JPS61235548A - Manufacture of co-fe-al-b magnetic alloy - Google Patents

Abstract

PURPOSE:To prevent crack initiation in a solidified alloy by melting a Co-Fe-Al- B magnetic alloy to be solidified in a mold and by subjecting the solidified alloy to heat treatment under specific conditions. CONSTITUTION:As starting raw material, high-purity Co, Fe, Al, and B are heated to 1100-1150 deg.C by high-frequency heating under a vacuum of 10<-4>-10<-6> torr to form a molten Co-Fe-Al-B magnetic alloy. The molten alloy is cast in a mold equipped outside with an electric heater to be solidified, which is maintained at the temp. between the solidification temp. and a temp. lower than the solidification temp. by 100 deg.C for >=30min and is then allowed to stand to be cooled to ordinary temp. In this way, no cracks occur to the ingot of the magnetic alloy, so that the Co-Fe-Al-B magnetic alloy excelling in hardness and wear resistance and having superior workability as well as highly efficient magnetic properties can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a magnetic alloy, particularly a Go-Fa-Al alloy that is crack-free, sound, and has excellent magnetic properties.
The present invention relates to a method for manufacturing a B-based magnetic alloy.

With the development of magnetic recording media with high performance as the sun shines, the performance of magnetic head materials has improved. For this.

A magnetic recording medium with a coercive force He of 1000 Oe or more now requires a head material with a magnetic flux density B1° of 7000 Gauss or more. Furthermore, for the purpose of narrowing the track, it is required to have good precision machinability at the same time.

However, the Ni-Zn and Mn-Zn ferrites used so far for oxide recording media have a magnetic flux density of B1.
Since the angle is at most 6,000 Gauss, the characteristics of a high-performance magnetic recording medium cannot be fully exploited. For this reason, research on sendust, amorphous alloys, etc. is progressing, but Sendust has the disadvantage of deterioration of the sliding surface due to problems with heat treatment and adhesive technology, and amorphous alloys also require heat treatment, adhesive technology, and track processing. These are still at the prototype stage due to problems with
It has not yet been put into practical use.

For this reason, Co-Fe-Al, which is hard, has excellent wear resistance, and has high performance magnetic properties, is suitable for this type of magnetic material.
-B-based magnetic alloys have attracted attention, but they have the drawback of being difficult to process.

However, with the progress of processing technology, this difficulty has been solved, and the advantages of high hardness improve wear resistance and precision machinability have come to be recognized, but this is a hard and brittle material. Therefore, there was a disadvantage that it was very difficult to obtain a healthy ingot without cracks.

Conventionally, Go-Fe-Al-B-based magnetic alloys have been produced by high-frequency melting of raw acid in an aluminium crucible, then pouring into a mold and solidifying. It had a lot of cracks. Although it is possible to obtain a healthy ingot without cracks by selecting the mold material and optimizing the cooling conditions, another drawback arises. For example, if the solidification rate of molten metal is slowed down, Go, B
.

Crystal phases other than cubic crystals such as Co and B are precipitated, and as the amount of foreign phases increases, the coercive force Hc increases, resulting in the deterioration of the magnetic properties as a soft magnetic material. This also differs depending on the manufacturing method.

For example, when raw materials of the same composition are melted, poured into a mixing mold, and left to cool, there is less precipitation of different phases, and the coercive force Hc is 0.0.
3 to 0.05 oersted, but when this molten metal is poured into a lime mold and slowly cooled, there is a relatively large amount of precipitation of different phases.
Its coercive force He will be 0.1 to 0.2 Oersted,
A peak of a different phase with a lattice spacing of d=1.99 was observed (by measurement of an X-ray powder diffraction pattern).

The deterioration of magnetic properties in this type of alloy corresponds to the amount of precipitated foreign phases, and it is thought that the amount of precipitated foreign phases increases as the solidification rate slows down. Therefore, in order to prevent deterioration of magnetic properties, increase the solidification rate. It is important to suppress the precipitation of foreign phases. If a mold with good thermal conductivity and large heat capacity is used to rapidly cool the molten metal in order to increase the solidification rate, it becomes difficult to obtain a healthy ingot without cracks. However, if a healthy ingot is obtained by allowing a certain amount of foreign phase precipitation, heat treatment can remove or reduce the foreign phase. .

. In order to achieve this, the present inventors high-frequency melt a Go-Fa-Al-B based magnetic alloy based on a known method, and when solidifying and cooling it in a mold, the holding temperature range and holding temperature of the solidified magnetic material are determined. The present invention was completed by conducting research on time, cooling rate, etc. In other words, after melting and solidifying a magnetic material containing Co, Fa, Al, and B, the entire solidified body is held between the solidification temperature and a temperature 100°C lower than that temperature for 30 minutes or more, and then cooled. Co-Fa-
This is a method for producing an Al-B based magnetic alloy.

