JPH086134B2 - Method for manufacturing cold rolled steel sheet for TV CRT mask frame with excellent magnetic properties - Google Patents

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 cold-rolled steel sheet for a TV CRT mask frame having excellent magnetic properties and capable of obtaining a high-quality CRT image.

[0002]

2. Description of the Related Art The basic structure of a color cathode ray tube is composed of an electron gun and a fluorescent screen for converting an electron beam into an image, and further, a magnetic shield material for preventing the electron beam from being deflected by geomagnetism (about 0.35 Oe). Although it covers the inside,
Mask frame materials are important as frame materials that support these structures. In addition, since there is a strong demand for screen clarity due to the recent increase in size and high definition of TVs, the mask frame material is also required to have magnetic shielding properties, that is, high magnetic permeability in a magnetic field region of about 0.35 Oe. .

The cold-rolled steel sheet for a mask frame is usually 0.5 to
This steel plate coil is a 2.5 mm steel plate, and after being pressed by an electric manufacturer, it is blackened in a humid atmosphere at a temperature of about 550 to 650 ° C. and then incorporated inside a cathode ray tube. The purpose of the blackening treatment is to prevent rust, increase the thermal emissivity, and prevent diffuse reflection of electrons. Incidentally, in order to form the blackened film stably, Ni plating may be performed before the blackening treatment.

As a conventional mask frame material having improved magnetic characteristics, a technique disclosed in Japanese Patent Application Laid-Open No. 2-250942 is known. However, since this is a hot rolled steel sheet, the coil longitudinal direction and the width direction. However, there is a difficulty in eliminating the unevenness of the magnetic characteristics, and there is a limit in improving the absolute value of the magnetic characteristics.

[0005]

SUMMARY OF THE INVENTION To solve the above problems, the present invention is specifically directed to a DC permeability μ at 0.35 Oe.
A method of manufacturing a cold-rolled steel sheet for a mask frame having a sheet thickness of 0.5 to 2.5 mm, which has a stable and excellent magnetic characteristic of _0.35 or more, is provided.

[0006]

In order to achieve the above object, the present invention has the following structures. That is, in weight%, C ≦ 0.01%, Si ≦ 0.05%, Mn:
0.1-1.0%, P ≦ 0.2%, S ≦ 0.02%, S
ol. Al: 0.002 to 0.015%, N ≦ 0.00
A slab consisting of 5% and the balance of iron and unavoidable impurities is heated at 950 to 1200 ° C., the finishing temperature is 910 ° C. or higher to obtain a hot rolled coil, and then cold rolling is performed to 0.5 to
2.5 mm, and then recrystallization annealing at 750 to 900 ° C. by continuous annealing, and gradually cooling from recrystallization temperature to 450 ° C. at 1 to 40 ° C./sec to give elongation of 0.6% or less to the steel sheet. A method for producing a cold rolled steel sheet for a TV CRT mask frame having a magnetic permeability of 0.35 Oe of 700 or more and excellent magnetic properties, and C ≦ 0.01% by weight%, Si ≦ 0.05%, Mn:
0.1-1.0%, P ≦ 0.2%, S ≦ 0.02%, S
ol / Al: 0.002 to 0.015%, N ≦ 0.00
5%, B: 0.0003 to 0.005% as B / N.
A TV cathode ray tube having excellent workability as described in the above item characterized by using a slab having a balance of 5 to 2.0 and the balance being iron and unavoidable impurities, and having excellent magnetic characteristics with a magnetic permeability of 0.35 Oe of 700 or more. It is a method for manufacturing a cold rolled steel sheet for a mask frame. In addition, as a method of giving elongation of 0.6% or less to the steel sheet,
Temper rolling or levelers can be employed.

