Dynamic adjustment method for manufacturing thermally treated steel sheets

Abstract

This invention provides a dynamic adjustment method for manufacturing thermally treated steel sheets. [Solution] A method of dynamic adjustment comprising: A. A control step in which at least one sensor detects any deviation occurring during heat treatment; B. A calculation step performed when a deviation is detected during heat treatment, comprising: 1) a calculation substep in which at least two thermal paths, which are TPx corresponding to one microstructure mx obtained at the end of TPx, are calculated based on the microstructure mi of the steel sheet to reach TT and mtarget; 2) a selection substep in which one new thermal path TPtarget to reach mtarget is selected, and TPtarget is selected such that it is selected from the TPX and mX is closest to mtarget; C. A new heat treatment step in which TPtarget is performed online on the steel sheet.

Description

[Technical Field]

[0001] This invention relates to a microstructure in a heat treatment line that includes a chemical steel composition and at least one phase selected from ferrite, martensite, bainite, pearlite, cementite, and austenite, comprising 0-100%. target The present invention relates to a method of dynamic adjustment for manufacturing a thermally treated steel sheet having [a specific characteristic]. [Background technology]

[0002] It is known that coated or uncoated steel sheets are used in the manufacture of automobile vehicles. Numerous steel grades are used in the manufacture of vehicles. The selection of steel grade depends on the end use of the steel part. For example, IF (very low carbon) steel may be produced for exposed parts, TRIP (transformation-induced plasticity) steel may be produced for seats and floor cross members or A-pillars, and DP (duplex) steel may be produced for rear rails or roof cross members.

[0003] During the production of these steels, crucial treatments are carried out on the steel to obtain the desired parts with the mechanical properties expected for a particular application. Such treatments may include, for example, continuous annealing or quenching and distribution treatments before the application of a metal coating. These treatments are carried out within a suitable furnace line.

[0004] During these processes, some unexpected deviations may occur online. For example, the furnace temperature, steel plate thickness, or line speed may change.

[0005] Patent application US4440583 relates to a controlled cooling method for a steel strip, implemented by using a cooling device that includes a plurality of nozzles arranged in the direction of the steel strip's movement for spraying a coolant onto a hot, moving steel strip, and flow control valves attached to pipes supplying the coolant to the nozzles. The heat transfer coefficient required to obtain the desired cooling rate is calculated using a formula that includes the thickness of the steel strip, the starting and ending temperatures for cooling, and the desired cooling rate, and the resulting heat transfer coefficient is corrected according to the natural cooling effect in idle pass zones before and after the coolant spray zone. The coolant flow rate is then derived and set from a pre-established relationship between the coolant flow rate and the heat transfer coefficient. The length of the coolant spray zone along the path of the steel strip is calculated using the speed of the steel strip, the starting and ending temperatures for cooling, and the desired cooling rate. The nozzles are set to be on or off so that the coolant is sprayed from only a number of nozzles corresponding to the calculated value. If the thickness of the steel strip changes while controlled cooling is being performed, the heat transfer coefficient is recalculated based on the above settings to correct the coolant flow rate accordingly. As the speed of the steel strip changes, the length of the coolant spray area is recalculated to compensate for the nozzle's on / off pattern.

[0006] In this method, if a deviation occurs, the heat transfer coefficient or the length of the coolant spray area is recalculated to compensate for the deviation. This method does not take into account the properties of the steel sheet, including chemical composition, microstructure, properties, and surface characteristics. Therefore, there is a risk that the same correction will be applied to any type of steel sheet, even if each steel sheet has its own properties. This method allows for undifferentiated cooling treatment of a large number of steel grades.

