KR20020042099A - A method for manufacturing cold rolled steel sheet for braun tube mask frame with superior magnetic property - Google Patents

Abstract

PURPOSE: A method for manufacturing cold rolled steel sheets for Braun tube mask frame with superior magnetic property is provided, which can secure low coercive force less than 1.2Oe. CONSTITUTION: The method includes the steps of reheating a steel slab comprising C <=0.003 wt.%, Si<=0.10 wt.%, 0.1 wt.%<=Mn<=0.70 wt.%, P<=0.015 wt.%, S<=0.02 wt.%, sol-Al<=0.03 wt.%, a balance of Fe and other inevitable impurities in the temperature range of 1080 to 1250°C; hot rolling the steel slab in the temperature range of 820 to 950°C; coiling the hot rolled steel sheet in the temperature range of 650 to 750°C; cold rolling the hot coil in a reduction ratio of 20 to 50 %; and continuous annealing the cold rolled steel sheet in the temperature range of 820 to 880°C. In this method, slab reheating temperature is calculated by the following equation: MPF=0.023xSRT+100x(sol.Al£%|+1.6x(S£%|-0.06xMn£%|)-30.0).

Description

Method for manufacturing cold rolled steel sheet for CRT mask frame with excellent magnetic properties {A METHOD FOR MANUFACTURING COLD ROLLED STEEL SHEET FOR BRAUN TUBE MASK FRAME WITH SUPERIOR MAGNETIC PROPERTY}

The present invention relates to a method for manufacturing a cold rolled steel sheet for a CRT mask frame, and more particularly, to provide a cold rolled steel sheet having excellent magnetic properties of coercive force of 1.2 Oe or less, and to optimize the steel component and reheating temperature during manufacture of the cold rolled steel sheet. It is about how to.

In recent years, with the trend of larger and more advanced CRTs, the mask frame used for the purpose of supporting shadow masks and inner shields in the CRTs has become increasingly important along with the shadow masks and inner shields, and the blackening is favorable even in the characteristics thereof. In addition to the processability, excellent magnetic properties (earth magnetic shielding ability) are required. That is, since the mask frame occupies a substantial portion (about 30%) of the total moving path from the electron gun to the fluorescent surface of the scanned electron beam, the magnetic shielding characteristics of the earth's magnetic field are similar to that of the inner shield (shielding is also ∝ 1 / Coercive force) is required.

As described above, as a technique related to the magnetic properties and blackening processability of the mask frame member, Japanese Patent Application Laid-Open No. 61-174360 discloses C≤0.01%, 0.05% ≤Mn≤0.4%, Ti: 0.01 to 0.4% (more than 4 times of C + N), sol-Al ≤ 0.10%, N ≤ 0.015% after the blackening treatment with a component system disclosed a method for controlling the yield point stretching In this case, cost increase due to Ti addition is a problem.

In another example, Japanese Patent Laid-Open No. 2-166230 hot rolls a steel sheet of C≤0.005%, sol-Al: 0.005-0.06%, and Ti: 0.005-0.08% for hot rolling to produce a magnetic shield material. , A coiling temperature ≥ 600 ℃ and an annealing temperature of 620 ℃ or more to disclose a technique for producing a steel material excellent in magnetic properties by cold rolling once, according to the technique to control the texture by ferritic reverse rolling Therefore, there is an advantage that a steel material having excellent magnetic properties can be manufactured even if the production by conventional two rolling is performed once. However, in this case, there is a problem that can cause a rolling process load during low-temperature rolling, that is, ferrite rolling.

In addition, Japanese Patent Application Laid-Open No. 11-50149 discloses C≤0.005%, Si≤0.02%, Mn: 0.05-0.35%, P≤0.02, S≤0.02%, sol- to manufacture a shadow mask frame member for a color CRT. Al: 0.003 ~ 0.015%, N ≦ 0.005%, B: 0.0025 ~ 0.01%, O ≦ 0.02%, and the slab whose B / N ratio is 1.6 or more by weight ratio is heated to 1000 ~ 1150 ° C, and hot rolling finish temperature 750 ~ 800 ℃, the coiling temperature is 680 ℃ or more, the cold rolling rate is 45 ~ 65% range, the annealing temperature is operating at 750 ~ 850 ℃, excellent magnetic properties, weldability and blackening treatment In this case, however, the slab heating temperature is low and the hot rolling temperature is low, which causes a load in the field operation.

