JPH09125147A - Production of ferritic stainless steel sheet excellent in magnetic property - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a stainless steel sheet excellent in magnetic properties and weldability by annealing a rolled sheet of ferritic stainless steel at specific temp. to regulate crystalline grain size to specific value and applying specific stress relief annealing to the rolled steel sheet after forming. SOLUTION: A slab of a ferritic stainless steel, containing, e.g. <=0.01%, by weight, C, 0.1-0.6% Si, 0.1-1.0% Mn, 9-13% Cr, 0.05-0.5% Ti, and <=0.015% N, is hot-rolled. The resultant plate is cold-rolled once or is cold-rolled two or more times subjected to intermediate annealing between cold rolling stages. The resultant cold rolled sheet is annealed at 925-1100 deg.C, by which grain size is grown to 70-300μm. Then, this steel sheet is formed into product shape and further subjected to stress relief annealing at 750-1000 deg.C for about 30sec to 30min.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a soft magnetic stainless steel plate used for electric and electronic parts such as a TV CRT support frame.

[0002]

2. Description of the Related Art So-called soft magnetic stainless steel sheets used for electric and electronic parts for TV cathode ray tube support frames and the like have hitherto been disclosed in, for example, JP-A-62-23962. There is an example of adding Si and Al to a ferritic stainless steel sheet as disclosed in US Pat. However, Si,
Excessive addition of Al deteriorates the workability of the material, particularly the elongation, and cracks occur when bending the TV CRT support frame, which is a problem.

On the other hand, in order to improve the magnetic properties by another means, for example, in Japanese Patent Laid-Open No. 2-182834, final annealing of a ferritic stainless steel sheet is carried out in a temperature range of two stages to obtain a Goss orientation ({110 } <001>) is strongly aggregated to obtain a texture, and an example of enhancing magnetic properties is disclosed. However, it is not preferable to perform the final annealing in the temperature range of two stages because it is difficult in operation and the cost increases.

[0004]

SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide a stainless steel plate having excellent magnetic properties and workability.

[0005]

The gist of the present invention is as follows. (1) A ferritic stainless steel slab is hot-rolled to form a hot-rolled sheet, and subsequently cold-rolled once or twice or more including intermediate annealing to obtain a cold-rolled sheet.
Anneal in the temperature range of ~ 1100 ° C to reduce the grain size to 70
.About.300 .mu.m, then formed into a product shape, and further subjected to strain relief annealing in a temperature range of 750 to 1000.degree. C., and (2) wt%, C.ltoreq.0.01%, Si: 0. 1 to 0.6%, Mn: 0.1 to 1.0%, Cr: 9 to 13%, Ti: 0.05 to 0.5%, N ≤ 0.015%, the balance being Fe and unavoidable A ferritic stainless steel slab containing impurities is hot-rolled to form a hot-rolled sheet, and then cold-rolled by one or more cold rolling including intermediate annealing to obtain a cold-rolled sheet. 110
Annealing is performed in the temperature range of 0 ° C., and then the crystal grain size is 70 to
It grows up to 300 μm, and then it is formed into a product shape,
Further, strain relief annealing is performed in the temperature range of 750 to 1000 ° C.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The reasons for limiting the alloy of the present invention will be described in detail below. If the content of C is too large, carbides are formed in the alloy to deteriorate magnetic properties, so the upper limit was made 0.01%. More preferably, 0.0
07% or less is good. Si is effective as a deoxidizer,
Although it is an element that improves the magnetic properties, if it is less than 0.1%, its effect is small, and if it exceeds 0.6%, the workability, especially elongation is reduced. Therefore, the range of Si is 0.10 to 0.60%. More preferably, 0.30 to 0.50% is good. Mn is effective as a desulfurizing and deoxidizing agent, but if it is less than 0.1%, its effect is small, and if it exceeds 1.0%, the corrosion resistance deteriorates. Therefore, the range of Mn is 0.10 to 1.0%. More preferably, it is 0.20 to 0.50%.

[0007] Cr is a basic element that imparts the corrosion resistance of stainless steel. If it is contained in less than 9.0%, its effect is small, while if it exceeds 13.0%, the magnetic properties are deteriorated. Therefore, the Cr range is 9.0 to 13.0.
%. More preferably, it is 10.0 to 11.5%. Ti is an element that improves corrosion resistance and magnetic properties, but if less than 0.05%, its effect is small, and
Addition of more than 0.5% lowers workability, especially elongation. Therefore, the range of Ti is set to 0.05 to 0.5%. More preferably, it is 0.1 to 0.3%. N
When the content is too large, a nitride is formed in the alloy to deteriorate the magnetic properties, so the upper limit was made 0.015%. More preferably, it is 0.01% or less.

