Method for manufacturing cold-rolled steel strip

Abstract

The present invention relates to a method for manufacturing cold-rolled steel strips.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing cold-rolled steel strips.

Background Art

[0002] In some applications, mechanical properties are of utmost importance. For example, in structural applications of structures, mechanical properties such as the value of tensile strength, the value of yield strength, and the value of elongation are at a certain level so that materials can be applied to structures such as buildings or vehicles to function reliably and safely.

[0003] In other cases, surface properties are of utmost importance. For example, in applications where the material is press-formed, the surface of the base material slides along the press tool, and high contact pressure and poor lubrication may cause surface damage such as galling of the base material. When a zinc coating is applied, it may cause zinc contamination of the press tool. To mitigate these effects, state-of-the-art solutions are to make the tool surface extremely smooth, make the strip surface slightly rough, and apply lubricating oil. One hypothesis is that the high roughness of the strip helps to capture oil for good lubrication properties. This strategy of increasing the roughness of the strip under important forming conditions to improve press performance has been proven effective in press factories. However, generally, high roughness leads to increased waviness, which has an adverse effect on the appearance of painting and thus also affects the painting process and appearance. Therefore, for these applications such as automotive exterior parts, it is necessary that the surface properties be at a certain level so that the appearance is beautiful even after press forming and painting, and materials can be applied to structures to function reliably and safely.

[0004] Often, both mechanical and surface properties need to meet a certain minimum level. To improve mechanical properties, the temper rolling reduction after recrystallization annealing or hot dip galvanizing is increased, but to control the surface texture, it may be required to decrease the temper rolling reduction in a temper rolling mill (TRM).

[0005] Thin gauge flat steel products are typically manufactured by a process of hot rolling, pickling, and cold rolling. To complement strain hardening during cold rolling and obtain desired mechanical properties, such as yield strength (Rp 0.2 ) or elongation, annealing is required after cold rolling. Optionally, (hot dip) galvanizing can be applied to form a rust-preventive coating on the steel substrate.

[0006] After annealing, the steel softens but becomes more susceptible to the so-called "yield point elongation". This yield point elongation results in uncontrolled local strains and bands of local plastic deformation, also known as slip-banding or Lüder's bands, when tensile strain is applied in a tensile test or when flat steel is deformed into a three-dimensional shape, such as an automotive chassis part or outer panel. Such uncontrolled visible plastic deformation is highly undesirable.

[0007] Known solutions to this problem are temper rolling (i.e., skin pass rolling), in which a small bulk elongation of usually 0.5 to 3% is applied in a temper rolling mill (TRM). In this process, fine Luders bands are generated in the steel substrate, and it is thought that plastic deformation in subsequent normal sheet metal forming becomes homogeneous. Another solution is the application of tension levelling, in which a controlled bulk strain is applied by stretching and bending in a tension leveller (TL).

[0008] Both skin pass rolling and tension levelling need to achieve further purposes. Skin pass rolling is used to correct the strip shape by varying the elongation across the strip width and to apply a surface property also called surface roughness by using work rolls with a relatively high roughness. The peaks of the roughness on the work roll cause locally high contact pressures and local plastic deformation of the steel substrate and / or the metal coating. In tension levelling, the main purpose is to flatten the steel strip by producing a small bulk elongation. Tension levelling may also be used for the purpose of strip bulk elongation when the rolling force of the temper rolling mill is insufficient to apply the strip bulk elongation required to solve the yield point elongation problem.

[0009] The problem is that both skin pass rolling and tension leveling have conflicting objectives. In skin pass rolling, it is necessary to balance the bulk elongation to solve yield point elongation and the local plastic strain on the surface to form roughness. For example, in the case of a hard steel substrate, a small-diameter work roll is required to prevent the rolling force from becoming too high. On the other hand, in the case of a soft steel substrate, by rolling with a large-diameter work roll, the desired roughness transfer can be achieved with a predetermined bulk elongation. As a result, when a work roll type is installed in a skin pass rolling mill, the rolling force depends on the bulk elongation required to solve yield point elongation (and to define the yield strength Rp 0.2 ), and the roughness transfer is also fixed. By adjusting the line tension, and thus the required rolling force, while maintaining the bulk elongation, only small variations in the strip roughness are possible. An improvement in roughness control is strongly desired to enable narrower strip roughness specifications, to compensate for work roll surface wear, and to accommodate variations in steel substrate properties. SUMMARY OF THE INVENTION

[0010] Accordingly, an object of the present invention is to provide a method capable of obtaining good surface properties and good mechanical properties.