In addition, as technologies related to blackening processability, Korean Patent Publication (B1) No. 1177 improves the adhesion of an oxide film formed by blackening treatment to a shadow mask, a mask frame, and an inner shield embedded in a color receiving tube, and removes the oxide film. In order to prevent this problem, Si, Cr, and Al (however, Cr ≥ 1/3 (Al + Si) has been reported to have a composition characterized in that, in Japanese Patent Laid-Open No. 9-41086 steel sheet excellent in blackening treatment In order to prepare, C≤0.05%, Si≤0.5%, Mn: 0.04-1.0%, P≤0.05%, S≤0.02%, sol-Al≤0.005%, O: 0.008-0.06%, Cu≤0.04% , N≤0.01%, containing at least one of B: 5-50ppm, Ti: 0.003-0.1%, and Nb: 0.003-0.1%, the remainder being composed of Fe, the surface average roughness (Ra ) Has been reported to improve the blackening film adhesion by blackening treatment by constructing 1.1μm or more. It is improved even if there is a problem that may lead to magnetic degradation by the addition of alloying elements, such as a grain refinement element Ti, Nb.

Japanese Patent Application Laid-Open No. 60-67642 describes a technique for manufacturing a steel plate for a mask frame. The Fe ₂ O ₃ scale, which appears during blackening, adversely affects image reproduction by an electron gun inside a CRT, and Fe ₂ O ₃ is a Fe ₃ C. Since more C tends to increase, an appropriate amount of Cr is added to satisfy the following Equation (1) to reduce Fe ₃ C. However, it also does not consider the improvement of magnetic properties.

[Relationship 1]

[C] Fe ₃ C = [C] -12/165 ([Mn] -55/32 [S])-24/156 [Cr] <0.005

* Where [C] Fe ₃ C will subtracting the amount of Mn to be formed into C ₃ and Cr ₃ C ₂ from the Fe ₃ C in the [C], [Mn] -55/32 [S] is MnS in the total of [Mn] Minus the amount formed by

In summary, there are reports of changes in alloying elements, coating of Ni and Cr, ferritic reverse rolling, and techniques related to blackening treatment to improve the magnetic and aging characteristics of the mask frame material. There is no technology to improve the magnetic properties through investigating the correlation between alloying elements and manufacturing conditions.

Therefore, the present inventors can obtain the appropriate slab reheating temperature by studying and examining the correlation between the alloying element and the slab reheating temperature, and also control the cold reduction rate and the annealing temperature, thereby ensuring the coercive force (Hc) of 1.2Oe or less. The present invention provides a method for manufacturing a cold rolled steel sheet, the object of which is.

1 is a graph showing the change of coercive force according to Mn content

2 is a diagram showing the change of coercive force according to slab reheating temperature

3 is a graph showing the relationship between the MPF value and the coercive force

The present invention for achieving the above object,

Steel slab consisting of C≤0.003%, Si≤0.10%, 0.1% ≤Mn≤0.70%, P≤0.015%, S≤0.02%, sol-Al≤0.03%, balance Fe and other unavoidable impurities Prepare and obtain the reheating temperature (hereinafter referred to as 'SRT') of the steel slab by the following relation (2),

[Relationship 2]

MPF <0

Where MPF = 0.023 × SRT + 100 × (sol.Al [%] + 1.6 × (S [%]-0.06 × Mn [%])-30.0)

After reheating the steel slab in the SRT obtained in the above relation (1), finishing hot rolling at 820 to 950 ° C., winding it in the range of 650 to 750 ° C., and then cold rolling at a cold rolling rate of 20 to 50%. Next, the present invention relates to a method for producing a cold rolled steel sheet for a CRT mask frame having excellent magnetic properties including continuous annealing at 820 to 880 ° C.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated.

In order to lower the coercive force in the cold rolled steel sheet used for the mask frame, the content of sol.Al and S in the steel component should be properly adjusted because these elements are finely precipitated by AlN precipitate and MnS precipitate during hot rolling. This is because the coercive force of the material is increased by miniaturizing austenite grains and ultimately ferrite grains. In view of this, the present inventors have previously proposed a correlation between the addition amount of sol.Al and S and the coercive force in Korean Patent Application No. 2000-55658.

However, the inventors of the present invention found that in addition to the contents of sol.Al and S, the slab reheating temperature (hereinafter referred to as 'SRT') and the Mn content are also related to the coercive force. That is, by reducing the SRT, fine precipitates formed after hot rolling are suppressed to produce coarse grains which are advantageous for magnetic enhancement, and the Mn content is increased to suppress fine MnS precipitates to coarse grains and at the same time magnetic. Forming an advantageous texture for improvement, the coercivity can be lowered while relaxing the content range of sol.Al and S. Therefore, in the present invention, by deriving a correlation such as the following relation (2) from these variables, it is intended to lower the coercive force in the manufactured cold rolled steel sheet to 1.2 Oe or less.

[Relationship 2]

Magnetic Property Factor (MPF) <0

Where MPF = 0.023 × SRT + 100 × (sol.Al [%] + 1.6 × (S [%]-0.06 × Mn [%])-30.0)

Hereinafter, a steel component and manufacturing conditions are demonstrated.

