Semi-hard magnetic steel materials and semi-hard magnetic steel parts

Abstract

To provide a low-cost semi-hard magnetic steel having sufficient workability and sufficient semi-hard magnetic properties, and to provide a semi-hard magnetic steel component.SOLUTION: A semi-hard magnetic steel is provided, containing: 0.10 mass% or more and 1.50 mass% or less of C; more than 0 mass% and 0.75 mass% or less of Si; more than 0 mass% and 1.00 mass% or less of Mn; more than 0 mass% and 0.050 mass% or less of P; more than 0 mass% and 0.050 mass% or less of S; more than 0 mass% and 0.30 mass% or less of Cu; more than 0 mass% and 0.30 mass% or less of Ni; more than 0 mass% and 1.00 mass% or less of Mo; 0.50% or more and 2.00 mass% or less of Cr; more than 0 mass% and 0.100% or less of Al; and more than 0 mass% to 0.0100 mass% or less of N; and the balance composed of iron and inevitable impurities, wherein the magnetic steel includes 80 area% or more of a tempered martensitic phase, and a half width of the X-ray diffraction peak from the (211) plane is 3.1° or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This disclosure relates to semi-hard magnetic steel materials and semi-hard magnetic steel components. [Background technology]

[0002] In recent years, there has been an increasing demand for electromagnetic components that require excellent magnetic properties both when energized and de-energized. These components utilize semi-rigid magnetic materials with coercivity (500-20000 A / m) that is intermediate between that of permanent magnets and soft magnetic materials.

[0003] Semi-hard magnetic materials, while normally exhibiting soft magnetism as a raw material, achieve higher coercivity than soft magnetic materials by controlling the metallic structure to suppress the movement of magnetic domain walls. Generally, semi-hard magnetic materials are desired to have a coercivity of 500-20000 A / m while maintaining a high angularity ratio, which depends on the magnitude of the base material's magnetic moment and the ease of magnetic domain wall movement.

[0004] Patent Document 1 discloses a semi-hard magnetic steel material containing 5.0 mass% or more of Ni. Patent Document 2 discloses a semi-hard magnetic steel material containing 2.0 mass% or more of Cu. Non-Patent Document 1 discloses an Fe-Co-V type semi-hard magnetic steel material (Co content is, for example, 30 mass% or more, and V content is, for example, 3 mass% or more). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2013 / 027665 [Patent Document 2] Japanese Patent Publication No. 2008-274399 [Non-patent literature]

[0006] [Non-Patent Document 1] Yasuo Kimura, "Current Status of Semi-Hard Magnetic Materials," Bulletin of the Japan Institute of Metals, 1970, Vol. 9, No. 11, pp. 703-707. [Overview of the project]

Problems to be Solved by the Invention

[0007] In the prior art as disclosed in Patent Documents 1 to 2 and Non-Patent Document 1, all semi-hard magnetic steel materials contain a large amount (for example, 2.0 mass% or more) of expensive elements such as Ni, Cu, Co, and / or V. In such a case, the raw material cost becomes extremely high, and there is also a risk of deterioration in workability. Simply reducing the amount of the above elements can reduce costs and increase the magnetic moment, but the above elements are also useful elements for suppressing the movement of magnetic walls. In the prior art, reducing the above elements has a greater impact on the semi-hard magnetic properties than increasing the magnetic moment because the effect of suppressing magnetic wall movement is reduced. That is, in the prior art, reducing the amount of the above elements can significantly reduce the semi-hard magnetic properties. Therefore, in the prior art as disclosed in Patent Documents 1 to 2 and Non-Patent Document 1, it has been difficult to obtain a steel material having sufficient workability and sufficient semi-hard magnetic properties at a low cost.

[0008] The present disclosure has been made in view of such a situation, and one of its purposes is to provide a semi-hard magnetic steel material and a semi-hard magnetic steel component that are low in cost and have sufficient workability and sufficient semi-hard magnetic properties.

Means for Solving the Problems

[0009] Aspect 1 of the present invention is C: 0.10 mass% or more and 1.50 mass% or less, Si: More than 0 mass% and 0.75 mass% or less, Mn: More than 0 mass% and 1.00 mass% or less, P: More than 0 mass% and 0.050 mass% or less, S: More than 0 mass% and 0.050 mass% or less, Cu: More than 0 mass% and 0.30 mass% or less, Ni: More than 0 mass% and 0.30 mass% or less, Mo: More than 0 mass% and 1.00 mass% or less, Cr: 0.50 mass% or more and 2.00 mass% or less, Al: More than 0 mass% and 0.100 mass% or less, and N: More than 0 mass% and 0.0100 mass% or less, and contains The balance consists of iron and inevitable impurities, Contains 80 area% or more of tempered martensite phase, It is a semi-hard magnetic steel material with the half-value width of the X-ray diffraction peak from the (211) plane being 3.1° or less.

[0010] Aspect 2 of the present invention is The semi-hard magnetic steel material according to Aspect 1, wherein the area ratio of carbides is 4.00% or more.

