JPS60231469A - Thermally hydrostatic press formation for soft ferrite - 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: Industrial Field The present invention relates to an improvement in a method for hot isostatic press forming of soft ferrites such as 1-7η series and Ndi-Zn series. The present invention relates to a hot isostatic press molding method that prevents cracks and splits in a processed product from occurring frequently.

BACKGROUND ART In recent years, hot isostatic pressing (hereinafter referred to as HIP) molding method has been widely used as a method to increase the density of soft ferrite, and Denryobe Ko Materials has been manufacturing it for use in magnetic heads and other applications. has been done.

Normally, HIP processing conditions include temperature, pressure, holding time, etc., and the performance of the processed object depends on these conditions.

Although the characteristics etc. are determined, for example, even if the materials are the same,
If the dimensions are different, in addition to the above conditions, conditions such as temperature increase rate and temperature decrease rate become important.

In general, soft ferrite used for magnetic heads is manufactured from small sizes of 10 mm x 10 mm x 5 mm to large sizes of 75 mm x 75 mm x 10 mm, and various conditions are selected depending on the size and composition. However, under HIF' conditions, argon or nitrogen gas is used as the atmospheric gas, and the temperature is 1000°C to 1400°C.
Pressure 50 (lkq/cm2 to 2000kg/ctn2.
It is 0.5 to 5 hours.

In addition, the temperature increase and temperature decrease rates are shown in Figure 2).
The process is carried out in the 'P apparatus under conditions of 300°C/hr-600°C/hr.

However, under the above conditions, 50 mm or more x 50 mm or more x
When a soft ferrite object with a large size of 10 mm or more is subjected to HIP treatment, a humidity difference is created between the inside and outside of the object, resulting in thermal distortion due to the difference in thermal expansion, resulting in cracks and cracks due to so-called thermal shock. There was a problem in that this caused a significant drop in product yield.

Purpose of the Invention The present invention aims to solve the problem of cracks in the processed product due to thermal shock that occurs during hot isostatic press molding of soft ferrites such as Mn-Zn type and Nj-Zn type, especially large size soft ferrites. The objective is a hot isostatic press molding method that can prevent cracking.

Structure and Effects of the Invention The present invention is directed to the maximum size of soft ferrite currently used for magnetic heads, which is 75 mm x 75 mm x
As a result of various studies on HIP processing conditions that do not cause cracks due to thermal shock even for 10 mm size products, we found that
By specifying the rate of temperature rise and temperature drop before and after the +-t ip treatment temperature, reducing the pressure at a specific temperature drop after HIP treatment, taking it out of the HIP device and cooling it in a cooling room, it is possible to prevent scratches due to thermal shock. It was discovered that this did not occur and that the HIP equipment could be used efficiently.

That is, the present invention is a method for hot isostatic press forming of soft ferrite, which is characterized by hot isostatically press forming a primary sintered body of soft ferrite having a density of 95% or more in the following order.

(2) The above sintered body is heated to 1000°C to 1400°C at a heating rate of 100°C/hr to 170°C/hr.

■After heating up, temperature 1000℃~1400℃, pressure 500k
Hot isostatic press treatment under conditions of M cm2 to 2000 ka/cm2.0.5 to 5 hours.

■After hot isostatic pressing, cooling at a cooling rate of 100℃/hr to 170℃/hr,
Hold at 600°C to 900°C for 0.5 to 3 hours and reduce pressure to atmospheric pressure.

(2) After depressurizing, take out from the hot isostatic press and cool to below 100°C in a cooling chamber filled with inert gas.

This invention uses the above-mentioned means (1) to (2) to prevent cracking due to thermal shock, not only in the maximum dimensions of 75 mm x 75 mm x 10 mm, which are the maximum dimensions of soft ferrite used for magnetic heads, but also in all sizes. HIP processing can be performed without creating cracks, and furthermore, the HIP processing time can be shortened. In addition, since most of the cooling process of the processed object after 1" IP processing is performed in another cooling chamber, there is no space in the HIP equipment. This has the advantage that the time occupied by the device for loaded objects to be processed can be shortened, the next object to be processed can be loaded immediately, and the HIP device can be used efficiently.

