JPS63183707A - Skew roll rolling method for metal tube - Google Patents

Abstract

PURPOSE:To form high quality tubes having no thickness deviation by maintaining respective specific relations of a skew roll outlet face angle, an angle of a plug reeling part, and a guide shoe outlet face angle to the path center of a rolled stock. CONSTITUTION:Angles of an outlet face 13 of skew rolls 1l, 1r a reeling part 22 of a plug 2, and a guide shoe outlet face respectively forming with the path center of a rolled stock are denoted by theta1, theta2 and theta3, respectively. Rolling is performed under conditions between theta1-theta3 such that -2<=theta2-theta1<=-0.5 deg. when 0 deg.<theta3<=1.5 deg., -1 deg.<theta2-theta1<=0 deg. when 1.5 deg.<=theta3<=3.0 deg., and 0<theta2-theta1<=1.0 deg. when 3.0 deg.<theta3<=5 deg.. Thus, the high quality tube having not thickness deviation is formed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to the perforation 831 (
This relates to a rolling method using a piercer.

[Prior art]

In general, seamless steel pipes made using the Mannesmann pipe manufacturing method are first made by passing a heated round piece of steel through a piercer, drilling a hole in its center to obtain a hollow shell, and expanding it either directly or, if necessary, by passing the hollow shell through an elongator. After being subjected to diameter and elongation rolling, it is further elongated and rolled in a plug mill, for example, to form a reeler,
The tube is polished using a sizer, the shape is corrected to F3, and sizing is performed, and the product is manufactured through a refining process. By the way, the piercer mentioned above
In this case, the axis line is tilted 11 with respect to the pass center of the round steel piece.
A so-called inclined rolling mill is used, which is a combination of barrel-shaped rolling rolls (hereinafter referred to as inclined rolls) and a 7° lug. ′
For example, as shown in FIG. 5, a piercer is provided with a gorge portion 11 having a maximum diameter in the middle in the axial direction,
On both sides of this gorge part 11, there is a pair of inclined rolls 11°1r each having an inlet surface 12 and an outlet surface 13, each having a truncated conical shape with a diameter that gradually decreases toward the end, and a warhead-shaped roll as a whole. A rolled portion 21 having a substantially conical shape,
The diameter of the reeling portion 22, which follows this and has a substantially truncated conical shape, is reduced toward the base end floor. It is constructed by combining a plug 2 with a relief part 23, and a double inclined roll I.
C'lr is on both sides of the pass center of the round steel piece B, and the axis line is parallel to the pass center (or inclined by the intersection angle α) in plan view, and one inclined roll has the entrance surface 12 facing upward in side view. The inclination angle β is set so that the
The plug 2 is disposed so as to be inclined relative to the pass center, and the plug 2 is disposed with its axis aligned with the pass center. The heated round steel piece B is transferred in the axial direction as shown by the white arrow, and is transferred to the double inclined roll 11. The plug 2 is inserted between the artificial surfaces 12 and 12 of the lr, and is rotated around the axis and transferred in the axial direction, so-called spiral movement, and the plug 2 is penetrated into the center of the inclined roll B. .

1r and plug 2 to perform piercing rolling.

By the way, various defects occur in the seamless pipes manufactured in this way depending on the rolling conditions, and in particular, uneven thickness bottoms that occur in a spiral shape on the inner and outer surfaces of the hollow shell are treated with elongators, mandrel mills, and trenches in the subsequent process.・Reducer,
There was a problem in that it was difficult to solve even if it was passed through a leeler, and it had an extremely large effect on the quality of the finished product.

The inventor of the present invention conducted an experimental study on the cause of the uneven bottom thickness as described above, and as a result, as shown in FIG.

The angle θ1 between the surface facing the exit surface 13 of lr or its tangent to the pass center, that is, the angle θ1 between the inclined roll Il facing the reeling part 22 of the plug 2, the 10 surface 13 of lr or its tangent, and the pass center. The relationship between the angle θ2 between the surface or tangent of the reeling part of the plug and the path center is 01≦
It was discovered that the reason for this was that it was 02. The reeling part 22 of such a plug 2 and the inclined roll 11. The angle θ1 between the surface of lr opposite to the exit surface 13 or its tangent and the path center. The reason why θ2 causes the spiral thickness unevenness phenomenon is estimated as follows.

