JP2003027138A - Deformed steel wire with heat treatment, and its producing method and apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a deformed steel wire with a heat treatment, which is subjected to quench-heat treatment without a small bending, in one process. SOLUTION: A heating means 6 for rolling, a four-way type roll rolling mill 7 and a quenching and cooling means 8 are adjacently disposed in a tandem, and a blank W1 for wire rod is rapidly heated to the rolling temperature with a heating means 6 and rolled into the deformed steel wire W2 having a prescribed cross section with the four-way type roll rolling mill 7 and rapidly cooled with the quenching and cooling means 8 just after rolling while loading tension to the wire rod W2 with pinch rolls 9 to perform the worked quenching. In this case, since the pinch rolls 9 are driven with a motor 9a with a torque converter, the variation of the torque is little and the variation of the size in the deformed steel wire is not caused. A heating coil 10 for tempering is arranged in the tandem at the rear part of the quenching and cooling means to perform a continuous tempering.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-treated deformed steel wire having a square or rectangular or approximated trapezoidal cross-section for coil springs and other applications, and its manufacture.

[0002]

2. Description of the Related Art Conventionally, for example, as shown in FIG. 5, a coil spring using a deformed section steel wire is first drawn into a deformed section by drawing from a rolled steel material having a round section. Then, the drawn steel wire is hardened and tempered by a method such as an oil temper as shown in the step of FIG. 5 (a) and then coiled into a coil spring shape to be manufactured, or as shown in FIG. 5 (b). After being coiled into a shape, it was manufactured by quenching and tempering with an electric furnace or the like.

[0003]

However, the above-mentioned conventional method for manufacturing the coil spring requires two steps, that is, a step of drawing the deformed wire and a heat treatment step of quenching and tempering, which increases the number of steps. Therefore, there is a problem that it is difficult to reduce the cost.

Further, in the method of coiling the heat-treated steel wire of FIG. 5 (a), if the wire has meandering, twisting or small bending, the wound coil is deformed and the yield of the product is greatly reduced. However, in the case of the conventional wire that has been quenched and tempered by furnace heating after wire drawing, sufficient quality cannot be obtained in this respect. Therefore, a hardened steel wire with even better linearity is required.

On the other hand, in order to obtain a hardened steel wire having a high linearity, a method of heating and quenching while applying tension is carried out. When the steel wire heated to a high temperature is applied with tension, the steel wire is stretched and its cross section is increased. There is a problem that the cross-sectional size changes due to the reduction in size and the change in tension.

Therefore, the present invention provides a method for producing a heat-treated deformed steel wire which is heat-treated in one step by continuously hot-forming a steel wire having a round cross-section into a deformed cross-section and simultaneously performing forming and quenching heat treatment. The purpose is to provide. Moreover, by performing tension hardening with little fluctuation in tension during quenching and cooling,
It is an object of the present invention to provide a method for manufacturing a heat-treated deformed steel wire which has a high dimensional accuracy and good linearity. The present invention is particularly suitable for steel wires for high strength coil springs,
In addition, it can be used for a wide range of applications such as a heat-treated deformed steel wire having a deformed cross section such as a torsion bar having a square cross section and requiring linearity.

[0007]

In order to achieve the above object, the heat-treated deformed steel wire of the present invention and the method for producing the same are provided by rapidly heating to a rolling temperature for a short time by induction heating and / or direct current heating means. It is characterized in that it is hot-rolled and molded into a modified cross section, quenched immediately after rolling, work-hardened, and then tempered.

That is, it is known that such rapid heating for a short period of time by induction heating or the like has less defects such as decarburization and higher work-quenching effects than ordinary furnace heating. Then, by quenching immediately after rolling, growth of crystal grains is prevented and Ar ₃ transformation in the surface layer portion is also prevented. As a result, it is possible to prevent the ferrite structure from precipitating due to the progress of cooling of the surface, and to obtain a sufficiently hardened structure up to the surface layer portion. By carrying out work quenching by rapid cooling immediately after rolling in this way, shaping of a modified cross section and quenching heat treatment are carried out in one step, and work hardening gives higher strength than normal quenching.

In the above-mentioned roll forming, if a four-way rolling roll is used, it is possible to easily form an irregular cross section with a small number of rolling stands.

Further, the steel wire to be processed is rapidly heated to a temperature of Ac ₃ or higher at a heating rate of 100 ° C./s or higher, rolled at a temperature of Ar ₃ or higher to a predetermined irregular cross section by a rolling roll, and immediately after rolling, Ar is rolled. _In order to obtain high tensile strength, it is preferable to quench the work from a temperature of ₁ or more by quenching and cooling means arranged in tandem in the vicinity of the rolling roll to perform work hardening. It is desirable that the quenching and cooling means be arranged as close to the rolling roll as possible. In this case, crystal growth is prevented by quenching immediately after rolling, and high quenching hardness can be obtained.