Next, the reasons for defining the manufacturing method will be described. An alloy slab having a predetermined chemical composition is hot-rolled to form a hot-rolled sheet, and subsequently cold-rolled once or twice or more including intermediate annealing to obtain a cold-rolled sheet, followed by annealing 925 to 1100.
The crystal grain size is grown to 70 to 300 μm in the temperature range of ° C. When the annealing temperature is less than 925 ° C., the crystal grain size grows to less than 70 μm, and in that case, high magnetic properties cannot be obtained. As for the magnetic properties, it is desired that the maximum relative permeability be as high as 5000 or more.

FIG. 1 shows the relationship between the crystal grain size and the magnetic characteristics. The reason why the magnetic properties are low when the crystal grain size is less than 70 μm is that the crystal grain boundary area becomes large when the crystal grain size is less than 70 μm, and the movement of the domain wall is easily pinned by the grain boundaries during the magnetization process. The growth of the crystal grain size due to the higher annealing temperature reduces the grain boundary area and improves the magnetic properties. However, the annealing temperature is 1
If the temperature exceeds 100 ° C. and the crystal grain size exceeds 300 μm and the product shape is subjected to bending or the like, roughening of the processed surface occurs, which is not desirable. Therefore, the annealing temperature range is 925 to 1
It was 100 ° C. More preferably 950 to 1050 ° C
Is good. The holding time for annealing is preferably 30 seconds to 10 minutes. The particle size range was 70 to 300 μm. Further, it is preferably 70 to 220 μm.

After that, when temper rolling is performed, a predetermined elongation is imparted, or when temper rolling is not performed, the product is directly shaped into a product shape. Incidentally, in order to carry out work molding without causing cracks or the like, it is desired that the elongation is 34% or more. Then, strain relief annealing is performed in the temperature range of 750 to 1000 ° C. If the temperature is lower than 750 ° C., high magnetic properties cannot be obtained due to residual strain after processing. On the other hand, when the temperature exceeds 1000 ° C., the effect of strain relief is saturated and a load is added to the process, which is not desirable. Therefore, the strain relief annealing temperature range is set to 750 to 1000 ° C. Further, it is preferably 800 to 900 ° C.
The retention time of the strain relief annealing is preferably 30 seconds to 30 minutes.

[0011]

【Example】

(Example 1) Next, the present invention will be described with reference to Examples and Comparative Examples.
This will be specifically described. % By weight, C: 0.01%, S
i: 0.14%, Mn: 0.33%, Cr: 9.3%,
Ti: 0.12%, N: 0.0133%, balance F
An alloy consisting of e and unavoidable impurities was melted in a vacuum induction melting furnace and made into a slab by a continuous casting method. Then one
After heating at 250 ℃ for 2 hours, hot rolling is performed and the plate thickness is 3.7 mm.
Was obtained. Then, the edges of the hot-rolled sheet were slit to remove the surface flaws, cold rolled to obtain an intermediate cold-rolled thin sheet having a sheet thickness of 2.0 mm, and intermediate annealing was performed at 900 ° C. for 1 minute in the atmosphere. After that, pickling with nitric hydrofluoric acid, cold rolling again to obtain a cold rolled thin sheet with a thickness of 1.0 mm, and annealing at 915 to 1120 ° C.
After 1 minute in the atmosphere, a pickling treatment was performed with nitric hydrofluoric acid. From the L-direction cross-sectional structure of the obtained final annealed plate, the particle size was measured by a comparative method using an optical microscope. Then 3
A 0 mm wide × 300 mm long test piece was cut out and subjected to strain relief annealing at 770 ° C. for 5 minutes in the atmosphere.

The magnetic properties were measured according to JIS C2550 by stacking eight test pieces by the 25 cm Epstein method and measuring the maximum relative magnetic permeability μm. The relationship between the crystal grain size and the maximum relative magnetic permeability is shown in FIG. When the annealing temperature, which is out of the range of the present invention, is 915 ° C., the crystal grain size is 38 μm, and the maximum relative magnetic permeability is as low as 2850. When the annealing temperature is out of the range of the present invention and the annealing temperature is 1120 ° C., the crystal grain size grows to 355 μm and the maximum relative magnetic permeability becomes 13900, but roughening occurs after processing. On the other hand, at the annealing temperature within the range of the present invention, the maximum relative magnetic permeability is 5000 or more and the crystal grain size is 70 to 300 μm.

