JP3498933B2 - Soft magnetic stainless steel with high magnetic flux density - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soft magnetic stainless steel used for various relay iron cores and yoke parts of various motors. 2. Description of the Related Art Conventionally, electromagnetic soft iron (SUYP), galvanized steel sheet (SECP), and the like have been widely used as yoke parts for various relay iron cores and various motors. Since electromagnetic soft iron has poor corrosion resistance, it is usually used after plating after component processing. [0003] Problems to be Solved by the Invention [0004] Ni plating or unichrome plating is applied for the purpose of improving the corrosion resistance of electromagnetic soft iron. However, the plating deteriorates the magnetic characteristics originally possessed by the electromagnetic soft iron. Electromagnetic soft iron cannot always exhibit stable and excellent characteristics, such as variations in magnetic properties due to variations in plating thickness for each product. In addition, galvanized steel sheets not only do not originally exhibit magnetic properties as excellent as electromagnetic soft iron, but also have the characteristic that it is difficult to obtain the same stability as electromagnetic soft iron by plating. It is well known that the performance of a relay iron core and a motor yoke depends on the magnetic flux density.
JP-A-5-255817 proposes an Fe-Cr alloy as a material having a high magnetic flux density and excellent corrosion resistance. This Fe-Cr alloy is a material having an advantage that the plating step can be omitted because of its excellent corrosion resistance. Fe-Cr alloys, like electromagnetic soft iron and galvanized steel sheets, are used in relay iron cores and motor yokes when cold-rolled steel sheets are stamped or pressed. If the steel plate is large, that is, if the steel plate has an unnecessarily large undulation and the shape is not good, it becomes difficult to process. Further, even if processing is possible, the shape and dimensional accuracy of the parts after processing are not always satisfactory, and as a result, there is a problem that the performance as a relay iron core or a motor yoke varies. [0005] Therefore, the shape of a cold-rolled steel sheet having a large steepness after annealing and pickling is corrected before being subjected to punching or pressing. However, Fe-C
r-based steel sheets have higher proof strength than electromagnetic steel sheets and plain steel sheets made of galvanized steel sheets, and in order to correct the shape, larger stress must be applied than electromagnetic steel sheets and ordinary steel sheets. On the other hand, a large residual stress tends to be generated in the Fe-Cr-based steel sheet after the shape correction, and this residual stress acts as a factor for deteriorating magnetic properties. [0006] Also, since a small amount of residual stress is generated in a part after processing by punching or pressing, even after slight processing after forming into a relay iron core or a motor yoke part, including the one caused by the above-mentioned shape correction. Usually, heat treatment called magnetic annealing for removing residual stress and restoring magnetic properties is performed. Magnetic annealing is performed at a temperature of 850
It seems that the method is generally carried out at 1150 ° C. for 30 minutes to 3 hours under a hydrogen atmosphere or a vacuum. The magnetic annealing complicates the process, takes a long time, causes a decrease in productivity, and requires a consumable material to increase production costs. The present invention has been made to solve these problems, has good corrosion resistance, does not require plating, suppresses steepness, and provides excellent punching and press workability. Another object of the present invention is to develop a soft magnetic stainless steel suitable for use as a relay iron core or a motor yoke component having a high magnetic flux density without suppressing the generation of residual stress and performing magnetic annealing. [0008] The object of the present invention is to provide, by weight%, C:
0.02% or less, Si: 0.1 to 3.0%, Mn: 1.
