JPH0633110A - Electrical heating and sintering device - Google Patents

Abstract

PURPOSE:To carry out the exact control of the temp. of green compacts by measuring the water feed temps. of cooling water and the draining temps. after cooling and determining the temp. of the green compacts from the differences from the temps. obtd. from experimental data. CONSTITUTION:The temp. of the cooling water flowing in a main cooling water supply system is measured by a thermometer 11 and the temps. of the cooling water flowing in respective branch cooling water discharge systems are measured by thermometers 15. The differences between both temps. are determined by a controller 20. The temp. of the green compacts under sintering is estimated from the temp. differences between the thermometers 11 and 15. The flow rates of the cooling water are calculated according to the differences from the specified temp. required for the temp. of the green compacts and the opening degrees of flow rate control valves 12, 13 are calculated. The controller 20 controls the opening degrees of the flow rate control valves 12, 13, thereby controlling the flow rates of the cooling water to be passed to a furnace 1, an upper clamp 4, a lower clamp 6 and a base plate 2. The flow rates of the cooling water to be passed to the furnace 1, the upper clamp 4, the lower clamp 6 and the base plate 2 are measured by flow meter; 14 of the respective branch cooling water supply systems and the information contributing to the opening degree control of the flow rate control valves 13 is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric heating and sintering apparatus for electrically heating a green compact to sinter it.

[0002]

2. Description of the Related Art When manufacturing a member made of a metal having a high melting point such as tungsten or molybdenum, a rod-shaped green compact made of powder of these metals is molded and the powder compact is directly energized. An electric heating sintering method in which sintering is performed by self-heating generated at that time is adopted. Further, in this electric heating and sintering method, a furnace in which a green compact is placed, a supporting means for supporting the green compact, a means for energizing the green compact, and a cooling water are supplied and supplied to the supporting means. An electric heating and sintering apparatus provided with a cooling water flow means for discharging the cooling water is used.

In this electric heating sintering method, since a rod-shaped green compact is sintered, the amount of heat generated from the green compact itself and Since the sintering temperature fluctuates depending on the balance of the amount of cooling heat from the cooling means, the temperature of the green compact is accurately measured to obtain a stable sintering temperature, and the temperature of the green compact is measured based on this measurement result. It is necessary to control the temperature. The temperature control of the green compact is carried out by controlling the heat generation temperature of the green compact by controlling the value of the current passing through the green compact.

Conventionally, in order to measure the temperature of the green compact,
The furnace is provided with a peep window that allows the inside to be seen through from the outside, and the method of measuring the temperature of the green compact placed inside the furnace through the peek window from the outside of the furnace using a radiation thermometer is adopted. . That is, the radiation thermometer receives the light (thermal energy) emitted from the powder compact whose temperature has risen through a viewing window to measure the temperature of the powder compact. In this case, the viewing window is formed so as to face the central portion of the green compact arranged inside the furnace.

[0005]

However, such a conventional electric heating and sintering apparatus has the following problems in measuring the temperature of the green compact.

When the temperature of the green compact rises, the doping agents such as SiO ₂ , K ₂ O and Al ₂ O ₃ contained in the powder forming the green compact are evaporated and diffused inside the furnace. The dope residue adheres to the viewing window of the furnace. In this case, the light emitted from the powder compact is blocked by the dust of the dope agent adhering to the viewing window, and the amount reaching the radiation thermometer through the viewing window is reduced. The temperature may not be measured accurately.

Further, since the peep window is provided so as to face the central portion of the green compact, when the temperature is measured through the peep window, it is necessary to measure only the temperature of the central portion of the green compact. Become. However, during sintering, the temperature rises at one end, the other end, and the center of the green compact may not be uniform for various reasons. In this case, the temperature of the entire green compact cannot be accurately measured even if the temperature is measured through the viewing window. As a countermeasure for this, it is conceivable to provide the furnace with a window except for each end and center of the green compact. However, in this case, the structure for temperature measurement is complicated and the number of parts is increased. Moreover, even if the temperature of each part of the green compact is individually measured through each peep window, it cannot contribute to the accurate control of the temperature of the green compact having different temperatures. As described above, it is difficult to accurately measure the temperature of the green compact with the conventional electric heating sintering apparatus, and as a result, it has not been possible to contribute to the accurate control of the temperature of the green compact.

