US3574000A - High flexibility steel wire and method of treating same - Google Patents

High flexibility steel wire and method of treating same Download PDF

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Publication number
US3574000A
US3574000A US805941*A US3574000DA US3574000A US 3574000 A US3574000 A US 3574000A US 3574000D A US3574000D A US 3574000DA US 3574000 A US3574000 A US 3574000A
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Prior art keywords
wire
temperature
transformation
cooling
patented
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US805941*A
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English (en)
Inventor
Hans Geipel
Wilfried Heinemann
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Huettenwerk Oberhausen AG
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Huettenwerk Oberhausen AG
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Priority claimed from DE19681583986 external-priority patent/DE1583986A1/de
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
    • B21B45/02—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for lubricating, cooling, or cleaning
    • B21B45/0203—Cooling
    • B21B45/0209—Cooling devices, e.g. using gaseous coolants
    • B21B45/0215—Cooling devices, e.g. using gaseous coolants using liquid coolants, e.g. for sections, for tubes
    • B21B45/0224—Cooling devices, e.g. using gaseous coolants using liquid coolants, e.g. for sections, for tubes for wire, rods, rounds, bars
    • 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

Definitions

  • Our present invention relates to a method of treating steel Wire to improve its tensile, fiexural and torsional properties, and to a wire so treated.
  • the conventional practice is to wind the hot wire from the last rolling station into a coil, allowing the coil to cool and thereafter heattreating the wire in a fused bath, such as molten lead.
  • This type of heat treatment is generally referred to as patenting, a term which may also be used more broadly for the cooling of wire in any medium at a controlled rate from a level above the critical point Ac (transformation of austentite to ferrite) to a range in which austentite is transformed into pearilte.
  • the wire so treated should have a predominantly sorbitic crystal structure.
  • Sorbite is a fine-grained variant of pearlite and comes into existence upon transformation of austenitic steel at a temperature of approximately 550 C. If the transformation occurs at a lower level, generally below 500 C., the pearlite crystals are still smaller and form a structure known as bainite. This structure is considerably harder than the sorbite and unsuitable for drawing.
  • a method of patenting such a wire in a cooling medium of the fluidized-base type i.e. a stream of carrier gas with entrained solid particles such as ceramic granules of elevated heat-transfer coefiicient (preferably between about 500 and 1000 Cal./m. /hr./C.).
  • the particles may consist, for example, of magnesia and may range "ice between 0.03 and 0.15 mm. in diameter, with a bulk weight of 1.5 to 5 g./cm.
  • Hydrogen, carbon monoxide or other relatively inert gases conventionally used in metallurgical processes may serve as the carrier fluid.
  • the temperature of the cooling medium may be well below the bainite-formation level of about 500 C.
  • transformation is completed above that level because the wire is led out of the fluidized bed in a state of incipient transformation before its temperature falls below the 500 C. mark.
  • This method can be applied directly to wire coming hot from a rolling mill and thus represents a more economical process for obtaining the desired sorbitic structure with substantial exclusion of bainite.
  • the general object of our present invention is to provide a steel wire of high fiexural and torsional endurance, e.g. for use in coil springs.
  • austenitic steel wire with a carbon content between about 0.3 and 0.9% (by Weight) is treated in a manner resulting, independently of the type of cooling medium employed, in a structure having the desired ductility and strength for the purposes specified above. This is accomplished by immediately cooling the hotrolled wire at a rapid rate of at least 20 C. per second to a temperature within the austentite/pearlite transformation range, i.e. a temperature lying generally between 500 and 550 C. although its lower and upper boundaries may be around 480 and 580 C., respectively.
  • the forcedcooling process which should start not later than about one second after the wire has left the last rolling stage at a minimum temperature of about 800 0., should lower the temperature of the Wire to a level below the 608 line of the iron-carbon equilibrium diagram within a few seconds and should be terminated after not more than about 10 seconds from the time of its inception: the G08 line should be penetrated during the first half of that phase, preferably within the first two seconds after discharge of the wire from the rolling mill.
  • the final transformation phase may proceed substantially isothermally over a period of about 10 seconds.
  • the initial cooling phase (past the GOS line) may be carried out by quenching in water while the subsequent cooling is performed in a fluidized bed as described above.
  • a wire so treated has surprisingly high stress resistance along with the necessary ductility allowing it to be drawn to the desired final diameter. Without wishing to commit our to any definite theories in explaining these phenomena, we ascribe them to a freezing of the molecular structure produced by rolling which may be characterized by a high density of dislocations.
  • transformation proceeds to completion under substantially isothermic conditions, i.e. without the use of a cooling medium other than the surrounding atmosphere.
  • a cooling medium other than the surrounding atmosphere.
  • the final cooling, subsequent to transformation, may also take place in air.
  • the temperature of the emerging wire In order to stabilize the temperature of the emerging wire within the desired range of approximately 500 to 550 C., we prefer to measure that temperature and to compare it with a predetermined value to compensate for deviations therefrom by a corrective adjustment of the bed temperature and/ or of the residence time of the wire in the fluidized bed.
