US3630724A

US3630724A - Alloy having a low thermal expansion coefficient and a high spring bending limit

Info

Publication number: US3630724A
Application number: US814995A
Authority: US
Inventors: Toshinari Hirayama; Hideharu Ohara; Noboru Ichiyama
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 1968-04-17
Filing date: 1969-04-10
Publication date: 1971-12-28
Anticipated expiration: 1988-12-28
Also published as: DE1919114B1; NL6905869A

Abstract

A material having a low thermal expansion coefficient (a linear thermal expansion coefficient of less than about 7 X 10 6/* C) and a high spring bending limit (more than about 64 kg./mm.2) has been demanded for mechanical or electronic device, physicochemical machine, industrial measurement device. A nickeliron alloy which consists essentially of 33-46 percent of Ni, 0.1-5 percent of Ti, 0.5-5 percent of Mo and the balance iron and has a linear thermal expansion coefficient of (2.2-7.1) X 10 6/* C and a spring bending limit of 64-125 kg./mm.2 is obtained as a material which suffices said demand.

Description

United States Patent [72] Inventors ToshinarlHlrayama Kokubunji-shl; Hldeharu Ohara, Tokyo; Noboru Iehlyiuna, Kokubunil-shl, all 01 Japan [21] Appl. No. 814,995 [22] Filed Apr. 10, 1969 [45] Patented Dec. 28, 1971 [73] Assignee Hitachi, Ltd.

Tokyo, Japan 32 Priority Apr. 17, 1968 J p [31] 43/ 25,221.

[54] ALLOY HAVING A LOW THERMAL EXPANSION COEFFICIENT AND A HIGH SPRING BENDING Primary Examiner-L. Dewayne Rutledge Assistant Examiner-Joseph E. Legru Attorney-Craig, Antonelli, Stewart & Hill ABSTRACT: A material having a low thermal expansion coefficient (a linear thermal expansion coefficient of less than about 7 10'/ C) and a high spring bending limit (more than about 64 kgJmm?) has been demanded for mechanical or electronic device, physicochemical machine, industrial measurement device. A nickel-iron alloy which consists essentially of 33-46 percent of Ni, 0.1-5 percent of Ti, 0.5-5 percent of Mo and the balance iron and has a linear thermal expansion coefficient of (2.2-7.1) X10'/ C and a spring bending limit of 64-125 ltgJmm. is obtained as a material which suffices said demand.

ALLOY HAVING A LOW THERMAL EXPANSION COEFFICIENT AND A HIGH SPRING BENDING LIMIT This invention relates to a metal material which has a low thermal expansion coefficient and a high spring bending limit.

Recently, the high mechanical accuracy of a mechanical or electronic device, a physicochemical machine, an industrial measurement device, etc. has been increasingly demanded and further the change in temperature of atmosphere in which devices are operated has been increased.

Therefore, a metal material to be used in the important parts of such devices as mentioned above is required to have a high strength and further a high spring bending limit which affects recoverity against deformation and a low thermal expansion coefficient which affects the mechanical displacement with the change of temperature.

The term spring bending limit" used herein means a surface stress required for obtaining a strain at the center of a span of 0.005 cm. (or 0.0025 cm.) when a plate span is bent and then restored. Said plate span, both end of which are freely supported, suffices the equation l-8,000 h (or 4,000 h) wherein h is the thickness and l is span length.

As the most familiar example, a cathode-ray tube for a color television which uses a shadow mask will be shown below.

ln FIGS. 1 and 2, 1 is a shadow mask, 2 is a frame which holds the shadow mask 1, 3 is a cathode-ray tube pannel (which is called pannel hereinafter) and 4 is a flat leaf spring (called leaf spring hereinafter) which is located between said frame 2 and pannel 3 and which supports shadow mask 1 at pannel 3, and whose one end is fastened to pannel 3 by mounting stud 5 and another end is fastened to frame 2 by welding and the like.

Said mounting stud maintains said frame 2 at a correct position to assure that electron beams emitted from three electron guns accurately impinge upon three colored fluorescence medium dots applied to the inside of the cathode-ray tube pannel through the shadow mask 1.

In this case, a difficulty exists in the fact that the thermal expansion of said leaf spring or pannel causes change in the relative position between the fluorescence medium dots coated on the inside of the pannel and holes of the shadow mask, due to which color misregistration occurs on a screen. The term color misregistration" herein used means the change of relative positions of said dots and holes.

However, among the parts on which the thermal expansion has effect, said pannel and shadow mask cannot be changed in their qualities and sizes according to other conditions. Therefore, only the leaf spring can be dealt with in order to decrease color misregistration.

As the qualities of said leaf spring, the thermal expansion coefficient thereof should be as low as possible. Further, high strength and high recoverity against mechanical deformation are desirable.

As an example, an experiment was conducted on a cathoderay for inch type color television to obtain the following results.

