JPH01266904A - Method for reduction rolling round tube and rolling mill therefor - Google Patents

Abstract

PURPOSE:To improve the dimensional accuracy by composing at least one roll group of rolls having different roll widths and reducibly rolling a tube section by plural passes containing at least one pass by the above combined roll group. CONSTITUTION:A stand composed of grooved rolls l1-l3 whose roll widths m1-m3 being m1 m2=m3 is contained in a stand line of a reduction rolling mill instead of composition of grooved rolls of an equal roll width (k) in respective stands. Hence, points, at which flow directions in the peripheral direction of a round tube stock are changed, are distributed in the peripheral direction to form an internal angular shape into a polygon shape and to bring the shape close to a really round circle.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for reducing and rolling circular pipes and a rolling mill therefor.

[Prior art] The conventional reduction rolling method uses a 20-rule, 3-roll groove with approximately circular arc grooves.
A plurality of rolling stands equipped with 0-roll or 40-roll are lined up, a circular tube is passed between the rolls of each stand, and tension is applied to the circular tube between the stands to roll the tube to a predetermined outer diameter. And it is divided into thick parts. Figure 2 shows 3
An example of a reduction rolling method using a 0-roll is shown.

This reduction rolling is usually the final step in the forming stage of electric resistance welded steel pipes or seamless steel pipes, and plays an important role in determining the dimensional accuracy and shape of the product. However, a characteristic of reduction rolling is that the inner surface is rolled with a free surface, so it is the recirculation that makes the inner surface a perfect circle in the cross section perpendicular to the tube axis, and the polygonal shape is This causes so-called angularity, which significantly impairs shape and dimensional accuracy, especially wall thickness accuracy.

In other words, taking the case of reduction rolling using 30-mill steel as an example, the second
Explaining according to the diagram, the roll hole shape of each stand is a triangle with one side being a substantially circular arc of the same length, and in one stand, the roll flange and groove bottom have different wall thicknesses. be done. For example, approximately circular arc work of the same length.

b2. When a material tube with a uniform wall thickness distribution and a perfect circle on both the inner and outer surfaces enters the first stand consisting of rolls a11 all a with b3, the material of the circular tube is indicated by e in Fig. 2 due to the rolls. Since the direction of this movement is opposite between the rolls, the thickness C of the flange portion and the thickness d of the groove bottom portion are rolled differently.

The uneven thickness that occurs in one stand is caused by the fact that the roll arrangement of the second stand is such that the position of the flange part is 60' out of phase with the adjacent stand 1~, for example, the first stand. , in this second stand the first
This occurs due to a 60' phase shift with respect to the uneven thickness that occurs in the stand. The uneven thicknesses of both stans 1 are overlapped to form an inner surface 11 in a hexagonal shape. Further, since the hole shape of the final n-th stand is a perfect circle, the outer shape i of the tube becomes a perfect circle along this hole shape, but the hexagonal shape J on the inner surface remains.

As mentioned above, at 30-le, the phase of the adjacent stand is 60
', the angular shape of the inner surface becomes hexagonal, but the phase difference between adjacent stands differs depending on the number of rolls, and therefore the angular shape of the inner surface also differs. That is, in the case of 20-L, the phase difference between adjacent stands is 90', and the inner angular shape is square, 40-L.
- In the case of a double-sided stand, the phase difference between adjacent stands is 45 degrees and the inner angular shape is hexagonal.

Conventionally, efforts have been made to correct the hole shape as a method of preventing deterioration of dimensional accuracy due to this angularity. but,
Hiraoka Baka: "Tetsu to Hagane J ('80).

51005 (Reference 1), the angular shape changes significantly depending on the rolling conditions, and depending on the tension state, the phase of the corners of the inner polygonal shape may even change. Also, Hirose et al.: [Plasticity and Processing J, 10-
As shown in No. 101,412 (Reference 2), the range in which the hole shape can be modified is limited to an extent that does not adversely affect the external shape, and there is a natural limit to the effect.

As a way to solve this problem,
No. 60-152308 (Reference-4) discloses that the polygonal shape of the inner surface has more corners by shifting the phase of the roll hole type between the stands. A technique has been disclosed to make the polygon closer to a perfect circle.

[Problems to be Solved by the Invention] The deterioration of dimensional accuracy due to angularity has been largely eliminated by the techniques disclosed in Documents 3 and 4, but this method cannot be used with conventional reducing rolling mills. It is difficult to implement this method as is, and it can only be achieved by constructing a completely new rolling mill or by majorly remodeling an existing reducing mill.

In view of the above-mentioned circumstances, it is an object of the present invention to provide a method for easily manufacturing a circular tube with good dimensional accuracy and shape, and a rolling mill for the same.

[Means for Solving the Problems] The present invention relates to a method for reducing and rolling circular pipes characterized by combining different roll widths, and a rolling mill for the same. In a rolling method for reducing the cross section of a pipe by forming passes, in the one pass, at least one of the roll sets is formed by rolls each having a different width (caliber width), A reduction rolling method for a circular tube characterized in that rolling is performed to reduce the cross section of the tube by a plurality of passes having at least one of the above passes, and one pass is constituted by a plurality of rolls, and the cross section of the tube is reduced by the plurality of passes. A rolling mill for performing rolling to reduce the size of the roll, the rolling mill comprising at least one of the rabbit rolls constituting the one pass.
This is a circular tube reducing mill in which a pass is formed by a plurality of rolls, one of which has a different roll width (caliber width) from the others.

[Embodiments and Effects] The reduction rolling method according to the present invention will be explained below with reference to FIG. 1, taking a 30-roll case as an example.

