KR19980028328A - Manufacturing method of cold rolled steel sheet for inner shield with excellent black film adhesion and self-shielding property - Google Patents

Abstract

Even invention relates to a method for manufacturing cold rolled steel sheet for inner shield (inDer s1lield) used in color TV CRT, etc. The object is to provide a cold rolled steel sheet for inner shield excellent in black film adhesion and excellent magnetic shielding effect.

In order to achieve the above object, the present invention provides a cold rolled steel sheet for inner shield, which is C: 0.003% or less, MI1: 0.2% or less, P: 0.03% or less, S: 0.008% or less, solid solution Al: 0.Q3% by weight. Above: N: 0.006% or less, Cr: 0.02-0.040%, and the rest of the A1-killed steel, which is composed of Ee and inevitable impurities, is homogenized at a temperature range of 1200-1250 ° C, and then finished directly on Ar _3. Cold rolling for inner shield with excellent black film adhesion and self-shielding properties, which are rolled, wound at a temperature of 700 ° C. or higher, and cold rolled to a final thickness at a reduction ratio of 90% or more, and subsequently subjected to phase annealing in the range of 600-680 ° C. The technical gist of the method for producing a steel sheet is described.

Description

Manufacturing method of cold rolled steel sheet for inner shield with excellent black film adhesion and self-shielding property

The present invention relates to a method of manufacturing a cold rolled steel sheet for inner shield (Inner Shield) to enter the color TV CRT and monitor CRT, and more particularly, a method of manufacturing a cold rolled steel sheet for inner shield excellent in self-shielding effect and black film adhesion It is about.

The inner shield is a component that increases the clarity of the screen by blocking the interference outside the CRT tube so that the beam generated from the electronic layer reaches the fluorescent surface through the shadow mask hole. Typically, the inner shield is divided into a general inner shield mounted on a small TV of less than 25 and a high permeability inner shield mounted on a large TV of 25 or larger and a PC monitor. The cold rolled steel used for the shield is manufactured by hot rolling, pickling, cold rolling and annealing using special element-free ultra low carbon A1 killed steel. The cold rolled products manufactured in this way are mounted on the CRT through the blackening process for the purpose of the beading processing, the prevention of the electron beam diffuse reflection, and the absorption of the electron beam collision heat.

In general, inner shields manufactured to a thickness of 0.18 mm or less should have excellent magnetic properties, that is, high permeability and low coercive force, and should have excellent surface properties to improve adhesion during blackening process. The chemical microstructure of the material should be adjusted through the selection of material components and the appropriate material manufacturing process.

On the other hand, the known techniques can be divided into four categories, that is, steel grades of low carbon or less components without adding special elements (Japanese Patent Application No. 64-212597), and ② steel grades of ultra-low carbon component added with Ti (Japan 63-321324), ③ Extremely low-carbon steel grades in which B is added at a weight ratio of 'B / N = 0.5-2.0' (Japanese Patent Application No. 64-283834), ④ B is more than B / N = 0.5 at middle rain ratio, (B / N = 1) + 0.005% of ultra-low carbon-based steel grades (Korean Patent Application No. 95-50135) added in the following conditions are produced by hot rolling and cold rolling under appropriate conditions.

But. The well-known technique of ① is a non-solid-solution precipitated element in the low carbon steel base material, so the strainer strain (Strecher strain) occurs due to aging at the time of processing, the surface uniformity is hard to meet the demand of black film during the processing process It becomes bad. In addition, since it is manufactured through a low carbon base material and a conventional continuous annealing, the particle structure is small, the coercive force is high, there is a disadvantage that the magnetic shielding effect is poor.

The well-known technique of ② is excellent in surface properties by adding Ti, but the coercivity due to the addition of Ti increases, making it difficult to satisfy the quality as an inner shield material. Also, since the continuous annealing is used, the coercive force is high and the magnetic shielding is high. The disadvantage is that the effect is poor.

The well-known technique of the above ③ is to add [B] to the ultra-low carbon steel base material to precipitate [N], which is an element of solid solution, so that surface uniformity through aging prevention is excellent, but remaining [B] in addition to BN precipitation is grain. Since the coercive force is increased due to the finer property, and the continuous coarse annealing is used, the coercive force is high due to the small particle structure, and thus the magnetic shielding effect is poor.

