JPH0366403A - Drawing rolling method for metal pipe and device used for execution thereof - Google Patents

Abstract

PURPOSE:To prevent the abrupt stress variation of a pipe rolling part and to improve the dimensional accuracy and quality by gradually increasing a tensile force to a specific value, gradually increasing the tensile speed of a pipe to the specific value or holding the above speed constant as well as making a pushing force zero with its gradual reduction after holding the pipe. CONSTITUTION:A drawing rolling device of a metal pipe A is equipped with a rolling mill having inclined rolls 1, 2, 3 arranged around the pass lines X, X of the pipe A, a pushing device 6 projecting the pipe A to the outlet side of the rolling mill by giving a pushing force Pc to the pipe A in which the plug 5 of the pipe inner face regulating tool supported by a mandrel 4 from the inlet side of the rolling mill, a tensile device 7 giving a tensile force PT to the pipe A by holding the projecting end of the pipe A at the outlet side of the rolling mill, a timer 11 starting a time count by detecting the completion of the holding of the pipe A, a push force arithmetic control means 8 gradually decreasing the push force Pc corresponding to the time counted by the timer 11 and a tensile speed arithmetic control means 9 gradually increasing the tensile speed PT of the pipe A to a specific value corresponding to the time or holding the speed PT constant.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for cold or warm elongation rolling of a pipe by applying a pushing force from the input side of a rolling mill and a tensile force from the exit side. and the equipment used for its implementation.

[Conventional technology]

Hot-produced seamless or welded pipes are often subjected to cold or warm drawing processing in order to improve the dimensional accuracy and surface accuracy of the pipe, or to improve mechanical properties.

Methods for cold or warm pipe drawing include:
There is a drawing method in which the wall thickness is reduced between a die and a plug, and a pilger rolling method in which the wall thickness is reduced between a roll having a pair of upper and lower special grooves and a seven-drill. However, the drawing method involves chemical lubrication treatment of the metal tube, mouth drawing, etc.5, and the pilger rolling method has the problem of reducing costs due to the use of a special groove-shaped a-ru. Ta.

On the other hand, when the spinning method is used, there is no need for chemical lubrication treatment of the metal tube, and tool costs are low.
High precision cold or warm drawing force processing can be performed. The spinning method involves pressing a plurality of rolling rolls arranged around the pass line against a tube attached to a mandrel that rotates on the pass line, and moving a carriage incorporating the rolling rolls in the axial direction of the tube. The wall thickness is reduced over the seigan and long sections.

Conventionally, stretching using the spinning method was limited to processing short products such as cylindrical mechanical parts and containers, but in recent years, spinning methods have been proposed that can mass-produce long tubes. (Advanced Techn.
ology of plasticity vol.
1pp, 401-409 <1984>, B.
Agarwala, The shearspinn
ing technology of Tubes
with ) Iigh Dimensional Pr
selection).

FIG. 1O is a partially cutaway side view of an apparatus used to carry out the spinning method disclosed in the above-mentioned document. A pushing force is applied to the tube A to be rolled by a pushing device (not shown), in which a mandrel bar 40 is penetrated in the axial direction. As a result, the tube A is pushed into the entry side of a rolling mill having a housing 41 that is driven to rotate around the pass line, and push rolling is started. The tube A is pushed in the axial direction, that is, toward the exit side of the housing 41, and its wall thickness is reduced by a pair of rolling rolls 42, 43 and a mandrel bar 40 built around the pass line on the exit side of the housing 41. .

Then, the tip of the tube A protrudes toward the exit side of the rolling mill, and the protruding end is gripped by the chuck part 44 of the tensioning device on the exit side of the rolling mill.
A tensile force is applied to tube A. As a result, the tube A is subjected to tension rolling in the axial direction, and a force 11-[ is applied to the rolling rolls 42 and 43 over the entire length of the tube A, thereby tightening the wall thickness. At this time, the pipe A and the mandrel bar 40 inserted therein do not rotate, and the housing 41 in which the rolling rolls 42 and 43 are incorporated rotates to perform rolling, thereby improving the properties of the pipe A due to its circulation. deterioration can be prevented. Note that depending on the type of rolling, the tube A may be rotated and rolled by rotating the rolling rolls 42 and 43.

