WO2022129434A1 - Procédé de commande du refroidissement d'une table de sortie de laminoir à chaud - Google Patents

Procédé de commande du refroidissement d'une table de sortie de laminoir à chaud Download PDF

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Publication number
WO2022129434A1
WO2022129434A1 PCT/EP2021/086338 EP2021086338W WO2022129434A1 WO 2022129434 A1 WO2022129434 A1 WO 2022129434A1 EP 2021086338 W EP2021086338 W EP 2021086338W WO 2022129434 A1 WO2022129434 A1 WO 2022129434A1
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WIPO (PCT)
Prior art keywords
strip
cooling
banks
temperature
coiling
Prior art date
Application number
PCT/EP2021/086338
Other languages
English (en)
Inventor
Mustapha BSIBSI
Ramon Cornelis Jan SPEETS
Original Assignee
Tata Steel Ijmuiden B.V.
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Filing date
Publication date
Application filed by Tata Steel Ijmuiden B.V. filed Critical Tata Steel Ijmuiden B.V.
Priority to KR1020237022871A priority Critical patent/KR20230118901A/ko
Priority to EP21839514.3A priority patent/EP4263879A1/fr
Publication of WO2022129434A1 publication Critical patent/WO2022129434A1/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D11/00—Process control or regulation for heat treatments
    • C21D11/005—Process control or regulation for heat treatments for cooling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/02—Hardening articles or materials formed by forging or rolling, with no further heating beyond that required for the formation
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/84—Controlled slow cooling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
    • B21B37/74—Temperature control, e.g. by cooling or heating the rolls or the product
    • B21B37/76—Cooling control on the run-out table
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B15/00—Systems controlled by a computer
    • G05B15/02—Systems controlled by a computer electric

Definitions

  • the invention relates to a method for controlling the cooling of a steel strip by a hot strip mill run out table to produce a hot rolled steel strip, wherein the cooling on the run-out table until the coiling of the strip is controlled.
  • the steel is cast in a continuous casting machine. At the end of the casting process, the cast strand is cut into slabs.
  • the slabs are transported to the hot strip mill and first reheated to a temperature of approximately 1150 - 1270 °C in a reheating furnace. At these temperatures the microstructure of the steel slab is austenitic.
  • the slab usually has a thickness of approximately 250 mm.
  • the reheated slab is then rolled by roughing mills, of which usually five stands with horizontal and sometimes also vertical rolls are present.
  • the thickness of the strip is thereby reduced to approximately 40 mm.
  • the temperature of the slab is approximately 1050 - 1120 °C.
  • the slab Afterthe rolling in the roughing mills the slab is transported to the finishing mills. Between the roughing and finishing mills the velocity of the slab is controlled. The velocity, thickness and temperature of the slab are measured before the slab enters the finishing mill stands.
  • finishing mill stands are present.
  • the velocity at the entry of the finishing mill stands is determined on the basis of the required thickness of the strip after the last finishing mill stand.
  • the thickness of the strip afterthe last finishing mill stand is also calculated on the basis of the measured thickness after the roughing mills.
  • the temperature of the strip and the velocity of the strip are measured.
  • the thickness of the strip after the finishing mills is calculated as described above.
  • the velocity of the strip entering the finishing mills can be increased as soon as the head of the strip has entered the last finishing mill stand.
  • the velocity of the strip after the last finishing mill stand usually is not constant during hot strip rolling.
  • the strip After the strip has left the finishing mills the strip is cooled on a run out table. At the end of the run-out table, the strip is coiled. On entering the run-out table (or ROT) the strip has a temperature of approximately 900 °C or more, so the strip still has an austenitic microstructure.
  • the temperature of the strip is usually roughly between 550 and 700 °C. Most steels have a predominantly ferritic microstructure at this temperature.
  • the coiling temperature is realized by the cooling on the ROT (referred to as run out table cooling (ROT-cooling)).
  • the ROT-cooling consists of a number of cooling banks, for instance 60 cooling banks, of which the first 52 form the main cooling and the last 8 are called the trimmers, intended to fine-tune the cooling. The trimmers are used to ensure that the coiling temperature is within the required range.
  • the cooling banks are present both above and below the pass line of the strip.
