JPH03174367A - Method for producing sintered body and apparatus for producing the same - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a method and apparatus for manufacturing a sintered body, and more particularly to a method and apparatus for continuously manufacturing a sintered body of ceramics or metals. It is.

[Conventional technology] Conventionally, hot press equipment used in ceramics and full-thickness related industries places sintered material in a graphite press mold, charges it into a sintering furnace, and gradually raises the material under pressure using a hydraulic cylinder, etc. This is a so-called batch type device that repeats a series of operations for each material, such as heating, holding at the sintering temperature for a certain period of time, then slowly cooling and then taking out the resulting sintered body from the furnace, which has poor productivity. Sintered bodies and equipment are becoming larger. In order to improve the productivity of other equipment, press molds filled with sintering material are stacked vertically or horizontally, and the press molds are sequentially moved to apply pressure at appropriate locations to sinter the sintering material. A method has been proposed. (For example, JP-A-49-36513, JP-A-55-134283)
In the case of these methods, productivity is certainly improved by continuous sintering, but in the former case, since there is only one pressurizing part, the sintering inside the press die during the temperature raising and non-pressing process is There is a drawback that the material cannot be sufficiently densified even if it is pressurized at the pressurizing section because grain growth (for example, boron carbide, boron nitride, etc.) or phase transition (for example, α-type titanium nitride) occurs in the binder material. In the latter case, although the effects of grain growth and phase transition of the sintering material can be avoided, multiple pressure mechanisms are required;
Because it is horizontal, the press die moving mechanism is a large-scale device, and because the press die are separated from each other, there are problems such as poor heat transfer characteristics and a large installation space, making the equipment expensive. There is.

In addition, there is a method in which a small amount of sintering powder material is repeatedly fed from the upper part of a heated vertical heating furnace and pressurized to obtain a long rod-shaped sintered body.

(“Powder and Powder Metallurgy” Vol. 28 No. 6 or rCe
ramic BulletinJVol.

55 No. 3 (1976)) In these cases, the sintered body passes through the mold while being pushed down, causing damage to the inner wall surface of the mold. As the number of times of sintering increases, the damage on the inner wall of the mold becomes larger and eventually the mold is damaged, making it impossible to operate continuously over a long period of time, resulting in a significant drop in productivity.

For this reason, there has been a strong desire in the ceramics and metal-related industries to develop a method and apparatus for producing sintered bodies that are inexpensive and have excellent productivity, making it easier to sinter various sintering materials.

[Problems to be Solved by the Invention] The present invention solves the problems of the prior art, and provides a method and apparatus for manufacturing a sintered body that is compatible with various sintered materials, is inexpensive, and has excellent productivity. It provides:

[Means for Solving the Problems] The inventors of the present invention have conducted extensive studies regarding the method of manufacturing sintered bodies and the manufacturing equipment thereof, and have found that the large temperature difference in the heating furnace causes the sintered material filling container to move. It has been discovered that by applying pressure in the same direction and pressurizing the sintering material over the entire range from low to high temperatures, it is possible to densify the sintered body without being affected by grain growth or phase transition. In addition, by adapting the sintering material filling container to the vertical heating furnace, unlike when filling the sintering powder material directly into the furnace, wear due to friction on the inner wall of the furnace material is reduced, and the life of the vertical heating furnace is extended. The present invention was completed based on the discovery that the time can be extended significantly.

That is, in the present invention, sintering material filling containers filled with ceramic or metal powder and compacts are stacked in multiple stages in a vertical heating furnace, and the upper and lower ends of the stacked containers are pressurized by a pair of pressurizing devices. The sintered body is heated while being pressed, and after a predetermined period of time, the laminated container is lowered by the unit length of the container, taken out of the furnace from the lower stage, and a new material-filled container is supplied from the upper end. A manufacturing method, a vertical heating furnace having a heating means and a cooling means, and a pair of pressurizing devices above and below a heating area of a furnace core, and a sintering material filled from the side at the upper end of the heating furnace. A sintered body manufacturing apparatus comprising a supply means for supplying a container, a discharge means for taking out a first stage container at the lowermost stage on the lower end side of the furnace, and a chuck means for holding the side of the second stage container, This solved the problem mentioned above.

In the present invention, the sintering material filling container must have sufficient pressure resistance.

