JPS61137612A - Skew rolling method of metallic pipe and plug used for rolling - Google Patents

Abstract

PURPOSE:To prevent the wall-thickness deviation of a metallic pipe by rolling again a part, rolled by a roll of one side and a reeling part of plug, by a roll of the other side and the reeling part of plug, in piercing the pipe by skew rolls. CONSTITUTION:With respect to a plug 2 used for skew rolling, the length LR of a reeling part 22 in the axial direction of plug 2 is decided by the relation between the outer diameter DS of a stock B after rolling and the slant angle betaof skew rolls 1(l), 1(r). In case of piercing the stock B; the rolled part, rolled by the roll 1(l) of one side and the part 22, is rolled again by the other roll 1(r) and the part 22. In this way, a metallic pipe having uniform wall thickness is obtained regardless of its circumferential position.

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 inclined rolls, such as Elongator, and a plug used in the rolling.

[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, both the above-mentioned piercer and elongator are MM oblique rolling mills that combine a barrel-shaped rolling roll (hereinafter referred to as an "inclined roll") whose axis line is inclined with respect to the bus center of a round billet or hollow shell and a plug. For example, in the case of a piercer, as shown in FIG. A pair of inclined rolls lj!, 1r each having an inlet surface 12 and an outlet surface 13 which are gradually reduced in the shape of a truncated cone; It is constructed by combining a reeling part 22 having a substantially truncated conical shape and a plug 2 having a relief part 23 whose diameter is reduced toward the base end, and the both inclined rolls 11°lr are formed by a reeling part 22 having a substantially truncated conical shape, and a plug 2 having a relief part 23 whose diameter decreases toward the base end. On both sides of the bus center, the axis lines are parallel to the bus center in plan view, and in side view, one inclined roll faces upward (and the other side faces downward), so that the center line is parallel to the bus center by an inclination angle β. The plug 2 is arranged at an angle with respect to the
is arranged with its axis aligned with the bus 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 H! , lr population side 12.1
The plug 2 is inserted into the center of the plug 2 while being rotated in the axial direction and transferred in the axial direction, in a so-called semi-advanced movement. It is adapted to be pierced and rolled.

[Problem that the invention seeks to solve]

FIG. 4 is a schematic cross-sectional view taken along the line ff-IV in FIG. Pressure is applied between the opposing surfaces with lr.

The hollow shell H is stretched and formed into a hollow shell H. In this process, the hollow shell H, which is pressurized between the facing surfaces of the plug 2 and the inclined roll L1.1r, 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, on the hollow shell H, the T: part is Guyton knee 3u.

Since it is in sliding contact with the plug 3d 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 isometric roll le.

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 1'JIi
Roll H! , a plane passing through the center of the facing surface with lr (Y-'Y
The thickness of the hollow shell in each cross section taken by the plane (Z-2 plane) and the plane (Z-2 plane) perpendicular thereto is about 1:1; l-1.4.

By the way, each time the hollow shell H that is pierced and rolled by such a piercer is rotated twice around its axis, the sliding contact positions between the plug 2 and the inclined rolls lIt, lr and with the guyton knees 3u and 3d are alternated. Then, the thinning process and thickening process are repeated.

FIG. 5 is a schematic cross-sectional view taken along line V-V in FIG. 4,
After two revolutions of the hollow shell H, the portion A I of the hollow shell H that is currently located between the facing surfaces of the plug 2 and the rolling roll b moves to the portion A2 that contacts the guide shoe 3d.
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 becomes large. When the hollow shell H rotates further ×, A
The second portion moves to the A3 portion between the reeling portion 22 and the inclined roll Hz in the plug 2, but the gap between the plug 2 and the inclined roll lIL becomes narrower, resulting in a large thickness reduction rate. Then, when the hollow shell H rotates a further A, the A3 portion moves to the A4 portion where it contacts the guy knee 3u, but in this process, the A3 portion passes through the portion of the plug 2 that faces the relief portion 23, so the diameter of the hollow shell H increases. The pressing force is small, so the compressive force is also small, and the rate of increase in thickness is also small, resulting in a thin wall at A48.