  • the cooling banks can usually only be open, half-open or closed, but nowadays cooling banks can also be fully variably open.
  • the cooling banks may provide cooling water at high pressure.
  • cooling patterns To cool the strip on the ROT in a standard hot rolling mill only a limited number of cooling patterns is available, for instance five cooling patterns, in which a number of cooling banks are available to provide cooling water.
  • a cooling pattern is a selection of all the cooling banks of the ROT-cooling that is used to cool the strip. These cooling banks can be fully or partly open. For instance, the cooling banks are alternately available and fully open and not available.
  • the strip on the ROT will have a temperature profile along its length on the ROT.
  • This temperature profile is called the cooling path of the strip.
  • the cooling path thus starts with the temperature of the strip directly after the hot strip finishing mills, and ends with the coiling temperature of the strip at (or just before) the coiling of the strip. In between these temperatures, the cooling path is seen as a smooth temperature curve, though in practice the impingement of the waterjets of cooling water from the cooling banks results in peaks in the cooling path, particularly when looking at the surface temperature.
  • a cooling pattern is chosen on the basis of the composition of the strip and the required coiling temperature, consisting of determined cooling banks.
  • the cooling on the ROT is mainly controlled on the basis of the finishing temperature as measured, the velocity as measured and the thickness as controlled and determined by the finishing rolls. Since especially the velocity will change during hot rolling, the control of the ROT-cooling determines how many cooling banks are actually used from the selected cooling banks made available by the cooling pattern that has been chosen.
  • the control of the ROT-cooling is not only determined feed-forward by the three input parameters as described above, but also in a feed-back loop by the coiling temperature that is measured at coiling.
  • this intermediate temperature of the strip is used as a feed-forward to calculate and control the coiling temperature, and as a feed-back loop.
  • the intermediate temperature is for instance important when dual-phase steel is hot rolled. In some cases two intermediate temperatures of the strip are measured.
  • the ROT-cooling is controlled so as to reach a targeted coiling temperature and cooling rate, and - if present - a targeted intermediate temperature.
  • one or more of these objects are reached by providing a method for controlling the cooling of a steel strip on a hot strip mill run out table comprising a plurality of cooling banks to produce a hot rolled steel strip, wherein the cooling on the run-out table until the coiling of the strip is controlled using the following input parameters: 1. surface temperature T1 of the hot rolled strip directly after hot strip finishing mill stands.
  • the grain size G3 is the average austenite grainsize of the steel as it is present directly after leaving the last finishing mill.
  • the term “directly after the hot strip finishing mill” intends to mean “as soon as possible after the strip leaves the finishing mill” and in any case before the first cooling bank of the ROT- cooling.
  • the term “directly after the hot strip finishing mill” means within 2 seconds after leaving the last finishing stand. The thinner d1 , the higher the velocity v1 , and therefore also the shorter the time between leaving the hot strip finishing mill.
  • the time increases and may be more than 2 seconds, but still it means “as soon as possible after the strip leaves the finishing mill” and in any case before the first cooling bank of the ROT-cooling.
  • the invention thus provides a method that makes it possible to provide any cooling pattern on the ROT between the situation wherein no cooling by the cooling banks is used, and the situation wherein all the cooling banks are switched on at their maximum water flow capacity.
  • any cooling pattern of selected cooling banks and cooling flow of the selected individual cooling banks can be provided to determine a cooling path so as to reach the targeted aspect of the microstructure as accurate as possible, preferably real time.
  • the cooling pattern is determined on the basis of a number of input parameters. These are the usual input parameters 1 - 4 as indicated above, but as an additional input parameter the grain size G3 of the hot-rolled strip directly after the finishing mills is used. This grain size is often determined in a hot strip mill, but the method according to the invention uses the grain size G3 also as an input parameter for determining the cooling pattern.
  • the cooling pattern is determined on the basis of a targeted aspect of microstructure M4 at the coiling of the strip.
  • the cooling of the strip is controlled on the basis of a number of input parameters.
  • This is normal practice in many hot rolling mills, but according to the method of the invention also the grain size G3 and a measured aspect of the microstructure M4 of the steel strip at the coiling of the strip are used as input parameters to control the cooling.
