JPH0971819A - Heat treating device for small-diameter metallic columnar material and method for controlling driving of this device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a device for driving a work and to allow this work to travel in such a manner as to obviate the occurrence of the deformation in a test at the time of subjecting a work to hardening with high efficiency and a method for controlling the driving of this device. SOLUTION: This device for subjecting the work 3, such as small-diameter metallic columnar material, to a heat treatment by passing the work through a heat treatment zone by allowing the work to travel in a longitudinal direction is arranged with plural sets of skew roller sets each having two pieces of receiving skew rollers for supporting the work 3 and a pressing skew rollers for pressing the work placed on these receiving skew rollers in a direction where the work 3 is made to travel. A heat treatment means is arranged between the skew roller sets, by which a heat treatment zone is formed. Driving systems are connected to the pressing skew rollers positioned on the inlet side and outlet side of the heat treatment zone to constitute inlet side driving rollers 4 and outlet side driving rollers 5. In addition, the driving operations of the work 3 by the inlet side driving rollers 4 and outlet side driving rollers 5 are separately set and controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for heat-treating a solid or hollow small-diameter metal cylindrical material (hereinafter referred to as "work") with high efficiency without causing buckling or bending, The present invention relates to a drive control method for this device. As a typical example of the above work, there is a round steel for a precision machine shaft having a diameter of mm order but a length of m order.

[0002]

2. Description of the Related Art Conventionally, heat treatment such as quenching has been carried out by a batch system even for a work having a small diameter and a long length as described above, like a work having a general size. When the work having a small diameter and a long length as described above is heated to a high temperature of 700 to 1200 ° C., it is buckled by a slight force, and bending is likely to occur in the cooling process following the heating. As a result of inefficient work to avoid these problems, it has been difficult to reduce costs commensurate with mass-produced materials.

The inventors of the present invention aim to carry out the above heat treatment at a low cost by running a work in the longitudinal direction and passing it through a heat treatment zone using an induction heating method or the like. Attention was paid to a transfer treatment system in which the work was continuously heat-treated. Then, a device as illustrated in FIGS. 1 and 2 using a scroll roller as a traveling means of the work is manufactured, and the quenching is performed by a moving system using a small diameter long steel bar as a work. As a result, the problem that the work heated to a high temperature buckled frequently occurred. This is the same as the drive rollers on both sides (the same as the free-roller), which applies the driving force to the work.
Type)), a compressive force in the longitudinal direction due to various factors such as thermal expansion of the work is applied to the working work located between both drive rollers. Moreover, in the above test, the diameter of the work was as thin as 10 mm and the work was
It is probable that the work, in which the deformation resistance was extremely reduced, was likely to buckle because the section for heating the work was long.

Next, a quenching test similar to that described above was performed as shown in FIG.
When the press rollers of the four free rollers in the middle of the device of FIG. 2 were opened, the work was swayed,
There is an added tendency for the quenching products to exhibit a bend that is believed to be due to this.

[0005]

Through the above test, it was confirmed that the desired quenching can be performed with high efficiency by the apparatus shown in FIGS. 1 and 2, except for the problem of deformation such as buckling and bending. Therefore, the problem to be solved by the present invention is to drive and work the work so as not to cause the deformation as in the above test in carrying out the quenching for the work with high efficiency. And a drive control method for this device.

[0006]

Means for Solving the Problems The inventors of the present invention have completed the present invention through intensive research aimed at solving the above problems. That is, the device of the present invention is a device for running a work such as a small-diameter metal columnar material in the longitudinal direction and passing through a heat treatment zone for heat treatment, and supporting the work. For running the work with a receiving roller and a pressing roller set for holding the work mounted on the receiving roller. In addition to arranging a plurality of sets in the direction in which the heat treatment is performed, heat treatment means is disposed between the above-mentioned scroll rollers to form a heat treatment zone, and a holding scroll located at the inlet side and the outlet side of the heat treatment zone. -Connect a drive system to the roller to make an input side drive roller and an output side drive roller,
Further, the driving operation of the work by the entrance side driving roller and the exit side driving roller is separately set and controlled.

In the present invention, the running of the work is performed by the work.
The reason why the work is carried out while rotating the work is to make the heat treatment effect on the work uniform in the circumferential direction as well, and to prevent bending due to the deviation of the thermal strain in the circumferential direction. In the present invention, a scroll roller system is adopted as a means for rotating the work. Here, the skew rollers are a plurality of thin rollers arranged at an angle (skew angle) with respect to the circumferential direction of the work to be run, and the rollers enable the workers to work. The work can be run in such a manner that the outer peripheral surface of the work advances spirally.

