JP2005060784A - Steel sheet for internal magnetic shielding and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steel sheet for internal magnetic shielding having excellent geomagnetic shielding property and to provide its manufacturing method. <P>SOLUTION: The steel sheet for internal magnetic shielding has ≥2.0 ratio of the non-hysteresis magnetic permeability in the rolling direction and to that in the direction orthogonal to the rolling direction, ≥20,000 non-hysteresis magnetic permeability in the rolling direction, and ≤3.20 Oe coercive force. The steel sheet for internal magnetic shielding is manufactured by hot rolling and cold rolling a steel containing by mass%, >0.005% and ≤0.1% C, <0.3% Si, ≤1.5% Mn, ≤0.05% P, ≤0.04% S, ≤0.1% sol. Al, and ≤0.005% O, then continuously annealing in the temperature range from 600°C to 780°C, adding specified tension in a cooling zone, and subjecting the steel to no temper rolling or to temper rolling with ≤0.2% elongation rate. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a steel plate that is a material of a magnetic shield component that is installed inside a color cathode ray tube so as to cover from the side in the electron beam passage direction, that is, a steel plate for an inner magnetic shield of a color cathode ray tube and its manufacture Regarding the method.

  The basic configuration of a color cathode ray tube includes an electron gun that emits an electron beam and a fluorescent screen that emits light by electron beam irradiation and forms an image. Since an electron beam is deflected by the influence of geomagnetism, and as a result color shift occurs in an image, an internal magnetic shield (also referred to as an inner shield or an inner magnetic shield) is generally installed as a means for preventing the deflection. ing. In general, in a color cathode ray tube, demagnetization processing is performed by applying AC current to a degaussing coil wound outside the cathode ray tube when the power is turned on, etc., in order to make the influence of external magnetism in the usage environment constant. Yes.

  In recent years, consumer TVs have become larger and wider, and the flight distance and scanning distance of electron beams have become longer, making them more susceptible to geomagnetism. That is, the deviation (referred to as geomagnetic drift) of the arrival point of the electron beam deflected by geomagnetism from the point where it should originally reach is larger than before. At the same time, with the spread of high-definition broadcasts and the start of digital broadcasts, higher definition screens are handled, so the demand for reducing geomagnetic drift is becoming more severe. In addition, since color cathode ray tubes for personal computers require higher-definition still images, color shift due to geomagnetic drift must be suppressed as much as possible.

  Under such circumstances, the characteristics of steel sheets conventionally used for magnetic shields are often evaluated using the low magnetic field permeability, coercive force, and residual magnetic flux density, which are almost equivalent to geomagnetism. It was.

  As a method for improving the properties of a steel sheet for magnetic shielding, Patent Document 1 discloses a technique for improving magnetic properties by setting the ferrite crystal grain size to 3 to 20 μm using steel having a specific composition, As magnetic characteristics required for a cold-rolled steel sheet for shielding, a magnetic shielding material having a coercive force of 3 Oe or more and a residual magnetic flux density of 9 kG or more and a manufacturing method thereof are disclosed. Non-Patent Document 1 describes the relationship between non-history permeability and magnetic shielding properties for improving magnetic shielding properties.

  However, steel plates for magnetic shielding applied to actual color cathode ray tubes are generally demagnetized in geomagnetism, and the magnetic properties of the steel plate change due to demagnetization treatment in geomagnetism. The technique disclosed in Document 1 has a problem that the magnetic shield property is insufficient because the change in characteristics is not taken into consideration. Further, in Non-Patent Document 1, studies are made on the relationship between the above-described non-history permeability and magnetic shielding properties, but for detailed examination such as what steel plate has a high non-history permeability, It has not been revealed.

  Therefore, the inventors of the present invention, in the above-described demagnetization treatment, demagnetize the magnetic shield inside the cathode ray tube in the geomagnetism. Therefore, the magnetic shield inside the cathode ray tube has a magnetic shield equivalent to the geomagnetism. In regard to the magnetic shielding steel sheet focusing on the non-historical permeability suitable as an evaluation index of magnetic characteristics, it has been proposed previously (for example, Patent Documents 2 and 3).

