JP2001303176A - Steel sheet for magnetic shield and its producing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a steel sheet for a magnetic shield excellent in bending workability and to provide its producing method. SOLUTION: A steel sheet having a yield point elongation of >=3% is used for a magnetic shield. The steel composition of this sheet is preferably composed of, by weight, 0.001 to 0.1% C, <0.3% Si, <=1.5% Mn, <=0.05% P, <=0.04% S, <=0.1% Sol.Al and <=0.01% N, and the balance substantially Fe.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic shielding steel sheet suitable as a material for a magnetic shielding component which is provided inside or outside a color cathode ray tube and is installed so as to cover from the side in the direction of electron beam passage. And its manufacturing method.

[0002]

2. Description of the Related Art The basic structure of a color cathode ray tube comprises an electron gun for emitting an electron beam and a phosphor screen for emitting an image by irradiating the electron beam to form an image. An electron beam is deflected by the influence of geomagnetism, and as a result, a color shift occurs in an image. As a means for preventing the deflection, an internal magnetic shield (also referred to as an inner shield or an inner magnetic shield) is generally installed. I have. Further, an external magnetic shield (also referred to as an outer shield or an outer magnetic shield) may be installed outside the color cathode ray tube (hereinafter, these internal magnetic shields and external magnetic shields are collectively referred to as magnetic shields).

[0003] Some magnetic shields for color cathode ray tubes have been manufactured by press deep drawing using an internal magnetic shield, but in recent years, manufacturing methods by bending and spot welding are mainly used. Since bending of a magnetic shield steel plate requires a high degree of bending angle precision, complicated work is required for mold design and adjustment of bending processing conditions.

Conventional techniques relating to bending workability and mechanical properties related thereto are disclosed in JP-A-53-44167, JP-A-55-154542, and JP-A-58-46547.
JP-A-59-173219, JP-A-61-174
No. 360, JP-A-62-280328, JP-A-62-280328
280329, JP-A-2-61029, JP-A-2-
170919, JP-A-3-146644, JP-A-9
-78130 and JP-A-10-46249.

JP-A-53-44167 discloses a color CRT having an inner shield having a yield point elongation of 5% or less after the blackening treatment as a method for preventing the blackening treatment film from peeling off. I have.

Japanese Unexamined Patent Publication No. 55-154042 discloses a technique in which metal parts in a color cathode ray tube are formed of two-phase steel. The duplex stainless steel has a relatively low yield stress and good workability during forming, while these metal members age during the blackening treatment, and yield stress, in other words, the shape maintenance function is about twice that of the conventional material. It is.

Japanese Patent Application Laid-Open No. 58-46547 discloses a method for producing an internal magnetic shield having excellent magnetic properties and surface blackening film performance, with an ASTM grain size of 8 for a steel sheet having a specific component composition. And that the press formability is also good.

Japanese Unexamined Patent Publication (Kokai) No. 59-173219 discloses a method for producing a magnetic shielding material having a high shielding effect. As an example, tensile strength (TS)
Is 65 to 67 kgf / mm ² , and the elongation (El) is 1 to 2%.
It is described that "as long as it is made by bending, spot welding, or the like, it can withstand the forming process sufficiently."

Japanese Unexamined Patent Publication (Kokai) No. 61-174360 discloses a magnetically shielded steel sheet in which the problem of peeling of a blackened film which occurs during bending processing having a specific component composition has been improved. The yield point elongation is described.

Japanese Patent Application Laid-Open Nos. 62-280328 and 62-280329 disclose a method for producing an inner shield material having excellent moldability and electromagnetic wave shielding properties. And mechanical properties such as tensile test values.

JP-A-2-61029 discloses an inner shield material having a specific component composition and a hardness Hv (500 g) of 90 or more.
No. 19 discloses a composition having a specific component composition and a hardness Hv (50).
0g) using a steel sheet material of 90 or more, and performing a bead forming or bending process on the inner shield material.

Japanese Patent Application Laid-Open No. 3-146644 discloses a steel sheet for a magnetic shield which has both a magnetic property having a specific component composition and formability. JP-A-9-781
Japanese Patent Publication No. 30 discloses a magnetic shield material for a color cathode ray tube, which is excellent in magnetic shield property and handling strength depending on a specific component composition and manufacturing conditions.

