JPH10330804A - Sintering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sinter both the ceramic and the conductive substance, and to cope with an increase in size by filling the raw powder in a sintering space of a sintering die, providing a heating body to generate the heat through the energization between an electrode and the raw powder, and achieving the pressure sintering. SOLUTION: The raw powder 3 is filled in a sintering space 2 in the center of a sintering mold 1. Heating bodies 4a, 4b which is solid and cylindrical and formed of graphite, etc., are slidably fitted to lower and upper parts inside the sintering die 1. Electrodes 5a, 5b are provided on upper and lower parts of the heating bodies 4a, 4b. The electrodes 5a, 5b comprise punches to press the heating bodies 4a, 4b, and energize the heating bodies 4a, 4b. A hydraulic device is connected to upper and lower end of the electrodes 5a, 5b to pressure the heating bodies 4a, 4b. The power from a power source 8 is controlled by a thyristor 9, and dropped by a transformer 10, and then, supplied to the electrodes 5a, 5b and resistance heaters 6a, 6b. A temperature sensor 11 is provided inside or outside the sintering die 1 to measure the temperature of the sintered body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sintering apparatus for sintering ceramic or conductive raw material powder filled in a sintering mold.

[0002]

2. Description of the Related Art A sintered body is manufactured by filling a raw material powder of a conductive object such as ceramics, metal, carbide, nitride or the like into a sintering mold, heating and pressing with a pair of punches. The sintering apparatus for producing this sintered body is classified into several types depending on the heating method. In the indirect heating method using a heater, a heater such as a resistance heater is arranged around a sintering die, the sintering die is heated from the surface, and the raw material powder in the sintering die is indirectly heated. This method is applicable to both sintering of ceramics and conductive materials and is widely used.

The induction heating method is a heating method in which a sintering mold is directly heated by electromagnetic induction. Therefore, the heating rate of the sintered body is higher than that of the resistance heating method. In the energization method, a direct current or a direct current and a pulse current are applied to the raw material powder using a pair of punches as electrodes, and the raw material powder is heated by resistance heat. The energization method is described in JP-A-64-55303 and JP-A-5-708.
04, JP-A-5-117707.

[0004]

In the indirect heating system such as a heater, the energy transfer to the sintering mold is mainly determined by the surface temperature of the heater and the temperature of the inner wall of the heat insulating enclosure surrounding the heater. Since the heat resistance of the heater material and the heat insulating enclosure material is limited, the energy transfer is limited, and the heating time cannot be reduced beyond a certain limit. With the increase in size of sintered bodies in recent years, objects to be heated, such as sintering dies and punches, have also increased in size. In the case of the indirect heating method, there is a limit in energy transfer for the above-described reason, and thus, the size of the object to be heated increases the heating time.
The induction heating method requires a high-frequency power generator, so that the power supply equipment is expensive and has a problem in economy.

In the energization method, the heating time is short because the raw material powder is directly heated, but the heating conditions vary depending on the type of the raw material powder, and the operation is difficult. In addition, the temperature tends to be highest at the center temperature of the raw material powder, and it is difficult to control the temperature of the sintered body. In the indirect heating, the temperature of the surface of the sintered mold is the highest, and the situation is completely opposite to the situation where the raw material powder is the lowest. In the case of the energization method, if a temperature sensor is provided at the center of the raw material powder, the temperature control of the sintered body becomes easy. Therefore, generally, the outer surface of the sintered mold or the inner surface of the sintered mold is measured by a sensor such as a thermocouple or a radiation thermometer. In the temperature control, it is necessary to control the maximum temperature of the raw material powder.

It is easy to control the temperature of the raw material powder by indirect heating by the temperature of the sensor provided in the sintering mold. However, in the case of the energization method, the temperature of the sensor provided in the sintering mold is lower than the temperature of the raw material powder. Because of the low temperature, the temperature of the sensor is the estimated temperature of the raw material powder. Therefore, it cannot be used for direct temperature control and requires compensation by calculation or the like, but strict compensation is generally difficult. Also, as the size of the raw material powder increases, the temperature difference between the sensor temperature and the powder center temperature increases. Therefore, it has been particularly difficult to increase the size of the apparatus in the case of the energization method.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a sintering apparatus capable of sintering both ceramics and a conductive substance and capable of coping with an increase in size.