However, even with the technique disclosed in Patent Document 2, it cannot be said that the video deterioration due to the color shift accompanying the recent increase in the size and widening of consumer TVs can be sufficiently dealt with. Further, it is difficult to say that color misregistration with respect to a cathode ray tube for a personal computer can be sufficiently suppressed. For these reasons, there is a strong demand for a steel plate for magnetic shielding having higher performance magnetic shielding properties.
Japanese Patent Laid-Open No. 10-168551 JP 2001-49401 A JP 2001-316777 A IEICE Transactions, Vol.J79-C-II No.6, p311-319, '96 .6

  This invention is made | formed in view of this situation, Comprising: It aims at providing the steel plate for internal magnetic shielding excellent in the geomagnetic shielding property which can further reduce the amount of geomagnetic drifts, and its manufacturing method.

  As a result of further studies to further improve the geomagnetic shielding performance, the present inventors have found that the non-history permeability in the rolling direction and the non-history permeability in the direction perpendicular to the rolling of the steel plate for internal magnetic shielding are greatly different. Specifically, when the non-history permeability ratio is 2.0 or more, the non-history permeability value in the rolling direction is 20000 or more, and the coercive force is 3.2 Oe or less, the geomagnetic drift is It was found that it was reduced.

The present invention has been completed based on such findings, and provides the following first to third inventions.
That is, in the first invention, the ratio of the non-history permeability in the rolling direction and the direction perpendicular to the rolling is 2.0 or more, the value of the non-history permeability in the rolling direction is 20000 or more, and the coercive force is 3.2 Oe or less. A steel sheet for internal magnetic shielding excellent in geomagnetic shielding properties, characterized by being

In the second invention, C: more than 0.005%, 0.1% or less, Si: less than 0.3%, Mn: 1.5% or less, P: 0.05% or less, S: 0.00%. 04% or less, sol. Al: 0.1% or less, O: 0.005% or less steel is hot-rolled and cold-rolled, and this cold-rolled steel strip is continuously annealed in a temperature range of 600 ° C to 780 ° C. after addition of ^{35.2N / mm 2 (3.6kgf / mm} 2) or less of line tension ^{4.9N / mm 2 (0.5kgf / mm} 2) or more cooling zones, or not subjected to temper rolling, Alternatively, the present invention provides a method for producing a steel plate for internal magnetic shielding excellent in geomagnetic shielding properties, characterized by performing temper rolling with an elongation rate of 0.2% or less.

3rd invention is mass%, C: more than 0.005% 0.1% or less, Si: less than 0.3%, Mn: 1.5% or less, P: 0.05% or less, S: 0.00. 04% or less, sol · Al: 0.1% or less, O: 0.005% or less, B: 0.0003% or more and 0.005% or less, hot rolled, cold rolled, continuous between rolled steel strip at a temperature range of 780 ° C. from 600 ° C. annealed, 4.9 N ^/ mm 2 in the cooling zone (0.5kgf / mm ²⁾ or more 35.2N ^/ mm 2 (3.6kgf ^/ mm ² ) A steel plate for internal magnetic shielding with excellent geomagnetic shielding, characterized by not applying temper rolling after applying the following line tension, or applying temper rolling with an elongation of 0.2% or less. A manufacturing method is provided.

  According to the present invention, since excellent geomagnetic shielding properties can be obtained, geomagnetic drift can be reduced.

Hereinafter, the present invention will be described in detail.
In the steel sheet for magnetic shielding according to the present invention, the ratio of the non-history permeability in the rolling direction and the direction perpendicular to the rolling is 2.0 or more, the value of the non-history permeability in the rolling direction is 20000 or more, and the coercive force is 3. 2 Oe or less.

  In this way, after increasing the anisotropy of the non-history permeability in the rolling direction and the direction perpendicular to the rolling, the non-history permeability value in the rolling direction is set to 20000 or more, and the coercive force is set to 3.2 Oe or less, It becomes possible to improve magnetic shielding properties.

  In the present invention, the component composition of the steel is not particularly limited as long as the above characteristics are satisfied. However, the preferred component composition is mass%, C: more than 0.005% and 0.1% or less, Si: 0.00. Less than 3%, Mn: 1.5% or less, P: 0.05% or less, S: 0.04% or less, sol. It is steel containing Al: 0.1% or less, O: 0.005% or less, or steel containing B: 0.0003% or less in addition to these. Hereinafter, each component will be described.

  C: An element important for increasing the non-history permeability of the steel sheet and increasing its anisotropy, and preferably contained in excess of 0.005%. However, if contained excessively, coercive force increases due to carbide precipitation, and demagnetization treatment sufficient to exhibit a high non-historical permeability becomes difficult, so 0.1% or less is preferable.

