JPS6146546B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a Fe-Cr-Co magnet alloy, particularly an Fe-Cr-Co magnet alloy having an oxygen content of 50 to 800 ppm, and a method for producing the same. It is widely known that an alloy consisting of 10 to 40% Cr, 3 to 30% Co, and the balance iron has excellent magnetic properties as a permanent magnet material. ~5% of Ti, Al, Mn, Zr, W, V,
It is also known that the magnetic properties can be further improved by adding Nb, Mo, Si, etc. as a residual active ingredient or as a deoxidizing agent that is not a residual active ingredient.

That is, by adding a small amount of the above-mentioned additive elements, at least one of the residual magnetic powder density Br, coercive force Hc, and maximum energy product (BH) max can be improved, or the magnetic properties can be improved. Although the squareness may be improved, the theoretical basis for this is not necessarily clear, and therefore the selection of the above additive elements, the amount added, and the heat treatment conditions are based solely on experience based on the results of numerous experiments. I had no choice but to decide.

Conventionally, when a spinodal decomposition type magnet alloy based on Fe, Cr, and Co is melted, deoxidation treatment is generally performed. The substances used for deoxidation treatment have affinity with oxygen.
It is an element with a high level of energy, and MM (Mitsuyu Metal), Ti, Al, Mn, Be, etc. are usually used.
The amount of these deoxidizing additives to be added depends on the oxygen content of the raw materials (Fe, Cr, Co), melting temperature, melting time, atmosphere during melting (air, inert gas, etc.), and whether stirring is used. However, experiments have shown that high-frequency melting in the atmosphere using these deoxidizing additives results in a large amount of dissolved oxygen during melting, and that Therefore, it has been confirmed that it generally contains about 1000 ppm of oxygen.

The present inventor focused on the amount of dissolved oxygen and discovered that by limiting it within a predetermined range, the magnetic properties could be significantly improved, and thus completed the present invention.

That is, the optimal range of this oxygen amount is 50 to 800 ppm.
It was confirmed that the highest performance magnetic alloy can sometimes be obtained by setting the concentration to more preferably 100 to 500 ppm.

Therefore, the magnet alloy of the present invention contains oxygen within the above range, and in its production,
The additives and atmosphere are controlled so that the oxygen content is within the above range, and the process is carried out by melt casting.
A system magnet alloy is obtained. Also, conventionally,
Instead of the fragility of the physical basis when small amounts of Ti, Zr, W, Mo, V, etc. were simply added empirically,
By recognizing the general physical background rather than the oxygen content, we can provide a general guideline for selecting additives and their amounts, as well as Fe-- which can be extended even when no additives are used. A new method for manufacturing a Cr--Co magnetic alloy is provided.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

Figure 1 shows 27.5% Cr and 8% Cr by weight percentage.
This is a graph showing the relationship between the magnetic properties and nitrogen content with respect to the oxygen content of a magnet alloy consisting of Co, the balance Fe, and unavoidable impurities of about 0.5% or less.
Comparing the relationship between He and maximum energy product (BH) max, the oxygen content is between 50 and 800 ppm, especially
It can be seen that excellent magnetic properties can be obtained at 100 to 500 ppm.

Therefore, the physical background of the role played by the amount of oxygen in Fe-Cr-Co alloys is interpreted to be the pinning effect caused by oxides in the domain wall.

This is because in the correlation between the amount of oxygen and the coercive force Hc, Hc tends to decrease as the amount of oxygen decreases, and the residual magnetic flux density Br increases as the amount of oxygen decreases, and the hysteresis loop. It is known that the squareness, ie, η=(BH)max/Br·Hc, decreases as the amount of oxygen increases, and a maximum value of (BH)max occurs.

On the other hand, when performing deoxidation treatment by adding deoxidizing elements during melting of the above alloy, deoxidizing elements (e.g.
It is known that when a large amount (2% or more) of Ti) is added, Br decreases and (BH)max decreases rapidly. In other words, this indicates an adverse effect due to the above-mentioned additive elements remaining in the alloy, and although it depends on the type of additive elements, the deoxidizing elements and other additive elements themselves do not contribute to improving magnetic properties. Rather, it shows that its moderate deoxidizing effect plays a major role.