[0011] Another object of the present invention is to provide a cold-rolled steel strip having good surface properties and good mechanical properties for press forming.

[0012] One or more objects are achieved by the method according to claim 1. Preferred embodiments are described in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0014] The present invention uses a control scheme that combines a prediction model, an optimization routine, and a conventional controller to solve the problem of insufficient strip surface roughness control by an integrated system that includes both a skin pass rolling mill and a tension leveler in order to obtain accurate control of the surface roughness while maintaining the yield strength characteristics.

[0015] The generation of the set value is shown in Figure 1 and includes the following five elements.

[0016] Input: 1. Coil: A coil having a certain chemical composition and dimensions (thickness, width, length), cold rolled, annealed, and optionally coated. Process: 2. Skin pass rolling: A rolling process that slightly reduces the thickness, forms a surface texture on the strip surface, and optionally adjusts the strip shape. The internal control system targets a set value of elongation and continuously adjusts the rolling force. 3. Tension leveling: The process of applying bulk strain by stretching and bending. The internal control system targets the set value of elongation and continuously adjusts the tension and roll position. 4. Finishing: The process of performing quality inspection, measuring surface roughness, and applying oil. Output: 5. Finished coil: The finished product with the characteristics according to the order.

[0017] The desired output is achieved based on the given input and the implementation of the process steps in between. The input consists of a physical coil that is processed for its mechanical and surface characteristics upon entry, and the target requirements that the final finished coil must meet according to the customer's requirements and the applicable standards. Usually, the final finished coil needs to meet one or more target mechanical properties (prop-tar), including at least the yield strength. The yield strength is usually represented as Rp 0.2 and the 0.2% offset yield strength is defined as the stress that needs to be imposed on the material in a tensile test that results in a plastic strain of 0.2% (ISO 6892-1:2019). The claimed system, for example Rp 0.5It should be noted that it can also accommodate different defined yield strengths. Another important prop-tar can be the yield point elongation (Ae or YPE, which may also be called the yield point elongation). This is defined as the elongation between the start of yielding and the start of uniform work-hardening in a tensile test and is expressed as a percentage of the extensometer gauge length Le (ISO 6892-1:2019). The effect of the post-treatment of the metal strip in TRM and / or TL is that the YPE decreases, and it may decrease to 0 depending on the steel type and the requirements of the customer and / or standard. The final finished coil should also meet one or more target surface texture specifications (text-tar), such as the roughness value Ra (ISO 21920-2:2021), which is the average value or arithmetic mean of the profile height deviations from the average line. Setting these target values is the task of step a: the order section.

[0018] Based on these target values, the work rolls are selected, the work roll diameter is defined by the prop-tar, and the work roll roughness and peak count are determined by the text-tar. This task is performed in step b: work roll selection.

[0019] The relevant data from steps a and b are supplied to an initial setpoint generator, which, in step c, uses a table or model based on past data to generate the initial setpoints for the temper rolling mill (TRM) and the tension leveller (TL). The past data corresponds to data collected from the process. The main initial setpoints are the line tension in the TRM, the elongation in the TRM (e_TRM), the work roll bending force in the TRM, and the total elongation (e_tot) of the metal strip processed in the TRM and TL (TRM+TL). The total elongation (e_tot) is the sum of the elongation in the TRM and the elongation in the TL (e_TRM+e_TL). The line tension in the TRM is important for controlling the flatness of the entering strip and is combined with the work roll bending force in the TRM to also control the flatness of the exiting strip from the skin pass rolling mill. e_TRM+e_TL needs to be controlled to obtain the required yield strength (Rp) and to obtain suppression of the yield point elongation (YPE), where e_TRM is the elongation in the TRM and e_TL is the elongation in the TL. e_YPE is defined as the minimum elongation required to suppress the influence of YPE. e_tot in the present invention needs to be distributed across the TRM and TL, and the distribution of the elongation across the TRM and TL is defined according to equations 1 and 2: Rp = a*e_TRM + b*e_TL + c (Equation 1) e_YPE = d*e_TRM + e*e_TL (Equation 2)