  Si: It is an element that easily concentrates on the surface during annealing of the steel sheet and deteriorates the adhesion of the plating or the adhesion of the blackened film, so it is not preferable to contain it excessively, and it is preferably less than 0.3%. More preferably, it is 0.1% or less.

  Mn: An element effective in increasing the anisotropy of the non-history permeability of the steel sheet, but if added excessively, the cost increases, so 1.5% or less is preferable.

  P: An element effective for increasing the strength of the steel sheet and improving the handleability of the steel sheet, but if the amount added is too large, cracking is likely to occur during production due to segregation, so 0.05% or less is preferable.

  S: From the viewpoint of maintaining the degree of vacuum inside the color cathode ray tube, a smaller amount is preferable, and 0.04% or less is preferable.

  sol. Al: Al is an element necessary for deoxidation, but if added excessively, inclusions increase, which is not preferable, and 0.1% or less is preferable.

  In the present invention, O: O needs to be reduced in order to keep the coercive force below a specified value. If O exceeds 0.005%, 3.2 Oe or less cannot be obtained at any annealing temperature, so 0.005% or less.

  B: B is a preferable element for increasing the non-history permeability. When B is added, the content is preferably 0.0003% or more and 0.005% or less.

  As other components, N is desirably 0.01% or less because defects are likely to occur on the steel sheet surface if excessively contained.

Next, the manufacturing conditions of this magnetic shielding steel plate will be described.
First, steel having the above composition is melted to form a steel slab by continuous casting, which is hot-rolled. In the hot rolling, the continuously cast slab may be directly or slightly heated and then rolled, or the once cooled slab may be reheated and rolled. The reheating temperature is preferably 1050 ° C. or higher and 1300 ° C. or lower. When the heating temperature is lower than 1050 ° C., it is difficult to set the finishing temperature to the Ar ₃ transformation point or higher during hot rolling. Moreover, when it exceeds 1300 degreeC, the oxide amount produced | generated on the surface of a slab will increase, and it is not desirable. The finishing temperature of the hot rolling is not less than the Ar ₃ transformation point in order to make the crystal grain size after hot rolling uniform. The coiling temperature is 700 ° C. or lower. When the coiling temperature exceeds 700 ° C., Fe ₃ C precipitates in the form of a film at the grain boundary after hot rolling, which is not preferable.

  Next, the hot-rolled steel sheet is pickled and cold-rolled at a rolling rate of 70% or more and less than 94%. If the cold pressure ratio is less than 70%, the crystal grains after annealing become coarse and the steel sheet becomes excessively soft, which is not desirable. Further, if the cold rolling rate exceeds 94%, the non-historical permeability tends to deteriorate.

  If the steel plate for magnetic shielding is too thin, even if it is a steel plate with high non-historical permeability, the magnetic shielding properties will be insufficient, and the rigidity as a magnetic shielding component will not be obtained. And In order to improve the magnetic shielding properties, it is desirable to have a large plate thickness. However, with the recent trend toward larger and wider color TVs, it is desired to reduce the weight of TV sets. Is desirable.

Subsequently, for the purpose of recrystallizing the cold-rolled steel sheet, the temperature at this time is set to 600 ° C. or higher and 780 ° C. or lower in the present invention. If it is less than 600 ° C., recrystallization is not completed completely and cold rolling strain remains, which is not preferable. On the other hand, if the annealing temperature is excessively high, the non-historical permeability is deteriorated, which is not preferable. More preferably, annealing is performed in the ferrite single phase region or in a temperature region below the Ac ₁ transformation point.

One effective technique for obtaining target magnetic properties is to control the line tension of the cooling zone after continuous annealing. In the present invention, the following 4.9 N ^/ mm 2 the line tension of the cooling zone after the continuous annealing (0.5kgf / mm ²⁾ or more ^{35.2N / mm 2 (3.6kgf / mm} 2). FIG. 1 is an explanatory view showing a change in the non-historical permeability values in the rolling direction and the direction perpendicular to the rolling direction shown in Example 1 to be described later due to tension during cooling in annealing, and FIG. It is explanatory drawing which shows the mode of the change by the tension | tensile_strength at the time of cooling in the annealing of the ratio of the non-hysteresis magnetic permeability of a rolling direction shown in FIG. Setting the line tension within the range of the present invention is effective in increasing the anisotropy of the non-historical permeability of the steel sheet. At a line tension of 35.2 N / mm ² (3.6 kgf / mm ² ) or more, the steel sheet undergoes plastic deformation, and therefore no effect on the anisotropy of the line tension appears.

