JP3224484B2 - Inclined rolling method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plurality of inclined rolls disposed around a pass line while applying a tensile force to a material pipe from the front of the material pipe, and an inner surface such as a mandrel inserted into the pipe. The present invention relates to an inclined rolling method and a device for producing a thin metal tube by elongating and rolling a material tube with a regulating tool.

[0002]

2. Description of the Related Art As a method of extending a metal pipe,
JP-A-3-66403, JP-A-3-151104
There is known a method disclosed in Japanese Patent Application Laid-Open Publication No. H10-26095. In this method, an inner surface regulating tool such as a mandrel is inserted into a heated material pipe, and one end of the material pipe is pulled along a feed direction with a predetermined tension to rotate and drive a forming roll to draw and roll the material pipe. To produce thin metal tubes.

The method of performing inclined rolling by applying tension from the front of a material has the following features. By applying the axial tension, the straightness of the product tube is good. Since the axial speed can be controlled, stable molding is possible.

[0004] Axial tension can assist in the winding of material by the forming rolls.

[0005]

In tilt rolling of a forward tension applying type, there are many processing parameters, and it is difficult to specify a formable region. For this reason, the above publication (Japanese Unexamined Patent Publication No.
As shown in No. 151104), even when control is performed to automatically search for molding conditions, a database constructed by a preliminary experiment is required.

[0006] Despite the so-called die-less machining in which the tool is not restricted by the product dimensions, the inclined rolling is an essential advantage in that the formable area is narrow and complicated as described above. It is an obstacle for application to small-lot production. In addition, forming is performed in a pseudo-steady state, but due to the increase in deformation resistance due to a decrease in the temperature of the material tube during rolling and the change in friction conditions between the surface of the forming roll and the material tube, etc. Since the load changes during rolling, it has been difficult to stabilize the forming and increase the efficiency.

[0007] Japanese Patent Publication No. 52-29253 discloses an inclined rolling machine having a movement mechanism for adjusting a feed angle of a forming roll. However, in such conventional inclined rolling mills, even if there is a mechanism for adjusting the feed angle, it does not control the pulling speed in connection with this, and it is difficult to satisfactorily perform the inclined rolling of the tube material. Was.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the problems associated with the above-mentioned prior art, and provides a tilt rolling method and apparatus capable of stably rolling a metal pipe with high efficiency. With the goal.

[0009]

In order to achieve the above-mentioned object, a tilt rolling method according to the present invention is directed to a method of pulling a pipe while applying a tensile force to the pipe from the front along a traveling direction of the pipe, thereby forming a pipe around a pass line. the tube in the inclined rolling method for elongation rolling, within an upper limit driving torque driving torque is allowed to the inclined rolls before Symbol inclined rolls with the plurality of inclined rolls and inserted inner surface restricting tool in a tube arranged in And so that the tensile force applied to the pipe is within a certain range equal to or less than the breaking limit tension, the tensile speed of the pipe and the
The inclination angle of the inclined roll is controlled.

[0010] In the tilt rolling method of the present invention, the tilt angle of the tilt roll is such that the tensile force applied to the pipe is 0.2 to 0.8 times, preferably 0.4 to 0 times the breaking limit tension. .6
Preferably, the angle is controlled to be within the double range. Further, in order to achieve the above object, the inclined rolling device of the present invention is disposed around the pass line and a pulling means for pulling the pipe while applying a tensile force to the pipe from the front along the traveling direction of the pipe. A plurality of inclined rolls, having an inner surface regulating tool inserted into the pipe, in an inclined rolling device that elongates and rolls the pipe between the inclined roll and the inner surface regulating tool,
An inclination angle applying means for applying an inclination angle to the inclined roll,
A roll driving torque detecting means for detecting a driving torque of the inclined roll; a forward tension detecting means for detecting a pulling force applied to the pipe by the pulling means; and controlling operations of the pulling means and the tilt angle applying means. Control means for performing
The control means has a drive force detected by the roll drive torque detection means within the upper limit drive torque allowed for the inclined roll, and the tensile force detected by the front tension detection means is broken The operation of the pulling means and the operation of the tilt angle applying means are controlled so as to be within a certain range equal to or less than the limit tension.

