FIELD OF INVENTION
The present invention generally relates to refining of molten material for steel making.
More particularly, the invention relates to a system for simultaneous collection of liquid
steel sample and acquisition of temperature data from LD vessel in steel making
process. The invention further relates to a method of simultaneous collection of liquid
steel sample and acquisition of temperature data from LD vessel.
BACKGROUND Of INVENTION
In integrated steel plant raw materials such as Iron ore lumps, sinter and pellet, coke
and fluxes such as limestone and dolomite are used to produce steel.
Following processes are generally followed for steel making :
a) Melting : Raw materials are charged into a blast furnace, where hot air is
pumped to melt iron and fluxes at 1600°C. The molten metal is then refined to
make steel.
b) Refining : Molten metal from the blast furnace is transferred to an oxygen
furnace (LD converter) to remove the impurities in liquid steel. The crude steel in
liquid form is taken from the blast furnace in a ladle for further refining/addition
of Ferro alloys.
c) Casting : The liquid steel is cast into semi-finished products such as billets,
blooms and slabs.
d) Rolling : The semis such as billets, blooms and slabs are heated to make the
metal malleable and then rolled into finished products. Slabs are rolled to HR
plate/strip/coil. HR sheet thickness can be further reduced by cold rolling i.e.
rolling in CR mill at room temperature. CR coils are zinc coated in a galvanizing
plant to make galvanized plates or corrugated sheets (GP/GC).
A detailed schematic process flow diagram is shown in Figure 1. Depending on the
design and layout, a process with a minimum requirement, decides the production
capacity of the plant.
PROCESS OF PRODUCING STEEL ACCORDING TO PRIOR ART AND
ASSOCIATED PROBLEMS =
As shown in Figure 2, the liquid steel from the blast furnace is tapped in torpedo cars
and thereafter tapped into ladles. The liquid steel tapped at about 1400CC is converted
to steel at 1650°C in the LD vessel by an exothermic oxidation of metalloids dissolved in
the iron. No external heating is necessary and most of the heat generated in the process
comes from the oxidation of silicon, manganese and phosphorus. Approximately 30% of
the charge is steel scrap, which is added to control temperature and to recycle in-house
scrap. Thereafter, in a step of removal of the impurities from the liquid steel, oxygen
with over 99.9% purity is blown at supersonic velocity through water-cooled multi-hole
lance onto the surface of the mixture of liquid steel, scrap and fluxes in the LD vessel.
During this step, oxidation of impurities takes place to form steel. Before the steel is
tapped, a sample of steel and temperature is taken respectively using a sampler and a
thermocouple. The sample of steel is taken to ensure that the desired chemistry of steel
is achieved wherein the temperature sample is taken to ensure that sufficient heat
energy is present for further secondary steel making processes. All these activities are
shown in Figure 3.
The activities involving collection of steel sample and a sample temperature, takes
around 4 minutes of time, which is approximately 10% of the entire steel making cycle
time (Figure 3). The major problem with LD steel making resides in monitoring the
temperature and composition of the metal. Normally, the LD vessel is tilted to measure
i
the temperature (using a thermocouple) and a sample for metal composition (using a
sampler). The most common design of the thermocouple and a sampler is shown in
Figures 9 and 10. It is important to note that the sampler and the thermocouple is
respectively the sample collecting and temperature measuring devices. In order to bring
the devices in contact with molten steel, a plurality of holding and dipping devices,
called lances are used. The lance used as a sampler is called 'Thermocouple Lance'
(Figure 4).
The prior art process of taking the temperature and the sample in the LD vessel is
shown in Figures 2 & 3 and can be illustrated as under:
• Scrap is charged into the vessel by tilting the vessel,
• Then Liquid steel is charged in the vessel. The vessel is then rotated into
vertical position,
• A water-cooled multi-hole lance is lowered into the vessel, which blows oxygen
at supersonic speed,
• Oxygen cause oxidation of various impurities in the metal and causes an
exothermic reaction,
• This increases temperature in the vessel making the metal more fluid,
• After blowing the oxygen, the lance is drawn back and the vessel is again titled,
• A worker walks to the Sampler, Lance collects the lance and insert sampler into
the lance,
• The worker approaches the tilted vessel and dips the Sampler Lance,
• The sampler lance is kept dipped for about 5-6 seconds and then taken out,
• The worker breaks the sampler probe and dips the sample into water to cool it.
