JPS60206514A - Skew rolling method of metallic pipe - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention applies to piercing machines (piercers), elongation rolling machines ( The present invention relates to a rolling method using a rolling mill using so-called (iJ oblique rolls) such as Elongator).

[Prior art]

In general, seamless metal pipes made using the Mannesmann pipe manufacturing method are first made by passing a heated round steel piece through a piercer, drilling a hole in its center to obtain a hollow shell, and then passing this directly or, if necessary, passing the hollow shell through an elongator. After being subjected to diameter expansion and elongation rolling, it is further elongated and rolled using, for example, a plug mill, and is polished using a reeler and sipe, shape correction, and sizing, and is manufactured through a refining process. By the way, the above-mentioned piercer and elongator both use a so-called inclined rolling mill that combines a plug and a comb-shaped rolling roll (hereinafter referred to as an inclined roll) whose axis line is inclined with respect to the bus center of the round steel billet or hollow shell. used. For example, in the case of a piercer, as shown in Fig. 1, a gorge part 11 having a maximum diameter is provided in the middle in the axial direction, and a conical shape is formed on both sides of the gorge part 11, the diameter of which gradually decreases toward the terminal side. A pair of inclined rolls lj with a trapezoidal entrance surface 12 and exit surface 13! , Ir, and a rolled part 21 which has a warhead shape as a whole and has a substantially conical shape from the tip side, a reeling part 22 which has a substantially truncated conical shape following this, and a relief part 23 whose diameter decreases toward the base end. It is constructed by combining a plug 2 having a. Double tilt roll II! .

1r is supported by reduction screws 14f and 14r for the reduction position on both sides of the pass center of the round steel piece B, respectively, and the axis line is parallel to the pass center in plan view (or the axis is parallel to the pass center by the intersection angle α).
One of the inclined rolls is arranged at an angle of inclination β with respect to the pass center so that the inlet surface 12 faces upward and the other faces downward when viewed from the side. The plug 2 is arranged with its axial center line 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! , 1r
The plug 2 is inserted between the inlet faces 12° and 12, rotated between the axes and transferred in the axial direction. Roll Ij! , Ir and the plug 2 are used for piercing and rolling.

By the way, various defects occur in the hollow shell manufactured in this way depending on the rolling conditions, but in particular uneven thickness defects that occur in a spiral shape on the inner and outer surfaces of the hollow shell are treated with an elongator, mandrel mill, stretch reducer, etc. in the subsequent process. There was a problem in that it was difficult to solve the problem even if it was passed through a leeler, and the effect on the quality of the finished product was extremely large.

For this reason, various considerations have been made in the past to make the wall thickness of the hollow seal constant, but the central idea is that the wall thickness of the hollow seal is determined by the inclined roll lβ.

Correction of uneven thickness or uneven thickness is achieved by keeping the distance between the opposing surfaces of the outlet surface 13 of the plug 2 and the reeling part 22 of the plug 2 constant, and making the length of this opposing part as long as possible in the direction of movement of the hollow seal. This is desirable in terms of preventing meat formation.

For this purpose, specifically, the dimensional accuracy of the plug 2, especially the reeling portion 22, is increased, and the axial length of the reeling portion 22 is increased. Another tilt roll 1/! , lr is its entrance surface 12
The angle that the exit surface 13 makes with the roll axis (referred to as face angle) is set to about 3° to 4.5°1, and the roll axis is extended at a predetermined inclination angle with respect to the pass center of the round billet B. However, when adjusting the reduction amount in this state, the faces of the plug 2 facing the reeling part 22 should be moved parallel to each other so as not to be displaced, and the angle of inclination should not be changed unless it is unavoidable. Also, if you change it, screw down screw 1.
4f and 14b individually and change the intersecting angle with respect to the pass center to align the inclined roll ILIr and the reeling part 22.
The distance between the opposing surfaces is maintained constant.

Furthermore, inclined roll lj2. The relative position between lr and the plug 2 is set so that the rolling reduction ratio of the plug 2 by the rolling part 21 is large, and conversely, the rolling reduction ratio by the reeling part 22 is small.

However, with such considerations alone, it is still difficult to sufficiently suppress uneven thickness, which has been a major obstacle in improving pipe quality.

The inventor of the present invention conducted an experimental study on the causes of uneven thickness defects as described above, and as a result, the reason for the uneven thickness phenomenon is estimated to be as follows.

FIG. 2 is a schematic cross-sectional view taken along the line ■-■ in FIG.
The round steel piece drilled by the plug 2 is pressed between the facing surfaces of the plug 2 and the inclined roll IC1r.