The well-known technique of ④ adds [B] to the ultra-low carbon steel base material to precipitate [N], which is an element of solid solution, and has excellent surface uniformity through aging prevention, and minimizes residual [B] in addition to BN precipitation to prevent particle micronization. As a matter of course, the addition of B itself produces fine precipitates, which leads to inevitable particle refinement, thereby increasing the coercive force. In addition, since continuous annealing is used, the particle structure is small, the coercive force is high, and the magnetic shielding effect is poor. Therefore, there is a problem that it is not suitable for inner shield use.

Therefore, the present invention has been proposed to solve the above-described problems, and the present invention maximizes the coarsening of tissue particles using BAF (Batch Annealing Furnece) annealing, not continuous annealing, and has excellent blackening film adhesion and coercive force. It is low to provide a cold rolled steel sheet for inner shield excellent magnetic shielding effect, the purpose is.

1 is a graph showing the correlation between grain size and coercive force of a general cold rolled steel sheet

Figure 2 is a photograph of the tissue after completion of annealing the comparative steel (a) and the invention steel (b) (particle size comparison)

The present invention for achieving the above object in the cold rolled steel sheet for inner shield, C: 0.003% or less, Mn: 0.2% or less, Si: 0.5-1.0%, P: 0.03% or less, S: 0.008% or less, Employment Al: more than 0.03%, N: 0.006% or less. Cr: 0.02-0.060%. The remainder of the ultra-low carbon A1-killed steel composed of Fe and inevitably contained impurities were homogenized at a temperature in the range of 1200-1250 ° C., followed by finishing rolling over Ar ₃ , winding at a temperature of 700 ° C. or higher, and then 90% The present invention relates to a method for producing a cold rolled steel sheet for inner shield having excellent blackening film adhesion and self-shielding properties, which are cold rolled to the final thickness at the above reduction ratio and subsequently subjected to annealing in the range of 600 to 680 ° C.

Hereinafter, the present invention will be described in detail.

When the carbon content is more than 0.0035, the carbon content is 0.003 because the solid solution carbon increases, causing item point stretching after the final annealing, resulting in poor press formability and surface uniformity, and causing self aging to increase the coercive force, thus damaging the magnetic shielding effect. It is preferable to limit it to% or less, and the lower the carbon content, the better.

If the Mn content is 0.2% or more, the material hardens or deteriorates formability due to the solid solution strengthening of Mn, and also increases the coercive force by increasing the precipitates by Mn, thereby damaging the magnetic shielding effect. It is preferable to limit it to% or less.

The P is a substitutional alloy element having the largest solid solution effect, and when added in an amount of 0.03% or more, the material hardening and moldability deteriorate, so the content of P is preferably limited to 0.03% or less.

S is a fragile element that causes hot brittleness, and the lower the component range, the better. In addition, the lower the coercive force, the lower the limit is 0.008%.

The A1 is a component that is added for deoxidation of the steel, as in [Si], is a resistivity heavy-weight element, and the magnetic shielding effect is increased as the amount of the additive is increased. However, A1 combines with [N] to form A1N precipitates. Fine A1N precipitates interfere with grain growth during annealing during product production, thereby increasing the coercive force to reduce the magnetic shielding effect.

For this reason, A1 should add more than 0.03% of the pure solid solution A1 combined with [N], and when it is added less than 0.03%, the effect of securing low coercive force will be reduced, thereby damaging the magnetic shielding function.

Specifically, if the amount of solid solution A1 is more than 0.035, the binding amount of [N] to A1 must be added to (27/14) [N]. Therefore, the amount of solid solution A1 must be limited to not less than (27/14) [N] + 0.03%.

N is an invasive element, which inhibits {111} or texture, impairs workability, impedes grain growth, lowers elongation, forms nitride, increases coercive force, and impairs self-shielding function. It is desirable to limit the upper limit to 0.006% in order to minimize the problem.

The Cr is an element that improves the black film adhesion. When the black film adhesion is deteriorated, a small amount of Cr is added so that the small pieces of the black film dropped in the CRT deteriorate the color of the TV screen and degrade the withstand voltage characteristics. But. When the amount is 0.02% or less, the effect is weak, and when it is 0.06% or more, the blackening film adhesion improvement is not only saturated, but also increases the manufacturer's material and material hardening effect.

Hereinafter, the manufacturing conditions of the cold rolled steel sheet according to the present invention will be described in detail.

The continuously cast slab manufactured to have the composition as described above is heated at 1200-1250 ° C. where the austenitic structure before hot rolling can be sufficiently homogenized, and then finish hot rolling is performed directly at the Ar ₃ temperature. If the hot finishing rolling temperature is less than the Ar ₃ transformation point, rolling is performed in the ferrite + pearlite two-phase structure, so that abnormal coarse grains are generated, thereby causing defects in product processing. Therefore, the hot finish rolling temperature is preferably limited to more than Ar ₃ transformation point, specifically 910 ℃ or more.