  • Controlling the cooling means that the number of selected cooling banks in the cooling pattern is changed, thus switching on or off one or more cooling banks, and/or changing the cooling flow of water of the selected cooling banks in the cooling pattern.
  • microstructure of the steel strip encompassed the following aspects:
  • the phases that are present in the strip such as the amount of austenite, ferrite, pearlite, bainite and/or martensite in the strip
  • At least one aspect of the microstructure is a target to be reached at the coiling of the strip, and that measured aspect of the microstructure at the coiling of the strip is used to control the selected cooling banks.
  • that measured aspect of the microstructure at the coiling of the strip is used to control the selected cooling banks.
  • the cooling pattern of selected cooling banks is also determined on the basis of a targeted coiling temperature Tct of the strip, wherein the number of selected cooling banks is also controlled on the basis of a measured surface temperature Tc of the strip at coiling.
  • a targeted coiling temperature Tct is used as input parameter, and the surface temperature Tc of the strip at coiling is measured, but this is not done in combination with the grain size directly after the finishing mills and/or one or more aspects of the microstructure at coiling of the strip.
  • the strip surface temperature T1 and velocity v1 are measured directly after the hot strip mill finishing stands. These measurements make the process according to the invention more reliable than the use of a predicted temperature T1 and velocity v1 based on a predictive model that uses the temperatures before or during the use of the finishing mills.
  • the strip chemistry is determined by analysis of a sample taken from the molten steel that is used to cast a strand from which a slab is cut as input to produce the steel strip in the hot strip mill.
  • the input parameter number 4 of all the input parameters thus is preferably not determined at any point in the hot rolling mill, and also is preferably not a chemistry that is a targeted chemistry for the steel strip, but is measured during the steel making process that precedes the hot rolling of the steel.
  • an aspect of the microstructure M4 at the coiling of the strip is the percentage of the austenite phase that is transformed into another phase, such as pearlite and/or ferrite, wherein preferably either the amount of transformed austenite is measured or the amount of transformed austenite is calculated based on at least three measured surface temperatures of the strip along the length of the run-out table.
  • the cooling pattern can be determined and the selected cooling banks can be controlled.
  • the percentage of recrystallized austenite in the strip directly after the hot strip mill finishing stands and/or the amount of precipitates in the strip directly after the hot strip mill finishing stands can be used, and preferably also the type of precipitates in the strip.
  • These input parameters can be determined on the basis of the percentage of recrystallization and the amount of precipitates and the type of precipitates determined in the stages of hot rolling before the ROT and on the basis of the chemistry of the steel strip. These parameters are determined in many hot rolling mills and the person skilled in the art knows how to determine these.
  • the following measured parameters o strip temperature TO before hot strip finishing mill stands o strip thickness dO before hot strip finishing mill stands o strip velocity vO before hot strip finishing mill stands and a calculated grain size G2 before hot strip finishing mill stands are used to determine the thickness d1 and the grain size G3 of the steel strip directly after the finishing mills. If it is not possible to measure the grain size G3 and the thickness d1 directly after the finishing mills, the measured parameters TO, dO and vO and the calculated grain size G2 are used to calculate d1 and G3. This calculation is normal practice in many hot rolling mills today.
  • the grain size G2 is calculated on the basis of measured grain sizes of slabs with a corresponding composition, and on the basis of the time/temperature path in the reheating furnace of the slab that is processed into the steel strip in the roughing mills, and on the basis of the time/temperature path and thickness reduction of the slab in the roughing mills. This means that the grain size G2 is calculated with the available input to do so. This calculation is normal practice in many hot rolling mills today.
  • one or more of the parameters strip temperature T, strip velocity v and one or more aspects of strip microstructure M are calculated and/or measured at one or more places along the length of the run out table, and used to control the number of selected cooling banks and/or the cooling flow of each selected cooling bank that is used to cool the strip.
  • the parameters strip temperature T and/or one or more aspects of strip microstructure M are calculated and/or measured at one or more places over the width of the strip, at one or more places along the length of the run-out table line. This means that for instance not only the temperature and/or microstructure are calculated and/or measured at the centre line of the strip, as is the usual practice, but also for instance near the edge of the strip.
