JPH035005A - Reducing device for pipe - Google Patents

Abstract

PURPOSE:To decrease the inner shrink of the inside surface generated between a material and a mandrel and to prevent inclination by forming a pair of rolls for rolling reduction of the material to an hourglass shape. CONSTITUTION:The roll gap of a pair of the hourglass rolls 11a, 11b is set at a prescribed value and the material 30 fitted onto the mandrel 20 is subjected to the working of the 1st pass and is thereby formed to the tubular material having the smooth outside surfaces facing each other in the rolling reduction direction, a circular inside surface and deformed outside surface. The mandrel 20 is then retreated and the material is rotated together with the mandrel 20 90 deg. around the axial center. The spacings between the roll gap and guide blocks 12a, 12b are then set at the working of the 2nd pass. The working is executed in the same manner as in the 1st path to form the tubular material having the smooth surfaces on the four sides of the outside surfaces in the rolling reduction direction and the direction orthogonal therewith, the circular inside surface and the deformed outside surfaces. This material is held inserted with the mandrel 20 and is pushed and inserted in this state into the die having the truly circular inside diameter of the same size as the outside diameter of the product pipe or slightly larger than this diameter and is thereby formed into the produce pipe having the circular sections on both the inside and outside surfaces with a low reduction ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a tube punching apparatus used for manufacturing forged tubes.

[Conventional technology]

As a manufacturing technology for forged tubes, a punching technique in which a mandrel is inserted into a bottomed tube, an axial thrust is applied to the mandrel, and the bottomed tube is inserted into a roll stand is disclosed in JP-A No. 64-71507. Disclosed in the official gazette. As shown in FIG. 5, the roll stand includes a pair of four-column flat rolls la that are supported and opposed to each other with a rotation axis extending in a direction perpendicular to the pass line and whose rolling position can be adjusted. , lb, and the flat rolls la, lb, which are supported and opposed to each other across a pass line so that the interval can be adjusted.
A pair of guide locks 2a, 2b are provided.

A bottomed tubular material 3 heated to a predetermined temperature is pushed by a mandrel 4 between the flat rolls la and lb in the roll stand, whereby the material 3 is subjected to a thinning process. At this time, material 3 is flat roll la, lb
Width expansion is prevented by being restrained from both sides by a pair of guidebooks 2a and 2b between them. By rotating the material 3 in the circumferential direction and repeating rolling from different directions, the material 3 is made into a forged tube.

This type of forged tube manufacturing technology uses flat rolls with adjustable spacing, so it has the advantage of being able to manufacture tubes with a variety of finished diameters using one type of roll, and eliminates the conventional use of ring dies. Compared to manufacturing technology using punching, the number of tools in stock can be significantly reduced. Further, since the flat roll has a structure that can be rolled down freely as described above, the roll interval can be minimized to the width of the guide lock. Furthermore, if the strength of the flat roll, its housing, etc. allows, it is possible to process a material with a large diameter, as long as the width of contact between the material and the flat roll does not exceed the length of the roll.

[Problem to be solved by the invention]

When manufacturing forged tubes using a conventional pre-punching machine that incorporates a cylindrical flat roll in the stand, you can enjoy the various advantages mentioned above, but on the other hand, the following two problems arise during operation. Become.

The first problem is that a so-called inner surface sink occurs between the flat roll and the guide plotter, where the inner surface of the material does not come into contact with the outer surface of the mandrel. As long as processing is performed using flat rolls, the outer surface shape of the tube will not be a perfect circle, and therefore, after punching using the above-mentioned device, punching using a perfect circular ring die or the like is required as a finishing process. At this time, if the degree of internal sinking is large, the internal sinking cannot be completely removed by finishing using a perfectly circular ring die, etc., resulting in a situation where uneven thickness remains in the product tube.

The second problem is that the outer surface of the material becomes square in the process of repeated rolling without changing the rolling direction, and depending on the direction of the material, the guide plotter may not be able to sufficiently restrain the material, resulting in This is the occurrence of so-called folding, where the material is twisted around the axis.

