JP2020063473A - Ferritic stainless steel plate excellent in magnetic characteristics - Google Patents

Abstract

To provide a ferritic stainless steel plate excellent in magnetic characteristics.SOLUTION: A ferritic stainless steel plate contains C:0.020% or less, Si:1.00% or less, Mn:1.00% or less, P:0.035% or less, S:0.0030% or less, Cr:10.0-18.0%, N:0.020% or less, Nb:0.5% or less, Ti:0.5% or less, Al:0.10% or less, and the balance Fe with impurities, in which an aggregate structure in the plate surface satisfies the following (i) and (ii): (i) an area ratio of grains in the {110}±15° orientation where an angle difference between a normal direction on the surface of the steel plate in the plate surface and {110} orientation is within 15° of more than 3.0% and less than 30%; and (ii) when an area ratio of the grains in the {110}±15° orientation on the plate surface is represented by A and an area ratio of the grains in the {111}±15° orientation is represented by B, a relationship of 0.10<A/B<0.80 is held.SELECTED DRAWING: None

Description

  The present invention relates to a ferritic stainless steel sheet having excellent magnetic properties, and particularly to a ferritic stainless steel sheet suitable as a contact material for a magnetic circuit breaker.

  Hybrid vehicles and electric vehicles are equipped with a plurality of magnetic circuit breakers per vehicle in order to reliably interrupt current in a high-voltage circuit mounted on the vehicle. Particularly in these vehicles, it is necessary to cut off a large amount of current. As a magnetic circuit breaker used for this purpose, one having a contact device and an electromagnetic switch is known. The contact device is provided with a fixed contact member having a fixed contact portion, a movable contact member having a movable contact portion, and a housing for housing these, and the movable contact member is movable by an opening / closing device. There is. When the high-voltage circuit is interrupted by the magnetic circuit breaker, the movable contact member is driven by the switchgear to bring the movable contact portion and the fixed contact portion into a non-contact state to interrupt the current.

  The current interruption by the magnetic circuit breaker is frequently performed depending on the driving situation of the vehicle. Therefore, impact resistance is required for the movable contact and the fixed contact. Some magnetic circuit breakers generate a magnetic field inside the casing of the contact device in order to quickly extinguish the arc discharge generated when the current is cut off. That is, when the fixed contact and the movable contact are separated from each other, the arc generated between the contacts is moved to the end of each contact by the action of the magnetic field, and further, the arc is extended to increase the arc voltage. The shutoff is complete. For this reason, the fixed contact member and the movable contact member arranged inside the housing are required to have excellent magnetizing properties (magnetic characteristics).

  For the fixed contact member and the movable contact member, a conductive metal (for example, copper or copper alloy) itself or a composite of ceramics and a conductive metal is used. However, copper or copper alloys do not have sufficient magnetic properties. Further, ceramics have a problem that impact resistance and magnetic properties are low. Therefore, application of stainless steel can be considered as a material having excellent impact resistance and magnetic properties.

  In Patent Document 1, as a ferritic stainless steel sheet having excellent magnetic properties, C ≦ 0.01%, Si: 0.1 to 0.6%, Mn: 0.1 to 1.0% in weight%. , S ≦ 0.004%, Cr: 5 to 13%, Ti: 0.05 to 0.5%, O ≦ 0.004%, N ≦ 0.015%, and C + N ≦ 0.015% And the balance consists of Fe and inevitable impurities, the sum of the (111) plane strengths in the surface layer and the central layer is 10 or less, and the maximum relative magnetic permeability is ≧ 4000.

  Further, in Patent Document 2, as a ferritic stainless steel sheet having excellent magnetic properties, C: 0.015% or less, N: 0.015% or less, Si: 1.5% or less, Mn: 1 by weight%. A slab containing 0.0% or less, Cr: 10 to 14%, and Ti: 0.05 to 0.30% is hot-rolled into a hot-rolled sheet, and the hot-rolled sheet has a reduction rate of 20 to 60%. Of the ferritic stainless steel sheet manufactured by subjecting the steel sheet to cold rolling, followed by annealing at 800 to 930 ° C.

Japanese Patent No. 3629102 JP-A-11-61255

  The ferritic stainless steel sheets described in Patent Documents 1 and 2 are superior in impact resistance and magnetic properties as compared with copper, copper alloys or ceramics. However, regarding magnetic properties, they do not have magnetic properties that are satisfactory as contact materials for magnetic circuit breakers.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a ferritic stainless steel sheet which is excellent in impact resistance and magnetic characteristics and which is suitable as a contact member of a magnetic circuit breaker.

