EP0263300A1 - Method and apparatus for manufacturing coil springs - Google Patents

Method and apparatus for manufacturing coil springs Download PDF

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Publication number
EP0263300A1
EP0263300A1 EP87112672A EP87112672A EP0263300A1 EP 0263300 A1 EP0263300 A1 EP 0263300A1 EP 87112672 A EP87112672 A EP 87112672A EP 87112672 A EP87112672 A EP 87112672A EP 0263300 A1 EP0263300 A1 EP 0263300A1
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Prior art keywords
rod
spring
heating
winding
austenite phase
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EP87112672A
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German (de)
French (fr)
Inventor
Josef Dipl.-Ing. Wienand
Horst Dipl.-Ing. Beihammer
Werner Nitschke
Berthold Kühnert
Klaus Broscheit
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Krupp Bruninghaus GmbH
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Krupp Bruninghaus GmbH
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B21MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21FWORKING OR PROCESSING OF METAL WIRE
    • B21F3/00Coiling wire into particular forms
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D9/00Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/02Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for springs

Definitions

  • the invention relates to a method and a device for producing a coil spring from a rod or wire made of spring steel with a constant circular cross section by heating the rod to austenitizing temperature, winding the rod in the stable austenite phase (at austenitizing temperature), hardening the spring thus formed by quenching in a suitable medium, such as oil or water, and tempering the hardened spring.
  • thermoformed coil springs which are mainly made from steels according to DIN 17 221.
  • the primary material used in this case is unrefined, rolled, drawn, ground or turned round steel in rod form with diameters of approx. 8 - 60 mm.
  • the rods are usually austenitized in natural gas-heated, temperature-controlled walking beam furnaces, i.e., heated to temperatures between 820 and 860 ° C depending on the steel composition. This temperature range is also the one in which the springs are first formed and from which they are quenched or hardened in oil immediately after the shaping.
  • the shaping itself takes place on winding machines, in which the rod material is wound around a shaft, the so-called winding mandrel.
  • a guide roller arranged parallel to the winding mandrel and having a helical groove for guiding the spring bar is often used to control the pitch of the windings.
  • HTMB high-temperature thermomechanical treatment. It is about the sensible combination of a heat treatment with a deformation of the material, e.g. It is used for the so-called controlled rolling of high-strength, weldable sheets.
  • Controlled rolling is a treatment of the steel in which the final rolling temperature and the degree of deformation are set so that they lead to recrystallization with the finest possible austenite grain.
  • the deformation of the stable austenite is followed by a targeted cooling of the rolling stock with conversion in the pearlite, intermediate or martensite stage.
  • the favorable mechanical properties of a steel after HTM treatment result mainly from the grain refinement achieved with it, which is expressed in particular in the significantly improved toughness behavior and at the same time increased yield strength of the material.
  • significantly higher strengths can be achieved with an HTM-treated steel that is also converted in the martensite stage with the same toughness.
  • HTM-treated steel also has extremely fine and evenly distributed carbide deposits. It is highly resistant to brittle fracture and has an often usable texture.
  • the relationship between the yield point 6, a steel and its grain size is mentioned by the well-known and experimentally often confirmed Hall-Petch equation described.
  • the object of the invention is to provide a method with a device with which a substantial improvement in the mechanical properties of the material can be achieved in the case of thermoformed coil springs.
  • This object is achieved in that after heating and before winding in the stable austenite phase by rotating about its longitudinal axis, plastic deformation is forced while maintaining its outer shape.
  • all conditions for an optimal thermomechanical treatment are fulfilled, namely the heating of the rod material to the austenitizing temperature, the necessary strong plastic deformation of the austenitized rod and the - rapid cooling of the wound spring in an oil bath to convert the structure in the martensite stage.
  • a y R of 0.45 is to be realized with a rod with a diameter of 12.5 mm and a length of 2800 mm, with dimensions such as those found in common automobile chassis coil springs, then it can be calculated that its two ends are around 32 revolutions must be turned against each other.
  • P is the angle of rotation and n is the number of revolutions.
  • the described grain refinement is the most important but not the only advantage that the twisting of the austenitized spring bars brings.
  • This treatment also has a very positive effect on the durability of the springs due to the helical alignment of the grains (texture) in the rods.
  • the twisting treatment also proves to be extremely useful in that the glow skin formed on the bars during the heating by oxidation completely flakes off.
  • the glow skin will only come loose when the springs are wound, i.e. when the springs are shaped. Experience has shown that it is partially rolled into the rod surface, leaving harmful notches.
  • the torsion treatment creates internal stresses in the spring bars, which, as tests have shown, lead to springback or. Reverse effects lead. If, for example, a compression spring with a pitch to the right is formed from a spring bar that has been turned to the right, then as a result of the spring-back in the hardened state, it has significantly larger turns than specified by the winding tool (the guide roller). If, on the other hand, a compression spring with a left-hand pitch is wound from a "clockwise" rod, this results in turn spacings that are smaller than those in the guide roller. The total length or total height of the spring is thus larger in the first example and smaller than the predetermined one in the second case.
  • the springback effect of the twisted rods can be used to advantage in many ways. Among other things, this makes it possible for the first time to manufacture thermoformed compression springs with considerable internal preload.
  • the twisting device according to FIG. 2 consists of two drive units 10 with clamping elements 11 (gripping claws) and is also a heating device at the same time.
  • the electrical current is fed to the rod 12 treated therein via the tensioning elements 11.
  • the drive units 10 are displaceably arranged on guide rails 13 for the purpose of adaptation to different rod lengths. Particularly advantageous with this connection of heating and deformation is the possibility of leaving the spring rod 12 in the device for a certain small period of time at a constant temperature after twisting , with the aim of obtaining an optimally fine-grained structure during the recrystallization of the material.

