EP0756015A1 - Nickel-iron alloy for planar masks - Google Patents

Abstract

Alloy is used to make a mask for use inside a cathode ray tube and comprises 69-83 wt.% Ni, and up to the following amounts of other elements with the residue being Fe: 7% Mo, 8% Cu, 1.5% Co, 7% W, 7% Nb, 7% V, 7% Cr, 7% Ta, 0.1% C, 1% Mn, 1% Si, 1.2% Ti, 1.2% Al, 1.2% Zr, 1.2% Hf and 0.010% S. The following equations also restrict the percentages: Co+Ni+1.5 x Cu ≥ 79.5%; 3 x (Co+Ni)-2 x Cu ≥ 206%; Co+Ni+7 x Cu ≤ 130%; 7 x(Co+Ni)+2 x Cu ≤ 581%; Mo+W+Nb+V+Cr+Ta ≤ 7%; Ti+Al+Zr+Hf ≤ 1.2%; C+Mn+Si ≤ 1%; 80.5 ≤ Co+Ni+0.80 x Cu ≤ 81.7%. The mask is also claimed.

Description

The present invention relates to the use of an alloy of the Iron-Nickel type for the manufacture of a stretched shadow mask for cathode-ray display tube.

In order to improve the quality of the image obtained, cathode-ray viewing tubes for color television comprise a shadow mask consisting of a very thin metal sheet, pierced, by chemical attack, with a multitude of holes. The shadow mask, placed inside the tube near the display screen, is used to ensure that the impact of the electron beam takes place at the desired points so that the image obtained is clear. But it also serves, or can serve, magnetic shielding in order to eliminate the disturbances generated by the terrestrial magnetic field which distort the image.

In flat-screen television tubes, the metal sheet pierced with holes is held taut by a rigid frame. The elongations imposed by the voltage make it possible to avoid the deformations which would be caused by the local heating caused by the impact of the electron beam. The shadow mask is then said to be "stretched".

In order to withstand the tensioning forces necessary to obtain sufficient elongation, the shadow mask must be made of an alloy having high mechanical characteristics, in particular a tensile strength greater than 500 Mpa. This alloy must also have suitable magnetic properties, in particular a low coercive field, a high permeability and a high saturation induction, to effectively fulfill the magnetic shielding function. The alloy must also have a coefficient of expansion compatible with that of the frame which supports and ensures the tension of the shadow mask. It must be able to be blackened by a surface treatment in order to increase its emissivity in order to limit its heating under the effect of very energetic electron beams. Finally, the alloy sheet must be able to be easily etched by chemical attack, which requires that it be as thin as possible and as flat as possible.

To make the stretched shadow masks, extra mild steels calmed with aluminum (AK steels) are used. However, these steels have several drawbacks: their mechanical characteristics and their magnetic characteristics are insufficient to simultaneously obtain a high tensile strength, a good magnetic shielding effect and a good aptitude for chemical etching.

Iron-nickel alloys are also used containing, by weight, either approximately 79% or approximately 80% of nickel, approximately 4% of molybdenum, optionally from 0% to 2% of at least one element chosen from vanadium, titanium , hafnium and niobium, the remainder being iron and unavoidable impurities such as carbon, chromium, silicon, sulfur, copper and manganese; the content of impurities not exceeding 1%. These alloys are used in the form of cold-rolled strips cold worked so as to have a tensile strength greater than 800 Mpa. During the manufacture of the stretched shadow mask, the alloy is subjected to annealing at a temperature of approximately 450 ° C. which makes it possible to obtain relatively high magnetic properties without deteriorating the tensile strength. The presence of vanadium, titanium, hafnium or niobium allows, by an adapted surface treatment, to achieve a good blackening of the surface.

However, these alloys do not completely solve the problem of the magnetic screen, and, to avoid images being distorted by the earth's magnetic field, complicated and expensive electronic means of correction must be used. The need for an electronic correction is all the greater when the cathode screen is large and the shadow mask is thin, that is to say, easy to engrave.

