JPH0114295B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a material for a shadow mask with excellent magnetic properties, and more specifically, the present invention relates to a method for producing a material for a shadow mask that is not affected by external magnetic fields and therefore does not cause color shift. Regarding manufacturing methods. Conventional materials for shadow masks are mainly made by first cold rolling continuously cast low carbon aluminum killed hot rolled steel strip, passing it through an electric cleaning line, decarburizing it by open coil annealing, and then second cold rolling. It was manufactured by making a cold-rolled coil of a predetermined thickness and making it into a slit coil of a predetermined width. The reason for choosing continuous casting low-carbon aluminum killed steel as a raw material steel is that it is more suitable for the mask material for the product shadow mask than the previous ingot material rimmed steel or capped steel (both of which may be referred to as rimmed steel hereinafter). It has excellent etching properties and mechanical properties in the manufacturing process. In other words, the previous ingot-based rimmed steel had a high-purity rim layer on the surface and was characterized by a beautiful surface, but because it was an ingot material, there was a difference in composition between the top and bottom parts of the ingot. In addition, many impurities such as nonmetallic inclusions were present, making it impossible to obtain a homogeneous product shadow mask material. For this reason, for example, there was a tendency for so-called gaza holes to occur during the etching process. Furthermore, since the N in the rimmed steel is not fixed as AlN as in aluminum killed steel, there is a problem in the mechanical properties of the mask that stretcher strain occurs during press forming in the subsequent process. Therefore, the previous problems were successfully solved by using continuous cast aluminum killed steel material, which is homogeneous and has high cleanliness. However, surprisingly, there were hidden problems with this latest material for shadow masks, which was thought to be perfect. This is a color shift phenomenon in completed color cathode ray tubes. That is, it is true that color cathode ray tubes are constantly exposed to the earth's magnetic field and other external disturbing magnetic fields, and that the electron beams in the cathode ray tubes are affected by this. As a countermeasure against this problem, color TV receivers usually incorporate a degaussing mechanism. However, from the viewpoints of cost reduction, compactness, and energy saving, this demagnetization mechanism is not perfect, and re-magnetization always occurs after demagnetization. Therefore, the magnetic properties of the shadow mask itself in the color cathode ray tube are related to the color shift phenomenon. As a result of the study, it is coercive force that has the most influence on demagnetizing characteristics among magnetic properties.
It was confirmed that it was _Hc . In other words, it has been found that the smaller the coercive force, the easier it is to demagnetize, and therefore the less likely color misregistration will occur. It was discovered that the coercive force of the shadow mask made from continuously cast aluminium-killed steel was slightly larger than that of conventional rimmed steel. Further investigation revealed that the reason why the coercive force of the shadow mask made from continuously cast aluminium-killed steel material is rather large is mainly due to the fineness of the crystal grains, and therefore the grain boundaries become an obstacle to domain wall movement. It was inferred. Therefore, the inventors of the present invention have improved the composition and manufacturing process of the material for shadow masks, which is made from continuously cast aluminum killed steel, to grow the crystal grains of the product shadow masks larger and improve their magnetic properties. The inventors have discovered that it is possible to reduce color shift in cathode ray tubes, and have arrived at the present invention. The purpose of the present invention is to produce a material for a shadow mask that not only has good etching properties, press formability, and blackening film adhesion, but also has excellent magnetic properties, especially low coercive force, and does not cause color shift in product color cathode ray tubes. It is about providing law. Another object of the present invention is to partially change the components of conventional shadow mask materials and add high dew point annealing and tertiary cold rolling processes to the manufacturing process.
It is an object of the present invention to provide a method for producing a material for a shadow mask that has improved magnetic properties. According to the present invention, the continuously cast low carbon aluminum killed hot rolled steel strip, which is a raw material, is subjected to at least primary cold rolling, open coil decarburization annealing, secondary cold rolling, high dew point annealing,
By applying each step of tertiary cold rolling, C≦
0.01% (weight%, same below), Mn＜0.20%, Si≦
0.03%, P≦0.10%, S≦0.05%, Sol.Al: 0.01~
Provided is a method for producing a material for a shadow mask, which is characterized by producing a thin steel plate comprising 0.50% Cr, 0.01 to 0.50 Cr, and the balance Fe and unavoidable impurities. In the present invention, "at least the first cold rolling...