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

Abstract

The coil spring is produced from a bar or wire of spring steel of constant cross-section by heating the bar to the austenitisation temperature, winding the bar in the stable austenite phase, hardening the spring thus formed by quenching in a suitable medium and annealing of the hardened spring, and a plastic deformation is forced upon the bar after heating and before winding in the stable austenite phase by rotating it about its longitudinal axis, while maintaining its external shape. <IMAGE>

Description

Die Erfindung betrifft ein Verfahren und eine Vorrichtung zur Herstellung einer Schraubenfeder aus einem Stab bzw. Draht aus Federstahl mit konstantem Kreisquerschnitt durch Erwärmen des Stabes auf Austenitisierungstemperatur, Wickeln des Stabes in der stabilen Austenitphase (bei Austenitisierungstemperatur), Härten der so geformten Feder durch Abschrecken in einem geeigneten Medium, wie Öl oder Wasser, und Anlassen (Tempern) der gehärteten Feder.The invention relates to a method and a device for producing a coil spring from a rod or wire made of spring steel with a constant circular cross section by heating the rod to austenitizing temperature, winding the rod in the stable austenite phase (at austenitizing temperature), hardening the spring thus formed by quenching in a suitable medium, such as oil or water, and tempering the hardened spring.

Bei der Herstellung von Schraubendruck-und Schraubenzugfedern unterscheidet man zwei verschiedene, hinsichtlich ihrer technischen Bedeutung etwa gleichrangige Formgebungsverfahren, die Warm-und Kaltformgebung. Das beim Kaltformen zum Einsatz kommende Vor-material hat häufig bereits vor der Verarbeitung, also im Anlieferungszustand, die Festigkeitseigenschaften, die von der fertigen Feder verlangt werden, das heißt, es hat vorab bereits eine geeignete Vergütebehandlung, z.B. eine Ölschlußvergütung erfahren. Federn aus derartigem Vormaterial werden vorwiegend auf Windeautomaten geformt, wobei Drähte mit Durchmessern von weniger als 1 mm bis max. etwa 15 mm verarbeitbar sind. Kaltgeformt werden jedoch Schraubenfedern nicht selten auch aus "weichen" bzw. unvergüteten Drähten mit Durchmessern von etwa 8 bis 20 mm. Die Vergütung erfolgt in solchen Fällen nach der Formgebung, also an der Feder selbst.In the manufacture of helical compression springs and tension coil springs, a distinction is made between two different shaping processes, which are roughly equivalent in terms of their technical importance, hot and cold forming. The pre-material used in cold forming often already has the strength properties required by the finished spring before processing, i.e. in the delivery state, i.e. it has already undergone a suitable tempering treatment, e.g. experience an oil final remuneration. Springs made from such primary material are predominantly formed on automatic winders, with wires with diameters of less than 1 mm to max. about 15 mm can be processed. However, coil springs are not infrequently cold-formed from "soft" or non-tempered wires with diameters of approximately 8 to 20 mm. In such cases, remuneration is based on the shape, i.e. on the spring itself.

