EP0285741A1 - Process for the production of a highly ductile semi-finished tantalum product - Google Patents

Process for the production of a highly ductile semi-finished tantalum product Download PDF

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Publication number
EP0285741A1
EP0285741A1 EP88100151A EP88100151A EP0285741A1 EP 0285741 A1 EP0285741 A1 EP 0285741A1 EP 88100151 A EP88100151 A EP 88100151A EP 88100151 A EP88100151 A EP 88100151A EP 0285741 A1 EP0285741 A1 EP 0285741A1
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melting
slab
semi
block
mbar
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French (fr)
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EP0285741B1 (en
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Michael Dr. Hörmann
Otto Bach
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WC Heraus GmbH and Co KG
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WC Heraus GmbH and Co KG
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22DCASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D27/00Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
    • B22D27/15Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting by using vacuum
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22FCHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/16Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of other metals or alloys based thereon
    • C22F1/18High-melting or refractory metals or alloys based thereon

Definitions

  • the invention relates to a method for producing highly ductile semi-finished tantalum products for use in the field of high-speed forming.
  • the object of the present invention is to provide a method for producing highly ductile semi-finished tantalum product which is suitable for use in the field of high-speed forming, in particular for projectiles.
  • the melting block obtained by melting the body made of powder by pressing is advantageously melted in the electron beam furnace at a higher melting rate (kg / h) than the aforementioned body.
  • the melt rate for the melt block has proven to be at least twice as large as the melt rate for the body produced by pressing the powder.
  • the melting block obtained from the last remelting cycle is first cold-forged into a blank, which is divided into block-shaped individual pieces. Then each individual piece is heated to a temperature of about 650 ° in a slightly oxidizing atmosphere and, after removal from the oven, if the individual piece still has a temperature in the range from 450 to 600 ° C., is compressed. After cooling completely to room temperature, the compressed body is cold forged into a slab.
  • the tantalum semi-finished products produced according to the invention are texture-free and have a grain size that is finer than 30 ⁇ m (according to ASTM E 112). Their tensile strength is less than 200 N / mm2, their elongation is greater than 60%.
  • the overall purity of the materials according to the invention is calculated by determining the residual resistance ratio (electrical resistance at the temperature of 273 K: by electrical resistance at the temperature of 4.2 K). It is at least 200 for materials according to the invention.
  • a method for producing a highly ductile tantalum semi-finished product according to the invention is described with the aid of the exemplary embodiment below.
  • Sodium-reduced tantalum powder was used to produce the rod-shaped body produced by pressing.
  • a rod-shaped body was produced from this tantalum powder by cold isostatic pressing.
  • This body was used as a melting electrode in an electron beam furnace and melted at a melting rate in the range from 25 to 35 kg / h.
  • a pressure of 2 ⁇ 10 ⁇ 4 mbar was maintained during the melting process.
  • the melt was collected in a water-cooled mold and a melting block (ingot) with a diameter of 150 mm was formed. This melting block was then three times in the Electron beam furnace remelted by melting, the melt block formed in each case being used again as the melting electrode.
  • a pressure of 8 ⁇ 10 ⁇ 5 mbar was maintained in the electron beam furnace, the melting rate was in the range of 70 to 100 kg / h.
  • the corresponding values for the second remelting process were 6 ⁇ 10 ⁇ 5 mbar, the melting rate was again in the range from 70 to 100 kg / h, while during the last remelting process the pressure in the electron beam furnace was reduced to 3 ⁇ 10 ⁇ 5 mbar and the melting rate was 120 Kg / h.
  • the diameter of the melting block obtained from the last remelting cycle was 175 mm.
  • the melting block was first cold forged on 150 mm octagon, after which it was cut into block-shaped individual pieces of 350 mm length. Each individual piece was then heated to 650 ° C. in a slightly oxidized atmosphere in a gas-heated hearth furnace and held at this temperature for a period of about 2 to 3 hours. After removal from the hearth furnace, the individual pieces were compressed at a temperature of approx. 550 ° C on a forging hammer. After it had completely cooled to room temperature, the compressed individual piece was cold-forged into a slab, down to dimensions in mm of approx. 160 ⁇ 65 ⁇ 800.
  • the smoothed slab was degreased and first pickled in aqua regia and then in an acid mixture consisting of one part by volume of concentrated hydrofluoric acid, two parts by volume of concentrated nitric acid and two parts by volume of water.
  • the degree of deformation was ⁇ ⁇ 1.3 ( ⁇ ⁇ 75%). After this cold rolling process, the cold-rolled part was degreased and pickled.
  • a relaxation annealing was carried out in an inductively heated furnace, in which a pressure of 2 ⁇ 10bar mbar was maintained during the heat treatment.
  • the annealed part was subjected to several cold rolling steps, in which case rolling was again carried out in the direction along and transversely to the axis of the last melting block obtained.
  • This cold rolling process was also carried out with a high number of individual passes.
  • the degree of deformation was ⁇ ⁇ 1.9 ( ⁇ ⁇ 85%).
  • the workpiece was again cold-rolled, as described above, ground, degreased and pickled and then subjected to recrystallization annealing at 875 ° C. in a resistance-heated vacuum oven.
  • the highly ductile tantalum semi-finished product thus obtained was texture-free and had a grain size finer than 30 ⁇ m according to (ASTM E 112). Its tensile strength was 192 N / mm2, its elongation was 65%, the residual resistance ratio was found to be 220.