Note that θ1 in the present invention. The definition of θ2 is the inclination angle β = 0
This is the value in the state of

FIG. 6 is a schematic sectional view taken along the vr-vr line in FIG. '+1r and pressurize between opposing surfaces.

The hollow shell H is stretched and formed into a hollow shell H. In this process, the hollow shell H that is pressurized between the facing surfaces of the plug 2 and the inclined rolls 1j'+1r is thinned in this part, and the material in this part is thinned in the axial direction. , the hollow shell H is expanded in the circumferential direction, but due to the expansion in the circumferential direction, the hollow shell H receives a force that tends to increase the outer diameter. However, the upper and lower parts of the hollow shell H are guide shoes 33u.

Since it is in sliding contact with 33d and the expansion of the outer diameter is suppressed, the force that tries to expand the outer diameter acts as a compressive force, and this compressive force is applied to the plug 2 and the inclined roll B.

Thickening is caused in other parts except for the part between the opposing surfaces with 1r. By the way, the wall thickness of the hollow shell in each cross section taken by the axial center of the plug 2, the plane passing through the center of the facing surfaces of the plug 2 and the inclined rolls l# and lr (Y-Y plane), and the plane perpendicular to this (Z-Z plane) is l: about 1.1 to 1.4.

By the way, the hollow shell H that is pierced and rolled by such a piercer is rotated twice around its axis each time by the plug 2 and the inclined roll IIl.

It alternately passes through sliding contact positions with the guide shoes 33u and 33d, and repeats the thinning process and the thickening process.

FIG. 7 is a schematic cross-sectional view taken along the line ■-■ in FIG.
The portion Al of the hollow shell H currently located between the facing surfaces of the plug 2 and the rolling roll 1r moves to the portion A2 in contact with the guide shoe 33d after × rotation of the hollow shell H.
In this process, immediately after the rolled part 21 of the plug 2 penetrates into the round steel piece B, the diameter expansion rate is large, and the compressive force that the hollow shell H receives is correspondingly large. Naturally, the thickness increase rate of the hollow shell H is also large. If you rotate A further, A
The second part is the plug and the inclined roll 17! However, in this process, due to the relationship θ1≦02 as described above, the plug 2 and the inclined roll II! This also results in a large thinning rate due to the narrowing of the gap between the two. And Hollow Shell H
When it rotates further A, the A3 part moves to the A4 part that contacts the guide shoe 33u, but in this process, the A3 part passes through the part of the plug 2 that faces the relief part 23, so the hollow shell H tries to expand its diameter. The force is small, so the compressive force is also small, and the rate of increase in thickness is also small, making the A4 portion thin.

On the other hand, in FIG. 7, when looking at the part B which contacts the lower guide shoe 33d at a position facing the front end of the reeling part 22 at a distance of 2 openings in the circumferential direction from the part A1, when the hollow shell H is rotated A, the plug 2 and It moves to the B2 part between the facing surfaces with the rolling roll Il, but when the zero-order hollow shell H, which is thinned in this process, is rotated A, the 82 part moves to the 83 part that contacts the upper guide and the shoe 33u. However, the diameter expansion rate during this process is large and the compression force applied to the hollow shell H is also large, resulting in a large increase in thickness. When the hollow shell H is further rotated A, the portion 83 moves to the portion 84, but in this process, it passes through the relief portion 23 of the plug 2, so there is almost no thinning, leaving the portion 84 thick.

As a result, the portions A of the hollow shell H that are cornered in the circumferential direction alternately appear as thin portions A4 and thick portions B, so that an a'-circular uneven thickness is formed. It becomes.