[Problem to be solved by the invention]

In the cold or warm elongation rolling process using the spinning process with ε rollers, in order to give the tube A the largest possible wall thickness, the roll surface angle of the rolling rolls 42 and 43 should be x.
It is known that it is preferable to make a predetermined angle (2(J'□~30') with respect to -x'.

However, cold or warm rolling differs from hot rolling in that the coefficient of friction between the rolling rolls 42.43 and the tube A is small, so the axis of the rolling rolls 42.43 is aligned with the pass line x- Tube A cannot be advanced simply by providing an axial velocity component from the rolls by tilting it relative to x'. Therefore, in the cold or warm elongation rolling process, it is necessary to apply a pushing force and a tensile force to the tube A as described above.

However, in the elongation rolling process 9, the progress of rolling is temporarily stopped when switching from push rolling to tension rolling, so when the rolling stops, the dimensions of the pipe located directly below the rolling rolls 22 and 23 are different from other parts. There was a problem in that it changed compared to the previous one and also caused peeling-like surface flaws. In addition, it is necessary to prevent surface flaws due to stopping of rolling (if the transition from push rolling to tension rolling occurs instantaneously, the stress state of the rolled part of pipe A changes suddenly,
Dimensional fluctuations are likely to occur. In addition, slips tend to occur at the tip of the tube A, that is, the portion to be nayaked by the chuck portion, and chunking may become impossible. In particular, slips are more likely to occur when the rolling speed is increased during tension rolling than during push rolling.

In this way, indentation force and tensile force are applied in the cold or warm elongation rolling process.1. Because the above-mentioned problems occur when the tube is stretched and rolled, the yield of the product is poor, and for example, the tip of tube A is often discarded as a defective product, which hinders the reduction of product costs. Ta.

The present invention was made in view of such circumstances.

By gradually transitioning from push rolling to tension rolling and preventing sudden changes in the stress state in the rolled pipe section, products with good dimensional accuracy and quality can be obtained. It is an object of the present invention to provide a stretch rolling method that can improve product yield and reduce manufacturing costs, and an apparatus used for carrying out the method.

[Means for Solving the Problems] The elongation rolling method of the present invention applies a pushing force to a tube in which a tube inner surface regulating tool is inserted into a rolling mill having a plurality of inclined rolls arranged around a pass line of the tube. 7.
In the method of elongating and rolling the tube while applying tensile force to the tube by grasping the protrusion @ of the wire tube, after the completion of grasping the tube, 1. The pushing force is gradually decreased to zero, and the pulling force is gradually increased to a predetermined value, or the speed at which the tube is pulled is gradually increased to a predetermined value, or the speed is increased to C. It is characterized by being held constant.

The metal tube elongation rolling equipment used for this purpose consists of a rolling mill with a plurality of inclined rolls arranged around the bus line of the tube, and a tube into which a tube inner surface regulation tool is inserted from the entry side of the rolling mill. A pushing device applies a pushing force to the wire tube so as to protrude it from the exit side of the rolling machine, and a pushing device grips the protruding end of the pipe at the exit side of the rolling machine.
S1. ．． + In a stretching device equipped with a tensioning device that applies a tensile force to the tube, a gripping detection means detects completion of gripping the tube, and when the gripping detection means detects completion of gripping, a time measurement is started. a timer that gradually decreases the pushing force in accordance with the time measured by the timer; and a pushing force calculation control means that gradually increases the speed at which the tube is pulled up to a predetermined value in accordance with the time; It is characterized by comprising a tensile speed calculation control means for keeping constant.