Abstract

Es wird ein Verfahren zur Herstellung von hochduktilem Tantal-Halbzeug für die Verwendung auf dem Gebiet der Hochgeschwindigkeitsumformung angegeben. Zunächst wird aus direkt reduziertem Tantal-Pulver vorgegebener Reinheit ein stabförmiger Körper hergestellt, der in einem Elektronenstrahlofen mehrmals durch Abschmelzen umgeschmolzen wird. Der zuletzt erhaltene Schmelzblock wird zu einer Bramme verformt, die nach spanabhebender Glättung in üblicherweise zu einem Halbzeug weiterverarbeitet wird. Dabei ist in den Herstellungsprozeß für das Halbzeug mindestens eine Wärmebehandlung unter Vakuum einbezogen.A method for the production of highly ductile semi-finished tantalum for use in the field of high-speed forming is specified. First, a rod-shaped body is produced from directly reduced tantalum powder of a specified purity, which is remelted several times in an electron beam furnace by melting. The melting block obtained last is deformed into a slab, which is usually further processed into a semi-finished product after machining smoothing. At least one heat treatment under vacuum is included in the manufacturing process for the semi-finished product.

Description

Die Erfindung betrifft ein Verfahren zur Herstellung von hochduktilem Tantal-Halbzeug für die Verwendung auf dem Gebiet der Hochgeschwindigkeits­umformung.The invention relates to a method for producing highly ductile semi-finished tantalum products for use in the field of high-speed forming.

Auf dem Gebiet der Hochgeschwindigkeitsumformung, wie sie z. B. bei Geschoßen vorkommt, wird üblicherweise hochduktiles Eisen oder Kupfer verwendet. Die Eindringtiefe der Geschoße ist eine Funktion sowohl der Dichte des verwendeten hochduktilen Werkstoffes als auch der Dichte des Werkstoffes, auf den das Ge­schoß auftrifft. Man ist daher seit langem bestrebt, einen hochduktilen Werk­stoff sehr hoher Dichte herzustellen.In the field of high-speed forming, e.g. B. occurs in the case of bullets, usually highly ductile iron or copper is used. The penetration depth of the projectiles is a function of both the density of the highly ductile material used and the density of the material that the projectile strikes. For this reason, efforts have long been made to produce a highly ductile material of very high density.

Die Aufgabe der vorliegenden Erfindung besteht darin, ein Verfahren zur Her­stellung von hochduktilem Tantal-Halbzeug bereitzustellen, das für die Verwen­dung auf dem Gebiet der Hochgeschwindigkeitsumformung, insbesondere für Ge­schosse, geeignet ist.The object of the present invention is to provide a method for producing highly ductile semi-finished tantalum product which is suitable for use in the field of high-speed forming, in particular for projectiles.