The present invention has been made in view of the above circumstances, and provides an electric heating and sintering apparatus capable of accurately measuring the temperature of a green compact during sintering and accurately controlling the temperature of the green compact. The purpose is to

[0009]

In order to achieve the above object, an electric heating and sintering apparatus of the present invention is a furnace apparatus for energizing a green compact to sinter the green compact by self-heating generated at this time. A furnace in which the green compact is placed, a supporting means for supporting the green compact, a means for energizing the green compact, and a cooling device for supplying cooling water to the supporting means and discharging the supplied cooling water. Water circulation means, means for measuring the temperature of the cooling water supplied to the support means and the temperature of the cooling water discharged from the support means, and the supply temperature of the cooling water received from the temperature measurement means. It is characterized by comprising a means for estimating the temperature of the green compact and / or detecting an abnormality of this temperature by obtaining a difference from the drainage temperature and a furnace.

[0010]

The means for supporting the green compact is cooled by cooling water because it is subjected to electric current sintering and is heated to a high temperature by the green compact to be sintered. The difference between the water supply temperature of this cooling water and the drainage temperature after cooling is proportional to the temperature of the green compact, and the temperature of the green compact can be estimated by measuring this temperature difference. This is the basic idea of the invention.

Specifically, the relationship between the temperature difference between the water supply and drainage of the cooling water and the temperature of the green compact when sintering the green compact made of the same kind of powder as the green compact is obtained in advance by an experiment. . Then, during sintering, the supply temperature of the cooling water and the drainage temperature after cooling are measured, and the temperature of the green compact is determined from the difference between these temperatures based on the experimental data obtained in advance.

The temperature of the cooling water is regulated by the flow rate of the cooling water. Therefore, if the flow rate of the cooling water is controlled based on the difference between the supply and discharge temperatures of the cooling water, the temperature of the cooling water can be controlled, and as a result, the temperature of the green compact can be controlled.

Further, the current value to be passed through the green compact is controlled on the basis of the temperature difference between the water supply and drainage of the cooling water and the flow rate of the cooling water.
Alternatively, the temperature of the green compact can be controlled by combining and controlling the flow rate of the cooling water and the value of the current flowing through the green compact on the basis of the difference between the supply and discharge temperatures of the cooling water.

[0014]

Embodiments of the present invention will be described with reference to the drawings. The configuration of the electric heating and sintering apparatus will be described with reference to FIG. The apparatus of this embodiment uses a bell jar type furnace.

In the figure, reference numeral 1 designates a bell jar type furnace having a water-cooled double wall structure, which is provided with an inlet 1a connected to a cooling water supply system and an outlet 1b connected to a cooling water discharge system. 1c is a viewing window. Reference numeral 2 denotes a base, which is detachably attached to the bottom opening portion of the furnace 1. The base 2 is water-cooled, and an inlet and an outlet are provided for cooling water (not shown). A powder compact P is placed upright in a space formed by the furnace 1 and the base 2.

Reference numeral 3 is a conductive pipe made of a conductive metal such as copper. The conductive pipe 3 is arranged inside the furnace 1,
Both ends extend through the base 2 to the outside, and an upper clamp 4 for gripping the upper end of the green compact P is provided at the center of the upper part.

Reference numeral 5 is a conductive pipe made of a conductive metal such as copper. The conductive pipe 5 is arranged inside the furnace 1,
Both ends extend through the base 2 to the outside, and a lower clamp 6 for holding the lower end of the green compact P is provided at the center of the upper part. These conductive pipes 3 and 5 constitute a conductive member for passing an electric current through the powder compact P, and terminals 7 and 8 connected to a current-carrying circuit are attached to one end of each of them. Each of the conductive pipes 3 and 5 constitutes a cooling water passage, one end of which is connected to the cooling water supply system and the other end of which is connected to the cooling water drainage system. The furnace 1 is provided with a gas inlet 9a connected to an inert gas supply system such as hydrogen,
The base 2 is provided with a gas outlet 9b connected to a gas exhaust system. A configuration for measuring the temperature of the green compact and controlling the temperature will be described with reference to FIG.

Each of the cooling water inlets of the furnace 1, the upper clamp 4, the lower clamp 6 and the base 2 for cooling with cooling water is connected in common, and cooling water is supplied from a cooling water supply device (not shown). It is connected to the cooling water supply system. A thermometer 11 and a flow control valve 12 are connected to the main cooling water supply system, and each branch is branched from the main cooling water supply system and connected to the furnace 1, the upper clamp 4, the lower clamp 6 and the base 2. Each cooling water supply system has a flow rate control valve 13
And the flowmeter 14 are connected.