Die hier in Rede stehende Erfindung betrifft den Bereich der warmgeformten Schraubenfedern, die hauptsächlich aus Stählen nach DIN 17 221 hergestellt werden. Das verwendete Vormaterial ist in diesem Fall unvergüteter, gewalzter, gezogener, geschliffener oder gedrehter Rundstahl in Stabform mit Durchmessern von ca. 8 - 60 mm. Üblicherweise werden die Stäbe in erdgasbeheizten, temperaturgeregelten Hubbalkenöfen austenitisiert, das heißt je nach Stahlzusammensetzung auf Temperaturen zwischen 820 und 860° C erwärmt. Dieser Temperaturbereich ist gleichzeitig jener, in dem die Federn zunächst geformt und aus dem heraus sie unmittelbar im Anschluß an die Formgebung in Öl abgeschreckt bzw. gehärtet werden. Die Formgebung selbst geschieht auf Wickelmaschinen, bei denen das Stabmaterial um eine Welle, den sogenannten Wickeldorn, gewickelt wird. Zur Steuerung der Steigung der Windungen dient dabei häufig eine parallel zum Wickeldorn angeordnete Leitrolle, die in ihrer Mantelfläche eine schraubenförmige Nut zur Führung des Federstabes aufweist.The invention in question relates to the field of thermoformed coil springs, which are mainly made from steels according to DIN 17 221. The primary material used in this case is unrefined, rolled, drawn, ground or turned round steel in rod form with diameters of approx. 8 - 60 mm. The rods are usually austenitized in natural gas-heated, temperature-controlled walking beam furnaces, i.e., heated to temperatures between 820 and 860 ° C depending on the steel composition. This temperature range is also the one in which the springs are first formed and from which they are quenched or hardened in oil immediately after the shaping. The shaping itself takes place on winding machines, in which the rod material is wound around a shaft, the so-called winding mandrel. A guide roller arranged parallel to the winding mandrel and having a helical groove for guiding the spring bar is often used to control the pitch of the windings.

Ein besonderes Vergüteverfahren, mit dem wesentliche Verbesserungen der mechanischen Werkstoffeigenschaften erzielt werden können, ist weltweit unter der Abkürzung HTMB bekannt geworden, was Hochtemperaturthermomechanische-Behandlung heißt. Es geht hierbei um die -sinnvolle Kombination einer Wärmebehandlung mit einer Verformung des Werkstoffs, wie sie z.B. Anwendung findet beim sogenannten kontrollierten Walzen von hochfesten, schweißbaren Blechen.A special tempering process with which significant improvements in mechanical material properties can be achieved has become known worldwide under the abbreviation HTMB, which means high-temperature thermomechanical treatment. It is about the sensible combination of a heat treatment with a deformation of the material, e.g. It is used for the so-called controlled rolling of high-strength, weldable sheets.

Unter kontrolliertem Walzen wird eine Behandlung des Stahles verstanden, bei der die Endwalztemperatur und der Endverformungsgrad so eingestellt werden, daß sie zu einer Rekristallisation mit einem möglichst feinen Austenitkorn führen. An die Verformung des stabilen Austenits schließt sich eine gezielte Abkühlung des Walzgutes mit Umwandlung in der Perlit-,Zwischen-oder Martensitstufe an.Controlled rolling is a treatment of the steel in which the final rolling temperature and the degree of deformation are set so that they lead to recrystallization with the finest possible austenite grain. The deformation of the stable austenite is followed by a targeted cooling of the rolling stock with conversion in the pearlite, intermediate or martensite stage.

