JPS6362821A - Production of shadow mask material - Google Patents

Abstract

PURPOSE:To produce a shadow mask material which has excellent perforatability by etching and obviates the generation of uneven permeation after press forming by subjecting a cold rolled steel of a low-C aluminum killed steel having a specific compsn. to decarburization annealing then to secondary cold rolling. CONSTITUTION:The steel consisting of <=0.060wt% C, 0.05-0.50% Mn, <=0.007% S, 0.010-0.080% solAl, <=0.0100% N, 0.05-0.50% Fe and unavoidable impurities is melted by out-of-furnace desulfurizing and converter. The molten steel is made into an ingot by ordinary ingot making or continuous casting. The ingot is subjected to hot rolling and cold rolling. The rolled steel is thereafter subjected to decarburization annealing in a decarburization annealing furnace until the content of C decreases to <=0.004%. The annealed steel is subjected further to temper rolling and secondary color rolling to form a thin sheet having <=0.3mm thickness. The shadow mask material which obviates the generation of uneven permeation after perforating by etching and press forming is obtd. by the above-mentioned method.

Description

[Detailed Description of the Invention] <Field of the Invention> The present invention provides a method for producing a shadow mask material for use in shadow masks for color televisions and color displays, which has excellent etching perforation properties and does not cause uneven transmission even after press molding. Regarding.

<Background of the Invention> Conventionally, low-carbon rimmed cold-rolled steel sheets have been used as shadow mask materials for cathode ray tubes used in color televisions and color displays. Poor hole shape occurs, and when low-temperature annealing is performed to prevent adhesion between flat masks during final annealing, the crystal grains of the steel become smaller. There were drawbacks such as easy occurrence of stretcher strain due to yield point elongation due to solid solution C and solid solution N. This stretcher strain distorts the edge of the hole and causes unevenness in one color, so its occurrence must be prevented in order to satisfy the performance of the shadow mask.

In addition, when rimmed steel is annealed at high temperatures, the crystal grains become coarse and the edges of the pores are distorted when pressing the shadow mask. had to be severely restricted.

In order to improve these drawbacks, recently the C content has been reduced to 0.
A low carbon AM killed cold rolled steel sheet having a carbon content of 0.005% or less is used.

However, in recent years, the definition of shadow masks has become higher and higher, and it has become necessary to drill many holes with high precision in cold-rolled steel sheets with a thickness of about 0.11II11. In addition, as another movement toward improving color cathode ray tubes, so-called FS tubes, in which the front screen panel of the cathode ray tube is rectangular and flattened, are on the rise. By making the front square and flat, the aim is to increase the amount of information and reproduce images more faithfully, and also to reduce eye fatigue due to reflection of external light when viewing. The shadow mask used is a cold-rolled steel plate with a thickness of about 0.2 to 0.3 mm in order to suppress the occurrence of color shift due to the doming phenomenon caused by thermal expansion.

As the definition of shadow masks increases and the number of FS tubes increases, it is no longer completely satisfactory even when using low carbon AQ killed cold rolled steel sheets, which had no problems in the past. .

First, the manufacturing process for shadow masks consists of two steps: first, degreasing a cold-rolled steel sheet, applying a resist film, baking the pattern, developing it, and then etching it with a solution containing mainly ferric chloride to create a flat mask. Furan 1 after perforation - After annealing the mask, it is shaped into a predetermined shape.

It consists of a step of forming a black oxide film on the surface of the shadow mask by heat treatment and a step of forming a black oxide film on the surface of the shadow mask by heat treatment.In the etching and perforation step, segregated substances mainly composed of MnS due to center segregation are removed from the base material. Since the etched wall surface is preferentially corroded, a hole-like defect occurs in the etched wall surface at that portion, which causes a problem of so-called uneven transmission. This is due to the fact that in recent years, the area that would be perforated by blind etching has increased dramatically due to the high definition of shadow masks in recent years, so even if materials that used to be used had no problems, the probability of defects has increased in recent years. This is because the price has become higher.

In addition, even if you are lucky that no uneven transmission occurs during the etching and perforation process, uneven transmission sometimes occurs during the subsequent process of annealing the flat mask and press-forming it into a predetermined shape after press-forming. When this was investigated in detail, it was found that segregated substances mainly composed of MnS were present in that part due to center segregation, and the elongation characteristics of the part with this center segregation and the clean part with no center segregation were found. It was discovered that because of the slight difference in the pore shape, press molding could cause even a slight deviation in the hole shape, resulting in uneven transmission.