The length of change of the center position of the shadow mask was about 26 1. depending upon the materials and under the temperature rise as mentioned in the above table I. In general, it is desirable to keep the change of the center position of the shadow mask at less than l0 1 to reduce the color misregistration to such degree as is negligible. Therefore, the material of the leaf spring shown in table 1 is not satisfactory.

According to the same example as mentioned above except that as the leaf spring, Kovar (29 Ni-l7 Co-54 Fe by weight and linear thermal expansion coefficient which is called merely thermal expansion coefficient hereinafter is about 5 l0'6/ C.), lnvar (36 %Ni-64 Fe by weight and thermal expansion coefficient about l.2 l0/ C.), or Super lnvar (32 Ni-5 Co-63 Fe by weight and thermal expansion coefficient about 0.1Xl06/ C.) was used, the center position of the shadow mask shifts by about 7 p.0 and no or substantially no color misregistration of the color television occurred. Usually, such leaf spring is required to have a thermal expansion coefficient of at most 8 l0'6/ C.

Regarding the spring bending limit of said materials, percent cold rolled plate of Kovar had about 65 kg./mm. after it was annealed at 550 C., and 80 percent cold rolled plates of lnvar and Super lnvar had about 40 kgjmm. and about 32 kg./mm., respectively, and merely about 60 kg./mm. even after they were annealed at 550 C.

In general, said leaf spring is required to stand against a considerably large mechanical shift and experientially, it should have a spring bending limit of at least 65 kg./mm. Said three materials have a spring bending limit of merely 65 kg./mm. at most. In many cases, the constructive materials of other mechanical or electronic device, physicochemical machine, industrial measurement device are also required to have a spring bending limit of more than 64 kg./mm.

The object of this invention is to provide a metal material which has a lower thermal expansion coefficient and a higher spring bending limit.

A specific object of this invention is to provide a metal material which has a thermal expansion coefficient of less than 8Xl06/ C. and simultaneously has a spring bending limit of more than 64 kg./mm.

FIG. 1 is a side view of a cathode-ray tube for color television which is suitable for applying this invention and FIG. 2 is a cross-sectional view at [I II.

The metal material for attaining the object of this invention consists essentially of 33-46 percent of Ni, 0.1-5 percent of Ti, 0.5-5 percent of Mo and the balance Fe. It may additionally contain other elements in such a small amount as does not greatly afi'ect the effect of this invention.

TABLE 2 Components (weight Thermal Spring percent) expansion bending coeflielent limit Ni Ti Mo Fe X10-/ C. (kg/mm 33 0. 1 0.5 Balance 4. 0 64 36 0.1 0.5 do.... 2.2 65 39 1.5 3.0 do. 4. 0 94 41 2.5 0.5 do.. 5.1 108 41 2.5 5.0 .do 3,6 11!) 46 5.0 6.0 do 7.1

The above table 2 shows examples of the metal materials of this invention and each alloy having the indicated compositions was rolled at a reduction rate of 60-90 percent, then heated for 10 minutes-4 hours at a temperature of 500750 C., and subjected to ageing treatment. Thus treated metal materials of this invention showed a thermal expansion coefficient of (2.27.l)Xl0/ C. and a spring bending limit of (64-125) kgjmmf. Thus, it was recognized that according to this invention, a conspicuously excellent alloy which has a low thermal expansion coefficient and simultaneously has a high spring bending limit can be provided.

In this invention, when the content of Ni is less than 33 percent, the thermal expansion coefficient of the alloy increases and simultaneously the spring bending limit conspicuously decreases and when the content of Ni is more than 46 percent, a high spring bending limit is attained, while the thermal expansion coefficient remarkably increases.

Addition of Ti in an amount of 0.1-5.0 percent, can increase the spring bending limit when Ni is added in the said range of the content within which a low thermal expansion coefficient can be attained, but when the content of Ti is less than 0.1 percent, said increase of the spring bending limit is only a little and when more than 5 percent, the thermal expansion coefficient increases to result in undesirable effect.

Addition of M in an amount of 0.5- percent increases the spring bending limit with a low thermal expansion coefficient, but said increase of the spring bending limit is smaller than that due to Ti. However, said addition of Mo results in the rise of recrystallization temperature of the alloy and, therefore, the alloy can be heat treated at a higher temperature and thus the time required for ageing treatment can be shortened.

In this invention, when a high spring bending limit (more than 90 kg./mm. is especially required, a composition of 39-46 percent of Ni, 1.5-5.0 percent of Ti and 0.5-5.0 percent of M0 is suitable and when a low thermal expansion coefficient (less than 5.0X/ C.) is especially required, a composition of 33-41 percent of Ni, 0.1-2.5 percent of Ti and 0.5-5.0 percent of M0 is suitable.

In order to obtain an alloy having a high spring bending limit (more than 90 kgJmmF) and a low thermal expansion coefficient (less than 5.0Xl0 C.), a composition of 39-41 percent of Ni, 1.5-2.5 percent of Ti and 0.5-5.0 percent of M0 is the most suitable.

