JPS6087907A - Continuous rolling mill for steel pipe - Google Patents

Abstract

PURPOSE:To make wall thickness distribution uniform and to roll a steel pipe to have both thin walled ends by constituting the caliber of a stand of four rolls consisting of a pair of driving rolls and a pair of non-driven rolls having the shafts intersecting orthogonally therewith. CONSTITUTION:A roll stand P or Q consists of total four rolls; a pair of driving rolls 4 and a pair of non-driven rolls 4a, to each of which rolls a hydraulic rolling down cylinder 5 is installed. The adjacent stands P and Q of such four- roll type hydraulic rolling down stand are disposed in such a way that the roll shafts incline by 45 deg.. Formation of both ends of the pipe to a reduced wall thickness without thickness deviation in the circumferential direction is thus made possible and the product free from the increased thickness part at the pipe ends after reducing is thus rolled.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a continuous elongation rolling mill for steel pipes, and in particular to a method for uniformly reducing the wall thickness at the ends of the pipe by 1-10 mm in order to make the wall thickness distribution in the longitudinal direction of the steel pipe uniform. This article relates to a hydraulic downstream mechanism for hole-shaped rolls.

Many methods have been developed and put into practical use for manufacturing steel pipes without joints, but the manufacturing process can be roughly divided into a drilling process to produce a hollow pipe, and a process of thinning and stretching the pipe. 3. Stretching and rolling process, and drawing process to finish the outer diameter to the specified size.
It can be broadly divided into The present invention relates to the structure of a stretching mill used in the stretching process of these processes, and its purpose is to uniformly distribute the wall thickness in the longitudinal direction of the finished tube manufactured through the drawing process. It is to do so. To explain in more detail, if the wall end is not thinned during the elongation rolling process, when the tube outer diameter is reduced by applying a tensile force in the longitudinal direction in the next reducing rolling process, a tensile force will be applied to the tube end before and after the tube end. Since this part is not coated, the thickness of this part will increase and will be discarded in the later process. Therefore, the thickness of the leading and trailing ends of the tube is thinned in advance during the elongation rolling process, so that even if the leading and trailing ends of the tube exiting the drawing process become thicker, the thickness is adjusted to be the same as the center of the tube. The present invention provides a hydraulic rolling mechanism for a stretching mill.

A conventional hydraulic reduction control method for thinning both pipe ends using a 20-hole type mandre mill is disclosed in, for example, Japanese Patent Application Laid-Open No. 49-113752.
However, this proposal had a drawback in that the circumferential thickness of the thinned tube end portion was not uniform.

The present invention provides a hydraulic pressure reduction mechanism that makes the thickness distribution in the circumferential direction more uniform and reduces the thickness of both ends to 111 mm.

The gist of this book ff1Dl for achieving the purpose stated in item 2 is that in a continuous rolling mill that continuously stretches and rolls a pipe by inserting mandrel bars into the raw pipe and using a plurality of hole-shaped roll stands arranged, The hole shape of the arbitrary stand is made up of a total of four rolls, a pair of drive rolls and a pair of non-drive rolls whose axes are orthogonal to the drive roll axis,
The continuous rolling mill for steel pipes is characterized in that the pair of drive rolls and the pair of non-drive rolls are each provided with a hydraulic reduction cylinder so that the downstream amount can be adjusted.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The hydraulic rolling mechanism and its control force method for a continuous tube rolling mill according to the present invention will be described below with reference to the drawings. Fig. 1 is a perspective view conceptually showing the jf 4f* manlr l/lumil, and Fig. 2 is a diagram showing how to assemble the hydraulic pressure reduction cylinder 5 in the 20-l type stand. This figure shows the A arrow view of M and the B arrow view of the roll stand N. The raw tube 2 that has passed through the mandrel bar 1 is thinned through several roll stands consisting of hole-shaped rolls 4, becomes the mandrel mill outlet tube material 3, and is sent to the next process. 6
Appropriate reduction blades are applied to the hole-shaped roll 4 through the
When reducing the wall thickness of a pipe using a 20-roll type stand, use two sets of roll stands M and N whose roll axes are tilted at 90 degrees to each other, and roll stands M and N are used to reduce the wall thickness of the pipe in the circumferential direction of the pipe at 90 degrees to each other. A common method is to reduce the wall thickness. According to this conventional pipe material thinning method using the 20-square stand method, uneven thickness occurs in the wall thickness of the pipe material in the circumferential direction (a) and (b), as shown in Fig. 3. It is inevitable. FIG. 3 is a contour view showing a cross section of the tube end portion of the tube member 3. As shown in FIG. Amount of deviation in pipe thickness Δt in this cross-sectional shape
m m (difference between the wall thickness at the bottom of the roll hole groove and the wall thickness in the direction tilted at a center angle of 45 degrees from the center of the groove bottom) is Δt = t, where the amount of thinning at the bottom of the roll hole groove is tmm. -tXcos45° (mm).

For example, in Fig. 3, if the thickness reduction amount t is 2 mm with a 20-hole roll for rolling a pipe material with a wall thickness of 5 mm, and the wall thickness of the roll hole groove bottom center (a) is 3 mm, then the groove bottom center The wall thickness of the part (b) in the direction tilted 45 degrees from the central angle is 3
．． 58 mm, and the thickness deviation rate in the circumferential direction ((maximum thickness -
The ratio (minimum wall thickness)/average wall thickness) reaches approximately 18%. A tube material having such a large thickness deviation in the circumferential direction cannot be an excellent product.

A schematic diagram of the hydraulic downstream mechanism of the 40-level stand according to the present invention is shown in FIG. FIG. 4 shows a front view of two 40 roll stands of the present invention, and stand P on the left and stand Q on the right in FIG. 4 show adjacent roll stands of a mandrel mill. 1, the mandrel bar 13 is made of I6 material.

The roll stand P or Q of the present invention consists of a total of four rolls, a pair of drive rolls 4 and a pair of non-drive rolls 4a, and each roll is provided with a hydraulic pressure reduction cylinder 5, respectively. If adjacent stands P and Q of this 40-type hydraulic reduction stand are arranged so that their roll axes are inclined at 45 degrees, the cross-sectional shape of the pipe material at the thinned portion will be as shown in FIG. 5. In the cross section of FIG. 5, the amount of thickness deviation Δtmm is as follows, where tmm is the amount of thinning at the center of the groove bottom, Δt=t−tX, cos 22.5° (mm).

For example, as shown in Fig. 5, if the thickness reduction 1ift is 2 mm with a 40-hole roll for rolling a pipe material with a wall thickness of 5 mm, and the wall thickness at the groove bottom center part (a) is 3 mm, then The thickness of the part (C) at 22.5 degrees from the center of the bottom is 3.15 m.
m, and the thickness deviation rate in the circumferential direction is approximately 5%. As described above, according to the continuous tube rolling machine having the 40-hole type hydraulic rolling mechanism according to the present invention, it is possible to perform thinning forming at both tube ends with little thickness deviation in the circumferential direction.

Next, what happens when pipe end thinning rolling is carried out using the 40-L hydraulic downstream stand according to the present invention, and when using the conventional 20-L hydraulic downstream stand? 11. The results of comparing the dimensions of finished pipes when end thinning rolling is performed will be explained. For reference, the experimental results obtained when no tube end wall thinning rolling was performed are also listed.

The operating conditions were a 5-stand mandrel mill with an outer diameter of 89.
0mm, wall thickness 8.0mm, length 2m, outside diameter 74.0mm.
Finished as an intermediate product with a diameter of 0 mm, a wall thickness of 4.0 mm, and a length of 4.6 m, and further reduced to an outer diameter of 48.3 mm and a wall thickness of 5.0 mm using an lO stand and stretch reducer. 'Om m, length 6m
This is the case when finished.

The experimental results are as follows: (If pipe end thinning rolling is not carried out in the mandrel mill (Figures 6 and 7) When pipe end thinning rolling was carried out (Fig. 8, Fig. 9) ■ Pipe end thinning rolling was carried out by using the 40-type hydraulic reduction stands of the present invention as the third and fourth stands of the mandrel mill. (Figs. 10 and 11), and are classified into three conditions and shown in Figs. 6 to 11.

Figures 6, 8, and 10 show the longitudinal distribution of the circumferential average wall thickness of the tube material on the outlet side of the stretch reducer, respectively, and Figures 7, 9, and 11 show the longitudinal distribution of the average wall thickness in the circumferential direction of the tube material on the outlet side of the stretch reducer, respectively. FIG. 10 is a measurement result of the circumferential wall thickness distribution of the tube material cross section at a portion 100 mm from the rear end of the tube, which corresponds to FIG.

From these measurement results, as shown in Fig. 1O and Fig. 1'1, when tube end thinning is rolled using the 40-type hydraulic reduction stand according to the present invention, the results are shown in Figs. It is clear that the wall thickness distribution in the longitudinal direction and circumferential direction of the finished tube is significantly improved compared to FIGS. 8 and 9.

[Brief explanation of the drawing]

Fig. 1 is a perspective view conceptually showing the rolling state of a conventional mandrel mill, and Fig. 2 is a front view of two adjacent roll stands. View from arrow B of roll stand N in Figure 1 (marked II,
Fig. 3 is a cross-sectional profile view of the end portion of a pipe material that has been thinned using a conventional 20-L hydraulic pressure stand, and Fig. 4 is a cross-sectional view of two adjacent stands of a 40-L hydraulic pressure stand according to the present invention. (P and Q) are front views. Figure 5 shows the pipe material that has been subjected to wall thinning processing using the 40-L hydraulic downstream stand according to the present invention. ii is a cross-sectional profile diagram of the end portion; Figure 6, Figure 8,
Figure 10 shows the case where both pipe ends are not thinned by a mandrel mill, the pipes are rolled under 20-1 hydraulic pressure, and the 3-end pipes are rolled with thinning at 40-1 hydraulic pressure. Graphs showing the wall thickness distribution in the longitudinal direction of the double-barrel pipe in the case of the embodiment of the present invention in which six ends were thinned and rolled, FIGS. 7, 9, and 11 are shown in FIGS. 6 and 8, respectively. , is a graph showing the circumferential wall thickness distribution at a position 1.00 mm from the tube end of the finished bond shown in FIG. 1O. ■... Mandrel par 2... Raw pipe 3... Mandrel mill outlet pipe material 4... Hole roll 5... Hydraulic reduction cylinder 6... Bearings M, N... Conventional adjacent Roll stand P, Q...
・Adjacent roll stand of the embodiment of the present invention Applicant Kawasaki Steel Corporation Ishikawajima Harima Heavy Industries Co., Ltd. Agent Patent attorney Yoshio Kosugi Figure 1 Figure 2 Figure 3 Figure 5

Claims (1)

[Claims] 1 By inserting mandrel pars into the raw pipe and using a hole-shaped roll stand with multiple units arranged, i! 1! In a continuous rolling mill that continuously stretches and rolls pipes, the hole shape of an arbitrary stand is determined by the old four-wheel configuration of a pair of drive rolls and a pair of non-drive rolls whose axes are orthogonal to the drive roll axis. It is characterized in that the roll bearings of the pair of drive rolls and the pair of non-drive rolls are each equipped with a hydraulic pressure ring for adjusting the pressure h1-. ! i
1'+Ai continuous rolling mill.