The object of the present invention is to remedy these drawbacks by proposing an alloy of the iron-nickel type which can be used for the manufacture of a stretched shadow mask which fulfills the function of magnetic screen, even for small thicknesses. , and making it possible to obtain good quality images without the need for correction by electronic means.

$$\text{0\% ≤ Mo ≤ 7\%}$$

$$\text{0\% ≤ Cu ≤ 8\%}$$

$$\text{0\% ≤ Co ≤ 1,5\%}$$

$$\text{0\% ≤ W ≤ 7\%}$$

$$\text{0\% ≤ Nb ≤ 7\%}$$

$$\text{0\% ≤ V ≤ 7\%}$$

$$\text{0\% ≤ Cr ≤ 7\%}$$

$$\text{0\% ≤ Ta ≤ 7\%}$$

$$\text{0\% ≤ C ≤ 0,1\%}$$

$$\text{0\% ≤ Mn ≤ 1\%}$$

$$\text{0\% ≤ Si ≤ 1\%}$$

$$\text{0\% ≤ Ti ≤ 1,2\%}$$

$$\text{0\% ≤ Al ≤ 1,2\%}$$

$$\text{0\% ≤ Zr ≤ 1,2\%}$$

$$\text{0\% ≤ Hf ≤ 1,2\%}$$

$$\text{S ≤ 0,010\%}$$

le reste étant du fer et des impuretés résultant de l'élaboration, la composition chimique satisfaisant, en outre, les relations: $$\text{Co+Ni+1,5xCu ≥ 79,5\%}$$

$$\text{3x(Co+Ni)-2xCu ≥ 206\%}$$

$$\text{Co+Ni+7xCu ≤ 130\%}$$

$$\text{7x(Co+Ni)+2xCu ≤ 581\%}$$

$$\text{Mo+W+Nb+V+Cr+Ta ≤ 7\%}$$

$$\text{Ti+Al+Zr+Hf ≤ 1,2\%}$$

$$\text{C+Mn+Si ≤ 1\%}$$

$$\text{80,5 ≤ Co+Ni+0,80xCu ≤ 81,7\%}$$

To this end, the subject of the invention is the use of an iron-nickel alloy strip for the manufacture of a stretched shadow mask of thickness e, expressed in mm, characterized in that the chemical composition of the iron-nickel alloy comprises, by weight: $$\text{69\% ≤ Ni ≤ 83\%}$$

$$\text{0\% ≤ Mo ≤ 7\%}$$

$$\text{0\% ≤ Cu ≤ 8\%}$$

$$\text{0\% ≤ Co ≤ 1.5\%}$$

$$\text{0\% ≤ W ≤ 7\%}$$

$$\text{0\% ≤ Nb ≤ 7\%}$$

$$\text{0\% ≤ V ≤ 7\%}$$

$$\text{0\% ≤ Cr ≤ 7\%}$$

$$\text{0\% ≤ Ta ≤ 7\%}$$

$$\text{0\% ≤ C ≤ 0.1\%}$$

$$\text{0\% ≤ Mn ≤ 1\%}$$

$$\text{0\% ≤ If ≤ 1\%}$$

$$\text{0\% ≤ Ti ≤ 1.2\%}$$

$$\text{0\% ≤ Al ≤ 1.2\%}$$

$$\text{0\% ≤ Zr ≤ 1.2\%}$$

$$\text{0\% ≤ Hf ≤ 1.2\%}$$

$$\text{S ≤ 0.010\%}$$

the remainder being iron and impurities resulting from the preparation, the chemical composition satisfying, moreover, the relationships: $$\text{Co + Ni + 1.5xCu ≥ 79.5\%}$$

$$\text{3x (Co + Ni) -2xCu ≥ 206\%}$$

$$\text{Co + Ni + 7xCu ≤ 130\%}$$

$$\text{7x (Co + Ni) + 2xCu ≤ 581\%}$$

$$\text{Mo + W + Nb + V + Cr + Ta ≤ 7\%}$$

$$\text{Ti + Al + Zr + Hf ≤ 1.2\%}$$

$$\text{C + Mn + Si ≤ 1\%}$$

$$\text{80.5 ≤ Co + Ni + 0.80xCu ≤ 81.7\%}$$

et il est souhaitable que: $$\text{S < 0,001\%}$$

Preferably, the chemical composition of the alloy is such that: $$\text{0.04\% ≤ Ti + Al + Zr + Hf ≤ 1.2\%}$$

and it is desirable that: $$\text{S <0.001\%}$$

The shadow mask fulfills the magnetic screen function all the better since: $$\text{Mo + W + Ti + Nb + Al + Si + V + Cr + Ta ≤ 100xe}$$

