JPS61163252A - Manufacture of magnetic co-fe-al-b alloy - Google Patents

Abstract

PURPOSE:To prevent the cracking of a solidified body of a magnetic material contg. Co, Fe, Al and B by uniformly holding the whole of the solidified body at a prescribed temp. close to the solidifying temp. and by cooling the solidified body. CONSTITUTION:A magnetic material contg. essentially Co, Fe, Al and B is melted and solidified, and the whole of the solidified body is uniformly held at a temp. between the solidifying temp. and a temp. >=100 deg.C below the solidifying temp. The solidified body is then cooled. Thus, a sound ingot with no crack is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing a high permeability magnetic material, particularly a method for producing a Co-
The present invention relates to a method for obtaining a Fe-Al-B metal magnetic material as a crack-free and sound ingot.

(Prior Art) With the development of high-performance magnetic recording media, high-performance magnetic head materials are required.
A material with a strength of 0.00 Gauss or higher is required, and it is also required that this material satisfies good precision machinability in order to narrow the track.

However, the Ni-Zn and Mn-Zn-based ferrites that have been used for oxide recording media so far have a Boo of e or ooo Gauss at most, so it is difficult to fully bring out the characteristics as a high-performance metal recording medium. could not. For this reason, research into head materials such as Sendust and amorphous alloys is underway, but Sendust has problems with heat treatment, adhesion technology, deterioration of the sliding surface, etc.
Amorphous alloys have problems with heat treatment, adhesion, track processing, etc., so these are still at the prototype stage.
It has not yet been put into practical use.

Therefore, as a magnetic material of this type, Co-Fe is hard, has excellent wear resistance, and has high magnetic properties.
-Al-B alloys are attracting attention,
With the advancement of processing technology, problems related to processing have been solved, and the advantages of high hardness improving wear resistance and precision machinability are being recognized. It has the disadvantage that it is very difficult to obtain a sound ingot without cranks because it is a hard cell material.

In other words, conventional methods for producing Co-Fe-Al-B alloys include the melt solidification method (see Japanese Patent Publication No. 43-14591), the reaction sintering method (see Japanese Patent Publication No. 43-14591), and the boron diffusion method. (Refer to Japanese Patent Publication No. 55-12085). However, in the melting and solidifying method in which this type of alloy is melted with high frequency and solidified in a mold, many cracks occur in the ingot. In order to produce this, a method has been adopted in which the core is cut out from the fragments of this ingot, but this method has the disadvantage of a very low yield due to the presence of microcracks and the removal of the core from irregularly shaped fragments. . Regarding the sintering reaction method, 200
It has the disadvantage that it requires a sintering time of about 1 hour.
This method has the disadvantage that it is difficult to perform precision machining on the micron order because the alloy is obtained as a sintered body.
Since it is carried out through the steps of immersing it in boron after cold rolling and then subjecting it to a diffusion heat treatment, it has the disadvantage that the process is long and there are concerns about reproducing the magnetic properties of the obtained product.

(Structure of the Invention) The present invention relates to a method for producing a Co-Fe-Al-B based magnetic material as a high magnetic permeability magnetic material that solves such disadvantages.
, Al, and B are melted and solidified, the entire solidified body is held at a uniform temperature between the solidification temperature and a temperature at most 100°C lower than the solidification temperature, and then It is characterized by cooling.

That is, the present inventors melted a Co-Fe-Al-B alloy using high frequency according to a known method, poured it into a mold, and solidified and cooled it in the mold.
If the magnetic material that has reached the solidification temperature is held at a constant temperature lower than the solidification temperature but at least 100°C or higher than the solidification temperature and then cooled, the ingot obtained after cooling will be crack-free. The present invention was completed by conducting research on the holding temperature range, holding time, cooling speed, etc.

The present invention relates to Co-Fe-Al as a high permeability magnetic material.
- The raw material for obtaining this alloy is electrolytic cobalt with a purity of 99.8% or more, which is the same as <! 39.9% or more iron, 9
Known pure metals such as 9.99% or more flaky aluminum or 98.8% or more crystalline boron may be used, but if electrolytic cobalt is used as the cobalt, it will release absorbed gas when melted. Since there is a risk that the desired ingot may contain bubbles, it is preferable to melt these alloy materials, solidify them, and then crush them to use as a starting material.

In the method of the present invention, this co-'Fe-Al-B alloy material is first melted and solidified, and this is done by melting the starting material obtained above in an alumina crucible according to a known method. After high-frequency melting under the vacuum of the furnace, argon gas is introduced to create an inert gas atmosphere inside the furnace.
For example, it may be poured into a mold made of calcia (Ca0), magnesia (MgO), etc., in which a thermocouple is installed and a heater is placed around it so that the overall temperature can be controlled. The molten metal poured into this mold has a solidification temperature of about 1100'O to 1150°C.
Therefore, it solidifies when it is cooled to this temperature, but there is no need to particularly control the time until solidification, so it can be left to cool.

