WO2021037567A1 - Spring wire, tension clamp formed therefrom and method for producing such a spring wire - Google Patents

Spring wire, tension clamp formed therefrom and method for producing such a spring wire Download PDF

Info

Publication number
WO2021037567A1
WO2021037567A1 PCT/EP2020/072650 EP2020072650W WO2021037567A1 WO 2021037567 A1 WO2021037567 A1 WO 2021037567A1 EP 2020072650 W EP2020072650 W EP 2020072650W WO 2021037567 A1 WO2021037567 A1 WO 2021037567A1
Authority
WO
WIPO (PCT)
Prior art keywords
spring wire
weight
content
steel
spring
Prior art date
Application number
PCT/EP2020/072650
Other languages
German (de)
French (fr)
Inventor
Lei HU
Dennis Wolf
Original Assignee
Vossloh Fastening Systems Gmbh
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Vossloh Fastening Systems Gmbh filed Critical Vossloh Fastening Systems Gmbh
Priority to US17/636,964 priority Critical patent/US20220275490A1/en
Priority to CN202080059418.3A priority patent/CN114341387B/en
Publication of WO2021037567A1 publication Critical patent/WO2021037567A1/en

Links

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
    • 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
    • C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
    • 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
    • C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
    • C21D8/065—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires 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
    • C21D9/02—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for springs
    • 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
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • 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
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • 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
    • C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
    • 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
    • C22C38/34—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of silicon
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C21D1/25—Hardening, combined with annealing between 300 degrees Celsius and 600 degrees Celsius, i.e. heat refining ("Vergüten")
    • 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
    • C21D6/02—Hardening by precipitation

Definitions

  • the invention relates to a spring wire made from a spring steel with a carbon content of 0.35-0.42% by weight.
  • the invention relates to a tension clamp for holding down a rail for rail vehicles in a rail fastening point, which is formed from such a spring wire, and a method for producing a spring wire of the type in question here.
  • the rail to be fastened is fastened to the subsurface that supports the track to which the rail belongs.
  • the subsurface can be formed by a conventional sleeper made of wood or by sleepers or plates that are formed from a concrete or a plastic material.
  • the rail fastening point typically comprises at least one guide plate, which rests laterally on the rail and, during use, transfers the transverse forces acting on the rail into the ground, and a tension clamp which is braced against the ground against the tension clamps. With the end of at least one spring arm, the tension clamp exerts an elastically resilient hold-down force on the rail foot, by means of which the rail is held pressed against the ground.
  • the hold-down forces can be applied particularly effectively by means of W- or W-shaped tension clamps, which act on the rail foot with the free ends of their two spring arms.
  • tension clamps of this type are the products explained under URL https://www.vossloh.com/de/ effort-und-loesungen / . . .finder / (found on August 12, 2019).
  • the spring wires that are required to produce tension clamps typically have a circular diameter of 9-15 mm.
  • the individual sections of a tension clamp are either predominantly subjected to bending or torsion loads, with more or less strong proportions of the other form of load being added to the dominant load in each case.
  • the usual manufacturing route for their production includes the steps of “casting molten steel into bars”, “heating the bars through” and “hot rolling the bars to form a spring wire”, “cooling the hot-rolled spring wire” and depositing or winding the spring wire into a coil ", whereby the hot rolling is usually carried out in several steps, which include rolling, intermediate rolling and finish rolling of the slab to form the spring wire.
  • the work steps to be carried out and the influencing variables to be observed are known to the person skilled in the art (see, for example, Stahl Fibel, 2015, Verlag Stahleisen GmbH, Düsseldorf, ISBN 978-3-514-00815-1).
  • the tension clamps are cold-formed from the spring wires produced in this way.
  • rods are cut to length from the spring wires, which are then usually bent in several steps to form the tension clamp. In this way it is possible to produce tension clamps with a complex shape.
  • the tension clamps obtained are then subjected to a heat treatment in which they are heated to a temperature above Ac3 and then quenched in order to optimize their mechanical properties by hardening.
  • the aim is to set high tensile strengths Rm and high yield strengths Rp0.2.
  • a ratio of Rm / Rp0.2 of «1 is aimed for in order to be able to apply high resilient hold-down forces with the tension clamps on the one hand and to be able to Extend the range of elastic deformability of the tension clamp and the associated fatigue strength to a maximum.
  • the tensile strengths Rm and elongation limits Rp0.2 for tension clamps of the type in question are in the range of 1200-1400 MPa.
  • thermomechanical rolling In addition to the alloying measures, the mechanical properties of a spring wire provided for the production of spring elements can also be improved by so-called “thermomechanical rolling”.
  • thermomechanical rolling aimed particularly at spring wire, which is intended for the production of flexurally loaded springs, the spring wire is hot-rolled in a temperature range in which its structure has not yet fully recrystallized, but which is above the Ar3 temperature of the steel. In this way, spring wires with a particularly fine structure can be produced, which contributes to a high strength and an optimized spring behavior of the tension clamp (DE 19546204 C1).
  • thermomechanical forming in particular on the treatment of spring wire which is intended for the production of torsion-loaded springs, the rod-shaped starting material is heated to a temperature above at a rate of at least 50 K / s The recrystallization temperature is heated and then reshaped at a temperature at which a dynamic and / or static recrystallization of the austenite results.
  • the austenite of the formed product recrystallized in this way is quenched and tempered (DE 19839383 A1).
  • the spring steel described in CN 105 112774 A should also be mentioned, which can be hardened by air cooling and is said to have high deformability with a comparatively low content of carbon and microalloy elements.
  • this well-known spring steel consists of, in% by weight, 0.15 - 0.50%
  • the steel assembled in this way has been heated to 900 - 1050 ° C and kept at this temperature, it is given a structure through controlled cooling, the main components of which are bainite and martensite and which can also contain smaller amounts of retained austenite.
  • the properties of the steel can be further improved by tempering at low temperatures.
  • the steel treated in this way should have a tensile strength Rm of at least 1350 MPa, a yield point Rp0.2 of at least 1050 MPa and an elongation A of at least 10%.
  • a spring wire which achieves this object has at least the features specified in claim 1.
  • a tension clamp with optimized properties and a method should be specified that enables the practice-oriented production of spring wires according to the invention.
  • a tension clamp for holding down rails for rail vehicles in a rail fastening point which solves this problem, is formed from a spring wire provided according to the invention.
  • a method that achieves the above object comprises, according to the invention, at least the work steps and features specified in claim 14. It goes without saying that when carrying out the method according to the invention, the person skilled in the art not only completes the method steps mentioned in the claims and explained in detail here, but also carries out all other steps and activities that are necessary in the practical implementation of such methods in the prior art Technique should be carried out regularly if the need arises.
  • a spring wire according to the invention is accordingly produced from a steel which, in% by weight,
  • V 0.020-0.10%
  • AI £ 0.03%, and the remainder consists of iron and unavoidable impurities, the content of the sum of impurities being limited to a maximum of 0.2% and including up to 0.025% P and up to 0.025% S among the impurities.
  • the alloy concept provided for the spring wire according to the invention is based on the fact that the tensile strength Rm and the yield strength Rp0.2 are increased by adding additional alloying elements. This makes it possible to keep the carbon content and the associated cold deformability of the spring wire at an optimally low level for practical processing, while at the same time increasing the strength Rm and yield strength Rp0.2 significantly compared to the prior art.
  • the individual alloy components and their contents in the alloy of a spring wire according to the invention have been determined as follows:
  • Carbon (“C”) is present in the spring steel of a spring wire according to the invention in contents of 0.35-0.42% by weight in order to have good deformability, high toughness, good corrosion resistance and low sensitivity to stress- or hydrogen-induced cracking to ensure.
  • C contents of at most 0.40% by weight, in particular less than 0.40% by weight, have proven particularly useful in terms of optimized ductility and the associated optimized deformability at room temperature.
  • Si Silicon
  • the Si content is limited to 1.8% by weight.
  • Manganese (“Mn”) is present in the steel of a spring wire according to the invention in contents of 0.5-0.8% by weight in order to ensure that the spring steel can be sufficiently hardened.
  • Mn binds the sulfur, which is usually unavoidable in steel, to form MnS and thus prevents its harmful effect.
  • This requires at least 0.5% by weight, in particular at least 0.50% by weight, of Mn in the steel, with an optimized effect being achieved with contents of at least 0.6% by weight, in particular at least 0.60% by weight. -% or at least 0.7% by weight, adjusts.
  • Excessively high Mn contents would, however, worsen the brittle-ductile transition temperature (Ductile-Brittle temperature "DBTT”), therefore the Mn content is at most 0.8% by weight, in particular 0.80% by weight, limited.
  • DBTT brittle-ductile transition temperature
  • Chromium (“Cr”) is present in the spring steel of a spring wire according to the invention in contents of 0.05-0.25% in order to further improve the hardenability of the steel.
  • the presence of Cr in the steel according to the invention ensures that the structure of a tension clamp formed from a spring wire according to the invention consists of more than 95 area% of martensite after hardening.
  • a C content of at least 0.05% by weight can reduce the carbon activity and the risk of surface layer decarburization during the heat treatment.
  • the positive effects of Cr in the spring steel of a spring wire according to the invention can be used particularly reliably if a Cr content of at least 0.1% by weight, in particular at least 0.10% by weight or in particular at least 0.18% by weight. -%, is provided.
  • Niobium (“Nb”) is of particular importance for the invention and is present in the spring steel of a spring wire according to the invention in contents of 0.02-0.1% by weight. Nb delays the recrystallization during a thermomechanical rolling carried out in the temperature range of the recrystallization stop temperature-Ar3 temperature of the spring steel, by means of which a particularly fine-grain structure of the spring wire according to the invention is obtained. At the same time, the presence of Nb limits the grain growth if the spring wire according to the invention is heated to the austenitizing temperature and held there during the heat treatment of the tension clamp formed from it.
  • the Nb content of the spring steel of a spring wire according to the invention can be at least 0.0250% by weight, at least 0.0280% by weight or at least 0.030% by weight. Nb can be used particularly effectively at contents of up to 0.070% by weight, in particular up to 0.050% by weight.
  • Vanadium is present in the spring steel of a spring wire according to the invention in contents of 0.020-0.10% by weight.
  • V forms carbides and nitrides with carbon and nitrogen, which are typically fine, for example 8-12 nm, in particular about 10 nm, large carbonitride precipitates are present and, through precipitation hardening, significantly to increase the strength contribute a spring wire according to the invention.
  • V in this way contributes to the relaxation resistance of the spring steel from which a spring wire according to the invention is made.
  • the V content of the spring steel of a spring wire according to the invention can be at least 0.0250% by weight, at least 0.0280% by weight or at least 0.030% by weight.
  • V can be used particularly effectively at contents of up to 0.070% by weight, in particular up to 0.060% by weight.
  • Nb and V according to the invention results in high tensile strengths Rm and, as a rule, approximately the same elongation limits Rp0.2, so that in a tension clamp made from spring wire according to the invention the ratio Rm / Rp0.2 is regularly in the range that is optimal for its service life and spring behavior from 1 to 1.2.
  • N Nitrogen
  • contents of 0.0040-0.0120% by weight (40-120 ppm) in order to enable the formation of vanadium nitrides or vanadium carbonitrides.
  • Excessively high N contents would, however, promote the stretching aging of the spring wire according to the invention, which would be diametrically opposed to the toughness of the spring wire according to the invention and the fatigue strength required by a tension clamp.
  • Negative effects of the presence of N in the spring steel of a spring wire according to the invention can be excluded particularly reliably by limiting the N content to a maximum of 0.0100% by weight (100 ppm).
  • a spring wire composed of a spring steel composed in the manner according to the invention achieves in the hot-rolled condition a tensile test according to DIN EN ISO 6892-1 of at least 55% at break and is therefore regularly higher than the break at break that can be determined for spring wires from a conventionally alloyed 38Si7 steel.
  • DIN EN ISO 6892-1 of at least 55% at break and is therefore regularly higher than the break at break that can be determined for spring wires from a conventionally alloyed 38Si7 steel.
  • ASTM 10 fine-grain structure of at least ASTM 10
  • ASTM E112 This fineness of the structure is largely retained through the cold forming of the spring wire into a tension clamp and the subsequent heat treatment of the tension clamp.
  • tension clamps according to the invention ready for installation in a rail fastening point, regularly have a fineness of their structure which, determined according to ASTM E112, corresponds to at least ASTM 8. This corresponds to an improvement in the fine grain size by at least one of the grain size classes specified in ASTM E112 compared to a tension clamp that is bent from a spring wire made from conventional 38Si7 steel.
  • the method according to the invention for producing a spring wire according to the invention comprises the following work steps: a) Melting a steel made from, in% by weight, C: 0.35-0.42%, Si:
  • Mn 0.50-0.80%
  • Cr 0.05-0.25%
  • Nb 0.020-0.10%
  • V 0.020 - 0.10%
  • N 0.0040 - 0.0120%
  • AI £ 0.03%
  • the remainder consists of iron and unavoidable impurities, the content of the total of impurities being limited to a maximum of 0.2% is limited and the impurities include up to 0.025% P and up to 0.025% S
  • cooling the thermomechanically finished hot-rolled spring wire at a cooling rate of 1 - 5 ° C / s to a winding temperature of 550 - 650 ° C
  • the spring wire is thus subjected to a thermomechanical rolling step in the course of hot rolling, in which it is rolled at temperatures which are rolled below the recrystallization stop temperature and above the Ar3 temperature of the steel.
  • the “recrystallization stop temperature” is the temperature at which the spring wire has cooled down to such an extent that its previously austenitic structure no longer recrystallizes. Due to the thermomechanical rolling carried out in the temperature range specified according to the invention in combination with the alloy selected according to the invention, in particular due to the simultaneous presence of Nb and V, the particularly fine-grain structure is obtained, which characterizes a spring wire according to the invention in the hot-rolled state.
  • the cooling of the hot-rolled spring wire at the cooling speeds specified according to the invention and compliance with the winding temperatures of 550-650 ° C prescribed according to the invention ensure that a maximum hardness of the spring wire according to the invention is achieved as a result of precipitation hardening.
  • the “thermomechanical rolling” sub-step in a separate operation. to be carried out, which is carried out after the actual hot rolling of the spring wire.
  • the then hot-rolled spring wire provided is first opened Austenitizing temperature, then cooled to a temperature below the recrystallization stop temperature but above the Ar3 temperature of the spring steel and hot-rolled at this temperature with a sufficient degree of deformation. This is followed by the cooling and the laying down or winding of the spring wire as indicated in steps d) and e) of the method according to the invention.
  • a technologically and economically optimized variant of the method according to the invention provides that all partial steps of hot rolling (work step c)) are completed in a continuous cycle, that is, a thermomechanically finished hot-rolled spring wire is present when the spring wire leaves the hot-rolling section used in each case.
  • a comparative melt V1 was melted, the C, Si, Mn, P, S and N contents of which corresponded to the requirements applicable to the known 38Si7 steel, but which also had an effective content of Cr.
  • the composition of the comparative melt V1 is also given in Table 1.
  • the recrystallization stop temperature of the respective spring steel from which the respective spring wire E1-E5.V1 is produced can be determined experimentally in a manner known per se or can be estimated with the aid of empirically determined formulas.
  • the Ar3 and Ar1 temperatures of the respective spring steel from which the respective spring wire E1-E5, V1 is produced can be determined experimentally in a manner known per se, for example by means of dilatometry in a thermomechanical simulator.
  • the hot-rolled spring wires obtained were cooled at a cooling rate of 1-5 ° C./s to a winding temperature of 550-650 ° C., at which they were wound into a coil.
  • the spring wires in the coil were then cooled to room temperature.
  • ASTM E112 the grain size "ASTM_F” of the structure and according to DIN EN ISO 6892-1 the fracture necking "Z_F” was determined on the hot-rolled spring wires obtained.
  • the obtained values "ASTM_F” and “Z_F” are given in table 2 for the spring wires made of steels E1 - E5 and V1.
  • the tension clamps After quenching, the tension clamps have undergone a tempering process in which they are heated to a tempering temperature of 400-450 ° C over a period of 60-120 minutes and held there. The tension clamps, which had been tempered in this way, were then cooled to room temperature in air.
  • the tensile strength Rm and the yield strength Rp0.2 were determined in accordance with DIN EN ISO 6892-1.
  • DIN EN ISO 148-1 the notched impact energy KV-20 has been determined as a characteristic value for toughness.
  • the measured values obtained are listed in Table 2. It was found that not only the tensile strength Rm and the yield strength Rp0.2 of the tension clamps produced from spring steel E1 composed according to the invention in the manner according to the invention could be significantly increased with unchanged impact work KV-20 compared to the tension clamps made from the comparative steel V1, but that the ratio Rm / Rp0.2 has also remained practically the same.
  • the tension clamps produced from the spring steels E1-E5 according to the invention had a significantly better fine-grain “ASTM” structure, determined in accordance with ASTM E112, than the tension clamps made from the comparative steel V1.

