Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/004—Very low carbon steels, i.e. having a carbon content of less than 0,01%
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
• • 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
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J2229/00—Details of cathode ray tubes or electron beam tubes
  • H01J2229/07—Shadow masks
  • H01J2229/0727—Aperture plate
  • H01J2229/0733—Aperture plate characterised by the material

Definitions

• This invention relates to a Fe—Ni based alloy for a shadow mask having an excellent corrosion resistance, which is used in a cathode tube for a color television or the like, and a shadow mask material, and more particularly to a Fe—Ni based alloy having an excellent corrosion resistance, a high stiffness and a low thermal expansion, which is less in the generation of rust even when being exposed to an atmosphere after the bright annealing at a production step of a starting material, and a shadow mask material using this alloy.
• a low carbon aluminum killed steel sheet is used as a shadow mask material.
• This steel sheet is produced, for example, by subjecting a steel sheet after a middle cold rolling to a stress relief middle annealing in a continuous annealing furnace or a batch annealing furnace and then to a finish cold rolling and a temper rolling (including dull rolling).
• a material for a cathode tube or display of a high-quality color television for example, a shadow mask for the cathode tube of the color television is sometimes heated to a temperature reaching to about 80° C. because not more than 1 ⁇ 3 of electron beams pass through openings of the shadow mask and the remaining electron beams collide with the shadow mask.
• the shadow mask material is strained by thermal expansion and brings about the deterioration of color purity.
• Fe-36 Ni based invar alloy being less in the influence of thermal expansion is recently used instead of the above aluminum killed steel sheet.
• Fe—Ni based alloy plates a low thermal expansion Fe-36 Ni based alloy plate reducing Mn as an alloying element (JP-A-5-186853), an alloy plate having a high strength by adding of Nb (U.S. Pat. No. 3,150,831) and the like with the recent flattening and large-sizing of display face.
• the low thermal expansion Fe-36 Ni based alloy having a reduced Mn and the high-strength Fe-36 Ni based alloy added with Nb are not exposed to corrosion environment in the cathode tube because the atmosphere is vacuum, but are exposed in air for a long time in the course of circulation and transportation after the bright annealing as a middle step in the production of the raw material, so that there is caused a case that rust is generated not to provide a product and there is left a problem in the rust prevention.
• the inventors have made various studies with respect to conditions of Fe—Ni based alloys hardly generating rust even when it is exposed to air after the bright annealing as a middle step in the production of the starting material and obtained the following knowledge. It has been found that the rust generated in the starting material (Fe—Ni based alloy) is apt to be easily caused after the bright annealing and also the rust is apt to be generated in low thermal expansion Fe-36 Ni alloy having a reduced Mn rather than the usual Fe-36 Ni alloy.
• the S concentration in the alloy ranging from its surface to a depth of 150 ⁇ is considerably higher than that of a bulk portion (interior portion).
• S is enriched in such a surface layer portion
• S promotes the dissolution of a metal ion and induces the rust.
• such a phenomenon may be solved when the surface layer portion of the alloy plate is removed mechanically and chemically, but it is difficult to conduct this treatment in a commercial scale.
• the inventors attempt to control the enrichment of S in the surface layer of the alloy plate.
• the enrichment of S in the surface layer portion of the Fe-36 Ni alloy plate is zero in the Fe—Ni based alloy having a high Mn content but is conspicuous in the low thermal expansion type Fe-36 Ni alloy having a low Mn content, and that S is entrapped into Mn based inclusion of the Fe—Ni based alloy having the high Mn content, but the enriched amount of S decreases in inverse proportion to the Mn content in the low thermal expansion type Fe-36 Ni alloy having the low Mn content.
• the corrosion resistance of Fe—Ni alloy is largely dependent upon the crystal grain size. That is, it has been confirmed that the corrosion resistance after the bright annealing largely depends on the crystal grain size of the starting material and particularly the corrosion resistance of the material is improved as the crystal grain size becomes small (crystal grain number (ASTM) becomes large). This is considered due to the fact that as the crystal grain size becomes small, the area of the crystal grain boundary increases and the diffusion distance of S becomes long.
• the non-metallic inclusion is effective to include one or more selected from silica (SiO 2 ), spinel (MgO Al 2 O 3 ) and niobium oxide (Nb 2 O 5 ) in addition to MnO—FeO—SiO 2 —Nb 2 O 5 —MgO—Al 2 O 3 -CaO base composite oxide.