The scroll roller system is adopted because the equipment structure is simple, the heat treatment means and other equipment elements can be easily connected, and the work is fed one after another to improve the efficiency. This is because it is suitable for good operation.

In the skew roller, a set of two receiving rollers is usually used in series, but in the present invention, a small-diameter and long-length work is run so as not to cause runout. Therefore, the work placed on the receiving roller is further pressed by the pressing roller to prevent the shake.

According to the present invention, the receiving roller and the pressing roller as described above.
A plurality of skew roller sets made of la were arranged in series in the direction in which the work was run, and the necessary heat treatment means was arranged between the roller sets. That is, as shown in FIGS. 1 and 2, one example of the device of the present invention is configured as a heat treatment device for quenching high-grade steel, and an induction coil for induction heating is provided over a long section for heating and maintaining temperature. In addition to the above, the water injection mechanism is arranged as a cooling means for work quenching to form a heat treatment zone. Here, the heating means in the present invention is not limited to the above induction heating method, and gas burner heating or the like can also be adopted, but rapid heating to a predetermined temperature and necessary temperature holding can be performed with high efficiency and high accuracy. It is desirable to adopt the induction heating method.

Of the above-mentioned skew roller sets having a plurality of sets arranged, a driving system is connected to one pressing roller of each of the skew roller sets located before and after the heat treatment zone, and an input side driving roller is connected. -The roller and the outlet side driving roller are used to feed the work into and out of the heat treatment zone. Here, the arrangement intervals of both drive rollers must be arranged so that the span is shorter than the entire length of the work wheels to be traveled, and the work spaces between the both drive rollers are naturally set. A plurality of skews with intervals that do not bend or shake
It is necessary to place the roller set,
It is desirable that the diameter and the heat treatment pattern are arranged so as to be widely covered. By the series of measures described above, the bending of the product due to the bending and the deflection can be avoided. The same applies to the skew roller sets (not shown) arranged on both outer sides of both drive rollers. In addition to the drive rollers provided before and after the heat treatment zone, the drive rollers may be appropriately added outside or inside the heat treatment zone.

In the present invention, the drive operation of the drive roller can be separately set and controlled on the inlet side and the outlet side of the work. When a load is applied, the compressive force in the longitudinal direction applied to the work is adjusted by various factors to adjust the work in the heat treatment zone.
This is to prevent Ku from buckling. Here, the situation in which the drive rollers on both the entry and exit sides are subject to work not only occurs for one work, but also for two work traveling in series Each of the driving rollers of the above type also occurs in such a manner, but in this case as well, a longitudinal compressive force can be applied to the work. When the drive rollers are added as described above, it is desirable that the drive operation of the added drive rollers can be separately set and controlled as needed.

The type of the drive system connected to the drive roller is not limited, but in terms of the degree of freedom of operation setting, accuracy and controllability, an electric motor operating with AC or DC is used. Is suitable. The setting and control of the operation of the motor and the like may be performed by the usual method.

In the present invention, as a concrete means for preventing the compressive force in the longitudinal direction from being applied to the work when the work is heat-treated by the above-mentioned heat treatment apparatus of the present invention, in the present invention, The drive operation of the output side drive roller is set as follows.

That is, the structure of the first driving method of the driving roller in the heat treatment apparatus as the above means is such that the driving of the work by the output side driving roller is performed by the driving by the input side driving roller. The speed is also increased so that the work is run while releasing the compressive strain in the longitudinal direction, which is mainly caused by thermal expansion, which is added to the work when the work is applied to both drive rollers. It is a feature. That is, this method
The most important factor for applying the compressive force in the longitudinal direction to the work is the thermal expansion strain caused by the heating of the work between both driving rollers, so at least the speed increment corresponding to the increase in length due to this thermal expansion. Is to prevent the buckling from occurring by speeding up the drive by the output side drive roller to release the compression strain so that no compressive force is applied to the work.