(Function) In the elongation rolling method of the present invention, a pushing device placed on the inlet side of the rolling mill applies a pushing force to the tube, and the tube is projected to the outlet side of the rolling mill. The projecting end of the tube is gripped by a chuck part of a tensioning device disposed on the exit side of the rolling mill. When the grasping is completed, a timer is activated, and the pushing force is gradually decreased in accordance with the time measured by the timer, and the pulling force is gradually increased to a predetermined value, or the speed of pulling the tube is kept constant. or gradually increase the speed to a predetermined value. As a result, the transition from push rolling to tension rolling is carried out gradually, and sudden changes in stress state are prevented from being applied to the pipe rolling section.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on drawings showing embodiments thereof. FIG. 1 is an explanatory diagram showing the apparatus used to carry out the stretch rolling method of the present invention, and FIG. 2 is an explanatory diagram showing the apparatus used to carry out the stretch rolling method of the present invention, viewed from the input side to the output side in the rolling direction. Figure 3 is a partial sectional view taken along line II [= i in Figure 2, taken at the start of rolling, and Figure 4 is a partial sectional view similar to Figure 3, taken as rolling progresses. It is something.

1.2.3 in the figure is a so-called barrel type rolling roll. The rolling rolls 1.2.3 have a roll face angle α with respect to the pass line X-X' and are arranged at intervals of 120' around the pass line .

In the illustrated example, the roll axes of the rolling rolls 1, 2.3 are arranged parallel to the pass line χ-X', but they are arranged at a predetermined angle with respect to the pass line The tube A may also be arranged in a twisted state, in which case an auxiliary forward thrust can be applied to the tube A from the rolling rolls 1, 2.3.

A plug 5, which is a tube inner surface regulating tool, supported by a mandrel 4 is installed on the pass line xx' from the input side in the rolling direction indicated by an open arrow. Further, a pushing device 6 for applying a pushing force to the tube A is provided on the input side in the rolling direction, and a tensioning device 7 for applying a tensile force to the tube A is provided on the exit side. The pushing device 6 is provided with a load meter 6L for measuring the pushing force Pc, and the tensioning device 7 is provided with a speed meter 71 for measuring the pulling speed V'r. The pushing force P
.

is manually input to the pushing force calculation controller 8, and the pulling speed Vt is input to the pulling speed calculation controller 9.

The pushing device 6 consists of a pushing head 62 and a driving source (not shown) such as a hydraulic device, water pressure device, or electric device connected to the pushing head 62, and the rear end of the pipe A is rotated in the same direction and at the same rotation speed as the pushing head 62. The tube A is abutted by the rotatable pushing head 62.
A pushing force Pe is applied to. As a result, the tube A is fed in the direction of the white arrow while penetrating the mandrel 4 from the input side in the rolling direction.

The wall thickness is reduced between the rolling rolls 1, 2.3, which are rotated in the same direction and at the same rotational speed by a drive system (not shown), and the plug 5 supported by the mandrel 4.

The tensioning device 7 includes a chuck portion 72 and a drive source (not shown) connected thereto, such as a hydraulic device, a water pressure device, an electric device, etc. When the tube A protrudes, its protruding end is gripped (chucked) by the chuck portion 72, which is rotatable in the same rotational direction and at the same rotation speed, and a tensile force is applied to the tube A. As a result, the tube A is subjected to tension rolling and the wall thickness is reduced over the entire length of the tube A.

The chuck part 72 is equipped with a chucking detector 73 such as a pressure load meter that is used to detect when the chuck part 72 grips the tip of the tube A, and detects when the chuck part 72 has gripped the tip of the tube A. After detecting, the chucking detector 73
An operation start signal is sent from the timer 11 to the timer 11. Upon receiving this signal, the timer 11 starts operating, measures the elapsed time t after the completion of chucking, and inputs this to the pushing force calculation controller 8 and the pulling speed calculation controller 9. The pushing force calculation controller 8 sets the pushing force initial value P, corresponding to the time t. From P,=
A pushing force setting value Po is calculated that gradually reduces the pushing force after chucking is completed until it reaches O, and the pushing force Pc is controlled by the pushing force setting value pcs. In addition, the tension speed calculation controller 9 sets the tension speed initial value ■ corresponding to the time t.
a. A tensioning speed setting value Vt3 is calculated that gradually increases the tensioning speed from 1 to a predetermined final target value VTl, and the tensioning speed (2) is controlled by the tensioning speed setting value VtS.