The hot rolled steel sheet is preferably wound at 700 ° C. or higher. The reason for this is that when the coiling temperature is lowered to 700 ° C. or lower, the grain size of the final product becomes fine, and the coercivity increases, making it unsuitable for inner shield applications. Therefore, in order to lower the coercive force, the particle size should be increased. Therefore, the hot rolled coiling temperature is preferably carried out at a temperature of 700 ° C or higher.

Since the cold rolling rate varies depending on the required thickness of the inner shield, cold rolling is performed in consideration of shape and thickness precision control. When cold rolling is performed with the cold rolling rate being 90% or less, a cold rolled plate having the same thickness is obtained. Since it means that the thickness of the hot rolled sheet required for the thinning is applied to the hot rolling process, the problem of deterioration of the shape of the hot rolled sheet occurs, so it is preferable to perform the rolling reduction in the cold rolling in the range of 90% or more.

The cold rolled steel sheet is subjected to annealing in order to give toughness of the steel. When continuous annealing, which is a conventional annealing method, is used, a short time annealing of rapid heating and quenching is performed, so that the grain size of the annealing plate is finely formed. This coercive force becomes high and the magnetic shielding effect is poor. Therefore, in the present invention, annealing is performed using BAF, which is an annealing for coarsening of the particles after annealing. When heated to 600 ° C. or lower, the same structure as that of the cold rolled counterpart is lower than the recrystallization temperature. It is preferable to limit the annealing temperature to 600-680 ° C. because the plated phenomenon due to heating at a temperature of 680 ° C. or higher and high temperature causes defects on the surface.

The cold rolled steel sheet manufactured as described above is excellent in blackening film adhesion and magnetic shielding properties, thereby making it suitable for inner shield.

Hereinafter, the present invention will be described in detail through examples.

(Example)

To prepare a steel slab by dissolving the ultra-low carbon A1-killed steel in the converter so as to have a composition as shown in Table 1 and then subjected to external refining treatment. At this time, the invention steel (1-2) and comparative steel (3-6) shown in Table 1 are all the final steel components after the out-of-furnace refining. In the case of the invention steel, in order to prevent aging and to secure a low coercive force, ultra-low management of the employment elements such as [D] and [N] was added, and Cr was added to improve the adhesion during blackening treatment. In order to ensure the addition of Si, more than 0.03% of solid solution Al (addition A1 (27/14) [N] + 0.03%) was added. Comparative steel (4) is a steel of the above-described known technology ① and comparative steel (5), (6) is a steel type corresponding to the known technology (2), ③ respectively.

Example Alloy component (wt%) Remarks C Mn Si P S A1 N Cr Ti B (27.14) × [N] Inventive Steel 1 0.0030 0.09 0.55 0.012 0.007 0.029 0.0020 0.035 - - 0.034 Inventive Steel 2 0.0028 0.13 0.83 0.009 0.003 0.050 0.0055 0.028 - - 0.040 Comparative Steel 3 0.0025 0.15 0.62 0.007 0.005 0.038 0.0058 0.025 - - 0.041 Comparative Steel 4 0.030 0.15 - 0.012 0.010 0.047 0.0029 - - - 0.036 Comparative Steel 5 0.0033 0.10 0.57 0.010 0.008 0.038 0.0058 - 0.041 - 0.041 Comparative Steel 6 0.0020 0.15 0.67 0.013 0.013 0.035 0.0045 - - 0.006 0.039

The steel slab having the composition as shown in Table 1 above was homogenized at a temperature of 1250 ° C, followed by finishing hot rolling to a thickness of 2.0 mm near 910 ° C, which is directly above Ar ₃ , at the hot rolling temperature indicated in Table 2. It was wound up and pickled in the usual manner. The pickled hot rolled steel sheet was cold rolled to 0.18 mm, and then subjected to BAF annealing or continuous annealing at 1.0 ° C. at the cold rolling annealing temperature given in Table 2 to obtain 1.0% crude rolling to obtain a cold rolled steel sheet having a thickness of 0.18 mm.

The mechanical properties of the obtained material and the quality of the final product after the inner shielding process are shown in Table 2.

