EP0239838A1 - Application of a fast quenched alloy to an iron-chrome-cobalt base - Google Patents

Application of a fast quenched alloy to an iron-chrome-cobalt base Download PDF

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EP0239838A1
EP0239838A1 EP19870103341 EP87103341A EP0239838A1 EP 0239838 A1 EP0239838 A1 EP 0239838A1 EP 19870103341 EP19870103341 EP 19870103341 EP 87103341 A EP87103341 A EP 87103341A EP 0239838 A1 EP0239838 A1 EP 0239838A1
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Prior art keywords
iron
cobalt
chromium
phase
alloys
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German (de)
French (fr)
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EP0239838B1 (en
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Robert Dr. Cremer
Kurt Dr. Emmerich
Hans-Rainer Dr. Hilzinger
Stefan Hock
Hans Prof. Dr. Warlimont
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Vacuumschmelze GmbH and Co KG
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/0302—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity characterised by unspecified or heterogeneous hardness or specially adapted for magnetic hardness transitions
    • H01F1/0306—Metals or alloys, e.g. LAVES phase alloys of the MgCu2-type
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C30/00—Alloys containing less than 50% by weight of each constituent
    • 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

  • the invention relates to the use of a quenched at a cooling rate of about 103 to 106 K / s iron-chromium-cobalt-type alloy of 10 to 45% chromium, 3 to 35% cobalt, the rest of iron including unavoidable impurities, one of ⁇ - and / or ⁇ -phase precipitates has practically free microcrystalline structure, as a magnetically hard or semi-hard material in the form of tape, wire or filament.
  • alloys based on iron-chromium-cobalt have become increasingly important as permanent magnet materials or as magnetically semi-hard materials in recent years acquired.
  • comparable permanent magnet properties can be achieved for this new material group as for the known AlNiCo permanent magnets.
  • the cause of the magnetic hardening of the alloys is a spinodal separation of the ferritic starting structure into a strongly ferromagnetic Fe-Co-rich ⁇ 1 phase and a non-magnetic or only weakly magnetic Cr-rich ⁇ 2 phase, which is caused by a hardening treatment at temperatures below 650 ° C is set.
  • the good ductility of the iron-chromium-cobalt alloys before the hardening treatment which means that the hot and cold processing of the Material on an industrial scale in the form of tape and wire material.
  • the warm and cold ductility of the alloys is limited by the tendency of the alloy to form the ⁇ phase, which causes the material to become brittle.
  • spinodal segregation which starts with slow cooling from the hot rolling temperature, must also be avoided, which, in addition to magnetic hardening, also causes mechanical hardening.
  • the alloys must therefore be cooled, which causes considerable manufacturing outlay, particularly in the case of larger processing units.
  • the material is cast in block casting after melting.
  • the subsequent hot forming by hot rolling or forging must be carried out at a sufficiently high temperature above the area of existence of the ⁇ phase, which limits the temperature range for the hot forming.
  • the temperature of the ⁇ phase formation essentially depends on the alloy composition, whereby the ⁇ phase formation shifts to higher temperatures with increasing chromium content.
  • the hot-worked material must be cooled immediately from the hot working process or from a subsequent solution treatment. This is achieved, for example, by quenching the material in water from temperatures above 1000 ° C.
  • the material can then be processed to the desired final dimensions by cold processing such as rolling to tape or drawing to wire.
  • the invention has for its object to provide thin strips, wires or filaments made of magnetic alloys of the iron-chromium-cobalt type which, after a suitable heat treatment, have improved mechanical and favorable magnetic properties.
  • the solution to this problem according to the invention consists in the use of an iron-chromium-cobalt-type alloy quenched with a cooling rate of about 103 to 106 K / s of 10 to 45% chromium, 3 to 35% cobalt, the rest iron including unavoidable impurities, which has a microcrystalline structure practically free of ⁇ and / or ⁇ phase precipitations, as a magnetically hard or semi-hard material in the form of a strip, wire or filament.
  • the cooling rate of about 103 to 106 K / s is achieved by bringing alloys in the liquid state into contact with one or more effective heat sinks using the known methods of rapid solidification technology (eg Journal of Metals (1984) 20).
  • the rapidly solidified product takes the form of tapes (one or two-roll casting process) or wires (Taylor process) or filaments (melt extraction process). All these rapidly solidified products have in common that they are extremely thin in at least one dimension and have a microcrystalline structure which essentially contains only the ⁇ phase. Due to the rapid solidification, the proportion of precipitates in the ⁇ and ⁇ phase can practically be avoided in comparison to conventionally produced and solution-annealed materials of the same composition.
  • the iron-chromium-cobalt-based alloys to be used according to the invention is, in particular, the extensive avoidance of the ⁇ and ⁇ phase precipitations responsible for unfavorable magnetic properties or for embrittlement.
  • the rapidly solidified end product, strip, wire or filament can be produced in a one-step process, avoiding the costly process steps of hot forming and solution annealing.
  • the alloy to be used is given a microcrystalline structure without complex cold forming.
  • the magnetic optimization of the alloy takes place by spinodal segregation by means of heat treatment measures known per se, which are expediently carried out in a magnetic field.
  • Figure 1 shows a longitudinal section of a light micrograph of the casting structure of an alloy of 29.5% chromium and 23% cobalt, the rest essentially iron.
  • FIG. 2 shows a transmission electron microscope (TEM) image of typical grain boundaries of the cast structure of an alloy made of 29.5% chromium, 23% cobalt, the rest essentially iron (magnification 21,000: 1).
  • TEM transmission electron microscope
  • FIG. 3 shows a TEM image of the segregation structure of an alloy made of 29.5% chromium, 23% cobalt, the rest essentially iron, after a gradual magnetic heat treatment in the temperature range from 550 to 650 ° C. (magnification 95,000: 1).
  • the structure of the rapidly solidified strip essentially shows stem crystallization, the mean grain diameter being 5 ⁇ m. An excretion of the magnetically unfavorable ⁇ phase could not be observed. A finely crystalline structure that is practically free of ⁇ -precipitates would only be achievable in the conventional manufacturing process by expensive solution annealing and subsequent cold working.
  • the rapidly solidified strip was subjected to a conventional heat treatment at temperatures below 650 ° C. for magnetic curing. Additional investigations of the structure of the heat-treated tapes showed that the material is completely spinodal segregated. Exceptions of ⁇ phase could only be found on the grain boundaries in very isolated cases. However, the volume fraction of the ⁇ phase precipitates was below 1%.
  • the magnetically hardened state was adjusted by a multi-stage final heat treatment in the temperature range from 550 to 650 ° C.
  • the ⁇ phase is spinodal separated into an ⁇ 1 and ⁇ 2 phase.
  • this segregation structure is shown in a TEM image.
  • the thin magnetic material strips produced with the single-roll process have a thickness of 20 to 300 ⁇ m and a microcrystalline structure with an average grain diameter of 1 to 50 ⁇ m.
  • the magnetic material to be used according to the invention can preferably be used wherever, in particular, broad strips of magnetic alloys of the iron-chromium-cobalt type are required, for example for the production of shadow masks for picture tubes.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Power Engineering (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Continuous Casting (AREA)
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Abstract