Gelöst wird diese Aufgabe erfindungsgemäß durch folgende Verfahrensschritte:

  • a) aus mit direkt-reduziertem Tantal-Pulver, das pro g-Pulver weniger als 100 µg Niob, Wolfram und/oder Molybdän enthält, wird durch Pressen ein stabförmiger Körper hergestellt,
  • b) der Körper wird in einem Elektronenstrahl-Ofen unter Aufrechterhal­tung eines Druckes von weniger als 5 × 10⁻⁴ mbar abgeschmolzen, die Schmelze in einer gekühlten Kokille gesammelt und ein Schmelzblock gebildet,
  • c) der Schmelzblock wird mindestens zweimal im Elektronenstrahlofen unter Aufrechterhaltung eines Druckes von weniger als 5 × 10⁻⁴ mbar durch Abschmelzen umgeschmolzen,
  • d) der vom letzten Umschmelzzyklus erhaltene Schmelzblock wird zu einer Bramme verformt,
  • e) die Bramme wird allseitig spanabhebend mit einer Rauhtiefe von maximal 25 µm geglättet,
  • f) aus der glatten Bramme werden in üblicher Weise Halbzeug durch Ver­formen hergestellt, wobei in diesen Herstellungsprozeß mindestens eine Wärmebehandlung in einem induktiv und/oder widerstandsbeheizten Ofen unter Aufrechterhaltung eines Druckes von weniger als 5 × 10⁻⁴ mbar einbezogen wird.
According to the invention, this object is achieved by the following process steps:
  • a) a rod-shaped body is produced by pressing with directly reduced tantalum powder, which contains less than 100 μg of niobium, tungsten and / or molybdenum per g powder,
  • b) the body is melted in an electron beam furnace while maintaining a pressure of less than 5 × 10⁻⁴ mbar, the melt is collected in a cooled mold and a melting block is formed,
  • c) the melting block is remelted by melting at least twice in the electron beam furnace while maintaining a pressure of less than 5 × 10⁻⁴ mbar,
  • d) the melting block obtained from the last remelting cycle is deformed into a slab,
  • e) the slab is machined on all sides with a maximum roughness of 25 µm,
  • f) from the smooth slab, semifinished products are produced in the usual way by shaping, with at least one heat treatment in an induction and / or resistance-heated furnace being maintained in this production process while maintaining a pressure of less than 5 × 10 diesen mbar.

Bewährt hat es sich bei dem erfindungsgemäßen Verfahren Natrium-reduziertes Tantal-Pulver zu verwenden. Der Schmelzblock, der durch Abschmelzen des aus Pulver durch Pressen hergestellten Körpers erhalten wird, wird vorteilhafter­weise mit einer höheren Schmelzrate (kg/h) im Elektronenstrahlofen abgeschmol­zen als der vorerwähnte Körper. Bewährt hat sich dabei die Schmelzrate für den Schmelzblock wenigstens doppelt so groß zu wählen wie die Schmelzrate für den durch Pressen des Pulvers hergestellten Körper.It has proven useful to use sodium-reduced tantalum powder in the process according to the invention. The melting block obtained by melting the body made of powder by pressing is advantageously melted in the electron beam furnace at a higher melting rate (kg / h) than the aforementioned body. The melt rate for the melt block has proven to be at least twice as large as the melt rate for the body produced by pressing the powder.

Zur Herstellung der Bramme wird vorteilhafterweise der vom letzten Umschmelz­zyklus erhaltene Schmelzblock zunächst durch Kaltschmieden zu einem Rohling verformt, der in blockförmige Einzelstücke zerteilt wird. Danach wird jedes Einzelstück in leicht oxidierender Atmosphäre auf eine Temperatur von etwa 650° aufgeheizt und nach Entnahme aus dem Ofen, wenn das Einzelstück noch eine Temperatur im Bereich von 450 bis 600°C besitzt, gestaucht. Nach vollständiger Abkühlung auf Raumtemperatur wird der gestauchte Körper kalt zu einer Bramme geschmiedet.To produce the slab, the melting block obtained from the last remelting cycle is first cold-forged into a blank, which is divided into block-shaped individual pieces. Then each individual piece is heated to a temperature of about 650 ° in a slightly oxidizing atmosphere and, after removal from the oven, if the individual piece still has a temperature in the range from 450 to 600 ° C., is compressed. After cooling completely to room temperature, the compressed body is cold forged into a slab.

