JP2019157227A - Fine particle sintering method and device - Google Patents

Abstract

To provide a fine particle sintering device for producing a sintered body in which contamination by impurities is extremely few, and to provide a fine particle sintering method using the device.SOLUTION: There is provided a fine particle sintering method for obtaining a sintered body (9) by heat compression of a compact (3) using the rolls (7a, 7b). The method is characterized in that rolls in which the coating layers (6) having the same material as the compact (3) are formed thereon are used as the rolls (7a, 7b), and the surface temperature of the compact (3) immediately before conveyance between the rolls (7a, 7b) is controlled to 600°C higher than that (550°C) of the coating layer (6) or about the same (550°C to less than 600°C). Thereby, the contact of the compact with a portion becoming an impurity contamination source at heat compression is eliminated to enable obtaining of the sintered body (9) extremely few in contamination by impurities.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for sintering powder.

  In the process of manufacturing ceramic products, ceramics, powder metallurgy, cermets, etc., sintered materials are manufactured by press-molding ceramic and metal powder raw materials and then heat-treating them at a temperature below the melting point of the powders. . As the sintering method, there are a normal pressure sintering method, a gas pressure sintering method, a hot press method, a hot isostatic pressing method (HIP), a current pressing method, a millimeter wave method, and the like. In order to obtain a denser sintered body, it is effective to heat the powder compact in a pressurized state by a gas pressure sintering method, a hot pressing method, a hot isostatic pressing method, an energization pressing method, or the like.

  However, when heated in a pressurized state, there is a concern about impurity contamination from a mold or the like with which the powder compact comes into contact. In particular, when the obtained sintered body is used for a part of an electronic component, the product quality may be deteriorated even if a trace amount of impurities is mixed. This includes, for example, the mixing of conductive elements into insulating parts and the mixing of metals into battery materials.

  On the other hand, for example, Patent Document 1 uses a molding die to which a sintering aid powder or the like is applied in order to obtain a nitrogen-silicon-based sintered body, and contamination from impurities derived from the material of the molding die is avoided. . Moreover, in patent document 2, the same element as the material to press is made to adhere to the press roll surface part, and the contamination derived from the material of a press roll is avoided similarly to patent document 1. FIG.

Japanese Patent No. 3981482 JP-A-2006-59870

  However, in Patent Document 1, an element that is not included in the raw material powder of the nitrogen-silicon sintered body is used for the sintering aid powder, and there is a concern that another impurity may be mixed.

  Instead of a powder sintering apparatus, Patent Document 2 discloses an application apparatus that applies a paint while continuously running a belt-like body of an object to be coated. This is such that the film of the paint remains on the surface of the press roll so that the surface of the press roll supplying the paint does not wear due to friction with the paint. However, if the same thing is performed at high temperature by diverting to a powder sintering apparatus, it is considered that the coating film applied to the press roll is cracked or peeled off. In addition, the transfer of the material to the press roll is uneven depending on the location, and the degree of sintering varies due to variations in the press pressure when sintering the material, or the coating film peels off from the press roll surface There is also a possibility that the uniformity of the product may be impaired, for example, contamination of the product from the press roll due to adhering to the product.

  An object of the present invention is to provide a powder sintering method capable of avoiding contamination from a portion in contact with a product during the sintering process and not impairing the uniformity of the degree of sintering.

  In order to achieve the above object, the powder sintering method of the present invention is a powder sintering method in which a compact is heated and compressed by a roll, and the coating layer made of the same material as the compact is surfaced as the roll. The surface temperature of the molded body immediately before being carried into the roll is adjusted to be higher or substantially the same as the temperature of the coating layer.

  In the powder sintering method, it is more preferable that the height of the unevenness of the base of the coating layer on the surface of the roll is 0.05 μm or more and 1.0 μm or less.

  The powder sintering apparatus of the present invention is a powder sintering apparatus that heat-compresses a molded body with a roll, and a roll having a coating layer of the same material as the molded body formed on the surface thereof, and is carried into the roll. A preheating unit for adjusting the surface temperature of the previous molded body to be higher or substantially the same as the temperature of the coating layer is provided.