Abstract

The invention provides a spring wire that can be effectively cold-formed even at a diameter of at least 9 mm and nevertheless has improved mechanical properties. To achieve this, a spring wire according to the invention is provided, made of steel which, in wt.%, consists of C: 0.35-0.42%, Si: 1.5-1.8%, Mn: 0.5-0.8%, Cr: 0.05-0.25%, Nb: 0.020-0.10%, V: 0.020-0.10%, N: 0.0040-0.0120%, AI: < 0.03%, and, as the rest, iron and unavoidable impurities, wherein the amount of the sum of impurities is limited to at most 0.2 % and the impurities include up to 0.025% P and up to 0.025% S. The spring wire according to the invention is suitable in particular for producing a tension clamp having optimised usage properties. The invention also discloses a method that enables spring wires according to the invention to be produced in a practical manner.

Description

FEDERDRAHT, DARAUS GEFORMTE SPANNKLEMME UND VERFAHREN ZUM HERSTELLEN EINES SOLCHEN FEDERDRAHTS SPRING WIRE, TENSION CLAMP SHAPED THEREOF AND METHOD FOR MANUFACTURING SUCH SPRING WIRE
Die Erfindung betrifft einen Federdraht, der aus einem Federstahl mit einem Kohlenstoffgehalt von 0,35 - 0,42 Gew.-% hergestellt ist. The invention relates to a spring wire made from a spring steel with a carbon content of 0.35-0.42% by weight.
Darüber hinaus betrifft die Erfindung eine Spannklemme zum Niederhalten einer Schiene für Schienenfahrzeuge in einem Schienenbefestigungspunkt, die aus einem solchen Federdraht geformt ist, und ein Verfahren zur Herstellung eines Federdrahts der hier in Rede stehenden Art. In addition, the invention relates to a tension clamp for holding down a rail for rail vehicles in a rail fastening point, which is formed from such a spring wire, and a method for producing a spring wire of the type in question here.
In einem „Schienenbefestigungspunkt“ ist die jeweils zu befestigende Schiene auf dem Untergrund befestigt, der das Gleis, zu dem die Schiene gehört, trägt. Der Untergrund kann dabei durch eine konventionelle, aus Holz bestehende Schwelle oder durch Schwellen oder Platten gebildet sein, die aus einem Beton- oder einem Kunststoff-Werkstoff geformt sind. Der Schienenbefestigungspunkt umfasst typischerweise mindestens eine Führungsplatte, die seitlich an der Schiene anliegt und im Gebrauch die auf die Schiene wirkende Querkräfte in den Untergrund äbleitet, und eine Spannklemme, die gegen den Untergrund die Spannklemmen verspannt ist. Die Spannklemme übt mit dem Ende mindestens eines Federarms auf den Schienenfuß eine elastisch federnde Niederhaltekraft aus, durch die die Schiene gegen den Untergrund gedrückt gehalten wird. Besonders effektiv lassen sich die Niederhaltekräfte durch W- oder w-förmig geformte Spannklemmen aufbringen, die mit den freien Enden ihrer beiden Federarme auf den Schienenfuß wirken. Beispiele für derartig geformte Spannklemmen sind die unter URL https://www.vossloh.com/de/produkte-und- loesungen/produktfinder/ (Auffindedatum 12. August 2019) erläuterten Produkte. In a "rail fastening point", the rail to be fastened is fastened to the subsurface that supports the track to which the rail belongs. The subsurface can be formed by a conventional sleeper made of wood or by sleepers or plates that are formed from a concrete or a plastic material. The rail fastening point typically comprises at least one guide plate, which rests laterally on the rail and, during use, transfers the transverse forces acting on the rail into the ground, and a tension clamp which is braced against the ground against the tension clamps. With the end of at least one spring arm, the tension clamp exerts an elastically resilient hold-down force on the rail foot, by means of which the rail is held pressed against the ground. The hold-down forces can be applied particularly effectively by means of W- or W-shaped tension clamps, which act on the rail foot with the free ends of their two spring arms. Examples of tension clamps of this type are the products explained under URL https://www.vossloh.com/de/produkte-und-loesungen / produktfinder / (found on August 12, 2019).
Die Federdrähte, die für die Erzeugung von Spannklemmen benötigt werden, weisen typischerweise kreisrunde Durchmesser von 9 - 15 mm auf. Dabei sind im praktischen Gebrauch die einzelnen Abschnitte einer Spannklemme, entweder überwiegend biege- oder torsionsbelastet, wobei zu der jeweils dominierenden Belastung mehr oder weniger starke Anteile der jeweils anderen Belastungsform hinzukommen können. The spring wires that are required to produce tension clamps typically have a circular diameter of 9-15 mm. In practical use, the individual sections of a tension clamp are either predominantly subjected to bending or torsion loads, with more or less strong proportions of the other form of load being added to the dominant load in each case.
Die übliche Herstellungsroute für ihre Herstellung umfasst die Arbeitsschritte „Vergießen einer Stahlschmelze zu Barren“, „Durcherwärmen der Barren“ und „Warmwalzen der Barren zu einem Federdraht“, „Abkühlen des warmgewalzten Federdrahts“ und Ablegen oder Wickeln des Federdrahts zu einem Coil“, wobei das Warmwalzen üblicherweise in mehreren Schritten durchgeführt wird, die ein Vonvalzen, Zwischenwalzen und Fertigwalzen der Bramme zu dem Federdraht umfassen. Die hierbei zu durchlaufenden Arbeitsschritte und zu beachtenden Einflussgrößen sind dem Fachmann bekannt (s. beispielsweise Stahl Fibel, 2015, Verlag Stahleisen GmbH, Düsseldorf, ISBN 978-3-514-00815-1). The usual manufacturing route for their production includes the steps of "casting molten steel into bars", "heating the bars through" and "hot rolling the bars to form a spring wire", "cooling the hot-rolled spring wire" and depositing or winding the spring wire into a coil ", whereby the hot rolling is usually carried out in several steps, which include rolling, intermediate rolling and finish rolling of the slab to form the spring wire. The work steps to be carried out and the influencing variables to be observed are known to the person skilled in the art (see, for example, Stahl Fibel, 2015, Verlag Stahleisen GmbH, Düsseldorf, ISBN 978-3-514-00815-1).
Aus den so erzeugten Federdrähten werden die Spannklemmen kaltgeformt. Hierzu werden von den Federdrähten Stäbe abgelängt, die dann in der Regel in mehreren Schritten zu der Spannklemme gebogen werden. Auf diese Weise ist es möglich, Spannklemmen von komplexer Formgebung zu erzeugen. Die erhaltenen Spannklemmen werden abschließend einer Wärmebehandlung unterzogen, bei der sie auf eine oberhalb der Ac3 liegenden Temperatur erwärmt und anschließend abgeschreckt werden, um durch Härten ihre mechanischen Eigenschaften zu optimieren. Ziel ist dabei die Einstellung hoher Zugfestigkeiten Rm und hoher Dehngrenzen Rp0,2. Dabei wird ein Verhältnis Rm/Rp0,2 von « 1 angestrebt, um einerseits mit den Spannklemmen hohe federnde Niederhaltekräfte aufbringen zu können und um andererseits den Bereich der elastischen Verformbarkeit der Spannklemme und damit einhergehend ihr Dauerschwingfestigkeit maximal auszudehnen. Typischerweise liegen die Zugfestigkeiten Rm und Dehngrenzen Rp0,2 bei Spannklemmen der hier in Rede stehenden Art hierzu im Bereich von 1200 - 1400 MPa. The tension clamps are cold-formed from the spring wires produced in this way. For this purpose, rods are cut to length from the spring wires, which are then usually bent in several steps to form the tension clamp. In this way it is possible to produce tension clamps with a complex shape. The tension clamps obtained are then subjected to a heat treatment in which they are heated to a temperature above Ac3 and then quenched in order to optimize their mechanical properties by hardening. The aim is to set high tensile strengths Rm and high yield strengths Rp0.2. A ratio of Rm / Rp0.2 of «1 is aimed for in order to be able to apply high resilient hold-down forces with the tension clamps on the one hand and to be able to Extend the range of elastic deformability of the tension clamp and the associated fatigue strength to a maximum. Typically, the tensile strengths Rm and elongation limits Rp0.2 for tension clamps of the type in question are in the range of 1200-1400 MPa.
Eine Steigerung der Festigkeit durch beispielsweise die Erhöhung des Kohlenstoffgehalts sind hier durch die Anforderung, dass der Federdraht noch kaltverformt verwenden soll, Grenzen gesetzt. Ein in der Praxis für die Herstellung von Federdrähten für Spannklemmen bewährter, gemäß DIN EN 10089:2002 Unter der Bezeichnung „38Si7“ genormter und mit der Werkstoffhummer 1.5023 in der StahlEisen-Liste verzeichneter Stahl besteht daher aus, in Gew.-%, 0,35 - 0,42 % C, 1,50 - 1 ,80 % Si, 0,50 - 0,80 % Mn und als Rest aus Eisen und unvermeidbaren Verunreinigungen, wobei zu den unvermeidbaren Verunreinigungen bis zu 0,025 % P und bis zu 0,025 % S zählen. An increase in strength, for example by increasing the carbon content, is limited here by the requirement that the spring wire should still be cold-formed. A steel that has proven itself in practice for the production of spring wires for tension clamps, in accordance with DIN EN 10089: 2002 under the designation "38Si7" and listed with the material number 1.5023 in the StahlEisen list, therefore consists of, in% by weight, 0, 35-0.42% C, 1.50-1, 80% Si, 0.50-0.80% Mn and the remainder of iron and unavoidable impurities, with the unavoidable impurities up to 0.025% P and up to 0.025 Count% S.