The above-mentioned increase in length due to thermal expansion usually does not match the calculated value obtained from the literature data on the assumption that the thermal expansion is isotropic, and is often larger than this. It is preferable to experimentally set the speed increment of the side drive roller. Further, it is possible to set the speed increment setting to a value (about 1.5 to 3 times) larger than an experimentally obtained value in consideration of the fluctuation of the compression force due to the fluctuation of thermal expansion strain and other factors. In this case, tensile force is applied to the work on average,
There are few obstacles compared with the case where a compressive force is applied. However, since it is not preferable to set the speed increment excessively so as to cause the extension deformation of the work or the slip of the driving roller and the work, the first driving method described above is not used unless such an excessive setting is required. This eliminates the problem of buckling.

The structure of the second driving method of the driving roller in the above-mentioned device of the present invention is such that the diameter of the work is particularly small and the running, but the compression force is apt to fluctuate, and the buckling is caused. It is also an effective means for situations in which the drive rollers on both the entry and exit sides are working when both drive rollers are on work. One of the driving torques is controlled so that the longitudinal compression force applied to the work does not exceed the upper limit compression force at which the work in the heat treatment zone does not buckle. Is a method characterized by.

The regulation of the driving torque may be performed by driving the motor to regulate the torque, or by setting the torque limiter to a desired numerical value. When the torque limiter is used, either a motor current regulation system, or a clutch or slip system may be used. The drive roller that is not the torque regulation drive is preferably the normal speed regulation drive. As a result, the work runs at a substantially constant speed, and the uniformity of the heat treatment effect in the work longitudinal direction is ensured.

Now, the situation in which the work is driven by the two drive rollers for which the drive operation is classified will be described with reference to FIG. FIG. 5 schematically shows a situation in which the inlet side drive roller is driven by a torque regulating motor and the outlet side drive roller is driven by a speed regulating motor, and a work whose drive load is varied is driven. In the speed-torque diagram, the fluctuation of the driving load is absorbed in the form that the driving speed of the torque regulation roller and the driving torque of the speed regulation roller fluctuate. That is, since the work is driven with an almost constant torque including a small fluctuation, the work is
Excessive compressive force is not applied to the cylinder, and the problem of buckling is avoided. The second driving method naturally works effectively against the compressive force applied to the work due to the thermal expansion, and the second driving method of the inlet side driving roller and the outlet side driving roller in FIG. The difference in speed between load points A and B indicates that the output side drive roller drives the work at a slightly higher speed than the input side drive roller. There is.

Regarding the torque, there is a difference between the inlet side (push side) roller and the outlet side (pull side) roller. Even if the drive torque is restricted by the torque limiter, an excessive compression force will not be applied to the work.

In the second drive method, it is arbitrary whether the drive roller on the input side or the output side is subjected to the torque regulation. However, the increase / decrease in the torque has a positive relationship, which leads to the increase / decrease in the compression force. It is preferable that the drive roller has a torque restriction because it is easy to use in terms of equipment technology.

When the work is in a state where the torque is driven only by the regulating roller, the torque is regulated so that the work passes through the heat treatment zone at a constant speed during that time. It is more preferable that the roller is once speed-regulated, but even if the roller is continuously driven with the torque-regulated drive, the torque is properly set and the speed-regulated roller is driven.
It is solved by driving the work while maintaining an almost proper speed difference with the vehicle.

According to the third driving method of the driving roller, the work is run without being driven by both driving rollers at the same time, and a compressive force that causes buckling is generated. -It is characterized in that it does not participate in ku.
That is, the work begins to drive by the drive roller on the entrance side, but at the same time the tip of the work approaches the drive roller on the exit side and the drive by the drive roller on the entrance side is released. In the following, a method is adopted in which only the output side driving roller is in charge of driving so that the compressive force against the work is not generated. Here, as means for releasing the drive by the inlet side roller, a method of lifting the inlet side roller to disconnect the contact with the work, or a clutch (Fig. It is possible to exemplify a system in which a clutch (not shown) is provided and the clutch is turned off to set a free roller. The third driving method described above requires a little attention to the setting of the timing for releasing the drive of the entrance side roller, etc., but is a configuration in which no compressive force is applied to the running work and buckling The problem of can be avoided in principle.

In the above, the case where three kinds of drive modes are adopted for the drive roller has been described in order to prevent the work from being compressed, but which of these drive modes is adopted. It may be appropriately determined according to the specifications of the work or the heat treatment conditions.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an example of the heat treatment apparatus of the present invention will be described with reference to FIGS. 1 and 2 are a front view and a side view of the heat treatment apparatus of the present invention, wherein 1 is a pair of receiving rollers provided on the frame F and 2 is a receiving roller 1 In order to prevent run-out of the work 3 placed on the work roll 3, the press rollers provided in correspondence with the receiving rollers 1 and 4, 5 are the press rollers as well. Here, the presser roller 2 having a width wider than that of the presser roller 2 is used, and the rollers 4 are connected to the motors 6 and 7, respectively, so that the roller 4 can be driven into the entrance side.
The roller and the roller 5 are used as the output side driving roller. Further, the motors 6 and 7 are both connected to a servo controller (not shown) so that their respective driving operations are controlled separately.