  • To control the temperature of the cooling medium we prefer to remove particles continuously from the bed and to let them pass through a cooling chamber before returning them to the bed; this recirculation of the particles is best accomplished with the air of a flow of carrier gas which may itself be recirculated.
  • Wire so treated when observed under the electron microscope, exhibits a structure of distinct lamellate zones, not encountered in conventionally lead-cooled material, which account for a significant part of the cross-sectional area, the lamellae of the several zones extending in different directions while lying substantially parallel to one another within each zone.
  • This lamellate structure may account for the surprising fact that the treated wire according to our invention has both a torsional and a flexural endurance appreciably greater than those of lead-patented wire of like composition and dimensions.
  • Particularly good results are obtained with steels having a carbon content between about 0.5 and 0.7%, by weight, which pass the GOS line near the 750 level so that a workpiece with an initial temperature of 800 to 850 C. can be brought to that level in 1 to 3 seconds by forced cooling at a rate of 30 to 50 C. per second.
  • the wire so treated is cold-drawn, in a manner known per se, so as to undergo a deformation of approximately 80 to 90% in terms of reduction of cross-sectional area, corresponding to a decrease in diameter by a factor of roughly 1.5 to 3.5.
  • the drawn wire exhibits a torsional capacity exceeding that of conventionally lead-patented drawn Wire of like dimensions and composition by about 20%, its bending capacity lying by about 10% above that of the conventional wire.
  • a plant suitable for carrying out the aforedescribed method comprises a conveyor, preferably in the form of an apertured belt, passing through a channel together with the stream of carrier gas and entrained solid particles; the discharge end of the channel is provided with a gate through which the cooled wire may emerge while the particles are retained and form a nearly stationary accumulation around the exiting wire.
  • the hot incoming wire may be deposited on the conveyor in a succession of loops, advantageously with the aid of a transversely oscillating dispenser as disclosed and claimed in our commonly owned application Ser. No. 675,405 filed Oct. 16, 1967.
  • FIG. 1 is a transformation diagram showing the conversion of austenitic steel to sorbite by conventional means and by our present process
  • FIG. 2 is a somewhat diagrammatic side-elevational view of a plant for carrying out the process
  • FIG. 3 is a fragmentary view similar to FIG. 2, showing a modification
  • FIG. 4' represents part of the iron-carbon-equilibrium diagram, including the G05 line.
  • FIGS. 5 and 6 are two electron micrographs taken, respectively, of wire according to the invention and of conventionally lead-patented wire.
  • FIG. 1 we have shown at A and B the boundaries of the austenite/pearlite transformation range for a typical steel wire of 5.5 mm. diameter, made from unalloyed steel with a carbon content of 0.5%.
  • Graph e represents an idealized process whereby the wire is rapidly cooled, from a starting temperature of 860 C. attained at the output stage of the rolling mill, to a level of 550 C. which it reaches after 1 /2 seconds and where the graph intersects the boundary curve A of the transformation range. After a further interval of about 18 /2 seconds, with gradual cooling to a point at or above 500 C., the transformation to sorbite would be completed without the formation of appreciable quantities of bainite.
  • Such an idealized cooling process e.g. with quenching in water, would be difficult to realize because of the problems of temperature 4 control and appears to be impractical for any but the thinnest wires.
  • the treatment of wire in accordance with out present invention is represented by graphs b, c and h.
  • Graph c applies to ceramic particles with 850. The particle temperature is maintained Well below 500 0, yet contact between the particle stream and the wire is terminated at a point p or q, thus after 9 or 6 seconds, respectively, when the wire temperature drops to a level of 520 C.
  • Curve i represents the limiting case of cooling at a rate of 20 C. per second down to a level of 580 C. within about 10 seconds, followed by substantially isothermal completion of transformation at that level during an interval of slightly less than 15 seconds.
  • the other boundary of the operative region has been partly shown by a horizontal line j marking the 480 level.
  • the boundary between austenite and the ferrite/austenite mixture lies at a level of approximately 750 C. for steel having a carbon content of about 0.6%.
  • the G08 line has been indicated at that level and is shown to intersect the curves b, c and h within the first two seconds and at points where the rate of cooling, as represented by the slopes of these curves, is well over 20 C. per second. If the initial cooling is carried out by an air stream or by water, e.g, with the aid of spray nozzles, the transition to a fluidized bed may take place immediately below the 603 line, thus at a temperature of about 700 C.
  • the plant comprises a fluid zed bed 1 confined within a tunne 24, forming an elongated flow channel, to the vicinity of the upper run of an endless conveyor belt 2 which is continuously driven by a motor 15 so that a hot wire 3, deposited thereon after leaving the last stage of a hot-rolling mill and preferably after preliminary quenching as indicated in FIG. 1, is transported on a downwardly sloping path from right to left.
  • Wire 3 passes through a guide tube 4 and a continuously rotating dispenser arm 25, driven by a motor 26, whose rotation forms the wire into a succession of loops deposited on the conveyor 2; the dispenser arm 25 may be subject to continuous transverse oscillations at a frequency related to the loop-deposition rate, as described in our copending application Ser. No. 675,405, for the purpose of insuring optimum distribution of the loops over the available conveyor surface.