In the meanwhile, another personnel walks to the temperature lance and picks
it up and insert thermocouple into it,
• The worker approaches the vessel and dips the thermocouple into the Liquid
steel,
• The thermocouple is kept in this position for 6-7 seconds and the temperature is
obtained on the display, and
• The lance is taken out and the Vessel starts rotating back into vertical position.
The inventors during their research and experimentation observed that there are
multiple problems with the way the sampler and the thermocouple are used in the prior
art, namely :
• Sampler rejection : The inventors observed that during usage of the sampler,
at least 22% of the samplers are rejected due to various reasons (rejected
means sampler not able to collect steel sample). Since taking the steel sample is
important to understand the steel composition, any rejection increases the steel
making cycle- time due to use of another sampler. As shown in Figure 3, a
sample collection takes around 2 minutes in a total steel making cycle time,
which means any rejection of a sampler increase the steel making cycle time by
at least 5%.
• Bending of lance : The lances used for holding and dipping the sampler and
the thermocouples in steel bath are generally made of mild steel (Figure 4).
Because of inherent property of mild steel and the design of prior art lance, the
lances bend under the influence of high temperature of 1600°C (Figure 4).
• Spare lance : After taking temperature from the thermocouple, it is displayed
electronically. Therefore, the lance for thermocouple needs to have an electrical
connectivity whereas the lance for the sampler does not require the same.
Because of this difference, the lances of sampler and thermocouple is different
and therefore the users perforce keep two different types of lance in stock.
• Ergonomics : Temperature in the LD vessel (unit for converting liquid iron into
steel) is about ~ 1500°C. For taking the sample and temperature using a
sampler and a thermocouple, at least two people are involved. In this process
they get exposed to high temperature and cost increases.
The prior art methodology for steel making in LD vessel can be briefly summarized as
under:
TEMPERATURE MEASUREMENT : a stainless steel lance made of SS304 having a
front lance of about 1.2 meter long and a back pipe about 5 meters long is used. There
is a bend between the front and the back pipe. The front pipe lances with a bend of
about 15 degrees are used to carry out the temperature measurement using dipped
probes into the steel bath. This lance carries a compensating cable running inside it to
carry the mV signal a system for simultaneous collection of liquid steel sample and
acquisition of temperature data from an LD vessel in a process of steel making, of a
thermocouple from the probe to a measuring instrument.
SAMPLER LANCE : Another lance is used with a bend of 40 degrees to carry the
sample probe into the steel bath. The OD of this lance is % inches and there is no cable
inside this lance.
OBJECTS OF INVENTION
It is therefore an object of the invention to propose a system for simultaneous collection
of liquid steel sample and acquisition of temperature data from an LD vessel in a process
of steel making, which eliminates the disadvantages of prior art.

Another object of the invention is to propose a system for simultaneous
collection of sample and acquisition of temperature data from an LD vessel in a process
of steel making, which reduces the time for liquid steel sample collection and acquiring
temperature data in the LD-vessel by at 50%. This object reduces the steel making cycle
time by 5% and substantially eliminates rejection of the sampler probe device.
A further object of the invention is to propose a method of simultaneous collection of
liquid steel sample and acquisition of temperature data from an LD vessel, which
eliminates the multiple activities and reduces the complexities of steel making process.
A still further object of the invention is to propose a dual-acting probe device which is
enabled to simultaneously collect hot sample including temperature data from an LD-
vessel in a process of steel making.
Yet further object of the invention is to propose a common single lance adaptable to the
dual-acting probe device in a process of steel making through LD-route.
