JP2000096188A - Iron - nickel alloy with low coefficient of thermal expansion and excellent hot workability, and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an Fe-Ni alloy in which hot workability is improved and thermal expansion coefficient is small as to have <=1×10-6/ deg.C thermal expansion coefficient at the service temperature of a shadow mask. SOLUTION: The alloy has a composition containing 34-37% Ni, <=0.01% C, <=0.0040% N, <=0.05% Si, <=0.1% Mn, <=0.003% Al, <=0.005% S, 0.0005-0.0040% B, and 10(C+N) to 0.2% Ti and shows <=1.0×10-6/ deg.C thermal expansion coefficient at 30 to 100 deg.C. This alloy can be manufactured by an ingoting process or a continuous casting process. In the case of an ingoting process, an ingot after component regulation is heated to 1,280 to 1,350 deg.C in >=3 hr total heating time and worked into a slab by a single or plural-time slabbing or forging, and the slab is heated to 1,100 to 1,350 deg.C for 1 to 6 hr and then hot rolled. In the case of a continuous casting process, the resultant cast slab is heated to 1,280 to 1,350 deg.C for 1 to 6 hr and then hot rolled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an Fe--Ni alloy suitable as a shadow mask exhibiting a small coefficient of thermal expansion at a use temperature and a method for producing the same.

[0002]

2. Description of the Related Art Fe--Ni alloys represented by invar alloys have a small coefficient of thermal expansion of 1.2 to 2.0.times.10.sup.- ⁶ / .degree. C. at 30 to 100.degree. It is used for expansion adjustment equipment, LNG tanker lining, etc. Recently, it has begun to be used as a shadow mask for a color picture tube, for which the demand for higher definition has been increasing by utilizing the low thermal expansion coefficient. The shadow mask is placed just before the color picture tube fluorescent screen,
Heat is generated by the impact of the electron beam emitted from the electron gun, and the temperature rises. When the shadow mask thermally expands with the rise in temperature, and the shape and dimensions of the electron beam passage holes change,
The predetermined electron beam does not hit the predetermined phosphor screen, causing a color shift and a doming phenomenon in which an image becomes unclear.

[0003] Fe-Ni alloys having a low coefficient of thermal expansion are less likely to be affected by temperature, and are therefore suitable as materials for shadow masks. However, as the number of still images tends to increase in addition to an increase in the screen size and definition of a television, a strong electron beam often hits a local portion of a shadow mask for a long time. For this reason, color misregistration caused by local thermal expansion is also problematic, and the conventional Fe-Ni
An Fe-Ni-based alloy having a smaller thermal expansion coefficient than that of a system-based alloy has been desired.

[0004] In order to reduce the thermal expansion coefficient of an Fe-Ni-based alloy, various alloy designs have been conventionally proposed. For example, Japanese Patent Application Laid-Open No. 62-290846 discloses a Ni: 34
To 37% by weight, Mn: 0.4% by weight or less, Si: 0.1%
A Fe-Ni-based alloy containing less than 0.05% by weight of Al, Mg, Ti, Ca, C, and Zr in total is introduced. This Fe—Ni alloy is 30 to 70 ° C.
Coefficient of thermal expansion in the temperature range of 1.0 to 1.2 × 10 ^-6
/ ° C, and the thermal expansion coefficient of an ordinary Fe-Ni alloy is 1.
It is smaller than 2 to 2.0 × 10 ⁻⁶ / ° C.
Also, in JP-A-7-3401, C: 0.009
% By weight, Mn: 0.1% by weight or less, Ni: 34% by weight or more, and by adjusting the Fe / Ni ratio in the range of 1.75 to 1.83, the thermal expansion in the range of 20 to 100 ° C. The coefficient is reduced to less than 1 × 10 ⁻⁶ / ° C.

[0005]

In the use as a shadow mask, if a large amount of inclusions are present, a predetermined hole shape cannot be obtained after etching, so that a material having high cleanliness is required. For high cleaning, it is necessary to remove O in the Fe—Ni alloy as much as possible, and a deoxidizing agent such as C, Mn, Si, or Al is added. As a result, C, M derived from the deoxidizing agent
A material containing a large amount of n, Si, Al or the like is melted.
It is necessary to lower the coefficient of thermal expansion from the required characteristics as a shadow mask. However, C, Si, Mn, Al, and the like tend to increase the coefficient of thermal expansion as the content increases, as introduced in Japanese Patent Publication No. Hei 8-512363.