[0020] Therefore, e_TL is derived from the initial setpoint e_TRM. However, the target Rp and the minimum e_YPE need to be satisfied.

[0021] The values of coefficients a to e may be based on past results or on a model that determines these parameters based on relevant product and process data. The determination of the initial set values is performed in step c.

[0022] The initial set values are then checked and verified against the limitations imposed by the TRM process, the TL process, and the installations. The rolling force model calculates the rolling force based on e_TRM, line tension, work roll characteristics, and strip characteristics. The roughness model performs the calculation of the strip roughness based on the rolling force, work roll characteristics, and strip characteristics, and also verifies whether the calculated YPE, Rp 0.2 and Ra achieve the values of prop-tar and text-tar. The verification of the initial set values is performed in step d. In this way, as described above, a setpoint validator is obtained that uses a prediction model to verify whether the initial set values achieve one or more target mechanical characteristics and one or more target surface finish specifications of the outgoing strip.

[0023] If the initial set values are verified, that is, if the target values are in principle achievable based on the input coil and the selected process, then as a final step, the set values may be optimized. For example, to avoid the risk that the realized characteristic values are too close to the reject value, and to make the process conditions as stable and reproducible as possible, for example, the set values are adjusted so that the target values are directed towards the center of their respective specification windows. If it is considered that the target values cannot be achieved by the initial set values, the set values are adjusted by optimization of the set values until it becomes possible to achieve the target values by the optimized set values. The optimization of the set values is performed in step e.

[0024] Explanation by way of non-limiting example: If the verification of the setpoint in step d indicates that the text-tar specification is not achieved, the setpoint optimizer adjusts the initial setpoint according to one or more of the following strategies: I. Adjust the line tension (TRM) to affect the rolling force while maintaining a constant e_TRM and observing the limits of the equipment and process, thereby then affecting the surface properties; II. Adjust e_TRM to affect the rolling force, thereby then affecting the surface properties, and modify e_TL to maintain a constant Rp 0.2 ; III. Without adjusting e_TL, adjust e_TRM to affect the rolling force, thereby then affecting the surface properties.

[0025] The final step is to introduce the final setpoints into the TRM and TL and execute the process to produce a strip with the desired prop-tar and text-tar. This is step f. During the execution of the process, the measured rolling force, the observation of the strip shape, and the measured surface property values can be fed back to the control system in a feedback loop to adapt the setpoints of the running process, or, as past results, or as an improvement to the model for determining parameters based on relevant product data and process data, for later use.

[0026] The control system of the present invention is different from the conventional closed-loop control system as defined in Chinese Patent Application CN107008758B. In CN107008758B, real-time measurements on the final product are used to modify process settings such as e_TRM and e_TL in real time. The control system of the present invention is an open loop control system or a feed forward control system. The drawback of closed-loop control as described in CN107008758B is that the system reacts to the difference between the actual state and the desired state of the system, that is, it reacts to the error of target characteristics such as roughness as in CN107008758B. On the other hand, the present invention is based on an open loop control or a feed forward control system, and uses the information obtained from the models using Equations 1 and 2 to define the optimal settings, thereby preventing the error or difference between the desired state and the actual state (prop-tar). A model for predicting the surface characteristics (text-tar) is also used for generating the set values. To further improve the accuracy of the model for small effects not included in the model, correction factors or adaptation factors are used based on the difference between the characteristics of the final product and the model prediction.