In the method of the present invention, if the solidified body obtained in this way is left to cool to room temperature, the obtained ingot will have many cracks. However, the temperature must be maintained at 100°C or less at most, and for this purpose, the mold temperature is maintained within the above temperature range by using the above-mentioned mold external heater for the solidified material. However, this method provides an industrial advantage in that it is possible to easily obtain an ingot with no cracks even if it is left to cool in the furnace to room temperature after the predetermined time has elapsed.

The time period for holding this solidified material within the temperature range indicated in "-" is usually 30 minutes or more, but this time varies depending on the size of the mold, and for larger sizes it is necessary to hold the culm for a longer period of time. It is sufficient to carry out a preliminary test for each size and measure and determine the cooling curve. Furthermore, since the solidification temperature differs depending on the alloy composition of the intended magnetic material, the solidification temperature should be measured in advance for each composition, and the range should be within 100 degrees Celsius or less below that temperature. Although it is necessary, cobalt 7 is the most standard.
0-80% by weight, iron 1O-20% by weight, aluminum 2
~10% by weight, and 2% to 10% by weight of boron have a solidification temperature of 1100°C to 1150°C, so this is 1000°C.
The temperature may be in the range of -1050 to 1100 to 1150°C, but it is necessary to prevent the temperature of the coagulated material from falling below 1000°C, even temporarily, within this holding time. After holding the solidified material in this temperature range for a predetermined period of time, the solidified material may be cooled down to room temperature by leaving it to cool in the furnace at a rate of about 50°C/minute, but if necessary, it may be necessary to gradually cool the solidified material while heating it. You may also do so.

Next, examples of the present invention will be given.

Example: A mixture consisting of 74.33% by weight of Kobal, 18.08% 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 −4 Torr or less. 1400℃ in an aluminum crucible in a vacuum of
After high-frequency melting in
It was crushed to about +s angle and used as an alloy raw material.

Next, 500g of this alloy raw material was heated 1x in an aluminum crucible.
1024 Melt by high frequency heating in a vacuum below □,
After it became molten metal and began convection, 10 torr of argon gas was introduced, and the high-frequency power was adjusted so that the temperature of the molten metal reached 1400°C while measuring it with a light thermometer. When this molten metal was poured into a mold made by molding lime powder with ethyl alcohol as a binder and baking it in the air at 950°C for 1 hour and left to cool, it started to solidify at 1130°C. At this point, the mold was heated using a heater installed outside the mold so that the temperature did not go below 1100°C, and the mold was kept at this temperature for 30 minutes, then cooled to room temperature at a cooling rate of 2°C/min to form a 25-diameter dragon circle. When a rod-shaped ingot was made, it had a good appearance and no cracks occurred on the cut surface. Next, the obtained ingot was processed using an ultrasonic processing machine to produce an outer diameter of 8mm and an inner diameter of 3mm.
．． 5. When we pulled out a ring with a thickness of 1.5 mm and examined its magnetic properties, we found that it had a magnetic flux density B1o? , 200
Gauss and coercive force Hc was 0.10 oersted.

In addition, in the above case, when cooling after being held at 1100°C for 30 minutes is done by cooling in the furnace at a rate of about 50°C/min without using a heater, the heating and holding temperature is 1050°C.

When the ingot was heated for 30 minutes at 1050°C for 30 minutes and then allowed to cool in a furnace without using a heater, the same treatment as above was performed, and in both cases, ingots with no cracks were obtained.

Comparative Example 1 In the method of the above-mentioned example, pouring into a lime mold 11
When the solidified body solidified at 30°C was allowed to cool without heating, the obtained ingot had a good appearance, but when this ingot was cut, many cracks were generated inside. When the lime mold was replaced with a copper mold and the solidified material was allowed to cool without being heated, the ingot broke into pieces when taken out from the mold.

Comparative Example 2 In the method of the above-mentioned example, the solidified body solidified in the lime mold was held at 1000°C for 30 minutes using a heater, and then cooled to room temperature at a cooling rate of 2°C/min. Although the ingot had a good appearance, cracks had occurred inside.

Further, in the above case, when the ingot was held at 1000° C. for 30 minutes and then allowed to cool in the furnace to room temperature without using a heater, cracks were generated inside the obtained ingot.

Claims (1)

[Claims] After melting and solidifying a magnetic material containing at least Co, Fe, Al, and B, the entire solidified body is maintained at a uniform temperature between the solidification temperature and a temperature at most 100°C lower than the solidification temperature. , followed by cooling C
Method for producing o-Fe-Al-B magnetic alloy