Die günstigen mechanischen Eigenschaften eines Stahles nach HTM - Behandlung resultieren hauptsächlich aus der damit erzielten Kornverfeinerung, die ihren Ausdruck insbesondere in deutlich verbessertem Zähigkeitsverhalten und gleichzeitig erhöhter Streckgrenze des Werkstoffs findet. Im Vergleich zu einem in herkömmlicher Weise in der Martensitstufe gehärteten und dann angelassenen Stahl lassen sich demnach bei einem HTM -behandelten, ebenfalls in der Martensitstufe umgewandelten Stahl bei gleicher Zähigkeit deutlich höhere Festigkeiten realisieren. HTM-behandelter Stahl weist außerdem extrem feine und gleichmäßig verteilte Karbidausscheidungen auf. Er ist in hohem Maße Sprödbruchsicher und besitzt eine oft vorteilhaft nutzbare Textur. Der erwähnte Zusammenhang zwischen der Streckgrenze 6, eines Stahles und seiner Korngröße wird durch die bekannte und experimentell oft bestätigte Hall-Petch-Gleichung

Figure imgb0001
beschrieben. Darin bezeichnet 5, eine Reibungsspannung, die der Bewegung von Versetzugnen in sehr großen Körnern entgegenwirkt, ky einen Korngrenzenwiderstand und dkden mittleren Korndurchmesser. 6, ist also gemäß der Hall-Petch-Gleichung linear abhängig von der reziproken Wurzel aus dk.The favorable mechanical properties of a steel after HTM treatment result mainly from the grain refinement achieved with it, which is expressed in particular in the significantly improved toughness behavior and at the same time increased yield strength of the material. Compared to a steel hardened and then tempered in a conventional manner in the martensite stage, significantly higher strengths can be achieved with an HTM-treated steel that is also converted in the martensite stage with the same toughness. HTM-treated steel also has extremely fine and evenly distributed carbide deposits. It is highly resistant to brittle fracture and has an often usable texture. The relationship between the yield point 6, a steel and its grain size is mentioned by the well-known and experimentally often confirmed Hall-Petch equation
Figure imgb0001
described. 5 denotes a frictional tension which counteracts the movement of dislocations in very large grains, ky a grain boundary resistance and d k the mean grain diameter. 6, is linearly dependent on the reciprocal root of d k according to the Hall-Petch equation.

Der Erfindung'liegt die Aufgabe zugrunde, ein Verfahren mit einer Vorrichtung zu schaffen, mit dem bei warmgeformten Schraubenfedern eine wesentliche Verbesserung der mechanischen Werkstoffeigenschaften erzielt werden kann.The object of the invention is to provide a method with a device with which a substantial improvement in the mechanical properties of the material can be achieved in the case of thermoformed coil springs.

Diese Aufgabe wird erfindungsgemäß dadurch gelöst, daß dem Stab nach dem Erwärmen und vor dem Wickeln in der stabilen Austenitphase durch Verdrehen um seine Längsachse eine plastische Verformung bei Einhaltung seiner äußeren Gestalt aufgezwungen wird. Auf diese Weise sind alle Bedingungen für eine optimale thermomechanische Behandlung erfüllt, nämlich die Erwärmung des Stabmaterials auf Austenitisierungstemperatur, die notwendige starke plastische Verformung des austenitisierten Stabes und die - schnelle Abkühlung der gewickelten Feder im Ölbad zur Umwandlung des Gefüges in der Martensitstufe.This object is achieved in that after heating and before winding in the stable austenite phase by rotating about its longitudinal axis, plastic deformation is forced while maintaining its outer shape. In this way, all conditions for an optimal thermomechanical treatment are fulfilled, namely the heating of the rod material to the austenitizing temperature, the necessary strong plastic deformation of the austenitized rod and the - rapid cooling of the wound spring in an oil bath to convert the structure in the martensite stage.