The reason for this is that other auxiliary processes, such as electric cleaning, temper rolling, leveling, slitting, etc., may be added as needed. First, for comparison, a conventional method of manufacturing a shadow mask material and a method of manufacturing a shadow mask using the shadow mask material will be briefly described. Conventional materials for shadow masks are made by first cold-rolling low-carbon rimmed steel or continuously cast aluminium-killed steel, which is not particularly low in Mn, and then passing it through an electric cleaning device and decarburizing it by so-called open coil annealing. It was then generally manufactured by performing secondary cold rolling to a predetermined thickness to form a slit coil. The slit coil then goes through a photoetching process and a mask forming process. That is, the slit coil is coated with photoresist on both sides, dried, and then a reference pattern (slot or dot shape) is vacuum-adhered to both sides, and then exposed and developed from both sides. The photoresist in the unexposed area (the area to be perforated) is dissolved and removed by development, and then the remaining photoresist is hardened by heating (burning). The slit coil is then etched with a ferric chloride solution to form holes of a predetermined size in the portions not protected by the photoresist. The remaining photoresist on the surface of the slit coil is then dissolved and removed by a hot alkaline solution. The slit coil that has undergone the etching process is then sheared and subjected to an inspection process to become a flat mask. The flat mask is then annealed in a gas atmosphere (flat mask annealing). This annealing includes so-called dry annealing in a dry atmosphere for the sole purpose of removing distortion, and so-called wet annealing in a wet atmosphere for the purpose of decarburization treatment to further improve workability. The flat mask after annealing is then passed through a leveler (leveling). This eliminates the elongation at yield point and prevents stretcher strain in the next press forming process.
This is also to correct plate distortion caused by annealing. Subsequently, the flat mask is press-molded to have a predetermined curved surface, and finally subjected to a blackening treatment using a vapor phase or liquid phase to become a shadow mask. The above is a conventional general shadow mask material and a method for manufacturing a shadow mask. Therefore, the features of the present invention are that, as mentioned above, in the manufacturing process of the thin steel sheet that is the material for the shadow mask, the components of the conventional material for the shadow mask are partially changed, and the manufacturing process includes high dew point annealing and tertiary cold rolling. It consists in adding the next step. However, since the purpose is to improve the performance of preventing color shift in color cathode ray tubes, it is not unrelated to the shadow mask manufacturing process mentioned above. The features of the present invention will be explained in detail below. Composition and steel type In the composition of the hot rolled steel strip which is the raw material in the present invention,
Mn, Cr, etc. are controlled in the steel manufacturing stage, and other components such as C, N, etc. are appropriately controlled not only in the steel manufacturing stage but also in each subsequent process, and ultimately the scope of claim 1 is described. A thin steel plate, ie, a material for a shadow mask, having the following composition is obtained. The reasons for limiting each component of the present invention will be described below. C: If the content exceeds 0.01%, carbides tend to precipitate and crystal grains also become difficult to grow, resulting in poor magnetic properties. Therefore, the upper limit was limited to 0.01% or less. The lower limit is not particularly limited because it is better to be as small as possible. Methods for reducing C to 0.01% or less include vacuum degassing during steel manufacturing, open coil decarburization annealing during annealing after primary cold rolling, and/or flat mask in a wet atmosphere. There is a way to decarburize it. Mn: If Mn is contained in an amount of 0.20% or more as in the past, grain growth tends to be hindered even after high dew point annealing and tertiary cold rolling, which is undesirable in terms of magnetic properties.
Therefore, the Mn component was set to less than 0.20%. The lower limit is not limited because the smaller the better. Although baked iron is originally known to exhibit very good magnetic properties, it is difficult to use it industrially as a material for shadow masks. In other words, the lower the Mn content as possible, the better the magnetic properties will be.However, as a result of various studies including industrial possibilities, we found that the Mn content should be reduced to 0.20%.