On the other hand, in FIG. 5, when looking at the part 81 which contacts the lower guy knee 3d at a position facing the iii end of the reeling part 22 at an interval A in the circumferential direction from A+9f1, when the hollow shell H is rotated A, the plug 2 and the rolling roll 11
When the zero-order hollow shell H is rotated A, it moves to the 82 part between the facing surfaces of the
The 2nd part moves to the 83rd part where it contacts the upper guide shoe 3u, but the diameter expansion rate in this process is large and the hollow shell I]
The compressive force it receives is also large, resulting in a large increase in thickness. Then, when the hollow shell H is further rotated by A, B>fR becomes 84
However, in this process, the relief part 23 of the plug 2
84 is in a thick state with almost no thickness reduction.

As a result, the portions of the hollow shell H spaced apart by two intervals in the circumferential direction alternately appear as thin portions A4 and thick portions B, resulting in the formation of a spiral uneven thickness. be.

FIG. 6 is a graph showing the change in wall thickness of the A1 portion marked 1iI and the Bls portion as it passes through the plug 2 from the position facing the tip of the plug 2, and the horizontal axis is in the direction of movement of the hollow shell H. The vertical axis shows the wall thickness.

As is clear from this graph, when drilling is started by the plug 2, which position in the circumferential direction is that part located, that is, the position facing the left and right inclined rolls IN and lr?
Alternatively, it becomes thinner or thicker depending on whether it faces the upper or lower guy knee 3u or 3d, and after passing through the plug 2, thick portions and thin portions appear alternately in the axial length direction of Holononyl H. It can be seen that a dIx spiral thickness unevenness occurs.

The uneven thickness that occurs in this way is elongated in the subsequent process.
There was a problem in that it was difficult to solve the problem even by passing it through a mandrel mill, stretch reducer, or leeler, and it had an extremely large effect on the quality of the finished product.

〔principle〕

The inventor of the present application has determined that the above-mentioned cause of the non-uniformity of wall thickness occurs.
As a result of experiments and research, it was found that the thick portion was rolled only once by the reeling part of the plug 2 and the rolls. That is, in Figure 5 of the song description,
When drilling by plug 2 starts, Guyton z
The part between 3u, 3d and the reeling part 22 of the plug 2 (part 81 in Fig. 5) is thinned by one roll after rotating A, but (part 82 in Fig. 5), After that, when A is rotated, the thickness is increased between the reeling part 22 of the plug 2 and the guy's knee (Fig. 5, B3), and further A
When it rotates, that part leaves the area around the reeling part 22 of the plug 2 and reaches the area around the relief part 23 (
Figure 5, B), no thinning is performed by external rolls. In other words, the part that becomes thicker is the part that has been rolled only by one roll, and the part that has been rolled by at least both rolls is the part that has reduced thickness.

Therefore, in order to eliminate unevenness in the thickness of the rolled material,
It is sufficient that the part rolled by one roll and the reeling part of the plug 2 is rolled by another roll and the reeling part of the plug 2. In other words, the axial length of the rolled material during two rotations is sufficient. If the distance traveled in the direction is at least plug 2
The length in the axial direction of the reeling portion may be greater than or equal to the length in the axial direction of the reeling portion.

Conventionally, there is no theoretical basis for determining the length of the reeling portion 22 in the axial direction of the plug 2, and it has been empirically determined to be 0.15 to 0.25 with respect to the entire length of the plug 2.