Die Erfindung wird anhand der Zeichnung im folgenden näher beschrieben. Es zeigen:

  • Fig.1 einen geraden Stab während der Verdrehung;
  • Fig. 2 schematisch einen in einer Verdrehvorrichtung eingespannten Stab.
The invention is described below with reference to the drawing. Show it:
  • 1 shows a straight rod during the rotation;
  • Fig. 2 schematically shows a clamped in a twisting device.

Die größte Verformung erfährt ein runder Federstab 12 gemäß Figur 1 während der Verdrehung ( Torsion) an seiner Oberfläche bzw. in seiner Randschicht, d.h. genau in jener Zone, die einen entscheidenden Einfluß auf wichtige Eigenschaften der fertigen Feder, wie z. B. die Schwingfestigkeit und den Relaxationswiderstand, hat. Der Grad der Verformung an der Staboberfläche wird am treffensten durch die dort beim Verdrehen auftretende Schiebung ( Randschiebung) yR ausgedrückt. Wird dieses Verformungsmaß als feste Größe vorgegeben, so läßt sich in Abhängigkeit von der Länge I und dem Durchmesser d eines betrachteten Stabes berechnen, um wieviele Umdrehungen n ein Stabende relativ zum anderen verdreht werden muß. Figur 1 macht diesen Zusammenhang in Verbindung mit folgenden einfachen Formeln deutlich:

Figure imgb0002
The greatest deformation is experienced by a round spring rod 12 according to FIG. 1 during the twisting (torsion) on its surface or in its surface layer, that is to say in precisely that zone which has a decisive influence on important properties of the finished spring, such as, for. B. has the fatigue strength and relaxation resistance. The degree of deformation on the surface of the rod is best expressed by the displacement (edge displacement) y R that occurs during twisting. If this dimension of deformation is specified as a fixed quantity, it can be calculated as a function of the length I and the diameter d of a rod under consideration by how many revolutions n one rod end must be rotated relative to the other. Figure 1 makes this connection clear in connection with the following simple formulas:
Figure imgb0002

Versuche haben gezeigt, daß ein Wert von etwa 0,4 - 0,5 für yp. ausreicht, um im austenitisierten Federstahlstab die gewünschte, möglichst spontane Rekristallisation einzuleiten.Experiments have shown that a value of about 0.4-0.5 for yp. is sufficient to initiate the desired, as spontaneous as possible recrystallization in the austenitized spring steel rod.

Soll z.B. bei einem Stab mit 12,5 mm Durchmesser und 2800 mm Länge, mit Abmessungen also, wie sie bei gängigen PKW - Fahrgestellschraubenfedern anzutreffen sind, ein yR von 0,45 realisiert werden, so läßt sich berechnen, daß seine beiden Enden um 32 Umdrehungen gegeneinander verdreht werden müssen. P ist der Verdrehwinkel und n ist die die Anzahl der Umdrehungen.If, for example, a y R of 0.45 is to be realized with a rod with a diameter of 12.5 mm and a length of 2800 mm, with dimensions such as those found in common automobile chassis coil springs, then it can be calculated that its two ends are around 32 revolutions must be turned against each other. P is the angle of rotation and n is the number of revolutions.