The invention also relates to the use of a strip of an alloy according to the invention produced by induction under vacuum and then remelted under electroconductive slag before being rolled and then annealed in a passing oven at a temperature between 800 ° C. and 1200 ° C for a period of approximately 1 minute and planed under tension, so that the grain is between 8 and 11 ASTM, the tensile strength is greater than or equal to 500 MPa, the texture index n is less than 2, the coercive field is less than or equal to 0.5 A / cm and the saturation induction is greater than or equal to 0.7 Tesla.

The invention finally relates to a stretched shadow mask consisting of a sheet pierced with holes, cut from a strip of iron-nickel alloy in accordance with the invention.

The invention will now be described in more detail, but without limitation.

$$\text{3x(Co+Ni)-2xCu ≥ 206\%}$$

$$\text{Co+Ni+7xCu ≤ 130\%}$$

$$\text{7x(Co+Ni)+2xCu ≤ 581\%}$$

$$\text{80,5\% ≤ Co+Ni+0,80xCu ≤ 81,7\%}$$

$$\text{Mo+W+Nb+V+Cr+Ta ≤ 7\%}$$

assurait une fonction de blindage magnétique suffisamment efficace pour qu'il ne soit pas nécessaire d'utiliser un dispositif de correction électronique de l'image pour compenser les effets du champ magnétique terrestre.The inventors have found, unexpectedly, that a tense shadow mask made of an iron-nickel alloy whose chemical composition comprises, in particular, from 69% to 83% by weight of nickel, from 0% to 8% in weight of copper, from 0% to 1.5% by weight of cobalt from 0% to 7% by weight of at least one element chosen from molybdenum, tungsten, niobium, vanadium, chromium and tantalum, and satisfies relationships: $$\text{Co + Ni + 1.5xCu ≥ 79.5\%}$$

$$\text{3x (Co + Ni) -2xCu ≥ 206\%}$$

$$\text{Co + Ni + 7xCu ≤ 130\%}$$

$$\text{7x (Co + Ni) + 2xCu ≤ 581\%}$$

$$\text{80.5\% ≤ Co + Ni + 0.80xCu ≤ 81.7\%}$$

$$\text{Mo + W + Nb + V + Cr + Ta ≤ 7\%}$$

provided a sufficiently effective magnetic shielding function that it was not necessary to use an electronic image correction device to compensate for the effects of the earth's magnetic field.

This area of chemical composition makes it possible to obtain at the same time a tensile strength greater than or equal to 500 MPa, a thermal expansion coefficient close to 13 × 10 ^-6 / K, a high magnetic permeability and a weak coercive field.

Cobalt is optional and replaces part of the nickel at a rate of approximately 1% of cobalt for approximately 1% of nickel. Above 1.5%, cobalt has an unfavorable effect on the effectiveness of the magnetic shielding function of the stretched shadow mask.

Molybdenum, tungsten, niobium, vanadium, chromium and tantalum, improve the magnetic permeability and decrease the coercive field, but, when the sum of the contents of these elements exceeds 7% the alloy loses its magnetic properties and, in addition, becomes much more difficult to hot and cold roll.

To improve the emissivity of the shadow mask, one or more elements taken from titanium, aluminum, zirconium and hafnium can be added to the alloy in contents such as the sum Ti + Al + Zr + Hf is greater than or equal to 0.04% and less than or equal to 1.2%. These elements favor the formation on the surface of the shadow mask of a thin layer of black oxides which improves the emissivity and limits the heating of the shadow mask during its use. The sum of the contents of these elements must be greater than or equal to 0.04% for the oxidation to be frank, but must remain less than or equal to 1.2% because, beyond, rolling is very difficult.

The composition domain, thus defined, makes it possible to obtain alloys having an induction at saturation Bs of between approximately 0.5 and approximately 1 Tesla.

