During manual operation of continuous casting tundish, temperature measurement, sampling, addition of protective slag and shroud loading and unloading work, the operator will be exposed to high temperature and dust environment, labor intensity, accidental reaction splashing or ladle formation in the tundish There is a certain danger when the shell falls. Working in this environment, these indispensable operational tasks must be completed to ensure the stability of the continuous casting process and the quality of the slab. By using two robots to realize automatic tundish operations, safety and operating efficiency can be greatly improved, and process reliability can be improved. This article introduces the layout, composition, characteristics and operation of the tundish robot project in detail.
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Industrial robots have been used in the automotive industry for many years, but so far, robots are rarely used due to the harsh environment of steel plants. The main problem is that industrial robots and their auxiliary systems (such as material magazines or tool warehouses) must adapt to this Challenging environment, work that meets customer requirements for reliability. However, in the past 10 years, more and more robot systems have been successfully installed worldwide to perform sampling, measurement and processing tasks in the fields of oxygen converter steelmaking, electric furnace steelmaking and continuous casting. [1~3]
In the area of the
continuous casting machine, most of the robots are installed in the tundish
area, because during the manual operation of the tundish, the operator will be
exposed to high temperature and dust. The labor intensity and the internal
reaction and splashing of the tundish or ladle are dangerous. , There is even a
danger of crusting slag falling from the ladle. Working in this harsh
environment, the following important operational tasks must be completed to
ensure continuous casting process stability and product quality:
Temperature measurement.
Determination of hydrogen.
sampling.
Covering agent for tundish.
Loading and unloading operation of ladle long nozzle.
Long nozzle oxygen cleaning.
Burn the oxygen bow when it is not automatic pouring|flow blow open the ladle nozzle.
First of all, the
introduction of robots can greatly improve the safety of the operators, because
the operators operate remotely and avoid dangerous areas, and there is a
sufficient safety distance between the operators and the molten steel.
The second important
factor in the use of machines is to improve production efficiency and maintain
the stability of product quality. The robot can add covering agent to the
tundish according to the set program timing, quantification and positioning,
which ensures that the tundish starts and repeats various actions quickly and
safely. It installs, disassembles, oxygenates and checks the ladle nozzle,
reducing the time for ladle replacement During the replacement, no molten steel
falls into the tundish, which improves the safety. At the same time, because
the height of the molten steel level in the tundish is quickly maintained, the
quality of the castings related to the inclusions caused by the change of the
drawing speed and the drop of the liquid level can be avoided problem.
In addition to adding the
covering agent, the continuous casting tundish robot can also repeat and
accurately complete the temperature measurement and sampling according to the
production process steps, and the temperature measurement and sampling position
and the immersion depth of the molten steel are executed at a predetermined
time according to the production specifications. Therefore, The automatic operation
of the tundish further improves the reliability of the entire continuous
casting process. All data of the robot operation and the quantity of
consumables are recorded, and further analysis and process optimization are
carried out through the secondary automation system or the manufacturing
execution system (MES), so the process operability has also been enhanced.
The current work
describes the use of two robots in the tundish area of two continuous casting
machines of Ternium, Brazil, to implement robot operations, and introduces the
main components, characteristics and operating performance of the system in
detail.
l Project scope
In August 2017, the
Brazilian steel mill of Dexing Company's Tener Group (the former Thyssen-Krupp
steel mill) awarded Vesuvius a turnkey project. The project is a robot system
(robot continuous casting technology Or RCT), can perform 7 related operations
in the tundish area of the two-strand slab caster.
In the first phase of the
project, four functions were implemented (temperature measurement, hydrogen
determination, sampling and addition of covering agent). Since the replacement
of the ladle nozzle requires the replacement of a new casting slide mechanism
(LTC), it was implemented in December 2018. From January to March 2019, the
ladle opening pouring mechanism was transformed, and all functions were
completed in the second project phase.
The robot system was put into operation on the No. 1 continuous casting machine in May 2018 and on the No. 2 continuous casting machine in November 2018, with four new functions. The tundish. The upper platform must be reinforced and reconstructed during the five-day planned maintenance shutdown period. System optimization, thermal commissioning and operator training do not require additional downtime. Finally, all 7 functions of the robot were fully put into use on two continuous casting machines in April .
l Robot system (RCT)
The equipment position on
the upper platform of the tundish has been carefully designed and reinforced to
ensure safe operation, optimize the operating procedures of the robot, and
minimize changes to the continuous casting machine. Since the operating space
of the two robots is very limited, in order to optimize the position of the
robot and the auxiliary system of the cargo magazine, the whole project was
simulated in a virtual three-dimensional environment. In addition, the movement
of the robot, the accessibility of all material magazines, storage racks and
tools are all simulated and verified in this virtual environment for collision
detection.
Despite extensive 3D
simulations, the robot was assembled and tested in Vesuvius, Belgium, along with
all tools, material magazines and consumables. In this controlled environment,
the programming of the robot trajectory and the testing of the complete
automation package (tool function, shroud and safety mechanism, including all
failure scenarios) are completed. The Brazilian Ternium project team members
participated in several factory tests, reviewed functions and requirements, and
received extensive operation and maintenance training. The following figure
shows some pictures of these workshop tests. (Picture 1)
The figure below shows
the layout of the robot system and all its main components. Generally speaking,
the design of robot system should meet some safety standards, such as EN ISO
12100:2010 (General Principles of Mechanical Safety Design), ISO/TR 202218
-1:2018 (Safety Design of Robot-Industrial Robot System), ENISO 10218-2 :2011
(safety requirements for robotic systems and integration) and IS013849-1:2006
(machine safety-part of the safety control system). (Figure II)
The design of the robot
system uses two industrial six-axis robots (Robot No. 1 (1) and Robot No. 2
(2), these two robots are specially modified for the harsh conditions of the
casting platform. Both robots have-a special The sleeve is protected to deal
with the environment of the steel factory, that is, to prevent molten steel
splashing, heat radiation, and dust from entering. Because these two robots are
standard industrial robots of KUKA⑧, they are widely used in the automotive
industry and can provide spare parts and 24 Hours of technical assistance.
Robot No. 1 completes all the shroud replacement operations and the addition of the tundish covering agent at the two positions of the tundish. However, this robot does not need to support it for a long time during casting after installation of the shroud, because the ladle shroud has a supporting structure in the new LTC mechanism. The layout of the robot allows to retain the existing shroud manipulator as a backup solution, allowing a smooth transition from manual operation to fully automatic operation during commissioning.
The second smaller number
two robot (2) handles different probes: temperature measurement, hydrogen
determination and sampling. In the case that the automatic pouring cannot be
started, the oxygen-burning top opens the ladle nozzle for drainage, and the tundish-one
position with covering agent. Both robots are equipped with special fixtures
(tool converters) to grasp different tools, and transmit the required media or
signals through the tool (with and without argon sampling, hydrogen
measurement, molten steel temperature detection or any Other specific media
such as oxygen). As a safety measure, the tool changer remains clamped
(self-locking) to prevent air pressure leakage failure.
The robot system is
installed in place after dismantling the existing cabinets and operating
tables, rearranging the current operating panels, power, fluid and gas
pipelines, and installing on the existing tundish platform (3). Since both
robots will generate additional static and dynamic loads on the continuous
casting platform, the structure of the existing platform must be reinforced. It
can be seen from Figure 2 that due to the realization of the robot system, the
casting platform is expanded into two movable platforms (4), which can be
easily removed when the casting machine repairs and replaces parts.
All robot movements occur
in a closed robot space, separated by fences on the platform, and the operator
enters intelligently through the door (5) and the door (6). According to
IS013849-1:2006 automatic i door lock mechanism, connected to A safety
programmable logic controller (PLC), which allows or denies the operator access
according to the actual operating state of the robot system.
During normal continuous casting operations, the operator usually does not need to enter this enclosed space because all consumables are provided to the system from outside the robot space. The robot obtains the detection head and the sampling head from the material magazine (7). After use, the robot puts them into the sampling head scrap box or the sampling sample box (8), and the operator processes them.
The tundish insulation
bag (10 kilograms of synthetic powder or carbonized rice husk) is loaded into
the movable insulation shelf (9) and (10); the robot is taken by tools. The
ladle shroud rack (11) provides storage for up to 6 shrouds, which can be used
for continuous casting for a long time without the need for manual handling of
shrouds in the robot motion space unit during shift operation.
Both robots grab tools
from specific shelves (12), (13) and (14). Figure 3 shows the robot system
assembled before the start of the hot test phase of the continuous casting
machine in May 2018.
Ladle opening mechanism (LTC)
Before the implementation
of this project, the downward flow of molten steel between the ladle and the
tundish was controlled by the pouring slide mechanism. The upper part of the
conventional shroud is an upper wrist aligning with the pouring mechanism with
a taper nozzle, which is flushed with argon gas to protect and seal ( See
Figure 4a). However, robot automatic replacement of the shroud requires
different methods, and there is no way to use a manipulator to keep the shroud
fixed on the ladle opening mechanism. The LTC mechanism of Vesuvius is a ladle
pouring slide device with an integrated shroud device to load and keep the
shroud fixed on the ladle pouring mechanism. During the casting of the LTC
mechanism, the integral ladle shroud is pressed to the lower plate, and the
robot only needs to load and unload the shroud from the LTC (Figure 4b).
Because there is no physical connection between the ladle and the platform
during the casting process, it is guaranteed that the turntable can rotate
freely in an emergency situation.
Compared with the
conventional ladle slide pouring mechanism, two hydraulic cylinders are used to
operate the LTC mechanism, and the larger hydraulic cylinder (1) controls the
movement of the slide plate, thereby controlling the speed of the ladle steel
underwater flowing into the tundish (see figure) 5). The smaller hydraulic
cylinder (2) switches between the conical upper end (3) of the shroud (the
conventional shroud operation uses a manipulator), and the robot operates the
shroud (4). The good switching between these two operation modes can make the
machine debugging stage flexible, and also can use the backup manual operation
manipulator to install and remove the shroud. In the first phase of the
implementation of LTC, the hydraulic system and hydraulic cylinder support of
the ladle turret were improved to operate the new LTC mechanism and the
original pouring mechanism at the same time. After these modifications, the LTC
structure was gradually installed on each ladle. The modification of the ladle
is limited, and is limited to the adjustment of the radiation protection plate
and the assembly of the intermediate adapter plate.
As mentioned above, in
the first stage of implementation, LTC was used as a conventional ladle slide
mechanism, using a manipulator to cover the long nozzle on the taper of the
pouring mechanism. After the first implementation phase, only a few adjustments
(replace a few parts) are required to allow the robot to replace the shroud in
a full LTC operation.
The possibility of
switching between the two operating modes provides huge benefits for the
non-self-opening state. In this case, the oxygen-burning drainage needs to
continue the casting sequence. In the full-time operation, the oxygen blast
tube is inserted into the taper nozzle, and the integral ladle long reservoir
is still installed in the pouring mechanism. Therefore, the time interval
between the drainage and the use of the long nozzle (and therefore the The
negative impact of steel quality) is reduced to a minimum. Therefore, after
successfully completing the task of oxygen burning and drainage, the overall
ladle nozzle is ready to quickly change the casting position at any time.
From the perspective of slab quality, the traditional long nozzle is connected with the taper nozzle of the pouring mechanism. (1) The use of the LTC mechanism can better protect the secondary oxidation and nitrogen absorption of the steel flow (Figure 6). After the improvement, the long nozzle (2) is in flat and sealed contact with the upper pouring mechanism slide block (3). The spring compression force is about 1.5 tons, and there is an argon-blowing annular seam to keep the positive pressure and shield the atmosphere from entering (4). The idea of plane connection can perfectly align the shroud vertically and provide a symmetrical stream of molten steel into the tundish, so the product quality and the cleanliness of molten steel can be maintained.
Another advantage of the
LTC mechanism is that the bottom slag detection ring is integrated on the
bottom plate, which improves the reliability of the bottom slag detection,
thereby improving process stability and product quality.
Another advantage of the
LTC mechanism is that the bottom slag detection ring is integrated on the
bottom plate, which improves the reliability of the bottom slag detection,
thereby improving process stability and product quality.
- Tundish operations
As mentioned earlier, the commissioning
phase is divided into two phases, and in the first phase, the robot system has
four functions available:
Molten steel temperature measurement
The temperature is
measured through the hole on the right side of the tundish cover. For the No. 1
continuous caster, it is near the second flow stopper, and for the No. 2
continuous caster, it is near the 4 flow stopper. Robot No. 2 grabs the
temperature measuring tool from the specific tool rack, takes out the
temperature measuring probe from the material magazine, and dips it into the
molten steel in the tundish through the hole on the tundish cover. Since the
material bomb warehouse has temperature probes, fixed hydrogen heads and
samplers (Figure 7a), it must be designed to correctly extract
"error-proof" to prevent shutdowns with the wrong probe. After the
temperature measurement system evaluates the temperature measurement data
normally or after the maximum immersion time has elapsed, the robot removes the
probe and discards it in the probe waste box. After each temperature
measurement, use a bag of tundish covering agent to cover the exposed point of
molten steel caused by temperature measurement. This is a better method of
operation. In order to make the smallest possible opening when the temperature
measuring gun is immersed in the covering agent and molten steel during
temperature measurement, and to avoid the formation of crusts on the tundish
cover hole, it is a good way to use a probe with a cardboard structure with a
splash-proof coating. 7b shows the temperature measurement of the tundish of
No. 1 continuous casting machine.
Tundish molten steel hydrogen determination
From the program point of
view, the indirect hydrogen measurement is very similar to the temperature
measurement, except that the tool and probe type are different, and the
immersion time into the molten steel is much longer than the temperature
measurement.
sampling
Sampling
is also very similar to temperature measurement, the probe is replaced with a
sampler, and the sampling time is immersed in the molten steel for a long time.
After sampling, the robot places the sampler in the sample box, cools and
processes it by the operator, and then sends the sample to the laboratory.
According to the requirements of steel type, in the casting process of a ladle,
at most three tundish samples are taken for a given ladle molten steel weight.
Sampling and measurement tasks are automatically triggered by the actual ladle
weight signal (automatic ladle mode) to ensure that the required measurement
sampling is accurately timed. The task list and bribes of different steel grade
families through the human-machine interface (HMI) stored in the robot PLC Set
up within the casting time.
Tundish covering agent
Two
robots can add covering agent to the tundish at the same time. Robot No. 1 is
responsible for adding the left and middle holes of the tundish cover, and
Robot No. 2 is responsible for adding the right hole of the tundish cover. The
robot uses a tool for adding covering agent. Enable the robot to pin and grab
the cover pack stored on the shelf (Figure 8a). The operator puts a sufficient
number of bags of covering agent on the shelf according to the regulations.
Robot No. 1 can put up to 6 bags of covering agent into the tundish at a time;
Robot No. 2 can handle up to 4 bags at a time. Figure 8b and Figure 8c show the
application of the cover hole on the left side of the cover agent tundish on
the No. 1 continuous casting machine. At the beginning of the pouring process
or after the tundish is replaced, a large amount of covering agent must be
added in a relatively short period of time. The precise time and rapid addition
of the covering agent are essential to prevent secondary oxidation of the
molten steel and maintain the temperature of the molten steel in the tundish.
The task of adding and adding the tundish covering agent is performed by the
tundish electronic scale according to the actual molten steel weight according
to the program (automatic sequence start function).
This pre-determined
approach ensures that the covering agent cannot be used prematurely during the
filling process of the tundish, because the turbulence formed by the molten
steel in the tundish will contaminate the molten steel in the first slab and
cause the cleanliness of the steel. decline. On the other hand, due to the late
addition of the covering agent, the covering agent accumulates near the
addition hole, and its movement speed is relatively low, and it is difficult to
spread to the entire molten steel surface. It can isolate the air and keep
warm. The implemented process practice also ensures that the Synthetic covering
agent-spread evenly on the meniscus of the tundish refractory material, and the
carbonized rice husk is only used for the insulation of the tundish. The
program sets the automatic sequential start function, that is, the first
temperature measurement is performed immediately after the covering agent is
added, so as to show the actual superheat of the inter-species molten steel as
soon as possible. In the second debugging stage, the operation tasks that need
to use the LTC mechanism are realized. These tasks are as follows:
long nozzle
During
the casting process, 6 integral shrouds are placed on the storage rack, and
each position of the storage rack has an optical sensor to identify the
existence of the shroud. After using the pneumatic tool to grab the shroud from
the storage rack, the robot arm stretches to the LTC machine, the ladle turning
head is already in place, and the pouring mechanism is already in the casting
position. The installation of the shroud requires precise knowledge of the
exact position of the pouring mechanism (fixture tool). Because the machining
accuracy and positioning of the ladle rotary head cannot meet the requirements
for automatic installation of the shroud, optical measurement technology is
used to detect each time the shroud is disassembled and assembled. At a precise
location, the three-dimensional laser measurement system installed on the robot
arm measures the characterization topography of the specially designed
three-dimensional body installed on the LTC mechanism (see Figure 9a). The
topography of the measured LTC provides the exact installation of the shroud
Position and positioning provide complete three-dimensional information for the
robot fixture. This method of determining the location of the ladle pouring
mechanism has strong resistance to interference from changes in dust and light
conditions. According to the information of the location of the LTC, the robot
moves to the vicinity of the LTC with the shroud and is ready to be inserted. The
installation of the integral shroud only needs to move vertically and is
automatically locked by spring loading. Figure 9b shows the installation of the
ladle shroud. (Picture 9 a, b)
When the robot returns to
its original position, the ladle lifting mechanism of the turntable moves, and
the ladle descends under the action of the hydraulic cylinder, and the shroud
is immersed in the tundish molten steel to open the pouring mechanism.
Before disassembling the
integral ladle shroud, the precise position of the LTC mechanism was determined
again by laser measurement technology. The ladle shroud was clamped by the
robot, and the nozzle was released from the LTC and rotated 45 degrees. Finally,
when the robot arrives at the starting position with the nozzle, it checks the
nozzle and uses oxygen to clean the cavity of the nozzle, or adze it in the
trash can of the nozzle.
Cleaning of the long nozzle
To remove the ladle
nozzle from the LTC and clean it requires two robots to operate jointly. In
this operation task, robot 1 is responsible for blessing the nozzle, robot 2 is
responsible for oxygen purging and cleaning, and the purge oxygen flow is controlled
by RCT PLC during the cleaning process. In the middle, the ladle nozzle faces
the tundish to minimize the safety and operational risks caused by molten steel
splash (see Figure 10).
Oxygen burning and drainage.
If the ladle nozzle
cannot open automatically, the operator can request the robot system to use the
oxygen-burning opening function. As mentioned earlier, the design of the LTC
opening and sliding mechanism takes this into consideration, and the overall
shroud remains attached to the LTC mechanism. Therefore, after successful
oxygen firing, it quickly switches to the shroud protection casting mode and
opens the casting time. (This has a negative impact on the quality of steel) is
reduced to a minimum. After grabbing the retractable oxygen blowing tube, the
robot positions the end of the oxygen blowing tube directly below the tapered
drain of the LTC. The operator can use the joystick in the console to adjust
the position of the pipeline. During this adjustment process (Usually only
minor adjustments are needed to align the end of the oxygen blowing pipe with
the drain). The actual position of the oxygen blowing pipe port can be
monitored through the camera installed on the robot and the screen of the
console. After the inside of the drain, the operator activates the oxygen
switch to perform the oxygen-burning top boiling procedure. The oxygen blowing
tube itself is used as a telescopic pipe. The pressure of oxygen is applied to
the inner cavity of the nozzle, and the effect of oxygen burning and the force
of oxygen pressure are added to push out the molten molten steel. After the
ladle is successfully drained, the robot moves the oxygen lance tool back to
the frame, and the hydraulic cylinder of the LTC mechanism immediately moves to
switch the pouring position to the overall shroud. The ladle lifting mechanism
of the ladle turntable begins to descend.
Operational aspects
The robot system is not a
completely independent system, but is fully integrated into the continuous
casting machine automation system, which is essential for handling emergency
situations, tracking the operations performed through the secondary automation
system and MES, measurement results, and the quantity of consumables.
In an emergency situation, the rotating ladle and the tundish need to leave the casting position, and the robot must also perform the corresponding tasks at the same time to make a full and rapid response. The "emergency signal" sent by the continuous caster PLC is directly sent to the robot PLC, so there is no delay in the movement of the robot back to its original position. In order to minimize the movement time, a number of simulations were carried out during the I-program design stage. The results show that in the emergency evacuation process, it is advantageous to disassociate the probe and the tool from the robot, and to leave the tool in place before starting the escape action. When performing this kind of emergency task, the robot decoupling tool will not cause an increase in time. The time from receiving the emergency signal to reaching the original position is only 6 to 9 seconds. It needs to be pointed out again that the use of the LTC mechanism does not require a fixed ladle nozzle manipulator, so during the pouring operation, there is no physical connection between the ladle and the pouring platform, which ensures the freedom of the ladle turning head during emergency evacuation. Rotation, in an emergency, in order to save time, the ladle does not need to be raised when the ladle is evacuated and rotated, and the shroud is directly collided on the tundish cover and ruptured to continue rotating the ladle and evacuate the tundish.
Before the start of this project, only two types of intermediate package operation data were sent to the Level 2 system and MES, which is the result of manual temperature measurement and hydrogen determination. So far, the exact time of sampling and the weight of the corresponding ladle molten steel have not been recorded, and the type and quantity of the tundish covering agent and the replacement operation of the shroud are also not recorded. After the robot is adopted, since all the intermediate package operations are recorded in the robot PLC, it is easy to send the data to the secondary computer and MES to prepare for further processing of the data.
The introduction of robot
systems in continuous casting is not only a technological advancement, but to a
certain extent, it has also completely changed the daily work experience of
operators, which is a worrying issue before the start of the project. However,
before the implementation of the robot system in the steel plant, practical
training in the workshop of the Vesuvius plant in Belgium will help all those
involved in this project adapt to this new technology. A very important factor
controlling the robot and its operation is the various panels and man-machine
interfaces in the console. The new air-conditioning and noise prevention
console is shown in Figure 12.
The new operating table
has the operating panels of the existing operators: ladle slewing head (1),
slag detection (2), communication system (3), and the new panel includes a
tundish robot operating panel (4), oxygen burning and drainage The joystick (5)
and oxygen panel (6) of the camera system. The robot operating panel allows the
traditional button operation mode to perform measurement and sampling
operations, but all operating functions and their adjustments can also be
performed through the HMI using a 30-inch touch screen.
In the first few weeks of the operation of the No. 1 continuous casting machine, the robot RTC carried out 152 cover agent additions, 192 temperature measurements, 20 constant hydrogen measurements and 89 samples. As shown in Figure 13, the robot system proved the high efficiency, practicality and excellent performance (execution success rate) of four different tasks during this period, and achieved the required 95% availability and performance during the first few weeks of continuous operation.
During the start-up
phase, it can be observed that the different ladle has obvious deviations when
the lifting mechanism lowers it to the lowest pouring position. These
deviations are caused by the different positions of the ladle on the ladle arm
of the turntable and the inevitable deformation of the ladle during the service
period. Therefore, in order to ensure that the covering agent is added to the
tundish, the distance between the central hole cover of the tundish cover and
the ladle opening mechanism must be optimized to allow enough space for the
robot to add the covering agent to the motion trajectory. The gradual
optimization process reduces the workload of the initial testing phase.
During the first few weeks of operation, crusts were formed in the tundish and molten steel splashed into the lid hole of the tundish, which affected the temperature measurement and sampling of the robot. When the detector has been immersed in molten steel during temperature measurement and sampling, when the detector collides with these crusts, the collision detection function of the robot will start and stop the task. The collision detection function monitors the torque of each drive to prevent damage to the robot and its detection tools.
By optimizing the amount
of covering agent, adding a bag of insulating powder or synthetic slag after
each measurement or sampling, to prevent the formation of a solid slag shell on
the liquid surface of the refractory steel slag in the tundish. By applying
"splash-proof" material coatings on different probes, the splashing
of molten steel can be significantly reduced and the formation of crusts at the
hole of the tundish cover can be significantly reduced.
The LTC mechanism is
still being continuously tested and improved. By the end of May 2019, 8 out of
a total of 23 ladles have been transformed into LTC pouring mechanisms, and in
the first test phase, the shroud robot was successfully replaced , Oxygen
cleans the shroud nozzle and burns the oxygen to open the ladle nozzle.
Conclusion
The introduction of the
robot system in continuous casting is not only a major advancement in
technology, but also a major change in the daily operation of continuous
casting. The implementation of the robot system on the pouring platform and the
new ladle slide plate pouring mechanism of Brazil’s Taina continuous casting
machine has a profound impact on the safety of operators, process reliability,
process operability, productivity and product quality. influences.
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