  It is most preferable not to perform temper rolling after annealing, and even when temper rolling is performed, it is necessary to make the elongation rate as small as possible and to make it 0.2% or less at the maximum. As a result of investigating the influence of the temper rolling elongation ratio on the anisotropy of the non-historic permeability of the steel sheet, the inventors have found that the non-history permeability in the rolling direction is significantly reduced when temper rolling is performed. On the other hand, it was found that the non-hysteresis permeability in the direction perpendicular to the rolling hardly decreases or is significantly lighter than that in the rolling direction even if it decreases. In general, since the non-history permeability in the rolling direction is larger than the non-history permeability in the direction perpendicular to the rolling in the annealed state, the above knowledge is that the anisotropy of the non-history permeability is reduced by temper rolling. Don't be.

  In general, temper rolling is performed on a working steel sheet for the purpose of preventing surface defects called stretcher strain marks after work forming. However, in the case of an internal magnetic shield, since the forming and processing are not strict in nature, no significant surface defects occur even without temper rolling. Therefore, from the viewpoint of increasing the anisotropy of the non-history magnetic permeability, it is most preferable not to perform temper rolling, and when it is performed, it is necessary to make the elongation rate 0.2% or less.

  In addition, the above manufacturing conditions are illustrations, and as long as the steel plate of this invention is obtained, it is not limited to the said manufacturing conditions.

  The steel plate for internal magnetic shield of the present invention may be subjected to Cr plating and / or Ni plating as necessary. This is desirable from the viewpoint of preventing rust, particularly when the blackening heat treatment is omitted. Such a plating layer may be a single layer or a multilayer, and the surface on which the plating layer is formed may be one surface or both surfaces of the steel plate. By forming the plating layer, it is effective to suppress the generation of rust on the steel sheet and also to suppress the generation of gas from the steel sheet when incorporated in the cathode ray tube. The amount of adhesion is not particularly limited, and an amount of adhesion that can substantially cover the steel sheet surface may be selected as appropriate. Further, the steel plate surface may be coated by performing chromate treatment after partially or entirely plating Ni.

After melting the test steel shown in Table 1, it was heated to 1200 ° C to 1250 ° C, and hot-rolled to a sheet thickness of 2.3 mm at a finishing temperature of 870 ° C to 890 ° C and a winding temperature of 620 ° C. The obtained hot-rolled sheet was pickled and cold-rolled to a sheet thickness of 0.3 mm, and then annealed at 630 ° C. for 300 seconds. When cooled, no tension or 4.9 N / mm ² (0.5 kgf / mm ² ) adds tension ^{~39.2N / mm 2 (4.0kgf / mm} 2), to obtain a test material. Note that temper rolling was not performed.

  About the test material obtained in the above manner, strip-shaped test pieces having a width of 10 mm and a length of 100 mm with the rolling direction and the perpendicular direction of the rolling as the longitudinal direction are sampled, and the test pieces are overlapped in a cross-girder shape to form a closed magnetic circuit. The non-history permeability was measured by the following procedure.

Method of measuring non-history permeability 1) Pass a decaying AC current through the exciting coil to completely demagnetize the test piece.
2) In a state where a DC electric field is applied to the DC bias magnetic field coil to generate a DC bias magnetic field of 0.35 Oe, a decaying AC current is applied again to the exciting coil to demagnetize the test piece.
3) Current is passed through the exciting coil to excite the test piece, and the generated magnetic flux is detected by the detecting coil to measure the BH curve.
4) The non-history permeability is calculated from the BH curve.

The measurement results are shown in Table 2. As shown in Table 2, among steel plates produced by the above-described procedure, a steel plate that was cooled after annealing (corresponding to No. 1 in Table 2) and 39.2 N / mm ² during cooling after annealing. A steel plate to which a tension of (4.0 kgf / mm ² ) is applied (corresponding to No. 6 in Table 2) is a comparative steel plate in which the ratio between the rolling direction and the rolling perpendicular direction is out of the range of the present invention. Of the steel sheets produced in accordance with the procedure described above, were added tension of 4.9 N ^/ mm ² when the cooling after annealing ^{(0.5kgf / mm 2) ~29.4N /} mm 2 (3.0kgf / mm 2) steel (Corresponding to Nos. 2 to 5 in Table 2) are all steel plates of the present invention that satisfy the scope of the present invention.