Neben den legierungstechnischen Maßnahmen können die mechanischen Eigenschaften eines zur Herstellung von Federelementen vorgesehenen Federdrahts auch durch ein so genanntes „thermomechanisches Walzen“ verbessert werden. Bei einer insbesondere auf Federdraht, der zur Herstellung von biegebelasteten Federn vorgesehen ist, abzielenden Variante eines solchen thermomechanischen Walzens wird der Federdraht in einem Temperaturbereich warmgewalzt, in dem sein Gefüge noch nicht vollständig rekristallisiert ist, der jedoch oberhalb der Ar3-Temperatur des Stahls liegt. Auf diese Weise lassen sich Federdrähte mit besonders feinem Gefüge erzeugen, welches zu einer hohen Festigkeit und einem optimierten Federverhalten der Spannklemme beiträgt (DE 19546204 C1). Bei einer insbesondere auf die Behandlung von Federdraht, der für die Herstellung von torsionsbelasteten Federn vorgesehen ist, anderen Variante einer thermomechanischen Umformung wird das stabförmige Ausgangsmaterial mit einer Aufheizgeschwindigkeit von wenigstens 50 K/s auf eine Temperatur oberhalb der Rekristallisationstemperatur aufgeheizt und anschließend bei einer Temperatur umgeformt, bei der sich eine dynamische und/oder statische Rekristallisation des Austenits ergibt. Der derart rekristallisierte Austenit des Umformerzeugnisses wird abgeschreckt und angelassen (DE 19839383 A1). In addition to the alloying measures, the mechanical properties of a spring wire provided for the production of spring elements can also be improved by so-called “thermomechanical rolling”. In a variant of such thermomechanical rolling aimed particularly at spring wire, which is intended for the production of flexurally loaded springs, the spring wire is hot-rolled in a temperature range in which its structure has not yet fully recrystallized, but which is above the Ar3 temperature of the steel. In this way, spring wires with a particularly fine structure can be produced, which contributes to a high strength and an optimized spring behavior of the tension clamp (DE 19546204 C1). In another variant of thermomechanical forming, in particular on the treatment of spring wire which is intended for the production of torsion-loaded springs, the rod-shaped starting material is heated to a temperature above at a rate of at least 50 K / s The recrystallization temperature is heated and then reshaped at a temperature at which a dynamic and / or static recrystallization of the austenite results. The austenite of the formed product recrystallized in this way is quenched and tempered (DE 19839383 A1).
Ergänzend zu dem voranstehend erläuterten Stand der Technik ist noch der in der CN 105 112774 A beschriebene Federstahl zu nennen, der durch Luftkühlung härtbar ist und bei einem vergleichbar niedrigen Gehalt an Kohlenstoff und Mikrolegierungselementen eine hohe Verformbarkeit besitzen soll. Hierzu besteht dieser bekannte Federstahl aus, in Gew.-%, 0,15 - 0,50 %In addition to the prior art explained above, the spring steel described in CN 105 112774 A should also be mentioned, which can be hardened by air cooling and is said to have high deformability with a comparatively low content of carbon and microalloy elements. For this purpose, this well-known spring steel consists of, in% by weight, 0.15 - 0.50%
C, 0,30 - 2,00 % Si, 0,60 - 2,50 % Mn, bis zu 0,020 % S, bis zu 0,025 % P, 0,0005 - 0,0035 % B und als Rest aus Fe. Nachdem der so zusammengesetzte Stahl auf 900 - 1050 °C erhitzt und bei dieser Temperatur gehalten worden ist, erhält er durch kontrolliertes Abkühlen ein Gefüge, dessen Hauptbestandteile Bainit und Martensit sind und das zusätzlich kleinere Anteile an Restaustenit aulweisen kann. Durch Tieftemperaturanlassen können die Eigenschaften des Stahls weiter verbessert werden. Der so behandelte Stahl soll eine Zugfestigkeit Rm von mindestens 1350 MPa, eine Streckgrenze Rp0,2 von mindestens 1050 MPa und eine Dehnung A von mindestens 10 % aufweisen. C, 0.30-2.00% Si, 0.60-2.50% Mn, up to 0.020% S, up to 0.025% P, 0.0005-0.0035% B and the remainder of Fe. After the steel assembled in this way has been heated to 900 - 1050 ° C and kept at this temperature, it is given a structure through controlled cooling, the main components of which are bainite and martensite and which can also contain smaller amounts of retained austenite. The properties of the steel can be further improved by tempering at low temperatures. The steel treated in this way should have a tensile strength Rm of at least 1350 MPa, a yield point Rp0.2 of at least 1050 MPa and an elongation A of at least 10%.
Ausgehend von dem voranstehend erläuterten Stand der Technik hat sich die Aufgabe gestellt, einen Federdrahtzu schaffen, der sich auch bei Durchmessern von mindestens 9 mm gut kaltverformen lässt, dabei jedoch verbesserte mechanische Eigenschaften besitzt. Based on the prior art explained above, the task has been to create a spring wire which can be cold worked well even with diameters of at least 9 mm, but which has improved mechanical properties.
Ein diese Aufgabe lösender Federdraht besitzt gemäß der Erfindung mindestens die in Anspruch 1 angegebenen Merkmale. According to the invention, a spring wire which achieves this object has at least the features specified in claim 1.
Darüber hinaus sollte eine Spannklemme mit optimierten Eigenschaften und ein Verfahren angegeben werden, das die praxisgerechte Erzeugung von erfindungsgemäßen Federdrähten ermöglicht. Eine Spannklemme zum Niederhalten von Schienen für Schienenfahrzeuge in einem Schienenbefestigungspunkt, die diese Aufgabe löst, ist aus einem erfindungsgemäß beschaffenen Federdraht geformt. In addition, a tension clamp with optimized properties and a method should be specified that enables the practice-oriented production of spring wires according to the invention. A tension clamp for holding down rails for rail vehicles in a rail fastening point, which solves this problem, is formed from a spring wire provided according to the invention.
Ein Verfahren, dass die voranstehende Aufgabe löst, umfasst gemäß der Erfindung mindestens die in Anspruch 14 angegebenen Arbeitsschritte und Merkmale. Dabei versteht es sich von selbst, dass bei der Durchführung des erfindungsgemäßen Verfahrens der Fachmann nicht nur die in den Ansprüchen erwähnten und hier im Detail erläuterten Verfahrensschritte absolviert, sondern auch alle sonstigen Schritte und Tätigkeiten ausführt, die bei der praktischen Umsetzung derartiger Verfahren im Stand der Technik regelmäßig durchgeführt werden, wenn sich hierzu die Notwendigkeit ergibt. A method that achieves the above object comprises, according to the invention, at least the work steps and features specified in claim 14. It goes without saying that when carrying out the method according to the invention, the person skilled in the art not only completes the method steps mentioned in the claims and explained in detail here, but also carries out all other steps and activities that are necessary in the practical implementation of such methods in the prior art Technique should be carried out regularly if the need arises.
Vorteilhafte Ausgestaltungen der Erfindung sind in den abhängigen Ansprüchen angegeben und werden wie der allgemeine Erfindungsgedanke nachfolgend im Einzelnen erläutert. Advantageous embodiments of the invention are specified in the dependent claims and, like the general inventive concept, are explained in detail below.
Im vorliegenden Text sind, soweit nicht explizit etwas anderes vermerkt ist, Angaben zu den Gehalten von Legierungsbestandteilen stets in Gew.-% gemacht. Unless explicitly stated otherwise, information on the content of alloy components is always given in% by weight in the present text.
Ein erfindungsgemäßer Federdraht ist demnach hergestellt aus einem Stahl, der aus, in Gew.-%, A spring wire according to the invention is accordingly produced from a steel which, in% by weight,
C: 0,35 - 0,42 %, C: 0.35-0.42%,
Si: .1,5 - 1,8 %, Si: 1.5-1.8%,
Mn: 0,5 - 0,8 %, Mn: 0.5-0.8%,
Cr 0,05 - 0,25 %, Cr 0.05-0.25%,
Nb: 0,020 - 0,10 %, Nb: 0.020-0.10%,
V: 0,020 - 0,10 %, V: 0.020-0.10%,
N: 0,0040 - 0,0120 %, N: 0.0040 - 0.0120%,
AI: £ 0,03 %, und als Rest aus Eisen und unvermeidbaren Verunreinigungen besteht, wobei der Gehalt der Summe an Verunreinigungen auf höchstens 0,2 % beschränkt ist und zu den Verunreinigungen bis zu 0,025 % P und bis zu 0,025 % S zählen. AI: £ 0.03%, and the remainder consists of iron and unavoidable impurities, the content of the sum of impurities being limited to a maximum of 0.2% and including up to 0.025% P and up to 0.025% S among the impurities.
Das erfindungsgemäß für den Federdraht vorgesehene Legierungskonzept basiert darauf, dass die Zugfestigkeit Rm und die Dehngrenze Rp0,2 durch Zugabe zusätzlicher Legierungselemente erhöht werden. Dies erlaubt es, den Kohlenstoffgehalt und damit einhergehend die Kaltverformbarkeit des Federdrahts auf einem für die praktische Verarbeitung optimal niedrigen Niveau zu halten, gleichzeitig aber die Festigkeit Rm und Dehngrenze Rp0,2 deutlich gegenüber dem Stand der Technik anzuheben. Im Einzelnen sind die einzelnen Legierungsbestandteile und ihre Gehalte in der Legierung eines erfindungsgemäßen Federdrahts wie folgt bestimmt worden: The alloy concept provided for the spring wire according to the invention is based on the fact that the tensile strength Rm and the yield strength Rp0.2 are increased by adding additional alloying elements. This makes it possible to keep the carbon content and the associated cold deformability of the spring wire at an optimally low level for practical processing, while at the same time increasing the strength Rm and yield strength Rp0.2 significantly compared to the prior art. In detail, the individual alloy components and their contents in the alloy of a spring wire according to the invention have been determined as follows:
Kohlenstoff („C“) ist im Federstahl eines erfindungsgemäßen Federdrahts in Gehalten von 0,35 - 0,42 Gew.-% Vorhanden, um eine gute Verformbarkeit, eine hohe Zähigkeit, eine gute Korrosionsbeständigkeit und eine geringe Empfindlichkeit gegen stress- oder wasserstoffinduzierte Rissbildung zu gewährleisten. Dabei haben sich C-Gehalte von höchstens 0,40 Gew.-%, insbesondere weniger als 0,40 Gew.-%, im Hinblick auf eine optimierte Duktilität und eine damit einhergehend optimierte Verformbarkeit bei Raumtemperatur besonders bewährt. Carbon (“C”) is present in the spring steel of a spring wire according to the invention in contents of 0.35-0.42% by weight in order to have good deformability, high toughness, good corrosion resistance and low sensitivity to stress- or hydrogen-induced cracking to ensure. C contents of at most 0.40% by weight, in particular less than 0.40% by weight, have proven particularly useful in terms of optimized ductility and the associated optimized deformability at room temperature.
