JP2007038263A - Reducer for rolling pipe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for reducing a pipe diameter by rolling, which method can reduce uneven thickness of the pipe by suppressing generation of inside angularity and can prevent generation of defects on the outside surface of the pipe. <P>SOLUTION: In the reducer for rolling the pipe, the reducer having M stands with N rolls, a pitch of a phase angle for one or a plurality of selected groups composed of the stands, which do not include the last four stands, and are not less than continued three stands and are not more than (M-4) stands, is set to be less than 180/N degrees, and the pitch of the phase angle for the residual groups composed of the remaining stands is set to be 180/N degrees. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pipe rolling reducer used when drawing and rolling a metal pipe such as a steel pipe.

  For example, as shown in FIG. 6 in the case of N = 3, the tube (metal tube) 1 is subjected to a drawing rolling apparatus in which a plurality of N roll stands 2 are arranged in tandem (hereinafter referred to as N roll reducer or N 2 The above natural number is substituted and used, for example, a 3-roll reducer). Here, the N roll stand refers to a rolling mill stand (hereinafter simply referred to as a stand) in which N caliber rolls (hereinafter simply referred to as rolls) 2 are arranged at equal intervals in the circumferential direction. N-roll reducers do not use internal tools such as plugs. A tube rolling reducer in which M rolls (M stands) of N roll reducers are referred to as an N roll M stand pipe rolling reducer.

  In each stand, the moving radius around the center of the pass line in the plane common to each roll central axis is the entry side (starting from the position where the moving radius overlaps with the half line extending vertically upward from the rotation center) If the rotation angle to the caliber center point of the roll where the moving radius first intersects when it is rotated clockwise as viewed from the material (pipe) side is called the phase angle of the stand, 3 In the case of a roll reducer, the phase angle between adjacent stands is normally set to be shifted by 60 ° (normally 180 / N ° for an N roll reducer), that is, the phase angle difference between the stands is 60 ° (see FIG. 2). However, when the phase angle difference between adjacent stands is set to the usual 60 °, a portion where the thickness is thinner than the other portion is generated in the circumferential direction of the material at the pitch of 60 °. As a result, it has an angular cross-sectional shape on the inner surface side where there is no inner tool (and therefore is not constrained). There is a growing problem. Similarly, in the case of a 2-roll reducer, when the phase angle difference is set to the usual 90 °, there is a problem that the inner surface is squared when the phase angle difference is set to the usual 45 °.

  As a technique for reducing the uneven thickness due to the occurrence of so-called inner surface angularity, for example, in Patent Document 1, in an N roll reducer in which the phase angle difference between adjacent stands is 180 / N °, at least a pair of adjacent stands is It has been proposed to change the phase angle difference to 90 / N ° and at least another pair to 45 / N °. In FIG. 3 shown as an example, the phase angle difference between the (i + 1) th stand and the (i + 2) th stand is changed from the usual 180/3 ° = 60 ° to 90/3 ° = 30 °.

In addition to the above, Patent Documents 2 and 3 proposed by the present inventors are given as conventional techniques related to the pipe rolling method.
Japanese Patent Laid-Open No. 61-216806 JP 2005-46869 A JP 2005-46874 A

  A stand whose phase angle difference from the previous stand is 90 / N ° or 45 / N °, and more generally a stand that does not coincide with either -180 / N ° or 180 / N ° is a stand that performs asymmetric rolling. . That is, for example, when N = 3, as shown in FIG. 4A, the tube 1 and the roll 3 asymmetrically contact 6 at the biting position (the contact point between the material 1 and the roll at the biting position is Deviation from the center of Kariba.) On the other hand, a stand having an absolute value of the phase angle difference with the previous stand equal to 180 / N ° is a stand that performs symmetrical rolling. That is, for example, as shown in FIG. 4B, the pipe 1 and the roll 3 are in contact with each other 6 symmetrically at the biting position (the contact point between the material 1 and the roll at the biting position coincides with the center of the caliber. .)

