JP2001040420A - Manufacture of age hardening steel sheet with superior magnetic permeability for cathode-ray tube band - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a steel sheet for cathode-ray tube band, capable of being easily manufactured and having high strength and high magnetic permeability. SOLUTION: A steel slab, which has a composition containing 0.005-0.06% C, 0.05-1.5% Mn, <=0.02% S, <0.019% Al, and 0.003-0.015% N and also containing, if necessary, either or both of <=0.9% Si and <=0.15% P, is hot rolled. The resultant steel plate is cold rolled at 5-60% cold rolling rate and then continuously annealed at 720-900 deg.C. The resultant steel sheet is used as a solid material or as a plated steel sheet prepared by the application of electroplating with Zn, Ni, Cr, or alloys thereof to improve corrosion resistance. It is preferable to coil the hot rolled steel strip at 500-700 deg.C at hot rolling. Moreover, the continuously annealed steel sheet or the continuously annealed and electroplated steel sheet can be subjected to temper rolling at <=2.5% elongation percentage and then to roller leveling at <=2.0% elongation percentage at sheet surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used as a CRT band for fastening around a panel portion of a cathode ray tube incorporated in a television, an OA apparatus, etc., and produces a steel plate having a high magnetic permeability and being strengthened by age hardening. About the method.

[0002]

2. Description of the Related Art A cathode ray tube has a high vacuum inside.
Around the panel to prevent concave deformation of the panel surface and internal explosion.
The area is fastened with a CRT band. CRT van
As for the temperature, the perimeter of the panel part should be 0.2 ~
0.8-2.0m thickness with 0.6% shorter inner circumference
m steel plates are used. CRT band band
When wearing, thermal expansion by heating at 450-500 ° C
The CRT band around the panel,
To the panel due to heat shrinkage caused by rapid cooling
A tight shrink fit method is employed. CRT van
Tightening force generates tightening force. Tightening force is in the pipe
Is 10 ^-6100 to 100 tons due to high vacuum
The shape of the panel surface that was deformed into a concave shape
It has the function of compensating and eliminating concave deformation. Also, soft
CRT band made from steel plate which is magnetic material,
Permeability μ of about 200_{0. 35}(Magnetic field strength: 0.35 Els
Magnetic shield inside the cathode ray tube.
It also has the effect of

A material used for a cathode ray tube band having such a function is required to be excellent in both tensile properties and magnetic shielding properties. In particular, in accordance with the recent tendency for cathode ray tubes to be larger, flatter, lighter, and more precise, the demand for materials having both excellent tensile properties and magnetic shielding properties is increasing. The tension performance of the CRT band is an important characteristic for large size, flatness and light weight. For high definition, it is necessary to suppress landing fluctuation (geomagnetic drift) of the electron beam due to terrestrial magnetism which is one of the causes of color shift. Magnetic shielding performance is an important characteristic.

[0004] In steel plates used for CRT bands,
There is a contradictory relationship between the high strength required for improving the tensile properties and the high magnetic permeability required for improving the magnetic shield. By the way,
A CRT band using a high-strength steel plate for high strength deteriorates geomagnetic drift due to insufficient magnetic shielding performance and cannot be put to practical use. In order to obtain a cathode ray tube band having both contradictory characteristics of high strength and high magnetic permeability, a large amount of Si, which is a solid solution strengthening element, was added to a very low carbon steel composition of C: 0.005% by weight or less. A method of manufacturing a cathode ray tube band from a cold-rolled steel sheet, a so-called silicon steel sheet (electromagnetic steel sheet), is introduced in Japanese Patent Application Laid-Open Nos. 10-208670 and 10-214578. When this cold-rolled steel sheet is lightly cold-rolled with a rolling reduction of 3 to 15%, a magnetic field strength of 0.3 is obtained after a heating and cooling cycle equivalent to shrink fitting.
It is reported that the permeability μ _0.3 in Oersted is 250 or more and the yield stress is 400 N / mm ² or more.