SUMMARY OF THE INVENTION
Accordingly there is provided in a first aspect of the invention a system for simultaneous
collection of liquid steel sample including acquisition of temperature data from an LD
Converter in a process of steel making, the system comprising a dual acting probe
device with a meltable protective cap enabled to collect liquid steel sample from the LD
converter and simultaneously acquire temperature data inside the converter for
transmission of the acquired data via a triangle piece connector for display in a display
unit; and a common single Lance adaptable to the probe device and allowing dipping of
the system inside the LD converter at different angles including withdrawal of the
system from the converter subsequent to collection of sample and transmission of
temperature data, Characterized in that the dual acting probe device comprises a
thermocouple including a copper wire, and being connected to a bath temperature
indicator for acquiring and transmitting temperature data; a splitted metal mould
enabled to produce a cavity when closed at a first end to allow ingress of molten steel
via a silica tube upon insertion of the system into the converter, the second end of the
mold attached to said silica tube; a guide bush to connect the probe device with the
common single lance; and a sand shell accommodating the thermocouple, metal mould,
silica tube, and the triangle piece connector, the shell allowing the hot molten metal to
cool down quickly when the metal introduced into the mold.
In a second aspect of the invention, there is provided a method for simultaneous
collection of liqujd steel sample including acquisition of temperature data from an LD
converter in a process of steel making, the method comprising the steps of manually
dipping the system into the LD vessel containing liquid steel, the metal cap being
punctured by the liquid steel; allowing the hot molten metal to enter the mould via the
silica tube for filling the mould; generating mv signals representing the temperature of
the both through the thermocouple which being transmitted via the copper connector;
displaying the temperature data in the display device corresponding to the mv - signals
transmitted from the,connector through the triangle piece; allowing the liquid steel to
solidify in the metal mold; withdrawing the system from the vessel and collecting the
sample by destroying the probe.
Thus, the inventors through research and experimentation developed a new system
which can simultaneously collect sample and measure temperature. In other words, the
functions of sampling and temperature determination have been combined in this new
system which basically comprises a dual acting probe device adaptable to a single
common lance.
BRIEF DESCRIPTION OP THE ACCOMPftHYING DRAWINGS
Figure 1 - Shows a schematic diagram of an integrated steel plant depicting the
features of melting, refining, casting, and rolling to produce steel
materials.
Figure 2 - Shows a generic process flow of liquid steel from blast finance till the
tapping of steel from an LD vessel.
Figure 3 - Shows a prior art activity break-up of tilting of LD-vessel during the steps
of sample collection and temperature data collection.
Figure 4(a) - Shows a prior art sampler probe and a prior art thermocouple.
Figure 4(b) - Shows the prior art lances for sampler probe and thermocouple.
Figure 5 - Shows a pictorial view of prior art lances.
Figure 6 - Shows a pictorial view of a common single lance of the invention.
Figure 7 - Shows an activity break-up of the invention in respect of the steps of
Figure-3.
Figure 8 - Shows a prior art thermocouple for measuring temperature.
Figure 9 - Shows a prior art sampler probe.
Figure 10 - Shows a dual-acting probe device according to the invention.
Figure 11 - Shows a common single lance acceding to the invention adaptable to the
dual acting probe device of Figure 10.
Figure 12 - Shows a system for simultaneous collection of liquid steel sample and
acquisition of temperature data from an LD converter according to the
invention.
Figure 13 - Shows an operational sequence diagram of the dual acting probe device
of the Invention.
Figure 14 - Shows a flow chart depicting the operational steps of the method
according to the invention.
PETAIL DESCRIPTION Of THE INVENTION
As shown in figures 6, 10, 11 and 12 the inventive system comprises a dual-acting probe
device (DAPD) and a single common lance (ACSL) adaptable to the probe device
(DAPD).
