JPH09256061A - Production of thin steel sheet for aperture grill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a thin steel sheet having high strength and high permeability, in which residual stress is sufficiently reduced for suppressing and preventing the defect in the shape of a slit to be subjected to etching working and having a good flattening degree by improving the stock steel sheet of an aperture grill incorporated into the cathode-ray tube of a color television. SOLUTION: A hot rolling stock of a dead-soft steel contg., by weight, <=0.06% C, 0.3 to 0.5% Si, 0.3 to 0.5% Mn, <=0.03% P, <=0.03% S, <=0.01% Al, <=0.08% N, <=0.01% O, and the balance Fe is subjected to primary cold rolling, is subjected to continuous annealing treatment at 730 to 780 deg.C for 50 to 65sec for recovering its cold workability, is thereafter subjected to secondary cold rolling at 60 to 80% cold rolling ratio to regulate its sheet thickness to a prescribed one, is next subjected to shape modification by a tension leveler and a roller leveler and is moreover subjected to continuous annealing treatment at 450 to 500 deg.C for 14 to 60sec for removing residual stress.

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 thin steel plate for an aperture grill which is incorporated in a color television picture tube as a color selection electrode.

[0002]

2. Description of the Related Art Aperture grille, which is a color selection electrode for cathode ray tubes of color televisions, is made of a thin steel plate (plate thickness of about 0.1 to 0.3 mm) such as ultra-low carbon steel, which is resist masked and etched to make many Is a thin plate member in which the slits are formed in a "comed-like shape". Tension is applied to the comb-shaped thin plate member, which is stretched over the frame and fixed by welding, and then black for forming a dense oxide film on the surface. After chemical treatment (temperature: about 400 to 600 ° C.), it is incorporated into a cathode ray tube. The thin steel plate for the aperture grill has high strength (tensile strength: approx. 700 N / mm ² or higher) and high magnetic permeability (μ _0.5 : approx. 170 Ga / Oe or higher) in view of the function of the grill and the manner of attachment to the frame. In addition to that, it is required that the residual stress is small and the flatness is excellent. When the flatness is poor and the residual stress is large, in the slit forming process by etching, shape defects such as distortion and misalignment (so-called “line disturbance”) are likely to occur in the slit “blind shape”, and the line This is because the disturbance disturbs the function of the aperture grill as a color selection electrode.

The thin steel plate for an aperture grill is cold-rolled (primary cold-rolled) from a hot-rolled material such as ultra-low carbon steel or aluminum killed carbon steel, and subjected to an intermediate annealing treatment for recovering the cold workability. After being applied, it is subjected to re-cold rolling (secondary cold rolling), rolled to a predetermined plate thickness, and then subjected to shape correction processing by a tension leveler to be manufactured. Shape correction by the tension leveler is to bend a thin steel plate under tension, and compressive residual stress is generated in the surface layer of the steel plate, and tensile residual stress is generated in the central part, so the residual stress is reduced. As a measure for relaxing, strain relief annealing below the recrystallization temperature is performed. The strain relief annealing process is performed in a tight coil state in a batch annealing furnace. The thin steel plate after the annealing process has a coil winding (warpage), and the thermal expansion in the annealing process causes The shape is slightly deformed. As a measure for correcting the deformation of the thin steel sheet, the final product is finished by finely adjusting the shape with a roller leveler after the annealing treatment.

[0004]

As described above, the conventional manufacturing process of the raw material steel plate for the aperture grill is, after the secondary cold rolling, shape correction by the tension leveler, strain relief annealing, and fine shape adjustment by the roller leveler. It consists of various processing operations such as adjustment processing, and the process is complicated and inefficient. Moreover, since the fine adjustment of the shape by the roller leveler in the final step is to apply stress to the thin steel sheet, the generation of residual stress is unavoidably accompanied, and the residual stress is caused by the slit formed by the etching process. It causes a line defect in the shape of the wire. The present invention provides a method for manufacturing a thin steel plate for an aperture grill having high strength and high magnetic permeability, excellent flatness for ensuring a good slit shape, and low residual stress.