By hot working the deformed cross section with a rolling roll in this manner, scratches and the like are reduced as compared with conventional forming such as drawing wire drawing, and a spring steel wire having a good surface texture can be obtained. Further, although high alloy steel and the like have a large work hardening and are difficult to cold draw, the present rolling method also facilitates the processing of a deformed cross section of the high alloy steel.

[0012] In the work hardening, it is desirable to perform tension work hardening in which the steel wire to be worked is rapidly cooled while applying a tension immediately after hot rolling in order to improve the straight elongation of the heat treated steel wire.
The tension applied to the steel wire to be processed is given by a pinch roller or a winder or a capstan device driven by a driving device with a torque converter that absorbs the tension fluctuation of the steel wire. Desirable to lose.

As described above, when coiling for forming a coil spring, the constant large curvature of the wire does not affect the product, but the wire may meander, twist, or bend slightly. However, a defective product shape causes a decrease in product yield. In the method of the present invention, during work quenching after quenching after rolling, since tension work quenching is performed in which quenching is performed while applying tension to the wire rod, a quenching spring steel wire having high linearity without such small bends can be obtained. . As a result, the yield of products in coil spring molding is improved. In addition to the coil spring, even in applications such as a deformed torsion bar used in a straight line, the number of forming steps such as straightening can be significantly reduced, and the cost can be reduced.

However, since the high temperature wire rod at the time of quenching has low strength, there is a possibility that the cross-sectional dimension may change if the tension applied to the wire rod changes. Therefore, the present invention uses a drive device with a torque converter to drive a pinch roller, a winder, and a capstan device, and absorbs fluctuations in the tension of the wire rod by the torque converter to quench the wire rod while applying a constant tension to the wire rod. It is characterized by that. This makes it possible to obtain a quenched spring steel wire with a uniform cross-sectional dimension and high dimensional accuracy. In particular, in the case of deformed wire with a small diameter cross section, when the tension is directly applied to the wire, the cross-sectional dimension changes greatly,
By applying tension through the torque converter of the present invention, it has become possible to perform tension hardening even on deformed wire rods having a small diameter cross section, which has been difficult in the past. Here, the drive device with the torque converter does not necessarily mean that the torque converter and the drive device are integrated, but includes all devices that are driven via the torque converter.

It is desirable to continuously heat the alloy by induction heating to a tempering temperature after the work quenching so that the quenching and tempering heat treatment can be continuously carried out. This tempering is performed after the quenching and cooling means. It is desirable to carry out continuously with a tempering induction heating coil arranged in tandem.

The manufacturing method of the present invention is widely effective for processing a deformed wire having a square or rectangular or approximately trapezoidal cross section, and a heat-treated deformed steel wire having a tensile strength of 1600 N / mm ² or more can be easily manufactured.

The apparatus for continuously producing a heat-treated deformed steel wire according to the present invention for producing the heat-treated deformed steel wire has a rolling heating means for heating a raw steel wire to a rolling temperature and / or a direct heating method and a predetermined heating section. The rolling means for hot forming, the quenching and quenching means for quenching and quenching while applying tension to the steel wire to be worked immediately after the rolling and quenching and the tension applying means are arranged in tandem. .

It is desirable that the rolling means is a four-way roll rolling machine and the tension applying means is a pinch roller driven by a driving device with a torque converter, or a winder or a capstan device, and behind the quenching and quenching means. By providing the tempering heating means for heating to the tempering temperature in tandem, quenching and tempering can be continuously performed.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to one embodiment shown in the drawings. FIG. 1 is a conceptual diagram showing an overall configuration of a heat treatment deformed steel wire manufacturing apparatus according to an embodiment of the present invention, and FIG. 2 is an example of a sectional shape of a heat treated deformed steel wire used in the present embodiment,
FIG. 3 is a diagram showing a roll shape of a four-way roll rolling machine (rolling means) for rolling it, and FIG. 4 is a flowchart showing a manufacturing process of the heat-treated deformed steel wire according to the embodiment of the present invention.

In FIG. 1, the rolling heating coil (rolling heating means) 6, four-way roll mill (rolling means) 7, water-cooling jacket (quenching cooling means) 8, pinch roll 9 (tensioning) from the left upstream side of the drawing. Means) and tempering heating coil (tempering heating means) 10 are arranged in tandem, and finally a winding machine 11
Is provided. The pinch roll 9 is driven by a motor 9a with a torque converter speed reducer.

