JPS5953321B2 - powder sintering equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a sintering apparatus for electrically sintering metal, alloy powder, or mixed powder of carbon, ceramic, or the like.

The powder filled in the pear-shaped mold is pressurized and energized at the same time, and this is done in a controlled manner, and the pressure is usually 0.5 to 10 kg/c.
By applying a light pressure of about 1.5 m'', electric discharge is generated between the powders to produce heating, diffusion, decomposition and removal of gases attached to the oxide film, etc., and at the same time, heat is generated by Joule heat to remove impurity gases. As a result, the entire powder filling inside the pear mold gradually shrinks, but the sintering process continues while controlling this shrinkage, and finally sintering is performed by applying upset pressure. particle size 1,
The properties of the sintered body vary depending on the material properties, the amount of adsorbed gas in the material, the degree of oxidation, the sintering temperature, how pressure is applied to the powder, the state of the medium gas, etc., and uniform sintering is difficult. Ta.

The present invention is uniform for any powder, mixed powder,
We propose a sintering device that can perform high-density and good sintering.The energizing pole/pressure punch is divided into any number of punches according to the sintering shape and size. By installing press devices that apply pressure independently and with unit power supplies that can each be controlled, it is possible to sinter the entire product uniformly, and to sinter parts of the product so that the entire product can be sintered uniformly. This is a characteristic feature.

The present invention will be explained below with reference to the drawings.

In FIG. 1, 1 is a mold, into which sintered powder 2 is filled.

3a, 3b, 3C, and 3d are divided punches that are energized polarized and pressurized punches that are pressurized and sintered from the upper surface, and each is provided with an independent pressurizing cylinder 4a, 4b, 4C, and 4d.

5 is a bottom pressure punch, 6 is a commercial AC power supply input terminal, 7 is
is a rectifier that performs full-wave rectification of alternating current to obtain direct current power.

81゜82. 83 and 84 are switches that control the on/off switching of the DC output, and 10 is an oscillator, which generates a sufficiently higher frequency than the commercial AC frequency, for example, 500Hz to 50KH.
It oscillates at a frequency of about Z or even higher frequency, and controls the oscillation output by adding it to each of the switches to generate a high frequency alternating current or pulse.

91.92, 93.94 are the respective switches 81.82,
A transformer that transforms the high frequency alternating current generated at 83 and 84,
101, 102, 103, and 104 are rectifiers that rectify the transformer output, and each rectified output is sent to each of the dividing punches 3a, 3.
Connect to b, 3C, and 3d.

11 controls the oscillator 10, and each switch 81, 82
, 83 and 84, and 19 is an induction heating coil provided around the mold 1, which is particularly effective for powder sintering of ceramics and the like, which is difficult to conduct with electricity.

Sintering is performed as follows.

The filled powder 2 is pressed with punches 3a, 3b, 3C, 3d, and each pressurizing cylinder 4a, 4b,
4C and 4d are controlled simultaneously or with a time difference, and are controlled, for example, by a program by an NC control device (not shown), and powder pressurization is performed.

Each rectifier 101, 102 of the unit power supply is applied to the two powder parts pressurized by each punch 3a, 3b, 3C, 3d
103.104 outputs are energized.

The pressure applied by the punch is usually 0.5 to 10 k as mentioned above.
The control is performed using a light pressurization of about 112 g/cI, and in this pressurized state, powder volume discharge and Joule heat are generated by energization in response to the pressurization, and the filling powder 2 is reduced by surface purification, activation, ionization, heating, etc. gradually shrinks,
For this powder shrinkage, each cylinder 3a, 3b,
3C and 3d are subjected to follow-up control so that the treatment by the discharge and Joule heat is continued with constant pressurization.

The energizing power source that energizes each of the divisional punches generates high frequency HF by turning on and off the direct current DC obtained by rectifying the commercial alternating current AC input to the terminal 6 with the rectifier 7 using switches 81, 82, . . . , this transformer 91, 92...
... and a rectifier 101. 102...
・AC-DC rectified DC to obtain DC output
- HF-DC inverter circuit, switch 81,
The AC output is It can generate alternating current, which is almost a square wave and has extremely high efficiency, and can also be used with transformers 91.92
Because the frequency is high, it can be constructed extremely compactly, and the power supply can be made smaller and lighter, and output control is highly responsive and extremely easy.

That is, by controlling the duty of the output control high frequency of the oscillator 10, the output power can be easily controlled, and moreover, this oscillates at a sufficiently higher frequency than the above-mentioned commercial AC.
Since it is a control, it can be controlled with extremely high response.

This control may be controlled according to a program, but is most preferably controlled by the processing state and shrinkage state of the sintered powder.

Figure 2 shows an embodiment of a device for detecting volume changes due to powder shrinkage, in which a transformer-coupled primary coil 12 and secondary coil 13 are fixedly supported on a rod that moves under pressure, and a movable iron core 14 is connected to another Provided on the mobile device.

Reference numeral 15 denotes a motor controlled by a predetermined signal, which rotates a shaft 16 parallel to the rod, engages a moving piece 17 with this rotating shaft 16, and connects the iron core 14 to this moving piece 17 to control its movement.

18 is a detection signal output terminal of the secondary coil 13, and this signal is applied to the control circuit 11 to control the oscillator 10.

Note that this detection device applies to each cylinder 4a, 4b, 4C, 4d.
are provided for each.

As a result, the filling powder 2 in the pressurized portion of each punch 3a, 3b, 3C, 3 (H:) is processed by generating powder amount discharge and Joule heat as described above by controlling the pressurization and energization. The powder gradually shrinks due to surface purification, activation, ionization, heating, etc., and each cylinder 4a responds to this powder shrinkage.

4b, 4C, and 4d perform follow-up control.

Therefore, the motor 15 is driven at a predetermined speed, the screw shaft 16 is rotated, and the moving piece 17 is moved.

As a result, the movable iron core 14 moves downward together with the moving piece 17 at a predetermined speed, and on the other hand, as the rod of the cylinder 4a moves, the primary and secondary coils 12, 13 also descend, and at first the moving (descending) speed of both is The depth of insertion of the iron core 14 into the coil 12.13 is also constant, and the output voltage of the secondary coil is applied to the control circuit 11 and controlled to a predetermined value.

As the powder shrinkage speed increases as the powder discharge and Joule heat treatment progresses, the descending speed of the coil 12, 13 along with the rod increases, and the relative speed with the movable core 14, which descends at a predetermined speed, changes and the core gradually 14
is inserted deeply into the coils 12 and 13.

As a result, the output voltage of the secondary coil 13 increases, and the output voltage of the secondary coil 13 increases.
The signal applied from 8 to the control circuit 11 increases and the oscillator 10
The duty of the punch 3a is controlled (increased), and the power applied to the powder 2 from the punch 3a is controlled to be increased (reduced).

As the treatment by energization progresses further, the shrinkage speed of the powder increases,
This is detected by the relative speed change between the coils 12, 13 and the movable iron core 14, and the increase (reduction) of the energizing force is controlled.

In this way, the energization is controlled in accordance with the powder shrinkage state, and the energization is optimized.

Furthermore, the power supply control for the other punches 3b, 3C, and 3d is similarly optimally controlled according to the volume change.

Although current control differs depending on the sintering material, sintering shape, sintering purpose, etc., for example, in order to perform high-density sintering, it is generally necessary to increase the current application power, but if the power increases more than necessary, sintering will occur. The powder may gasify and enter the sintered product, requiring power control.

Therefore, in the early stages of sintering, it is best to control the power to generate a sufficient amount of powder discharge, and increase the power during the period when the powder shrinks due to the discharge treatment to achieve sufficient heating and diffusion to complete sintering. , high-quality sintering can be achieved by controlling the powder shrinkage.

Of course, the power supply control may be digital control in which the power is controlled to be constant until the powder shrinkage reaches a certain value, and the power is increased (or decreased) when the powder shrinkage exceeds this value.

If the pressure and energization are controlled simultaneously by each punch 3a, 3b, 3C, and 3d, the entire powder 2 will be sintered by being pressurized and energized at the same time. Since each part is sintered under optimal control independently, each part can be sintered in the best condition.In some cases, it is better to sinter parts by controlling the time difference, so that the pressurization and energization processes can be performed using adjacent punches. This is done alternately to give a kneading effect to the filler powder 2 during the sintering process, and also improves the degassing effect of decomposed gas during sintering, which is extremely effective, especially in ceramic sintering, as it improves transparency. A high quality sintered body can be obtained.

Also, during this sintering, an induced current is passed through the coil 19 to the internal powder 2.
In this case, the coil 19
It is also possible to use the high frequency output of the transformer 91 by energizing it.

Figure 3 shows an example in which the lower punches are also divided into sections 5a, 5b, 5C corresponding to the upper punches 3a, 3b, 3C, and electricity is supplied between the opposing punches 3a, 5a, 3b, 5b, 3C.
, 5C is energized.

The punches 3a and 5a, 3b and 5b, and 3C and 5C are simultaneously pressurized to perform partial sintering of the filling powder 2 in the opposing portions.

Simultaneous pressure control and energization control of the upper and lower opposing punches ensure sufficient powder processing by electrical discharge and Joule heat treatment, which are partially simultaneously performed and sequentially with time differences, and finally By adding upsets, the entire product can be sintered uniformly.

In addition to the above-mentioned embodiments, the pressure punches are provided in the x, y, and z directions, and are each divided into multiple parts, each of which can be sintered under program control using an NC control device, so that it can be made of any material, particle size, or A sintered body having the optimum size, shape, and density can be easily and uniformly sintered and formed.

In addition, the energizing power source is not limited to the above-mentioned AC-DC-HE-DC inverter, and can be implemented so that the energizing power can be controlled, so that it can be controlled in accordance with changes in the volume of the powder to achieve optimal energization. This allows for better sintering.

Moreover, the control of the current supply source may be program controlled by an NC device or the like in which the sintering process is programmed in advance.

As described above, the present invention provides an independent pressure press device and an independent energization power source for each divided punch of the current-carrying polarity/pressure punch, and applies pressure controlled by each divided punch. and energization is applied to the filled sintered powder part, and the pressure and energization by each punch are performed simultaneously or sequentially with a time difference, and the powder is discharged by partially optimal pressure and energization. Since sintering is performed by press forming without sufficient heat treatment, uniform sintering can be achieved as a whole.

According to this method, even if the sintered crystal is large or has an irregularly shaped complex shape, it can be easily and uniformly sintered, and it can be sintered easily and uniformly, depending on the particle size of the material, material properties, material adsorption, gas amount, oxidation degree, medium gas condition, etc. It has the effect of enabling sintering and uniform sintering.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is a block diagram of an embodiment of a device for detecting changes in the volume of powder/powder, and Fig. 3 is a partial block diagram of a modified embodiment of Fig. 1. . 1 is a mold, 2 is a powder, 3a, 3b, 3C, 3d are division punches, 4a, 4b, 4C, 4d are cylinders, 5 is a pressure punch, 5a, 5b, 5C are division punches, 6 is an AC power terminal, 7 is a rectifier, 81, 82, 83, 84 is a switch, 9
1. 92. 93°94 is a transformer, 10 is an oscillator,
11 is a control circuit, 101, 102, 103, 104 is a rectifier, 12.13 is a coil, 14 is a movable core, 15 is a motor, 16 is a screw shaft, 17 is a moving piece, 18 is a detection terminal, and 19 is an induction coil. be.

Claims (1)

[Scope of Claims] 1. A current-carrying electrode/pressure punch is provided to pressurize and energize the filled sintered powder, and a power source for energizing the powder through the punch and a press device for pressure pressing are provided. ,
In a powder sintering device that performs sintering by simultaneously controlling pressure and energization, a plurality of divided punches are provided as the energizing electrode and pressure punch, and each punch is provided with a press device that performs an independent pressure press. A powder sintering apparatus characterized in that the powder sintering apparatus is further provided with an energizing power source that energizes each of the punches independently. 2. The powder sintering apparatus according to claim 1, which uses an AC-DC-HF-DC inverter energizing power source.