The size of each roller is not particularly specified, and each receiving roller 1 is required to support a work 3 having various diameters of several mm to 20 to 30 mm for stable rotation. A diameter of around ~ 30mm is suitable. On the other hand, each press roller 2 is 100m long when the work 3 is pressed by one press roller 2 from above.
The one with a large diameter of m or more (the one shown in the figure) is suitable, but instead of pressing with one large diameter pressing roller 2 as described above, it is also possible to press with a set of two small diameter rollers. Good.

The installation interval in the running direction of the work 3 of the scroll roller set constructed as described above should be experimentally optimized so that the work 3 does not bend or shake during heat treatment. However, for example, a work with a small diameter of 5 mm is 300 m
When running and quenching while heating to 1200 ° C. over a length of m, the above-mentioned problems of bending and deflection are avoided by setting a set interval of about 100 mm.

These rollers 1, 2, 4, 5 are arranged so as to be in contact with each other at a constant angle (skew angle) in the circumferential direction of the work 3. The tangent of the skew angle is
Since the value obtained by multiplying the circumference of the work 3 corresponds to the pitch of the skew running in which the outer peripheral surface of the work 3 progresses spirally, the phenomenon that the trace of heat treatment is spirally marked on the product ( In order not to generate so-called bar mark, it is preferable to set the above pitch to a sufficiently small value, and a desirable pitch is a work.
Since the diameter is about 1/10 to 1/30 of the diameter, the desirable skew angle is about 0.5 ° to 2 °.

In FIGS. 1 and 2, reference numeral 8 denotes an induction coil arranged as heating means, which is connected to a high frequency power source (not shown) through a high frequency transformer 9 and is supplied with power from the power source. -Kuh 3 can be induction-heated. The power supply frequency is preferably about 10 kHz to 100 kHz in terms of efficiency, but is not limited to this. 1 and 2
The device of (1) is intended for quenching of high-grade steel, and therefore, after rapidly heating to around 1200 ° C, it is necessary to maintain this temperature for about 10 seconds. Therefore, the induction coil 8 and the The heat treatment zone 11 is constructed by arranging a cooling means by the water injection device 10 for the subsequent rapid cooling. Assuming that the temperature rise time is t ₁ , the temperature hold time is t ₂ , and the longitudinal traveling speed of the work 3 is v, the length L of the section where the induction coil 8 is arranged is L = v (t ₁ + T ₂ ). That is, t ₁ +
When t ₂ ≈ 10 s, if the length of L is 300 mm, v = L
/ (T ₁ + t ₂ ) = 30 mm / s, and if the work 3 is continuously fed to the above-mentioned equipment, high efficiency production of 100 m / hr can be achieved. By the way, if the work 3 is fed without interruption, the heating conditions at the end of the work will not be disturbed and uniform quenching will be performed up to the end of the work, improving the yield. To do.

It should be noted that, as in the apparatus shown in FIGS.
When the rollers 1, 2, 4, 5 and the induction coil 8 are arranged without a distance, a ceramic roller or the like is used so that the rollers 1, 2, 4, 5 are not heated by induction. desirable. Further, it is desirable to prevent the abrasion and the accumulation of foreign matter due to the rolling contact with the heated work 3 by spraying a heat-resistant material on the rollers 1, 2, 4, 5 and the like.

Here, when heat-treating the work 3 by the above-mentioned apparatus of the present invention, the drive rollers 4 and 5 for driving both the inlet side and the outlet side for preventing buckling of the work 3 are driven. The operation settings are as follows.

First, in the first driving method, the driving speeds v ₁ and v ₂ in the longitudinal direction with respect to the work 3 of the input side and output side driving rollers 4 and 5 are set to v ₂ = v ₁ + Δv. The work 3 is run. Here, the above Δv is, for example, when the length increase due to the thermal expansion of the work in the heat treatment zone 11 is calculated to be 1.5% assuming that the thermal expansion is isotropic,
If the work 3 is heat-treated with a ratio of about 3 times the thermal expansion ratio as Δv = 0.05v ₁ , the work 3 still buckles. On the contrary, when slippage with the work 3 is observed in any of the drive rollers 4 and 5, it can be set by a trial experiment of reducing the above ratio.