[0005]

Means for Solving the Problems The method for manufacturing a raw material steel plate for an aperture grill according to the present invention is C: 0.006% or less,
Si: 0.3-0.5%, Mn: 0.3-0.5%,
P: 0.03% or less, S: 0.03% or less, Al: 0.
01% or less, N: 0.01% or less, O: 0.01% or less, the balance is a cold rolled ultra-low carbon steel consisting essentially of Fe, which is first cold-rolled, and the cold-rolled material is continuously annealed. On the line
After performing an intermediate annealing treatment for holding in the temperature range of 730 to 780 ° C for 50 to 65 seconds, secondary cold rolling with a cold rolling rate of 60 to 80% is performed, and then a cold rolled steel sheet is shaped by a tension leveler and a roller leveler. After the straightening process,
Continuous annealing line with a temperature range of 450-500 ℃ 14 ~
It is characterized by performing a strain relief annealing treatment for holding for 60 seconds.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION A thin steel sheet obtained by final cold rolling is shaped by a tension leveler and a roller leveler, and then strain relief annealing is performed in a continuous annealing line so that a tight coil annealing in a batch annealing furnace is performed. A thin steel sheet having no deformation, good flatness, and sufficiently reduced residual stress can be obtained, and the accuracy of the shape of the slit formed by the subsequent etching process can be improved. Also, by performing the intermediate annealing treatment after the primary cold rolling in the continuous annealing line, the crystal structure of the steel sheet is refined, and as a result, the strength of the product steel sheet obtained through the final cold rolling can be increased. With the control of the cold rolling rate in the final cold rolling and the effect of strain relief annealing, a thin steel plate for an aperture grill having high strength and high magnetic permeability can be obtained.

The present invention will be described below. First, the reasons for limiting the composition of the raw steel are as follows. C: 0.006% or less C has a solid solution strengthening action and enhances the strength of steel. However, when the amount is large, the magnetic permeability is lowered and so on, so 0.006% is made the upper limit.

Si: 0.3 to 0.5% Si is an element effective for improving the magnetic properties, and at least 0.3% is required to secure high magnetic permeability. Si also contributes to the strength improvement of steel. However, if contained in a large amount, the cleanliness of the steel decreases as the amount of Si compound in the steel increases. The decrease in cleanliness causes the smoothness of the groove surface of the slit formed by etching. Therefore, the upper limit is 0.5%.

Mn: 0.3-0.5% Mn improves the hot workability of the steel, and strengthens the steel by forming a solid solution in the substitution type in the steel. To obtain this effect, 0.3
% Or more is required. However, when the content exceeds 0.5%, the effect is almost saturated, and when the content is more than 0.5%, the smoothness of the groove surface of the slit is impaired as the cleanliness of the steel decreases.
This is the upper limit.

P: 0.03% lower, S: 0.03% or less,
Al: 0.01% or less, N: 0.01% or less, O: 0.
01% or less All of these elements are impurities that are unavoidably mixed in the steel melting process. Since P impairs the rollability of steel due to grain boundary segregation and the like, it should not exceed 0.03%. S
Is harmful to the hot workability of the steel and forms MnS to deteriorate the cleanliness of the steel, so is made 0.03% or less. Al impairs the cleanliness of the steel and should not exceed 0.01%. N lowers the cleanliness of steel, so the upper limit is 0.01%. O also lowers the cleanliness of the steel, so 0.01% is made the upper limit.

Next, the manufacturing process of the present invention will be described.
The steel cast after the melting and degassing treatment is subjected to hot rolling, pickling treatment, and cold rolling (primary cold rolling).
Hot rolling, in order to ensure the homogeneity of the material, the hot rolling finishing temperature A ₃ transformation point or more austenite single-phase region (about 9
The temperature of the hot rolled material is about 500 to 54
It is preferable to carry out in the temperature range of 0 ° C. There is no particular limitation on the primary cold rolling, and the cold rolling rate is appropriately set in consideration of the plate thickness of the product steel sheet and the cold rolling rate in the secondary cold rolling.

After the primary cold rolling, secondary cold rolling (secondary cold rolling)
Prior to the above, an intermediate annealing treatment for recovering the cold workability is performed. In the conventional method, this annealing treatment is performed by a tight coil box annealing method, but in the present invention, this is performed by a continuous annealing method. In the tight coil box annealing treatment, the cooling rate in the temperature decreasing process after the annealing treatment is slow, so that the crystal structure is remarkably coarsened, and as a result, the strength of the product steel sheet becomes low. In the case of the continuous annealing method, cooling is performed at a relatively high cooling rate to avoid coarsening of crystal grains, and high strength (tensile strength of about 700 N / mm ² or more) can be imparted to the product steel sheet. The intermediate annealing process by the continuous method is 730 to
It is achieved by maintaining the temperature range of 780 ° C. for 50 to 65 seconds. As a result, the cold workability of the steel sheet is sufficiently restored, and the fine crystal structure (grain size number N, JIS
G 0552: about 8.9-9.4) is formed. The lower limit of the processing temperature is 730 ° C., and the lower temperature is lower than 780 ° C., because the recrystallization necessary for recovering the workability becomes insufficient.
The reason why the upper limit is set is that in a high temperature range, the crystal grains are coarsened and it becomes difficult to impart high strength to the product steel sheet. In the intermediate annealing treatment, the temperature is 73
After heating and holding at 0 to 780 ° C., a temperature of 33
A heat treatment of heating and holding at 0 to 430 ° C. for 3 to 4 minutes is added. In that case, high ductility can be imparted to the product steel sheet as an effect of overaging (fixation of C and N in the steel).

After the intermediate annealing treatment, the secondary cold rolling is performed.
A thin steel plate having a predetermined plate thickness is obtained. Secondary cold rolling rate is 60-80%
It is necessary to set to. Cold rolling rate is less than 60%
And the strength of the product steel sheet cannot be increased, while the other 80%
Higher magnetic permeability cannot be secured at cold rolling ratios exceeding
Because it becomes. Steel plate obtained by this secondary cold rolling
Is because the intermediate annealing process is a continuous annealing method.
Inheriting the micronization effect of the structure, sufficient strength (tensile strength:
About 700 N / mm^TwoAbove), and also high permeability
(Μ _0.5: About 170 Ga / Oe or more). What
It is important to give an appropriate surface roughness to the product steel sheet by
Resist in the subsequent slit formation process (etching process)
Adhesion of masking
It is essential to improve the accuracy of shape)
Therefore, in accordance with the conventional method, secondary cold rolling finish rolling is performed.
Is a dull roll, and the required roughness (R_a
About 0.3 to 0.5 μm).

The thin steel sheet obtained through the final cold rolling step is accompanied by medium elongation (center buckle), selvage (edge wave), warpage and the like. Medium stretch is a wavy uneven deformation that occurs in the central region of the width of the steel plate, a selvage is a wavy uneven deformation that occurs at the ears (edges) of the steel plate, and warpage is a curled deformation of the steel plate. Also deteriorates the flatness of the steel sheet. In order to reduce or eliminate these deformations, shape correction processing is performed with a tension leveler and a roller leveler. FIG. 1 schematically shows a tension leveler and a roller leveler. (A) is a tension leveler part, (B) is a roller leveler part, ( _RA ),
(R _B) is a straightening roll of sheet steel for adding bending stress required straightening of the (S), group of rolls arranged above and below the steel plate. Steel sheet (S) is introduced into the tension leveler portion (A), then it is introduced into the roller leveler portion (R _B).

In the tension leveler section (A), steel
The board (S) is a bridle roll (R ₁) (R_Two) Between
Running under the action of high tension (steel plate elongation is 0.3%, for example)
And straightening roll (R_A)
On the other hand, the middle stretch and the deformation of the ear wave are reduced. roller
ー Leveler (R_B), The tension leveler part
Different from (A), high enough to cause elongation of steel plate (S)
There is no tension and the steel plate (S) is bridle roll (R
_Two) (R_Three) While running under low tension,
(R_BBy repeatedly receiving bending stress due to
Warp deformation is reduced. In addition, residual stress is relaxed to some extent
Is done. The figure shows the tension leveler (A) and
Tensioner and leveler section (B)
Shape correction by leveler and shape by roller leveler
An example of continuous straightening is shown, but both processes are separated.
The same effect can be obtained even when performed as an independent process.
Can be.

The thin steel plate (S) which has been subjected to the shape correction processing by the tension leveler and the roller leveler is
It is desirable that the maximum wave height (Hw) of middle stretch and ear wave is 1 mm or less and the amount of warp (Hc) is 20 mm or less. Here, the maximum wave height (Hw) of the middle stretch and the ear wave is the maximum value of the height difference (however, the plate thickness of the steel plate is subtracted) between the peaks and troughs of the wavy unevenness shown in FIG. The wave height (Hw) was measured by cutting the thin steel plate (S) through the plate in the width direction as shown in FIG. 4 to obtain a length (L) 1500 mm cut plate (P).
It can be measured by using a laser beam and placing it on a flat surface plate (T). Further, the warp amount (Hc) is obtained by cutting the thin steel plate (S) through the plate width direction as shown in FIG. 4 to obtain a cut plate (P) having a length (L) of 500 mm.
As shown in FIG. 3, along the vertical wall surface (W) (the length of the cutting plate is 500 mm is the vertical direction), the upper edge (a) of the cutting plate is attached to the vertical wall surface (W). It is the size of the curl at the lower edge measured in the closed state. The shape-correcting effects of medium elongation, seismic waves, and warpage depend on the tension of the steel plate in the tension leveler and the inter-mesh of the straightening roll in the tension leveler, and the interface of the straightening roll in the roller leveler depending on the amount of deformation of the thin steel plate before straightening. It is secured by adjusting the mesh etc.

After the shape is corrected by the tension leveler and the roller leveler, an annealing treatment for removing the residual stress is performed. By performing this strain relief annealing on the continuous annealing line, unlike the conventional annealing treatment of the tight coil by the batch annealing furnace, it is possible to remove the residual stress without deteriorating the shape of the thin steel sheet. The continuous annealing treatment is performed at a temperature of 450 to 500 ° C. for a treatment time of 14
Set to ~ 60 seconds. If the annealing temperature is 450 ° C. or higher and the treatment time is 14 seconds or longer, the effect of removing residual stress is insufficient at lower temperatures or shorter times, while at 500 ° C.,
The upper limit of 60 seconds is that the strength of the steel plate decreases when treated at a higher temperature or for a longer time, and the high strength required for the aperture grill (tensile strength: about 700 N / mm ² or more) is satisfied. Because it will not be possible.

[0018]

[Example] Hot rolled material of ultra low carbon steel (RH degassed material) having the chemical composition shown in Table 1 (finish rolling temperature: 900 to 935)
℃, coiling temperature: 505 〜 545 ℃) was cold-rolled first, followed by intermediate annealing in a continuous line, and then cold-rolled secondary, and then thin steel plate (sheet thickness: 0.1-0.15 mm, Board width: 7
00 mm). The thin steel sheet is subjected to shape correction processing by a tension leveler and a roller leveler, then strain relief annealing is performed by a continuous annealing line or a batch annealing furnace, or the annealing treatment is omitted to obtain a thin steel sheet for an aperture grill. .