Bewährt hat es sich, in den Herstellungsprozeß für das Halbzeug einen Kalt­walzschritt mit Umformgraden von ρ ≧ 1,2 (ε ≧ 70 %) einzuschalten, der sowohl ein Walzen in Richtung der Achse des zuletzt erhaltenen Schmelzblockes als auch in einer dazu quer verlaufenden Richtung umfaßt. Dabei ist es zweckmäßig, vor dem Kaltwalzschritt eine Entspannungsglühung bei einer Temperatur von etwa 650°C und nach dem Kaltwalzschritt eine Rekristallisationsglühung im Bereich von etwa 900°C durchzuführen.It has proven useful to use a cold rolling step with degrees of deformation of ρ ≧ 1.2 (ε ≧ 70%) in the manufacturing process for the semifinished product, which includes both rolling in the direction of the axis of the last melt block obtained and in a direction transverse thereto . It is expedient to carry out a stress relief annealing at a temperature of about 650 ° C. before the cold rolling step and a recrystallization annealing in the range of about 900 ° C. after the cold rolling step.

Als Ergebnis des erfindungsgemäßen Verfahrens erhält man hochduktile Tantal-Halbzeuge, die bezüglich ihrer mechanischen Eigenschaften und ihres Gefügeaufbaus isotrop sind. Die erfindungsgemäß hergestellten Tantal-Halbzeuge sind Textur-frei und besitzen eine Korngröße, die feiner als 30 µm (nach ASTM E 112) ist. Ihre Zugfestigkeit ist kleiner als 200 N/mm², ihre Dehnung ist größer als 60 %. Die Gesamtreinheit der erfindungsgemäßen Werkstoffe wird durch die Bestimmung des Restwiderstandsverhältnisses (elektrischer Widerstand bei der Temperatur von 273 K : durch elektrischen Widerstand bei der Temperatur von 4,2 K) errechnet. Es beträgt bei erfindungsgemäßen Werkstoffen wenigstens 200.As a result of the process according to the invention, highly ductile semi-finished tantalum products are obtained which are isotropic with regard to their mechanical properties and their structure. The tantalum semi-finished products produced according to the invention are texture-free and have a grain size that is finer than 30 μm (according to ASTM E 112). Their tensile strength is less than 200 N / mm², their elongation is greater than 60%. The overall purity of the materials according to the invention is calculated by determining the residual resistance ratio (electrical resistance at the temperature of 273 K: by electrical resistance at the temperature of 4.2 K). It is at least 200 for materials according to the invention.

Anhand des nachfolgenden Ausführungsbeispiels wird ein Verfahren zur Herstel­lung eines erfindungsgemäßen hochduktilen Tantal-Halbzeuges beschrieben.A method for producing a highly ductile tantalum semi-finished product according to the invention is described with the aid of the exemplary embodiment below.

Zur Herstellung des durch Pressen erzeugten stabförmigen Körpers wurde Natrium-reduziertes Tantal-Pulver verwendet, dessen Verunreinigungsgehalte (µg/g) sich aus nachstehender Tabelle ergeben:

Figure imgb0001
Sodium-reduced tantalum powder was used to produce the rod-shaped body produced by pressing.
Figure imgb0001