It is stretched and formed into a hollow shell H, but in this process, the plug 2 and the inclined rolls 1j2. The hollow shell H that is pressurized between the surfaces facing lr is thinned in this part, and the material in this part is spread in the axial direction and the circumferential direction. It receives a force that tries to expand its diameter. However, the upper and lower parts of hollow shell H are guide shoes 3u.

Since it is in sliding contact with the plug 2 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 acts on the plug 2 and the inclined roll lI! .

Thickening is caused in other parts except for the part between the opposing surfaces with 1r. By the way, the axis center of plug 2, plug 2 and inclined roll 111. The amount of increase in thickness of the hollow shell that occurs during the process from the plane passing through the center of the surface facing lr (Y-Y plane) to the plane orthogonal to this (<2-2 plane) is approximately 2 to 5 degrees.

The inventor of the present invention also discovered the following fact in the course of the experiments and research described above. That is, as shown in FIG. 1, the circumferential surface of the reeling part of the plug 2 and each inclined opening rule I2. The angle θ1 between the exit surface 13 of the inclined roll 1β+1r facing the reeling part 22 of the plug 2 or the tangent thereof and the path center and the plug It has been found that there is a close relationship between the angle θ2 between the surface or tangent of the glue ring portion and the bus center, particularly the difference between the two (hereinafter referred to as the "opposing surface angle difference"), and the thickness unevenness rate. FIG. 3 is a graph showing the relationship between the above-mentioned opposing surface angle difference and thickness unevenness rate (average value), where the horizontal axis represents the opposing surface angle difference, and the vertical axis represents the average thickness unevenness rate (longitudinal wall thickness unevenness). It is shown by taking the weighted average of the distribution. As is clear from this graph, the thickness unevenness rate reaches its minimum value at or before or after the value of the opposing surface angle difference is 2゜, but when it is above or below, the thickness unevenness rate increases and the difference becomes 2゜. It can be seen that it increases approximately linearly below 2° and in a quadratic curve above 2°. Incidentally, the thickness unevenness rate δ in a region of 2° or less is approximated by the following formula.

δ-C-A (θ1-θ2) However, C, A: Constant The graph in Figure 3 above is made of low carbon steel, and 147 holes were drilled in a round piece of steel with a diameter of 187 m1. The results showed that when holes of different diameters were drilled in a round steel piece made of the same material and of the same diameter, there was a difference in the angles of opposing surfaces that exhibited the lowest thickness unevenness, and that Although the surface angle difference was different, it was confirmed that the relationship with the thickness unevenness ratio exhibited a pattern substantially similar to the graph shown in FIG. 3 above.

〔the purpose〕

The present invention has been made based on this knowledge, and its purpose is to determine the relationship between the angle difference between the facing surfaces of the oblique roll and the plug around f and the thickness unevenness rate, so that the thickness unevenness rate becomes the target thickness unevenness rate. By adjusting the intersection and/or inclination of the inclined rolls in order to adjust the angle difference of the facing surfaces to match the above, it is possible to effectively reduce the thickness unevenness rate and significantly improve the pipe quality. The present invention provides a method for rolling a metal tube with inclined rolls.

〔composition〕

A process in which the material to be rolled is moved forward in the axial direction using a plurality of inclined rolls, and a plug is penetrated along the axial line, and the material to be rolled is subjected to piercing rolling or diameter expansion/elongation rolling. In , the wall thickness of the pipe after rolling was measured to determine the wall thickness unevenness,
The relationship between the thickness unevenness rate and the facing surface angle difference of the inclined roll and the plug is determined, and the facing surface angle difference that allows the thickness unevenness rate to match the target thickness unevenness rate is determined, and the sloped roll is used to adjust the facing surface angle difference. It is characterized by adjusting the crossing angle and/or the oblique angle around 1.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment in which the present invention is applied to a piercer will be described in detail based on the drawings. FIG. 1 is an explanatory diagram showing the relationship between the plug and the inclined roll used in the method of the present invention,
In the figure, B indicates a round steel piece, H indicates a hollow shell, 111.1r indicates an inclined roll, and 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, fed into the piercer, and rotated along the axial line by inclined rolls IjLjr that are in contact with the outer peripheral surface. The plug 2 is moved in the axial direction while being rotated, and the plug 2 is inserted into the center and bored.

Each inclined roll IC1r 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 having a truncated conical shape whose diameter decreases toward the end of the roll. On both sides of the pass center of the round billet B, roll shafts are supported by reduction screws 14f and 14b, respectively, and the inlet faces 12 and 12 are respectively aligned with the axis line relative to the bus center in plan view. In other words, the Okayama entrance faces 13 and 13 are inclined at a predetermined intersection angle α in the direction in which they approach each other, and in side view, the inclined roll 1r has its entrance face 12 facing upward, and the inclined roll 11
are arranged at predetermined angles of inclination upward and downward relative to the bus center with their exit surfaces I3 facing downward, and are each driven to rotate in the same direction as indicated by the arrows by drive sources (not shown). I'm being forced to do it.

