JPS60152308A - Draw rolling method of circular pipe - Google Patents

Abstract

PURPOSE:To prevent the inner surface of a pipe from becoming angular and to improve the quality and yield of a product by twisting the pipe in a titled method where plural sets of rolling mills consisting each of plural rolls are arranged in series. CONSTITUTION:Each stand of a drawing mill constituted of 28 sets of stands, for instance, has three rolls, and the calibers of adjoining two (n)th, (n+1)th stands are in the positional relation as shown by the figure, and the (n)th stand has a characteristic value (ovality) of b/a. Thereupon, all the stands are separated into two blocks of the 1st-14th and the 17th-28th stands to set a twisting device of material at the position of the 16th stand by removing the rolls of the 15th stand. That is, the rolls having the same shapes as those of the 14th stand are cut into the rolls having each a 15 deg. inclination, to use them as a twisting device. The material after being subjected to rolling reduction by the 14th stand is twisted while passing through the 16th stand, and is subjected to rolling reduction by the 17th stand while being twisted by 30 deg.. Thus the material is rolled by the succeeding stands in a state of being deviated by 30 deg. in phase from the state in the first half stands into a dodecagonal inner face thereby making the angular one uniform.

Description

Detailed Description of the Invention (Industrial Application Field) This invention provides a method for shrinking a metal tube using a reducing mill to obtain a circular tube with a smaller diameter than the starting tube. Concerning a rolling method that does not produce tension.

Conventionally, seamless circular tubes have been produced by using a solid billet to create a hollow tube using the Mannesmann Piaser method, the Fu/Yubenchi method (Erhardt method), hot extrusion method, etc., and then milling it using a plug mill, mandrel mill, or Rolled using a semi-floating mandrel mill, etc., and generally has a tube outer diameter of 3 to H-
1 (76.2 to 101.6 mm) or more is then shaped into a product using a sizing mill.

Pipe outer diameter is 3~4 inches (76,2~]C11,6van)
After rolling with a mandrel mill or the like, products with a diameter of less than 100 mm are reheated and subjected to degeneracy rolling with a stretching mill (stretch resuser) to obtain circular tube products with various outer diameters and wall thicknesses.

By the way, as this reducing rolling equipment, several to more than 20 rolling mills having 2 to 4 rolling rolls are continuously arranged in series, and the above-mentioned rolling mill having 2 to 4 rolling rolls has a In the plane perpendicular to the rolling direction, each roll has an angle of 180° in the rolling direction of each roll when there are two rolls, 120° when there are three rolls, and 90° when there are four rolls. A row of rolling mills arranged so as to form a circular path is applied.

The rolls in the rolling mills constituting the rolling mill row are 90° with respect to the adjacent rolling mills in the case of a two-roll mill, 60° in the case of a three-roll mill, and 60° in the case of a four-roll mill. 45 for rolling mill
The angle is shifted by ° in the plane perpendicular to the rolling direction.

The diameter of the circular bus formed by the hole shape of each of the multiple rolls in each rolling mill from the first stage rolling mill to the last stage rolling mill is gradually decreased as the number of stages increases, and the diameter of the circular bus is gradually reduced as the number of stages increases. At this time, in order to obtain a product with a predetermined wall thickness, the roll rotation speed is set so that tension is applied to the tube between each rolling mill, and the thickness of the tube is reduced by tension rolling. Controls thickness.

(Problems with the prior art) By the way, the rolling mills in the above-mentioned reduction rolling mill row are
It has ~4 rolls, and the corresponding roll axes between adjacent rolling mills are 90° and 60° in a plane perpendicular to the rolling direction.
There is an angular shift such as 45° or 45°. This means that, for example, when a reduction rolling mill row is composed of three rolling mills, the rolls are arranged at an angle of 60° between adjacent rolling mills. Circular pipes subjected to pipe shrinking in a row undergo repeated plastic changes in six circumferentially divided areas, resulting in the problem of hexagonal inner surface angularity as shown in FIG.

As shown in Fig. 2, this so-called squaring phenomenon is related to the elongation ratio in the longitudinal direction of the pipe during reduction rolling and the butcher and outer diameter of the pipe after rolling. As you can see, there is a tendency for the squareness ratio to increase. Therefore, if an attempt is made to suppress the angularity to a certain level or less, there is a problem in that reduction rolling, which requires large stretching, is not possible.

(Objective of the Invention) The present invention was made in order to suppress angularity to a low level in the above-mentioned reduction rolling of a circular pipe, thereby making it possible to improve product quality and yield.

In order to solve this problem, an invention has been proposed that suppresses angularity, improves product quality and yield, and enables reduction rolling under large stretching conditions (Tokukosho!
No. 54-4336).

The invention (technique) disclosed in this Japanese Patent Publication No. 54-4336
By arranging a plurality of rolling stands consisting of 2 to 4 rolls in series and displacing the rolls at a constant angle in a plane perpendicular to the rolling direction for each stand, In a reduction rolling method in which a circular tube of a predetermined diameter is manufactured by sequentially displacing the composite hole shape formed by the rolls at a constant angle, a group of rolling stands described in "-" is used in two or more rolling stands. and the phase of the angular displacement of the roll arrangement in at least one block is shifted from the phase of the angular displacement of the other blocks, or any block is divided into an arbitrary number of blocks consisting of It is characterized by a circular tube reduction rolling method in which the phase of the displacement of the roll composite hole shape is shifted by changing the hole shape of the roll in the block from that of other blocks.

However, a drawback of the method described above is that it involves the need to mechanically tilt some of the constituent stands. That is, inclining an existing stand to a certain angle requires major modification of the equipment, which is not easy. Conversely, if the monthly interest rate itself can be twisted regularly within a specific stand or between stands, then...
The present invention has been accomplished by focusing on the fact that effects equivalent to those described above can be obtained.

(Structure of the Invention) That is, the present invention is characterized by arranging a plurality of rolling mills each having a plurality of rolls in series, and changing the arrangement of the plurality of rolls in each rolling mill. For each rolling mill, the metal tube is passed through a series of composite grooves that vary at a constant angle in a plane perpendicular to the rolling direction. The rolling mill row is divided into an arbitrary number of blocks of 7 to 7 rolling mills, and a twisting device for rolling tubes is installed between the blocks to twist the rolling mills. By twisting the tube with a device, the corresponding position between the pierce and the roll in the preceding block of an arbitrary block and the corresponding position between the pierce and the roll in one block can be made different ( 7/
It's here and there.

4-/The second invention of the present invention is the configuration of the specific invention described in (
(The 24-Harness of the tube in the last rolling mill of the block on the first stream side of the six rolling mill rows is made higher than that in the other rolling stages in the block, ]
Kashi, / here and there are -1゛ characteristically.

Furthermore, the third invention of the present invention is the above! The specific invention (1) is characterized in that the groove shape formed by the plurality of rolls in the first rolling mill of the block on the downstream side of the rolling mill row is approximately circular. do.

Hereinafter, the present invention will be explained in detail by application examples.

FIG. 3 shows a reduction rolling mill (stretch resuser) consisting of 28 stands, each stand having three rolls. Therefore, two adjacent stands n
, n-1-1 have a positional relationship as shown in FIG. 4, and the stand (1) has a characteristic value (called opacity) of 1]/a.

FIG. 5 is an example in which the present invention is applied to FIG. 3.

All the stands are divided into two blocks (1), 1-14, 1.7-28, ■, the roll of the 15th stand is removed, and the monthly interest twisting device is placed in the position of the 16th stand. That is, as shown in detail in FIGS. 5(b) and 5(c),
- A roll having the same shape as the 14th stand (Figure 5) is turned into a roll with an inclination angle of 15°, and placed in the 16th stand as a twisting device (Figure 5C). The wood that has been subjected to the pressure of the 14th stand is twisted by passing through the 16th stand, twisted by 30 degrees at the 17th stand, and is compressed as shown in Figure 7. In the stud after this μ, the phase of the first half of the stand is always shifted by 30°, the inner surface shape becomes dodecagonal, and the angularity is made uniform.

At this time, a plurality of stands may be used as twisting devices, and for example, the first stand may twist 10 degrees, and the second stand may twist further 10 degrees. The twisting angle is appropriately determined depending on the position of the twisting device from the front stand.

The more stands you can remove the roll from, the easier it will be to twist, but since there is a finite number of stands, in reality it is only 1 to 3 stands.
limited to individuals.

Furthermore, the twist of the U old does not depend on the roll, for example, the 6th twist.
As shown in the figure, a guide whose shape changes sequentially in the longitudinal direction may be used. At this time, it is effective to use ceramic as the raw material to prevent seizure.

The twisted material is rolled down in the 17th stunt as shown in FIG. 7, but at this time, unless the contact between the restraint and the roll is symmetrical, the material may topple over. To prevent this, the 17th stand should be made into an almost circular hole shape (oat; Rity: 1.0), and the 18th stand should be
You can also put the oats back on the stand and apply pressure.