Aus diesem Tantal-Pulver wurde durch kalt-isostatisches Pressen ein stab­förmiger Körper hergestellt. Dieser Körper wurde als Abschmelzelektrode in einen Elektronenstrahlofen eingesetzt und mit einer Schmelzrate im Bereich von 25 bis 35 kg/h abgeschmolzen. Während des Abschmelzprozesses wurde ein Druck von 2 × 10⁻⁴ mbar aufrechterhalten. Die Schmelze wurde in einer wasser­gekühlten Kokille gesammelt und ein Schmelzblock (Ingot) mit einem Durchmesser von 150 mm gebildet. Dieser Schmelzblock wurde anschließend dreimal in dem Elektronenstrahlofen durch Abschmelzen umgeschmolzen, wobei der jeweils gebil­dete Schmelzblock wieder als Abschmelzelektrode eingesetzt wurde. Während des ersten Umschmelzvorganges wurde in dem Elektronenstrahlofen ein Druck von 8 × 10⁻⁵ mbar aufrechterhalten, die Schmelzrate lag im Bereich von 70 bis 100 Kg/h. Die entsprechenden Werte für den zweiten Umschmelzvorgang betru­gen 6 × 10⁻⁵ mbar, die Schmelzrate lag wiederum im Bereich von 70 bis 100 Kg/h, während beim letzten Umschmelzvorgang der Druck im Elektronenstrahlofen auf 3 × 10⁻⁵ mbar abgesenkt war und die Schmelzrate 120 Kg/h betrug. Der Durchmesser des vom letzten Umschmelzzyklus erhaltenen Schmelzblocks betrug 175 mm.A rod-shaped body was produced from this tantalum powder by cold isostatic pressing. This body was used as a melting electrode in an electron beam furnace and melted at a melting rate in the range from 25 to 35 kg / h. A pressure of 2 × 10⁻⁴ mbar was maintained during the melting process. The melt was collected in a water-cooled mold and a melting block (ingot) with a diameter of 150 mm was formed. This melting block was then three times in the Electron beam furnace remelted by melting, the melt block formed in each case being used again as the melting electrode. During the first remelting process, a pressure of 8 × 10⁻⁵ mbar was maintained in the electron beam furnace, the melting rate was in the range of 70 to 100 kg / h. The corresponding values for the second remelting process were 6 × 10⁻⁵ mbar, the melting rate was again in the range from 70 to 100 kg / h, while during the last remelting process the pressure in the electron beam furnace was reduced to 3 × 10⁻⁵ mbar and the melting rate was 120 Kg / h. The diameter of the melting block obtained from the last remelting cycle was 175 mm.

Der zuletzt erhaltene Schmelzblock wurde danach durch thermo-mechanische Um­formung zu einer Bramme vorformt. Dabei wurde zunächst der Schmelzblock an 150 mm achtkant kaltgeschmiedet, danach wurde er in blockförmige Einzelstücke von 350 mm Länge zerteilt. Jedes Einzelstück wurde dann in leicht oxidierender Atmosphäre in einem gasbeheizten Herdofen auf 650 °C aufgeheizt und bei dieser Temperatur während einer Dauer von etwa 2 bis 3 Stunden gehalten. Nach der Entnahme aus dem Herdofen wurden die Einzelstücke bei einer Temperatur von ca. 550 °C auf einem Schmiedehammer gestaucht. Nach seiner vollständigen Abkühlung auf Raumtemperatur wurde das gestauchte Einzelstück zu einer Bramme kalt­geschmiedet, bis an Abmessungen in mm von ca. 160 × 65 × 800. Hieran schloß sich ein Fräsvorgang mit einer Rauhtiefe von 20 µm zur Glättung der Bramme an. Die geglättete Bramme wurde entfettet und zunächst in Königswasser und danach in einem Säuregemisch, das aus einem Volumenanteil