METHOD FOR OPTIMALLY PRODUCING METAL STEEL AND IRON ALLOYS IN HOT-ROLLED AND THICK PLATE FACTORIES USING A MICROSTRUCTURE SIMULATOR, MONITOR, AND/OR MODEL

Abstract

In a method for controlling a metallurgical production plant by means of a microstructure model, which comprises a program which calculates at least one mechanical strength property of a product being produced, which program calculates the strength property on the basis of calculated metallurgical phase components of the microstructure of the produced product, wherein the metallurgical plant comprises a terminating cooling line, and wherein operating parameters for the metallurgical plant with adjustable output values, which are established at least partially in advance, are factored into the calculation of the mechanical strength property, the object of the method is to enable an advantageous adjustment of operating parameters in order to achieve desired mechanical strength properties in a product consisting of a metal steel and/or iron alloy. This object is achieved in that, as the operating parameters that are factored into the calculation of the strength property, the mass fraction of at least one alloy element that is present in the chemical composition of the metal steel and/or iron alloy being used, and at least one additional operating parameter, preferably a cooling rate which is set as part of a cooling process carried out after a rolling process, are detected, and an increase in the strength property in question of the produced product, said increase being achieved by modifying at least said additional operating parameter, is at least partially compensated for by reducing the mass fraction of one or more of the alloying elements of the metal steel and/or iron alloy being used.

Description

A method for optimizing the production of metal steel and iron alloys in hot rolling and heavy plate mills using a microstructure simulator, monitor and/or model

The invention is directed toward a method for controlling a metallurgical production plant for producing a product from a metal steel or iron alloy, wherein the production process is controlled at least in part by means of a microstructure simulator and/or microstructure monitor and/or microstructure model which comprises a program for calculating at least one mechanical strength property of the product being produced which contains the metal steel and/or iron alloy, said program calculating the at least one mechanical strength property as a function of a respective process chain, based on calculated metallurgical phase components and/or the respective fractions thereof in the resulting metallurgical microstructure of the product that is produced, wherein the process chain of the metallurgical production plant comprises a hot rolling and/or heavy plate rolling mill having a terminating cooling line, and wherein operating parameters for the metallurgical production plant, on which the resulting at least one mechanical strength property is based, along with adjustable output values, at least some of which are established in advance, are factored into the calculation of the at least one mechanical strength property.

In the operation of hot strip and/or heavy plate mills, the reeling temperature or cooling stop temperature and the cooling rate, along with the forming process in the rolling mill, are defined as essential target variables because they significantly influence the mechanical strength properties of the resulting product. Changes to these parameters are therefore necessarily also perceived in changes in the mechanical strength properties, however these changes can be detected only post-production on the basis of tensile tests conducted on tensile samples of the finished product. Adjusting the desired mechanical strength properties to the desired extent in each case is one of the main goals in a rolling process, since these properties have a significant determining influence on the market price that can be obtained for the finished product. In the production of a product from a metal steel and/or iron alloy in a metallurgical plant, the mechanical strength properties of the product are impacted by additional (operating) parameters, such as the rolling speed and the final rolling temperature, for example. Thus a constant reeling temperature will not necessarily guarantee constant mechanical strength properties of the desired type in each case. The temperatures of the finished product can be measured directly online immediately after rolling or upstream of the coiler, for example using pyrometers or other temperature gauging instruments, and can thus be used directly for regulating purposes. However, mechanical strength properties are typically measured by means of tensile tests after production with a significant time delay, and therefore cannot be used directly for regulating the respective metallurgical process. Thus presetting the process or method parameters of a metalworking train in a rolling mill and in the cooling line downstream will not necessarily result in compliance with target values for the desired mechanical (strength) properties. Moreover, these cannot be measured directly and immediately, hence a prompt correction of the process or method parameters or the operating parameters of the metallurgical plant is not possible.

To address this problem, models and even microstructure models have been developed in the prior art, which allow obtained mechanical strength values to be calculated online, enabling the operating parameters of the metallurgical plant to be influenced immediately.