C is present as an impurity in the steel, and as the content increases, the coercivity increases greatly, and magnetic properties may deteriorate due to the occurrence of magnetic aging due to carbide precipitation. Considering the range in which mass production is possible, the upper limit is preferably set to 0.003%.

Si is usually an element mainly used as a deoxidizer, but the addition of trace amounts of Si has an effect of increasing the coercive force and also leads to deterioration of the blackening film adhesion due to the release of residual gas. Therefore, the upper limit is limited to 0.10%. desirable.

P is an element that promotes ferrite formation and increases ductility without compromising the strength of steel, but since segregation is an extreme element, it causes material degradation due to central segregation. Therefore, it is desirable to manage as low as possible, and it is usually desirable to set it to 0.015% or less, which is a level that can generally achieve low P by the current steelmaking method.

S is an element that easily cracks during processing of steel, and has a bad effect on magnetism since it refines crystal grains by fine MnS precipitation during production of a steel sheet having excellent magnetic properties as in the present invention. Therefore, since the S is advantageously managed as low as possible, it is preferable to set the upper limit to 0.02% or less.

Al is added for the purpose of deoxidation, and sol.Al remaining after the deoxidation in the added Al combines with N to form an AlN precipitate to make grains fine. Therefore, in the case of a material requiring magnetic properties as in the present invention, it is preferable to limit the upper limit to 0.03%.

On the other hand, Mn is a characteristic element of the present invention, but usually serves to prevent the red light brittleness by S, in the present invention serves to improve the magnetism in addition to this. In other words, the MnS precipitates are coarsened to coarse grains of the material, and also to increase the magnetism by forming an aggregate structure of the magnetization easy orientation. In order to play such a role, 0.1% or more should be added, but if the content is too large, the strength is increased and workability is lowered, so the upper limit is preferably set to 0.7%.

The steel slab formed as described above is reheated, but in the present invention, as described above, it is preferable to reheat the steel slab at a reheating temperature satisfying the following expression (2).

[Relationship 2]

Magnetic Property Factor (MPF) <0

Where MPF = 0.023 × SRT + 100 × (sol.Al [%] + 1.6 × (S [%]-0.06 × Mn [%])-30.0)

In other words, the SRT is obtained so that the MPF becomes negative, and the slab is reheated at this temperature. When the MPF becomes positive, the coercivity exceeds 1.2 Oe, which causes a problem of deteriorating magnetic properties. Moreover, it is more preferable to reheat the said steel slab by selecting the range of 1250-1080 degreeC which is easy to operate among STR which satisfy | fills said MPF <0.

Then, in hot rolling and winding, the final hot rolling temperature is an important factor in determining the hot rolled material, and if excessively high or low, there is a problem in the field operability, so it is limited to the optimum temperature range of 820 to 950 ° C. It is desirable to. In addition, the winding temperature is preferably set to 650 ~ 750 ℃, because when wound in the temperature range there is no significant change in the magnetic properties.

Thereafter, cold rolling and annealing are performed. The cold rolling reduction rate during cold rolling is 20 to 50%, and the annealing temperature is preferably set to 820 to 880 ° C. The cold reduction rate is an important variable for the magnetic properties, which is advantageous in terms of magnetic properties since the reduction in the reduction rate decreases the coercive force, but when the reduction rate is too small, the grain size becomes too coarse, which acts somewhat disadvantageously in terms of workability. do. Moreover, since the possibility of defects, such as a shape defect, increases in the field operation, it is preferable to set it as 20-50%. The annealing temperature is related to the size of the recrystallized grains. As the temperature increases, the grain size increases and the coercive force tends to decrease. Therefore, from the standpoint of magnetic properties, the higher the annealing temperature is, the more advantageous it is. However, if the annealing temperature is too high, the workability of the continuous annealing process is bad.

The cold rolled steel sheet thus manufactured has a low coercive force of 1.2 Oe or less and exhibits excellent magnetic properties.

Hereinafter, the present invention will be described in more detail with reference to Examples.

(Example 1)

To the steel slab composition as shown in Table 1 was prepared as a test material according to the manufacturing conditions of Table 1. At this time, the coiling temperature was 700 ° C., the cold reduction rate was 48%, and the annealing temperature was the same at 850 ° C.