Now, the appropriate speed of the material to be rolled is V (its circumferential direction component is V, -
The component in the 5-axis direction is ν11), and the pressure i! If the outer diameter of the latter hollow shell is Ds, and the reeling length of plug 2 is LR, then
The conditions under which the rolled material rotates more than 〃 while the rolled material moves in the axial direction by the reeling power LR are expressed as follows. [! II. The time required for the rolled material to move by LR in the axial direction is expressed by LLI/vl, and the distance the rolled material moves in the circumferential direction during this time is expressed by Vy·LIL/vjl.

As long as this distance is larger than the A circumference of the hollow shell, the following equation (1) holds true.

v2・LR/vn≧□・Ds −・−(.

If the inclination angle of the inclined rolls 1ffi and 1r is β, the rolled material is moved forward by the inclined rolls rotating at an inclination, so the circumferential direction component V1 of the advancing speed V of the rolled material is , the relationship between the axial component Vy and the inclination angle β is the seventh
As shown in the figure, it is expressed by the following equation (2).

Vu/V2=tanβ・−f2+(1), (
From equation 2), the following equation holds true.

LQ □ I) stan β - (31 On the other hand, when designing the plug 2, if the reeling length LR of the plug 2 is made larger than necessary, the workability will be compromised due to the increased weight of the plug 2, and Economic efficiency is also affected by one mouth.Therefore, the use of reeling LPs should be suppressed as much as possible.

The inventor of the present application manufactured plugs and conducted experiments by changing the reeling length LR within a range that satisfies the relationship of equation (3).

The results are shown in FIG. As is clear from Fig. 8, even if the reeling length Lt+ is π・Ds・jan β or more, in other words, even if rolling is performed four or more times between the plug and the roll, the rolled material It was found that there was almost no difference in the thickness unevenness rate after rolling.

Therefore, the critical length of the reeling length LP with respect to uneven thickness may be π·DS tanβ, and the following equation holds true.

LQ≦π・DS Lanβ −+41 (3), (4
), the following equation (5) holds true.

−Ds −tan β≦R≦π−Ds・Lan β
...(6) [Operation] Figure 1 shows a schematic cross-sectional view of the piercing rolling process when a plug with a reeling length LR that satisfies the above formula (5) is used, and the wall thickness distribution in this case. is shown in Figure 2. Second
In the figure, like FIG. 5, it is shown as a cross section taken along the line ■--■ in FIG. 4. Now, the portion C1 of the hollow shell H located between the opposing surfaces of the plug 2 and the rolling roll lr is rolled to reduce its thickness by both, and after the A rotation of the hollow shell H, it moves to the portion C2 in contact with the guide nonny 3d, where it increases slightly. Become meat. When the hollow shell H further rotates ×, the C2 portion moves to the 03 portion between the plug 2 and the stop roll IIt, and is thinned again due to the wall thickness, and with the next rotation of A, the 03 portion becomes the Guyton knee 30. It reaches the contacting C1 part. At this time, since the reeling length LR satisfies the relationship of equation (5) above, the C4 portion is in the circumferential region of the reeling portion 22, and the reeling portion 22 and the guide nony 3u cause the hollow nonyl I( The wall thickness increases slightly due to compressive stress in the circumferential direction due to the restriction of pipe expansion.On the other hand, in Fig.
Looking at the part D1 in contact with the separated guide nony 3d, the hollow shell H rotates twice and moves to the D2 part between the facing surfaces of the plug 2 and the rolling roll B, and the zero-order hollow shell H is thinned by both. When it rotates twice, the D2 portion moves to the D3 portion that contacts the upper guide nony 30, but the diameter expansion rate during this process is large, and therefore the compression force applied to the hollow nonyl H is also large, so the thickness is increased significantly.

(Mugi, and when Hollow Shell H is rotated twice, D3
The part is between the plug 2 and the roll lr.

However, since the length LR of the reeling part 22 of the plug 2 satisfies the above formula (5), the D4 portion does not reach the circumferential area of the escape part 23 of the plug 2 (the reeling part 22, and the reeling part 22 and the roll l
The thickness is reduced by being rolled down by r.