To allow the thickness of the shadow mask to be reduced, which facilitates drilling by chemical attack, while retaining the efficiency of a magnetic screen, it is desirable for the alloy to have an induction at saturation Bs greater than 0, 7 Tesla and preferably greater than 0.8 Tesla. For this, the contents of elements such as molybdenum, tungsten, titanium, niobium, aluminum, silicon, vanadium, chromium, and tantalum must be limited. Also, preferably, the chemical composition must be such that: $$\text{Mo + W + Ti + Nb + Al + Si + V + Cr + Ta ≤ 3\%}$$

This is particularly the case when the thickness is less than or equal to 0.05mm.

More generally, this sum must be smaller the smaller the thickness. If e is the thickness expressed in millimeters, it is preferable that: $$\text{Mo + W + Ti + Nb + Al + Si + V + Cr + Ta ≤ 100xe}$$

To facilitate the preparation and hot rolling, the alloy must contain between 0% and 0.1%, and preferably, between 0% and 0.05% of carbon, between 0% and 1%, and preferably , between 0.2% and 0.6% of manganese in order to fix the sulfur to obtain a good aptitude for plastic deformation when hot, and, between 0% and 1%, and preferably, between 0% and 0.3 % silicon. However, to obtain a high saturation induction, the sum of the carbon, manganese and silicon contents must remain less than or equal to 1%.

The rest of the composition consists of iron and impurities resulting from the production, such as phosphorus, sulfur, oxygen or nitrogen.

The sulfur content is generally less than or equal to 0.01%. However, to obtain good quality drilling by chemical cutting, the sulfur content should preferably remain less than or equal to 0.001%.

$$\text{2\% ≤ Mo ≤ 4\%}$$

$$\text{Cu ≤ 0,2\%}$$

$$\text{0,2\% ≤ Mn ≤ 0,6\%}$$

$$\text{Si ≤ 0,1\%}$$

$$\text{0\% ≤ C ≤0,03\%}$$

$$\text{0,04\% ≤ Ti + Al + Zr + Hf ≤ 0,5\%}$$

$$\text{S < 0,001\%}$$

le reste étant du fer et des impuretés résultant de l'élaboration.The best composition is: $$\text{80.5 ≤ Ni ≤ 81.5}$$

$$\text{2\% ≤ Mo ≤ 4\%}$$

$$\text{Cu ≤ 0.2\%}$$

$$\text{0.2\% ≤ Mn ≤ 0.6\%}$$

$$\text{If ≤ 0.1\%}$$

$$\text{0\% ≤ C ≤0.03\%}$$

$$\text{0.04\% ≤ Ti + Al + Zr + Hf ≤ 0.5\%}$$

$$\text{S <0.001\%}$$

the remainder being iron and impurities resulting from processing.

To make a shadow mask, an alloy as defined above is produced, preferably by vacuum induction melting (VIM) followed by remelting under electroconductive slag (ESR), in order to obtain a very clean metal. , which allows a better quality of drilling by chemical attack.

The alloy thus produced is cast in an ingot or in the form of a slab, then hot rolled then cold to obtain a thin strip of thickness less than 0.20 mm and preferably less than 0.10 mm.

The lamination is carried out in such a way that the texture is weak, and in particular that the texture index n is less than 2. This makes it possible to obtain a shadow mask whose properties are the same in all directions.

The texture index n is the maximum value of the ratio of the intensity of an X-ray beam reflected by a sample of the band studied, to the intensity of an X-ray beam reflected by an isotropic sample consisting of the same alloy; the ratio being measured for all the incidences corresponding to each of the families of theoretical textures.

For example, to manufacture a cold rolled strip with a thickness of about 0.05mm, we start with a hot rolled strip whose thickness is between 4 and 5mm. This strip is cold rolled in several passes interspersed with annealing in a passage oven, for example at intermediate thicknesses of 2mm, 0.25mm and 0.08mm. By doing so, the mechanical and magnetic anisotropies induced by rolling are minimized.

After rolling, the strip is subjected to recrystallization annealing, for example in a passage annealing oven, at a temperature between 800 ° C and 1200 ° C for a period of the order of 1 min. This annealing makes it possible to obtain a fine grain of size between 8 ASTM and 11 ASTM, which is also necessary for the quality of the chemical drilling. Finally, the strip is planed under tension.