Silizium („Si“) ist im Stahl eines erfindungsgemäßen Federdrahts in Gehalten von 1,5 - 1,8 Gew.-%, insbesondere 1,50 - 1,80 Gew.-%, vorhanden, um durch Mischkristallverfestigung eine hohe Festigkeit zu gewährleisten. Darüber hinaus sichert der hohe Si-Gehalt eine gute Beständigkeit („Relaxationsbeständigkeit“) gegen eine Abnahme der Festigkeitswerte des Federdrahts im Züge der Wärmebehandlung, die aus erfindungsgemäßem Federdraht geformte Spannklemmen nach ihrer Kaltformgebung regelmäßig durchlaufen. Hierzu sind Si-Gehalte von mindestens 1,5 Gew.-% erforderlich. Zu hohe Si-Gehalte würden jedoch die Zähigkeit herabsetzen, das Risiko der Entkohlung im Zuge der Wärmebehandlung erhöhen und darüber hinaus zur Grdbkombildung beitragen. Daher bleibt der Si-Gehalt erfindungsgemäß auf 1,8 Gew.-% beschränkt. Silicon (“Si”) is present in the steel of a spring wire according to the invention in contents of 1.5-1.8% by weight, in particular 1.50-1.80% by weight, in order to ensure high strength through solid solution strengthening . In addition, the high Si content ensures good resistance (“relaxation resistance”) against a decrease in the strength values of the spring wire in the course of the heat treatment, which tension clamps formed from spring wire according to the invention regularly go through after their cold forming. This requires Si contents of at least 1.5% by weight. However, excessively high Si contents would reduce the toughness and the risk of decarburization in the course of the process increase the heat treatment and also contribute to the formation of grdbkom. Therefore, according to the invention, the Si content is limited to 1.8% by weight.
Mangan („Mn“) ist im Stähl eines erfindungsgemäßen Federdrahts in Gehalten von 0,5 - 0,8 Gew.-% vorhanden, um eine ausreichende Härtbarkeit des Federstahls zu gewährleisten. Darüber hinaus bindet Mn den im Stahl in der Regel herstellungsbedingt unvermeidbaren Schwefel zu MnS und verhindert so dessen schädliche Wirkung. Hierzu sind mindestens 0,5 Gew.-%, insbesondere mindestens 0,50 Gew.-%, Mn im Stahl erforderlich, wobei sich eine optimierte Wirkung bei Gehalten von mindestens 0,6 Gew.-%, insbesondere mindestens 0,60 Gew.-% oder mindestens 0,7 Gew.-%, einstellt. Zu hohe Mn-Gehalte würden allerdings die Spröd-Duktil-Übergangstemperatur (Ductile-Brittle- Temperature „DBTT“) verschlechtern, daher ist der Mn-Gehalt auf höchstens 0,8 Gew.-%, insbesondere 0,80 Gew.-%, beschränkt. Manganese (“Mn”) is present in the steel of a spring wire according to the invention in contents of 0.5-0.8% by weight in order to ensure that the spring steel can be sufficiently hardened. In addition, Mn binds the sulfur, which is usually unavoidable in steel, to form MnS and thus prevents its harmful effect. This requires at least 0.5% by weight, in particular at least 0.50% by weight, of Mn in the steel, with an optimized effect being achieved with contents of at least 0.6% by weight, in particular at least 0.60% by weight. -% or at least 0.7% by weight, adjusts. Excessively high Mn contents would, however, worsen the brittle-ductile transition temperature (Ductile-Brittle temperature "DBTT"), therefore the Mn content is at most 0.8% by weight, in particular 0.80% by weight, limited.
Chrom („Cr“) ist im Federstahl eines erfindungsgemäßen Federdrahts in Gehalten von 0,05 - 0,25 % vorhanden, um die Härtbarkeit des Stahls weiter zu verbessern. Dabei stellt die Anwesenheit von Cr im erfindungsgemäßen Stahl sicher, dass das Gefüge einer aus einem erfindungsgemäßen Federdraht geformten Spannklemme nach dem Härten zu mehr als 95 Flächen-% aus Martensit besteht. Durch einen C-Gehalt von mindestens 0,05 Gew.-% kann darüber hinaus die Kohlenstoffaktivität und das Risiko einer Randschichtentkohlung bei der Wärmebehandlung vermindert werden. Die positiven Effekte von Cr im Federstahl eines erfindungsgemäßen Federdrahts lassen sich dabei dadurch besonders sicher nutzen, däss ein Cr-Gehalt von mindestens 0,1 Gew.-%, insbesondere mindestens 0,10 Gew.-% oder insbesondere mindestens 0,18 Gew.-%, vorgesehen wird. Bei oberhalb von 0,25 Gew.-% liegenden Cr-Gehalten besteht dagegen die Gefahr, dass die Zähigkeit und die Relaxationsbeständigkeit des Federstahls beeinträchtigt würden. Aluminium („AI“) wird im erfindungsgemäßen Stahl nicht zur Desoxidation bei der Stahlerzeugung benötigt, kann aber dem Federstahl optional in Gehalten von bis zu 0,03 Gew.-% zugegeben werden, um die Ausprägung eines feinkörnigen Gefüges zu unterstützen. Höhere Al-Gehalte würden jedoch durch eine übermäßige Bildung von Al-Oxiden oder -Nitriden die Reinheit des Stahls eines erfindungsgemäßen Stahls und damit einhergehend seine Zähigkeit beeinträchtigen. Chromium (“Cr”) is present in the spring steel of a spring wire according to the invention in contents of 0.05-0.25% in order to further improve the hardenability of the steel. The presence of Cr in the steel according to the invention ensures that the structure of a tension clamp formed from a spring wire according to the invention consists of more than 95 area% of martensite after hardening. In addition, a C content of at least 0.05% by weight can reduce the carbon activity and the risk of surface layer decarburization during the heat treatment. The positive effects of Cr in the spring steel of a spring wire according to the invention can be used particularly reliably if a Cr content of at least 0.1% by weight, in particular at least 0.10% by weight or in particular at least 0.18% by weight. -%, is provided. In contrast, if the Cr content is above 0.25% by weight, there is a risk that the toughness and the relaxation resistance of the spring steel would be impaired. Aluminum (“Al”) is not required in the steel according to the invention for deoxidation during steel production, but can optionally be added to the spring steel in contents of up to 0.03% by weight in order to support the development of a fine-grain structure. However, higher Al contents would impair the purity of the steel of a steel according to the invention and, as a result, its toughness due to an excessive formation of Al oxides or nitrides.
Niob („Nb“) ist von besonderer Bedeutung für die Erfindung und im Federstahl eines erfindungsgemäßen Federdrahts in Gehalten von 0,02 - 0,1 Gew.-% vorhanden. Nb verzögert die Rekristallisation während eines im Temperaturbereich Rekristallisationsstopptemperatur - Ar3-Temperatur des Federstahls durchgeführten thermomechanischen Walzens, durch das ein besonders feinkörniges Gefüge des erfindungsgemäßen Federdrahts erhalten wird. Gleichzeitig wird durch die Anwesenheit von Nb das Komwachstum begrenzt, wenn der erfindungsgemäße Federdraht bei der Wärmebehandlung der aus ihm geformten Spannklemme auf Austenitisierungstemperatur erwärmt und dort gehalten wird. Im Ergebnis wird durch die erfindungsgemäße Zugabe von Nb und die dadurch bewirkte Ausprägung eines besonders feinkörnigen Gefüges, das auch über die Wärmebehandlung, die eine Spannklemme abschließend durchläuft, erhalten bleibt, eine deutliche Verbesserung der Festigkeit erzielt. Um die positive Wirkung von Nb besonders sicher einsetzen zu können, kann der Nb-Gehalt des Federstahls eines erfindungsgemäßen Federdrähts mindestens 0,0250 Gew.-%, mindestens 0,0280 Gew.-% oder mindestens 0,030 Gew.-% betragen. Besonders effektiv lässt sich Nb dabei bei Gehalten von bis zu 0,070 Gew.-%, insbesondere bis zu 0,050 Gew.-%, nutzen. Niobium (“Nb”) is of particular importance for the invention and is present in the spring steel of a spring wire according to the invention in contents of 0.02-0.1% by weight. Nb delays the recrystallization during a thermomechanical rolling carried out in the temperature range of the recrystallization stop temperature-Ar3 temperature of the spring steel, by means of which a particularly fine-grain structure of the spring wire according to the invention is obtained. At the same time, the presence of Nb limits the grain growth if the spring wire according to the invention is heated to the austenitizing temperature and held there during the heat treatment of the tension clamp formed from it. As a result, the addition of Nb according to the invention and the resulting development of a particularly fine-grain structure, which is also retained through the heat treatment that a tension clamp finally undergoes, achieves a significant improvement in strength. In order to be able to use the positive effect of Nb particularly reliably, the Nb content of the spring steel of a spring wire according to the invention can be at least 0.0250% by weight, at least 0.0280% by weight or at least 0.030% by weight. Nb can be used particularly effectively at contents of up to 0.070% by weight, in particular up to 0.050% by weight.
Vanadium („V") ist im Federstahl eines erfindungsgemäßen Federdrahts in Gehalten von 0,020 - 0,10 Gew.-% vorhanden. V bildet mit Kohlenstoff und Stickstoff Karbide und Nitride, die typischerweise als feine, beispielsweise 8 - 12 nm, insbesondere etwa 10 nm, große Karbonitrid-Ausscheidungen vorliegen und durch Ausscheidungshärtung wesentlich zur Steigerung der Festigkeit eines erfindungsgemäßen Federdrahts beitragen. Gleichzeitig trägt V auf diese Weise zur Relaxationsbeständigkeit des Federstahls bei, aus dem ein erfindungsgemäßer Federdraht besteht. Um die positive Wirkung von V besonders sicher einsetzen zu können, kann der V-Gehalt des Federstahls eines erfindungsgemäßen Federdrahts mindestens 0,0250 Gew.-%, mindestens 0,0280 Gew.-% oder mindestens 0,030 Gew.-% betragen. Besonders effektiv lässt sich V dabei bei Gehalten von bis zu 0,070 Gew.-%, insbesondere bis zu 0,060 Gew.-%, nutzen. Vanadium ("V") is present in the spring steel of a spring wire according to the invention in contents of 0.020-0.10% by weight. V forms carbides and nitrides with carbon and nitrogen, which are typically fine, for example 8-12 nm, in particular about 10 nm, large carbonitride precipitates are present and, through precipitation hardening, significantly to increase the strength contribute a spring wire according to the invention. At the same time, V in this way contributes to the relaxation resistance of the spring steel from which a spring wire according to the invention is made. In order to be able to use the positive effect of V particularly reliably, the V content of the spring steel of a spring wire according to the invention can be at least 0.0250% by weight, at least 0.0280% by weight or at least 0.030% by weight. V can be used particularly effectively at contents of up to 0.070% by weight, in particular up to 0.060% by weight.
Die erfindungsgemäß kombinierte Anwesenheit von Nb und V führt im Ergebnis zu hohen Zugfestigkeiten Rm und regelmäßig annähernd gleich hohen Dehngrenzen Rp0,2, so dass bei einer aus erfindungsgemäßem Federdraht hergestellten Spannklemme das Verhältnis Rm/Rp0,2 regelmäßig im für deren Lebensdauer und Federverhalten optimalen Bereich von 1 - 1,2 liegt. The combined presence of Nb and V according to the invention results in high tensile strengths Rm and, as a rule, approximately the same elongation limits Rp0.2, so that in a tension clamp made from spring wire according to the invention the ratio Rm / Rp0.2 is regularly in the range that is optimal for its service life and spring behavior from 1 to 1.2.