[0005]

The addition of a large amount of Si aims at improving the magnetic permeability by lowering the magnetic anisotropy constant and improving the yield stress by solid solution strengthening. Light cold rolling has the effect of improving the yield stress of a steel sheet by work hardening. The addition of a large amount of Si is effective for achieving both high strength and high magnetic permeability in combination with light cold rolling, but introduces a new problem. In a steel type mass-produced by a steel maker, the extremely low carbon content of C: 0.005% by weight or less and the addition of a large amount of Si are causes of soaring steelmaking costs. Further, when a large amount of Si is added, not only does the cold rolling property, productivity, etc. decrease, the production cost increases, but also the material becomes very brittle, and the material may be broken even by light working such as bending. .

[0006] In this regard, the steel plates introduced in JP-A-10-208670 and JP-A-10-214578 are not general steel plates and correspond to special steel plates. Moreover, although light cold rolling is effective in improving the yield stress by work hardening, it is a cause of significantly lowering the magnetic permeability. Work in the direction to negate. It is said that the relative deterioration of magnetic permeability due to the increase in yield stress can be suppressed to a low level by properly combining the annealing conditions and the cold rolling rate during light cold rolling, but it is still sufficient to recover the deteriorated magnetic permeability. I have not been able to.

[0007]

The present invention utilizes age hardening by solid solution C and solid solution N to increase the strength, and determines the precipitation morphology, size, and ferrite crystal grain size of cementite (Fe ₃ C). By controlling the pressure, it is possible to achieve extremely low carbon and S
Provides steel plates for cathode ray tube bands that do not require a large amount of i and have a composition that is equivalent to that of general materials, and have both high strength and high magnetic permeability. The purpose is to do.

In order to achieve the object of the production method of the present invention, C: 0.005 to 0.06% by weight, Mn: 0.0
5 to 1.5% by weight, S: 0.02% by weight or less, Al:
After hot-rolling a steel slab containing less than 0.019% by weight, N: 0.003 to 0.015% by weight, and the balance being substantially Fe, the steel is cold-rolled at a cold-rolling rate of 5 to 60%. Rolling and then continuous annealing in a temperature range of 720 to 900 ° C. As the steel slab, a steel slab containing one or two of Si: 0.9% by weight or less and P: 0.15% by weight or less can be used.

The obtained steel sheet can be used as a solid material or Z
It is used as a plated steel sheet having improved corrosion resistance by electroplating n, Ni, Cr or an alloy thereof. In the hot rolling, it is preferable to wind the hot-rolled steel strip at a temperature of 500 to 700 ° C. Alternatively, the continuously annealed steel sheet or the steel sheet electroplated after the continuous annealing may be subjected to temper rolling at an elongation of 2.5% or less, and then subjected to a roller leveler having an elongation of 2.0% or less.

[0010]

The present invention is directed to a steel having a normal composition which does not require extremely low carbon and a large amount of Si. And, among the material properties required for steel plates for CRT bands,
The improvement in strength (high yield stress) is improved by the age hardening of solid solution C and solid solution N remaining in the matrix. Higher permeability is improved by adjusting the precipitation form and precipitation size of cementite (Fe ₃ C) and enlarging ferrite crystal grains.

In the present invention for increasing the strength of a steel sheet by age hardening, a steel type containing 0.005% by weight or more of C and 0.003% by weight or more of N is basically targeted.
Unlike the prior art in which the strength is increased by using solid solution strengthening of Si, the carbonization is not required to be extremely low carbon of 0.005% by weight or less, so that the steelmaking cost is not increased. Since the age hardening is used for increasing the strength, the CRT band before being shrink-fitted to the panel portion is soft and has good workability.
Therefore, when forming into a cathode ray tube band, forming is easy, and there is no occurrence of defects such as bending cracks. And
When shrink-fitting a CRT band attached to a panel portion, solid solution C and solid solution N precipitate at dislocations during a heating / cooling cycle of about 450 to 500 ° C. The precipitated C and N act as inhibitors for fixing dislocations and increase the yield stress of the steel sheet.