As shown in figures 6 and 11, the dual-acting probe device (DAPD) comprises:
a protection cap (1) : Once the probe device (DAPD) is dipped in molten steel
the protecting steel cap (1) melts down and allows the steel to go into a sample
chamber (4). The function of the cap (1) is to prevent a Silica tube (7) from
getting damaged;
a thermocouple (2) : The thermocouple (2) is selected of Type "B"
Platinum/6% Rhodium-Platinum 30% Rhodium alloy suitable for high
temperature measurement. When the thermocouple (2) senses the temperature,
a milli-volt (mV) output is generated;
a Copper Wire (3) : This acts as a ± mv output terminals of the thermocouple,
(2) which is irt turn connected to a plastic connector (5) to carry the mV signal
up to a bath temperature indicator, which is a display unit, and which converts
the mV signals in terms of temperature and display it;
a Sample chamber (4) : This is made of thick steel sheet and operates as a
mold. This steel mould (4) comprises two halves split axially at the centerline. A
cavity is formed by joining the two split moulds. The mould (4) is closed at one
end while at the other end is fitted with the silica tube (7). When the molten
metal flows into the tube (7), the air present in the chamber (4) gets exhausted
through an air duct (9);
a PVC Triangle Place (5) : This acts as a connector, which transmits the mV
signal generated by the thermocouple (2) to a temperature measurement means
for display. This connector (5) is made of Polyvinyl Chloride (PVC) as it is easily
moldable;
a PVC Guide bush (6) : This is a plastic component and the function is to
guide the probe assembly to connect with a steel lance (Figure 12).
A SUka tube (7^ : This tube (7) as described hereinabove acts as the entry
point of the molten steel into the sample chamber (4). The function of the tube
(7) is to guide the molten metal from the molten steel bath of the LD converter
to the sample chamber (4). The q uartz glass (7) is having a high melting
point and thus does not melt at 1800 degrees c. This facilitates the molten metal
to rise up into the sample chamber (4) without melting the tube (7);
a Sand Shell (8) : This is a resin-coated sand shell, which houses all the
components of the dual acting probe device. The components like thermocouple
(2), mild steel moulds (4) (in two halves), quartz tube (7) and PVC triangle piece
connector (5) are fitted into the sand shell(8), the airduct adjoins the sample
chamber which allows the metal to cool down quickly, when it comes into
contact with the metallic mould (4).
As shown in figure 11, the present invention provides a common single lance
(AOSL) which is adaptable to the dual acting probe device. The inventive lance
comprises:
a front lance (10), which is a SS 304 pipe of about % inch nominal bore. In the
front end of the pipe (10) there is a holder to attach a contact block (15), which
is substantially an electrical socket used to connect the triangle plastic connector
(5);
a Bend Socket (11) which is bent to achieve a 40-degree angle to facilitate the
slag penetration;
a Back pipe (12) which is a SS 304 pipe having a nominal diameter about %"
and allows acquiring temperature from a distance;
a Handle (13) which enables handling of the lance (ACSL);
a Guide Bush means (14) made of MS for guiding the silice tube (7) of the probe
device (DAPD). The means (14) comprises at least one guide bush and a contact
block. There are three slots in the guide bush to allow hot gases to go out at the
end of the front pipe (10);
a Contact Block holder (15) made of MS;
a Cladding (16) which constitutes a cladding pipe slipped over the back pipe
(12), and a first end of the cladding welded near is the front lance (10), a
second end is provided with a handle (13), the cladding pipe (16) provides
higher stiffness to the back pipe (12) and maintains an angle of approximately
40 degree under the hot conditions of the L.D. Vessel; and
lance cable (17) running through the inside of the lance (ACSL) and carrying the
mV signal up to the temperature indicator.
The common single Lance of the invention is enabled to eliminate many problems of
the prior art sampler lance and thermocouple lance, with an improved configuration
allowing adaptation of the dual acting probe device and enhance its penetration in
the molten steel and including reduction in the bending of the lance under the
influence of high temperature environment.
The new lance is capable to carry out alone the function of prior art sampling lance
as well as the prior art temperature lance. The front end (10) of the lance is bent at
40°, to penetrate the slag and also to allow hot gases out through ducting made into
the front (10) pipe. The compensating cable run through inside the lance to carry
temperature signal. In order to address the lance bending issue, considering the
temperature of 1600°C, the cladding pipe (16) is provided near the Bend Socket (11)
as shown in the Figure 11.