Of course, it is needless to say that the thermal expansion coefficient and the spring bending limit of the metal material of this invention which are embodied by said composition ranges are varied depending upon the reduction rate and the conditions of heat treatment.

As mentioned above, the metal material of this invention has an extremely low thermal expansion coefficient and further has a high spring bending limit. Thus, according to this invention, a difficulty that the conventional metal material has not been above to possess both of said properties can be overcome.

Therefore, without an example of a cathode-ray tube for a color television which uses said shadow mask, this invention provides a material which is extremely useful for other various equipments, devices, etc. as mentioned above which requires maintenance of a high accuracy in an atmosphere in which temperature widely changes and a high recoverity against the mechanical deformation.

1n this specification, the percentage which indicates the content ofthe components is by weight.

What we claim is:

l. A metal material having a low thermal expansion coefficient and a high spring bending limit, which consists essentially of 33-46 percent weight percent of Ni, 0. l-5 weight percent ofTi, 0.5-5.0 weight percent of Mo and the balance Fe.

2. A metal material according to claim I, which consists essentially of 39-46 weight percent of Ni, 1.5-5 weight percent of Ti, 0.5-S weight percent ofMo and the balance Fe.

3. A metal material according to claim 1, which consists essentially of 33-41 weight percent of Ni, 0.1-2.5 weight percent of Ti, 0.5-5 weight percent of Mo, and the balance Fe.

4. A metal material according to claim 1, which consists essentially of 39-41 weight percent of Ni, 1.5-2.5 weight percent ofTi, 0.5-5 weight percent of Mo and the balance Fe.

5. An alloy having a linear thermal expansion coefficient of less than about 8Xl0/ C. and a high spring bending limit of greater than about 64 kg./mm. which consists essentially of about 33 to 46 weight percent of Ni, about 0.1 to 5 weight percent of Ti, about 0.5 to 5.0 weight percent of Mo and the balance Fe.

6. The alloy of claim 5 having a linear thermal expansion coefficient of about 2.2 to 7. l Xl0'/ C. and a spring bending limit of about 64 to 125 kg./mm.

7. An alloy having a low thermal expansion coefficient and a high spring bending limit of greater than about kg./mm. which consists essentially of about 39 to 46 weight percent of Ni, about 1.5 to 5.0 weight percent of Ti, about 0.5 to 5.0

weight percent of Mo and the balance Fe.

8. An alloy having a low thermal expansion coefiicient of less than about 5.0X10' C. and a high spring bending limit which consists essentially of about 33 to 41 weight percent of Ni, about 0.1 to 2.5 weight percent of Ti, about 0.5 to 5.0 weight percent of Mo and the balance Fe.

9. An alloy having a low thermal expansion coefficient of less than about 5.0X10 C. and a high spring bending limit of greater than about 90 kg./mm. which consists essentially of about 39 to 41 weight percent of Ni, about 1.5 to 2.5 weight percent of Ti, about 0.5 to 5.0 weight percent of Mo and the balance Fe.

Claims

2. A metal material according to claim 1, which consists essentially of 39-46 weight percent of Ni, 1.5-5 weight percent of Ti, 0.5-5 weight percent of Mo and the balance Fe.
3. A metal material according to claim 1, which consists essentially of 33-41 weight percent of Ni, 0.1-2.5 weight percent of Ti, 0.5-5 weight percent of Mo, and the balance Fe.
4. A metal material according to claim 1, which consists essentially of 39-41 weight percent of Ni, 1.5-2.5 weight percent of Ti, 0.5-5 weight percent of Mo and the balance Fe.
5. An alloy having a linear thermal expansion coefficient of less than about 8 X 10 6/* C. and a high spring bending limit of greater than about 64 kg./mm.2 which consists essentially of about 33 to 46 weight percent of Ni, about 0.1 to 5 weight percent of Ti, about 0.5 to 5.0 weight percent of Mo and the balance Fe.
6. The alloy of claim 5 having a linear thermal expansion coefficient of about 2.2 to 7.1 X 10 6/* C. and a spring bending limit of about 64 to 125 kg./mm.2.
7. An alloy having a low thermal expansion coefficient and a high spring bending limit of greater than about 90 kg./mm.2 which consists essentially of about 39 to 46 weight percent of Ni, about 1.5 to 5.0 weight percent of Ti, about 0.5 to 5.0 weight percent of Mo and the balance Fe.
8. An alloy having a low thermal expansion coefficient of less than about 5.0 X 10 6/* C. and a high spring bending limit which consists essentially of about 33 to 41 weight percent of Ni, about 0.1 to 2.5 weight percent of Ti, about 0.5 to 5.0 weight percent of Mo and the balance Fe.
9. An alloy having a low thermal expansion coefficient of less than about 5.0 X 10 6/* C and a high spring bending limit of greater than about 90 kg./mm.2 which consists essentially of about 39 to 41 weight percent of Ni, about 1.5 to 2.5 weight percent of Ti, about 0.5 to 5.0 weight percent of Mo and the balance Fe.