Hereinafter, the present invention will be described in detail. In order to obtain a high magnetic permeability in a low magnetic field, the present inventors 1) reduce as much as possible fine-sized precipitates that hinder the movement of domain walls. 2) Minimize the internal stress that hinders the movement of the domain wall. 3) To reduce the number of crystal grain boundaries that hinder the movement of the domain wall (to increase the crystal grain size). 4) When importance is attached to workability, the particle size is controlled so that coarse particles of 80 μm or more are not formed. 5) Change the texture of crystals to increase the number of {100} grains in the product. The invention was completed by designing a manufacturing means and conducting a test on the assumption that

First, the reasons for limiting the component composition will be described.

C: If the amount of C is large, carbides are precipitated and the magnetic properties are deteriorated, so the content is made 0.01% or less. Si: Si forms SiO ₂ on the surface of the steel sheet, and the blackened film F
e ₃ O ₄ becomes unstable, so it is preferable that the amount be small, and the upper limit is made 0.05%. Mn: Mn is important for controlling the precipitation size of sulfides, and if it is 0.1% or less, MnS finely precipitates and hinders crystal grain growth and movement of domain walls, and particularly deteriorates excitation characteristics in a low magnetic field. Must be avoided. Further, if 1.0% or more, there is a problem of addition cost, so the content is made 1.0% or less.

P: P is an element which is very effective in increasing the strength of the steel sheet, but if too much, there is a problem of addition cost, so it is made 0.2% or less. S: S forms sulfides, which inhibits grain growth and also suppresses domain wall movement to deteriorate low magnetic field characteristics.
02% or less. Sol. Al: Sol. Al forms a nitride and inhibits grain growth and at the same time suppresses domain wall movement to deteriorate the low magnetic field characteristics, so the content is made 0.015% or less. Also, 0.0
If it is less than 02%, there is a large amount of oxide, and this forms nuclei and causes blistering on the surface of the steel sheet called blister during annealing. Al needs to be 0.002 to 0.015%. N: N combines with Al to form a nitride, which inhibits grain growth and at the same time suppresses domain wall motion to deteriorate the low magnetic field characteristics, so is made 0.005% or less.

B: B has the effect of adjusting the grain size of the crystal grains. That is, in the case where B is not added, 8 parts of the steel plate after annealing
Coarse grains having a size of 0 μm or more may be generated, and the surface of the steel sheet may be roughened by press working, which may impair the appearance. However, since the mask frame material is incorporated inside the cathode ray tube, some electric manufacturers do not have problems such as rough skin, and at this time, the addition of B is unnecessary. The lower limit of the sizing effect of B is 0.0003%, but 0.0
If it exceeds 05%, cracks occur in the slab. For this reason,
B is controlled to 0.0003 to 0.005%. Further, B is contained in the steel in a relation of N content in steel and weight ratio B / N. If the B / N is 0.5 or less or 2.0 or more, the crystal sizing effect is lost, so the B / N needs to be 0.5 to 2.0. However, the addition of B has no adverse effect on the magnetic properties.

A grain boundary segregation type element such as Sn or Sb may be added for the purpose of improving the texture, that is, improving the magnetism, but it is not used in the present invention because of the problem of addition cost.
Further, a sulfide-forming element such as Cu may be added for the purpose of promoting crystal grain growth, but it is not included in the present invention because the addition cost is also high.

Molten steel containing the above elements is continuously cast to form a slab and slab heating is carried out at a heating temperature of 950 to 950.
The temperature is 1200 ° C. The reason for this is that if the temperature exceeds 1200 ° C., a solid solution of sulfides or nitrides occurs, and fine precipitates are generated during hot rolling to suppress grain growth. Also, 9
This is because if the temperature is lower than 50 ° C., a finishing temperature of 910 ° C. or higher, which will be described later, cannot be secured.

In the hot rolling, it is necessary to control the finish rolling completion temperature (finishing temperature), and the temperature is set to 910 ° C. or higher. This is because a hot coil structure having a large crystal grain size can be obtained at a temperature of 910 ° C. or higher in the γ phase, which allows coarse crystal grains to be obtained even in the final product. This is because it can be increased.

The winding temperature is not particularly limited, but it is preferably 600 ° C. or higher from the standpoint of self-annealing. The hot coil thickness is preferably 1.5 to 6.5 mm, because the reduction ratio of the subsequent cold rolling is preferably 40 to 75% from the viewpoint of texture.

