EP0054343B1 - Verfahren und Vorrichtung zur Herstellung verjüngter Stangen - Google Patents

Verfahren und Vorrichtung zur Herstellung verjüngter Stangen Download PDF

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Publication number
EP0054343B1
EP0054343B1 EP19810304219 EP81304219A EP0054343B1 EP 0054343 B1 EP0054343 B1 EP 0054343B1 EP 19810304219 EP19810304219 EP 19810304219 EP 81304219 A EP81304219 A EP 81304219A EP 0054343 B1 EP0054343 B1 EP 0054343B1
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EP
European Patent Office
Prior art keywords
metallic material
temperature
heating
blank
accordance
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP19810304219
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English (en)
French (fr)
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EP0054343A2 (de
EP0054343A3 (en
Inventor
Tetsuo Kato
Shozo Abeyama
Makoto Saito
Hiroyasu Nagasaka
Masashi Mizuno
Toshio 1811-5 Aza-Kamiyashiki Endo
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Daido Steel Co Ltd
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Daido Steel Co Ltd
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Publication date
Priority claimed from JP17503180A external-priority patent/JPS5797819A/ja
Priority claimed from JP17627680A external-priority patent/JPS57100816A/ja
Application filed by Daido Steel Co Ltd filed Critical Daido Steel Co Ltd
Priority to AT81304219T priority Critical patent/ATE8970T1/de
Publication of EP0054343A2 publication Critical patent/EP0054343A2/de
Publication of EP0054343A3 publication Critical patent/EP0054343A3/en
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Publication of EP0054343B1 publication Critical patent/EP0054343B1/de
Expired legal-status Critical Current

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    • 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
    • C21D9/0075—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for rods of limited length
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES, PROFILES OR LIKE SEMI-MANUFACTURED PRODUCTS OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
    • B21C37/00—Manufacture of metal sheets, rods, wire, tubes, profiles or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape
    • B21C37/04—Manufacture of metal sheets, rods, wire, tubes, profiles or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape of rods or wire
    • 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 of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/06—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
    • 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
    • C21D2281/00—Making use of special physico-chemical means
    • C21D2281/02—Making use of special physico-chemical means temperature gradient

Definitions

  • This invention relates to a method for manufacturing tapered rods and an apparatus therefor. More particularly, it relates to the method for manufacturing tapered rods and bars from a predetermined metallic material extremely efficiently, i.e., minimizing the material loss and maximizing the productivity, and also to an apparatus applicable for the method.
  • tapered rods employed for the rapidly prevailing tapered coil springs are provided with a larger diametered portion (a) in the central portion and a continuously diameter diminishing tapered portions (b) on either side of the former, as shown in Fig. 1.
  • a rod having the larger diametered portion (a) in the central portion and the diameter diminishing portions (b) on either side is actually employed as a material in production plants of the tapered coil springs.
  • a coil spring made of a tapered rod of this type the varying trend of its height which is observed according to the variation of load is non-linear (A) as can be seen in Fig.
  • the tapered rods as material of the tapered coil springs have been conventionally manufactured chiefly by machining wires or rods of a desired metallic material. Machining of the metallic material naturally yields a great deal of material loss, and needs in addition much time, remarkably degrading the productivity.
  • the invention concerns a method for manufacturing a tapered rod according to claims 1 and 13 and concerns an apparatus for carrying out the method according to claims 17 and 21.
  • the pre-selected metallic material is imparted locally temperature-gradient in the axial direction by heating and that the heated metallic material with the locally gradient temperature pattern is axially stretched by pulling.
  • the metallic material placed under tensile force for pulling will be a tapered rod having a locally varied diameter in the axial direction according to the gradient pattern of the heating temperature.
  • a metallic material or blank can be made into a desired tapered rod, in this invention, only by being imparted a desired pattern of temperature-gradient heating to the taper needed portions thereof alone before being given the axial tensile force.
  • a desired tapered rod can be obtained in a remarkably short time, eliminating all of the conventional tedious and time-consuming processes such as machining process which needs much time and material loss, hot forging process which requires a long and inefficient forging time, etc.
  • This method can be said to have much contributed to the cost reduction of the tapered rods through the simplification of the process and the shortening of the required time.
  • strain rate i.e., rate of deformation of the sectional area of the metallic material per unit of time when it is stretched or pulled to be deformed in the axial direction is of extreme importance. It is furthermore important that the deformation of the sectional area in the minimum diametered portion is kept within a predetermined extent. They have found that effective manufacturing of the desired tapered rods can be achieved by observing this principle in the actual practice.
  • timewise pattern of pulling has given the following features to the method of this invention.
  • a metallic material is pulled by tensile force, under the influence of axially temperature gradient heating, at a rate of strain or deformation within the range of 0.5 %/sec-1000 %/sec in the minimum diametered portion for forming a tapered rod with an axially varied diameter
  • the speed of pulling must be varied such as gradually from high speed to low, reducing intermittently or stepwise the pulling speed by dividing the whole pulling amount into several sections.
  • This pattern of pulling enabled to form effectively a desired tapered portion without incurring breakage of material by local necking and to simultaneously from a cylindrical and parallel portion with a constant diameter in the minimum diametered portion.
  • Metallic materials used for forming the tapered rods in accordance with this invention are usually in the form of wires and rods. Usually they are of steel, but other non-ferrous metals are by no means excluded.
  • the metallic material is desired to be steel wire rod containing carbon of 0.35-1.10% by weight, and further containing, if desired, silicon not exceeding 2.5%, manganese not exceeding 1.5%, copper not exceeding 3.0%, nickel not exceeding 3.0%, chromium not exceeding 5.0%, molybdenum not exceeding 1.0%, vanadium not exceeding 1.0%, boron not exceeding 0.05%, aluminum not exceeding 0.1 %, and titanium, niobium, zirconium, tantalum, tungsten, hafnium respectively not exceeding 0.5%, and the balance in iron.