[0007] As a result, the correction is not tailored to a specific steel, and therefore the desired properties are not obtained at the end of the process. Furthermore, after processing, the steel may exhibit greater variability in its mechanical properties. Finally, even if a wide range of steel grades can be produced, the quality of the processed steel may be insufficient. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] U.S. Patent No. 4440583 [Overview of the project] [Problems that the invention aims to solve]

[0009] Therefore, the object of the present invention is to achieve a specific chemical steel composition and a specific microstructure to be reached within a heat treatment line. target The objective is to solve the aforementioned drawbacks by providing a method for dynamic adjustment of thermally treated steel sheets having [specific properties]. Another objective is to adjust the thermal path online by providing a process tailored to each steel sheet, such a process being calculated with great accuracy in the shortest possible computation time. Another objective is to provide steel sheets having the expected properties, i.e., with the smallest possible variation. [Means for solving the problem]

[0010] This objective is achieved by providing the method according to claim 1. The method may also include any of the characteristics described in claims 2 to 20.

[0011] Another objective is achieved by providing the coil described in claim 21. The coil may also include the properties described in claim 22 or 23.

[0012] Another objective is achieved by providing the thermal processing line described in claim 24.

[0013] Finally, this objective is achieved by providing the computer program product described in claim 25.

[0014] Other features and advantages of the present invention will become apparent from the following embodiments for carrying out the invention.

[0015] To illustrate the present invention, various non-limiting embodiments and trials will be described with particular reference to the following figures. [Brief explanation of the drawing]

[0016] [Figure 1] This figure shows an example according to the present invention. [Figure 2] This figure shows the continuous annealing of a steel sheet, including a heating step, a soaking step, a cooling step, and an overaging step. [Figure 3] This figure shows a preferred embodiment of the present invention. [Figure 4] This figure shows an example according to the present invention in which continuous annealing is performed on a steel sheet before the coating is applied by melting. [Modes for carrying out the invention]

[0017] The following terms are defined: - CC: Chemical composition in percentage by weight. - m target : Target values ​​for microorganisms, - m standard : Microstructure of the selected product, - P target : Target values ​​for mechanical properties, - m i Initial microstructure of steel sheet, - X: Pseudonym in weight percent, - T: Temperature in Celsius (°C) units. - t: time (s), - s: seconds, - UTS: Maximum tensile strength (MPa) - YS: Yield stress (MPa) - Zinc-based metal coating means a metal coating containing more than 50% zinc. - Aluminum-based metal coating means a metal coating containing more than 50% aluminum, and - TT: Heat treatment and - Thermal paths, TT, TP target , TP x and TPxint includes at least one rate selected from time, heat treatment temperature, and cooling rate, isothermal rate, or heating rate. The isothermal rate means a rate having a constant temperature, and - Nanofluid: A fluid containing nanoparticles.

[0018] The term "steel" or "steel plate" means a steel plate, coil, or plate having a composition that enables the component to achieve a tensile strength of up to 2500 MPa, more preferably up to 2000 MPa. For example, the tensile strength is 500 MPa or more, preferably 1000 MPa or more, and advantageously 1500 MPa or more. Since the method according to the invention can be applied to any type of steel, a wide range of chemical compositions is included.

[0019] The present invention relates to a method of dynamic adjustment for manufacturing a heat-treated steel plate having a chemical steel composition and a microstructure m including at least one phase selected from 0 to 100% of ferrite, martensite, bainite, pearlite, cementite, and austenite, in which a predetermined heat treatment TT is carried out on the steel plate in a heat treatment line target and is a method of dynamic adjustment for manufacturing a heat-treated steel plate having a chemical steel composition and a microstructure m including at least one phase selected from 0 to 100% of ferrite, martensite, bainite, pearlite, cementite, and austenite, in which a predetermined heat treatment TT is carried out on the steel plate in a heat treatment line A. A control step in which at least one sensor detects any deviation occurring during the heat treatment TT, B. A calculation step carried out when a deviation is detected during the heat treatment, in which target a new heat path TP target is determined taking into account the deviation in order to reach m 1) A calculation sub-step in which at least two heat paths corresponding to one microstructure m x at the end of TP x are calculated based on TT and m x for the steel plate microstructure m target to reach m i and 2) One new heat path TP target for reaching m target is selected, TP target is selected from TP X and m X is mtarget Select the substep that is closest to it. Calculation steps, C.TP target However, a new heat treatment step is performed online on the steel plate. This includes methods.