[0011] Aspect 3 of the present invention is The semi-hard magnetic steel material according to Aspect 1 or 2, wherein the Vickers hardness is 570 or less.

[0012] Aspect 4 of the present invention is C: 0.10 mass% or more and 1.50 mass% or less, Si: More than 0 mass% and 0.75 mass% or less, Mn: More than 0 mass% and 1.00 mass% or less, P: More than 0 mass% and 0.050 mass% or less, S: More than 0 mass% and 0.050 mass% or less, Cu: More than 0 mass% and 0.30 mass% or less, Ni: More than 0 mass% and 0.30 mass% or less, Mo: More than 0 mass% and 1.00 mass% or less, Cr: 0.50 mass% or more and 2.00 mass% or less, Al: More than 0 mass% and 0.100 mass% or less, and N: More than 0 mass% and 0.0100 mass% or less, and contains The balance consists of iron and inevitable impurities, Contains 80 area% or more of tempered martensite phase, It is a semi-hard magnetic steel part with the half-value width of the X-ray diffraction peak from the (211) plane being 3.1° or less.

[0013] Aspect 5 of the present invention is This is a semi-hard magnetic steel part according to Embodiment 4, wherein the area ratio of carbides is 4.00% or more.

[0014] Aspect 6 of the present invention is, A semi-hard magnetic steel component according to embodiment 4 or 5, wherein the Vickers hardness is 570 or less. [Effects of the Invention]

[0015] According to embodiments of the present invention, it is possible to provide semi-hard magnetic steel materials and semi-hard magnetic steel parts that are low-cost, have sufficient machinability and sufficient semi-hard magnetic properties. [Modes for carrying out the invention]

[0016] The inventors of this invention have investigated from various angles in order to realize a semi-hard magnetic steel material (and semi-hard magnetic steel parts) that is low-cost, has sufficient machinability and sufficient semi-hard magnetic properties. First, in order to achieve low cost, the inventors considered limiting the total content of expensive elements such as Ni, Cu, Co, and / or V to less than 2.0% by mass (preferably less than 1.0% by mass). Within the constraints of the above-mentioned component composition, the inventors focused on the martensite phase in order to obtain sufficient semi-hard magnetic properties. The blocks (or packets) of the martensite phase can be made finer than, for example, the crystal grains of the ferrite phase, in which case the movement of the magnetic domain walls is suppressed, and high semi-hard magnetic properties can be obtained. Furthermore, in order to obtain sufficient workability, the inventors focused on a tempered martensite phase with reduced strain, and found that in order to obtain sufficient workability and sufficient semi-hard magnetic properties, the tempered martensite phase must be at least above a predetermined area ratio.

[0017] Furthermore, the inventors focused on the fact that the full width at half maximum (FHA) of the diffraction peaks in the X-ray diffraction pattern indicates the degree of strain introduction. The inventors hypothesized that the smaller the peak FHA, the smaller the strain in the steel, resulting in a decrease in the hardness of the steel and improved workability. They also hypothesized that the smaller the peak FHA, the smaller the strain and the reduced interaction due to the strain field, thereby increasing the magnetic moment of the matrix phase and improving the semi-hard magnetic properties. The inventors have found that by controlling the component composition to a predetermined range, ensuring that the tempered martensite phase has a predetermined area ratio or higher, and keeping the full width at half maximum of the X-ray diffraction peak from the (211) plane below a predetermined value, it is possible to obtain a low-cost steel material with sufficient processability and sufficient semi-hard magnetic properties.

[0018] The details of each requirement defined in the embodiments of the present invention are shown below. Note that, in this specification, "steel material" refers to material that has not undergone part formation, while "steel part" refers to material that has undergone part formation. For example, steel material may have a simple shape, such as a cylindrical or rectangular parallelepiped, that extends linearly in one direction, as a result of rolling and / or wire drawing. On the other hand, steel part may have a complex shape that does not extend linearly in one direction, such as having ground portions, bent portions, and / or openings, as a result of further part formation such as forging and cutting in addition to rolling and / or wire drawing. Furthermore, in this specification, "semi-hard magnetic steel" means steel having a coercivity of 500 to 20,000 A / m, and "semi-hard magnetic steel parts" means steel parts having a coercivity of 500 to 20,000 A / m.

[0019] <1. Ingredient composition> The semi-hard magnetic steel material (or semi-hard magnetic steel part) according to the embodiment of the present invention preferably has a component composition containing C: 0.10% by mass or more and 1.50% by mass or less, Si: greater than 0% by mass and 0.75% by mass or less, Mn: greater than 0% by mass and 1.00% by mass or less, P: greater than 0% by mass and 0.050% by mass or less, S: greater than 0% by mass and 0.050% by mass or less, Cu: greater than 0% by mass and 0.30% by mass or less, Ni: greater than 0% by mass and 0.30% by mass or less, Mo: greater than 0% by mass and 1.00% by mass or less, Cr: 0.50% by mass or more and 2.00% by mass or less, Al: greater than 0% by mass and 0.100% by mass or less, and N: greater than 0% by mass and 0.0100% by mass or less, with the remainder being iron and unavoidable impurities. The following provides a detailed description of each element.

[0020] (C: 0.10 mass% or more and 1.50 mass% or less) Carbon (C) forms carbides, and the effect of suppressing magnetic domain wall movement by these carbides (i.e., pinning effect of magnetic domain wall movement) contributes to improving semi-hard magnetic properties. To effectively exert the above effect, the C content should be 0.10 mass% or more. Preferably, the C content is 0.15 mass% or more, and more preferably 0.18 mass% or more. It is even more preferable, in order, for the C content to be 0.25 mass% or more, 0.32 mass% or more, 0.39 mass% or more, 0.46 mass% or more, 0.53 mass% or more, or 0.60 mass% or more. Furthermore, if the C content is 0.25 mass% or more and the high-temperature holding temperature in the quenching process is 780 to 950°C, the area ratio of carbides described later can be made 4.00% or more (however, if the high-temperature holding temperature in the quenching process is 900°C or higher, it is necessary to further adjust the high-temperature holding temperature in the tempering process as described later), which is preferable as it allows for further improvement of semi-hard magnetic properties. If the carbon content is excessive, the hardness after quenching and tempering increases, and the machinability decreases. Therefore, the carbon content should be 1.50% by mass or less. Preferably, the carbon content is 1.30% by mass or less, and more preferably 1.20% by mass or less.

[0021] (Si: more than 0 mass% and 0.75 mass% or less) Si acts effectively as a deoxidizing agent and also contributes to improving the semi-hard magnetic properties. To effectively exert these effects, the Si content should be greater than 0% by mass. Preferably, the Si content is 0.010% by mass or more, more preferably 0.050% by mass or more, and even more preferably 0.10% by mass or more. If the Si content is excessive, the magnetic moment decreases, and the semi-hard magnetic properties deteriorate. Also, if the Si content is excessive, the hardness after quenching and tempering increases due to solid solution strengthening, etc., and the machinability deteriorates. Therefore, the Si content should be 0.75% by mass or less. Preferably, the Si content is 0.65% by mass or less, more preferably 0.55% by mass or less, and even more preferably 0.35% by mass or less.

[0022] (Mn: more than 0 mass% and 1.00 mass% or less) Mn is an element that acts effectively as a deoxidizing agent and contributes to improving hardenability. To fully exhibit the above effects, the Mn content should be greater than 0% by mass. Preferably, the Mn content is 0.05% by mass or more, more preferably 0.10% by mass or more, and even more preferably 0.20% by mass or more. If the Mn content is excessive, the magnetic moment decreases, and the semi-hard magnetic properties deteriorate. Also, if the Mn content is excessive, the hardness after quenching and tempering increases due to solid solution strengthening, etc., and the machinability deteriorates. For this reason, the Mn content should be 1.00 mass% or less. Preferably, the Mn content is 0.95 mass% or less, more preferably 0.90 mass% or less, and even more preferably 0.85 mass% or less.

[0023] (P: more than 0% by mass and 0.050% by mass or less) Phosphorus (P) is an unavoidable impurity and a harmful element that causes grain boundary segregation in steel, adversely affecting its toughness. Therefore, the P content should be 0.050% by mass or less. Preferably, the P content is 0.030% by mass or less, and more preferably 0.020% by mass or less. While a lower P content is preferable, it may be greater than 0% by mass, and may even be 0.001% by mass or more.

[0024] (S: more than 0% by mass and 0.050% by mass or less) S (sulfur) is an unavoidable impurity that forms MnS in steel, degrading ductility and thus being detrimental to workability. Therefore, the sulfur content should be 0.050% by mass or less. Preferably, the sulfur content is 0.030% by mass or less, more preferably 0.020% by mass or less, and even more preferably 0.010% by mass or less. While a lower sulfur content is preferable, it may be greater than 0% by mass, and may even be 0.001% by mass or more.

[0025] (Cu: more than 0 mass% and less than 0.30 mass%, Ni: more than 0 mass% and less than 0.30 mass%, Mo: more than 0 mass% and less than 1.00 mass%) Cu, Ni, and Mo are all elements that improve the hardenability of steel materials (or steel parts) and contribute to the improvement of semi-hard magnetic properties. Therefore, the content of Cu, Ni, and Mo should be greater than 0 mass% each. However, if the content of these elements is excessive, the hardness after quenching and tempering will increase, and the workability will decrease. Furthermore, the magnetic moment may decrease, and the semi-hard magnetic properties may also decrease, so Cu and Ni should be 0.30 mass% or less each, and Mo should be 1.00 mass% or less. The content of Cu and Ni is preferably 0.25 mass% or less each, more preferably 0.20 mass% or less each, and even more preferably 0.10 mass% or less each. Furthermore, from the viewpoint of further reducing costs, it is even more preferable that Cu be less than 0.05 mass%. Similarly, from the viewpoint of further reducing costs, it is even more preferable that Ni be less than 0.05 mass%. The Mo content is preferably 0.50% by mass or less, more preferably 0.30% by mass or less, even more preferably less than 0.30% by mass, and even more preferably 0.20% by mass or less. Furthermore, from the viewpoint of further reducing costs, it is even more preferable that the Mo content be less than 0.05% by mass.