The larger the aperity (b/a) of the wire (closer to a triangular shape), the easier it is to twist.

For this reason, for example, it may be necessary to make the auto-retention of the 14th stand particularly larger than the other stands.

Figure 8 shows a material with 12 stands, 48.6 φ x 5.9 t, an outer surface reduction rate of 7 inches, a hole shape opacity of 1.05, the 6th stand being omitted, and the 7th stand having the same hole shape as the 5th stand. The effect of the example when used as a twisting device by tilting it by 10 degrees was compared with that of a normal device.

It can be seen that the angularity is reduced by about half.

(Effects of the Invention) According to the invention described above, it has become possible to significantly reduce the inner angularity of the metal tube rolled by a so-called stretch reso user, and the quality and yield have been improved.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing the inner angularity of a circular pipe, and Fig. 2 is a graph showing the relationship between the angularity ratio, elongation ratio, wall thickness, and outer diameter.
Figure 3 is a configuration diagram of a stand for a normal stretch reso user, and Figure 4 is a diagram of the stand 1. Figure 5 (a) is a diagram of the positional relationship of the holes of n-1-1, Figure 5 (a) is a configuration diagram of the stand to which the present invention is applied, Figure 5 (b), ←・), 2) is Figure 5 (
Fig. 6 is a perspective view showing a specific example of the twisting device; Fig. 7 is a diagram of the 17th stand in Fig. 5 (a). FIG. 8 is a graph showing the effect of the present invention. Patent applicant Representative patent attorney Tomoyuki Yabuki (and 1 other person) Figure 1 Figure 2 Figure 3 Light 4 Figure 71 Figure 5 (a)

Claims (1)

[Claims] (]) A plurality of rolling mills each having a plurality of rolls are arranged in series, and the arrangement of the plurality of rolls in each rolling mill is perpendicular to the rolling direction. In the reduction rolling method for circular tubes, in which the metal tube is passed through a row of composite grooves that vary by a fixed angle in a plane and differ by a fixed angle for each rolling mill, the rolling mill row is divided into two or more. − consisting of a rolling mill, divided into any number of flocks, seven in number,
A twisting device for the tube to be rolled is installed between these blocks, and by twisting the tube with the twisting device, the corresponding position of the material and the roll in the previous block of the arbitrary block and the abrasive material in the relevant flock can be determined. A unique reduction rolling method whose first feature is that the S7 position is different from that of the rolls. At the same time, the arrangement of the plurality of rolls in each rolling mill is changed by a fixed angle in a plane perpendicular to the rolling direction for each rolling mill, and the arrangement is changed by a fixed angle for each rolling mill. In the reduction rolling method for circular tubes in which a metal tube is passed through a composite groove row, the rolling mill row is divided into an arbitrary number of blocks each consisting of two or more rolling mills, and rolling is carried out between the blocks. By installing a pipe twisting device and twisting the pipe with the twisting device, the corresponding position of the material and the roll in the previous block of the arbitrary block,
The corresponding positions of the material and the rolls in the block are made different, and the opening of the tubes in the final stage rolling mill of the block on the downstream side of the rolling mill row is made different than in the other rolling mills in the block. A reduction rolling method for circular pipes characterized by rolling at a high height. (3) A plurality of rolling mills consisting of a plurality of rolls are arranged in series, and the arrangement of the plurality of rolls in each rolling mill is fixed within a plane perpendicular to the rolling direction for each rolling mill. In the reduction rolling method for a circular tube in which the metal tube is passed through a composite groove row that changes angle by a constant angle for each rolling mill, the rolling mill row may be any number of rolling mills consisting of two or more rolling mills. In addition to dividing into blocks, a twisting device for the tube to be rolled is installed between the blocks, and by twisting the tube with the twisting device, the corresponding position of the material and the roll in the preceding block of any block can be determined. and the corresponding positions of the material and the roll in the block are made different,
Furthermore, a method for reducing a circular tube, characterized in that the groove shape formed by the plurality of rolls in the first stage rolling mill of the block on the downstream side of the rolling mill row is rolled into a substantially circular shape. (4) The rolling method according to any one of claims 1 to 3, wherein the twisting of the tube between the blocks is performed using one or more stands each consisting of a plurality of rolls. (5) Twisting the tube between the blocks in the longitudinal direction,
A rolling method according to any one of claims 1 to 3, which is carried out using a fixed guide whose cross-sectional shape changes.