Description:FORM 2
THE PATENT ACT 1970
(39 OF 1970)
&
The Patent Rules, 2003
COMPLETE SPECIFICATION
(See Section 10 and Rule 13)

1 TITLE OF THE INVENTION :
A SYSTEM FOR AUTOMATIZED CONTROL OF COOLING RATE IN ROT AREA OF EXPERIMENTAL ROLLING MILL.



2 APPLICANT (S)

Name : STEEL AUTHORITY OF INDIA LIMITED.

Nationality : Indian.

Address : Research & Development Centre for Iron & Steel,
Doranda, Ranchi, Jharkhand, India. PIN-834002.






3 PREAMBLE TO THE DESCRIPTION

COMPLETE

The following specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF INVENTION:

The present invention relates to a system for automatized control of cooling rate in Run Out Table(ROT) area of Experimental Rolling Mill (ERM). More particularly, the present invention is directed to a system for control of cooling rate in ROT of ERM wherein movement and speed control of moving hot rolled sample and ROT cooling flow control system is integrated and automatized in a safe and reliable manner to achieve the stipulated mechanical properties of hot rolled samplesas per the product requirement.

BACKGROUND OF INVENTION:

Research & Development Centre for Iron & Steel (RDCIS) is having an Experimental Rolling Mill (ERM) of Hille (England) make, which was commissioned in its laboratory in the year 1983. It is a single stand mill of reversing type which can be used for both hot and cold rolling of steels. The ERM is installed in shed no-3 at RDCIS. Roller tables are provided at both exit and entry to the ERM. Since, ERM is reversing mill, these tables are used to feed the material and collect the material during rolling. Run-out Table (ROT) cooling system consisting of top laminar headers and bottom spray headers to spray water are also located on the exit roller table. The complete setup of ERM is shown in Fig.1.

In the existing practice, samples intended for hot rolling are heated and soaked at anelevated temperature (~1200°C) in reheating furnace (installed along with ERM). Thereafter samples are subject to subsequent reductions in ERM in multiple passes. Normally 60-70% reduction is given in ERM during hot rolling. The rolled samples coming out of ERM is then cooled on ROT using laminar water jets from the finishing rolling temperature (~900°C) to the final temperature (<700°C). The coiling temperature and the cooling rate are important parameters to control the final properties of the hot rolled samples. Laminar cooling is an efficient method of cooling for a hot strip for the reason of high value of local heat transfer coefficient between cooling water and hot strip. The microstructure and grain size of hot rolled sample is decided by the ROT cooling rate. The metallurgical transformation from austenite phase to ferrite phase in the grain brings a dramatic change in the mechanical properties of the strip during ROT cooling of the strip. The quality of the final product can change for a variation of cooling rate and the final temperature. Hence, the cooling rate is important as it in turn determines the metallurgical properties and mechanical properties. The cooling of samples by laminar cooling exhibits a complete description of heat transfer mechanism.

The exit roller table of ERM is used to collect the feedstock during odd number of passes and feed the material during even number of passes. Exit table is also used to move the final rolled sample to ROT cooling area. Due to manual movement of rolled sample from ERM to ROT cooling area, it is very difficult to control the cooling rate during ROT cooling.
ROT cooling system consist of top and bottom headers to spray water on the hot rolled samples from both side. These headers are located on the exit roller table. For top laminar headers, cooling water is supplied from an overhead tank. The water flow rate is controlled by an electrically operated control valve, installed in 50 NB main headers. The pressure at laminar header is ~0.2 bar. Cooling water to bottom spray headers is supplied by a booster pump at 0.5-2 bar pressure and flow rate is controlled by another electrically operated control valve. There was no flow measurement and integrated cooling control system. The speed control of moving hot rolled sample and ROT cooling flow control system is essential to achieve the desired cooling rate as per the product requirement.

Earlier, there was no automated movement of samples and hot rolled sample was moved manually on roller table. Manual movement of hot samples was unsafe and also the speed of samples in ROT area could not be controlled. Also there was no flow control system for ROT cooling system. Both systems are required to control the cooling rate to achieve the stipulated mechanical properties of hot rolled samples.

