A graphite crucible for a hot isostatic pressing process of silicon nitride ceramic balls

Abstract

The present application relates to a kind of silicon nitride ceramic ball hot isostatic pressing process graphite crucible, it includes main body, gland and door plate, main body design is cylinder, upper end middle is opened with round groove, main body side is opened with side door, round groove is connected with main body outside through side door, side door position inserts one door plate, main body upper end cap has a gland;The bottom of the round groove of the main body is provided with a plurality of waist-shaped through holes, the hollow column is arranged in the middle of the main body, the upper surface of the gland is also provided with a plurality of waist-shaped through holes, the gland middle is opened with an upper circular hole, hollow column is installed in the middle bottom of round groove, the bottom middle of round groove is also opened with a lower circular hole, the lower circular hole is communicated with the lower end of the center hole of hollow column, and the upper circular hole of the gland is communicated with the upper circular hole of the hollow column.The advantages are that the design is ingenious, the structure is reasonable and compact, the ceramic ball is sintered through the graphite crucible, the temperature uniformity and gas flow in the hot isostatic pressing furnace are improved, so that all the ball blanks in the furnace can obtain the same sintering temperature.

Description

Technical Field

[0001] This invention relates to the field of ceramic ball processing, and more specifically to a graphite crucible for the hot isostatic pressing process of silicon nitride ceramic balls. Background Technology

[0002] Hot isostatic pressing (HIP) of silicon nitride ceramic spheres involves placing silicon nitride spheres, which are placed in a graphite crucible, into the high-pressure vessel of a hot isostatic press. High-pressure nitrogen gas is then applied uniformly to the spheres, and the combined effects of high temperature and high pressure densify the ceramic material. Under high temperature and external force, the material undergoes plastic deformation and diffusion creep. Inspection of the sintered spheres revealed snowflake-like spots inside the spheres in the graphite crucible, indicating over-burning. Lowering the sintering temperature did not resolve the over-burning issue, indicating poor temperature uniformity and poor gas flow within the furnace during sintering. The existing graphite crucibles cannot meet the requirements for processing ceramic balls. The original crucibles did not have openings at the bottom, and the silicon nitride spheres were in a relatively sealed environment. During the actual hot isostatic pressing sintering process, when N2 was injected into the furnace for heating, the gas expanded. Since there was no way to provide gas flow at the bottom of the graphite crucible, the high-temperature gas could not evenly coat each sphere, resulting in uneven heating of the spheres inside the crucible. The temperature of the inner silicon nitride spheres was much lower than that of the outer silicon nitride spheres. When the thermocouple temperature measurement detected that the overall temperature did not reach the set requirement, the power was increased to bring the temperature of the inner spheres to the set requirement, which caused the outer spheres to exhibit overheating and snowflake-like spots. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention proposes a graphite crucible for the hot isostatic pressing process of silicon nitride ceramic spheres. The crucible is ingeniously designed, has a reasonable and compact structure, and meets production needs.

[0004] The technical solution of this invention:

[0005] A graphite crucible for the hot isostatic pressing process of silicon nitride ceramic balls includes a main body, a pressure plate, and a door panel. The main body is cylindrical with a circular groove in the middle of the upper end. A side door is located on one side of the main body, and the circular groove connects to the outside of the main body through the side door. A door panel is inserted into the side door. A pressure plate covers the upper end of the main body. The bottom of the circular groove of the main body has several oblong through holes. A hollow column is located in the middle of the main body. The pressure plate also has several oblong through holes on its top. A top circular hole is located in the middle of the pressure plate. The hollow column is installed at the bottom of the circular groove. A bottom circular hole is also located in the middle of the bottom of the circular groove, and the bottom circular hole is connected to the lower end of the central hole of the hollow column. The top circular hole of the pressure plate... The hole is connected to the upper circular hole of the hollow column; the radius of the main body is 125mm and the height of the main body is 150mm; the waist-shaped hole has a diameter of 6mm and a length of 20mm, and the width of the side door is 161mm; the main body and the hollow column are integrally formed from graphite; the cover and the door panel are also made of graphite; a notch is provided on one side of the cover corresponding to the position of the side door, and an upper annular step is designed around the lower end of the cover, which is locked onto the circular groove of the main body; a lower annular step for stacking is also designed around the lower end of the main body, which is locked onto the circular groove of the main body below.

[0006] The pressure cap and the several waist-shaped holes on the bottom of the circular groove of the main body are evenly distributed in a fan shape at 45°.

[0007] The hollow column is designed as a cylinder with a diameter of 30mm. The inner diameter of the central hole of the hollow column is 12mm, and a threaded hole is designed at the upper end of the hollow column.

[0008] The hollow column is designed as a conical column with an upper diameter of 30mm, a root diameter of 55.58mm, a central hole inner diameter of 12mm, and a threaded hole at the upper end.