The pushing force calculation controller 8 and the pulling speed calculation controller 9 receive the input pushing force measurement value P6. Tensile speed measurement) JV? %also E
Indentation rolling and tension rolling are controlled as follows based on the pushing force setting value PCSr and the tensioning speed setting value V□. That is, as shown in the flow chart showing the push rolling process in FIG. 5 and the flow chart showing the tension rolling process in FIG. 6, when chucking is completed, the timer 11 is activated and the push setting 4i0. Difference between r'es and pushing force measurement (la)'e Pcr Pc and 1Nii 6j! , the tensile speed set value VtS, the tensile speed measured value (■), and which difference v0 - (■) are calculated, respectively. 'XJiJ: Pushing device 6 based on the value
If the drive source of the tensioning device is, for example, a hydraulic device, the hydraulic valve opening/closing correction amount is calculated, and the pushing force setting value PC1! and tensile speed setting value ■7. Modify the pushing force and pulling speed so that this is achieved.

Figure 7 shows the drawing F type of the present invention, the change in indentation speed vo at the time of transition from indentation EE rolling to tension rolling in the rolling method, and indentation force PC.
Change in , change in tensile speed ■, change in tensile force P.

This is a graph showing the changes in this order, with the vertical axis showing the amount of change, and the horizontal axis showing time.

Pushing speed■. is the initial pushing speed VCO that is constant until chucking is completed, and after the chucking completion point indicated by a in the figure, the pushing speed is gradually increased until the pushing force reaches Pc''O, and then immediately VC = O. becomes.

The pushing force P is a constant initial pushing force PCO until chucking is completed, and is gradually decreased until it reaches Pe-0 after chucking is completed.

Tensile speed V? Is the initial value V? of the pulling speed constant given by the pushing force PC from just before chucking until chucking is completed? . This means that the rolling state is substantially caused only by the pushing force. After chucking is completed, the tensile speed is gradually increased to the above ■□ stored in the tensile speed calculator 9, and Vtt
Once achieved, vT remains constant.

The tensile force P, is O until chucking is completed, and after chucking is completed, it is gradually increased until it reaches pt+, and P? li! ! After the precept, it remains constant.

That is, as described above, the pushing device 6. By controlling the tensioning device 7, the pushing device 6 can reliably continue contacting the rear end surface of the tube A until the pushing force set value pc3 reaches O, and can smoothly reduce the pushing force Pc. Further, after the pushing force Pc becomes 0 as set, the pushing device 6 retreats and prepares for the next rolling. Furthermore, the tensile speed V is the final target value V? 1, the pulling speed becomes constant, and after rolling is completed, the chucking at the tip of the tube A is released, and the finished product 10 is carried out to the next process.

Note that the time tc-P from when the timer 11 starts operating until the pushing force Pc becomes 0. /ΔPc (where ΔPc - increment amount of P per unit time) and tensile speed V? is V, and the time tr = (Vt+Vro)/ΔV
t (however, ΔVy=increase in tensile speed vT per unit time) does not necessarily have to match.

Further, the increment amounts ΔPc and Δ■7 do not need to be constant values, and may be changed within the times tc and t.

Furthermore, in the present embodiment, a case has been described in which the tensile speed (7) is controlled to increase gradually, but the same effect can be obtained even if the tensile force P7 is controlled to increase gradually. Also, is the tensile speed V a the initial value V of the tensile speed? . However, from the viewpoint of the load capacity of the tensioning device 7, etc., vyi may be kept constant at its initial value. In other words, as the tensioning speed increases, the amount of wall thickness machining during one rotation of the tube increases, and the tensile load increases. Therefore, when the load capacity of the tensioning device 17 is small, the increase in the tensile load is set by setting vto=vt+. It can be suppressed.