Reasons for Limiting the Invention The reasons for limiting the processing conditions of the present invention, such as HIP temperature, pressure, time, heating rate, cooling rate, and retention humidity and time during cooling, will be explained below.

In this invention, if the density of the primary sintered body is less than 95%, the object to be processed cannot be densified after HIP treatment and its properties will deteriorate. is necessary.

)-1I P treatment temperature is 1000°C because if it is less than 1000°C, high density of the processed material cannot be obtained, and if it exceeds 1400°C, the crystals of the processed material will become abnormally coarse and the properties will deteriorate.・~1400°C = ru.

[I11] If the pressure is less than 500 kiJ, the densification of the material to be processed will not be achieved, and if it exceeds 2000 M, the pressure will be 1-
1 Not only is it necessary to increase the capacity of the IP device, but it is also undesirable because the effect of high density saturates.
The IP pressure is 500-d to 2000 ki-J.

If the temperature increase rate or temperature decrease rate exceeds 1.170°C/hr, cracks will occur in workpieces larger than 60mm x 60mm x 10mm due to thermal shock, and The speed of vortex is not preferable because it takes a long time for HIP treatment and is not suitable for mass production.
r~170°C/hr.

The retained humidity during cooling is less than 600°C, the effect of shortening IP processing time is small, and when it exceeds 900°C, 1-I
When the pressure inside the IPI equipment is lowered to atmospheric pressure, the HI P
Since the temperature of the pressure-resistant container itself of the apparatus is 200'C or higher, which is not preferable, the temperature is set at 600°C to 900°C.

Holding time when reducing HIPIP device power to atmospheric pressure is 0
．． If the time is less than 5 hours, it is not preferable because when the pressure is reduced to atmospheric pressure, the object to be treated will be rapidly cooled due to adiabatic expansion of the gas, and cracks will occur due to thermal shock. Also, if it exceeds 3 hours, I
This is not preferable because there is no point in lowering the pressure inside the IP device to atmospheric pressure.

Further, it is not preferable to cool the product to 100° C. or lower in a cooling chamber filled with inert gas, since a temperature exceeding 100° C. will cause cracking when taken out outdoors.

Based on the Drawings <Disclosure of the Invention Figure 1 is a graph of the relationship between time, pressure, and temperature showing the HIP treatment method according to the present invention, and Figure 3 is a graph of the relationship between HIP treatment method according to the present invention.
FIG. 2 is an explanatory diagram of an IP device.

) (The IP apparatus places a workpiece (2) made of a primary sintered body with a density of 95% or more in the center of a base (1), and encloses the workpiece (2). A heat insulating cylinder (4) containing a built-in heater (3) is placed on the base (1), and a pressure-resistant container (5) is placed on the base (1) so as to cover the whole. The pressure vessel (5) is provided with a gas supply hole (6) for introducing an inert pressure medium into the vessel.

In the above IIP device, while supplying argon gas or nitrogen gas from the gas supply hole (6), the heater (
In step 3), the temperature of the object to be treated (2) is raised. In other words, (1) The object to be treated (2) is heated to 1000° C. to 1400° C. at a temperature increase rate of ioo° C./hr to 110° C./hr.

■ After heating up, temperature 1ooo℃~1400'C, pressure 500
kg/cm2~2000ko/c! 02. Hot isostatic pressing for 0.5 to 5 hours.

■After hot isostatic press treatment, 100℃/hr~170'
During cooling at a cooling rate of C/hr, soo'c ~ 900°
C for 0.5 to 3 hours, and then exhaust the gas from the gas supply hole (6) of the pressure vessel (5) to reduce the internal pressure of the pressure vessel (5) to atmospheric pressure.

