JP2008031553A - Method for manufacturing semi-hard magnetic material, and semi-hard magnetic material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for easily and industrially manufacturing a semi-hard magnetic material and the semi-hard magnetic material, without including a process for generating a reverse transformation austenite structure and a process for controlling the formation of the austenite with a cold-rolling after heat treatment for quenching the reverse transformation austenite structure, on the way of manufacturing process of the semi-hard magnetic material. <P>SOLUTION: In the manufacturing method for the semi-hard magnetic material, after adjusting a blank for semi-hard magnetic material composed, by mass, of 10.0-25.0% Ni, 2.0-6.0% Mo and the balance substantially Fe to ≥90% martensite structure with a heat treatment or a hot-working, the blank having ≥95% martensite having extensive structure by applying a cold-working of ≥50% reducing surface ratio, is obtained, and thereafter, the heat treatment for generating <30.0% the reverse transformation austenite structure, is applied at 400-570°C more desirably in the range of 470-530°C. The semi-hard magnetic material manufactured by this method has 1000-5600 A/m coercive force. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a semi-hard magnetic material used as a bias material for a security sensor, for example, and a semi-hard magnetic material.

A magnetic sensor tag (hereinafter referred to as a security sensor) that is attached to a product in order to prevent theft in a large mass retailer or the like includes a resonating magnetostrictive thin piece and a bias that applies a magnetic field thereto.
The security sensor system has a function that the magnetostrictive flakes resonate when the product is taken out of the store without paying the fee, but the alarm sounds, but if the fee is paid normally, the magnetostrictive flakes Therefore, it is necessary to change the resonance frequency so as not to resonate. In order to change the resonance frequency of the magnetostrictive flakes, it is necessary to change the magnitude of the magnetic field applied to the magnetostrictive flakes. More specifically, the bias that is in a magnetized state until the fee is paid, Needs to be changed to a demagnetized state.
For this reason, after the fee is paid, an operation of demagnetizing the bias is performed by a demagnetizing device attached to the counter counter. At this time, if the coercive force of the material constituting the bias is too large, it is difficult to demagnetize. Conversely, if the coercive force is too small, demagnetization tends to occur, but there is a problem that the magnetic field applied to the magnetostrictive thin piece in the magnetized state becomes small. Furthermore, since a function as a security sensor is lost when a slight reverse magnetic field is applied to the bias, reliability is poor.

The aforementioned biasing material has a coercive force of an intermediate size between a hard magnetic material (permanent magnet) having a high coercive force of 8000 A / m or more and a soft magnetic material having a low coercive force of 800 A / m or less. Semi-rigid magnetic materials are preferred.
Specifically, coercive force _{H c} is 1000~5600A / m, and more preferably the magnetic properties in the range of 1200~4000A / m, the difference of the on-off in magnetic state and demagnetized state is clear Therefore, it is desirable that the material has both a magnetic property exhibiting a high saturation magnetic flux density B _s and a residual magnetic flux density B _{r and a} high squareness ratio B _r / B _s in the BH curve. It is.

Semi-rigid magnetic materials are also used for relay applications and motor applications in addition to the security sensor applications described above.
As one of such semi-hard magnetic materials, Japanese Patent Application Laid-Open No. 60-116109 (Patent Document 1) describes Ni: 16.0 to 30.0% by mass and Mo: 3.0 to 10. An Fe—Ni—Mo based semi-hard magnetic material consisting of 0% and the balance being substantially Fe and a manufacturing method thereof are disclosed.
In this proposal, rolling, drawing, and swaging are performed at a processing rate of 20 to 80%. The metal structure at this time increases in the martensite structure according to the degree of processing and becomes an austenite + martensite structure. Then, the reverse transformed austenite is produced by maintaining the temperature at 600 to 700 ° C. for 10 minutes to 5 hours to obtain a mixed structure of 30 to 70% austenite structure and martensite structure, and processing with a reduction ratio of 50 to 98% again. And a final aging treatment is maintained at a temperature of 500 to 600 ° C. for 10 minutes to 5 hours to produce a reverse-transformed austenite structure, which is adjusted to an austenite structure of 30 to 70% by mass%. Disclosure.

  In Japanese Patent Publication No. 2000-504069 (Patent Document 2), Ni: 16.0 to 30.0%, Mo: 3.0 to 10.0% in mass%, and the balance is substantially Fe. As a method for producing a Fe—Ni—Mo semi-hard magnetic material, a material having a martensite structure is heated at about 475 to 625 ° C. for about 4 minutes to produce reverse transformed austenite, and then this reverse transformation is performed by cold rolling. Proposals have been made to obtain a desired coercive force (2400 A / m or more) by elongating austenite into an elongated structure.

JP 60-116109 A Special table 2000-504069 gazette

In the above-mentioned two proposals, in order to obtain a final martensite + austenite mixed structure, a reverse-transformed austenite is intentionally generated even in an intermediate process to obtain a martensite + austenite mixed structure.
In Patent Document 1, in order to generate a 30 to 70% austenite structure in a martensite structure, a mixed structure of an austenite structure and a martensite structure is continuously maintained during each step, and a desired metal structure is obtained by the last aging. adjust. However, the metal structure before final aging is likely to change each time due to, for example, thermal history, and the metal structure is also changed by the rolling reduction in each pass during cold rolling, so fix the final aging conditions. As a result, the magnetic characteristics may vary.

In Patent Document 2, the produced reverse-transformed austenite is cold-rolled to obtain an extended structure, and a layered structure of martensite and reverse-transformed austenite is being obtained. However, according to the study of the present inventor, when reverse-transformed austenite is cold-rolled, it transforms into martensite with a slight reduction rate, and the amount of transformation also depends on the temperature of the rolling roll in contact with the material (rolling temperature). It changes depending on. Therefore, a technique for adjusting the amount of reverse transformed austenite with the cold rolling process as the final process requires a high production technique.
In view of the above problems, an object of the present invention is to provide a method for producing a semi-rigid magnetic material that is capable of efficient industrial production and is relatively easy to adjust the amount of reverse transformed austenite. Furthermore, it is to provide a semi-hard magnetic material having a desired material structure and magnetic properties (coercive force and squareness ratio).

The inventor has intensively studied an optimal method for obtaining a semi-hard magnetic material having a desired coercive force by mixing a ferromagnetic martensite structure and a paramagnetic reverse-transformed austenite structure.
As a result, at least 95% or more of the martensite structure is substantially before the heat treatment that is performed prior to cold working or just before the heat treatment that produces reverse transformed austenite that determines the magnetic properties (particularly coercive force). The most stable method is to generate a paramagnetic reverse transformed austenite structure by heat treatment that produces a reverse transformed austenite that determines the magnetic properties to be performed at the end. The inventors have found that characteristics can be obtained and have reached the present invention.
Furthermore, as a result of studying the relationship between the structure of the semi-hard magnetic material, the residual magnetic flux density, and the squareness ratio, the present inventor has obtained a high residual magnetic flux density and angularity by forming a high hardness structure in which an intermetallic compound is finely precipitated. As a result of finding that the mold ratio can be obtained and examining the heat treatment temperature and holding time for obtaining a high hardness structure during the heat treatment for generating reverse transformed austenite, the present invention has been achieved.

