EP3259378A1 - Method for producing a strand from stainless steel, and strand made of stainless steel - Google Patents

Method for producing a strand from stainless steel, and strand made of stainless steel

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Publication number
EP3259378A1
EP3259378A1 EP16704447.8A EP16704447A EP3259378A1 EP 3259378 A1 EP3259378 A1 EP 3259378A1 EP 16704447 A EP16704447 A EP 16704447A EP 3259378 A1 EP3259378 A1 EP 3259378A1
Authority
EP
European Patent Office
Prior art keywords
strand
stainless steel
less
cold
gas atmosphere
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP16704447.8A
Other languages
German (de)
French (fr)
Other versions
EP3259378B1 (en
Inventor
Thomas FROBÖSE
Udo RAUFFMANN
Christofer HEDVAL
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Alleima GmbH
Original Assignee
Sandvik Materials Technology Deutschland GmbH
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Filing date
Publication date
Application filed by Sandvik Materials Technology Deutschland GmbH filed Critical Sandvik Materials Technology Deutschland GmbH
Publication of EP3259378A1 publication Critical patent/EP3259378A1/en
Application granted granted Critical
Publication of EP3259378B1 publication Critical patent/EP3259378B1/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
    • C21D9/525—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length for wire, for rods
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
    • B21C23/00—Extruding metal; Impact extrusion
    • B21C23/02—Making uncoated products
    • B21C23/04—Making uncoated products by direct extrusion
    • B21C23/08—Making wire, bars, tubes
    • B21C23/085—Making tubes
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/008—Heat treatment of ferrous alloys containing Si
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/10—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies
    • C21D8/105—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/08—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for tubular bodies or pipes
    • C21D9/14—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for tubular bodies or pipes wear-resistant or pressure-resistant pipes
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
    • 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
    • C22C38/04—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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
    • 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
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/001—Austenite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/002—Heat treatment of ferrous alloys containing Cr

Definitions

  • the present invention relates to a method for producing a strand of stainless steel by cold-forming a billet into the work-hardened strand and subsequently annealing the strand.
  • the present invention also relates to a strand of stainless steel produced by such a process.
  • Stranded stainless steel products i. In particular profiles, rods and tubes are often produced by cold forming a semi-finished product referred to in this application as a lead to the actual strand.
  • the billet undergoes cold work hardening during cold forming.
  • the strand of stainless steel therefore receives properties that can not be achieved by hot forming.
  • strands having high tensile strengths can be produced, as they are otherwise difficult or impossible to achieve.
  • the elongation of cold-formed stainless steel strands is rather small compared to strands made by other forming processes.
  • At least one of the foregoing objects is achieved by a method of producing a cold consolidated stainless steel strand by cold working a billet into the work hardened strand and then annealing the strand, wherein as the strand anneals the strand is heated to a temperature in a range of 400 ° C is heated to 460 ° C, wherein the work-hardened strand is surrounded during the heating of a protective gas atmosphere.
  • a cold-worked strand of stainless steel, which is produced in this way, surprisingly has a high elongation, at the same time the high achieved by cold forming tensile strength is maintained or even improved.
  • the cold forming takes place in particular by cold pilger rolling or cold drawing.
  • an expanded, hollow-like billet as a semi-finished product is cold reduced in the fully cooled state by compressive stresses.
  • the billet is transformed into a tube with a defined, reduced outside diameter and a defined wall thickness or thickness.
  • the billet is calibrated over a calibrated, i. pushed the inner diameter of the finished tube having mandrel and calibrated from the outside of two calibrated, i. comprising the outer diameter of the finished tube defining rollers and rolled in the longitudinal direction over the rolling mandrel.
  • the billet undergoes a gradual advance toward the mandrel or over it.
  • the rollers are rotated over the mandrel and thus the doll moves and roll out the doll.
  • the rolls release the billet and this is advanced by a further step towards the tool, ie the rolling mandrel (s).
  • the feed of the billet over the mandrel takes place with the aid of a translationally driven feed tension slide, which executes a translatory movement in a direction parallel to the axis of the rolling mandrel and transfers it to the billet.
  • the billet is also rotated about its longitudinal axis to allow uniform rolling of the billet. By multiple rolling over each pipe section a uniform wall thickness and roundness of the tube and uniform inner and outer diameter are achieved. Therefore, as a rule, the feed steps are smaller than the total stroke of the roll stand between the two reversal points.
  • a strand-like billet is drawn through a drawing die having an inside diameter smaller than the outside diameter of the billet, and thereby reshaped and resized.
  • hoist in which the deformation is reduced only with a previously described draw die (also referred to as draw ring, hollow or die), and the so-called core pull or rod pull, in which the Inner diameter and the wall thickness of the drawn pipe are defined by a arranged inside the billet core.
  • draw die also referred to as draw ring, hollow or die
  • core pull or rod pull in which the Inner diameter and the wall thickness of the drawn pipe are defined by a arranged inside the billet core.
  • the tensile strength in the sense of the present application is understood to mean the stress which is calculated in the tensile test from the maximum tensile force attained immediately before the fracture of the sample in relation to the original cross section of the sample.
  • the dimension of the tensile strength is force per area.
  • elongation is understood to mean the permanent extension of a strand, which is pulled under the action of force until it ruptures, based on the initial measuring length.
  • This elongation is also called breaking elongation or yield strength.
  • the elongation at break is calculated as the quotient of the remaining change in length after the break divided by the initial length before the action of force. This gives a dimensionless size and is often given as a percentage. It is astonishing that in the specified temperature range of 400 ° C to 460 ° C, the solidification of the strand by the cold working, ie the high tensile strength achieved by the annealing is still increased, while the elongation is not significantly reduced. A macroscopic or microscopic change of strands, which were annealed by the applicant after cold working in this temperature range is not detectable.
