U.S. patent application number 15/077474 was filed with the patent office on 2016-09-22 for rolling method.
The applicant listed for this patent is PRIMETALS TECHNOLOGIES GERMANY GMBH. Invention is credited to John BEAUMONT, Sandip SAMANTA, Birger SCHMIDT.
Application Number | 20160271661 15/077474 |
Document ID | / |
Family ID | 49553306 |
Filed Date | 2016-09-22 |
United States Patent
Application |
20160271661 |
Kind Code |
A1 |
BEAUMONT; John ; et
al. |
September 22, 2016 |
ROLLING METHOD
Abstract
A method of rolling a metal plate from an ingot or thick slab
(1,2) includes setting a work roll gap with a mechanical screw (24)
and rolling the ingot or slab through a first pass to produce a
rolled product (21). The rolled product (21) is removed from the
roll gap and the mechanical screw (24) is used to set a reduced
roll gap (34a). The rolled product (21) is rolled through the
reduced roll gap (34a) over a partial pass extending over less than
the full length of the rolled product (21), to form a further
rolled product (22, 21); and the further rolled product is removed
from the roll gap. Repeat prior step. Then turn the rolled plate
and carrying out a further roll pass in a width direction of the
plate.
Inventors: |
BEAUMONT; John; (Sheffield,
GB) ; SAMANTA; Sandip; (Rotherham, GB) ;
SCHMIDT; Birger; (Brand-Erbisdorf, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
PRIMETALS TECHNOLOGIES GERMANY GMBH |
Erlangen |
|
DE |
|
|
Family ID: |
49553306 |
Appl. No.: |
15/077474 |
Filed: |
March 22, 2016 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
PCT/EP2014/067678 |
Aug 19, 2014 |
|
|
|
15077474 |
|
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B21B 37/26 20130101;
B21B 1/06 20130101; B21B 1/026 20130101; B21B 31/24 20130101 |
International
Class: |
B21B 1/02 20060101
B21B001/02 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 24, 2013 |
GB |
1316917.2 |
Claims
1. A method of rolling a metal plate from an ingot or thick slab in
a screwdown mill featuring rolls defining a roll gap between the
rolls and a mechanical roll gap screw, the method comprising:
setting a first work roll gap between the rolls defining the roll
gap, using the mechanical roll gap adjusting screw, rolling the
ingot or slab through a first pass extending through the first roll
gap over the full length of the ingot or slab in the rolling
direction to produce a first rolled product; removing the first
rolled product from the first roll gap after the first pass;
operating the first roll gap mechanical screw to set a second,
reduced work roll gap reduced from the first roll gap; performing a
first rolling iteration comprising rolling the first rolled product
through the second, reduced roll gap over a partial pass, the
partial pass extending over less than the full length of the first
rolled product in the rolling direction, to form a second rolled
product; removing the second rolled product from the roll gap at
conclusion of the first iteration; then turning the second rolled
product through 90.degree. and performing a further roll pass on
the second rolled product in a width direction broadsiding the
second rolling product to form a further rolled product.
2. A method according to claim 1, further comprising: after
removing the further rolled product from the roll gap and prior to
the turning of the further rolled product, operating the roll gap
mechanical screw to set a further third reduced roll gap; and
rolling the still further rolled product through the further third
reduced roll gap over a partial pass, the partial pass extending in
the rolling direction over less in the rolling direction than the
full length of the further rolled product.
3. A method according to claim 1, further comprising: successively
repeating the steps each time of removing the then further rolled
product from the roll gap, operating the mechanical screw to
successively set each time a further reduced roll gap, and rolling
the then further product over a successive partial pass; and
repeating the steps for a set number of iterations to produce a
rolled plate.
4. A method according to claim 3, further comprising selecting a
number of the iterations according to parameters of required yield
loss and rolling time.