[0026] (Cr: 0.50 mass% or more and 2.00 mass% or less) Cr improves the hardenability of steel and forms carbides and / or nitrides, and contributes to improving semi-hard magnetic properties without significantly reducing the magnetic moment by suppressing magnetic domain wall movement due to precipitates (i.e., pinning effect of magnetic domain wall movement). In order to effectively exert these effects, the Cr content is 0.50 mass% or more, preferably 0.70 mass% or more, more preferably 0.85 mass% or more, even more preferably 0.90 mass% or more, and even more preferably 0.95 mass% or more. Excessive Cr content reduces the magnetic moment and degrades the semi-hard magnetic properties. Furthermore, excessive Cr content increases hardness after quenching and tempering due to solid solution strengthening, reducing machinability. Therefore, the Cr content should be 2.00% by mass or less. Preferably, the Cr content is 1.75% by mass or less, and more preferably 1.60% by mass or less.

[0027] (Al: more than 0% by mass and 0.100% by mass or less) Al is an element that acts effectively as a deoxidizing agent, and it has the effect of reducing impurities through deoxidation. In order to effectively exert this effect, the Al content should be greater than 0% by mass. The Al content is preferably 0.005% by mass or more, and more preferably 0.010% by mass or more. If the Al content is excessive, the amount of nonmetallic inclusions increases, reducing toughness and workability. Therefore, the Al content should be 0.100% by mass or less. Preferably, the Al content is 0.080% by mass or less, more preferably 0.050% by mass or less, and even more preferably 0.040% by mass or less.

[0028] (N: more than 0% by mass and less than 0.0100% by mass) N is an unavoidable impurity in steel, but if the steel contains a large amount of solid-solution N, it leads to an increase in hardness and a decrease in ductility due to strain aging, resulting in reduced workability. Therefore, the N content should be 0.0100% by mass or less, preferably 0.0090% by mass or less, more preferably 0.0080% by mass or less, and even more preferably 0.0070% by mass or less.

[0029] The semi-hard magnetic steel material (or semi-hard magnetic steel part) according to the embodiment of the present invention contains the above-described component composition, and in one embodiment of the present invention, the remainder is preferably iron and unavoidable impurities. As unavoidable impurities, the inclusion of trace elements (e.g., As, Sb, Sn, etc.) introduced depending on the conditions of the raw materials, materials, manufacturing equipment, etc., is permissible. Note that, for example, elements such as P, S, and N are generally preferable in smaller amounts and are therefore unavoidable impurities, but their composition range is separately defined as described above. For this reason, in this specification, "unavoidable impurities" refers to a concept excluding elements whose composition range is separately defined.

[0030] <2.Metal structure> The semi-hard magnetic steel material (or semi-hard magnetic steel component) according to the embodiment of the present invention contains 80 area% or more of tempered martensite phase, and the half-width of the X-ray diffraction peak from the (211) plane is 3.1° or less. In this specification, "tempered martensite phase" includes not only the general tempered martensite phase, but also the tempered bainite phase and / or the martensite phase from which carbon (C) has been removed and decomposed into a ferrite phase.

[0031] If the area ratio of the tempered martensite phase is less than 80 area%, the workability may decrease, and the semi-hard magnetic properties may also decrease. The area ratio of the tempered martensite phase is preferably 85 area% or more, more preferably 90 area% or more. The metal structure of the semi-hard magnetic steel material (or semi-hard magnetic steel part) according to the embodiment of the present invention may include retained austenite in addition to tempered martensite. Furthermore, the semi-hard magnetic steel material (or semi-hard magnetic steel part) according to the embodiment of the present invention may include carbides, sulfides, nitrides, oxides, etc. It is conceivable to calculate the area ratio of the tempered martensite phase based on these metal structures and compounds (hereinafter sometimes referred to as "metal structures, etc."). However, considering the component composition of the semi-hard magnetic steel material (or semi-hard magnetic steel part) according to the embodiment of the present invention, it is assumed that the total area ratio of sulfides, nitrides, and oxides is very small (for example, the total area ratio may be less than 3%). Therefore, in the embodiments of the present invention, the following formula (1) is used to calculate the area ratio of the tempered martensite phase. f m =100-f γ -f θ ...(1) In the above equation (1), f m This is the area percentage (%) of the tempered martensite phase, and f γ This is the area percentage (%) of the retained austenite layer, and f θ This represents the area percentage (%) of carbides.