  • a particularly advantageous improvement in tensile strength while maintaining a high elongation over a cold forming process which completely omits annealing after cold working is in a range of 410 ° C to 450 ° C, preferably in a range of 435 ° C to 445 ° C and most preferably reached at 440 ° C.
  • the annealing takes place in a protective gas atmosphere which surrounds the strand during annealing.
  • This protective gas atmosphere advantageously has argon in one embodiment, preferably an argon content of more than 95% by volume.
  • the oxygen content of the inert gas atmosphere during annealing is less than 50 ppm, preferably less than 15 ppm and more preferably less than 10 ppm. Then, oxidation processes to the surface of the strand are negligible.
  • the dew point of the inert gas atmosphere at atmospheric pressure (1013 mbar) is at a temperature of -40 ° C or less, preferably -50 ° C or less.
  • an austenitic stainless steel is understood to mean a cubic face-centered mixed crystal of an iron alloy, in particular a ⁇ mixed crystal.
  • the effect occurs with stainless steel, the carbon in a proportion of not more than 0.06 wt .-%, manganese in a proportion of not more than 2 wt .-%, silicon in a proportion of not more than 0.7 wt %
  • chromium having a content of from 16% by weight to 20% by weight
  • molybdenum having a proportion of from 2.0% by weight to 2.6% by weight, with the remainder being iron and unavoidable Impurities on.
  • a strand in the sense of the present application is a workpiece with a larger, in particular much larger longitudinal extent compared to its cross section. Examples of strands are profiles, rods, in particular round rods and tubes.
  • While the method of the invention may be used for all types of strands, it is particularly advantageous in the manufacture of pipes. Tubes with a high tensile strength and at the same time high elongation are needed above all in the field of medical implants but also as high-pressure lines for a very wide variety of applications. While one could initially assume that the described effect of annealing occurs at the temperatures according to the invention only in thin-walled cold-strengthened stainless steel tubes, it has surprisingly been found that this also occurs in stabformigen cold-worked strands with a solid cross-section and especially in thick-walled pipes. Such thick-walled tubes are required in high-pressure technology for fluid guidance.
  • the billet and the finished strand have an inner diameter and an outer diameter.
  • Tubes in which the inner diameter is half the outer diameter or less, preferably one third of the outer diameter or less, are considered to be high pressure resistant and are referred to in the context of the present application as high pressure tubes.
  • the work-hardened strand is a tube having an inner diameter and an outer diameter, wherein the inner diameter is half the outer diameter or less, preferably one third of the outer diameter or less.
  • FIG. 1 shows a flow chart of the method for manufacturing a stainless steel pipe according to an embodiment of the present invention.
  • a tube was made as a billet of an austenitic stainless steel according to DIN1 .44 / 41, the carbon in a proportion of not more than 0.06 wt .-%, manganese in a proportion of not more than 1, 8 wt. %, Silicon in a proportion of not more than 0.7 wt .-%, Nickel having a content of 1% by weight, chromium having a content of 17% by weight, and molybdenum having a content of 2.3% by weight, with the balance being iron and unavoidable impurities.
  • the billet was first cold-reduced by cold pilgering rollers to a finished dimensioned stainless steel tube.
  • the tube thus rolled has an elongation A (H) of 25.0% and a tensile strength Rp 0.2 of 762 N / mm 2 .
  • this cold-pilfered pipe was annealed under a protective gas atmosphere with an argon content of more than 95% by volume at a temperature of 440 ° C.
  • the oxygen content in the protective gas atmosphere was less than 10 ppm.
  • the annealed tube has an elongation A (H) of 15.1% after annealing.
  • the tensile strength Rp 0.2 is 812 N / mm 2 .
  • a tube made of austenitic stainless steel is provided as a starting material.
  • the stainless steel contains, in addition to iron and unavoidable impurities, carbon in a proportion of not more than 0.06% by weight, manganese in a proportion of not more than 1.8% by weight, silicon in a proportion of not more than 0, 7 wt .-%, nickel with a share of 1 1 wt .-%, chromium with a share of 17 wt .-% and molybdenum with a share of 2.3 wt .-%.
  • This billet is then cold formed by cold pilgering rollers in step 2 to the finished sized pipe.
  • the finished tube is then annealed in step 3 under a blanket gas atmosphere with an argon content greater than 95% by volume and an oxygen content in the blanket gas atmosphere of less than 10 ppm at a temperature of 440 ° C.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Heat Treatment Of Steel (AREA)
  • Heat Treatment Of Articles (AREA)

Abstract

The invention relates to a method for producing a strand from stainless steel by cold-forming a bloom into the cold-hardened strand and subsequently annealing the strand. The aim of the invention is to provide a corresponding method for producing a strand from stainless steel, said method allowing stainless steel strands to be produced which have both a high tensile strength as well as a high degree of elongation. According to the invention, this is achieved in that the strand is heated to a temperature ranging from 400 °C to 460 °C while the strand is being annealed, and the cold-hardened strand is surrounded by a protective gas atmosphere during the heating process.

Description

Verfahren zum Herstellen eines Strangs aus Edelstahl sowie Strang aus Edelstahl  Method for producing a strand of stainless steel and strand of stainless steel
Die vorliegende Erfindung betrifft ein Verfahren zum Herstellen eines Strangs aus Edelstahl durch Kaltfumformen einer Luppe zu dem kaltverfestigten Strang und nachfolgend Glühen des Strangs. The present invention relates to a method for producing a strand of stainless steel by cold-forming a billet into the work-hardened strand and subsequently annealing the strand.
