JPH0788532B2 - Method for producing Fe-Co soft magnetic material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a Fe—Co soft magnetic material having an extremely high saturation magnetic flux density, which is excellent in cold workability.

(Prior Art) The saturation magnetic flux density of an iron-based magnetic material is defined by the density of electrons (d electron density) that bear a magnetic moment per atom. According to the Slater-Pauling curve, the saturation magnetic flux density increases on the side having a smaller atomic number than Fe and decreases on the side having a larger atomic number than Co in the periodic table. That is, the Fe-Co alloy has the highest saturation magnetic flux density. The maximum is at the composition of Co: 30%, but the Curie temperature rises as the amount of Co increases,
The saturation magnetic flux density near room temperature is maximum at Co: 40%.

The Fe-Co alloy has a body-centered cubic lattice at 0 to 70% Co at room temperature, but becomes a CsCl type ordered alloy when the composition is about 50% Co. As the alloy is ordered, the soft magnetic properties are improved, such as an increase in magnetic permeability and a decrease in coercive force.

Therefore, the Fe-Co alloy has become the soft magnetic material with the highest saturation magnetic flux density, and has been used for the cores of devices such as small motors and printer heads that require a large output in a small volume.

The Fe-Co soft magnetic alloy has a stable ordered phase at room temperature and brings good magnetic properties, but it is a very brittle phase and cold working becomes difficult. Therefore, conventionally, prior to cold working, the material is quenched from the temperature range of the ordered disorder transformation temperature of 730 ° C or higher, that is, the disordered phase region or the γ phase region, and the precipitation of the ordered phase is prevented. By doing so, the workability was improved. The cooling rate in the quenching process is 73
When quenching from 0 ° C to 980 ° C (α: disordered phase), at a cooling rate of 400 ° C / sec or more that can prevent ordered disordered transformation, and in a temperature range of 980 ° C / sec or more (γ phase region) ) Quenching can cause martensitic transformation.
At a cooling rate of ℃ / sec or more, ordered phase cannot be precipitated. 50
It is necessary to cool to a temperature below 0 ° C. ("Jou
rnal of Applied Physics "Vol.32.348s," Hitachi Metals Technical Report "Vol.13.20, etc.) That is, after the conventional hot working is finished, the material is reheated for quenching treatment and then the above-mentioned conditions are applied. There is. Therefore, after hot working, bending, shearing, etc. of the material cannot be performed until the quenching process is performed, so it is processed into a sheet at a high temperature immediately after hot working, and subsequent quenching, It is subjected to steps such as pickling and cold working. The productivity is extremely low because of the small batch production.

Therefore, according to the conventional technique, the manufacturing cost of the Fe—Co based soft magnetic material has been extremely high.

(Problems to be Solved by the Invention) The present invention solves the problem of productivity in the prior art, and continuously, in a large amount, quickly and inexpensively after hot working the material,
It was made for the purpose of providing a manufacturing process of an Fe-Co based soft magnetic material that brings even a cold working step.

(Means for Solving the Problem) The gist of the present invention is as follows: (1) A steel containing Co: 40 to 60% by weight, the balance: Fe and inevitable impurities, in a temperature range of 730 ° C. or higher. It is characterized in that after processing, within the time when the processing strain is not released after processing, it is cooled from a temperature range of 730 ° C or higher to a temperature of 300 ° C or lower at a cooling rate of 100 ° C / s or higher, and then cold worked. Method for manufacturing Fe-Co soft magnetic material.

(2) Co: 40-60% by weight, and further V, Cr, C, Nb, T
It contains 0.01 to 3.5% in total of at least one of i, Mn, Mo, Sn, Pb, Zn, Ta, W, Ni and Al, and the balance: Fe
And steel consisting of unavoidable impurities are processed in the temperature range of 730 ° C or higher, and within the time when the processing strain is not released after the processing is completed, from the temperature range of 730 ° C or higher to the cooling rate of 100 ° C / s or higher, 30
A method for producing a Fe—Co soft magnetic material is characterized by cooling to a temperature of 0 ° C. or lower and then cold working.

The present invention will be described in detail below.

The Fe-Co soft magnetic material has a Co content of 40 to 60%, that is, Co: F
The magnetic permeability becomes maximum near e = 1: 1. Therefore, Co: 40-60
%.

The additive element shown in claim 2 is added to further improve the workability of the material. If the addition amount is not found in 0.01%, no effect is exhibited, while if it is added in excess of 3.5%, the composition ratio of Fe and Co responsible for magnetism is lowered, and the saturation magnetic flux density is lowered.

Next, the process conditions will be described.

As mentioned above, the Fe-Co soft magnetic material has a Co content of 40-60.
%, That is, the magnetic permeability becomes maximum in the vicinity of Co: Fe = 1: 1, but in this component range, the material has an ordered phase as a thermal equilibrium phase at room temperature. The object of the present invention is a high magnetic permeability alloy having this ordered phase.

The ordered phase is generally hard to deform and extremely difficult to process because a plurality of dislocations must move simultaneously during plastic deformation. It is difficult to apply cold working such as rolling, shearing, punching, etc. at room temperature to a hot-worked material in which the alloy targeted by the present invention is still in the ordered phase.