  • one or more of the following targeted parameters are used as additional input parameter for determining the cooling pattern of the selected cooling banks of the cooling installation in the run-out table and/or the cooling flow of each selected cooling bank:
  • These input parameters can influence the cooling pattern and/or the cooling flow that is chosen, for instance when the cooling rate should be comparatively low, the number of selected cooling banks will be higher and the cooling flow will be lower.
  • cooling pattern of selected cooling banks in the runout table and/or the cooling flow of each selected cooling bank is controlled such that the cooling of the strip meets one or more of the following requirements:
  • the input parameter grain size G3 is determined real time so as to control the selected cooling banks real time. Since the grain size G3 that is used as input is based on a model to predict the grain size G3 directly after the finishing mills, it is advantageous to predict the grain size G3 real time so as to determine the cooling pattern and control the selected cooling banks as accurately as possible.
  • cooling banks in the run-out table have two or more different cooling capacity settings, and/or wherein one or more cooling banks in the run-out table have continuously adjustable cooling capacity settings.
  • cooling banks With such cooling banks, the cooling of the steel strip on the ROT can be performed as accurately as possible. It is preferable that all cooling banks have two or more different cooling capacity settings or that all cooling banks have continuously adjustable cooling capacity settings.
  • two or more targeted or measured parameters are used as input parameters with a weighing factor when these parameters are used to determine the selected cooling banks of the cooling pattern and/or the cooling flow of the selected cooling banks, and/or to control the number of selected cooling banks that is used to cool the strip.
  • two targeted parameters for instance an aspect of microstructure M4 and coiling temperature Tc both exactly at coiling of the strip.
  • At least the targeted input properties coiling temperature Tct and an aspect of microstructure M4 are used with a weighing factor, for instance such that the microstructure M4 is more important than the coiling temperature Tc.
  • the invention is elucidated with a number of examples showing the result of the use of the method according to the invention.
  • Fig. 1 shows the cooling pattern of the ROT-cooling for Example 1.
  • Fig. 2 shows the selected cooling banks of the ROT-cooling used for Example 1.
  • Fig. 3 shows the calculated temperatures for Example 1 .
  • Fig. 4 shows the resulting transformation for Example 1 .
  • Fig. 5 shows the cooling pattern of the ROT-cooling for Example 2.
  • Fig. 6 shows the selected cooling banks of the ROT-cooling used for Example 2.
  • Fig. 7 shows the calculated temperatures for Example 2.
  • Fig. 8 shows the resulting transformation for Example 2.
  • Fig. 9 shows the cooling pattern of the ROT-cooling for Example 3.
  • Fig. 10 shows the selected cooling banks of the ROT-cooling used for Example 3.
  • Fig. 11 shows the calculated temperatures for Example 3.
  • Fig. 12 shows the resulting transformation for Example 3.
  • Fig. 13 schematically shows the cooling banks of the ROT-cooling and the range of cooling paths that is possible with these cooling banks.
  • Fig. 14 shows the production line to produce a coiled strip with the different phases in the production process and the settings and parameters used to calculate the input parameters for the method according to the invention.
  • Fig. 15 shows the process to determine the cooling pattern of cooling banks and the flow of these cooling banks, and the control of the cooling pattern and flow of the cooling banks.
  • Fig. 13 schematically shows at the top a number of cooling banks that is available in a run out table cooling.
  • the graph below the cooling banks shows that cooling in the ROT- cooling can be performed between an upper limit where none of the cooling banks is used (Cmin), and a lower limit where all cooling banks are used with maximal flow (Cmax). These limits result in a maximum coiling temperature (Tc max) and a minimum coiling temperature (Tc min) that can be reached for a certain strip.
  • Tc max maximum coiling temperature
  • Tc min minimum coiling temperature
  • Fig. 13 shows an example wherein a cooling pattern (PT) is chosen as indicated by the black boxes representing cooling banks that are used to cool.
  • CP Cooling Path
  • the microstructure at coiling of the strip has to fulfil predetermined criteria.
  • the microstructure at coiling should contain predetermined amounts of pearlite and ferrite.
  • the grain size is important.
  • the cooling path to reach that Tc would not be relevant and many cooling patterns could be used to reach that Tc.
  • the cooling path is important because the cooling path determines the start of the phase transformation in the strip, the evolution of the phase transformation and the resulting phases. The method according to the invention makes it possible to use the cooling path that is required to achieve the microstructure of the strip at coiling.