• the invention is based on the above knowledge and the gist and construction thereof are as follows.
• the invention is a Fe—Ni based alloy for a shadow mask having an excellent corrosion resistance comprising C ⁇ 0.01 wt %, Si: 0.01-0.1 wt %, Mn: 0.01-0.1 wt %, Ni: 35-37 wt %, Cr ⁇ 0.1 wt %, Nb: 0.01-1.0 wt %, S ⁇ 0.0020 wt %, Al ⁇ 0.005 wt % and the balance being Fe and inevitable impurity.
• the alloy of the invention is preferable to contain 0.005-1.0% in total of one or more selected from Ti, V, Zr, Ta, Hf and REM in addition to the above component composition.
• a maximum value of S concentration in a region ranging from a surface of the alloy to 150 ⁇ is not more than 20 times of a bulk.
• a crystal grain size is not less than No. 9 of ASTM grain size number.
• the alloy of the invention is preferable to contain one or more selected from silica (SiO 2 ), spinel (MgO. Al 2 O 3 ) and niobium oxide (Nb 2 O 5 ) in addition to MnO—FeO—SiO 2 -Nb 2 O 5 -MgO—Al 2 O 3 -CaO base composite oxide.
• silica SiO 2
• spinel MgO. Al 2 O 3
• Nb 2 O 5 niobium oxide
• the invention proposes a shadow mask material having a high corrosion resistance, a high rigidity and a low thermal expansion comprised of the above Ni—Fe based alloy and having a proof strength at 0.2% of not less than 300 N/mm 2 and a thermal expansion coefficient of not more than 1.0 ⁇ 10 ⁇ 6 /OC.
• C is an element contributing to strengthen the material through solid solution and work hardening action.
• the content thereof exceeds 0.01 wt %, a great amount of carbide is precipitated to deteriorate the etching property, press formability, graphitizing property and low thermal expansion property. Therefore, the C content is limited to not more than 0.01 wt %. Preferably, it is not more than 0.005 wt %.
• Mn 0.01-0.1 wt %
• Mn is useful as a solid-soluting element and further is required to add in an amount of not less than 0.01 wt % as a deoxidizing material in the refining of the alloy.
• the addition amount exceeds 0.1 wt %, the thermal expansion is increased, so that the amount is limited to a range of 0.01-0.1 wt %.
• it is 0.01-0.05 wt %.
• Mn is added to produce Mn inclusion, which fixes S diffused in the bright annealing, so that a constant amount of Mn inclusion is required. Therefore, it is necessary that the relation of Mn and S is controlled to satisfy Mn/S ⁇ 25 in view of the corrosion resistance.
• Ni is an element largely exerting upon the thermal expansion property of the Fe—Ni alloy. When the Ni content is 36 wt %, the thermal expansion is minimum, so that Ni is limited to 35-37 wt %.
• Cr is an element considerably improving the corrosion resistance.
• the content exceeds 0.1 wt %, the thermal expansion coefficient becomes high and also the graphitizing property is deteriorated, so that it is limited to not more than 0.1 wt %.
• Nb 0.01-1.0 wt %
• Nb increases the proof strength at 0.2% when being added to the alloy. Also, it has an effect that the crystal gain size is remarkably fined to increase the area of the crystal boundary and to prolong the diffusion distance of S to control the enrichment of S on the surface. Also, not only the toughness, etching property and press formability but also the graphitizing property are improved.
• Nb is required to be added in an amount of at least 0.01 wt %. Preferably, it is added in an amount of not less than 0.10 wt %. However, when the amount exceeds 1.0 wt %, the toughness, press formability and low thermal expansion property rather lower, so that it is limited to 0.01-1.0 wt %.
• S is an element characterizing the alloy according to the invention and is an element largely affecting the corrosion resistance.
• S diffuses near to the neighborhood of the surface of the raw material after the bright annealing and hence the S concentration in a region from the surface of the raw material to a depth of 150 ⁇ (surface layer portion) considerably rises to a bulk to thereby deteriorate the corrosion resistance.
• the S content is limited to not more than 0.0020 wt %, and is preferably not more than 0.0010 wt %.
• Al is a relatively active element, so that if it is included in a great amount, oxidation is preferentially caused on the surface of the steel sheet to obstruct the graphitizing property. Further, Al based oxide is increased to obstruct the etching property. Particularly, when it exceeds 0.005 wt %, the low thermal expansion property lowers, so that it is limited to 0.005 wt %.
• Ti, V, Zr, Ta, Hf and REM are elements contributing to finely divide crystal grains by bonding to C and N to form carbide and nitride and contribute to corrosion resistance by bonding to S to form sulfide.
• one or more selected from Ti, V, Zr, Ta, Hf and REM is less than 0.005 wt % alone or in total, the above effect is insufficient. While when it exceeds 1.0 wt %, the solid soluted amount of the element becomes too large and the low thermal expansion property lowers, so that the amount is limited to 0.005-1.0 wt %.
• the S concentration in a region ranging from the surface of the alloy sheet to 150 ⁇ is made to not more than about 20 times. Because, if the degree of S enriched in the surface layer exceeds 20 times the S concentration of a bulk (base), the dissolution of the metal ion is promoted and the rust is induced. Moreover, the S concentration is preferably not more than 18 times.