Stickstoff („N“) ist im Federstahl eines erfindungsgemäßen Federdrahts in Gehalten von 0,0040 - 0,0120 Gew.-% (40 - 120 ppm) vorgesehen, um die Bildung von Vanadium-Nitriden oder Vanadium-Karbonitriden zu ermöglichen. Zu hohe N-Gehalte würden jedoch die Reckalterung des erfindungsgemäßen Federdrahts begünstigen, was der Zähigkeit erfindungsgemäßen Federdrahts und der von einer Spannklemme geforderten Dauerschwingfestigkeit diametral entgegenstehen würde. Negative Auswirkungen der Anwesenheit von N im Federstahl eines erfindungsgemäßen Federdrahts können dabei dadurch besonders sicher ausgeschlossen werden, dass der N-Gehalt auf höchstens 0,0100 Gew.-% (100 ppm) beschränkt wird. Nitrogen (“N”) is provided in the spring steel of a spring wire according to the invention in contents of 0.0040-0.0120% by weight (40-120 ppm) in order to enable the formation of vanadium nitrides or vanadium carbonitrides. Excessively high N contents would, however, promote the stretching aging of the spring wire according to the invention, which would be diametrically opposed to the toughness of the spring wire according to the invention and the fatigue strength required by a tension clamp. Negative effects of the presence of N in the spring steel of a spring wire according to the invention can be excluded particularly reliably by limiting the N content to a maximum of 0.0100% by weight (100 ppm).
Ein aus einem in erfindungsgemäßer Weise zusammengesetzten Federstahl bestehender Federdraht erreicht im warmgewalzten Zustand eine im Zugversuch gemäß DIN EN ISO 6892-1 ermittelte Brucheinschnürung Z von mindestens 55 % und liegt damit regelmäßig höher als die Brucheinschnürung, die bei Federdrähten ermittelt werden kann, die aus einem konventionell legierten 38Si7-Stahl bestehen. Gleichzeitig weist er im warmgewalzten Zustand eine gemäß ASTM E112 bestimmte Feinkörnigkeit seines Gefüges von mindestens ASTM 10 auf. Diese Feinheit des Gefüges bleibt über die Kaltumformung des Federdrahts zu einer Spannklemme und die anschließende Wärmebehandlung der Spannklemme weitestgehend erhalten. So weisen erfindungsgemäße, für den Einbau in einem Schienenbefestigungspunkt fertige Spannklemmen regelmäßig eine Feinheit ihres Gefüges auf, die, nach ASTM E112 bestimmt, mindestens ASTM 8 entspricht. Dies entspricht einer Verbesserung der Feinkörnigkeit um mindestens eine der in ASTM E112 angegebenen Körnigkeits-Klassen gegenüber einer Spannklemme, die aus einem Federdraht gebogen ist, der aus dem konventionellen 38Si7-Stahl besteht. A spring wire composed of a spring steel composed in the manner according to the invention achieves in the hot-rolled condition a tensile test according to DIN EN ISO 6892-1 of at least 55% at break and is therefore regularly higher than the break at break that can be determined for spring wires from a conventionally alloyed 38Si7 steel. At the same time, in the hot-rolled state, it has a fine-grain structure of at least ASTM 10, determined in accordance with ASTM E112. This fineness of the structure is largely retained through the cold forming of the spring wire into a tension clamp and the subsequent heat treatment of the tension clamp. Thus tension clamps according to the invention, ready for installation in a rail fastening point, regularly have a fineness of their structure which, determined according to ASTM E112, corresponds to at least ASTM 8. This corresponds to an improvement in the fine grain size by at least one of the grain size classes specified in ASTM E112 compared to a tension clamp that is bent from a spring wire made from conventional 38Si7 steel.
Das erfindungsgemäße Verfahren zum Herstellen eines erfindungsgemäß beschaffenen Federdrahts umfasst folgende Arbeitsschritte: a) Erschmelzen eines Stahls, der aus, in Gew.-%, C: 0,35 - 0,42 %, Si: The method according to the invention for producing a spring wire according to the invention comprises the following work steps: a) Melting a steel made from, in% by weight, C: 0.35-0.42%, Si:
1,5 - 1,8·%, Mn: 0,50 - 0,80 %, Cr: 0,05 - 0,25 %, Nb: 0,020 - 0,10 %,1.5-1.8%, Mn: 0.50-0.80%, Cr: 0.05-0.25%, Nb: 0.020-0.10%,
V: 0,020 - 0,10 %, N: 0,0040 - 0,0120 %, AI: £ 0,03 % und als Rest aus Eisen und unvermeidbaren Verunreinigungen besteht, wobei der Gehalt der Summe an Verunreinigungen auf höchstens 0,2 % beschränkt ist und zu den Verunreinigungen bis zu 0,025 % P und bis zu 0,025 % S zählen; b) Vergießen des Stahls zu einem Vorprodukt; c) Warmwalzen des Vorprodukts zu einem warmgewalzten Federdraht mit einem Enddurchmesser von 9 - 15 mm, wobei das Warmwalzen in mindestens zwei Teilschritten durchgeführt wird, wobei der Federdraht im letzten Teilschritt des Warmwalzen thermomechanisch bei einer Temperatur fertig warmgewalzt wird, die unterhalb der Rekristallisationsstopptemperatur des Stahls des Federdrahts und oberhalb der Ar3-Temperatur des Stahls des Federdrahts liegt; d) Abkühlen des thermomechanisch fertig warmgewalzten Federdrahts mit einer Äbkühlgeschwindigkeit von 1 - 5 °C/s auf eine Wickeltemperatur von 550 - 650 °C; e) Ablegen oder Wickeln des auf die Wickeltemperatur abgekühlten Federdrahts zu einem Coil; f) Abkühlen des Federdrahts im Coil auf Raumtemperatur. V: 0.020 - 0.10%, N: 0.0040 - 0.0120%, AI: £ 0.03% and the remainder consists of iron and unavoidable impurities, the content of the total of impurities being limited to a maximum of 0.2% is limited and the impurities include up to 0.025% P and up to 0.025% S; b) casting the steel into a preliminary product; c) Hot rolling of the preliminary product to a hot-rolled spring wire with a final diameter of 9-15 mm, the hot rolling being carried out in at least two sub-steps, the spring wire being finished thermomechanically in the last sub-step of hot rolling at a temperature below the recrystallization stop temperature of the steel of the spring wire and is above the Ar3 temperature of the steel of the spring wire; d) cooling the thermomechanically finished hot-rolled spring wire at a cooling rate of 1 - 5 ° C / s to a winding temperature of 550 - 650 ° C; e) depositing or winding the spring wire cooled to the winding temperature to form a coil; f) Cooling the spring wire in the coil to room temperature.
Erfindungsgemäß wird somit der Federdraht im Zuge des Warmwalzens einem thermomechanischen Walzschritt unterzogen, bei dem er bei Temperaturen gewalzt wird, die unterhalb der Rekristallisationsstopp-Temperatur und oberhalb der Ar3-Temperatur des Stahls gewalzt wird. Als „Rekristallisationsstopp- Temperatur“ wird dabei die Temperatur bezeichnet, bei der der Federdraht so weit abgekühlt ist, dass keine Rekristallisation seines bis dahin austenitischen Gefüges mehr stattfindet. Durch das im erfindungsgemäß vorgegebenen Temperaturbereich durchgeführte thermomechanische Walzen in Kombination mit der erfindungsgemäß ausgewählten Legierung, insbesondere in Folge der gleichzeitigen Anwesenheit von Nb und V, wird das besonders feinkörnige Gefüge erhalten, welches einen erfindungsgemäßen Federdraht im warmgewalzten Zustand auszeichnet. According to the invention, the spring wire is thus subjected to a thermomechanical rolling step in the course of hot rolling, in which it is rolled at temperatures which are rolled below the recrystallization stop temperature and above the Ar3 temperature of the steel. The “recrystallization stop temperature” is the temperature at which the spring wire has cooled down to such an extent that its previously austenitic structure no longer recrystallizes. Due to the thermomechanical rolling carried out in the temperature range specified according to the invention in combination with the alloy selected according to the invention, in particular due to the simultaneous presence of Nb and V, the particularly fine-grain structure is obtained, which characterizes a spring wire according to the invention in the hot-rolled state.
Gleichzeitig wird durch die Abkühlung des warmgewalzten Federdrahts mit den erfindungsgemäß vorgegebenen Abkühlgeschwindigkeiten und durch Einhaltung der erfindungsgemäß vorgeschriebenen Wickeltemperaturen von 550 - 650 °C sichergestellt, dass sich in Folge von Ausscheidungshärtung ein Maximum an Härte des erfindungsgemäßen Federdrahts einstellt. At the same time, the cooling of the hot-rolled spring wire at the cooling speeds specified according to the invention and compliance with the winding temperatures of 550-650 ° C prescribed according to the invention ensure that a maximum hardness of the spring wire according to the invention is achieved as a result of precipitation hardening.
Grundsätzlich wäre es denkbar, den Warmwalz-Teilschritt „thermomechanisches Walzen“ in einem separaten Arbeitsgang. durchzuführen, der nach dem eigentlichen Warmwalzen des Federdrahts durchgeführt wird. Hierzu wird der dann warmgewalzte bereitgestellte Federdraht zunächst auf Austenitisierungstemperatur erwärmt, anschließend auf eine unterhalb der Rekristallisationsstopptemperatur, aber oberhalb der Ar3-Temperatur des Federstahls liegende Temperatur abgekühlt und bei dieser Temperatur mit ausreichendem Verformungsgrad warmgewalzt. Daran anschließend erfolgt die Abkühlung und das Ablegen oder Wickeln des Federdrahts wie in den Arbeitsschritten d) und e) des erfindungsgemäßen Verfahrens angegeben. In principle, it would be conceivable to carry out the “thermomechanical rolling” sub-step in a separate operation. to be carried out, which is carried out after the actual hot rolling of the spring wire. For this purpose, the then hot-rolled spring wire provided is first opened Austenitizing temperature, then cooled to a temperature below the recrystallization stop temperature but above the Ar3 temperature of the spring steel and hot-rolled at this temperature with a sufficient degree of deformation. This is followed by the cooling and the laying down or winding of the spring wire as indicated in steps d) and e) of the method according to the invention.