Ductile strips of magnetically hard or semihard alloys of the iron/chromium/cobalt type are required, in particular, for producing picture tube shadow masks. According to the invention alloys consisting of 10 to 45% chromium, 3 to 35% cobalt, the remainder essentially being iron and quenched at a cooling rate of about 10<3> to 10<6> K/s are proposed for this purpose. These have a microcrystalline structure free of gamma-phase and/or sigma-phase precipitates. Preferably, the structure has a mean grain diameter of 1 to 50 mu m.

Description

Die Erfindung betrifft die Verwendung einer mit einer Abkühlgeschwindigkeit von etwa 10³ bis 10⁶ K/s abgeschreckten Legierung des Eisen-Chrom-Kobalt-Typs aus 10 bis 45 % Chrom, 3 bis 35 % Kobalt, Rest Eisen einschließlich unvermeidbarer Ver­unreinigungen, die ein von γ- und/oder σ-Phasenausscheidungen praktisch freies mikrokristallines Gefüge aufweist, als magnetisch harten bzw. halbharten Werkstoff in Band-, Draht- oder Filament­form.The invention relates to the use of a quenched at a cooling rate of about 10³ to 10⁶ K / s iron-chromium-cobalt-type alloy of 10 to 45% chromium, 3 to 35% cobalt, the rest of iron including unavoidable impurities, one of γ - and / or σ-phase precipitates has practically free microcrystalline structure, as a magnetically hard or semi-hard material in the form of tape, wire or filament.