[0008]

In order to achieve the above object, according to the first aspect of the present invention, a raw material powder filled in a sintering sintering space is pressurized by an electrode composed of a pair of punches and energized for firing. In the sintering apparatus, a heating element that generates heat when energized is provided between the electrode and the raw material powder, and the sintering mold is formed of a conductor that generates heat when energized.

Electric power is supplied to the heating element and the sintering mold to generate heat by the electric resistance of the heating element and to heat the raw material powder. This allows sintering regardless of whether the raw material powder is a ceramic or a conductive substance. When the raw material powder is a conductive substance, the raw material powder is also energized and generates heat by its own electric resistance, so that the heating capacity is improved.

According to the second aspect of the present invention, the calorific value of the heating element is made larger than the calorific value of the electrode.

By making the calorific value of the heating element larger than the calorific value of the electrodes, the raw material powder can be effectively heated.

According to the third aspect of the present invention, the sintering mold is energized from the electrode via the heating element.

The current flowing from one electrode first passes through one heating element and causes the heating element to generate heat, and then passes through a sintering mold to generate heat. Then, after the other heating element is heated, the process returns to the other electrode. As a result, even if the electric resistance of the heating element is higher than the electric resistance of the sintering type, the electric current surely flows through the heating element to generate heat.

In the invention of claim 4, the sintering mold is energized from the electrode via the heating element, and is also energized directly from the electrode.

By setting the electric resistance of the heating element and the electric resistance of the sintering mold to appropriate values, the amount of heat generated can be set. By allowing current to flow from both the electrode and the heating element in the sintered mold, the degree of freedom in setting the heat generation amount can be increased.

In the invention of claim 5, a heater is provided around the sintering mold.

The temperature setting and temperature distribution of the raw material powder are one of the important factors of sintering. In particular, in the treatment of a sintered body under severe temperature conditions and the treatment of a large-sized sintered body, a sufficient temperature control of the sintered body cannot be achieved by an energization method in which a heating element or a sintering mold is energized and heated. By employing an indirect heating method using a heater, the accuracy of controlling the temperature of the sintered body can be improved.

According to the present invention, the amount of energy input to the heater is made larger than the amount of energy input to the electrode, the heating element and the sintering mold heated by the energization, and the energy amount is set to be lower than the temperature of the sintering mold. The raw material powder is heated so that the temperature thereof becomes low.

A heater is provided around the sintering mold, and a temperature sensor is provided on the outer surface of the sintering mold to heat while controlling the temperature. The amount of energy input to the heater is made larger than the amount of energy by energization, and the energy ratio is set so that the temperature of the raw material powder becomes lower than the temperature of the sintering mold. This makes it possible to perform heating of the sintered body in a short time by compensating the released heat by energizing while maintaining the same temperature control characteristics as the indirect heating method using a heater.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below.
This will be described with reference to the drawings. FIG. 1 is a configuration diagram of a sintering apparatus according to a first embodiment of the present invention. The sintering mold 1 has a hollow cylindrical shape and is made of graphite, and the center of the inside is a sintering space 2 in which the raw material powder 3 is filled. Heating elements 4a and 4b made of graphite and having a solid cylindrical shape are slidably fitted to upper and lower portions of the inside of the sintered mold 1. Heating element 4a,
Electrodes 5a and 5b are provided above and below 4b. The electrodes 5a and 5b constitute a punch for pressing the heating elements 4a and 4b, and energize the heating elements 4a and 4b. Resistance heaters 6a and 6b are provided around the sintering mold 1 to heat the sintering mold 1. Sintering mold 1, heating elements 4a, 4b, electrodes 5a, 5
The heating element 4 side of b and the resistance heaters 6a and 6b are surrounded by a heat insulating wall 7 and maintain heat insulation.

