U.S. patent application number 16/082334 was filed with the patent office on 2019-01-24 for method for producing h-shaped steel.
This patent application is currently assigned to NIPPON STEEL & SUMITOMO METAL CORPORATION. The applicant listed for this patent is NIPPON STEEL & SUMITOMO METAL CORPORATION. Invention is credited to Ryo HASHIMOTO, Hiroshi YAMASHITA.
Application Number | 20190022719 16/082334 |
Document ID | / |
Family ID | 60160496 |
Filed Date | 2019-01-24 |
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United States Patent
Application |
20190022719 |
Kind Code |
A1 |
YAMASHITA; Hiroshi ; et
al. |
January 24, 2019 |
METHOD FOR PRODUCING H-SHAPED STEEL
Abstract
To efficiently and stably produce an H-shaped steel product with
a flange width larger than a conventional flange width by creating
deep splits on end surfaces of a material such as a slab using
projections in acute-angle tip shapes and sequentially bending
flange portions formed by the splits to thereby suppress occurrence
of shape defects in a material to be rolled and reduce growth of a
crop portion. A first caliber and a second caliber of a plurality
of calibers are formed with projections configured to create splits
vertically with respect to a width direction of the material to be
rolled to form divided parts at end portions of the material to be
rolled; a third caliber and subsequent calibers excluding a final
caliber of the plurality of calibers are formed with projections
configured to come into contact with the splits to sequentially
bend the divided parts formed; and in at least one pass or more of
rolling and shaping in the plurality of calibers, the rolling and
shaping is performed with a rolling roll gap for a predetermined
section at a rear end portion in a rolling longitudinal direction
of the material to be rolled expanded as compared with a rolling
roll gap for other than the predetermined section.
Inventors: |
YAMASHITA; Hiroshi; (Tokyo,
JP) ; HASHIMOTO; Ryo; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NIPPON STEEL & SUMITOMO METAL CORPORATION |
Tokyo |
|
JP |
|
|
Assignee: |
NIPPON STEEL & SUMITOMO METAL
CORPORATION
Tokyo
JP
|
Family ID: |
60160496 |
Appl. No.: |
16/082334 |
Filed: |
April 24, 2017 |
PCT Filed: |
April 24, 2017 |
PCT NO: |
PCT/JP2017/016180 |
371 Date: |
September 5, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B21B 1/088 20130101;
B21B 1/12 20130101 |
International
Class: |
B21B 1/088 20060101
B21B001/088 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 28, 2016 |
JP |
2016-090165 |
Claims
1-11. (canceled)
12. A method for producing H-shaped steel, the method comprising: a
rough rolling step; an intermediate rolling step; and a finish
rolling step, wherein: a rolling mill that performs the rough
rolling step is engraved with a plurality of calibers configured to
roll and shape a material to be rolled, the number of the plurality
of calibers being five or more; shaping in one or a plurality of
passes is performed on the material to be rolled in the plurality
of calibers; a first caliber and a second caliber of the plurality
of calibers are formed with projections configured to create splits
vertically with respect to a width direction of the material to be
rolled to form divided parts at end portions of the material to be
rolled; a third caliber and subsequent calibers excluding a final
caliber of the plurality of calibers are formed with projections
configured to come into contact with the splits to sequentially
bend the divided parts formed; the final caliber of the plurality
of calibers is a flat shaping caliber; in the second caliber and
subsequent calibers excluding the final caliber of the plurality of
calibers, reduction is performed in a state where end surfaces of
the material to be rolled are in contact with peripheral surfaces
of the calibers in shaping in at least one pass or more; and in at
least one pass or more of rolling and shaping in the plurality of
calibers, the rolling and shaping is performed with a rolling roll
gap for a predetermined section at a rear end portion in a rolling
longitudinal direction of the material to be rolled expanded as
compared with a rolling roll gap for other than the predetermined
section.
13. The method for producing the H-shaped steel according to claim
12, wherein a tip portion angle of the projections formed in the
first caliber and the second caliber is 25.degree. or more and
40.degree. or less.
14. The method for producing the H-shaped steel according to claim
12, wherein in all passes of rolling and shaping in the first
caliber of the plurality of calibers, the rolling and shaping is
performed with the rolling roll gap for the predetermined section
at the rear end portion in the rolling longitudinal direction of
the material to be rolled expanded as compared with the rolling
roll gap for the other than the predetermined section.
15. The method for producing the H-shaped steel according to claim
12, wherein in all passes of rolling and shaping in at least the
third caliber and a fourth caliber of the plurality of calibers,
the rolling and shaping is performed with the rolling roll gap for
the predetermined section at the rear end portion in the rolling
longitudinal direction of the material to be rolled expanded as
compared with the rolling roll gap for the other than the
predetermined section.
16. The method for producing the H-shaped steel according to claim
12, wherein in a pass where reduction is performed with the end
surfaces of the material to be rolled are in contact with
peripheral surface of the second caliber in the rolling and shaping
in the second caliber of the plurality of calibers, the rolling and
shaping is performed with the rolling roll gap for the
predetermined section at the rear end portion in the rolling
longitudinal direction of the material to be rolled expanded as
compared with the rolling roll gap for the other than the
predetermined section.
17. The method for producing the H-shaped steel according to claim
12, wherein in all passes of rolling and shaping in the final
caliber of the plurality of calibers, the rolling and shaping is
performed with the rolling roll gap for the predetermined section
at the rear end portion in the rolling longitudinal direction of
the material to be rolled expanded as compared with the rolling
roll gap for the other than the predetermined section.
18. The method for producing the H-shaped steel according to claim
12, wherein in all passes of rolling and shaping in all calibers
excluding the first caliber and the final caliber of the plurality
of calibers, the rolling and shaping is performed with the rolling
roll gap for the predetermined section at the rear end portion in
the rolling longitudinal direction of the material to be rolled
expanded as compared with the rolling roll gap for the other than
the predetermined section.
19. The method for producing the H-shaped steel according to claim
12, further comprising: an intermediate crop cutting step performed
only on a web portion of the material to be rolled after the rough
rolling step and at a preceding stage of the intermediate rolling
step.
20. The method for producing the H-shaped steel according to claim
12, wherein a crop-shaped portion formed at an end portion in a
longitudinal direction of the material to be rolled is removed only
after completion of all of the rough rolling step, the intermediate
rolling step, and the finish rolling step.
21. The method for producing the H-shaped steel according to claim
12, wherein the rolling mill that performs the rough rolling step
is provided with a reduction mechanism configured to change a roll
gap of a caliber roll of the rolling mill.
22. An H-shaped steel product produced by the method for producing
the H-shaped steel according to claim 12, wherein a web height is
1000 mm or more, or a flange width is 400 mm or more.
23. The method for producing the H-shaped steel according to claim
13, wherein in a pass where reduction is performed with the end
surfaces of the material to be rolled are in contact with
peripheral surface of the second caliber in the rolling and shaping
in the second caliber of the plurality of calibers, the rolling and
shaping is performed with the rolling roll gap for the
predetermined section at the rear end portion in the rolling
longitudinal direction of the material to be rolled expanded as
compared with the rolling roll gap for the other than the
predetermined section.
24. The method for producing the H-shaped steel according to claim
13, further comprising: an intermediate crop cutting step performed
only on a web portion of the material to be rolled after the rough
rolling step and at a preceding stage of the intermediate rolling
step.
25. The method for producing the H-shaped steel according to claim
13, wherein a crop-shaped portion formed at an end portion in a
longitudinal direction of the material to be rolled is removed only
after completion of all of the rough rolling step, the intermediate
rolling step, and the finish rolling step.
26. The method for producing the H-shaped steel according to claim
23, further comprising: an intermediate crop cutting step performed
only on a web portion of the material to be rolled after the rough
rolling step and at a preceding stage of the intermediate rolling
step.
27. The method for producing the H-shaped steel according to claim
23, wherein a crop-shaped portion formed at an end portion in a
longitudinal direction of the material to be rolled is removed only
after completion of all of the rough rolling step, the intermediate
rolling step, and the finish rolling step.
Description
TECHNICAL FIELD
Cross-Reference to Related Applications
[0001] This application is based upon and claims the benefit of
priority of the prior Japanese Patent Application No. 2016-090165,
filed in Japan on Apr. 28, 2016, the entire contents of which are
incorporated herein by reference.
[0002] The present invention relates to a method for producing
H-shaped steel using a slab or the like having, for example, a
rectangular cross section as a material, and an H-shaped steel
product.
BACKGROUND ART
[0003] In the case of producing H-shaped steel, a material such as
a slab or a bloom extracted from a heating furnace is shaped into a
raw blank (a material to be rolled in a so-called dog-bone shape)
by a rough rolling mill. Thicknesses of a web and flanges of the
raw blank are subjected to reduction by an intermediate universal
rolling mill, and flanges of a material to be rolled are subjected
to width reduction and forging and shaping of end surfaces by an
edger rolling mill close to the intermediate universal rolling
mill. Then, an H-shaped steel product is shaped by a finishing
universal rolling mill.
[0004] There is a known technique in which in shaping a raw blank
in a so-called dog-bone shape from a slab material having a
rectangular cross section in such a method for producing H-shaped
steel, splits are created on slab end surfaces in a first caliber
at a rough rolling step, the splits are then widened or made deeper
and edging rolling is performed in second and subsequent calibers,
and the splits on the slab end surfaces are erased in subsequent
calibers (refer to, for example, Patent Document 1).
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0005] [Patent Document 1] Japanese Laid-open Patent Publication
No. H7-88501
[0006] In recent years, with an increase in size of structures and
the like, production of large-size H-shaped steel products is
desired. In particular, a product having flanges, which greatly
contribute to strength and rigidity of H-shaped steel, wider than
conventional flanges is desired. To produce the H-shaped steel
product with widened flanges, it is necessary to shape a material
to be rolled with a flange width larger than a conventional flange
width from the shaping at the rough rolling step.
[0007] However, for example, in the technique disclosed in Patent
Document 1, there is a limit in widening of flanges in the method
of creating splits on end surfaces of a material such as a slab
(slab end surfaces), edging the end surfaces, and performing rough
rolling utilizing the spread of width. In other words, in order to
widen flanges in conventional rough rolling method, techniques such
as wedge designing (designing of a split angle), reduction
adjustment, and lubrication adjustment are used to improve the
spread of width. However, it is known that since none of the
methods greatly contribute to a flange width, the rate of spread of
width, which represents the rate of a spread amount of the flange
width to an edging amount, is approximately 0.8 even under a
condition that the efficiency at the initial stage of edging is the
highest, decreases as the spread amount of the flange width
increases under a condition that edging is repeated in the same
caliber, and finally becomes approximately 0.5. It is also
conceivable to increase the size of the material such as a slab
itself and increase the edging amount, but there are circumstances
where product flanges are not sufficiently widened because there
are device limits in facility scale and reduction amount of a rough
rolling mill.
[0008] Besides, it is generally known that in the production of
H-shaped steel, an unrequired portion called a crop portion is
generated at a tip rear end portion in a longitudinal direction of
the material to be rolled. On such a crop portion, intermediate
crop cutting is performed in the middle of a series of rolling
steps to thereby avoid a trouble such as clogging of the crop
portion in the rolling machine.
[0009] In particular, in production of a large-size H-shaped steel
product, the weight per unit length of the material to be rolled is
large and the elongation length of the product at rolling is small,
and therefore the proportion of the crop portion in the whole
length is large, and growth of the crop portion is likely to lead
to a decrease in yield. Accordingly, the actual fact is that the
growth of the crop portion is required to be decreased as much as
possible, in particular, in producing the large-size H-shaped steel
product.
[0010] In view of the above circumstances, an object of the present
invention is to provide a technique for producing H-shaped steel,
capable of efficiently and stably producing an H-shaped steel
product with a flange width larger than a conventional flange width
by creating deep splits on end surfaces of a material such as a
slab using projections in acute-angle tip shapes and sequentially
bending flange portions formed by the splits, at a rough rolling
step using calibers in producing H-shaped steel to thereby suppress
occurrence of shape defects in a material to be rolled and reduce
growth of a crop portion which has been conventionally a large loss
in yield, in particular, in producing large-size H-shaped
steel.
Means for Solving the Problems
[0011] To achieve the above object, according to the present
invention, there is provided a method for producing H-shaped steel,
the method including: a rough rolling step; an intermediate rolling
step; and a finish rolling step, wherein: a rolling mill that
performs the rough rolling step is engraved with a plurality of
calibers configured to roll and shape a material to be rolled, the
number of the plurality of calibers being five or more; shaping in
one or a plurality of passes is performed on the material to be
rolled in the plurality of calibers; a first caliber and a second
caliber of the plurality of calibers are formed with projections
configured to create splits vertically with respect to a width
direction of the material to be rolled to form divided parts at end
portions of the material to be rolled; a third caliber and
subsequent calibers excluding a final caliber of the plurality of
calibers are formed with projections configured to come into
contact with the splits to sequentially bend the divided parts
formed; the final caliber of the plurality of calibers is a flat
shaping caliber; in the second caliber and subsequent calibers
excluding the final caliber of the plurality of calibers, reduction
is performed in a state where end surfaces of the material to be
rolled are in contact with peripheral surfaces of the calibers in
shaping in at least one pass or more; and in at least one pass or
more of rolling and shaping in the plurality of calibers, the
rolling and shaping is performed with a rolling roll gap for a
predetermined section at a rear end portion in a rolling
longitudinal direction of the material to be rolled expanded as
compared with a rolling roll gap for other than the predetermined
section.
[0012] A tip portion angle of the projections formed in the first
caliber and the second caliber may be 25.degree. or more and
40.degree. or less.
[0013] In all passes of rolling and shaping in the first caliber of
the plurality of calibers, the rolling and shaping may be performed
with the rolling roll gap for the predetermined section at the rear
end portion in the rolling longitudinal direction of the material
to be rolled expanded as compared with the rolling roll gap for the
other than the predetermined section.
[0014] In all passes of rolling and shaping in at least the third
caliber and a fourth caliber of the plurality of calibers, the
rolling and shaping may be performed with the rolling roll gap for
the predetermined section at the rear end portion in the rolling
longitudinal direction of the material to be rolled expanded as
compared with the rolling roll gap for the other than the
predetermined section.
[0015] In a pass where reduction is performed with the end surfaces
of the material to be rolled are in contact with peripheral surface
of the second caliber in the rolling and shaping in the second
caliber of the plurality of calibers, the rolling and shaping may
be performed with the rolling roll gap for the predetermined
section at the rear end portion in the rolling longitudinal
direction of the material to be rolled expanded as compared with
the rolling roll gap for the other than the predetermined
section.
[0016] In all passes of rolling and shaping in the final caliber of
the plurality of calibers, the rolling and shaping may be performed
with the rolling roll gap for the predetermined section at the rear
end portion in the rolling longitudinal direction of the material
to be rolled expanded as compared with the rolling roll gap for the
other than the predetermined section.
[0017] In all passes of rolling and shaping in all calibers
excluding the first caliber and the final caliber of the plurality
of calibers, the rolling and shaping may be performed with the
rolling roll gap for the predetermined section at the rear end
portion in the rolling longitudinal direction of the material to be
rolled expanded as compared with the rolling roll gap for the other
than the predetermined section.
[0018] An intermediate crop cutting step may be performed only on a
web portion of the material to be rolled after the rough rolling
step and at a preceding stage of the intermediate rolling step.
[0019] A crop-shaped portion formed at an end portion in a
longitudinal direction of the material to be rolled may be removed
only after completion of all of the rough rolling step, the
intermediate rolling step, and the finish rolling step.
[0020] The rolling mill that performs the rough rolling step may be
provided with a reduction mechanism configured to change a roll gap
of a caliber roll of the rolling mill.
[0021] According to the present invention from another viewpoint,
there is provided an H-shaped steel product produced by the
above-described method for producing the H-shaped steel according,
wherein a web height is 1000 mm or more, or a flange width is 400
mm or more.
Effect of the Invention
[0022] According to the present invention, it becomes possible to
efficiently and stably produce an H-shaped steel product with a
flange width larger than a conventional flange width by creating
deep splits on end surfaces of a material such as a slab using
projections in acute-angle tip shapes and sequentially bending
flange portions formed by the splits at a rough rolling step using
calibers in producing H-shaped steel to thereby suppress occurrence
of shape defects in a material to be rolled and reduce growth of a
crop portion which has been conventionally a large loss in yield,
in particular, in producing large-size H-shaped steel.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a schematic explanatory view about a production
line for H-shaped steel.
[0024] FIG. 2 is a schematic explanatory view of a first
caliber.
[0025] FIG. 3 is a schematic explanatory view of a second
caliber.
[0026] FIG. 4 is a schematic explanatory view of a third
caliber.
[0027] FIG. 5 is a schematic explanatory view of a fourth
caliber.
[0028] FIG. 6 is a schematic explanatory view of a fifth caliber
(flat shaping caliber).
[0029] FIG. 7 is a schematic explanatory view regarding the
conventional H-shaped steel production technique.
[0030] FIG. 8 is a schematic explanatory view in the case of
applying AGC rough rolling to rolling and shaping in a first
caliber in a method for producing H-shaped steel according to this
embodiment.
[0031] FIG. 9 is a schematic explanatory view in the case of
applying AGC rough rolling to rolling and shaping in the fifth
caliber in the method for producing H-shaped steel according to
this embodiment.
[0032] FIG. 10 is a graph illustrating the verification results of
Reference Example 1 and Reference Example 2.
[0033] FIG. 11 is an explanatory view for comparing the shape of a
flange portion after edging rolling in the conventional production
method and the shape of a flange portion shaped in the first
caliber to the fourth caliber according to this embodiment.
[0034] FIG. 12 is a graph illustrating the measurement result of a
reference example.
[0035] FIG. 13 is a graph illustrating the measurement result of an
example.
BEST MODE FOR CARRYING OUT THE INVENTION
[0036] Hereinafter, an embodiment of the present invention will be
explained referring to the drawings. Note that in this description
and the drawings, components having substantially the same
functional configurations are denoted by the same numerals to omit
duplicated explanation.
[0037] FIG. 1 is an explanatory view about a production line T for
H-shaped steel including a rolling facility 1 according to this
embodiment. As illustrated in FIG. 1, in the production line T, a
heating furnace 2, a sizing mill 3, a rough rolling mill 4, an
intermediate universal rolling mill 5, and a finishing universal
rolling mill 8 are arranged in order from the upstream side.
Further, an edger rolling mill 9 is provided close to the
intermediate universal rolling mill 5. Note that, in the following,
a steel material in the production line T is sometimes collectively
described as a "material to be rolled A" for explanation and its
shape is sometimes illustrated using broken lines, oblique lines
and the like in the drawings.
[0038] As illustrated in FIG. 1, in the production line T, a
rectangular cross-section material (a material to be rolled A
described later) such as a slab 11 or the like extracted from the
heating furnace 2 is subjected to rough rolling in the sizing mill
3 and the rough rolling mill 4. Then, the rectangular cross-section
material is subjected to intermediate rolling in the intermediate
universal rolling mill 5. During the intermediate rolling,
reduction is performed on flange tip portions (flange corresponding
portions 12) of the material to be rolled by the edger rolling mill
9 as necessary. In a normal case, edging calibers and so-called
flat shaping calibers for decreasing the thickness of a web portion
to form the shapes of flange portions are engraved on rolls of the
sizing mill 3 and the rough rolling mill 4, and an H-shaped raw
blank 13 is shaped by reverse rolling in a plurality of passes
through those calibers, and the H-shaped raw blank 13 is subjected
to application of reduction in a plurality of passes using a
rolling mill train composed of two rolling mills such as the
intermediate universal rolling mill 5 and the edger rolling mill 9,
whereby an intermediate material 14 is shaped. The intermediate
material 14 is subjected to finish rolling into a product shape in
the finishing universal rolling mill 8, whereby an H-shaped steel
product 16 is produced.
[0039] Here, a slab thickness T of the slab 11 extracted from the
heating furnace 2 is in a range of, for example, 240 mm or more and
310 mm or less. This is a slab dimension used in producing a
standard H-shaped steel product.
[0040] Next, caliber configurations and caliber shapes engraved on
the sizing mill 3 and the rough rolling mill 4 illustrated in FIG.
1 will be explained below referring to the drawings. FIG. 2 to FIG.
6 are schematic explanatory views about calibers engraved on the
sizing mill 3 and the rough rolling mill 4 which perform a rough
rolling step. All of the first caliber to the fourth caliber
explained here may be engraved, for example, on the sizing mill 3,
or five calibers such as the first caliber to a fifth caliber may
be engraved separately on the sizing mill 3 and the rough rolling
mill 4. In other words, the first caliber to the fourth caliber may
be engraved across both the sizing mill 3 and the rough rolling
mill 4, or may be engraved on one of the rolling mills. In the
rough rolling step in production of standard H-shaped steel,
shaping in one or a plurality of passes is performed in each of the
calibers.
[0041] Besides, a case where there are five calibers to be engraved
will be described as an example in this embodiment, and the number
of the calibers does not always need to be five, but the number of
the calibers may be plural such as five or more. In short, the
caliber configuration only needs to be suitable for shaping the
H-shaped raw blank 13. Note that in FIG. 2 to FIG. 6, a schematic
final pass shape of the material to be rolled A in shaping in each
caliber is illustrated by broken lines.
[0042] FIG. 2 is a schematic explanatory view of a first caliber
K1. The first caliber K1 is engraved on an upper caliber roll 20
and a lower caliber roll 21 which are a pair of horizontal rolls,
and the material to be rolled A is subjected to reduction and
shaping in a roll gap between the upper caliber roll 20 and the
lower caliber roll 21. Further, a peripheral surface of the upper
caliber roll 20 (namely, an upper surface of the first caliber K1)
is formed with a projection 25 protruding toward the inside of the
caliber. Further, a peripheral surface of the lower caliber roll 21
(namely, a bottom surface of the first caliber K1) is formed with a
projection 26 protruding toward the inside of the caliber. These
projections 25, 26 have tapered shapes, and dimensions such as a
protrusion length of the projection 25 and the projection 26 are
configured to be equal to each other. A height (protrusion length)
of the projections 25, 26 is h1 and a tip portion angle thereof is
.theta. 1a.
[0043] In the first caliber K1, the projections 25, 26 are pressed
against upper and lower end portions (slab end surfaces) of the
material to be rolled A and thereby form splits 28, 29. Here, a tip
portion angle (also called a wedge angle) .theta. 1a of the
projections 25, 26 is desirably, for example, 25.degree. or more
and 40.degree. or less.
[0044] Here, a caliber width of the first caliber K1 is preferably
substantially equal to the thickness of the material to be rolled A
(namely, a slab thickness). Specifically, when the width of the
caliber at the tip portions of the projections 25, 26 formed in the
first caliber K1 is set to be the same as the slab thickness, a
right-left centering property of the material to be rolled A is
suitably secured. Further, it is preferable that such a
configuration of the caliber dimension brings the projections 25,
26 and part of caliber side surfaces (side walls) into contact with
the material to be rolled A at upper and lower end portions (slab
end surfaces) of the material to be rolled A during shaping in the
first caliber K1 as illustrated in FIG. 2 so as to prevent active
reduction at the upper surface and the bottom surface of the first
caliber K1 from being performed on the slab upper and lower end
portions divided into four elements (parts) by the splits 28, 29.
This is because the reduction by the upper surface and the bottom
surface of the caliber causes elongation of the material to be
rolled A in the longitudinal direction to decrease the generation
efficiency of the flanges (later-described flange portions 80). In
other words, in the first caliber K1, a reduction amount at the
projections 25, 26 (reduction amount at wedge tips) at the time
when the projections 25, 26 are pressed against the upper and lower
end portions (slab end surfaces) of the material to be rolled A to
form the splits 28, 29 is made sufficiently larger than a reduction
amount at the slab upper and lower end portions (reduction amount
at slab end surfaces) and thereby forms the splits 28, 29.
[0045] FIG. 3 is a schematic explanatory view of a second caliber
K2. The second caliber K2 is engraved on an upper caliber roll 30
and a lower caliber roll 31 which are a pair of horizontal rolls. A
peripheral surface of the upper caliber roll 30 (namely, an upper
surface of the second caliber K2) is formed with a projection 35
protruding toward the inside of the caliber. Further, a peripheral
surface of the lower caliber roll 31 (namely, a bottom surface of
the second caliber K2) is formed with a projection 36 protruding
toward the inside of the caliber. These projections 35, 36 have
tapered shapes, and dimensions such as a protrusion length of the
projection 35 and the projection 36 are configured to be equal to
each other. A tip portion angle of the projections 35, 36 is
desirably a wedge angle .theta. 1b of 25.degree. or more and
40.degree. or less.
[0046] Note that the wedge angle .theta. 1a of the first caliber K1
is preferably the same angle as the wedge angle .theta. 1b of the
second caliber K2 at a subsequent stage in order to ensure the
thickness of the tip end portions of the flange corresponding
portions, enhance inductive property, and secure stability of
tolling.
[0047] A height (protrusion length) h2 of the projections 35, 36 is
configured to be larger than the height h1 of the projections 25,
26 of the first caliber K1 so as to be h2>h1. Further, the tip
portion angle of the projections 35, 36 is preferably the same as
the tip portion angle of the projections 25, 26 in the first
caliber K1 in terms of rolling dimension accuracy. In a roll gap
between the upper caliber roll 30 and the lower caliber roll 31,
the material to be rolled A passed through the first caliber K1 is
further shaped.
[0048] Here, the height h2 of the projections 35, 36 formed in the
second caliber K2 is larger than the height h1 of the projections
25, 26 formed in the first caliber K1, and an intrusion length into
the upper and lower end portions (slab end surfaces) of the
material to be rolled A is also similarly larger in the second
caliber K2. An intrusion depth into the material to be rolled A of
the projections 35, 36 in the second caliber K2 is the same as the
height h2 of the projections 35, 36. In other words, an intrusion
depth h1' into the material to be rolled A of the projections 25,
26 in the first caliber K1 and the intrusion depth h2 into the
material to be rolled A of the projections 35, 36 in the second
caliber K2 satisfy a relation of h1'<h2.
[0049] Further, angles .theta. f formed between caliber upper
surfaces 30a, 30b and caliber bottom surfaces 31a, 31b facing the
upper and lower end portions (slab end surfaces) of the material to
be rolled A, and, inclined surfaces of the projections 35, 36, are
configured to be about 90.degree. (almost right angle) at all of
four locations illustrated in FIG. 3.
[0050] Since the intrusion length of the projections at the time
when pressed against the upper and lower end portions (slab end
surfaces) of the material to be rolled A is large as illustrated in
FIG. 3, shaping is performed to make the splits 28, 29 formed in
the first caliber K1 deeper in the second caliber K2 to thereby
form the splits 38, 39. Note that based on the dimensions of the
splits 38, 39 formed here, a flange half-width at the end of a
flange shaping step in the rough rolling step is decided.
[0051] Further, the shaping in the second caliber K2 is performed
by multi-pass, and in the multi-pass shaping, shaping is performed
to bring the upper and lower end portions (slab end surfaces) of
the material to be rolled A into contact with the caliber upper
surfaces 30a, 30b and the caliber bottom surfaces 31a, 31b facing
them in a final pass. This is because if the upper and lower end
portions of the material to be rolled A are made to be out of
contact with the inside of the caliber in all passes in the second
caliber K2, a shape defect such as flange corresponding portions
(parts corresponding to later-described flange portions 80) being
shaped to be laterally asymmetrical possibly occurs, bringing about
a problem in terms of a material passing property.
[0052] FIG. 4 is a schematic explanatory view of a third caliber
K3. The third caliber K3 is engraved on an upper caliber roll 40
and a lower caliber roll 41 which are a pair of horizontal rolls. A
peripheral surface of the upper caliber roll 40 (namely, an upper
surface of the third caliber K3) is formed with a projection 45
protruding toward the inside of the caliber. Further, a peripheral
surface of the lower caliber roll 41 (namely, a bottom surface of
the third caliber K3) is formed with a projection 46 protruding
toward the inside of the caliber. These projections 45, 46 have
tapered shapes, and dimensions such as a protrusion length of the
projection 45 and the projection 46 are configured to be equal to
each other.
[0053] A tip portion angle .theta. 2 of the projections 45, 46 is
configured to be larger than the aforementioned angle .theta. 1b,
and an intrusion depth h3 into the material to be rolled A of the
projections 45, 46 is smaller than the intrusion depth h2 of the
above projections 35, 36 (namely, h3<h2). This angle .theta. 2
is preferably 70.degree. or more and 110.degree. or less.
[0054] Further, angles .theta. f formed between caliber upper
surfaces 40a, 40b and caliber bottom surfaces 41a, 41b facing the
upper and lower end portions (slab end surfaces) of the material to
be rolled A, and, inclined surfaces of the projections 45, 46, are
configured to be about 90.degree. (almost right angle) at all of
four locations illustrated in FIG. 4.
[0055] As illustrated in FIG. 4, in the third caliber K3, the
splits 38, 39 formed in the second caliber K2 at the upper and
lower end portions (slab end surfaces) of the material to be rolled
A passed through the second caliber K2 are pressed against the
projections 45, 46 and thereby become splits 48, 49. Specifically,
in a final pass in shaping in the third caliber K3, a deepest
portion angle (hereinafter, also called a split angle) of the
splits 48, 49 becomes .theta. 2. In other words, shaping is
performed so that divided parts (the parts corresponding to the
later-described flange portions 80) shaped along with the formation
of the splits 38, 39 in the second caliber K2 are bent outward.
[0056] Besides, the shaping in the third caliber K3 illustrated in
FIG. 4 is performed by at least one pass or more, and the at least
one pass or more are performed with the upper and lower end
portions (slab end surfaces) of the material to be rolled A in
contact with the inside of the caliber (upper surface and the
bottom surface of the third caliber K3). In the state where the
upper and lower end portions (slab end surfaces) of the material to
be rolled A are in contact with the inside of the caliber, it is
preferable to perform light reduction on the end portions.
[0057] FIG. 5 is a schematic explanatory view of a fourth caliber
K4. The fourth caliber K4 is engraved on an upper caliber roll 50
and a lower caliber roll 51 which are a pair of horizontal rolls. A
peripheral surface of the upper caliber roll 50 (namely, an upper
surface of the fourth caliber K4) is formed with a projection 55
protruding toward the inside of the caliber. Further, a peripheral
surface of the lower caliber roll 51 (namely, a bottom surface of
the fourth caliber K4) is formed with a projection 56 protruding
toward the inside of the caliber. These projections 55, 56 have
tapered shapes, and dimensions such as a protrusion length of the
projection 55 and the projection 56 are configured to be equal to
each other.
[0058] A tip portion angle .theta. 3 of the projections 55, 56 is
configured to be larger than the aforementioned angle .theta. 2,
and an intrusion depth h4 into the material to be rolled A of the
projections 55, 56 is smaller than the intrusion depth h3 of the
projections 45, 46 (namely, h4<h3).
[0059] Further, angles .theta. f formed between caliber upper
surfaces 50a, 50b and caliber bottom surfaces 51a, 51b facing the
upper and lower end portions (slab end surfaces) of the material to
be rolled A, and, inclined surfaces of the projections 55, 56, are
configured to be about 90.degree. (almost right angle) at all of
four locations illustrated in FIG. 5 similarly to the above third
caliber K3.
[0060] In the fourth caliber K4, the splits 48, 49 formed in the
third caliber K3 at the upper and lower end portions (slab end
surfaces) of the material to be rolled A passed through the third
caliber K3 are pressed against the projections 55, 56 and thereby
become splits 58, 59. Specifically, in a final pass in shaping in
the fourth caliber K4, a deepest portion angle (hereinafter, also
called a split angle) of the splits 58, 59 becomes .theta. 3. In
other words, shaping is performed so that divided parts (the parts
corresponding to the later-described flange portions 80) shaped
along with the formation of the splits 48, 49 in the third caliber
K3 are further bent outward. The parts of the upper and lower end
portions of the material to be rolled A shaped in this manner are
parts corresponding to flanges of a later-described H-shaped steel
product and called the flange portions 80 here.
[0061] The shaping in the fourth caliber K4 illustrated in FIG. 5
is performed by at least one pass or more, and at least one pass or
more of them are performed with the upper and lower end portions
(slab end surfaces) of the material to be rolled A in contact with
the inside of the caliber (the upper surface and the bottom surface
of the fourth caliber K4). In the state where the upper and lower
end portions (slab end surfaces) of the material to be rolled A are
in contact with the inside of the caliber, it is preferable to
perform light reduction on the end portions.
[0062] FIG. 6 is a schematic explanatory view of a fifth caliber
K5. The fifth caliber K5 is composed of an upper caliber roll 85
and a lower caliber roll 86 which are a pair of horizontal rolls.
As illustrated in FIG. 6, in the fifth caliber K5, the material to
be rolled A shaped until the fourth caliber K4 is rotated
90.degree. or 270.degree., whereby the flange portions 80 located
at the upper and lower ends of the material to be rolled A until
the fourth caliber K4 are located on a rolling pith line. Then, in
the fifth caliber K5, reduction on the web portion 82 being a
connecting part connecting the flange portions 80 at two positions
and reduction on the flange tip portions of the flange portions 80
are performed to thereby perform dimension adjustment of the flange
width. Thus, an H-shaped steel blank in a so-called dog-bone shape
(the H-shaped steel blank 13 illustrated in FIG. 1) is shaped. Note
that the fifth caliber K5 thins the web portion 82 by reduction,
and is therefore called also a web thinning caliber or a flat
shaping caliber.
[0063] The H-shaped raw blank 13 thus shaped is subjected to
reverse rolling in a plurality of passes using the rolling mill
train composed of two rolling mills such as the intermediate
universal rolling mill 5 and the edger rolling mill 9 which are
already-known rolling mills, whereby an intermediate material 14 is
shaped. The intermediate material 14 is subjected to finish rolling
into a product shape in the finishing universal rolling mill 8,
whereby an H-shaped steel product 16 is produced (refer to FIG.
1).
[0064] The first caliber K1 to the fourth caliber K4 according to
this embodiment are used to create splits in the upper and lower
end portions (slab end surfaces) of the material to be rolled A and
perform processing of bending to right and left the portions
separated to right and left by the splits to perform the shaping of
forming the flange portions 80 as explained above, thereby enabling
shaping of the H-shaped raw blank 13 without performing substantial
vertical reduction on the upper and lower end surfaces of the
material to be rolled A (slab). In short, it becomes possible to
shape the H-shaped raw blank 13 with the flange width made wider as
compared with the rough rolling method of reducing at all times the
slab end surfaces conventionally performed, resulting in production
of a final product (H-shaped steel) having a large flange
width.
[0065] Here, in the method for producing H-shaped steel according
to this embodiment, the shape of the flange portion 80 of the
material to be rolled A shaped by the aforementioned first caliber
K1 to fourth caliber K4 is a shape closer to the shape of the
product flange as compared with the shape of the flange portion
before the shaping in a flat caliber in the conventional production
method. This results from employment of a shaping technique of
performing the processing of bending the split parts (the flange
portions 80) shaped by creating splits without changing the end
portion shapes of the material (slab) having the rectangular cross
section used as the material. Note that FIG. 11 is an explanatory
view for comparing the shape of the flange portion after the edging
rolling in the conventional production method and the shape of the
flange portion 80 shaped in the above-described first caliber K1 to
fourth caliber K4. It is found also from FIG. 11 that the shape of
the flange portion shaped by the method for producing H-shaped
steel according to this embodiment is a shape closer to the product
flange.
[0066] In such a shaping technique, the rolling and shaping is
advanced without actively performing reduction on the upper and
lower end portions (slab end surfaces) of the material to be rolled
A in the shaping in the first caliber K1 to the fourth caliber K4,
so that the elongation of the material to be rolled A (in
particular, the flange portions 80) in the longitudinal direction
becomes extremely small.
[0067] On the other hand, in the conventional H-shaped steel
production technique, a configuration is employed which actively
performs reduction on the flange portion at an edging rolling stage
(corresponding to the rolling and shaping in the first caliber K1
to the fourth caliber K4 in this embodiment), and it has been known
that the flange portion is elongated more than the web portion
regarding the longitudinal direction of the material to be rolled A
to cause a cutoff shape (a so-called crop shape) at the end portion
in the longitudinal direction of the material to be rolled, which
is a so-called fish tail. Further, it has been known that since the
reduction rate of the web portion is larger than the reduction rate
of the flange portion, a crop shape called a tongue occurs at a
flat caliber rolling stage (the rolling and shaping in the fifth
caliber K5 in this embodiment). Hereinafter, the crop shapes will
be described referring to FIG. 7.
[0068] FIG. 7 is a schematic explanatory view regarding the
conventional H-shaped steel production technique, (a) is a
schematic side view of the conventional edging rolling as seen from
the side, and (b) is a schematic plan view of the conventional flat
caliber rolling as seen from above. Note that the left side in FIG.
7 indicates a rolling upstream side.
[0069] As illustrated in FIG. 7(a), in the conventional H-shaped
steel production technique, since reduction on the flange portion
is actively performed at the edging rolling stage, the elongation
of the flange portion exceeds the elongation of the web portion in
the longitudinal direction of the material to be rolled A and a
crop-shaped portion 90 being a so-called fish tail comes to be
formed (refer to a broken line portion in FIG. 7(a)).
[0070] Thereafter, as illustrated in FIG. 7(b), in the conventional
H-shaped steel production technique, since the reduction rate of
the web portion is relatively larger than that of the flange
portion at the flat caliber rolling stage, the elongation of the
web portion exceeds the elongation of the flange portion in the
longitudinal direction of the material to be rolled A and a
crop-shaped portion 92 being a so-called tongue comes to be formed
(refer to a broken line portion in FIG. 7(b)).
[0071] The crop-shaped portion 90, 92 called a fish tail or a
tongue is formed and grown at both a rolling bite end and a rolling
ejection end, and it is known that the growth at the rolling
ejection end is significant.
[0072] Note that the length in the longitudinal direction of the
crop-shaped portion 90 thus formed is L1, and the length in the
longitudinal direction of the crop-shaped portion 92 is L2.
[0073] The crop-shaped portion 90, 92 thus formed possibly causes a
bite defect into the rolling mill at a subsequent step
(intermediate rolling step) and has a problem of difficulty in
continuing the intermediate rolling. Specifically, the crop-shaped
portion 90, 92 illustrated in FIG. 7(b) causes the following
problem.
[0074] More specifically, in the case where the crop-shaped portion
90 called a fish tail has been formed, the flange portion of the
material to be rolled A is rolled between a horizontal roll side
surface and a vertical roll during the universal rolling in the
intermediate rolling being the subsequent step and the vertical
roll is normally an undriven roll, thus easily leading to folding
of the material to be rolled A on the exit side of the universal
rolling mill and to rolling that the material to be rolled A is
drawn into a chock. Further, the crop-shaped portion 90 in a shape
such as the flange portion preceding has a possibility that when an
upper-lower deviation occurs at the time of bite in the rolling
mill, the rolling mill bites the flange portion as it is and the
web portion is replaced to lead to a serious rolling trouble and
degradation in dimension, such as tearing a base portion being the
web-flange connecting part.
[0075] Besides, the crop-shaped portion 92 in a shape such a the
web preceding has a possibility that when a right-left deviation
occurs at the time of bite in the rolling mill, the rolling mill
rolls the flange portion at a position as it is to lead to a
serious rolling trouble and degradation in dimension, such as
tearing a base portion being the web-flange connecting part.
[0076] In consideration of existence of the various problems
leading to degradation in dimension, the conventional H-shaped
steel production technique copes with the problems by providing an
intermediate crop cutting step of cutting the above-described
crop-shaped portion 90 or crop-shaped portion 92 as a cutoff
portion, for example, between the rough rolling step and the
intermediate rolling step.
[0077] In consideration of the above circumstance described
referring to FIG. 7, the present inventors have examined the
technique of suppressing the growth of the crop-shaped portion 90
and crop-shaped portion 92 formed at the rough rolling step (edging
rolling and flat caliber rolling) and found the knowledge described
below.
[0078] Though the use of the first caliber K1 to the fifth caliber
K5 for the rolling and shaping has been described in FIG. 2 to FIG.
6 in the method for producing H-shaped steel according to this
embodiment, the caliber roll engraved with a caliber can be freely
changed in roll gap in the rolling using these calibers. Further,
the change in the roll gap can be performed during rolling and
shaping of the material to be rolled A, and the reduction amount
can also be changed. Note that the change in the roll gap is
performed, for example, by employing a rolling mill (a sizing mill
3, a rough rolling mill 4) having a configuration provided with a
reduction mechanism (a hydraulic mechanism, not illustrated in FIG.
2 to FIG. 6) for moving the caliber roll to change the roll
gap.
[0079] Based on the configuration of the rolling mill, the present
inventors have invented performing rolling and shaping using one or
any number of calibers by a method called AGC (Automatic Gage
Control) rough rolling at the time when performing the rolling and
shaping using the first caliber K1 to the fifth caliber K5. The AGC
rough rolling is a technique of expanding the roll gap only when
rolling and shaping a section of a predetermined length at a rear
end portion in the longitudinal direction of the material to be
rolled A to make the reduction amount in the caliber lower than the
normal reduction amount or set the reduction amount to 0, in all of
the passes in each of which the material to be rolled A is
reciprocated, for example, in the case of performing reverse
rolling in a plurality of passes on the material to be rolled A in
one caliber. Note that the caliber which performs the AGC rough
rolling may be any one of the first caliber K1 to the fifth caliber
K5 or may be a plurality of, namely two or more calibers of
them.
[0080] As described above, in the conventional production
technique, the crop-shaped portion 90, 92 called a fish tail or a
tongue is formed and grown at both a rolling bite end and a rolling
ejection end, and the growth, in particular, at the rolling
ejection end is significant, but the growth of the crop-shaped
portion 90, 92 can be suppressed by decreasing the reduction amount
for the predetermined section or set the reduction amount to 0 by
applying the AGC rough rolling.
[0081] FIG. 8 is a schematic explanatory view in the case of
applying the AGC rough rolling to the rolling and shaping in the
first caliber K1 in the method for producing H-shaped steel
according to this embodiment, and is a schematic side view as seen
from the side. Note that FIG. 8 illustrates the material to be
rolled A before rolling and shaping in a certain pass (on a left
side in the drawing), the material to be rolled A directly before
the end of the rolling and shaping in the pass (at a middle in the
drawing), and the material to be rolled A after the end of the
rolling and shaping in the pass (on a right side in the drawing)
for explanation.
[0082] As illustrated in FIG. 8, in the certain pass in the rolling
and shaping in the first caliber K1 according to this embodiment,
the rolling and shaping is performed in a required roll gap (the
interval between the upper caliber roll 20 and the lower caliber
roll 21) for performing the rolling and shaping illustrated in FIG.
2 from start of the rolling and shaping until directly before the
end of the rolling and shaping. On the other hand, the rolling and
shaping is performed with the roll gap expanded (refer to a broken
line portion in FIG. 8) in the rolling and shaping for a
predetermined section L from directly before the end of the rolling
and shaping until the end of the rolling and shaping in the pass.
Specifically, the roll gap may be expanded stepwise to gradually
decrease the reduction amount from directly before the end of the
rolling and shaping, or the roll gap may be greatly expanded to set
the reduction amount to 0.
[0083] In the rolling and shaping performed in the above manner,
the rolling and shaping is performed on the material to be rolled A
with the reduction amount smaller for the predetermined section L
than that for other sections (or with no reduction amount), so that
not so much reduction is performed in the longitudinal direction of
the material to be rolled A. Accordingly, it rarely occurs that the
elongation of the flange portion exceeds the elongation of the web
portion at the edging rolling stage and a shape defective portion
being a so-called fish tail is formed described above referring to
FIG. 7(a). In other words, the reduction amount for the
predetermined section L decreases or becomes 0 at the rolling
ejection end, thus suppressing the growth of the crop-shaped
portion 90 as described above. Therefore, the above-described
omission or simplification of the intermediate crop cutting step
becomes possible to realize the improvement in yield and efficient
rolling.
[0084] Note that in the case of employing the reverse rolling at
the edging rolling stage, in a pass next to the pass described in
FIG. 8, rolling and shaping is performed in a direction opposite to
the direction indicated in FIG. 8, so that the predetermined
section L is at the bite end. At this time, the roll gap is set to
be a roll gap enabling the predetermined rolling and shaping, and
therefore the rolling and shaping is performed for the
predetermined section L as the bite end in this pass. In short,
sufficient rolling and shaping is performed also for the
predetermined section L.
[0085] Here, though the first caliber K1 is exemplified for
explanation in FIG. 8, the same operation and effect also applies
to each caliber used at the edging rolling stage, and the AGC rough
rolling is also applicable to one or a plurality of calibers used
at the edging rolling stage.
[0086] At the rough rolling step according to this embodiment
described above referring to FIG. 2 to FIG. 6, the crop growth is
significant, in particular, in the first caliber K1 for forming
first splits on the slab end surfaces and in the third caliber K3
and the fourth caliber K4 for performing shaping of bending divided
parts formed by the splits, of the edging rolling stage. This is
because edging is performed in a strong constraint state by the
caliber side wall at the step of forming the first splits on the
slab end surfaces, and is because a predetermined amount of
reduction is loaded in the slab width direction during bending
deformation and the slab end surfaces are finally edged while in
contact with the caliber peripheral surface at the step of bending
the divided parts. This is clear also from the fact that the crop
length grows mainly at G1 and G3 in G1 to G3 corresponding to the
edging rolling in the first caliber K1 to the third caliber K3 in a
later-described example (refer to FIG. 10).
[0087] More specifically, it is preferable to apply, in particular,
the AGC rough rolling to the first caliber K1, and/or, an edging
rolling and shaping caliber in the third caliber K3 and subsequent
calibers (the third caliber K3 and the fourth caliber K4 in this
embodiment) where the shape defective portion being a so-called
fish tail is possibly formed.
[0088] Note that the AGC rough rolling does not always have to be
applied to the second caliber K2 for performing shaping to further
deepen the splits formed in the first caliber K1 because the growth
of the shape defective portion (crop portion) is small.
[0089] However, also in the second caliber K2, in a pass in which
reduction is performed with the end surfaces of the material to be
rolled and the caliber peripheral surface in contact with each
other, the growth of the crop portion is larger than in other
passes. Accordingly, it is preferable to perform rolling and
shaping with the rolling roll gap for the predetermined section at
the rear end portion in the rolling longitudinal direction of the
material to be rolled expanded as compared with the rolling roll
gap for other than the predetermined section in a pass in which
reduction is performed with the end surfaces of the material to be
rolled and the caliber peripheral surface in contact with each
other also in the rolling and shaping in the second caliber K2.
[0090] Further, in the predetermined section in which the rolling
and shaping is performed with the rolling roll gap expanded, the
end surfaces of the material to be rolled and the caliber
peripheral surface do not have to be in contact with each other.
However, when the pass in which the end surfaces of the material to
be rolled and the caliber peripheral surface are in contact with
each other is one pass, an unreduced portion possibly remains at
the rear end portion in the longitudinal direction of the material
to be rolled, and therefore the contact pass needs to be increased
by one to arrange the shape in some cases. In such a case, the AGC
rough rolling may be performed in all passes in the second caliber
K2.
[0091] Further, FIG. 9 is a schematic explanatory view in the case
of applying the AGC rough rolling to the rolling and shaping in the
fifth caliber K5 (flat shaping caliber) in the method for producing
H-shaped steel according to this embodiment, and is a schematic
plan view as seen from above. Note that FIG. 9 illustrates the
material to be rolled A before rolling and shaping in a certain
pass (on a left side in the drawing), and the material to be rolled
A after end of the rolling and shaping in the pass (on a right side
in the drawing) for explanation.
[0092] As illustrated in FIG. 9, also in the flat caliber rolling
in the fifth caliber K5, the rolling and shaping is performed in a
required roll gap for performing the rolling and shaping
illustrated in FIG. 6 from start of the rolling and shaping until
directly before the end of the rolling and shaping as at the above
described edging rolling stage. On the other hand, the rolling and
shaping is performed with the roll gap expanded in the rolling and
shaping for the predetermined section L from directly before the
end of the rolling and shaping until the end of the rolling and
shaping in the pass. Specifically, the roll gap may be expanded
stepwise to gradually decrease the reduction amount from directly
before the end of the rolling and shaping, or the roll gap may be
greatly expanded to set the reduction amount to 0.
[0093] In the rolling and shaping performed in the above manner,
the rolling and shaping is performed on the material to be rolled A
with the reduction amount smaller for the predetermined section L
than that for other sections (or with no reduction amount), so that
not so much reduction is performed on both the flange portion and
the web portion in the longitudinal direction of the material to be
rolled A. Accordingly, even in the case where the reduction rate on
the web portion is relatively large as compared with that on the
flange portion at the flat caliber rolling stage, the reduction
rate itself is extremely low, so that a shape defective portion
being a so-called tongue (refer to FIG. 7(b)) is not significantly
formed as illustrated in FIG. 9 even if the elongation of the web
portion exceeds the elongation of the flange portion in the
longitudinal direction of the material to be rolled A. In other
words, the reduction amount in the predetermined section L
decreases or becomes 0 at the rolling ejection end, thus
suppressing the growth of the crop-shaped portion 92 as described
above. Therefore, the above-described omission or simplification of
the intermediate crop cutting step becomes possible to realize the
improvement in yield and efficient rolling.
[0094] Note that the reverse rolling is performed also at the flat
caliber rolling stage, so that in a pass next to the pass described
in FIG. 9, rolling and shaping is performed in a direction opposite
to the direction indicated in FIG. 9. In other words the
predetermined section L becomes the bite end in the next pass. At
this time, the roll gap is set to be a roll gap enabling the
predetermined rolling and shaping, and therefore the rolling and
shaping is performed for the predetermined section L as the bite
end in this pass. In short, sufficient rolling and shaping is
performed also for the predetermined section L. However, as the
reduction amount relating to the predetermined section L in a pass
next to the pass described in FIG. 9, the reduction amount in the
next pass needs to be simultaneously applied in addition to the
reduction amount in the pass at the preceding stage, and therefore
it is important to sufficiently examine the reduction amount for
the predetermined section L in the design of the pass schedule.
[0095] The case of applying the AGC rough rolling at the edging
rolling stage (FIG. 8) and the case of applying the AGC rough
rolling in the flat caliber rolling stage (FIG. 9) have been
described referring to FIG. 8 and FIG. 9 respectively. In the case
of applying the AGC rough rolling in the method for producing
H-shaped steel according to this embodiment, the AGC rough rolling
may be applied only to the edging rolling stage (namely, the
rolling and shaping corresponding to the first caliber K1 to the
fourth caliber K4), only to the flat caliber rolling stage (namely,
the rolling and shaping corresponding to the fifth caliber K5), and
to both the edging rolling stage and the flat caliber rolling
stage. In any of the cases, it is possible to omit or simplify the
intermediate crop cutting step to realize the improvement in yield
and efficient rolling.
[0096] Besides, in the case of employing the reverse rolling in
each of the rolling and shaping stages, the AGC rough rolling may
be applied to a predetermined arbitrary pass or may be applied to
all passes. From the viewpoint that it is desirable to suppress the
growth of the crop portion without forming the shape defective
portion, it is desirable to apply the AGC rough rolling to all
passes.
[0097] Note that regarding the case of applying the AGC rough
rolling described referring to FIG. 8 and FIG. 9, the predetermined
section L for which the rolling and shaping is required to be
performed with the roll gap expanded can be arbitrarily set. For
example, the sections L1, L2 in the longitudinal direction of the
material to be rolled A where the shape defective portions 90, 92
formed in the conventional H-shaped steel production technique
described referring to FIG. 7(a), (b) are preferably set as the
above-described predetermined section L.
[0098] At the time when deciding the predetermined section L, it is
necessary to clarify the boundary between an unsteady part and a
steady part in rolling of the material to be rolled A and to make
at least the unsteady part be included in the predetermined section
L. If the steady part is included in the predetermined section L,
the roll gap is expanded in a part of the range of the steady part
to possibly causes residual reduction in the steady part. However,
since there is little influence caused by shift of reduction in the
steady part to a pass at a subsequent stage, the predetermined
section L preferably takes a range including the whole range of the
unsteady part and expandable to a part of the steady part. At the
time when concretely deciding the predetermined section L, the
predetermined section L will be decided based on all elements such
as the material cross section, dimension of the material to be
rolled, caliber shape, pass schedule and so on, and therefore a
laboratory experiment or an actual machine test will be performed
to measure the unsteady part length for each pass so as to decide a
preferable length.
[0099] According to the method for producing H-shaped steel
according to this embodiment described above, creating splits in
the upper and lower end portions (slab end surfaces) of the
material to be rolled A and performing processing of bending to
right and left the portions separated to right and left by the
splits to perform the shaping of forming the flange portions 80,
enables shaping of the H-shaped raw blank 13 substantially without
performing vertical reduction on the upper and lower end surfaces
of the material to be rolled A (slab). In short, it becomes
possible to shape the H-shaped raw blank 13 with the flange width
made wider as compared with the rough rolling method of reducing at
all times the slab end surfaces conventionally performed, resulting
in production of a final product (H-shaped steel) having a large
flange width.
[0100] Further, in addition to the above operation and effect,
according to the method for producing H-shaped steel according to
this embodiment, expanding the roll gap at the rolling and shaping
for the predetermined section L (a rear end at the rolling and
shaping) of the material to be rolled A and performing the AGC
rough rolling, at the edging rolling stage (namely, the rolling and
shaping corresponding to the first caliber K1 to the fourth caliber
K4), and/or, the flat caliber rolling stage (namely, the rolling
and shaping corresponding to the fifth caliber K5), makes it
possible to suppress the growth of the shape defective portion at
the rear end portion in the longitudinal direction of the material
to be rolled formed in the conventional H-shaped steel production
technique. This enables omission or simplification of the
intermediate crop cutting step to realize the improvement in yield
and efficient rolling. In other words, most ideally, all of the
rough rolling step, the intermediate rolling step, and the finish
rolling step can be performed without the intermediate crop cutting
step intervening therebetween. Only performing the cop cutting
after all steps (the rough rolling step, the intermediate rolling
step, and the finish rolling step) enables completion of removal of
the crop portion caused in the longitudinal direction of the
material to be rolled. Note that the intermediate crop cutting step
may be performed as necessary only on the web portion of the
material to be rolled after the rough rolling step and at a
preceding stage or at a middle stage of the intermediate rolling
step (between rolling passes at the intermediate rolling step).
[0101] In particular, in production of a large-size H-shaped steel
product having a web height of 1000 mm or more or a flange width of
400 mm or more, the weight per unit length of the material to be
rolled A is large and the elongation length of the product at
rolling is small, and therefore the proportion of the crop portion
in the whole length is large, and growth of the crop portion is
likely to lead to the decrease in yield. Accordingly, the technique
of suppressing the growth of the crop portion according to this
embodiment is useful particularly in producing the large-size
H-shaped steel product.
[0102] One example of the embodiment of the present invention has
been explained above, but the present invention is not limited to
the illustrated embodiment. It should be understood that various
changes and modifications are readily apparent to those skilled in
the art within the scope of the spirit as set forth in claims, and
those should also be covered by the technical scope of the present
invention.
[0103] The technique of performing the shaping on the material to
be rolled A using four calibers such as the first caliber K1 to the
fourth caliber K4 and then performing the flat shaping and rolling
thereon using the fifth caliber K5 has been explained in the above
embodiment. However, the number of calibers for performing the
rough rolling step is not limited to this, but much more calibers
may be used to perform the rolling and shaping step represented by
the first caliber K1 to the fourth caliber K4. In other words, the
caliber configuration illustrated in the above embodiment is one
example, and the number of calibers engraved on the sizing mill 3
and the rough rolling mill 4 can be arbitrarily changed and
appropriately changed to an extent at which the rough rolling step
can be suitably performed.
[0104] Further, explanation has been made by exemplifying a slab as
a material when producing H-shaped steel, but the present invention
is naturally applicable also to other materials in a similar shape.
In other words, the present invention is also applicable to a case
of shaping, for example, a beam blank material to produce H-shaped
steel.
EXAMPLES
[0105] The effect of the present invention will be verified using
examples.
[0106] In the following, the result of an experiment carried out to
compare the production method (hereinafter, also called a wedge
method) according to the conventional H-shaped steel production
technique exemplified in Patent Document 1 or the like and the
production method (hereinafter, also called a split method)
according to the technique of the present invention is illustrated
first as Experimental Example 1. In addition, the result of an
experiment of comparing the presence or absence of application of a
so-called "AGC rough rolling" described in the above embodiment
carried out in the split method is illustrated as Experimental
Example 2.
Experimental Example 1
[0107] As Reference Example 1, the edging rolling was performed
using the H-shaped steel production technique by the wedge method
being the conventional method and the length of the crop portion
(crop length) at that time was measured. Meanwhile, as Reference
Example 2, the edging rolling by the split method was performed
using the first caliber K1 to the third caliber K3 illustrated in
FIG. 2 to FIG. 4 and the length of the crop portion at that time
was measured. Note that as the conditions of this verification, the
material slab cross section was set to 1800 mm.times.300 mm and the
wedge angle in the edging rolling in the example was set to
30.degree. in the first caliber K1 and the second caliber K2 and
set to 90.degree. in the third caliber K3. Further, the edging
amount was set to the reduction amount at the projection tip end
position (wedge tip position) in each caliber.
[0108] FIG. 10 is a graph illustrating the verification results of
Reference Example 1 (the wedge method in the drawing) and Reference
Example 2 (the split method in the drawing), and is a graph
illustrating the relation between the edging amount (reduction
amount by the edging rolling) and the crop length in each of the
cases. Note that indication of G1 to G3 in FIG. 10 corresponds to
the edging rolling in the first caliber K1 to the third caliber K3
according to the above embodiment. Besides, the plot in FIG. 10 is
made by calculating the average value of the crop lengths at both
ends in the longitudinal direction of the material to be
rolled.
[0109] As illustrated in FIG. 10, in Reference Example 1, the crop
length grew in substantially proportional to the edging amount, and
the crop length grew up to about 250 mm, for example, when the
edging amount was 600 mm.
[0110] On the other hand, in Reference Example 2, little growth was
observed in the crop length, but the growth of the crop portion was
not observed, in particular, in the second caliber K2 (G2 in the
drawing), showing that the growth of the crop length was suppressed
as compared with a comparison example. For example, the crop length
stays at about 80 mm when the edging amount is 900 mm.
Experimental Example 2
[0111] As a comparative example, the edging rolling was performed
by the split method using the first caliber K1 to the fourth
caliber K4 illustrated in FIG. 2 to FIG. 5 without applying the AGC
rough rolling, and the length of the crop portions (crop lengths)
at both ends of the material to be rolled at that time were
measured. FIG. 12 is a graph illustrating the measurement result of
the comparative example, and two plots in the graph indicate the
crop lengths at both ends in the longitudinal direction of the
material to be rolled.
[0112] Further, as an example, the AGC rough rolling was performed
in all passes of the rolling and shaping in the first caliber K1,
the third caliber K3, and the fourth caliber K4 (corresponding to
G1, G3, G4 in the drawing respectively) in the split method using
the first caliber K1 to the fourth caliber K4 illustrated in FIG. 2
to FIG. 5, and the lengths of the crop portions (crop lengths) at
both ends of the material to be rolled at that time were measured.
FIG. 13 is a graph illustrating the measurement result of the
example, and two plots in the graph indicate the crop lengths at
both ends in the longitudinal direction of the material to be
rolled.
[0113] In the case where the AGC rough rolling was performed in the
example, the roll gap was expanded from about 400 mm at the
terminal end portion of the material to be rolled and the roll was
opened at the final end portion in each rolling pass.
[0114] Note that the material slab used in the comparison example
and the example is a slab having a cross section of 2300
mm.times.300 mm and a length of 4000 mm. Besides, the rolling pass
schedule in each caliber is as listed in following Table 1.
TABLE-US-00001 TABLE 1 PASS CALIBER ROLL GAP (mm) 1 G1 2200 2 G1
2120 3 G2 2000 4 G2 1900 5 G2 1800 6 G2 1700 7 G2 1600 8 G2 1500 9
G2 1460 10 G3 1460 11 G3 1460 12 G3 1416 13 G4 1416 14 G4 1416
However, the "roll gap" in Table 1 indicates the interval
(distance) between wedge (projection) tip end portions of the upper
and lower rolls of the caliber, and is synonymous with the "edging
amount" in above Experimental Example 1.
[0115] As is found from the comparison in FIG. 12 and FIG. 13, the
crop growth amount in each caliber is suppressed in the case of
applying the AGC rough rolling (FIG. 13) as compared with the case
of not applying the AGC rough rolling (FIG. 12). In particular, the
crop growth amount at G1, G3, G4 (corresponding to the first
caliber K1, the third caliber K3, and the fourth caliber K4) are
greatly suppressed. The final crop length was little less than
about 40 mm in the case of applying the AGC rough rolling and was
little less than about 90 mm in the case of not applying the AGC
rough rolling, so that the crop length became 1/2 or less by
applying the AGC rough rolling.
[0116] The result of above Experimental Example 2 shows that the
growth of the crop length is greatly suppressed at the edging
rolling stage in the H-shaped steel production technique applying
the AGC rough rolling according to the present invention. This
makes it possible to perform the rolling and shaping without
performing the intermediate crop cutting step which has been
constantly performed in the conventional H-shaped steel production
technique. In other words, the improvement in yield and efficient
rolling are realized.
INDUSTRIAL APPLICABILITY
[0117] The present invention is applicable to a producing technique
of producing H-shaped steel using a slab or the like having, for
example, a rectangular cross section as a material.
EXPLANATION OF CODES
[0118] 1 rolling facility [0119] 2 heating furnace [0120] 3 sizing
mill [0121] 4 rough rolling mill [0122] 5 intermediate universal
rolling mill [0123] 8 finishing universal rolling mill [0124] 9
edger rolling mill [0125] 11 slab [0126] 13 H-shaped raw blank
[0127] 14 intermediate material [0128] 16 H-shaped steel product
[0129] 20 upper caliber roll (first caliber) [0130] 21 lower
caliber roll (first caliber) [0131] 25, 26 projection (first
caliber) [0132] 28, 29 split (first caliber) [0133] 30 upper
caliber roll (second caliber) [0134] 31 lower caliber roll (second
caliber) [0135] 35, 36 projection (second caliber) [0136] 38, 39
split (second caliber) [0137] 40 upper caliber roll (third caliber)
[0138] 41 lower caliber roll (third caliber) [0139] 45, 46
projection (third caliber) [0140] 48, 49 split (third caliber)
[0141] 50 upper caliber roll (fourth caliber) [0142] 51 lower
caliber roll (fourth caliber) [0143] 55, 56 projection (fourth
caliber) [0144] 58, 59 split (fourth caliber) [0145] 80 flange
portion [0146] 82 web portion [0147] 85 upper caliber roll (fifth
caliber) [0148] 86 lower caliber roll (fifth caliber) [0149] 90, 92
crop-shaped portion [0150] K1 first caliber [0151] K2 second
caliber [0152] K3 third caliber [0153] K4 fourth caliber [0154] K5
fifth caliber (flat shaping caliber) [0155] T production line
[0156] A material to be rolled
* * * * *