For instance, DE 198 81 711 B4 discloses a generic process for controlling a metallurgical plant for producing steel or aluminum, in particular a rolling mill. In this case, steel or aluminum having certain material properties that are dependent on the microstructure of the steel or the aluminum are produced in the metallurgical plant from input materials, and the material properties of the steel or aluminum are dependent on the operating parameters with which the metallurgical plant is run. Here, the operating parameters are determined by means of a microstructure optimizer as a function of the desired material properties of the steel or the aluminum, the possible material properties including the yield strength, proof stress, tensile strength, elongation at fracture, hardness, transition temperature, anisotropy and consolidation index of the steel or aluminum.

DE 10 2007 007560 A1 discloses a method for assisting the at least partially manual control of a metalworking line in which material in the form of strips or slabs, or pre-profiled material is processed. In this case, the proportion of at least one metallurgical phase of the metal is determined continuously with respect to a specific location on the metal processing line, taking into account operating parameters of the metal processing line that impact the phase state and/or taking into account state parameters of the metal, by calculation, on the basis of a model which includes a model for determining the phase state; the proportion of the at least one phase, with respect to a specific location on the metal processing line, is then displayed to an operator. For example, the proportions of ferrite, austenite, pearlite and cementite are displayed.

WO 2005/099923 A1 discloses the use of a conversion model for the cooling line of a rolling mill during the production of steel to calculate the metallurgical phase fractions of the steel, in addition to its temperature, along the steel strip in real time. Described is a regulating system which holds the phase fractions of the steel strip being wound onto a coiling device at a constant level. The process comprises the following steps: In a first step, the degree of conversion, and thus a certain phase fraction, is determined from data. In a second step, when the strip enters the cooling line of the rolling mill, one or more parameters of the cooling strategy (control variables) are adapted online by way of a regulation step in such a way that the desired phase fraction of the cooled steel on the coiling device is maintained at a constant level. The goal is to comply as precisely as possible with the requisite properties or material properties of the metal that is produced.

By directly calculating mechanical properties using a suitable model, the process parameters that are required for this purpose can be defined with the greatest possible accuracy. In the case of steel, it is essentially the phase components of austenite, ferrite, pearlite, bainite and martensite that are decisive for the resulting mechanical strength properties.

Alloying elements are added to steel materials in order to obtain optimum mechanical strength properties in a product produced from these materials under the given process and method conditions. The amount of alloying elements to be added to each steel material is dependent primarily on the mechanical strength properties that are desired for a specific application. Alloying elements are very expensive, and as a result, efforts have been made to reduce or optimize the costs of alloys. Since it is not yet possible to make precise predictions as to the result to be achieved in terms of mechanical strength values of a steel product by adding alloying elements, experimental testing must be used to determine the impact a specific quantity of a specific alloying element will have on the mechanical properties or mechanical strength properties of a respective steel product.

WO 98/18970 A1 discloses a method for monitoring and controlling the quality of rolled products from hot rolling processes, in which production conditions such as temperatures, pass reductions, etc. are detected online throughout the entire rolling process, and from these, by means of interrelated physical/metallurgical and/or statistical models that describe the entire rolling process, the mechanical/technological material properties to be expected in the rolled product, in particular the yield strength, the tensile strength, and the elongation at fracture, are calculated in advance. The online detection of actual and current production conditions enables the prediction of anticipated material properties in this method. In this case, the chemical analysis of each primary material, among other things, is identified, and is provided to a physical/metallurgical austenitization and precipitation model. In addition, any changes to the time/temperature curve for heating, the time/temperature deformation curve during rolling, and the time/temperature curve during cooling that are necessary in order to comply with the requisite mechanical/technological material properties are calculated and are transmitted to the control systems for the heating, rolling and cooling systems. Adherence to the required mechanical/technological material properties of the rolling process is thereby ensured. With the method known from this document, the chemical target-state analysis of the starting material and the production conditions are optimized by applying physical/metallurgical austenitization, deformation, recrystallization, conversion, precipitation, cooling and material models, and are defined for related new product qualities. In this method, for example, the carbon content or the manganese content of the material being used are factored into the calculation of a strength property, therefore this model also shows the impact of alloying elements on a mechanical strength property of the resulting product.