That is, the present invention is a heat treatment or hot working of a semi-rigid magnetic material material in which Ni is 10.0 to 25.0% by mass, Mo is 2.0 to 6.0%, and the balance is substantially Fe. After adjusting to a martensite structure of 90% or more by cold working, a cold working with a surface reduction rate of 50% or more is performed to obtain a material having a martensite structure of 95% or more and having an extended structure, This is a method for producing a semi-hard magnetic material, which is subjected to a heat treatment for producing less than 30.0% of reverse transformed austenite in the range of 400 to 570 ° C.
Preferably, in the above semi-hard magnetic material manufacturing method, the amount of Ni in the semi-hard magnetic material is 15.0 to 22.0% by mass.
Preferably, the semi-hard magnetic material is a method for producing a semi-hard magnetic material in which the heat treatment or hot working performed on the semi-hard magnetic material is performed at 800 to 1150 ° C.
More preferably, it is a method for producing a semi-hard magnetic material in which the heat treatment for generating reverse transformed austenite is performed in the range of 470 to 530 ° C., and the method for producing a semi-hard magnetic material wherein the holding time of the heat treatment is 10 minutes or more. .

In the present invention, the mass is Ni: 10.0-25.0%, Mo: 2.0-6.0%, the balance is substantially Fe, and the metal structure is martensite and reverse transformed austenite. It is a semi-hard magnetic material that has a structure, exhibits a metal structure in which the amount of reverse transformed austenite in the structure is less than 30.0%, and has a coercive force Hc of 1000 to 5600 A / m.
Preferably, the Vickers hardness is 400 Hv or more, and the ratio B _r / B ₈₀₀₀ between the magnetic flux density B ₈₀₀₀ (T) and the residual magnetic flux density Br (T) at a magnetic field of 8000 A / m is 0.70 or more. Semi-rigid magnetic material.
More preferably, the semi-hard magnetic material is Ni: 15.0 to 22.0% by mass.

According to the present invention, the coercive force can be adjusted more easily than the case where the final process is cold-rolled by making the final manufacturing process of the semi-hard magnetic material a heat treatment that generates reverse transformed austenite. Therefore, the present invention is an important technique in industrially manufacturing a semi-hard magnetic material.
In addition, the semi-hard magnetic material of the present invention can obtain a desired range of coercive force, high residual magnetic flux density and squareness ratio by adjusting the amount and hardness of reverse transformed austenite. Can be used as a material.

As described above, an important feature of the present invention is that the austenite is formed by a process of intentionally generating reverse transformed austenite in the course of manufacturing a semi-hard magnetic material, or by cold rolling after heat treatment for producing reverse transformed austenite. The method of adjusting the amount of reverse transformed austenite and, in turn, the magnetic properties of the semi-hard magnetic material is adopted only by the heat treatment step for producing reverse-transformed austenite after the final cold rolling, and the semi-hard magnetic property is not included. The material manufacturing process is simplified.
Hereinafter, the manufacturing method of the semi-hard magnetic material of the present invention and the reason for the definition in the semi-hard magnetic material will be described.

First, the reason for defining the semi-hard magnetic material material and the chemical components of the semi-hard magnetic material of the present invention in the production method of the present invention will be described. In addition, content of each element is the mass%.
Ni: 10.0-25.0%
Ni is an essential element of the present invention necessary for adjusting the coercive force of the semi-hard magnetic material by generating a paramagnetic austenite structure by heat treatment for generating reverse transformed austenite. When the amount of Ni is lower than 10.0%, the temperature ( _Ms point) at which transformation starts from austenite to martensite increases in the process in which the reverse-transformed austenite generated during the heat treatment is cooled to room temperature.
As a result, most of the austenite generated during the heating of the heat treatment for generating reverse transformed austenite is transformed into martensite, and there is a concern that an appropriate amount of austenite cannot be left after the heat treatment for generating reverse transformed austenite. Therefore, the lower limit of the Ni amount is defined as 10.0%. On the other hand, if the upper limit of the Ni content exceeds 25.0%, the reverse transformed austenite although stabilized, remanence B _r of the semi-hard magnetic material decreases. Therefore, the upper limit of the amount of Ni is defined as 25.0%. A more desirable range of the amount of Ni is 15.0 to 22.0%.

Mo: 2.0-6.0%
Mo is an element effective for stabilizing austenite generated by reverse transformation from martensite. Further, Mo is finely precipitated in the structure as an intermetallic compound with Ni to increase the hardness of the semi-hard magnetic material, and consequently, to increase the residual magnetic flux density and the squareness ratio of the semi-hard magnetic material. However, both smaller effect of precipitation as an effect intermetallic compound of austenite stabilizing is less than 2.0%, since the range of more than 6.0% in the reverse remanence B _r of the semi-hard magnetic material decreases, It was specified in the range of 2.0 to 6.0%. From the viewpoint of increasing the hardness of the semi-hard magnetic material by fine precipitation as an intermetallic compound, a more desirable range of Mo is 3.0 to 5.5%.

The rest: substantially Fe
The balance is essentially Fe, in a semi-rigid magnetic material with a single chemical composition, which includes a ferromagnetic martensite structure (body-centered cubic lattice) and a paramagnetic austenite structure (face-centered cubic lattice). This is because it is necessary to make use of the phase transformation of the Fe-based alloy.
The semi-hard magnetic material of the present invention naturally includes inevitable impurities such as C, Si, Mn, P, S, O, and N. These impurity elements have a range that does not particularly affect the magnetic properties (saturation magnetic flux density B _S , residual magnetic flux density B _r , squareness ratio B _r / B _S , coercive force H _c ) of the semi-hard magnetic material, ≦ 0.10%, Si ≦ 1.0%, Mn ≦ 1.0%, P ≦ 0.10%, S ≦ 0.10%, O ≦ 0.010%, N ≦ 0.010% It is preferable to regulate.

Next, the reason for defining the manufacturing process of the present invention will be described.
The most characteristic feature of the production method of the present invention is that the martensite structure is 90% until just before the heat treatment that is performed prior to cold working or the heat treatment that produces reverse transformed austenite that determines the magnetic properties from the hot working step. It is a method of generating a paramagnetic reverse-transformed austenite structure by a heat treatment that generates a reverse-transformed austenite that determines the magnetic properties to be performed at the end, in a process that continues to maintain a substantially single phase of the martensite structure as described above. .
The martensite amount described below is calculated by the X-ray integral intensity ratio. Together with the calculation method of the reverse transformation austenite structure described later, the calculation method of the structure amount is shown below.

<Organization calculation method>
For example, a martensite structure of 90% or more refers to a structure in which the value of X _α (%) represented by the following formulas (1) to (3) is 90% or more.
Further, in the present invention, the term “reversely transformed austenite amount (or austenite amount)” means X _γ (%) represented by the formula (2).
X _α (%) = 100 × {ΣI _α / (ΣI _α + ΣI _γ )} (1)
_Xγ (%) = 100−X _α (%) (2)
ΣI _α = I _{α (110)} + I _{α (200)} + I _{α (211)} (3)
_{ΣI γ = I γ (111)} + I γ (200) + I γ (220) + I γ (311) ... (4)
Here, I _{α (110)} , I _{α (200)} , I _{α (211)} , I _{γ (111)} , I _{γ (200)} , I _{γ (220)} , I _{γ (311)} is the α (110), α (200), α (211) plane of the martensite structure, and γ (of the austenite structure, which are detected when the surface of the material is electropolished and X-ray diffracted, respectively. 111), γ (200), γ (222), and γ (311) planes.