  The powder sintering apparatus of the present invention is a powder sintering apparatus for producing a sintered body by heat-compressing raw materials, the feeder unit supplying the raw materials, and the raw materials having a certain size. A molding unit formed into a molded body, a preheating unit for heating the molded body to a predetermined temperature before heating and compressing the molded body, and a coating layer made of the same material as the raw material is applied to the surface of a roll having irregularities on the surface. A heating / compression unit for producing a sintered body by heating and pressing the carried molded body, a transport unit for transporting the molded body from the molding unit to the preliminary heating unit and the thermal compression unit, and the preliminary heating A first control unit for controlling the temperature of the unit and a second control unit for controlling the temperature and pressure of the heating / compression unit are provided.

  In the powder sintering apparatus, it is more preferable that the surface temperature of the formed body heated by the preheating unit is higher or substantially the same as the temperature of the coating layer.

  Moreover, in the powder sintering apparatus, it is more preferable that the height of the unevenness of the base of the coating layer on the surface of the roll is 0.05 μm or more and 1.0 μm or less.

  According to the powder sintering method of the present invention, a roll having a surface formed with a coating layer of the same material as the molded body is used, and the surface temperature of the molded body before being carried into the roll is set as a preheating unit. The temperature of the coating layer is adjusted to be higher or substantially the same as the temperature of the coating layer, so even if high temperature and high pressure heat compression is applied, there is no contamination from the powder sintering equipment and there is little variation in the degree of sintering. Can be obtained.

Configuration diagram of a powder sintering apparatus for executing the powder sintering method of the present invention (A) Cross-sectional view of the roll and (b) Enlarged view of the main part in the initial operation

  Hereinafter, the powder sintering method of the present invention will be described with reference to the drawings.

  FIG. 1 shows a powder sintering apparatus for executing the powder sintering method of the present invention.

  This apparatus includes a feeder unit 2 for supplying the raw material 1, a molding unit 4 for forming the raw material 1 supplied by the feeder unit 2 into a molded body 3 of a certain size, and a predetermined unit before the molded body 3 is heated and compressed. A preheating unit 5 for heating to a temperature, a heat compression unit 10 for producing a sintered body 9 by heating and pressurizing the molded body 3 treated by the preheating unit 5, and the molded body 3 from the molding unit 4. A transport unit 11 that transports the preheating unit 5 and the heating / compression unit 10, a first control unit 12 that controls the temperature of the preheating unit 5, and a second control unit 13 that controls the temperature and pressure of the heating / compression unit 10. And have.

  The feeder unit 2 includes a hopper 2a and a screw feeder 2b.

  The molding unit 4 includes pressure rollers 4a and 4b having a diameter of 300 mm and a roller cutter 4c.

  The preheating unit 5 is a heating furnace heated by a heater, and the heating temperature and time are controlled by the first control unit 12. The processing temperature of the preheating unit 5 is set to be equal to or lower than the melting point of the raw material 1.

  The heating / compression unit 10 includes a heater 8 and a pair of rolls 7a and 7b each having a concavo-convex 14 formed on the peripheral surface thereof as shown in FIGS. 2 (a) and 2 (b). The surfaces of the rolls 7 a and 7 b are covered with the coating layer 6. The material of the coating layer 6 is the same material as the raw material 1. The temperature and pressure of the heat compression by the heat compression unit 10 and the respective times are controlled by the second control unit 13.

  The processing temperature of the preheating unit 5 and the processing temperature of the heating and compression unit 10 are such that the surface temperature of the molded body 3 immediately before being carried into the rolls 7 a and 7 b of the heating and compression unit 10 is higher or substantially lower than the temperature of the coating layer 6. It is adjusted to the same. The surface temperature of the molded body 3 is substantially the same as the temperature below the temperature of the coating layer 6 and near the temperature of the coating layer 6. In the examples described later, detailed description will be given with specific set temperatures.

  In addition, the heating compression unit 10 of the powder sintering apparatus immediately after production is covered with the coating layer 6 leaving a part of the apex 14a of the unevenness 14 as shown in FIG. 2B, for example. The apex 14a is further coated with the material of the coating layer 6 that has been peeled off from the molded body 3 during a trial run after the start of operation, and the entire unevenness 14 is not exposed.