It has become clear that if the amount is less than 100%, the necessary properties can be satisfied in addition to additional steps. Specifically, Mn is added as ferromanganese during the steelmaking process in a converter in order to prevent hot embrittlement caused by the S component in normal steel by forming MnS. Therefore, the present inventors reduced S by in-furnace desulfurization method, out-of-furnace desulfurization method, in-converter desulfurization method, and especially out-of-furnace desulfurization method. We have manufactured a steel material that does not suffer from inter-embrittlement. Note that the desulfurizing agent is CaO, CaC ₂ ,
Ca compounds such as CaCN ₂ and CaF ₂ , Na ₂ CO ₃ ,
Alkaline compounds such as NaOH, KOH, NaCl, NaF, and Mg to Mg compounds are used. Si: Si is a major component of nonmetallic inclusions, and since these nonmetallic inclusions deteriorate the precision of holes, it was set to 0.03% or less. P: If the P content increases, press formability will be inhibited due to hardening of the steel, so it was set to 0.10% or less. S: Regarding S, sulfide-based inclusions are a major factor that inhibits etching properties and are undesirable for shadow mask materials, and Mn
Due to the above-mentioned reasons, it is preferable to reduce the range of ingredients as much as possible.
It was set to 0.05% or less. Al: Al is added as a deoxidizing agent in the ladle after converter melting and has the effect of improving cleanliness.
If Al exceeds 0.50%, abnormal growth of crystal grains tends to occur when the hot-rolled coil winding temperature is high;
and nonmetallic inclusions Al ₂ O ₃ increase and impede etching properties, which is undesirable, and 0.01%
If it is less than that, the deoxidizing effect and anti-aging effect will not be sufficient. Therefore, Sol and Al were set at 0.01 to 0.50%. Note that Al fixes N in the steel as AlN, has the function of suppressing elongation at yield point after mask leveling, and is a major factor in improving press formability. In addition, in the present invention,
Although the deoxidizing agent is limited to Al, Ti, Zr, Nb, B, etc., which have the same effect as Al, can also be applied.
Needless to say, it can also be used in combination with Al. Cr: Cr fixes C as chromium carbide, improves press formability, and at the same time contributes to improving mask blackening film adhesion. For this reason, ferrochrome is added during steelmaking to reduce the effective lower limit of Cr content to 0.01.
%, and the upper limit was set at 0.50% from the standpoint of economy and press formability. In the present invention, a low carbon aluminum killed hot rolled steel strip is selected as the material, and the reason for this will be described below. As mentioned earlier, in order to improve the perforation characteristics during etching in the photoetching process, the material itself must have few inclusions, that is, have excellent cleanliness, the crystal grains must be fine and uniform, and the plate Although it is required that the thickness and composition be uniform over the entire length of the thin steel sheet coil, and that the shape of the thin steel sheet coil be flat, advances in cold rolling technology have improved the uniformity of the sheet thickness and shape. are generally satisfied. Therefore, it can be said that the drilling characteristics are influenced by the cleanliness of the steel (few inclusions) and the uniformity of the components. However, conventionally, emphasis has been placed on the surface properties of thin steel sheets during the etching and perforation process, and low carbon rimmed steels with excellent surface properties have been selected, as seen in Japanese Patent Publication No. 54-25492. However, since rimmed steel is limited to ingot material (rimmed steel made by continuous casting has not yet been put to practical use), there is a considerable difference in composition between the top and rimmed parts of the ingot, and due to the limited composition, even if the whole Even if the cleanliness of the hole was improved, there were still relatively many inclusions in the top part, and the inclusions were often exposed on the inner wall of the hole during etching, resulting in so-called gaza holes. In addition, there is a tendency for dark bands to occur. On the other hand, aluminum killed steel has traditionally been said to be inferior to rimmed steel in terms of surface quality and is therefore unsuitable as a material for shadow masks. However, with the recent development of steel manufacturing technology, especially continuous casting technology, It has become comparable to rimmed steel, and due to its manufacturing method, continuous casting materials have uniform metallurgical and mechanical properties in the longitudinal direction of the coil, making it easier to maintain plate thickness accuracy and shape during the cold rolling process. It is far more advantageous than rimmed steel. In particular, regarding cleanliness, as shown in Table 1, continuous casting aluminum killed steel is significantly superior to rimmed steel.