OBJECTIVE OF THE INVENTION:

The basic of the present invention, is aimed to achieve desired cooling rate during ROT cooling of Experimental Rolling Mill by automated movement of samples on Exit roller table and implementation of flow control systemto achieve the stipulated mechanical properties of hot rolled samples.

A further object of the present invention is directed to said system for automatized control of cooling rate in ROT of ERM wherein motorized-chain driven conveyor type table is provided for moving hot rolled plates/ samples from ERM to ROT cooling area where the conveyor chain is driven by a variable speed motor whose speed is controlled by Variable Frequency Drive.

A still further object of the present invention is directed to said system for automatized control of cooling rate in ROT of ERM wherein Flow control module in PLC and HMI has been developed to precisely control the speed of conveyor table carrying samples and control the water flow rate in ROT cooling system based on online measurement of actual flow through top and bottom headers by flow meters and measured temperature of sample involving pyrometers.

SUMMARY OF THE INVENTION:

The basic aspect of the present invention is directed to a system for automatized control of cooling rate in ROT area of Experimental Rolling Mill (ERM) comprising:

exit roller table including variable speed motor driven conveyor type table having Variable Frequency Drive (VFD) for controlled and automatized movement of samples;

said ROT laminar cooling area of said conveyor type table having both bottom and top spray headers for water flow required for said cooling and cover means to arrest spillage of cooling water outside the conveyor type table ;

said top and bottom headers having flow meters for measurement and control of water flow in said headers for desired cooling purposes

temperature sensors selectively installed at (a) entry of said ERM (T1) (b) at the exit of said ERM (T2) and (c ) at the end of said laminar cooling area (T3) ;

a PLC based system and flow control module for controlling the speed of the variable speed motor driven conveyor type table and also control of the water flow rate in the said ROT laminar cooling area.

A further aspect of the present invention is directed to said system wherein said PLC based system and flow control module control the flow for both top and bottom spray headers and integrate with HMI adapted to preset flow rate.

A still further aspect of the present invention is directed to said system comprising

temperature data of the installed pyrometers fed into in the PLC as follows:
T1: temperature at the entry of the mill
T2: temperature at the exit of the mill (Finishing Temperature)
T3: temperature after ROT cooling area (Final Temperature)
DelT: Drop in Temperature
t: time taken in ROT Area
L= Length of Roller Table
V= preset speed of roller table,

means for computing the cooling rate as follows:
DelT = T2-T3
t= L/V
Average Cooling Rate in ROT = DelT/t; said flow control module generating
Variable Average Water Flow Rate to achieve the desired cooling rate.

A still further aspect of the present invention is directed to said system comprising water collection tray for collecting the cooling water from said ROT cooling unit and cooperative piping arrangement to transfer collected water to pump suction.
A still further aspect of the present invention is directed to said system wherein motorized- chain driven conveyor table comprises conveyor chain with rollers/ rods, said chains supported by load bearing sprockets to prevent sagging of chain with movement of rod/ roller-chain controlled through a motorized sprocket and other load bearing sprocket and configured to handle hot rolled sample length in the range of 200-1000 mm.

A still further aspect of the present invention is directed to said system wherein capacity of motor is selected as 3KW and its speed is controlled by said Variable Frequency Drive (VFD) so that the roller table can be operated in both Forward & Reverse direction, the movement of roller table being operated from Human Machine Interface (HMI) whereby the speed of the table can be varied from 0-30 m/min.
Another aspect of the present invention is directed to said system wherein said conveyor table cover is detachable type, fabricated from heat resistant transparent material, so that ROT cooling process can be visible from outside and provided with sliding arrangement for ease of sample handling during or after cooling as well as facilitating temperature measurement by installed pyrometers at selected locations.

Yet another aspect of the present invention is directed to said system wherein input signals logged from mill instrumentation system are being displayed and recorded in the HMI of the PLC system including the temperature signals from the fixed pyrometers displayed and recorded in the HMI.

A further aspect of the present invention is directed to said system wherein magnetic flow meters are incorporated in the ROT cooling circuit for both top and bottom headers for accurate measurement of water flow, with flow rate of the flow meters selected in the range of 0-40 m3/hr at the operating pressure of 0.5-2 kg/cm2, having material of construction selected for measuring element is SS 304 (Stainless Steel) with measuring accuracy of +/-0.5% of measured value, and cooperating Microprocessor based flow transmitter selected to get the flow reading in PLC and HMI.

A still further aspect of the present invention is directed to said system wherein control valves provided for controlling the flow of top and bottom headers and the signal of control valve are hooked up with PLC system of ERM.

A still further aspect of the present invention is directed to said system wherein motorized-chain driven conveyor table speed can be controlled through Flow Control Module where speed can be preset in HMI for ERM before rolling starts and Flow Control Module also control the flow rate for both top and bottom spray headers by controlling the respective flow control valve to achieve the flow rate preset by using HMI.

The above and other aspects and advantages of the present invention are described hereunder in greater details with reference to the following accompanying non limiting illustrative drawings.

BRIEF DESCRIPTION OF ACCOMPANYING DRAWING:

Fig.1: Experimental Rolling Mill
Fig.2: Design of Chain Driven Modified Conveyor Table
Fig.3:Model of Conveyor Table Cover
Fig.4: Conveyor Table with Cover
Fig.5:Complete Design of Chain Driven Modified Roller Table
Fig.6:Installed Flow meter
Fig.7:Previous Bottom Headers
Fig.8: Modified Bottom Headers
Fig.9: Flow Control Module in HMI

DETAIL DESCRIPTION OF THE INVENTIONWITH REFERENCE TO ACCOMPANYING DRAWINGS:

The present invention relates to an automatized system to achieve desired cooling rate during ROT cooling of Experimental Rolling Mill by automated movement of samples on Exit roller table and implementation of flow control to achieve the stipulated mechanical properties of hot rolled samples.

To achieve the desired cooling rate, exit roller table has been redesigned with motorized- chain driven conveyor type table. The modified conveyor table is capable to move the hot rolled samples using motorized chain drive. The conveyor chain can be driven by a variable speed motor whose speed will be controlled by Variable Frequency Drive (VFD). Normally there is spillage of water during use of ROT cooling system. Thus, suitable cover has also been designed for the ROT cooling area of the motorized- chain driven conveyor table, so that there is no spillage of cooling water outside the roller table. The suitable water collection tray has been designed and fabricated for collecting the cooling water from the ROT cooling system and piping arrangement has been provided to transfer the collected water to pump suction.

Modification of ROT cooling flow control has been done by incorporating flow meter to read the actual flow of the top and bottom headers. Pyrometers have been incorporated for actual measurement of sample temperature before entry to mill after exit of the mill and after ROT cooling area. Flow control module has been developed in existing PLC and HMI to control the speed of modified conveyor table, and control the water flow rate in ROT cooling system.

Salient features of Major Items:
a) Motorized Chain Driven Modified Conveyor Table:
The motorized- chain driven conveyor table (Fig.2) has been designed as conveyor chain with rollers/ rods. Overall dimensions of the conveyor table is: length- 4 meter, width- 0.4 meter and height: 0.88 meter. The movement of rod/ roller-chain is controlled through a motorized sprocket and other load bearing sprocket. The chain has been supported by load bearing sprockets to prevent sagging of chain. Diameter of the rod/ roller is kept as 16 mm. Spacing of rod/ rollers has been kept such that the chain does not sag appreciably under sample weight of maximum 10 kg and at the same time there is enough space for spray cooling from the bottom. The system has been designed to handle hot rolled sample length in the range of 200-1000 mm. The material of construction of chain and sprocket is chosen as SS 316 (Stainless Steel). The capacity of motor is selected as 3KW and its speed is controlled by Variable Frequency Drive (VFD). The roller table can be operated in both Forward & Reverse direction. The movement of roller table is operated from Human Machine Interface (HMI). The speed of the table can be varied from 0-30 m/min.
b) Cover for Conveyor Table:
Suitable cover has been designed for the ROT cooling area of the modified conveyor table, so that there is no spillage of cooling water outside the table. The scheme of the cover of the conveyor table is shown in Fig.3. The conveyor table cover has been fabricated from heat resistant transparent material, so that ROT cooling process can be visible from outside. Maximum temperature of sample during cooling shall be 900°C. Sliding arrangement has been provided with the cover for ease of sample handling during or after cooling. Cover has been designed such that it does not hinder temperature measurement by pyrometer. The cover is designed detachable type from maintenance point of view and ease of operation of manual valves of bottom headers. The conveyor table with cover is shown in Fig.4.
c) Collection Tray
The water collection tray has been fabricated with SS sheet for collecting the cooling water from the ROT cooling system and piping arrangement has been provided to transfer the collected water to pump suction.
The complete chain driven conveyor table is shown in Fig.5.

d) Pyrometers:
Temperature measurement in ERM was done previously through handheld infrared pyrometers. The ERM is controlled with a S7-300 series Siemens PLC System. The input signals of different mill parameters are connected to the PLC. Provision in PLC made for logging the measured temperature data. However, logging of temperature data from handheld pyrometers was not possible and therefore, suitable fixed pyrometers has been installed in the mill. The input signals logged from mill instrumentation system are being displayed and recorded in the HMI of the PLC system. The temperature signals from the fixed pyrometers are also displayed and recorded in the HMI.

The fixed pyrometer has been installed to eliminate human error of measurement using handheld pyrometers. One pyrometer has been installed at the entry of the mill (T1), one pyrometer has been installed at the exit of the mill (T2) and the third pyrometer has been installed at the end of the laminar cooling zone (T3). The pyrometers are focused to the roller table of the mill. The output of the pyrometers are displayed in display unit. The signals are also connected to the Analog Input (AI) module of the existing PLC of the mill. The pyrometers are non-contact type two-colour type to measure temperature even with spray of water over the rolled steel. There measuring range kept as 350 °C to 1300 °C. The emissivity of pyrometers varies in the range of 0.2-1.0. the sighting of pyrometer is through laser pointer. The error of measurement is less than ± 0.5%.

e) Flow Meter:
A suitable magnetic flow meter (Fig.6) has been incorporated in the ROT cooling circuit for both top and bottom headers for accurate measurement of water flow. The flow rate of the flow meter selected in the range of 0-40 m3/hr at the operating pressure of 0.5-2 kg/cm2. The material of construction selected for measuring element is SS 304 (Stainless Steel). The measuring accuracy of the flow meter is +/-0.5% of measured value. Microprocessor based flow transmitter selected to get the flow reading in PLC and HMI.

f) Development of Flow Control Module
Existing top ROT cooling headers have been used. The bottom spray cooling headers has been modified as per the new chain driven conveyor table. the design of previous bottom header is shown in Fig.7 and the design of modified bottom headers is shown in Fig.8. Communication between motor, VFD and existing PLC & HMI has been established so that speed of table is set and controlled using PLC. The existing control valves have been used for controlling the flow of top and bottom headers. The signal of control valve shall be hooked up with existing PLC system of ERM. Flow meter shall be installed for both top and bottom headers and their signals shall be given to existing PLC system of ERM. “Flow Control Module” has been developed in the PLC/ HMI to control the speed of modified conveyor table, and control the water flow rate in ROT cooling system.

The speed of motorized- chain driven conveyor table speed can be controlled through Flow Control Module. The speed can be preset in existing HMI for ERM, before rolling starts. The conveyor table run with preset speed after the last rolling pass.

Flow Control Module control the flow rate for both top and bottom spray headers. This is achieved by controlling the flow control valve to achieve the preset flow rate. The flow rate is preset by using existing HMI.

The temperature data of the installed pyrometers are also taken in the PLC as follows:
T1: temperature at the entry of the mill
T2: temperature at the exit of the mill (Finishing Temperature)
T3: temperature after ROT cooling area (Final Temperature)
DelT: Drop in Temperature
t: time taken in ROT Area
L= Length of Roller Table
V= preset speed of roller table
The cooling rate is calculated as follows:
DelT = T2-T3
t= L/V
Average Cooling Rate in ROT = DelT/t
Average Water Flow Rate is varied to achieve the desired cooling rate. The screenshot of the Flow Control Module is shown in Fig.9.