Furthermore, in order to reliably chuck the tip of the tube A, it is desirable to minimize the relative movement between the tube A and the chuck section 72 when starting chucking. It is preferable that the forward speed of the portion 72 in the rolling direction is made to match the forward speed of the tube A (8).

However, Ao: cross-sectional area A of pipe A, : cross-sectional area Vc of finished product 10, , : initial pushing speed, or to obtain more accurately, measure the speed with a speedometer, etc. on the exit side of the rolling machine before chucking for each rolling ■8 Measure V
It may be reflected in tO.

In addition, the time when the tip of the tube A reaches the predetermined position of the chuck part 720 when chucking is started is determined by measuring the time when the tip of the tube A passes an appropriate position on the exit side of the rolling mill before chucking. It is determined by considering this and the rolling speed before chucking. Or the roll load at the time when the tip of the tube A is caught between the rolling rolls 1, 2.3 and the plug 5.

The rolling start time may be determined by detecting an increase in the motor current, etc., and the chucking start time may be calculated from this.

Furthermore, in order to reduce the relative movement in the rotational direction of the tube A and the chuck section 72, the chuck section 72 is rotated in the same direction as the rotation direction of the tube A at the same rotation speed before chucking starts. Just leave it there. The rotation speed of tube A can be easily predicted from the roll rotation speed.

Furthermore, if water, air, organic solvent, etc. are injected toward the inner or outer surface of the tip of the tube A on the exit side of the rolling machine before chucking starts, and the rolling lubricant adhering to the surface of the tube A is removed, - 1HI can really do chucking.

Furthermore, the chuck part 72 is equipped with a load meter for measuring the load applied to the pipe A by the chuck part 72 in its radial direction.
It is possible to detect chaffing using this load meter and to adjust the pressing force of the tube A to suppress the occurrence of flaws on the surface of the tube A.

In addition, especially when rolling a thin long tube, the chuck part 7
The torsional moment generated in the tube A due to the MI of the rotating parts rotating together with the tube A in the tensioning device 7 and the pushing device 6 including the tube A may impair the properties of the tube A. In order to prevent this, it is desirable to rotate the rotating parts in the tensioning device 7 and the pushing device 6 by drive means such as a medium-sized rolling mower to suppress the generation of torsional moments.

Next, the concept of rolling speed setting during push rolling and tension rolling will be described.

Figure 8 shows the maximum workability that can be rolled for [rolling speed/number of revolutions of finished product]: θ during indentation rolling (indentation force applied only: solid line O) and tension rolling (tensile force applied alone: broken line H). This is a graph. The vertical axis shows the degree of machining, and the horizontal axis shows θ. The degree of work represents the length of the finished product/the length of the pipe A (stretched length ratio), and the rolling speed means the advancing speed of the product at the exit side of the rolling mill.

In the figure, the area below the solid line O shows the rollable range during push rolling, and similarly the area below the broken line H shows the rollable range during tension rolling. That is, as θ becomes larger than each of the rollable ranges shown in the figure, the feed pitch of the tube A becomes larger, and cracks occur in the tube A during rolling, making rolling impossible. Further, the smaller θ is, the smaller the feeding pitch to the tube becomes, and peel-like surface flaws occur on the tube A during rolling, making normal rolling impossible. Needless to say, the rollable range varies depending on the roll shape, tube dimensions, material, etc.

Here, for example, when the required machining degree is R1, the settable θ
During push rolling, θ1≦θ≦θ2. During tension rolling, θ,
≦θ≦04. Therefore, during push rolling at the initial stage of rolling, θ
−θ. If (θ3≦θ.≦θ2), normal rolling can be continued without changing θ when transitioning from push rolling to tension rolling.

Furthermore, in order to improve the rolling efficiency, that is, shorten the rolling time, it is also effective to set θ=θE (θ, <θC≦θ4) after transitioning to tension rolling. Especially θ2kuθ.

Setting ≦θ4 has a high effect of improving rolling efficiency.

However, if θ is smaller than 03 during tension rolling, normal rolling will not be possible, so during push rolling θ=θ, (θ≦θC〈θ3
), θ after transition to tension rolling is θ1 or more θ
Must be changed to 4 or less.