The raw materials used in the method of the present invention are electrolytic cobalt with a purity of 99.9% or more, iron with a purity of 99.9% or more, and purity 99.99%.
Known pure metals such as flaky aluminum with a purity of 99.8% or higher and crystalline boron with a purity of 99.8% or higher may be used, but when electrolytic cobalt is used, absorbed gas is released during melting.

Since the ingot may contain air bubbles, it is better to melt and solidify these alloy materials as a pretreatment, and then crush them to form the starting material.

The method of the present invention will be explained in detail below.

After the starting materials obtained by the above method were high-frequency melted under a vacuum of 10-4 to 10-Torr, argon gas was introduced to create an inert gas atmosphere in the furnace. The mold is made of calcia (Cab), magnesia (MgO), etc., and a thermocouple is embedded in the wall to measure the temperature.

Always monitor. This molten metal reaches a temperature of approximately 1100°C to 1150°C and begins to solidify. There is no need to particularly control the time until solidification, and it is sufficient to allow it to cool.

If the solidified body obtained in this way is left to cool to room temperature, the obtained ingot will have many cracks. It is to be kept as such. This holding is carried out by adjusting the electric power of a heater provided outside the mold. After a predetermined period of time, an ingot without any cracks can be easily produced even if it is left to cool in the furnace to room temperature.

The time for holding this solidified body is usually 30 minutes or more in order to produce a sound ingot, but at least 1 hour or more is required to produce a sound ingot with excellent magnetic properties.

The most standard is 70-80% by weight of cobalt and 10-80% of iron.
Since the starting material consisting of 20% by weight and 2 to 10% by weight of boron has a solidification temperature of 1100°C to 1150°C, (1
000-1050) to (1100-1150)'C. Within this holding time, even temporarily
It is necessary to prevent the temperature from falling below 000°C.

After the solidified body is maintained in this temperature range for a predetermined period of time, it may be left to cool in a furnace at a rate of about 50° C./min to room temperature, but it may be slowly cooled while being heated if necessary.

Backyard hill, a mixture consisting of 74.33% by weight of cobalt, 16.08% by weight of iron, 4.20% by weight of aluminum, 5.05% by weight of boron, and 0°34% by weight of titanium was heated to 1×10° below 3 Torr. The mixture was melted at high frequency in a vacuum using an aluminum crucible, poured into a mixing mold, allowed to cool, and then crushed to an average particle size of about 10 square centimeters to produce a starting material having a predetermined composition ratio. Next, put this starting material soo g into an aluminum crucible,
High frequency melting is carried out in a vacuum of less than lXl0-' Torr. When the molten metal begins to generate convection, argon gas is introduced in an amount of 10 Torr, and the molten metal is heated to 1400°C by adjusting the high frequency power.
(measured with a light thermometer).

Next, this molten metal was poured into the lime mold, and the entire mold was cooled to 1100°C, held for 2 hours, and then cooled to room temperature at a cooling rate of 2°C/min. The obtained round bar ingot with a diameter of 25 m had a good appearance and was sliced.
The disc thus obtained was sound with no internal cracks. Outer diameter 8 extracted from this disc using an ultrasonic processing machine
(2) When we investigated the magnetic properties of a ring with an inner diameter of 3.5 mm and a thickness of 1 (2), we found that the coercive force Hc was 0.04 oersted and the magnetic flux density was B. was 7500 Gauss. Table 1 shows the results of tests conducted at different holding temperatures and holding times.

Pour the molten metal of the same starting material as in Example 1 into a lime mold,
The ingot obtained by holding at 000°C for 10 hours and then cooling at 2°C/min had internal cracks and was not sound. A disc with an outer diameter of 8 m and an inner diameter of 3.5 m was extracted using an ultrasonic processing machine from a disk sliced from this ingot.
When we investigated the magnetic properties of a ring with a thickness of 1 m, we found that the coercive force H
e is 0.07 oersted, magnetic flux density BL is 7400
It was Gauss.

As described above, according to the present invention, a healthy Go-Fe-Al-B-based magnetic alloy with excellent magnetic properties and no cracks can be manufactured.

Claims (1)

[Claims] After melting and solidifying a magnetic material containing Co, Fe, Al, and B, the entire solidified body is heated to the solidification temperature and 100% higher than that temperature.
A method for producing a Co-Fe-Al-B magnetic alloy, which comprises holding the temperature at a low temperature for 30 minutes or more, and then cooling it.