The heat-treated deformed steel wire of this embodiment has an approximate trapezoidal cross section as shown in FIG. As shown in FIG. 3, the four-way roll rolling machine 7 for rolling this is composed of a pair of upper and lower horizontal rolls 1 and 1 and a pair of left and right vertical rolls 2 and 2. Then, the upper and lower horizontal rolls 1 form the side surfaces of the approximate trapezoidal cross section, and the left and right vertical rolls 2 form the top and bottom surfaces.

The manufacturing process will be described below with reference to FIGS. First, as a pre-process, a material of a rolled steel material having a predetermined diameter is descaled and then drawn by a circular wire drawing to a material steel wire W1 having a circular cross section having a predetermined diameter. The material steel wire W1 is supplied to the rolling heating coil 6 from an unwinder (not shown). After the raw material steel wire W1 is induction-heated by the rolling heating coil 6,
The wire rod W2 having an approximate trapezoidal cross section shown in FIG. 2 is hot-rolled by the four-way roll mill 7, and immediately after hot-rolling, it is rapidly cooled by the water-cooling jacket 8 and work-quenched. At this time, since the pinch roll 9 is rotating at a feeding speed slightly higher than the rolling exit speed, the deformed wire W2 is rapidly cooled while being fed by the pinch roll 9 under tension. By cooling while applying tension in this way, a hardened steel wire with high linearity can be obtained. Further, since the pinch roll 9 is driven by the motor 9a with the torque converter reducer, an excessive tensile force does not act on the wire W2, and the dimensional fluctuation of the wire is prevented. The quenched wire is heated to the tempering temperature by the tempering heating coil 10 and tempered,
It is wound by the winder 11. The heat-treated deformed steel wire which is heat-treated and wound into a coil is coiled into a predetermined shape and formed when used for a coil spring.

That is, in the conventional method, as shown in FIG. 5, the step of drawing a deformed section and the step of quenching and tempering are carried out in two steps. It is characterized by being performed.

In this embodiment, the wire rod is tensioned by the pinch rolls, but a capstan device may be used instead of the pinch rolls, or tension may be applied by a winder. In this case, a motor with a torque converter is used to drive the capstan device or the winder.
Further, the rolling heating may be performed by direct energization, or the induction heating and direct energization may be used together.

[Embodiment] An embodiment will be described below.
Table 1 shows the chemical composition of the rolled wire used in the examples.

[0026]

[Table 1]

After this rolled wire rod was drawn into a round wire, it was rolled into a trapezoidal cross section having the shape shown in FIG. 2 using this wire. Table 2 shows the dimensions of the rolled deformed steel wire having a trapezoidal cross section and the diameter of the corresponding wire. The area reduction rate from the strand wire to the deformed steel wire is about 0.9. The steel wire rolled into a trapezoidal cross-section with various dimensions was quenched by applying tension, work-quenched, and then continuously tempered. Deformed wire rods with small diameter cross sections such as 40 series, 30 series, and 25 series shown in Table 2 were difficult in conventional tension quenching because of large fluctuations in cross-sectional dimensions. Therefore, it is possible to perform tension hardening even on deformed steel wire with such a small diameter cross section.

[0028]

[Table 2]

Of the products in Table 2, an example of L-60 will be described as an example. L-60 is 14.40m high
m × bottom 7.10 mm−top 4.70 mm, which is an approximate trapezoidal cross section shown in FIG. 2, but was rolled into this shape using a round wire rod having a material diameter of 10.80 mm. The area reduction rate is 0.9059
Met. The cross-sectional dimension variation was 0.05 mm or less, and the heat-treated deformed steel wire with high accuracy was obtained.

The heating conditions were such that the temperature was raised to the rolling temperature in 7 seconds and the feed rate of the steel wire was 100 mm / s at the outlet side.
The heat treatment temperature was measured on the outlet side of the heating coil in FIG. 1, at the position after heating and soaking, at the roll inlet, at the roll outlet, before the water cooling jacket, and at each position after tempering heating. The measurement results are shown in Table 3.

[0031]

[Table 3]

That is, the steel wire is heated to about 1024 ° C. which is higher than the Ac ₃ temperature by the rolling heating coil 6 to form a γ structure, and is rolled by the four-direction roll 7 in the temperature range of 850 to 760 ° C. of Ar ₃ or higher. It And immediately after rolling, Ar
It was hardened by quenching from _one or more temperature 740 ° C.. As a result, a fine hardened structure of martensite was obtained, and high strength was obtained. The quenched steel wire was heated to about 500 ° C. by the tempering heating coil 10 and tempered.