FIG. 2 is a schematic diagram of an example of heat treatment recommended for manufacturing a magnetic alloy having the following composition according to the present invention. The raw material used was a mixture of 27% Cr, 8% Co, and the balance Fe, which was solution-treated by high-frequency melting at 900℃ or higher for about 30 minutes.
It takes about a minute to an hour. After that, it is once cooled with water, then reheated to around 620-640℃, the first stage of magnetic field treatment is performed in a magnetic field of about 2000-3000Oe or more, and then furnace-cooled to a temperature of around 600-620℃. The second step is magnetic field treatment and water cooling. In order to enter the so-called aging stage, first, the material is heated to approximately 600 to 620°C, which is almost the same temperature as the second stage magnetic field treatment, and then maintained at a constant temperature for several hours, followed by cooling at a rate of approximately 2.5°C to approximately 520°C. Aging treatment is performed by slow cooling continuously or in multiple stages at a temperature of about 20
It is cooled down to around 500°C at a rate of °C/h and then cooled with water. The magnetic field processing time for the first stage is approximately
The second stage takes about 40 minutes, the constant temperature aging time takes about 5 hours, and the slow cooling time takes about 40 hours, making the total processing time about 47 hours.

In addition, in the above heat treatment, for example, the temperature of the solution treatment for α single phase is particularly dependent on the Co content of the alloy, so it is necessary to set it a little higher in consideration of safety. Accurate control of cooling may require an expensive control system, so we adopted an appropriate multi-stage aging method with a temperature difference of 10°C or 20°C, etc., which allows production of magnets with virtually identical performance. It's okay.

The process of adjusting the oxygen content in the alloy to 50 to 800 ppm, preferably 100 to 500 ppm, is performed during the melting period before the solution treatment.

That is, after the alloy is melted and cast, the alloy is not melted again, and during the heat treatment period after the above-mentioned solution treatment, the content state is unlikely to change significantly, such as oxygen melting, and if necessary, This is because it is possible to carry out heat treatment by controlling the atmosphere such as an inert atmosphere, and on the other hand, it is possible to change the content by dissolving oxygen during the melting of the alloy, greatly changing the content, or conversely, by deoxidizing treatment.

Therefore, in the above adjustment process, first, the raw materials Fe,
After weighing the amount of oxygen contained in each of Cr and Co and averaging them according to the alloy composition, if this is less than 50 ppm, oxygen is supplied to the melting atmosphere under the optimum oxygen partial pressure. By controlling the temperature and melting time, oxygen is melted and injected until the above-mentioned preferred oxygen amount reaches 100 to 500 ppm.

Further, even when the amount of oxygen contained in the material is less than the total average measured amount, i.e., 50 to 300 ppm, a small amount of oxygen is supplemented and dissolved and injected by substantially the same process as in the above case.

When the raw material oxygen content is 300 to 500 ppm, it is melted in an inert gas atmosphere with the oxygen partial pressure set to 0.

When the amount of oxygen contained in the material is 500 to 800 ppm,
In an atmosphere of partial pressure of a reducing gas such as H ₂ or NH ₃ , the melting temperature and time are controlled to remove a portion of the oxygen contained.

Alternatively, a trace amount of a metal containing H may be mixed into the melt.

Furthermore, when the amount of oxygen contained in the material is 800 ppm or more, the material contains, for example, M.M.
Mix an appropriate amount of metals with strong oxygen affinity such as Ti, TiH ₁ to ₄ , Al, Mn, Be, etc., and preferably stir and dissolve under reduced pressure of oxygen or in a reducing gas atmosphere to convert the oxygen in the raw materials into metals with strong oxygen affinity. The amount of oxygen in the magnet alloy is suppressed to 100 to 500 ppm by fixing it and collecting it as oxide slag with a light specific gravity and removing it. If the amount of the oxygen-affinity metal added is too small, the desired deoxidizing effect will not be obtained, and if it is too large, it will have an adverse effect on the magnetic properties.
Depending on the amount of oxygen contained in the material, the weight percentage is about 0.1 to 5%.

The deoxidation or oxygen injection treatment described above preferably involves extruding a portion during the melting process and detecting and checking the oxygen content using a means such as spectrophotometry, preferably automatically determining the amount of oxygen in the atmosphere. This is done by controlling the heating rate, heating time, stirring, etc.