5. A method according to claim 1, further comprising counting a
number of revolutions of the roll as the rolled product is removed
from the roll gap for setting the next roll gap for obtaining a
difference in thickness between adjacent roll gap thickness
settings; using the number of revolutions and the difference in
thickness for calculating the then length of the rolled product for
thereby deriving the length of the rolled product to be rolled at
the next rolling stage.
6. A method according to claim 3, wherein each partial pass through
a successively further reduced roll gap is of a length over the
product less than the length over the product over the length of
the respective partial pass over the preceding roll product that
had passed the preceding roll gap.
7. A method according to claim 6, wherein the lengths of the
successive partial passes are selected to define a stepped surface
of the product which has passed through a respective successive
roll gap in each partial pass.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation in part of
PCT/EP2014/067678, filed Aug. 19, 2014, which claims priority of
Great Britain Patent Application No. 1316917.2, filed Sep. 24,
2013, the contents of which are incorporated by reference herein.
The PCT International Application was published in the English
language.
TECHNICAL FIELD
[0002] This invention relates to a method of rolling metal, in
particular for production of high quality thick plate from ingots
or thick slabs.
TECHNICAL BACKGROUND
[0003] Market demand for high quality thick plate for the
construction industry requires that the plates are rolled from
either traditional ingots or thick cast slabs. Both create
significant processing problems and yield loss on the final plate.
Normally, ingots have variations or tapers in both thickness and
width down their length, which have to be removed during rolling.
Once the variations have been removed, the ingot can be processed
in the same manner as a thick cast slab. For this application,
reference to either ingot or thick slab should include the other,
unless otherwise stated.
[0004] Traditionally thick plate rolling from ingots has been done
using a rolling mill and a detached edger in a series of reversing
passes, for example as described in JP01053703.
[0005] Starting from a tapered slab, JP58044904 describes the use
of tapered rolling to spread the material in the tapered slab, then
turning the rolled material and applying further rolling, for
eventually forming a rectangular plate.
[0006] As described in a paper given at the 49th Rolling
Seminar--Processes, Rolled and Coated Products, Vila Velha, Brasil,
October 2012, entitled--Production of high quality thick
construction plate from ingots and thick slabs, by S Samanta et al,
mathematical models can be used with high speed long stroke
hydraulic gap control cylinders to remove thickness and width
variations before standard thick cast slab processing of the plate
to minimize poor edge shape and increase final yield.
[0007] However, a number of older mills are either not suitable or
economical to convert to hydraulic gap control, thereby limiting
the type of plate that they can produce.
DESCRIPTION OF THE INVENTION
[0008] In accordance with the present invention, a method awning a
metal plate from an ingot or thick slab comprises in sequence:
setting a work roll gap with a mechanical screw and rolling the
ingot or slab through a first pass through the roll gap to produce
a rolled product; removing the rolled product from the roll gap;
using the mechanical screw to set a reduced roll gap; rolling the
rolled product through the reduced roll gap over a partial pass,
wherein the partial pass extends over less than the full length of
the rolled product, to form a further rolled product; and removing
the further rolled product from the roll gap. There may be a series
of successive stages of rolling the rolled product through a
further reduced roll gap over a further partial pass, wherein each
successive partial pass extends over less than the length of the
preceding partial pass, forming a stepped profile of the rolled
product. After the series of rolling stages, the method further
comprises turning the rolled plate and carrying out a further roll
pass in a width direction of the plate, herein called
broadsiding.
[0009] Rolling a metal plate, whether from an ingot or thick slab,
using the method of the present invention to produce a rolled plate
having a stepped profile allows older screwdown mills to be used to
roll plate which has the required quality, without the loss of
yield, rendering the process uneconomical. Broadsiding of the
rolled plate converts the stepped thickness profile to a flattened
thickness profile and the narrow width region to be widened,
thereby causing the plate rolled to become a flattened
rectangle.
[0010] Preferably, the method further comprises using the
mechanical screw to seta further reduced roll gap in each of the
successive stages described above; rolling the further rolled
product through the further reduced roll gap over a partial pass,
in each stage with the partial pass extending over less than the
full length of the further rolled product.
