JP2010222689A - Sintering mold for electric pressurizing and sintering apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sintering mold for an electric pressurizing and sintering apparatus, in which a powder of an electroconductive material can be heated efficiently even when a large-sized sintered article is produced from the electroconductive material. <P>SOLUTION: The sintering mold 80 for the electric pressurizing and sintering apparatus is provided with: a mold 81 having a hollow portion; and a pair of upper and lower punches 82, 83 which are installed in the hollow portion of the mold 81 to be freely inserted in/removed from there and which are connected to a power source. A sintering chamber A is formed by the mold 81 and the pair of upper and lower punches 82, 83 in the hollow portion of the mold 81. A spacer 95 is disposed between the upper punch 82 and the powder m, which is to be sintered and is housed in the sintering chamber A, and also between the lower punch 83 and the powder m to be sintered. The spacer 95 has a non-electroconductive area in the center part thereof and an electroconductive area in the outer peripheral part thereof. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a sintering mold of an electric pressure sintering apparatus. More specifically, the present invention relates to a sintering die of an electric current pressure sintering apparatus suitable for sintering conductive powder such as metal and conductive ceramics.

FIG. 4 is a longitudinal sectional view of a sintering die 180 of a conventional energization pressure sintering apparatus. As shown in the figure, reference numeral 181 denotes a mold of a sintering mold 180 used in the energization pressure sintering apparatus. The mold 181 has a through-hole penetrating vertically, and a pair of upper and lower punches 182 and 183 are inserted into the through-hole. The mold 181 and the pair of upper and lower punches 182 and 183 constituting the sintering mold 180 are formed of a conductive material such as carbon, and a positive electrode and a negative electrode of a DC power source or a DC pulse power source are connected to the pair of upper and lower punches 182 and 183, respectively. . The pair of upper and lower punches 182 and 183 are configured such that the end portions inserted into the through holes are close to and away from each other by a pressing means (not shown).
For this reason, if the powder m is contained in the space between the pair of upper and lower punches 182 and 183 in the through hole of the mold 181 and the pair of upper and lower punches 182 and 183 are brought close to each other, the powder m is added by the upper and lower punches 182 and 183. Can be pressed. Moreover, if the pair of upper and lower punches 182 and 183 are energized by a DC power source, current flows through the sintering mold 180 and the powder m, and the sintering mold 180 and the powder m generate heat, so that the powder m can be pressure-sintered. .
In the current heating and sintering apparatus as described above, since the sinter mold 180 and the powder m are directly energized, the sintering mold 180 and the powder m self-heat and rapidly rise in temperature. There is an advantage that it can be shortened.

However, when the conductive powder m such as copper (Cu) or nickel (Ni) is sintered in the current heating and sintering apparatus as described above, since the electric resistance of the powder m itself is small, the powder m Even if an electric current flows through it, it is hard to self-heat. Then, sufficient heat generation cannot be generated in the powder m with respect to the supplied current amount, and it becomes difficult to sufficiently raise the temperature of the powder m.
Moreover, the current supplied to the sintering mold 180 flows through both the sintering mold 180 and the powder m. However, when the conductivity of the powder m is higher than that of the mold 181, the current flows to the powder m. While the flowing current increases, the current flowing through the mold 181 decreases. As a result, the mold 181 cannot sufficiently generate heat with respect to the supplied current amount, and the mold 181 is also difficult to sufficiently raise the temperature.

Therefore, a technique is disclosed in which an insulating plate 185 is installed between the powder m and the pair of upper and lower punches 182 and 183 so that the insulation is maintained up to a predetermined temperature and breaks down when the predetermined temperature is exceeded (Patent Document). 1, FIG. 5).
In the technique of Patent Document 1, at the initial stage of sintering, only the mold 181 is heated, and the temperature of the outer peripheral portion of the powder m, which does not easily rise in temperature, is raised before the inside. Heat is generated by self-heating of m. Therefore, since the temperature distribution inside the powder m during sintering can be made uniform, it is possible to prevent variations in the sintered state and density from occurring inside the sintered product and improve the quality of the sintered product. can do.

