The present invention relates to a device for controlling
automatically the depth of the vertical and horizontal loops formed
in steel wire rods during rolling thereof in a rolling mill of
steel plants.
The invention relates more particularly to a device in
which the depths of loops formed in the vertical and horizontal
planes of steel wire rods during rolling are sensed by conventional
sensors to produce corresponding electrical signals, an electronic
control unit is provided to amplify the difference of the sensed
signals from the corresponding reference signals and generate
time delays required for applying the amplified output signals to
control the speed of drawing rolls for maintaining the depths of
the said loops formed in the wire rods at the preset levels and
also for lifting the loops left at the back ends of the wire
rods.
In the production of wire rods in the wire rod rolling
mill of steel plants, billets of typical cross section 85 x 85 mm
and length 12 m are rolled in a series of stands each having a
pair of drawing rolls, arranged in tandem and finally coiled in
a coiler machine.
A typical wire rod rolling mill is provided with 23
rolling stands and coiler machine of Eden Boron type and contains
four strands each of twentythree stands. The hot rolled wire
rods produced in the mill are of diameters such as 5.5, 6.0,
8.0 and 10.0 mm.
For precise control of diameter and ovality of the
wire rods to be within acceptable tolerance limits, it is
necessary to maintain the depths of the vertical and horizontal
loops formed in the v/ire rods at intermediate stages of the
rolling operation to be at predetermined levels as shown in Table I
and to lift the loops present in the back ends of the wire rods.
At present the control of loop depths and lifting of
the loops at the back ends of wire rods are both performed
manually by adjusting the speed of the appropriate drawing rolls
at appropriate times. Since the mannual control is subject to
unavoidable variations depending on the skill of the operating
personnel, a sizeable proportion of the wire rods produced are
found to be of diameter and ovality beyond the prescribed
tolerance limits and an appreciable quantity of scraps in the
form of cobbles is found to be generated in rolling plants.
The object of the present invention is to provide a
device in replacement of the existing manual method for
maintaining the depth of loops as well as lifting of the loops
at the back ends of wire rods with a view to reducing the
quantity of rejections of off-standard rods and scrap generation
in the form of cobbles.
Thus the invention provides a device for controlling
automatically the depth of the vertical and horizontal loops
formed in steel wire rods in the rolling mill of a steel plant
characterised in that the device comprises: (a) a vertical
loop sensor of a conventional type for producing electrical
signals corresponding to the depths of the vertical loop;
(b) a horizontal loop sensor of a conventional type for producing
electrical signals corresponding to the depths of the horizontal
loop; (c) three hot metal detectors of conventional types
positioned adjacent to the respective stands of a known rolling
machine for detecting the presence of the wire rod therein and
producing the corresponding electrical signals; (d) a vertical
loop control unit for adjusting the speed of the drawing rolls
in the appropriate stands in response to the signals received
from the vertical loop sensor and the hot metal detectors; and
(e) a horizontal loop control unit for adjusting the speed of
the drawing rolls in the appropriate stands in response to the
signals received from the horizontal loop sensor and hot metal
detectors, the said units (a) to (e) being connected for
functioning in an interdependent manner.
The invention is described fully and particularly in
an unrestrictive manner with reference to the accompanying
drawings in which -
Figure 1 is a schematic view of one strand of a wire
rod in a rolling mill and of the vertical and horizontal loops
formed in the v/ire rod during the rolling operation;
Figure 2 is the schematic block diagram of the vertical
loop controller unit used for controlling the depth of the
vertical loop; and
Figure 3 is the schematic block diagram of the
horizontal loop controller unit used for controlling the depth
of the horizontal loop.