[0011] Preferably, the method further comprises repeating the steps
of removing the further rolled product from the roll gap, using the
mechanical screw to set a further reduced roll gap and rolling the
product over a partial pass for a set number of iterations to
produce a rolled plate. Preferably, the number of iterations is
determined according to parameters of required yield loss and
rolling time. For each iteration, a section of the rolled product
furthest from the work rolls, is left unrolled.
[0012] Preferably, the method further comprises counting the number
of revolutions of the roll as the rolled product is removed from
the roll gap to allow the next roll gap to be set; determining a
difference in thickness between adjacent roll gap thickness
settings; using the number of revolutions and determined difference
in thickness to calculate the length of the product; and thereby
deriving the length of the rolled product to be rolled at the next
rolling stage.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] An example of a method of rolling a metal plate from an
ingot or thick slab in accordance with the present invention will
now be described with reference to the accompanying drawings in
which:
[0014] FIG. 1A shows a top view before rolling of an ingot having a
width taper across the ingot in the prior art;
[0015] FIG. 1B shows a front view of the ingot having a thickness
taper in the prior art;
[0016] The arrow indicates conventional rolling.
[0017] FIG. 1C shows a top view of the ingot after conventional
rolling, and the increased width taper in the prior art;
[0018] FIG. 1D shows a front view of the ingot after conventional
rolling and no thickness taper in the prior art;
[0019] FIG. 2A shows a top view of an ingot before rolling in the
prior art and;
[0020] FIG. 2B shows a front view of the ingot before rolling in
the prior art;
[0021] FIGS. 3A, 3B and 3C illustrate how the resulting ingot of
FIGS. 2A and 2B can be rolled in the prior art to form a
rectangular product, wherein the rolled ingot of FIGS. 2A and 2B
has been rotated by 90.degree.;
[0022] The arrow indicates a conventional rolling;
[0023] FIG. 3C indicates a plate produced by conventional rolling
and being without taper in the prior art;
[0024] FIGS. 4A to 4D illustrate an example of steps in a method
according to the present invention;
[0025] FIG. 5A is a perspective view of an ingot that has passed
through the rolling process of FIGS. 4A to 4D several iterations,
before a broadsiding step;
[0026] FIG. 5B is a front view of that ingot;
[0027] FIG. 5C is a top view thereof;
[0028] FIG. 5D is a front view of a plate formed from the ingot of
FIG. 5B after a broadsiding step; and
[0029] FIG. 5E is a top view of the plate after the broadsiding
step.
DESCRIPTION OF A PRIOR ART EMBODIMENT
[0030] Use of edger controlled multiple reversing passes to produce
thick plate has been the most common method to date, although the
advent of hydraulically operated automatic gauge control has
enabled mills to be constructed which are able to overcome the
problems of rolling tapered ingots or thick slabs, while still
providing sufficient austenite strain for a fine-grained, high
quality product. However, there are still many older mills using
mechanical screw roll loading technology which either are not
suitable or not economical to adapt to hydraulic cylinders and
automatic gauge control.
[0031] The present invention aims to improve the yield during thick
plate production in these screwdown mills.
[0032] FIGS. 1A-1D illustrate how traditional cast ingots are
tapered in thickness and width along their length. The ingot 1, in
top view FIG. 1A, has a width taper, i.e. it tapers across its
width direction from lateral side to side in FIG. 1A, becoming
narrower from side 12 to side 12A in width as it becomes thicker
from bottom 13 to top 14. If standard hydraulically controlled
rolling loads are applied to this type of ingot, without any
special rolling strategy, then it can be seen, after rolling for
example, from FIG. 1A to FIG. 1C that the width taper increases
into FIG. 1C, wherein the ingot is changed in its form to ingot 3,
and broken lines enclose regions 5, which indicate the increase in
width taper.