Wie beispielsweise aus IEEE Transactions on Magnetics Mag-16, Nr. 1 (1980) Seiten 139 bis 146 bekannt ist, haben Legierungen auf der Basis Eisen-Chrom-Kobalt in den letzten Jahren als Dauermagnetwerkstoffe bzw. als magnetisch halbharte Werkstoffe eine zunehmende technische Bedeutung erlangt. Im optimal wärme­behandelten Zustand lassen sich für diese neue Werkstoffgruppe vergleichbare Dauermagneteigenschaften erreichen wie für die bekannten AlNiCo-Dauermagnete. Ursache für die magnetische Härtung der Legierungen ist eine spinodale Entmischung des ferritischen Ausgangsgefüges in eine stark ferromagnetische Fe-Co-reiche α₁-Phase und eine unmagnetische oder nur schwach magnetische Cr-reiche α₂-Phase, die durch eine Aushärtungs­behandlung bei Temperaturen unterhalb 650°C eingestellt wird. Von großer technologischer Bedeutung ist insbesondere die gute Duktilität der Eisen-Chrom-Kobalt-Legierungen vor der Aus­härtungsbehandlung, die eine Warm- und Kaltverarbeitung des Materials im großtechnischen Maßstab in Form von Band- und Drahtmaterial ermöglicht. Die Warm- und Kaltduktilität der Legierungen wird jedoch durch die Neigung der Legierung zur Bildung von σ-Phase eingeschränkt, die eine Versprödung des Materials verursacht. Zur Kaltverarbeitung des Materials muß außerdem die bei langsamer Abkühlung von der Warmwalztemperatur einsetzende spinodale Entmischung vermieden werden, die neben der magnetischen Härtung auch eine mechanische Härtung bewirkt. Nach der Warmverarbeitung müssen die Legierungen deshalb abgekühlt werden, was insbesondere bei größeren Verarbeitungseinheiten einen erheblichen fertigungstechnischen Aufwand verursacht.As is known, for example, from IEEE Transactions on Magnetics Mag-16, No. 1 (1980) pages 139 to 146, alloys based on iron-chromium-cobalt have become increasingly important as permanent magnet materials or as magnetically semi-hard materials in recent years acquired. In the optimal heat-treated condition, comparable permanent magnet properties can be achieved for this new material group as for the known AlNiCo permanent magnets. The cause of the magnetic hardening of the alloys is a spinodal separation of the ferritic starting structure into a strongly ferromagnetic Fe-Co-rich α₁ phase and a non-magnetic or only weakly magnetic Cr-rich α₂ phase, which is caused by a hardening treatment at temperatures below 650 ° C is set. The good ductility of the iron-chromium-cobalt alloys before the hardening treatment, which means that the hot and cold processing of the Material on an industrial scale in the form of tape and wire material. However, the warm and cold ductility of the alloys is limited by the tendency of the alloy to form the σ phase, which causes the material to become brittle. For cold processing of the material, spinodal segregation, which starts with slow cooling from the hot rolling temperature, must also be avoided, which, in addition to magnetic hardening, also causes mechanical hardening. After hot processing, the alloys must therefore be cooled, which causes considerable manufacturing outlay, particularly in the case of larger processing units.

Bei der bisher in der Regel üblichen Herstellung von Eisen-Chrom-­Kobalt-Legierungen wird das Material nach dem Schmelzen im Block­guß abgegossen. Die anschließende Warmverformung durch Warmwalzen oder Schmieden muß bei ausreichend hoher Temperatur oberhalb des Existenzgebiets der σ-Phase durchgeführt werden, wodurch der Temperaturbereich für die Warmumformung eingeschränkt wird. Die Temperatur der σ-Phasenbildung hängt im wesentlichen von der Legierungszusammensetzung ab, wobei sich die σ-Phasenbildung mit ansteigendem Chromgehalt zu höheren Temperaturen verschiebt. Zur Einstellung einer ausreichenden Kaltduktilität ist eine Abkühlung des warmbearbeiteten Materials unmittelbar aus dem Warmverarbeitungsvorgang oder aus einer nachfolgenden Lösungs­glühbehandlung erforderlich. Dies wird zum Beispiel durch Abschrecken des Materials in Wasser von Temperaturen oberhalb von 1000°C erreicht. Danach kann das Material durch Kaltverarbeitungs­prozesse wie Walzen zu Band oder Ziehen zu Draht auf die gewünsch­te Endabmessung verabeitet werden.In the previously usual production of iron-chromium-cobalt alloys, the material is cast in block casting after melting. The subsequent hot forming by hot rolling or forging must be carried out at a sufficiently high temperature above the area of existence of the σ phase, which limits the temperature range for the hot forming. The temperature of the σ phase formation essentially depends on the alloy composition, whereby the σ phase formation shifts to higher temperatures with increasing chromium content. In order to achieve sufficient cold ductility, the hot-worked material must be cooled immediately from the hot working process or from a subsequent solution treatment. This is achieved, for example, by quenching the material in water from temperatures above 1000 ° C. The material can then be processed to the desired final dimensions by cold processing such as rolling to tape or drawing to wire.