In order to solve the above problems, the present invention adopts the following configurations.
[1] In mass%,
C: 0.020% or less,
Si: 1.00% or less,
Mn: 1.00% or less,
P: 0.035% or less,
S: 0.0030% or less,
Cr: 10.0 to 18.0%,
N: 0.020% or less,
Nb: 0.5% or less,
Ti: 0.5% or less,
Al: including 0.10% or less,
The balance consists of Fe and impurities,
A ferritic stainless steel sheet having excellent magnetic properties, characterized in that the texture on the plate surface satisfies the following (i) and (ii).
(I) The area difference of {110} ± 15 ° orientation grains, in which the angular difference between the normal direction of the steel sheet surface and the {110} plane orientation on the plate surface is within 15 °, is more than 3.0% and less than 30%.
(Ii) When the area ratio of {110} ± 15 ° oriented grains on the plate surface is A and the area ratio of {111} ± 15 ° oriented grains is B, 0.10 <A / B <0.80.
[2] Further, in mass%,
Sn: 0.001-0.5%,
B: Ferrite-based stainless steel sheet having excellent magnetic properties according to [1], which contains one or two 0.005% or less.
[3] Further, in mass%,
Ni: 1% or less,
Cu: 1% or less,
Mo: 1% or less,
Sb: 0.2% or less,
V: 0.5% or less,
W: 0.5% or less,
Zr: 0.5% or less,
Co: 0.5% or less,
Mg: 0.005% or less,
Ca: 0.005% or less,
Ga: 0.015% or less,
La: 0.1% or less,
Y: 0.1% or less,
Hf: 0.1% or less,
REM: A ferritic stainless steel sheet having excellent magnetic properties according to [1] or [2], which contains 0.1% or less of one type or two or more types.
[4] The ferritic stainless steel sheet having excellent magnetic properties according to any one of [1] to [3], which is used as a contact member arranged in a magnetic field.

  According to the present invention, it is possible to provide a ferritic stainless steel sheet having excellent impact resistance and magnetic properties. Further, the ferritic stainless steel sheet of the present invention can be suitably used as a material for a contact member of a magnetic circuit breaker.

It is a cross-sectional schematic diagram which shows an example of a magnetic circuit breaker.

  In order to solve the above-mentioned problems, the present inventors have earnestly studied alloy elements that affect impact resistance and magnetic properties in ferritic stainless steel sheets, and obtained the following new findings to form the present invention. Came to.

(A) As described above, the characteristics required for the contact material of the magnetic circuit breaker include impact resistance and magnetic characteristics. Although stainless steel is superior in impact resistance and magnetic characteristics to other contact materials such as copper, no one having suitable magnetic characteristics as a contact member for a magnetic circuit breaker has been obtained. The value of relative permeability, which is an index of magnetic properties, depends on the external magnetic field, and the external magnetic field for in-vehicle use is assumed to be an applied magnetic field force (for example, 1000 A / m) that does not necessarily reach the saturation magnetization of stainless steel. Need to be evaluated. In general, stainless steel contains an alloying element in order to improve the corrosion resistance, but when the alloying element is contained, the content of Fe relatively decreases and the magnetic properties decrease. Therefore, in order to realize a stainless steel suitable as a contact material for a magnetic circuit breaker, it is necessary to reduce the content of alloying elements as much as possible, and especially the content of Cr is suppressed to 18% or less. It was found that this is preferable.
(B) The magnetic properties of stainless steel are affected by grain boundaries. The crystal grain boundaries serve as a magnetic barrier and easily deteriorate the magnetic characteristics. Particularly in stainless steel, impurity elements such as P and S segregate at the crystal grain boundaries to deteriorate the magnetic properties. In addition to P and S, there are elements such as C and N as elements that segregate at the crystal grain boundaries and obstruct magnetic properties. The present inventors have found that the control of the texture is effective for improving the magnetic properties without depending on the excessive reduction of P, S, C and N described above.
(C) Further, by containing Ti and Nb, P, S, C, N, etc. are combined to form phosphide, sulfide, carbide, nitride, etc. It was found that there is an effect of suppressing the deterioration of magnetic characteristics by fixing. The present inventors have also found that segregation of Ti and Nb themselves at grain boundaries can suppress grain boundary segregation of P and S and prevent deterioration of magnetic properties.
(D) Further, in stainless steel, impurity elements such as P and S segregate in the crystal grain boundaries to deteriorate the magnetic properties, but the present inventors have focused on Sn. Sn is a grain boundary segregation element, and is an element effective in improving the magnetic properties by suppressing grain boundary segregation such as P and S. It has been found that further improvement of magnetic properties is expected by incorporating Sn in a predetermined range.
(E) Regarding magnetic characteristics, conventionally, in order to improve the magnetic characteristics, the crystal characteristics in the {110} direction, which is the easy magnetization direction, are grown and coarsened to improve the magnetic characteristics. However, the toughness of the steel was deteriorated by this. The present invention focuses on the texture of steel and generates {110} oriented grains in the range of more than 3.0 to less than 30% to divide {111} or {211} oriented grains to obtain magnetic properties. It has been found that both toughness can be improved.

The gist of the present invention made based on the findings (a) to (e) is as follows.
The ferritic stainless steel sheet of the present embodiment is, in mass%, C: 0.020% or less, Si: 1.00% or less, Mn: 1.00% or less, P: 0.035% or less, S: 0.0. 0030% or less, Cr: 10.0 to 18.0%, N: 0.020% or less, Nb: 0.5% or less, Ti: 0.5% or less, Al: 0.10% or less, and the balance Is Fe and impurities, and the texture on the plate surface is a ferritic stainless steel sheet having excellent magnetic properties satisfying the following (i) and (ii).
(I) The area difference of {110} ± 15 ° orientation grains, in which the angular difference between the normal direction of the steel sheet surface and the {110} plane orientation on the plate surface is within 15 °, is more than 3.0% and less than 30%.
(Ii) When the area ratio of {110} ± 15 ° oriented grains on the plate surface is A and the area ratio of {111} ± 15 ° oriented grains is B, 0.10 <A / B <0.80.
Further, the ferritic stainless steel sheet of the present embodiment preferably further contains, by mass%, one or two of Sn: 0.001 to 0.5% and B: 0.005% or less.
Further, the ferritic stainless steel sheet of the present embodiment is further mass%, Ni: 1% or less, Cu: 1% or less, Mo: 1% or less, Sb: 0.2% or less, V: 0.5% or less. , W: 0.5% or less, Zr: 0.5% or less, Co: 0.5% or less, Mg: 0.005% or less, Ca: 0.005% or less, Ga: 0.005% or less, La : 0.1% or less, Y: 0.1% or less, Hf: 0.1% or less, REM: 0.1% or less, or two or more thereof may be contained.
Further, the ferritic stainless steel plate of the present embodiment is preferably used as a contact member arranged in a magnetic field.