[0020] While we do not wish to be limited by any theory, when the method according to the present invention is applied, it appears possible to compensate for any deviations that occur during the heat treatment by providing individualized heat treatment according to each steel sheet. To do so, a precise and specific new heat path TP target However, m target , in particular the proportion of all phases according to the process, m i The calculations are performed in a short computation time, taking into account variations in the microstructure along the steel sheet and the resulting misalignment. In fact, the method according to the present invention considers thermodynamically stable phases, namely ferrite, austenite, cementite, and pearlite, as well as thermodynamically metastable phases, namely bainite and martensite, for the calculations. Thus, a steel sheet with the expected properties and the smallest possible variation is obtained.

[0021] Preferably, microstructure m x Phase, m target Phase and m i A phase is defined by at least one element selected from size, shape, and chemical composition.

[0022] Preferably, the microstructure to be reached m target teeth, - 100% austenite, - 5-95% martensite, 4-65% bainite, the remainder being ferrite. - 8-30% retained austenite, 0.6-1.5% carbon in the solid solution, the remainder being ferrite, martensite, bainite, pearlite and / or cementite. - 1% to 30% ferrite and 1% to 30% bainite, 5% to 25% austenite, the remainder being martensite. - 5-20% retained austenite, the remainder being martensite. - Ferrite and retained austenite, - Retained austenite and intermetallic phases, - 80-100% martensite and 0-20% retained austenite - 100% martensite, - 5-100% perlite and 0-95% ferrite, - At least 75% isometric ferrite, 5-20% martensite, and 10% or less bainite. Includes.

[0023] Advantageously, the steel sheet may be any type of steel grade, including duplex DP, transformation-induced plasticity (TRIP), quenched and distributed steel (Q&P), twinning-induced plasticity (TWIP), carbide-free bainite (CFB), press-hardened steel (PHS), TRIPLEX, DUPLEX, and high-ductility duplex (DP HD).

[0024] The chemical composition depends on the type of steel sheet. For example, the chemical composition of DP steel may include the following: 0.05 <C<0.3%、 0.5 ≤ Mn < 3.0%, S ≤ 0.008%, P ≤ 0.080%, N ≤ 0.1%, Si ≤ 1.0%, The remainder of the composition, consisting of iron and unavoidable impurities resulting from growth.

[0025] Figure 1 shows an example according to the present invention in which TT is performed on a steel sheet in a heat treatment line, and such a steel sheet has a chemical composition CC and to be achieved m target It holds.

[0026] According to the present invention, in step A), some deviation occurring during heat treatment is detected. Preferably, the deviation is caused by a change in a process parameter selected from furnace temperature, steel plate temperature, amount of gas, gas composition, gas temperature, line speed, malfunction in the heat treatment line, changes in the molten bath, changes in steel plate emissivity, and changes in steel thickness.

[0027] The furnace temperature can be the heating temperature, soaking temperature, cooling temperature, or overaging temperature, particularly in continuous annealing.

[0028] The steel plate temperature can be changed at any point in the heat treatment process, at various locations along the heat treatment line, for example, - Preferably, the heating section is a direct-fired furnace (DFF), a radiant-tube furnace (RTF), an electric resistance furnace, or an induction furnace. - Inside the cooling section, especially inside the cooling jet, inside the quenching system or inside the snout and - Preferably within an isothermal section of an electric resistance furnace It can be measured using [this method].

[0029] To detect temperature changes, the sensor may be a pyrometer or a scanner.

[0030] Typically, heat treatment can be carried out in an oxidizing atmosphere, i.e., in an atmosphere containing an oxidizing gas such as O2, CH4, CO2, or CO. Heat treatment can also be carried out in a neutral atmosphere, i.e., in an atmosphere containing a neutral gas such as N2, Ar, or He. Finally, heat treatment can also be carried out in a reducing atmosphere, i.e., in an atmosphere containing a neutral gas such as H2 or HN. x This can be carried out in an atmosphere containing a reducing gas.