Die beschriebene Kornverfeinerung ist zwar der wichtigste aber nicht der einzige Vorteil, den die Verdrehung der austenitisierten Federstäbe mit sich bringt. Sehr positiv in bezug auf die Haltbarkeit der Federn wirkt sich diese Behandlung auch durch die in den Stäben entstehende schraubenlinienförmige Ausrichtung der Körner ( Textur) aus. Man kann hier von einem deutlich ausgesprägten Faserverlauf sprechen, der tendenzmäßig dieselbe Richtung aufweist wie die Hauptzugspannungen, die im gekrümmten Draht ( Stab) der fertigen Feder unter einer Betriebsbelastung entstehen.Voraussetzung dafür ist allerdings, daß die Windungen der Feder unter der Betriebslast nicht andersherum tordiert werden als der gerade Stab beim Verdrehvorgang. Ebenfalls außerordentlich nützlich erweist sich die Verdrehbehandlung dahingehend, daß hierbei die auf den Stäben während der Erwärmung durch Oxydation entstehende Glühhaut vollständig abplatzt. Werden die Stäbe, wie bisher üblich, am Ende der Austenitisierungsphase nicht verdreht, so löst sich die Glühhaut erst beim Wickeln, also bei der Formgebung der Federn. Erfahrungsgemäß wird sie dabei teilweise unter Hinterlassung schädlicher Kerben in die Staboberflächen eingewalzt.The described grain refinement is the most important but not the only advantage that the twisting of the austenitized spring bars brings. This treatment also has a very positive effect on the durability of the springs due to the helical alignment of the grains (texture) in the rods. One can speak of a clearly pronounced fiber course, which tends to have the same direction as the main tensile stresses that arise in the curved wire (rod) of the finished spring under an operating load, provided that the windings of the spring do not twist the other way around under the operating load as the straight rod during the twisting process. The twisting treatment also proves to be extremely useful in that the glow skin formed on the bars during the heating by oxidation completely flakes off. If the rods are not twisted at the end of the austenitizing phase, as has been customary up to now, the glow skin will only come loose when the springs are wound, i.e. when the springs are shaped. Experience has shown that it is partially rolled into the rod surface, leaving harmful notches.

Zu erwähnen ist auch noch, daß in den Federstäben durch die Verdrehbehandlung Eigenspannungen entstehen, die, wie Versuche gezeigt haben, zu Rückfederungs-bzw. Rückdreheffekten führen. Wird beispielsweise aus einem Federstab, der rechtsherum verdreht wurde, eine Druckfeder mit Rechtssteigung geformt, dann weist diese als Folge der Rückfederung im gehärteten Zustand wesentlich größere Windungsabstände auf, als vom Wickelwerkzeug ( der Leitrolle ) vorgegeben. Wird dagegen aus einem " rechtsverdrehten " Stab eine Druckfeder mit Linkssteigung gewickelt, so ergeben sich Windungsabstände, die kleiner sind als jene in der Leitrolle. Die Gesamtlänge bzw. Gesamthöhe der Feder fällt also im ersten Beispielfall größer und im zweiten Fall kleiner als die vorgegebene aus. Der Rückfederungseffekt der verdrehten Stäbe läßt sich in mancherlei Hinsicht vorteilhaft ausnutzen. Unter anderem ist es damit erstmals möglich, warmgeformte Schraubendruckfedern mit einer beträchtlichen inneren Vorspannung herzustellen.It should also be mentioned that the torsion treatment creates internal stresses in the spring bars, which, as tests have shown, lead to springback or. Reverse effects lead. If, for example, a compression spring with a pitch to the right is formed from a spring bar that has been turned to the right, then as a result of the spring-back in the hardened state, it has significantly larger turns than specified by the winding tool (the guide roller). If, on the other hand, a compression spring with a left-hand pitch is wound from a "clockwise" rod, this results in turn spacings that are smaller than those in the guide roller. The total length or total height of the spring is thus larger in the first example and smaller than the predetermined one in the second case. The springback effect of the twisted rods can be used to advantage in many ways. Among other things, this makes it possible for the first time to manufacture thermoformed compression springs with considerable internal preload.