0% or less, P: 0.04% or less, S: 0.01% or less,
Cr: 9.0-17.0%, N: 0.02% or less, N
i: 1.0% or less, Al: 1.0% or less, Ti: 1.0
%, The balance being Fe and inevitable impurities, the steepness of the cold-rolled steel sheet after annealing and pickling is 1.5% or less, and the residual stress on the steel sheet surface is less than 1.5%. It can be achieved by a soft magnetic stainless steel having an absolute value of 10 kgf / mm ² or less and a magnetic flux density B ₁₀ of 6000 G or more. BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have conducted various studies on factors affecting the magnetic flux density of a steel sheet,
It has been found that there is a relationship between the residual stress value on the steel sheet surface and the magnetic flux density. Fe- having a chemical composition within the scope of the present invention
Residual stress value and intensive investigation result the relationship between the magnetic flux density B ₁₀ of Cr-based steel sheet surface, as shown in each of FIGS. 1 and 2, in the residual stress value of the steel sheet surface is tensile and is compressed though, centralized relationship is established between the residual stress value and B _10, the larger the absolute value of the residual stress values B ₁₀
Was found to decrease. Further, in the case of an Fe—Cr-based steel sheet having a chemical composition within the range of the present invention, by setting the absolute value of the residual stress on the steel sheet surface to 10 kgf / mm ² or less, a relay iron core, a motor yoke part, etc. in B ₁₀ necessary to secure performance of the 600
It has been clarified that characteristics of 0 G or more can be obtained. [0011] Further, as described above, when punching and pressing, the steel plate is required to have a small steepness. Because of the difficulty in working with the steepness of the steel sheet is large, it is necessary to the correction of steepness, the problem that the magnetic flux density B ₁₀ is lowered caused by straightening. Therefore, in order to satisfy workability and obtain a desired magnetic flux density, the steepness of the steel sheet must be reduced. If the steel sheet of the present invention is to be processed into a motor yoke, a relay iron core, or the like, which is a use of the steel sheet of the present invention, the steepness may be 1.5% or less. Here, the steepness means a value defined in FIG. [0012] Generally, a steel sheet is finish-annealed and pickled after cold rolling. However, if the roll crown or roll load is inappropriate during cold rolling, the steel sheet bends even after finish annealing and pickling. There is a defective shape. In the Fe-Cr system intended in the present invention, a steepness of 1.5
In order to obtain a steel sheet of not more than%, it is necessary to adjust the taper amount and the roll load of the backup roll during the cold rolling to an appropriate range, and to balance the settings of both. For example, when the diameter of the work roll is 45 to 55,
When the cold rolling of the stainless steel of the present invention is carried out by a Sendzimir rolling mill having a thickness of 10 mm, the taper amount of the backup roll adjacent to the work roll is set to 10/1000 to 30.
By adjusting the roll load to 450 to 550 tons, a good steel plate having a shape with a steepness of 1.5% or less can be obtained. Here, the taper amount of the backup roll refers to a value defined in FIG. Further, the steepness is 1.5% by cold rolling.
When the steel sheet exceeds the limit, while performing temper rolling for shape correction to reduce the steepness to 1.5% or less,
Thereafter, re-annealing, for example, annealing at 800 ° C. × 0 min, is performed to remove the residual stress of the straightening rolling to an absolute value of 10 kgf / mm ² or less and obtain a desired magnetic flux density B ₁₀ 6000
G or more can be obtained. [0014] The steel sheet of the present invention is basically used without magnetic annealing even after part processing such as punching and pressing. However, when the component processing is a strong processing, the residual stress after the processing may exceed 10 kgf / mm ² in absolute value, and in such a case, the magnetic flux density is lowered and the component is not suitable for use.
In this case, too, a low temperature and a short time after processing the parts, for example, 800
By performing magnetic annealing at a temperature of 0 ° C. × 0 min, the residual stress of the component can be removed and a good magnetic flux density can be obtained, so that it can be used. [0015] The steel sheet of the present invention has a steepness of 1.5% or less after finish annealing and pickling, allows easy processing of parts such as punching and pressing, and has an absolute value of residual stress on the steel sheet surface. Value is 10 kgf / mm ² or less and the magnetic flux density B ₁₀ is 6
Since it is 000G or more, it is used in a motor, a relay, or the like, and exhibits excellent characteristics. The reasons for limiting the chemical composition of the steel which is the subject of the present invention will be described below. C: 0.02% by weight or less C forms carbides, deteriorates corrosion resistance and adversely affects magnetic properties. Si: 0.1% by weight or more and 3.0% by weight or less Si is an element which effectively acts to improve the magnetic properties.