Since Cr, Ti, Zr, etc. have an affinity for nitrogen, when the above melting treatment is performed in the atmosphere or under nitrogen partial pressure, the content is reduced as shown in Figure 1. It has been found that the nitrogen content also reaches its maximum value in the range where the oxygen content is optimal. Therefore, when performing the above melting treatment in an atmosphere containing nitrogen, the amount of nitrogen contained in the molten metal is detected instead of being detected, and deoxidation or oxygen injection treatment is performed depending on the amount of nitrogen. Control is also recommended.

As mentioned above, the amount of oxygen contained is 100 to 500 ppm
The magnetic alloy of the present invention created as follows:
By appropriately selecting the blending ratio of raw materials, heat treatment conditions, etc., the performance can be improved to the above 8% Co, 27%
When using the above-mentioned heat treatment method for Cr and balance Fe alloys, extremely high performance products with residual magnetic flux density Br of 14.5 KG, coercive force Hc of 600 Oe, and maximum energy product (BH) max of 6.5 MGOe can be obtained. confirmed.

Since the present invention is configured as described above, according to the present invention, it is necessary to contain additive elements such as Mo, Ti, Zr, W, Si, V, Ni, etc. as active ingredients in an amount of about 0.5% or more. To provide an Fe--Cr--Co based magnet alloy in which the amount of addition is easily determined even when it is not required or is required, and which always has equally excellent magnetic properties regardless of the raw material. It is something.

It should be noted that the manufacturing method of the present invention is not limited to the above-mentioned examples, and in particular regarding deoxidation and oxygen injection treatment means, widely known means can be used within the scope of the purpose of the present invention. The present invention encompasses all of them.

[Brief explanation of the drawing]

Figure 1 shows 27.5% Cr and 8% Cr by weight percentage.
2 is a graph showing the relationship between magnetic properties and nitrogen content with respect to oxygen content of a magnet alloy consisting of Co and the balance iron; FIG. 2 is a schematic diagram showing an example of heat treatment during production of the magnet alloy according to the present invention. It is.

Claims (1)

[Scope of Claims] 1 Fe-Cr made by melting 10 to 40% Cr, 3 to 30% Co, and the balance iron by weight percentage
-In Co-based magnetic alloy, its oxygen content is 50
Fe―Cr― characterized by having a content of 800ppm to 800ppm
Co-based magnetic alloy. 2. Fe according to claim 1, wherein the oxygen content is 100 to 500 ppm.
-Cr-Co magnetic alloy. 3 Heat and melt 10 to 40% Cr, 3 to 30% Co, and the balance iron in terms of weighed percentage, and desorb during the melting process mentioned above so that the oxygen content becomes 50 to 800 ppm. A method for producing a Fe-Cr-Co magnetic alloy, which comprises performing acid treatment or oxygen injection treatment. 4. Claim 3, characterized in that the oxygen content is 100 to 500 ppm.
Manufacturing method of Fe-Cr-Co magnet alloy. 5. Claim 3 or 4, characterized in that when the oxygen content is 300 ppm or less, the melting treatment is performed in an oxygen partial pressure atmosphere.
Manufacturing method of Fe-Cr-Co magnet alloy. 6. Fe- as defined in claim 3 or 4, characterized in that when the oxygen content is 300 to 500 ppm, the melting treatment is performed in an inert gas atmosphere with an oxygen partial pressure of 0. Manufacturing method of Cr-Co magnetic alloy. 7 When the oxygen content is 500 ppm or more, the above melting treatment is performed in a reducing gas atmosphere, and if necessary, a metal having an affinity for oxygen is added in an amount of 0.1 to 5% by weight percentage into the alloy material. A method for producing a Fe--Cr--Co based magnetic alloy according to claim 3 or 4, characterized in that: 8. Claims 3 and 4, characterized in that during the melting treatment period, the oxygen content is detected and the deoxidation treatment or oxygen injection treatment is performed according to the detected value. , Section 5, Section 6 or Section 7
A method for producing the Fe-Cr-Co magnetic alloy described in . 9. Claims 3 and 4, characterized in that during the melting treatment period, the nitrogen content is detected and the deoxidation treatment or oxygen injection treatment is performed according to the detected value. , Section 5, Section 6 or Section 7
A method for producing the Fe-Cr-Co magnetic alloy described in .