  Hereinafter, each requirement of the present invention will be described in detail. The “%” display of the content of each element means “mass%”.

C: 0.020% or less When C is too much, C forms carbides in the alloy and segregates at grain boundaries to deteriorate magnetic properties, and further reduces toughness to deteriorate impact resistance. The lower the content, the better, and the upper limit is 0.020% or less. However, in order to reduce the amount of carbon, the refining process becomes complicated and the cost increases. Therefore, the C content is preferably 0.001% or more. Considering the refining cost, the preferable range is 0.003 to 0.015%, and the more preferable range is 0.003 to 0.010%.

Si: 1.00% or less Si is an element that is effective as a deoxidizing element and is also effective in improving magnetic properties. However, if it is contained in excess, Si acts as a solid solution strengthening element, which lowers workability. Therefore, the upper limit is made 1.00% or less. In order to secure magnetic properties, the lower limit is preferably 0.01% or more. Considering the effect and manufacturability, the preferable range is 0.05 to 0.50%, and may be 0.05 to 0.30%.

Mn: 1.00% or less Mn is an element that is effective as a deoxidizing element and is also an element that is effective for fixing S that deteriorates magnetic properties. On the other hand, Mn causes deterioration of corrosion resistance and oxidation resistance, so the upper limit is made 1.00% or less. In order to secure the effects of deoxidation and S fixing, the lower limit is preferably 0.01% or more. The preferable range is 0.05 to 0.50% in consideration of the effect and manufacturing cost, and may be 0.05 to 0.30%.

P: 0.035% or less P is an element that segregates at grain boundaries to deteriorate magnetic properties and impairs manufacturability. The lower the content, the better. Therefore, the upper limit is 0.035%. . However, excessive reduction leads to an increase in refining cost, so the lower limit is made 0.005% or more. The preferable range is 0.010 to 0.030% in consideration of manufacturing cost, and may be 0.010 to 0.020%.

S: 0.0030% or less S contains S in a large amount to form sulfides in the alloy to deteriorate the magnetic properties, and also segregates at the grain boundaries to deteriorate the magnetic properties. The smaller the better, the better, and the upper limit is made 0.0030% or less. However, excessive reduction leads to an increase in raw materials and refining costs, so the lower limit is made 0.0001% or more. A preferable range is 0.0002 to 0.0015%, and may be 0.0002 to 0.0008% in consideration of improvement of magnetic properties and manufacturing cost.

Cr: 10.0 to 18.0%
Cr is a basic element of the ferritic stainless steel of this embodiment, and is an essential element for ensuring corrosion resistance and magnetic properties. The lower limit is made 10.0% or more in order to secure the corrosion resistance assuming the use as the contact material of the magnetic circuit breaker of the present embodiment. The upper limit is 18.0% or less from the viewpoint of improving magnetic properties. If Cr, which is a non-magnetic element, exceeds 18.0%, the magnetic properties deteriorate. The more preferable range of Cr may be 10.0 to less than 15.0%, or may be 10.0 to 12.0%.

N: 0.020% or less N, like C and S, when contained in excess, forms a nitride in the alloy to deteriorate the magnetic properties, and also segregates N at the grain boundaries to deteriorate the magnetic properties. Therefore, the smaller the content, the better, and the upper limit is made 0.020% or less. However, excessive reduction leads to an increase in refining cost, so the lower limit is preferably made 0.001% or more. A preferable range is 0.005 to 0.015% in consideration of magnetic properties and manufacturing cost.

Nb: 0.5% or less Ti: 0.5% or less Nb and Ti segregate at the grain boundaries to suppress the grain boundary segregation of P and S, and have the effect of improving the magnetic properties. In addition, Nb and Ti also have a function as a stabilizing element for fixing C, N, P, and S that obstruct magnetic properties. Both Nb and Ti exhibit these two actions, but it is presumed that Nb works particularly effectively on the former action and Ti works effectively on the latter action. Due to these actions, Ti and Nb become effective elements for improving the corrosion resistance as well as for improving the magnetic properties targeted by the present invention. When it is contained, the content is set to 0.01% or more so that the respective effects are exhibited. However, an excessive content leads to an increase in alloy cost and a decrease in workability, and further, the toughness decreases and the impact resistance deteriorates, so the upper limits are made 0.5% or less. Considering the effect of improving the magnetic properties, alloy cost and manufacturability, the preferable ranges are 0.05 to 0.5% for Nb and Ti, respectively. A more preferable range is 0.08 to 0.3%, and each may be 0.1 to 0.3%.

Al: 0.10% or less Al is an extremely effective element as a deoxidizing element. On the other hand, since the toughness of steel is reduced, the upper limit is made 0.10% or less. The lower limit is preferably 0.005% or more in consideration of the deoxidizing effect. Considering manufacturability and performance, the preferable range is 0.01 to 0.07%, and may be 0.01 to 0.05%.

  Other than the above-mentioned elements, it consists of Fe and impurities. However, the elements described below other than the above can be selectively contained within a range that does not impair the effects exhibited by the technical features of the present invention. The reasons for limitation are described below.

Sn: 0.001-0.5%
Sn is an element effective for improving the magnetic characteristics targeted by the present invention, in addition to corrosion resistance. Impurity elements such as P and S segregate in the crystal grain boundaries of stainless steel to deteriorate the magnetic properties. Sn is a grain boundary segregation element itself, and is an element effective for improving the magnetic properties by suppressing grain boundary segregation such as P and S. Since the improvement of magnetic properties is expected by containing Sn in a predetermined range, in the present invention, it is contained in a range of 0.001 to 0.5%. When Sn is contained in an amount of 0.001% or more, the above-described effect is exhibited and the magnetic characteristics are improved. However, an excessive content increases the Sn concentration in the crystal grain boundary and leads to deterioration of magnetic properties, and also lowers toughness and causes deterioration of impact resistance, so the upper limit is made 0.5% or less. It is preferably 0.005 to 0.3%, and may be 0.010 to 0.2%.

B: 0.005% or less B is a grain boundary segregation element, which, like Sn, improves magnetic properties and hot workability, and should be contained in the ferritic stainless steel of the present embodiment. Is valid. The lower limit of B is preferably 0.0003% or more in order to improve the magnetic properties. However, excessive B content causes a decrease in elongation and reduces manufacturability, so the upper limit is made 0.005% or less. It is preferably 0.0005 to 0.002%, and may be 0.001 to 0.002%.

Ni: 1% or less Cu: 1% or less Mo: 1% or less Ni, Cu, and Mo are elements effective for corrosion resistance. In order to exert this effect, each of Ni, Cu, and Mo may be contained in the range of 0.05% or more. Excessive content hinders recrystallization and crystal grain growth of stainless steel and causes deterioration of magnetic properties. Therefore, the upper limit of each content is set to 1% or less. A more preferable range is 0.1% or more and 0.8% or less, and a still more preferable range is 0.3% or more and 0.6% or less.

Sb: 0.2% or less V: 0.5% or less W: 0.5% or less Zr: 0.5% or less Co: 0.5% or less Sb, V, W, Zr, and Co improve corrosion resistance. It is an element effective in suppressing the grain boundary segregation of P and S and improving the magnetic properties, and is contained if necessary. In particular, Sb is a strong grain boundary segregation element and, like Sn and B, has a function of eliminating grain boundary segregation of impurity elements such as P and S. When these elements are contained, the content of each element is set to 0.01% or more. Since excessive content leads to deterioration of manufacturability and magnetic properties, Sb is set to 0.2% or less, and V, W, Zr, and Co are each set to 0.5% or less. A more preferable range of Sb is 0.02 to 0.15%, further preferably 0.02 to 0.1% or less. A more preferable range of V, W, Zr, and Co is 0.02 to 0.3%, and a further preferable range is 0.02 to 0.2%.

Mg: 0.005% or less Mg forms Mg oxide with Al in molten steel and acts as a deoxidizing agent, and also acts as a crystallization nucleus of TiN. TiN serves as a solidification nucleus of the ferrite phase in the solidification process, and promotes crystallization of TiN, so that the ferrite phase can be finely generated during solidification. By refining the solidified structure, recrystallization and crystal grain growth can be promoted and magnetic characteristics can be improved. When it is contained, the content is set to 0.0001% or more for exhibiting these effects. However, if Mg exceeds 0.005%, the magnetic properties deteriorate, so the upper limit is made 0.005% or less. It is preferably 0.0003 to 0.002%, and more preferably 0.0003 to 0.001%.

Ca: 0.005% or less Ga: 0.015% or less Ca and Ga are elements that improve the cleanliness of steel, and are contained as necessary. When it is contained, Ca is 0.0003% or more and Ga is 0.001% or more in order to exert these effects. However, since excessive content leads to deterioration of magnetic properties, the upper limits are set to 0.005% or less for Ca and 0.015% or less for Ga. Ca is preferably 0.0003 to 0.0015%, more preferably 0.0003 to 0.001%. Ga is preferably 0.001 to 0.013% and 0.005 to 0.010%.

La: 0.1% or less Y: 0.1% or less Hf: 0.1% or less REM: 0.1% or less La, Y, Hf, and REM improve the cleanliness of steel similarly to Ca and Ga. It is an element and may be contained if necessary. When it is contained, the content is 0.001% or more in order to exert the effect. However, excessive contents lead to deterioration of magnetic properties, so the upper limits are made 0.1% or less. It is preferably 0.001 to 0.05%, and more preferably 0.001 to 0.03%.

  REM (rare earth element) is a general term for two elements, scandium (Sc) and yttrium (Y), and 14 elements (lanthanoids) from cerium (Ce) to lutetium (Lu) in the periodic table. These elements may be contained alone or in a mixture.

  Incidentally, the impurities contained in the balance, when industrially manufacturing a steel sheet, ore as a raw material, scrap, or those that are mixed from the manufacturing environment, etc., the range that does not adversely affect the steel sheet of the present invention Means acceptable.