When sagging occurs, uneven thickness occurs in the material behind it, and if this uneven thickness cannot be prevented in subsequent buses, the entire material will be scrapped. Furthermore, even if uneven thickness can be prevented in subsequent buses, the number of passes usually needs to be increased, which increases the number of man-hours and, in some cases, requires reheating the cooled material, leading to an increase in manufacturing costs.

Since the mandrel is fixed in the circumferential direction, there is no risk of sagging if the inner surface of the material adheres strongly to the outer surface of the mandrel, but if this adhesion is too strong, the material may be pulled out with the mandrel after processing. In actual work, the material and the mandrel are not in tight contact, as this makes the stripping work difficult. In addition, since the above-mentioned inner surface sink exists between the two, the tube is more likely to sag than in the case of a punched tube made using a normal ring die. Needless to say, sagging should be prevented, so restrictions on bus schedules such as not applying heavy pressure in conditions where sagging is likely to occur are necessary.

In other words, if conventional equipment is used to prevent collapse, the equipment capacity will be severely limited, and only very inefficient processing will be possible.

The present invention has been developed in view of the above circumstances, and is a pre-punching method that can suppress the inner surface sink that occurs between the mandrel and the material to a problem-free degree, and can prevent collapse without imposing any major restrictions on the equipment capacity. The purpose is to provide processing equipment.

[Means to solve the problem]

The pre-punching device of the present invention is a pre-punching device for thinning a bottomed tube by inserting it into a stand using a mandrel, wherein the stand connects a rotating shaft to a pass line with a pass line in between. A pair of rolling drum-shaped rolls extending in orthogonal directions and supported and opposed to each other so that the rolling position can be adjusted; and a pair of guide locks.

[For production]

By using a pair of drum-shaped rolls for material reduction, if the amount of reduction at the center of the rolls is the same, the circumferential contact length between the material and the rolls becomes longer, and the free surface of the outer surface of the material increases. portions will be smaller.

As a result, internal sinkage between the material and the mandrel is reduced. Further, the material is effectively held in the circumferential direction by the drum-shaped roll, and the range of sink marks is suppressed, making it difficult for the material to sag.

〔Example〕

The present invention will be described below with reference to Examples.

As shown in FIGS. 1 and 2, the front pressing device of this embodiment includes a roll stand IO and a mandrel 20 provided on the entry side thereof.

The roll stand 10 includes a pair of drum-shaped rolls lla and llb for rolling down the material and a pair of guide blocks 12a and 1.
2b is incorporated. A pair of drum-shaped rolls lla and llb for rolling down the material are separated from each other by the pass line L, and have their rotational axes extending in a direction perpendicular to the pass line L, and are arranged parallel to each other. is idle-supported by a bearing (not shown) so that it can freely rotate in forward and reverse directions. The bearings are attached to a roll stand housing (not shown) via a screw jack and/or a hydraulic pressure lowering device (also not shown), thereby controlling the lowered position of the drum-shaped rolls lla, llb, in other words. It is said that the roll gap can be adjusted by doing this.

Regarding the shape of the drum-shaped rolls lla and flb, in order to process the material without protruding from the roll hole, the hole shape is defined by a radius of curvature larger than the radius of curvature of the outer surface of the material 30 before processing. There is a need. That is, the radius of curvature that defines the hole shape needs to have the lower limit as the radius of curvature of the outer surface of the material before processing.

On the other hand, the main feature of the tube punching apparatus of the present invention is that it can freely change the distance between the roll and the center of the tube axis to accommodate the processing of materials of many different sizes. Normally, the material size of pipes made by punching is such that the ratio of the maximum diameter to the minimum diameter is within 4, so if you try to punch all sizes with one type of roll hole type, the maximum diameter When using a hole mold that matches the outer diameter of the material, the material with the smallest diameter will be processed with a roll hole mold having a radius of curvature four times the outer diameter of the material. That is, in order not to lose the above features of the present invention, it is better to make the radius of curvature of the hole shape larger than the radius of curvature of the outer surface of the material. However, this causes the roll to become more of a flat roll, increasing the free surface area of the outer surface of the material when the material is rolled down.