[0027] In one embodiment, the value of the actual rolling force measured by TRM is used as an input to the set value validator for the next coil. This feedback adaptation improves the prediction ability of the method of the present invention.

[0028] In one embodiment, the actual surface property parameters measured after TRM and TL are used as an input to the set value validator for the next coil. This feedback adaptation improves the prediction ability of the method of the present invention, enables achieving the desired surface properties of future coils with better accuracy, thereby reducing the production scrap of out-of-spec products.

[0029] Adjustment of the line tension in the TRM by the setpoint optimizer is preferably performed so that the adjusted line tension does not exceed the lower or upper limit. The line is operated most flexibly when the initial line setting is in the middle of the operating window.

[0030] In another embodiment, adjustment of the e_TRM by the setpoint validator is performed such that the rolling force is adjusted so that at least one target surface quality specification falls within the specification window.

[0031] In one embodiment, adjustment of the elongation in the TRM by the setpoint optimizer is performed such that at least one target surface quality parameter or target surface quality specification falls within the specification window as a result of correcting the rolling force of the TRM by adjusting the elongation in the TRM.

[0032] In one embodiment, the e_TL is adjusted according to Equation 1 so that one or more target mechanical properties are maintained within the specification window, preferably without affecting the surface roughness properties. By using an equation that describes the relationship between e_TRM and e-TL on the one hand and an equation that describes the relationship between mechanical or microstructural properties on the other hand, an optimal combination of e_TRM and e-TL can be selected, thereby reducing the manufacturing risk of off-spec products.

[0033] In one embodiment, the e_TRM elongation and the e_TL elongation are adjusted according to Equation 1 so that one or more target mechanical properties are maintained within the specification window and one or more target surface quality parameters are maintained within the specification window. By using an equation that describes the relationship between e_TRM and e-TL on the one hand and an equation that describes the relationship between e_TRM and surface quality parameters on the other hand, an optimal combination of e_TRM and e-TL can be selected, thereby reducing the manufacturing risk of off-spec products.

[0034] In one embodiment, the e_TRM elongation is adjusted according to Equation 1 such that one or more target mechanical properties are maintained within a specification window and one or more target surface texture parameters are maintained within a specification window. By using an equation that describes the relationship between e_TRM and e-TL on the one hand and an equation that describes the relationship between e_TRM and surface texture parameters on the other hand, an optimal e_TRM can be selected, thereby reducing the manufacturing risk of out-of-spec products.

[0035] In one embodiment, the setpoint optimizer is set such that one or more target mechanical properties and / or one or more target surface texture specifications are at the center of their respective specification windows. To give the control system sufficient operating margin, the target value is preferably at the center of the specification window and not close to one or the other end of the specification. This also reduces the manufacturing risk of out-of-spec products.

[0036] In one embodiment, the models for predicting skin pass rolling force and surface roughness are statistical models based on past process data. The more process data is available, the higher the reliability of these models, the fewer outliers in the process or the likelihood of manufacturing out-of-spec products, and the higher the likelihood of obtaining the desired properties.

[0037] In a preferred embodiment, the method of the present invention is used in a line setup where the skin pass rolling step precedes the tension leveling step, but can equally be used in situations where the skin pass rolling step follows the tension leveling step.

[0038] In a preferred embodiment, the method of the present invention is as follows. a. The skin-pass reduction (e_TRM) is between 0 (excluding 0) and 3.0%, or b. The tension levelling reduction (e_TL) is between 0 (excluding 0) and 3.0%, and e_TL is preferably at least 0.20%, more preferably at least 0.50%, or c. The sum of e_TL and e_TRM (Σ(e_TL + e_TRM)) is between 0.20 and 6.0%, and the tension levelling reduction is at least 0.20%.

[0039] The inventors have found that within the above ranges, the operator and the method of the present invention enable the process to be reproducibly controlled and have sufficient leeway to produce the desired product to the required specifications.

[0040] According to a second aspect, the present invention is also embodied in a computerized process automation for a continuous processing line, and the process automation is embodied to implement the method of the present invention during operation. The method of the present invention controls the TRM and TL processes in an automated manner, controls the process reproducibly, and is optimal for producing the desired product to the required specifications.