To reduce the thermal expansion, it is important to reduce the components derived from the deoxidizing agent as much as possible. However, due to limitations in the refining technology including deoxidizing, the contents of C, Si, Mn, Al and the like are reduced to some extent. It is difficult to: C, Si, Mn, Al
Such reduction may not be desirable due to other characteristics required for steel materials. For example, if S is fixed as MnS, S
In view of Mn, which has an effect of preventing a decrease in hot workability caused by grain boundary segregation, it is not preferable to reduce the Mn content from the viewpoint of manufacturability.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been devised in order to solve such a problem, and it is intended to detoxify C mixed as a deoxidizing agent and N mixed in manufacturing by adding Ti. Accordingly, an object of the present invention is to provide an Fe-Ni-based alloy having a lower coefficient of thermal expansion than a conventional Fe-Ni-based alloy and having good hot workability and suitable for a shadow mask. In order to achieve the object, the Fe—Ni-based alloy of the present invention contains 34 to 37% by weight of Ni, 0.01% by weight or less of C, 0.0040% by weight or less of N, and 0.05% by weight of Si. , Mn: 0.1 wt% or less, Al: 0.003 wt% or less, S: 0.005 wt% or less, B: 0.000
5 to 0.0040% by weight, Ti: 10 (C + N) to 0.
2% by weight, with the balance having a substantially Fe composition,
It exhibits a thermal expansion coefficient of 1.0 × 10 ⁻⁶ / ° C. or less in a temperature range of 0 to 100 ° C.

This Fe—Ni alloy can be produced by any of the ingot casting method and the continuous casting method. In the ingot-making method, the steel ingot with the adjusted composition is heated to 1280 to 1 for a total heating time of 3 hours or more.
Heated to 350 ° C, processed into slabs by one or more slab rolling or forging, and heated to 1100-1350 ° C for 1-6
After heating for an hour, hot rolling is performed. In the continuous casting method, the obtained slab is heated to 1280 to 1350 ° C. for 1 to 6 hours and then hot-rolled.

[0009]

As described above, C, Si, M as deoxidizing agents
There is a limit in reducing the content of n and Al from the viewpoint of production including deoxidation. Further, reduction of elements having an effect of improving hot workability such as Mn and B is not industrially preferable.
Furthermore, there is a technical limit in reducing the inevitable elements such as P, S, and N. Conventional Fe—Ni-based alloy materials are manufactured under such restrictions, and are a factor that hinders a reduction in the coefficient of thermal expansion. On the other hand, in the present invention, solid solution C and N are further reduced by fixing C and N by adding Ti, and Ti which is harmless to low thermal expansion is added.
By setting (C, N), 1.0 × 10 ⁻⁶ can be stably obtained.
An Fe-Ni-based alloy having a low thermal expansion coefficient of not more than / ° C is obtained. Moreover, since C is made harmless by the addition of Ti, it is possible to secure the amount of C necessary for deoxidation.

Hereinafter, alloy components, contents, and the like included in the Fe—Ni alloy of the present invention will be described. Ni: 34 to 37% by weight Ni is an essential alloy component for lowering the coefficient of thermal expansion of the Fe-Ni alloy, and shows a low coefficient of thermal expansion in the range of 34 to 37% by weight. If the Ni content is outside the range of 34 to 37% by weight, the coefficient of thermal expansion tends to increase. C: 0.01% by weight or less A component that exhibits a deoxidizing effect, but not only increases the coefficient of thermal expansion, but also forms carbides that are harmful to etching properties when contained in a large amount in the alloy. Therefore, in the present invention,
The upper limit of the C content was set to 0.01% by weight.

N: 0.0040% by weight or less is an element inevitably mixed, and not only the coefficient of thermal expansion increases with an increase in the N content, but also bubbles that cause defects are generated in the steel ingot. Easier to do. Therefore, in the present invention, the upper limit of the N content is set to 0.0040% by weight. Si: a component added as a deoxidizing agent in an amount of less than 0.05% by weight , but if a large amount of Si is contained in the alloy, the Si concentration in the surface layer increases after bright annealing, and black formed on the shadow mask surface The degree of blackening of the oxide film decreases. Therefore, in the present invention, the Si content is set to 0.1.
It was set to less than 05% by weight. Mn: 0.1% by weight or less S which has a strong tendency to segregate at the grain boundary is fixed as MnS, and has an effect of improving hot workability. However, since the coefficient of thermal expansion increases as the amount of addition increases, the present invention
The upper limit of the n content was set to 0.1% by weight.

Al: 0.003% by weight or less Al is a component exhibiting a strong deoxidizing effect, but tends to remain as hard Al ₂ O ₃ -based inclusions in the deoxidized steel material. A
l ₂ O ₃ based inclusions becomes a cause of surface defects in the product, reducing the surface quality. Therefore, in the present invention, the upper limit of the Al content is set to 0.003% by weight. S: 0.005% by weight or less S is a harmful element that significantly reduces hot workability, and it is necessary to remove S as much as possible in the refining stage. In order to prevent remarkable cracking during hot working such as hot rolling, the S content is limited to 0.005% or less (preferably 0.003% by weight or less).