The object of the invention is to provide a solution that will enable an advantageous adjustment of operating parameters, as compared with the previous approach, in order to achieve desired mechanical strength properties in a product made of a metal steel and/or iron alloy and desired metallurgical phase fractions in the product being produced in a rolling mill.

This object is achieved according to the invention in a method of the aforementioned type, in that, as the operating parameters of the metallurgical production plant that are factored into the calculation of the at least one strength property, the mass fraction of at least one alloy element, preferably of all alloy elements, that is/are present in the chemical composition of the metal steel and/or iron alloy being used, and at least one additional operating parameter, in particular a cooling rate which impacts the product during the production thereof, preferably a cooling rate which is adjusted as part of a cooling process carried out after a rolling process, are detected, and an increase in the strength property in question, said increase being achieved by a change in at least said additional operating parameter, in particular by increasing the cooling rate, is at least partly compensated and/or offset by reducing the mass fraction of one or more of the alloying elements in the chemical composition of the metal steel and/or iron alloy being used.

With the invention, it is therefore possible to optimize the use of alloying agent(s) such that only the mass fractions of alloying agent(s) that are absolutely essential in each case for at least achieving the strength property in question with the achievable cooling rates or with any other of the additional operating parameters are present in the chemical composition of the respective steel and/or iron alloy. The strength property in question to be achieved in the finished product is thus defined, specified and regulated, for example, by means of the potential or adjusted cooling rate, whereas the chemical composition is adjusted as a function of this.

Thus according to the invention, the impact and the contribution of each of the alloying elements on the mechanical strength properties of the product being produced, based on the mixed crystal precipitation hardening induced or influenced by these elements, are factored into the calculation of the mechanical strength properties or the at least one mechanical strength property. The method according to the invention allows the impact of alloying elements on mechanical strength properties to be precisely determined. If, for example, a certain amount of manganese is added, this change will be calculated immediately by the program provided in the microstructure simulator and/or microstructure model, so that the impact of this change on the mechanical strength properties or on at least one mechanical strength property of the product being produced can be ascertained.

With this knowledge, an operator can modernize the cooling line of a rolling mill, for example, in order to increase the cooling rate. This higher cooling rate has an impact on mechanical strength properties, and may be used selectively to modify mechanical strength properties. The microstructure simulator and/or microstructure monitor and/or the microstructure model with the program provided therein supplies the information necessary for this. The program factors in the higher cooling rate, and calculates the resulting change in strength properties. Thus different mechanical strength properties can be obtained with the same chemical analysis or composition of the alloy being used and a higher cooling rate, or the same mechanical strength properties can be achieved with fewer alloying elements, that is to say, with a lower mass fraction or weight percentage (percentage by weight) of alloying elements, resulting in a cost savings. These costs may be quantified using the program provided in the microstructure simulator and/or microstructure monitor and/or microstructure model, which calculates the at least one mechanical strength property of the product being produced as a function of the respective process chain of a rolling mill, on the basis of calculated metallurgical phase components and/or the respective fractions thereof in the resulting metallurgical microstructure of the finished product.

It is further possible to calculate the impact of modified process parameters using the provided program. If, for example, the temperature of the rolling mill train or finishing train is increased while the coiling temperature is decreased, the provided program will calculate the necessary changes to the process or operating parameters, and will accordingly calculate the mechanical strength properties that will result from these changes. The microstructure simulator and/or microstructure monitor and/or microstructure model and the program provided therein provide the operator with a new tool for material development through the optimal adjustment of the process, method and/or operating parameters of the process chain of the metallurgical plant, which comprises the rolling mill with a cooling line, and for obtaining a desired mechanical strength property of the material.

In its embodiment, the invention provides that the mass fraction of alloying element(s) detected in each case and/or the at least one additional operating parameter detected in each case, in particular the cooling rate detected in each case, is assigned a countable numerical value of a valuation unit that represents a valuation standard. This enables a cost value to be assigned to both the impact to be attributed to the change in the alloy composition and the impact, caused by a change in the additional operating parameter, in particular the cooling rate, on the change in the mechanical strength property in question of the finished product.