It is necessary to contain the above. However, excessive content increases the hardness and makes punching or pressing difficult, so that the content is set to 3.0% by weight or less. Mn: 1.0% by weight or less Mn is an element necessary for deoxidation at the time of steel making, but an excessive content degrades magnetic properties. P: not more than 0.04% by weight P has an effect of deteriorating magnetic properties.
% By weight or less. S: not more than 0.01% by weight S is an element exhibiting an effect of remarkably deteriorating magnetic properties, and is therefore limited to not more than 0.01% by weight. Cr: 9.0% by weight or more, 17.0% by weight
In the following, Cr is an essential element for securing the corrosion resistance required for the intended use in the present invention, and requires a content of 9.0% by weight or more. However, an excessive content has an effect of lowering the magnetic flux density, so that the content is set to 17.0% by weight or less. Ni: 1.0% by weight or less Ni lowers the magnetic flux density by 1.0% by weight or less. N: 0.02% by weight N has the same effect of deteriorating corrosion resistance and magnetic properties as C, and is therefore not more than 0.02% by weight. Al and Ti: 1.0% by weight or less each Al and Ti are elements necessary for deoxidation during steelmaking.
Because it contributes to the reduction of impurities by the deoxidation function accompanying the addition,
Improve magnetic properties. However, if added in excess, they may remain in the steel as inclusions and conversely exhibit the effect of deteriorating magnetic properties. Hereinafter, the present invention will be described in detail with reference to examples. Various test steels having the chemical compositions shown in Table 1 were melted through an electric furnace-converter-degassing-continuous casting process to have a thickness of 20%.
A slab of 0 mm was obtained. Among the test steels shown in Table 1, A
1 to A5 are examples of the present invention, and B1 and B2 are comparative examples. After hot rolling, all steels were subjected to annealing and pickling and then subjected to cold rolling. In cold rolling, the taper amount of the backup roll is reduced by 1
The adjustment was performed in the range of 0/1000 to 30/10000, the roll load was adjusted in the range of 450 to 550 tons, and the final finished plate thickness was 1.0 mm. Then 9
Finish annealing was performed at 00 ° C. × 0 min, followed by pickling with mixed acid of hydrofluoric and nitric acids. [Table 1] Each of the test cold-rolled steel sheets was subjected to a final annealing
A test piece having a size of 00 mm × 1000 mm was sampled, placed on a surface plate having a flat surface, and l and h shown in FIG. 3 were measured to determine the steepness. In addition, a ring test piece having an outer diameter of 45 mm and an inner diameter of 33 mm was collected from each test steel sheet. Next, the obtained ring test piece was subjected to a process corresponding to a strain of about 1% using an Amsler type testing machine, assuming the effect of residual stress, that is, the application of strain due to punching and pressing part processing. Thereafter, the magnetic flux density was measured B ₁₀ without magnetic annealing. The surface residual stress of each ring test piece was measured by an X-ray diffractometer method. Further, the corrosion resistance of each test steel was determined according to JIS-Z
Evaluation was performed by a 24-hour salt spray test according to 2371. The evaluation was made by visual judgment, and those with almost no rusting were evaluated as ○ with good corrosion resistance, and those with rust with an area ratio of 10% or more were evaluated as x with poor corrosion resistance. Table 2 shows the test results. Test steels A1 to A5
Has a chemical composition within the range of the present invention, a steepness of 1.5% or less, excellent steel sheet shape, an absolute value of surface residual stress of 10 kgf / mm ² or less, and a magnetic flux density B ₁₀ of 600
It shows excellent magnetic properties of 0 G or more, and also has excellent corrosion resistance. On the other hand, test steels B1 and B2 as comparative examples
For, B1 is superior to the magnetic flux density B ₁₀ is high magnetic properties because of the steepness and surface residual stresses present invention range, corrosion resistance is inferior because the Cr content is low. B2 has both steepness and surface residual stress in the range of the present invention,