Die Anwendung der elektrischen Widerstandserwärmung für das Austenitisieren der Federstäbe warmgeformter Schraubenfedern bietet vor allem im Vergleich zur Ofenerwärmung mit Erdgas enorme technische Vorteile, wie z.B. hohe Gleichmäßigkeit der Temperatur sowohl über den Querschnitt als auch die Länge der Stäbe, kurze Aufheizzeiten, einen geringen Zunderanfall, eine verminderte Gefahr von Entkohlungen und Korngrenzenoxydationen sowie eine feinfühlige Regelbarkeit der Temperatur.The use of electrical resistance heating for the austenitizing of the spring bars of hot-formed coil springs offers enormous technical advantages, especially in comparison to furnace heating with natural gas, e.g. high temperature uniformity over the cross-section as well as the length of the rods, short heating-up times, a small amount of scale, a reduced risk of decarburization and grain boundary oxidation as well as a sensitive controllability of the temperature.

In Kombination mit der vorgesehenen Verdrehbehandlung der Federstäbe ist der Einsatz der elektrischen Widerstandserwärmung völlig neu.In combination with the proposed torsion treatment of the spring bars, the use of electrical resistance heating is completely new.

Die Verdrehvorrichtung gemäß Figur 2 besteht aus zwei Antriebseinheiten 10 mit Spannelementen 11 ( Greifklauen ) und ist gleichzeitig auch eine Erwärmungsvorrichtung. Der elektrische Strom wird dem darin behandelten Stab 12 über die Spannelemente 11 zugeführt. Die Antriebseinheiten 10 sind zwecks Anpas-" sung an unterschiedliche Stablängen auf Führungsschienen 13 verschiebbar angeordnet. Besonders vorteilhaft bei dieser Verbindung von Erwärmung und Verformung ist die Möglichkeit, den Federstab 12 nach dem Verdrehen noch eine gewisse kleine Zeitspanne bei konstanter Temperatur in der Vorrichtung zu belassen, mit dem Ziel, bei der dann ablaufenden Rekristallisation des Werkstoffs ein optimal feinkörniges Gefüge zu erhalten.The twisting device according to FIG. 2 consists of two drive units 10 with clamping elements 11 (gripping claws) and is also a heating device at the same time. The electrical current is fed to the rod 12 treated therein via the tensioning elements 11. The drive units 10 are displaceably arranged on guide rails 13 for the purpose of adaptation to different rod lengths. Particularly advantageous with this connection of heating and deformation is the possibility of leaving the spring rod 12 in the device for a certain small period of time at a constant temperature after twisting , with the aim of obtaining an optimally fine-grained structure during the recrystallization of the material.

Claims (4)

1. Verfahren und Vorrichtung zur Herstellung einer Schraubenfeder aus einem Stab bzw. Draht aus Federstahl mit konstantem Kreisquerschnitt durch Erwärmen des Stabes auf Austenitisierungstemperatur, Wickeln des Stabes in der stabilen Austenitphase ( bei Austenitisierungstemperatur), Härten der so geformten Feder durch Abschrecken in einem geeigneten Medium, wie Öl oder Wasser, und Anlassen ( Tempern ) der gehärteten Feder, dadurch gekennzeichnet, daß dem Stab nach dem Erwärmen und vor dem Wickeln in der stabilen Austenitphase durch Verdrehen um seine Längsachse eine plastische Verformung bei Einhaltung seiner äußeren Gestalt aufgezwungen wird.1. Method and device for producing a coil spring from a rod or wire made of spring steel with a constant circular cross section by heating the rod to the austenitizing temperature, winding the rod in the stable austenite phase (at the austenitizing temperature), hardening the spring thus formed by quenching in a suitable medium , such as oil or water, and tempering the hardened spring, characterized in that, after heating and before winding in the stable austenite phase, the rod is forced to undergo plastic deformation while maintaining its outer shape. 2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß die bei dem Verdrehen des Stabes an seiner Mantelfläche ( Randschicht ) auftretende Schiebung yR zwischen 0,4 und 0,5 liegt.2. The method according to claim 1, characterized in that which occurs during the rotation of the rod on its outer surface (surface layer) shift y R lies between 0.4 and 0.5. 3. Vorrichtung zur Durchführung des Verfahrens nach Anspruch 1, gekennzeichnet durch zwei den Stab ( 12 ) an seinen Enden erfassende und einspannende Greifvorrichtungen, von denen mindestens eine Vorrichtung den Stab ( 12) um seine Längsachse verdrehende, angetriebene Greifklauen ( 11 ) od. dgl. aufweist.3. Device for carrying out the method according to claim 1, characterized by two gripping devices which grip and clamp the rod (12) at its ends, of which at least one device rotates the rod (12) about its longitudinal axis, driven gripping claws (11) or the like . having. 4. Vorrichtung nach Anspruch 3, dadurch gekennzeichnet, daß die Greifvorrichtungen an den Stabenden als einen elektrischen Strom zur Widerstandserwärmung in den Stab ( 12 ) einleitende Elektroden ausgebildet sind.4. The device according to claim 3, characterized in that the gripping devices at the rod ends are designed as an electrical current for resistance heating in the rod (12) leading electrodes.
EP87112672A 1986-09-29 1987-08-31 Method and apparatus for manufacturing coil springs Withdrawn EP0263300A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3633058 1986-09-29
DE19863633058 DE3633058C1 (en) 1986-09-29 1986-09-29 Method and device for producing a coil spring