This phenomenon is also a problem that has been increasing because the spherical shape of the shadow mask has become different with the increase in the number of FS tubes in recent years, and is truly a problem that has never existed before.

<Structure of the Invention> In view of the above-mentioned circumstances, the present inventors have attempted to improve the conventional low carbon AQ killed steel, particularly to reduce segregation mainly composed of MnS. , C0,060% or less in weight%, M n 0 , 05-0.50%
, S 0.007% or less, SolAl 0.010-0.
Steel consisting of 0.080%, N0.0100% or less, the balance iron and unavoidable impurities is melted by desulfurization outside the furnace and a converter, then made into billets by ordinary ingot making or continuous visiting making, and this billet is hot rolled. After cold rolling, decarburization annealing is performed in a decarburization annealing furnace until C becomes 0.004% or less, and further cold rolling is performed to obtain a plate thickness of 0.
A method for producing a shadow mask material characterized by using three or fewer countries.

<Specific Description of the Invention> Next, in order to explain the present invention more specifically, the reasons for limiting the components and manufacturing conditions will be explained.

C: When the amount of C in a cold rolled steel sheet is large, iron carbides are generated, and these carbides impair etching perforability.

Furthermore, when a flat mask is annealed after perforation as a shadow mask, non-uniform molding (occurrence of stretcher strain) will occur during press molding unless the solid solution C is reduced.

In order to satisfy both of these requirements, it is necessary to set the upper limit of the C content of the cold-rolled aluminum killed steel sheet to 0.004%. C
If the content is within this range, the amount of solid solute C will be sufficiently small and there will be no problem. In order to efficiently reduce the C content to this level in a decarburization annealing furnace, it is necessary to reduce the C content to 0.060% or less at the steel manufacturing stage.

From the above, the C content of the cold-rolled steel sheet is 0.004% or less, and the C content before the hot-rolled steel sheet is 0.060% or less.

Mn: In addition to the purpose of deoxidizing, Mn is useful for improving the strength of steel without degrading the properties of the shadow mask.

In addition, the role of Mn is to combine with S in the steel to prevent red heat embrittlement of the steel. Therefore, Mn is at least 0
．． 05%, and it is necessary that the weight ratio of Mn and S is M n (%)/S (%)≧7. However, when Mn exceeds 0.50%, it becomes too hard as a shadow mask and impairs the formability of a flat mask. Therefore, the component range of Mn is set to 0.05 to 0.50%.

S: Reducing S in steel directly leads to reducing center segregation of M n S. When focusing on the center segregation of MnS, which is a problem in etching holes and press forming, the first
As shown in the figure, the effect appears below 0°007%.

In addition, when forming ingots by continuous casting, further improvement effects are observed when electromagnetic stirring is used.

5oQAR: In addition to deoxidizing steel and reducing inclusions, 5oQAR is used to fix Nti-A QN as a solid solution and prevent stretcher strain during press forming.
AQ must be contained as AQ (acid-soluble AQ). However, when it is contained in a large amount, it deteriorates ductility.

From the viewpoint of deoxidation, 0.010% or more is required, and from the viewpoint of ductility, the upper limit is o, oso%.

In addition, in order to fix solid solution N as Al2N (So
It is necessary to add an amount of AQ that satisfies fiAQ%~0.003)/N%≧6.

N: Since N increases the elongation at yield point and causes stretcher strain, it is preferable that it be as small as possible. However, if it is reduced excessively, it will be costly, so in this patent, it is set to 0.0100% or less.

Prior to melting steel with such a composition, hot metal is first desulfurized to 0.007% or less of S by out-of-furnace desulfurization. After that, it is melted in a converter, and after the composition is adjusted, it is tapped. For casting, a normal ingot-forming method may be used, but if continuous casting is performed while electromagnetic stirring is performed, a high-quality product with less center segregation of M n S can be obtained. At this time, if the S content of the hot metal desulfurized outside the furnace is not sufficiently reduced, the efficiency in the converter will be poor, and it will be difficult to melt steel with the target S content.

In regulating S to 0.007% or less, it is preferable to ensure the final finish rolling start temperature in the hot rolling process to be 1000° C. or higher.