  Table 3 shows a steel plate (No. 1 in the table) having the composition shown in Table 1 and not subjected to temper rolling according to the manufacturing procedure belonging to the examples of the present invention in Table 2, and the elongation ratio. The non-hysteresis permeability in the rolling direction and the direction perpendicular to the rolling direction of the steel sheet (No. 2 to 7 in the table) subjected to temper rolling of 0.2 to 4.7% and the ratio thereof are shown. From this table, it is understood that the ratio of non-historical permeability is less than 2.0 when the temper rolling is performed with the elongation rate exceeding 0.2%.

After melting the test steel shown in Table 4, it was heated to 1200 ° C to 1250 ° C and hot-rolled to a sheet thickness of 2.3 mm at a finishing temperature of 870 ° C to 890 ° C and a winding temperature of 620 ° C. The obtained hot-rolled sheet was pickled, cold-rolled to a sheet thickness of 0.3 mm, and then annealed at 630 ° C. for 90 seconds while applying a tension of 9.8 N / mm ² (1.0 kgf / mm ² ). . The tension during cooling was 2.0 N / mm ² (0.2 kgf / mm ² ), and a test material was obtained. Note that temper rolling was not performed.

  Table 5 shows the results of measuring the non-historical permeability and the like of the specimens thus obtained. As shown in Table 5, in the test material having the composition shown in Table 4 (O is more than 0.005%), the coercive force, non-historical permeability value, and the ratio of the rolling direction and the direction perpendicular to the rolling direction are the present invention. It turns out that it is out of the range.

  As described above, the steel sheet of the present invention is suitable for magnetic shield parts, particularly for the internal magnetic shield of a color cathode ray tube, because it provides excellent geomagnetic shielding properties that reduce geomagnetic drift.

Explanatory drawing which shows the change by the tension | tensile_strength at the time of cooling in the annealing of the non-hysteresis permeability value of a rolling direction and a rolling orthogonal direction. Explanatory drawing which shows the change by the tension | tensile_strength at the time of cooling in the annealing of the ratio of the non-hysteresis permeability of a rolling direction and a rolling orthogonal direction.

Claims (5)

  The ratio of the non-history permeability in the rolling direction and the direction perpendicular to the rolling is 2.0 or more, the value of the non-history permeability in the rolling direction is 20000 or more, and the coercive force is 3.2 Oe or less. Steel plate for internal magnetic shield with excellent geomagnetic shielding properties.   The steel plate for internal magnetic shield is in mass%, C: more than 0.005% and 0.1% or less, Si: less than 0.3%, Mn: 1.5% or less, P: 0.05% or less, S : 0.04% or less, sol. The steel plate for internal magnetic shielding according to claim 1, comprising Al: 0.1% or less and O: 0.005% or less.   The steel plate for internal magnetic shield is in mass%, C: more than 0.005% and 0.1% or less, Si: less than 0.3%, Mn: 1.5% or less, P: 0.05% or less, S : 0.04% or less, sol.Al: 0.1% or less, O: 0.005% or less, B: 0.0003% or more and 0.005% or less. Steel plate for internal magnetic shield. In mass%, C: more than 0.005% and 0.1% or less, Si: less than 0.3%, Mn: 1.5% or less, P: 0.05% or less, S: 0.04% or less, sol . Al: 0.1% or less, O: 0.005% or less steel is hot-rolled and cold-rolled, and this cold-rolled steel strip is continuously annealed in a temperature range of 600 ° C to 780 ° C. after addition of ^{35.2N / mm 2 (3.6kgf / mm} 2) or less of line tension ^{4.9N / mm 2 (0.5kgf / mm} 2) or more cooling zones, or not subjected to temper rolling, Alternatively, a method for producing a steel sheet for internal magnetic shielding excellent in geomagnetic shielding properties, characterized by performing temper rolling with an elongation of 0.2% or less. In mass%, C: more than 0.005% and 0.1% or less, Si: less than 0.3%, Mn: 1.5% or less, P: 0.05% or less, S: 0.04% or less, sol・ Al: 0.1% or less, O: 0.005% or less, B: 0.0003% or more and 0.005% or less of steel is hot-rolled and cold-rolled. continuous at a temperature range of 780 ° C. from 600 ° C. annealed, 4.9 N in the cooling zone ^{/ mm 2 (0.5kgf / mm 2} ) or more ^{35.2N / mm 2 (3.6kgf / mm} 2) or less of line A method for producing a steel plate for an internal magnetic shield excellent in geomagnetic shielding characteristics, wherein after applying tension, temper rolling is not performed, or temper rolling is performed at an elongation rate of 0.2% or less.

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