konzentrierter Fluorwasserstoffsäure, zwei Volumenanteilen konzentrierter Salpetersäure und zwei Volumenanteile Wasser bestand, gebeizt. Hieran schloß sich ein Kaltwalzen mit hoher Einzelstichabnahme an, wobei sowohl in Richtung der Achse des zuletzt erhaltenen Schmelzblockes als auch in einer quer dazu verlaufenden Richtung gewalzt wurde. Der Verformungsgrad betrug ρ ≧ 1,3 (ε ≧ 75 %). Nach diesem Kaltwalzvorgang wurde das kaltgewalzte Teil entfettet und gebeizt. Danach wurde eine Entspannungsglühung in einem induktiv beheizten Ofen durch­geführt, in dem während der Wärmebehandlung ein Druck von 2 × 10⁻⁴ mbar auf­rechterhalten wurde. Nach dieser Entspannungsglühung wurde das geglühte Teil mehreren Kaltwalzschritten unterworfen, wobei wiederum ein Walzen in Richtung längs und quer zur Achse des zuletzt erhaltenen Schmelzblocks durchgeführt wurde. Auch dieser Kaltwalzvorgang wurde mit hoher Einzelstichabnahme durch­geführt. Der Verformungsgrad betrug ρ ≧ 1,9 (ε ≧ 85 %). Im Anschluß an diesen Kaltwalzschritt wurde das Werkstück wieder, wie bereits oben geschildert, ge­schliffen, entfettet und gebeizt und dann in einem widerstandsbeheizten Vakuumofen einer Rekristallisationsglühung bei 875 °C unterworfen.The last block obtained was then preformed into a slab by thermo-mechanical shaping. The melting block was first cold forged on 150 mm octagon, after which it was cut into block-shaped individual pieces of 350 mm length. Each individual piece was then heated to 650 ° C. in a slightly oxidized atmosphere in a gas-heated hearth furnace and held at this temperature for a period of about 2 to 3 hours. After removal from the hearth furnace, the individual pieces were compressed at a temperature of approx. 550 ° C on a forging hammer. After it had completely cooled to room temperature, the compressed individual piece was cold-forged into a slab, down to dimensions in mm of approx. 160 × 65 × 800. This was followed by a milling process with a roughness depth of 20 μm to smooth the slab. The smoothed slab was degreased and first pickled in aqua regia and then in an acid mixture consisting of one part by volume of concentrated hydrofluoric acid, two parts by volume of concentrated nitric acid and two parts by volume of water. This was followed by cold rolling with a high single pass reduction, rolling both in the direction of the axis of the last melting block obtained and in a direction transverse to it. The degree of deformation was ρ ≧ 1.3 (ε ≧ 75%). After this cold rolling process, the cold-rolled part was degreased and pickled. Thereafter, a relaxation annealing was carried out in an inductively heated furnace, in which a pressure of 2 × 10bar mbar was maintained during the heat treatment. After this stress relief annealing, the annealed part was subjected to several cold rolling steps, in which case rolling was again carried out in the direction along and transversely to the axis of the last melting block obtained. This cold rolling process was also carried out with a high number of individual passes. The degree of deformation was ρ ≧ 1.9 (ε ≧ 85%). Following this The workpiece was again cold-rolled, as described above, ground, degreased and pickled and then subjected to recrystallization annealing at 875 ° C. in a resistance-heated vacuum oven.