Eine technologisch und wirtschaftlich optimierte Variante des erfindungsgemäßen Verfahrens sieht allerdings vor, dass alle Teilschritte des Warmwalzens (Arbeitsschritt c)) im kontinuierlichen Durchlauf absolviert werden, dass also ein auch thermomechanisch fertig warmgewalzter Federdraht vorliegt, wenn der Federdraht die jeweils genutzte Warmwalzstrecke verlässt. A technologically and economically optimized variant of the method according to the invention, however, provides that all partial steps of hot rolling (work step c)) are completed in a continuous cycle, that is, a thermomechanically finished hot-rolled spring wire is present when the spring wire leaves the hot-rolling section used in each case.
Nachfolgend wird die Erfindung anhand von Ausführungsbeispielen näher erläutert. The invention is explained in more detail below on the basis of exemplary embodiments.
Es wurden erfindungsgemäß legierte Schmelze E1-E5 erschmolzen, deren Zusammensetzungen in Tabelle 1 angegeben sind. Melts E1-E5 alloyed according to the invention were melted, the compositions of which are given in Table 1.
Zum Vergleich wurde eine Vergleichsschmelze V1 erschmolzen, deren Gehalte an C, Si, Mn, P, S und N den für den bekannten Stahl 38Si7 geltenden Maßgaben entsprachen, die jedoch zusätzlich auch noch Cr in einem wirksamen Gehalt aufwies. Auch die Zusammensetzung der Vergleichsschmelze V1 ist in Tabelle 1 angegeben. For comparison, a comparative melt V1 was melted, the C, Si, Mn, P, S and N contents of which corresponded to the requirements applicable to the known 38Si7 steel, but which also had an effective content of Cr. The composition of the comparative melt V1 is also given in Table 1.
Aus den Schmelzen E1 - E5.V1 sind konventionelle Barren gegossen worden, die in ebenso konventioneller Weise zu Federdrähten in mehreren Stufen vor- und zwischengewalzt worden sind, bevor sie in einer letzten Stufe des Warmwalzens fertig warmgewalzt worden sind. Diese letzte Stufe des Warmwalzens wurde als thermomechanisches Walzen durchgeführt. Hierzu ist der Federdraht vor dem Eintritt in die letzte Warmwalzstufe auf eine Temperatur abgekühlt worden, die unterhalb der hier im Bereich von 850 - 950 °C liegenden Rekristallisationsstopptemperatur der Stähle E1 - E5 und V1 und oberhalb der hier etwa 750 - 800 °C betragenden Ar3-Temperatur der Stähle E1 - E5 und V1 lag. Conventional billets were cast from the melts E1 - E5.V1, which were rolled in an equally conventional manner into spring wires in several stages before they were finally hot-rolled in a final stage of hot rolling. This last stage of hot rolling was carried out as thermomechanical rolling. For this purpose, the spring wire is at a temperature before entering the last hot rolling stage was cooled, which was below the recrystallization stop temperature of the steels E1 - E5 and V1, which is in the range of 850 - 950 ° C, and above the Ar3 temperature of steels E1 - E5 and V1, which is around 750 - 800 ° C.
Die Rekristallisationsstopptemperatur des jeweiligen Federstahls, aus dem der jeweilige Federdraht E1 - E5.V1 erzeugt ist, kann in an sich bekannter Weise experimentell ermittelt oder mit Hilfe empirisch ermittelter Formeln abgeschätzt werden. The recrystallization stop temperature of the respective spring steel from which the respective spring wire E1-E5.V1 is produced can be determined experimentally in a manner known per se or can be estimated with the aid of empirically determined formulas.
Genauso können die Ar3- und Ar1 -Temperaturen des jeweiligen Federstahls, aus dem der jeweilige Federdraht E1 - E5,V1 erzeugt ist, in an sich bekannter Weise experimentell, beispielsweise mittels Dilatometrie in einem thermomechanischen Simulator bestimmt werden. Likewise, the Ar3 and Ar1 temperatures of the respective spring steel from which the respective spring wire E1-E5, V1 is produced can be determined experimentally in a manner known per se, for example by means of dilatometry in a thermomechanical simulator.
Nach dem Ende des Warmwalzens sind die erhaltenen warmgewalzten Federdrähte mit einer Abkühlrate von 1 - 5°C/s auf eine Wickeltemperatur von 550 - 650 °C abgekühlt worden, bei der sie zu einem Coil gewickelt worden sind. Anschließend sind die Federdrähte im Coil auf Raumtemperatur abgekühlt worden. After the end of the hot rolling, the hot-rolled spring wires obtained were cooled at a cooling rate of 1-5 ° C./s to a winding temperature of 550-650 ° C., at which they were wound into a coil. The spring wires in the coil were then cooled to room temperature.
An den erhaltenen warmgewalzten Federdrähten ist gemäß ASTM E112 die Komfeinheit „ASTM_F“ des Gefüges und gemäß DIN EN ISO 6892-1 die Brucheinschnürung „Z_F“ bestimmt worden. Die erhaltenen Werte „ASTM_F“ und „Z_F“ sind für die aus den Stählen E1 - E5 und V1 bestehenden Federdrähte iri Tabelle 2 angegeben. According to ASTM E112, the grain size "ASTM_F" of the structure and according to DIN EN ISO 6892-1 the fracture necking "Z_F" was determined on the hot-rolled spring wires obtained. The obtained values "ASTM_F" and "Z_F" are given in table 2 for the spring wires made of steels E1 - E5 and V1.
Von den warmgewalzten, äus den Federstählen E1 - E5, V1 bestehenden Federdrähten sind Stäbe äbgelängt worden, die nach einem in konventioneller Weise durchgeführten Beizen und Richten in mehreren Stufen kalt, d.h. bei Raumtemperatur, zu einer konventionell geformten, w-förmigen Spannklemme gebogen worden sind. Nach dieser Kaltformgebung sind die erhaltenen Spannklemmen einer Wärmebehandlung unterzogen worden, bei der sie auf eine Austenitisierungstemperatur von 850 - 950 °C durcherwärmt worden sind, so dass ihr Gefüge vollständig austenitisch war. Anschließend sind die so austenitisierten Spannklemmen in Wasser abgeschreckt worden, so dass ihr Gefüge zu mehr als 95 Flächen-% martensitisch war. From the hot-rolled spring wires consisting of the spring steels E1 - E5, V1, rods have been cut to length, which, after pickling and straightening carried out in a conventional manner, have been bent in several stages cold, i.e. at room temperature, to a conventionally shaped, W-shaped tension clamp . After this cold forming, the tension clamps obtained were subjected to a heat treatment in which they were heated through to an austenitizing temperature of 850-950 ° C. so that their structure was completely austenitic. The tension clamps that were austenitized in this way were then quenched in water so that their structure was more than 95% by area martensitic.
Nach dem Abschrecken haben die Spannklemmen ein Anlassen durchlaufen, bei dem sie über eine Dauer von 60 - 120 min auf eine 400 - 450 °C betragende Anlasstemperatur erwärmt und dort gehalten worden sind. Anschließend sind die so angelassenen Spannklemmen an Luft auf Raumtemperatur abgekühlt worden. After quenching, the tension clamps have undergone a tempering process in which they are heated to a tempering temperature of 400-450 ° C over a period of 60-120 minutes and held there. The tension clamps, which had been tempered in this way, were then cooled to room temperature in air.
An den so erhaltenen Spannklemmen sind gemäß DIN EN ISO 6892-1 die Zugfestigkeit Rm und die Dehngrenze Rp0,2 ermittelt worden. Darüber hinaus ist gemäß DIN EN ISO 148-1 als Kennwert für die Zähigkeit die Kerbschlagarbeit KV-20 bestimmt worden. Die erhaltenen Messwerte sind in Tabelle 2 aufgeführt. Es zeigte sich, dass nicht nur die Zugfestigkeit Rm und die Dehngrenze Rp0,2 der aus erfindungsgemäß zusammengesetztem Federstahl E1 in der erfindungsgemäßen Weise erzeugten Spannklemmen bei unveränderter Kerbschlagarbeit KV-20 gegenüber den aus dem Vergleichsstahl V1 gefertigten Spannklemmen deutlich gesteigert werden konnte, sondern dass dabei auch das Verhältnis Rm/Rp0,2 praktisch gleich geblieben ist. On the tension clamps obtained in this way, the tensile strength Rm and the yield strength Rp0.2 were determined in accordance with DIN EN ISO 6892-1. In addition, according to DIN EN ISO 148-1, the notched impact energy KV-20 has been determined as a characteristic value for toughness. The measured values obtained are listed in Table 2. It was found that not only the tensile strength Rm and the yield strength Rp0.2 of the tension clamps produced from spring steel E1 composed according to the invention in the manner according to the invention could be significantly increased with unchanged impact work KV-20 compared to the tension clamps made from the comparative steel V1, but that the ratio Rm / Rp0.2 has also remained practically the same.
Gleichzeitig wiesen die aus den erfindungsgemäßen Federstählen E1 - E5 erzeugten Spannklemmen eine deutlich bessere, gemäß ASTM E112 bestimmte Feinkörnigkeit „ASTM“ des Gefüges auf als die aus dem Vergleichsstahl V1 bestehenden Spannklemmen. At the same time, the tension clamps produced from the spring steels E1-E5 according to the invention had a significantly better fine-grain “ASTM” structure, determined in accordance with ASTM E112, than the tension clamps made from the comparative steel V1.
Anschließend sind die aus den erfindungsgemäßen Stählen E1 - E5 und dem Vergleichsstahl V1 bestehenden Spannklemmen unter identischen Bedingungen in einem Befestigungspunkt verbaut worden und die von ihnen ausgeübten Niederhaltekräfte im Neuzustand „TLn“ und nach 3 Millionen Lastwechseln „TL3M“ bestimmt worden. Auch die Ergebnisse dieser Messung sind in Tabelle 2 angegeben. Es zeigt sich, dass die aus den erfindungsgemäßen Federstählen E1 - E5 bestehenden Spannklemmen nicht nur im Neuzustand eine höhere Niederhaltekraft TLn liefern, sondern dass diese Niederhaltekraft auch nach 3 Millionen Lastwechseln nur geringfügig zurückgeht, wogegen sie bei den aus dem Vergleichsstahl V1 bestehenden Spannklemmen um einen deutlich größeren Betrag abnimmt. Subsequently, the tension clamps consisting of the steels E1-E5 according to the invention and the comparative steel V1 were installed in a fastening point under identical conditions, and those of them The hold-down forces exerted in the new condition "TL n " and after 3 million load changes "TL 3M " have been determined. The results of this measurement are also given in Table 2. It can be seen that the tension clamps made of the spring steels E1 - E5 according to the invention not only deliver a higher hold-down force TLn when new, but that this hold-down force only decreases slightly after 3 million load changes, whereas it decreases by one with the tension clamps made of the comparative steel V1 significantly larger amount decreases.
Figure imgf000017_0001
Figure imgf000017_0001
Rest Eisen und sonstige unvermeidbare VerunreinigungenRemainder iron and other unavoidable impurities
Tabelle 1
Figure imgf000017_0002
Table 1
Figure imgf000017_0002
Tabelle 2 Table 2