[0011] In the tilt rolling device of the present invention, the tilt angle applying means has a tensile force detected by the forward tension detecting means of 0.2 to 0.8 times, preferably 0.4 to 1.0 times the breaking limit tension.
It is preferable to control the inclined roll to an angle within the range of 0.6 times. Here, the breaking limit tension is a critical load at break at the temperature of the material pipe exit determined by the heat generated during processing and the heat generated by friction of the material pipe. In this way, the upper limit is set for the pulling force in consideration of the safety factor for preventing the material pipe from being thinned, and the lower limit is set to the effect of reducing the roll driving torque and the roll rolling force due to the forward tension. The straightness of the product is determined so that a compressive force acts in the product axial direction and the straightness of the product does not deteriorate.

[0012]

According to the inclined rolling method and apparatus of the present invention, the pulling speed of the pipe and the inclined angle of the inclined roll are set so that the driving torque of the inclined roll is within the upper limit driving torque allowed for the inclined roll. And, it is controlled so that the tensile force applied to the pipe is within a certain range equal to or less than the breaking limit tension. According to this, it is possible to maintain a high production efficiency while avoiding circumferential buckling since the relative advance amount can be large, and furthermore, under this condition, the forward tension is within a certain range equal to or less than the product breaking strength. Since the inclination angle is controlled, the inclined rolling forming is performed with high efficiency in the stable forming region.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a tilt rolling method and a tilt rolling device according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram illustrating a main part of the inclined rolling device, and FIG. 2A is a diagram illustrating a state during rolling by the inclined rolling device illustrated in FIG. FIG. 2B is a cross-sectional view taken along the line BB of FIG. 2A, and FIG. 2C is a view taken along the arrow C of FIG. 2B.

[0014] As shown in FIG.
After the heating step, the raw material tube 10 to be rolled taken out of the heating furnace is carried in and mounted at a predetermined position, and has a forming roll portion 14 for tilt-rolling the raw material tube 10. As shown in FIG. 10, the left hand side of the forming roll unit 14 in the drawing is the loading side of the material pipe 10,
Mandrel 15 as inner surface regulating tool inserted into pipe
(See FIG. 2) and a mandrel holding device 50 that holds the mandrel shaft 22 is provided. The mandrel shaft 22 is longer than the raw material tube 10 before processing. The mandrel 15 shown in FIG. 2 is made of a material (for example, a Ni-base heat-resistant alloy or the like) having a higher deformation resistance than the material tube 10 at a processing temperature. The mandrel holding device 50 shown in FIG. 10 waits at a position where the material tube exits from the heating furnace and is placed on the material tube carry-in bed 52 at the retraction stop position, and the forming roll is lowered by the elevating cylinder to perform the forming. At the start, it is inserted into the material tube 10.

As shown in FIG. 10, on the side opposite to the mandrel holding device 50 with respect to the forming roll portion 14, the metal tube 16 is fed at a predetermined tension or at a predetermined pulling speed along the feeding direction during the rolling operation. A pulling device 17 for pulling is provided.
As shown in FIG.
Three forming rolls 20a around the pass line 19,
20b and 20c are provided rotatably at 120 ° intervals. Each forming roll 20 (forming rolls 20a, 20b, 2
0c) are shown in FIGS. 3B and 3C.
As shown in the figure, the path line 19 is inclined at an intersection angle α and an inclination angle β. Propulsion force is applied to the metal tube 16 along the feed direction 21 by the rotation speed and the inclination angle β of the forming roll 20.

The forming roll crossing angle α is fixed in a direction converging toward the material advancing direction, for example, 30 to 45 °, preferably about 45 °, and the inclination angle β is, for example, about 0 ° to about 2 °.
It is freely variable in the range of 5 °. Note that all three forming rolls 20 have the same intersection angle α and inclination angle β.

As shown in FIG. 1, the forming roll 20 is attached to the tip of the drive shaft of a roll drive motor 25 by a tapered shank. By fixing with a taper shank, the detachment of each forming roll 20 is easy,
In addition, a large load can be received. A drive shaft of a tilt angle providing motor 26 as a tilt angle adjusting means is connected to a casing of the roll drive motor 25, and the forming roll 20 is rotated together with the roll drive motor 25 by drive adjustment of the tilt angle providing motor 26. The inclination angle β given to the forming roll 20 is adjusted.