Thermometers 15 are connected to the cooling water discharge systems connected to the cooling water outlets of the furnace 1, the upper clamp 4, the lower clamp 6 and the base 2, respectively. The gas supply system connected to the gas inlet 9a of the furnace 1 is connected with a thermometer 16, a flow control valve 17, and a flow meter 18, and the gas outlet 9b of the furnace 1 is connected.
A thermometer 19 is connected to the gas supply system connected to.

Reference numeral 20 is a control device. This control device 20
Receives the measurement signals from the thermometer 11 of the main cooling water supply system and the thermometers 15 of the cooling water discharge system, and receives the measurement information from the thermometer 16 of the gas supply system and the thermometer 19 of the gas supply system. ing. The controller 20 is adapted to receive measurement information from the flow meter 14 of each branch cooling water supply system and the flow meter 18 of the gas supply system. Control device 2
0 indicates that the relationship between the temperature difference between the water supply / drainage of cooling water and the temperature of the green compact when the green compact of the same kind as the green compact to be sintered was previously sintered was experimentally determined. Enter experimental data.

Then, the control device 20 compares the above-mentioned respective measurement information with the preceding experimental data to obtain the temperature of the green compact during sintering. The controller 20 gives a command to the flow rate control valve 12 of the main cooling water supply system and the flow rate control valve 13 of each branch cooling water supply system according to the obtained temperature to control the opening degree. Also,
The control device 20 uses an energization sintering circuit 21 for supplying an electric current to the green compact P.
Is instructed to control the value of the current flowing through the green compact P.

Reference numeral 22 is a monitoring device for monitoring the flow rate of the cooling water in the flow meter 14 of each branch cooling water supply system and the flow rate of the gas in the flow meter of the gas supply system, and 23 is the thermometer 15 of each cooling water discharge system. It is a monitoring device for monitoring the temperature of the cooling water in and the temperature of the gas in the thermometer 19 of the gas discharge system. A case where sintering is performed in the electric heating sintering apparatus configured as described above will be described.

A rod-shaped green compact P made of refractory metal powder is vertically arranged inside the furnace 1, and an upper clamp 4 is provided at the upper end.
Then, the lower ends are gripped by the lower clamps 6, respectively. An electric current is passed from the energizing circuit to the circuit connecting the conductive pipe 3, the upper clamp 4, the green compact P, the lower clamp 6 and the conductive pipe 5. When an electric current flows through the green compact P, the green compact P generates heat due to its own resistance and its temperature rises. As a result, the green compact P is electrically heated at a predetermined temperature for a predetermined temperature and sintered.

Cooling water is supplied from the main cooling water supply system to each branch cooling water supply system. By flowing cooling water from the branch cooling water supply system to the furnace 1 to cool the entire furnace 1, heat transfer occurs more due to the heat transfer relationship between radiation and heat conduction, and the green compact P is cooled. In addition, from the branch cooling water supply system to the conductive pipe 3
By flowing cooling water to the upper clamp 4 to cool the upper clamp 4 and cooling water to the conductive pipe 6 to cool the lower clamp 4, the green compact P is cooled due to the heat transfer of radiation and heat conduction. The base 2 is cooled by flowing cooling water. The cooling water that has cooled the furnace 1, the upper clamp 4, the lower clamp 6, and the base 2 is discharged through each cooling water discharge system. Gas is supplied from the gas supply system to the inside of the furnace 1 to make the inside of the furnace 1 have a predetermined atmosphere. Next, a method for measuring and controlling the temperature of the green compact P when sintering the green compact P will be described.

The thermometer 11 of the main cooling water supply system measures the temperature of the cooling water flowing through the main cooling water supply system and gives the measurement information to the controller 20. Further, each thermometer 15 provided in each branch cooling water discharge system measures the temperature of the cooling water flowing through each branch cooling water discharge system, and the measured information is used as the control device 2.
Give to 0. The controller 20 obtains the difference between the cooling water supply temperature measured by the thermometer 11 and the drainage temperature measured by each thermometer 15. Here, the temperature of the green compact P to be sintered is estimated from the difference between the feed water temperature and the drain water temperature of the cooling water, based on the preceding experimental data input to the control device 20 in advance.