  A detailed configuration of the heat compression unit 10 will be described based on a powder sintering process.

  The raw material 1 put into the feeder unit 2 is sent to the molding unit 4 at a constant volume per unit time. In the molding unit 4, the raw material 1 is pressed and hardened to form a molded body 3 that has a certain shape and has a strength that does not collapse even when transported by the transport unit 11. The molded body 3 is transported to the preheating unit 5 by the transport unit 11 and heated to a predetermined temperature. The predetermined temperature of the preheating unit 5 is a temperature lower than the melting point of the raw material 1.

  The heated molded body 3 is carried to the heating and compression unit 10 by the transport unit 11. When the compact 3 is heated to a predetermined temperature by the heating and compression unit 10 and given a predetermined load by the rolls 7 a and 7 b, a sintering reaction occurs and becomes a sintered body 9.

  The irregularities 14 of the rolls 7a and 7b are 0.05 μm or more and 1.0 μm or less in height, and the rolls 7a and 7b are formed by sintering coating the raw material 1. The coating material 6 is applied in a state in which the raw material 1 is transferred to the surface by being heat-compressed several times at a predetermined temperature and load using the molded body 3 and sintered.

  If the height of the unevenness 14 is less than 0.05 μm, the anchor effect for attaching the coating layer 6 is too small, and if it is greater than 1.0 μm, the local pressure variation during heating and compression increases, so the density of the sintered body 9 The variation becomes remarkable.

  In this way, the coating layer 6 applied to the rolls 7a and 7b repeats adhesion / sintering of the raw material 1 and peeling of the sintered film at the time of heat compression, and this series of behaviors is caused by the preheating unit 5. The heating process and the high-temperature and high-pressure pressing process by the heating compression unit 10 are greatly involved.

  In the high-temperature and high-pressure press process used for sintering, since the crystallization of the coating layer 6 is promoted as the processing proceeds, the coating layer 6 is in a fragile state because the hardness is high but the flexibility is impaired. For this reason, a large number of cracks are generated in the coating layer 6 by the high-pressure press by the heat compression unit 10. When the coating layer 6 becomes thicker due to the transfer from the molded body 3, it peels off from the crack starting from the point where it exceeds a certain thickness, and a part is taken into the sintered body 9.

  In the case of this peeling, when the surface temperature of the molded body 3 heated by the preheating unit 5 and carried into the heat compression unit 10 and the surface temperature of the coating layer 6 of the heat compression unit 10 are the same or substantially the same, Only a small amount of the coating layer 6 is peeled off, leaving a film thickness sufficient to fill the recess due to the anchor effect of the irregularities 14 formed on the surfaces of 7a and 7b. Therefore, the coating layer 6 that remains on the rolls 7a and 7b after adhering to the recesses of the projections and depressions 14 is not taken into the sintered body 9, so that contamination of the sintered body 9 with impurities can be suppressed.

  When the surface temperature of the molded body 3 is higher than the surface temperature of the coating layer 6, the raw material 1 adheres to the rolls 7 a and 7 b side while applying heat from the molded body 3 after contact to the coating layer 6. The crystallization of the coating layer 6 is promoted, and the vicinity of this interface tends to be a crack generation source. Therefore, as in the case where the surface temperature of the molded body 3 and the surface temperature of the coating layer 6 are substantially equal, it is possible to suppress contamination of impurities into the sintered body 9. Further, since the variation in the position of the crack generation source in the coating layer 6 is smaller than in the case where the surface temperature of the molded body 3 and the surface temperature of the coating layer 6 are substantially equal, the local pressure variation during heating and compression is reduced. Density variation of the sintered body 9 is reduced.

  On the other hand, when the surface temperature of the molded body 3 immediately before contacting the coating layer 6 is lower than the surface temperature of the coating layer 6, the molded body 3 after contact takes heat from the coating layer 6. At this time, the coating layer 6 is contracted, and a gap is generated at the interface between the coating layer 6 and the rolls 7a and 7b. In the case of significant separation due to this void, the separated coating layer 6 is taken into the sintered body 9, and metal impurities adhering to the portions that have been in contact with the rolls 7a and 7b are mixed. For this reason, mixing of impurities cannot be sufficiently suppressed.