Hydraulic devices (not shown) are connected to the upper and lower ends of the electrodes 5a, 5b to press the heating elements 4a, 4b. As the power supply 8, a commercial power supply such as 50 or 60 Hz is used. The power from the power source 8 is controlled by the thyristor 9,
After the voltage is reduced by the transformer 10, the electrodes 5a and 5b and the resistance heaters 6a and 6b are energized. A temperature sensor 11 is provided on the inner surface or the outer surface of the sintering mold 1, and measures the temperature of the sintered body. The control unit 12 controls the thyristor 9 based on the measurement value of the temperature sensor 11 to control the current. The above description is based on both the upper and lower electrodes 5a, 5b and the heating elements 4a, 4b.
Is pressurized from above and below by a hydraulic device, but it is also possible to pressurize only one of the upper and lower electrodes 5 and the heating element 4 and fix the other. Note that this method can also be applied to the embodiments described below.

FIG. 2 is a sectional view taken along line XX of FIG. The heaters 6 are arranged concentrically around the sintering mold 1 at regular intervals. The heater 6 includes a right heater 6a and a left heater 6 in the drawing.
b and is controlled by being energized. The cross-sectional views of the following embodiments have the same configuration.

The electric resistances of the heating elements 4a, 4b and the sintering mold 1 are set in consideration of the amount of heat generated respectively. The junction between the heating elements 4a, 4b and the electrodes 5a, 5b is configured to be outside the sintering mold 1 in a state where the raw material powder 3 is pressed, and current flows through the heating elements 4a, 4b. And flows into the sintering mold 1. Thus, even if the electric resistance of the heating elements 4a, 4b is larger than that of the sintered mold 1, the current surely passes through the heating elements 4a, 4b to generate heat. When the raw material powder 3 is ceramics, heating is performed by the heating elements 4a and 4b, the sintering mold 1, and, if necessary, the resistance heaters 6a and 6b. The control of the current to the electrodes 5a, 5b and the resistance heaters 6a, 6b is performed by the thyristor 9. The heating of the resistance heaters 6a and 6b may be controlled on and off by dividing the resistance heaters 6a and 6b one by one or into a plurality of groups. When the raw material powder 3 is a conductive substance such as a metal, carbide, or nitride, the raw material powder 3 is also energized and generates heat due to its resistance. This increases the heating capacity.

Next, the ratio of the electric power supplied to the indirect heating by the heater 6 (6 represents 6a and 6b; the same applies to other symbols) and the electric heating by the heating element 4, the electrode 5, and the sintering mold 1. An example will be described. FIG. 3 shows a temperature distribution in the case of indirect heating by the heater 6 and a relationship between the temperature and the supplied power. (A) shows a temperature distribution on a straight line P passing through the center of the raw material powder 3 in the vertical direction. Point a is the position where the temperature sensor 11 is provided on the outer surface of the sintering mold 1, point b is the surface of the raw material powder 3, and point c is the center of the raw material powder 3. The temperature distribution becomes lower toward the center from the point a, and becomes the lowest at the point c. (B) shows the temperature T at points a, b, and c.
a, Tb, and Tc show the lapse of time, and (C) shows the lapse of the power supply value at this time. Electric power P1 is supplied until Ta reaches M, and thereafter electric power P0 that maintains M is supplied. The period until Ta becomes M is referred to as a heating and heating period.
The period during which a is maintained at the temperature M is defined as a steady heating period.
After point f where the temperature is saturated in (B), Ta> T
The relationship of b> Tc is established.

FIG. 4 shows a temperature distribution in the case of electric heating and a relationship between the temperature and the supplied power. (A) shows a temperature distribution on a straight line P passing through the center of the raw material powder 3 in the vertical direction. Point a is the position where the temperature sensor 11 is provided on the outer surface of the sintering mold 1, point b is the surface of the raw material powder 3, and point c is the center of the raw material powder 3. The temperature distribution becomes higher from the point a toward the center and becomes the highest at the point c. (B) shows a, b,
(c) shows the lapse of time of the temperatures Ta, Tb, and Tc of (c).
Indicates the lapse of time of the power supply value at this time. Electric power Q1 is supplied until Ta reaches temperature N, and thereafter electric power Q0 that maintains N is supplied. In (B), depending on the type of the raw material powder 3, the size of the sintering mold 1, and the like, Ta,
The relationship between Tb and Tc changes, and does not become a fixed relationship unlike indirect heating.

Considering the characteristics of the indirect heating and the energization heating shown in FIGS. 3 and 4, an example of the power supply ratio when both heating methods are used together will be described. FIG. 5 shows indirect heating by the heater 6. FIG. 5 is the same as the content shown in FIG. 3, and in this figure, the heat loss from the electrode 5 and the heating element 4 during the steady heating period of (C) will be described. P0 ≒ Lw + Lr (1) P0: Steady heat loss Lw: Heat loss from sintering mold 1 Lr: Heat loss from heating element 4 and electrode 5

In order to maintain the outer surface temperature Ta of the sintering mold 1 at M, electric power P0 must be supplied. This P0 is called a steady heat loss, and the loss Lw lost from the sintering mold 1
And the loss Lr lost from the heating element 4 and the electrode 5. This loss Lr is measured. As a measurement method,
For example, when the electric power P01 when the sintering mold 1 is heated so as to maintain Ta at M while being adiabatically shielded is obtained,
This P01 represents the loss Lr.

FIG. 6 is a diagram for explaining the ratio of the power supply between the indirect heating and the energization heating. Heating is performed as follows. Heating / heating period: The power supplied (the power supplied to the sintering mold 1, the heating element 4, and the electrode 5) is the power of the loss Lr from the heating element 4 and the electrode 5 measured in FIG. The power to the heater 6 for the indirect heating is supplied in a state where the power is supplied.
Ta is an electric power at which a predetermined temperature M is reached in a predetermined temperature heating period T. Steady-state heating period: The energized power is set to zero, and the steady-state power loss P
All 0 are the indirect heating power of the heater 6.

With the above-mentioned distribution of the supplied power, the indirect heating is performed at the same time as the energization heating at the time of the heating heating, so that the heating heating period T is shortened even with the same power as in the case of the indirect heating alone. In addition, since only indirect heating is performed during the steady heating period, the relationship of Ta>Tb> Tc is maintained, and the temperature Ta is controlled by the temperature sensor 11 attached to the outer surface of the sintering mold 1 so that the surface temperature of the raw material powder 3 is controlled. Tb, center temperature T
c can be reliably controlled to a temperature lower than Ta.

FIGS. 6A and 6B show the above. In the heating-up heating period T, the energized power indicated by the hatched portion in FIG. 6B is added to the indirect heating power. If the period T is the same as the case of the indirect heating by the heater 6 alone, the indirect heating power is reduced, and if the indirect heating power is the same, the heating-up heating period T is shortened. During the steady heating period, only indirect heating is performed. It should be noted that the electric heating power and the heater 6
The indirect heating power ratio can be applied to the embodiments described below.

Next, a second embodiment will be described. FIG. 7 shows the second
1 shows a configuration of an embodiment. 7 that are the same as those in FIG. 1 represent members or devices having the same function. In the second embodiment, the electrodes 5a, 5b and the heating elements 4a, 4
The current passing cross-sectional area b is made smaller for the heating elements 4a and 4b so as to increase the electric resistance and generate heat, and the other parts are the same as those of the first embodiment. Electrode 5
a, 5b and the heating elements 4a, 4b are made of graphite,
The shape of the electrodes 5a and 5b is made larger than that of the heating elements 4a and 4b to reduce the electric resistance, and the shape of the heating elements 4a and 4b is made small to increase the electric resistance and increase the heat generation.
The materials of the electrodes 5a, 5b and the heating elements 4a, 4b may be the same, but the materials of the heating elements 4a, 4b are changed to the electrodes 5a, 5b.
Assuming that the resistance value is larger than b, the heating elements 4a and 4b
The amount of heat generated can be increased.

FIG. 8 shows a third embodiment. This embodiment is a modification of the second embodiment shown in FIG. In the second embodiment, the diameters of the electrodes 5a and 5b are made larger than the diameters of the heating elements 4a and 4b, and the diameters of the electrodes 5a and 5b are the same as the diameters of the heating elements 4a and 4b. Is electrode 5
The electrodes 5a and 5b of the heating elements 4a and 4b are not squeezed.
This is an extension of the junction with the above. In this way, if the diameters of the electrodes 5a and 5b are the same, compatibility with the device of the first embodiment shown in FIG. 1 can be provided. Further, since the contact area between the electrodes 5a, 5b and the heating elements 4a, 4b is increased, the contact resistance at this portion is reduced, so that unnecessary heat generation is reduced and the contact surface is prevented from deteriorating with time.