The forming roll 20 is composed of two truncated cones, and the half cone angle of the first truncated cone portion is equal to the intersection angle α,
The half cone angle of the second truncated cone provided continuously with the first truncated cone portion is formed smaller than the intersection angle α. When the material pipe 10 is inclinedly rolled, first, the material pipe 10 is rolled by a rolling surface S1 which is relatively inclined to the pass line 19, and then is rolled by a rolling surface S2 which is inclined relatively small to the pass line 19. .

The mandrel 15 is shown in FIG.
As shown in (C), when the material pipe 10 is inclinedly rolled in the forming roll section 14 to produce the thin metal pipe 16, it has a role of defining the shape of the hollow portion of the produced metal pipe 16. . The mandrel shaft 22 to which the mandrel 15 is rotatably attached at the tip is, for example, a material pipe 10.
And is inserted into a hollow portion of the raw material tube 10 from an end of the raw material tube 10 to a rolling position by the forming roll unit 14.

As shown in FIG. 10, the pulling device 17 is provided on the pass line 19 so as to be able to move forward and backward with respect to the forming roll portion 14. The pulling device 17 grips the front end of the material tube 10 and rotates together with the material tube 10. A gripper 23, a tension rod 24 for holding the gripper 23, and a tensile force source (not shown). And, during the rolling operation, the material pipe 10
While being gripped by the gripper 23, is pulled at a predetermined tension or a predetermined pulling speed along the feed direction 21.

The tilt rolling was performed under various forming conditions using the tilt rolling apparatus 13 having the above-mentioned structure, and the following results were obtained. Experiments were performed at several stretching ratios within the range of 2.0 to 5.0, and the experiments at each stretching ratio showed almost the same tendency. FIG. 3 is a diagram showing a moldable region, which is a region surrounded by a buckling limit line 30, a fracture limit line 31, and an axial tension shortage limit line 32. Here, the buckling limit line 30 indicates the relative advance amount (V1
/ Nr, V1: tensile speed, Nr: number of rotations of the forming roll)
Is less than a certain value, which indicates a limit to the occurrence of circumferential buckling, that is, polygonalization of the cross section. The breaking limit line 31 indicates a limit at which a product breaks due to excessive forward tension acting on the rolling exit. Further, the axial tension shortage limit line 32 indicates a limit at which the axial tension becomes insufficient due to the excessive thrust due to the friction with the surface of the forming roll 20 and the axial compressive force increases to cause axial buckling. I have. The moldable region shows the same result even when the material of the material tube 10 is changed.

FIG. 4 is a diagram showing the relationship between the inclination angle β and the forward tension at each relative advance amount, and shows the effect of the inclination angle β on the tensile force. As is clear from the figure, when the relative advance amount is constant and the inclination angle β is small, or when the inclination angle is constant and the relative advance amount is large, the tensile force (forward tension) acting on the metal tube 16 as a product becomes large. growing.

FIG. 5 is a diagram showing the relationship between the inclination angle β and the roll driving torque at each relative advance amount, and shows the effect of the inclination angle β on the roll driving torque. As is clear from the figure, when the relative advance amount is constant and the inclination angle β increases, or when the inclination angle is constant and the relative advance amount increases, the roll driving torque increases. Here, the roll drive torque is a torque generated on the rotating shaft of the forming roll 20. The upper limit torque Tc, which is the upper limit of the roll driving torque, is determined by the capacity of the inclined rolling device 13 itself.

Based on the results shown in FIGS. 3 to 5, the inventor of the present application can maintain high production efficiency while avoiding circumferential buckling by increasing the relative advance amount as much as possible. Under this condition, the forward tension is 0.2 to less than the product breaking strength.
When the inclination angle β is controlled to be 0.8, preferably 0.4 to 0.6 times, it is found that the inclined rolling can be performed with high efficiency in the stable forming area, and the present invention is completed. Reached.

