sintering. Extend the heating time from 300°C to 600°C during sintering. Pre-press 100T when sintering at 1800°C.

[0016] In some embodiments, in step three, when sintering at 1500° C., the temperature is kept constant for half an hour.

[0017] In some embodiments, the mold includes a cover plate 1 and a receiving groove 2, a pressure plate 11 and a lifting member are arranged inside the cover plate 1, and the lifting member is slidably connected to the cover plate 1, a placement area 21, a support member 3 and a heat preservation area 22 are arranged inside the receiving groove 2, a transmission pipe 23 is arranged on one side of the placement area 21 and the heat preservation area 22 in the receiving groove 2, and a temporary storage area 24 is arranged on the other side, the transmission pipe 23 connects the cover plate 1 and the heat preservation area 22, an air transmission hole 4 is opened in the heat preservation area 22, and the cover plate 1 is connected with the temporary storage area 24.

[0018] In some embodiments, the lifting member includes a pressing plate 11, to which a U-shaped plate 12 is fixedly connected, a storage area 13 is arranged between the pressing plate 11 and the U-shaped plate 12, a sliding groove 14 is arranged between the pressing plate 11 and the cover plate 1, and a vent 16 is arranged on the U-shaped plate 12, and the surface of the vent 16 is covered with a polyimide film. In some embodiments, bending portions 15 are provided at both ends of the cover plate 1 , each bending portion 15 is provided with a connecting hole, the connecting holes are respectively connected to the transmission pipe 23 and the temporary storage area 24 , and the bending portion 15 is in contact with the pressing plate 11 .

[0019] In some embodiments, the support member 3 includes a support screw 31 , on which an internal thread column 32 is screwed, and the top of the internal thread column 32 is rotatably connected to a support plate 33 , on which boron carbide sintering raw materials are placed.

[0020] In some embodiments, the edges of the bending portion 15 that contact the pressing plate 11 are all provided with arcuate surfaces. The arcuate surfaces can improve the fluidity of the gas, thereby accelerating the inert gas and quickly driving the air into the temporary storage area 24.

[0021] In some embodiments, a gas delivery channel 241 is provided in the temporary storage area 24, the bottom of the gas delivery channel 241 is connected to the gas storage tank 242, an L-shaped plate 243 and a horizontal plate 244 are provided in the gas storage tank 242, a pad 245 is provided between the end of the L-shaped plate 243 and the horizontal plate 244, and the pad 245 is made of polyimide. The gas storage tank 242 is located above the L-shaped plate 243 and has a gas outlet 246.

[0022] Working principle: The operator places the raw material on the carrier plate 33 in the receiving tank 2 in advance, and then passes the inert gas into the storage area 13 and the insulation area 22 from the vent hole 16 and the gas delivery hole 4 respectively. When placing the raw material (i.e., the blank), the distance between the carrier plate 33 and the top of the receiving tank 2 can be adjusted by rotating the internal thread column 32 to rise or fall on the support screw 31, thereby changing the volume of the placement area 21 and adjusting the thickness of the boron carbide plate after sintering. Then the operator places the mold into the sintering furnace for sintering. As the sintering temperature increases, the inert gas in the storage area 13 and the insulation area 22 in the lifting part are heated and accelerated, and the inert gas in the insulation area 22 passes through the storage area 13 and the insulation area 22. The inert gas in the storage area 13 becomes active, and after sensing the upward trend of the pressing plate 11, the pressing plate 11 is also lifted upward, thereby forcing the pressing plate 11 to move upward in the sliding groove 14, exposing the connecting holes at both ends of the cover plate 1 without blocking them, so that the heat preservation area 22 is connected with the temporary storage area 24, and then the inert gas in the heat preservation area 22 slowly enters the placement area 21, and gradually drives the air in the placement area 21 and the glue in the gasified state into the gas storage tank 242 of the temporary storage area 24, and discharges them through the gas outlet 246, ensuring that there will be no air bubbles in the green body during sintering, which will cause defects in the sintered flat plate. When the temperature reaches 300°C, the polyimide film covering the surface of the vent 16 and the polyimide pad 245 are melted, so that the vent 16 escapes, causing the pressing plate 11 to lose a supporting force. The pressing plate 11 falls under the influence of gravity to cover the connecting holes at both ends of the cover plate 1, and at the same time, all the gas in the placement area 21 is driven into the temporary storage area 24. After the pad 245 melts, the L-shaped plate 243 falls and fits with the cross plate 244 to prevent air from entering from the air outlet 246. At the same time, the gas storage tank 242 is isolated from the gas transmission channel 241, which provides double insurance. During the sintering temperature period of 300°C-600°C, the holding time of this temperature section is extended, and the existing exhaust system in the sintering furnace is used to exhaust the gas in the mold. The glue and air are completely extracted to avoid the impact damage of the blank caused by the binder removal, and then the sintering temperature is increased. When the sintering temperature reaches 1500℃, the blank begins to shrink. The operator extends the temperature period to keep the blank in the mold warm. At this time, there is no gas in the storage area 13, the insulation area 22, the transmission pipe 23 and the gas transmission channel 241, and the heat can be completely transferred to the surrounding of the blank, thereby enhancing the insulation effect. When the sintering temperature reaches 1800℃, the blank grains grow. At this time, the operator controls the existing pressure system in the sintering furnace to pre-press the mold by 100T, so that the blank expansion has a binding force to rearrange the particles and reduce the volume diffusion of the grain boundaries. Finally, the sintering is completed to obtain a boron carbide plate of qualified quality.