The present inventors have conducted research on process conditions for obtaining a cold-workable Fe-Co-based soft magnetic material, and as a result, immediately after hot working in a temperature range of 730 ° C or higher, 100 ° C / sec or higher was immediately obtained. It was found that cold working becomes possible if cooling is performed at a cooling rate of 300 ° C or lower. That is, in the present invention,
First, a steel ingot (steel piece) is hot-worked into a shape (= plate thickness) suitable for heat treatment. If the hot working is completed in the temperature range of 730 ° C or higher and immediately cooled from the temperature range, the heat treatment for preventing the appearance of the ordered phase can be realized and the reheating step can be omitted.

When the reheating process is performed as in the conventional technique, a cold-rollable material can be obtained by starting cooling from a temperature range of 730 ° C or higher and 980 ° C or lower, but a cooling rate of 400 ° C / sec or higher. Is required. When the plate thickness after hot working is 2 to 3 mm In order to perform such cooling just after hot working, a huge cooling tank or a powerful cooling water spray is required. The limit of the cooling capacity of the cooling equipment that is generally installed is 200 ℃ / se
c. Therefore, in the case of the conventional technique, the cooling must be started from the temperature range of 980 ° C. or higher which is the γ single phase range. This is because even if a part of the α phase is present, it is transformed into an ordered phase and causes cracks, scratches, etc. without plastic deformation during cold working, for example, cold rolling.

According to the process of the present invention of immediately cooling without reheating after hot working, even if cooling is started from a temperature range of 980 ° C. or higher, cooling can be performed.

First, consider the case where hot working is performed in the α single phase region. A work strain is introduced into a material during hot working, but if cooling is performed before the strain is released, the strain is frozen. That is, the material has a very high dislocation density. If this state is maintained and cooled below the ordered disordered transformation temperature, dislocations hinder the rearrangement of atoms and the ordered transformation is prevented or delayed. Therefore, it becomes possible to obtain a disordered phase even at an ordered disordered transformation temperature or lower.

By the way, in this temperature range, the ordered phase is thermally stable. If the cooling end temperature is not low enough or the cooling rate is not high enough, the thermal driving force for transformation is superior to the force that prevents transformation due to the above strain, and the ordered phase precipitates and the material Becomes brittle. The cooling end temperature of this limit is 300 ° C., and the cooling rate is 100 ° C./sec.

The time required to release the strain introduced by hot working is 5 seconds at temperatures above 730 ° C. Further, if the alloy addition shown in (2) of the claims is performed, the time is further extended to ten and several seconds.

When processing strain does not remain, that is, when processing is performed in a temperature range where dynamic recovery and dynamic recrystallization occur, the effect of the present invention cannot be obtained. However, in the present alloy, since it becomes a γ phase door in such a high temperature range, a martensite phase precipitates when cooled at a cooling temperature of 100 ° C./sec or more. This phase is cold rollable. Therefore, even if the ordered transformation is not prevented by the working strain, the ordered phase does not appear and cold working becomes possible.

However, even in this case, if the time from the hot working to the start of cooling is long, the α phase appears due to the temperature decrease. Since no processing strain is introduced into this α phase, it transforms into an ordered phase at a cooling rate of about 100 ° C / sec. Therefore, it is still necessary to start cooling immediately after hot working.

(Example) Table 1 shows an example of the present invention and a comparative example.

From Test Nos. 1 to 7, it can be seen that according to the present invention, the hot working material excellent in cold workability was obtained by cooling at 100 ° C./sec or more. However, No. 10 with a slow cooling rate has poor cold workability. From the test No.8, the time until the start of cooling after hot working becomes impossible after 8 seconds without the added alloy, but when there is the added alloy, as in No.5. Cold working was possible even after 12 seconds. But after 20 seconds N
The o.11 sample is not allowed. Test No. 9 is an example in which the cooling end temperature was high and the ductility deteriorated after the cooling end.
As in Test Nos. 2 and 3, when it was finished at 300 ° C or lower, cold working was possible.

(Effect of the Invention) According to the present invention, it is possible to mass-produce a Fe-Co alloy, which is a soft magnetic material having a very high saturation magnetic flux density, at low cost.

Claims (2)

[Claims] 1. A steel consisting of Co: 40 to 60% by weight, the balance: Fe and unavoidable impurities is processed in a temperature range of 730 ° C. or higher, and 730 ℃
Characterized by cooling from the above temperature range to a temperature of 300 ° C or less at a cooling rate of 100 ° C / s or more, and then cold working
Method for manufacturing Fe-Co soft magnetic material. 2. Co: 40-60% by weight, further V, Cr,
C, Nb, Ti, Mn, Mo, Sn, Pb, Zn, Ta, W, Ni and Al
Steel containing at least one of 0.01 to 3.5% in total, the balance: Fe and unavoidable impurities, at 730 ° C.
After processing in the above temperature range, within the time when the processing strain is not released after processing, cool from the temperature range of 730 ℃ or more to the temperature of 300 ℃ or less at a cooling rate of 100 ℃ / s or more, then cold work A method for producing an Fe-Co based soft magnetic material characterized by the above.