FIG. 8 is a graph showing the change in wall thickness of the A1 portion and the 81 portion as they pass through the plug 2 from the position facing the tip of the plug 2, and the horizontal axis is the hollow shell H.
The distance in the traveling direction is shown, and the vertical axis shows the wall thickness.

As is clear from this graph, when drilling is started by the plug 2, the position of that part in the circumferential direction, that is, the position facing the left and right inclined rolls LL1r, or the upper and lower guide shoes 33u .

Depending on the position facing the plug 33d, the wall will be thinner or thicker, and as a result, as shown in FIG.
It can be seen that after passing through the hollow shell H, a spiral thickness unevenness occurs in which thick and thin parts alternate in the axial direction of the hollow shell H.

Therefore, in order to suppress the occurrence of uneven thickness during piercing rolling and to significantly improve pipe quality, the applicant has proposed that the facing surface between the exit surface of the inclined roll and the reeling portion of the plug, or the tangent line thereof, be covered. proposed a method of rolling while maintaining the angle formed with the pass center of the rolled material in the relationship θ1>θ2 (Japanese Unexamined Patent Publication No. 6
No. 0-191609).

Next, this method will be specifically explained.

As shown in FIG. 8, if the range of wall thickness variation occurring in the hollow shell H is δ, then δ is given by the following equation (1), where l is the axial length of the reeling part 22 of the plug 2, and δ= l tan Δθ .・(11) This Δθo (=arc tan(δ/E)) is defined as the angle θ1 between the exit surface of the inclined roll facing the reeling part of the plug or its tangent and the pass center of the rolled material, and the exit surface of the inclined roll. The correction angle for the angle θ2 formed by the surface of the plug glue-ring part facing or its tangent line and the pass center of the rolled material is set as θIO+θ2o, which is the value added to θ1 and subtracted from θ2. That is, θlo=θ1+Δθ ., θ20 = θ2... (2) or θ1o - θ1. θ20 = θ2 - Δθ... (3) Furthermore, according to the experimental results of the inventors, Δθ0 is usually as shown in equation (4) below. From the above +21. (Equation 31 and (4
), the relationship in equation (5) holds true.

Δθ. 〉θ2-01≧0 ... (4) θIo>
θ2o...(5) Therefore, the outlet face angle of the inclined roll and the face angle of the reeling part of the plug are designed to realize this, and the angle of the axis of the inclined roll with respect to the pass center, that is, the intersection angle α and the inclination angle β, are designed. The selected material will be rolled.

In the case of this method, as shown in the first diagram, the facing surface of the outlet surface 13 of the rolling roll 11 (lr) and the reeling surface 22 of the plug 2 is aligned with the pass center of the material to be rolled, such as the round billet B. Since the angle of the outlet surface 13 of the rolling roll 11 is set larger than the angle of the reeling surface 22 of the plug 2, the part where the material to be rolled is perforated and subjected to elongation rolling is the same as that shown in FIG. As shown in FIG. 11, the circumference can be finished with a uniform wall thickness regardless of the directional position, and the quality of the pipe can be significantly improved.

[Problem that the invention seeks to solve]

However, when the gap between the exit surface portion facing the reeling surface 22 of the guide shoe and the pass center is constant along the pass center, it is possible to suppress the occurrence of uneven thickness and manufacture a metal tube of good quality. In order to manufacture a higher quality metal tube by adjusting the compression force, when using a guide shoe in which the gap is wider on the exit side of the pass center than on the entrance side of the pass center, the exit surface of the guide shoe is It has been found that depending on the size of the spread angle between the path center and the path center, a spiral thickness unevenness can be formed as in the conventional case.

The present invention has been made in view of the above circumstances, and provides a method for rolling a metal tube with inclined rolls, which can prevent the occurrence of uneven thickness regardless of the size of the spread angle between the exit surface of the guide shoe and the pass line. The purpose is to

[Means for solving problems]

The present invention is designed to adjust the angle between the outlet surface of the inclined roll facing the reeling part of the plug or its tangent to the pass center and the surface of the plug glue-ring part or its tangent, depending on the spread angle formed between the exit surface of the guide shoe and the pass center. Set the angle with the path center.

That is, the method for rolling a metal tube with inclined rolls according to the present invention involves spirally moving a material to be rolled in the axial direction between a plurality of inclined rolls and a plurality of guide shoes arranged alternately around a pass line. In the process of piercing and rolling the material to be rolled by penetrating the plug along the axial center line, the outlet surface of the inclined roll facing the plug glue-ring portion or its tangent line is made with respect to the pass center of the material to be rolled. Angle (θ1) and
Angle (θ2) between the exit surface of the inclined roll and the surface of the reeling part of the plug facing the surface or its tangent with respect to the pass center
and the angle (θ3) formed by the exit surface of the guide shoe facing the plug glue-ring portion or its tangent with respect to the pass center during rolling.

When Q'<03≦1.5", -2°≦θ2-01≦
-0.5°, 1.5°≦θ3≦3.0°
When °<θ2-θ, ≦0°, 3.0°<θ3≦5°, 0°<θ2-01≦1.0°.In other words, depending on the slope of the guide shoe exit surface or its tangent, θ2-θ May be positive or negative.

[Effect]

In the present invention, when θ3 is large, the gap between the plug and the guide shoe widens toward the exit side, and the reduction rate of the compressive force applied from the guide shoe to the rolled material increases. , this reduces the thickness increase rate, but at this time, θ2 - θ is a positive value (sometimes negative, but small), so when setting the inclination angle β, it is The gap between the plug and the inclined roll becomes substantially constant or becomes small, and therefore, regardless of changes in the thickness increase rate, the rolling reduction rate becomes substantially constant in the same circumferential direction portion.

In addition, the part of the rolled material that is bitten with a 1/4 rotation delay is also rolled in the same way, and as a result, the thickness increase and decrease due to the guide shingle are suppressed, and the wall thickness increases in the pipe circumferential direction and the axial direction.
The outer diameters are set to the same value.

In addition, when θ3 is small, the degree of widening of the gap between the plug and the guide shoe toward the exit side becomes small, and the rate of decrease in the compressive force received from the guide shoe on the rolled material becomes small.
This increases the thickness increase rate, but at this time θ2-01
Since is a negative value, the gap between the plug and the inclined roll increases from the entrance side to the exit side of the reeling section, and therefore, the rolling reduction rate is approximately constant in the same circumferential direction regardless of changes in the thickness increase rate. Become. In addition, the part of the rolled material that is bitten with a 1/4 rotation delay is rolled in the same way, and as a result, thickness increase and decrease are suppressed, and the wall thickness and outer diameter are reduced in the circumferential direction and axial direction. They are all set to the same value.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing an embodiment in which the present invention is applied to a piercer. FIG. 1 (this rolled material is a sectional view taken along the line Y-Y in FIG. 2) is an explanatory diagram showing the relationship between the plug and the inclined roll used in the method of the present invention,
The figure is a sectional view taken along line 11 in Figure 1, where B is a round steel piece, H is a hollow shell, and II! , lr are (15! diagonal rolls, 2 indicates a plug. The round steel piece B is heated to a predetermined temperature and is transferred from the direction of the white arrow in the axial direction,
It is fed into the piercer, and an 11° inclined roll is placed on the outer circumferential surface.
r comes into contact with each other, and as a result, the plug 2 is rotated around the axis and moved in the axial direction, and the plug 2 is inserted into the center and bored.

Each inclined roll 17! , 1r is provided with a gorge part 11 having a maximum diameter at the middle part in the axial direction, and on both sides thereof, an inlet face 12 and an outlet face 13 each having a truncated conical shape, the diameter of which decreases toward the roll end. On both sides of the bus center of the round steel piece B, the entrance surfaces 12.12 are oriented away from each other with respect to the bus center in plan view, in other words, the exit surfaces 13.13 are oriented toward each other. In side view, the inclined roll 1r has its entrance surface 12 facing upward, and the inclined roll IIt has its exit surface 13 facing downward, so that they are oriented upwardly and downwardly with respect to the bus center. They are respectively arranged to be inclined at predetermined inclination angles, and are driven to rotate in the same direction as indicated by arrows by a drive source (not shown).

On the other hand, the plug 2 is formed in the shape of a warhead, and is placed along the bus center with its tip side facing the side from which the round steel piece B is being transferred, and is carefully placed around the axial line at the tip base of the mandrel bar M. It is rotatably supported. The plug 2 includes a rolled portion 21 having a substantially conical shape with a rounded tip.
A reeling part 22 that is connected to the reeling part 22 and has a substantially truncated conical shape, and a relief part 23 that is connected to the reeling part 22 and has a reduced diameter on the proximal end side.
It is equipped with

Above and below the transfer area of the round steel piece B in the vicinity of the inclined rolls 11 and 1r, there are guide shoes 3u whose surfaces facing the plug 2 are concave toward the plug 2 and which are long in the longitudinal direction of the tube axis.
3d is provided. The guide shoes 3u, 3d have outlet surfaces 31u, 31d facing the reeling surface 22 of the plug 2.
The outlet surfaces 31u and 31d are formed such that the gap with the plug 2 becomes wider toward the outlet side in the longitudinal direction of the tube axis.

The method of the present invention is carried out using an inclined rolling mill configured as described above. That is, the angle θ1 between the reeling surface of the plug 2, the outlet surface 13.13 of the inclined rolls Ll, 1r facing the opposite side, or a tangent thereof, and the bus center, and the angle θ2 between the reeling surface of the plug 2, or its tangent, and the bus center, Depending on the range of the angle θ3 between the exit surface of the guide shoe and the bath center, that is, 0≦θ3≦1.5, 1.5≦θ3≦3.0, 3.
0 The following (61, (71,
(Rolling is carried out in a manner that satisfies formula 81. At this time,
Consider the piercing and rolling ratio (E/).

-2°≦Δθ≦−0.5° ・・・(6)−1°≦
Δθ≦O° ... (7) 0° Δθ≦1.
0° ... (8) However, Δθ = θ2-01 If it is necessary to take into account θ3 and piercing rolling (E J ), replace E with (6), 17), f8)
The relationship between l and the correction amount Δβ at the time of setting the inclination angle may be obtained, for example, from a regression equation shown in equation (9) below.

1 for θ2- ・2 for θ1+ ・3 for θ3+ ・E7!
+Δβ...(9) However, K, 2. 3: Regression coefficient Also, when θ2 is determined in this way, θ.

The roll crossing angle may be adjusted to ensure the difference Δθ between and 02.

FIG. 3 is a drawing corresponding to FIG. 7.10, and the upper part of the pass line XX passes through the pass line XX,
A cross section taken by a plane passing through the center of the facing surfaces of the plug 2 and the inclined roll 11 (or lr), and a section below the pass line XX line passing through the pass line XX line, the guide shoe 3d (
or 3u) Each shows a cross section taken by a plane passing through the center.

The part A of the hollow shell l located now between the facing surfaces of the plug 2 and the inclined roll 1r is 1/4 of the hollow shell H.
A2 every time it rotates. A3. As shown in A4, the part Bl is similarly changed to B2 every time the hollow shell H rotates 1/4,
Although the positions and wall thicknesses of parts A and 84 change as in B3 + B4, the wall thicknesses of portions A and 84 are rolled to approximately the same thickness. The reason for this is explained as follows.

First, the A1 portion of the hollow shell H located between the rolling portion 21 of the plug 2 and the gorge portion 11 of the inclined roll ll moves to the portion A2 in contact with the guide shoe 3d after 1/4 rotation of the hollow shell H; Since a force is applied to enlarge the diameter of the hollow shell H, this force acts as a compressive force due to contact with the guide shoe 3d, and the A2 portion becomes thickened.

The amount of increase in thickness changes depending on the compressive force that changes depending on the exit surface angle θ3 of the guide shoe 3d. That is, as θ3 (>0) becomes smaller, the compression force becomes larger and the amount of increase in thickness becomes larger, and conversely, as 03 becomes larger, the compression force becomes smaller and the amount of increase in thickness becomes smaller. Further, when the hollow shell H rotates another 174 times, the A2 portion moves to the A3 portion between the plug 2 and the inclined roll 1r, and is thinned. At this time, as described above, the distance between the facing surfaces of the reeling part 22 of the plug 2 and the exit surface of the inclined roll 1r is such that the progress of the hollow shell H increases or decreases as the exit surface angle of the guide shoe 3d becomes larger or smaller within a positive range. It gradually increases or decreases in the direction. Therefore, the thick part is A3
If the thickness is A3, the spacing between the facing surfaces is large, and if the thin wall is an A3 portion, the spacing between the facing surfaces is narrow. can be achieved.

Furthermore, when the hollow shell H rotates 1/4, the A3 part changes to A2.
However, in this process, it passes through the part facing the relief part of the plug 2, so the diameter expansion force is small, the compressive force of the hollow shell is also small, and the thickness increase rate is small. When the parts B located between 3u and 3d rotate 174 times according to the rotation of the hollow shell H, they become B2. B3°B, but in the process of reaching the B2 part, the reeling part 22 of the plug 2 and the inclined roll I
When the sixth hollow shell H, which is thinned by the gorge part 11 of Il, rotates 1/4, the 82 part becomes the guide shoe 3d.
However, in this process, the distance between the facing surfaces of the guide shoe and the bus center becomes even larger than that of the A3 part due to the movement in the axial length direction due to the 1/4 rotation. The diameter expansion force is reduced accordingly, and the compressive force that the hollow shell H receives is also reduced.

This tendency for the compressive force to decrease also changes depending on the exit surface angle of the guide shoe 3d, and decreases as the exit surface angle of the guide shoe 3d becomes smaller, and conversely, increases as the exit surface angle of the guide shoe 3d increases. Become.

At this time, the reeling part 22 of the plug 2 and the inclined roll 1
The distance between r and the exit surface gradually decreases or gradually increases in the traveling direction of the hollow shell H when the exit surface angle of the guide shoe 3d becomes larger or smaller than a value in a positive range. Therefore, when there is a small tendency for the compressive force to decrease, the distance between the opposing surfaces becomes large, and conversely, when the tendency that the compressive force tends to decrease significantly, the distance between the opposing surfaces becomes narrow.

Therefore, regardless of the thickness change caused by the change component in the distance between the plug and the inclined roll due to the 1/4 rotation difference, and the change component in the distance between the guide shoe and the plug due to the difference in exit surface angle of the guide shoe, the rolling blade Adjustments will be made.

Furthermore, when the hollow shell H turns 1/4, the 83 part becomes 84
However, in this process, the 83 part passes through the part facing the relief part 23 of the plug 2, so there is almost no thinning, and the thickness at the B1 part is the same as the thickness at the A2 part. It can be done.

Therefore, in the case of the method of the present invention, as a result of suppressing thickness reduction and thickness increase, the difference in wall thickness at the A1.84 portion after passing through the plug 2 is eliminated, and the thickness is uniform in the circumferential direction and the axial direction as a whole. This results in a thicker wall.

Next, θ1 of the present invention. θ2. The reason for limiting θ3 will be explained. Table 1 is a table summarizing the uneven wall thickness, rolling method, and rolling conditions of the pipes produced by piercing and rolling while changing θ3 and Δθ. The piercing rolling conditions are roll crossing angle:
0°, roll inclination angle: 12°, roll gorge diameter: 3
50t*φ, roll inlet face angle: 3.5°, roll exit face angle = 2.5°, 3°.

4 levels of 3.5', 4", perforation ratio: 1.5-3.7,
Plug reel ring surface angle: l°~4", plug diameter: 381
1φ~54φ, roll opening: 521, guide opening = 5
9-61 dragon, billet diameter: 60 heavy diameter.