  For this reason, the surface temperature of the molded body 3 immediately before coming into contact with the coating layer 6 is adjusted to be higher or substantially the same as the temperature of the coating layer 6 by the preheating unit 5 and the first control unit 12.

− Examples −
An example of sintering powder of the raw material 1 containing silicon oxide as a main material will be described.

  In this embodiment, the raw material 1 will be described by taking as an example a case where a material having a melting point of 1030 ° C. is sintered.

  In this apparatus, the pressure rollers 4a and 4b are constituted by rollers having a diameter of 300 mm. The preheating unit 5 is a heating furnace that is heated by an infrared heater. The thermal compression unit 10 used was a coating layer 6 made of the same material as the raw material 1 on Φ300 mm rolls 7a and 7b, and an infrared heater was installed as the heater 8 inside the rolls 7a and 7b. The heat compression unit 10 is a hot roll press device that manufactures the sintered body 9 by heating and pressurizing the molded body 3 with the rolls 7a and 7b. The unevenness 14 has a height of 0.05 μm or more and 1.0 μm or less. The unevenness 14 is uniformly formed on the entire surface of the rolls 7a and 7b. The numerical value of the height of the unevenness 14 is determined from an experiment of the anchor effect and the change of the unevenness 14 when the formed body 3 is sandwiched between stainless steel plates and heated and pressed with a roll. When the height of the irregularities 14 was 0.05 μm, the material adhered to the stainless steel plate, but when the height was lower than this, the material did not adhere. When the height of the unevenness 14 exceeds 1.0 μm by blasting or acid processing, for example, about 1.5 μm, the apex 14a of the unevenness 14 becomes small after pressing, and the apex of the convex portion disappears from SEM observation. It was seen. In 1.0 μm, the apex 14a of the unevenness 14 remained. The aspect ratio of the irregularities 14 was 2 or more and less than 5.

  Note that the surfaces of the rolls 7a and 7b are made of tungsten-based high-speed steel, and stainless steel SUS316 is used in the portions where the raw material 1, the molded body 3 and the sintered body 9 are in contact with other units.

  The powder sintering process using this apparatus will be described in detail in comparison with a comparative example.

The raw material 1 having a melting point of 1030 ° C. charged into the hopper 2a of the feeder unit 2 is sent to the pressure rollers 4a and 4b of the molding unit 4 by the screw feeder 2b at a speed of about 600 cm ³ / min. The pressure rollers 4a and 4b press and harden the raw material 1 at a gap of 4 mm between the rollers, a load of 10 tons, and a peripheral speed of 1 m / min, and are cut with a roller cutter 4c to have a thickness of about 4 mm, a width of about 100 mm, and a length of about 100 mm. The molded body 3 is molded.

  The molded body 3 is transported to the preheating unit 5 by the transport unit 11 and heated to a temperature of 600 ° C. by processing for 60 seconds. The heated molded body 3 is further transported to the heat compression unit 10 by the transport unit 11.

  When the temperature of the molded body 3 immediately before being carried into the heat compression unit 10 is 600 ° C., the heat compression unit 10 has a gap between the rolls 7a and 7b of 2 mm, a load of 30 tons, a peripheral speed of 4 m / min, and approximately 600 ° C. A sintered body 9 is produced by heating and compressing the molded body 3 under a roll temperature condition of 550 ° C. that can be regarded as the same.

  The result of measuring this sintered body 9 by ICP emission spectroscopy using a high frequency inductively coupled plasma (ICP) as a light source is shown in the following Table 1 as metal impurity measurement results of the examples.

  In addition, the case where the processing temperature of the preheating unit 5 in the above embodiment is 25 ° C. and the rolls 7a and 7b of the heating and compression unit 10 are rolls to which the coating layer 6 is not applied is referred to as Comparative Example 1, and similarly a sintered body. Nine metal impurity measurement results were measured.

