EP1732716A1

EP1732716A1 - Method for producing a metal

Info

Publication number: EP1732716A1
Application number: EP04725880A
Authority: EP
Inventors: Klaus Weinzierl
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2004-04-06
Filing date: 2004-04-06
Publication date: 2006-12-20
Anticipated expiration: 2024-04-06
Also published as: EP1732716B1; DE502004005051D1; ES2291867T3; US7853348B2; DE112004002902A5; CN101056721A; WO2005099923A1; US20070198122A1; CN101056721B; JP2007531629A

Abstract

During the production of steel, a conversion model (10) is used for the cooling line (5). Said model is used to calculate the phase fractions (Pi), in addition to the temperature (T) of the steel, along the steel strip in real time. A regulating system, which maintains the phase fractions (Pi) of a steel strip that is wound onto a reeling device (12) at a constant level, is implemented. The method comprises the following steps: in a first step, the degree of conversion, for multi-phase steel e.g. the ferrite fraction, is determined from data obtained from the primary data (P) of the steel strip. In a second step, when the strip enters the cooling line (5), one or more parameters of the cooling strategy, i.e. control values (S), are adapted online in such a way that the ferrite content of the cooled steel on the reeling device (12) is maintained at a constant level.

Description

description

Method of making a metal

The invention relates to a method for producing a metal, wherein the thermoformed metal is cooled in a cooling section, the temperature and at least one phase component of the metal in at least one in a first step with the aid of primary data for the metal by means of a cooling section model Location of the cooling section 3oerech.net. Furthermore, the invention relates to a computing device for the corresponding control and modeling of a cooling section, as well as a corresponding system for producing a metal and a correspondingly manufactured metal.

DE 101 29 565 AI discloses a cooling method for a hot-rolled rolling stock, in particular a metal strip. In this known method, an initial temperature is recorded in front of the cooling section for a rolling stock point, a coolant quantity curve f is determined on the basis of a cooling section model and predetermined target properties of the rolling stock, a coolant is applied to the rolling stock point in accordance with the determined coolant quantity curve over time, on the basis of the cooling section model and of the coolant over time, an expected temperature change over time

Rolled goods are determined at the rolling stock point over the cross section of the rolling stock and a heat conduction equation is solved in the cooling section model to determine the temperature profile in the rolling stock, which correlates the enthalpy, the thermal conductivity, the phase conversion degree, the density and the temperature of the rolling stock. In the method described in DE 101 29 565 AI are expected of the metal strip compared with the target temperature curves. On the basis of this comparison, a new coolant quantity curve is then calculated. Warm-formed metals produced and cooled in accordance with known processes often do not meet the properties or material properties required for their later use, or do so with insufficient reliability.

It is an object of the invention to enable the production of metal with high-quality material properties, the required properties or material properties of the metal being observed as precisely as possible.

This object is achieved by a method of the type mentioned in the introduction, in which in a second step at least one. Measured value is recorded during the production of the metal and, with the aid of the at least one measured value, at least one phase component of the metal to be expected is calculated at the at least one point of the cooling segment by means of the cooling path model, the phase component to be expected in the second step being calculated with that calculated in the first step Phase component is compared and this comparison is used to adapt at least one manipulated variable of the cooling section.

In this way, even with fluctuating production conditions in the manufacture of the metal, the phase components at the end of the cooling section can be kept largely constant over the metal. By adapting at least one manipulated variable of the cooling section, deviations between different belts with the same primary data are largely eliminated. In the first step, the at least one phase component is calculated in such a way that the system fluctuations are not included in the calculation, ie a degree of reference conversion is determined. In the second step, this reference degree of conversion is regulated, the actual fluctuations in the system being largely compensated for by adapting local control variables of the cooling section. According to the invention, in the manufacture of tall a constant quality can be ensured much better than with known methods.

In order to further improve the accuracy of the method according to the invention and to keep the phase components at the end of the cooling section even more reliably constant, it is expedient for the at least one point at which at least one phase component of the metal is located in the first or in the second step of the method is calculated, located at the end of the cooling section.

Alternatively, the expected phase component calculated in the second step is advantageously compared in the second step with a predetermined phase component. In this case, it is no longer necessary to compare the expected phase component calculated in the second step with the phase component calculated in the first step. In this way, direct specifications, for example by an operator, are taken into account when setting the phase component.

The second step is advantageous online, i.e. executed iteratively in real time during the manufacture of the metal. By repeating the second step, i.e. Repeated measurement acquisition, calculation, comparison and, if necessary, adjustment, the accuracy of the method is further improved.