This will be described with reference to FIGS. 6 and 7. FIG. 6 is an isotorque diagram of the roll driving torque in the moldable region shown in FIG. 3, and FIG. 7 is an iso-forward tension diagram in the moldable region shown in FIG.
To increase the production efficiency, the larger the roll driving torque, the better. However, the upper limit torque Tc is determined by the capacity of the inclined rolling device 13 itself, as described above. Therefore,
It is assumed that the upper limit of the roll driving torque in a certain inclined rolling mill is “T5” shown in FIG. 6, and the forward tension is “F ₃ (0.2 to 0.8 times the breaking limit tension, (Preferably in the range of 0.4 times to 0.6 times) ", if inclined rolling forming is started at point A shown in FIG. In the present invention, the pulling device 1 is moved to point B in order to perform
7 and the inclination angle β of the forming roll 20 are controlled.

In order to realize such control, in the inclined rolling device 13 of the present embodiment, as shown in FIG.
On the side, a roll drive torque detector 35 for detecting a torque T generated on the rotating shaft of the forming roll 20 and a forming roll 2
And a tilt angle detector 36 for detecting a tilt angle β of 0. Further, on the pulling device 17 side, a pulling speed detector 37 for detecting a pulling speed V1 of the metal tube 16 accompanying the pulling of the pulling device 17 and a forward tension detector for detecting a tension applied from the front of the metal tube 16. 38 are provided.

As the roll driving torque detector 35, a known torque sensor is used. The inclination angle detector 36 is
For example, the tilt angle imparting motor 2 is configured by an encoder.
The inclination angle β is detected by counting the number of rotations of the drive shaft 6 as the number of pulses by the encoder. As the pulling speed detector 37, for example, one having a configuration that electromagnetically or optically detects a displacement generated in the pulling rod 24 and calculates the pulling speed V1 of the metal tube 16 may be used.

The torque data detected by the roll drive torque detector 35 and the front tension data detected by the front tension detector 38 are input to the arithmetic and control unit 39.
The tilt angle data detected by the tilt angle detector 36 is used as a tilt angle control unit 40 for controlling the driving of the tilt angle imparting motor 26.
The tensile speed data detected by the tensile speed detector 37 is input to a tensile speed control unit 41 that controls the driving of the tensile device 17. In addition, in order to set an upper limit value of the roll driving torque specific to the device, the arithmetic control unit 39 includes:
Data input unit 42 composed of a keyboard, operation panel, etc.
Is connected. Further, a data output unit 43 composed of a memory or the like is connected to the arithmetic control unit 39 in order to store the finally set molding conditions such as the inclination angle β.

The arithmetic control unit 39 outputs a control signal based on the torque data and the forward tension data to the inclination angle control unit 40 and the pulling speed control unit 41. The tilt angle control unit 40 controls the drive of the tilt angle imparting motor 26 based on the control signal from the arithmetic control unit 39, and the pulling speed control unit 41 controls the pulling device 17 based on the control signal from the arithmetic control unit 39.
Is controlled.

Next, the operation of this embodiment will be described with reference to the flowchart shown in FIG. First, in step S1, an upper limit value of the roll driving torque determined by the specifications of the inclined rolling device and a target value of the forward tension (for example, “F ₃ ” shown in FIGS. 6 and 7) are set via the data input unit. I do.

Next, the initial pulling speed V1 of the pulling device 17
And an increment value ΔV1 per one time of the pulling speed. Further, an initial inclination angle β of the forming roll 20 and an increment value Δβ per one time of the inclination angle are set via the data input unit 42 (S2). The mandrel 15 is inserted from one end of the raw material tube 10 which has been subjected to the predetermined processing in the previous process and is carried into the inclined rolling device 13, and the other end is gripped by the gripper 23. And the raw material tube 10 is connected to the tension device 17.
As a result, the inclined rolling is started at the portion in contact with the rotating forming roll 20 while being pulled along the feed direction 21 at the initial pulling speed V1. When the material pipe 10 is inclinedly rolled, first, the material pipe 10 is rolled at a relatively large reduction ratio by the rolling surface S1 which is relatively inclined with respect to the pass line 19, and then is inclined relatively small with respect to the pass line 19. Rolling is performed at a relatively small area reduction rate by the rolling surface S2.