Figure 12 shows the inventive system in an operational mode for simultaneous
collection of liquid steel sample from the laddie and acquisition of temperature data.
Figure 12A & 12B each shows the lance (ACSL) before and after assembly with the
double acting probe device (DAPD).
Figure 13 and Figure 14 illustrate respectively the operational sequence of the dual-
acting probe device (DAPD) and operational method of the inventive system. At the
first step, the dual-acting probe device (DAPD) according to Figure 13, is hooked to
the bend lance (ACSL). The lance in dipped into the liquid vessel, and the liquid steel
punctures the steel cap (1) enabling the thermocouple (2) to sense the
temperature, and the sample chamber (4) being filled with liquid metal. On
completion of the step, a hooter indicates a finish signal when the common lance
(ACSL) is pulled out. The display shows the measured temperature and the sample is
recovered by tapping the probe device (DAAD).
As shown in figure 14, the inventive system allows at a first step the dual acting
probe device (DAPD) to be dipped into the liquid steel, and with the puncturing of
the steel cap (1), the MS mold (4) is filled up with liquid steel, transmitted through
the silica tube (7). The thermocouple (2) is enabled to generate mv-signals which
are transmitted through the copper wire (3) and then to the triangle piece (5).
Meanwhile the collected liquid sample get solidified, and the triangle piece (5)
transmits further, v-signals for display representing the temperature of the solidified
steel sample. The probe device (DAPD) is withdrawn from the LD vessel and the
sample is collected after tapping and breaking the device.
In other words, the inventive system is dipped into the LD converter steel bath,
which is to be sampled. The system is dipped up to 3 feet under the molten steel
inside the LD Vessel. As the prove device (DAPD) is exposed to the molten metal
and the metal punctures the steel cap (1) of the probe device, and the thermocouple
(2) senses the temperature while the sample chamber (4) gets filled up with the
molten steel. As soon as the measurement is complete a hooter gives an indication
of the completion of the process. The operator then pulls out the lance (ACSL) at
this stage and strips the probe (DAPD) off the lance (ACSL). Now the probe (DAPD)
is tapped on the ground and the sample falls out of the steel moulds (4). The
temperature measurement meanwhile is indicated at the temperature indicator thus
completing the function of temperature and sampling in one dipping which was
earlier done in two separate dipping. This saves the critical time in the steel making
process.
PROBE ASSEMBLY : The sand shell assembly (8) is pressed into a long paper
tube. This tube acts as a carrier of the probe device (DAPD). This assembly is in turn
hooked on to the bend lance (ACSL) (Figure 11) and dipped into the molten steel.
The function of the paper tube is to protect the bend lance (ACSL) from melting
down. The paper tube does not melt because it carbonizes in the absence of oxygen.
ADVANTAGE OF THE INVENTION
Reduction in steel making cyde time: With the development of the new
system, steel making cycle time reduces by 5%. This is possible because, the dual
acting probe device can take sample and temperature both in one dip. Since the
sampler and thermocouple of prior art take around 2 minutes of time each, sample
and temperature taking time for one heat in LD vessel is ~4 minutes. But, by using
the inventive probe device, in place of prior art sampler and thermocouple, both
sample and temperature can be taken in just 2 minutes (Figure 6). In other words,
the invention reduces the time take taken for making one heat by up to 2 minutes
which is ~ 5% of the total steel making cycle time. The time hence saved can be
used to increase production.
Elimination of samolw rejection : As mentioned hereinabove, poor quality
samplers were getting rejected and every sampler rejection used to increase the
prior art steel making cycle time by 5%. In order to address this disadvantage, the
inventors carried out root cause failure analysis. As a result, the inventive system is
capable to minimize the rejection. Secondly, a delay leading to increase in steel
making cycle time due to sampler rejection has also become negligible.