[0009] The door panel has triangular vertical edges on both sides near the inner side, and the outer surface of the vertical edges fits into the inner wall of the circular groove. The graphite crucible also includes a lifting ring for hoisting, the lower end of which passes through the upper circular hole of the pressure cap and is rotatably installed in the threaded hole of the hollow column.

[0010] The main body is designed with several vertical waist-shaped holes around its perimeter. The inner side of the vertical waist-shaped holes is connected to a circular groove, and the outer side of the vertical waist-shaped holes is connected to the outer circumference of the main body.

[0011] The bottom of the circular groove is provided with four reinforcing ribs, which are designed to intersect at the bottom of the circular groove.

[0012] When the graphite crucibles are used for hot isostatic pressing of silicon nitride ceramic balls, silicon nitride ball blanks with a diameter of φ20mm or less are evenly placed into 7 graphite crucibles. The 7 crucibles are stacked and the corresponding pressure caps are placed on top. The stacked graphite crucibles are then lifted into the hot isostatic pressing furnace cavity in sequence using lifting rings. After inputting the program segment, sintering begins.

[0013] The advantages of this invention are its ingenious design and reasonable and compact structure. By using this graphite crucible to assist in the sintering of ceramic balls, the uniformity of temperature and gas flow in the hot isostatic pressing furnace are improved, allowing all the ball blanks in the furnace to obtain the same sintering temperature. Attached Figure Description

[0014] Figure 1 This is a cross-sectional schematic diagram of the present invention.

[0015] Figure 2 This is a top view of the present invention.

[0016] Figure 3 This is a top view of the main body of the invention.

[0017] Figure 4 This is a top view of the door panel of the present invention.

[0018] Figure 5 This is a schematic diagram of another design of the main body of the present invention.

[0019] Figure 6 This is a top view of another design of the main body of the present invention. Detailed Implementation

[0020] See attached document Figure 1-5A graphite crucible for the hot isostatic pressing process of silicon nitride ceramic balls includes a main body 1, a pressure plate 2, and a door panel 3. The main body 1 is cylindrical with a circular groove 11 in the middle of the upper end. A side door 10 is opened on one side of the main body 1, and the circular groove 11 is connected to the outside of the main body 1 through the side door 10. A door panel 3 is inserted into the side door 10. A pressure plate 2 covers the upper end of the main body 1. The bottom of the circular groove 11 of the main body 1 is provided with several waist-shaped through holes. A hollow column 4 is provided in the middle of the main body 1. The pressure plate 2 is also provided with several waist-shaped through holes. The pressure plate 2 has an upper circular hole in the middle. The hollow column 4 is installed in the middle bottom of the circular groove 11. A lower circular hole is also opened in the middle of the bottom of the circular groove 11, and the lower circular hole is connected to the lower end of the central hole of the hollow column 4. The upper circular hole of the cover 2 is connected to the upper circular hole of the hollow column 4; the radius of the main body 1 is 125mm and the height of the main body 1 is 150mm; the waist-shaped hole 5 has a diameter of 6mm and a length of 20mm, and the width of the side door 10 is 161mm; the main body 1 and the hollow column 4 are integrally formed from graphite; the pressure cover 2 and the door panel 3 are also made of graphite; a notch is provided on one side of the pressure cover 2 corresponding to the side door position, and an upper annular step 21 is designed around the lower end of the pressure cover, which is locked onto the opening of the circular groove 11 of the main body; a lower annular step 12 for stacking is also designed around the lower end of the main body 1, which is locked onto the opening of the circular groove 11 of the main body below.

[0021] The pressure cap 2 and the main body 1 have several waist-shaped holes 5 on the bottom of the circular groove 11, which are evenly distributed in a fan shape at 45°.

[0022] The hollow column 4 is designed as a cylinder with a diameter of 30mm. The inner diameter of the center hole of the hollow column 4 is 12mm, and the upper end of the hollow column 4 is designed with a threaded hole.

[0023] The hollow column 4 is designed as a conical column 41 with an upper diameter of 30mm and a root diameter of 55.58mm. The inner diameter of the central hole of the hollow column 4 is 12mm, and a threaded hole 42 is designed at the upper end of the hollow column 4.

[0024] The door panel 3 has triangular vertical edges 31 on both sides near the inner side, and the outer side of the vertical edges 31 is in contact with the inner wall of the circular groove 11.

[0025] The graphite crucible also includes a lifting ring for hoisting. The lower end of the lifting ring passes through the upper round hole of the pressure cap 2 and is rotatably installed in the threaded hole of the hollow column 4.

[0026] The main body 1 has several vertical waist-shaped holes around its perimeter. The inner side of the vertical waist-shaped holes is connected to the circular groove 11, and the outer side of the vertical waist-shaped holes is connected to the outer peripheral surface of the main body 1.

[0027] The bottom of the circular groove 11 is provided with four reinforcing ribs 6, which are designed to intersect at the bottom of the circular groove 11.