Referring to Fig. 1 the vertical loop VL is formed in
the space between STAND 19 and STAND 20, and the horizontal loop
Hl/ris formed between STAND 21 and STAND 22. A hot metal detector
^— to
HMD7 is positioned adjacent/STAND 7 (not shown); and hot metal
to
detectors HMD 16 and HMD 20 are positioned adjacent/STAND 16
and STAND 20 respectively. The wire rod WR is drawn through a
pair of drawing rolls DR contained in each STAND. A pair of
fixed guide angles GA for guiding the wire rod is used in
tandem in the space between each pair of adjacent STANDS,
except the space between STAND 19 and STAND 20, and that between
STAND 21 and STAND 22. For guiding the wire rod in the space
between STAND 19 and STAND 20, one upper and one lower guide
angles (not shown) are provided, of which the upper one is kept
fixed in position and the lower one is movable side ways by
actuating a solanoid. For guiding the wire rod in the space
between STAND 21 and STAND 22, a horizontal table (not shown)
is provided to support the wire rod thereon.
When the leading end of wire rod enters into STAND 20,
the hot metal detector HMD 20 is put on to actuate a solenoid
(not shown) which shifts the movable lower guide angle,
supporting the wire rod in the space between STAND 19 and
STAND 20, sideways allowing thereby the wire rod to sag
downwards by its own weight for forming the vertical loop VL.^^
After a delay of about 2 sec the speed of drawing rolls in each
of STAND 20 to STAND 23 is gradually reduced till the depth of
as shown in Table I.
the vertical loop VL/attains a predetermined limit/ After a
delay of A sec the speed of drawing rolls In STAND 22 Is
further reduced gradually by varying the dc voltage supplied
to the driving motors to allow formation of the horizontal
loop HL by means of a mechanical guide (not shown) which pushes
the wire rod lying on the horizontal table sideways in the
space between STAND 21 and STAND 22 till the horizontal loop
formed is of a predetermined depth.
After the back end of the wire rod leaves STAND 7,
the hot metal detector HMD 7 is put off to produce a signal
which increases the speed of drawing rolls in each of STAND 20
to STAND 23 slowly to reduce the depth of the vertical loop.
After the back end of the wire rod leaves STAND 16 the hot metal
detector HMD 16 is put off to produce a signal which increases
the speed of drawing rolls in STAND 20 at a relatively fast
rate to lift the vertical loop at the back end of the wire rod.
After the back end of the wire rod leaves the drawing rolls in
STAND 20, the hot metal detector HMD 20 is put off to produce
a signal which increases the speed of drawing rolls in STAND 22
and STAND 23 each, and also actuates the mechanical guide to
remove the horizontal loop at the back end of wire rod before
being wound in coil CL.
A vertical loop sensor VLS and a horizontal loop
sensor HLS, both of conventional type, are mounted in the
space between STAND 19 and STAND 20, and that between STAND 21
and STAND 22 respectively to produce electrical signals
corresponding to the depth of the loops formed in the vertical
and horizontal directions.
Referring to Fig. 2, in the vertical loop control
unit VLCU the output signal of vertical loop sensor VLS and a
reference signal from potentiometer POT 1 are supplied at the
input of the electronic amplifier unit EAU 1 comprising three
separate modules of conventional circuitry, of which one module
being a proportional amplifier amplifies the difference between
the signals from VLS and POT 1 by means of known operational
amplifiers and produces an output signal current of upto 10 mA,
till the back end of a wire rod remains within the grip of
drawing rolls in STAND 19, another module provides a signal
output suitable for lifting the back end of the wire rod when
lying in the space between STAND 19 and STAND 20, and another
module generates the time delays required for changing the speed
of drawing rolls in each of STAND 20 to STAND 23 in response to
the signals produced by the hot metal detectors HMD 7, HMD 16
and HMD 20 for controlling the performance of the to III as machine
in the manner as described herein before.
The output signals of the electronic control unit ECU 1
are passed through the control panel CPL to magnetic amplifier/
thyristor unit MAT to produce AC signals of 76 to 86 volts,
which are applied through potentiometer POT 2 to the driving
units of the drawing rolls in each of STAND 20 to STAND 23 for
controlling the speed thereof in predetermined manners.
Referring to Fig. 3, in the horizontal loop control
unit HLCU the output signal of horizontal loop sensor HLS and
a reference signal from potentiometer POT 3 are supplied at the
input of electronic amplifier unit EAU 2 which acting as a
conventional proportional amplifier and a comparator with known
operational amplifiers, produces an output signal corresponding
to the difference of the signals obtained from HLS and POT 3,
which is supplied to the power amplifier unit PAU which supplies
power through terminals A1 and A2, and resistors R1, R2, R3 to
tachogenerator TG1 for controlling, the speed of drawing rolls
in STAND 22, and through terminals A1 and A2, and resistors
R1, R4, R5 to tachogenerator TG2 for controlling the speed, of
drawing rolls in STAND 23.