A semi-hard magnetic material having the above composition is adjusted to a martensite structure of 90% or more by heat treatment or hot working.
In order to adjust to a martensite structure of 90% or more, the metal structure can be martensite by heating to a temperature high enough to cause martensite transformation and cooling at a cooling rate higher than air cooling. Heating for that purpose may be only heat treatment, only hot working, or a combination of heat treatment and hot working depending on the product weight and product dimensions. If the weight or size is large, blast cooling may be performed to increase the cooling rate. However, if the plate has a thickness of about 1.5 to 5.0 mm such as a hot rolled material, air cooling It doesn't matter.
In addition, water cooling that involves excessive deformation in the cooling process requires the addition of a process to correct the deformation before cold processing in the subsequent process, so air cooling, blast cooling, and mist cooling that sprays liquid are applied. Good to do.

The heating temperature during this heat treatment or hot working is preferably in the temperature range exceeding 700 ° C.
The reason for this is that if the cooling is performed by air cooling or higher after heating to a temperature range exceeding 700 ° C., the metal structure is easily adjusted to a martensitic structure of 90% or more. A temperature range of 800 ° C. or higher is particularly preferable, and the metal structure can be adjusted to a martensite structure of 90% or higher with more certainty.
Further, since the upper limit of the heating temperature cannot be expected to be further martensitic even when heated to a temperature exceeding 1200 ° C., the upper limit is preferably 1200 ° C., and a particularly desirable upper limit is 1150 ° C.
When heat treatment is performed, the heat treatment conditions may be a temperature of 800 to 1000 ° C. and a treatment time of 0.5 to 5.0 hours, and in the case of hot working such as hot rolling, about 900 to 1150 ° C. Is optimal.

Next, the material in which the above-described metal structure is adjusted to a martensite structure of 90% or more is subjected to cold working with a surface reduction rate of 50% or more, and the martensite structure is 95% or more and has a stretched structure. The material.
The reason why the area reduction ratio is set to 50% or more is to maintain and improve the martensite structure amount after the above-described heat treatment or hot working step to the same level or more, and to make the metal structure sufficiently stretched. Moreover, when the area reduction ratio is high, there is an effect of increasing the driving force of reverse transformation from martensite to austenite and the precipitation site of intermetallic compounds during the subsequent heat treatment for generating reverse transformed austenite. The area reduction rate is preferably 70% or more, and more preferably 90% or more.

Here, the reason why the structure of the material before heat treatment for generating reverse transformed austenite is defined in the method for producing a semi-hard magnetic material of the present invention will be described.
The first reason that the structure of the material is an extended structure is that this structure is necessary for stably presenting austenite generated at high temperature to room temperature by heat treatment for generating reverse-transformed austenite as a subsequent process. Because it is an organization. The stability of the reverse-transformed austenite generated at high temperature is related to the crystal grain size of austenite, and is stabilized by increasing the resistance to martensite transformation as the crystal grain size is finer.
An extended structure in which each crystal grain is finely stretched is suitable for stabilizing reverse transformed austenite. On the other hand, in a material having a recrystallized structure by hot working or heat treatment after hot working, the reverse transformed austenite generated at a high temperature is difficult to stabilize due to the large crystal grains. Therefore, the structure of the material was defined as an extended structure.

In addition, the second reason that the material has a stretched structure is that this anisotropic structure is required to obtain a high residual magnetic flux density B _r and a squareness ratio B _r / B _8000. is there. Furthermore, the reason why the material structure is composed of 95% or more of the martensite structure is that this structure is necessary for obtaining a high residual magnetic flux density _Br . More preferably, the martensite structure is 98% or more.

As an example for obtaining a plate-like material having the above-described stretched martensite structure of 95% or more, a plate-like material wound in a coil shape produced by hot rolling at a high temperature of 1000 ° C. or more is used. After holding for 0.5 to 5.0 hours in a batch furnace maintained at a temperature of ℃ or higher and then performing a heat treatment to air-cool to form a recrystallized martensite structure, cold rolling with a reduction in area of 90% or more is performed. It is recommended that the martensite structure be finely stretched.
In addition, since the material after hot rolling often has a recrystallized structure due to dynamic recrystallization during rolling, heat treatment using a batch furnace is required to shorten the process when manufacturing the material. The process may be omitted.

In addition, when there is a concern about cracking of the end portion of the material due to work hardening during cold working, a heat treatment step (hereinafter referred to as intermediate heat treatment) may be inserted in the middle of the cold working step. In this case, the intermediate heat treatment is the heat treatment in the present invention.
However, if the intermediate heat treatment is performed in a batch furnace, the production efficiency of the material is significantly reduced. Therefore, the intermediate heat treatment is preferably performed in a continuous furnace, and the heat adjusted so that the temperature of the material is 800 ° C. or higher. It is good to go through the furnace sequentially.
By performing this intermediate heat treatment, the plate material can be adjusted to a recrystallized martensite structure. When the intermediate heat treatment is performed, it is preferable to perform cold working after the intermediate heat treatment to obtain a stretched martensite structure again, and the area reduction rate during the cold working after the intermediate heat treatment is 90% or more. In other words, it is preferable to determine the thickness of the intermediate heat treatment so that the final area reduction rate is 90% or more when cold-working to the final thickness.
As described above, a plate-like material having an extended martensite structure of 95% or more can be obtained by the method described above.

Next, the reason why the temperature range of the heat treatment for generating reverse transformed austenite is set to 400 to 570 ° C. will be described. This heat treatment step for generating austenite is the final step.
The heat treatment for generating reverse-transformed austenite is an important process for adjusting the amount of austenite in the semi-hard magnetic material and thus adjusting the coercive force of the semi-hard magnetic material. This heat treatment also serves as an aging treatment for precipitating intermetallic compounds in conjunction with the formation of reverse transformed austenite, and the precipitation of this intermetallic compound reduces the residual magnetic flux density and the squareness ratio of the semi-hard magnetic material. It is also an important process for adjustment.
According to the study of the present inventor, for example, in order to obtain a coercive force in the range of 1000 to 5600 A / m desired for a bias material for a security sensor, the amount of reverse transformed austenite is adjusted to a range of less than 30.0%. It is necessary to do. Furthermore, in order to obtain a coercive force of 1200 to 4000 A / m, which is a more desirable range, the amount of reverse transformed austenite may be adjusted to a range of less than 30.0% (excluding 0%), and more preferably 5. It is good to adjust to the range of 0 to 25.0%.