When the inclined rolling is started (S3), the arithmetic and control unit 39 reads the torque value detected by the roll drive torque detector 35 (S4), and compares this with the torque upper limit value set in step S1 ( S5) If YES, that is, if the detected torque value is smaller than the torque upper limit value, since the capacity of the inclined rolling device 13 has room, the pulling speed V1 of the pulling device 17 is increased by the increment value ΔV1 in order to increase production efficiency. Is output to the pulling speed controller 41 (S6). Based on this control signal, the pulling speed controller 41 controls the driving of the pulling device 17 to increase the pulling speed V1.

On the other hand, if the determination in step S5 is NO,
That is, when the detected torque value is equal to or greater than the torque upper limit value, the control signal for decreasing the pulling speed V1 of the pulling device 17 by the increment value ΔV1 is used because the specified value exceeds the specification limit of the inclined rolling device 13. Output to the unit 41 (S
7). Based on this control signal, the pulling speed controller 41
Controls the driving of the tension device 17 to decrease the tension speed V1 (S8).

Next, the arithmetic and control unit 39 reads the forward tension value detected by the forward tension detector 38 (S9) and compares this with the forward tension target value set in step S1 (S10). When the obtained front tension value is smaller than the front tension target value, in order to increase the front tension and increase the production efficiency, a control signal for decreasing the inclination angle β of the forming roll 20 by the increment value Δβ is transmitted to the inclination angle control unit 40.
(S11). Based on this control signal, the tilt angle control unit 40 controls the drive of the tilt angle imparting motor 26 to reduce the tilt angle β.

On the other hand, if the determination in step S10 is NO
That is, when the detected front tension value is equal to or greater than the target front tension value, the control signal for increasing the inclination angle β of the forming roll 20 by the increment value △ β is set in order to reduce the front tension and avoid the risk of product breakage. Output to the angle control unit 40 (S1
2). Based on this control signal, the tilt angle control unit 40
The drive of the tilt angle imparting motor 26 is controlled to increase the tilt angle β (S13).

Next, the current tensile speed V1 and the inclination angle β are displayed (S14), and thereafter, it is determined whether or not the forming is completed (S15).
The processes from 4 to S15 are repeated. Then, upon detecting the end of forming (S15), the arithmetic and control unit 39 determines the finally set pulling speed V1 of the pulling device 17 and the forming roll 2
Is stored in the data output unit 43 (S1).
6), control is completed. When the next forming is performed, by using the stored final tensile speed V1 and inclination angle β as initial values in step S2, the convergence of the next control is facilitated, and the optimum processing conditions are reached. The time is shortened, resulting in increased production efficiency. When the apparatus is started, buckling in the circumferential direction is likely to occur due to insufficient rolling reduction. However, in this embodiment, as described above, the stored final tensile speed V1 and inclination angle β are determined in step S
2, the initial circumferential buckling at the time of startup can be minimized.

Control of the pulling speed V1 of the pulling device 17 in steps S4 to S8 and steps S9 to S8
The control of the inclination angle β of the forming roll 20 in FIG.
As shown in FIG. Note that the processing in steps S21 to S36 in FIG. 9 is the same as the processing in steps S1 to S16 in FIG.

According to this embodiment, the pulling speed V1 of the pulling device 17 is set within a range smaller than the upper limit of the roll driving torque.
By adjusting the inclination angle β of the forming roll 20, highly efficient and stable inclined rolling can be performed. further,
Since the upper limit value of the roll driving torque is determined in advance as the performance of each inclined rolling device 13, there is no need to construct a database through a preliminary experiment, and the essential advantage of the inclined rolling device 13 is that it can be used for high-mix low-volume production. It is extremely easy and economical to apply.

The rolling conditions change due to an increase in deformation resistance due to a decrease in the temperature of the material tube 10 during rolling and a change in the friction condition between the surface of the forming roll 20 and the material tube 10. Since the change in the load on the inclined rolling device 13 appears as a change in the roll driving torque value or the forward tension value, the change in the rolling conditions can be easily absorbed in the control routine, and the forming can be stabilized and the efficiency can be improved. Can be planned.

[0040]

As described above, according to the present invention,
By adjusting the pulling speed of the pulling means and the tilt angle of the tilting roll within a range smaller than the upper limit of the roll driving torque, it is possible to easily and stably perform tilt rolling with high efficiency. In particular, in the present invention, even a Ni-based alloy material tube that is difficult to process can be easily subjected to tilt rolling.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a main part of a tilt rolling device.