Since a high content outside the range of the present invention, corrosion resistance is good low magnetic flux density B _10. Next, in order to produce cold-rolled steel sheets having various steepnesses using the test steel A6 shown in Table 3 whose chemical composition is within the range of the present invention, as shown in Table 4, Cold rolling was performed to a thickness of 1.0 mm by changing the cold rolling conditions. In Test Nos. 1, 2 and 4, finish annealing pickling was performed after cold rolling, and the steepness was measured. In test number 3, after finish annealing pickling,
Re-annealing (800 ° C. × 0 min) was performed to remove strain caused by the leveler passing plate and the leveler, and the steepness was measured after pickling. In Test No. 5, the steepness was measured without passing through a leveler but re-annealing for the purpose of removing strain. After the measurement steepness with test material of each test number, outer diameter 45 mm, a ring test piece having an inner diameter of 33mm was taken to measure the magnetic flux density B _10. However, test number 2
In order to clarify the effect of surface residual stress on both of Nos. 5 and 5, after processing into a ring test piece, the test piece of test No. 2 was processed with 1% strain and the test of test no. after giving the process of the 3% strain into pieces, the magnetic flux density was measured B _10. Further, the surface residual stress of the ring test piece of each test number was measured by the same method as described above. [Table 3] [Table 4] Table 5 shows the measurement results. In Test Nos. 1 and 2 of the present invention, since the cold rolling conditions are appropriate, the steepness is small, and the applied strain in the final step is small, the absolute value of the surface residual stress is 10 kgf / mm ² or less. Density B
₁₀ also shows a good value of 6000 G or more. On the other hand, in Test No. 4, in which the cold rolling conditions were inappropriate, but the leveler was not passed for shape correction, the absolute value of the surface residual stress was 10 kgf /
while indicating good value of more than the magnetic flux density B ₁₀ 6000 G in mm ² or less, high steepness, are accompanied difficulties in processing into the test piece, unsuitable as part material such as forced machining manual Met. In Test No. 5, although leveler passing was performed for shape correction, not only the subsequent strain relief and reannealing was not performed, but also the final applied strain was 3%.
Therefore, although the steepness is small, the absolute value of the surface residual stress exceeds 10 kgf / mm ² , and thus the magnetic flux density B ₁₀ is less than 6000 G, and the magnetic properties are not good. [Table 5] As described above, according to the present invention, according to the present invention, the shape of a steel sheet having magnetic characteristics and corrosion resistance suitable for various relay iron cores and motor yoke components, and suitable for automation of component processing, etc. Can be obtained.

Diagram showing the relationship between BRIEF DESCRIPTION OF THE DRAWINGS [Figure 1] compressive residual stress value and the magnetic flux density B _10. Diagram showing the relationship [2] the tensile residual stress value and the magnetic flux density B _10. FIG. 3 is a diagram illustrating steepness. FIG. 4 is a diagram illustrating a taper amount of a roll. [Table 2]

────────────────────────────────────────────────── ─── Continuing on the front page (72) Koji Seto 4976 Nomura Minami-cho, Shinnanyo-shi, Yamaguchi Pref. Nissin Steel Engineering Co., Ltd. (56) References JP-A-7-233452 (JP, A) 5-255817 (JP, A) JP-A-58-174525 (JP, A) JP-B-43-26992 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C22C 38/00 , 38/50

Claims (1)

(57) [Claims 1] By weight%, C: 0.02% or less, Si:
0.1-3.0%, Mn: 1.0% or less, P: 0.04
%, S: 0.01% or less, Cr: 9.0-17.0
%, N: 0.02% or less, Ni: 1.0% or less, Al:
1.0% or less, Ti: 1.0% or less, the balance being F
e) and a stainless steel comprising unavoidable impurities, the residual stress of the steel sheet surface of which is 10 kgf / mm ² or less in absolute value, the magnetic flux density B ₁₀ is 6000 G or more, and the cold-rolled steel sheet after annealing and pickling. A soft magnetic stainless steel having a steepness of 1.5% or less.