For this reason, it is desirable to limit the radius of curvature R of the hole shape to within the range of R0≦R≦4×R0 with respect to the maximum radius R8 of the material, and the optimal range is R0≦R≦2×R0. do. However, if processing is to be carried out with a roll shape within the optimum range, it is necessary to prepare two or more types of grooved rolls in order to carry out processing of all sizes.

The pair of guide blocks 12a, 12b combined with the hourglass-shaped rolls lla, 11b in the roll stand IO,
A prismatic body with a rectangular cross section that is long in the direction of the pass line L, and
In a direction perpendicular to the opposing direction of the pair of hourglass-shaped rolls 11a and 1 lb, in other words, between the opposing installation of the hourglass-shaped rolls lla and llb, opposite surfaces 13a are separated by a pass line L,
13b are arranged opposite to each other so as to be parallel to the pass line L. The back surfaces 14a and 14b are attached to a roll stand housing (not shown) via suitable position adjustment means such as a screw jack mechanism or a tapered wedge mechanism (also not shown), and thereby the guide block Opposing surfaces 13a of 12a and 12b,
13b can be adjusted. Opposing surfaces 13a and 13b of guide blocks 12a and 12b are hourglass-shaped rolls lla.

It may be curved to correspond to the hole shape of 11b.

The mandrel 20 has a circular cross section, its outer diameter is the same as or slightly smaller than the inner diameter of the product tube with the circular cross section to be obtained, its length is longer than the length of the product tube, and its proximal end (Left side in Figure 1) is similar to a so-called bush bench pipe making apparatus, in which a universal joint or the like is connected to the ram head of a hydraulic press by a jig.

The forged tube manufacturing process using the tube punching apparatus having such a configuration is as follows in the case of two-pass machining.

First, the roll gap between the pair of drum-shaped rolls lla and llb is set to a predetermined value, specifically, in the case of two-pass processing, to a value that is the same as or slightly larger than the outer diameter of the product tube to be obtained, and The distance between the pair of guide blocks 12a and 12b is set to be equal to or slightly larger than the outer diameter of the bottomed tubular material 30 to be processed. After that, mandrel 2
The mandrel 20 is advanced to perform the first pass processing on the material 30 that has been fitted onto the outer surface of the material 30, and is formed into a tubular material whose opposing outer surfaces in the rolling direction are smooth, whose inner surface is approximately circular, and whose outer surface is irregularly shaped. . After forming, the mandrel 20 is moved back to pull the tubular material back to the entrance side of the roll stand 10, and the tubular material is rotated by 90 degrees around its axis by a tube rotating device (not shown) together with the mandrel 20.

During this rotation operation of the material, the roll gap and the space between the guide blocks 12a and 12b are respectively set in preparation for the second pass of processing. That is, the roll gap is set to substantially the same value as in the first pass, and the interval between the guide blocks is set to a size that is the same as or slightly larger than the roll gap in the first pass. After that, the mandrel 20 is advanced in the same way as the first pass to perform the second pass, and the inner surface is approximately circular and the outer surface is irregularly shaped, with the four sides of the outer surface smooth in the direction perpendicular to the rolling direction. Form into tubular material.

In the first and second pass processing, since the drum-shaped rolls lla and llb have concave peripheral surfaces, the contact length in the circumferential direction between the outer surface of the material 30 and the roll peripheral surface becomes long, and the drum-shaped rolls lla and llb have concave circumferential surfaces. Since the free surface portion of the outer surface of the material between the rolls 11a, 1 lb and the guide blocks 12a, 12b is limited, the inner surface sink of the material 30 is suppressed. In addition, the material 30 is sufficiently held in the circumferential direction when being rolled down by the hourglass rolls lla and Nlb, and the contact area with the mandrel 20 is expanded due to suppression of inner surface sinkage, which makes the rotation of the material 30 easier. thwarted. Note that the second
For the processing of the passes, the arrangement of the drum-shaped rolls lla and 1ib is 9.
Two roll stands 10 having a 0° phase difference are installed in series,
Processing of the first pass can be performed continuously by moving the mandrel 20 forward only once.