  Next, the texture of the ferritic stainless steel sheet of this embodiment will be described. In the ferritic stainless steel sheet of the present embodiment, the texture on the sheet surface satisfies the following (i) and (ii).

(I) The area difference of {110} ± 15 ° orientation grains, in which the angular difference between the normal direction of the steel sheet surface and the {110} plane orientation on the plate surface is within 15 °, is more than 3.0% and less than 30%.
(Ii) 0.10 <A / B <0.80, where A is the area ratio of {110} ± 15 ° oriented grains and B is the area ratio of {111} ± 15 ° oriented grains on the plate surface.

  The {110} orientation is called the Goss orientation and has good magnetic properties because the rolling direction coincides with the easy axis of magnetization of iron. In the present invention, it has been found that it is effective to control the area ratio of oriented grains of {110} ± 15 ° or less on the plate surface without depending on the excessive generation of these Goss orientations. By including the area ratio of the {110} ± 15 ° oriented grains in the range of more than 3.0% and less than 30%, the {111} and {112} oriented grains may be divided to contribute to an increase in magnetic properties. it can. From the viewpoint of characteristics and manufacturability, the preferable range is 5.0 to 25%, and the more preferable range is 10 to 20%.

  When the area ratio of {110} ± 15 ° oriented grains on the plate surface is A and the area ratio of {111} ± 15 ° oriented grains is B, {111} ± 15 which is the main orientation of the recrystallization texture. It is effective to increase the ratio (A / B) with the orientation grains to a range of more than 0.10 and less than 0.80.

  The upper limit of A / B is less than 0.80 because of the deterioration of workability. The upper limit of A / B may be less than 0.70 in order to reduce manufacturability. From the viewpoint of characteristics and manufacturability, the preferable A / B range is 0.20 to 0.70, and the more preferable range is 0.40 to 0.70.

  In the present invention, the “plate surface” is a region up to t / 8 of the plate thickness t of the steel plate, and refers to a region from the surface of the steel plate to a thickness of 1/8 t in the surface direction on both sides of the steel plate. Further, the (111) ± 15 ° orientation grains mean crystal grains having a crystal orientation in which an angle difference between the normal direction of the steel sheet surface and the {111} plane orientation is within 15 °.

  The influence of the texture on the magnetic properties described above can be analyzed using electron beam backscattering diffraction (hereinafter referred to as EBSD). EBSD is to measure and analyze the crystal orientation of each crystal grain in a micro region of the sample surface at high speed. The crystallographic orientation group that contributes to the magnetic properties should be digitized by displaying a crystallographic orientation map divided into two regions of {110} ± 15 ° oriented grains and {111} ± 15 ° oriented grains in the center of plate thickness. You can For example, in a plane parallel to the steel plate surface, EBSD is measured with a magnification of 100 in a measurement region of a plate width direction of 850 μm and a rolling direction of 2250 μm, and an angle between the normal direction of the plane parallel to the steel plate surface and the {110} plane orientation. The area ratio can be displayed by displaying a crystal orientation map of crystal grains having a difference of 15 ° or less (that is, {110} ± 15 ° orientation grains).

The ferritic stainless steel sheet of the present embodiment preferably has high magnetic permeability and low coercive force as magnetic characteristics. The relative permeability and the coercive force are evaluated for their applicability to contact members by the numerical values obtained under the following measurement conditions. The measurement conditions were such that a ring-shaped test piece with an outer diameter of Φ45 mm and an inner diameter of Φ33 mm was prepared, the number of windings was 100, the applied magnetizing force was 1000 A / m, and magnetic measurement (B-H curve) was performed at room temperature to obtain a relative permeability ( μ) and coercive force (Hc [A / m]). The applied magnetizing force evaluates the ease of magnetization as a value that does not reach saturation magnetization. The ease of magnetization is better as the relative permeability is higher, and the hysteresis loss is better as the coercive force is smaller.
The relative permeability μ is preferably 500 or more, preferably 600 or more, and more preferably 700 or more. The coercive force Hc is 400 A / m or less, preferably 300 A / m or less, and more preferably 250 A / m or less.
A high relative magnetic permeability and a low coercive force are preferable because when the ferritic stainless steel is applied to a contact member, it is easy to magnetize and the hysteresis loss is small.

Next, a method for manufacturing the ferritic stainless steel sheet according to this embodiment will be described.
The ferritic stainless steel sheet of the present embodiment will secure the magnetic properties targeted by the present invention even if it is manufactured under normal process conditions such as casting, hot working, cold working, etc., if the above-mentioned chemical components are satisfied. It is possible.
More preferably, the ferritic stainless steel sheet of the present embodiment is a steel having the above chemical composition, after hot rolling, the heat treatment is omitted or heat treatment is performed at 700 ° C. or less, and then cold rolling at a rolling ratio of 40% or less. And heat treatment at over 900 ° C. to manufacture.

  After hot rolling, heat treatment is omitted and cold rolling is performed, or heat treatment is performed at a soaking temperature of 700 ° C. or less and then cold rolling is performed. When the heat treatment after hot rolling is carried out at a soaking temperature higher than 700 ° C., the {110} oriented grains effective for enhancing the magnetic properties in the present invention may decrease. The {110} ± 15 ° oriented grains, which are effective for enhancing magnetic properties, are easily recrystallized from grain boundaries with high strain energy, so heat treatment after hot rolling is omitted or strain energy during hot rolling is eliminated. It is preferable to carry out cold rolling after heat treatment at 700 ° C. or lower.