As the material used for the filling container (1), graphite is suitable because it can withstand use at high temperatures, has excellent lubricity and can reduce wear on the inner wall of the vertical heating furnace, and is inexpensive. There is. The outer diameter of the filling container (1) needs to be slightly smaller than the inner wall of the vertical heating furnace. In the vertical heating furnace, material-filled containers are stacked and stacked in multiple stages in series, and the upper ends of the uppermost stage and the lower ends of the lowermost stage of these containers are pressurized at a predetermined pressure, heated to a required temperature, and then the containers are lowered. while sintering. The sintering material is a mixture of ceramic powder, its sintering aid, metal powder, etc. according to a conventional method, or a molded body shaped into a predetermined shape.

The material filling container is as shown in FIGS. 1 and 2, and is in contact with a cylinder (3), upper and lower push rods (4) and (5) inserted into the cylinder, and the lower surface of the lower push rod. A bottom plate (7>) having a convex portion (6) is provided, and the cylinder space (2) is filled with material.

The cylinder (3) may be accompanied by an inner cylinder or a split die (3a), and the material filling space (2) may be divided by a partition plate (8), a spacer (9), etc. Of course, the shape should be arbitrarily formed depending on the shape of the sintered body to be obtained.

The temperature is appropriately selected depending on the material to be sintered. For example, aluminum is 600-650°C, copper is 1000°C.
~1050℃, iron 1500~1550℃, and among ceramics, boron nitride 1800~2100℃, silicon carbide 1900~2200℃, silicon nitride 1600~1800℃
℃, aluminum nitride is about 1700 to 1900℃. These temperatures vary depending on whether the sintering material is a composite material or the selection of the sintering aid used for sintering. Also, the pressure for pressurizing the sintering material is selected to be an appropriate pressure depending on the selection of the sintering material and sintering aid. However, the pressure should be such that the cylinder or upper and lower push rods of the container filled with sintering material do not break, preferably 500 Kg/cut or less, or more. can improve thermal energy efficiency.

Containers loaded in multiple stages will have a temperature gradient above and below centering on one heated location. In addition, by pressurizing the top end of the top layer and the bottom end of the bottom layer of the stacked container, the sintering material filled in the container can be pressurized from a low temperature range where it is not affected by grain growth or phase transition. Since the sintering process is started, it becomes possible to easily densify the sintering material. Moreover, this method has the advantage that the sintering apparatus can be manufactured at low cost since only one set is required without requiring a large number of pressurizing mechanisms as in the conventional method.

By creating a small gap between the inner wall of the vertical heating furnace and the outer surface of the container, it is possible to move the container freely in the vertical heating furnace, and by reducing the friction on the inner wall of the vertical heating furnace. The type heating furnace can be used for a long period of time. Furthermore, the downward extraction of the container enables continuous sintering and improves productivity. The moving speed of the sintering material filling container is arbitrarily set depending on the size of the vertical heating furnace and the material filling container and the sintering material.

After sintering, the container is taken out of the furnace and then dismantled to obtain a sintered body. Although the relative density of the obtained sintered body varies depending on the sintering material, it is possible to obtain a dense sintered body with a relative density of over 99%.

Next, the sintered body manufacturing apparatus will be explained with reference to FIG.

The vertical heating furnace (10) has a high frequency induction coil (11) on the outer periphery.
and has a graphite heating element (12) in its center. Fireproof and insulating bricks (13) are placed above and below the graphite heating element (12), and these are connected to the zero heating element (12) and the bricks (13), which serve to heat the material filling container (1) and guide the inside of the furnace. ) is surrounded by a heat insulating material (14), and the outside thereof is further surrounded by a cooling tank (15) which fills the inside of the furnace.

A supply means consisting of a material filling container insertion device (17) and a container slide table (24) is provided in the upper part of the heating furnace, and a container side chuck device (1g) is provided in the lower part.

and a container extraction device (19) are installed, and automatic insertion and extraction of containers is performed by their cooperative operation.

The heating method of the furnace may be a resistance heating method.

Further, the atmosphere in the heating furnace is preferably an inert gas such as argon or helium or N2 gas atmosphere in order to prevent the graphite heating element and the fireproof insulation brick from being consumed by oxidation.

The temperature distribution inside the heating furnace (10) is such that the heat generated by the graphite heating element (12) mainly flows in the vertical direction due to thermal conduction, so the temperature near the graphite heating element (12) is highest, and the temperature distribution in the vertical direction increases. The distribution becomes progressively lower.