  • Carbon content of the above-mentioned steel wire rod as the preferable material for the tapered rods should be regulated within the range of 0.35-1.10%.
  • quench hardness is difficult to be obtained in the heat treatment process after the coil formation, which deteriorates necessary characteristics as a spring.
  • proeutectoid cementite will become enormous, which deteriorates life of the spring due to fatige.
  • silicon is effective for improving load loss resistance
  • manganese is good for improving hardenability
  • copper is effective for enhancing weather proof and preventing decarburization during the heat treatment
  • nickel is effective for improving the hardenability and strength (toughness)
  • chromium and molybdenum improve hardenability and resistance to temper softening
  • vanadium is good for improving strength by fining crystal particles
  • boron is capable of improving hardenability by adding trace amount thereof
  • aluminum is effective in elongating the life against fatigue as well as in fining crystal particles so as to lower the ductile-to-brittle transition temperature
  • titanium, niobium, zirconium, tantalum, tungsten, hafnium are respectively advantageous in forming fine carbides so as to improve the resistance to temper softening.
  • All of those additives may be contained separately or in combination within the predetermined ratio of content.
  • Other inevitably contained elements as trace amount of impurities in the course of industrial manufacturing process of the steel wires as the material such as phosphorus, sulphur, arsenic, tin, antimony, zinc, selenium, etc. are all harmless.
  • the pattern thereof should be varied in many ways according to the materalistic quality and dimension of the steel wire, the heating temperature, the tensile condition, the shape of the taper desired, etc. It may be determined specifically for each case, not be decided uniformly or indiscriminately. What can be said in general is that a portion of the steel wire under a high temperature will become finer or thinner in the later tensile operation and a portion under a low temperature less thin. Consequently, for the formation of a continuous taper where the diameter increases or decreases continuously as shown in Fig. 1 a temperature gradient pattern in (a) or (b) of Fig. 3, for example, is preferably utilized.
  • the maximum heating temperature is preferred to be maintained within the range of 600°C-1000°C.
  • breaking elongation of the material becomes low, for example, in case of the earlier mentioned steel wire the elongation against breakage being less than 40%.
  • the material may be broken before it is finally made into an aimed tapered rod due to a possible local necking.
  • oxidization and decarburization of the material surface rapidly progresses so as to greatly deteriorate the life of the final product as a spring against fatigue, which is an undesirable phenomenon.
  • the temperature gradient heating As to a way of imparting the temperature gradient heating, all of the known methods such as direct heating, high frequency induction heating, gas burning heating, infrared ray heating, indirect heating by an electric furnace, etc. are permissible. Any one of those methods may be chosen in accordance with the circumstances.
  • the following two are, for example, recommended as preferable, (1) heating the metallic material directly so that the predetermined temperature-gradient pattern may be formed thereon in the axial direction, and (2) after having heated or while heating the metallic material up to a predetermined high temperature cooling down the same, thereby adjusting the temperature, so as to form the predetermined gradient pattern thereon in the axial direction.
  • heating amount or cooling amount per each portion of the metallic material in the axial direction can be varied according to the pattern of the desired taper, such as by dividing the whole length of a taper, from the central portion to the end portion on either side thereof, into several sections for giving to each section respectively varied amount of cooling air required according to the pattern of the taper, by positionwise varying the diameter or the pitch of electric coils used in a high frequency induction heater in the axial direction of the metallic material according to the pattern of the taper, or by positionwise varying the flow amount of the fuel gas for varying the extent of heating according to position in the axial direction of the metallic material according to the pattern of the taper, and in case of electric resistance heater input amount of the power to a plural series of resistance heating elements can be preferably adjusted per each position of the metallic material according to the pattern of the taper.
  • a metallic material which is given in this predetermined temperature gradient pattern is applied tensile force in the axial direction while being under the gradient heat so as to become a desired tapered rod by gradually changing its diameter according to the pattern of the temperature gradient.
  • a portion under a high temperature becomes small in the diameter and a portion under a low temperature becomes less small in diameter.
  • This tensile force is applied on a metallic material under the influence of the temperature-gradient heating according to the quality, shape, and the targeted form of the taper so as to get a desired rate or speed of strain on the material.
  • this rate of strain of the material must be controlled by all means, for efficiently producing tapered rods of desired shape, while the material is pulled under the temperature-gradient heating. It was also discovered by the inventors that controlling of the rate of strain is preferably made at the minimum diametered portion (maximum uniformly contracted portion) of the formed tapered rod within the range of a certain predetermined value.
  • the tapered rods made by the method of this invention should be applied tensile force at the minimum diametered portion, i.e., the portion under the highest temperature of heating, within the range of process-strain rate (e) 0.5 %/sec-1000 %/sec.
  • process-strain rate e
  • 0.5%/sec should be regarded the lowest limit, because the temperature-gradient pattern in the axial direction actually functions as if it were flat or non- gradient at a rate less than this limit value 0.5%/sec.
  • the rate or speed of strain (e) is meant the amount of deformation per unit of time at the minimum diametered portion, more specifically, the amount of variation of the sectional area, which can be determined in general by the following formula, wherein
  • a metallic material under a predetermined temperature gradient heating when it is pulled at a constant crosshead speed, possibly produces a contracted (constricted) portion at a relatively early stage of pulling, forming a tapered portion only without parallel portion some time, or forming parallel portion only some other time with a tapered portion, even if it is made, having a relatively small rate of reduction.
  • a good tapered rod with a large rate of reduction can not be got by this pulling way of a constant speed.
  • This invention has succeeded in obtaining an excellent tapered rod with a large rate of reduction, perfectly eliminating the conventional disadvantage, by adopting the above-mentioned specific pattern or mode of pulling.