In Japanese Patent Application Laid-Open No. 10-46249, a steel having a specific composition is hot-rolled, then cold-rolled twice with intermediate annealing, and then finish-annealed. A method for manufacturing a shield material is disclosed.

[0014]

However, in JP-A-53-44167, from the viewpoint of preventing peeling of the blackened film due to local deformation after the formation of the blackened film, the yield after the blackening treatment is reduced. It defines the point elongation,
It does not disclose a technique relating to bending workability before blackening treatment.

The "shape maintaining function" described in Japanese Patent Application Laid-Open No. 55-15442 refers to the maintenance of the shape after aging, and does not refer to the so-called springback, which deviates from a predetermined shape during bending. Therefore, it does not improve the bending workability itself. Further, JP-A-58-46547 only has an ASTM particle size of 8 for materials other than the components, and does not describe an index of moldability such as mechanical properties.

Japanese Unexamined Patent Publication No. Sho 59-173219 presupposes the use of rimmed steel (capped steel) instead of the currently mainstream killed steel, and also includes open coil annealing.
Since cold rolling is performed twice, the production cost is high, and this is not necessarily suitable for mass production at low cost. In addition, there is a description that "it is confirmed that the material can be formed sufficiently by bending, spot welding, etc., so that it can withstand the forming process", but there is no mention as to whether or not the bending process is easy.

Japanese Patent Application Laid-Open No. 61-174360 is intended to solve the problem of peeling of a blackened film which occurs at the time of bending, and does not relate to bending workability of a base material before blackening.

Japanese Unexamined Patent Publications Nos. 62-280328 and 62-280329 do not disclose a specific form of processing although they are excellent in moldability. In particular, there is no description of mechanical properties for improving bending workability. The index is not shown.

In Japanese Unexamined Patent Publication No. 2-61029, the reason why the hardness Hv (500 g) is limited to 90 or more is as follows.
It is to eliminate troubles in steel plate manufacturing, improve the shape of product materials, and improve handling at the time of press working and blackening at the customer. No relationship with bending workability is shown. JP 2
Japanese Patent Application Laid-Open No. 170919/170 also discloses that the hardness Hv (500
g) is limited to 90 or more, because the reasons are to eliminate problems during steel plate manufacturing, to improve the shape of the product material, and to improve handling during press working and blackening at the customer site.
No relationship with bending workability is shown. It also shows that the bending can reduce the deterioration of the magnetic properties, and there is no description on the bending workability.

In Japanese Patent Application Laid-Open No. 3-146644, the formability is evaluated based on the breaking limit diameter and the effective depth in the cylindrical drawing test in the examples. It cannot be said that it shows an index for a steel sheet that is excellent.

Japanese Unexamined Patent Application Publication No. 9-78130 discloses that as a mechanical property, the target value of the tensile strength is 40 kgf / mm ^2.
It is described that the above is the purpose, but the purpose is to secure the handling strength, and the relationship with the bending workability is not shown.

Japanese Patent Application Laid-Open No. 10-46249 describes that a target value of tensile elongation is 35% or more as a mechanical property, but a specific index for achieving excellent bending workability is as follows. Not shown.

As described above, none of the techniques shows a specific guideline for improving the bending workability, and in the actual bending work of the magnetic shield material, much design and adjustment of the molding conditions are required for the bending work of the magnetic shield material. The current situation is that great effort is required.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a magnetic shielding steel sheet having excellent bending workability and a method of manufacturing the same.

[0025]

Means for Solving the Problems In order to solve the above problems, the present inventors investigated and examined the effect of mechanical properties on the bending workability of a steel sheet for magnetic shielding, and found that the yield point elongation of the steel sheet was 3%. %, It was found that springback during bending was reduced, and the present invention was completed.

That is, in the first invention, the yield point elongation is 3%
The present invention provides a magnetic shielding steel sheet characterized by the above.

In the second invention, C: 0.001% by weight.
Not less than 0.1%, Si: less than 0.3%, Mn: 1.5
%, P: 0.05% or less, S: 0.04% or less, S
ol. Al: 0.1% or less, N: 0.01% or less, the balance being substantially composed of Fe, and a yield point elongation of 3% or more.