If the technique of patent document 1 is adopted, the temperature of the outer peripheral portion of the powder can be sufficiently increased only by heat generation from the mold in a small sintered product (for example, a diameter of 100 mm or less), so that the quality is improved. It is possible.
However, when sintering large sintered products (for example, 300 mm or more in diameter), there is a possibility that the temperature of the outer periphery of the powder cannot be sufficiently increased by only the heat generated from the mold for the limited current value. There is. Then, while the temperature of the powder outer peripheral portion is not sufficiently high, the inside of the powder m is heated by self-heating, and the temperature difference between the inside of the powder m and the powder outer peripheral portion may increase. If such a temperature difference arises, the sintered state and density will vary within the manufactured sintered product, and the quality of the sintered product will deteriorate.

Patent No. 3681993

  In view of such circumstances, the present invention is capable of efficiently heating powder even when manufacturing a large-sized sintered product from a conductive material, and is capable of sintering a current-pressure compression sintering apparatus that can prevent deterioration of the quality of the sintered product. The purpose is to provide a mold.

The sintering mold of the electric pressure sintering apparatus of the first invention is a sintering mold of the electric pressure sintering apparatus, and the sintering mold includes a mold having a hollow portion and a hollow portion of the mold. A pair of upper and lower punches connected to a power source, which are detachably attached, and a sintering chamber is formed in the hollow portion of the mold by the mold and the pair of upper and lower punches. Spacers are respectively provided between the punches and the powder to be sintered accommodated in the sintering chamber, and each spacer has a non-conductive region in the center and a conductive region in the outer periphery. It is characterized by having.
In the sintering die of the energization and pressure sintering apparatus of the second invention, in the first invention, the spacer is formed such that the conductive region has a rotationally symmetric shape with respect to the central axis of the spacer. It is characterized by that.
In the sintering die of the electric pressure sintering apparatus of the third invention, in the first or second invention, the non-conductive region of the spacer is formed of a material that is carbonized at a temperature at which the powder to be sintered is sintered. It is characterized by.
According to a fourth aspect of the present invention, there is provided the sintering die of the current pressure sintering apparatus according to the first, second or third invention, wherein the spacer comprises a pair of upper and lower conductive sheets made of a conductive material and the pair of upper and lower conductive layers. And an insulating sheet made of an insulating material having an outer diameter smaller than that of the conductive sheet, the spacer being disposed between the powder to be sintered and the punch. In this state, the outer peripheral edge is disposed so as not to contact the inner surface of the mold.
The sintering method using the electric pressure sintering apparatus of the fifth invention is a sintering method using the sintering mold of the electric pressure sintering apparatus of the first, second, third, or fourth invention, The pressurizing force at the beginning of the start is made smaller than the pressurizing force in other periods during the sintering.

According to the first invention, since the spacer having the nonconductive region is disposed between the punch and the powder to be sintered, the resistance when current flows through the powder to be sintered can be increased. . In addition, since the spacer is provided with a conductive region on the outer peripheral portion thereof, the outer peripheral portion of the powder to be sintered can be heated not only by heat from the mold but also by heat generated by the powder to be sintered itself. Then, even if the sintered product is large, the temperature of the outer peripheral portion of the powder can be sufficiently raised in the initial stage of sintering, so that the temperature distribution inside the powder during sintering can be made uniform. Therefore, it is possible to prevent variations in the sintered state and density from occurring in the sintered product, and the quality of the sintered product can be improved.
According to the second aspect of the present invention, since the conductive regions of the spacer are provided so as to be rotationally symmetric, it is possible to prevent the bias of the energization path in the cross section of the powder to be sintered. Therefore, local heat generation due to non-uniform contact resistance between the punch and the mold can be suppressed, so that it is possible to prevent the formation of a region that is partially strongly heated in the powder to be sintered. Then, since the temperature in the cross section of the powder to be sintered during sintering can be made uniform, a sintered product having predetermined characteristics can be manufactured.
According to the third invention, the non-conductive region of the spacer is carbonized at the temperature at which the powder to be sintered sinters. Therefore, when the powder to be sintered reaches the sintering temperature, the spacer is uniformly distributed over the entire cross section of the powder to be sintered. Current can flow. Therefore, at the end of sintering of the powder to be sintered, heat is generated in the whole powder to be sintered, so that sintering can be promoted.
According to the fourth invention, when the powder is pressed by a pair of upper and lower punches, the pair of upper and lower conductive sheets are in contact with each other at a portion where the insulating sheet is not provided. Then, a path through which a current flows from the punch to the powder to be sintered can be formed in the spacer. And since it can process and use a general sheet-like member, it is not necessary to use a special spacer and can suppress sintering cost.
According to the fifth aspect of the present invention, the resistance of the powder at the beginning of the sintering at which the temperature of the powder is low can be increased, so that the heat generation of the powder can be promoted and the temperature can be raised rapidly. In addition, variations in the characteristics of the manufactured sintered product can be prevented.