Claims

PATENTANSPRÜCHE PATENT CLAIMS
1. Federdraht hergestellt aus einem Stahl, der aus, in Gew.-%, 1.Spring wire made from a steel which, in% by weight,
C: 0,35 - 0,42 %, C: 0.35-0.42%,
Si: 1,5 1,8%, Mn: 0,5 - 0,8%, Si: 1.5 1.8%, Mn: 0.5-0.8%,
Cr: 0,05 - 0,25 %, Cr: 0.05-0.25%,
Nb: 0,020 - 0,10%, Nb: 0.020-0.10%,
V: 0,020 - 0,10 %, V: 0.020-0.10%,
N: 0,0040 - 0,0120 %, N: 0.0040 - 0.0120%,
AI: £ 0,03 %, und als Rest Eisen und unvermeidbaren Verunreinigungen besteht, wobei der Gehalt der Summe an Verunreinigungen auf höchstens 0,2 % beschränkt ist und zu den Verunreinigungen bis zu 0,025 % P und bis zu 0,025 % S zählen. AI: £ 0.03%, and the remainder consists of iron and unavoidable impurities, the total content of impurities being limited to a maximum of 0.2% and impurities including up to 0.025% P and up to 0.025% S.
2. Federdraht nach Anspruch 1, dadurch gekennzeichnet, d a s s sein C-Gehalt höchstens 0,40 Gew.-% beträgt. 2. Spring wire according to claim 1, characterized in that its C content is at most 0.40% by weight.
3. Federdraht nach einem der voranstehenden Ansprüche, dadurch gekennzeichnet, dass sein Cr-Gehalt mindestens 0,1 Gew.-% beträgt. 3. Spring wire according to one of the preceding claims, characterized in that its Cr content is at least 0.1% by weight.
4. Federdraht nach Anspruch 2, dadurch gekennzeichnet, dass sein Cr-Gehalt mindestens 0,18 Gew.-% beträgt. 4. Spring wire according to claim 2, characterized in that its Cr content is at least 0.18% by weight.
5. Federdraht nach einem der voranstehenden Ansprüche, dadurch gekennzeichnet, dass sein Mn-Gehalt mindestens 0,6 Gew.-% beträgt. 5. Spring wire according to one of the preceding claims, characterized in that its Mn content is at least 0.6% by weight.
6. Federdraht nach Anspruch 5, dadurch gekennzeichnet, dass sein Mn-Gehalt mindestens 0,7 Gew.-% beträgt. 6. Spring wire according to claim 5, characterized in that its Mn content is at least 0.7% by weight.
7. Federdraht nach einem der voranstehenden Ansprüche, dadurch gekennzeichnet, dass sein Nb-Gehalt mindestens 0,030 Gew.-% beträgt. 7. Spring wire according to one of the preceding claims, characterized in that its Nb content is at least 0.030% by weight.
8. Federdraht nach einem der voranstehenden Ansprüche, dadurch gekennzeichnet, dass sein Nb-Gehalt höchstens 0,070 Gew.-% beträgt. 8. Spring wire according to one of the preceding claims, characterized in that its Nb content is at most 0.070% by weight.
9. Federdraht nach einem der voranstehenden Ansprüche, dadurch gekennzeichnet, dass sein V-Gehalt höchstens 0,060 Gew.-% beträgt. 9. Spring wire according to one of the preceding claims, characterized in that its V content is at most 0.060% by weight.
10. Federdraht nach einem der voranstehenden Ansprüche, dadurch gekennzeichnet, dass sein N-Gehalt mindestens 0,0060 Gew.-% beträgt. 10. Spring wire according to one of the preceding claims, characterized in that its N content is at least 0.0060% by weight.
11. Federdraht nach einem der voranstehenden Ansprüche, dadurch gekennzeichnet, dass er eine im Zugversuch gemäß DIN EN ISO 6892-1 ermittelte Brucheinschnürung Z von mindestens 55 % erreicht. 11. Spring wire according to one of the preceding claims, characterized in that it achieves a necking at break Z of at least 55% determined in the tensile test according to DIN EN ISO 6892-1.
12. Federdraht nach einem der voranstehenden Ansprüche, dadurch gekennzeich net, da s s die gemäß ASTM E112 bestimmte Feinkörnigkeit seines Gefüges mindestens ASTM 10 entspricht. 12. Spring wire according to one of the preceding claims, characterized in that the fine-grain structure of its structure determined in accordance with ASTM E112 corresponds to at least ASTM 10.
13. Spannklemme zum Niederhalten einer Schiene für Schienenfahrzeuge in einem Schienenbefestigungspunkt hergestellt aus einem gemäß einem der voranstehenden Ansprüche beschaffenen Federdraht. 13. Tension clamp for holding down a rail for rail vehicles in a rail fastening point made from a spring wire provided according to one of the preceding claims.
14, Verfahren zum Herstellen eines gemäß einem der Ansprüche 11 oder 12 beschaffenen Federdrahts umfassend folgende Arbeitsschritte a) Erschmelzen eines Stahls, der aus, in Gew.-%, C: 0,35 - 0,42 %, Si: 14, a method for producing a spring wire provided according to one of claims 11 or 12, comprising the following steps a) melting a steel made from, in% by weight, C: 0.35-0.42%, Si:
1,5 - 1,8 %, Mn: 0,50 - 0,80 %, Cr: 0,05 - 0,25 %, Nb: 0,020 - 0,10 %, V: 0,020 - 0,10 %, N: 0,0040 - 0,0120 %, AI: £ 0,03 % und als Rest aus Eisen und unvermeidbaren Verunreinigungen besteht, wobei der Gehalt der Summe an Verunreinigungen auf höchstens 0,2 % beschränkt ist und zu den Verunreinigungen bis zu 0,025 % P und bis zu 0,025 % S zählen; b) Vergießen des Stahls zu einem Vorprodukt; c) Warmwalzen des Vorprodukts zu einem warmgewalzten Federdraht mit einem Enddurchmesser von 9 - 15 mm, wobei das Warmwalzen in mindestens zwei Teilschritten durchgeführt wird, wobei der Federdraht im letzten Teilschritt des Warmwalzens thermomechanisch bei einer Temperatur fertig warmgewalzt wird, die unterhalb der Rekristallisationsstopptemperatur des Stahls des Federdrahts und oberhalb der Ar3-Temperatur des Stahls des Federdrahts liegt; d) Abkühlen des thermomechanisch fertig warmgewalzten Federdrahts mit einer Abkühlgeschwindigkeit von 1 - 5 °C/s auf eine Wickeltemperatur von 550-650 °C; e) Ablegen oder Wickeln des auf die Wickeltemperatur abgekühlten Federdrahts zu einem Coil; f) Abkühlen des Federdrahts im Coil auf Raumtemperatur. 1.5-1.8%, Mn: 0.50-0.80%, Cr: 0.05-0.25%, Nb: 0.020-0.10%, V: 0.020-0.10%, N : 0.0040 - 0.0120%, AI: £ 0.03% and the remainder consists of iron and unavoidable impurities, the total content of impurities being limited to a maximum of 0.2% and up to 0.025% for the impurities P and up to 0.025% S count; b) casting the steel into a preliminary product; c) Hot rolling of the preliminary product to a hot-rolled spring wire with a final diameter of 9-15 mm, the hot rolling being carried out in at least two sub-steps, the spring wire being thermomechanically in a final sub-step of hot rolling Temperature is finished hot-rolled, which is below the recrystallization stop temperature of the steel of the spring wire and above the Ar3 temperature of the steel of the spring wire; d) cooling the thermomechanically finished hot-rolled spring wire at a cooling rate of 1-5 ° C / s to a winding temperature of 550-650 ° C; e) depositing or winding the spring wire cooled to the winding temperature to form a coil; f) Cooling the spring wire in the coil to room temperature.
15. Verfahren nach Anspruch 14, dadurch gekennzeichnet, dass die Teilschritte des Warmwalzens (Arbeitsschritt c)) im kontinuierlichen Durchlauf absolviert werden. 15. The method according to claim 14, characterized in that the partial steps of hot rolling (work step c)) are completed in a continuous cycle.
PCT/EP2020/072650 2019-08-23 2020-08-12 Spring wire, tension clamp formed therefrom and method for producing such a spring wire WO2021037567A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
US17/636,964 US20220275490A1 (en) 2019-08-23 2020-08-12 Spring Wire, Tension Clamp Formed Therefrom and Method for Manufacturing Such a Spring Wire
CN202080059418.3A CN114341387B (en) 2019-08-23 2020-08-12 Tension clamp and method for producing such a tension clamp