  • a perforated base 27 within tunnel 24 forms the lower boundary of bed 1 and is connected to outlets of a manifold 10 through which a carrier gas, as indicated by the arrows, is passed at longitudinally spaced locations by way of the interstices of belt 2 into the space thereabove.
  • the branch conduits of manifold 10 contain respective valves 9 for controlling the amount of gas thus introduced.
  • a further valve 28 controls the input from a compressor or other high-pressure source, not shown, whereas two other valves 29, 30 determine the proportion in which a portion of the gas is branched off into a conduit 5 into which opens an outlet of a cooling chamber 6, the latter containing a coil 22 traversed by a coolant.
  • Conduit 5 opens into the tunnel 24 in the vicinity of the housing 23 of the dispenser arm 25.
  • Solid particles entrained by the gas stream accumulate in a pile just ahead of the shutter 8 where the tunnel 24 is formed with a discharge port 7 for these particles.
  • a similar accumulation is formed at the entrance end of the tunnel by means of a stationary plate 31 undnerlying the upper run of conveyor belt 2 beneath an inlet branch 32 of conduit 5.
  • Port 7 communicates with a further conduit 33 which leads to the top of cooling chamber 6 and which may include means, such as a pump 34, to promote the return of solid particles from the discharge end of tunnel 24 to the cooler.
  • a bypass 20, controlled by a valve 38, enables the recirculation of some or all of the gas to manifold 10.
  • a temperature feeler 11 just beyond shutter 8 senses the temperature of the emerging wire loops and feeds this information to a comparator 13 receiving a reference signal from a storage device 12 adjusted to the desired exit temperature (e.g. 520 C.).
  • Comparator 13 sets a controller 14 which, if necessary, adjusts the speed of motor to vary the residence time of the wire in the fluidized bed 1 in a manner compensating for any deviations of its exit temperature from the preset reference value.
  • Dispensing arm is, of course, representative of any conventional type of loop depositor including, for example, devices of the type shown in US. Pats. Nos. 3,056,433 and Re. 26,052.
  • FIG. 3 where elements corresponding to those of FIG. 2 have been designated by the same reference numerals with addition of a prime mark, we have shown the temperature sensor 11 disposed ahead of shutter 8'. Sensor 11' ascertains the exit temperature of the wire in terms of the temperature of the fluidized bed 1 at the discharge end of tunnel 24' and, as before, communicates this information to a controller 14'; the output of this controller, in contradistinction to the previous embodiment sets a servomotor 40 which adjusts a valve 41 to regulate the amount of cooling fluid passing through coil 22 of chamber 6'.
  • the system operates otherwise in the same manner as the arrangement of FIG. 2.
  • the control systems 11,-11' shown in FIGS. 2 and 3 could also be combined in a single plant.
  • EXAMPLE I Steel wire containing 0.58% C, 0.38% Mn, 0.24% Si, 0.01% P and 0.02% S (all percentages by weight), balance Fe and usual impurities, is rolled to a diameter of 5.5 mm. at a temperature of 800 C. One second after leaving the last rolling stage, forced cooling of the wire is started, proceeding at an average rate of 40 C. per second to a level of 520 C., this temperature being maintained for 12 seconds while the transformation from gamma to alpha iron proceeds to completion.
  • the wire After pickling and rustoproofing (bonderizing), the wire is drawn without further heat treatment to a diameter of 1.8 mm., this corresponding to a deformation of about Wire so drawn exhibited a tensile strength of kg./ mm. and withstood 22 consecutive cycles of flexing and straightening.
  • a cable formed from six strands of seven such wires each was found to have a service life two to four times as long as identical cables made from conventional lead-patented wire.
  • Example II The procedure of Example I is followed, using a wire with a content of 0.65% C, 0.55% Mn, 0.24% Si, 0.012% P and 0.2% S, rolled to the same diameter of 5.5 mm. After pickling and bonderizing, the wire is drawn without further heat treatment to a diameter of 2.2 mm., this corresponding to a deformation of about 85%.
  • EXAMPLE III The composition of the steel is 0.66% C, 0.76% Mn, 0.23% Si, 0.019% P and 0.029% S, balance again iron and usual impurities.
  • the further treatment is the same as in Example H.
  • FIG. 5 The structure of the drawn wire obtained by Example III and deformed in accordance with Table 2, as observed under the electron microscope with a magnification of 4,000: 1, has been illustrated in FIG. 5 whicn shows distinct lamellate zones distributed throughout the cross-sectional area of the steel sample;
  • FIG. 6 representing a similar electron micrograph for lead-patented wire subjected to the same drawing process, exhibits only the rudiments of such lamellae at isolated locations.
  • Coil springs of 85 mm. diameter, 110 mm. length and 5 four turns, formed from this wire showed an axial compression of only 7% after 10,000 alternate cycles of compression and relaxation, compared with a 20% for shortening in the case of identical springs of conventionally lead-patented wire.
  • An appreciable loss of stability occurred only after 60,000 compression cycles, as compared with approximately 40,000 cycles for the conventional spring.
  • Strands of such wire may also be twisted into a cable of great flexibility.
  • a method of producing wire of high torsional and fiexural capacity comprising the steps of:
  • a method as defined in claim 1 wherein the rate of 35 forced cooling is between substantially 30 and 50 C.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Silicon Compounds (AREA)
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US805941*A 1968-02-15 1969-02-17 High flexibility steel wire and method of treating same Expired - Lifetime US3574000A (en)

