Wire sizing rolling method

Details Wire sizing rolling method Wire sizing rolling method

2001-04-27

2002-09-03

Tolan, Ed (Department: 3725)

Metal deforming

By use of roller or roller-like tool-element

Included in roller-cluster

C072S227000, C072S235000, C072S250000

Reexamination Certificate

active

06442989

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a method of sizing rolling a wire by a 4-roll rolling mill.
BACKGROUND ART
A conventional example of a sizing rolling method using a 4-roll rolling mill (rolling method of manufacturing a bar and wire having a different diameter using the same rolling rolls and changing a gap therebetween) is disclosed in, for example, Japanese Examined Patent Application Publication No. 3-6481.
In this method, two sets of 4-roll rolling mills, which incline a rolling direction by 45° each other, are installed in series along a rolling line. Each of the rolling rolls used here includes a groove formed on the outer circumferential surface thereof and the groove is composed of an arc-shaped perfect circle forming section and a suitable escape section. Further, the publication describes it is preferable that the central angle of the perfect circle forming section of the groove be as small as possible and that an amount of escape (the angle between the escape section and the perfect circle forming section) be as large as possible in the range in which no flaw is caused in order to increase a size range (hereinafter, referred to as “size free range”) of products which can be sizing rolled by the same rolls within an allowable range of dimensional error.
In contrast, the applicant proposed a sizing rolling mill capable of increasing the size free range in consideration of bitten-out and falling-down which are a problem in actual rolling carried out by 4 rolls while suppressing the occurrence of the problem (refer to Japanese Unexamined Patent Application Publication No. 9-225502). In the proposal, at least three sets of 4-roll rolling mills are installed and the central angles of the perfect circle forming sections of the grooves of the respective rolling rolls are set to at least 15° in a first path, to at least 45° in a final path and to at least 30° in an intermediate path (second path).
“Bitten-out” used here means that a workpiece
7
is protruded form the space (caliber) surrounded by the outer circumferential surfaces of 4 rolling rolls
50
as shown in FIG.
5
. When the center of the workpiece
7
does not pass through the center of the caliber in rolling, the bitten-out is liable to be arisen. When an amount of bitten-out is large, a bitten-out portion
75
is folded in the caliber in the next path and made to a folded flaw.
Further, “falling-down” means that the workpiece
7
is rotated between paths as shown in
FIG. 6. A
degree of falling-down is represented by the angle (falling-down angle) &ggr; between the line L
1
showing the central position of one of the rolling rolls
50
in the width direction thereof and the line L
2
showing the position of the workpiece
7
which is to be located at the central position of the rolling roll
50
in the width direction thereof in the path. When an amount of falling-down is large, a faulty product is made due to a surface flaw and a bent flaw.
In the sizing rolling mill disclosed in Japanese Unexamined Patent Application Publication No. 9-225502, however, it has been found that there is a tendency that is liable to be arisen in a second path particularly in a wire having a small diameter (for example, a wire having a diameter of 7 mm or less) and there is a possibility that a bent flaw is caused in a third path accordingly.
An object of the present invention is to obtain an excellent surface property in a sizing rolling method which is carried out by at least 3 sets of 4-roll rolling mills installed in series in a wire particularly having a small diameter.
To solve the above problem, an invention according to claim
1
provides a wire sizing rolling method which is characterized by comprising the steps of installing at least 3 sets of 4-roll rolling mills in series with each rolling mill having 2 pairs of 4 rolling rolls each having a groove formed on an outer circumferential surface and composed of an arc-shaped perfect circle forming section and escape sections and setting central angles of the perfect circle forming sections of the rolling rolls to less than 15° in the first path of final three paths, to at least 30° in the second path thereof, and to at least 45° in the third path thereof; and installing a roller guide on the inlet side of the second path and introducing a workpiece to the second path while holding and guiding the workpiece by the guide rollers of the roller guide such that the surface of the workpiece which was not rolled in the first path is located at the central portions of the guide rollers.
DISCLOSURE OF INVENTION
According to this method, since the central angle of the perfect circle forming section of each rolling roll in the first path of the final three paths is set to less than 15° as well as the free surface of the workpiece is held and guided by the guide rollers of the roller guide installed on the inlet side of the second path, the holding/guiding capability of the guide rollers of the roller guide for the workpiece can be improved as compared with the case in which the central angle of the perfect circle forming section of each rolling roll in the first path is set to at least 15°, whereby it is made difficult for falling-down to occur in the second path. Further, in addition to the above, since the central angle of the perfect circle forming section of each rolling roll is set to at least 30° in the second path of the final three paths and to at least 45 in the final path, an excellent surface property can be obtained in a resulting product.
An invention of claim
2
is characterized in the wire sizing rolling method according to claim
1
such that the escape section of each rolling roll in the first path is formed by straight lines, the straight lines act as tangential lines to both the ends of the arc forming the perfect circle forming section, a V-shaped groove for holding and guiding the workpiece is formed on the outer circumferential surface of each guide roller of the roller guide installed on the inlet side of the second path, and an angle of the V-shaped groove is set similar to the angle between the straight lines forming an escape section between the adjacent rolling rolls in the first path.
An invention according to claim
3
provides a wire sizing rolling method of sizing rolling a wire by a 4-roll rolling mill each having two pairs of 4 rolling rolls, the method being characterized by comprising the steps of installing at least 3 sets of the 4-roll rolling mills in series, using flat rolls as rolling rolls each having an outer circumferential surface on which no groove is formed in the first path of final three paths, and using rolls as rolling rolls each having an outer circumferential surface having a groove composed of an arc-shaped perfect circle forming section and escape sections in the second and subsequent paths thereof with the central angles of the perfect circle forming sections of the respective rolling rolls set to at least 30° in the second path and to at least 45° in the third path; and installing a roller guide on the inlet side of the second path and introducing a workpiece to the second path while holding and guiding the workpiece by the guide rollers of the roller guide such that the surface of the workpiece which was not rolled in the first path is located at the central portions of the guide rollers.
In the 4-roll rolling mill, since one rolling roll receives the cross section of the workpiece in the range of 90°, when an arc-shaped groove is formed on the outer circumferential surface of each rolling roll, the central angle of the arc is 90° or less. Then, when the central angle of the arc is 0°, the rolling roll is arranged as the flat roll whose outer circumferential surface has no groove. Accordingly, the method of claim
3
corresponds to the case in which the central angle (&thgr;
1
) of the perfect circle forming section of each rolling roll in the first path is set to 0°.
That is, in the method of claim
1
, since it is set forth as a premise that the grove of each rolling roll is composed of a perfect circle form

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