FIG. 2A is a diagram showing a state during rolling by the inclined rolling device shown in FIG.
FIG. 2B is a sectional view taken along the line BB of FIG.
(C) is a view on arrow C of FIG. (B).

FIG. 3 is a diagram showing a moldable area.

FIG. 4 is a diagram showing a relationship between the inclination angle β and the forward tension at each relative advance amount.

FIG. 5 is a diagram showing a relationship between the inclination angle β and the roll drive torque at each relative advance amount.

FIG. 6 is an isotorque diagram of a roll driving torque in a moldable region shown in FIG. 3;

FIG. 7 is an isometric tension diagram in the moldable region shown in FIG. 3;

FIG. 8 is a flowchart showing a control procedure of the inclined rolling mill.

FIG. 9 is a flowchart showing another control procedure of the inclined rolling device.

FIG. 10 is a schematic configuration diagram showing the entire tilt rolling device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Material pipe (pipe) 15 ... Mandrel (inner surface regulation tool) 16 ... Metal pipe (pipe) as a product 17 ... Tension device (pulling means) 19 ... Pass line 20 ... Forming roll (tilted roll) 26 ... Tilt angle imparting Motor (inclination angle applying means) 35 ... Roll drive torque detector (roll drive torque detection means) 36 ... Inclination angle detector 37 ... Tension speed detector 38 ... Front tension detector (forward tension detection means) 39 ... Calculation control unit (Control Means) 40 ... Inclination Angle Control Unit (Control Means) 41 ... Tension Speed Control Unit (Control Means) β ... Inclination Angle Fc ... Limiting Tension Tc ... Upper Limit Drive Torque

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor, Eihiko Tsukamoto 4-6-22, Kannonshinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture Inside the Hiroshima Research Laboratory, Mitsubishi Heavy Industries, Ltd. (72) Inventor Hiroshi Shioda 4 Kanonshinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture No. 6-22, in the Hiroshima Laboratory, Mitsubishi Heavy Industries, Ltd. (56) References JP-A-61-71111 (JP, A) JP-A-3-151104 (JP, A) JP-A-60-221105 (JP, A) JP-B-52-29253 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) B21B 19/06 B21B 37/00

Claims (4)

(57) [Claims] 1. A pipe is pulled from the front along a traveling direction of the pipe while applying a pulling force to the pipe, and a plurality of inclined rolls arranged around a pass line and an inner surface regulating tool inserted into the pipe. in the inclined rolling method for drawing and rolling the pipe, before SL as the driving torque of the inclined rolls is within acceptable upper limit driving torque to the inclined rolls, and tension is less fracture limit the tension applied to the tube The pulling speed of the pipe and the inclination angle of the inclined roll are set so as to be within a certain range
And a gradient rolling method. 2. The method according to claim 1, wherein the inclination angle of the inclined roll is controlled so that a tensile force applied to the pipe is in a range of 0.2 to 0.8 times a critical breaking tension. The inclined rolling method as described. 3. A pulling means for pulling the pipe while applying a pulling force to the pipe from the front along the traveling direction of the pipe, a plurality of inclined rolls arranged around a pass line, and an inner surface inserted into the pipe. A tilting rolling device that has a regulating tool, and elongates and rolls the pipe between the inclined roll and the inner surface regulating tool; a tilting angle applying unit that applies a tilting angle to the inclined roll; and driving of the inclined roll. Roll driving torque detecting means for detecting torque, forward tension detecting means for detecting a pulling force applied to the pipe by the pulling means, control means for controlling operations of the pulling means and the tilt angle applying means, The control means is configured to control the drive torque detected by the roll drive torque detection means to be within an upper limit drive torque allowed for the inclined roll, In so detected tension is within a range of less fracture limit tension gradient rolling apparatus characterized by controlling the operation of said pulling means, and actuation of the tilt angle imparting means. 4. The tilt angle applying means according to claim 1, wherein the tensile force detected by the front tension detecting means is 0.2 to 0.8 times the breaking limit tension.
The inclined rolling device according to claim 3, wherein the inclined roll is controlled to an angle within a range of twice.