In the second step, at least one manipulated variable of the cooling section is advantageously adapted in accordance with the comparison by a cooling section controller. The cooling section controller directly adjusts the manipulated variables of the cooling section based on the comparison of the phase components in accordance with the calculations from the first or second step. This ensures high control accuracy.

Alternatively, a cascaded control structure is provided, in which case the cooling section controller is provided with setpoints by a superimposed phase component controller. In the second step, the phase proportion controller fits at least one setpoint for the cooling section controller and the cooling section controller adjusts at least one manipulated variable of the cooling section, taking into account set values that are predetermined for it.

A temperature model is advantageously used in at least one of the two steps, which calculates the temperature profile of the metal in the cooling section. With regard to the temperature of the metal, a particularly high control accuracy is achieved.

The temperature model is advantageously adapted with the aid of the at least one measured value. In this way, fluctuations in the production of the metal can be compensated for more effectively.

In order to improve the control accuracy with regard to the phase components, a conversion model is preferably used which calculates the course of the at least one phase component in the cooling section.

A multi-phase steel is advantageously produced. Especially with multi-phase steels, e.g. Dual phase steels or trip steels, keeping the phase components constant and thus the degree of conversion in the cooling section is particularly critical and important. These steels have particularly good material properties, for example for the automotive industry.

The metal in the cooling section is advantageously cooled in at least two cooling sections. In this way, desired phase fractions, in particular in the case of multi-phase steels, can be set in a targeted manner.

A holding time is preferably adjusted.

A holding temperature is advantageously adjusted. When cooling in several cooling sections, sizes such as holding Time and holding temperature are particularly critical for the phase components in metal.

At least one manipulated variable for coolant actuators is advantageously adapted. Coolant actuators are local actuators of the cooling section and therefore, for example, have no effect on a finishing train upstream of the cooling section. The finishing train is not undesirably influenced by the adjustment of the manipulated variables for the coolant actuators.

In the production of heavy plate, at least one manipulated variable is advantageously adapted for the speed of the metal in the cooling section. In the production of heavy plate, the speed of the metal in the cooling section can be influenced as far as possible regardless of the speed at which the metal passes through parts of the system upstream of the cooling section.

In the production of heavy plate, at least one manipulated variable is advantageously adapted for a metal lay time. In the production of heavy plate, the metal's idle time is another local control variable for setting the phase proportions of the metal.

The object on which the invention is based is also achieved by a computing device according to claim 16 or 17.

The invention is also achieved by a system for producing a metal with a cooling section and with such a computing device, the computing device for controlling and modeling the cooling section being coupled to signal transmitters and actuators of the Kuril section via suitably designed interfaces. The invention is also achieved by a metal according to claim 19. The result is particularly uniform material properties in the metal.

The advantages with regard to the computing device, the system and the metal result analogously to the advantages of the method.

Further advantages and details emerge from the following description of exemplary embodiments in conjunction with the drawings. In principle, the following show:

1 shows a cooling section,

2 shows a temperature profile

3 shows a simple control system for the cooling section, and

4 shows a cascaded control system for the cooling section.

1 shows a cooling section 5 and a computing device 3 for controlling or regulating and modeling the cooling section 5. In the example shown, a thermoformed metal 1 runs out of a roll stand 4 at a speed v in the strip running direction x. The roll stand 4 is, for example, the last roll stand of a so-called finishing train. Another cooling or processing device for the metal 1 can also be arranged upstream of the cooling section 5. The cooling section 5 and any one or more devices upstream of it for shaping or processing the metal 1 and any devices downstream of the cooling section 5 form a system for producing a metal 1. In the example shown, the cooling section 5 is followed by a reel device 12 with the help of which the cooled metal 1 is coiled into a coil. However, the cooling section 5 can also be used for other devices not shown in the drawing Processing and / or storage of the metal 1 may be subordinate.

The metal 1 is steel in the solid state in the present case. However, it could also have an at least partially liquid state of matter. According to Figure 1, the metal 1 is designed as a metal strip or slab. But there are also other forms of metal 1, e.g. Rod-shaped profiles such as wires, pipes or U profiles are conceivable.

In order to influence the temperature of the metal 1, the cooling section 5 has one or more actuators 2. The temperature T of the metal 1 can be influenced directly or indirectly by means of the actuator 2 - as a rule by cooling, but in some cases also by heating. An actuator 2 can have, for example, one or more valves for applying a cooling medium to the metal 1. For example, water or a mixture of water with other substances can be used as the cooling medium. The cooling section 5 is controlled by the computing device 3. In particular, that too

Actuator 2 controlled by computing device 3 according to a manipulated variable S. Measuring elements 6, 6 are provided, by means of which the temperature T of the metal 1 is detected. A first measuring element 6 for temperature detection is arranged at the entrance of the cooling section, in the example shown behind the last roll stand 4. Another measuring element 6 ^X for temperature detection is arranged at the end of the cooling section 5 or in the example shown in front of the reel device 12.