Next, the heating mechanism is provided so as to be able to pressurize the material filling container <1) in the direction in which it moves within the vertical heating furnace 10>. Upper hydraulic cylinder <20> and lower hydraulic cylinder (
The pressure exerted by 21> is applied to the material filling containers stacked in multiple stages and causes the internal sintering material to shrink. The sintering material located in the fireproof insulation brick (13a) part, which is in the low temperature range, is also pressurized, so it is not affected by grain growth or phase transition, so a dense sintered body can be obtained. Become.

Furthermore, this pressurizing mechanism is also used as a jig for moving the material filling container (1) inside the furnace.

[Operation method] When starting the operation of the sintered body manufacturing equipment, a dummy such as a graphite cylinder is placed in the inner metal body of the vertical heating furnace 10, and a material-filled container (
Insert in place of 1>. In this insertion method, the dummy is placed on the pressing plate (23) fixed to the lot end of the lower hydraulic cylinder (21), the cylinder (21) is pushed up, and the dummy is inserted from the bottom of the vertical heating furnace (10). , the material filling container is held by a side chuck device (18) to prevent it from falling. After that, the cylinder (21) is lowered, another dummy is placed on the pressing plate (23), and the cylinder (21) is raised until the upper surface of the dummy contacts the lower surface of the previously inserted dummy, and then the chuck device (18) is opened, the cylinder (21) is further raised, and the dummy placed on the press plate (23>) is clamped and held by the chuck device.After this, this operation is repeated until the inside of the heating furnace (10) is reached. After filling with the dummy, the chuck device is released.

Thereafter, current is passed through the high frequency induction coil (11) to induction heat the graphite heating element (12).

Heat from the graphite heating element (12) flows toward the dummy, the upper and lower refractory heat bricks (13), and the heat insulating material (14), raising the temperature of the entire vertical heating furnace (10).

After the heating element (12) reaches a predetermined temperature, the dummy is inserted and removed repeatedly, so that the temperature of the heating furnace repeats a fixed pattern.

That is, the cylinder (21), the chuck device (18), and the extraction device are operated in a predetermined order to extract the dummy located at the lowest stage in the furnace, and a new dummy is stacked on the top stage by the material filling container insertion device (17). The entire laminated container is lowered by this.The temperature of the heating element (12) decreases, so the output is increased and the temperature is raised, and after reaching a predetermined temperature, the temperature is maintained for a predetermined time.Here, the predetermined temperature and various temperatures are reached. The time required for sintering differs depending on the sintering material, etc.After that, the vertical heating furnace (1
0>, the dummies are inserted and removed until a certain temperature pattern as shown in FIG. 4 is repeated.

After the temperature of each part of the vertical heating furnace (10) begins to repeat a constant pattern, replace it with a dummy and start inserting the sintering material filling container (1), which has been filled with sintering material in advance.The operation is as follows. After inserting the sintering material filling container (1) in the same manner as the dummy insertion method, the graphite heating element (12) reaches a predetermined temperature by the upper and lower hydraulic cylinders (20) and (21), and then The material-filled container (1) is intermittently lowered to a predetermined position, and as it is lowered through the furnace from the top, it is heated and heated by the graphite heating element. The predetermined maximum temperature is reached.The contraction of the sintering material starts from the upper fireproof insulation brick part, and almost completes the contraction at the graphite heating element part.The sintering material filling container (1> When lowered into the brick part, the sintering material filling container (1) is cooled according to the temperature distribution inside the vertical heating furnace (10).The sintering material filling container (1) is a vertical heating furnace (10) The dummies are supplied one after another from the top of the vertical heating furnace (10), and the dummies are pulled out one after another from the bottom of the vertical heating furnace (10), leaving only the sintering material filling container (1) inside the vertical heating furnace (10). The tying is done.

As explained above, when the sintered body manufacturing apparatus according to the present invention is used, it is possible to use a batch-type hot press apparatus, which was conventionally inefficient, or a hot press apparatus that directly supplies sintering materials to a vertical heating furnace. Compared to conventional methods, sintered bodies can be obtained efficiently with a longer life, and productivity is improved. In addition, the sintering material is not affected by grain growth or phase transition (a sintered body with the same quality as a sintered body obtained with a conventional batch type hot press machine can be obtained). Further, since only one system of pressurizing mechanism for the sintering material is required, and this pressurizing mechanism also serves as a moving mechanism for the sintering material filling container, the apparatus itself can be manufactured at low cost.