  The soaking time during heat treatment is preferably 10 seconds to 10 minutes. A soaking time of 10 seconds or more is preferable because the material for cold rolling can be softened. Further, if the soaking time is 10 minutes or less, the {110} oriented grains effective for enhancing the magnetic properties are not dissipated and the {110} ± 15 ° oriented grains effective for enhancing the magnetic properties are strained. It is possible to facilitate recrystallization from a grain boundary having high energy.

  Cold rolling is preferably cold-dark rolling at a reduction rate of 40% or less. If the cold rolling rate exceeds 40%, the {110} ± 15 ° oriented grains may be lowered due to the formation and growth of {111} ± 15 ° oriented grains which are recrystallized textures. Therefore, the rolling reduction of cold rolling is preferably 40% or less.

  The heat treatment after cold rolling is preferably performed at a heat treatment temperature of more than 900 ° C. in order to grow {110} ± 15 ° oriented grains. Excessive temperature rise causes reduction and disappearance of {110} ± 15 ° oriented grains, so the upper limit of the heat treatment temperature is preferably 1050 ° C. Further, the atmosphere during the heat treatment is not particularly specified, but it is preferable that the atmosphere is LNG fuel atmosphere or BA atmosphere.

  The soaking time of the heat treatment after cold rolling is preferably 1 second to 5 minutes. In order to generate the Goss orientation, the soaking time is preferably 1 second or longer. Further, if the soaking time is 5 minutes or less, it is possible to prevent the {110} ± 15 ° oriented grains from being reduced or lost.

The ferritic stainless steel sheet of this embodiment can be suitably used as a contact member arranged in a magnetic field.
FIG. 1 shows an example of a magnetic circuit breaker. The magnetic circuit breaker 1 shown in FIG. 1 includes a relay unit 10 and a drive unit 20. The magnetic circuit breaker 1 is configured such that the movable contact member 13 provided in the relay unit 10 is driven up and down by the drive unit 20 so that the movable contact member 13 contacts or does not contact the pair of fixed contact members 12. ing. The fixed contact member 12 is connected to an external circuit. The current of the external circuit is not cut off when the movable contact member 13 and the fixed contact member 12 are in contact with each other, and the current of the external circuit is cut off when they are in non-contact with each other. The structure of the magnetic circuit breaker 1 will be described below. The ferritic stainless steel plate of this embodiment is applied to the materials of the movable contact member 13 and the fixed contact member 12.

  The relay unit 10 includes a hollow box-shaped relay unit casing 11, two columnar fixed contact members 12 penetrating the upper surface 11 a of the relay unit casing 11, and a rod-shaped member arranged inside the relay unit-side casing 11. Of the movable contact member 13 and a spring 14 for urging the movable contact member 13 toward the fixed contact member 12 side. The movable contact member 13 and the fixed contact member 12 are formed of the ferritic stainless steel of this embodiment. The two fixed contact members 12 are arranged apart from each other. The columnar fixed contact member 12 is provided with a fixed contact portion 12a on one end side and an external terminal portion 12b on the other end side. The fixed contact portion 12 a is inserted inside the relay portion housing 11 and is arranged so as to face the movable contact member 13. The external terminal portion 12b is arranged outside the relay casing member 11 and is connected to an external circuit.

  The rod-shaped movable contact member 13 has a movable contact portion 13a on the upper surface. The movable contact member 13 is arranged in the relay housing 11 such that the movable contact portion 13a faces the two fixed contact portions 12b. The movable contact member 13 is connected to the connection shaft 24 of the drive unit 20. FIG. 1 shows a state in which the movable contact member 13 is located at the bottom of its movable range. In this state, the movable contact portion 13a and the fixed contact portion 12a are separated from each other and the current of the external circuit is cut off. Further, the alternate long and short dash line shown in FIG. 1 indicates a state in which the movable contact member 13 is located at the uppermost part of its movable range. In this state, the movable contact portion 13a and the fixed contact portion 12a are in contact with each other and the current of the external circuit is not interrupted.

  A spring 14 is arranged inside the relay unit housing 11. The spring 14 biases the movable contact member 13 toward the fixed contact member 12 in order to bring the movable contact member 13 into contact with the fixed contact member 12. The connection shaft 24 is inserted through the spring 14. A magnetic field is formed inside the relay housing 11 by a magnet (not shown).

  The drive unit 20 includes a drive unit housing 21, an electromagnet coil 22 arranged inside the drive unit housing 21, a cylindrical yoke 23 inserted into a hollow portion 22 a of the electromagnet coil 22, and a yoke 23. The connecting shaft 24 and the hollow tubular guide member 25 that guides the yoke 23 are provided. The connection shaft 24 penetrates the drive unit casing 21 and is connected to the movable contact member 13.

  The operation of the magnetic breaker 1 will be described. When the electromagnet coil 22 is not energized, the movable contact member 13 is biased toward the fixed contact member 12 by the spring 14, and the movable contact portion 13a and the fixed contact portion 12a come into contact with each other. As a result, the current of the external circuit is passed. On the other hand, when the electromagnet coil 22 is energized to generate a magnetic force, the yoke 23 is attracted to the electromagnet coil 22 against the urging force of the spring 14, whereby the movable contact member 13 is fixed to the fixed contact via the connecting shaft 24. The member 12 is separated from the member 12, and the current of the external circuit is cut off. A magnetic field is formed inside the relay housing 11 by a magnet (not shown), and the arc generated when the current is cut off is extended even by the magnetic field inside the relay housing 11, resulting in a large current. Even if it is cut off surely.