To be able to perform a directly valued comparison of different combinations of changes to the chemical composition of the steel and/or iron alloy material being used and changes to the cooling rates, the invention also provides in a further embodiment that the program calculates and displays the total values of each of the countable valuation units that are obtained for the strength property in question with different combinations of a mass fraction of alloying agent(s), valued with a number of countable valuation units, and an additional operating parameter, in particular a cooling rate, valued using a number of countable valuation units.

To enable the comparative valuation to be performed, it is expedient for the program to comprise a mathematical term and/or algorithm with which the respective number of valuation units and/or the various calculated total values are compared.

The method according to the invention therefore also comprises a valuation of the impact of the alloy composition and the cooling rate with respect to the desired mechanical strength property/properties to be achieved in each case. The valuation is carried out using valuation units that represent a valuation standard, with which values are assigned to the alloy composition and the cooling rates. The valuation units can be technically quantitative, such as Δ strength increase/Δ percentage by mass of the total of alloying elements over Δ strength increase/Δ volume of cooling water. However, costs, that is to say monetary values, may also be assigned (additionally) to these valuation units, as is clear from FIG. 1. In said figure, the additional monetary outlays (EUR 40.00 to EUR 215.00) that are required in each case for the change in yield strength to higher-strength steel grades (of S315MC to S650MC) are plotted. This allows various different combinations of alloy compositions and cooling rates to then be compared with one another based on the valuation units assigned to each of these. The total values of countable valuation units expressed in each case as comparison values can then be used to select a particularly (cost) favorable or suitable combination of an alloy composition and a cooling rate for use in implementing the production process. A valuation unit that represents a valuation standard may be a currency unit, for example, or a valuation unit assigned to the valuation unit. In that case, it is possible to assign a cost value to each of the various cooling rates and the various alloy compositions individually, but also in total. Thus with the method according to the invention, the impact of alloying costs can be compared with the costs for achieving a specific desired mechanical strength property, which are obtained from the costs for achieving a particular cooling rate. With the method according to the invention, it is therefore possible to quantify the alloying costs that are required to adjust the specific desired mechanical property. The costs for implementing the cooling rate that is necessary to adjust the desired mechanical strength property are likewise quantifiable. Since a higher cooling rate and the alloying elements in the steel or iron alloy both significantly impact the mechanical properties of the product that is obtained, the costs of an alloy change with respect to a change in the mechanical strength properties can be quantified precisely using the method according to the invention. Thus when an existing cooling line is retrofitted with a higher, adjustable cooling rate, for example, the values for the desired mechanical strength property may also increase. This increase can be used to reduce individual alloying elements in the alloy composition of the steel and/or iron material being used, whereby a cost savings for the overall process is achieved due to the use of a reduced quantity of one or more alloying elements. With the method according to the invention, such an estimation and valuation is possible.

This estimation and valuation can be carried out with the invention by means of the microstructure model and/or microstructure monitor and/or microstructure simulator. More specifically, the impact of the respective parameters can then also be quantified in monetary terms, according to the invention, by using the valuation units that represent a valuation standard, as long as such economic or monetary dependencies are stored in the microstructure model and/or microstructure monitor and/or microstructure simulator, as shown in FIG. 1. As is clear from FIG. 1, an increase in yield strength by about 100 MPa will increase costs by approximately 30.00 EUR. For example, increasing the yield strength from steel S420MC to steel S500MC will increase costs from 65.00 EUR to 85.00 EUR, for a difference of 20.00 EUR. This average cost increase of EUR 30.00 and in the aforementioned example EUR 20.00 must take the form of an addition of alloying elements or an increase in the cooling rate of the respective steel strip during its production in a rolling mill, with the higher cooling rate resulting in a smaller ferrite grain size, resulting in an increase in the strength property “yield strength”. This relationship is stored in the microstructure model of the invention and can therefore also be quantitatively distinguished in the form of the correspondingly formulated and valued countable valuation units.