[0031] Changes in gas volume can be detected by a barometer.

[0032] Line speed can be detected by a laser sensor.

[0033] For example, failures in a heat treatment line can include the following: - Inside the open-fire furnace: The burner is no longer working. - Radiant tube inside the furnace: Radiant tubes no longer functioning, - Inside an electric furnace: A resistor or - Inside the cooling section: One or more cooling jets are no longer working.

[0034] In such cases, the sensor could be a thermometer, barometer, power consumption meter, or camera.

[0035] Changes in steel thickness can be detected using a laser sensor or an ultrasonic sensor.

[0036] When a discrepancy is detected, m x At least two corresponding thermal paths TP x However, TT and m target m to reach i Calculated based on such TP x This takes the discrepancy into account. TP x This calculation is based on the thermal and metallurgical behavior of the steel plate, compared to conventional methods that only consider thermal behavior.

[0037] Figure 2 shows the continuous annealing of a steel sheet, including a heating step, a soaking step, a cooling step, and an overaging step. soaking A shift D caused by the change is detected. Therefore, as shown in Figure 2 for the first cooling step only, m target A large number of TP x The following is calculated. In this example, the calculated TP x This also includes a second cooling step and an overaging step (not shown).

[0038] Preferably, at least 10 TP x This is calculated, more preferably at least 50, favorably at least 100, and more preferably at least 1000 TP x The following is calculated: For example, the calculated TP x The number is between 2 and 10,000, preferably between 100 and 10,000, and preferably between 1,000 and 10,000.

[0039] In step B.2), m target A new thermal path TP to reach target This is selected. TP target , TP x Selected from, and m x ga m target It is selected to be the closest to TP. Therefore, in Figure 1, target , a large number of TP x Selected from. Preferably, m target and m x The difference in phase ratios between the various phases present within the material is ±3%.

[0040] To the advantage of step B.1), m i and m target The thermal enthalpy H released or consumed during this period is

[0041]

number

[0042] While we do not wish to be limited by any theory, H represents the energy released or consumed along all heat pathways when a phase transformation takes place. Some phase transformations are considered exothermic, and some are considered endothermic. For example, the transformation from ferrite to austenite in the heating pathway is endothermic, while the transformation from austenite to pearlite in the cooling pathway is exothermic. Preferably, H x , TP x This is taken into consideration in the calculation.

[0043] In a preferred embodiment, in step B.1), all thermal cycle TP x but,

[0044]

number

[0045] Preferably, in step B.1), the intermediate heat path TP xint at least one intermediate steel microstructure m corresponding to xint and thermal enthalpy H xint This is calculated. In this case, TP x The calculation involves a large number of TP xint It is obtained by the calculation of . Therefore, preferably, TP x all TP xint It is the sum of H x All H xint This is the sum. In this preferred embodiment, TP xint It is calculated periodically. For example, CP xint This is calculated every 0.5 seconds, preferably every 0.1 seconds or less.

[0046] Figure 3 shows that in step B.1), TP xint1 and TP xint2 The corresponding m int1 and m int2 and H xint1 and H xint2 A preferred embodiment is shown in which H in all heat paths is calculated. x However, TP x This is determined to calculate. According to the present invention, a large number of, i.e., more than two TPs xint , m xint and H xint However, TP x This is calculated to obtain (not shown).

[0047] In a preferred embodiment, before step B.2), at least one target mechanical property P selected from yield stress YS, maximum tensile strength UTS, elongation, hole expansion property, formability target is selected. In this embodiment, preferably, m target is calculated based on P target .

[0048] Although not wishing to be limited by any theory, it is considered that the properties of the steel sheet are defined by the process parameters applied during steel production. Therefore, advantageously, in step B.1), the process parameters that the steel sheet undergoes before entering the heat treatment line are considered for calculating TP x . For example, the process parameters include at least one element selected from the cold rolling reduction rate, coiling temperature, run-out table cooling path, cooling temperature, and coil cooling rate.