WE CLAIM:
1. A system for simultaneous collection of liquid steel sample including acquisition of
temperature data from an LD Converter during the steel making process, the
system comprising :
a dual acting probe device with a meltable protective cap enabled to collect liquid
steel sample from the LD converter and simultaneously acquire temperature data
inside the converter for transmission of the acquired data via a triangle piece
connector for display in a display unit; and
a common single Lance adaptable to the probe device and allowing dipping of
the system inside the LD converter at different angles including withdrawal of the
system from the converter subsequent to collection of sample and transmission
of temperature data,
Characterized in that the dual acting probe device comprises a thermocouple
including a copper wire, and being connected to a bath temperature indicator for
acquiring and transmitting temperature data; a splitted metal mould enabled to
produce a cavity when closed at a first end to allow ingress of molten steel via a
silica tube, upon insertion of the system into the converter, the second end of the
mold attached to said silica tube; a guide bush to connect the probe device with
the common single lance; and a sand shell accommodating the thermocouple,
metal mould, silica tube, and the triangle piece connector, the shell allowing the
hot molten metal to cool down quickly when the metal introduced into the mold.
2. The system as claimed in claim 1, wherein the thermocouple is formed of Rhodeim
alloy with type 'B' platinium 6%.
3. The system as claimed in claim 1, wherein the copper wire acts as a ± mv output
terminal of the thermocouple and connected to the triangle piece connector, and
wherein the connector is made of plastic.
4. The system as claimed in claim 1, wherein the guide bush is made of plastic.
5. The system as claimed in claim 1, wherein the common single lance comprises a
front lance and a back lance, and wherein the front lance is provided with a contact
block holder to connect the triangle piece connector.
6. The system as claimed in claim 1 or 5, wherein the back lance is enabled the probe
device to acquire temperature from a distance, and wherein the back lance allows a
cladding pipe to be rigidly joined at a first end with the front pipe, the second end of
the cladding pipe being fixed to a handle.
7. The system as claimed in claim 1 or 5, wherein a bend socket is provided between
the front and back lance to achieve at least 40° bent of the front lance.
8. The system as claimed in claim 5, wherein the front lance and the back lance
comprises SS;304 pipe.
9. A method for simultaneous collection of liquid steel sample including acquisition of
temperature data from an LD converter in a process of steel making, the method
comprising the steps of :
manually dipping the system into the LD vessel containing liquid steel, the metal
cap being punctured by the liquid steel;
allowing the hpt molten metal to enter the mould via the silica tube for filling the
mould;
generating mv signals representing the temperature of the both through the
thermocouple which being transmitted via the copper connector;
displaying the temperature data in the display device corresponding to the mv -
signals transmitted from the connector through the triangle piece;
allowing the liquid steel to solidify in the metal mold;
withdrawing the system from the vessel and collecting the sample by destroying
the probe.
10. A system for simultaneous collection of liquid steel sample including acquisition of
temperature data from an LD Converter during steel making process, as substantially
described and illustrated herein with reference to the accompanying drawings.

The invention relates to a system for simultaneous collection of liquid steel sample
including acquisition of temperature data from an LD Converter during steel making
process. The system comprise a dual acting probe device with a meltable protective
cap enabled to collect liquid steel sample from the LD converter and simultaneously
acquire temperature data inside the converter for transmission of the acquired data
via a triangle piece connector for display in a displaying unit. The system also
includes a common single Lance adaptable to the probe device, allowing dipping of
the system inside the LD converter at different angles including withdrawal of the
system from the converter subsequent to collection of sample and transmission of
temperature data. The system is characterized in that the dual acting probe device
comprises a thermocouple including a copper wire, and being connected to a bath
temperature indicator for acquiring and transmitting temperature data; a splitted
metal mould enabled to produce a cavity when closed at a first end to allow ingress
of molten steel via a silica tube upon insertion of the system into the converter, the
second end of the mold attached to said silica tube; a guide bush to connect the
probe device with the common single lance; and a sand shell accommodating the
thermocouple, metal mould, silica tube, and the triangle piece connector, the shell
allowing the hot molten metal to cool down quickly when the metal introduced into
the mold.