Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C19/00—Alloys based on nickel or cobalt
  • C22C19/03—Alloys based on nickel or cobalt based on nickel
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
  • H01J9/02—Manufacture of electrodes or electrode systems
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
  • H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
  • H01J29/06—Screens for shielding; Masks interposed in the electron stream
  • H01J29/07—Shadow masks for colour television tubes

Definitions

• 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.
• 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.
• 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".
• the shadow mask 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.
• 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.
• 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.
• 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.
• 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: 69% ⁇ Ni ⁇ 83% 0% ⁇ Mo ⁇ 7% 0% ⁇ Cu ⁇ 8% 0% ⁇ Co ⁇ 1.5% 0% ⁇ W ⁇ 7% 0% ⁇ Nb ⁇ 7% 0% ⁇ V ⁇ 7% 0% ⁇ Cr ⁇ 7% 0% ⁇ Ta 7% 0% ⁇ C ⁇ 0.1% 0% ⁇ Mn ⁇ 1% 0% ⁇ If ⁇ 1% 0% ⁇ Ti ⁇ 1.2% 0% ⁇ Al ⁇ 1.2% 0% ⁇ Zr ⁇ 1.2% 0% ⁇ Hf ⁇ 1.2% S ⁇ 0.010% the remainder being iron and impurities resulting from the preparation, the chemical composition satisfying, moreover, the relationships: Co + Ni + 1.5xCu ⁇ 79.5% 3x (Co +
• the chemical composition of the alloy is such that: 0.04% ⁇ Ti + Al + Zr + Hf ⁇ 1.2% and it is desirable that: S ⁇ 0.001%
• the shadow mask fulfills the magnetic screen function all the better since: 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.
• 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: Co + Ni + 1.5xCu ⁇ 79.5% 3x (Co + Ni) -2xCu ⁇ 206% Co + Ni + 7xCu ⁇ 130% 7x (Co + Ni) + 2xCu ⁇ 581% 80.5% ⁇ Co + Ni + 0.80xCu ⁇ 81.7% 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.
• 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.
• 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.
• the alloy 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.
• the contents of elements such as molybdenum, tungsten, titanium, niobium, aluminum, silicon, vanadium, chromium, and tantalum must be limited.
• the chemical composition must be such that: Mo + W + Ti + Nb + Al + Si + V + Cr + Ta ⁇ 3%
• 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.
• 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%.
• the best composition is: 80.5 ⁇ Ni ⁇ 81.5 2% ⁇ Mo ⁇ 4% Cu ⁇ 0.2% 0.2% ⁇ Mn ⁇ 0.6% If ⁇ 0.1% 0% ⁇ C ⁇ 0.03% 0.04% ⁇ Ti + Al + Zr + Hf ⁇ 0.5% S ⁇ 0.001% the remainder being iron and impurities resulting from processing.
• 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.
• VIM vacuum induction melting
• ESR electroconductive slag
• 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.
• 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.
• the strip 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.
• 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.
• the softened strip 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.
• the final coercive field is approximately three times higher and the permeability three times lower than with the alloy according to the invention.
• 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.
• 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.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Manufacturing & Machinery (AREA)
• Electrodes For Cathode-Ray Tubes (AREA)
• Heat Treatment Of Sheet Steel (AREA)
• Other Surface Treatments For Metallic Materials (AREA)

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• 1995
  • 1995-07-18 FR FR9508642A patent/FR2737043B1/fr not_active Expired - Fee Related
• 1996
  • 1996-06-20 AT AT96401346T patent/ATE196782T1/de not_active IP Right Cessation
  • 1996-06-20 EP EP96401346A patent/EP0756015B1/de not_active Expired - Lifetime
  • 1996-06-20 ES ES96401346T patent/ES2150646T3/es not_active Expired - Lifetime
  • 1996-06-20 DE DE69610535T patent/DE69610535T2/de not_active Expired - Fee Related
  • 1996-06-20 PT PT96401346T patent/PT756015E/pt unknown
  • 1996-07-12 TW TW085108466A patent/TW438895B/zh not_active IP Right Cessation
  • 1996-07-16 KR KR1019960028852A patent/KR100215522B1/ko not_active IP Right Cessation
  • 1996-07-17 JP JP8206562A patent/JPH09184034A/ja active Pending
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