The performance of the invented system has been
studied over a period in a steel plant. The following
advantages have been attained by using the system :- s
1. The shape and depth of the vertical and horizontal
as shown in Table I.
loops have been controlled automatically to the preset limits^
2. The back ends of wire rods have been straightened
automatically.
3. The rejections of wire rods have been reduced
significantly, i.e. around 35-40% .
^ 4. The generation of scraps in the form of cobbles has
decreased appreciably.
5. The tripping of the driving units of drawing rolls -
due to lifting of the back ends of wire rods has been eleminated.
6. The system has been found to be cost effective.
We Claim :-
1. A device for controlling automatically the depth of
the vertical and horizontal loops formed in steel wire rods
during rolling thereof in the rolling mill of a steel plant,
characterised in that the device comprises: (a) a vertical loop
sensor VLS of a conventional type for producing electrical
signals corresponding to the depths of the vertical loop VL;
(b) a horizontal loop sensor HLS of a conventional type for
producing electrical signals corresponding to the depths of
the horizontal loop HL; (c) three hot metal detectors HMD 7,
HMD 16 and HMD 20 of conventional types positioned adjacent
to the respective stands STAND 7, STAND 16 and STAND 20 of a
known rolling machine for detecting the presence of the wire
rod therein and producing the corresponding electrical signals;
(d) a vertical loop control unit VLCU for adjusting the speed
of the drawing rolls in the appropriate stands in response to
the signals received from the vertical loop sensor VLS and the
hot metal detectors; and (e) a horizontal loop control unit HLCU
far adjusting the speed of the drawing rolls in the appropriate
stands in response to the signals received from the horizontal
loop sensor HLS and hot metal detectors, the said units (a) to
(e) being connected for functioning in an inter-dependent
manner.
2. The device as claimed in claim 1, v/herein the vertical
loop control unit comprises an electronic amplifier unit EAU 1,
a control panel CPL and a magnetic amplifier/thyristor unit
Mat.
3. The device as claimed in claim 2, wherein the
electronic amplifier unit comprises three separate modules of which
one is a proportional amplifier for amplifying difference
signals, another provides output signal suitable for lifting
the back end of the wire rod when required and the remaining
one is a generator of time delays required for the operation of
the device in the predetermined manner.
4. The device as claimed in claim 1, wherein the
horizontal loop control unit comprises an electronic amplifier
unit EAU 2 and a power amplifier unit PAU.
5. A device for controlling automatically the depth of
vertical and horizontal loops formed in steel wire rods during
rolling thereof in a rolling mill of a steel plant* substantially
as herein described with reference to the accompanying drawings.

A device for controlling automatically the depth of
the vertical and horizontal loops formed in steel wire rods
during rolling thereof in the rolling mill of a steel plant,
characterised in that the device comprises: (a) a vertical loop
sensor VLS of a conventional type for producing electrical
signals corresponding to the depths of the vertical loop VL;
(b) a horizontal loop sensor HLS of a conventional type for
producing electrical signals corres;onding to the depths of
the horizontal loop HL; (c) three hot metal detectors HMD 7,
HMD 16 and HMD 20 of conventional types positioned adjacent to
the respective stands STAND 7, STAND 16 and STAND 20 of a known
rolling machine for detecting the presence of the wire rod therein
and producing the corresponding electrical signals; (d) a vertical
loop control unit VLCU for adjusting the speed of the drawing rolls
in the appropriate stands in response to the signals received from
the vertical loop sensor VLS and the hot metal detectors; and
(e) a horizontal loop control unit HLCU for adjusting the speed
of the drawing rolls in the appropriate stands in response to
the signals received from the horizontal loop sensor HLS and hot
metal detectors, the said units (a) to (e) being connected for
functioning in an inter-dependent manner.