In the third invention, C: 0.001% by weight.
Not less than 0.1%, Si: less than 0.3%, Mn: 1.5
%, P: 0.05% or less, S: 0.04% or less, S
ol. Al: 0.1% or less, N: 0.01% or less, B:
Provided is a steel sheet for magnetic shielding, which is 0.0003% or more and 0.01% or less, the balance being substantially made of Fe, and having a yield point elongation of 3% or more.

According to a fourth aspect of the present invention, in any one of the first to third aspects of the present invention, Cr and / or N
Provided is a steel sheet for magnetic shield characterized by having i-plating.

According to a fifth aspect of the present invention, a steel slab having the composition described in the second or third aspect of the invention is directly or reheated, hot-rolled, pickled, cold-rolled, and annealed. ,
Thereafter, a method for producing a steel sheet for magnetic shielding is provided, wherein temper rolling at an elongation of 1.5 or less is performed as necessary.

According to a sixth aspect of the present invention, a steel slab having the composition described in the second or third aspect of the invention is directly or reheated, hot-rolled, pickled, cold-rolled, and annealed. ,
Thereafter, a method for manufacturing a steel sheet for a magnetic shield characterized by performing temper rolling at an elongation of 1.5 or less as necessary and further performing Cr plating and / or Ni plating is provided.

In the present invention, "the remainder is substantially F
The phrase "consisting of e" means that in addition to Fe, unavoidable impurities and other trace added components that do not affect the effects of the present invention can be contained. Further, in the following description, all percentages indicating the components of steel are% by weight.

[0033]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described specifically. The steel sheet for magnetic shielding of the present invention has a yield point elongation of 3
% Or more. The yield point elongation is the most important factor for the present invention, and by setting the yield point elongation to 3% or more, the amount of springback when bending a steel sheet can be reduced as compared with conventional materials. . Further, as the yield point elongation increases, the amount of springback monotonously decreases. Therefore, it should have a yield point elongation of preferably 5% or more, more preferably more than 8%.

Next, the composition of the steel will be described. In the present invention, the component composition of the steel is not particularly limited as long as the yield point elongation is 3% or more, but as a preferable component composition, C: 0.001% or more and 0.1% or less by weight%,
Si: less than 0.3%, Mn: 1.5% or less, P: 0.0
5% or less, S: 0.04% or less, Sol. Al: 0.1
%, N: 0.01% or less, or B: 0.0003% or more and 0.01% or less.
Hereinafter, the reason for defining each component as described above will be described.

C: C is an important element in securing the yield point elongation, and from this point, the C content is set to 0.001% or more. From the viewpoint of increasing the yield point elongation, the C content is preferably more than 0.005%. On the other hand, if C is excessively contained, carbides are coarsened and magnetic characteristics are deteriorated. Therefore, the C content is set to 0.1% or less. Preferably it is 0.06% or less.

Si: Si is undesirable because it tends to concentrate on the surface during annealing and deteriorates the adhesion of plating. Therefore, the Si content is set to less than 0.3%.

Mn: Mn is an effective element for increasing the strength of the steel sheet and improving the handleability of the steel sheet. However, excessive addition of Mn increases the cost.
5% or less.

P: P is an element effective for increasing the strength of the steel sheet. However, if the addition amount is too large, cracks are liable to occur during the production due to segregation. Therefore, the P content is set to 0.0
5% or less.

S: From the viewpoint of maintaining the degree of vacuum inside the cathode ray tube, it is desirable that the content of S is as small as possible. From such a viewpoint, the content is set to 0.04% or less.

Al: Al is an element necessary for deoxidation,
If the amount is too large, inclusions increase, which is not desirable. Al was set to 0.1% or less.

N: Like N, N is an effective element for increasing the yield point elongation. However, if added in a large amount, defects are likely to be generated on the steel sheet surface.
% Or less.

B: B is an element effective for hardening the steel sheet and improving the handleability of the magnetic shield member, and is added as necessary. However, the amount is 0.
If it is less than 0003%, the effect cannot be exhibited effectively, and
Excessive addition exceeding 01% causes problems such as raising the recrystallization temperature and excessively hardening the steel sheet. Therefore, when B is added, its content is made 0.0003% or more and 0.01% or less.