  • Fig. 14 shows how and where these input parameters can be measured or calculated based on earlier input during the production process.
  • M0..M4 Micro-structure or one of its aspects
  • Fig. 14 shows that the production process of a hot rolled strip starts with the providing of a slab SL.
  • This slab is re-heated in a reheating furnace RH to provide it with the required temperature, after which it is transported to the roughing mill RM.
  • the slab is transported to the finishing mill FM, where the thickness is reduced such that it has the required thickness of that specific hot rolled strip.
  • a hot rolled strip has a thickness between 2 and 10 mm, but it can be thinner or thicker.
  • the strip is cooled on the run-out table ROT and thereafter coiled on a coiler CR.
  • Fig. 14 also shows that in a hot strip mill nowadays a number of models is used.
  • Each of the above-mentioned installations in the production process uses its own model to calculate the microstructure of the slab or strip resulting from the use of that installation.
  • To calculate the microstructure measurements in and after each installation are used, and the model also generates settings for the installations.
  • each installation there is a model using the measurements as input and generating the settings as output. There is also a separate model to calculate the microstructure. In this way each subsequent installation uses the resulting microstructure M generated by the model for the preceding installation. Only the first input microstructure MO is not calculated based in the slab that is hot rolled, but is based on a general model made on the basis of earlier produced slabs, having the same or almost the same composition. Hence the dotted line in Fig. 14.
  • Fig. 14 shows five positions P0 to P4. Each position has its own microstructure MO to M4 , before or after one of the installations in the hot strip mill.
  • Most hot strip mills use the models as shown in Fig. 14 and whereas the models itself may vary, the resulting microstructure can be calculated by the person skilled in the art.
  • Fig. 15 shows how the input parameters M, d, v and T are used to generate a cooling pattern together with the targeted material property or properties, and how these parameters are also used to control the cooling banks of the cooling pattern.
  • Fig. 15 shows that a reiterating loop is used to calculate a cooling pattern, and that this cooling pattern is used to calculate what the resulting material properties will be. By comparing the calculated material properties with the required material properties, the cooling pattern can be optimised.
  • a reiterating loop is also used to control the use of the selected cooling pattern, by measuring or calculating (based on other measurements along the ROT) targeted material properties just before the coiling of the strip and comparing these with the required material properties. In this way the number of active cooling banks in the selected cooling pattern and the flow thereof can be optimised.
  • Fig. 15 shows that for both reiterating loops the same input parameters temperature T3, strip thickness d3, velocity v3 and microstructure M3 are used, as well as the targeted microstructure M4.
  • the grain size is the aspect of the microstructure used as input parameter; as targeted microstructure M4 different aspects of the microstructure can be used, as indicated above.
  • targets Apart from these targets also other targets can be used such as the coiling temperature Tc or the surface quality on the ROT, as indicated above.
  • High Carbon steel grades are characterised by a carbon content above 0.5 wt.%.
  • the High Carbon steel grade used in the below Examples has the following composition (in wt.%):
  • Nb, Ti, S, B, Cu, Ni, Mo, V and N are present as an impurity, that means present at a maximum of 0.01 wt.% each.
  • Other possible elements are unavoidable impurities, the remainder being iron. This is a commercially available grade.
  • Example 1 In Figure 1 the lay-out of a ROT-cooling is shown as used for the present examples.
  • the ROT-cooling is in general indicated with the number 10, and the strip 1 that is coiled into a coil 2 is shown, departing from the last stand 5 of the finishing mill as shown in Figure B.
  • the cooling banks 1 to 54 of the main cooling are each indicated, and the trimmers 55 to 62 as well, according to the ROT-cooling of the present examples.
  • the lay-out of the ROT-cooling as shown in Figure 1 is used for all examples.
  • the inputs for the use of the invention are a Finishing Mill Temperature T1 of 880° C, a strip thickness d3 after the Finishing Mill of 2.5 mm, a strip speed v3 of 13.0 m/s and a grain size G3 of 11 .5 pm. These input variables are shown in Figure C.
  • the only targeted material property is a targeted pearlite fraction of 100%.
  • the targeted material property that 100% pearlite is reached is chosen so as to get mechanical properties and homogeneity of the strip that is as good as possible, since all austenite will then have transformed into pearlite before coiling.