  • Theoretical reasoning for this simultaneous achieving of the tapered portion with a large rate of reduction and the parallel portion can be made as follows:
  • tapered rods having a pair of opposite tapered portions c, d are made from a continuous long wire or a rod by a continuous and repetitive forming operation
  • a long wire or rod having a plurality of tapered portions with a predetermined equal distance therebetween can be, before or after a necessary after-treatment and/or after-process, cut at a predetermined position one after another to have finished tapered rods of constant length.
  • this method is also effective to form one or two tapered rods from a relatively short material of limited length instead of the earlier mentioned long material.
  • the taper portion formed on the material may be various in its shape, such as linearly and continuously diameter increasing or decreasing like one show in Fig. 3(c), with one or two steps in c (d) portion, or outwardly convex or inwardly concave.
  • various modifications are permissible, for example, forming only one taper portion, forming a large diametered portion in the middle with two small diametered portions on either side thereof just contrary to the mode in Fig. 3(c), in addition to the mode having two large diametered portions on either end as can be seen in Fig. 3(c).
  • the undermentioned apparatus is preferably employed.
  • An apparatus including a pulling mechanism for pulling a metallic material of wire stack chucked at two points on the axial direction of the material in a direction enlarging the distance between the two points, and heating means composed of plural steps arranged between the two points for heating the metallic material at each step so as to form a predetermined temperature gradient pattern to the material, whereby the metallic material is imparted the temperature-gradient heating while being pulled in either direction by the pulling mechanism to become a tapered rod with a varying diameter in the axial direction thereof.
  • An example of the apparatus is shown as a diagrammatic view in Fig. 4, wherein numeral 1 designates a round steel rod.
  • the rod 1, which is chucked at a chuck 2, 2 on either end thereof is pulled by a suitable means such as a hydraulic cylinder (not shown) so that the distance between the two chucks 2, 2 may be enlarged. That is to say, the rod 1, is pulled in two directions marked with D arrows so as to be elongated between the chucks 2, 2.
  • a suitable means such as a hydraulic cylinder (not shown) so that the distance between the two chucks 2, 2 may be enlarged. That is to say, the rod 1, is pulled in two directions marked with D arrows so as to be elongated between the chucks 2, 2.
  • high frequency induction heaters n pieces from H 1 to H n , whose number of coil winding is identical for each, are arranged in the axial direction of the rod 1 such that each of the heaters constitutes a heating zone for each position of the rod 1 in the axial direction thereof.
  • each of the coils H 1 ⁇ H n independently controlled or regulated high-frequency current to a predetermined extent is flowed from a controlling means 3.
  • a controlling means 3 By means of varying the amount of current flowed to each coil H,-Hn' density of the induction current flowed in each position of the rod 1 is varied, which means the heating amount to the rod 1 is varied according to the position thereof. It can be said further in other words that a temperature-gradient pattern is formed corresponding to each position of the rod 1.
  • the invented apparatus is further provided with a series of heat-measuring meters or temperature detectors T l- T n , each being faced to each of the heating zones on the rod 1, for measuring or detecting the actual temperature of the heated zone respectively. In order to adjust the heating temperature at each heating zone, the temperature picked up at the meters T,-T n is respectively fed back to the controlling means 3 for thereby controlling the current amount flowed to each of the coils H,-H n independently.
  • the rod 1 which is given a temperature-gradient heating to each heating zone thereof while being pulled in either D direction at the chuck 2, 2, is affected by respectively different amounts of high-frequency heating according to position in the axial direction.
  • the rod 1 will show different rates of extension or elongation, although it is under one uniform tensile force, according to the position in the axial direction of the rod 1. This is why a desired taper is formed.
  • the current flowing to the stepped coils H i -H n is respectively controlled or regulated, and the actual temperature at each heating zone formed by the coils H I -H n is measured by the meters T I -T N and fed back for thereby controlling the temperature of the coils H i -H n to a target value. Consequently the temperature of each coil H i -H n can be regulated at will for desirably varying the form of the taper. The heating temperature and consequently the form of the taper can be exactly controlled in such an apparatus.
  • the density of the coil turn number should be made larger in the induction heating coils located in the central portion of the metallic material in the axial direction and that of the coils located the farther away from the central portion made smaller, and similarly the diameter of the coil should be, if a way of varying the coil diameter is adopted, made smaller in the induction heating coil located in the central portion of the metallic material in the axial direction and that of the coils located the farther away from the central portion made larger.
  • direct resistance heating method is also preferably applicable. While directly flowing electric current to a wire state metallic material from the two points thereon in the axial direction, dispose a plurality of cooling zones in the axial direction of the material for imparting portionwise controlled cooling to each of the positions on the material. The heated material by the current flowing while being under pulling in either direction is pattern- wise cooled by the temperature gradient cooling zone. The material thus can be formed into a tapered rod with varying diameter in the axial direction.
  • the heating amount by the direct resistance heating is measured at any suitable position between the two points on the material for controlling the heating amount by the data of the measurement.
  • This apparatus is characterized in that the temperature of heating at the measuring position itself is so controlled as to be at the targeted level.
  • Numeral 11 designates a round steel rod, each end thereof is chucked respectively by a chuck 12, 22 for being pulled by a not-shown suitable pulling means such as a hydraulic cylinder in an inter-chuck distance enlarging direction, i.e., in the direction marked with D arrows enlarging the length of the rod.
  • the chucks 12, 22 simultaneously function in this connection as a contact for flowing the current of direct resistance heating.
  • the current led through a current adjuster 15 is fed, having been regulated to a predetermined amount, to the rod 11 by way of the chucks 12, 22 to directly heat the same.
  • C 1 -C n are arranged to constitute cooling zones at each position of the rod 11 to be cooled.