Thus if the operator of a metallurgical production plant is able to achieve a higher cooling rate during the cooling of the product being produced, which is essential and is carried out after the rolling process, for example, by retrofitting the cooling line to increase cooling capacities, for example, he can also thereby achieve an increase in strength, i.e. an increase in the mechanical strength property in question. The effect of increased strength achieved by this increased cooling rate can then be used to achieve an opposite effect by modifying the chemical composition of the steel and/or iron alloy being used. With the method according to the invention and the program that is applied therein, it is possible to calculate the impact of a modified chemical composition of an alloy being used that contains reduced mass fractions of alloying elements on the mechanical strength property in question to be obtained in the resulting product. This calculation is then repeated until the increase in strength induced by the increased cooling rate is reduced to “0”, and therefore the increase in strength or the increase in the value of the mechanical strength property caused by the increased cooling rate has been exhausted and the mechanical strength property has returned to its original value. The cost savings realized by the savings on alloying elements then offsets the cost increase that results from the higher cooling rate. With a typical Nb alloyed fine grained construction steel containing approximately 0.07% C, 0.7% Mn, 0.2% Si, 0.04% Nb, 0.084% Ni, 0.034% Mo, 0.084% Cr, 0.0084% V and 0.0084% Ti, a savings of approximately 4% of alloying costs, which typically amount to 30.00 EUR/t, can be realized in this manner through reduced alloy contents, reducing alloying costs in this example to 28.80 EUR/t. In the operation of a metallurgical production plant with an annual production output of 1 million tons, this results in a per year savings of approximately 1.20 million EUR in alloying costs for a fine grained construction steel of this type.

The method according to the invention can be used to calculate for each material the potential savings that may be realized by reducing the quantity of alloying elements used. Materials with high alloy fractions offer a high savings potential, while materials with lower alloy fractions offer a correspondingly lower savings potential. The method according to the invention or the program provided therein can be used to calculate the potential savings for the entire yearly production output of a metallurgical production plant, as long as the alloying costs for the specific material in question, i.e. the steel and/or iron alloy in question, are known.

To factor in the impact of alloying elements on yield strength as a mechanical strength property of the resulting product, the invention is further characterized in that the program comprises a mathematical term and/or algorithm for expressing the impact of mass fractions of alloying elements in the chemical composition of the metal steel and/or iron alloy being used on the yield strength of the product being produced.

In a particularly advantageous embodiment of the invention, it is provided that the term comprises the equation

ΔYS=ΣA_iC_i^Bi.

In this equation, C_i is the fraction of each of the different alloying elements, each in percent by weight, A_i and B_i are corresponding regression coefficients, which are defined in advance through experimental testing, and YS is yield strength (Yield Strength) the change (Δ) in which is calculated. The regression coefficients are calculated based on series of tests, in which the impact of carbon (C), silicon (Si), manganese (Mn), chromium (Cr), molybdenum (Mo), nickel (Ni), vanadium (V), nitrogen (N), copper (Cu), aluminum (Al), niobium (Nb), titanium (Ti) and phosphorus (P) as alloying elements in a steel and/or iron alloy are/were taken into account, and in which the measurement data from the experiments to determine the regression parameters are/were available or are known.

It is further advantageous for the grain size that will ultimately be obtained in the finished product after retrofitting to also be calculated using the program provided in the microstructure simulator and/or microstructure monitor and/or microstructure model, since according to the Hall-Petch equation, grain size impacts mechanical strength properties. The invention therefore further provides in its embodiment that the program comprises a term in the form of the equation

$\Delta \mathrm{YS}=A\frac{1}{\sqrt{d}}$

which expresses the impact of the ferrite grain size (d) of the ferrite microstructure that forms during a final cooling of the product on yield strength. In addition to calculating the phase components and the impact of alloying elements, it is also important to calculate the grain size of the converted metal. The ferrite grain size has a significant impact on the resulting mechanical strength properties, since according to the Hall-Petch equation, an increase ΔYS in the strength property “yield strength” is to be expected with a decrease in grain size. In the equation, d is the ferrite grain size, A is a regression parameter and YS is the yield strength, the change (Δ) in which is calculated.