Most of C dissolved in the matrix precipitates as cementite (Fe ₃ C). Generally speaking, the permeability decreases due to the precipitation of cementite (Fe ₃ C), but the effect on the degree of decrease in the permeability is greatest when finely dispersing cementite (Fe ₃ C) in ferrite crystal grains. When cementite (Fe ₃ C) precipitates and agglomerates at the ferrite crystal grain boundaries and the ferrite crystal grains grow large, the influence on the degree of decrease in magnetic permeability becomes extremely small. As a result, a high magnetic permeability characteristic required for a steel plate for a cathode ray tube band can be obtained. Suitable cementite (Fe ₃ C) precipitation morphology, precipitation size, and coarsening of ferrite grains are achieved by a combination of hot rolling of high-temperature winding, cold rolling with a specified cold-rolling rate, and high-temperature continuous annealing. Is done.

[0013] The magnetic permeability is also reduced by the refining step after continuous annealing or the temper rolling performed to secure the sheet shape after electroplating. The temper rolling is generally light cold rolling with an elongation of about 0.5 to 3%, and the plastic strain and residual stress introduced at this time are causes of a decrease in magnetic permeability.
The magnetic permeability lowered by the temper rolling can be recovered by applying a roller leveler after the temper rolling.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The components and compositions of steel used in the present invention, manufacturing conditions, and the like will be described below. C: 0.005 to 0.06% by weight An alloy component effective for improving the strength. In the present invention, it is an essential component for increasing the strength required particularly for a steel plate for a cathode ray tube band. Part of C becomes solid solution C in the state of continuous annealing, and imparts high yield stress to the steel sheet by age hardening during shrink fitting. For this, 0.005
It is necessary to contain C in an amount of at least% by weight, but if a large amount of C exceeding 0.06% by weight is included, the magnetic permeability μ _0.35 after shrink fitting tends to be deteriorated. Mn: 0.05 to 1.5% by weight An alloy component that fixes S inevitably mixed as MnS and improves hot workability. The effect of Mn becomes remarkable at 0.05% by weight or more, but when an excessive amount of Mn exceeding 1.5% by weight is included, the workability is deteriorated, and the magnetic permeability μ _0.35 after shrink fitting is also deteriorated.

S: 0.02% by weight or less S is a harmful component to the steel sheet, and if present as an inclusion in the steel sheet, adversely affects both the heat ductility and the magnetic permeability. However, excessively lowering the S content causes an increase in steelmaking costs,
In the present invention, the upper limit of the S content is set to 0.02% by weight so as not to adversely affect the magnetic permeability. Al: less than 0.019% by weight As a deoxidizing agent, it is effective in reducing inclusions in steel, but fixes N in steel as AlN and consumes solute N, which is effective in increasing strength. In this regard, the smaller the Al content, the more preferable. In the present invention, the Al content is set to less than 0.019% by weight.

N: 0.003 to 0.015% by weight An alloy component which exists in a solid solution state in steel, precipitates due to an aging effect at the time of shrink fitting, and strengthens the steel sheet. Solid solution N
The age hardening effect due to N becomes remarkable when the N content is 0.003% by weight or more, but when a large amount of N exceeds 0.015% by weight, bubbles are generated on the surface of the steel slab, and the surface quality of the steel sheet is reduced. to degrade. Si: 0.9% by weight or less An alloy component added as necessary, and increases the strength of the steel sheet by solid solution strengthening. However, if a large amount of Si is contained, the workability deteriorates. Therefore, in the present invention, the upper limit of the Si content is set to 0.9% by weight. P: 0.15% by weight or less An alloy component added as necessary, and exhibits an effect of increasing the strength of a steel sheet by solid solution strengthening. In addition, it is an effective alloy component for increasing the amount of solid solution C. However, it is easily segregated in the steel sheet, and a large amount of P content exceeding 0.15% by weight causes the steel sheet to be embrittled.