  • cooled gas such as air is supplied from a gas supplying means 14, for example, a compressor, through each passage P 1 ⁇ P n under control of flow amount controllers S 1 ⁇ S n so as to cool each position of the rod 11 faced respectively to the coolers-by-air C 1 -C n .
  • a known temperature detector consisting of a lense 16 capable of detecting the surface temperature of the rod 11 covering the whole length thereof and an image sensor 17 is disposed for measuring the surface temperature of the rod 11 at least at a portion opposite to a cooler C m located in the central portion of the rod 11 between the two chucks 12, 22.
  • the temperature detector collects radiated energy from the surface of the rod 11 to generate a signal corresponding to the temperature.
  • the signal from the temperature detector (16, 17) which is corresponding to the surface temperature of the rod 11, is applied to a temperature converter 19 for being, after having been converted there to an electric signal, led to the current adjuster 15 and a cooling control system 18.
  • the current to be flowed to the rod 11 is so regulated based on the received temperature signal as to be adapted to the set value therein, i.e., the targeted heating temperature at the measurement position.
  • a commanding signal is generated, caused by an electric signal from the temperature convertor 19, to motors M 1 ⁇ M n according to the set controlling pattern therein.
  • Flow amount adjustors S 1 ⁇ S n are respectively actuated by each motor M 1 ⁇ M n to adjust the air amount V 1 ⁇ V n led to each of the coolers-by-air C 1 -C n .
  • the rod 11 is cooled in this mode to a predetermined temperature at a desired axial position, that is to say, the rod 11 receives a predetermined pattern of heating under a predetermined pattern of temperature-gradient.
  • the temperature of the central portion m of the rod 11 is adjusted by the regulation of the current amount flowed there. This adjustment of heating is carried out by regulating with PID action the current amount flowed to the rod 11, through the current adjuster 15 aiming the target temperature value Tm, based on the input value from the temperature converter 19 which is under the influence of the detected data of the surface temperature of the rod 11 at the middle portion by means of the temperature detector (16, 17).
  • the whole heating condition of the rod 11 can be detected or known.
  • heat adjustment or regulation conducted at the middle portion of the rod 11 is preferably adopted. It is of course possible to detect the surface temperature at a place of the rod 11 other than the middle portion for presuming therefrom the whole heating condition of the rod 11 and conduct the heat adjustment suited for the detected condition. If and when the temperature pattern given to the rod 11 is altered the detection places of the surface temperature are naturally altered, and it is also possible to detect the surface temperature at plural places of the rod 11 for performing the heating regulation based on the predetermined targeted value.
  • the cooling control i.e., current flow heating plus air cooling
  • the cooling control is normally not practiced. Only when the temperature T m at the position m has largely overshot cooled air is blown through the passage P m into the cooler-by-air C m . In some cases, however, it is rather preferable, according to the pattern of the temperature-gradient, to carry out the heating regulation at the position m by parallelly using the current flow heating and the air cooling, which naturally permits the heating regulation at other places of the rod 11.
  • Temperature at other places than the position m is usually started to be adjusted by cooling when the temperature at the position m has reached the targeted temperature T m , because the position m is the place to be heated highest. It is of course permissible to begin adjusting the temperature of the other places by regulating the heating temperature by air cooling at the beginning of heating, if the circumstances require.
  • the cooling adjustment is executed by controlling the flow amount V 1 ... V n of cooling gas (air) delivered to the coolers-by-air C, ... Cn which is conducted by the motors M,, M 2 , ... M n through suitable adjustment of the degree of opening of the valve or slit in the flow amount adjusters S 1 ,... S n .
  • the flow amount or supply amount of the cooling gas can be determined beforehand, according to each temperature gradient pattern by experiments or the like.
  • the temperature of the rod 11 can be thus regulated in two ways, one being the heating regulation to the current flowing thereto by regulating the current amount through adapting the actually measured surface temperature of the rod 11 to the target temperature, and the other being the cooling control executed by the plurality of coolers-by-air C1,... C n axially arranged which are variable in the cooling capacity from each other due to the predetermined amount of cooling gas flown to each of them.
  • Such parallel regulation of heating and cooling enables effective formation of a temperature-gradient pattern shown in Fig. 3(a), for example.
  • a material, or a rod 11, placed under such a temperature gradient is, when bidirectional predetermined tensile force is applied between the two chucks 12, 22, formed into a tapered rod with taper portions c, d shown in Fig. 3(c) because of positionwise different rate of elongation of the material.
  • the temperature of the rod 11 at the temperature measuring position m which is the reference for the heating regulation, can be exactly controlled to the target value T m , but as to the temperature at other places some discrepancy or difference may take place between the actual heating temperature and the target temperature, because it is controlled in two ways, i.e., cooling from the coolers-by-air C 1 ,..., C n , whose amount of cooling gas is determined by experiments or the like, and direct resistance heating.
  • the flow amount of the cooling gas introduced to the coolers-by-air C 1 ,..., C n is also controlled by the temperature data measured by the temperature detector (16, 17).
  • the temperature detector (16, 17) carries out for this reason the temperature detecting at plural positions in the axial direction of the rod 11, and a commanding signal from the cooling control system 18 is generated after each termination of one taper formation cycle for being received by the coolers-by-air C 1 ,..., C n as data for controlling the flow amount of the cooling gas in the next taper formation cycle.
  • determination of the cooling gas flow amount is executed per each heating and temperature raising of the rod 11 for one taper formation cycle, but the determined value is by no means changed during one heating and temperature raising cycle, which means the control of the cooling gas flow amount is executed only intermittently.
  • Determination of cooling gas flow amount to each of the coolers-by-air C 1 ,..., C n is performed, more specifically, in the undermentioned mode.