[0049] In another embodiment, the process parameters of the treatment line that the steel sheet undergoes within the heat treatment line are considered for calculating TP x . For example, the process parameters include at least one element selected from the specific hot steel sheet temperature to be reached, line speed, cooling capacity of the cooling section, heating capacity of the heating section, overaging temperature, cooling temperature, heating temperature, and soaking temperature.

[0050] Preferably, the heat path, TP x , TP xint , TT or TP target includes at least one treatment selected from heat treatment, isothermal treatment, or cooling treatment. For example, the heat path can be recrystallization annealing, press hardening path, recovery path, two-phase region annealing, or full austenite annealing, tempering path, partitioning path, isothermal path, or quenching path.

[0051] Preferably, recrystallization annealing is performed. Recrystallization annealing optionally includes a preheating step, a heating step, a soaking step, a cooling step, and optionally a homogenization step. In this case, recrystallization annealing is performed in a continuous annealing furnace which optionally includes a preheating section, a heating section, a soaking section, a cooling section, and optionally a homogenization section. Although we do not wish to be limited by any theory, recrystallization annealing is considered a more difficult thermal path to handle because it involves many steps to consider, including the cooling and heating steps.

[0052] Advantageously, each time a new steel sheet enters the heat treatment line, a new calculation step B.1) is automatically performed. In fact, since the actual properties of each steel often differ, the method according to the present invention allows for the calculation of the heat path TP even when the same steel grade enters the heat treatment line. target The system is adapted to each steel plate. New steel plates can be detected, their new properties measured, and pre-selected. For example, the sensor can detect a weld between two coils.

[0053] Preferably, to prevent large changes during the process, thermal path adaptation is performed on the first few meters of the steel sheet when it enters the heat treatment line.

[0054] Preferably, an automated calculation is performed during the heat treatment to check if any deviation has occurred. In this embodiment, the calculation is performed periodically to check if a slight deviation has occurred. In reality, the sensor's detection threshold may be too high, meaning that slight deviations may not necessarily be detected. For example, an automated calculation performed every few seconds is not based on a detection threshold. Therefore, if the calculation leads to the same heat treatment, i.e., if the heat treatment is performed online, TT does not change. If the calculation leads to a different treatment due to a slight deviation, the treatment changes.

[0055] Figure 4 shows an example according to the present invention in which continuous annealing is performed on the steel sheet before the coating is attached by melting. When a displacement D appears in the method according to the present invention, TP x However, mi , selected products, TT and m target It is calculated based on the following. In this example, the intermediate heat path TP xint1 ~TP xint4 , corresponding to m xint1 ~m xint4 and H xint1 ~H xint4 This is calculated. TP x To obtain H x This is determined. In this figure, the TP shown target is TP x Selected from.

[0056] According to the method of the present invention, when a discrepancy occurs, m target To reach TP target A new heat treatment step, including the following, is performed on the steel sheet.

[0057] Therefore, a coil made of steel sheet is obtained, including the aforementioned predetermined product types, including DP, TRIP, Q&P, TWIP, CFB, PHS, TRIPLEX, DUPLEX, and DP HD, and such a coil has a standard deviation of mechanical properties of 25 MPa or less, preferably 15 MPa or less, and more preferably 9 MPa or less, between any two points along the coil. In fact, although we do not wish to be limited by any theory, the method including calculation step B.1) is considered to take into account the variation in the microstructure of the steel sheet along the coil. Therefore, the TP applied to the steel sheet target This enables the homogenization of microstructure and mechanical properties.

[0058] A low standard deviation value indicates TP target This is due to the precision. Preferably, the mechanical properties are selected from YS, UTS, or elongation.

[0059] Preferably, the coil is covered with a metal coating based on zinc or aluminum.