This is because in steels with S≦0.010% or less, the adhesion of scales generated during the hot rolling process improves, resulting in poor descaling on the entry side of the finishing rolling stand, which causes surface defects such as biting scales. This is because it becomes the cause.

It is also an effective means to increase the descaling property by ensuring sufficient humidity at the entry side of finish rolling and increasing the scale thickness by taking a sufficient time from the end of rough rolling to the start of finish rolling.

The copper strip hot-rolled under the above conditions is subjected to open coil decarburization annealing through a cold rolling process to obtain a C content of 0°004% or less.

After decarburization annealing, it is preferable to perform skin pass rolling or roller leveling and then re-cold rolling for handling in the next process. Re-cold rolling reduces the plate thickness to 0.3I or less, which is required by shadow mask manufacturers. do.

The AQ killed cold-rolled steel sheet produced in this manner has excellent etching perforation properties, and can be processed uniformly in press forming, resulting in a shadow mask material free from uneven transmission.

Figure 1 shows the relationship between the S content and MnS center segregation in various shadow mask materials.The number of MnS center segregation in Figure 1 is the cross section perpendicular to rolling of the various shadow mask materials (plate thickness x 600 mm width). Thirty arbitrary cross sections were taken, these cross sections were etched with a ferric chloride solution, and then examined under a microscope to measure the number of groups with a size of 20 μm or more. As is clear from Fig. 1, there is a correlation between the S content and the M n S center segregation that causes transmission unevenness, and when the S content is 0.007% or less, the M n S segregation of 20 μ or more occurs. It can be seen that the amount of generated substances is 0, but when it exceeds 0.007%, the amount of generated substances increases rapidly.

In this way, the S content is closely related to the occurrence of uneven transmission,
The critical condition of 0.007% or less has an important meaning in high-definition shadow masks.

Next, the functions and effects of the present invention will be explained with reference to Examples and Comparative Examples of the present invention.

<Examples and Comparative Examples> The test materials were first made by converting hot metal into CaO with an S content of 0°010%.
It is desulfurized outside the furnace until it reaches the following levels and then converted to hot metal in a converter.

After adjusting the ingredients, the ingot was formed by continuous casting. C after casting is 0.00
The content ranged from 5 to 0.008%.

This steel piece was made into a 0.25-thin steel plate through the steps of hot rolling→pickling→cold rolling→charcoal annealing→temper rolling→re-cold rolling.

The composition of this cold rolled steel is shown in Table 1.

After degreasing this cold rolled steel, apply a resist film - exposure - development -
A flat mask was manufactured using a process of etching perforation and resist film removal, and the occurrence of uneven transmission was investigated. In addition, among these, 75
After annealing in a decarburizing atmosphere at 0° C. for 10 minutes, it was press-molded into an FS tube, and the occurrence of uneven transmission during the press-forming process was investigated.

The results are also shown in Table 1, and Nal~5 gave good results with no uneven penetration occurring after etching and perforation and after press molding.

&6.7 had a large amount of S, so after etching and perforation, streak-like permeation unevenness occurred parallel to the rolling direction. Further, in &8, no noticeable unevenness in penetration occurred after etching, but unevenness in penetration parallel to the rolling direction also occurred due to press forming.

Effect> As is clear from the above, the shadow mask obtained by the manufacturing method of the present invention has almost no uneven transmission after etching and perforation, and almost no uneven transmission after press molding.
A good shadow mask material can be obtained, and as color cathode ray tubes are becoming increasingly high-definition these days, the present invention has the remarkable effect of providing an extremely excellent shadow mask material.

[Brief explanation of the drawing]

Figure 1 shows the S content and M n of various shadow mask materials.
It is a graph showing the relationship of S center segregation. Figure 1 S content ('10)

Claims (1)

[Claims] (1) C0.060% or less, Mn0.05-0 in weight%
．． 50%, S0.007% or less, SolAl0.010
Steel consisting of ~0.080%, N0.0100% or less, balance iron and unavoidable impurities is melted by desulfurization outside the furnace and a converter, then made into steel billets by ordinary ingot making or continuous casting, and this steel billet is heated. After rolling and cold rolling, C is 0.004% in a decarburization annealing furnace.
1. A method for producing a shadow mask material, which comprises decarburizing and annealing the material to a thickness of 0.3 mm or less, and further cold-rolling the material to a thickness of 0.3 mm or less.