  • set value un of the motor M 1 for determining the cooling gas flowing amount for the next controlling cycle of the cooler-by-air C is determined by the calculation of the following equation in the cooling control system 18 wherein designates a set value for the motor M, in the previous cooling cycle, and k and k' are constants in the adjusting operation.
  • the set value for the motor M for determining the flow amount of the cooling gas can be calculated in the above-mentioned method, which enables a further exact cooling control well suited to the target temperature distribution in the next taper formation process or cycle. It is also possible, instead of respectively calculating from the data of actual measurement of the surface temperature at each position of the rod 11, to measure at plural positions thereon the actual temperature for deducting the temperature distribution in general and to determine the cooling amount or blowing air amount each of the coolers-by-air C 1 ,..., C n , based on comparison between the measured temperature distribution and the targe temperature distribution.
  • FIG. 8 A further excellent embodiment of an apparatus for this direct resistance heating method is shown in Fig. 8, wherein dimensional data of the actually produced taper pattern is entered to a calculator, in addition to the conventional control of the taper pattern based only on the surface temperature of the rod 11, for performing more exact cooling control adapted to the target taper pattern. Allotting the same numerals and signs to the same places as in the previous embodiment for omitting the description, only the dissimilar places are explained hereunder.
  • Numeral 13 designates a temperature detector including a lense and an image sensor as in the previous embodiment, and to each of the coolers-by-air C,, ... , C n arranged in the axial direction of the rod 11 predetermined amount of cooling gas which is controlled under a command from the cooling control system will be led in.
  • a tapered portion in an article processed in one taper formation cycle is measured dimensionally of its taper portion by a dimension measuring device 20 for being entered to a temperature pattern adjuster 21, wherein adjustment or correction of the target temperature distribution pattern is carried out. More specifically, comparison between the target temperature pattern set in the temperature pattern adjuster 21 and the measured temperature pattern just entered is conducted for altering the temperature pattern which has been so far the reference for the cooling control. Relation between the dimensionally indicated taper and the temperature distribution pattern is made more close and intimate. Relation between the attempted taper pattern and the temperature pattern are not necessarily accordance in actual experiments, but discrepant sometime, wherein the temperature pattern adjuster 21 has ita raison d'etre.
  • Adjusted temperature pattern information from the temperature pattern adjuster 21 is entered into the cooling adjustment system 18, wherein regulating command for directing the cooling gas flow amount to each of the coolers-by-air C 1 ,..., C n for the next taper pattern formation process is generated based on the entered temperature pattern from the temperature converter 19 according to the corrected temperature pattern.
  • the metallic material made into tapered rods is usually in a wire state, but it may be a rod member, a hollow pipe member.
  • shape of the material rectangular, square, etc. in section are all permissible; as to the species of the material non-ferrous metals are permissible besides the usually employed steel.
  • the tapered rods obtained by a method as claimed have a variety of uses, besides the use as tapered coil springs, such as for antennas, ski stocks if the material is of hollow, lamp posts, etc.
  • Test pieces (round bars) A and B of steel material SAE 9254 at room temperature, whose diameter was 6.35 mm and length 170 mm, were grasped on either end by a water cooling chuck leaving the heatable area approx. 100 mm inbetween. Direct resistance heating was made in both pieces so that the middle portion thereof might be heated up to 850°C ⁇ 5°C. Temperature distribution at that time is shown in Fig. 9. The piece A which was imparted such a temperature distribution was applied tensile force at an average rate of strain 10%/sec under the pulling speed of 50 mm/sec, and the piece B under the same condition of the temperature distribution was applied tensile force at an average rate of strain 100%/sec under the pulling speed of 100 mm/sec. Result of taper formation on both pieces are shown in Fig. 10.
  • both pieces A and B which had been heated to form a temperature gradient were stretched or elongated by the axial pulling action at the validly affected distance from 100 mm up to 130 mm.
  • a taper having the minimum diametered portion substantially in the middle thereof was formed, with a diameter continuously increasing towards either end in both pieces.
  • the diameter in the middle of both pieces A, B were respectively 4.83 mm, wherein rate of reduction was 42.1%, and 4.70 mm wherein rate of reduction 45.2%.
  • test piece (round bar) C of the same steel material was heated so as to be of uniform temperature in the axial direction distribution for being pulled axially at an average rate of strain 100%/sec, at a pulling speed of 100 mm/sec, as shown in Fig. 9. It was turned out, as can be seen in Fig. 10, that the minimum diameter portion did not fall in the middle portion of the piece, the diameter did not continuously diminish, and a local necking took place.
  • the resultant temperature distribution is shown in Fig. 11.
  • the diameter in the central portion was 7.1 mm and the rate of reduction observed there was 44.1%.
  • a test piece E of steel rod of JIS SUP 7 at room temperature having a diameter of 9.50 mm and a length of 900 mm, was chucked by a water cooling chuck and applied high-frequency induction heating, with coil individually different in diameter so as to form a temperature gradient pattern along the heatable area of 500 mm, wherein the temperature in the central portion being 900°C ⁇ 5°C and that on either end portion 650°C.
  • the temperature distribution was in such a state as shown in Fig. 11.
  • an average rate of strain was 60%/sec and speed of pulling 300 mm/sec.
  • the piece E which possessed the inter-chuck distance of 500 mm was elongated to 700 mm, and the formed taper had the minimum diametered portion in the central portion and a continuously diminishing diameter.
  • the diameter of the piece E in the central portion was 6.45 mm and the then rate of reduction was 53.0%.
  • Axial tensile force applied afterwards with an average rate of strain 50%/sec at a pulling speed of 150 mm/sec showed an elongation of the inter-chuck distance of 300 mm up to 390 mm.
  • the minimum diametered portion was located substantially in the middle thereof and the diameter was continuously decreased towards the middle.
  • the diameter in the central portion of the piece F was 4.55 mm and the rate of reduction observed there was 48.9%.
