Metal founding – Process – With measuring – testing – inspecting – or condition determination
Reexamination Certificate
1999-08-19
2001-10-02
Dunn, Tom (Department: 1725)
Metal founding
Process
With measuring, testing, inspecting, or condition determination
C164S428000, C164S480000, C164S154800
Reexamination Certificate
active
06296046
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an edge dam position control device and method of controlling the upper and lower positions of an edge dam, which is installed on both edge faces of twin rolls in a twin roll strip casting process that produces a strip(hot coil) directly in melt, without having a process of producing slab. More particularly, this invention helps minimize the force applied to the edge dam during the casting, minimize the wear and tear of the edge dam and improve the quality of both end faces of a strip, by calculating the height of the solidification point using the roll reduction ratio and the roll reduction force, and adjusting the height of the edge dam in the casting to correspond to the height of the solidification point.
2. Discussion of Related Art
Referring to
FIGS. 1 and 2
, the strip casting method in a conventional twin roll strip casting device will be discussed. First, melt
207
is received within a ladle
200
and flows to a tundish
210
through a nozzle
205
. Then, the melt
207
goes down to the space between a pair of rolls
220
and edge dams
230
that are mounted on the end faces of the pair of rolls
220
. Next, the melt
207
is solidified on the surface of the rolls
220
rotating in opposite directions. The solidified shells
227
meet each other at the solidification point, which is generally above the roll nip point, which is a roll kissing point. Hence, the solidified shell is hot rolled at this stage.
Then, the cast strip
240
through the roll nip point passes through a cooling process and is coiled by a coiling system(not shown). In the above process, the thickness of the strip
240
is adjusted in accordance with the control of the interval between the rolls
220
, and an adequate reduction of the solidified shell
227
is performed by means of a rolling force control unit
235
, which is comprised of the roll assembly, hydraulic systems and control system. In this case, the rolling force of the rolls
220
can be measured by the load cell, which is connected to the cylinder rod
237
b
supporting a roll chock
220
a.
Hence, in the twin roll strip casting process that directly casts the strip
240
with about 10 mm or less thickness from the melt
207
, what is important is that the melt
207
should be properly infused into the space between the water cooled twin rolls
220
through the nozzle
225
from the tundish
210
, so that the strip
240
can be produced with the desired thickness.
As shown in
FIG. 1
, in the conventional edge dam position control method, the bottom of the edge dams
230
is located on a roll nip point
222
. Japanese Laid Open Application No. 4-46656 discloses a structure to support the edge dam
230
with a predetermined force using a hydraulic device against both end faces of the rolls
220
.
In the above prior art, however, it is noted that upon a casting operation, the edge dam
230
is moved backward in a horizontal direction(in a vertical direction to the sheet of
FIG. 1
) due to the rolling force of the rolls
220
or the formation of skull(not shown) on a pool of the melt
207
. Skull is a solidified slab which is formed by local solidification at the circumference of a nozzle on the melt pool surface or at the joint between an edge dam and molten metal. In this case, the force applied to the edge dam
230
is maintained at a constant state by means of the hydraulic device. In general, a main object of the edge dam is to prevent the leakage of the melt
207
from the both sides of the rolls
220
. But in this case, the main object of edge dam cannot be achieved. Thus, good quality of the edge of the strip
240
may not be obtained.
In detail, when the edge dam
230
is moved backward due to the rolling force of the rolls
220
or the formation of the skull on the pool of melt
207
, the melt
207
has a leakage through a crevice. This results in an irregular formation of edge flash on both edge faces of the strip
240
, deteriorating the quality of the strip
240
. When the solidified shell is inserted between the edge dam
230
and the rolls
220
, the edge dam
230
and the twin rolls
220
are extremely damaged. Moreover, when the edge dam
230
is supported by a constant force against the rolls
220
, a serious problem occurs because the edge dam
230
or the rolls
220
are extremely damaged on the side.
SUMMARY OF THE INVENTION
Accordingly, the object of this invention is to provide an improved position control method and device of an edge dam in a twin roll strip casting process, which can minimize the force applied to an edge dam during casting and can reduce the degree of abrasion of the edge dam.
Another object of the invention is to provide an edge dam position control method and device in a twin roll strip casting process. This can efficiently prevent a leakage of melt because an edge dam is not moved backward even by the application of a slight force, thereby ensuring the quality of strip.
According to an aspect of the present invention, there is provided an edge dam position control method in a twin roll strip casting process for controlling the position of an edge dam to improve the quality of strip, said method including the steps of: calculating the position of a solidification point to the rolling force of the rolls and the calculated result; measuring a real rolling force of the rolls upon casting by means of a load cell; determining whether the position of the solidification point to the measured rolling force of the rolls corresponds to the current height of the edge dam; and moving the edge dam to a position where the height of the edge dam corresponds to the position of the solidification point of the measured rolling force of the rolls.
According to another aspect of the present invention, there is provided an edge dam position control device for improving the quality of the strip by controlling the edge dam position in the twin roll strip casting process that casts strip from melt between the rolls, being equipped with a pair of cast rolls and the edge dams on both sides of the rolls, said device comprising:
an edge dam horizontal control unit having a firs. hydraulic cylinder which is adapted to be connected with the edge dam installed on both end faces of the rolls, respectively, to thereby allow the edge dam to maintain a predetermined force on the edge portions of both sides of the rolls, respectively, and having a horizontal position measuring sensor for measuring a horizontal displacement of the edge dam;
an edge dam vertical control unit disposed on the bottom surface of the edge dam horizontal control unit and having a second hydraulic cylinder which is adapted to ascend/descend the edge dam horizontal control unit and a vertical position measuring sensor to measure a vertical displacement of the edge dam to thereby control the upper and lower movement of the edge dam;
a first load cell for measuring the force of the edge dam which is exerted by the casting;
a second load cell for measuring the rolling force of the rolls applied to the strip which is exerted by the casting and hot rolling; and
a controller For moving the edge dam by using the edge dam vertical control unit to a position where the height of the edge dam corresponds to the position of the solidification point of a pool of melt calculated on the basis of the rolling force of the rolls measured by the second load cell.
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patent: 5060714 (1991-10-01), Yamauchi et al.
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patent: 5628359 (1997-05-01), Legrand et al.
patent: 5638892 (1997-06-01), Barbe et al.
patent: 5706882 (1998-01-01), Fellus et al.
patent: 5927375 (1999-07-01), Damasse et al.
patent: 6079480 (2000-06-01), Oka et al.
patent: 4046656 (1992-02-01), None
patent: 6015414 (1994-01-01), None
patent: 7290205 (1995-11-01), None
Jeong Seong In
Kim Dong Koon
Song Je Myeong
Dunn Tom
Kerns Kevin P.
Pohang Iron & Steel Co. Ltd.
Webb Ziesenheim & Logsdon Orkin & Hanson, P.C.
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