Das so erhaltene hochduktile Tantal-Halbzeug war Textur-frei und wies eine Korngröße feiner als 30 µm nach (ASTM E 112) auf. Seine Zugfestigkeit betrug 192 N/mm², seine Dehnung betrug 65 %, das Restwiderstandsverhältnis wurde mit 220 ermittelt.The highly ductile tantalum semi-finished product thus obtained was texture-free and had a grain size finer than 30 μm according to (ASTM E 112). Its tensile strength was 192 N / mm², its elongation was 65%, the residual resistance ratio was found to be 220.

Claims (6)

1. Verfahren zur Herstellung von hochduktilem Tantal-Halbzeug für die Ver­wendung auf dem Gebiet der Hochgeschwindigkeitsumformung, gekennzeichnet durch folgende Verfahrensschritte: a) aus mit direkt reduziertem Tantal-Pulver, das pro g-Pulver weniger als 100 µg Niob, Wolfram und/oder Molybdän enthält, wird durch Pressen ein stabförmiger Körper hergestellt, b) der Körper wird in einem Elektronenstrahl-Ofen unter Aufrechter­haltung eines Druckes von weniger als 5 × 10⁻⁴ mbar abgeschmolzen, die Schmelze in einer gekühlten Kokille gesammelt und ein Schmelzblock gebildet, c) der Schmelzblock wird mindestens zweimal im Elektronenstrahlofen unter Aufrechterhaltung eines Druckes von weniger als 5 × 10⁻⁴ mbar durch Abschmelzen umgeschmolzen, d) der vom letzten Umschmelzzyklus erhaltene Schmelzblock wird zu einer Bramme verformt, e) die Bramme wird allseitig spanabhebend mit einer Rauhtiefe von maximal 25 µm geglättet, f) aus der glatten Bramme werden in üblicher Weise Halbzeuge durch Verformen hergestellt, wobei in diesen Herstellungsprozeß mindestens eine Wärmebehandlung in einem induktiv und/oder wider­standsbeheizten Ofen unter Aufrechterhaltung eines Druckes von weniger als 5 × 10⁻⁴ mbar einbezogen wird. 1. Process for the production of highly ductile semi-finished tantalum for use in the field of high-speed forming, characterized by the following process steps: a) a rod-shaped body is produced by pressing with directly reduced tantalum powder, which contains less than 100 μg of niobium, tungsten and / or molybdenum per g powder, b) the body is melted in an electron beam furnace while maintaining a pressure of less than 5 × 10⁻⁴ mbar, the melt is collected in a cooled mold and a melting block is formed, c) the melting block is remelted by melting at least twice in the electron beam furnace while maintaining a pressure of less than 5 × 10⁻⁴ mbar, d) the melting block obtained from the last remelting cycle is deformed into a slab, e) the slab is machined on all sides with a maximum roughness of 25 µm, f) from the smooth slab, semi-finished products are produced in the usual way by shaping, with at least one heat treatment in an inductive and / or resistance-heated furnace being maintained in this manufacturing process while maintaining a pressure of less than 5 × 10 diesen mbar. 2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß der Schmelzblock mit einer höheren Schmelzrate (kg/h) abgeschmolzen wird als der durch Pressen hergestellte Körper.2. The method according to claim 1, characterized in that the melting block is melted at a higher melting rate (kg / h) than the body produced by pressing. 3. Verfahren nach Anspruch 2, dadurch gekennzeichnet, daß die Schmelzrate für den Schmelzblock wenigstens etwa doppelt so groß gewählt wird wie die Schmelzrate für den durch Pressen hergestellten Körper.3. The method according to claim 2, characterized in that the melting rate for the melting block is chosen at least about twice as large as the melting rate for the body produced by pressing. 4. Verfahren nach den Ansprüchen 1 bis 3, dadurch gekennzeichnet, daß der vom letzten Umschmelzzyklus erhaltene Schmelzblock durch Kaltschmieden zu einem Rohling umgeformt, der in blockförmige Einzelstücke zerteilt wird, wonach jedes Einzelstück in leicht oxidierender Atmosphäre auf eine Temperatur von etwa 650 °C aufgeheizt, nach geringer Abkühlung bei einer Temperatur im Bereich von 450 bis 600 °C gestaucht und nach vollständiger Abkühlung auf Raumtemperatur kalt zu einer Bramme geschmiedet wird.4. Process according to claims 1 to 3, characterized in that the melt block obtained from the last remelting cycle is cold-forged into a blank which is divided into block-shaped individual pieces, after which each individual piece is heated to a temperature of about 650 ° C in a slightly oxidizing atmosphere , compressed after slight cooling at a temperature in the range from 450 to 600 ° C. and cold forged to a slab after complete cooling to room temperature. 5. Verfahren nach den Ansprüchen 1 bis 4, dadurch gekennzeichnet, daß in den Herstellungsprozess für das Halbzeug ein Kaltwalzen mit Umformgraden von ρ ≧ 1,2 (ε ≧ 70 %) eingeschaltet wird, das sowohl ein Walzen in Richtung der Achse des letzterhaltenen Schmelzblockes als auch in einer dazu quer verlaufenden Richtung umfaßt.5. The method according to claims 1 to 4, characterized in that in the manufacturing process for the semifinished product a cold rolling with degrees of deformation of ρ ≧ 1.2 (ε ≧ 70%) is switched on, both rolling in the direction of the axis of the last melting block obtained as well as in a direction transverse thereto. 6. Verfahren nach Anspruch 5, dadurch gekennzeichnet, daß vor dem Kaltwalzen eine Eintspannungsglühung bei einer Temperatur von etwa 650°C und nach dem Kaltwalzen eine Rekristallisationsglühung im Bereich von etwa 800 bis 900°C durchgeführt werden.6. The method according to claim 5, characterized in that before the cold rolling, a single-annealing at a temperature of about 650 ° C and after the cold rolling, a recrystallization annealing in the range of about 800 to 900 ° C are carried out.
EP88100151A 1987-04-10 1988-01-08 Process for the production of a highly ductile semi-finished tantalum product Expired - Lifetime EP0285741B1 (en)

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DE3712281 1987-04-10
DE19873712281 DE3712281A1 (en) 1987-04-10 1987-04-10 METHOD FOR PRODUCING HIGHLY DUCTILE TANTALE SEMI-FINISHED PRODUCTS

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Also Published As

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DE3712281C2 (en) 1989-09-14
EP0285741B1 (en) 1990-10-10
DE3712281A1 (en) 1988-10-27
DE3860768D1 (en) 1990-11-15
US4844746A (en) 1989-07-04

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