  • the piece was heated by directly current flowing, while simultaneously employing a plurality of air cooling means, individually different in the amount of blowing air, arranged in the axial direction of the test piece, so as to form a mountain "like temperature gradient pattern along the inter-chuck distance of 200 mm, with a peak in the central portion of 850°C.
  • the piece of steel having the above-mentioned temperature gradient pattern was deformed afterwards by pulling while varying the rate of strain i in the central minimum diametered portion.
  • the maximum reduced ratio under uniform deformation at each rate of strain are shown in Table 1 as the resultant data.
  • the maximum reduced ratio under uniform deformation (%) signifies here the amount of deformation until immediately before the occurring of a necking as a premonition to a breakage, that is (A o ⁇ A) ⁇ 100/A o , i.e., (sectional area of the material-sectional area of the minimum diametered portion) ⁇ 100/sectional area of the material.
  • the numerical data in Table 1 is shown in Fig. 15 as a graph.
  • the resultant data of the MR ratio (%) is parallelly shown in Table 3. In any case of steel material an excellent MR ratio was well proved.
  • a piece of steel rod containing C: 0.61 %, Si: 1.94%, and Mn: 0.81%, having a diameter of 6.35 mm, obtained by rolling and drawing was grasped on either end by a water cooling chuck for being heated by the direct resistance heating method, accompanied by a plurality of cooling means individually different in the amount of air blowing and arranged in each position in the axial direction of the piece so as to form a mountain like temperature gradient pattern along the heatable distance between the chucks of 200 mm wherein the peak of the pattern was 850°C.
  • the MR ratio i.e., the rate of reduction could be made large by the gradual decrease of the rate of strain. Deformation by pulling in the range of such a large MR ratio made the formation of an aimed taper quite easy, because it diminishes the labour hour or labour amount. As can be observed in the figure the larger the rate of variation from the initial speed to the final speed becomes, the larger MR ratio is obtained.
  • the obtained MR ratio was only 26% or so.
  • Example 6 On a piece which had been imparted the temperature gradient pattern in Example 6 was applied a two-stepped pulling as shown in Fig. 17(a) and (b).
  • the two-stepped pulling mode is effective in improving the MR ratio, and further the higher the rate of strain in the first stage is, the larger becomes the MR ratio.
  • a test piece of steel rod which had been imparted a predetermined temperature gradient pattern by the mode described in Example 6 was given a three-stepped pulling operation as shown in Fig. 8(a) and (b).
  • Second way was different from the first way only in the rate of strain applied in the third stage, which was changed to 10%/sec.

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Claims (26)

1. Verfahren zur Herstellung einer konischen Stange aus einem Rohling (1, 11) aus einem metallischen Werkstoff, dadurch gekennzeichnet, daß an den Rohling aus einem metallischen Werkstoff (1, 11) in dessen axialer Richtung (D) eine Zugkraft angelegt wird, während der Rohling aus dem metallischen Werkstoff (1, 11) erhitzt wird, wobei ein Temperaturgefälle in axialer Richtung (D) des Rohlings aus dem metallischen Werkstoff (1, 11) besteht, wodurch die ausgebildete Stange einen konischen Teil (c, d) erhält, der einen sich axial ändernden Durchmesser besitzt, der der Form des Temperaturgefälles entspricht.
2. Verfahren gemäß Anspruch 1, dadurch gekennzeichnet, daß die Zugkraft auf den Rohling aus dem metallischen Werkstoff (1, 11) aufgebracht wird, nachdem der Rohling aus dem metallischen Werkstoff (1, 11) so erhitzt wurde, daß er in seiner axialen Richtung (D) ein Temperaturgefälle besitzt.
3. Verfahren gemäß Anspruch 1, dadurch gekennzeichnet, daß der Rohling (1, 11) aus dem metallischen Werkstoff, der auf eine vorgegebene Temperatur erhitzt wurde, geregelt abgekühlt wird (C1-Cn), so daß in axialer Richtung (D) ein Temperaturgefälle besteht, bevor die Zugkraft aufgebracht wird.
4. Verfahren gemäß Anspruch 1, dadurch gekennzeichnet, daß eine Zugkraft mit einer vorgegebenen Dehnungsgeschwindigkeit an den Rohling (1, 11) aus dem metallischen Werkstoff angelegt wird, der mit dem Temperaturgefälle erhitzt wurde.
5. Verfahren gemäß Anspruch 1, dadurch gekennzeichnet, daß der konische Teil (c, d) einen Durchmesser besitzt, der sich in axialer Richtung (D) des Rohlings (1, 11) aus dem metallischen Werkstoff fortlaufend ändert.
6. Verfahren gemäß Anspruch 1, dadurch gekennzeichnet, daß das Temperaturgefälle bergförmig ausgebildet ist, wobei die Temperatur im axialen Mittelteil des Rohlings (1, 11) aus dem metallischen Werkstoff höher ist und mit zunehmenden Abstand vom Mittelteil fortlaufen abfällt.
7. Verfahren gemäß Anspruch 6, dadurch gekennzeichnet, daß der Rohling (1, 11) aus dem metallischen Werkstoff, ein Endlosdraht oder eine Stange ist und die Erwärmung auf das Temperaturgefälle fortlaufend auf den endlosen Metalldraht in einem vorgegebenen Intervall aufgebracht wird, während der Rohling (1, 11) aus dem metallischen Werkstoff unter einer Zugspannung steht.
8. Verfahren gemäß Anspruch 1, dadurch gekennzeichnet, daß die maximale Heiztemperatur, die bei der Erwärmung mit dem Temperaturgefälle auf den metallischen Werkstoff in dessen axialer Richtung (D) aufgebracht wird, in den Bereich von 600°C bis 1000°C fällt.