Leveling under tension generates a small plastic deformation of the strip which has the effect of slightly degrading the permeability and the coercive field of the metal, but this planing is essential to obtain a perfect flatness of the strip, necessary for the manufacture of shadow masks.

The strip thus treated has an elastic limit of 350 Mpa, a tensile strength of 650 Mpa, a coercive field Hc of the order of 0.1 A / cm and an induction at saturation Bs greater than 0.7 Tesla. . It is important to note that, when the strip is subjected to a traction of around 200 MPa, the coercive field remains unchanged, around 0.1 A / cm.

With the alloys according to the prior art, when the softened strip is deformed by the planing operation under tension and then subjected to stresses, the magnetic properties are degraded more markedly than with the alloy according to the invention. As a result, the final coercive field is approximately three times higher and the permeability three times lower than with the alloy according to the invention.

By way of example, bands were made with five alloys according to the invention, marked A, B, C, D, E, and two bands, marked F and G, according to the prior art. The cold rolled strips were 0.07mm thick. They were all annealed in the oven at 1050 ° C for about 1 minute.

The chemical compositions, expressed in percent by weight, are given in Table 1. Table 1 % in weight AT B VS D E F G Or 81.1 80.8 77.0 80.9 81.0 79.7 77.0 Mo 5.80 5.55 3.90 2.90 0 4.95 3.20 Cu <0.01 <0.01 5.50 <0.01 <0.01 0.04 <0.01 Mn 0.50 0.50 0.50 0.60 0.30 0.40 0.40 Yes <0.05 <0.05 0.10 0.05 0.10 0.20 0.12 VS 0.008 0.012 0.010 0.007 0.015 0.015 0.011 Nb 0 0 0 0 3.80 0 0 Fe rest rest rest rest rest rest rest

The mechanical and magnetic characteristics in the annealed state then slightly deformed by leveling and subjected to stresses are given in Table 2. Table 2 AT B VS D E F G Coercive field A / cm 0.16 0.08 0.18 0.11 0.15 0.32 0.41 Induction at saturation T 0.7 0.7 0.7 0.85 0.8 0.75 0.9 Relative permeability 12000 36000 11000 19000 12000 4000 3000 yield strength MPa 340 345 320 350 390 362 295 Breaking load MPa 654 683 630 655 710 671 660 Elongation at break% 28 35 32 35 29 25 35 HV hardness 180 175 165 185 190 170 160

It can be seen that the alloys A, B, C, D, E according to the invention correspond to the weakest coercive fields and to the highest permeabilities, and that the alloys F and G according to the prior art have coercive fields and less good permeabilities, in a 2 to 3 ratio.

With band B, we made a stretched shadow mask of 30cmx22cm and 0.12mm thick which did not require electronic correction of defects caused by the Earth's magnetic field.

Claims (10)

Use of an iron-nickel alloy strip for the manufacture of a stretched shadow mask of thickness e, expressed in mm, characterized in that the chemical composition of the iron-nickel alloy comprises, by weight: $$\text{69\% ≤ Ni ≤ 83\%}$$

$$\text{0\% ≤ Mo ≤ 7\%}$$

$$\text{0\% ≤ Cu ≤ 8\%}$$

$$\text{0\% ≤ Co ≤ 1.5\%}$$

$$\text{0\% ≤ W ≤ 7\%}$$

$$\text{0\% ≤ Nb ≤ 7\%}$$

$$\text{0\% ≤ V ≤ 7\%}$$

$$\text{0\% ≤ Cr ≤ 7\%}$$

$$\text{0\% ≤ Ta ≤ 7\%}$$

$$\text{0\% ≤ C ≤ 0.1\%}$$

$$\text{0\% ≤ Mn ≤ 1\%}$$

$$\text{0\% ≤ If ≤ 1\%}$$

$$\text{0\% ≤ Ti ≤ 1.2\%}$$

$$\text{0\% ≤ Al ≤ 1.2\%}$$

$$\text{0\% ≤ Zr ≤ 1.2\%}$$

$$\text{0\% ≤ Hf ≤ 1.2\%}$$

$$\text{S ≤ 0.010\%}$$

the remainder being iron and impurities resulting from the preparation, the chemical composition satisfying, moreover, the relationships: $$\text{Co + Ni + 1.5xCu ≥ 79.5\%}$$