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EP0263300A1 true EP0263300A1 (en) 1988-04-13

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0526689A1 (en) * 1991-07-23 1993-02-10 Krupp Brüninghaus GmbH Process for the making of a helical compression spring
WO2004087968A2 (en) * 2003-04-04 2004-10-14 Thyssenkrupp Automotive Ag Method for the thermomechanical treatment of steel
CN1332058C (en) * 2003-01-10 2007-08-15 西北工业大学 Prepn of rod superfine crystal material
CN101956777A (en) * 2009-07-14 2011-01-26 上海中洲特种合金材料有限公司 Heat treating method of nickel-base alloy cylinder spiral torsion spring

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102014214592B4 (en) * 2014-07-24 2018-07-12 Volkswagen Aktiengesellschaft Spring spring made of spring steel and method for producing a helical spring

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DE676746C (en) * 1935-11-09 1939-06-10 Bosch Gmbh Robert Method of making a coil spring from twisted wire
DE1758510A1 (en) * 1968-06-15 1971-01-21 Brueninghaus Gmbh Stahlwerke Process for the production of austenitic form-hardened coil springs and system for executing the process
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DE1945597A1 (en) * 1968-09-13 1972-03-02 Ford Werke Ag Process for making improved fatigue resistant steels
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US2082580A (en) * 1933-10-24 1937-06-01 Spencer Mfg Company Bodies for withstanding alternating stresses and manufacture thereof
DE676746C (en) * 1935-11-09 1939-06-10 Bosch Gmbh Robert Method of making a coil spring from twisted wire
DE1758510A1 (en) * 1968-06-15 1971-01-21 Brueninghaus Gmbh Stahlwerke Process for the production of austenitic form-hardened coil springs and system for executing the process
DE1945597A1 (en) * 1968-09-13 1972-03-02 Ford Werke Ag Process for making improved fatigue resistant steels
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SU688528A1 (en) * 1977-06-27 1979-09-30 Yasenchuk Pavel D Method of manufacturing springs

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SOVIET INVENTIONS ILLUSTRATED, Sektion Chemie, Woche C21, Zusammenfasssungsnr. M24 P52, Derwent Publications Ltd., London, GB; & SU - A - 688 528 (P D YASENCHUK) 30.09.79 *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0526689A1 (en) * 1991-07-23 1993-02-10 Krupp Brüninghaus GmbH Process for the making of a helical compression spring
CN1332058C (en) * 2003-01-10 2007-08-15 西北工业大学 Prepn of rod superfine crystal material
WO2004087968A2 (en) * 2003-04-04 2004-10-14 Thyssenkrupp Automotive Ag Method for the thermomechanical treatment of steel
WO2004087968A3 (en) * 2003-04-04 2005-04-28 Thyssen Krupp Automotive Ag Method for the thermomechanical treatment of steel
CN101956777A (en) * 2009-07-14 2011-01-26 上海中洲特种合金材料有限公司 Heat treating method of nickel-base alloy cylinder spiral torsion spring

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