9. Verfahren gemäß jedem der Ansprüche 1 bis 8, dadurch gekennzeichnet, daß das Erhitzen des Rohlings (1, 11) aus dem metallischen Werkstoff mit dem Temperaturgefälle in dessen axialer Richtung (D) durchgeführt wird, bevor die axiale Zugkraft an den Rohling (1,11) gelegt wird, um diesen Rohling (1, 11) in axialer Richtung (D) periodisch und immer wieder zu verformen, wobei der konisch verformte metallische Werkstoff an den Stellen mit minimalem Durchmesser (e) geschnitten wird, um die konischen Stangen fortlaufen zu erhalten, die an beiden Enden konisch ausgebildet sind.
10. Verfahren gemäß Anspruch 1, dadurch gekennzeichnet, daß die konische Verformung, um einen konischen Teil (c, d) zu erhalten, mit einer Dehnungsgeschwindigkeit innerhalb eines Bereichs von 0,5°//sec-1000%/sec aufgebracht wird, wobei die Messung beim Teil mit minimalem Durchmesser (e) erfolgt.
11. Verfahren gemäß Anspruch 10, dadurch gekennzeichnet, daß die Zugkraft am Rohling (1, 11) aufgebracht wird, nachdem der Rohling aus dem metallischen Werkstoff auf ein vorgegebenes Temperaturgefälle erhitzt wurde, wobei die Ziehgeschwindigkeit des Rohlings (1, 11) aus dem metallischen Werkstoff allmählich von einer niedrigen auf eine hohe Geschwindigkeit verändert wird.
12. Verfahren gemäß Anspruch 11, dadurch gekennzeichnet, daß die Ziehgeschwindigkeit des Rohlings (1, 11) aus dem metallischen Werkstoff periodisch und schrittweise herabgesetzt wird, indem die Zugstärke in mehrere Schritte geteilt wird.
13. Verfahren zur Herstellung einer konischen Stange aus einem Rohling (11) eines metallischen Werkstoffs, der drahtförmig ausgebildet ist, dadurch gekennzeichnet, daß der Rohling (11) aus dem metallischen Werkstoff direkt erhitzt wird, indem zwischen zwei Punkten auf dem Rohling (11) aus dem metallischen Werkstoff ein elektrischer Strom zum Fließen gebracht wird, wobei ein vorgegebenes Temperaturgefälle der Erwärmung zwischen den beiden Punkten auf dem Rohling (11) aus dem metallischen Werkstoff durch eine Einzelregelung einer Kühlgröße (V1, Vn) bei einer Vielzahl von Kühlbereichen ausgebildet wird, die zwischen den beiden Punkten angeordnet sind, bevor die Zugkraft zwischen den beiden Punkten angelegt wird, um einen konischen Teil (c, d) auszubilden, dessen Durchmesser sich in axialer Richtung (D) des Rohlings (11) aus dem metallischen Werkstoff ändert, wobei die Oberflächentemperatur an irgendeiner Stelle des Rohlings (11) aus dem metallischen Werkstoff gemessen wird, um auf Grund dieser Messdaten, die Stromstärke zu regeln, so daß die Temperatur an der Temperaturmeßstelle auf eine Zeiltemperatur eingestellt werden kann.
14. Verfahren gemäß Anspruch 13, dadurch gekennzeichnet, daß die Messung der Oberflächentemperatur in einem Mittelteil zwischen den beiden Punkten auf dem Rohling 11 aus dem metallischen Werkstoff ausgeführt wird.
15. Verfahren gemäß Anspruch 13, dadurch gekennzeichnet, daß die Messung der Oberflächentemperatur zusätzlichen zur Regelung der direkten Widerstandsheizung an einer Vielzahl von Stellen zwischen den beiden Punkten auf dem Rohling (11) aus dem metallischen Werkstoff durchgeführt wird, wobei die Temperaturdaten, die man auf diese Weise erhält, dazu verwendet werden, um die Kühlgröße (V1-Vn) in jedem Kühlbereich beim nächsten konischen Formvorgang zu verändern.
16. Verfahren gemäß Anspruch 15, dadurch gekennzeichnet, daß die tatsächliche Abmessung eines konisch ausgebildeten Teils (c, d), der durch Erhitzen und Ziehen mit der Zugkraft ausgebildet wurde, gemessen wird, um dadurch das Temperaturgefälle einzustellen, wobei das eingestellte Temperaturgefälle für die Regelung der Kühlgrößen (V1-Vn) in jedem Kühlbereich beim nächsten konischen Formvorgang verwendet wird, der auf den Temperaturdaten beruht.
17. Gerät zur Ausführung des Verfahrens gemäß Anspruch 13 bis 16 für die Herstellung einer konischen Stange aus einem metallischen Werkstoff ( 1 1 der länglich ausgebildet ist, dadurch gekennzeichnet, daß das Gerät enthält: eine Zieheinrichtung (12, 22), um den metallischen Werkstoff (11) an zwei Punkten einzuspannen und ihn (11) mit einer Zugkraft in eine Richtung (D) zu ziehen, um den Abstand zwischen den beiden Punkten zu vergrößern; eine elektrischen Stromquelle (15), um einen Strom mit vorgegebener Stromstärke zwischen den beiden Punkten fließen zu lassen, um den mechanischen Werkstoff (11) direkt zu erhitzen; eine Vielzahl von Kühleinrichtungen (C1-Cn), die zwischen den beiden Einspannpunkten des metallischen Werkstoffs (11) angeordnet sind und ein jeweils einstellbares Kühlvermögen (Vl-Vn) besitzen; eine Temperaturfühlereinrichtung (16, 17), die die Oberflächentemperatur des metallischen Werkstoffs (11) an zumindest einer Stelle zwischen den beiden Punkten messen kann; und eine Heiztemperaturregeleinrichtung (19), um auf Grund eines Eingangssignals der Temperaturfühlereinrichtung (16, 17) die Größe der Erwärmung zu regeln, die durch den Strom der elektrischen Stromquelle (15) hervorgerufen wird-18. Gerät gemäß Anspruch 17, dadurch gekennzeichnet, daß es weiters eine Kühlregeleinrichtung (18) enthält, um das Kühlvermögen (V1-Vn) einer jeden der vielen Kühleinrichtung (C1-Cn) auf Grund eines Eingangssignals von der Temperaturfühlereinrichtung (16, 17) einzeln zu regeln.