Usefulness of the Invention: The concept of automated movement of samples using chain driven conveyor and Flow Control Module in ROT area can be used in other Experimental Rolling Mill for precise control of cooling rate and heat transfer rate during ROT cooling.
Industrial Applicability: The system is designed and developed for laboratory scale Experimental Rolling Mill to replicate industrial scale operation for standardisation. The system can be deployed in similar facilities available in other research/ academic institutes.
, Claims:We Claim:
1. A system for automatized control of cooling rate in ROT area of Experimental Rolling Mill (ERM) comprising :

exit roller table including variable speed motor driven conveyor type table having Variable Frequency Drive (VFD) for controlled and automatized movement of samples;

said ROT laminar cooling area of said conveyor type table having both bottom and top spray headers for water flow required for said cooling and cover means to arrest spillage of cooling water outside the conveyor type table ;

said top and bottom headers having flow meters for measurement and control of water flow in said headers for desired cooling purposes

temperature sensors selectively installed at (a) entry of said ERM (T1) (b) at the exit of said ERM (T2) and (c ) at the end of said laminar cooling area (T3) ;

a PLC based system and flow control module for controlling the speed of the variable speed motor driven conveyor type table and also control of the water flow rate in the said ROT laminar cooling area.

2. The system as claimed in claim 1 wherein said PLC based system and flow control module control the flow for both top and bottom spray headers and integrate with HMI adapted to preset flow rate.

3. The system as claimed in anyone of claims 1 or 2 comprising

temperature data of the installed pyrometers fed into in the PLC as follows:
T1: temperature at the entry of the mill
T2: temperature at the exit of the mill (Finishing Temperature)
T3: temperature after ROT cooling area (Final Temperature)
DelT: Drop in Temperature
t: time taken in ROT Area
L= Length of Roller Table
V= preset speed of roller table,

means for computing the cooling rate as follows:
DelT = T2-T3
t= L/V
Average Cooling Rate in ROT = DelT/t; said flow control module generating
Variable Average Water Flow Rate to achieve the desired cooling rate.

4. The system as claimed in anyone of claims 1 to 3 comprising water collection tray for collecting the cooling water from said ROT cooling unit and cooperative piping arrangement to transfer collected water to pump suction.

5. The system as claimed in anyone of claims 1 to 4 wherein motorized- chain driven conveyor table comprises conveyor chain with rollers/ rods, said chains supported by load bearing sprockets to prevent sagging of chain with movement of rod/ roller-chain controlled through a motorized sprocket and other load bearing sprocket and configured to handle hot rolled sample length in the range of 200-1000 mm.

6. The system as claimed in anyone of claims 1 to 5 wherein capacity of motor is selected as 3KW and its speed is controlled by said Variable Frequency Drive (VFD) so that the roller table can be operated in both Forward & Reverse direction, the movement of roller table being operated from Human Machine Interface (HMI) whereby the speed of the table can be varied from 0-30 m/min.
7. The system as claimed in anyone of claims 1 to 6 wherein said conveyor table cover is detachable type, fabricated from heat resistant transparent material, so that ROT cooling process can be visible from outside and provided with sliding arrangement for ease of sample handling during or after cooling as well as facilitating temperature measurement by installed pyrometers at selected locations.

8. The system as claimed in anyone of claims 1 to 7 wherein input signals logged from mill instrumentation system are being displayed and recorded in the HMI of the PLC system including the temperature signals from the fixed pyrometers displayed and recorded in the HMI.

9. The system as claimed in anyone of claims 1 to 8 wherein magnetic flow meters are incorporated in the ROT cooling circuit for both top and bottom headers for accurate measurement of water flow, with flow rate of the flow meters selected in the range of 0-40 m3/hr at the operating pressure of 0.5-2 kg/cm2, having material of construction selected for measuring element is SS 304 (Stainless Steel) with measuring accuracy of +/-0.5% of measured value, and cooperating Microprocessor based flow transmitter selected to get the flow reading in PLC and HMI.

10. The system as claimed in anyone of claims 1 to 9 wherein control valves provided for controlling the flow of top and bottom headers and the signal of control valve are hooked up with PLC system of ERM.

11. The system as claimed in anyone of claims 1 to 10 wherein motorized-chain driven conveyor table speed can be controlled through Flow Control Module where speed can be preset in HMI for ERM before rolling starts and Flow Control Module controls the flow rate for both top and bottom spray headers by controlling the respective flow control valve to achieve the flow rate preset by using HMI.

Dated this the 17th day of February, 2023
Anjan Sen
Of Anjan Sen & Associates
(Applicant’s Agent)
IN/PA-199