  • the ROT- cooling control system determines a cooling pattern for the cooling banks in the ROT-cooling which is used as starting point for the cooling process. This cooling pattern is calculated as soon as the input parameters temperature T3, strip thickness d, grain size G3 and optionally strip velocity v are measured or calculated when the head of the strip passes the spot where the temperature T3 is measured.
  • the cooling pattern as shown in Figure 1 is calculated. This cooling pattern is used for the cooling of this strip, but the cooling banks that are actually used are determined on the basis of the measurements/calculations.
  • Figure 1 shows that the calculated cooling pattern makes no use of the trimmers 55 - 62.
  • Figure 1 shows the measurement of the finishing temperature T1 , the measurement of the temperature before the trimming section (Tbt) and the measurement of the coiling temperature (Tct).
  • the temperature T3, the velocity v3 and the thickness d3 are measured, and the grain size G3 is calculated. Based on these actual values, the cooling path is calculated, which means that it is calculated which cooling banks have to be actually used from the cooling pattern that has been calculated. In this example all cooling banks can be used from cooling bank 1 to cooling bank 9; none of the trimmers will be used. Moreover, for the cooling banks 1 - 9 a flow rate of 100% is determined. This is shown in Figure 1 with the hatched blocks.
  • Figure 2 shows the actual cooling path that is calculated for cooling the strip using the method according to the invention, based on the above input values T3, d3, G3 and v3 for this example 1.
  • the cooling banks 1 - 8 are used at 100% flow rate, shown as the black blocks, and as indicated above none of the trimmers. Less or more cooling banks can be used depending on the velocity of the strip, in accordance with the cooling banks determined in the cooling pattern.
  • the input parameter T2, d2, v2 and G2 are not necessary.
  • the method according to the invention can be used with only the input parameters T3, d3, G3 and optionally v3, but then a powerful computer is needed to directly calculate the actual cooling path of the cooling banks when the head of the strip passes the spot where T1 is measured, since otherwise a first part of the strip will not be accurately cooled.
  • T2, d2, v2 and G2 it is preferred to use T3, d3, G3 and optionally v3 so as to determine a cooling pattern before the strip enters the ROT-cooling.
  • the calculated temperatures of the strip are shown in Figure 3 as function of the location along the run-out table. Shown is the average temperature of the strip, halfway the upper and the lower surface of the strip. With the method according to the invention the temperature at the upper and the lower surface of the strip can also be calculated.
  • the dotted lines at 645° C and 665° C show the temperature limits between which the Coiling Temperature Tc should preferably be kept. However, the Coiling Temperature Tc is not a targeted material property in this example 1.
  • Figure 3 shows the calculated cooling temperatures. It is clear that a very fast cooling of the strip is obtained directly from the start of the cooling on the ROT.
  • the strip is even cooled to a temperature of about 50° C below the preferred Coiling Temperature Tc, but the strip is heated again in its course over the ROT due to the transformation energy that is released as a result of the transformation from austenite into pearlite (and ferrite, if present).
  • Example 2 In example 2 there are two targeted material properties. One is the Targeted Coiling Temperature TCT, which is 655°. The other targeted material property is a perlite fraction target of 100% just before the coiling of the strip, as in example 1. All other input variables are the same as in example 1 , thus also the grain size of 11.5 pm. Both targeted material properties are given equal weight, so the ROT-cooling control system should try to reach both material properties at the same time.
  • TCT Targeted Coiling Temperature
  • TCT Targeted Coiling Temperature
  • the other targeted material property is a perlite fraction target of 100% just before the coiling of the strip, as in example 1. All other input variables are the same as in example 1 , thus also the grain size of 11.5 pm. Both targeted material properties are given equal weight, so the ROT-cooling control system should try to reach both material properties at the same time.
  • Figure 5 shows the cooling pattern of the ROT-cooling. This cooling pattern is determined in the same way as in example 1 . It shows that of the banks 1 to 31 only the first out of three can be used, and that all the trimmers 55 - 62 can be used. Banks and trimmers will be used at 50% flow rate. This is shown as the hatched blocks in Figure 5.