It is a schematic longitudinal cross-sectional view of the sintering type | mold 80 of the electric current pressurization sintering apparatus of this embodiment. It is a schematic explanatory drawing of the sintering operation | work using the sintering type | mold 80 of this embodiment. (A) is a single plan view of the spacer 95, and (B) is a schematic sectional view of another spacer 95B. It is a schematic explanatory drawing of the conventional electricity pressurization sintering apparatus. It is a schematic explanatory drawing of the conventional electricity pressurization sintering apparatus.

Next, an embodiment of the present invention will be described with reference to the drawings.
In FIG. 1, the code | symbol 80 has shown the sintering type | mold of the electricity pressurization sintering apparatus of this embodiment, and the code | symbol m has shown the to-be-sintered powder sintered by the sintering type | mold 80 of this embodiment. .
As shown in the figure, a sintering die 80 (hereinafter, simply referred to as a sintering die 80 of this embodiment) of the energization pressure sintering apparatus of this embodiment is divided into a sintering die 80 and a powder m to be sintered. A pair of upper and lower punches 82 and 83, which will be described later, are used to sinter a conductive powder m (for example, copper, nickel, etc.) having electrical conductivity by applying pressure while energizing. A feature is that a spacer 95 is provided between the sintered powder m and the sintered powder m.

  First, based on FIG. 1, the sintering type | mold 80 of this embodiment is demonstrated easily.

  As shown in FIG. 1, the mold 81 of the sintering die 80 is a member provided with a hollow portion having a circular cross section. The mold 81 is made of a conductive material such as carbon graphite, cemented carbide, conductive ceramics, or the like.

The pair of upper and lower punches 82 and 83 are members formed of a conductive material, for example, carbon graphite, cemented carbide, conductive ceramics, or the like. The pair of upper and lower punches 82 and 83 are provided so that one end thereof can be inserted into and removed from the hollow portion of the mold 81. Specifically, the pair of upper and lower punches 82 and 83 are formed so that the cross section thereof has the same cross sectional shape as the hollow portion of the mold 81. That is, the pair of upper and lower punches 82 and 83 are cylindrical and formed so that the diameter thereof is substantially the same as the diameter of the hollow portion of the mold 81.
Therefore, if the lower end portion of the upper punch 82 and the upper end portion of the lower punch 83 are respectively inserted into the hollow portion of the mold 81, the inner surface of the mold 81, the lower end of the punch 82, and the punch are inserted into the hollow portion of the mold 81. A space surrounded by the upper end of 83 can be formed. A space surrounded by the inner surface of the mold 81, the lower end of the punch 82, and the upper end of the punch 83 is a sintering chamber A in which the powder m to be sintered is accommodated.

  A spacer 95 is provided at the lower end of the upper punch 82 and the upper end of the lower punch 83. That is, the spacer 95 is located between the sintered powder m and the lower end of the punch 82 and between the sintered powder m and the upper end of the punch 83 in a state where the sintered powder m is accommodated in the sintering chamber A. It is provided so as to be located between them. Details of the spacer 95 will be described later.