  The movable contact member 13 and the fixed contact member 12 of the magnetic circuit breaker 1 are made of the ferritic stainless steel of this embodiment. The ferritic stainless steel sheet of the present embodiment is superior in impact resistance as compared with the conventional contact material such as copper alloy, so that contact / non-contact between the movable contact member 13 and the fixed contact member 12 is repeated many times. Even if it is broken, the movable contact member 13 and the fixed contact member 12 can be prevented from being damaged. In addition, since the ferritic stainless steel sheet of this embodiment has excellent magnetic characteristics, the movable contact member 13 and the fixed contact member 12 are easily magnetized by the magnetic field generated inside the relay housing 11. As a result, the distribution of the magnetic field inside the relay part housing 11 is not disturbed by the movable contact member 13 and the fixed contact member 12, and the extension of the arc at the time of interruption of the current due to the magnetic field is not hindered, and the current flow is reduced. It can be surely shut off.

  The ferritic stainless steel sheet of the present embodiment is not limited to the magnetic circuit breaker 1 shown in FIG. 1, and any circuit breaker that extinguishes an arc by a magnetic field can be suitably used as a contact material. it can.

Examples of the present invention will be described below.
Ferritic stainless steel having the composition of the components shown in Table 1 was melted, heated to a heating temperature of 1150 to 1250 ° C. and hot-rolled to manufacture a hot-rolled steel sheet having a thickness of 4.0 mm. The hot-rolled steel sheet was annealed under the conditions shown in Table 2, pickled and then cold-rolled to a sheet thickness of 1.5 to 3.0 mm, followed by finish annealing at 880 to 980 ° C and pickling. In this way, ferritic stainless steel was manufactured. The obtained ferritic stainless steel was evaluated for magnetic properties and impact resistance.

The evaluation of magnetic properties was carried out according to the following procedure according to JIS C 2556.
To evaluate the magnetic properties, a ring-shaped test piece with an outer diameter of Φ45 mm and an inner diameter of Φ33 mm was prepared, the number of windings was 100, the applied magnetizing force was 1000 A / m, and the magnetic measurement (B-H curve) was performed at room temperature to determine the relative permeability. The magnetic susceptibility (μ) and the coercive force (Hc [A / m]) were obtained. The applied magnetic field force evaluated the ease of magnetization as a value that did not reach saturation magnetization. The evaluation criteria are as follows. The evaluation ranks 1 to 3 were passed, and the evaluation rank 4 was rejected.

Evaluation rank 1: The relative magnetic permeability is 700 or more and the coercive force is 250 A / m or less.
2: The relative magnetic permeability satisfies 600 or more and less than 700 and the coercive force exceeds 250 A / m and 300 A / m or less.
3: A relative magnetic permeability of 500 or more and less than 600 and a coercive force of more than 300 A / m and 400 A / m or less are satisfied.
4: Either the relative magnetic permeability is less than 500 or the coercive force exceeds 400 A / m, or both are satisfied.

The impact resistance was evaluated by the Charpy impact test. The Charpy impact test was performed according to JIS Z 2242. The test piece had a V-notch shape with a plate thickness x 10 mm width x 55 mm length, and the test temperature was -40 ° C. The case where the impact value was 20 J / cm ² or more was judged as pass (◯), and the case where the impact value was less than 20 J / cm ² was judged as fail (x). When the impact value was 20 J / cm ² or more, a ductile fracture surface shape appeared, so this was accepted, and when the impact value was less than 20 J / cm ² , a brittle fracture surface shape appeared, and therefore it was rejected.

  The texture was analyzed using an electron backscatter diffraction method (hereinafter referred to as EBSD). The crystal orientation group that contributes to the magnetic properties was quantified by displaying a crystal orientation map divided into two regions of {110} ± 15 ° oriented grains and {111} ± 15 ° oriented grains in the central portion of the plate thickness. That is, on the plane parallel to the steel plate surface, EBSD was measured with a magnification of 100 in the measurement region of the plate width direction 850 μm and the rolling direction 2250 μm, and the angle between the normal direction of the plane parallel to the steel plate surface and the {110} plane orientation. A crystal orientation map of crystal grains having a difference of 15 ° or less (that is, {110} ± 15 ° orientation grains) was displayed, and the area ratio was displayed and measured.

The test results are summarized in Table 2.
No. Nos. 1 to 13 were all ferritic stainless steels having the chemical composition and texture within the scope of the present invention, and had good magnetic properties and impact resistance properties. In particular, the steel sheet after hot rolling was subjected to heat treatment at 700 ° C. or lower, or the heat treatment was omitted, cold rolling was performed at a rolling ratio of 40% or lower, and further heat treatment was performed at over 900 ° C. Nos. 5, 7, 9, and 11 have the same chemical composition, but were manufactured under conditions deviating from the above manufacturing conditions. Compared with 4, 6, 8 and 10, the magnetic characteristics were further improved. No. Since Nos. 5, 7, and 9 were manufactured under more preferable manufacturing conditions, the ratio A / B of the area ratio A of {110} ± 15 ° oriented grains and the area ratio B of {111} ± 15 ° oriented grains was 0.40. It is inferred that the magnetic property was further improved because it was in a more preferable range of 0.70.