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

Below is the margin Example 1 Silicon nitride powder (manufactured by Denki Kagaku Kogyo ■, GRADE 5N-9
FW, purity 98.5%, average particle size 0.8 μm.

α rate 91%) 92 parts by weight of alumina powder (commercial product purity 9)
9%, specific surface area 8rd/g) 3 parts by weight, yttrium powder (commercial product, high purity yttrium oxide, purity 99.9%)
After adding 5 parts by weight, it was mixed in a vibrating ball mill to obtain a mixed powder for molding. Next, this mixed powder was mixed at 500 kg/c
A rectangular parallelepiped (shape 40 x
40 x 30 mm). The obtained compact is shown in Fig. 2 (0)) in a container filled with sintering material (made of graphite).

(outer diameter 200mm, length 150m), 4 pieces per stage, 3
After filling the sintering material into stages, the container filled with the sintering material was supplied to the apparatus shown in FIG. 3, and hot pressing was performed continuously. As a condition for hot pressing, the maximum temperature of the graphite heating element is 650"C.
The holding time was 20 minutes, and the molding pressure was 200 kg/cd. In this case, it takes 30 minutes for the material-filled container inserted into the fireproof insulating brick part to fall into the graphite heating element and the temperature of the graphite heating element to drop to reach a temperature of 1650°C again. It took 50 minutes to lower the container by one level. Production rate is 1 per hour
It reached 44 pieces.

The measurement results of relative density 1 bending strength and Vickers hardness of the obtained sintered body are shown in the table. Although continuous operation was performed under these conditions for 90 days, no damage was observed to the vertical heating furnace.

Examples 2 to 4 Various sintering materials shown in Table 1 were sintered using the sintered body manufacturing apparatus and sintering material filling container used in Example 1. Manufacturing conditions and production speed of the sintered body.

The number of continuous operation days and the physical properties of the sintered body are also shown in the table.

The following materials were used as raw material powders.

Boron nitride powder (manufactured by Denki I, Gakkogyo ■, Great 5P-
9FW, purity 96%, specific surface area 50 po/g) (Example 2
), boric anhydride (reagent purity 99%), calcium oxide (reagent purity 99%), boron carbide (manufactured by Denki Kagaku Kogyo ■, gray) HP M degree 98%, average particle size 2 μm)
, aluminum nitride powder (manufactured by Denki Kagaku Kogyo ■, GRADE AP-10, purity 99%, specific surface area 4n (/g), titanium boride powder (manufactured by Denki Kagaku Kogyo ■, purity 98%,
average particle size 9 μm), boron nitride powder (manufactured by Denki Kagaku Kogyo ■, grade GP, purity 99%, specific surface area 6 rrr/
g) Comparative Example 1 A batch type hot press apparatus was assembled using the heat source used in Example 1, and hot pressing was performed. The raw material powder used in Example 1 was used. The hot pressing conditions were a sintering temperature of 1650'C for 20 minutes. In this case, it took 90 minutes to heat the press mold to 1650°C, and it took about 10 hours to cool the press mold after hot pressing and extract the sintered body from the press mold. did. Productivity was very poor and only a little more than one sintered body could be obtained per hour. The physical properties of the obtained sintered body are shown in the table, and the physical properties of the sintered body were equivalent to those of the sintered body obtained by continuous hot pressing in Example 1.

Comparative Example 2 Using the heating source used in Example 1, JP-A-49-36513
In the hot press device described in the publication, press molds filled with sintering material are stacked in a vertical heating furnace, and the press molds are sequentially moved, reaching the direction of movement of the press molds and pressing the press molds from a perpendicular direction. We assembled a continuous hot press device that sintered the sintering material by applying pressure at one point where the material reached its maximum temperature, and hot pressing was carried out. The sintering materials and hot pressing conditions were the same as in Example 1.

The physical properties of the obtained sintered body are shown in the table. The physical property of the sintered body obtained by this method is the relative density of the sintered body.

Both the bending strength and Vickers hardness were lower than the sintered body obtained in Example 1, and the performance was poor.

Note that the productivity was the same as in Example 1.

Comparative Example 3 Hot pressing was carried out using the heating source used in Example 1, and the sintering material was directly supplied into the vertical heating furnace without using the sintering material filling container, and after the completion of sintering, the upper hydraulic pressure was Hot pressing was performed by lowering only the sintered body using a cylinder and extracting it from the lower part of the vertical heating furnace. The sintering material and the shape of the finally obtained sintered body were the same as in Example 1, and the hot pressing conditions were also the same as in Example 1.

