JPH03191023A - Manufacture of iron-nickel base alloy stock for shadow mask - Google Patents

Abstract

PURPOSE:To manufacture the stock in which the generation of unevenness of stripes is suppressed in the stage of etching by cutting and splitting an ingot of a iron - nickel base alloy for a shadow mask in a plane including its center axis and forming the split ingot into sheet stock. CONSTITUTION:An iron - nickel base alloy for a shadow mask (having about 30 to 45wt.% Ni content) is melted and cast to manufacture an ingot., and the ingot is cut and split in a plane including its center axis into sheet stock. In this way, the iron - nickel base alloy stock in which a segregate part appears in the vicinity of the surface and then the unevenness of stripes caused by componental segregation is perfectly solved even without executing forging at a high temp. to such a degree that oxidation is made a severe problem and useful for a shadow mask for a high definition color television or the like can be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing an iron-nickel based alloy material for a shadow mask of a color TV cathode ray tube, and particularly relates to a method for manufacturing an iron-nickel based alloy material for a shadow mask of a color television cathode ray tube, and in particular, a method for manufacturing an iron-nickel based alloy material for a shadow mask of a color television cathode ray tube. The present invention relates to a method of manufacturing an iron-nickel based alloy material for a shadow mask that can suppress the occurrence of uneven streaks. The shadow mask material produced according to the present invention enables the production of high-definition masks and is usefully utilized in the field of shadow masks for high-definition color television and computer displays.

11 Mild steel (rimmed steel or aluminum guild steel) is generally known as a shadow mask material for color television cathode ray tubes. In a color television cathode ray tube, an electron beam emitted from an electron gun passes through a small hole in a shadow mask and is precisely irradiated onto a predetermined point on a fluorescent screen, giving it a specific color tone. However, not all of the electron beams pass through the small holes in the shadow mask, and the shadow mask is heated by the electron beams that impinge on the shadow mask without passing through the small holes in the shadow mask. Therefore, the shadow mask undergoes deformation called doming due to thermal expansion. As a result, a misalignment occurs in the positional relationship between the shadow mask and the fluorescent screen, and the electron beam is not accurately irradiated onto the fluorescent screen.
There is a problem that color purity decreases.

In order to solve this problem, it has been proposed to use an iron-nickel based alloy such as amber, which has a small coefficient of thermal expansion, as a shadow mask.

However, such iron-nickel based alloys for shadow masks can be used in normal manufacturing processes, such as 42 for lead frames.
Manufacturing process similar to alloy materials (continuous casting - hot rolling - pickling,
When the shadow mask material is manufactured by polishing - cold rolling - annealing - cold rolling, and thereafter annealing and cold rolling are repeated as appropriate until a predetermined thickness is reached, etching is performed to make holes for the electron beam to pass through the shadow mask material. When it was applied afterwards, uneven streaks occurred. This streak unevenness is a phenomenon in which a large number of streaks appear parallel to the rolling direction when an etched shadow mask is observed under transmitted light (oblique light).

Even in mild steel, streaks may occur parallel to the rolling direction, but it is known that this is caused by nonmetallic inclusions in the mild steel. However, in the case of iron-nickel-based alloys such as Amber, the streaks do not disappear even if the non-metallic inclusions in the alloy are reduced, and it is thought that the cause is unique to the iron-nickel-based alloy, and improvements can be made. was desired.

Therefore, the applicant first conducted various studies on streak unevenness in iron-nickel base alloy materials, and found that the cause of streak unevenness is segregation of components such as nickel and manganese, and that the segregated area is different from the base material. It was discovered that due to the difference in etching properties, unevenness occurs on the etching hole wall surface, and these appear as stripes.

Therefore, in order to eliminate the uneven streaks caused by this segregation, the applicant of the present application has developed an iron-nickel based alloy ingot heated to 850°C.
We have proposed a manufacturing method in which the material is heated at a temperature above and below the melting point, and forged in one or two or more heats with a reduction in area of 40% or more (Japanese Patent Laid-Open No. 128253/1983).

The forging method described above was certainly effective in eliminating streaks. However, in shadow masks for high-definition computer displays, where reduction in color purity due to doming is particularly problematic, the problem has arisen that streak unevenness cannot be sufficiently eliminated. In addition, if this forging method is used to more fully eliminate the streak unevenness, the forging temperature must be increased, and in this case, problems arise such as a decrease in yield due to oxidation and forging cracks due to grain boundary oxidation.

As a result of conducting various studies on the problem of uneven streaks, the present inventors discovered that segregation mainly occurs in the center of the ingot. By cutting and dividing on a plane that includes the shaft, we were able to completely eliminate the unevenness of streaks caused by component segregation, without having to forge at such high temperatures that segregation occurs near the surface and oxidation becomes a serious problem.