The hot rolled coil is pickled and cold rolled. The finish thickness after cold rolling is 0.5 to 2.5 mm required for the mask frame material. The ultimate temperature of recrystallization annealing after cold rolling needs to be 750 to 900 ° C. At 750 ° C. or lower, μ _0.35 ≧ 700 cannot be secured because the crystal grain size is small. If it enters the γ phase at 900 ° C. or higher, the texture is randomized, and transformation strain is introduced during cooling, so that the magnetism is deteriorated, so it must be avoided.

The cooling rate from the highest temperature reached at this time is important. Further, the elongation rate by temper rolling or leveler for subsequent shape correction is also important. An example of an experiment conducted on the cold speed and the rolling reduction rate of the pressure regulation will be described below.
The components used in the experiment are shown in Table 1.

[0018]

[Table 1]

2. A slab containing this component and the balance substantially Fe is heated at 1060 ° C. to a finishing temperature of 960 ° C.
A hot coil having a thickness of 5 mm was produced, pickled, and cold rolled to a thickness of 1.2 mm, and the ultimate annealing temperature was 800 ° C.
When cooling from 800 ℃ to 450 ℃, after performing an experiment to change the cold speed, 0.58% temper rolling,
The magnetism (permeability) was measured. The results are shown in Fig. 1.
FIG. 2 shows an example of an experiment in which the elongation percentage of temper rolling was varied for these materials with different cold speeds. As can be seen from FIGS. 1 and 2, a cold speed of 40 ° C./sec or less and a temper rolling of 0.6% or less are necessary conditions for obtaining μ _0.35 ≧ 700. This cooling rate can be obtained, for example, by so-called steam cooling of nitrogen and water spray. It is important that the cooling rate is from the maximum temperature to 450 ° C. In the experiments conducted by the inventors of the present invention, even if the temperature is 450 ° C. or lower, there is no problem in magnetism even if it is rapidly cooled to 150 ° C./sec. Further, at a temperature of 450 ° C. or lower, cooling to the room temperature in the middle does not adversely affect the magnetic characteristics even if a heat history such as soaking is added. From the highest temperature to 45
The slower the cooling rate to 0 ° C., the better the magnetic properties, but the productivity is a problem with excessive slow cooling, so the lower limit is 1 ° C./sec.
After all, a suitable cooling rate from the maximum temperature to at least 450 ° C must be 1 to 40 ° C / sec, and the elongation of temper rolling must be 0.6% or less. It is also possible to use a leveler or the like instead of the shape correction of temper rolling.
The same result as in FIGS. 1 and 2 was obtained also by the elongation rate of the leveler. Therefore, the elongation rate of the steel sheet should be controlled to 0.6% or less. Next, examples will be described.

[0020]

【Example】

[Example 1] Molten steel containing the chemical components shown in Table 2 was continuously cast into a slab, and the slab was heated at 980 ° C and hot-rolled at a finishing temperature of 930 ° C and a winding temperature of 610 ° C. Then, a hot coil having a thickness of 3.1 mm was obtained. Then, by cold rolling, a cold rolled sheet having a thickness of 1.0 mm was soaked at 840 ° C. for 10 seconds and then cooled to 350 ° C. in 30 seconds (cooling speed:
16 ° C./second) and then cooled to room temperature at a cooling rate of 80 ° C./second. Further, temper rolling is performed at an elongation of 0.5% to correct the shape, and Epstein sample (3
0 mm × 300 mm), and the direct current magnetic characteristics were measured according to JIS C 2550 in the same manner as the non-oriented electrical steel sheet. The results are also shown in Table 2.