The tubular material obtained by the second pass processing is
With the mandrel 20 inserted, it is punched through a die having a perfect circular inner diameter that is the same as or slightly larger than the outer diameter of the product tube with a circular cross section to be obtained, and a product tube with a circular cross section on both the inner and outer surfaces is produced with light workability. Formation 1 Formed. This final forming process can be carried out consecutively to the second pass process by arranging a stand having a die or the like downstream of the roll stand 10. The inner surface sink marks that have occurred in the material 30 before the final molding process are slight and can be completely eliminated by a light final molding process.

Next, the results of implementing the present invention will be explained.

The groove bottom diameter is 540mm and the hole curvature radius is 280m+n, 3
Two types of 50 mm drum-shaped rolls were assembled into a roll stand, and nine baths were punched according to the schedule shown in Table 1. The guide plotter width is 150mm,
The opposing surfaces were curved surfaces with two types of curvature radii of 280 and 350 mm corresponding to the hole shapes of the drum-shaped roll. Also,
The material is 320C, and the outer diameter before processing is 280m.
The inner diameter was 185mm, the wall thickness was 47.5mm, and the heating temperature was 1200°C. The hole-shaped curvature radius of 280 in the drum-shaped roll corresponds to twice the outer surface radius of the material, and is 350 m.
m corresponds to 2°5 times.

2 The material was rotated 90 degrees after the odd number pass and before the even number pass, and 45 degrees after the even number pass and before the odd number pass, and then subjected to the next pass. The ninth pass is a punching process using a 220 mm hole die for the purpose of finishing it into a perfect circle.

For comparison, similar processing was performed using a flat roll instead of the drum-shaped roll.

Table 1 (Unit section) The cross-sectional shape of the material after 8 passes when using a flat roll is shown in FIG. 3(a), and the cross-sectional shape after 9 passes is shown in FIG. 3(b). Further, the cross-sectional shapes of each material after 8 passes and after 9 passes when a drum-shaped roll with a hole-shaped curvature radius of 280 mm is used are shown in FIGS. 4(a) and 4(b), respectively.

When using a flat roll, despite finishing with a perfect circular die in the 9th pass, there was an uneven thickness of 2 mm in depth due to internal sink marks in the area indicated by the arrow, and there was also a white mark on the external surface. There were also some bad hits in the indicated positions.

On the other hand, when a drum-shaped roll with a hole-shaped curvature radius of 28011I [11] was used, a good shape was obtained on both the inner and outer surfaces. Further, when a drum-shaped roll having a hole-shaped curvature radius of 350 mm was used, only a slight local thickness deviation of 0.5 mm in depth occurred.

【Effect of the invention〕

The pipe punching device of the present invention eliminates the inner surface sink marks that occur in the material.
It can be suppressed to the extent that it can be removed with a light finishing process, improving the quality of the product pipe.

Further, the material being processed can be effectively held in the circumferential direction by the drum-shaped roll, and the material can be prevented from sagging even when a sufficient rolling reduction is applied. Therefore, uneven thickness due to sagging and an increase in the number of man-hours due to its correction can be prevented, a sufficient degree of processing can be ensured, and the efficiency is significantly improved.

[Brief explanation of drawings]

Fig. 1 is a side view of a tube punching device showing an embodiment of the present invention, Fig. 2 is a front view thereof, Figs. Figures (a) and (b) are cross-sectional views of materials processed by the apparatus of the present invention, and FIG. 5 is a front view of the conventional apparatus. In the figure, 10: roll stand, lla, 11b: drum-shaped roll, 12a, 12b: guide plate 17, 20
: Mandrel, 30: Material. 5 6 3rd (Q) (b) Figure (CI) (b)

Claims (1)

[Claims] 1. A tube punching device for thinning a bottomed tube by inserting it into a stand using a mandrel, the stand having a rotating shaft extending in a direction orthogonal to the pass line across the pass line. A pair of drum-shaped rolls for rolling down are supported and arranged in opposition so that the rolling position can be adjusted, and a pair of guide locks are supported and arranged in opposition so that the interval between the drum-shaped rolls can be adjusted with a pass line between them. A pipe punching device comprising: