JPS6054203A - Guide device in push-in piercing rolling - Google Patents

Abstract

PURPOSE:To form the corners of a blank material having square cross section by preparing a billet guiding means formed by arranging four rolls in the surface perpendicular to the rolling direction at the front stage of a pass of hollow cross section constituted of rolling rolls and a plug. CONSTITUTION:In a press roll piercing equipment for manufacturing a round pipe stock from a billet 1 having square cross section; one of more billet guiding means formed by disposing four grooved rolls 9 arranged at 90 deg. intervals on the diagonals slanted by 45 deg. in the cross section perpendicular to the rolling direction, are installed in the rolling direction at the front stage of a pass of hollow cross section constituted of a pair of rolling rolls 3 and a plug. By this equipment, the blank material 1 having the sharp corner section is pierced by applying a push-in force by a pusher 4 whil forming the corners into proper ones. In this way, a rubbing down flaw in the outer surface of pipe stock is prevented, and the wall-thickness deviation of pipe stock is improved.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention mainly uses continuously cast bloom or billet with a rectangular cross section as a material, and a pusher installed at the entrance side of a rolling mill and circular holes are carved into the material. This invention relates to a guide device installed on the entry side of a piercing rolling mill for seamless steel pipe rolling, which punches and rolls a circular hollow raw tube using a pair of horizontal rolls and a conical plug installed at the center of a circular hole.

(Prior art) The principle of indentation piercing rolling for producing a circular cross-section hollow shell from a rectangular cross-section material is shown in Figure 1.
i:% A pair of upper and lower horizontal rolls 3 having a circular hole shape and a conical plug 5 set at the center of the circular hole shape,
The circular hollow blank tube 2 is rolled while applying pushing force over the entire length during rolling by a pusher 4 from the rear.

This method of rolling allows the direct use of continuously cast rectangular cross-section materials, resulting in low material costs, and compressive force is applied to the inside of the raw tube that is rolled with plugs, resulting in good quality raw tubes with no internal defects. is obtained. On the other hand, as shown in FIG. 2, since a rectangular cross-section material 1 is rolled through a circular hole 3, shear deformation tends to be concentrated at the corners of the material, which tends to cause scratches caused by the rolls. Since pushing force is applied from the rear, if the centering of the material with respect to the hole shape is poor, eccentricity of the plug will occur and uneven thickness of the raw pipe will likely increase. Product defects and uneven thickness are the most important issues in seamless steel pipe rolling.
In order to eliminate these problems, it is first necessary to prevent flaws and uneven thickness of the raw pipe during the initial stage of rolling, which is push-piercing rolling.

Currently, in order to deal with scratches on raw pipes, the corners of the material are processed offline using a grinder.

Alternatively, a corner sizing mill having a pair of horizontal rolls 6 with box hole shapes as shown in FIG. 3 is installed between the heating furnace and the indentation piercing mill to prevent this. In addition, in order to deal with uneven thickness of the raw pipe, a pair of horizontal guide rolls 8 and a pair of vertical guide rolls 7, each having a box hole shape that rotates freely as shown in Fig. 4, are alternately combined. A roller-type roller guide is installed just before the indentation rolling mill to prevent these problems.

However, each process and equipment in this indentation piercing rolling method is only effective for one problem, and when viewed as a whole, not only is the process wasteful, but material and equipment costs are also rising. There are problems such as a decrease in yield.

(Purpose of the Invention) Therefore, with the aim of omitting processes, rationalizing equipment, and improving yield, offline grinder processing and corner sizing mills were abolished.

In addition, he invented a guide device on the entry side of a rolling mill for push-piercing rolling, which allows the use of a continuous cast material with a square cross-section with sharp corners and still yields a raw tube with good thickness unevenness and no wear-down flaws. .

(Structure 1 of the Invention) The entrance guide device of the indentation rolling mill according to the present invention has a set of guides housed in one housing as shown in FIG. 90° on the diagonal of °
placed at intervals. It is composed of four grooved rolls 9, each of which rotates freely in the same direction as the diagonal line, and usually a sixth
As shown in the figure, a plurality of sets of guides are combined to form a block guide, but it is of course also possible to use only one set alone.

The guide of the present invention is manufactured by continuously casting a rectangular cross-section material with sharp corners, which is manufactured online by continuous casting, and is continuously formed into the appropriate corners immediately before entering the piercing mill. By piercing and rolling the material, it is possible to prevent scratches on the outer surface of the raw material pipe, and to improve the centering accuracy with respect to the center of the circular hole shape of the material by actively restraining the material corner and its two adjacent surfaces. It has the effect of improving the uneven thickness of the raw pipe.

In other words, as shown in FIG. 7, when comparing the constraint state of the material of the conventional 20-1 type roller guide and the guide according to the present invention, it is found that the 20-1 type roller guide has indirect molding of the corner part of the material due to the widening of the width. Although it is not possible to obtain very effective formability because the rolling is mainly performed, the guide according to the present invention directly
Extremely effective corner forming is possible because the material corners can be rolled down in the 5° direction with guide rolls, and since the guide rolls rotate freely, even if the material corners are rolled down, the material can still be rolled by the guide rolls. No outage will occur.

Furthermore, as is clear from FIG. 7, in the 20 mm roller guide, two opposing surfaces of the material are restrained, whereas in the guide according to the present invention, all 4 surfaces including the 4 corners are restrained. It can ensure centering accuracy that is equal to or better than that of a single roller guide. Furthermore, in push-piercing rolling, the material expands during rolling due to the pushing force of the pusher, but with a 20-roll roller guide, the contact area between the guide roll and the material is large, which increases the rolling reduction of the guide roll and improves rolling. Stopping is likely to occur; 1. Normally, it is necessary to provide an appropriate clearance between the guide roll and the material. In contrast, the guide according to the present invention has 1
Since the contact area of each piece is small, the load on the idle roll is not so large due to the expansion of the material, and therefore there is no need to provide clearance between the guide roll and the material, making it possible to obtain centering accuracy higher than that of the 20-12-ra guide. It is possible.

(Example) Next, a specific example will be described in which corner forming and push-piercing rolling of a rectangular cross-sectional material are performed simultaneously using the guide device according to the present invention.

In this case, the material has a cross-sectional dimension of 215+m, a corner R8,
The corner radius of the material when it enters the circular hole of the piercing rolling mill is 20R.
mm, the punch-rolled raw pipe has a cross-sectional dimension of 250φ and a wall thickness of 625W.

FIG. 8(a) uses three sets of guides according to the present invention,
The gaps between the first to third guide rolls were all kept constant at <215 mm, which is the same as the material size, and the groove bottom corner R of the kite roll was successively changed from the first guide roll to 10 mm, 15 R, and 20 m. This is an example of piercing rolling while performing corner forming. For comparison, Figure 8(b) uses a 20-hole type roller guide with a total of three sets of box holes carved in the order of vertical roll guide, horizontal roll guide, and vertical roll guide, and the guide roll settings. This is an example of piercing and rolling performed under the same conditions as the guide according to the present invention.

FIG. 8 shows an example in which three sets of 201-type roller guides are used, and all the guide roll gaps are closed by 215cm from the first guide to the third guide reed for piercing and rolling.

Figure 9 shows an example of measurement of the pusher pushing force at a speed ratio α=0.9 defined as %VR=: α・λ・■p (VR: roll circumferential speed, λ: stretching, Vp: pusher speed). It is something that Normal rolling is possible with the guide (a) of the present invention, but when the clearance between the material and the guide roll is set to rc Q (b) with a 20-roll type roller guide, rolling stops and the resistance of the guide roll is large. That is clear. Even with a 20-inch roller guide, normal rolling is possible if the clearance is about 5 inches.

Figure 10 shows the pushing force of the pusher when α is changed, and if the setting conditions of the guide rolls are the same, the guide of the present invention has a pushing force greater than that of the 20-roll two roller guide. Become smaller.

Even if the clearance between the material and the idle roll is 0, rolling will not stop.

Figure 1 shows the load on ≠3 guide rolls when α is changed. Compared to the 20-1 type roller guide, the load of the guide of the present invention is smaller, and the guide roll will continue to be used in the future. It is clear that the resistance is small.

FIG. 12 compares the cross-sectional shape of the material at the hole-shaped entrance of the piercing and rolling mill when α=11.

With the guide of the present invention, the desired material corner radius of 2oRWfn can be obtained, but with the 20-round type roller guide, only about half the desired corner radius can be obtained.

It is clear that the guide according to the invention has excellent corner formability.

Fig. 13 shows the average cross-sectional dimensions of the material at the hole entrance of the piercing rolling machine when α=11, and in the guide according to the present invention, the swelling of the material due to the pushing force is small and the variation in size is also small. .

Figure 14 shows the number of scratches generated on the outer surface of the raw tube when α = 1.1. Even if the cast material with sharp corners is used as is, it is possible to almost completely prevent scratches.

FIG. 15 shows the average thickness unevenness of the raw pipe when α is changed. In the guide according to the invention.

Since it is possible to set the clearance between the material and the guide roll to O, it is possible to obtain the same or better effect of preventing uneven thickness than the 20-roll type roller guide.

(Effects of the Invention) As is clear from the detailed description of the specific embodiments above, by using the guide device according to the present invention, the conventional off-line grinder processing maintenance and corner sizing mill can be avoided. without needing
Continuous casting materials can now be used as they are, making it possible to omit processes and rationalize equipment, reducing material and equipment costs and improving yields. Indentation piercing rolling became possible.

[Brief explanation of drawings]

Fig. 1 is an explanatory view showing the principle of indentation piercing rolling for manufacturing a circular cross-section hollow shell from a rectangular cross-section material, and Fig. 2 is a front explanatory view showing the state of contact between the rectangular cross-section material and the circular hole shape. Figure 3 is an explanatory diagram showing a horizontal 20-hole corner sizing mill with box hole shapes, Figures 4 (A) and ('
), (c) are overall views showing an example of the arrangement of a conventional 20-roll two roller guide on the entrance side of a piercing rolling machine, a vertical guide roll diagram and a horizontal kite roll diagram, and FIG. 5 is a roll arrangement of the guide according to the present invention. Figure 6 is a side view of the arrangement of guides when multiple sets of guides according to the present invention are used, and Figure 7 (A) is a side view of the arrangement of guides according to the present invention. FIG. 8 is a front view comparing the differences in corner formability of square cross-section materials according to the present invention, and FIG. These are explanatory diagrams showing examples of cases where a conventional 20-type roller guide is used, in which (a) is the guide according to the present invention, and (b) is a 20-type roller guide in which the clearance between the material and the guide roll is set to O, (c) is 20
This is a single roller guide with a clearance of 5%. FIG. 9 is a graph comparing measurement examples of the pusher pushing force in push-piercing rolling when the guide according to the present invention and the conventional 20-hole type roller guide are used.
The figure is a graph showing the relationship between the speed ratio α and the pusher pushing force in indentation piercing rolling. Figure 11 is a graph showing the load of the ≠3 guide roll in indentation piercing rolling.
Figure 2 is an explanatory diagram showing the cross-sectional shape of the material after passing through the guide at the hole entrance of the piercing rolling mill, and Figure 13 shows the average cross-sectional dimensions of the material from Top to Boil, which were measured by stopping rolling during push-piercing rolling. The graph shown in Figure 14 is a graph comparing the number of scratches on the outer surface of the raw pipe after indentation and rolling for the 1-piece inventive Sukanaru guide and the conventional 20-ru two-roller guide. FIG. 2 is a graph comparing the average wall thickness deviation ratio of the blank pipe after piercing and rolling for a guide according to the present invention and a conventional 20-type roller guide. FIG. 1 is a square cross section material, 2 is a hollow tube with a circular cross section. 3 is a horizontal roll 54 with a circular hole carved thereon, a pusher;
5 is a conical plug, and 6 is a horizontal a-shaped box hole.
7 is a vertical guide roll with a box hole shape, 8 is a horizontal guide roll with a box hole shape, and 9 is a grooved guide roll. Patent applicant Representative patent attorney Tomoyuki Yafuki (and 1 other person) m 21*1 Figure 3 Figure 5 g1!9 Property 1 qIfl 1110111 Behoki 11 Figure O, So 1.0 +, 1 1.2 1 .3rd +2! '
4+ 1i1N4F4 Fig. 15 (J,'/ 1.U 1.1 1.2 1.3〆

Claims (1)

[Claims] At the center of a circular bath formed by a pair of upper and lower rolling rolls, each having a semicircular hole. A plug supported by a mandrel constitutes a hollow cross-section bus, and a press roll for manufacturing a round tube by inserting a billet having a square cross section facing the hollow cross-section bus +9 while applying pressure in the axial direction. In piercing rolling equipment. In a plane perpendicular to the rolling direction, at the front stage of the hollow cross-sectional path constituted by the pair of rolling rolls and the plug. Each edge of the rectangular cross-section billet is processed to reduce the steepness of the edge, and in order to align the center of the hollow cross-section path with the center of the cross-section of the billet, at least four 1. A guide device for indentation piercing and rolling, characterized in that billet guide means comprising a plurality of rolls are provided in one or more directions of piercing and rolling.