  With the configuration as described above, a DC power source is connected between the pair of upper and lower punches 82 and 83 while the pair of upper and lower punches 82 and 83 are brought close to each other while the powder m to be sintered is accommodated in the sintering chamber A. Supply direct current. That is, a direct current is supplied between the pair of upper and lower punches 82 and 83 while pressing the powder m to be sintered by the pair of upper and lower punches 82 and 83. Then, a current flows from the upper punch 82 through the mold 81 to the lower punch 83. Similarly, a current flows from the upper punch 82 to the lower punch 83 through the spacer 95 and the sintered powder m. If a current flows, the pair of upper and lower punches 82 and 83, the mold 81, and the powder m to be sintered generate heat, and the powder m to be sintered can be sintered by this heat.

Next, the spacer 95 that is a feature of the present invention will be described.
As shown in FIG. 1, the spacer 95 that is a feature of the present invention includes a pair of upper and lower conductive sheets 96 and 96 and an insulating sheet 97 disposed between the pair of upper and lower conductive sheets 96 and 96. Has been.

  The pair of upper and lower conductive sheets 96, 96 are sheets formed of a conductive material such as carbon graphite, for example. The conductive sheet 96 is formed so that its shape is the same as the cross-sectional shape of the hollow portion of the mold 81. That is, the conductive sheet 96 is formed so that its diameter is substantially the same as the diameter of the hollow portion of the mold 81 (FIG. 3).

On the other hand, the insulating sheet 97 is a sheet formed of an insulating material such as alumina or mica. The insulating sheet 97 has a shape substantially similar to that of the conductive sheet 96 and is formed to have a smaller area than the conductive sheet 96. That is, the insulating sheet 97 is circular and has a diameter that is smaller than the diameter of the conductive sheet 96.
The insulating sheet 97 has a thickness such that when the sintered powder m is pressed by the pair of upper and lower punches 82 and 83, the pair of upper and lower conductive sheets 96 and 96 sandwiching the insulating sheet 97 are insulated from each other. The thickness of the sheet 97 is such that it can be contacted at a portion where the sheet 97 does not exist. For example, the insulating sheet 97 is formed with a thickness of about 0.2 to 1.0 mm, more preferably about 0.5 mm.

  The current-pressure-sintering of the powder m to be sintered by the sintering die 80 of the present embodiment using the spacer 95 as described above is performed as follows.

First, the upper end portion of the punch 83 is inserted into the hollow portion of the mold 81. Then, a spacer 95 in a state where an insulating sheet 97 is sandwiched between a pair of upper and lower conductive sheets 96 is disposed on the upper end of the punch 83. At this time, the center of the pair of upper and lower conductive sheets 96, 96 and the insulating sheet 97 is arranged so as to coincide with the central axis CL of the hollow portion of the mold 81.
Next, a predetermined amount of powder m to be sintered is placed on the spacer 95, and an insulating sheet 97 is sandwiched between the pair of upper and lower conductive sheets 96 on the powder m to be sintered. A spacer 95 is disposed. Also at this time, the center of the pair of upper and lower conductive sheets 96, 96 and the insulating sheet 97 is arranged so as to coincide with the central axis CL of the hollow portion of the mold 81.
When the lower end portion of the punch 82 is inserted into the hollow portion of the mold 81, preparation for sintering the powder m to be sintered is completed.

In the sintering operation, the powder m to be sintered is pressurized by a pair of upper and lower punches 82 and 83. Then, since the spacer 95 is pressed in a state sandwiched between the pair of upper and lower punches 82 and 83 and the powder m to be sintered, the spacer 95 is compressed and the upper and lower portions are separated in a portion where the insulating sheet 97 does not exist. A pair of conductive sheets 96 and 96 come into contact with each other. That is, a pair of upper and lower conductive sheets 96 and 96 are in contact with each other on the outer peripheral portion of the spacer 95, that is, around the insulating sheet 97 (FIGS. 2A and 2B).
When current is supplied between the pair of upper and lower punches 82 and 83 in this state, current does not flow in the central portion of the spacer 95 where the insulating sheet 97 is provided. A current flows between the pair of upper and lower punches 82 and 83 and the powder m to be sintered through the conductive sheets 96 and 96.