No. Nos. 14 to 19 are ferritic stainless steels having no chemical components within the scope of the present invention, and a preferable texture was not formed, so that either one or both of the magnetic characteristics and the impact resistance were inferior.
No. No. 14 had an excessive amount of C, segregated carbides at the grain boundaries, and did not form a more preferable texture, and thus both magnetic properties and impact resistance properties were poor.
No. In No. 15, the amount of Si was excessive and a preferable texture was not formed, so the magnetic properties and the impact resistance properties were poor.
No. In No. 16, the amount of Mn and the amount of Al were excessive and a preferable texture was not formed, so that the magnetic properties were poor.
No. In No. 17, the amount of P was excessive, P was excessively segregated at the grain boundaries, and a preferable texture was not formed, so that both magnetic properties and impact resistance properties were poor.
No. No. 18 had an excessive amount of S, formed sulfides in the alloy, and was excessively segregated at the grain boundaries, and a favorable texture was not formed, so that both magnetic properties and impact resistance properties were poor. It was
No. No. 19 has an excessive amount of Cr and N, an increased amount of Cr, which is a non-magnetic element, forms a nitride in the alloy, and N is excessively segregated at the crystal grain boundaries. Was not formed, the magnetic properties were poor and the impact resistance was also poor.

  DESCRIPTION OF SYMBOLS 1 ... Magnetic circuit breaker, 10 ... Relay part, 12 ... Fixed contact member, 13 ... Movable contact member, 20 ... Driving part.

In order to solve the above problems, the present invention adopts the following configurations.
[1] In mass%,
C: 0.020% or less,
Si: 1.00% or less,
Mn: 1.00% or less,
P: 0.035% or less,
S: 0.0030% or less,
Cr: 10.0 to 18.0%,
N: 0.020% or less,
Nb: 0.5% or less,
Ti: 0.5% or less,
Al: including 0.10% or less,
The balance consists of Fe and impurities,
Texture in the plate surface meets the (i) and (ii) below,
A ferritic stainless steel sheet having excellent magnetic properties, which has a relative permeability μ of 500 or more and a coercive force Hc of 400 A / m or less .
(I) The area difference of {110} ± 15 ° orientation grains, in which the angular difference between the normal direction of the steel sheet surface and the {110} plane orientation on the plate surface is within 15 °, is more than 3.0% and less than 30%.
(Ii) When the area ratio of {110} ± 15 ° oriented grains on the plate surface is A and the area ratio of {111} ± 15 ° oriented grains is B, 0.10 <A / B <0.80.
[2] Further, in mass%,
Sn: 0.001-0.5%,
B: Ferrite-based stainless steel sheet having excellent magnetic properties according to [1], which contains one or two 0.005% or less.
[3] Further, in mass%,
Ni: 1% or less,
Cu: 1% or less,
Mo: 1% or less,
Sb: 0.2% or less,
V: 0.5% or less,
W: 0.5% or less,
Zr: 0.5% or less,
Co: 0.5% or less,
Mg: 0.005% or less,
Ca: 0.005% or less,
Ga: 0.015% or less,
La: 0.1% or less,
Y: 0.1% or less,
Hf: 0.1% or less,
REM: A ferritic stainless steel sheet having excellent magnetic properties according to [1] or [2], which contains 0.1% or less of one type or two or more types.
[4] The ferritic stainless steel sheet having excellent magnetic properties according to any one of [1] to [3], which is used as a contact member arranged in a magnetic field.

Claims (4)

In mass%,
C: 0.020% or less,
Si: 1.00% or less,
Mn: 1.00% or less,
P: 0.035% or less,
S: 0.0030% or less,
Cr: 10.0 to 18.0%,
N: 0.020% or less,
Nb: 0.5% or less,
Ti: 0.5% or less,
Al: including 0.10% or less,
The balance consists of Fe and impurities,
A ferritic stainless steel sheet having excellent magnetic properties, characterized in that the texture on the plate surface satisfies the following (i) and (ii).
(I) The area difference of {110} ± 15 ° orientation grains, in which the angular difference between the normal direction of the steel sheet surface and the {110} plane orientation on the plate surface is within 15 °, is more than 3.0% and less than 30%.
(Ii) When the area ratio of {110} ± 15 ° oriented grains on the plate surface is A and the area ratio of {111} ± 15 ° oriented grains is B, 0.10 <A / B <0.80. Furthermore, in mass%,
Sn: 0.001-0.5%,
B: 0.005% or less of 1 type or 2 types is contained, The ferritic stainless steel sheet excellent in the magnetic characteristic of Claim 1 characterized by the above-mentioned. Furthermore, in mass%,
Ni: 1% or less,
Cu: 1% or less,
Mo: 1% or less,
Sb: 0.2% or less,
V: 0.5% or less,
W: 0.5% or less,
Zr: 0.5% or less,
Co: 0.5% or less,
Mg: 0.005% or less,
Ca: 0.005% or less,
Ga: 0.015% or less,
La: 0.1% or less,
Y: 0.1% or less,
Hf: 0.1% or less,
REM: A ferritic stainless steel sheet having excellent magnetic properties according to claim 1 or 2, containing 0.1% or less of one type or two or more types.   The ferritic stainless steel sheet having excellent magnetic properties according to any one of claims 1 to 3, which is used as a contact member arranged in a magnetic field.

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