JPS62135322A - Wet type molding equipment - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a wet molding apparatus for obtaining a molded body of an oxide permanent magnet from a slurry containing oxide magnetic powder.

(Prior art) As one method for manufacturing oxide permanent magnets such as ferrite magnets, a slurry (concentration of about 50 to 70%) in which oxide magnetic powder with a particle size of about 1 μm is dispersed in a solvent such as water, Wet molding in a magnetic field and the resulting molded product at 1100-1200°C
A so-called wet method is known in which sintering is performed at a temperature of . (
For example, see Japanese Patent Publications No. 55-6041, No. 55-10364, and No. 59-8047) A conventional example of a molding apparatus used in this wet method will be explained with reference to FIG. 1
is a die type, and is driven in the vertical direction by a lower hydraulic cylinder 2.

3 is a lower punch fixed on a base 17, and is inserted into the die 1 via a backing 4 such as an O-ring. Reference numeral 9 denotes an upper punch that contacts the upper surface of the die mold 1 via the filter body 7, and is driven in the vertical direction by an upper hydraulic cylinder 11. Further, inside the upper punch 9, a drain hole 8 and a drain chamber 10 communicating therewith are formed. 5 is a molding cavity formed by the die 1, the upper punch 9 and the lower punch 3, and is surrounded by a magnetic field coil 6 provided on the outer periphery of the die 1. This molding cavity 5 is connected to a slurry storage tank 16 via a slurry supply pipe 18. Two valves 13.15 are provided in the middle of the slurry supply pipe 18, and between the two valves, the supply pipe 1
A slurry pumping device 14 is provided at 8.

The molding operation with the above configuration is as follows. First, the valve 15 is closed, the valve 13 is opened, and the slurry pumping device 1
4 to inject a predetermined amount of slurry into the molding cavity 5 from the injection port 12 at a pressure of about 20 to about 50 kg/ca.Next, after closing the valve 13, the upper punch 9
Consolidation molding is performed without applying a magnetic field by relatively displacing the and lower punch 3. After molding for a predetermined time, the die 1 and upper punch 9 are moved to take out the molded product. FIG. 5 shows the displacement of the upper punch and die mold with reference to the upper surface of the upper punch indicated by X and the change in slurry pressure at point S near the die mold during such a forming process. In the figure, from the start of the operation to 22 (30), a molding cavity 5 with a predetermined volume is formed by the rise of the die 1 and the fall of the upper punch 9, and the slurry is formed between 22 (30) and 23 (32). Injected into the molding cavity 5, from 23 (32) to 25 (
34), the die mold and the upper punch 9 are simultaneously lowered to perform compression molding. Initial B (23
24), the lowering speed of the die 1 and the upper punch 9 is made slower in the latter period C (between 24 and 25). The final pressurization is carried out by gradually releasing the floating pressure of the lower hydraulic cylinder 2 and advancing the pressurization between both punches.

During this final pressurization, the floating pressure of the lower hydraulic cylinder 2 is released to a pressure sufficient to support the weight of the die mold, etc.

(Problems to be solved by the invention) In conventional molding equipment, the molding efficiency is ignored to some extent and the fifth
As shown in the figure, in the latter stages of compaction molding, the die and upper punch had to be lowered at a slower speed than in the early stages.

This is because the dehydration properties of the slurry are not sufficient, so if the above-mentioned descending speed is accelerated in the late stage of molding, the slurry that is being dehydrated and solidified will flow backwards, causing the slurry to form near the mold as shown by the broken line G in Figure 5. This is to prevent a rise in pressure and, as a result, defects in the molded product due to this backflow. That is, in the conventional molding apparatus, in the early stage of the molding process (23 to 24), the descending speed is increased to force the slurry to flow backwards from the molding cavity 5 through the injection port to the valve 13 side, thereby reducing this part of the molding process. The slurry pressure was kept high and lowered at a slower speed than the above in the latter stage of molding (24-25) to prevent defects due to backflow. In this case, the local decrease in density near the injection port 12 due to the backflow of the slurry at the initial stage of molding is eliminated by the subsequent flow of the raw material.

As mentioned above, in the conventional wet molding apparatus □, the molding time had to be lengthened in order to prevent defects due to backflow of slurry. Furthermore, even if backflow can be prevented, if the dewatering properties of the slurry are not improved, the product after firing will be affected due to an imbalance in the density of the compact between the upper punch side, which has drainage holes, and the lower punch side, which does not have drainage holes. The problem of deformation remains.

Therefore, an object of the present invention is to provide a wet molding apparatus that can improve the dewatering properties of slurry and perform molding with high efficiency without causing defects.

(Means for Solving the Problems) The wet molding apparatus of the present invention has a molding space formed by a pair of punches that move relatively and are provided with a filtering member on at least one of them, and a mold side wall surrounding the punches. A mold device comprising a mold device, a pumping device that pumps slurry containing oxide magnetic powder to the mold device at high pressure, and a heating device provided in the pumping device that heats the slurry. It is.

(Function) In the present invention, since the slurry is heated before being injected into the molding cavity, its viscosity is reduced and dewatering properties are improved. Moreover, the heated slurry is pumped at a high pressure of 300 kg/am" or more near the die mold, so the slurry inside the molding cavity is pressurized. As a result, the dehydration of the slurry is promoted. The slurry concentration becomes large.

Preforming is performed. Therefore, in the present invention, compression molding can be performed at a higher speed than conventional methods without backflow, and since preforming is performed, the stroke can be shortened, making it possible to significantly shorten the molding cycle time.

(Example) Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a sectional view showing an example of a wet molding apparatus of the present invention. , 1 is a die mold driven vertically by a lower cylinder 2, 3 is a lower punch fixed on a base 17 and inserted into the die mold via a backing 4, 8 is a drain hole 8 and a drain hole. This is an upper punch having a liquid chamber 10, in contact with the upper surface of the die mold 1 via the filter 4 body 7, and driven in the vertical direction by an upper hydraulic cylinder 11. 5 is die type 1
, a molding cavity formed by an upper bunch 8 and a lower punch 3, and a magnetic field coil 6 provided on the outer periphery of the die 1.
The six mold cavities 5 surrounded by are connected to a slurry storage tank 16 via a slurry supply pipe 18. Valves 13 and 15 are provided in the middle of the slurry supply pipe 18, and between the two valves, 300 kg/kg of slurry is supplied.
The wet molding apparatus shown in FIG. This device is significantly different from the conventional device shown in FIG. 4 in that the slurry pumping pressure of the device 14 is high and that the slurry pumping device 14 is provided with a slurry heating device 19.

Wet molding can be performed in the following manner using the apparatus shown in FIG.

First, the valve 15 is closed, the valve 13 is opened, and the slurry pumping device 14 is operated to pump a predetermined amount of slurry toward the molding cavity 5. At this time, the slurry heating device 19 is activated to heat the slurry to a temperature in the range of 20 to 95°C. The heated slurry is injected into the inlet 12.
After the start of injection, the injection is continued for a predetermined period of time (approximately 5 to 10 seconds) to perform dehydration.

Next, after the slurry has been pumped, the valve 13 is closed and the upper bunch 9 and lower punch 3 are moved relative to each other to perform dewatering and compaction forming. After the molding has been completed for a predetermined period of time, the upper punch 9 and the lower punch 3 are moved relative to each other to take out the molded product.

Figure 2 shows the relationship between the elapsed time in the forming process, the displacement of the upper punch and die based on X-rays, and the slurry pressure at point A near the die. .22~23.23~25
indicate the molding cavity forming period, slurry injection period, and consolidation molding period, respectively.

According to the present invention, the slurry is preheated before being injected into the molding cavity, thereby reducing its viscosity and improving its dewatering properties. The heating temperature for dehydration may be 20°C or higher, but 95°C or lower is sufficient, and the preferred range is 50 to 90°C. In addition, the heated slurry
As mentioned above, since the slurry is injected into the molding cavity S at a pressure of 300 kg/am2 or more, the slurry injection period 22
In periods 31 to 23, dehydration is sufficiently performed and the raw material concentration increases, and a kind of preforming is performed as shown by D, as is clear from the increase in slurry pressure in periods 31 to 32. In this case, if the slurry pumping pressure is too high, the slurry will solidify, so 400 kg/cm
”The following is better.

Next, in the consolidation molding period 23 to 25, since the dehydration properties of the slurry are improved as described above, the period 23 to 24 is
In the initial stage of molding shown in , high-speed molding can be performed without backflow of slurry. Furthermore, since preforming is performed before compression molding, the molding stroke H can be shorter than that of the conventional method. Therefore, according to the present invention, it is possible to significantly shorten the molding cycle time. Also in the present invention.

The molding stroke becomes shorter. In other words, since the gap length between the upper punch and the lower punch can be shortened, the magnetic field strength is improved,
It becomes possible to improve magnetic properties.

(Specific example) Ferrite particles (Sr0.6Fe
20. ) 60% by weight, polyvinyl alcohol 0゜1
Wet molding was carried out using the apparatus shown in FIGS. 1 and 4 using a slurry in which % by weight was dispersed in water. Here, in the device of the first section, the slurry is heated to 85°C,
300kg/cm” pressure, 500kg/am
Molding is performed at a pressure of 2, and in the device shown in Figure 4, the slurry pumping pressure is 40 kg/am2, and the molding pressure is 500 k.
g/cm".

FIG. 3 shows the relationship between the elapsed time, the slurry temperature, and the slurry pressure in the vicinity of the die mold A when wet molding was performed under the above conditions.

From FIG. 3, it can be seen that in the past, the slurry temperature was around 20° C. throughout the entire molding cycle, so a molding cycle time of about 60 seconds was required.

In contrast, in the present invention, the heated slurry
It can be seen that the molding cycle time can be shortened to 33 seconds, about 55% of the conventional time, because it is fed under a pressure of 0 kg/c+a2.

(Effects of the Invention) As described above, the apparatus of the present invention is equipped with a means for heating the slurry before it is injected into the molding cavity and a means for pumping the slurry under high pressure. Can be molded.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of an apparatus according to an embodiment of the present invention, FIG. 2 is a diagram showing the relationship between elapsed time, punch displacement, and slurry pressure in the apparatus of FIG. 1, and FIG. 3 is a diagram of the present invention. FIG. 4 is a longitudinal cross-sectional view of the conventional device;
Figure 5 shows the passage of time and the upper punch in the device shown in Figure 4.
FIG. 6 is a diagram showing the relationship between the displacement of the lower punch and the slurry pressure. 1: Dice type, 3: Lower punch, 9: Upper punch. 14 Nisslary pressure feeding device, 19 Nisslary heating device, Fig. 3

Claims (1)

[Scope of Claims] 1. A mold device having a molding space formed by a pair of punches that move relatively and each of which is provided with a filtering member and a mold side wall surrounding the punches, and the mold device A wet molding device comprising: a pumping device that pumps a slurry containing oxide magnetic powder under high pressure; and a heating device provided in the mold device that heats the slurry. 2. The wet molding apparatus according to claim 1, which uses a pressure feeding device that pumps the slurry at a pressure of 300 kg/cm^2 or more.