[Table] As mentioned above, in the present invention, the raw material is selected as a hot-rolled steel strip made of low-carbon aluminum killed steel, especially continuously cast material, but the components are only considered at the stage of cold-rolled steel sheets, so the above-mentioned The component limitations in the claims do not directly define the components of the hot rolled steel strip. The characteristic steps of the present invention will be described below. High dew point annealing High dew point annealing is a process applied to a hot rolled steel strip after it has undergone the following steps: primary cold rolling, electrical cleaning, open coil decarburization annealing, secondary cold rolling, and electrical cleaning. . The electric cleaning step after the secondary cold rolling is for removing rolling lubricating oil that adhered during the secondary cold rolling. In principle, high dew point annealing is performed by the box annealing method. The thickness of the steel strip after secondary cold rolling is approximately 0.1 to 0.6 mm, and if it is thicker than approximately 0.4 mm, open coil annealing using a loose coil is also possible.
Generally, box annealing is performed using tight coils. However, in the present invention, the soaking time is not particularly regulated, but only the dew point of the annealing atmosphere is regulated, so a continuous annealing method may be used. It goes without saying that a more homogeneous product can be obtained in a shorter time by open coil annealing or continuous annealing. The annealing temperature in this process is 560
The temperature is about 700℃. This is because recrystallization may not occur at temperatures below 560°C, and on the other hand, when the temperature exceeds 700°C, sticking occurs between the surfaces of the steel strips. The dew point of the annealing atmosphere is increased to create a decarburizing atmosphere. That is, the dew point of the atmosphere inside the annealing furnace is set to 0°C to +60°C, preferably 0°C to +25°C. Various modified gases are mainly used as the carrier gas.
Metamorphic gases include exothermic gases such as NX gas, HNX gas, and BC gas. Also HX gas, AX gas, _N2
Non-carburizing (low CO/CO ₂ partial pressure ratio) endothermic metamorphosed gases such as gas and SAX gas are also used. In addition, the carrier gas may be one or a combination of two or more of H ₂ gas, N ₂ gas, and inert gases such as Ar and He. In short, the atmospheric gas in the high dew point annealing of the present invention only needs to be a decarburizing atmosphere, and includes not only a decarburizing non-oxidizing region but also an oxidizing region. Therefore, although it is called high dew point annealing, a low dew point (dry) gas with a dew point of 0° C. or lower may be used in some cases. For example, in the case of _H2 gas, it is not necessary to
Even if the partial pressure of H ₂ O (water vapor) is not high, it may function as a non-carburizing or decarburizing gas if the partial pressure ratio of CO/CO ₂ is sufficiently small. In the present invention, annealing using such a low dew point gas is also included in the concept of high dew point annealing to distinguish it from other processing steps. The point is that due to the preceding open coil decarburization annealing, the C component of the steel strip has become extremely small to 0.004% (wt%) or less, making it extremely easy to carburize.
This is to prevent carburization. Therefore, the atmospheric gas dew point range mentioned above is 0°C to +60°C.
℃ does not necessarily limit the present invention. That is, high dew point annealing in the present invention means non-carburizing annealing.
In the case of box annealing, a well-known decarburization cycle is used: a low dew point (dry) atmosphere gas is supplied into the furnace at the initial stage of heating, and a high dew point (wet) atmosphere is supplied after the coil temperature reaches a certain temperature. supply gas,
Gradually lower the dew point and perform so-called dry soaking.