[0028] When using the graphite crucibles for hot isostatic pressing (HIP) sintering of silicon nitride ceramic spheres, 100 kg of silicon nitride spheres with a diameter of φ20 mm or less are evenly placed into seven graphite crucibles. The seven crucibles are stacked, and corresponding pressure caps (2) are placed on top. The stacked graphite crucibles are then hoisted into the HIP furnace cavity using lifting rings, and a heat insulation cover is installed. The upper cover of the HIP furnace is then installed, and the sintering process begins after the program segment is input. Finally, the HIP-pressed ceramic spheres are inspected. No over-firing or under-firing is observed, and the sphere quality is qualified, meeting production requirements and improving product quality.

[0029] The table below shows the temperature measurement results at four points on each layer of a conventional crucible without a waist-shaped hole, and the temperature measurement results at the same four points on each layer of the improved crucible of this invention.

[0030]

[0031] The table above shows that previously, the internal temperature of each crucible layer was uneven, and even among the seven layers, the temperature was still uneven. This severely led to over-burning and under-burning problems, resulting in substandard silicon nitride pellet quality. This invention changes the structure of the graphite crucible, increasing the depth of each individual graphite crucible, allowing a single graphite crucible to hold more silicon nitride pellets. When loading the same weight of pellets, the number of graphite crucibles is reduced, mitigating the gas flow obstruction caused by stacking. Sixteen waist-shaped holes, each φ6mm in diameter and 20mm in length, are evenly distributed in a fan shape at 45° on the bottom of the graphite crucible. This does not affect the overall strength of the crucible, and the bottom openings allow for better internal gas flow, ensuring product quality.

Claims

1. A graphite crucible for the hot isostatic pressing process of silicon nitride ceramic spheres, characterized in that, It comprises a main body, a cover, and a door panel. The main body is cylindrical with a circular groove in the center of the top. A side door is located on one side of the main body, and the circular groove connects to the outside of the main body through the side door. A door panel is inserted into the side door. A cover is placed on top of the main body. The bottom of the circular groove of the main body has several oblong holes. A hollow column is located in the center of the main body. The cover also has several oblong holes, with an upper circular hole in the center. The hollow column is installed at the bottom center of the circular groove, and a lower circular hole is located in the center of the bottom of the circular groove, connecting to the lower end of the center hole of the hollow column. The upper circular hole of the cover connects to the upper circular hole of the hollow column. The radius of the main body is 125mm, and the height of the main body is 150mm. The oblong holes are 6mm in diameter and 20mm in length. The width of the side door is 161mm. The main body and the hollow column are integrally formed from graphite. The cover and door... The plates are also made of graphite. A notch is provided on one side of the pressure cap corresponding to the side door position, and an upper annular step is designed around the lower end of the pressure cap, which is locked onto the circular groove of the main body. A lower annular step for stacking is also designed around the lower end of the main body, which is locked onto the circular groove of the main body below. A threaded hole is designed at the upper end of the hollow column. The graphite crucible also includes a lifting ring for hoisting. The lower end of the lifting ring passes through the upper circular hole of the pressure cap and is rotatably installed in the threaded hole of the hollow column. When the graphite crucible is used for hot isostatic pressing of silicon nitride ceramic balls, silicon nitride ball blanks with a specification of less than φ20mm are evenly placed into 7 graphite crucibles. The 7 crucibles are stacked and the corresponding pressure caps are placed on top. The stacked graphite crucibles are hoisted into the hot isostatic pressing furnace cavity in sequence using the lifting ring. After inputting the program segment, sintering begins.

2. The graphite crucible for the hot isostatic pressing process of silicon nitride ceramic spheres according to claim 1, characterized in that, The pressure cap and the several waist-shaped holes on the bottom of the circular groove of the main body are evenly distributed in a fan shape at 45°.

3. The graphite crucible for the hot isostatic pressing process of silicon nitride ceramic spheres according to claim 1, characterized in that, The hollow column is designed as a cylinder with a diameter of 30mm, and the inner diameter of the central hole of the hollow column is 12mm.

4. The graphite crucible for the hot isostatic pressing process of silicon nitride ceramic spheres according to claim 1, characterized in that, The hollow column is designed as a conical column with an upper diameter of 30mm, a root diameter of 55.58mm, and a central hole inner diameter of 12mm.

5. The graphite crucible for the hot isostatic pressing process of silicon nitride ceramic spheres according to claim 1, characterized in that, The door panel has triangular vertical edges on both sides near the inner side, and the outer side of the vertical edges fits into the inner wall of the circular groove.

6. The graphite crucible for the hot isostatic pressing process of silicon nitride ceramic spheres according to claim 1, characterized in that, The main body is designed with several vertical waist-shaped holes around its perimeter. The inner side of the vertical waist-shaped holes is connected to a circular groove, and the outer side of the vertical waist-shaped holes is connected to the outer circumference of the main body.

7. The graphite crucible for the hot isostatic pressing process of silicon nitride ceramic spheres according to claim 1, characterized in that, The bottom of the circular groove is provided with four reinforcing ribs, which are designed to intersect at the bottom of the circular groove.

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