B: 0.0005 to 0.0040% by weight Addition of B improves hot workability and increases the rigidity of the shadow mask. S: When 0.0040% by weight or less and 0.0005% by weight or more of B is added, the surface cracks of the slag which tend to occur during hot working become extremely small,
Cracking that occurs when hot rolling a slab obtained by forging or slab rolling or continuous casting of a steel ingot is reduced. But,
Excessive addition of B exceeding 0.0040% by weight increases the coefficient of thermal expansion and causes B to concentrate on the surface of the shadow mask during softening annealing, thereby forming an uneven blackening film in the subsequent blackening treatment. Becomes

Ti: 10 (C + N) to 0.2% by weight In the Fe—Ni alloy of the present invention, Ti is the most important alloy component. According to research and research by the present inventors, 10 (C
It has been found that when the Ti content is set in the range of + N) to 0.2% by weight, the coefficient of thermal expansion is lower than that of a conventional Fe-Ni alloy. The effect of Ti on the coefficient of thermal expansion is presumed as follows. That is, although Ti is generally known, it combines with C and N in steel to form Ti.
(C, N) is generated, and the amount of solid solution of C and N is reduced.
C and N act in the direction of increasing the thermal expansion coefficient by promoting the thermal vibration of the crystal lattice in the solid solution state.
In the state fixed as N), there is no influence on the thermal expansion. The adverse effects of C and N on the coefficient of thermal expansion are significantly suppressed when the amount of Ti added is 10 (C + N) or more.
By adding Ti at least ten times the amount of (C + N), the amount of solid solution C and the amount of solid solution N are greatly reduced. However, when a large amount of Ti exceeding 0.2% by weight is added, the thermal expansion coefficient tends to be rather increased.

[0015] The Fe-Ni-based alloy whose components have been adjusted as described above can be produced by any of the ingot casting method and the continuous casting method. In the ingot making method, a steel ingot heated to 1280 to 1350 ° C is subjected to slab rolling or hot forging. In the Fe—Ni system targeted by the present invention, S segregates or concentrates at the austenite grain boundary during solidification, and precipitates such as oxides and sulfides having a low melting point are easily generated. The low melting point precipitate causes a large number of cracks during slab rolling and hot forging. Therefore, the steel ingot was heated to 1280 ° C.
By heating at the above temperature for a total of 3 hours or more, the precipitate in which S is concentrated is decomposed, and the solid solution of S in the matrix is promoted. As a result, the grain boundaries are strengthened in combination with the addition of B, and cracks generated during hot working are greatly reduced. On the other hand, a heating temperature exceeding 1350 ° C. promotes oxidation of the steel ingot and lowers the yield.

[0016] The heating of the steel ingot also affects the stripe unevenness that occurs when etching is performed in the final stage of the shadow mask manufacturing process. In this regard, when the steel ingot which has been heated to a temperature of 1280 ° C. or more to decompose precipitates and diffused into the matrix is hot-worked, the F for shadow mask which has no stripe unevenness due to segregation.
An e-Ni-based alloy is obtained. The longer the heating, the more effective it is to reduce streak unevenness. However, an excessively long heating time promotes oxidation of the steel ingot and reduces the yield. Therefore, in the present invention, the total heating time is set to 96 hours or less (preferably 24 hours or less) even when a slab is manufactured by repeating slab rolling or forging.

When hot-rolling a slab,
Heat to 1100-1350 ° C for 1-6 hours prior to hot rolling. At a heating temperature of 1100 ° C. or more, the deformation resistance is sufficiently reduced, and hot rolling becomes easy. However, 1350 ° C
If the heating temperature exceeds, the yield is significantly reduced due to oxidation. When hot rolling a continuously cast slab, the temperature is set to 1280 to 1350 ° C. for the same reason as the heating condition for the steel ingot.
Heat for ~ 6 hours. Since S, which is a relatively light element, diffuses quickly, hot workability can be improved by heat treatment for a relatively short time at a temperature equal to or higher than the decomposition temperature of the low melting point precipitate. When the bulk slab or the continuously cast slab thus heat-treated is hot-rolled, since the crystal grain boundaries are strengthened by S diffusion and B addition to the matrix, generation of cracks is suppressed, and a high yield is obtained. A hot rolled Fe-Ni alloy sheet is manufactured.

[0018]

EXAMPLE The molten steel melted in an electric furnace was roughly decarburized in a converter, purified by a vacuum degasser, and adjusted to the components and compositions shown in Table 1.