[0032] In the above equation (1), f θ This can be calculated as follows. A sample is taken so that the cross-section of a semi-hard magnetic steel material (or a semi-hard magnetic steel part) can be observed. Next, after the sample is embedded in resin, emery polishing is performed as rough polishing on the observation surface and diamond buff polishing is performed as finish polishing. Further, in order to dissolve carbides, electropolishing (etching solution: aqueous sodium picrate solution) is performed on the observation surface. Then, using a scanning electron microscope (SEM: Scanning Electron Microscope), an image is acquired from the observation surface at a magnification of 5000 to 10000 times. After binarizing the image using image analysis software, the black part is taken as the area of the carbide and f θ is calculated. Note that for the semi-hard magnetic steel material (or semi-hard magnetic steel part) according to the embodiment of the present invention, the calculated result of f θ does not vary significantly depending on the observation position. However, depending on the quenching method, for example, the degree of quenching on the steel surface may change compared to the degree of quenching at other positions, so it is preferable to observe the vicinity (for example, within a range of 1.0 mm centered on the separated position) of a position that is a certain distance (for example, 2.0 mm or more) away from the steel surface in a direction perpendicular to the steel surface from the steel surface toward the inside of the steel. For a small sample where a position more than 2.0 mm away from the steel surface in a direction perpendicular to the steel surface cannot be used as the measurement center, it is preferable to observe the vicinity of the position farthest in the direction perpendicular to the steel surface.

[0033] In the above formula (1), f γ can be obtained as follows. First, a sample is taken so that the cross-section of a semi-hard magnetic steel material (or a semi-hard magnetic steel part) can be measured. Next, after the sample is embedded in resin, emery polishing is performed as rough polishing on the measurement surface and diamond buff polishing is performed as finish polishing. Then, an X-ray diffraction pattern is acquired from the measurement surface using a PSPC (Position Sensitive Propotional Counter) micro X-ray stress measurement device (manufactured by Rigaku Corporation). Note that the measurement conditions are: target: Cr, acceleration voltage: 40 kV, acceleration current: 40 mA, collimator: φ1.0 mm, measurement time: 100 seconds. And f γWe seek. f γ / 100=I γ / (RI α +I γ )···(2) In the above equation (2), I γ This is the integrated intensity of the peak located at 119°~138° in the X-ray diffraction pattern, and I α R is the integrated intensity of the peak located at 148-165° in the X-ray diffraction pattern, and R is a constant that depends on the diffraction angle, diffraction plane, and type of material. As long as the measurement is performed using the above apparatus and conditions, R can be assumed to be 0.36746. Furthermore, the measurement results for the semi-hard magnetic steel material (or semi-hard magnetic steel part) according to the embodiment of the present invention do not change significantly depending on the measurement position. However, depending on the method of quenching, there is a non-zero possibility that, for example, the degree of quenching of the steel surface may differ from the degree of quenching at other locations. Therefore, it is preferable to set the measurement center at a position that is a certain distance (for example, 2.0 mm or more) from the steel surface in a direction perpendicular to the steel surface toward the interior of the steel. For small samples where it is not possible to set the measurement center at a position that is 2.0 mm or more away from the steel surface in a direction perpendicular to the steel surface toward the interior of the steel, it is preferable to set the measurement center at the position furthest away in a direction perpendicular to the steel surface.

[0034] If the full width at half maximum (FWHM) of the X-ray diffraction peak from the (211) plane exceeds 3.1°, the steel becomes hard and its machinability decreases, and / or the magnetic moment of the matrix phase decreases, resulting in a decrease in semi-hard magnetic properties. The peak FWHM is preferably 2.8° or less, more preferably 2.6° or less, even more preferably 2.4° or less, and even more preferably 2.1° or less. The lower limit of the peak FWHM is not particularly limited, but considering the component composition and manufacturing conditions according to the embodiment of the present invention, it is generally about 0.1°. Regarding the above, although the same trend is observed regardless of the crystal orientation of the bcc phase, such as the tempered martensite phase, in the embodiment of the present invention, the peak half-width of the (211) plane of the bcc phase, which allows for a clear understanding of the trend, is representatively defined.

[0035] The full width at half maximum of the X-ray diffraction peak from the (211) plane is calculated as follows. First, a sample is taken so that the cross-section of the semi-hard magnetic steel material (or semi-hard magnetic steel part) can be measured. Next, the sample is embedded in resin, and the measurement surface is subjected to emery polishing and / or diamond buff polishing. Then, an X-ray diffraction pattern is obtained from the measurement surface using a PSPC micro-X-ray stress analyzer (manufactured by Rigaku Corporation), and the half-width of the peak located at 148° to 165° is taken as the half-width of the X-ray diffraction peak from the (211) plane. The measurement conditions are as follows: target: Cr, acceleration voltage: 40kV, acceleration current: 40mA, collimator: φ1.0mm, measurement time: 100 seconds. Furthermore, in the case of the semi-hard magnetic steel material (or semi-hard magnetic steel part) according to the embodiment of the present invention, the measurement results do not change significantly depending on the measurement position. However, depending on the method of quenching, there is a non-zero possibility that, for example, the degree of quenching of the steel surface may differ from the degree of quenching at other locations. Therefore, it is preferable to set the measurement center at a position that is a certain distance (for example, 2.0 mm or more) from the steel surface in a direction perpendicular to the steel surface toward the interior of the steel. In the case of small samples where it is not possible to set the measurement center at a position that is 2.0 mm or more away from the steel surface in a direction perpendicular to the steel surface toward the interior of the steel, it is preferable to set the measurement center at the position furthest away in a direction perpendicular to the steel surface.

[0036] The semi-hard magnetic steel material (or semi-hard magnetic steel component) according to the embodiment of the present invention is f θ It is preferable that it is 4.00% or more. θ By setting the content to 4.00% or more, the amount of solid solution elements such as C in the matrix can be reduced, thereby suppressing the increase in hardness due to solid solution strengthening and improving workability. Furthermore, the carbides can suppress the movement of magnetic domain walls, contributing to the improvement of semi-hard magnetic properties. θ The amount is preferably 4.05% or more, and more preferably 4.10% or more. On the other hand, in order to maintain toughness, f θ It is preferable that the percentage be 20% or less.

[0037] The semi-hard magnetic steel material (or semi-hard magnetic steel component) according to the embodiment of the present invention is f γ It is preferable that it is 10.0% or less. γ By setting it to 10.0% or less, a high magnetic moment can be obtained, and the semi-hard magnetic properties may be improved. γ Preferably, it is 8.0% or less, and more preferably 6.0% or less.

[0038] The semi-hard magnetic steel material (or semi-hard magnetic steel part) according to the embodiment of the present invention can exhibit sufficient machinability and sufficient semi-hard magnetic properties. Specifically, it can exhibit a Vickers hardness of 570 or less as sufficient machinability, and a square aspect ratio (Br / B10k) of 0.760 or more as sufficient semi-hard magnetic properties. A preferred Vickers hardness is 470 or less, a more preferred Vickers hardness is 450 or less, and a preferred square aspect ratio (Br / B10k) is 0.835 or more. Hereinafter, "Br" is the residual magnetic flux density (unit: T), and "B10k" is the magnetic flux density (unit: T) at a magnetic field of 10 kA / m.

[0039] A semi-hard magnetic steel material (or semi-hard magnetic steel part) according to an embodiment of the present invention can be manufactured by subjecting a steel material (or steel part) having the above-described component composition to a quenching and tempering treatment. A steel material having the above-described component composition can be obtained, for example, by melting it according to a normal melting method to satisfy the above-described component composition, and then appropriately performing casting, hot rolling, and secondary processing (wire drawing, annealing). A steel part having the above-described component composition can be obtained, for example, by melting it according to a normal melting method to satisfy the above-described component composition, and then appropriately performing casting, hot rolling, and secondary processing (wire drawing, annealing), in addition to subjecting it to part shaping such as forging and cutting. Note that if quenching and tempering treatment is performed after part shaping, the metal structure, etc., is reset by the quenching treatment, so part shaping before quenching and tempering treatment does not affect the requirements for the metal structure, etc., as defined in the embodiments of the present invention. The semi-hard magnetic steel parts according to the embodiment of the present invention may be manufactured by subjecting a steel part having the above-described component composition to quenching and tempering treatment, or by melting according to a normal melting method to satisfy the above-described component composition, performing casting, hot rolling, and secondary processing (wire drawing, annealing) as appropriate, and then subjecting the quenching and tempering treatment to part shaping such as forging and cutting. For part shaping, the desired conditions can be set as appropriate according to the required characteristics of various parts. In order to obtain a metallic structure containing 80 area percent or more of tempered martensite phase and having a half-width of the X-ray diffraction peak from the (211) plane of 3.1° or less, it is necessary to adjust the component composition to the above-described composition, and to set the high-temperature holding temperature during the quenching treatment to 780°C to 1030°C and the high-temperature holding temperature during the tempering treatment process to 480°C to 680°C. Preferably, the high-temperature holding temperature during the quenching treatment is 780 to 950°C. However, if the high-temperature holding temperature during the quenching process is 900°C or higher, the dissolution of carbides present in the steel material (or steel parts) before the quenching process is promoted during high-temperature holding at that temperature. Therefore, it is preferable to set the high-temperature holding temperature in the tempering process to 550°C or higher to allow for the precipitation of a large amount of carbides that contribute to improving the semi-hard magnetic properties during the tempering process. Furthermore, from the viewpoint of further reducing Vickers hardness, it is even more preferable that the high-temperature holding temperature in the tempering process be 570°C or higher. The high-temperature holding time and cooling after high-temperature holding in the quenching process, as well as the high-temperature holding time and cooling after high-temperature holding in the tempering process, may be arbitrary. For example, in the quenching process, the high-temperature holding time may be 10 to 90 minutes, and cooling after high-temperature holding may be rapid oil cooling. In the tempering process, the high-temperature holding time may be 30 to 150 minutes, and cooling after high-temperature holding may be rapid water cooling or air cooling. The atmosphere during heat treatment does not significantly affect the microstructure, so it may be carried out in any atmosphere. Without departing from the objective of the embodiments of the present invention, other steps may be included after the quenching and tempering process, for example. In the embodiments of the present invention, if the temperature is below the high-temperature holding temperature of the tempering process, it will not significantly affect the metal structure, etc., as defined in the embodiments of the present invention, so other steps may be included, for example, a heat treatment below 480°C. Also, even if surface treatments such as nitriding and / or plating are performed, the metal structure, etc., inside the steel will not change, so other steps may be included, for example, such surface treatments. Furthermore, in the method for manufacturing a semi-hard magnetic steel part according to the embodiment of the present invention, part molding may be included as another step, as long as the provisions of the embodiments of the present invention are satisfied.