Note that each inclined roll 1j2. The crossing angle and inclination angle of Ir are set by a crossing angle adjustment section 15 and an inclination angle adjustment section 16, respectively.

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 transferred, and placed between the shaft center and the tip base of the mandrel mill M. It is pivoted so that it can rotate freely. As shown in Fig. 5.6, the plug 2 includes a rolled part 21 having a substantially conical shape with a rounded tip, a reeling part 22 connected to the rolled part 21 and having a substantially truncated conical shape, and this reeling part 22. It is provided with a relief part 23 which is connected to the base end and has a reduced diameter on the proximal end side.

Reference numeral 30 denotes an arithmetic control unit for optimally setting the above-mentioned opposing surface angle difference, and includes a sensor S for detecting the intersecting angle and inclination angle, which is attached to the intersecting angle adjusting unit 15.1 and the oblique angle adjusting unit 16.
A+, Sj! The crossing angle α and the inclination angle β are detected based on the signals from z, Sr1, and Sr2, and the output signals from the wall thickness measuring device 31 placed on the exit side of the piercer are read at a predetermined timing, and the signals are detected from each sensor Sβ1, etc. Tilt roll B based on the signal.

While calculating the opposing surface angle difference Δθ (=θ, −θ2) between the outlet surface 13 of the lr and the reeling part 22 of the plug 2, the thickness unevenness rate of the hollow shell H is calculated based on the signal from the wall thickness measuring device 31. Therefore, the average thickness unevenness rate is calculated based on a predetermined number of thickness unevenness rates, and the relationship between the opposing surface angle difference and the average thickness unevenness rate is calculated, and the average thickness unevenness rate is calculated from the relationship between the two thus determined. The optimum opposing surface angle difference Δθ0 necessary to match the target thickness unevenness ratio is determined, and in order to achieve this, the crossing angle adjustment section 15 and the inclination angle adjustment section 1 are used.
A control signal is output to each of the rollers 111.1r to control the attitude of the inclined roll 111.1r. Then, after the attitude control, the average thickness unevenness ratio as described above is calculated again, the influence of disturbances such as thermal expansion and wear is removed, and the above process is repeated so as to match the target thickness unevenness ratio.

Next, the above-mentioned control process will be explained in detail according to the flowchart shown in FIG. First, the dimensions of the round billet B, the target dimensions of the hollow shell H, and the inclined roll ljl! ,l
r, the dimensions of the plug 2, and various data such as the target outer diameter, wall thickness, target wall thickness deviation rate, etc. are input to the calculation control unit 30, and the initial opposing surface angle difference is empirically calculated (step 2). , , and the intersection angle α to realize this opposing surface angle difference Δθ0
, calculate the inclination angle β (step ■). This intersection angle α,
Calculation of the inclination angle β is based on the relationship between the intersecting angle and inclination angle and the opposing surface angle difference due to each change, and based on this and the change distribution ratio of the intersecting angle and inclination angle (set on a case-by-case basis). Calculated based on Cross angle to be set.

When the f11 oblique angle is calculated, the position of the plug 2 is adjusted in accordance with the amount of movement of the gorge section 11 due to the change of the intersecting angle (Step 2), and then each intersecting angle and inclination angle adjustment section 15.1 is performed.
A control signal is output to 6 to change the crossing angle and inclination angle to set the inclination roll IC'lr to a predetermined attitude (step 2). Intersection angle, around 1 Whether the bevel angle is set to a predetermined angle is determined by the sensor 5I11+ attached to each adjustment section 15.16.
It is detected by taking in the signal from 5lt2+Srl+Sr2.

Next, the reeling part 22 of the plug 2 and the oblique roll 11 around 1,
Exit surface 1 at the shortest distance from exit surface 1i of lr
3 and the path center X-X line, predict the minimum wall thickness tmin on the exit side of the piercer, and calculate the minimum wall thickness tm
The interval between the inclined rolls 1° C. and 1r relative to the plug 2, that is, the roll opening degree, is set so that in coincides with the target wall thickness (Step 2), and piercing rolling is started (Step 2). The arithmetic control unit 3 receives the wall thickness measurement signal of the hollow shell H detected by the wall thickness measuring device 31 placed on the exit side of the PIA at a predetermined timing.
0, and calculate its thickness unevenness rate (Step ■). When the calculated number of pieces with thickness unevenness reaches a predetermined value m (Step ■), calculate and store the average thickness unevenness rate for it (Step ■).
Step ■).