  • Figure 6 shows the actual cooling path that is calculated for cooling the strip using the method according to the invention, based on the above input values for this example 2. Only the cooling banks 1 - 22 are used, and none of the trimmers.
  • Figure 8 shows that the transformation of the strip on the ROT is almost as high as in Example 1. More than 85% of the austenite is transformed into pearlite, and some 5% ferrite is formed just before the strip is coiled. The remainder is maintained as austenite just before the coiling of the strip.
  • Example 3 This last example shows how the method according to the invention works out when more than 2 targeted material properties are chosen. In this case, 4 targeted material properties are used:
  • Figure 10 shows the actual cooling path that is calculated for cooling the strip using the method according to the invention, based on the above input values for this example 3.
  • the cooling banks 1 and 2 are used at 100% flow rate, and the cooling banks 3 - 10 are used at 50% flow rate. This is shown as the black blocks. As indicated above none of the trimmers is used.
  • Figure 11 shows the calculated cooling temperatures. It is clear that the use of 4 targeted material properties in the method according to the invention results in cooling that looks very much like the cooling in example 1 , where only the targeted transformation was used as target input. However, the calculated graph shows that the Coiling Temperature Tc is higher in this example 3. Moreover, the cooling is clearly not as fast after the temperature of the strip is below 800° C.

Abstract

L'invention concerne un procédé de commande d'une table de sortie de laminoir à chaud pour produire une bande laminée à chaud en utilisant un processus de refroidissement, le processus de refroidissement sur la table de déroulement étant commandé en utilisant un certain nombre de paramètres d'entrée directement après des cylindres de laminoir finisseur de bande à chaud, qui sont soit mesurés, soit basés sur un modèle, et un schéma de refroidissement d'une installation de refroidissement avec de multiples bancs de refroidissement dans la table de déroulement étant déterminé.
PCT/EP2021/086338 2020-12-17 2021-12-16 Procédé de commande du refroidissement d'une table de sortie de laminoir à chaud WO2022129434A1 (fr)

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KR1020237022871A KR20230118901A (ko) 2020-12-17 2021-12-16 열간 압연기 런아웃 테이블의 냉각을 제어하는 방법
EP21839514.3A EP4263879A1 (fr) 2020-12-17 2021-12-16 Procédé de commande du refroidissement d'une table de sortie de laminoir à chaud

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998018970A1 (fr) * 1996-10-30 1998-05-07 Voest-Alpine Industrieanlagenbau Gmbh Procede pour la surveillance et la gestion de la qualite de produits lamines obtenus par laminage a chaud
EP3430175A1 (fr) * 2016-03-14 2019-01-23 SMS Group GmbH Procédé de laminage et/ou de traitement thermique d'une bande métallique
EP3612651A1 (fr) * 2017-04-18 2020-02-26 SMS Group GmbH Dispositif et procédé pour le refroidissement de bandes ou de tôles métalliques

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998018970A1 (fr) * 1996-10-30 1998-05-07 Voest-Alpine Industrieanlagenbau Gmbh Procede pour la surveillance et la gestion de la qualite de produits lamines obtenus par laminage a chaud
EP3430175A1 (fr) * 2016-03-14 2019-01-23 SMS Group GmbH Procédé de laminage et/ou de traitement thermique d'une bande métallique
EP3612651A1 (fr) * 2017-04-18 2020-02-26 SMS Group GmbH Dispositif et procédé pour le refroidissement de bandes ou de tôles métalliques

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
LIU ZHENGDONG ET AL: "Experiments and mathematical modelling of controlled runout table cooling in a hot rolling mill", CENTRAL IRON AND STEEL RESEARCH INSTITUTE, 31 March 2001 (2001-03-31), pages 1 - 314, XP055788531, ISBN: 978-0-612-71495-3, Retrieved from the Internet <URL:https://open.library.ubc.ca/media/download/pdf/831/1.0078513/1> [retrieved on 20210322] *
MUKHOPADHYAY A ET AL: "Implementation of an on-line run-out table model in a hot strip mill", JOURNAL OF MATERIALS PROCESSING TECHNOLOGY, ELSEVIER, NL, vol. 169, no. 2, 10 November 2005 (2005-11-10), pages 164 - 172, XP027806255, ISSN: 0924-0136, [retrieved on 20051110] *

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