• the crystal grain size it is effective to make the crystal grain size to not less than No. 9 as an ASTM grain size number in addition to the above composition planning.
• the corrosion resistance after the bright annealing largely depends upon the crystal grain size of the starting material, and particularly the corrosion resistance of the material is improved as the crystal grain size becomes small (the grain size number becomes large).
• the proof strength at 0.2% largely depends upon the crystal grain size, it is desirable that the crystal grain size is not less than ASTM No. 9 in order to obtain excellent corrosion resistance and rigidity.
• the control of the non-metallic inclusion is further conducted in the invention. That is, the non-metallic inclusion included in the alloy of the invention is required to be a non-metallic inclusion further containing one or more selected from SiO 2 , MgO. Al 2 O 3 and Nb 2 O 5 in addition to MnO—FeO—SiO 2 —Nb 2 O 3 —MgO—Al 2 O 3 —CaO base composite oxide. According to the inventors' studies, it has been confirmed that if acid-soluble MgO single inclusion or CaO single inclusion is produced, the corrosion resistance in the dewing in air is deteriorated.
• a material to be tested is produced by adjusting the components of the alloy so as to have a component composition shown in the following Table 1, and the test material is melted in an air induction furnace to prepare an ingot. Then, the ingot is subjected to a hot forging work at a temperature of 1000-1150° C., hot rolled at a rolling reduction of not less than 80% and then subjected to a solid-soluting heat treatment at 900° C. for 60 seconds in an atmosphere of 30% H 2 +N 2 having a dew point of ⁇ 40° C. Thereafter, it is gradually cooled to obtain a Fe—Ni alloy having a thickness of 0.12 mm.
• the thermal expansion coefficient shown in the table is measured in a range of from room temperature to 300° C. and is determined by an average thermal expansion coefficient at 30-100° C., and the proof strength at 0.2% is measured by a tension test. Also, a maximum value of S enriched amount in a region ranging from the surface of the sheet to 150 ⁇ is carried out by sputtering at an interval of 50 ⁇ through an OJ electron spectroscopic apparatus and conducting an elementary analysis every time to calculating an atomic concentration of S to show a ratio to bulk (the bulk in this examples is a value chemically reviewing of the starting material as a whole). The corrosion resistance is evaluated by a rust generating area ratio at a corrosion state after the exposure in an outdoor air exposure test.
• the alloys adaptable in the invention have sufficient properties such as corrosion resistance, rigidity and low thermal expansion property. That is, the test materials according to the invention have a high rigidity as the proof strength at 0.2% is not less than 300 N/mm 2 , and are low thermal expansion as the thermal expansion coefficient is not more than 1.0 ⁇ 10 ⁇ 16 /° C. Also, they have an excellent corrosion resistance as the rust generating area ratio after the exposure test in air is not more than 0.5%. On the contrary, the comparative materials 19, 20 are poor in the corrosion resistance because the S amount in the bulk is large. Also, the comparative materials 21, 22 are poor in the corrosion resistance because the form of the inclusion contains MgO single body or CaO single body.
• the comparative material 23 is poor in the corrosion resistance and rigidity because the crystal grain size is large.
• the comparative material 24 is poor in the corrosion resistance because the maximum value of the S enriched amount in the region from the sheet surface to 150 ⁇ is not less than 20.
• the Fe—Ni based alloy according to the invention can be produced as a material for shadow mask without generating the rust after the bright annealing.
• the starting material for shadow mask having a high rigidity and a low thermal expansion can be produced, in which the proof strength at 0.2% is not less than 300 N/mm 2 and the thermal expansion coefficient is not more than 1.0 ⁇ 10 ⁇ 6 /° C. as a quality of the material before the formation of the mask.
• the shadow mask material in a cathode tube for a color television or display can be surely produced in a high yield.

Landscapes

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

Applications Claiming Priority (3)

Publications (1)

Family

ID=19140077

Family Applications (1)

Country Status (6)

Cited By (3)

Families Citing this family (2)

Citations (8)

Family Cites Families (9)

• 2001
  • 2001-10-22 JP JP2001323145A patent/JP3854121B2/ja not_active Expired - Fee Related
• 2002
  • 2002-10-16 WO PCT/JP2002/010718 patent/WO2003035920A1/ja active Application Filing
  • 2002-10-16 CN CNB028207742A patent/CN100343405C/zh not_active Expired - Fee Related
  • 2002-10-16 US US10/488,257 patent/US20040238076A1/en not_active Abandoned
  • 2002-10-16 EP EP02777848A patent/EP1445341A4/en not_active Withdrawn
  • 2002-10-16 KR KR1020047005785A patent/KR100595393B1/ko not_active IP Right Cessation

Patent Citations (8)

Also Published As

Similar Documents

Legal Events