At this time, the area in which current is supplied to the sintered powder m from the pair of upper and lower punches 82 and 83 is smaller than the case where the spacer 95 is not provided. Then, since the area through which the current flows in the cross section of the powder to be sintered m is reduced, the resistance of the path (current path) through which the current flows in the powder m to be sintered can be increased.
Therefore, at the initial stage of sintering, the amount of heat generated by self-heating of the powder m to be sintered can be increased compared to the case without the spacer 95, so that the powder m to be sintered can be heated quickly and sufficiently. Can do.

Usually, when manufacturing a large-sized sintered product (for example, a diameter of 300 mm or more), it is difficult to quickly and sufficiently raise the temperature of the outer peripheral portion of the powder m to be sintered only by heat generation from the mold 81 in the initial stage of sintering. .
However, the sintering die 80 of the present embodiment using the spacer 95 can heat the outer peripheral portion of the powder m to be sintered by the heat generated by the powder m itself in addition to the heat from the mold 81. Even when a large sintered product is manufactured, the temperature of the outer peripheral portion of the powder m to be sintered can be sufficiently raised at the initial stage of sintering.

  As described above, according to the sintering mold 80 of the present embodiment, the temperature of the outer peripheral portion of the powder m to be sintered can be sufficiently increased in the initial stage of sintering, so even if the sintered product is large, The temperature distribution inside the sintered powder m during the sintering can be made uniform. Therefore, it is possible to prevent variations in the sintered state and density from occurring in the sintered product, and the quality of the sintered product can be improved.

In the spacer 95, the pair of upper and lower conductive sheets 96, 96 are circular with the same shape and the same diameter as the cross section of the hollow portion of the mold 81, while the insulating sheet 97 is circular, but the diameter is the conductive sheet 96. It is formed to be smaller than that. The pair of upper and lower conductive sheets 96 and 96 and the insulating sheet 97 are arranged so that the centers thereof coincide with the central axis of the hollow portion of the mold 81.
For this reason, the part (conductive area CA in FIG. 3A) where the pair of upper and lower conductive sheets 96 and 96 come into contact with each other during sintering becomes a ring shape centering on the central axis of the hollow part of the mold 81. . That is, the conductive area CA has a rotationally symmetric shape with respect to the central axis of the hollow portion of the mold 81 (FIG. 3A).
Then, even if an electric current flows into the to-be-sintered powder m, it can prevent that the bias | inclination of an electricity supply path arises in the cross section of the to-be-sintered powder m. That is, since a substantially uniform current flows through the outer peripheral portion of the powder m to be sintered, the powder m to be sintered generates heat substantially uniformly around the central axis of the hollow portion of the mold 81.
Accordingly, in the powder m to be sintered, the portion located at the same distance from the center is heated almost uniformly, so that it is possible to prevent the area to be heated strongly in the powder m to be sintered. it can. Therefore, a sintered product having predetermined characteristics can be manufactured.

  In particular, as the insulating sheet 97 of the spacer 95, the temperature at which the powder m is sintered, for example, 800 ° C. or higher, preferably 1200 ° C. or higher, can be maintained, but the temperature at which the powder m is sintered. If it exceeds the upper limit, it is preferably formed of a material that burns and carbonizes or breaks down. If the insulating sheet 97 is formed of such a material, a current can be applied uniformly to the entire cross-section of the sintered powder m at the final stage of sintering of the sintered powder m. Then, since the whole powder to be sintered m can be heated at the end of sintering of the powder to be sintered m, the sintering of the powder to be sintered m can be promoted.

  In the spacer 95, a region where the insulating sheet 97 is present (a region IA surrounded by a dotted line in FIG. 3A) is a non-conductive region referred to in the claims. Note that the conductive region CA is a region surrounded by a dotted line and a solid line in FIG.