Then, it is determined whether this average thickness unevenness rate has reached the target thickness unevenness rate (Step @l). If the target thickness unevenness rate is not obtained, Δθ is slightly changed to a level that allows optimization. Return to step ① and repeat the calculation. Next, determine the opposing surface angle difference to obtain the target thickness unevenness rate (step ■), calculate the amount of change in the intersecting angle and/or inclination angle (mainly the intersecting angle), and correct the intersecting angle in order to achieve this (step ①). Step @).

Further, the minimum wall thickness on the exit side of the piercer is predicted by this intersection angle correction (Step o), the opening degree of the inclined rolls IJ and Ir is changed to obtain the target wall thickness (Step (2)), and piercing rolling is performed (Step (2)). Similarly, the thickness unevenness rate is determined based on the detection signal from the wall thickness measurement container 31 on the exit side of the piercer, and the average thickness unevenness rate is calculated (Step @). It is determined whether this is the target thickness unevenness rate. Step O). Returning to [phase], the above process is repeated again until the average thickness unevenness rate matches the target thickness unevenness rate.

In addition, in the above embodiment, the wall thickness of the hollow shell is measured on the exit side of the piercer, the average thickness unevenness is determined based on this, and the opposing surface angle difference is optimized based on the relationship between this average thickness unevenness and the opposing surface angle difference. Although we have explained the configuration in which the inclined roll posture is changed in order to set the value to The relationships shown in the graph shown in FIG. 3 are compiled into a table, input into the arithmetic and control section 30, and by inputting the dimensions and rolling conditions of the round billet B, the corresponding values are selected from the table. Determine the angle difference between the opposing surfaces that gives the target thickness unevenness,
In order to achieve this, the crossing angle and/or inclination angle of the inclined rolls are set and controlled, and if the thickness unevenness rate measured by the wall thickness measuring device 31 does not match the target thickness unevenness rate during piercing rolling, the mutual deviation is Assuming that it is caused by disturbances such as thermal expansion of plugs or wear, etc., the angle difference between opposing surfaces should be corrected according to the graph described above to make the uneven thickness rate match the target uneven thickness rate. , inclined roll B.

Of course, it is also possible to adopt a configuration in which the crossing angle and inclination angle of 1r are corrected.

〔effect〕

As described above, in the method of the present invention, the wall thickness of the pipe after piercing rolling or diameter expansion/stretch rolling is measured, the thickness unevenness is calculated, and the thickness unevenness and the angle of the facing surfaces of the inclined rolls and the plug are calculated. Considering the relationship with the difference, the opposing surface angle difference is adjusted to make the thickness unevenness rate match the target thickness unevenness rate, so the thickness unevenness rate can be effectively suppressed and the pipe quality can be significantly improved. The present invention has excellent effects such as high productivity and high yield.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing a general piercing rolling method using a piercer, Fig. 2 is a schematic cross-sectional view taken along the line ■-■ in Fig. 1,
FIG. 3 is a graph showing the relationship between the angle difference between opposing surfaces of the inclined roll and the plug and the thickness unevenness ratio, FIG. 4 is a schematic diagram showing the implementation state of the method of the present invention, and FIG. 5 is a flow chart showing the control process. . H! , lr...1 oblique roll 2... plug 3u
, 3d... 5 Guide shoe 11... Gorge part 1
2... Inlet surface 13... Outlet surface 21... Rolling section 22... Reeling section 23... Relief section 30.
...Arithmetic control unit 31...Thickness measuring device B...Round steel piece H...Hollow shell patent Applicant Sumitomo Metal Industries Co., Ltd. Agent Patent attorney Noboru Kono lr Iris lr Figure 1 2 3 t , 7 tetrahedral angle A (°) Fig. 3 (Continued from page 1 ■Inventor Kazuo Fujisawa Nishi-Nagasu Institute of Arts, Nishi City

Claims (1)

[Claims] 1. Using a plurality of inclined rolls, the material to be rolled is spirally moved in the axial direction of the material, and a plug is penetrated along the axial center line, and the material to be rolled is subjected to piercing rolling or diameter expansion/elongation rolling. In the process of rolling, the wall thickness of the pipe after rolling is measured to determine the wall thickness unevenness rate, the relationship between the wall thickness unevenness rate and the angle difference between the facing surfaces of the inclined rolls and the plug is determined, and the wall thickness unevenness rate is calculated based on this. A method for rolling a metal tube with inclined rolls, characterized in that the angle difference between opposing surfaces that can be matched with a target thickness unevenness is determined, and the crossing angle and/or the inclination angle of the inclined rolls are adjusted to realize the difference in opposing surface angles.