Since the ferrite grain size that forms is dependent on the cooling rate in each case, the invention further provides that the program comprises a term in the form of the equation d_a=(A₁−A₂·C_eq^A2)·d_y^0.3−ε0.5·CR^−0.15, which expresses the impact of the cooling rate on the ferrite grain size (d_a) of the ferrite microstructure that forms during the final cooling of the product. In this equation, d_a: is the ferrite grain size, A_i: is the empirical coefficient, C_eq is the carbon equivalent, d_Y: is the austenite grain size, ε: is the residual strength and CR: is the cooling rate. From this, it is clear that a higher cooling rate leads to a smaller ferrite grain. In production, the goal is usually to produce a material with the highest possible strength and the smallest possible ferrite grain. Ferrite grain size is impacted significantly by the cooling rate or speed of cooling, which can be adjusted, dependent upon available cooling capacity, in the cooling line—which is typically located at the end of the rolling mill train and thus at the end of the rolling process of the product being produced.

Since mechanical strength properties usually cannot be measured soon after production, according to the invention a model is used, which comprises a microstructure simulator and/or microstructure monitor and/or microstructure model, which has a program for calculating at least one mechanical strength property of the produced product containing the metal steel and/or iron alloy, which program calculates the at least one mechanical strength property dependent upon the respective process chain of the metallurgical plant, on the basis of calculated metallurgical phase components and/or the respective fractions thereof in the resulting metallurgical microstructure of the product being produced. One such model is the MPC (Mechanical Property Calculator) program, which determines the mechanical properties as a function of the process conditions throughout the entire process chain consisting of furnace, rolling mill train and cooling line. This program enables the adjustment of target values for the reeling temperature and the cooling rate. The model is also suitable for use in regulating the trim water zone. Yield strength and/or tensile strength after cooling may be used as control variables. In defining these set values, the model calculates the process parameters that are required for this purpose. The results are immediately visible and are updated with each new cyclic calculation. The core of the MPC program is the calculation of the mechanical strength properties of the material that is produced after cooling. Calculation is based on semi-empirical equations. The calculation is performed for various volume elements of the strip or sheet. The strip or sheet is therefore divided into small elements. During the calculation, the process variables such as rolling speed and rolling temperature are taken into account. In the event of a change, these are factored immediately into the new calculation. The result is a distribution of mechanical (strength) properties within the strip or sheet.

The basis for the calculation of mechanical (strength) properties is the calculation of the phase components of the material being produced. To accomplish this, it is first necessary to calculate the precise cooling progression for the metal, and based on this cooling progression, which is itself impacted by the metallurgical microstructure conversion, to model the decomposition of the austenite into the constituents ferrite, pearlite, bainite, and martensite. When this model is used for calculating mechanical (strength) properties, a comparison with measured values must be conducted in order to ensure an accurate prediction of the mechanical (strength) properties. Values calculated using the model were therefore compared with values obtained from tensile tests, from which it was determined that an excellent correlation exists between the calculated and measured values with low scattering of the measured values. This correlation exists with different types of systems (hot strip mill, heavy plate mill and continuous casting system, in particular a CSP system).

The calculations in the MPC model enable a currently existing production or process situation to be analyzed and optimized. Thus the costs of alloying elements can be reduced by improving the alloying concept, since a cost-benefit ratio can be calculated. The invention is therefore also characterized in a further enhancement in that, by means of the program, the operating parameters can be optimized, at least with respect to the at least one mechanical strength property to be achieved. With the method according to the invention, the strength properties of a product to be produced with a given chemical composition can be calculated. If the operating parameters, such as the load distribution in the finishing train (rolling), the final rolling temperature, the cooling strategy or the reeling temperature, are changed, the resulting mechanical strength properties will change. The program that is used to implement the method according to the invention optimizes the operating parameters that are or will be set, and thus determines the optimal strength properties.