[0040] The semi-hard magnetic steel components according to the embodiments of the present invention can be suitably used as composite magnetic components (components consisting of multiple members, at least partially of which are magnetic) such as relays (latching relays, reeds), reed switches, memories, motors (external rotors, internal rotors), electromagnetic clutches (movable elements, stators), and electromagnetic brakes, provided that appropriate component molding is performed. Composite magnetic components including the semi-hard magnetic steel components according to the embodiments of the present invention are industrially useful because they include steel components having sufficient semi-hard magnetic properties. [Examples]

[0041] The embodiments of the present invention will be described in more detail below with reference to examples. The embodiments of the present invention are not limited by the following examples, and can be implemented with appropriate modifications within the scope that is consistent with the spirit described above and below, and all such modifications are included within the technical scope of the embodiments of the present invention. In the following examples, the steel material (bar stock) is formed into a ring shape before the quenching and tempering treatment and then evaluated for its properties, that is, the evaluation results are shown for "steel parts". However, as mentioned above, whether or not the parts are formed before the quenching and tempering treatment does not affect the evaluation results, so these examples are positioned as showing the evaluation results for both "steel material" and "steel parts".

[0042] Steels No. I to VIII with the component compositions shown in Table 1 were melted in a converter and then cast, or cast in an experimental furnace to obtain steel billets. These billets were then hot-rolled or hot-forged to produce bars with diameters of 40 to 65 mm. Subsequently, ring-shaped test specimens with an outer diameter of 38 mm, an inner diameter of 30 mm, and a thickness of 4 mm were taken so that the circumferential direction of the test specimen and the circumferential direction of the bar were parallel, and the center of the test specimen and the center of the bar coincided. These were then quenched and tempered using a laboratory furnace at the temperatures shown in Table 2 to obtain test specimens No. 1 to 24. In Table 2, "-" in the "Quenching Holding Temperature" and "Tempering Holding Temperature" columns indicates that quenching and tempering were not performed.

[0043] [Table 1]

[0044] [Table 2]

[0045] For test specimens No. 1 to 24, f m ,f γ ,f θ The full width at half maximum, coercivity, angularity ratio, and Vickers hardness of the X-ray diffraction peak from the (211) plane were determined by the following method.

[0046] [f m and fγ ] A sample was taken from a ring-shaped test specimen so that a cross-section (4 mm x 4 mm) perpendicular to the circumferential direction could be measured. Next, the sample was embedded in resin, and the measurement surface was subjected to rough polishing (Emirly polishing) and finish polishing (diamond buffing). Then, an X-ray diffraction pattern was obtained from the measurement surface using a PSPC micro-X-ray stress analyzer (manufactured by Rigaku Corporation). The measurement conditions were as follows: target: Cr, acceleration voltage: 40 kV, acceleration current: 40 mA, collimator: φ1.0 mm, measurement time: 100 seconds, measurement position: two points near the center of the measurement surface. For the two measurement points, use the above formulas (1) and (2), as well as the f described later. θ Using f m and f γ The average of the two points was calculated and is shown in Table 3 below. In formula (2) above, R = 0.36746 was used.

[0047] [f θ ] A sample was taken so that a cross-section (4 mm × 4 mm) perpendicular to the circumferential direction of the ring-shaped test specimen could be observed. Next, the sample was embedded in resin, and the observation surface was subjected to rough polishing (Emilie polishing) and finish polishing (diamond buffing). Furthermore, to dissolve the carbides, the observation surface was subjected to electropolishing (etching solution: sodium picrate aqueous solution). Then, using a scanning electron microscope, the area near the center of the observation surface (within a 1.0 mm range from the center) was examined at a magnification of 5000x (field of view area 217 μm²). 2 ) or 10,000x (field of view area 108.5 μm) 2 Images were acquired from three fields of view. After binarizing the images using image analysis software, the black areas were used as the area of ​​carbonized material, and f θ The result was calculated.

[0048] [Half-width of X-ray diffraction peaks from the (211) plane] A sample was taken from a ring-shaped test specimen so that a cross-section (4 mm × 4 mm) perpendicular to the circumferential direction could be measured. Next, the sample was embedded in resin, and the measurement surface was subjected to either emery polishing as a rough polish or diamond buff polishing as a finish polish. Then, an X-ray diffraction pattern was obtained from the measurement surface using a PSPC micro-X-ray stress analyzer (manufactured by Rigaku Corporation), and the full width at half maximum (FWHM) of the peak located at 148° to 165° was taken as the FWHM of the X-ray diffraction peak from the (211) plane. The measurement conditions were: target: Cr, acceleration voltage: 40 kV, acceleration current: 40 mA, collimator: φ1.0 mm, measurement time: 100 seconds, measurement position: two points near the center of the measurement surface. The FWHM was calculated for the two measurement positions, and the average value of the two points is shown in Table 3 below.

[0049] [Coercivity and aspect ratio] After winding ring-shaped test specimens onto a magnetization application coil and a magnetic flux detection coil, the BH curve was measured using an automatic magnetization measuring device (RIKEN Electron Systems, Inc., DC magnetic measuring device, BHS-40CD) at room temperature and with a maximum magnetic field of 10 kA / m to determine the coercivity (Hc) and the angular ratio (Br / B10k).

[0050] [Vickers hardness] A sample was taken from a ring-shaped test specimen so that a cross-section (4 mm x 4 mm) perpendicular to the circumferential direction could be measured. Next, the sample was embedded in resin and polished with a diamond buff as a finish polish. Then, the Vickers hardness was measured at three points near the center of the cross-section under a load of 10 kgf, and the average value was adopted.

[0051] The above measurement results are summarized in Table 3. Note that in Table 3, "full width at half maximum" refers to "the full width at half maximum of the X-ray diffraction peak from the (211) plane."

[0052] [Table 3]

[0053] From the results in Table 3, the following conclusions can be drawn. Tests No. 1-9 and 19-24 in Table 3 all satisfied the requirements specified in the embodiments of the present invention, were low-cost, had sufficient machinability (Vickers hardness: 570 or less), and possessed sufficient semi-hard magnetic properties (square ratio (Br / B10k): 0.760 or more). Furthermore, since tests No. 1-4 and 19-24 had a carbon content of 0.25 mass% or more and a quenching and holding temperature of 780-950°C, f θ It met the desirable requirement of 4.00% or more, and showed a desirable Vickers hardness (470 or less) and a desirable squareness ratio (Br / B10k): 0.835 or more. Furthermore, tests No. 1-3 and 19-24 showed a more desirable Vickers hardness (450 or less) because the tempering holding temperature was 570-680°C. In addition, although test No. 9 had a carbon content of 0.25 mass% or more and a quenching holding temperature of 900°C within the range of 780-950°C, the tempering holding temperature was 500°C, and the tempering holding temperature when the quenching holding temperature was 900°C or higher was less than 550°C, therefore, f θ It did not meet the favorable requirement of 4.00% or higher. On the other hand, tests No. 10 to 17 in Table 3 had a holding temperature of less than 480°C during tempering and did not meet the requirement of having a half-width of 3.1° or less for the X-ray diffraction peak from the (211) plane, and therefore did not exhibit sufficient processability or sufficient semi-hard magnetic properties. Test No. 18 is an example where quenching and tempering were not performed, and the semi-hard magnetic properties (square aspect ratio (Br / B10k)) are insufficient. However, as with Tests No. 1-9 and 19-24, by quenching with a high-temperature holding temperature of 780°C to 1030°C and tempering with a high-temperature holding temperature of 480°C to 680°C, it is considered that the requirements specified in the embodiments of the present invention will be satisfied, and sufficient machinability and sufficient semi-hard magnetic properties will be observed.

Claims

1. C: 0.10% by mass or more and 1.50% by mass or less, Si: more than 0% by mass and not more than 0.75% by mass, Mn: more than 0% by mass and not more than 1.00% by mass, P: more than 0% by mass and not more than 0.050% by mass, S: more than 0% by mass and not more than 0.050% by mass, Cu: more than 0% by mass and not more than 0.30% by mass, Ni: more than 0% by mass and not more than 0.30% by mass, Mo: more than 0% by mass and not more than 1.00% by mass, Cr: 0.50% by mass or more and 2.00% by mass or less, Al: 0.005% by mass or more and 0.100% by mass or less, Contains N: more than 0% by mass and 0.0100% by mass or less, The remainder consists of iron and unavoidable impurities. Containing 80% or more of tempered martensite phase, A semi-hard magnetic steel material having a half-width of the X-ray diffraction peak from the (211) plane of 3.1° or less.

2. The semi-hard magnetic steel material according to claim 1, wherein the area ratio of carbides is 4.00% or more.

3. A semi-hard magnetic steel material according to claim 1 or 2, wherein the Vickers hardness is 570 or less.

4. C: 0.10% by mass or more and 1.50% by mass or less, Si: more than 0% by mass and not more than 0.75% by mass, Mn: more than 0% by mass and not more than 1.00% by mass, P: more than 0% by mass and not more than 0.050% by mass, S: more than 0% by mass and not more than 0.050% by mass, Cu: more than 0% by mass and not more than 0.30% by mass, Ni: more than 0% by mass and not more than 0.30% by mass, Mo: more than 0% by mass and not more than 1.00% by mass, Cr: 0.50% by mass or more and 2.00% by mass or less, Al: 0.005% by mass or more and 0.100% by mass or less, Contains N: more than 0% by mass and 0.0100% by mass or less, The remainder consists of iron and unavoidable impurities. Containing 80% or more of tempered martensite phase, (211) A semi-hard magnetic steel component in which the full width at half maximum of the X-ray diffraction peak from the plane is 3.1° or less.

5. The semi-hard magnetic steel component according to claim 4, wherein the area ratio of carbides is 4.00% or more.

6. A semi-hard magnetic steel component according to claim 4 or 5, wherein the Vickers hardness is 570 or less.

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