Zur Einstellung optimaler Dauermagneteigenschaften durch eine Wärmebehandlung im Temperaturbereich unterhalb der spinodalen Entmischungstemperatur der Legierungen muß von einem rein ferritischen Ausgangsgefüge (α-Phase) ausgegangen werden.In order to achieve optimal permanent magnet properties by means of a heat treatment in the temperature range below the spinodal segregation temperature of the alloys, a purely ferritic starting structure (α phase) must be assumed.

Der Existenzbereich der homogenen α-Phase wird bei ternären Legierungen mit Kobaltgehalten größer als 10 % nur bei hohen Temperaturen erreicht. Bei niedrigeren Temperaturen bzw. bei langsamer Abkühlung der Legierungen aus dem α-Phasenbereich wird unmagnetische γ-Phase ausgeschieden, die die magnetischen Eigenschaften des Materials erheblich verschlechtert. Die Bildung von γ-Phase läßt sich daher bei der Verarbeitung von größeren Fertigungseinheiten nicht vollständig unterdrücken.In the case of ternary alloys with cobalt contents greater than 10%, the area of existence of the homogeneous α phase is only reached at high temperatures. At lower temperatures or with slow cooling of the alloys from the α-phase range, non-magnetic γ-phase is eliminated, which considerably deteriorates the magnetic properties of the material. The formation of γ phase cannot therefore be completely suppressed when processing larger production units.

Vor der Schlußwärmebehandlung des Materials zur Einstellung der magnetischen Eigenschaften ist deshalb eine zusätz­liche Homogenisierungsglühung im α-Phasengebiet mit nachfolgender Abschreckung unerläßlich. Die Anforderungen bezüglich der Homo­genisierungstemperatur und an die Abschreckgeschwindigkeit werden mit steigendem Kobaltgehalt strenger. Bei ternären Legierungen mit Kobaltgehalten größer als 20 % sind Homogenisierungstempera­turen von etwa 1300°C und Abschreckgeschwindigkeiten von 200°C/s erforderlich, was erhebliche fertigungstechnische Probleme verur­sacht und die wirtschaftliche Fertigung dieser Werkstoffe stark beeinträchtigt.Before the final heat treatment of the material to adjust the magnetic properties, additional homogenization annealing in the α-phase region with subsequent quenching is essential. The requirements regarding the homogenization temperature and the quenching rate become more stringent with increasing cobalt content. In the case of ternary alloys with cobalt contents greater than 20%, homogenization temperatures of approximately 1300 ° C. and quenching speeds of 200 ° C./s are required, which causes considerable manufacturing problems and severely impairs the economical production of these materials.

Bei den notwendigen hohen Homogenisierungstemperaturen setzt außerdem ein starkes Kornwachstum ein. Das hierdurch erhaltene sehr grobkörnige Rekristallisationsgefüge führt zu zusätzlichen Verarbeitungsproblemen. Diese Probleme können zwar durch die Zulegierung von ferritbildenden Elementen, wie zum Beispiel Zirkon, Molybdän, Vanadium, Niob, Tantal, Titan, Aluminium, Silizium und Wolfram deutlich reduziert, jedoch nicht vollkommen behoben werden.At the necessary high homogenization temperatures, strong grain growth also begins. The resulting very coarse-grained recrystallization structure leads to additional processing problems. These problems can be significantly reduced by alloying ferrite-forming elements such as zirconium, molybdenum, vanadium, niobium, tantalum, titanium, aluminum, silicon and tungsten, but they cannot be completely eliminated.