In addition, the consequences of improved plant technology, for example an increased maximum rolling force or an increased maximum cooling rate or the like, may also be taken into account These improved production conditions enable improved (strength) properties of the material and/or reduced production costs to be achieved. It is thus possible to implement a material development by optimally adjusting the process parameters in the rolling mill and in the cooling line with respect to the requirements in a given case.

The operating parameters in individual processing steps of the process chain in the steel plant, rolling mill and cooling line can be optimized with respect to each desired mechanical strength property with the program used in the method according to the invention, in that the individual microstructural changes in the individual processing steps are calculated, and from this, a microstructure with optimized properties is iteratively determined. Conventional processes can thereby be optimized, or the development and production of new materials can be accelerated. This allows considerable cost savings in terms of materials development to be realized.

In addition, due to the large converter vessels, input material or slabs are frequently produced, which in some cases must be stored (intermediately) due to small order quantities or small batches. This results in high inventory levels with corresponding warehousing costs. The method according to the invention enables slabs having the same analysis, i.e. the same chemical composition, but different production parameters to be processed and adjusted to different strength properties based on the different production and/or operating parameters. This can be accomplished by applying a corresponding iteration process, by means of which potentially achievable mechanical strength properties are or can be calculated by means of the program that is applied in the method according to the invention. This allows inventory levels to be reduced and warehousing costs diminished, enabling efficiency to be increased.

The invention further enables online visualization of the mechanical (strength) properties being adjusted at any given time in that, in a further enhancement, the at least one mechanical strength property being calculated in each case is displayed online at a control station. This enables manual intervention based on information and status messages, and leads to lower production losses.

Additionally, however, an automatic control of target strength properties may also be used. Such automatic control enables real-time reaction to malfunctions and optimization of the continued production process so that the desired at least one mechanical strength property is achieved. This is accomplished by an automatic correction of the at least one or more process parameters in the rolling mill and the cooling line. A homogeneous distribution of the property over the entire length of the strip or sheet is thereby ensured. Thus the invention is also further characterized in that the calculated at least one mechanical strength property is used to control the operating parameters of the metallurgical plant and to automatically select the desired at least one mechanical strength property. If predefined target operating parameters (for example, the specified final rolling temperature) cannot be complied with, for example due to an operating malfunction, it may no longer be possible to achieve the stipulated mechanical strength property/properties. In such a case, in the method according to the invention, the program will perform a calculation using the current measured values/data, and will modify the remaining operating parameters (e.g., the cooling strategy and the reeling temperature) such that the desired mechanical target strength properties will still be achieved (if at all possible). The mechanical strength property/properties is/are thus controlled automatically.

The invention may be used or applied in a rolling mill, for example, a hot strip and heavy plate rolling mill, in the production of metal strips and sheets of steel and iron alloys, and at any point in a production process in which steel- or iron-containing materials are cooled, in particular a hot strip and heavy plate mill, with the respectively associated units. A metallurgical plant for implementing the method according to the invention preferably comprises a hot rolling and/or heavy plate mill, in which, downstream of a furnace, shaping is carried out in any number of stands, which may also be subdivided into one or more roughing stands and one or more finishing stands, and wherein the shaped material is then cooled in a cooling line to a reeling temperature and/or cooling stop temperature. The invention is therefore further characterized in that the metallurgical production plant has a process chain which comprises a furnace, a rolling mill, in particular the hot rolling and/or heavy plate rolling mill, and a cooling line, and in that operating parameters for the entire process chain of said metallurgical plant are factored into the program.

It is also possible, however, for the metallurgical production plant to comprise a steel mill and/or a continuous casting system, which is/are likewise included in the microstructure simulator and/or microstructure monitor and/or microstructure model, which then functions as a level 3 tool. Finally therefore, the invention also provides that the metallurgical plant comprises a zone, in particular a steel mill and/or a continuous casting system, in which the metal steel and/or iron alloy is in molten form, and in that operating parameters for the entire process chain of the metallurgical production system that comprises this zone are factored into the program.

Overall, the invention offers the following advantages:

• optimization of alloying costs due to an improved alloying concept
• material development through optimal adjustment of the process parameters
• real-time visualization of the mechanical properties and display of information messages
• fully automated real-time control of the or at least one mechanical strength property/properties
• use of the microstructure simulator and/or microstructure monitor and/or microstructure model enables operating costs to be lowered and the benefit of investment costs to be quantitatively assessed.