[0033] At the same time, conventional rolling of the ingot 1 of
FIG. 1B causes the resulting ingot 3 to have uniform thickness, and
the thickness taper of ingot 1 in FIG. 1B disappears as the
thickness taper is reduced from FIG. 1B to FIG. 1D. The result is a
plate 4 with uniform thickness as in FIG. 1D, but with a width that
tapers down along the length of the ingot as in FIG. 1C. This
results in a large amount of yield loss when shearing to form a
rectangular product for sale.
[0034] Using advances in hydraulic control of rolling loads, a
process has been developed to add a variable thickness taper to the
ingot, which is inversely proportional to the ingot width taper, as
illustrated by FIGS. 2A and 2B. The width of ingot 6 decreases in
FIG. 2A, while the thickness of that ingot decreases in FIG. 2B.
The dashed lines and the areas 8, 9 that the lines enclose define
the tapers. The respective tapers 9 showing width and 8 showing
thickness are inverse tapers, that is one taper increases as the
other decreases.
[0035] This taper can then be rolled out by turning the ingot
through 90.degree. rotation, as shown in FIGS. 3A and 3B, and
rolling it again in the width direction (called broadsiding) in
order to spread material and form a rectangular product, as shown
in FIG. 3C. That plate 10 has no width or thickness taper. It has
been assumed that these advantages are only achievable where
automatic gauge control and hydraulic cylinders are installed. The
present invention provides a method by which similar improvements
can be achieved in older screwdown mills.
DESCRIPTION OF AN EMBODIMENT OF THE INVENTION
[0036] FIGS. 4A to 4D illustrate an example of the method of the
present invention for rolling tapered ingots or thick slabs using a
screwdown system for causing multiple roll gap changes in a rolling
mill 24. An ingot having both a width taper and a thickness taper,
as in FIGS. 1A and 1B, is transformed into an ingot having a
stepped profile, schematically illustrated in FIGS. 5A, 5B and 5C.
In FIG. 4A, the ingot or slab 20 is supported on a roller table 27
and is moved in the direction of the arrow 30 to enter a roll gap
34a between opposing work rolls 25 which roll gap has been pre-set.
The slab 20 is rolled to a first thickness, as shown in FIGS. 4A
and 4B to produce rolled slab 21 in FIG. 4B, and the entire rolled
slab 21 exits the work roll gap supported on roller table 26.
Mechanical screws in plate mills cannot usually be moved under
load, so as shown in FIG. 4B, at least one screw 24 is operated to
reduce the gap to 34b between the work rolls 25 in FIG. 4C for the
next pass of rolled plate 21, typically narrowing the gap to 34b by
moving the at least one work roll 25 in the direction of the arrow
31.
[0037] In the next pass, shown in FIG. 4C, the rolled plate 21 is
moved through the now reduced roll gap 34b in the opposite
direction of the arrow 32, but only a part 22 of the length of the
rolled plate 21 is rolled again in gap 34b. When the required
length of the part of the rolled plate has been rolled to the new
thickness 34b, the rolling is stopped and. the plate is reversed
out of the mill to a position as in FIG. 4D. The plate is now
formed of two parts 22, 21 of different thickness, as illustrated
in FIG. 4D. The at least one screw 24 is operated to change the
roll gap by movement of the roll 25 in the direction of the arrow
33 to the next required smaller roll gap 34c. Then the process of
rolling part of the length of part 22, stopping and reversing out
of the roll gap is repeated as in FIGS. 4C and 4D. For each rolling
process, the work rolls 25 are set to have a slightly smaller gap
than the previous roll gap and the plate is then rolled again.
These are successive iterations of the rolling process. See FIGS.
5A and 5B.
[0038] For each iteration, part of the previously rolled section is
not rolled again, but the subsequent roll pass finishes at a
predefined boundary 35 between the previously rolled thickness,
e.g. 34a and the new thickness, e.g. 34b. Thus, the slab formed has
a section, e.g. 21 of the thickness of the first roil gap and a
respective section of the thickness, e.g. 22, of each subsequent
roll gap. For each change in roll gap, the slab is reversed out of
the work roll gap, so that the gap can be adjusted using the
mechanical screws. Then a next rolling pass reduces the thickness
of the slab over a partial length, but does not roll all of the
length of the previously rolled sections again. See FIGS. 4C and
4D. In each successive pass, the rolling is not over the full
length, but stops at a boundary, e.g. 35 between the immediately
preceding section and the most recent section. Iterations of
rolling, reversing out and adjustment of the roll gap continue
until a desired minimum thickness of the final section 37 of the
ingot has been reached. Several iterations successively reduce the
thickness of the ingot being rolled in steps. See the resultant
ingot of FIGS. 5A and 5B.
[0039] In each rolling pass, the rolled product becomes longer in
the advancing direction, so in order to control the point to which
each subsequent pass should roll, the number of revolutions of the
roll are counted. The difference in thickness between each roiled
step 21, 22, 37 along the taper is known from the different gaps
34a, b, c, etc. produced by each different screw setting, allowing
a calculation of how much longer the slab has become and therefore
how far to go back in for the next rolling stage. Instead of a
constant ramp change, which is used in systems having an AGC
cylinder controlled system, in a screwdown mill, multiple step
changes are induced to approximate the desired constant ramp change
during the introduction of variable thickness taper. (See FIGS. 5A
and 5B) This is performed by adjusting the roll gap using the
mechanical screw for multiple rolling stages of decreasing the roll
gap and increasing the roll length until the entire length is
rolled. The result produced is transformed into a plate with a
stepped thickness profile similar to a staircase. (See FIGS. 5A and
5B.) The resulting profile is illustrated in FIGS. 58 showing the
front view and 5C, which shows the profile in top or plan view from
above at 38 in FIG. 5C. and in front view at 39 in FIG. 5B.
[0040] After all of the roll passes in the long direction, the
ingot 11, is rotated 90.degree. on its roll plate on which the
ingot is supported. Then another roll pass is made, now in the
width direction of the rotated ingot, a step called broadsiding.
This further roll pass transforms the ingot into a rectangular
plate 40, seen in front view in FIG. 5D and in top view in FIG. 5E.
In those Figures, both the previously thinner part 37 and the
previously thicker parts 21 and 22 et al are further reduced in
thickness to the thickness of plate 14 and the reduced thickness
cooperates with the tapered width of the ingot to form the plate 14
as a rectangle, as in FIG. 5E. The broadsiding reduces the
thickness of all parts 21, 22 . . . 37 to the thickness of the
rectangular plate.
[0041] The precise number of step changes used in the rolling
method is determined according to the process requirements. Where
yield loss is less of an issue, a high yield loss is accepted by
using fewer steps to get a low rolling time per ingot. If rolling
time is not an issue, but reducing yield loss is important, then a
greater number of steps are used, over a longer period of time.
[0042] As with the hydraulic cylinder automatic gauge control
system of modern mills, the method applied to the screwdown mill
does not require the use of an edger with rolls before or after the
mill to impart force to the edges on the plate. This helps make the
process simpler and applicable to using basic mill technology.
[0043] Although, a mechanical method of this type takes longer than
using single pass AGC cylinder loading and results in more yield
loss due to the spreading of plate steps into a saw tooth profile
edge in final pass, the result is an improvement on existing
operation of screwdown mills which can process material of the
required quality.
[0044] The present invention provides a process for roiling steel
ingots, with both width and thickness tapers, into plate. The
process may be used where the resulting plate has a thickness above
120 mm, giving more uniform thickness and width throughout, without
the need to use an edger in any passes. Mechanical screw loading
using multiple unfinished passes, with discrete roll gap change
between each, forms a stepped thickness profile. A further pass in
width direction (broad siding) is used to convert the thickness
profile to a width increase in the plate geometry, as shown at 14
in FIG. 5E.
* * * * *