The reason why the lower limit of the heat treatment temperature for generating reverse transformed austenite is 400 ° C. is that reverse transformed austenite is not produced at a temperature lower than 400 ° C., and the effect of increasing the coercive force to 1000 A / m is small. Further, when the temperature is lower than 400 ° C., the effect of precipitating the intermetallic compound is small, and consequently the effect of increasing the residual magnetic flux density and the squareness ratio is small. However, when the heat treatment temperature is in the range of 400 to 470 ° C., even if reverse transformed austenite is generated, it may be less than 5.0% which is a desirable range. Therefore, the lower limit of the heat treatment temperature is desirably 470 ° C. in order to more reliably make the amount of reverse transformed austenite 5.0% or more.
On the other hand, the upper limit of the heat treatment temperature for generating reverse transformed austenite was set to 570 ° C. The reason is that when the heat treatment temperature is higher than 570 ° C., recrystallization starts and the stretched anisotropic structure begins to collapse, and the residual magnetic flux This is because the density and the squareness ratio are lowered. Therefore, the upper limit of the heat treatment temperature for generating reverse transformed austenite is defined as 570 ° C. However, when the heat treatment temperature is in the range of 530 to 570 ° C., the amount of reverse transformed austenite tends to be close to 30.0%, and the residual magnetic flux density and the squareness ratio may be lowered. Therefore, a more desirable upper limit of the heat treatment temperature for generating reverse transformed austenite is 530 ° C. A more desirable range of the heat treatment temperature for generating reverse transformed austenite is 490 to 520 ° C.

  Next, as a desirable range, the reason for setting the holding time of the heat treatment for generating reverse transformed austenite to 10 minutes or more is that both the formation of reverse transformed austenite and the precipitation of intermetallic compounds are not allowed when the holding time is less than 10 minutes. This is because the coercive force and the squareness ratio in a desired range are difficult to obtain because it is sufficient. A more desirable holding time is 30 minutes or more. Further, the upper limit of the heat treatment holding time for generating reverse transformed austenite is not particularly specified, but it is preferably 5 hours or less as a range in which the productivity of the semi-hard magnetic material is not deteriorated.

  The heat treatment for generating reverse transformed austenite as the final step may be performed by putting a plate-like material wound in a coil shape into a batch furnace. The heat treatment atmosphere may be performed in a non-oxidizing atmosphere such as argon, nitrogen, hydrogen, or in a vacuum. The cooling after the heat treatment may be air cooling or blast cooling in which air, argon gas or nitrogen gas is blown.

Next, the reasons for defining the magnetic properties in the semi-hard magnetic material of the present invention will be described. The reason why the range of the coercive force Hc is defined as a range of 1000 to 5600 A / m is that this range is a range required as a bias material for a security sensor, for example. More preferably, it is 1200-4000 A / m.
As a desirable range, the ratio B _r / B ₈₀₀₀ between the magnetic flux density B ₈₀₀₀ (T) and the residual magnetic flux density Br (T) at a magnetic field of 8000 A / m is 0.70 or more. However, this is because the difference between the on / off states in the magnetized state and the demagnetized state is clearly desired, and is preferable for use as a bias material for a security sensor, for example. More preferably, the ratio B _r / B ₈₀₀₀ is 0.80 or more. In the present invention, the range of the residual magnetic flux density Br is not particularly defined, but for example, it is preferably 1.0 T or more for use as a bias material for a security sensor.

Next, the reason for defining the structure of the semi-hard magnetic material of the present invention will be described. The structure of martensite and reverse-transformed austenite is to inhibit the domain wall motion in the magnetization process and increase the coercive force by the presence of paramagnetic reverse-transformed austenite in the ferromagnetic martensite. . In addition, the structure | tissue which consists of a martensite and reverse transformation austenite of this invention points out the state by which the phase of a martensite and an austenite is detected when a semi-hard magnetic material is analyzed by X-ray diffraction.
In this structure, the amount of reverse transformed austenite is less than 30.0% because the coercive force may exceed 5600 A / m and the residual magnetic flux density in the range where reverse transformed austenite is 30.0% or more. This is because the squareness ratio decreases. A more desirable upper limit of the amount of reverse transformed austenite is 25.0%.
On the other hand, the lower limit of the amount of reverse transformed austenite is not particularly specified, but is preferably not 0% in order to obtain a coercive force of 1000 A / m or more, and the more desirable lower limit of the amount of reverse transformed austenite is 5.0%.

A desirable range is that the Vickers hardness of the semi-hard magnetic material is 400 Hv or more. If the hardness is within this range, it can be considered that the intermetallic compound is finely precipitated, and as a result This is because the residual magnetic flux density and the squareness ratio of the hard magnetic material can be increased.
Since the intermetallic compound produced in the semi-hard magnetic material of the present invention is extremely fine, it is extremely difficult to directly observe the intermetallic compound using an optical microscope or an electron microscope. However, when the intermetallic compound is finely precipitated, the hardness is increased by precipitation hardening, and thus the Vickers hardness can be used as an indicator that the intermetallic compound is precipitated.
If the Vickers hardness is 400 Hv or more, it can be considered that the intermetallic compound is finely precipitated, and B _r / B ₈₀₀₀ can be adjusted to 0.70 or more. Therefore, the Vickers hardness is specified in the range of 400 Hv or more. Note that the intermetallic compound formed during the semi-hard magnetic material of the present invention is considered to be a compound of Ni and Mo, and more specifically it is considered that the Ni 3 _Mo.
Semi-hard magnetic material produced by the production method of the present invention, it is possible to adjust the coercive force H _c in the range of 1000~5600A / m, it is possible to increase the residual magnetic flux density, squareness ratio B _r / B ₈₀₀₀ can be adjusted to a desired range of 0.70 or more. Therefore, the semi-hard magnetic material of the present invention can be used as a bias material for a security sensor, for example.

The following examples further illustrate the present invention.
After melting in a vacuum using an industrial scale mass production facility, a hot forging process at 1100 ° C. is performed, and a semi-rigid magnetic material No. 1 was obtained. This semi-hard magnetic material material No. The chemical composition of 1 is shown in Table 1.

No. A semi-rigid magnetic material having a composition of 1 was hot-rolled at 1100 ° C. to a thickness of 2.5 mm, further maintained in an Ar atmosphere maintained at 830 ° C. for 1 hour, and then air-cooled.
At this time, the amount of martensite after hot rolling was 98.8%, and the amount of martensite after heat treatment was 99.0%. The martensite amount is measured by the above-mentioned X-ray integral intensity ratio, and the martensite after hot rolling and after heat treatment are both martensite in which recrystallized austenite is transformed during cooling. It was an organization.
As cold working to be performed on the coil-shaped material after the heat treatment, cold rolling was performed in a range of 60% to 96% to obtain a plate-shaped material.

As an example of the cross-sectional structure of the plate-shaped material described above, FIG. 1 shows the result of observing a plate-shaped material with a surface reduction ratio of 96% with a scanning electron microscope.
It can be seen that an extended anisotropic structure is obtained along the rolling direction. In the X-ray diffraction pattern of the plate-like material having a surface reduction rate of 96%, only the diffraction peak of the body-centered cubic lattice is detected as shown in FIG. 2, and the structure has a martensite amount of 100%. I understand.
In addition, the amount of martensite of the plate material subjected to cold rolling with a reduction in area of 60% to 96% was 100%. In addition, as the area reduction rate of cold rolling is larger, each crystal grain has a stretched structure that is finely stretched, which affects the magnetic properties obtained by the heat treatment that later generates reverse transformed austenite. became. This result will be described later.
From this, in the manufacturing method of a present Example, it was confirmed that the reverse transformation austenite has hardly arisen in the middle process until cold rolling is completed.