Auch die Verwendung von Saug- oder Stranggießverfahren zur Her­stellung von Eisen-Chrom-Kobalt-Legierungen macht eine Lösungs­glühung nicht überflüssig (vgl. DE-PS 33 34 369).The use of suction or continuous casting processes for the production of iron-chromium-cobalt alloys does not make solution annealing superfluous (cf. DE-PS 33 34 369).

Der Erfindung liegt die Aufgabe zugrunde, dünne Bänder, Drähte oder Filamente aus Magnetlegierungen des Eisen-Chrom-Kobalt-Typs zur Verfügung zu stellen, die nach einer geeigneten Wärmebehand­lung verbesserte mechanische und günstige magnetische Eigen­schaften aufweisen.The invention has for its object to provide thin strips, wires or filaments made of magnetic alloys of the iron-chromium-cobalt type which, after a suitable heat treatment, have improved mechanical and favorable magnetic properties.

Die erfindungsgemäße Lösung dieser Aufgabe besteht in der Ver­wendung einer mit einer Abkühlgeschwindigkeit von etwa 10³ bis 10⁶ K/s abgeschreckten Legierung des Eisen-Chrom-Kobalt-­Typs aus 10 bis 45 % Chrom, 3 bis 35 % Kobalt, Rest Eisen einschließlich unvermeidbarer Verunreinigungen, die ein von γ- und/oder σ-Phasenausscheidungen praktisch freies mikro­kristallines Gefüge aufweist, als magnetisch harten bzw. halb­harten Werkstoff in Band-, Draht- oder Filamentform.The solution to this problem according to the invention consists in the use of an iron-chromium-cobalt-type alloy quenched with a cooling rate of about 10³ to 10⁶ K / s of 10 to 45% chromium, 3 to 35% cobalt, the rest iron including unavoidable impurities, which has a microcrystalline structure practically free of γ and / or σ phase precipitations, as a magnetically hard or semi-hard material in the form of a strip, wire or filament.

Die Abkühlungsgeschwindigkeit von etwa 10³ bis 10⁶ K/s wird erreicht, indem Legierungen im flüssigen Zustand mit den bekannten Methoden der Rascherstarrungstechnologie (z. B. Journal of Metals (1984) 20) mit einer oder mehreren effektiven Wärme­senken in Kontakt gebracht werden. Das rasch erstarrte Produkt hat je nach verwendetem Prozeß die Form von Bändern (Ein- oder Zweiwalzengießverfahren) oder Drähten (Taylor-Prozeß ) oder Filamenten (Schmelzausziehverfahren). Allen diesen rasch erstarrten Produkten ist gemeinsam, daß sie mindestens in einer Dimension extrem dünn sind und ein mikrokristallines Gefüge aufweisen, das im wesentlichen nur α-Phase enthält. Aufgrund der raschen Erstarrung kann der Anteil von Ausscheidungen der γ- und σ-Phase im Vergleich zu konventionell hergestellten und lösungsgeglühten Materialien gleicher Zusammensetzung praktisch nahezu vermieden werden.The cooling rate of about 10³ to 10⁶ K / s is achieved by bringing alloys in the liquid state into contact with one or more effective heat sinks using the known methods of rapid solidification technology (eg Journal of Metals (1984) 20). Depending on the process used, the rapidly solidified product takes the form of tapes (one or two-roll casting process) or wires (Taylor process) or filaments (melt extraction process). All these rapidly solidified products have in common that they are extremely thin in at least one dimension and have a microcrystalline structure which essentially contains only the α phase. Due to the rapid solidification, the proportion of precipitates in the γ and σ phase can practically be avoided in comparison to conventionally produced and solution-annealed materials of the same composition.

Die erfindungsgemäß zu verwendenden rasch erstarrten Legierungen weisen vorzugsweise folgende Zusammensetzungen auf:

  • a) ternäre Eisen-Chrom-Kobalt-Legierungen mit 10 bis 45 Gew.% Chrom, 3 bis 35 Gew.% Kobalt, Rest Eisen einschließ­lich unvermeidbarer Verunreinigungen;
  • b) quasi-ternäre Eisen-Chrom-Kobalt-Legierungen mit bis zu 10 Gew.% eines oder mehrerer ferritbildender Elemente wie beispielsweise Aluminium, Molybdän, Niob, Silizium, Tantal, Titan, Vanadium, Wolfram und Zirkon;
  • c) quasi-ternäre Eisen-Chrom-Kobalt-Legierungen mit bis zu 5 Gew.% eines oder mehrerer der unter b) aufgeführten ferrit­bildenden Elemente.
The rapidly solidified alloys to be used according to the invention preferably have the following compositions:
  • a) ternary iron-chromium-cobalt alloys with 10 to 45% by weight of chromium, 3 to 35% by weight of cobalt, the rest of iron including unavoidable impurities;
  • b) quasi-ternary iron-chromium-cobalt alloys with up to 10% by weight of one or more ferrite-forming elements such as aluminum, molybdenum, niobium, silicon, tantalum, titanium, vanadium, tungsten and zircon;
  • c) quasi-ternary iron-chromium-cobalt alloys with up to 5% by weight of one or more of the ferrite-forming elements listed under b).

