JPS6123864B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an iron-nickel based alloy for use as a material for shadow masks of color television cathode ray tubes, and more particularly to a method for producing an iron-nickel based alloy for use in shadow masks that suppresses the occurrence of uneven streaks during etching. Mild steel is generally known as a shadow mask material for color television cathode ray tubes. In a color television cathode ray tube, electron beams emitted from three electron guns pass through microscopic holes in a shadow mask and are precisely irradiated onto a predetermined point on a fluorescent screen, giving a specific color tone. However,
When such a cathode ray tube is used continuously, the temperature of the phosphor screen and shadow mask supported by the glass body onto which the electron beam is irradiated gradually increases. In particular, the shadow mask becomes considerably hotter than the phosphor screen supported by the glass body, and since the shadow mask material has a much larger coefficient of thermal expansion than the glass body, mutual positional deviation occurs, making it difficult to accurately irradiate the electron beam. The image is not clear and the image is not clear. For this reason, efforts have been made to compensate for this by devising the structure of the support that serves as a suspension device for the shadow mask, but this is not sufficient. Therefore, it has been proposed to use a low thermal expansion material such as an iron-nickel based alloy such as invar as a shadow mask material. However, although such iron-nickel based alloys were supposed to give good results in terms of image clarity, in the process of manufacturing shadow masks from this shadow mask material, it was difficult to obtain good hole shapes during photoetching. When the etched shadow mask was visually observed from the surface, it was found that defects called uneven streaks remained. In the case of mild steel, it is known that nonmetallic inclusions or carbides (Fe ₃ C) in the steel are the cause of this uneven streaking. (Japanese Patent Laid-Open No. 55-62123) However, the uneven streaks that occur in iron-nickel based alloys such as amber do not disappear even if these nonmetallic inclusions are reduced, and it is believed that the cause is unique to the iron-nickel based alloy. This improvement was desired. The inventors of the present invention have conducted various studies on uneven streaks in iron-nickel based alloys, and have found that the cause of uneven streaks is the segregation of nickel components, and that there is a difference in etching performance between the nickel segregation area and the base material. As a result, it was found that the pore shape had deteriorated. The occurrence of uneven streaks becomes particularly noticeable when the nickel content exceeds 20% by weight. In view of these points, the present invention improves the drawback of conventional iron-nickel based alloys, such as the occurrence of uneven streaks during etching, and provides a method for producing an iron-nickel based alloy for shadow masks, which suppresses the occurrence of uneven streaks during etching. This is what we are trying to provide. The present invention provides iron-nickel based alloy ingots.
An iron-nickel based alloy for shadow masks that suppresses the occurrence of uneven streaks during etching by heating at a temperature of 850°C or higher and below the melting point and forging with a cross-section reduction rate of 40% or more over one or two heats. The present invention relates to a manufacturing method. Next, the reason for limiting the conditions constituting the alloy of the present invention will be explained. The reason why the heating temperature for forging is set to above 850℃ and below the melting point is that below 850℃, forgeability is poor and nickel segregation cannot be eliminated, and on the other hand, above the melting point, forging becomes impossible. be. The reason why the cross-section reduction rate of forging is set to 40% or more is that if it is less than 40%, nickel segregation cannot be sufficiently eliminated by forging. By forging iron-nickel based alloy ingots under specific forging conditions, it is possible to eliminate the segregation of nickel, thereby suppressing the occurrence of uneven streaks during etching. Due to the characteristics of this material, it has extremely excellent features that make images even clearer. The alloy of the present invention will be explained below using examples. Examples An ingot of the alloy of the present invention shown in Table 1 was melted in an electroslag melting furnace or a vacuum degassing furnace, then forged under various conditions shown in Table 1, and then hot rolled at 1150°C. , a plate with a thickness of 5 mm. Next, this plate was subjected to a conventional pickling treatment and then cold rolled to a thickness of 1.0 mm. After further annealing at 650°C for 1 hour, it was cold rolled into a plate with a thickness of 0.145 mm. This cold rolled material was further annealed at 650° C. for 1 hour, and then cold rolled into a plate having a thickness of 0.13 mm. As an evaluation of the sample prepared in this manner, actual photoetching was performed to examine the presence or absence of uneven streaks. This result, together with the comparative alloy, is
Shown in the table. As shown in Table 1, the alloy according to the present invention does not produce uneven streaks during etching compared to conventional iron-nickel based alloys, and is clearly an excellent alloy as a material for shadow masks. 【table】

Claims (1)

[Claims] 1. By heating the iron-nickel base alloy ingot at a temperature of 850°C or higher but below the melting point and forging it in 1 or 2 heats with a cross-section reduction rate of 40% or higher, the occurrence of uneven streaks during etching can be suppressed. A method for producing an iron-nickel based alloy for a shadow mask.