That is, whereas conventionally the hole shape of each stand was formed only with the same roll width as shown in FIGS. 1(a) and 1(b), in the present invention, .

As shown in (d), (e) and (f), for different roll widths, for example, in Fig. 1(c), the roll Q
1 ” 3 widths respectively ITI i, , m 2 ,
m 3, by including a stand with a roll hole shape formed so that m□≠m 2 = m 3 in the row of stands of the reducing mill, the circumference of the material of the circular tube can be reduced. By dispersing the points at which the direction of flow changes in the circumferential direction, the inner angular shape is made into a polygon that is closer to a perfect circle than the hexagonal shape conventionally produced in 30-square.

Here, in the present invention, the roll width is the caliber.
Assuming that the caliber corresponds to the engraved width, we will proceed with the explanation using the term roll width instead of caliber width.

In addition, Fig. 1 (c), (d), (e), (
In f), as an example of changing the roll width, 30° with respect to the axis of symmetry t.

Although the rolls are connected at 90' and 90', this angle can be freely selected depending on the number of corners of the target polygon with an angular inner surface. Furthermore, as a combination of roll widths, m1≠m2=m3. It shows that q□≠qz=93, but myu≠m2≠m3. q1≠92≠9
3, it is also possible to shift the point at which the flow direction in the circumferential direction of the circular tube changes in more various directions.

An embodiment of the method of the present invention will be described with reference to FIGS. 1 and 3.

That is, Fig. 3 shows the hole shapes of the first and second stands in a conventional reducing rolling mill row using seven stands in total as shown in Fig. 1 (a).
)・(b), The hole shapes of the 3rd and 4th stands are shown in Figure 1(a)・
(d), the hole shapes of the 5th and 6th stands are shown in Figures 1(e) and (f).
), with a combination of stands where the hole shape of the 7th stand is a perfect circle hole shape, 2 ], , 7 From a circular pipe of HnφX3nwnt, by changing the tension, a 15.2 field φX3, 4.5o
This shows the result of obtaining an n+t circular tube. Here, the squaring ratio shown in FIG. 3 refers to the internal large diameter D1 of the inner surface shape.
It is defined by the following formula from the minimum D2, and when the inner surface shape is a perfect circle, = 0. = 1 when the inner surface shape is a regular hexagon
00(%).

According to FIG. 3, the angularity according to the present invention was about 172 compared to the conventional method. Figure 4 shows the above [Effects of the Invention] As in the above embodiments, according to the present invention, by combining different roll widths, it is easy to significantly improve dimensional accuracy using the stand of a conventional reducing mill. It is clear that this will be achieved.

[Brief explanation of the drawing]

Figure 1 (aL (b), (c), (d), (
e) and (f) are explanatory diagrams of examples of combinations of rolls of different widths according to the present invention, Fig. 2 is an explanatory diagram of the conventional roll arrangement and angularity generation mechanism, and Fig. 3 is an explanatory diagram of an example of the combination of rolls of different widths according to the present invention. An explanatory diagram of the effect, FIG. 4, is an explanation of the definition of the squaring ratio = 8- diagram. a... Roll b... Arc C - Thickness of flange part d - Thickness of groove bottom e Thickness of flange part f...
・Roll axis g...Axis of symmetry h...Inner surface shape j-...Outer shape of the tube j...Inner surface of the tube (hexagonal) k...Roll width Q...Roll m...Roll Width q...Roll width P...Roll t16me 9 Snake Q ＼＼, ＼＼ 1 しC 10ゝ～ 3 -F-１"-" X: ・x7-' ward -' Trigram 'a' h t ku 〆) @z'11 = B Sakashi 1 is i et al. Related: Applicant 4, Agent Address: 3308 Marunouchi Shigesu Building, 2-6-2 Marunouchi, Chiyoda-ku, Tokyo Contents of Amendment The following matters in the specification and drawings of the application will be amended as shown in the attached document. Note 1: The scope of claims is amended as shown in the attached sheet. 2. On page 6, line 10, the phrase "roll is width" is corrected to "roll width." 3. On page 6, line 17, the phrase ``constituting rabbit rolls'' is corrected to ``constituting roles.'' 4. On page 8, line 17, ``Figure 1 (a), (dLJ) is corrected to ``Figure 1 (C), (d), J.'' 5. In the drawings, ``Figure 2'' and `` 4 is corrected as shown in the attached sheet. Claim 1: In a rolling method in which a plurality of rolls constitute one pass and the cross section of a pipe is reduced by the plurality of passes, the one pass is A drawing of a circular pipe, characterized in that rolling is performed to reduce the cross section of the pipe by a plurality of passes, at least one of which is composed of rolls having different roll widths (caliber @). Rolling method. 2. A rolling mill for performing rolling in which one pass is composed of a plurality of rolls and the cross section of a pipe is reduced by the plurality of passes, wherein one of the rolls constituting the one pass is A circular tube reducing rolling mill in which a pass is formed by a plurality of rolls, at least one of which has a different roll width (caliber width) from the others.

Claims (1)

[Scope of Claims] 1. A rolling method in which a plurality of rolls constitute one pass and the cross section of a pipe is reduced by the plurality of passes, wherein the one pass is performed by using at least one of the roll sets with different rolls. A reduction rolling method for a circular tube, characterized in that the tube is formed of rolls having a width (caliber width), and rolling is performed to reduce the cross section of the tube by a plurality of passes including at least one such pass. 2. A rolling mill for reducing the cross section of a pipe by forming one pass using a plurality of rolls, wherein at least one of the rolls forming the one pass is different from the others. A circular tube reducing mill in which a pass is formed by multiple rolls with different roll widths (caliber widths).