[0060] Preferably, in industrial production, the standard deviation of the continuously measured mechanical properties between two coils made of steel sheets, including the predetermined product types such as DP, TRIP, Q&P, TWIP, CFB, PHS, TRIPLEX, DUPLEX, and DP HD, produced on the same line, is 25 MPa or less, preferably 15 MPa or less, and more preferably 9 MPa or less.

[0061] A thermal treatment line for carrying out the method according to the present invention is TP target These are used to carry out the following. For example, thermal treatment lines include continuous annealing furnaces, press hardening furnaces, batch annealing, or quenching lines.

[0062] Finally, the present invention is TP target The present invention relates to a computer program product comprising at least a metallurgical module, a thermal module, and an optimization module that cooperate with each other to determine a method according to the present invention, wherein such modules include software instructions that, when executed by a computer, perform a method according to the present invention.

[0063] The metallurgical module is a microstructure (metastable phase: bainite and martensite and stable phase: ferrite, austenite, cementite and pearlite). x , m target ), or more precisely, predict the proportion of each phase throughout the entire process and predict the rate of phase transformation.

[0064] The thermal module predicts the steel sheet temperature based on the equipment used for heat treatment, such as a continuous annealing furnace, process parameters including the geometric properties of the band, cooling capacity, heating capacity, or isothermal capacity, and the dynamic thermal enthalpy H released or consumed along all heat paths when the phase transformation is performed.

[0065] The optimization module is performed according to the method of the present invention using a metallurgical module and a thermal module, m target The best heat path to reach, i.e., TP target To decide. [Examples]

[0066] In the following examples, DP780GI having the following chemical composition was selected:

[0067] [Table 1]

[0068] To obtain a thickness of 1.2 mm, the reduction ratio during cold rolling was set to 55%.

[0069] m to reach target The following P target It contained 12% martensite, 58% ferrite, and 30% bainite, corresponding to YS at 460 MPa and UTS at 790 MPa. A cooling temperature of 460°C T was used to carry out hot-dip galvanizing with a zinc bath. cooling This temperature must also be reached. To ensure good coverage within the Zn bath, this temperature must be reached with an accuracy of + / - 2°C.

[0070] The heat treatment TT applied to the steel plate is as follows: - Preheating step: The steel plate is heated from ambient temperature to 680°C for 37.5 seconds. - Heating step: The steel plate is heated from 680°C to 780°C for 40 seconds. - The steel plate is heated to a uniform temperature of 780°C T soaking A soaking step is performed, which involves heating for 24.4 seconds. - The steel plate is as follows HN x Cooling step: Cooled by 11 cooling jets that spray the solution:

[0071] [Table 2] - Hot-dip plating in a zinc bath at 460℃, - Cooling of the steel sheet to the top roll at 300°C for 27.8 seconds and - Cooling of the steel plate at ambient temperature.

[0072] [Example 1] <T soaking Discrepancy > Soaking temperature T soaking When the temperature drops from 780°C to 765°C, m target To reach the new heat path TP, take the deviation into consideration. target1 This is determined. For this purpose, a number of thermal paths TP x , TT, m target To reach the DP780GI m i The calculation was based on the and deviation.

[0073] TP x After the calculation, m target A new thermal path TP to reach target1 Select TP target1 , TP x Choose from, and m X ga m target I selected the one that was closest to it. TP target1 The following applies: - Due to displacement within the soaking section of the heat treatment line, the steel plate reaches a soaking temperature of 765°C T soaking A soaking step is performed, which involves heating for 24.4 seconds. - The steel plate is as follows HN x Cooling step: Cooled by 11 cooling jets that spray the solution:

[0074] [Table 3] - Hot-dip plating in a zinc bath at 460℃, - Cooling of the steel sheet to the top roll at 300°C for 27.8 seconds and - Cooling of the steel plate at ambient temperature.