  Providing a stand for asymmetric rolling is effective in terms of reducing uneven thickness due to the occurrence of internal angularity as described above. However, in this stand, as shown in FIG. Since the material portion having a sharp shape in contact with the end portion comes into contact with the position close to the end of the caliber at the biting position of the stand, a twist 7 is generated in the material 1 and an irregular inner surface is formed. There has been a problem that cornering occurs and uneven thickness increases. In addition, biting of the material from the gap between the caliber ends is likely to occur, and there is a problem that wrinkles (stepped wrinkles) due to the biting are likely to occur in the product. Furthermore, as shown in the schematic diagram of FIG. 5, in the former stage of the reducer, rolling with a high reduction ratio is performed in common for all sizes, so that the effect of reducing uneven thickness due to the addition of asymmetric rolling is large, whereas in the latter stage Since the stage where rolling with a low diameter reduction is performed differs depending on the size, the effect of reducing uneven thickness due to the addition of asymmetric rolling is poor. .

  An object of the present invention is to provide a tube rolling reducer that solves these problems, suppresses the occurrence of angular cornering on the inner surface, reduces uneven thickness, and prevents the occurrence of wrinkles on the outer surface of the product.

  As a result of intensive studies to achieve the above object, the inventors have made a stand arrangement with a phase angle pitch = 180 / N ° on the rear side, and all or a part of continuous stands (a group of continuous stand groups). The present invention has been made by conceiving a reducer in which the number of itself is one or more) with a stand arrangement with a phase angle pitch <180 / N ° and the rest with a stand arrangement with a phase angle pitch = 180 / N °.

  That is, according to the present invention, in the N-roll M stand tube rolling reducer, the phase angle pitch of one or a plurality of selected groups consisting of three or more (M-4) or less stands not including the last four is set to 180. It is a reducer for tube rolling characterized in that it is less than / N ° and the phase angle pitch of the remaining group consisting of the remaining stands is 180 / N °. The phase angle pitch of the selected group is preferably 90 / N ° or less.

In the present invention, the phase angle pitch of a group consisting of a plurality of consecutive stands is obtained by calculating all the phase angle differences between successive stands within the same group by using a common index n as “integer part × 10 ^n. "And is represented by a numerical value obtained by dividing the greatest common divisor of the data consisting of these integer parts by 10 ⁿ .

  According to the present invention, in the reducer for tube rolling of the N roll M stand, the phase angle pitch of one or a plurality of selected groups consisting of three or more (M-4) consecutive stands not including the last four is set. By setting the phase angle pitch of the remaining group consisting of the remaining stands to 180 / N °, less than 180 / N °, the occurrence of internal surface angularity is effectively suppressed on the front side, which is considered to have a high diameter reduction rate, and low Since biting is suppressed on the downstream side where the diameter reduction rate is set, both reduction in uneven thickness and prevention of wrinkle generation can be achieved.

  FIG. 1 is an explanatory diagram illustrating an embodiment of the present invention. In FIG. 1A, the first to (M-4) th continuous stands are set as a selected group (that is, a group having a phase angle pitch <180 / N °), and the rest are set as the remaining groups (that is, the phase angle pitch = 180 / N ° group). FIG. 1B shows a configuration in which the continuous stands from the first to less than 1 (M-4) are selected groups, and the rest are the remaining groups. FIG. 1C shows a form in which continuous stands from less than (M-4) to (M-4) th are selected groups, and the rest are the remaining groups. FIG. 1 (d) shows a configuration in which two different continuous portions from the first to (M-4) th continuous stands are selected groups and the rest are remaining groups. Although FIG. 1 shows the case where the number of selected groups is 1 to 2, the number of selected groups may be 3 or more.

  When the total number of stands is 12 or more, it is preferable to set the phase angle pitch of the selected group to 90 / N ° or less from the viewpoint of further enhancing the effect of suppressing the occurrence of internal surface angularity.