Überraschend ist bei den erfindungsgemäß zu verwendenden Legierungen auf Eisen-Chrom-Kobalt-Basis insbesondere die weit­gehende Vermeidung der für ungünstige magnetische Eigenschaften bzw. für eine Versprödung verantwortlichen γ- und σ-Phasenaus­scheidungen. Das rasch erstarrte Endprodukt Band, Draht oder Filament kann in einem nur einstufigen Prozeß unter Vermeidung der kostenintensiven Prozeßschritte der Warmumformung und der Lösungsglühung hergestellt werden. Die zu verwendende Legierung erhält dabei ein mikrokristallines Gefüge ohne aufwendige Kalt­umformungen.What is surprising in the case of the iron-chromium-cobalt-based alloys to be used according to the invention is, in particular, the extensive avoidance of the γ and σ phase precipitations responsible for unfavorable magnetic properties or for embrittlement. The rapidly solidified end product, strip, wire or filament, can be produced in a one-step process, avoiding the costly process steps of hot forming and solution annealing. The alloy to be used is given a microcrystalline structure without complex cold forming.

Die magnetische Optimierung der Legierung erfolgt durch spinodale Entmischung mittels an sich bekannter Wärmebehandlungsmaßnahmen, die zweckmäßigerweise in einem Magnetfeld durchgeführt werden.The magnetic optimization of the alloy takes place by spinodal segregation by means of heat treatment measures known per se, which are expediently carried out in a magnetic field.

Anhand von einigen Ausführungsbeispielen und drei Figuren, die Gefügeaufnahmen zu verwendender Legierungen zeigen, wird die Erfindung nachstehend noch näher erläutert.The invention is explained in more detail below with the aid of a few exemplary embodiments and three figures which show micrographs of alloys to be used.

Figur 1 zeigt einen Längsschliff einer lichtmikroskopischen Aufnahme des Gußgefüges einer Legierung aus 29,5 % Chrom und 23 % Kobalt, Rest im wesentlichen Eisen.Figure 1 shows a longitudinal section of a light micrograph of the casting structure of an alloy of 29.5% chromium and 23% cobalt, the rest essentially iron.

Figur 2 zeigt eine transmissionselektronenmikroskopische (TEM) Aufnahme typischer Korngrenzen des Gußgefüges einer Legierung aus 29,5 % Chrom, 23 % Kobalt, Rest im wesentlichen Eisen (Vergrößerung 21 000 : 1).FIG. 2 shows a transmission electron microscope (TEM) image of typical grain boundaries of the cast structure of an alloy made of 29.5% chromium, 23% cobalt, the rest essentially iron (magnification 21,000: 1).

Figur 3 zeigt eine TEM-Aufnahme des Entmischungsgefüges einer Legierung aus 29,5 % Chrom, 23 % Kobalt, Rest im wesentlichen Eisen, nach einer mehrstündigen stufenweisen Magnet-Wärmebehandlung im Temperaturbereich von 550 bis 650°C (Vergrößerung 95 000 : 1).FIG. 3 shows a TEM image of the segregation structure of an alloy made of 29.5% chromium, 23% cobalt, the rest essentially iron, after a gradual magnetic heat treatment in the temperature range from 550 to 650 ° C. (magnification 95,000: 1).

Es wurde nach dem Einwalzenverfahren eine Reihe von Legierungen auf Eisen-Chrom-Kobalt-Basis in Bandform mit einer Dicke von 20 bis 300 µm hergestellt, die durch einen Knicktest auf ihre Duktilität getestet wurden. Bänder wurden als "duktil" bezeichnet, wenn sie auf einen Radius r = 0 gebogen werden konnten, ohne zu brechen.