Hot Rolling: Winding Temperature 500-700 ° C. A steel slab having a predetermined composition is hot-rolled according to a conventional method.
It is wound around a coil at a removal temperature of 500 to 700 ° C. heat
Slab heating temperature and finishing temperature during hot rolling are particularly restricted
Although it is not a thing, 1100 ~ 1250 ℃
And a temperature range of 840 to 950 ° C.
No. The winding temperature is set to cementite (Fe _Three C) coarsening
500 ° C. or higher is preferable for promoting the temperature. But 7
At winding temperatures exceeding 00 ° C., cementite (Fe_Three 
Excessive coarsening of C), forming such as bending
Sometimes cracks originating from coarse cementite,
Processing cracks are likely to occur.

Cold Rolling: Cold Rolling Rate 5 to 60% The cold rolling rate has a large effect on the coarsening of ferrite grains, and the higher the cold rolling rate, the smaller the ferrite grains tend to be. It changes in proportion to the size of the grain. However, with a cold rolling reduction of less than 5%, it is difficult to obtain ferrite crystal grains that are coarse and stable. If the ferrite crystal grains are coarsened more than necessary, the magnetic permeability is improved but the yield stress is reduced. On the contrary, 60%
When the cold-rolling ratio exceeds, the ferrite crystal grains do not become coarse, and it becomes difficult to obtain a magnetic permeability μ _0.35 ≧ 300. For this reason, the cold rolling rate of the cold rolling is set in the range of 5 to 60%, preferably 10 to 50%.

High-temperature continuous annealing: Annealing temperature: 720 to 900 ° C. As annealing after cold rolling, continuous annealing is employed to recrystallize and coarsen ferrite crystal grains and leave solid solution C in the subsequent cooling process. You. The higher the annealing temperature, the more the ferrite crystal grains become coarser, and higher magnetic permeability characteristics can be obtained.
The coarsening of ferrite crystal grains becomes remarkable at an annealing temperature of 720 ° C. or higher. However, if the annealing temperature exceeds 900 ° C., defects such as surface flaws and plate breakage are likely to occur. Especially, it is preferable to set the annealing temperature in a temperature range of 750 to 880 ° C. By the way, in a normal continuous annealing line,
An overage zone is attached. When using this continuous annealing line, there is no particular restriction on the overaging condition. However, at a low overaging temperature, fine cementite (Fe ₃ C) starts to precipitate in the ferrite crystal grains. Therefore, it is preferable to set the overaging temperature to 350 ° C. or higher to suppress the precipitation of cementite in the ferrite crystal grains. . In the cooling after the overaging treatment, a cooling rate of 60 ° C./min or more is preferable.

Temper rolling: elongation rate of 2.5% or less The steel sheet has a relatively predetermined sheet shape even after continuous annealing. However, if a good sheet shape is required, after continuous annealing or continuous After the electroplating after annealing, it is temper rolled. However, permeability decreases due to plastic deformation and residual stress introduced by temper rolling. Therefore, it is preferable that the temper rolling is performed at the lowest possible elongation so that the magnetic permeability does not significantly decrease. Investigation of the effect of temper rolling on the decrease in magnetic permeability revealed that temper rolling in which the elongation was set to 2.5% or less could reduce the degree of decrease in magnetic permeability.

Roller leveler: elongation of 2.0% or less The permeability reduced by temper rolling is recovered by reducing residual stress in the roller leveler after temper rolling. In a roller leveler, the maximum distortion of 2.0% or less on the plate surface is effective for the recovery of the magnetic permeability, and the recovery of the magnetic permeability cannot be expected with the distortion of more than 2.0%.

[0022]

EXAMPLE 1 A steel slab having the composition shown in Table 1 was hot-rolled into a hot-rolled steel strip having a thickness of 1.6 mm under the conditions shown in Table 2, and was subjected to cold rolling at a cold-rolling rate of 25%. A 1.2 mm cold rolled steel strip was produced. Each cold-rolled steel strip is passed through a continuous annealing line, continuously annealed at an annealing temperature of 830 ° C. (860 ° C. for steel type No. 2, 850 ° C. for steel type No. 8), and overaged at a temperature of 490 ° C. in the subsequent cooling process. did. Next, the sheet was passed through an electroplating line and subjected to electric Zn-Ni plating with an adhesion amount of 20 g / m ² .

[0023]

A test piece was cut out from each electroplated steel strip in a direction parallel to the rolling direction and subjected to a contact bending test to evaluate workability by occurrence of cracks during bending. After heat treatment equivalent to shrink fitting (500 ° C. × 5 seconds → air cooling), it was subjected to a tensile test and a magnetic property test. In the adhesion bending test, JI
The close bending was performed in accordance with SZ2248, and the bending workability was investigated based on the presence or absence of cracks. In the tensile test, a JIS Z2201 No. 5 test piece was used, and JIS Z2
241 was measured for tensile properties. In the magnetic property test, a magnetic permeability μ _0.35 at a magnetic field strength of 0.35 Oe was measured according to JIS C2204.

As can be seen from the survey results in Table 2, the steel types 3 to 6 according to the present invention have a yield stress of 350 N / mm.
² or more, the magnetic permeability was as high as μ _0.35 ≧ 300, indicating that the steel sheet had high strength and high magnetic permeability. On the other hand, steel grade numbers 1 and 2
(Comparative Example) showed good magnetic permeability μ _0.35 , but the yield stress was low and required high strength was not obtained. The low yield stress has a small C content in steel type No. 1 and a small C content in steel type No. 2 and also includes Ti for fixing C as TiC, so that there is no improvement in yield stress by age hardening. That is the cause.

In steel type No. 7 containing a large amount of C, cementite (F) which is a precipitation site of solid solution C during continuous annealing is used.
e ₃ C) is dissolved C amount for abundant was decreased. Therefore, improvement of the yield stress by age hardening cannot be expected, but the effect of improving the yield stress by increasing the precipitation amount of cementite has been exhibited, and tentatively high yield stress has been exhibited. But,
A large amount of cementite (Fe ₃
Since C) was precipitated, the magnetic permeability μ _0.35 was low, and the required high magnetic permeability characteristics could not be obtained. Steel type No. 8 shows high yield stress and high magnetic permeability due to the high Si content.
Since the solid solution strengthening effect of the steel was large and the workability was poor, cracks occurred in the close contact bending test.

[0027]

[0028]

Example 2 A hot-rolled steel strip having a thickness of 1.6 mm obtained from a steel slab having a steel type number 4 (Table 1) was subjected to cold rolling at a cold-rolling rate of 25% to a cold-rolled steel strip having a thickness of 1.2 mm. I made it. The cold-rolled steel strip was passed through a continuous annealing line, continuously annealed at various annealing temperatures, aged at 480 ° C. in a subsequent cooling process, and then subjected to temper rolling at an elongation of 0.8%. Further, electric Zn-Ni plating with an adhesion amount of 20 g / m ² was applied in an electroplating line, and leveling was performed with a roller leveler having a maximum surface distortion of 1.0%. Cut out test specimens from each electroplated steel strip,
The same adhesion bending test as in Example 1 was performed, and workability was evaluated based on the occurrence of cracks during bending. After heat treatment equivalent to shrink fitting (500 ° C. × 5 seconds → air cooling), the same tensile test and magnetic property test as in Example 1 were performed.

As can be seen from the investigation results in Table 3, in Test Nos. 2 to 5 in which the annealing temperature was set in the range specified in the present invention, the yield stress was 350 N / mm ² or more and the magnetic permeability was μ _0.35
A steel sheet having a high strength of ≧ 300 and high strength and high magnetic permeability was obtained.
On the other hand, in Test No. 1 where the annealing temperature was low, the agglomeration and coarsening of cementite at the ferrite grain boundaries and the growth of ferrite grains were insufficient, so that the magnetic permeability was μ _0.35 = 200.
And good magnetic properties could not be obtained.

[0030]

[0031]

Example 3 A hot-rolled steel strip having a thickness of 2.0 mm obtained from a steel slab having a steel type number 4 (Table 1) was cold-rolled at various cold-rolling rates. The cold-rolled steel strip is passed through a continuous annealing line and an annealing temperature of 8
Annealed continuously at 60 ° C, adhesion amount 20g in electroplating line
/ M ² of electrical Zn-Ni plating. A test piece was cut out from each of the electroplated steel strips and subjected to the same contact bending test as in Example 1, and the workability was evaluated by the occurrence of cracks during bending.
Heat treatment equivalent to shrink fitting (500 ° C × 5 seconds → air cooling)
, And subjected to the same tensile test and magnetic property test as in Example 1.

As can be seen from the investigation results in Table 4, in Test Nos. 2 to 5 in which the cold rolling ratio was set within the range specified in the present invention, the yield stress was 350 N / mm ² or more and the magnetic permeability was μ _0.35
A steel sheet having a high strength of ≧ 300 and high strength and high magnetic permeability was obtained.
On the other hand, in Test No. 1 in which the cold rolling rate was as low as 2%, recrystallization was not completed and coarse ferrite grains were not obtained.
Although the yield stress was high, the magnetic permeability showed a low value of 210. In Test No. 6 in which the secondary cold rolling reduction was too high as 80%, although the ferrite crystal grains were refined to obtain a high yield stress, the magnetic permeability showed an extremely low value of μ _0.35 = 210.

[0033]

[0034]

As described above, in the present invention, the age hardening due to solid solution C and solid solution N is utilized for increasing the strength, and the ferrite crystal grains and cementite (Fe ₃ C) are coarsened and cementite is reduced. High permeability is achieved by suppressing (Fe ₃ C) precipitation in ferrite crystal grains. For this reason, there is no increase in steelmaking cost which is observed in a conventional ultra-low carbon steel sheet in which a large amount of Si is added, and a steel sheet suitable for a CRT band with good productivity can be obtained. In addition, since the required strength is given by age hardening in the heating and cooling cycle when shrink-fitting the CRT band to the panel part, workability is secured in the process until it is formed into a CRT band, and bending No cracks occur. As described above, according to the present invention, an age-hardened steel sheet for a high-permeability CRT band that sufficiently satisfies the required characteristics can be manufactured at low cost.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Seiichi Hamanaka 11-1 Showa-cho, Kure-shi, Hiroshima F-term in Nisshin Steel Co., Ltd. Technical Research Institute 4K037 EA01 EA04 EA05 EA11 EA13 EA15 EA18 EA20 EA23 EA25 EA27 FC04 FE01 FE02 FE03 FG01 FH01 FJ05 FJ06 FM01 GA05 JA06 5C012 AA02 BB01 BB07 5C032 AA02 CC03 CD01 CD06

Claims (4)

[Claims] 1. C: 0.005 to 0.06% by weight, M
n: 0.05 to 1.5% by weight, S: 0.02% by weight or less, Al: less than 0.019% by weight, N: 0.003 to
After hot rolling a steel slab containing 0.015% by weight and the balance being substantially Fe, cold rolling is performed at a cold rolling reduction of 5 to 60%, and then continuously in a temperature range of 720 to 900 ° C. A method for producing an age-hardened steel sheet for a CRT band having good magnetic permeability, characterized by annealing. 2. The composition according to claim 1, further comprising: Si: 0.9% by weight or less;
The method for producing an age-hardened steel sheet for a CRT band having good magnetic permeability according to claim 1, wherein a steel slab containing one or two kinds of not more than 15% by weight is used. 3. A method for producing an age-hardened steel sheet for a CRT band having good magnetic permeability, wherein the steel slab according to claim 1 or 2 is hot-rolled at a winding temperature of 500 to 700 ° C. 4. The steel sheet subjected to continuous annealing or electroplated after continuous annealing is subjected to temper rolling at an elongation of 2.5% or less, and then subjected to a roller leveler having an elongation of 2.0% or less. Item 4. The method for producing an age-hardened steel sheet for a CRT band having good magnetic permeability according to any one of Items 1 to 3.