■After depressurizing, place the object (2) on the base (1) and take it out while covering it with the heat insulating tube (4) (Figure 3), cooling container (7) with an inert gas hole. ) is placed on the base (1) soil and filled with inert gas (Fig. 3C).
Figure), the object to be treated (2) is cooled to 100°C or less.

The pressure container (5) from which the object to be processed (2) was taken out is kept at 100°C.
As shown below, the other workpiece (2) and the heat insulating cylinder (
By inserting the base (1) on which 4) is placed and performing H, IP processing, the HIP processing time can be shortened, continuous HIP processing can be performed, and the HIP device can be efficiently used.

Example FeaOa, MnCO3, and ZnO were each 53.
6-El%.

They were weighed to be 32.6 mol% and 13.8 mol%, mixed thoroughly in a ball mill, and then heated at 900°C in air.
The powder was pre-sintered and roughly ground in a ball mill to obtain a raw material powder with an average particle size of 1.0 mm.

Next, 1 wt % of PVA was added as a binder to the raw material powder, and after granulation, it was placed in a mold and molded at a pressure of 2000 kvJ.

The dimensions of the molded body (mm) are 30x 30x 12.59
There are 3 types: x 59 x 12.84
50X 1o, 75X 75X 10.

This molded body was heated to 125% in a nitrogen gas atmosphere containing 2% oxygen.
Sintering was performed at 0° C. for 3 hours, followed by cooling treatment in pure nitrogen.

The density of this secondary sintered body is as shown in Table 1.

The above sintered body was then processed using the conventional method and the method of the present invention in a )-11P apparatus under the following conditions as shown in Table 1: HIP treated. The number of cracks in each sintered body after the treatment was investigated and is shown in Table 1 along with the -1IP treatment time.

As is clear from Table 1, 75mmX 75mmX
In the case of the 10mm4 method, the heating rate and cooling rate are 170
The speed must be below .degree. C./hr; if this speed is exceeded, cracking will occur due to thermal shock.

In the method of this invention, temperature increase and lli'! Although the heating rate is slower than before, the processing time can be shortened because it is taken out during cooling after HIP processing and cooled separately in a cooling room, and the processing time is shorter than the conventional processing time of 300°C/hr. The device occupancy time for IP processing is shorter than before, and the device can be used more efficiently.
Even large sintered bodies of 5mm x 75n+m x 10mm can be subjected to +-1 IP treatment without cracking.

Margin below

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 shows the I-1I P treatment method according to the present invention, and is a graph of the relationship between time, pressure, and temperature, and Fig. 3 shows the I-1I P treatment method according to the present invention.
FIG. 1 is a cross-sectional explanatory diagram of the 1I IP device. Figure 2 shows the conventional
It is a graph showing the relationship between time, pressure, and temperature, showing the IP processing method. 1... Base, 2... Processed object, 3... Heater, 4
. . . Insulating tube, 5. Pressure resistant container, 6. Gas supply hole, 7. Cooling container. Applicant: Sumitomo Special Metals Co., Ltd. No. 1 @ 8 Sub U (hrl (a) '1fJ2 Figure 3 '@Kut (h') (b) (c)

Claims (1)

[Claims] 1. A hot isostatic press forming method for soft ferrite, which comprises hot isostatically press forming a primary sintered body of soft ferrite having a density of 95% or more in the following order. (2) The temperature of the sintered body is raised to 1000°C to 1400°C at a heating rate of ioo°C/hr-170°C/hr. ■After heating up, temperature 1000℃~1400℃, pressure 500k
Hot isostatic pressing is carried out under conditions of Mcm2 to 2000 kmMcm2.0.5 to 5 hours. ■After hot isostatic pressing, cooling at a cooling rate of 100℃/hr to 170℃/hr,
Hold at e o o'c ~ 900 °C for 0.5 to 3 hours,
and reduce the pressure to atmospheric pressure. (2) After depressurizing, take out the product from the hot isostatic press machine J and cool it to below 100°C in a cooling chamber filled with inert gas.