Further, in actual rolling operations, it is desirable to keep the roll rotation speed constant in order to save power consumption and to simplify equipment. In this case, since the rotational speed of the finished product is kept constant during rolling, the pushing speed and pulling speed of the tube A are determined by θ indicating the feed pitch. According to the above definition, θ=
Since V/N (where ■: rolling speed, N: rotational speed of the finished product), the pushing speed VC is determined by (1) 2. Also, the tensile speed ■ is V, = V = θ・N... (3)
The above is a case in which the rolling rolls 1, 2, and 3 rotate at fixed positions around the roll axis, but the device used to implement the spinning method shown in the conventional example, that is, the type in which the housing in which the rolls are assembled rotates. The method of the present invention can also be applied to the elongation rolling apparatus in the same manner as described above, where θ=rolling speed/housing rotation speed.

Further, the number of rolling rolls may be any number as long as it is two or more.

Further, the rolling rolls are not necessarily necessarily arranged evenly around the pass line. Furthermore, although the plug 5 is held by the mandrel 4 from the rolling mill entry side, it may be supported from the rolling mill exit side, or a floating plug that does not use a mandrel may be used.

Alternatively, the mandrel itself may be used as the inner surface regulating tool without using the plug.

Furthermore, the tension device 7 on the exit side of the rolling mill is, for example, a fan shown in FIG.
As shown in (b), the tube A is moved between two pairs of carriages 100.1.
00 alternately chucks the tube A, and the chuffing carriage 100 moves the tube A toward the exit side of the rolling mill (
A double chucking type tensioning device may be used, which applies a tensile force to the tube A by applying a tensile force in the direction of the white arrow (in the direction of the white arrow) and repeating this process alternately.

[Experiment example]

In accordance with the present invention, the following cold-formed specimens were made of 5O5304 stainless steel with a diameter of 121 mm, a thickness of 5.01 m, and a length of 10.0 mm.
0ra seamless pipe A with a diameter of 117 mm and a thickness of 3 and 5
An experimental example is shown in which stretch rolling was performed to process a product with a length of 14.6 m. At this time, processing degree (finished product length/raw pipe length) -=1.46. The range of θ (rolling speed/number of rotations of finished product) that can be rolled during push rolling and tension rolling was as follows according to a preliminary (FA test).

During push rolling: 0.005≦θ≦0.070 (mu/sec・rpffl) During tension rolling: 0.010≦θ≦0.
The 400 (mm/sec/rpm) rolling mill has three rolls similar to those shown in Figures 1 to 3.
The plug used was one with a diameter of 110 m and a length of 200 m.

θ-0.06 during push rolling. θ during tension rolling = 0.35
The roll rotation speed was set so that the rotation speed of the finished product was 11,000 rpm.

Therefore, from the previous equations (2) and (3), the pushing speed is V. =0
．． 06X 100OX 1 /1.46=41.1 phase/
seconds, tensile speed■a. =0.35X1000=350*
Stretch rolling according to the present invention was carried out at */second, and the finished product satisfied the predetermined dimensions over the entire length and did not have any surface flaws. Defective products have approximately 30% of damage at the end of the pipe, which is 0.2% of the total length of the pipe.
Only 0 cases occurred.

In addition, as a comparative example, under the same conditions, indentation rolling was interrupted when the tip of pipe A protruded 300 mm toward the exit side of the rolling machine (500 +n protrusion from directly below the roll), and after chucking was completed, tension rolling was performed using a tension device. When conventional elongation rolling was carried out, peel-like flaws occurred on the surface of tube A at the forward stagnant portion of tube A, and approximately 6,001 scratches occurred on the surface of tube A, accounting for 4.1% of the total length of the tube.
u defective products were produced.