From each plate-like material whose stretched martensite structure becomes 100% by cold rolling, a strip-shaped test piece of width 8 mm × length 90 mm and a test piece of width 10 mm × length 15 mm are cut out and reverse transformed austenite is obtained. As a heat treatment to be generated, a semi-hard magnetic material was obtained by performing a heat treatment by air cooling after holding in an Ar atmosphere furnace in a range of 425 to 650 ° C. for 1 hour.
The amount of austenite after heat treatment was measured by X-ray diffraction, and the hardness after cold rolling and after heat treatment was measured using a Vickers hardness meter under a load of 0.1 kg. Moreover, the direct current BH curve after the cold rolling and after the heat treatment was measured with a direct current magnetometer at a maximum applied magnetic field of 8000 A / m. From this BH curve, magnetic flux density B ₈₀₀₀ (T), residual magnetic flux density B _r (T), squareness ratio B _r / B ₈₀₀₀ and coercive force H _c (A / m) at a magnetic field of ₈₀₀₀ A / m are determined. did.

  As an example of an X-ray diffraction pattern after heat treatment for generating reverse transformed austenite, FIG. 3 shows an X-ray diffraction pattern of a material that has been subjected to a heat treatment that is air-cooled after holding a plate-like material with a surface reduction rate of 96% at 500 ° C. for 1 hour. . Martensite with a body-centered cubic lattice and austenite with a face-centered cubic lattice are detected, indicating that the structure is martensite and reverse transformed austenite.

FIG. 4 shows the influence of the heat treatment temperature for generating reverse transformed austenite on the amount of austenite for each plate-like material having a reduced area reduction ratio in cold rolling.
In any plate-shaped material with any reduction in area, the amount of austenite increases as the heat treatment temperature increases in the range of the present invention where the heat treatment temperature for generating austenite is 400 to 570 ° C. And after the austenite amount becomes maximum at 575 ° C., it decreases with increasing temperature. This is thought to be because austenite generated during heating becomes unstable because recrystallization starts at a temperature exceeding 575 ° C.
Moreover, in the range of 470-530 degreeC made into the more desirable range by this invention, it turns out that the amount of austenite is less than 30.0%.

On the other hand, FIG. 5 shows the influence of the heat treatment temperature for generating reverse-transformed austenite on the Vickers hardness for each plate-like material in which the reduction in cold rolling is changed.
In any plate-shaped material with any reduction in area, the Vickers hardness changes in an inverted V-shaped manner with respect to the heat treatment temperature for generating austenite, and the heat treatment temperature is in the range of 400 to 570 ° C. The hardness is higher than that in the cold rolled state.
From this, it can be seen that the intermetallic compound is precipitated after the heat treatment at 400 to 570 ° C. Furthermore, after heat treatment at 470-530 ° C., which is a more desirable range of the present invention, a hardness of 400 Hv or more is obtained, and it can be seen that intermetallic compounds are particularly finely precipitated.

FIG. 6 shows the residual magnetic flux density B _r (T), the squareness ratio B _r / B ₈₀₀₀ , the coercive force H after the heat treatment for generating reverse transformed austenite for the semi-hard magnetic material of each area reduction rate. _c shows the effect of heat treatment temperature on (A / m).
Remanence B _r after the heat treatment in the range of 425-500 ° C. showed higher values than state after cold rolling, in the temperature range exceeding 500 ° C., after lowering once again increases at temperatures above 575 ° C. is doing.
The squareness ratio B _r / B ₈₀₀₀ also shows a tendency similar to the residual magnetic flux density B _r, and increases in the range of 425 to 525 ° C. as the heat treatment temperature for generating reverse transformed austenite increases, but at 525 ° C. After reaching the maximum value, it decreases once and increases again at a temperature exceeding 575 ° C. Further, the coercive force generally increases with an increase in the heat treatment temperature for generating reverse transformed austenite, but once decreases at around 575 ° C. where the amount of austenite is maximum.
From FIG. 6, when the heat processing which produces | generates a reverse transformation austenite in the range of 400-570 degreeC prescribed | regulated by this invention is performed, the semi-hard magnetic material with a coercive force of 1000-5600 A / m is obtained. . Furthermore, when heat treatment for generating reverse transformed austenite at 470 to 530 ° C., which is a more desirable range in the present invention, is performed, a high squareness ratio (Br / B ₈₀₀₀ ) of 0.70 or more, which is a desirable range in the present invention. ) Is also obtained.

FIG. 7 shows the amount of reverse transformed austenite (%), Vickers hardness Hv0.1, residual magnetic flux density Br when a heat treatment for generating reverse transformed austenite is performed on a semi-hard magnetic material having a surface reduction ratio of 96%. The effects of the heat treatment temperature on (T), the squareness ratio Br / B ₈₀₀₀ and the coercive force Hc (A / m) are listed.
It can be seen that the behavior of the coercive force Hc accompanying the change in the heat treatment temperature is very similar to the behavior of the amount of reverse transformed austenite, and the coercive force can be controlled by adjusting the amount of reverse transformed austenite. Further, at a heat treatment temperature of 500 ° C. or higher, the behavior of the residual magnetic flux density Br and the squareness ratio Br / B ₈₀₀₀ has a reverse relationship with the reverse transformation austenite amount. It can also be seen that it is effective for controlling Br and B / B ₈₀₀₀ .
However, the behavior of Br and Br / B ₈₀₀₀ is very similar to the behavior of Vickers hardness Hv0.1 in the heat treatment temperature range of less than 500 ° C. with a small amount of reverse transformed austenite, and in this heat treatment temperature range, Br and Br / B ₈₀₀₀ indicates a high value.
This shows that in order to increase Br and Br / B ₈₀₀₀ , it is necessary to finely precipitate an intermetallic compound. Thus, there is a close relationship between the coercive force and the amount of reverse transformed austenite of the semi-hard magnetic material of the present invention, and there is also a close relationship with the higher precipitation state of Br or Br / B ₈₀₀₀ and intermetallic compounds.

In FIG. 6, the change in the magnetic characteristics accompanying the change in the heat treatment temperature for generating reverse transformed austenite shows a similar behavior when any of the area reduction ratios is applied, but Br, Br / B ₈₀₀₀ , Hc have different characteristic values depending on the area reduction rate, suggesting that the magnetic characteristics are dependent on the area reduction rate.
Therefore, the effect of the area reduction ratio on the respective characteristic values of Br, Br / B ₈₀₀₀ , and Hc in the case where the heat treatment is performed by air cooling after holding at 500 ° C. for 1 h after cold rolling. As shown in FIG. In the state of cold rolling (○ in the figure), even if the area reduction rate changes, the change of each characteristic value is not significant, but after heat treatment at 500 ℃ (● in the figure), the area reduction rate increases. At the same time, the characteristic values of Br, Br / B ₈₀₀₀ and Hc are increasing.
In addition, it can be seen that the increase in each characteristic value is particularly remarkable when the area reduction rate is 90% or more. From this, by increasing the reduction ratio of the cold rolling rate, a coercive force Hc of 1000 to 5600 A / m after heat treatment and a high squareness ratio Br / B _{8000 of} 0.70 or more, which is a preferable range, are obtained. It can be seen that the semi-rigid magnetic material has good results on the magnetic properties.

In order to interpret the results of FIG. 8 from the viewpoint of the material structure, after cold rolling, holding at 500 ° C. for 1 h, and then performing air-cooling heat treatment, reverse to Vickers hardness Hv0.1 in the cold-rolled state FIG. 9 shows the influence of the area reduction ratio on the amount of transformed austenite (%).
The hardness increases with an increase in the area reduction in any state after the heat treatment for generating reverse transformed austenite and after the cold rolling, but after the cold rolling (336 Hv) in the case of an area reduction of 60%. ) And after heat treatment (417 Hv), the difference in hardness is 81 Hv, whereas in the case of a surface reduction of 96%, the difference in hardness after cold rolling (378 Hv) and after heat treatment (484 Hv) is 106 Hv. Has spread.
Further, as described above, the amount of austenite after cold rolling is 0% in any area reduction material, but the amount of reverse transformed austenite generated after heat treatment is 1 when the area reduction rate is 60%. In the case of 0.2% and a reduction in area of 96%, it increased with the reduction in area to 6.3%.
As described above, the factors that depend on the area reduction rate in the post-heat treatment hardness and the amount of reverse transformation austenite that generate reverse transformed austenite are the aging precipitation sites of intermetallic compounds and the change from martensite to austenite due to the increase in the area reduction rate. This is probably because the driving force for reverse transformation increases. Then, the aging precipitation sites of these intermetallic compounds and the increase in the driving force of the reverse transformation from martensite to austenite are considered to be the causes of the change in magnetic properties accompanying the change in the area reduction ratio shown in FIG. Yes.

Based on the results of Example 1, an industrial trial production of a semi-hard magnetic material was performed in the following manufacturing process.
After melting in vacuum using an industrial scale mass production facility, a hot forging process at 1100 ° C. was performed to obtain a semi-rigid magnetic material material. This semi-hard magnetic material was hot-rolled at 1100 ° C. to a thickness of 2.5 mm, and then heat-treated in a vacuum heat treatment furnace. The chemical composition of the semi-hard magnetic material is the same as that shown in Table 1.
As heat treatment conditions, the temperature was raised to 830 ° C., held for 1 hour, and rapidly cooled with N ₂ gas. At this time, the amount of martensite after hot rolling was 98.8%, and the amount of martensite after heat treatment was 99.0%. In addition, the measuring method of the amount of martensite measured the amount of martensite by the above-mentioned X-ray integral intensity ratio, and the metal structures after hot rolling and after heat treatment were both recrystallized structures.
The heat-treated plate material is subjected to cold rolling with a surface reduction ratio of 60% to a plate thickness of 1 mm, and then the temperature of the plate material is about 900 ° C. as an intermediate heat treatment (continuous furnace heat treatment). The plate material was softened by passing it through the adjusted heating furnace. The plate-like material after the intermediate heat treatment was subjected to cold rolling with a reduction in area of 95% (hereinafter referred to as final cold rolling) to obtain a plate-like material having a thickness of 0.05 mm.
When the X-ray diffraction pattern of the plate-like material after the intermediate heat treatment and after the final cold rolling was examined, martensite was 100% in all cases.
Therefore, in the production process of Example 2, reverse transformed austenite is not generated in the middle of the process. Moreover, when the structure after the intermediate heat treatment and after the final cold rolling was observed, it was a recrystallized structure after the intermediate heat treatment, but after that, the final cold rolling with a reduction ratio of 95% became an extended structure. Confirmed that.

Further, from this plate-like material having a thickness of 0.05 mm, a test piece similar to that of Example 1 was cut out to produce reverse transformed austenite that was held for 1 hour in a small experimental Ar atmosphere furnace maintained at 475 to 525 ° C. After producing a semi-hard magnetic material by heat treatment, the amount of austenite and magnetic properties were evaluated. Furthermore, a heat treatment that generates reverse transformed austenite that is held in an Ar atmosphere maintained at 508 ° C. for 1 hour while being inserted into a large-scale heat treatment furnace for mass production in a state where a plate-like material having a thickness of 0.05 mm is wound in a coil shape After producing a semi-hard magnetic material, the amount of austenite and magnetic properties were evaluated.
Heat treatment temperature and austenite amount (%) for generating reverse transformed austenite, magnetic flux density B ₈₀₀₀ (T), residual magnetic flux density B _r (T), squareness ratio B _r / B ₈₀₀₀ , coercive force H _c (A / m) Table 2 shows a list of values. As an example of the BH curve of the semi-hard magnetic material, FIG. 10 shows a BH curve after heat treatment at 508 ° C. for 1 hour in a large-scale heat treatment furnace for mass production.

From Table 2, in the semi-hard magnetic material produced by the production method of the present invention, the amount of austenite falls within the desired range of 1.0 to less than 30.0%, and the coercive force in the range of 1000 to 5600 A / m. Has been obtained. Furthermore, it can be seen that the Vickers hardness is 400 Hv or more, which is a desirable range, and a high residual magnetic flux density of 1.16 T or more and a high squareness ratio of 0.797 or more can be obtained.
Moreover, the height of the squareness ratio in the semi-hard magnetic material of the present invention can also be seen from the BH curve shown in FIG.

Based on the results of Example 1, an industrial trial production of a semi-hard magnetic material was performed in the following manufacturing process.
After melting in vacuum using an industrial scale mass production facility, a hot forging process at 1100 ° C. was performed to obtain a semi-rigid magnetic material material. This semi-hard magnetic material was hot rolled at 1100 ° C. to a thickness of 2.5 mm. The chemical composition of the semi-hard magnetic material is the same as that shown in Table 1.
Next, in order to shorten the process, without performing heat treatment, cold rolling with a reduction rate of 98% was performed as it was to obtain a plate-like material having a plate thickness of 0.05 mm. Also in this plate-like material, it was confirmed that the martensite was 100% and had a stretched structure.
In the same manner as in Examples 1 and 2, a test piece was cut out from this plate-shaped material and subjected to a heat treatment for generating reverse transformed austenite in the range of 475 to 525 ° C. for evaluation.
Heat treatment temperature and austenite amount (%) for generating reverse transformed austenite, magnetic flux density B ₈₀₀₀ (T), residual magnetic flux density B _r (T), squareness ratio B _r / B ₈₀₀₀ , coercive force H _c (A / m) Table 3 shows a list of values.

  From Table 3, also in the manufacturing method of Example 3, the amount of austenite falls within the desired range of 1.0 to less than 30.0%, and a coercive force in the range of 1000 to 5600 A / m is obtained. Furthermore, a high residual magnetic flux density of 1.38 T or more and a high squareness ratio of 0.775 or more are obtained.

In the semi-rigid magnetic material produced by the production methods of Examples 1 to 3, reverse transformed austenite is produced by a process of intentionally producing reverse transformed austenite during the course of production, or by cold rolling after heat treatment for producing reverse transformed austenite. Even if it does not include the step of controlling the form of the semi-rigid magnetic material having the desired magnetic properties can be obtained by adjusting the amount of austenite in the heat treatment step of generating reverse transformed austenite after cold rolling. I understand.
That is, it has been proved that the manufacturing steps of the semi-hard magnetic material can be simplified by Examples 1-3.

A test piece was cut out from a semi-hard magnetic material having a surface reduction ratio of 95% and a thickness of 0.05 mm in the final cold rolling produced in Example 2, and the influence of the holding time during heat treatment for generating reverse transformed austenite was examined. The experiment was conducted.
FIG. 11 shows changes in Vickers hardness and austenite amount when the heat treatment temperature for generating reverse transformed austenite is fixed at 490 ° C. or 500 ° C. and the holding time is varied in the range of 5 to 60 minutes.
At any heat treatment temperature of 490 ° C. and 500 ° C., the Vickers hardness and the amount of austenite increase as the holding time increases. In addition, FIG. 12 shows changes in magnetic characteristics with increasing holding time.
As the retention time increases, the characteristic values of Br, Br / B ₈₀₀₀ , and Hc increase, and Br and Br / B ₈₀₀₀ are particularly characterized by holding for 10 minutes or more, which is a desirable range in the production method of the present invention. High value. Furthermore, it can be seen that Hc becomes 1000 A / m or more by holding for 30 minutes or more in a more desirable range. Thus, the heat treatment for generating reverse transformed austenite, which is the final step, is preferably performed for 10 minutes or more, more preferably 30 minutes or more, and thus heat treatment using a batch furnace is suitable.

In order to investigate the amount of austenite, hardness, and magnetic properties of the semi-hard magnetic material having the peripheral composition of the chemical composition shown in Table 1, 11 kinds of semi-hard magnetic material materials with varying amounts of Ni and Mo were vacuum-dissolved to 10 kg each. Each was made. The chemical composition of each semi-rigid magnetic material produced is shown in Table 4. 2-12.
These are all chemical compositions within the scope of the present invention. These were heated to 1100 ° C. and hot forged to obtain a forged material of about 20 mm × 60 mm × 600 mm, then each forged material was heated to 1100 ° C. and hot rolled, and hot rolled with a thickness of 2.5 mm. I got the material. After removing the oxide scale of the hot-rolled material, it was kept in an Ar atmosphere kept at 830 ° C. for 1 hour, and then heat-treated by air cooling. After this heat treatment, cold rolling with a reduction in area of 96% was performed to obtain a plate-like semi-hard magnetic material material having a plate thickness of 0.1 mm.

As in Example 1, a strip-shaped test piece having a width of 8 mm and a length of 90 mm is cut out from each semi-hard magnetic material, and heat treatment for generating reverse transformed austenite is performed in an Ar atmosphere furnace in a range of 425 to 650 ° C. After holding for 1 hour, heat treatment for air cooling was performed. By this heat treatment, each semi-hard magnetic material becomes a semi-hard magnetic material.
The DC BH curves after cold rolling and after heat treatment were measured with a DC magnetometer under the maximum applied magnetic field of 8000 A / m. From this BH curve, magnetic flux density B ₈₀₀₀ (T), residual magnetic flux density B _r (T), squareness ratio B _r / B ₈₀₀₀ and coercive force H _c (A / m) at a magnetic field of ₈₀₀₀ A / m are determined. did. Further, a sample having a width of about 8 mm and a length of about 15 mm was cut out from a part of the test pieces after the magnetic measurement, and subjected to an austenite amount measurement by X-ray diffraction and a Vickers hardness measurement.

Semi-hard magnetic material material No. 2, 3, 7, 9 and the semi-rigid magnetic material material No. FIG. 13 shows the influence of the heat treatment temperature on the amount of austenite when heat treatment for generating reverse transformed austenite is performed on 1. FIG.
No. 2, 3, 7, and 9 As in the case of No. 1, the amount of austenite increases with increasing heat treatment temperature. 3 and no. 9 shows the maximum austenite amount at 550 ° C. Although the amount of austenite to be generated varies depending on the difference in chemical composition, austenite is generated after heat treatment at any temperature of 400 to 570 ° C. of the present invention for any semi-hard magnetic material material, It can be seen that the amount of austenite is less than 30.0% after heat treatment at 470 to 530 ° C., which is a more desirable range in the present invention.

Also, semi-hard magnetic material material No. 2, 3, 7, 9 and the semi-rigid magnetic material material No. FIG. 14 shows the influence of the heat treatment temperature on the hardness when heat treatment for generating reverse transformed austenite is performed on No. 1.
Any semi-rigid magnetic material has a hardness higher than that in the cold-rolled state after heat treatment at any temperature of 400 to 570 ° C. of the present invention, and a hardening phenomenon due to fine precipitation of intermetallic compounds. Is happening. In particular, No. 1 with Mo amounts of 4.14%, 4.04%, and 5.95%, respectively. In Nos. 1, 2, and 7, a high hardness of 400 Hv or higher, which is desirable in the present invention, is obtained.

Next, semi-hard magnetic material material No. FIGS. 15 to 17 show the influence of the heat treatment temperature on the magnetic properties (Br, Br / B ₈₀₀₀ , Hc) when heat treatment for generating reverse transformed austenite is performed on 2 to 12. FIG.
15 shows a semi-rigid magnetic material No. in which the Mo amount is fixed to about 4% and the Ni amount is varied in the range of 12.52 to 20.19%. The influence of the heat treatment temperature on the magnetic properties of 2, 5, 8, and 11 is shown.
Br and Br / B ₈₀₀₀ increased with increasing heat treatment temperature, then once decreased in the range of 500 to 575 ° C. and then increased again. Further, Hc generally tends to increase with increasing heat treatment temperature. Each characteristic value of Br, Br / B ₈₀₀₀ , and Hc varies depending on the amount of Ni, but this factor is considered to be due to a difference in stability of reverse transformed austenite. That is, as the semi-hard magnetic material material of a high amount of Ni, since the austenite generated by reverse transformation from martensite is stable, as a result of a large amount of austenite remains at room temperature, Br, and Br / B ₈₀₀₀ is reduced, Conversely, Hc appears to rise.
Focusing on the relationship between the heat treatment temperature and the magnetic properties, after heat treatment at any temperature of 400 to 570 ° C. of the present invention, a coercive force of 1000 to 5600 A / m and a Br / B ₈₀₀₀ is obtained. Further, it can be seen that Br / B ₈₀₀₀ of 0.70 or more is more reliably obtained after heat treatment at 470 to 530 ° C., which is a more desirable range.

Similarly, FIG. 16 shows a semi-rigid magnetic material No. in which the Ni amount is fixed to about 15% and the Mo amount is varied in the range of 2.03 to 5.95%. The influence of the heat processing temperature on the magnetic characteristics of 3-7 is shown.
The heat treatment temperature dependence of the properties of Br, Br / B ₈₀₀₀ , and Hc shows a tendency similar to that shown in FIG. The value of each characteristic value varies depending on the amount of Mo. As the amount of Mo increases, Br decreases and Hc increases.
Focusing on the relationship between the heat treatment temperature and the magnetic properties, after heat treatment at any temperature of 400 to 570 ° C. of the present invention, a coercive force of 1000 to 5600 A / m and a Br / B ₈₀₀₀ is obtained. Further, it can be seen that Br / B ₈₀₀₀ of 0.70 or more is more reliably obtained after heat treatment at 470 to 530 ° C., which is a more desirable range.

Further, FIG. 17 shows a semi-rigid magnetic material No. in which the Ni amount is fixed to about 20% and the Mo amount is changed in the range of 2.10 to 5.08%. The influence of the heat processing temperature on the magnetic characteristics of 9-12 is shown.
The heat treatment temperature dependence of the properties of Br, Br / B ₈₀₀₀ , and Hc shows a tendency similar to that shown in FIGS.
Focusing on the relationship between the heat treatment temperature and the magnetic properties, after heat treatment at any temperature of 400 to 570 ° C. of the present invention, a coercive force of 1000 to 5600 A / m and a Br / B ₈₀₀₀ is obtained. Further, it can be seen that Br / B ₈₀₀₀ of 0.70 or more is more reliably obtained after heat treatment at 470 to 530 ° C., which is a more desirable range.
From the above examples, the semi-hard magnetic material of the present invention manufactured by the method defined in the present invention has the chemical composition of the semi-hard magnetic material within the scope of the present invention, and has a coercive force of 1000 to 5600 A / m. It can be seen that a high squareness ratio (Br / B ₈₀₀₀ ) of 0.70 or more can be obtained, and for example, it can be applied as a bias material for a security sensor.

It is a cross-sectional electron micrograph of the plate-shaped raw material which applied the manufacturing method of this invention. It is an X-ray diffraction pattern of the plate-shaped raw material which applied the manufacturing method of this invention. It is an X-ray diffraction pattern of the semi-hard magnetic material of the present invention. It is a figure which shows the influence of the heat processing temperature which produces | generates reverse transformation austenite which has on the amount of austenite. It is a figure which shows the influence of the heat processing temperature which produces | generates reverse transformation austenite which has on Vickers hardness. It is a figure which shows the influence of the heat processing temperature which produces | generates a reverse transformation austenite which acts on a residual magnetic flux density, a squareness ratio, and a coercive force. It is a figure which shows the influence of the heat processing temperature which produces | generates a reverse transformation austenite on the amount of austenite, Vickers hardness, a residual magnetic flux density, a squareness ratio, and a coercive force. It is a figure which shows the influence of the area reduction rate at the time of cold rolling which exerts on residual magnetic flux density, squareness ratio, and coercive force. It is a figure which shows the influence of the area reduction rate at the time of cold rolling which acts on the amount of austenite and Vickers hardness. It is a BH curve of the semi-hard magnetic material of the present invention. It is a figure which shows the influence of the holding time at the time of the heat processing which produces | generates reverse transformation austenite which has on the amount of austenite and Vickers hardness. It is a figure which shows the influence of the holding time at the time of the heat processing which produces | generates a reverse transformation austenite which has on a residual magnetic flux density, squareness ratio, and a coercive force. It is a figure which shows the influence of the heat processing temperature which produces | generates reverse transformation austenite which has on the amount of austenite. It is a figure which shows the influence of the heat processing temperature which produces | generates reverse transformation austenite which has on Vickers hardness. It is a figure which shows the influence of the heat processing temperature which produces | generates a reverse transformation austenite which acts on a residual magnetic flux density, a squareness ratio, and a coercive force. It is a figure which shows the influence of the heat processing temperature which produces | generates a reverse transformation austenite which acts on a residual magnetic flux density, a squareness ratio, and a coercive force. It is a figure which shows the influence of the heat processing temperature which produces | generates a reverse transformation austenite which acts on a residual magnetic flux density, a squareness ratio, and a coercive force.

Claims (18)

Ni: 10.0 to 25.0% by mass, Mo: 2.0 to 6.0%, and semi-hard magnetic material made of Fe substantially as the balance is 90% or more by heat treatment or hot working. After adjusting to a martensite structure, cold working with a reduction in area of 50% or more is performed to obtain a material having a martensite structure of 95% or more and an extended structure, and then the material is heated to 400 to 570 ° C. A method for producing a semi-rigid magnetic material, comprising performing a heat treatment to produce reverse transformed austenite in an amount of less than 30.0%. The method for producing a semi-rigid magnetic material according to claim 1, wherein the Ni content of the semi-rigid magnetic material is 15.0 to 22.0% by mass. 3. The method for producing a semi-hard magnetic material according to claim 1, wherein the Mo content of the semi-hard magnetic material is 3.0% to 5.5% by mass. The method for producing a semi-hard magnetic material according to any one of claims 1 to 3, wherein the heat treatment or hot working performed on the semi-hard magnetic material is performed at a temperature exceeding 700 ° C and not more than 1200 ° C. The method for producing a semi-hard magnetic material according to any one of claims 1 to 3, wherein the heat treatment or hot working performed on the semi-hard magnetic material is performed at 800 to 1150 ° C. The method for producing a semi-hard magnetic material according to any one of claims 1 to 3, wherein the semi-hard magnetic material is subjected to heat treatment at 800 to 1000 ° C and hot working at 900 to 1150 ° C. The method for producing a semi-rigid magnetic material according to any one of claims 1 to 6, wherein the area reduction rate of the cold working is 70% or more. The method for producing a semi-rigid magnetic material according to any one of claims 1 to 6, wherein the area reduction rate of the cold working is 90% or more. The method for producing a semi-hard magnetic material according to any one of claims 1 to 8, wherein the heat treatment for generating reverse transformed austenite is performed in a range of 470 to 530 ° C. The method for producing a semi-hard magnetic material according to any one of claims 1 to 8, wherein the heat treatment for generating reverse transformed austenite is performed in a range of 490 to 520 ° C. The method for producing a semi-hard magnetic material according to any one of claims 1 to 10, wherein a holding time of the heat treatment for generating reverse transformed austenite is 10 minutes or more. The method for producing a semi-rigid magnetic material according to any one of claims 1 to 11, wherein a heat treatment for generating reverse transformed austenite by over 0% and less than 30.0% is performed by heat treatment for producing reverse transformed austenite. . The method for producing a semi-hard magnetic material according to any one of claims 1 to 11, wherein a heat treatment for generating 5% to 25.0% of reverse-transformed austenite is performed by heat treatment for generating reverse-transformed austenite. Ni: 10.0-25.0% by mass%, Mo: 2.0-6.0%, the balance is substantially Fe, the metal structure is a martensite and reverse transformed austenite structure, and the structure A semi-hard magnetic material characterized in that the amount of the reverse transformed austenite is less than 30.0% and has a coercive force Hc of 1000 to 5600 A / m. Vickers hardness is 400 Hv or more, and ratio B _r / B ₈₀₀₀ between magnetic flux density B ₈₀₀₀ (T) and residual magnetic flux density Br (T) at a magnetic field of 8000 A / m is 0.70 or more. The semi-rigid magnetic material according to claim 14. The semi-rigid magnetic material according to claim 14 or 15, wherein Ni is 15.0 to 22.0% by mass. The semi-rigid magnetic material according to any one of claims 14 to 16, wherein the Mo content of the semi-rigid magnetic material is 3.0 to 5.5% by mass. The ratio B _r / B ₈₀₀₀ between the magnetic flux density B ₈₀₀₀ (T) and the residual magnetic flux density Br (T) at a coercive force Hc of 1200 to 4000 A / m and a magnetic field of 8000 A / m is 0.80 or more, and the residual magnetic flux density Br is The semi-rigid magnetic material according to any one of claims 14 to 16, wherein the semi-hard magnetic material is 1.0T or more.