[0019]

In Test Nos. 1 to 9, ingots manufactured by the ingot-making method were heated to a temperature of 1280 ° C. or higher or lower than 1280 ° C., and then slabs were formed by slab rolling. Test number 1
In Nos. 1-17, one ingot also produced by the ingot-making method
After heating to a relatively low temperature of less than 280 ° C., the slab was formed by slab rolling. In Test Nos. 10 and 18, slabs were directly manufactured by a continuous casting method. Hot rolling from each slab,
A cold rolled sheet was manufactured through the steps of annealing and pickling and cold rolling.

Since the Fe-Ni alloys of Test Nos. 1 to 9 all contain 0.0005% by weight or more of B, remarkable cracking that tends to occur on the surface of the slab is suppressed. It was possible to stop the generation of small cracks that could be removed in the subsequent surface care step. In addition, 128
As can be seen in Test Nos. 8 and 9, which were heated to a high temperature of 0 ° C. or more for a total heating time of 3 hours or more, in the case where the low-melting-point precipitates were decomposed and diffused by heat treatment, the occurrence of surface cracks due to slab rolling was almost infrequent It was suppressed so that it could not be observed. Test No. 1 in which a continuous casting slab was heat-treated and hot-rolled
As shown in FIG.
When heated to at least ℃, a hot-rolled sheet with almost no surface flaws was obtained.

When the coefficient of thermal expansion of the obtained cold-rolled sheet was measured, as shown in Table 2, the Ti content was changed from 10 (C + N) to
In Test Nos. 1 to 10 maintained in the range of 0.02% by weight, the average coefficient of thermal expansion in the temperature range of 30 to 100 ° C. showed a low value of 1.0 × 10 ⁻⁶ / ° C. or less. In contrast, Test No. 1 in which the Ti content exceeded 0.2% by weight
Nos. 1 to 13 had a high average thermal expansion coefficient exceeding 1.0 × 10 ⁻⁶ / ° C. because the required amount of solute Ti was contained in the alloy. Conversely, in Test Nos. 14 to 17 in which the Ti content does not reach 10 (C + N), the fixation of C and N is not sufficient,
It exhibited a large thermal expansion coefficient exceeding 1.0 × 10 ⁻⁶ / ° C. due to solid solution C and N. Test number 1 with a large amount of S
In Test No. 14, where the amount of 2, B was insufficient, remarkable surface cracks occurred during slab rolling. Furthermore, the continuous casting slab is 1200
In Test No. 18, in which S was segregated and hot rolled after heating at ℃ and then hot rolling, extremely deep scratches occurred frequently on the hot rolled sheet surface.

[0023]

[0024]

As described above, as described above, the Fe-
Ni-based alloys include C, Si, M used as a deoxidizing agent.
The contents of n and Al are regulated, S contained as impurities is reduced, and B is added to strengthen the crystal grain boundaries, and solid solution C and N are fixed by Ti. Therefore, cracking during hot working is suppressed, and a Fe—Ni-based alloy suitable as a high-quality shadow mask material having a low thermal expansion coefficient of 1 × 10 ⁻⁶ / ° C. or less can be obtained.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H01J 29/07 H01J 29/07 Z (72) Inventor Takashi Yamauchi 4976 Nomuraminamicho, Shinnanyo-shi, Yamaguchi Nisshin Steel Co., Ltd. F term in the company technology laboratory (reference) 4K032 AA01 AA02 AA04 AA16 AA21 AA25 AA29 AA31 AA35 BA01 CA02 CA03 5C027 HH02 HH30 5C031 EE05

Claims (3)

[Claims] 1. Ni: 34 to 37% by weight, C: 0.01
Wt% or less, N: 0.0040 wt% or less, Si: 0.
Less than 05% by weight, Mn: 0.1% by weight or less, Al: 0.
003% by weight or less, S: 0.005% by weight or less, B:
0.0005 to 0.0040% by weight, Ti: 10 (C +
N) to 0.2% by weight, with the balance having substantially the composition of Fe, and 1.0 × 10 ⁻⁶ / ° C. in a temperature range of 30 to 100 ° C.
Fe-Ni excellent in hot workability showing the following thermal expansion coefficient
System alloy. 2. A steel ingot having the composition of claim 1 is heated to 1280-1350 ° C. for a total heating time of 3 hours or more,
Processed into slabs by one or more times of slab rolling or forging, heated to 1100 to 1350 ° C for 1 to 6 hours, and then hot-rolled, characterized by a small coefficient of thermal expansion and excellent hot workability And a method for producing an Fe-Ni alloy. 3. A slab having the composition according to claim 1 manufactured by a continuous casting method, heated to 1280 to 1350 ° C. for 1 to 6 hours, and then hot-rolled. A method for producing an Fe-Ni-based alloy having excellent workability.