Die vorliegende Erfindung betrifft zudem einen Strang aus Edelstahl, welcher durch ein solches Verfahren hergestellt ist. Strangförmige Edelstahlprodukte, d.h. insbesondere Profile, Stäbe und Rohre werden häufig durch Kaltumformen eines in dieser Anmeldung als Luppe bezeichneten Halbzeugs zu dem eigentlichen Strang hergestellt. The present invention also relates to a strand of stainless steel produced by such a process. Stranded stainless steel products, i. In particular profiles, rods and tubes are often produced by cold forming a semi-finished product referred to in this application as a lead to the actual strand.
Neben einer Änderung ihrer Abmessungen erfährt die Luppe bei einer Kaltumformung auch eine Kaltverfestigung. In addition to a change in their dimensions, the billet undergoes cold work hardening during cold forming.
Durch die Kaltumformung erhält der Strang aus Edelstahl daher Eigenschaften, welche sich durch ein Warmumformen nicht erzielen lassen. Insbesondere können durch Kaltumformen Stränge mit hohen Zugfestigkeiten hergestellt werden, so wie sie auf andere Weise nicht oder nur schwer erreichbar sind. Dem gegenüber ist die Dehnung von kaltumgeformten Strängen aus Edelstahl verglichen mit durch andere Umformverfahren hergestellten Strängen eher gering. Due to the cold forming, the strand of stainless steel therefore receives properties that can not be achieved by hot forming. In particular, by cold forming, strands having high tensile strengths can be produced, as they are otherwise difficult or impossible to achieve. On the other hand, the elongation of cold-formed stainless steel strands is rather small compared to strands made by other forming processes.
Daher ist es Aufgabe der vorliegenden Erfindung, ein Verfahren zum Herstellen eines Strangs aus Edelstahl bereitzustellen, welches es ermöglicht, Stränge aus Edelstahl zu fertigen, die so- wohl eine hohe Zugfestigkeit als auch eine hohe Dehnung aufweisen. Zudem ist es Aufgabe der vorliegenden Erfindung, einen Strang aus Edelstahl bereitzustellen, welcher sowohl eine hohe Zugfestigkeit als auch eine hohe Dehnung aufweist. It is therefore an object of the present invention to provide a method for producing a strand of stainless steel, which makes it possible to produce strands of stainless steel, which have both a high tensile strength and a high elongation. In addition, it is an object of the present invention to provide a strand of stainless steel, which has both a high tensile strength and a high elongation.
Zumindest eine der vorgenannten Aufgaben wird durch ein Verfahren zum Herstellen eines kalt- verfestigten Strangs aus Edelstahl durch Kaltumformen einer Luppe zu dem kaltverfestigten Strang und nachfolgendes Glühen des Strangs erreicht, wobei bei dem Glühen des Strangs der Strang auf eine Temperatur in einem Bereich von 400° C bis 460° C erhitzt wird, wobei der kaltverfestigte Strang während des Erhitzens von einer Schutzgasatmosphäre umgeben ist. Ein kaltverfestigter Strang aus Edelstahl, welcher auf diese Weise hergestellt wird, verfügt überraschenderweise über eine hohe Dehnung, wobei gleichzeitig die hohe durch das Kaltumformen erzielte Zugfestigkeit erhalten bleibt oder sogar noch verbessert wird. At least one of the foregoing objects is achieved by a method of producing a cold consolidated stainless steel strand by cold working a billet into the work hardened strand and then annealing the strand, wherein as the strand anneals the strand is heated to a temperature in a range of 400 ° C is heated to 460 ° C, wherein the work-hardened strand is surrounded during the heating of a protective gas atmosphere. A cold-worked strand of stainless steel, which is produced in this way, surprisingly has a high elongation, at the same time the high achieved by cold forming tensile strength is maintained or even improved.
Dies ist insofern überraschend, da ein Glühen eines Strangs aus Edelstahl im Stand der Technik immer zum sogenannten Weichglühen bzw. Rekristalisationsglühen verwendet wird, d.h. um die Zugfestigkeit, zumeist zu Gunsten einer Bearbeitbarkeit des Strangs in einem weiteren Kaltumformschritt, herabzusetzen. This is surprising in that an annealing of a strand of stainless steel in the prior art is always used for so-called soft annealing or recrystallization annealing, i. to reduce the tensile strength, usually in favor of machinability of the strand in a further cold forming step.
Wenn im Sinne der vorliegenden Anmeldung Temperaturen des Strangs während dem Glühen beschrieben werden, so bezieht sich diese Angabe auf die Oberflächentemperatur des kaltverfestigten Strangs selbst. Kaltumformverfahren im Sinne der vorliegenden Anmeldung sind alle Umformverfahren, bei welchen die Luppe, d.h. das Halbzeug, bei Temperaturen umgeformt wird, die unterhalb der Rekris- talisationstemperatur des verwendeten Edelstahls liegen. When temperatures of the strand during annealing are described for the purposes of the present application, this information refers to the surface temperature of the work-hardened strand itself. Cold-forming processes in the sense of the present application are all forming processes in which the billet, i. the semifinished product is converted at temperatures which are below the recrystallization temperature of the stainless steel used.
Im Sinne der vorliegenden Anmeldung erfolgt das Kaltumformen insbesondere durch Kaltpilger- walzen oder Kaltziehen. For the purposes of the present application, the cold forming takes place in particular by cold pilger rolling or cold drawing.
Insbesondere zum Herstellen von präzisen Rohren aus Edelstahl wird eine ausgedehnte hohle, rohartige Luppe als Halbzeug im vollständig erkalteten Zustand durch Druckspannungen kaltreduziert. Dabei wird die Luppe zu einem Rohr mit definiertem, reduziertem Außendurchmesser und einer definierten Wanddicke bzw. -stärke umgeformt. In particular, for the production of precision stainless steel tubes, an expanded, hollow-like billet as a semi-finished product is cold reduced in the fully cooled state by compressive stresses. The billet is transformed into a tube with a defined, reduced outside diameter and a defined wall thickness or thickness.
Dazu wird beim Kaltpilgerwalzen (auch als Kaltpilgern bezeichnet) die Luppe über einen kalibrierten, d.h. den Innendurchmesser des fertigen Rohrs aufweisenden Walzdorn geschoben und dabei von außen von zwei kalibrierten, d.h. den Außendurchmesser des fertigen Rohrs definieren- den Walzen umfasst und in Längsrichtung über den Walzdorn ausgewalzt. For cold pilgering (also referred to as cold pilgering), the billet is calibrated over a calibrated, i. pushed the inner diameter of the finished tube having mandrel and calibrated from the outside of two calibrated, i. comprising the outer diameter of the finished tube defining rollers and rolled in the longitudinal direction over the rolling mandrel.
Während des Kaltpilgerns erfährt die Luppe einen schrittweisen Vorschub in Richtung auf den Walzdorn hin bzw. über diesen hinweg. Zwischen zwei Vorschubschritten werden die Walzen drehend über den Dorn und damit die Luppe bewegt und walzen die Luppe aus. An jedem Um- kehrpunkt des Walzgerüsts mit den daran drehend befestigten Walzen geben die Walzen die Luppe frei und diese wird um einen weiteren Schritt in Richtung auf das Werkzeug, d.h. den Walzdorn bzw. die Walzen, hin vorgeschoben. Der Vorschub der Luppe über den Dorn erfolgt mit Hilfe eines translatorisch angetriebenen Vorschubspannschlittens, welcher eine Translationsbewegung in einer Richtung parallel zur Achse des Walzdorns ausführt und diese auf die Luppe überträgt. Während dem Vorschub wird zudem die Luppe um ihre Längsachse gedreht, um ein gleichmäßiges Auswalzen der Luppe zu ermöglichen. Durch mehrfaches Überwalzen jedes Rohrabschnitts werden eine gleichmäßige Wanddicke und Rundheit des Rohrs sowie gleichmäßige Innen- und Außendurchmesser erreicht. Daher sind in der Regel die Vorschubschritte kleiner als der Gesamthub des Walzgerüsts zwischen den beiden Umkehrpunkten. During cold pilgering, the billet undergoes a gradual advance toward the mandrel or over it. Between two feed steps, the rollers are rotated over the mandrel and thus the doll moves and roll out the doll. At each point of inversion of the roll stand with the rolls mounted thereon, the rolls release the billet and this is advanced by a further step towards the tool, ie the rolling mandrel (s). The feed of the billet over the mandrel takes place with the aid of a translationally driven feed tension slide, which executes a translatory movement in a direction parallel to the axis of the rolling mandrel and transfers it to the billet. During feed, the billet is also rotated about its longitudinal axis to allow uniform rolling of the billet. By multiple rolling over each pipe section a uniform wall thickness and roundness of the tube and uniform inner and outer diameter are achieved. Therefore, as a rule, the feed steps are smaller than the total stroke of the roll stand between the two reversal points.
Im Gegensatz dazu wird beim Kaltziehen als einem weiteren hier beispielhaft zu betrachtenden Kaltumformverfahren eine strangförmige Luppe durch eine Ziehmatrize, welche einen Innendurchmesser aufweist, der geringer ist als der Außendurchmesser der Luppe, hindurchgezogen und damit umgeformt und neu dimensioniert. In contrast, in cold drawing as another cold forming method to be considered here by way of example, a strand-like billet is drawn through a drawing die having an inside diameter smaller than the outside diameter of the billet, and thereby reshaped and resized.
In Abhängigkeit von dem verwendeten Werkzeug unterscheidet man beim Ziehen von Rohren den sogenannten Hohlzug, bei welchem die Umformung lediglich mit einer zuvor beschriebenen Ziehmatrize (auch als Ziehring, Ziehhohl oder Ziehstein bezeichnet) reduziert wird, und den sogenannten Kernzug oder Stangenzug, bei welchem auch der Innendurchmesser sowie die Wanddicke des gezogenen Rohrs durch einen im Inneren der Luppe angeordneten Ziehkern definiert werden. Depending on the tool used is distinguished when pulling pipes the so-called hoist, in which the deformation is reduced only with a previously described draw die (also referred to as draw ring, hollow or die), and the so-called core pull or rod pull, in which the Inner diameter and the wall thickness of the drawn pipe are defined by a arranged inside the billet core.
Unter der Zugfestigkeit im Sinne der vorliegenden Anmeldung wird die Spannung verstanden, die im Zugversuch aus der maximal erreichten Zugkraft unmittelbar vor dem Bruch der Probe bezo- gen auf den ursprünglichen Querschnitt der Probe errechnet wird. Die Dimension der Zugfestigkeit ist Kraft pro Fläche. The tensile strength in the sense of the present application is understood to mean the stress which is calculated in the tensile test from the maximum tensile force attained immediately before the fracture of the sample in relation to the original cross section of the sample. The dimension of the tensile strength is force per area.
Unter Dehnung im Sinne der vorliegenden Anmeldung wird die bleibende Verlängerung eines Strangs, welcher unter Krafteinwirkung bis zum Bruch gezogen wird, bezogen auf die Anfangs- messlänge verstanden. Diese Dehnung wird auch als Bruchdehnung oder Dehngrenze bezeichnet. Berechnet wird die Bruchdehnung als Quotient aus der verbleibenden Längenänderung nach dem Bruch geteilt durch die Anfangslänge vor der Krafteinwirkung. Diese ergibt eine dimensionslose Größe und wird häufig als Prozentwert angegeben. Erstaunlich ist, dass in dem angegebenen Temperaturbereich von 400° C bis 460° C die Verfestigung des Strangs durch das Kaltumformen, d.h. die erzielte hohe Zugfestigkeit, durch das Glühen noch gesteigert wird, während gleichzeitig die Dehnung nicht nennenswert reduziert wird. Eine makroskopische oder mikroskopische Veränderung von Strängen, welche von der Anmelderin nach dem Kaltumformen in diesem Temperaturbereich geglüht wurden, ist nicht feststellbar. For the purposes of the present application, elongation is understood to mean the permanent extension of a strand, which is pulled under the action of force until it ruptures, based on the initial measuring length. This elongation is also called breaking elongation or yield strength. The elongation at break is calculated as the quotient of the remaining change in length after the break divided by the initial length before the action of force. This gives a dimensionless size and is often given as a percentage. It is astonishing that in the specified temperature range of 400 ° C to 460 ° C, the solidification of the strand by the cold working, ie the high tensile strength achieved by the annealing is still increased, while the elongation is not significantly reduced. A macroscopic or microscopic change of strands, which were annealed by the applicant after cold working in this temperature range is not detectable.
Eine insbesondere vorteilhafte Verbesserung der Zugfestigkeit bei Gleichzeitiger Beibehaltung einer hohen Dehnung gegenüber einem Kaltumformverfahren, welches auf ein Glühen nach dem Kaltumformen vollständig verzichtet, wird in einem Bereich von 410° C bis 450° C, vorzugsweise in einem Bereich von 435° C bis 445° C und besonders bevorzugt bei 440° C erreicht." A particularly advantageous improvement in tensile strength while maintaining a high elongation over a cold forming process which completely omits annealing after cold working is in a range of 410 ° C to 450 ° C, preferably in a range of 435 ° C to 445 ° C and most preferably reached at 440 ° C. "
Um die Oxidation des Edelstahlmaterials beim Glühen minimal zu gestalten, erfolgt das Glühen in einer Schutzgasatmosphäre, welche den Strang während dem Glühen umgibt. Diese Schutzgasatmosphäre weist vorteilhafterweise in einer Ausführungsform Argon auf, vorzugsweise einen Anteil an Argon von mehr als 95 Vol.-%. In order to minimize the oxidation of the stainless steel material during annealing, the annealing takes place in a protective gas atmosphere which surrounds the strand during annealing. This protective gas atmosphere advantageously has argon in one embodiment, preferably an argon content of more than 95% by volume.
In einer Ausführungsform der Erfindung beträgt der Sauerstoffgehalt der Schutzgasatmosphäre beim Glühen weniger als 50 ppm, vorzugsweise weniger als 15 ppm und besonders bevorzugt weniger als 10 ppm. Dann sind Oxidationsprozesse zu der Oberfläche des Strangs zu vernachlässigen. In one embodiment of the invention, the oxygen content of the inert gas atmosphere during annealing is less than 50 ppm, preferably less than 15 ppm and more preferably less than 10 ppm. Then, oxidation processes to the surface of the strand are negligible.
In einer Ausführungsform der Erfindung liegt der Taupunkt der Schutzgasatmosphäre bei Atmo- sphärendruck (1013 mbar) bei einer Temperatur von -40° C oder weniger, vorzugsweise von -50° C oder weniger. In one embodiment of the invention, the dew point of the inert gas atmosphere at atmospheric pressure (1013 mbar) is at a temperature of -40 ° C or less, preferably -50 ° C or less.
Während davon auszugehen ist, dass der beschriebene Effekt des Glühens bei den erfindungsgemäßen Temperaturen bei allen Edelstahlmaterialien eintritt, konnte er von den Erfindern insbe- sondere für austenitische Edelstähle explizit nachgewiesen werden. While it can be assumed that the described effect of annealing occurs at the temperatures according to the invention in all stainless steel materials, it could be explicitly demonstrated by the inventors, in particular for austenitic stainless steels.
Dabei wird im Sinne der vorliegenden Anmeldung unter einem austenitischen Edelstahl ein ku- bisch-flächenzentrierter Mischkristall einer Eisenlegierung, insbesondere ein γ-Mischkristall, verstanden. For the purposes of the present application, an austenitic stainless steel is understood to mean a cubic face-centered mixed crystal of an iron alloy, in particular a γ mixed crystal.
Insbesondere tritt der Effekt bei Edelstahl, der Kohlenstoff mit einem Anteil von nicht mehr als 0,06 Gew.-%, Mangan mit einem Anteil von nicht mehr als 2 Gew.-%, Silizium mit einem Anteil von nicht mehr als 0,7 Gew.-%, Chrom mit einem Anteil von 16 Gew.-% bis 20 Gew.-% und Molybdän mit einem Anteil von 2,0 Gew.-% bis 2,6 Gew.-% aufweist mit einem Rest Eisen und un- vermeidbaren Verunreinigungen auf. Ein Strang im Sinne der vorliegenden Anmeldung ist ein Werkstück mit einer verglichen mit seinem Querschnitt größeren, insbesondere viel größeren Längsausdehnung. Beispiele für Stränge sind Profile, Stäbe, insbesondere Rundstäbe sowie Rohre. Während das erfindungsgemäße Verfahren für alle Arten von Strängen verwendet werden kann, ist es insbesondere vorteilhaft bei der Herstellung von Rohren. Rohre mit einer hohen Zugfestigkeit bei gleichzeitig hoher Dehnung werden vor allem auf dem Gebiet medizinischer Implantate aber auch als Hochdruckleitungen für die unterschiedlichsten Anwendungszwecke benötigt. Während man aber zunächst davon ausgehen könnte, dass der beschriebene Effekt des Glühens bei den erfindungsgemäßen Temperaturen nur bei dünnwandigen kaltverfestigten Edelstahlrohren eintritt, hat sich überraschenderweise gezeigt, dass dieser auch bei stabformigen kaltverfestigten Strängen mit einem massiven Querschnitt und insbesondere auch bei dickwandigen Rohren auftritt. Solche dickwandigen Rohre werden in der Hochdrucktechnik zur Fluidfüh- rung benötigt. Bei einem rohrförmigen Strang weisen die Luppe und der fertige Strang einen Innendurchmesser und einen Außendurchmesser auf. Rohre, bei denen der Innendurchmesser die Hälfte des Außendurchmessers oder weniger, vorzugsweise ein Drittel des Außendurchmessers oder weniger, beträgt, gelten als hochdruckfest und werden im Sinne der vorliegenden Anmeldung als Hochdruckrohre bezeichnet. In particular, the effect occurs with stainless steel, the carbon in a proportion of not more than 0.06 wt .-%, manganese in a proportion of not more than 2 wt .-%, silicon in a proportion of not more than 0.7 wt % By weight, chromium having a content of from 16% by weight to 20% by weight, and molybdenum having a proportion of from 2.0% by weight to 2.6% by weight, with the remainder being iron and unavoidable Impurities on. A strand in the sense of the present application is a workpiece with a larger, in particular much larger longitudinal extent compared to its cross section. Examples of strands are profiles, rods, in particular round rods and tubes. While the method of the invention may be used for all types of strands, it is particularly advantageous in the manufacture of pipes. Tubes with a high tensile strength and at the same time high elongation are needed above all in the field of medical implants but also as high-pressure lines for a very wide variety of applications. While one could initially assume that the described effect of annealing occurs at the temperatures according to the invention only in thin-walled cold-strengthened stainless steel tubes, it has surprisingly been found that this also occurs in stabformigen cold-worked strands with a solid cross-section and especially in thick-walled pipes. Such thick-walled tubes are required in high-pressure technology for fluid guidance. In a tubular strand, the billet and the finished strand have an inner diameter and an outer diameter. Tubes in which the inner diameter is half the outer diameter or less, preferably one third of the outer diameter or less, are considered to be high pressure resistant and are referred to in the context of the present application as high pressure tubes.
Zumindest eine der zuvor genannten Aufgaben wird auch durch einen Strang aus Edelstahl gelöst, welcher durch eine Ausführungsform des zuvor beschriebenen Verfahrens hergestellt ist, gelöst. In einer Ausführungsform der Erfindung ist dabei der kaltverfestigte Strang ein Rohr mit einem Innendurchmesser und einem Außendurchmesser, wobei der Innendurchmesser die Hälfte des Außendurchmessers oder weniger, vorzugsweise ein Drittel des Außendurchmessers oder weniger beträgt. Weitere Vorteile, Merkmale und Anwendungsmöglichkeiten der vorliegenden Erfindung werden anhand der folgenden Beschreibung eines Beispiels deutlich. At least one of the aforementioned objects is also achieved by a strand of stainless steel, which is made by an embodiment of the method described above, solved. In one embodiment of the invention, the work-hardened strand is a tube having an inner diameter and an outer diameter, wherein the inner diameter is half the outer diameter or less, preferably one third of the outer diameter or less. Further advantages, features and applications of the present invention will become apparent from the following description of an example.
Figur 1 zeigt ein Flussdiagramm des Verfahrens zum Herstellen eines Edelstahlrohrs gemäß einer Ausführungsform der vorliegenden Erfindung. FIG. 1 shows a flow chart of the method for manufacturing a stainless steel pipe according to an embodiment of the present invention.
In einem Versuch wurde ein Rohr als Luppe aus einem austenitischen Edelstahl gemäß DIN1 .44/41 , das Kohlenstoff mit einem Anteil von nicht mehr als 0,06 Gew.-%, Mangan mit einem Anteil von nicht mehr als 1 ,8 Gew.-%, Silizium mit einem Anteil von nicht mehr als 0,7 Gew.-%, Nickel mit einem Anteil von 1 1 Gew.-%, Chrom mit einem Anteil von 17 Gew.-% und Molybdän mit einem Anteil von 2,3 Gew.-% aufweist mit einem Rest Eisen und unvermeidbaren Verunreinigungen hergestellt. Die Luppe wurde zunächst durch Kaltpilgerwalzen zu einem fertig dimensionierten Edelstahlrohr kalt reduziert. In one experiment, a tube was made as a billet of an austenitic stainless steel according to DIN1 .44 / 41, the carbon in a proportion of not more than 0.06 wt .-%, manganese in a proportion of not more than 1, 8 wt. %, Silicon in a proportion of not more than 0.7 wt .-%, Nickel having a content of 1% by weight, chromium having a content of 17% by weight, and molybdenum having a content of 2.3% by weight, with the balance being iron and unavoidable impurities. The billet was first cold-reduced by cold pilgering rollers to a finished dimensioned stainless steel tube.
Das so gewalzte Rohr hat eine Dehnung A(H) von 25,0 % und eine Zugfestigkeit Rp 0,2 von 762 N/mm2. The tube thus rolled has an elongation A (H) of 25.0% and a tensile strength Rp 0.2 of 762 N / mm 2 .
Nachfolgend wurde dieses kaltgepilgerte Rohr unter einer Schutzgasatmosphäre mit einem Anteil an Argon von mehr als 95 Vol.-% bei einer Temperatur von 440° C geglüht. Dabei war der Sauerstoffgehalt in der Schutzgasatmosphäre geringer als 10 ppm. Das geglühte Rohr weist nach dem Glühen eine Dehnung A(H) von 15,1 % auf. Die Zugfestigkeit Rp 0,2 beträgt 812 N/mm2. Subsequently, this cold-pilfered pipe was annealed under a protective gas atmosphere with an argon content of more than 95% by volume at a temperature of 440 ° C. The oxygen content in the protective gas atmosphere was less than 10 ppm. The annealed tube has an elongation A (H) of 15.1% after annealing. The tensile strength Rp 0.2 is 812 N / mm 2 .
Zur Erläuterung wird nun anhand des Flussdiagramms aus Figur 1 das Verfahren zur Herstellung eines Edelstahlrohrs gemäß der vorliegenden Erfindung noch einmal kurz zusammengefasst. For explanation, the method for producing a stainless steel tube according to the present invention will now briefly summarized again with reference to the flowchart of Figure 1.
Zunächst wird in Schritt 1 als Ausgangsmaterial ein Rohr aus austenitischem Edelstahl als Luppe bereitgestellt. Der Edelstahl enthält neben Eisen und unvermeidbaren Verunreinigungen Kohlenstoff mit einem Anteil von nicht mehr als 0,06 Gew.-%, Mangan mit einem Anteil von nicht mehr als 1 ,8 Gew.-%, Silizium mit einem Anteil von nicht mehr als 0,7 Gew.-%, Nickel mit einem Anteil von 1 1 Gew.-%, Chrom mit einem Anteil von 17 Gew.-% und Molybdän mit einem Anteil von 2,3 Gew.-%. Diese Luppe wird dann durch Kaltpilgerwalzen in Schritt 2 zum fertig dimensionierten Rohr kaltumgeformt. First, in step 1, a tube made of austenitic stainless steel is provided as a starting material. The stainless steel contains, in addition to iron and unavoidable impurities, carbon in a proportion of not more than 0.06% by weight, manganese in a proportion of not more than 1.8% by weight, silicon in a proportion of not more than 0, 7 wt .-%, nickel with a share of 1 1 wt .-%, chromium with a share of 17 wt .-% and molybdenum with a share of 2.3 wt .-%. This billet is then cold formed by cold pilgering rollers in step 2 to the finished sized pipe.
Das fertige Rohr wird sodann in Schritt 3 unter einer Schutzgasatmosphäre mit einem Anteil an Argon von mehr als 95 Vol.-% und einem Sauerstoffgehalt in der Schutzgasatmosphäre von weniger als 10 ppm bei einer Temperatur von 440° C geglüht. The finished tube is then annealed in step 3 under a blanket gas atmosphere with an argon content greater than 95% by volume and an oxygen content in the blanket gas atmosphere of less than 10 ppm at a temperature of 440 ° C.
Für Zwecke der ursprünglichen Offenbarung wird darauf hingewiesen, dass sämtliche Merkmale, wie sie sich aus der vorliegenden Beschreibung, den Zeichnungen und den Ansprüchen für einen Fachmann erschließen, auch wenn sie konkret nur im Zusammenhang mit bestimmten weiteren Merkmalen beschrieben wurden, sowohl einzeln als auch in beliebigen Zusammenstellungen mit anderen der hier offenbarten Merkmale oder Merkmalsgruppen kombinierbar sind, soweit dies nicht ausdrücklich ausgeschlossen wurde oder technische Gegebenheiten derartige Kombinatio- nen unmöglich oder sinnlos machen. Auf die umfassende, explizite Darstellung sämtlicher denkbarer Merkmalskombinationen wird hier nur der Kürze und der Lesbarkeit der Beschreibung wegen verzichtet. Während die Erfindung in den Zeichnungen und der vorangehenden Beschreibung dargestellt und beschrieben wurde, erfolgt diese Darstellung und Beschreibung lediglich beispielhaft und ist als Beschränkung des Schutzbereichs gedacht, so wie er durch die Ansprüche definiert wird. Die Erfindung ist nicht auf die offenbarten Beispiele beschränkt. Abwandlungen der offenbarten Beispiele sind für den Fachmann aus den Zeichnungen, der Beschreibung und den beigefügten Ansprüchen offensichtlich. In den Ansprüchen schließt das Wort „aufweisen" nicht andere Elemente oder Schritte aus, und der unbestimmte Artikel„eine" oder „ein" schließt eine Mehrzahl nicht aus. Die bloße Tatsache, dass bestimmte Merkmale in unterschiedlichen Ansprüchen beansprucht sind, schließt ihre Kombination nicht aus. Bezugszeichen in den Ansprüchen sind nicht als Beschränkung des Schutzbereichs gedacht. For purposes of the original disclosure, it is to be understood that all such features as will become apparent to those skilled in the art from the present description, drawings, and claims, even if concretely described only in connection with certain other features, both individually and separately Any combination with other features or groups of features disclosed herein can be combined, unless this has been expressly excluded or technical conditions such combinations make it impossible or pointless. On the comprehensive, explicit representation of all conceivable combinations of features is omitted here only for the sake of brevity and readability of the description. While the invention has been illustrated and described in the drawings and the foregoing description, this description and description is given by way of example only and is intended to limit the scope of the protection as defined by the claims. The invention is not limited to the disclosed examples. Variations of the disclosed examples will be apparent to those skilled in the art from the drawings, the description and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality The mere fact that certain features are claimed in different claims does not preclude their combination Reference numerals in the claims are not intended to limit the scope of protection.

Claims

P a t e n t a n s p r ü c h e P a n t a n s p r e c h e
Verfahren zum Herstellen eines Strangs aus Edelstahl durch Process for producing a strand of stainless steel
Kaltumformen einer Luppe zu dem kaltverfestigten Strang und Cold forming a billet to the work hardened strand and
nachfolgendes Glühen des Strangs, subsequent annealing of the strand,
dadurch gekennzeichnet, dass characterized in that
bei dem Glühen des Strangs der Strang auf eine Temperatur in einem Bereich von 400° C bis 460° C erhitzt wird, in the annealing of the strand, the strand is heated to a temperature in a range of 400 ° C to 460 ° C,
wobei der kaltverfestigte Strang während des Erhitzens von einer Schutzgasatmosphäre umgeben ist. wherein the work-hardened strand is surrounded during heating by a protective gas atmosphere.
Verfahren nach Anspruch 1 , dadurch gekennzeichnet, dass der Strang auf eine Temperatur in einem Bereich von 410° C bis 450° C, vorzugsweise in einem Bereich von 435° C bis 445° C und besonders bevorzugt auf 440° C erhitzt wird. A method according to claim 1, characterized in that the strand is heated to a temperature in the range of 410 ° C to 450 ° C, preferably in the range of 435 ° C to 445 ° C, and more preferably 440 ° C.
Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass das Verfahren zusätzlich den Schritt aufweist, Abkühlen des Strangs nach dem Erhitzen, wobei der Strang während dem Abkühlen von einer Schutzgasatmosphäre umgeben ist. A method according to claim 1 or 2, characterized in that the method additionally comprises the step of cooling the strand after heating, wherein the strand is surrounded during cooling by a protective gas atmosphere.
Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass die Schutzgasatmosphäre Argon, vorzugsweise mit einem Anteil an Argon von mehr als 95 Vol.-%, aufweist. Method according to one of the preceding claims, characterized in that the protective gas atmosphere argon, preferably with a proportion of argon of more than 95 vol .-% having.
Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass die Schutzgasatmosphäre einen Sauerstoffgehalt von weniger als 50 ppm, vorzugsweise von weniger als 15 ppm und besonders bevorzugt von weniger als 10 ppm aufweist. Method according to one of the preceding claims, characterized in that the inert gas atmosphere has an oxygen content of less than 50 ppm, preferably less than 15 ppm and more preferably less than 10 ppm.
Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass der Taupunkt der Schutzgasatmosphäre bei Atmosphärendruck bei einer Temperatur von -40° C oder weniger, vorzugsweise von -50° C oder weniger liegt. Method according to one of the preceding claims, characterized in that the dew point of the protective gas atmosphere at atmospheric pressure at a temperature of -40 ° C or less, preferably from -50 ° C or less.
Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass das Material der Luppe ein austenitischer Edelstahl ist. Method according to one of the preceding claims, characterized in that the material of the billet is an austenitic stainless steel.
Verfahren nach Anspruch 7, dadurch gekennzeichnet, dass der Edelstahl Kohlenstoff mit einem Anteil von nicht mehr als 0,06 Gew.-%, Mangan mit einem Anteil von nicht mehr als 2 Gew.-%, Silizium mit einem Anteil von nicht mehr als 0,7 Gew.-%, Chrom mit einem Anteil von 16 Gew.-% bis 20 Gew.-% und Molybdän mit einem Anteil von 2,0 Gew.-% bis 2,6 Gew.-% aufweist mit einem Rest Eisen und unvermeidbaren Verunreinigungen. A method according to claim 7, characterized in that the stainless steel carbon in a proportion of not more than 0.06 wt .-%, manganese in a proportion of not more than 2 wt .-%, silicon in a proportion of not more than 0 , 7 wt .-%, chromium with a From 16 wt .-% to 20 wt .-% and molybdenum in a proportion of 2.0 wt .-% to 2.6 wt .-%, with the remainder iron and unavoidable impurities.
Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass der Strang ein Rohr ist. Method according to one of the preceding claims, characterized in that the strand is a tube.
Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass die Luppe und der Strang in Form eines Rohrs mit einem Innendurchmesser und einem Außendurchmesser vorliegen, wobei durch das Kaltumformen ein Rohr ausgebildet wird, dessen Innendurchmesser die Hälfte des Außendurchmessers oder weniger, vorzugsweise ein Drittel des Außendurchmessers oder weniger beträgt. Method according to one of the preceding claims, characterized in that the billet and the strand in the form of a tube having an inner diameter and an outer diameter, wherein by cold forming a tube is formed whose inner diameter is half of the outer diameter or less, preferably one third of the Outside diameter or less.
Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass das Kaltumformen durch Kaltpilgerwalzen erfolgt. Method according to one of the preceding claims, characterized in that the cold forming is carried out by cold pilgering.
Strang aus Edelstahl hergestellt durch ein Verfahren nach einem der vorhergehenden Ansprüche. Stainless steel strand produced by a process according to any one of the preceding claims.
Strang aus Edelstahl nach Anspruch 12, dadurch gekennzeichnet, dass der Strang ein Rohr mit einem Innendurchmesser und einem Außendurchmesser ist, wobei der Innendurchmesser die Hälfte des Außendurchmessers oder weniger, vorzugsweise ein Drittel des Außendurchmessers oder weniger beträgt. A strand of stainless steel according to claim 12, characterized in that the strand is a tube having an inner diameter and an outer diameter, wherein the inner diameter is half of the outer diameter or less, preferably one third of the outer diameter or less.
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EP3259378B1 (en) 2021-10-13
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US10501820B2 (en) 2019-12-10
US20180223388A1 (en) 2018-08-09
DE102015102255A1 (en) 2016-08-18
JP7080639B2 (en) 2022-06-06
CN107406902A (en) 2017-11-28
WO2016131748A1 (en) 2016-08-25

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