Figure imgb0001
A series of iron-chromium-cobalt-based strip-form alloys with a thickness of 20 to 300 μm were produced using the roll-in process, and their ductility was tested by means of a kink test. Ribbons were said to be "ductile" if they could be bent to a radius r = 0 without breaking.
Figure imgb0001

An zwei ausgewählten Proben wurden weitergehende Gefügeunter­suchungen durchgeführt und zwar sowohl unmittelbar nach der Erstarrung als auch nach einer magnetischen Optimierung der rasch erstarrten Metallbänder. Zur Herstellung eines dünnen Metallbandes wurde zunächst eine Legierung der Zusammensetzung 25,5 Gew.% Chrom, 10,5 Gew.% Kobalt, Rest im wesentlichen Eisen, erschmolzen. Die Schmelze wurde dann durch eine Keramikdüse gepreßt und erstarrte auf der Oberfläche einer bewegten Kühlwalze.Further structural investigations were carried out on two selected samples, both immediately after solidification and after magnetic optimization of the rapidly solidified metal strips. To produce a thin metal strip, an alloy with the composition 25.5% by weight of chromium, 10.5% by weight of cobalt, the rest essentially iron, was first melted. The melt was then forced through a ceramic nozzle and solidified on the surface of a moving chill roll.

Wie lichtmikroskopische Untersuchungen zeigten, weist das Gefüge des rasch erstarrten Bandes im wesentlichen Stengelkristallisation auf, wobei der mittlere Korndurchmesser 5 µm betrug. Eine Ausscheidung der magnetisch ungünstigen γ-Phase konnte nicht beobachtet werden. Ein von γ-Ausscheidungen praktisch freies feinkristallines Gefüge wäre auf dem konventionellen Herstellweg nur durch aufwendige Lösungsglühungen und anschließender Kalt­verformung zu erreichen.As light microscopic investigations showed, the structure of the rapidly solidified strip essentially shows stem crystallization, the mean grain diameter being 5 μm. An excretion of the magnetically unfavorable γ phase could not be observed. A finely crystalline structure that is practically free of γ-precipitates would only be achievable in the conventional manufacturing process by expensive solution annealing and subsequent cold working.

Zur magnetischen Aushärtung wurde das rasch erstarrte Band einer üblichen Wärmebehandlung bei Temperaturen unterhalb 650°C unter­zogen. Ergänzende Untersuchungen des Gefüges der wärmebehandelten Bänder zeigten, daß das Material vollständig spinodal entmischt ist. Nur sehr vereinzelt konnten auf den Korngrenzen Ausscheidungen von σ-Phase gefunden werden. Der Volumenanteil der σ-Phasenaus­scheidungen lag jedoch unterhalb von 1 %.The rapidly solidified strip was subjected to a conventional heat treatment at temperatures below 650 ° C. for magnetic curing. Additional investigations of the structure of the heat-treated tapes showed that the material is completely spinodal segregated. Exceptions of σ phase could only be found on the grain boundaries in very isolated cases. However, the volume fraction of the σ phase precipitates was below 1%.

Für weitere Untersuchungen wurde eine Legierung der Zusammen­setzung 29,5 Gew.% Chrom, 23,0 Gew.% Kobalt und Rest im wesent­lichen Eisen erschmolzen und die Schmelze bei 1570°C durch eine schlitzförmige Düse mit einem Auspreßdruck von 200 mbar auf die Oberfläche einer Kühlwalze gespritzt. Die Kühlwalze hatte einen Durchmesser von 400 mm und die Geschwindigkeit der Oberfläche betrug 15 cm/s. Legierungen mit hohem Kobaltgehalt neigen erfahrungsgemäß verstärkt zur Bildung von γ- und σ-Phasenaus­scheidungen und stellen an die konventionelle Herstellung strengere Randbedingungen. Das Gußgefüge der rasch erstarrten Bänder wurde auf Ausscheidungen untersucht. In Figur 1 ist das mikrokristalline Gußgefüge in einer lichtmikroskopischen Aufnahme dargestellt. Daß die Korngrenzen hierbei praktisch frei von Ausscheidungen sind, konnte durch die in Figur 2 dargestellte TEM-Aufnahme nachgewiesen werden.For further investigations, an alloy with the composition 29.5% by weight chromium, 23.0% by weight cobalt and the rest essentially iron was melted and the melt at 1570 ° C. through a slot-shaped nozzle with an extrusion pressure of 200 mbar onto the surface of a Cooling roller sprayed. The chill roll was 400 mm in diameter and the surface speed was 15 cm / s. Experience has shown that alloys with a high cobalt content tend to form γ and σ phase deposits and place more stringent constraints on conventional production. The cast structure of the rapidly solidified strips was examined for excretions. In Figure 1, the microcrystalline cast structure is shown in a light micrograph. The fact that the grain boundaries are practically free of excretions was demonstrated by the TEM image shown in FIG. 2.