Immediately after the start of sintering, the sintered body could be easily extracted from the vertical heating furnace, but as the number of sintering increases, the inner wall of the heating element, which also serves as a mold, wears out and the outer surface of the sintered body becomes uneven. The pressure in the upper hydraulic cylinder required to lower the sintered compact in the vertical heating furnace gradually increased. The pressure required to lower the sintered compact may eventually reach the molding pressure of the sintered compact, and the pressure of the upper and lower hydraulic cinders is not transmitted to the sintering material, and the forming square press mold is It was found that the radiation was transmitted to a heating element that also served as a heating element. Therefore, the density of the obtained sintered body gradually decreased as the number of sinterings increased. Table 1 shows the physical properties of the obtained sintered body.

Furthermore, the strength of the heating element in the vertical heating furnace continued to deteriorate due to inner wall wear and eventually broke.

In this case, the maximum number of continuous operation days is 7 days,
In most cases, the heating element was destroyed within 3 to 4 days, and the continuous operation period was extremely short compared to the method of the present invention.

Comparative Examples 4 to 6 Sintered bodies were manufactured using the raw material powders used in Examples 2 to 5 using the batch type hot press apparatus used in Comparative Example 1.

Comparative Examples 7 to 9 Sintered bodies were manufactured using the raw material powders used in Examples 2 to 5 using the continuous hot press apparatus used in Comparative Example 2.

Comparative Examples 10 to 12 Sintered bodies were manufactured using the continuous hot press apparatus used in Comparative Example 3 using the raw material powders used in Examples 2 to 5.

In addition, each physical property described in the table was measured by the following method.

(1) Relative density: The volume was determined from the dimensions of the sintered body, the density was determined from the weight, and the density was calculated using the following formula.

Relative density (%) = (density (g/cffl) / theoretical density (
g/cj) ) X100 (2) Room temperature bending strength: Based on JIS R1601.

(3) Hardness, Vickers hardness (Hv)...JIS Z 22
51.

Shore hardness (Hs)...JIS Z 22
46.

[Effects of the Invention] When the sintered body manufacturing apparatus of the present invention is used, it can be operated continuously for a longer period of time compared to conventional hot press equipment, so sintered bodies can be obtained efficiently and productivity is greatly improved. . In addition, it has the effect of obtaining a sintered body without being affected by grain growth or phase transition, and has great industrial applications.

[Brief explanation of the drawing]

Figures 1 (a) and (b) and Figure 2 (a) and (b) are a vertical cross-sectional view and a cross-sectional plan view of a container filled with sintering material, respectively, and Figure 3 is a continuation of the present invention used in an example. FIG. 4, a longitudinal cross-sectional view of the hot press apparatus, is a graph showing a repeating pattern of heating furnace temperature. 1... Sintering material filling container 10... Vertical heating furnace 11... High frequency induction coil -12... Graphite heating element 13... Fireproof insulation brick 14...
Insulating material 15...Water cooling tank 17...Material filling container insertion device 18...Chuck device 0i19...Container extraction device 20.21...Hydraulic cylinder 22
．． 23...Press plate 24...Upper slide table Fig.

Claims (4)

[Claims] (1) Containers filled with sintering materials are stacked in multiple stages in a vertical heating furnace, and the upper and lower ends of the laminated containers are heated while being pressurized by a pair of pressure devices, and after a predetermined period of time, the laminated containers are stacked. A method for producing a sintered body, characterized in that sintering is carried out in a process of repeatedly lowering a container by a unit length of the container, taking it out of the furnace from the lower stage side, and supplying a new material-filled container from the upper end side. (2) The manufacturing method according to claim 1, wherein the stacked containers of the vertical heating furnace are supplied from the lower stage side and taken out from the upper stage side. (3) A vertical heating furnace that has a heating means and a cooling means and a pair of pressure devices above and below the heating area of the furnace core, and a sintering material is filled from the side at the upper end of the heating furnace. a supply means for supplying the container; and a first container at the lowermost stage on the lower end side of the furnace.
A sintered body manufacturing apparatus comprising a discharging means for taking out the stage container and a chuck means for holding the side of the second stage container. (4) Claim 3, wherein a discharge means for taking out the uppermost container in the furnace is provided at the upper part of the heating furnace, and a supply means is provided below the furnace for supplying the lowermost first container.
The device described.