It is desirable to adopt a decarburization cycle in which the material is cooled in a low dew point (dry) atmospheric gas. This is to prevent oxidation of the steel strip surface. It is also possible to apply the same cycle with continuous annealing. Tertiary cold rolling Tertiary cold rolling is performed on the steel strip subjected to the above-mentioned high dew point annealing. Although a two-stand four-high cold rolling mill is used in the embodiments described below, the rolling mill type may be any other type other than the four-high rolling mill. That is, it may be a cluster mill such as a Sendzimir mill or a Y-type mill, a five- or six-stage HC mill or VC mill, or a multi-stand tandem mill of these mills. The rolling lubricating oil can also be palm oil, tallow-based rolling oil, other synthetic rolling oils, or emulsions. That is, there are no particular regulations regarding rolling mills or rolling oil. In the tertiary cold rolling process, for example, 10% to
This involves applying a reduction rate of approximately 50% to the steel strip. However, due to the nature of the product, sufficient roughness and shape control must be performed. The tertiary cold rolling ratio of the present invention is preferably in the range of 10% to 50%. The reason is that when the tertiary cold rolling rate is less than 10%,
This is because the recrystallization temperature during flat mask annealing becomes high due to the small rolling strain, and grain growth is insufficient and a decrease in coercive force cannot be expected.On the other hand, the third cold rolling ratio exceeds 50%. This is because sufficient crystal grain growth cannot be achieved under normal flat mask annealing heating conditions due to excessive rolling strain. Steel strips that have been given a rolling reduction of 10 to 50% through tertiary cold rolling have been subjected to moderate processing strain, so their crystal grains grow during the flat mask annealing process of the shadow mask manufacturing process, resulting in fewer grain boundaries. . However, if the grains grow excessively, orange peel (rough skin) will occur during the pressing process, so the final grain size may be reduced.
Conditions for ASTM No. 5 to 9, preferably,
Conditions must be selected that result in ASTM No. 6-7. All of the above objectives are achieved by implementing the invention as detailed above. In other words, by using low-Mn, Cr-added raw materials and adding two steps of high dew point annealing and tertiary cold rolling to the shadow mask material manufacturing process, we have improved etching properties, press formability, blackened film adhesion, etc. It is possible to obtain a material for shadow masks for color TV cathode ray tubes that satisfies all the conventionally required performances and has extremely little color shift. The present invention will be explained in more detail below using Examples. Examples In Table 2, Nos. 1 to 3 are comparative examples, and Nos. 4 to 8 are examples of the present invention. Among these, only No. 1 is made of ingot-based capped steel (rimmed steel), which is not only decarburized but also denitrified in open coil decarburization annealing, which corresponds to primary annealing. , No.2～
All No. 8 steels are continuously cast aluminium-killed steel, and only decarburization is performed in the OCA process. In addition, in Nos. 1 to 3, which are comparative examples, high dew point annealing and tertiary cold rolling were not performed. As shown in the coercive force column of Table 2, the results show that the examples of the present invention are superior to the comparative examples. Among the comparative examples, No. 1 has a coercive force of 1.1 Oe, which is a fairly good value, but due to its aging properties, press formability is necessarily poor.

[Table] It was not very good, and there were variations peculiar to the ingot material, and even under the same conditions, some problems were observed in etching properties. In contrast, the examples of the present invention not only have excellent magnetic properties, but also show satisfactory results in all aspects of etching properties, press formability, and blackened film adhesion.
There was also very little color shift on the color cathode ray tube.

Claims (1)

[Scope of Claims] 1. At least primary cold rolling, open coil decarburization annealing, secondary cold rolling, high dew point annealing, and tertiary cold rolling are applied to the continuously cast low carbon aluminum killed steel hot rolled steel strip that is the raw material. By adding each process of rolling,
C≦0.01% (weight%, same below), Mn<0.20%,
Si≦0.03%, P≦0.10%, S≦0.05%, Sol.Al:
A method for producing a material for a shadow mask, characterized by producing a thin steel plate comprising 0.01 to 0.50% Cr, 0.01 to 0.50% Cr, and the remainder Fe and inevitable impurities. 2. The manufacturing method according to claim 1, wherein the high dew point annealing is box type annealing or continuous annealing in which the atmosphere is mainly a mixed gas of N ₂ and H ₂ and the dew point is 0°C to 25°C.