[0075] [Example 2] <Steel plates with different compositions> A new steel plate, DP780GI, entered the heat treatment line, and therefore the calculation steps were automatically performed based on the following new CC:

[0076] [Table 4]

[0077] m target To reach the new CC, consider the new thermal path TP target2 This decision was made. TP target2 The following applies: - Preheating step: The steel plate is heated from ambient temperature to 680°C for 37.5 seconds. - Heating step: The steel plate is heated from 680°C to 780°C for 40 seconds. - The steel plate is heated to a uniform temperature of 780°C T soaking A soaking step is performed, which involves heating for 24.4 seconds. - Steel plate, HN x Cooling step: Cooled by 11 cooling jets that spray the solution.

[0078] [Table 5] - Hot-dip plating in a zinc bath at 460℃, - Cooling of the steel sheet to the top roll at 300°C for 26.8 seconds and - Cooling of the steel plate at ambient temperature.

[0079] Table 1 shows TT, TP target1 and TP target2 The properties of the steel obtained by this method are shown below:

[0080] [Table 6]

[0081] The method according to the present invention makes it possible to adjust the thermal TT when a misalignment occurs or when a new steel sheet with a different CC enters the heat treatment line. target1 and TP target2 By applying this, it is possible to obtain a steel sheet having the desired expected properties, and each TP targetIt is precisely fitted to each misalignment.

Claims

1. Within the heat treatment line, a predetermined heat treatment TT is performed on the steel sheet, and the chemical steel composition and the microstructure m include at least one phase selected from ferrite, martensite, bainite, pearlite, cementite, and austenite in an amount of 0-100%. ｔａｒｇｅｔ A method for dynamically adjusting a thermally treated steel sheet having, A. A control step in which at least one sensor detects any deviation that occurs during the heat treatment, B. A calculation step performed when a certain deviation is detected during the heat treatment, m ｔａｒｇｅｔ To reach the aforementioned displacement, a new one heat path TP ｔａｒｇｅｔ This is to ensure that the following is determined. 1) TP ｘ The last microstructure obtained is m ｘ TP corresponding to ｘ At least two heat paths are TT and m ｔａｒｇｅｔ The microstructure of the steel plate to reach ｉ Calculation substeps calculated based on, 2) m ｔａｒｇｅｔ One new heat path TP to reach ｔａｒｇｅｔ is selected, and TP ｔａｒｇｅｔ is selected from the said TP Ｘ and m Ｘ is m ｔａｒｇｅｔ Selected sub-step selected to be closest to Calculation steps, C. TP ｔａｒｇｅｔ However, a new heat treatment step is performed online on the steel plate. Methods that include...

2. The method according to claim 1, wherein in step A), the deviation is due to a change in one process parameter selected from among furnace temperature, steel plate temperature, amount of gas, gas composition, gas temperature, line speed, malfunction in the heat treatment line, change in molten bath, change in steel plate emissivity, and change in steel thickness.

3. The method according to claim 1 or 2, wherein the phase is defined by at least one element selected from size, shape and chemical composition.

4. Microstructure m ｔａｒｇｅｔ for, - 100% austenite, - 5-95% martensite, 4-65% bainite, the remainder being ferrite. - 8-30% retained austenite, 0.6-1.5% carbon in the solid solution, the remainder being ferrite, martensite, bainite, pearlite and / or cementite. - 1% to 30% ferrite and 1% to 30% bainite, 5% to 25% austenite, the remainder being martensite. - 5-20% retained austenite, the remainder being martensite. - Ferrite and retained austenite, - Retained austenite and intermetallic phases, - 80-100% martensite and 0-20% retained austenite - 100% martensite, - 5-100% perlite and 0-95% ferrite, - At least 75% equiaxed ferrite, 5-20% martensite, and 10% or less bainite. The method according to any one of claims 1 to 3, which includes

5. The method according to any one of claims 1 to 4, wherein the steel sheet may be a two-phase, transformation-induced plastic, quenched and distributed steel, twin-induced plastic, carbide-free bainite, press-hardened steel, TRIPLEX, DUPLEX, and a highly ductile two-phase.