19. Gerät gemäß Anspruch 18, dadurch gekennzeichnet, daß es weiters eine Längenmeßeinrichtung (20) enthält, um die tatsächliche Abmessung des konisch geformten Teils (c, d) zu messen, der durch Erhitzen und Ziehen ausgebildet wird, sowie eine Einstelleinrichtung (21) enthält, um das Zieltemperaturgefälle auf Grund der Abmessungsdaten einzustellen, die von der Längenmeßeinrichtung (20) eingegeben werden, wodurch bei jeder Kühleinrichtung die Regelung des Kühlvermögens, die gemäß dem von der Einstelleinrichtung eingestellten Temperaturgefälle erfolgt, auf Grund eines Eingangssignals von der Temperaturfühlereinrichtung (13; 16, 17) in der Kühlregeleinrichtung (18) durchgeführt wird.
20. Gerät gemäß jedem der Ansprüche 17 bis 19, dadurch gekennzeichnet, daß die Zieheinrichtung (12, 22) sowohl dazu dient, um den metallischen Werkstoff (11) einzuspannen und zu ziehen, als auch dazu, um eine leitende Verbindung mit dem metallischen Werkstoff (11) herzustellen, um elektrischen Strom fließen zu lassen, um den metallischen Werkstoff (11) direkt zu erhitzen.
21. Gerät für die Ausführung des Verfahrens gemäß Anspruch 1 bis 9 für die Herstellung einer konischen Stange aus einem metallischen Werkstoff, der länglich ausgebildet ist, dadurch gekennzeichnet, daß das Gerät enthält: eine Zieheinrichtung (2), um den metallischen Werkstoff (1) an zwei Punkten einzuspannen und mit einer Zugkraft in eine Richtung (D) zu ziehen, um den Abstand zwischen den beiden Punkten zu vergrößern; und eine Vielzahl von Heizeinrichtungen (H1-Hn), um den metallischen Werkstoff (1) mit einem dadurch vorgegebenen Temperaturgefälle einzeln zu erhitzen, wodurch der metallische Werkstoff, dem von der Vielzahl von Heizeinrichtungen (H1-Hn) ein vorgegebenes Temperaturgefälle aufgeprägt wurde, von der Zieheinrichtung (2) gezogen wird, um ihn in eine konische Stange zu verformen, die einen konischen Teil (c, d) mit einem sich axial ändernden Durchmesser besitzt.
22. Gerät gemäß Anspruch 21, dadurch gekennzeichnet, daß zusätzlich zur Temperaturfühlereinrichtung (T1 Tn), mit der die Temperatur des metallischen Werkstoffs (1) gemessen wird, der mit der Vielzahl von Heizeinrichtungen (H1-Hn) erhitzt wird, eine Heizregeleinrichtung (3) vorgesehen ist, um die Heiztemperatur eines jeden Heizbereichs auf Grund der tatsächlichen Temperatur des metallischen Werkstoffs (1) einstellbar zu regeln, die von der Temperaturfühlereinrichtung (T1- Tn) gemessen wird.
23. Gerät gemäß Anspruch 21, dadurch gekennzeichnet, daß die Vielzahl von Heizeinrichtungen (H1­-Hn) Hochfrequenzinduktions-Heizeinrichtungen sind.
24. Gerät gemäß Anspruch 23, dadurch gekennzeichnet, daß die Hochfrequenzinduktions-Heizeinrichtung (H 1-Hn) aus einer Vielzahl von Spulen aufgebaut ist, die mit einer unterschiedlichen Anzahl von Spulenwicklungen versehen, in axialer Richtung des metallischen Werkstoffs (1) angeordnet und in Serie geschaltet sind, um in ihnen Strom mit vorgegebenen Stromstärken fließen zu lassen.
25. Gerät gemäß Anspruch 23, dadurch gekennzeichnet, daß die Hochfrequenzinduktions-heizeinrichtung (H1­-Hn) aus einer Vielzahl von Spulen mit unterschiedlichen Durchmessern aufgebaut ist, die in axialer Richtung des metallischen Werkstoffs (1) angeordnet und in Serie geschaltet sind, um in ihnen Strom mit vorgegebenen Stromstärken fließen zu lassen.
26. Gerät gemäß Anspruch 23, dadurch gekennzeichnet, daß die Hochfrequenzinduktions-Heizeinrichtung (H1­-Hn) aus einer Vielzahl von Spulen aufgebaut ist, wobei jeder Spule unabhängig elektrischer Strom zugeführt wird und die Spulen in axialer Richtung des metallischen Werkstoffs (1) angeordnet sind, wobei ein vorgegebenes Temperaturgefälle dadurch ausgebildet wird, daß die in jedem Teil des metallischen Werkstoffs fließende Stromdichte dadurch geändert wird, daß die jeder Spule zugeführte Stromstärke geändert wird.
EP19810304219 1980-12-11 1981-09-15 Verfahren und Vorrichtung zur Herstellung verjüngter Stangen Expired EP0054343B1 (de)

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JP17503180A JPS5797819A (en) 1980-12-11 1980-12-11 Manufacture of tapered rod
JP175031/80 1980-12-11
JP176276/80 1980-12-13
JP17627680A JPS57100816A (en) 1980-12-13 1980-12-13 Manufacture of tapered rod

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