As can be understood from this table, the uneven thickness of the product pipe changes depending on the combination of θ3 and Δθ. Therefore, if the plug paste-ring surface angle θ2 is incorrectly selected with respect to θ3, the thickness unevenness rate will worsen.

Therefore, in order to make the product pipe a good product with a thickness deviation rate of 5% or less, the present invention is based on this table, and when Q''<θ3≦1.5°, -20≦02-01≦-0.5″″ , when 1.5°≦θ3≦3.Oo, -1°≦θ2−θ1≦0a1, and when 3.0°<θ3≦5°, 0°<θ2−01≦1.0°.

C effect] Figure 4 (al is a diagram showing the results of investigating the amount of uneven thickness on the inner and outer surfaces of the tube manufactured by piercing and rolling according to the present invention. For comparison, the inner wall of the tube manufactured by the conventional method is shown. The investigation results of the amount of uneven thickness on the outer surface are also shown in Figure 4 (bl).In the case of the present invention, the piercing rolling conditions are θ
3=1.0', θ2-3.5°.

θ1-2° (?), in the case of the conventional method, θ3 = 1.
0°.

θ2−3.5°, al=3.5°.

As can be understood from this figure, when using the conventional method, there was a large difference in surface unevenness on both the inner and outer surfaces, for example, the difference in unevenness on the outer surface was about one crane, but in the case of the present invention, the difference in unevenness on both the inner and outer surfaces was large. For example, the unevenness difference on the outer surface can be reduced to 0.2
It was possible to make it about 115 w compared to the conventional one.

As described in detail above, the present invention is characterized by the angle that the exit surface of the inclined roll facing the plug glue ring part or its tangent line makes with the pass center of the rolled material, and the reeling of the plug facing the exit surface of the inclined roll. Since rolling is performed within a predetermined range, the angle that the part surface or its tangent line makes with the pass center of the material to be rolled, and the angle that the guide shoe exit surface facing the plug glue ring part or its tangent line makes with the pass center, It has the excellent effect of preventing uneven thickness and producing high-quality metal pipes.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing the relationship between the rolling roll and the plug in the piercer used in the method of the present invention, and Fig. 2 is the n of Fig. 1.
3 is a sectional view taken along line m-m in FIG. 2, FIG. 4 is a detailed explanatory diagram of the present invention, and FIG. 6 is a cross-sectional view taken along the ■-vr line in FIG. Fig. 9 is an external view of the upper half of the hollow shell obtained by the conventional method, Fig. 10 is an explanatory diagram showing the process of uneven thickness when using another conventional method, and Fig. 11 is a graph showing the change in wall thickness in that case. be. 1 j! , Ir... Inclined roll 2... Plug 3u
, 3d... Guide shoe 11... Gorge part 12...
・Entrance surface 13...Exit surface 21...Rolling part 22・
... Reeling part 23 ... Relief part B ... Round steel piece
H...Hollow shell patent Applicant Sumitomo Kinjo Industries Co., Ltd. Agent Patent attorney Noboru Kono No. 41!1 Coconut G Figure

Claims (1)

[Claims] 1. A material to be rolled is spirally moved in the axial direction between a plurality of inclined rolls and a plurality of guide shoes arranged alternately around the pass line, and the material is moved along the axial center line. In the process of piercing and rolling a material to be rolled by penetrating the plug into the material to be rolled, the angle (θ_1) that the exit surface of the inclined roll facing the reeling part of the plug or its tangent line makes with the pass center of the material to be rolled, and the inclination The angle (θ_2) that the surface of the reeling part of the plug, which faces the exit surface of the roll, or its tangent line makes with the pass center, and the angle that the exit surface of the guide shoe, which faces the reeling part of the plug, or its tangent, makes with the pass center. (θ_3) is maintained in the following relationship during rolling. A method for rolling a metal tube with inclined rolls. When 0°<θ_3≦1.5°, -2°≦θ_2-θ_1≦-0.5°; When 1.5°≦θ_3≦3.0°, -1°<θ_2-θ_1≦0°, 3 .0°<θ_3≦5°, 0°<θ_2−θ_1≦1.0°