Wire rod rolling line

Details Wire rod rolling line Wire rod rolling line

2000-11-02

2002-06-18

Tolan, Ed (Department: 3725)

Metal deforming

By use of roller or roller-like tool-element

Plural roller-couples

C072S249000

Reexamination Certificate

active

06405573

ABSTRACT:

BACKGROUND OF THE INVENTION
This application is a 35 USC 371 of PCT/JP00/00814 filed Feb. 15, 2000.
1. Technical Field
The present invention relates to a wire rod rolling line in which a finishing mill group rear stage is composed of a combination of a plurality of 4-roll mills. In particular, stable operation can be carried out with pinpoint dimensional accuracy by installing 4-roll mills whose motor drive system is improved at the end of the finishing mill group final stage of the wire rod rolling line. Further, a manufacturing efficiency can be improved by simplifying pass schedules as well as a size free range can be expanded and an-equipment cost can be lowered.
2. Description of Related Art
FIG. 1A
shows an example of an ordinary wire rod rolling line using 2-roll mills and pass schedules. The wire rod rolling line is composed of a roughing mill group, an intermediate mill group and a finishing mill group,and each mill group has a plurality of mills installed in series. The disposition of the mills in the intermediate and subsequent mill groups is shown on the uppermost row of FIG.
1
A. Pass schedules are shown on the second and subsequent rows of
FIG. 1A
by means of the cross sections of raw materials and products and the roll cavities in respective stands. Note that the roll cavity means the shape of the roll pass of a mill. A billet
1
having a side of 150 mm and an angular cross-section passes through a not shown roughing mill group (first stand-sixth stand). Then, the billet
1
is continuously rolled finally to wire rods
41
-
49
having a predetermined product size (rod diameter) and a round cross-section by an intermediate mill group
2
composed of a seventh stand
21
—a tenth stand
24
and a finishing mill group
3
composed of an eleventh stand
31
—an eighteenth stand
38
. Note that the stands of odd numbers have vertical rolls assembled therein and the stands of even numbers have horizontal rolls assembled therein. Further, the product sizes are
41
: 9.0 mm,
42
: 9.3 mm,
43
: 9.5 mm,
44
: 9.75 mm,
45
: 10.0 mm,
46
: 10.2 mm,
47
: 10.3 mm,
48
: 10.5 mm and
49
: 11.0 mm.
FIG. 1A
individually shows pass schedules to obtain wire rods of these products sizes. Oval passes each having an oval roll cavity and round passes each having a round roll cavity are alternately repeated by the 2-roll mills of the respective seventh-eighteenth stands.
FIG. 1B
is a front elevational view showing the rolling state carried out by the oval pass. Numeral R
1
denotes an upper horizontal roll, numeral R
2
denotes a lower horizontal roll, and numeral
8
denotes a pass line. Further,
FIG. 1C
shows the rolling state carried out by a round pass. Numerals R
3
and R
4
denote right and left vertical rolls numeral
8
denotes a pass line.
All the cavities shown in
FIG. 1A
have a different size. That is, a dedicated cavity must be prepared for each product size. Thus, each time a product size is changed, the stands must be recombined by stopping a line once. In the case of
FIG. 1
, nine kinds of products sizes are obtained by preparing nine kinds of lines. To manufacture the nine kinds of the products, the line must be stopped nine times and 76 sets of stands to be recombined are necessary.
In contrast, there has been recently proposed a “size free rolling technology” capable of steplessly manufacturing products of different size with pinpoint dimensional accuracy by using rolls having the same cavity and changing the roll pass of the rolls.
That is, a wire rod rolling technology for installing two 4-roll mills in series with the reducing directions thereof dislocated by 45° as the final finishing rolling stands of a wire rod rolling line is disclosed in, for example, Japanese Examined Patent Publication No. 3-6841 and Japanese Unexamined Patent Publication No. 6-63601.
FIG. 2A
shows an example of a wire rod rolling line and pass schedules to which the free size rolling technology is applied. The disposition of the mills in the intermediate and subsequent mills in the wire rod rolling line on an uppermost row. The arrangements of the mills of an intermediate mill group
2
and a finishing mill group front stage
3
are similar to those shown in
FIG. 1. A
finishing mill group rear stage
5
is disposed further downstream of the finishing mill group front stage
3
. A finishing mill group is composed of a combination of the finishing mill group front stage
3
and the finishing mill group rear stage
5
. The finishing mill group rear stage
5
is composed of the 4-roll mills
51
and
52
of two stands which are installed with the reducing directions thereof dislocated by 45°.
FIG. 2B
is a front elevational view showing the rolling state carried out by the 4-roll mill
51
and
FIG. 2C
is a front elevational view showing the rolling state carried out by the 4-roll mill
52
, respectively. Numerals R
1
-R
4
denote rolling rolls and numeral
8
denotes a pass line. Two kinds of pass schedules having a different size free range are shown on the second row and the third row of
FIG. 2A
by means of roll cavities at the respective stands. A wire rod
61
whose product size is 9.0-10.0 mm can be size-free-rolled by the pass schedule of the second row. A wire rod
62
whose product size is 10.1-11.1 mm can be size-free-rolled by the pass schedule of the third row. Therefore, any optional product size can be obtained which includes the products of the nine sizes of the pass schedules of
FIG. 1A
when the size is within the range of 9.0-11.1 mm. Moreover, the number of stops of the line which is necessary to change a size is only twice. In addition, the number of stands to be recombined which is necessary to change the size is only 24 stands.
As described above, the range of product sizes which can be manufactured without replacing a cavity can be increased by assembling the two 4-roll mills, which are arranged as one set, to the finishing mill group. Therefore, a line stop time necessary to replace a cavity for the change of a size is shortened, whereby the operating ratio of the line can be increased.
In contrast, when a wire rod is rolled using conventional 2 rolls and 3 rolls, a dedicated cavity must be prepared for each size of wire rods. Therefore, the number of sizes which can be manufactured is limited as well as there is a limit in dimensional accuracy because the wire rod is deformed by the increase of the width thereof.
However, in the example of
FIG. 2
, each one set of a mill motor (hereinafter, simply referred to as a motor) is disposed to each of the two 4-roll mills used as the final pass and the two 4-roll mills are driven by the different motor, respectively. When the two 4-roll mills each provided with the motor are installed in series, the distance between the stands is restricted as a matter of course because the interference of motor spaces must be avoided. As a result, the following problems are arisen.
(1) The space where the two stands of the final finishing pass cannot help being increased. → Space saving and the reduction of an equipment cost are difficult.
(2) When the distance between the stands is long, a wire rod is naturally rotated between both the stands. The cross-section of a wire rod having passed through the upstream 4-roll mill is formed to a shape near to approximate square shape. A product having a round cross-section can be obtained by rolling the approximate square shaped material by the downstream 4-roll mill while dislocating the reducing direction of the wire rod by 45°. The rotation of the angular wire rod must be avoided between both the stands to maintain an accurate reducing direction. Accordingly, expensive guide rollers must be conventionally interposed between both the stands to maintain the attitude of the wire rod so that the angular cross-section thereof is not rotated. → It is difficult to reduce the equipment cost.
In contrast, when two 4-roll mills are driven by commonly using the one motor, the following problems are arisen.
(3) While the 4-roll mills can steplessly change a rolling size only b

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