Table 2 shows the processing conditions of each step from the primary cold rolling to the strain relief annealing, and Table 3 shows the measurement results of various properties of the obtained thin steel sheet. In Table 3, the values of "Medium elongation" and "Ear wave" in the "Shape of steel sheet" column are the values obtained by cutting a flat steel plate (length: 1500 mm, width: the same as cold-rolled steel plate). It is the maximum wave height (H _W ) measured by laser light after being placed on the surface plate (Fig. 2), and the "warpage" column shows the cut plate (length: 500 mm plate width: cold rolled) taken from a thin steel plate. Same as steel plate)
Is used to show the value (Hc) measured by the vertical suspension test (FIG. 3). "Amount of change in warpage before and after etching" means that one side of a strip plate (width 30 mm, length 200 mm) cut out from the central area of a thin steel plate is removed by etching (corrosion solution: ferric chloride solution, removal layer). The thickness is 30 μm), and the amount of change in warp obtained by measuring the amount of warp at the lower end of the strip before and after etching in a suspension test. This warp variation is also one of the indexes of residual stress. The "slit shape accuracy" indicates the level of line disturbance visually determined by transmitted light and oblique light after forming a large number of slits by etching. In the same column, ◎ indicates “slit shape is good (line disturbance is slight)”, △ is “line disturbance use limit”,
X means "line disturbance and out of use limit".

No. 5 in which the strain relief annealing after the shape correction processing of the thin steel sheet was omitted, the warp fluctuation amount before and after the etching test was remarkably large, and a large line disturbance (out of use limit) was generated in the slit due to the etching processing. There is. No. 3 and No. 4, which were subjected to strain relief annealing after shape correction in a tight coil state in a batch annealing furnace, did not have sufficient residual stress reduction effect and could not be used in slits formed by etching. Disturbance is occurring. On the other hand, the invention example (No. 1 and 2) in which strain relief annealing after shape correction was performed in a continuous line
Has excellent flatness, a small amount of change in warpage before and after the etching test, and the shape accuracy of the slit formed by the etching process is extremely good. Further, the invention examples are capable of forming the slits with high shape accuracy as described above, and are provided with high strength and high magnetic permeability (tensile strength: 700 N / mm ² or more, μ _0.5 : 170 Ga / Oe). (The tensile strength is the measured value before slit formation, and the initial magnetic permeability μ _0.5 is the measured value after blackening treatment (450 ° C. × 15 min)).

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

[Table 3]

[0024]

EFFECTS OF THE INVENTION The raw material steel plate for an aperture grill manufactured according to the present invention has a small residual stress and a good flatness, enhances the shape accuracy of the slit by etching, and causes product defects due to line disturbance. Reduction can be prevented. The material steel sheet is also excellent in strength and magnetic properties, and as an improvement effect of these, the function of the aperture grill is improved and stabilized, and it is possible to sufficiently cope with the recent enlargement and flattening of the cathode ray tube. Is.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view of shape correction processing of a thin steel plate by a tension leveler and a roller leveler.

FIG. 2 is a diagram showing a procedure for measuring the middle height of a thin steel plate and the height of the wave height of an ear wave.

FIG. 3 is a diagram showing a procedure for measuring a warp deformation amount of a thin steel plate.

FIG. 4 is an explanatory view of cutting and sampling a deformation amount measuring cut plate from a thin steel plate.

[Explanation of symbols]

A: tension leveler part B: roller leveler part R _A, R _B: straightening roll S: thin steel sheet T: surface plate W: vertical wall. P: Deformation amount measuring plate

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01J 29/07 H01J 29/07 B

Claims (1)

[Claims] 1. C: 0.006% or less, Si: 0.3-
0.5%, Mn: 0.3 to 0.5%, P: 0.03% or less, S: 0.03% or less, Al: 0.01% or less, N:
0.01% or less, O: 0.01% or less, balance substantially F
The ultra-low carbon steel hot-rolled steel consisting of e is first cold-rolled, and the cold-rolled steel is continuously annealed at 730 to 780 ° C.
After performing an intermediate annealing treatment for holding in the temperature range of 50 to 65 seconds, a secondary cold rolling with a cold rolling rate of 60 to 80% is performed, and then the cold rolled steel sheet is subjected to shape correction processing by a tension leveler and a roller leveler. In addition, a method for manufacturing a thin steel sheet for an aperture grill, which is characterized by performing a strain relief annealing treatment in which a temperature range of 450 to 500 ° C is maintained for 14 to 60 seconds in a continuous annealing line.