  Using a 3-roll 28 stand reducer and an ERW steel pipe (equivalent to JIS STKM13A) with an outer diameter of 110 mm and a wall thickness of 7.0 mm as a material, trial rolling was performed under the conditions shown in Table 1, and the target dimension = outer diameter of 25.4 mm. X A product tube having a wall thickness of 6.0 mm was obtained. The material was heated to 900 ° C. before rolling. Analyzing the cut surface of this product pipe and measuring the thickness distribution in the circumferential direction, based on the results, the degree of uneven thickness (within the center of the tolerance range of 4σ width ± σ: ◎, the tolerance range Outside the range of the center ± σ and within the range of the center ± 2σ: ○, out of the range of the center ± 2σ: x), on the other hand, the degree of wrinkles by visual observation of the outer surface of the product pipe (none: ◎ Within the allowable range: ○, outside the allowable range: x). The results are shown in Table 1. The selected groups in Table 1 are enclosed in double frames. As shown in Table 1, in the invention examples satisfying the requirements of the present invention, the degree of uneven thickness was ◎ or 疵, and the occurrence of wrinkles was ◎ or 、, whereas the last four stands in Invention Example A1 In Comparative Example A5 where the phase angle pitch of the group was 30 ° (<180/3 °), the thickness deviation was ◎, but the occurrence of wrinkles was x, and the phase angle pitch over the entire stand In the conventional example A6 in which the angle was 60 ° (= 180/3 °), the degree of wrinkles was ◯, but the degree of uneven thickness was x.

  Using 4 rolls and 16 stand reducers, an ERW steel pipe (equivalent to JIS STKM11A) with an outer diameter of 90 mm and a wall thickness of 6.0 mm is used as a raw material. X A product tube having a wall thickness of 5.0 mm was obtained. The material was heated to 950 ° C. before rolling. Analyzing the cut surface of this product pipe and measuring the thickness distribution in the circumferential direction, based on the results, the degree of uneven thickness (within the center of the tolerance range of 4σ width ± σ: ◎, the tolerance range Outside the range of the center ± σ and within the range of the center ± 2σ: ○, out of the range of the center ± 2σ: x), on the other hand, the degree of wrinkles by visual observation of the outer surface of the product pipe (none: ◎ Within the allowable range: ○, outside the allowable range: x). The results are shown in Table 2. The selected groups in Table 2 are enclosed in double frames. As shown in Table 2, in the invention examples satisfying the requirements of the present invention, the degree of uneven thickness was ◎ or 疵 and the occurrence of wrinkles was ◎ or 、, whereas the last four stands in Invention Example B1 In Comparative Example B4 where the phase angle pitch of the group was 11.25 ° (<180/4 °), the degree of unevenness was ◎, but the degree of wrinkles was x, and the phase over the entire stand In Conventional Example B5 in which the angular pitch was 45 ° (= 180/4 °), the degree of wrinkles was ◯, but the degree of uneven thickness was x.

It is explanatory drawing which illustrates embodiment of this invention. It is explanatory drawing which shows that inner surface hexagonal tension generate | occur | produces in the case of N roll stand (in the case of N = 3) when the phase angle difference of adjacent stands is 180 / N degree. It is explanatory drawing which shows an example of a prior art. It is explanatory drawing which shows the problem of a prior art. It is a schematic diagram which shows that the contribution of asymmetric rolling differs in the front | former stage and back | latter stage of a reducer. It is a conceptual diagram which shows the drawing-rolling method of the pipe | tube using a normal 3 roll reducer.

Explanation of symbols

1 tube (metal tube or material)
2 stands (N roll stand, 3 roll stand, 4 roll stand, etc.)
3 rolls (caliber rolls)
6 Contact (between roll and material) 7 Twist

Claims (2)

  In the N-roll M stand tube rolling reducer, the phase angle pitch of one or more selected groups consisting of three or more consecutive (M-4) or less stands not including the last four is set to less than 180 / N °. A reducer for pipe rolling, wherein the phase angle pitch of the remaining group consisting of the remaining stands is 180 / N °.   2. The tube rolling reducer according to claim 1, wherein a phase angle pitch of the selected group is 90 / N ° or less.

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