[0041] According to a third aspect, the present invention is also embodied in a continuous processing line controlled by the computerized process automation according to the present invention.

[0042] In a continuous processing line controlled by a computerized process automation, which is another aspect, the process automation is embodied to execute the method described in the above embodiments during operation.

Examples

[0043] This example shows how the present invention can be used to keep both Rp 0.2 and Ra within the required specification window by adjusting the set values, and to suppress YPE to keep Rp 0.2To show how the present invention can be used to fit both and Ra within the required specification window. The steelmaking process, annealing process, and skin pass rolling process always involve natural variations. Thus, Rp 0.2 and the target values of Ra are actively adjusted towards the center of the window using the present invention.

[0044] Example 1 is based on the following order information.

[0045]

Table 1

[0046] Examples 1, 2, and 3 relate to IF grades without YPE. In this grade, the values of a and b in Equation 1 are both 1.

[0047] In the generation of the initial setting values, · Line tension setting value · Work roll bending force setting value · Rp 0.2 = 190 ± 2 MPa (based on e_TRM = 1.7% and e_TL = 0.2%) · Rolling force are defined.

[0048] Comparison Case C1 The initial setting values defined in Example 1 are verified using the model (Figure 2), resulting in a predicted roughness Ra = 1.4 μm that exactly matches the upper limit of the Ra window. Considering the natural variations in the process and roughness measurements, the risk of being out of specification is high and undesirable.

[0049] Inventive Case I1 By using the present invention, the adjustment of case C1 is possible. After the set value optimization, the initial set value of the line tension is increased to the maximum (since these limit values depend on the processing line, the specific values are not relevant to this example), and the roughness is reduced to Ra = 1.3. In the second set value optimization step, the initial set value of e_TRM is reduced to 1.4%, and the roughness model predicts Ra = 1.2. At the same time, e_TL is adjusted to 0.5%, and Rp 0.2 = 190 MPa is targeted. By the setting optimization according to the present invention, the predicted Rp 0.2 (Equation 1) and both Ra achieve the target values.

[0050] Example 2 is based on the following order information.

[0051]

Table 2

[0052] In the generation of the initial set values, · Line tension set value · Work roll bending force set value · Rp 0.2 = 175 ± 2 MPa (based on e_TRM = 0.9% and e_TL = 0.4%) · Rolling force is defined.

[0053] Comparison Case C2 The initial set values defined in Example 2 are verified using the model (Figure 2), and although they are within the Ra window, they result in a roughness Ra = 1.05 μm, which does not achieve the Ra target value of 1.2 μm.

[0054] Inventive Case I2 By using the present invention, the adjustment of case C2 is possible. After the setting value optimization, the initial setting value of the line tension is required for a stable rolling process. Therefore, the initial setting values of e_TRM and e_TL are considered. By adjusting e_TRM to 1.2% and e_TL to 0.1%, it is possible to achieve the target Ra = 1.2 μm.

[0055] Example 3 is based on the following order information.

[0056]

Table 3

[0057] In the generation of the initial setting value, · Line tension setting value · Work roll bending force setting value · Rp 0.2 = 180 ± 2 MPa (based on e_TRM = 0.9% and e_TL = 0.6%) · Rolling force are defined.

[0058] Comparison Case C3 The initial setting values defined in Example 3 are verified using the model (Figure 2), resulting in a roughness Ra = 1.05 μm outside the Ra window.

[0059] Inventive Case I3 By using the present invention, it is possible to adjust case C3. After the setpoint optimization, first, the initial setpoint of the line tension is considered. However, since the strip has a defective shape and a high tension is required for a stable rolling process, the initial setpoint of the line tension cannot be decreased. Therefore, the initial setpoints of e_TRM and e_TL are considered. By adjusting e_TRM to 1.6% and e_TL to 0%, it is possible to achieve a target Ra = 1.35 μm, which is close to the target value. However, when rolling the first few meters of the coil with these setpoints, it becomes clear that the shape of the strip is still defective, and the operator adjusts the e_TL elongation to 0.3% to correct the shape problem. Automatically, the verification of the setpoints is Rp 0.2 is Rp 0.2 shown to be 190 MPa (Equation 1) at the boundary of the window. The setpoint optimizer adjusts e_TRM to 1.4%, and as a result, Rp 0.2 = 185 MPa and Ra = 1.26, both of which are within the window.