[Actual Example & 1] Next, tax will be deducted for the case where the present invention is implemented in a piercer that obtains a hollow pipe by piercing and rolling round steel.

Table 1 shows the specifications of the plug used in the implementation of the present invention, the drilling setup when using the plug, the specifications of the roll used, and the specifications of the rolled material. Table 1 also shows similar items in the case of carrying out.

Table 1 also shows the holononyl wall thickness reduction process and nonyl wall thickness distribution (
(circumferential direction, longitudinal direction) and holononyl uneven thickness weight 4 are shown in FIG. In addition, FIG. 1O shows the hollow nonyl wall thickness reduction process, nonyl wall thickness distribution (circumferential direction, longitudinal direction), and hollow wall thickness unevenness distribution of the unpierced material when piercing and rolling is performed by the conventional method. In both the graphs of Fig. 9 and 101iJ, the horizontal axis shows the distance from the tip of the plug to the direction of travel of the hollow/el, and the vertical axis shows the wall thickness. When the round steel piece B begins to be drilled, it shows the change in wall thickness of the part located above, that is, the part located on the guide shoe 3u side, and the Δ mark indicates the change in the wall thickness of the part located below, that is, on the guide shoe 3d side. The . mark indicates the change in wall thickness of the portion located on the inclined roll 1 e fllJ, and the mu mark indicates the change in the wall thickness of the portion located on the inclined roll Ir (II). As is clear from the graph, in the present invention, there is almost no difference in the wall thickness in the circumferential direction at the position after the plug 2 has passed.

Furthermore, the plots marked with X in the graph each indicate the thickness unevenness rate, and it can be seen that the thickness unevenness rate after passing through the plug 2 has been significantly improved.

In the above description, a piercer that manufactures a hollow shell using round steel has been described, but the present invention is not limited to this, and can also be applied to an elongate mill that elongates a hollow shell with thinning. Further, it is natural that the guide shoes may be of the di-roll type.

〔effect〕

As is clear from FIGS. 9 and 10, according to the present invention, the perforated and elongated portions of the rolled material are finished to have a uniform wall thickness regardless of the circumferential position, and the quality of the tube product is significantly improved.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the process of eliminating uneven thickness in the present invention,
Figure 2 is a graph showing the change in wall thickness, Figure 3 is a schematic diagram showing the relationship between the rolling roll and the plug, and Figure 4 is the r of Figure 3.
A schematic cross-sectional view along the V-rV line, Fig. 5 is a schematic diagram showing the uneven thickness ordering process, Fig. 6 is a graph showing the change in wall thickness, and Fig. 7 is a schematic diagram for explaining the velocity component of the hollow shell. , FIG. 8 is a graph showing the relationship between the number of times of rolling of a material to be rolled with a plug and a roll and the thickness unevenness ratio, FIG. 9 is a graph showing the wall thickness distribution in an embodiment of the present invention, and FIG. 1O is a conventional example. It is a graph showing wall thickness distribution in .

Claims (1)

[Claims] 1. Using a pair of inclined rolls disposed opposite to each other, the material to be rolled is spirally moved in the axial direction thereof, and a plug is penetrated into the material to be rolled along the axial direction. In the process of piercing rolling, diameter expansion, and elongation rolling, the part of the material to be rolled that has been rolled by one roll and the reeling part of the plug is rolled again by at least the other roll and the reeling part of the plug. Features: Inclined roll rolling method for metal tubes. 2. Using a pair of inclined rolls arranged to face each other, the material to be rolled is moved in a spiral direction in the axial direction, and a plug is penetrated along the axial direction to perform piercing rolling or diameter expansion of the material to be rolled. , in an inclined roll rolling mill that performs elongation rolling, the axial length L_R of the reeling portion is π/2・Ds・tanβ≦L_R≦π・Ds・tanβ
However, the plug is characterized in that Ds: outer diameter of the material to be rolled after rolling β: angle of inclination of the inclined roll.