L-60 heat treatment, which was a rolling heat treatment under the above conditions
Table 4 shows an example of mechanical properties of the irregularly shaped steel wire. Sanawa
The heat-treated deformed steel wire of the present invention has a tensile strength of 1600N.
/ Mm ²With the above, elongation is 10% or more, high strength and large elongation
was gotten.

[0034]

[Table 4]

Further, the heat-treated deformed steel wire did not show any small bend, and high linearity was obtained. In this example, a coil spring was formed using this heat-treated deformed steel wire. As a result, when the deformed steel wire in the conventional process that was heat-treated in a furnace or the like was used, the defective rate at the time of coil forming could reach several tens of percent, but according to the heat-treated deformed steel wire of the present invention, it was defective. The rate was almost 0%.

The heat-treated deformed steel wires having the other dimensions shown in Table 2 were also rolled, and in each case, the heat-treated deformed steel wire having a variation in cross-sectional dimension of 0.05 mm or less was obtained with high accuracy. An example of the obtained mechanical properties is also shown in Table 2. The linearity is good and high tensile strength and elongation are obtained as in the case of Example 1 above, and in all the modified wire rods of the present invention, coil forming is performed as described above. The defective rate at that time was almost 0%.

In this embodiment, a heat-treated deformed wire having an approximately trapezoidal cross section was manufactured, and the effect of the coil spring was confirmed. However, the present invention can be applied not only to a trapezoidal section but also to a heat-treated deformed wire having a square section or a rectangular section. Not only the coil springs are used, but also the linearity is good, so that the man-hours can be reduced and the product yield can be improved even in a deformed torsion bar used in a straight line. The present invention can be widely applied to other uses.

As described above, according to the heat-treated deformed steel wire of the present invention and the method for producing the same, since it is heated rapidly by induction heating or the like, defects such as decarburization do not occur unlike other heating methods. . In addition, since it is formed and rolled into a deformed shape and is simultaneously subjected to quenching heat treatment, a heat-treated deformed steel wire can be obtained in one step. Moreover, high strength can be obtained by rapid heating and work hardening.

In this work hardening, the steel wire to be worked is
c₃Rapid heating above temperature, Ar₃4 in the above temperature range
It is rolled into a predetermined irregular shape with a unidirectional rolling roll and immediately after rolling.
Ar ₁Quench directly from the above temperature by quenching cooling means
Tensile strength is 1600 N / m by quenching
m²The above high strength can be obtained. Furthermore, quenching and cooling means
A tempering induction heating coil is installed in tandem behind the
By tempering, it becomes possible to continuously quench and temper.
It

Further, since the deformed cross section is hot-formed by a rolling roll, surface defects such as scratches are reduced as compared with cold drawing, and a heat-treated deformed steel wire with good skin can be obtained. It is also possible to process high-alloy steel that is difficult to wire work.

Furthermore, after hot rolling, the material is rapidly cooled while applying tension to carry out tension work quenching, so that a heat-treated deformed steel wire having high linearity without small bends such as meandering and twisting can be obtained. Since the tension applied during the quenching is given by the pinch roller driven by the drive unit with the torque converter, or the winder or the capstan device, there is little variation in tension and there is little variation in cross-sectional dimension due to tension. Since this effect is particularly great for a wire having a small diameter cross section, the present invention makes it possible to perform tension hardening of a deformed wire having a small diameter cross section, which has been difficult in the past.

In this embodiment, the rolling heating is performed by induction heating, but it may be performed by direct current heating or both may be used together. Further, in the present embodiment, the four-roll rolling mill has one stand, but it may have two or more stands. Further, the cross-sectional shape of the heat-treated deformed steel wire may be various cross-sectional shapes such as corners and rectangular cross-sections other than the approximate trapezoidal shape of this embodiment.

[0043]

As described above, according to the heat-treated deformed steel wire of the present invention and the manufacturing method and apparatus thereof, excellent linearity,
Since a heat-treated deformed steel wire having high strength can be obtained in one step, when used as a coil spring element wire, the defective rate at the time of coil forming due to small bending can be reduced to almost 0, and the deformed spring wire Therefore, the manufacturing cost of the coil spring can be significantly reduced. In particular, it is effective for manufacturing a heat-treated deformed steel wire having a small diameter section, which has been difficult in the past. Also, it can be widely used for other applications such as a modified section torsion bar.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing the configuration of an apparatus for manufacturing a heat-treated deformed steel wire according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a cross-sectional shape of a heat-treated deformed steel wire according to an example of the present invention.