Claims

1-4. (canceled)

5. The method according to claim 14, characterized in that the program comprises a mathematical term and/or algorithm for expressing the impact of mass fractions of alloying elements in the chemical composition of the metal steel and/or iron alloy being used on the yield strength of the finished product.

6. The method according to claim 5, characterized in that the term has the equation

ΔYS=ΣAiCiBi.

7. The method according to claim 14, characterized in that the program comprises a term in the form of the equation d which expresses the impact of the ferrite grain size (d) of the ferrite microstructure that forms during a final cooling of the product on yield strength Δ   YS = A  1 d.

8. The method according to claim 14, characterized in that the program comprises a term in the form of the equation which expresses the impact of the cooling rate on the ferrite grain size (da) of the ferrite microstructure that forms during a final cooling of the product da=(A1−A2·CeqA2)·dy0.3−ε0.5·CR−0.15.

9. The method according to claim 14, characterized in that the program is used to optimize the operating parameters, at least with respect to the at least one mechanical strength property to be achieved.

10. The method according to claim 14, characterized in that the at least one mechanical strength property which is calculated in each case is displayed online at a control station for the metallurgical production plant.

11. The method according to claim 14, characterized in that the calculated at least one mechanical strength property is used to control the operating parameters of the metallurgical production plant, and to automatically select the desired at least one mechanical strength property.

12. The method according to claim 14, characterized in that the metallurgical production plant has a process chain which comprises a furnace, a rolling mill, in particular the hot rolling and/or heavy plate mill, and a cooling line, and in that operating parameters for the entire process chain of said metallurgical production plant are factored into the program.

13. The method according to claim 14, characterized in that the metallurgical production plant comprises a zone, in particular a steel mill and/or a continuous casting line, in which the metal steel and/or iron alloy is in molten form, and in that operating parameters for the entire process chain of the metallurgical production plant that comprises this zone are factored into the program.

14. A method for controlling a metallurgical production plant for producing a product from a metal steel and/or iron alloy, wherein the production process is controlled at least in part by means of a microstructure simulator and/or microstructure monitor and/or microstructure model, which comprises a program which calculates at least one mechanical strength property of the produced product containing the metal steel and/or iron alloy, and which calculates the at least one mechanical strength property dependent on a relevant process chain on the basis of calculated metallurgical phase components and/or the proportions of each of these phase components in the resulting metallurgical microstructure of the produced product, wherein the process chain of the metallurgical production plant comprises a hot rolling and/or heavy plate rolling plant having a terminating cooling line, and wherein operating parameters for the metallurgical production plant, on which the resulting at least one mechanical strength property depends, along with adjustable output values, at least some of which are defined in advance, are factored into the calculation of the at least one mechanical strength property,

characterized in that

as the operating parameters of the metallurgical production plant that are factored into the calculation of the at least one strength property, the mass fraction of at least one alloy element, preferably all alloy elements, that is/are present in the chemical composition of the metal steel and/or iron alloy being used, and as an additional operating parameter, a cooling rate which is adjusted as part of a cooling process carried out after a rolling process, is detected, and an increase in the strength property in question of the finished product, said increase being achieved by changing said at least additional operating parameter, in particular by increasing the cooling rate, is at least partly compensated and/or offset by reducing the mass fraction of one or more of the alloying elements in the chemical composition of the metal steel and/or iron alloy being used,

wherein the mass fraction of each alloying element(s) detected in each case, and the cooling rate detected in each case, are assigned a countable numerical value using a valuation unit that represents a valuation standard, and the program calculates and/or displays the total values of each of the countable valuation units that are obtained for each strength property in question with different combinations of a mass fraction of alloying agent(s), valued as a number of countable valuation units, and a cooling rate valued as a number of countable valuation units, and

wherein the program comprises a mathematical term and/or algorithm by means of which the respective number of valuation units and/or the various calculated total values are compared.