Der magnetisch ausgehärtete Zustand wurde durch eine mehrstufige Schlußwärmebehandlung im Temperaturbereich von 550 bis 650°C eingestellt. Die α-Phase ist hierbei spinodal in eine α₁ und α₂ Phase entmischt. In Figur 3 ist dieses Entmischungsgefüge in einer TEM-Aufnahme dargestellt. Die mit dem Einwalzenverfahren hergestellten dünnen Magnetwerkstoffbänder besitzen eine Dicke von 20 bis zu 300 µm und ein mikrokristallines Gefüge mit einem mittleren Korndurchmesser von 1 bis 50 µm.The magnetically hardened state was adjusted by a multi-stage final heat treatment in the temperature range from 550 to 650 ° C. The α phase is spinodal separated into an α₁ and α₂ phase. In Figure 3, this segregation structure is shown in a TEM image. The thin magnetic material strips produced with the single-roll process have a thickness of 20 to 300 µm and a microcrystalline structure with an average grain diameter of 1 to 50 µm.

Vorzugsweise kann der erfindungsgemäß zu verwendende Magnetwerk­stoff überall dort eingesetzt werden, wo insbesondere breite Bänder aus Magnetlegierungen des Eisen-Chrom-Kobalt-Typs benötigt werden, zum Beispiel für die Herstellung von Lochmasken für Bildröhren.The magnetic material to be used according to the invention can preferably be used wherever, in particular, broad strips of magnetic alloys of the iron-chromium-cobalt type are required, for example for the production of shadow masks for picture tubes.

Claims (4)

1. Verwendung einer mit einer Abkühlgeschwindigkeit von etwa 10³ bis 10⁶ K/s abgeschreckten Legierung des Eisen-­Chrom-Kobalt-Typs aus 10 bis 45 % Chrom, 3 bis 35 % Kobalt, Rest Eisen einschließlich unvermeidbarer Verunreinigungen, die ein von γ- und/oder σ-Phasenausscheidungen praktisch freies mikrokristallines Gefüge aufweist, als magnetisch harten bzw. halbharten Werkstoff in Band-, Draht- oder Filamentform.1. Use of an iron-chromium-cobalt-type alloy of 10 to 45% chromium, 3 to 35% cobalt, the rest of iron including unavoidable impurities which is one of γ- and. Quenched at a cooling rate of about 10³ to 10⁶ K / s / or σ-phase precipitates has a practically free microcrystalline structure as a magnetically hard or semi-hard material in the form of a strip, wire or filament. 2. Verwendung einer Legierung gemäß Anspruch 1, die insgesamt bis zu 10 % mindestens ein weiteres Element aus der Gruppe Aluminium, Molybdän, Niob, Silizium, Tantal, Titan, Vanadium, Wolfram und Zirkon enthält.2. Use of an alloy according to claim 1, which contains up to 10% in total at least one further element from the group aluminum, molybdenum, niobium, silicon, tantalum, titanium, vanadium, tungsten and zircon. 3. Verwendung einer Legierung gemäß Anspruch 1, die insgesmmt bis zu 5 % mindestens ein weiteres Element aus der Gruppe Aluminium, Molybdän, Niob, Silizium, Tantal, Titan, Vanadium, Wolfram und Zirkon enthält.3. Use of an alloy according to claim 1, which contains a total of up to 5% at least one further element from the group aluminum, molybdenum, niobium, silicon, tantalum, titanium, vanadium, tungsten and zircon. 4. Verwendung einer Legierung gemäß einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß das Kristall­korn einen mittleren Korndurchmesser von 1 bis 50 µm aufweist.4. Use of an alloy according to one of claims 1 to 3, characterized in that the crystal grain has an average grain diameter of 1 to 50 microns.
EP19870103341 1986-04-04 1987-03-09 Application of a fast quenched alloy to an iron-chrome-cobalt base Expired - Lifetime EP0239838B1 (en)

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