[0023] This specific embodiment is merely an explanation of the present invention and is not a limitation of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed. However, as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

Claims

1. A process for improving the sintering quality of boron carbide plates, characterized in that: The following steps are involved: Step 1: raw material preparation, grinding the boron carbide raw material in a sand mill into boron carbide powder, and adding a binder, a plasticizer, a dispersant, and a defoaming agent to mix and stir to obtain a raw material; Step 2: Discharging the material, adding the prepared raw material to the sintering aid and then placing it into the mold, and passing inert gas into the mold; Step 3: Sintering: Place the mold into a hot pressing sintering furnace for sintering. Extend the heating time from 300°C to 600°C during sintering. Pre-press 100T when sintering at 1800°C.

2. A process for improving the sintering quality of boron carbide plates according to claim 1, characterized in that: In the step 3, when sintering at 1500° C., the temperature is kept constant for half an hour.

3. A process for improving the sintering quality of boron carbide plates according to claim 1, characterized in that: The mold comprises a cover plate (1) and a receiving groove (2); a pressing plate (11) and a lifting member are arranged inside the cover plate (1); the lifting member is slidably connected to the cover plate (1); a placement area (21), a bearing member (3) and a heat preservation area (22) are arranged inside the receiving groove (2); a transmission pipe (23) is arranged on one side of the placement area (21) and the heat preservation area (22) in the receiving groove (2); and a temporary storage area (24) is arranged on the other side; the transmission pipe (23) is connected to the cover plate (1) and the heat preservation area (22); a gas transmission hole (4) is opened in the heat preservation area (22); and the cover plate (1) is connected to the temporary storage area (24).

4. A process for improving the sintering quality of boron carbide plates according to claim 3, characterized in that: The lifting member comprises a pressing plate (11), a U-shaped plate (12) is fixedly connected to the pressing plate (11), a storage area (13) is provided between the pressing plate (11) and the U-shaped plate (12), a sliding groove (14) is provided between the pressing plate (11) and the cover plate (1), and a vent hole (16) is provided on the U-shaped plate (12), and the surface of the vent hole (16) is covered with a polyimide film.

5. A process for improving the sintering quality of boron carbide plates according to claim 3, characterized in that: The cover plate (1) is provided with bent portions (15) at both ends, each of the bent portions (15) being provided with a communication hole, the communication holes being respectively connected to the transmission pipe (23) and the temporary storage area (24), and the bent portions (15) being in contact with the pressing plate (11).

6. A process for improving the sintering quality of boron carbide plates according to claim 3, characterized in that: The bearing member (3) comprises a supporting screw (31), an internal thread column (32) is screwed onto the supporting screw (31), a top of the internal thread column (32) is rotatably connected to a bearing plate (33), and boron carbide sintering raw materials are placed on the bearing plate (33).

7. A process for improving the sintering quality of boron carbide plates according to claim 5, characterized in that: The edges of the bending portion (15) that are in contact with the pressing plate (11) are both provided with arcuate portions.

8. A process for improving the sintering quality of boron carbide plates according to claim 3, characterized in that: The temporary storage area (24) is provided with a gas transmission channel (241), the bottom of the gas transmission channel (241) is connected to the gas storage tank (242), the gas storage tank (242) is provided with an L-shaped plate (243) and a transverse plate (244), a cushion block (245) is provided between the end of the L-shaped plate (243) and the transverse plate (244), the cushion block (245) is made of polyimide, and the gas storage tank (242) is provided with a gas outlet (246) above the L-shaped plate (243).

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