6. I understand ｔａｒｇｅｔ and m Ｘ The method according to any one of claims 1 to 5, wherein the difference between the phase ratios of the phases present is ±3%.

7. Step B. 1) In m ｉ and m ｔａｒｇｅｔ The thermal enthalpy H released or consumed during this period is [Math 1] (X is the phase fraction.) The method according to any one of claims 1 to 6, which is calculated as follows.

8. Step B. 1) All thermal cycle TP ｘ but, [Math 2] (In the formula, Cpe: specific heat of the phase (J·kg)) －１ ・K －１ ), ρ: density of steel (g.m³) －３ ), Ep: thickness of the steel (m), φ: heat flux (convection + radiation, W), H ｘ (J.kg) －１ ), T: temperature (°C) and t: time (s). ) The method according to claim 7, which is calculated as follows.

9. Step B. 1) Intermediate heat path TP ｘｉｎｔ at least one intermediate steel microstructure corresponding to m ｘｉｎｔ and thermal enthalpy H ｘｉｎｔ The method according to claim 7 or 8, wherein the following is calculated.

10. Step B. 1) TP ｘ However, all TP ｘｉｎｔ It is the sum of H ｘ However, all H ｘｉｎｔ The method according to claim 9, which is the sum of the two.

11. Step B. Before step 1), select at least one target mechanical property P from among yield strength YS, maximum tensile strength UTS, elongation, hole expandability, and formability. ｔａｒｇｅｔ The method according to any one of claims 1 to 10, wherein is selected.

12. I understand ｔａｒｇｅｔ However, P ｔａｒｇｅｔ The method according to claim 11, calculated based on the following:

13. Step B. 1) The process parameters that the steel sheet goes through before entering the heat treatment line are TP ｘ A method according to any one of claims 1 to 12, which is considered for calculating the following:

14. The method according to claim 13, wherein the process parameters include at least one element selected from cold rolling reduction ratio, winding temperature, runout table cooling path, cooling temperature, and coil cooling rate.

15. Step B. 1) In the heat treatment line, the process parameters (multiple) of the heat treatment line through which the steel plate passes are TP ｘ The method according to any one of claims 1 to 14, which is considered for calculating the following:

16. The method according to claim 15, wherein the process parameters include at least one element selected from a specific hot steel sheet temperature to be achieved, line speed, cooling capacity of the cooling section, heating capacity of the heating section, overaging temperature, cooling temperature, heating temperature, and soaking temperature.

17. The aforementioned heat path, TP ｘ , TP ｘｉｎｔ , TT or TP ｔａｒｇｅｔ The method according to any one of claims 1 to 16, wherein the method comprises at least one process selected from heat treatment, isothermal treatment, or cooling treatment.

18. The method according to any one of claims 1 to 17, wherein a new calculation step B. 1) is automatically performed each time a new steel sheet enters the heat treatment line.

19. The method according to claim 18, wherein when the steel plate enters the heat treatment line, the heat path adaptation is performed on the first few meters of the steel plate.

20. The method according to any one of claims 1 to 19, wherein an automated calculation is performed during the heat treatment to check for any deviations.

21. A coil made of a steel sheet, comprising a predetermined product type including DP, TRIP, Q&P, TWIP, CFB, PHS, TRIPLEX, DUPLEX, and DP HD, which can be obtained by the method according to any one of claims 1 to 20, wherein the coil has a standard deviation of mechanical properties of 25 MPa or less between any two points along the coil.

22. The coil according to claim 21, wherein the standard deviation between any two points along the coil is 15 MPa or less.

23. The coil according to claim 22, wherein the standard deviation between any two points along the coil is 9 MPa or less.

24. A thermal treatment line for carrying out the method according to any one of claims 1 to 23.

25. TP ｔａｒｇｅｔ A computer program product comprising at least a metallurgical module, an optimization module and a thermal module that cooperate with each other to determine, wherein such modules include software instructions that, when executed by a computer, perform the methods described in claims 1 to 20.

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