That is, the present invention involves cutting and dividing an ingot obtained by melting and casting an iron-nickel based alloy for shadow masks along a plane including the central axis of the ingot, and then using the divided ingot as a sheet material. The present invention provides a method for producing an iron-nickel based alloy material for a shadow mask, which can suppress the occurrence of uneven streaks during etching.

In the present invention, "iron-nickel base metal" is an alloy whose basic components are iron and nickel containing 30 to 45% by weight of nickel, in which Cr may be added as appropriate. , Mn%Co,
Ti, V% Nb, Zr.

MO1Includes those containing up to 5% by weight of subcomponents and additives such as Aβ and W.

The general manufacturing process of a shadow mask is as follows: After melting and casting a specified alloy raw material, the obtained ingot is passed through appropriate processing steps such as forging and rolling, and finally cold-worked to a specified shape. A shadow mask material is manufactured by forming a thick sheet. The shadow mask material is etched and perforated to form a flat mask. The flat mask is annealed to give it press formability and is then pressed into a spherical shape. The spherical mask is subjected to a blackening process to become a shadow mask. In addition,
There is also a method in which annealing to impart press formability is performed immediately after final rolling, and this is called a pre-annealing method.

To explain in more detail, the method for manufacturing the shadow mask material involves first melting an iron-nickel based alloy in a VOD furnace, casting it into an ingot, forging, hot rolling and cold rolling, and then annealing and cold rolling. The final cold rolling is repeated until the sheet has a predetermined thickness. Thereafter, it is slit to obtain a shadow mask material having a predetermined width. After degreasing, the shadow mask material is coated with photoresist on both sides, a pattern is baked, developed, etched with an etching solution, and perforated, and cut into individual flat masks.

The flat mask is annealed in a non-oxidizing atmosphere to impart press formability (in pre-annealing this annealing is performed on the final cold rolled material before etching). After leveling, it is spherically molded into a mask shape using a press.

Finally, the spherical mask is degreased and then subjected to a blackening treatment in a steam or combustion gas atmosphere to form a black oxide film on the surface. In this way, a shadow mask is produced.

Furthermore, without using the manufacturing process described above, and without recrystallizing the flat mask after perforation by recrystallization or forming it into a spherical surface by pressing, it is fixed to a frame etc. under tension, and after blackening treatment is applied to a cathode ray tube. There is also a manufacturing method that incorporates it.

It goes without saying that the present invention can be applied to any of these shadow mask manufacturing methods.

Next, the reason why uneven streaks can be eliminated by the present invention will be explained.

As mentioned above, the component segregation that causes uneven streaks mainly occurs in the center, so when the ingot is cut and divided into two along the plane that includes the central axis as shown in Figure 1, the segregated parts are separated into two parts. will appear near the surface.

Therefore, when heating is performed next for forging or other processing, the temperature near the surface quickly reaches a high temperature unlike the center, so segregation is eliminated in a shorter time than in the past. Furthermore, depending on the amount of peeling after forging, it is possible to remove the segregated portion. The long pieces and short pieces are thick like a slab (when cutting different ingots, cut the ingot in a plane that includes the central axis of the ingot (ingot) so that there is a lot of segregation on the surface (for example, when cutting different ingots) It is preferable to cut along the plane of the direction.

By adopting such a method, it is possible to prevent forging cracks and a decrease in yield due to oxidation during high-temperature annealing, which have been problems in the past.

Next, the present invention will be explained in detail with reference to Examples and Comparative Examples.

<Examples and Comparative Examples> Amber (36% Ni-remaining Fe) was used as the iron-nickel based alloy. After the alloy was produced by vacuum melting, it was cast into an ingot having the dimensions shown in FIG. 2 (unit: mm). Thereafter, as shown in FIG. 2, both the cut piece and the uncut piece were heated at 1200° C. for 10 hours and forged.

Next, after peeling, hot rolling was performed at 1100°C. Then pickling, cold rolling, annealing, cold rolling, annealing,
A shadow mask material having a plate thickness of 0.15 mm was produced by cold rolling.

When we actually etched the sample manufactured in this way into a high-definition mask and evaluated the unevenness of streaks, we found that there were no unevenness of streaks in the cut and divided ingots.
On the other hand, uneven streaks occurred in those that were not cut and divided.

As described above, according to the present invention, uneven streaks caused by component segregation can be easily eliminated without the need for a special thermal diffusion process. For this reason, etching holes can be precisely formed, greatly contributing to higher image quality and lower costs of color cathode ray tubes for color televisions and computer displays.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the principle of the present invention. Figure 2 shows Invoice used in the example Dimensions of and is an explanatory diagram showing a divided state. Figure 1 2nd @

Claims (1)

[Claims] 1) An ingot obtained by melting and casting an iron-nickel based alloy for shadow masks is cut and divided along a plane including the central axis of the ingot, and the divided ingot is then used as a sheet material. , a method for producing an iron-nickel based alloy material for a shadow mask that can suppress the occurrence of uneven streaks during etching.