(Example 2) Table 1 shows the chemical composition, annealing conditions, crystal grain size, magnetic properties and the like of the present invention and comparative examples.
The alloy of the present invention and the comparative alloy as shown in Table 1 were melted in a vacuum induction melting furnace and made into a slab by a continuous casting method. After that, heating is performed at 1250 ° C. for 2 hours and hot rolling is performed to obtain a plate thickness of 3.8.
A hot rolled sheet of mm was obtained. After that, the end of the hot-rolled sheet is slit and the surface is scratched to obtain a cold-rolled sheet having a thickness of 1.0 mm by one cold rolling, and annealed in the atmosphere at 910 to 1130 ° C for 1 minute. After that, a pickling treatment with nitric hydrofluoric acid was performed. From the L-direction cross-sectional structure of the obtained annealed plate, the crystal grain size was measured by a comparative method with an optical microscope. Then, temper rolling was performed at an elongation rate of 1%, a test piece having a width of 30 mm and a length of 300 mm was cut out, and strain relief annealing was performed at 760 to 1040 ° C. for 6 minutes in the atmosphere. In the magnetic property measurement, the maximum relative magnetic permeability μm was measured in the same manner as in Example 1.

[0014]

[Table 1]

No. Nos. 1 to 13 are examples of the present invention. 14-26
Is a comparative example. Comparative Example No. In No. 14, the amount of C exceeds the range of the present invention, and in this case, the crystal grain size becomes small and the magnetic properties are remarkably deteriorated. Comparative Example No.
In No. 15, the amount of Si was lower than the range of the present invention, the crystal grain size was small, and the magnetic properties were remarkably deteriorated. Comparative Example No. 16
Has a Si content higher than the range of the present invention and has high magnetic properties,
Low growth. Comparative Example No. In No. 17, the Mn content was lower than the range of the present invention, the particle size was small, and the magnetic properties were remarkably deteriorated. Comparative Example No. No. 18 had a Cr content higher than the range of the present invention,
The magnetic properties are significantly reduced. Comparative Example No. 19 is T
The i amount is lower than the range of the present invention, and the magnetic properties are remarkably deteriorated. Comparative Example No. In No. 20, the amount of Ti is higher than the range of the present invention, the magnetic properties are high, but the elongation is low. Comparative Example No. 21
Has a N content higher than the range of the present invention, has a small particle size, and has significantly deteriorated magnetic properties.

Comparative Example No. In No. 22, the amount of C and N is higher than the range of the present invention, the crystal grain size is small, and the magnetic properties are remarkably deteriorated. Comparative Example No. No. 23 has a chemical composition within the range of the present invention, but the annealing temperature is lower than the range of the present invention, the crystal grain size becomes small, and the magnetic properties are remarkably deteriorated. Comparative example
No. Although the chemical composition range of No. 24 is within the range of the present invention, the annealing temperature is higher than the range of the present invention, the crystal grain size becomes large and the magnetic characteristics are high, but roughening occurred when molded into a product shape. Comparative Example No. In No. 25, the chemical composition range is within the range of the present invention, but the strain relief annealing temperature is lower than the range of the present invention, and the strain after processing remains, so the magnetic properties are low. Comparative Example No. 26, the chemical composition range is within the range of the present invention,
Although the strain relief annealing temperature is higher than the range of the present invention and the strain after working is removed, the effect is saturated and the load on the process is considered to be large, which is not desirable. Incidentally, when the content of Cr is less than 9.0% and the content of Mn is 1.0, which is out of the range of the present invention.
If it exceeds%, the corrosion resistance deteriorates and this is not desirable, so the magnetic properties were not measured.

[0017]

As is apparent from the above, according to the present invention, it is possible to obtain a stainless steel plate having excellent magnetic properties and workability.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between particle size and maximum relative magnetic permeability.

Claims (2)

[Claims] 1. A ferritic stainless steel slab is hot-rolled to form a hot-rolled sheet, and subsequently cold-rolled once or two or more times including intermediate annealing to obtain a cold-rolled sheet. ˜1100 ° C., annealing is performed in the temperature range to grow the crystal grain size to 70 to 300 μm, the product shape is then formed, and strain relief annealing is performed in the 750 to 1000 ° C. temperature range. A method for producing a ferritic stainless steel sheet having excellent characteristics. 2. In weight%, C ≦ 0.01%, Si: 0.1-0.6%, Mn: 0.1-1.0%, Cr: 9-13%, Ti: 0. A ferritic stainless steel slab containing 0.05 to 0.5% and N ≤ 0.015% and the balance being Fe and unavoidable impurities is hot-rolled to form a hot-rolled sheet. Cold rolled at least twice including intermediate annealing to obtain a cold rolled sheet,
This cold-rolled sheet is annealed in the temperature range of 925 to 1100 ° C., then grown to a crystal grain size of 70 to 300 μm, and subsequently molded into a product shape, and further 750 to 1000 ° C.
A method for producing a ferritic stainless steel sheet having excellent magnetic properties, which comprises performing strain relief annealing in the temperature range of 1.