Next, in the second driving method, the entrance side driving roller 4 is driven while the torque is appropriately regulated, and the exit side driving roller 4 is driven.
For the case of La 5, the case of driving in the normal speed regulation mode will be described. The main purpose of the second drive method is the work process during heat treatment.
The work 3 is run so that a compressive force that causes buckling of the work 3 is not applied. When the heating temperature is 1200 ° C., the level of the upper limit compressive force at which the work 3 does not buckle is several MPa based on the well-known deformation resistance data and the results of confirmation experiments. Therefore, the skew angle is 1.0 ° and the diameter of the work is 8 m.
In the case of m, the upper limit drive torque is about 10 ^-2 Nm.

That is, when the work 3 is applied to at least both of the entrance side driving roller 4 and the exit side driving roller 5, the driving torque of the entrance side driving roller 4 is the above upper limit driving. The motor 6 is operated with a constant torque so as not to exceed the torque, or the drive torque limiter of the motor 6 is set to the above upper limit drive torque, or a slip type set to the above upper limit drive torque. The drive roller 4 is motor-driven via a torque limiter or the like to heat-treat the work. Then, the driving operation is optimized through the same trials as the first driving method.
When the torque limiter method is used, it is preferable to use it in combination with the first driving method.

Next, a mode in which the third driving method is performed by raising (moving away from the work 3) the entrance side driving roller 4 will be described. One of the points to be noted when carrying out this method is the timing of raising the entrance side drive roller 4. That is, if the timing is too early, the drive of the entrance side drive roller 4 with respect to the work 3 is released and the work 3 starts decelerating, and then the work side 3 is driven by the exit side drive roller 5. Will rise, and the smoothness of traveling will be impaired. On the other hand, if the above timing is too late, there will be a time zone in which the work 3 is driven from both drive rollers 4 and 5 at the same time. During this time, the work 3 is added to work 3 from both drive rollers 4 and 5. This is because the work 3 may buckle due to the compressive force, and the above timing should be adjusted experimentally. However, with respect to the latter problem, it is possible to prevent the compressive force from significantly occurring by using the first or second driving method together.

[0036]

EXAMPLE A round steel was quenched using the apparatus of the present invention shown in FIGS. (Main specifications of the equipment) ・ Span between roll-roller set 90mm ・ Span between drive rollers 450mm ・ Length of induction heating section 300mm (work drive fixed condition) ・ Skew angle 1.0 ° ・ Roller on output side Longitudinal drive speed of 20mm / s ・ Constant drive mode speed of outlet roller ・ Engage with outlet roller work always ON (specimen) ・ Material JIS SKH 51 ・ Dimensions 8mm diameter × Length 2000mm (Heat treatment condition) ・ Rapid heating to 1210 ± 10 ℃ and water cooling after maintaining temperature for 10s or more (work drive fluctuation condition) ・ Incoming drive roller 4 drive operation Set A. Longitudinal driving speed = 19 mm / s, constant speed driving This corresponds to the embodiment of the first driving method. Outgoing side
The velocity reduction ratio (20-19) /20=0.05 from La 5 is more than 3 times the thermal expansion ratio (0.015) calculated from the above heat treatment conditions assuming that the thermal expansion is isotropic. This is a little over 1.5 times the thermal expansion ratio (0.03) that was calculated. B. Constant torque drive so that longitudinal compressive force applied to the work 3 = 3 MPa This corresponds to one embodiment of the second drive method. C. Longitudinal drive speed = 19.5 mm / s constant speed drive, and the compression force applied to the work should not exceed 5 MPa.
Upper limit of torque (motor current) is regulated. This corresponds to the second embodiment of the second driving method and uses the first driving method together. D. It is configured to be driven at a constant speed with a longitudinal driving speed of 19.5 mm / s and to be lifted up when the tip of the work 3 reaches the exit side driving roller 5. This corresponds to an example of the third driving method that also uses the first driving method. E. FIG. Constant speed drive at longitudinal drive speed = 20 mm / s. This is a comparative example.

[0037]

[Table 1]

As described above, it was confirmed that the apparatus of the present invention and the method of the present invention enable a highly efficient quenching work without buckling or bending of the work. In general, other heat treatments that have a lower heating temperature than quenching can be performed more easily.