The spacer 95 is not limited to the insulating sheet 97 sandwiched between the pair of upper and lower conductive sheets 96, 96 as described above, and a spacer having a conductive region 96B and a non-conductive region 97B on a single sheet. 95B may be used (FIG. 3B). In this case, since the center of the spacer 95B can be made coincident with the central axis of the hollow portion of the mold 81 only by arranging the spacer 95B in the hollow portion of the mold 81, the installation work of the spacer 95B is simple. There is an advantage.
On the other hand, the area of the non-conductive region needs to be set appropriately depending on the material of the powder m to be sintered and the size of the sintered product. In the case of the spacer 95B, the area of the non-conductive region 97 can be adjusted. Since this is not possible, a dedicated spacer is required for each sintered product.
However, if the spacer 95 is composed of a pair of upper and lower conductive sheets 96, 96 and an insulating sheet 97, a general sheet-like member can be processed and used, or a commercially available product can be used as it is. The sintering cost can be suppressed.

In addition, if the spacer 95 is used, heat generation at the outer periphery of the powder m to be sintered at the initial stage of sintering when the temperature of the powder m is low can be promoted, and the temperature of the outer periphery can be quickly raised. The effect is obtained.
Furthermore, if the applied pressure at the initial stage of energization is made smaller than the applied pressure finally required for sintering (about 20 to 30% of the final stage of sintering), the resistance in the sintered powder m can be increased. The heat generation of the powder m to be sintered can be further promoted, and the temperature can be raised quickly.
The pair of upper and lower punches 82 and 83 are normally cooled by a cooling means. However, if the pressure applied to the pair of upper and lower punches 82 and 83 is reduced as described above, the pair of upper and lower punches 82 and 83 are interposed. The amount of heat taken from the powder m to be sintered can be reduced, which is preferable.

  Moreover, although the said embodiment demonstrated the case where the hollow part of the mold 81 and the cross-sectional shape of a pair of upper and lower punches 82 and 83 were circular, the cross-sectional shape of the mold 81 etc. is not restricted circularly, For example, rectangular or donut shape Etc. In this case, it goes without saying that the outer shape of the spacer 95, the shape of the conductive region CA, and the non-conductive region IA are made to match the cross-sectional shape of the mold 81 and the like.

  The sintering die of the electric current pressure sintering apparatus of the present invention is suitable for a sintering die for producing a sintered product having a diameter of 300 mm or more by sintering powder m having conductivity.

80 Sintering mold 81 Mold 82 Punch 83 Punch 95 Spacer 96 Conductive sheet 97 Insulating sheet A Sintering chamber m Powder to be sintered CA Conductive region IA Non-conductive region

Claims (5)

It is a sintering type of an electric pressure sintering apparatus,
The sintering mold is
A mold with a hollow portion;
A pair of upper and lower punches connected to a power source and attached to the hollow portion of the mold so as to be freely inserted and removed;
In the hollow portion of the mold, a sintering chamber is formed by the mold and a pair of upper and lower punches,
Spacers are provided between the pair of upper and lower punches and the powder to be sintered accommodated in the sintering chamber,
The spacer is
A sintering die for an electric pressure sintering apparatus having a non-conductive region at a central portion and a conductive region at an outer peripheral portion. The spacer is
2. The sintering die for an electric pressure sintering apparatus according to claim 1, wherein the conductive region is formed to have a rotationally symmetric shape with respect to the central axis of the spacer. The non-conductive region of the spacer is
3. A sintering die for an electric pressure sintering apparatus according to claim 1, wherein the sintering powder is formed of a material that carbonizes at a temperature at which the powder to be sintered is sintered. The spacer is
A pair of upper and lower conductive sheets made of a conductive material;
The outer sheet is disposed between the pair of upper and lower conductive sheets, and the outer diameter is an insulating sheet made of an insulating material smaller than the conductive sheet.
The insulating sheet is
2. The spacer is disposed such that an outer peripheral edge thereof is not in contact with the inner surface of the mold when the spacer is disposed between the powder to be sintered and the punch. A sintering mold of the electric current pressure sintering apparatus according to 2 or 3. A sintering method using the sintering mold of the electric pressure sintering apparatus according to claim 1, 2, 3 or 4,
A sintering method using an energization pressure sintering apparatus, characterized in that a pressing force at an initial stage of energization is made smaller than a pressing force in another period during sintering.

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