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP19193224.3A EP3783120B1 (en) 2019-08-23 2019-08-23 Spring wire, clamp formed from same and method for producing such a spring wire
EP19193224.3 2019-08-23

Publications (1)

Publication Number Publication Date
WO2021037567A1 true WO2021037567A1 (en) 2021-03-04

Family

ID=67742174

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP2020/072650 WO2021037567A1 (en) 2019-08-23 2020-08-12 Spring wire, tension clamp formed therefrom and method for producing such a spring wire

Country Status (7)

Country Link
US (1) US20220275490A1 (en)
EP (1) EP3783120B1 (en)
CN (1) CN114341387B (en)
ES (1) ES2963989T3 (en)
FI (1) FI3783120T3 (en)
PL (1) PL3783120T3 (en)
WO (1) WO2021037567A1 (en)

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19546204C1 (en) 1995-12-11 1997-03-20 Max Planck Inst Eisenforschung High strength steel object prodn.,esp. leaf spring
EP0974676A2 (en) * 1998-07-20 2000-01-26 Firma Muhr und Bender Process for thermo-mechanically treating steel for torsion spring elements
DE19839383A1 (en) 1998-07-20 2000-01-27 Muhr & Bender Process for the thermomechanical treatment of steel for spring elements subject to torsion
EP2612941A1 (en) * 2010-08-30 2013-07-10 Kabushiki Kaisha Kobe Seiko Sho Steel wire material for high-strength spring which has excellent wire-drawing properties and process for production thereof, and high-strength spring
CN102719759B (en) * 2012-07-12 2014-03-26 南车戚墅堰机车车辆工艺研究所有限公司 Elastic bar steel for high-speed rail fastener and smelting production method thereof
RU2512695C1 (en) * 2012-12-26 2014-04-10 Общество с ограниченной ответственностью "Мультимодальный центр МИИТ" Method for producing elastic terminal for rail attachment, and elastic terminal
CN105112774A (en) 2015-08-28 2015-12-02 浙江美力科技股份有限公司 Air cooling hardened spring steel with high obdurability, low-medium-carbon and microalloy and forming and heat treatment process thereof
CN105401072A (en) * 2015-12-18 2016-03-16 马鞍山钢铁股份有限公司 Steel for fastener for niobium-containing 12.9-grade rail transit mobile equipment and heat processing technology thereof

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH01116031A (en) * 1987-10-29 1989-05-09 Nippon Steel Corp Manufacture of hot rolled high si-high carbon steel sheet having superior toughness
JP2932943B2 (en) * 1993-11-04 1999-08-09 株式会社神戸製鋼所 High corrosion resistance and high strength steel for springs
JP2001049337A (en) * 1999-08-05 2001-02-20 Kobe Steel Ltd Production of high strength spring excellent in fatigue strength
EP1589124B1 (en) * 2003-01-27 2010-05-05 Nippon Steel Corporation High strength high toughness high carbon steel wire rod and process for producing the same
JP4393467B2 (en) * 2006-02-28 2010-01-06 株式会社神戸製鋼所 Hot rolled wire rod for strong wire drawing and manufacturing method thereof
CN101716721B (en) * 2009-12-23 2011-12-07 南京钢铁股份有限公司 Manufacturing process of spring steel wire rod
JP5250609B2 (en) * 2010-11-11 2013-07-31 日本発條株式会社 Steel for high strength spring, method for producing high strength spring, and high strength spring
CN109082592B (en) * 2018-08-27 2020-08-18 河钢股份有限公司 Corrosion-resistant spring steel hot-rolled wire rod with good comprehensive performance and production process thereof
CN109735765B (en) * 2019-01-17 2020-05-05 江苏利淮钢铁有限公司 Large-sized, ultra-fine grain, high-strength and high-toughness spring steel and production method thereof

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19546204C1 (en) 1995-12-11 1997-03-20 Max Planck Inst Eisenforschung High strength steel object prodn.,esp. leaf spring
EP0974676A2 (en) * 1998-07-20 2000-01-26 Firma Muhr und Bender Process for thermo-mechanically treating steel for torsion spring elements
DE19839383A1 (en) 1998-07-20 2000-01-27 Muhr & Bender Process for the thermomechanical treatment of steel for spring elements subject to torsion
EP2612941A1 (en) * 2010-08-30 2013-07-10 Kabushiki Kaisha Kobe Seiko Sho Steel wire material for high-strength spring which has excellent wire-drawing properties and process for production thereof, and high-strength spring
CN102719759B (en) * 2012-07-12 2014-03-26 南车戚墅堰机车车辆工艺研究所有限公司 Elastic bar steel for high-speed rail fastener and smelting production method thereof
RU2512695C1 (en) * 2012-12-26 2014-04-10 Общество с ограниченной ответственностью "Мультимодальный центр МИИТ" Method for producing elastic terminal for rail attachment, and elastic terminal
CN105112774A (en) 2015-08-28 2015-12-02 浙江美力科技股份有限公司 Air cooling hardened spring steel with high obdurability, low-medium-carbon and microalloy and forming and heat treatment process thereof
CN105401072A (en) * 2015-12-18 2016-03-16 马鞍山钢铁股份有限公司 Steel for fastener for niobium-containing 12.9-grade rail transit mobile equipment and heat processing technology thereof

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
"Stahl Fibel", 2015, VERLAG STAHLEISEN GMBH
DATABASE WPI Week 201624, Derwent World Patents Index; AN 2016-17839W, XP002797798 *

Also Published As

Publication number Publication date
US20220275490A1 (en) 2022-09-01
CN114341387B (en) 2023-06-23
EP3783120B1 (en) 2023-09-27
PL3783120T3 (en) 2024-02-19
ES2963989T3 (en) 2024-04-03
FI3783120T3 (en) 2023-11-15
EP3783120A1 (en) 2021-02-24
CN114341387A (en) 2022-04-12

Similar Documents

Publication Publication Date Title
EP1200635B1 (en) High tensile steel band or sheet and method for the production thereof
DE4040355C2 (en) Process for producing a thin steel sheet from steel with a high carbon content
EP3535431B1 (en) Steel product with an intermediate manganese content for low temperature application and production method thereof
EP3504349B1 (en) Method for producing a high-strength steel strip with improved properties for further processing, and a steel strip of this type
DE19610675C1 (en) Dual phase steel for cold rolled sheet or strip - contg. manganese@, aluminium@ and silicon
EP2690184B1 (en) Produit plat en acier laminé à froid et son procédé de fabrication
EP3305935A1 (en) High strength flat steel product and use of a high strength flat steel product
DE60300561T3 (en) Process for producing a hot-rolled steel strip
EP3724359B1 (en) High-strength, hot-rolled flat steel product with high edge crack resistance and simultaneously high bake-hardening potential and method for producing a flat steel product of this kind
DE102015112886A1 (en) High-strength aluminum-containing manganese steel, a process for producing a steel flat product from this steel and steel flat product produced therefrom
EP3512968B1 (en) Method for producing a flat steel product made of a manganese-containing steel, and such a flat steel product
EP1319725B1 (en) Hot strip manufacturing process
EP1052296B1 (en) Use of a steel for the manufacture of amour plates
DE60011666T2 (en) METHOD FOR PRODUCING ULTRA-FINE GRAIN STRUCTURE FOR UNITED OR LOW-ALLOYED STEELS
WO2016020519A1 (en) High-strength and at the same time tough semifinished products and components of high-alloy steel, method for the production thereof and use
EP3551776A1 (en) Method for producing a hot or cold strip and/or a flexibly rolled flat steel product made of a high-strength manganese steel and flat steel product produced by said method
WO2020038883A1 (en) Hot-rolled non-heat-treated and hot-rolled heat-treated flat steel product and method for the production thereof
EP3783120B1 (en) Spring wire, clamp formed from same and method for producing such a spring wire
DE102016115618A1 (en) Process for producing a high-strength steel strip with improved properties during further processing and such a steel strip
EP3469108A1 (en) Method for producing a cold-rolled steel strip having trip-characteristics made of a high-strength mangan-containing steel
WO2017157793A1 (en) Spring components made from a steel alloy and manufacturing method
DE19528671C1 (en) Steel for linear construction profiles for underground pit mining
WO2024068957A1 (en) Method for producing a steel strip from a high-strength multiphase steel, and the corresponding steel strip
DE102022102418A1 (en) High-strength, hot-dip coated steel strip having structural transformation-induced plasticity and method of making same
WO2023025635A1 (en) Cold-rolled flat steel product and method for the production thereof

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 20756843

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 20756843

Country of ref document: EP

Kind code of ref document: A1