Example Hot rolled winding temperature (℃) Annealing Method Annealing Temperature (℃) Mechanical property Characteristics Yield (㎏ / ㎠) Yield Elongation (%) Coercive force (Oe) Magnetic properties Black film adhesion Inventive Steel 1 720 BAF 650 12 0 1.22 Good Good Comparative Steel 1A 600 BAF 650 12 0 1.38 Bad Good Comparative Steel 1B 720 CAL 800 12 0 1.43 Bad Good Inventive Steel 2 700 BAF 660 11 0 1.23 Good Good Comparative Steel 3 720 BAF 650 12 0 1.35 Bad Good Comparative Steel 4 650 CAL 780 18 0 1.72 Bad Bad Comparative Steel 5 720 CAL 810 12 5 1.63 Bad Bad Comparative Steel 6 720 CAL 800 12 0 1.60 Bad Bad

BAF (Batch Annealing Furnace)

Continuous Annealing Line (CAL): Continuous Annealing

As shown in Tables 1 and 2, in the case of the invention (1-2), Cr was added to provide excellent blackening film adhesion, and [Si] was added at least 0.5% to secure a low coercive force. / 14) [N] + 0.03% or more, the hot-rolling coil temperature was increased, and the annealing process was performed in BAF instead of continuous annealing to make the particle size coarse and to minimize the coercive force as to excellent magnetic shielding properties.

On the other hand. In the case of the comparative steel (1A) in which the inventive steel (1) was wound at a low temperature at 600 ° C., despite the BAF annealing, the coercive force is high due to the refining of the particles due to the low temperature winding, and thus it is not suitable for use due to poor magnetic shielding. In addition, by continuously annealing the inventive steel (1) in CAL instead of BAF, the grain growth does not occur sufficiently, so the coercive force is high. In the case of the comparative steel (4), which corresponds to the known technology ①, the surface uniformity due to aging (YP-E1 = 5%) due to the high carbon content of 0.03% but no special element to fix the solid solution is added. The magnetic shielding properties were poor due to the high coercive force due to particle refinement due to low carbon steel and continuous annealing. Moreover, adhesiveness was bad at the time of blackening process by adding Cr.

In the case of the comparative steel (4), hot-rolled low temperature winding and BAF annealing were performed, but the [A1] component was added at 0.038%, which is less than 0.041%, which is (27/14) [N] + 0.03%. This was bad.

In the case of the comparative steel (5), which corresponds to the known technology ②, the coercive force was increased by adding [Ti] and continuous annealing as a special element for fixing a solid solution element, and [Al] became (27/14) [ Since it did not reach N] + 0.03%, the self-shielding property was poor, and the adhesion was poor when the black film was treated with no Cr addition. In the case of the comparative steel (6) corresponds to the known art (3), by adding B, grain boundary strengthening is caused by the solid solution B, so that the particles become fine, and by continuous annealing, the particles become fine. , [A1] was less than (27/14) [N] + 0.03%, and the coercive force was high, resulting in poor self-shielding properties and poor adhesion when blackening the film.

On the other hand, looking at the relationship between the grain size and the coercive force of the general cold-rolled steel sheet as shown in Figure 1 the larger the coercivity is smaller, it can be seen that the shielding effect is large.

In view of this fact, as in the case of Fig. 2 (a) (b) showing the respective structures when the annealing steel and the invention steel are annealed, the grain size of the invention steel (b) is maximized than that of the comparative steel (a). It is confirmed that the shielding effect is excellent.

As described above, the present invention provides a cold rolled steel sheet excellent in self-shielding effect due to excellent blackening film adhesion and low coercive force by maximizing the grain size of the steel sheet by appropriately controlling the composition and manufacturing conditions of the ultra-low carbon steel, and by applying annealing. This cold rolled steel sheet has an effect that can be very suitably useful for inner shields, such as color TV CRT.

Claims (2)

In the cold rolled steel sheet for inner shield, in mid-range%, C: 0.003% or less, Mn: 0.2% or less, P: 0.03% or less, S: 0.008%. Or less, solid solution A1: 0.03% or more, N: 0.006% or less, Cr: 0.02-0.060%, the remainder of the A1-killed steel composed of Fe and inevitably contained impurities after homogenizing treatment at a temperature range of 1200-1250 ° C Finish rolling directly on the Ar ₃ , wound at a temperature of 700 ° C. or higher, and then cold rolled to a final thickness at a rolling reduction ratio of 90% or higher, followed by annealing in the range of 600-680 ° C. Method of cold rolled steel sheet for inner shield The method according to claim 1, wherein the A1 amount is added in a range of (27/14) [N] + 0.03% or more.