JPS61223188A - Iron-nickel alloy for shadow mask which suppresses generation of uneven stripe during etching - Google Patents

Abstract

PURPOSE:To suppress the generation of uneven stripes in the stage of etching by specifying the component segregation rate and length of segregation zone of Ni in an Fe-Ni alloy. CONSTITUTION:The component segregation rate of Ni in the Fe-Ni alloy for a shadow mask which can be determined by the equation is limited to <=10% and the length of the segregation zone is adjusted to <=300mm. Such conditions can be attained by preventing the segregation in the stage of producing an ingot or executing the diffusion treatment of Ni by a heat treatment during the process for production of a bar. The generation of the uneven stripes in the stage of etching is suppressed by controlling the segregation rate of Ni and the length of the segregation zone in the above-mentioned manner. A sharp image is obtainable by the characteristic of the material having a low coefft. of thermal expansion.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an iron-nickel alloy for use as a shadow mask material for color television cathode ray tubes, 4IK, and an iron-nickel 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. Inside the color television plow tube, the electron beams emitted from three electron guns pass through microscopic holes in the shadow mask and are precisely irradiated onto a predetermined point on the fluorescent screen, giving a specific color tone. .

However, when such a cathode ray tube is used continuously, the temperature of the fluorescent surface and shadow mask supported by the glass body onto which the electron beam is irradiated gradually becomes higher. The special shadow mask is heated to a considerably higher temperature than the fluorescent surface supported by the glass body.

Moreover, since the shadow mask material has a much larger coefficient of thermal expansion than the glass body, mutual positional deviation occurs, and the electron beam irradiation is not performed accurately, resulting in an image being unclear.

For this reason, attempts 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 insufficient.

Therefore, it has been proposed to use a low thermal expansion material such as amber or an iron alloy or a Kel alloy as a shadow mask material.

However, although such an iron-nickel alloy was supposed to give good results in terms of image clarity, it was difficult to obtain a good hole shape during photoetching during the process of manufacturing a shadow mask from this shadow mask material. When the etched shadow mask was visually observed from the surface, it was found that defects called uneven streaks remained. It is known that, in the case of mild steel, the cause of this streak unevenness is nonmetallic inclusions or carbides (ye, c) in the steel. (Japanese Patent Application Laid-Open No. 55-62123) The uneven streaks that occur in iron-1 nickel alloys such as oak and amber do not disappear even if these nonmetallic inclusions are reduced, and iron-2.

It is believed that there is a cause inherent to Kel-based alloys, and improvement of this problem has been desired.

As a result of various studies conducted by the present inventors on streak unevenness in iron-nickel alloys, we found that the cause of streak unevenness is the component segregation of nickel, and that there is a difference in etching performance between the nickel segregation area and the base material. It was found that the hole shape had deteriorated. The occurrence of uneven streaks is particularly noticeable when the weight exceeds 20 kg.

In view of the above, the present invention improves the drawback of the conventional iron-nickel alloy, which is the occurrence of streaks during etching, and
The object of the present invention is to provide an iron-2, Kel-based alloy for shadow masks that suppresses the occurrence of streak unevenness during etching.

The present invention is an iron oxide film for shadow masks that suppresses the occurrence of streak unevenness during etching, and has a nickel component segregation rate expressed by a linear equation of 10- or less, and a segregation band length of 300- or less. , is a Kel-based alloy.

Next, the reasons for limiting the nickel segregated substances constituting the alloy of the present invention will be explained.

The reason why is set to 10- or less is that 2. Kel's component segregation rate is 1
This is because a segregation zone exceeding 01 shows a significant difference in etching performance from the base material, resulting in noticeable occurrence of syringe unevenness.

The reason why the length of one of the segregation bands is set to 300 m or less in the material before etching is that if the length of one of the segregation bands exceeds 300 cm, the occurrence of streaks becomes noticeable. That is,
The segregation zone is the N1 segregation area during casting that does not disappear during subsequent processing and heat treatment, but is stretched in the rolling direction by rolling while changing its shape, so when the plate is processed to the final thickness. The shorter the length of the segregation zone, the smaller its width and thickness. Therefore, when holes are etched, there is no noticeable difference in etching performance between the hole wall surface and the base material, and no streaks are observed. On the other hand, long segregation bands remain large in width and thickness.

This results in a defect in the etching hole. The length of this limit is 300 cm.

Generally, the length of the segregation zone in the cross section parallel to rolling is 500+
In the case of about w+, the width of the segregation zone in the width direction is 1~
21 and the thickness is about several microns.

In this way, by strictly controlling the segregation rate of Kel and the size of the segregation zone, it is possible to suppress the occurrence of uneven etching streaks, and due to the characteristics of these materials, which have a low coefficient of thermal expansion) It has an extremely excellent feature of making the image even clearer.

These conditions can be achieved by preventing segregation during ingot production or by performing nickel diffusion treatment by heat treatment during the strip production process.

Note that the iron-nickel alloy for shadow masks mentioned here refers to 30 to 5011N, such as Amber and 42 alloys.
This is a low thermal expansion material containing KCr and/or CO with a maximum of about 1011 added. Mn, day 1. A
It also includes a first grade deoxidizing agent and trace elements added for reasons such as improving manufacturability.

The alloy of the present invention will be explained below using examples.

(Example) After melting an ingot of the alloy of the present invention shown in Table 1 in an electroslag melting furnace or a vacuum degassing furnace,
It was hot rolled at 0°C to form a plate with a thickness of 5 cm. If there is a large amount of nickel segregation, heat treatment at 1100° C. for 1 hour or more is appropriately performed to perform nickel diffusion treatment.

Next, this plate was subjected to ordinary pickling treatment, and then cold-rolled to a thickness of 1
．． 0m1m Toshita. The plate was further annealed at 650°C for 1 hour, and then cold rolled into a plate having a thickness of α145cm. This cold-rolled material was further annealed at 650 CK for 1 hour, and then cold-rolled into a plate having a thickness of 13 mm. As an evaluation of the sample prepared in this manner, actual photoetching holes were performed to investigate the occurrence of streak unevenness.

The results are shown in Table 1 along with comparative alloys.

As shown in Table 1, the alloy according to the present invention is the conventional iron-2,
It is clear that the Kel-based alloy does not have dark spots or uneven streaks when etched, making it an excellent alloy as a material for shadow masks.

Table 1

Claims (1)

[Claims] Component segregation rate of nickel expressed by the following formula [component concentration in segregation area - average component concentration / average component concentration] x
100 is 10% or less, and the length of the segregation zone is 300
An iron-nickel alloy for shadow masks that suppresses the occurrence of streak unevenness during etching that is less than mm.