If the estimated temperature of the green compact P is different from the required predetermined temperature, the flow rate of the cooling water is controlled to control the temperature of the green compact. The control device 20 calculates the flow rate of the cooling water flowing through the furnace 1, the upper clamp 4, the lower clamp 6 and the base 2 in accordance with the difference between the estimated temperature of the green compact P and the required predetermined temperature. The opening of each flow control valve 12, 13 required to obtain the flow rate of the cooling water is calculated. The control device 20 is the flow control valve 12 of the main cooling water supply system.
And the opening degree of the flow rate control valve 13 of each branch cooling water discharge system is controlled to control the flow rate of the cooling water flowing to the furnace 1, the upper clamp 4, the lower clamp 6 and the base 2. At this time, the flow rate of the cooling water flowing through the furnace 1, the upper clamp 4, the lower clamp 6 and the base 2 is measured by the flow meter 14 of each branch cooling water supply system,
The information is information that contributes to the opening control of the flow control valve 13. This controls the temperature of the green compact P during sintering.

When the green compact P is heated, the doping agent contained in the green compact P evaporates and diffuses inside the furnace 1. When the gas inside the furnace 1 is discharged to the outside, the doping agent is discharged together with the gas, so that the heat of the green compact P is taken due to the convective heat transfer relationship. Therefore, it is preferable to control the gas supply amount and the gas discharge amount with respect to the furnace 1 in order to make the heat amount for discharging the gas inside the furnace 1 to the outside constant. That is, furnace 1
The temperature of the gas supplied to the furnace is measured by the thermometer 16, the temperature of the gas discharged from the furnace 1 is measured by the thermometer 19, and the measurement information is given to the controller 20. This information is used as information for estimating the temperature of the green compact P together with the temperature difference between the water supply and drainage of the cooling water. Then, the control device 20 controls the control valve 17 according to the temperature of the green compact P.
To control the flow rate of gas supplied to the furnace 1.

The sintering temperature of the green compact P depends on the conditions of the powder manufacturing process and the green compact forming process which are the preceding steps.
It changes slightly each time. That is, the sintering temperature of the green compact P changes due to fluctuations in the previous process. Flow rate control of cooling water is suitable for such a change in the sintering temperature of the green compact P.

Therefore, the flow meter 14 of each cooling water supply system
Of the cooling water flow rate information and the gas flow rate information of the flow meter 18 of the gas supply system are monitored and displayed by the monitoring device 22, and the cooling water drainage temperature information of the thermometer 15 of each cooling water discharge system and the thermometer of the gas discharge system are displayed. Monitoring device 2 for 19 gas discharge temperature information
Monitor and display in 3.

As a method for controlling the temperature of the green compact P, there is a method of controlling the current value to be applied to the green compact P on the basis of the temperature difference between the supply and drain of cooling water and the flow rate of the cooling water. In this case, the control device 20 calculates a current value according to the temperature required for the green compact P and gives a command to the electric sintering circuit 21,
The electric current sintering circuit 21 controls the value of the electric current applied to the green compact P.

Further, the temperature of the green compact P can be controlled by combining and controlling the flow rate of the cooling water and the value of the current flowing through the green compact based on the difference in the temperature of supply and drainage of the cooling water.

[0032]

As described above, according to the electric heating and sintering apparatus of the present invention, the difference between the feed water temperature of the cooling water and the drainage temperature after cooling is proportional to the temperature of the green compact. Since the temperature of the green compact is estimated by measuring the temperature of the green compact, it is possible to measure the temperature of the green compact as a whole without the obstacles of the conventional method of measuring the temperature of the green compact with a radiation thermometer. it can.

Therefore, according to the present invention, the temperature of the green compact can be accurately measured when sintering the green compact and the temperature of the green compact can be accurately controlled. A device can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of a configuration for measuring a powder compact temperature in an electric heating sintering apparatus of the present invention.

FIG. 2 is a cross-sectional view showing an example of the configuration of an electric heating sintering apparatus of the present invention.

[Explanation of symbols]

1 ... Furnace, 3, 5 ... Conductive pipe, 4, 6 ... Clamp, 1
1, 15 ... Thermometer, 20 ... Control device.

Claims (1)

[Claims] 1. A device for sintering a green compact by energizing the green compact by self-heating generated at this time, and a furnace for arranging the green compact inside, and a supporting means for supporting the green compact. A means for energizing the green compact, a cooling water circulating means for supplying cooling water to the supporting means and discharging the supplied cooling water, a temperature of the cooling water supplied to the supporting means and the discharging from the supporting means Means for measuring the temperature of the cooling water, and information from the temperature measuring means to obtain the difference between the feed water temperature and the drainage temperature of the cooling water to estimate the temperature of the green compact and / or An electric heating and sintering apparatus, comprising: means for detecting abnormality.