[0039]

The present invention is as described above, and by the group of three or four scyro-laser sets,
In order to prevent the work from flexing or swaying, the work is rotated to run in the longitudinal direction to pass the heat treatment zone, and the work is driven by the inlet side and the outlet side. Since the drive operation of the drive roller can be set separately, no inconvenient compression force is applied to the work, which allows the small-diameter metal cylindrical material to be raised without bending or buckling the product. It is possible to provide a device that efficiently performs heat treatment. Further, by using induction heating as the heating means in the heat treatment zone, quenching of high-grade steel which requires heating to a high temperature and strict temperature maintenance can be easily performed by the heat treatment.

Further, according to the present invention, the drive operation of the drive rollers on the input side and the output side is controlled with respect to the drive speed difference, the drive torque, and the drive procedure, so that the work can be performed in the apparatus of the present invention. It is possible to provide an operation method in which a compressive force that causes the buckling of the work is not applied to the work.

That is, the present invention can sufficiently achieve the object of the present invention to obtain a heat-treated product of a small-diameter metal columnar material having an excellent shape and uniformly processed at low cost.

[Brief description of drawings]

FIG. 1 is a front view of an example of the device of the present invention to which the method of the present invention is applied.

FIG. 2 is a right side view of the device of FIG.

3 is a plan view of a driving roller and a receiving roller portion in the apparatus of FIG.

FIG. 4 is a right side view of the roller shown in FIG.

FIG. 5: Drive speed in operation of input / output side drive roller
Torque diagram.

[Explanation of symbols]

 1 Receiver Roller 2 Presser Roller 3 Work 4 Incoming Side Drive Roller 5 Outgoing Side Drive Roller 6 Inlet Side Drive Roller Motor 7 Outgoing Side Drive Roller Motor 8 Induction coil 9 High frequency transformer 10 Water injection device

Front Page Continuation (72) Inventor, Yasuyuki Taniguchi, 2-17-8, Tonomachi, Kawasaki-ku, Kanagawa

Claims (5)

[Claims] 1. A small-diameter metal columnar material is run in the longitudinal direction,
An apparatus for performing heat treatment by passing through a heat treatment zone, comprising two receiving skew rollers for supporting the cylindrical material and the cylindrical material mounted on the receiving skew roller. A plurality of skew roller sets each having a pressing skew roller for pressing are arranged in the direction in which the columnar material is run, and a heat treatment means is arranged between the skew roller sets. And a drive system is connected to the presser skew rollers located on the inlet side and the outlet side of the heat treatment zone to form an inlet side drive roller and an outlet side drive roller,
Further, a heat treatment apparatus for a small-diameter metal columnar material, wherein the driving operation of the columnar material by the entrance side driving roller and the exit side driving roller is separately set and controlled. 2. A heat treatment means in the heat treatment zone for rapidly heating and maintaining a temperature of a small-diameter metal columnar material, an induction coil connected to a power feeding system, and a quenching arranged after the induction coil. A quenching means having a water injection mechanism.
The heat treatment apparatus for a small-diameter metal cylindrical material described in. 3. Using the device according to claim 1 or 2,
When heat-treating the columnar material, a longitudinal compressive strain due to thermal expansion of the columnar material, which is applied to the columnar material while both drive rollers are applied to the columnar material, is applied to the output side drive roller. A method for heat treating a small-diameter metal columnar material, characterized in that the work is run while being released by making the driving of the columnar material by the roller faster than the driving by the entrance side driving roller. 4. Using the device according to claim 1 or 2,
When heat-treating the columnar material, the entry-side drive roller
When the columnar material is applied to both the la and the outlet drive roller, a longitudinal compressive force exceeding the upper limit at which the columnar material is not buckled is applied to the columnar material being heat-treated,
A heat treatment method for a small-diameter metal columnar material, characterized in that the columnar material is caused to travel by limiting the drive torque of either one of the two drive rollers. 5. Using the device according to claim 1 or 2,
When heat-treating the columnar material, the entry-side drive roller
The driving of the columnar material is started by the drive of the roller, the tip of the columnar material comes into contact with the output side driving roller, and at the same time, the driving of the columnar material by the input side driving roller is released. A small-diameter metal columnar material, characterized in that the columnar material is made to travel without applying a compressive force in the longitudinal direction to the columnar material by a driving procedure in which the columnar material is made to travel by the drive of only the exit side drive roller. Heat treatment method.