The thickness of the steel sheet is not particularly limited in the present invention. However, in order to secure magnetic shielding properties and rigidity as a magnetic shielding part, 0.05 mm is required.
The above is preferred. On the other hand, in order to enhance the magnetic shielding properties, it is desirable that the plate thickness is large. However, with the recent enlargement and widening of color televisions, it is desired to reduce the weight of television sets.

Next, plating will be described. It is desirable to have a Cr plating layer and / or a Ni plating layer from the viewpoint of rust prevention. The plating layer may be a single layer or multiple layers, and the surface on which the plating layer is formed may be one surface or both surfaces of the steel sheet. The plating layer is effective not only for suppressing the generation of rust but also for suppressing the generation of gas from the steel sheet when incorporated in the cathode ray tube. It is not necessary to particularly define the amount of adhesion, and an amount of adhesion that can substantially coat the surface of the steel sheet may be appropriately selected. Alternatively, the surface of the steel sheet may be coated by performing a chromate treatment after partially or entirely applying Ni plating.

Next, the manufacturing method will be described. In the present invention, after smelting steel having the above component composition, a steel slab obtained by continuous casting is hot-rolled, pickled, cold-rolled, annealed, and then extended as necessary. Temper rolling at a rate of 1.5 or less is performed.

The hot rolling may be performed directly on the continuously cast slab, or may be performed after the slab once cooled is reheated. In the case of direct hot rolling, rolling may be performed after slightly heating. The heating temperature for reheating is desirably 1050 ° C. or higher and 1300 ° C. or lower. If the temperature is less than 1050 ° C., the finishing temperature is set to Ar during hot rolling.
It is difficult to set the temperature to _three transformation points or more. Also, 1300
If the temperature exceeds ℃, the amount of oxides generated on the slab surface increases, which is not desirable. The finishing temperature of the hot rolling is preferably at least the Ar ₃ transformation point in order to make the crystal grain size after the hot rolling uniform. The winding temperature is preferably 700 ° C. or less. 7
If the temperature is higher than 00 ° C., Fe ₃ C precipitates in a film shape at the crystal grain boundaries after hot rolling, and the uniformity is impaired.

The cold rolling reduction (reduction ratio) at the time of cold rolling is 7
It is preferably from 0% to 94%. If it is less than 70%, the crystal grains after annealing become coarse and the steel sheet becomes excessively soft, which is not desirable. On the other hand, if the cold rolling reduction exceeds 94%, the rolling load becomes excessive, which is not preferable. More preferably, it is 90% or less.

The annealing is preferably continuous annealing at a temperature of 600 ° C. or more and 850 ° C. or less. If the temperature is lower than 600 ° C., recrystallization is not completely completed and the strength of the steel sheet becomes excessive, which is not preferable. On the other hand, if the annealing temperature is too high, the crystal grains after annealing become coarse and excessively soft to deteriorate the handling property.
C or lower is desirable. More preferably, it is 780 ° C. or lower.

After annealing, temper rolling is performed if necessary. In order to secure a large yield point elongation, it is preferable that the cold rolling distortion is as small as possible. In this respect, it is preferable that temper rolling is not performed. However, when temper rolling is unavoidable for the purpose of correcting the shape of the steel sheet, the elongation rate should be as small as possible, and the upper limit is preferably 1.5%. When the problem with the shape of the steel sheet is minor, it is more preferable to set the content to 1.0% or less.

In this way, after temper rolling is performed as necessary, the surface of the steel sheet is subjected to Ni plating and / or Cr plating as necessary.

By the above series of processes, a magnetic shielding steel sheet having a yield point elongation of 3% or more can be obtained.

[0052]

EXAMPLES After smelting test steels indicated by AE in Table 1, steel A,
B has a finishing temperature of 890 ° C. and a winding temperature of 620 ° C .;
D and E were each hot-rolled at a finishing temperature of 870 ° C. and a winding temperature of 620 ° C., pickled, and cold-rolled at a cold rolling reduction of 85 to 92% to a sheet thickness of 0.3 mm. Then 630-8
After recrystallization annealing at 50 [deg.] C., the steel sheet was subjected to a temper rolling of 0.3 to 1.8% as it was, or partly, and then subjected to Cr plating on both surfaces of the steel sheet to obtain a test material. For the Cr plating, the lower layer is a metal Cr layer having an adhesion amount of 95 to 120 mg / m ² ,
The upper layer was a hydrated oxide Cr layer having an adhesion amount (in terms of metal Cr) of 12 to 20 mg / m ² . The steel A in Table 1 is a conventional material.