  Furthermore, the case where the processing temperature of the preheating unit 5 in the above embodiment was changed to 25 ° C. was set as Comparative Example 2, and the metal impurity measurement result of the sintered body 9 was measured in the same manner.

  Note that the treatment temperature 25 ° C. of the preheating unit 5 in Comparative Examples 1 and 2 is sufficiently lower than the treatment temperature 550 ° C. of the heat compression unit 10.

  As can be seen from this result, in the examples, the amount of metal impurities is almost the same as that of the raw material 1 powder. On the other hand, in Comparative Example 1 and Comparative Example 2, an increase in iron impurities is particularly observed.

  The configuration and processing conditions of the apparatus shown in this embodiment are merely examples, and are not limited by this embodiment.

Thus, it becomes possible to obtain the sintered body 9 in which mixing of metal impurities is suppressed by the powder sintering method using the apparatus of the present invention.
In addition, although the Example demonstrated the case where the processing temperature of the heating compression unit 10 was set to 550 degreeC, and the processing temperature of the preheating unit 5 was set to 600 degreeC higher than 550 degreeC, the roll of the heating compression unit 10 was demonstrated. The surface temperature of the molded body 3 immediately before being carried into 7a, 7b is adjusted to be the same as the temperature of the coating layer 6 by the preheating unit 5, specifically, the raw material 1 of the molded body 3 of the molded body 3 is adjusted by the preheating unit 5. Even if it heats to 600 degreeC below melting | fusing point, even if it processes by the heating compression unit 10 of the process temperature of 600 degreeC, compared with the comparative example 1 and the comparative example 2, the sintered compact 9 which suppressed mixing of a metal impurity is obtained. I was able to.

  The powder sintering method of the present invention contributes to improving the performance of various industrial products that require a sintered body that is heat-treated at a temperature lower than the melting point of the powder after the powder raw material is pressed. In particular, it is effective for improving the performance of insulating parts and battery materials.

DESCRIPTION OF SYMBOLS 1 Raw material 2 Feeder unit 2a Hopper 2b Screw feeder 3 Molded body 4 Molding unit 4a, 4b Pressure roller 4c Roller cutter 5 Preheating unit 6 Coating layer 7a, 7b Roll 8 Heater 9 Sintered body 10 Heat compression unit 11 Conveyance unit 12 1st control unit 13 2nd control unit 14 Unevenness

Claims (6)

A powder sintering method in which a compact is heated and compressed by a roll,
As the roll, use what formed the coating layer of the same material as the molded body on the surface,
A powder sintering method, wherein the surface temperature of the compact immediately before being carried into the roll is adjusted to be higher or substantially the same as the temperature of the coating layer.   2. The powder sintering method according to claim 1, wherein the height of the unevenness of the base of the coating layer on the surface of the roll is 0.05 μm or more and 1.0 μm or less. A powder sintering apparatus that heat-compresses a compact with a roll,
A roll in which a coating layer of the same material as the molded body is formed on the surface;
The powder sintering apparatus provided with the preheating unit which adjusts the surface temperature of the said molded object before carrying in to the said roll higher than the temperature of the said coating layer, or substantially the same. A powder sintering apparatus for producing a sintered body by heating and compressing raw materials,
A feeder unit for supplying the raw materials;
A molding unit for forming the raw material into a molded body of a certain size;
A preheating unit for heating the molded body to a predetermined temperature before heat compression;
A heating and compression unit for producing a sintered body by heating and pressurizing the molded body that has been provided with a coating layer of the same material as the raw material on the surface of a roll having irregularities on the surface;
A transport unit for transporting the molded body from the molding unit to the preheating unit and the heating and compression unit;
A first control unit for controlling the temperature of the preheating unit;
A second control unit for controlling the temperature and pressure of the heating and compression unit;
Powder sintering equipment. The surface temperature of the molded body heated by the preheating unit is higher or substantially the same as the temperature of the coating layer,
The powder sintering apparatus according to claim 4.   The powder sintering apparatus according to any one of claims 3 to 5, wherein the height of the unevenness of the base of the coating layer on the surface of the roll is 0.05 µm or more and 1.0 µm or less.

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