Next, a fourth embodiment will be described. FIG. 9 shows the fourth
1 shows a configuration of an embodiment. 9 that are the same as those in FIG. 1 indicate members and devices having the same function. The fourth embodiment is different from the first embodiment in that the power supply to the sintering mold 1 is performed directly from the electrodes 5a and 5b in addition to passing through the heating element 4. The calorific value is set by setting the resistance values of the sintering mold 1 and the heating elements 4a and 4b to appropriate values. The heat generation amount is increased by increasing the electric resistance value of the heating elements 4a and 4b, and the heating elements 4a and 4b are increased as in the first embodiment.
When a current is applied to the sintering mold 1 via the a and 4b, the current to the sintering mold 1 is reduced and the calorific value is reduced. However, by providing a bypass and allowing a part of the current to flow from the electrodes 5a and 5b, The calorific value of the sintering mold 1 can be set to an appropriate value.

In the embodiment described above, the resistance heaters 6a,
Although 6b is provided, it may not be provided when the sintered body is not large-sized, when the reduction of the sintering time is not required, or when accurate temperature control is not required. Heating elements 4a, 4
b and the heat generated by the sintering mold 1, and when the raw material powder is a conductive substance, can be sintered by its own resistance heat generation.

[0035]

As described above, according to the present invention, the sintering mold and the heating element are energized and heated by energizing.
Either ceramics or conductive materials can be sintered. In the case of a conductive substance, the heat generation capacity is increased by energizing the conductive substance. Further, by using the indirect heating method using a heater together, the temperature control accuracy, which has been an obstacle to the increase in the size of the device due to the energized heating method, can be secured to the same degree as that of the indirect heating method, and the device can be made larger. Further, the heating efficiency of the raw material powder is improved by the combined use of the electric heating method, and it is possible to suppress the increase in the heating time, which is a problem of enlarging the apparatus of the electric heating method, and as a result, the supply energy can be suppressed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line XX of FIG.

3A and 3B show indirect heating by a heater, wherein FIG. 3A shows a temperature distribution, FIG. 3B shows a temperature change curve, and FIG.

FIG. 4 shows energization heating, (A) shows a temperature distribution, (B) shows a temperature change curve, and (C) shows a supply power.

5A and 5B show indirect heating by a heater, wherein FIG. 5A shows a temperature distribution, FIG. 5B shows a temperature change curve, and FIG.

FIG. 6 shows an example of a combined method of indirect heating and electric heating.

FIG. 7 is a diagram showing a configuration of a second embodiment of the present invention.

FIG. 8 is a diagram showing a configuration of a third embodiment of the present invention.

FIG. 9 is a diagram showing a configuration of a fourth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sintering type 2 Sintering space 3 Raw material powder 4 Heating element 5 Electrode 6 Resistance heater 7 Heat insulation wall 8 Power supply 9 Thyristor 10 Transformer 11 Temperature sensor 12 Control part

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Tomotoshi Mochizuki 1 Shin-Nakahara-cho, Isogo-ku, Yokohama-shi, Kanagawa Ishikawashima Harima Heavy Industries, Ltd. Yokohama Engineering Center

Claims (6)

[Claims] 1. A sintering apparatus for sintering a raw material powder filled in a sintering space by pressurizing a raw material powder with an electrode composed of a pair of punches and sintering the raw material powder. A sintering apparatus comprising: a heating element that generates heat when energized; and the sintering mold is formed of a conductor that generates heat when energized. 2. The sintering apparatus according to claim 1, wherein the heating value of the heating element is larger than the heating value of the electrode. 3. The sintering apparatus according to claim 1, wherein the sintering die is energized from an electrode via the heating element. 4. The sintering apparatus according to claim 1, wherein the sintering mold is energized by an electrode via the heating element, and is also energized directly by the electrode. 5. The sintering apparatus according to claim 1, wherein a heater is provided around the sintering mold. 6. The amount of energy input to the heater is made larger than the amount of energy input to the electrode, the heating element and the sintering mold heated by the energization, and the temperature of the raw material powder is higher than the temperature of the sintering mold. The sintering apparatus according to claim 5, wherein the heating is performed so as to lower the temperature.