With respect to the test material obtained in the above manner, L
A tensile test in the direction was performed to measure the elongation at yield. In addition, a bending test piece of 30 mm ^W × 100 mm ^L was collected,
Using a punch having a tip radius of 2 mm, bending was performed at 90 degrees, and the bending angle after processing was measured. The springback amount is
It is defined as the difference between the bending angle after processing and 90 degrees.
Table 2 shows the steel type, annealing temperature, temper rolling elongation, yield point elongation, and bending test result (amount of springback) at this time.

As shown in Table 2, Test No. Test No. 1 and E No. 1 were used. 9 is
High temper rolling elongation, yield point elongation 3%
If it was less than the range of the present invention, the springback amount was large, and the bending workability was poor. In contrast,
Test N which has a yield point elongation of 3% or more and satisfies the range of the present invention.
o. In Nos. 2 to 8, the amount of springback was small and the bendability was excellent. In the case of the direction C, the same results as those in the case of the direction L were obtained.

[0055]

[Table 1]

[0056]

[Table 2]

[0057]

As described above, according to the present invention,
A magnetic shielding steel sheet having a small amount of springback during bending and excellent in bending workability can be obtained. The steel sheet for a magnetic shield of the present invention is particularly suitable for a color cathode ray tube, and by using the steel sheet according to the present invention, when bending the steel sheet and assembling it into a magnetic shield member for a color cathode ray tube, a bending mold is used. Adjustment work of design and processing conditions is reduced.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C23C 26/00 C23C 26/00 BC (72) Inventor Tatsuhiko Hiratani 1-1-1 Marunouchi, Chiyoda-ku, Tokyo No. 2 Nippon Kokan Co., Ltd. (72) Yasushi Tanaka, 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Yasuyuki Takada 1-2-1, Marunouchi, Chiyoda-ku, Tokyo, Japan No. Nippon Kokan Co., Ltd. (72) Inventor Kenji Tahara 1-2-1, Marunouchi, Chiyoda-ku, Tokyo F-term (in reference) 4K033 CA06 CA09 FA00 GA00 HA00 PA06 4K037 EA01 EA04 EA05 EA15 EA18 EA23 EA25 EA27 EB02 EB06 FB00 FG00 FH00 FM02 GA05 4K044 AA02 AB02 BA02 BA06 BA15 BB01 BB03 BC02 CA16 CA18 CA53

Claims (6)

[Claims] 1. A magnetic shielding steel sheet having a yield point elongation of 3% or more. 2. C: 0.001% to 0.1% by weight.
%, Si: less than 0.3%, Mn: 1.5% or less,
P: 0.05% or less, S: 0.04% or less, Sol. A
l: 0.1% or less, N: 0.01% or less, the balance being substantially composed of Fe, and a yield point elongation of 3% or more, characterized in that it is a steel sheet for magnetic shielding. 3. C: 0.001% to 0.1% by weight
%, Si: less than 0.3%, Mn: 1.5% or less,
P: 0.05% or less, S: 0.04% or less, Sol. A
l: 0.1% or less, N: 0.01% or less, B: 0.00
A steel sheet for magnetic shielding characterized by being at least 03% and at most 0.01%, the balance being substantially composed of Fe, and having a yield point elongation of at least 3%. 4. The steel sheet for a magnetic shield according to claim 1, wherein a surface of the steel sheet has Cr and / or Ni plating. 5. A steel slab having the component composition according to claim 2 or 3 is subjected to hot rolling by direct or reheating, pickling, cold rolling, annealing, and then necessary. A method for manufacturing a steel sheet for magnetic shielding, wherein temper rolling at an elongation ratio of 1.5 or less is carried out in accordance therewith. 6. A steel slab having the component composition according to claim 2 or 3 is subjected to hot rolling by direct or reheating, pickling, cold rolling, annealing, and then necessary. Temper rolling at an elongation of 1.5 or less is performed according to the
A method for producing a steel sheet for magnetic shielding, comprising plating and / or Ni plating.