[0060] Example 4 is based on the following order information.

[0061]

Table 4

[0062] This steel is a HSLA grade showing a high YPE. In this grade, d and e in Equation 2 are d = 1 and e = 1.1.

[0063] In the generation of the initial setpoints, · Line tension setpoint · Work roll bending force setpoint · e_YPE = 1.9% (based on e_TRM = 0.9% and e_TL = 0.9%), and as a result, Rp 0.2 = 352 ± 8 MPa · Rolling force is defined.

[0064] Comparison Case C4 For this steel grade, e_YPE = 1.9% is set, and as a result, Rp 0.2 is slightly higher than the target value, but still Rp 0.2 is within the window, resulting in Rp 0.2 By increasing e_tot so that it exceeds e_YPE = 1.9%, it is preferable not to further increase Rp 0.2 The initial set value is verified using the model (Figs. 4 and 5), and a roughness Ra = 1.3μm is obtained, which is within the Ra window but does not reach the Ra target value of 1.5μm.

[0065] Inventive Case I4 By using the present invention, the adjustment of case C4 is possible. After optimizing the set values, by adjusting e_TRM to 1.6% and e_TL to 0.2%, it is possible to achieve the target Ra = 1.5μm while keeping Rp 0.2 and YPE constant.

[0066] Brief Description of the Drawings Hereinafter, the present invention will be described using the following non-limiting figures.

[0067] The generation of the set values is shown in Fig. 1 and will be described in several steps. 1. Coil: A coil having a certain chemical composition and dimensions (thickness, width, length), cold-rolled, annealed, and optionally coated. 2. Skin-pass rolling: A rolling process that slightly reduces the thickness, forms surface properties on the strip surface, and optionally adjusts the strip shape. The internal control system targets the elongation set value and continuously adjusts the rolling force. 3. Tension leveling: A process that applies bulk strain by stretching and bending. The internal control system targets the elongation set value and continuously adjusts the tension and roll position. 4. Finishing: A process that performs quality inspection, measures the surface roughness, and applies oil. 5. Finished coil: A finished product having the characteristics according to the order.

[0068] Figure 1 shows various steps, their interactions, and feedback to the process and product data control system. Figure 2 shows the roughness (Ra) value according to the elongation (e_TRM) in the temper rolling mill in the case of the IP grade. Figure 3 shows the data used to create Figure 2. Figure 4 shows the relationship between the elongation (e_TRM) in the temper rolling mill and the elongation (e_TL) in the tension leveling, and the presence or absence of the YPE elongation (present: black circles, absent: white circles). Figure 5 shows the roughness (Ra) value according to the elongation (e_TRM) in the temper rolling mill in the case of the HSLA grade, and the presence or absence of the YPE elongation (present: black circles, absent: white circles). Figure 6 shows the data used to create Figure 5.