division Steel component (% by weight) Manufacture conditions Coercive force (Oe) C Mn S sol.Al SRT FDT MPF Comparative Material 1 0.0012 0.15 0.009 0.015 1250 839 0.25 1.26 Invention 1 0.0012 0.009 0.015 1100 839 -3.20 1.08 Comparative Material 2 0.0010 0.009 0.026 1250 877 1.35 1.32 Invention 2 0.0013 0.003 0.018 1250 898 -0.41 1.16 Invention 3 0.0013 0.003 0.018 1100 898 -3.86 1.06 Comparative Material 3 0.0013 0.010 0.027 1250 908 1.61 1.37 Comparative Material 4 0.0013 0.010 0.027 775 1.61 1.32 Invention 4 0.0012 0.009 0.009 904 -0.35 1.15 Invention 5 0.0012 0.009 0.002 908 -1.05 1.05 Invention 6 0.0012 0.003 0.002 901 -2.01 1.03 Comparative Material 5 0.0012 0.010 0.024 755 1.31 1.26 Invention 7 0.0013 0.30 0.010 0.023 910 -0.23 1.13 Invention Material 8 0.0012 0.50 0.010 0.017 910 -2.75 0.95 * SRT (℃): Slab reheating temperature, FDT (℃): Hot rolling finish temperature

As shown in Table 1, the invention materials (1) to (8) of the present invention all have a low coercive force of 1.2 Oe or less, while the comparative materials (1) to (5) in which MPF exhibits a positive value It can be seen that the coercive forces exceeded 1.2 Oe.

On the other hand, in order to examine the relationship between the Mn content and the coercivity, the Mn content and coercive force of the comparative material (1), the invention material 7, and the invention material 8 of Table 1 is shown in FIG. As shown in FIG. 1, in these test specimens having similar conditions, as the Mn content increases, the coercive force decreases to improve the magnetic properties. The reason is that the addition of Mn decreases the frequency of fine MnS precipitates that suppress grain growth, resulting in coarse grains. It is also considered that the addition of Mn causes an increase in the orientation of [100] in which the magnetization of the material is directed.

In addition, the comparative material (1), the invention material (1), and the invention material (2) and (3) of Table 1 are the same as the case where only the SRT is changed with different conditions, respectively, as shown in Table 1, When the SRT is lowered to 1100 ° C., the coercive force becomes smaller. This is because, when the SRT decreases, the size of precipitates produced during hot rolling is coarsened, and grain refinement is suppressed. At this time, it is understood that the coercive force exceeds 1.2 Oe in the case of the comparative material 1 in which the SRT shows a negative value in the present invention range or MPF at 1250 ° C.

On the other hand, in order to understand these results more easily, it is shown in Figures 2 and 3, Figure 2 is a diagram showing the change of the coercivity according to the slab reheating temperature, Figure 3 is a graph showing the relationship between the MPF value and the coercive force to be.

(Example 2)

In order to determine the change in the coercivity according to the cold rolling rate, steel components and cold rolling rate were changed as shown in Table 2 below. At this time, the slab reheating temperature was 1250 占 폚 and the coiling temperature was 700 占 폚.

division Steel component (% by weight) Manufacture conditions Coercive force (Oe) C Mn S sol.Al FDT (℃) Cold rolling reduction (%) SST MPF Invention Materiala 0.0012 0.15 0.009 0.002 908 48 850 -1.05 1.05 Comparative material a 0.0025 0.12 0.008 910 63 860 -0.92 1.26 Comparative material b 0.0025 0.12 0.008 910 72 860 -0.92 1.48

As shown in Table 2, it can be seen that the comparative material (a), (b) having a large cold reduction rate has a coercive force of more than 1.2 Oe even if the MPF has a negative value. The reason is considered to be that the grain size decreases as the reduction ratio increases.

As described above, according to the present invention, a coercive force of 1.2Oe or less can be obtained in the cold rolled steel sheet for a mask frame, thereby providing an excellent magnetic property.

Claims (3)

Steel slab consisting of C≤0.003%, Si≤0.10%, 0.1% ≤Mn≤0.70%, P≤0.015%, S≤0.02%, sol-Al≤0.03%, balance Fe and other unavoidable impurities Prepare and obtain the reheating temperature (hereinafter referred to as 'SRT') of the steel slab by the following relation (2), [Relationship 2] MPF <0 Where MPF = 0.023 × SRT + 100 × (sol.Al [%] + 1.6 × (S [%]-0.06 × Mn [%])-30.0) After reheating the steel slab in the SRT obtained in the above relation (1), finishing hot rolling at 820 to 950 ° C., winding it in the range of 650 to 750 ° C., and then cold rolling at a cold rolling rate of 20 to 50%. Next, a method for producing a cold rolled steel sheet for a CRT mask frame having excellent magnetic properties including continuous annealing at 820 to 880 ° C. According to claim 1, wherein the SRT is 1080 ~ 1250 ℃ excellent magnetic properties characterized in that the cold rolled steel sheet for CRT mask frame The method for manufacturing a cold rolled steel sheet for a CRT mask frame having excellent magnetic characteristics according to claim 1 or 2, wherein the cold rolled steel sheet is manufactured to have a coercive force of 1.2Oe or less.