JPS6376852A - Low strength and low thermal expansion alloy - Google Patents

Abstract

PURPOSE:To obtain an alloy having low thermal expansibility and low strength by providing a compsn. consisting of prescribed amounts of C, Si, Mn, Ni and Cr and the balance Fe with inevitable impurities. CONSTITUTION:This low strength and low thermal expansion alloy consists of, by weight, <=0.03% C, <=0.30% Si, <=1.0% Mn, 34.0-38.0% Ni 0.5-4.5% Cr and the balance Fe with inevitable impurities. The alloy having low thermal expansibility and low strength is obtd. by adding several % Cr to an Fe-36Ni alloy. It is an improved version of an 'Invar(R)' type Fe-Ni alloy used as a material for the shadow mask of the cathode-ray tube of a color TV set.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the improvement of an invar-type Fe--Ni alloy used in color television cathode ray tube shadow mask materials and the like.

[Conventional technology and its problems]

Low carbon A1 killed steel and low carbon rimmed steel have traditionally been used for color television cathode ray tube shadow masks.

When operating a cathode ray tube, most of the electron beams impinge on the shadow mask, which is heated to 80-90°C. Therefore, thermal expansion causes the position of the shadow mask to shift, resulting in color unevenness.

To prevent this, Fe36Ni with low thermal expansion was used.
The use of Amber-alloy is being considered.

However, the Fe36Ni amber alloy also has drawbacks in its use as a shadow mask material, and still has the problem of poor press formability.

The method of manufacturing a shadow mask consists of etching the material to make minute holes, annealing it to improve formability, and press-forming it into a mask.
Compared to low-carbon At-killed steel and rimmed steel, 36N i alloy has a higher yield strength due to its higher alloy content, but it has the problem of spring back after press forming, causing local deformation of the mask.6 .

For this reason, a low thermal expansion alloy with low yield strength is required, and it is said that a yield strength of 24 kg 47 mm or less is desirable in order to obtain good press formability. 3. is important.
A coefficient of thermal expansion of 0XIO-'/'C or less is required.

[Means to solve the problem]

The present inventors conducted various studies under the above circumstances, and found that by adding several percent of Cr to Fe-36Ni alloy, an alloy with both low thermal expansion and low strength could be obtained. I found out that it can be done.

[Structure of the invention]

In the present invention, in weight %, c: o, o 3% or less, Si:
0.30% or less, Mn: 1.0% or less, Ni:
34.0-38.0%, Cr: 0.5-4.5%,
A low-strength, low-thermal-expansion alloy comprising the balance Fe and unavoidable impurities is provided.

The reasons for limiting the ingredients in the present invention will be described below.

CTC forms an interstitial solid solution and increases yield strength.

Therefore, the smaller the amount of C, the more advantageous it is, but if it is less than 0.03%, the influence on the yield strength is small, so it is set to be less than 0.03%.

Si: Si is useful as a deoxidizing element, but when it exceeds 0.3%, the coefficient of thermal expansion increases significantly. Therefore, 0.3
% or less.

Mn: Like Si, it is useful as a deoxidizing element, but
If it exceeds 1.0%, the coefficient of thermal expansion will increase significantly, making it unsuitable for this purpose. Therefore, it should be 1.0% or less.

Ni: An important element that determines the coefficient of thermal expansion, 36%Ni
The coefficient of thermal expansion is the minimum at . If it is less than 34% or more than 38%, the coefficient of thermal expansion will increase significantly, making it unsuitable for this purpose.

Therefore, it is set in the range of 34.0 to 38.0%.

C": It is an element that is useful for reducing yield strength, but if it is less than 0.5%, it will not have a sufficient effect on reducing yield strength. On the other hand, C"
The addition of 2% causes an increase in the coefficient of thermal expansion, and if it exceeds 4.5%, the coefficient of thermal expansion increases significantly, making it unsuitable for this purpose. Therefore, it should be in the range of 0.5 to 4.5%.

(Specific description of the invention'R) Example 30kg 8ft 1'! Steel having the composition shown in Table 1 was melted using an empty melting furnace. A-D are alloys of the present invention,
A''-c is a comparative alloy. A steel ingot of the steel shown in Table 1 was forged, skinned, cold rolled, annealed, pickled, and cold rolled to a thickness of 5 mm and a temporary thickness of 31 m. The former plate was heat-treated at 900°C for 30 minutes to give a thickness of 0 to 1.
The average coefficient of thermal expansion at 00°C was measured. The latter plate thickness was heat-treated at 1,100° C. for a short time to adjust the crystal grain size to about 30 μm, and its 0.2% proof stress was measured. Figure 1 shows the results of proof stress organized in terms of CfJ. It is known that the yield strength decreases as the Cr content increases.In order to obtain a yield strength of 24klrf/am'' or less, which is required for zero wire applications, it is necessary to add 0.5% or more.

The influence of Cr on the thermal expansion coefficient from 0 to 100°C is shown in Figure 2a.The thermal expansion coefficient increases as Cr increases, but
In order to achieve a thermal expansion coefficient of 3.Ox 10-'/°C or less, which is desired in this application, up to 4.5% Cr can be tolerated.

Above, 0.5-4.5% C in Fe-36%Ni alloy
By adding r, it is possible to obtain a material that has low thermal expansion and low strength at the same time.

Table 1

[Brief explanation of the drawing]

Figure 1 is a graph showing the influence of Cr on yield strength;
The figure is a graph showing the influence of Cr on the coefficient of thermal expansion from 0 to 100°C.

Claims (1)

[Claims] At 1% by weight, C: 0.03% or less, Si: 0.30% or less, Mn: 1.0% or less, Ni: 34.0 to 38.0%, Cr: 0. A low-strength, low-thermal-expansion alloy containing 5 to 4.5% of Fe and the remainder consisting of Fe or unavoidable impurities.