Claims

1. A method for manufacturing a cold-rolled steel strip, comprising the following steps: The following steps: - A step of preparing a cold-rolled steel strip; - A step of recrystallization annealing the cold-rolled steel strip; - Optionally, a step of providing a metal coating layer on one or both main surfaces of the annealed cold-rolled steel strip; - A step of subjecting the steel strip to a combination of skin pass rolling on a skin pass rolling mill and tension leveling on a tension leveler, wherein the skin pass rolling mill and the tension leveler are controlled by a control system that determines the set values of the skin pass rolling mill and the tension leveler, The control system includes the following steps: a. Define one or more target mechanical or microstructural properties (prop-tar) including at least the yield strength (Rp), and based on at least one aspect of the chemical composition, mechanical properties, or microstructural properties of the incoming steel strip and at least one aspect of the surface properties of the outgoing steel strip, an order section that defines one or more target surface texture specifications (text-tar) of the outgoing steel strip; b. A work roll selection section that selects a work roll for the skin pass rolling mill having a combination of i) the work roll surface texture and ii) the work roll diameter based on a predefined table or model; c. An initial set value generator that generates initial set values based on i) at least one aspect of the prop-tar of the incoming steel strip, ii) at least one aspect of the surface properties of the outgoing steel strip, and iii) the selected work roll, wherein the initial set values are - The line tension in the temper rolling mill (TRM), - The work roll bending force, - The total elongation (e_tot) which is the sum of e_TRM and e_TL, - The elongation (e_TRM) in the TRM and The distribution of elongation across the TRM and TL is defined by Equations 1 and 2: Rp = a * e_TRM + b * e_TL + c (Equation 1) e_YPE = d * e_TRM + e * e_TL (Equation 2) is defined according to, Equation 1 defines the yield strength (Rp) of the manufactured product equal to the target Rp, e_YPE defines the minimum elongation required to suppress the yield point elongation, and the values of the coefficients a to e depend on the steel grade and are determined from past results or from a model; d. A setpoint validator that uses a prediction model to verify whether the initial setpoint achieves one or more target mechanical properties and one or more target surface finish specifications of the outgoing steel strip; e. If the setpoint validator indicates that the initial setpoint does not result in the achievement of one or more target mechanical properties and / or one or more target surface finish specifications, the setpoint optimizer i. e_TRM: Elongation in the TRM ii. e_TL: Elongation in the TL iii. Line tension in the TRM adjusts one or more of the above; f. Executing a combination of skin pass rolling and tension leveling based on the setpoints determined in steps a - e; - Coiling, slitting, or cutting the skin pass rolled and tension leveled steel strip to produce a coiled steel strip, a coiled slit steel strip, or a cut sheet or blank A method comprising. **Claim 2** The method according to claim 1, wherein the value of the actual rolling force measured in the TRM is used as an input to the setpoint validator for the next coil. **Claim 3** The actual surface finish specifications measured after the TRM and TL are used as an input to the setpoint validator for the next coil. The method according to claim 1. **Claim 4** The method according to any one of claims 1 - 3, wherein the adjustment of the line tension in the TRM by the setpoint validator is performed such that the adjusted line tension does not exceed the lower or upper limit. **Claim 5** The method according to any one of claims 1 - 4, wherein the adjustment of e_TRM by the setpoint validator is performed such that the rolling force is adjusted so that at least one target surface finish specification falls within the specification window. **Claim 6** The method according to claim 5, wherein e_TL is adjusted according to Equation 1 so that one or more target mechanical properties are maintained within the specification window. **Claim 7** The method according to any one of claims 1 - 6, wherein the setpoint optimizer is set so that one or more target mechanical properties and / or one or more target surface finish specifications are at the center of their respective specification windows. **Claim 8** The method according to any one of claims 1 - 7, wherein the model for predicting the skin pass rolling force and surface roughness is a statistical model based on past process data. **Claim 9** The method according to any one of claims 1 to 8, wherein the skin pass rolling step precedes the tension leveling step.

10. The method according to any one of claims 1 to 8, wherein the skin pass rolling step follows the tension leveling step.

11. a. The skin pass reduction rate (e_TRM) is between 0 (excluding 0) and 3.0%, or b. The tension leveling reduction rate (e_TL) is between 0 (excluding 0) and 3.0%, preferably at least 0.20%, more preferably at least 0.50%, or c. The sum of the tension leveling reduction rate (e_TL) and the skin pass reduction rate (e_TRM) is between 0.20 and 3.0%, and the tension leveling reduction rate (e_TL) is at least 0.20%. The method according to any one of claims 1 to 10.

12. A computerized process automation for a continuous processing line, wherein the process automation is embodied to execute the method according to any one of claims 1 to 11 during movement.

13. A continuous processing line controlled by the computerized process automation according to claim 12.

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