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DE19681583986 DE1583986A1 (de) 1968-02-15 1968-02-15 Verwendung von Walzdraht aus Stahl fuer die Herstellung von gezogenem Draht,der gleichzeitig hohe Biegefestigkeit und hohe Torsionswerte aufweist

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AT (1) AT294880B (de)
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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS4873323A (de) * 1972-01-07 1973-10-03
US3844848A (en) * 1972-11-15 1974-10-29 British Ropes Ltd Production of low alloy steel wire
US3926687A (en) * 1973-09-10 1975-12-16 Nippon Steel Corp Method for producing a killed steel wire rod
US4759806A (en) * 1986-01-10 1988-07-26 N.V. Bekaert S.A. Process for manufacturing pearlitic steel wire and product made thereby
US4770722A (en) * 1984-09-07 1988-09-13 Sumimoto Electric Inductries, Ltd. Methods for heat treatment of steel rods
US20020084009A1 (en) * 2000-09-15 2002-07-04 Metso Paper, Inc. Method for making a roll shell of a roll used in the manufacture or further processing of paper and/or board

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0611669A1 (de) * 1993-02-16 1994-08-24 N.V. Bekaert S.A. Wulstkern mit hoher Festigkeit

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS4873323A (de) * 1972-01-07 1973-10-03
JPS5323765B2 (de) * 1972-01-07 1978-07-17
US3844848A (en) * 1972-11-15 1974-10-29 British Ropes Ltd Production of low alloy steel wire
US3926687A (en) * 1973-09-10 1975-12-16 Nippon Steel Corp Method for producing a killed steel wire rod
US4770722A (en) * 1984-09-07 1988-09-13 Sumimoto Electric Inductries, Ltd. Methods for heat treatment of steel rods
US4759806A (en) * 1986-01-10 1988-07-26 N.V. Bekaert S.A. Process for manufacturing pearlitic steel wire and product made thereby
US20020084009A1 (en) * 2000-09-15 2002-07-04 Metso Paper, Inc. Method for making a roll shell of a roll used in the manufacture or further processing of paper and/or board

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GB1233522A (de) 1971-05-26
FR1600150A (de) 1970-07-20
AT294880B (de) 1971-12-10

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