Furthermore, as a comparative example, when rolling was carried out continuously without controlling the pushing force at the time of transition from push rolling to tension rolling, the tension force increased rapidly at the start of applying the tension force, and the chuck of the tension device 7 Pipe A that was chucked at section 72 was likely to come off, making stable rolling difficult. Furthermore, even when rolling could be achieved by ml, it was observed that there was a large dimensional variation in the rolled portion of the tube at the start of applying tensile force. Furthermore, by manually varying the pushing force, it became necessary to lower the roll rotation speed to 50 rpm or less in order to adjust the dimensional accuracy, which was found to be impractical from the standpoint of efficiency.

Note that similar effects were obtained even when the same rolling as described above was carried out at a warm temperature of 200°C to 400°C.

〔effect〕

As detailed above, according to the elongation rolling method and apparatus of the present invention, the transition from push rolling to tension rolling is carried out gradually, so that sudden changes in the stress state are prevented from being applied to the tube rolled section. Even when cold or warm stretching is applied to long tubes, products with good dimensional accuracy and quality can be obtained, which has excellent effects such as improving product yield and reducing manufacturing costs. play.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the apparatus used to carry out the stretch rolling method of the present invention, and FIG. 2 is an explanatory diagram showing the apparatus used to carry out the stretch rolling method of the present invention, viewed from the input side to the output side in the rolling direction. FIG. 3 is a partial sectional view taken along the line ■-m in FIG. 2, at the start of rolling; FIG. 4 is a partial sectional view similar to FIG. FIG. 5 is a flowchart showing the process of indentation rolling, FIG. 6 is a flowchart showing the process of tension rolling, and FIG. Change in force PC, pulling speed V. Graph showing the changes in the tensile force PT and the changes in the tensile force PT.
: A graph showing the degree of work versus θ, FIG. 9 is a schematic longitudinal cross-sectional view showing another embodiment of the present invention, and FIG. 10 is a partially cutaway side view of an apparatus used for carrying out the conventional elongation rolling method. .

Claims (1)

[Scope of Claims] 1. Feeding the tube by applying a pushing force to the tube into which the tube inner surface regulating tool is inserted into a rolling mill having a plurality of inclined rolls arranged around the pass line of the tube; In a method of elongating and rolling a tube while applying a tensile force to the tube by gripping the protruding end of the tube, after gripping the tube is completed, the pushing force is gradually reduced to zero, and the tensile force is increased to a predetermined value. 1. A method for drawing and rolling a metal tube, characterized in that the speed at which the tube is drawn is gradually increased, or the speed at which the tube is pulled is gradually increased to a predetermined value, or the speed is kept constant. 2. A rolling mill with a plurality of inclined rolls arranged around the pass line of the tube, and a tube inner surface regulating tool inserted from the entrance side of the rolling mill, applying a pushing force to the tube to move the tube through the rolling mill. In a metal tube elongation rolling machine that is equipped with a pushing device that causes the tube to protrude toward the exit side, and a tension device that grips the protruding end of the tube and applies a tensile force to the tube on the exit side of the rolling mill, it is possible to complete the gripping of the tube. a timer that starts measuring when the completion of gripping is detected by the gripping detection means; and a pushing force calculation control means that gradually reduces the pushing force in accordance with the time measured by the timer. . A stretching and rolling apparatus for a metal tube, comprising: a stretching speed calculation control means for gradually increasing the speed at which the tube is pulled up to a predetermined value or keeping the speed constant in accordance with the time. 3. A rolling mill with a plurality of inclined rolls arranged around the pass line of the tube, and a tube into which a tube inner surface regulating tool is inserted from the entrance side of the rolling mill, and a pushing force is applied to the tube to cause the tube to pass through the rolling mill. In a metal tube elongation rolling machine that is equipped with a pushing device that causes the tube to protrude toward the exit side, and a tension device that grips the protruding end of the tube and applies a tensile force to the tube on the exit side of the rolling mill, it is possible to complete the gripping of the tube. a timer that starts measuring when the completion of gripping is detected by the gripping detection means; and a pushing force calculation control means that gradually reduces the pushing force in accordance with the time measured by the timer. A stretching and rolling apparatus for a metal tube, comprising: a tensile force calculation control means for gradually increasing the tensile force in accordance with the time.