$$\text{3x (Co + Ni) -2xCu ≥ 206\%}$$

$$\text{Co + Ni + 7xCu ≤ 130\%}$$

$$\text{7x (Co + Ni) + 2xCu ≤ 581\%}$$

$$\text{Mo + W + Nb + V + Cr + Ta ≤ 7\%}$$

$$\text{Ti + Al + Zr + Hf ≤ 1.2\%}$$

$$\text{C + Mn + Si ≤ 1\%}$$

$$\text{80.5 ≤ Co + Ni + 0.80xCu ≤ 81.7\%}$$

Use of an alloy according to claim 1 characterized in that: $$\text{0.04\% ≤ Ti + Al + Zr + Hf ≤ 1.2\%}$$

Use of an alloy according to claim 1 or claim 2 characterized in that: $$\text{S <0.001\%}$$

Use of an alloy according to any one of Claims 1 to 3, characterized in that: $$\text{Mo + W + Ti + Nb + Al + Si + V + Cr + Ta ≤ 100xe}$$

Use of a strip of an alloy according to any one of Claims 1 to 4, characterized in that the alloy has been produced by vacuum induction and then remelted under an electrically conductive slag before being rolled and then annealed in a pass-through oven. a temperature between 800 ° C and 1200 ° C for a period of about 1 min and planed under tension, in that the grain is between 8 and 11 ASTM, the tensile strength is greater than or equal to 500 MPa, l texture index n is less than 2, the coercive field is less than or equal to 0.3A / cm and the saturation induction is greater than or equal to 0.7 Tesla. Stretched shadow mask of thickness e, expressed in mm, characterized in that it is made of an alloy whose chemical composition comprises, by weight: $$\text{69\% ≤ Ni ≤ 83\%}$$

$$\text{0\% ≤ Mo ≤ 7\%}$$

$$\text{0\% ≤ Cu ≤ 8\%}$$

$$\text{0\% ≤ Co ≤ 3\%}$$

$$\text{0\% ≤ W ≤ 7\%}$$

$$\text{0\% ≤ Nb ≤ 7\%}$$

$$\text{0\% ≤ V ≤ 7\%}$$

$$\text{0\% ≤ Cr ≤ 7\%}$$

$$\text{0\% ≤ Ta ≤ 7\%}$$

$$\text{0\% ≤ C ≤ 0.1\%}$$

$$\text{0\% ≤ Mn ≤ 1\%}$$

$$\text{0\% ≤ If ≤ 1\%}$$

$$\text{0\% ≤ Ti ≤ 1.2\%}$$

$$\text{0\% ≤ Al ≤ 1.2\%}$$

$$\text{0\% ≤ Zr ≤ 1.2\%}$$

$$\text{0\% ≤ Hf ≤ 1.2\%}$$

$$\text{S ≤ 0.010\%}$$

the remainder being iron and impurities resulting from the preparation, the chemical composition satisfying, moreover, the relationships: $$\text{Co + Ni + 1.5xCu ≥ 79.5\%}$$

$$\text{3x (Co + Ni) -2xCu ≥ 206\%}$$

$$\text{Co + Ni + 7xCu ≤ 130\%}$$

$$\text{7x (Co + Ni) + 2xCu ≤ 581\%}$$

$$\text{Mo + W + Nb + V + Cr + Ta ≤ 7\%}$$

$$\text{Ti + Al + Zr + Hf ≤ 1.2\%}$$

$$\text{C + Mn + Si ≤ 1\%}$$

$$\text{80.5 ≤ Co + Ni + 0.80xCu ≤ 81.7\%}$$

Stretched shadow mask according to claim 6 characterized in that: $$\text{0.04\% ≤ Ti + Al + Zr + Hf ≤ 1.2\%}$$

Stretch shadow mask according to claim 6 or claim 7 characterized in that: $$\text{S <0.001\%}$$

Stretch shadow mask according to any one of Claims 6 to 8, characterized in that: $$\text{Mo + W + Ti + Nb + Al + Si + V + Cr + Ta ≤ 100xe}$$

Stretched shadow mask characterized in that it consists of a sheet pierced with holes, cut from a strip according to claim 5.