[0021]

[Table 2]

As shown in Table 2, Samples 1, 2, 8 and 9 which are components of the present invention have a magnetic permeability μ _0.35 of more than 700. In addition, C, Mn, S, Sol. Samples 3, 4, 5, 6, 7 etc. in which Al, N, etc. are out of the range of the present invention have magnetic permeability μ
_0.35 ≧ 700 cannot be satisfied. Sample No. 8 and 9
(Corresponding to claim 2) is a material containing B content and satisfying B / N, and no rough skin was observed after the press molding of the mask frame material, but some of the other samples had rough skin. Admitted.

[Example 2] Sample Nos. Shown in Table 2 The slab containing the chemical composition of No. 1 was carried out by changing the hot rolling conditions as shown in Table 3. The coiling temperature was 720 ° C. and a 2.5 mm thick hot coil was manufactured. Then on the same line,
After cold rolling to 0.6 mm, recrystallization annealing at 820 ° C. for 2 seconds was performed in nitrogen, and after cooling to 450 ° C. at 30 ° C./second, after soaking at 450 ° C. for 30 seconds, 100 ° C
/ Sec to room temperature. A leveler was used for shape correction and the elongation rate was 0.5%. The magnetic characteristics were measured in the same manner as in Example 1 and are also shown in Table 2.

[0024]

[Table 3]

As seen in Table 3, the slab heating temperature and finishing temperature must be within the range of the present invention. Example 3 A slab was manufactured by continuous casting of molten steel having the components shown in Table 4, and this slab was heated at 1020 ° C. for 20 minutes,
A hot coil having a thickness of 3.0 mm was produced by hot rolling at a finishing temperature of 920 ° C. and a winding temperature of 730 ° C. Then, it was cold rolled to a thickness of 2.3 mm, the experiment of Table 5 was conducted, and the results of measuring the magnetism are also shown in the same table.

[0026]

[Table 4]

[0027]

[Table 5]

From the results shown in Table 5, the recrystallization temperature was 750 to 9
00 ° C. is required for μ _0.35 ≧ 700 (experiments of samples 1 to 4). The cooling rate up to 450 ° C. requires slow cooling of 40 ° C./second or less (experiments of Samples 5 to 8). The elongation of temper rolling is
0.6% or less is required (experiments of Samples 9 to 11). No rough skin was observed after the press molding of the mask frame material. From these facts, excellent magnetic properties and excellent workability can be obtained only by satisfying the range of the present invention.

[0029]

As described above, according to the present invention, it is possible to manufacture a cold rolled steel sheet for a TV CRT mask frame having excellent magnetic properties or workability.

[Brief description of drawings]

FIG. 1 shows the relationship between cooling rate and magnetic permeability.

FIG. 2 shows the relationship between elongation and magnetic permeability of temper rolling at each cold speed.

Claims (2)

[Claims] 1. C ≦ 0.01% by weight, Si ≦ 0.0
5%, Mn: 0.1 to 1.0%, P ≦ 0.2%, S ≦
0.02%, Sol. Al: 0.002-0.015
%, N ≦ 0.005%, the balance consisting of iron and unavoidable impurities is heated at 950 to 1200 ° C., the finishing temperature is 910 ° C. or higher to obtain a hot rolled coil, and then cold rolling is performed to 0. 0.5 ~ 2.5mm, then 750 by continuous annealing
Recrystallization annealing at ~ 900 ° C, slow cooling from recrystallization temperature to 450 ° C at 1-40 ° C / sec, giving elongation to steel sheet of 0.6% or less, permeability at 0.35 Oe Is 70
A method of manufacturing a cold-rolled steel sheet for a TV CRT mask frame having excellent magnetic properties of 0 or more. 2. C ≦ 0.01% by weight, Si ≦ 0.0
5%, Mn: 0.1 to 1.0%, P ≦ 0.2%, S ≦
0.02%, Sol. Al: 0.002-0.015
%, N ≦ 0.005%, B: 0.0003 to 0.005
% Of B / N is 0.5 to 2.0 and the balance is iron and unavoidable impurities, and a slab is used, which has excellent workability and a magnetic permeability of 0.35 Oe of 70.
A method for manufacturing a cold rolled steel sheet for a TV CRT mask frame, which is also excellent in magnetic properties of 0 or more.