FIG. 3 is a diagram showing a roll shape of a four-way rolling mill according to an embodiment of the present invention.

FIG. 4 is a flowchart showing a manufacturing process of the heat-treated deformed steel wire according to the embodiment of the present invention.

FIG. 5 is a flowchart showing a conventional method for manufacturing a coil spring using a heat-treated deformed steel wire.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 upper and lower horizontal rolls, 2 left and right vertical rolls, 6 induction heating coil (rolling heating means), 7 four-way roll rolling machine (rolling means), 8 water cooling jacket (quenching cooling means), 9
Pinch roll (tension applying means), 9a motor with torque converter, 10 tempering heating coil, 11 winder,
W1 material steel wire, W2 deformed steel wire

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kazuo Kinugasa             1586, Outer Shimogawara, Aza, Ako City, Hyogo Prefecture               High frequency heat smelting Co., Ltd. F-term (reference) 4E002 AC14 AD04 BA04 CA20                 4K032 AA06 AA11 AA16 AA27 AA29                       AA32 BA02 CA02 CC03 CD06                       CF01                 4K043 AA02 AB05 AB10 AB15 AB25                       AB26 AB28 BA01 BA03 BA04                       BA06 CA04 CA05 CB01 DA01                       DA04 EA07 FA03 FA05 FA12                       FA13

Claims (14)

[Claims] 1. A heat treatment characterized by being heated rapidly to a rolling temperature for a short time by induction heating or / and a direct electric heating means, hot-rolled and formed into a predetermined cross-section, and immediately after rolling, quenching and work-quenching. Deformed steel wire. 2. The heat-treated deformed steel wire according to claim 1, wherein the heat-treated deformed steel wire has a corner, a rectangular shape, or an approximate trapezoidal cross section. 3. A steel wire to be processed is rapidly heated to a rolling temperature for a short time by induction heating and / or a direct current heating means, hot-rolled and formed into a predetermined irregular cross section, and immediately after rolling, quenching is performed to perform work hardening. A method for manufacturing a heat-treated deformed steel wire, characterized by: 4. The method for manufacturing a heat-treated deformed steel wire according to claim 3, wherein the hot rolling is performed by four-way roll rolling. 5. A steel wire to be processed is rapidly heated to a temperature of Ac ₃ or higher at a heating rate of 100 ° C./s or higher, rolled at a temperature of Ar ₃ or higher by a rolling roll to a predetermined irregular cross section, and immediately after rolling, Ar is rolled. _The method for producing a heat-treated deformed steel wire according to claim 3, wherein quenching is performed by quenching and cooling means arranged in tandem in proximity to the rolling roll at a temperature of ₁ or more to perform work quenching. 6. The method for producing a heat-treated deformed steel wire according to claim 3, wherein the work-hardening is carried out by tension work-quenching in which the steel wire to be processed is rapidly cooled while being tensioned immediately after hot rolling. 7. The tension applied to the steel wire to be processed is given by a pinch roller driven by a drive device with a torque converter or a winder or a capstan device that absorbs a tension fluctuation of the steel wire. The method for manufacturing a heat-treated deformed steel wire according to claim 6. 8. The method for producing a heat-treated deformed steel wire according to claim 3, wherein after the work-quenching, the heat-treatment deformed steel wire is continuously heated by induction heating to a tempering temperature and tempered. 9. The tensile strength of the heat-treated deformed steel wire is 16
The method for producing a heat-treated deformed steel wire according to claim 8, wherein the heat-resistant deformed steel wire is at least 00 N / mm ² . 10. The heat-treated deformed steel wire has a square or rectangular or approximate trapezoidal cross section.
10. The method for manufacturing a heat-treated deformed steel wire according to any one of 1 to 9. 11. A rolling heating means for heating a raw steel wire to a rolling temperature by induction heating and / or direct energization, a rolling means for hot forming to a predetermined irregular cross section, and a rolling forming while applying tension to a steel wire to be processed. A continuous production apparatus for heat-treated deformed steel wire, characterized in that a quenching and quenching means for quenching immediately after that and a tension applying means are arranged in tandem. 12. The continuous production apparatus for heat-treated deformed steel wire according to claim 11, wherein the rolling means is a four-roll mill. 13. The tension applying means is a pinch roller driven by a drive device with a torque converter that absorbs fluctuations in the tension of the steel wire, a winder, or a capstan device. Continuous heat treatment equipment for deformed steel wire. 14. The continuous production apparatus for heat-treated deformed steel wire according to claim 11, wherein a tempering heating means for heating to a tempering temperature is disposed behind the quenching and quenching means in tandem.