The computing device 3 outputs manipulated variables S to the actuators 2 of the cooling section. Measured values such as the temperature T from the cooling section 5 and / or from the cooling section upstream or downstream devices are fed to the computing device 3. The actual speed v of the metal 1 can also be supplied to the computing device 3. The actual speed v of the metal can be measured and / or with the help of at least one Model are determined. The computing device 3 can also be supplied, for example, with the rotational speeds of the rolls of a roll stand 4 as measured values and / or calculated or modeled values. The computing device 3 is also supplied with so-called primary data P. Primary data P are generally used for the pre-calculation or presetting of a system and are dependent on the metal 1 to be produced. Different metal strips or slabs are usually characterized by different primary data. Primary data can also at least partially relate to the required properties of the metal 1 produced.

Figure 2 shows the course of the temperature T of the metal 1 in the cooling section 5 plotted over time t. The time t relates to the time during which a strip point of the metal 1 present in strip form according to FIG. 1 passes through the cooling section 5.

Alternatively, the temperature T could also be plotted over the strip running direction x, ie the position in the cooling section. The temperature T is used in its capacity as a quantity describing the energy content of the metal 1. One could therefore alternatively also consider, for example, the course of the enthalpy over time t or over the strip running direction x.

The phase components Pi at the end of the cooling section 5 or at the coiler device 12 are decisive for the material properties of the metal 1 or steel produced. The phase components Pi of a metal 1 are particularly critical in production, particularly in the case of multi-phase steels such as dual-phase steels. and trip steels. In the case of such steels, a customary cooling method is cooling divided into three cooling sections. The metal 1 is cooled in the cooling section 5 in several temporal cooling phases, cooling phases or temporal cooling sections I, II, III. The temporal cooling sections I, II, III can, but need not, coincide with spatial or component-related cooling sections. In the first cooling section I, or in the first cooling phase, the metal 1 is preferably cooled at a high cooling rate up to a holding temperature T _H. The holding temperature T _H is generally predetermined or dependent on the primary data P. In a second cooling section II, air cooling takes place with a predetermined holding time t _H. In the second cooling section II, the temperature T of the metal 1 or of the steel decreases only slightly. Subsequently, in a third cooling section III, the metal 1 is quenched to the temperature T or below the temperature T, which is to be achieved at the end of the cooling section or immediately before the winding up by means of the reel device 12. The metal 1 is preferably quenched below the martensite start temperature.

In order to obtain, for example, a structure with a phase component Pi of approximately 80% ferrite and a phase component Pi of approximately 20% martensite or bainite in dual-phase steels, a residual austenite content of typically 20% is usually aimed for before quenching begins. In the case of trip steels, a residual austenite content that is metastable at room temperature remains in the material, which converts to martensite when deformed.

Both dual-phase steels and trip steels can be deformed with little effort when they are later used; With increasing deformation, the strength increases strongly, whereby this behavior is even more pronounced with trip steels than with dual-phase steels. Typical applications of dual-phase and trip steels are body panels and rims for motor vehicles, where good deep-drawing properties, high final strength and high energy absorption capacity are required in the event of further deformation, for example due to accidents. In the manufacture of these steels, the phase components T? _x and thus the degree of conversion in the cooling section 5 is extremely critical. If, for example, undesired surface temperature impairments, such as so-called skid marks on the metal 1, here a steel slab, are caused in a hot rolling mill upstream of the cooling section 5, these undesirable skid marks lead to soft spots in the metal strip. At such soft spots, the degree of conversion in metal 1 has already progressed too far before quenching begins to form sufficient martensite or bainite. Other fluctuations in the process parameters in the cooling section 5 upstream devices can further deviations from the desired structure and the desired phase components Pj. cause in metal 1.

FIGS. 3 and 4 show control systems according to the invention for the cooling section 5. Both figures show a computing device 3 coupled to the cooling section 5 for controlling and modeling the cooling section 5. Interfaces are provided in order to supply the computing device 3 with signals for modeling and around the cooling section 5 Control signals to be supplied. Computing device 3 and cooling section 5 form part of a system for producing a metal 1.

According to FIG. 3, the computing device 3 has a cooling section model 7 and a cooling section controller 8. For a metal 1, for example a metal strip made of steel, which enters the cooling section 5, the cooling section model 7 is used in a first step to trim the temperature T and at least one phase component Pi at the end of the cooling section 5 based on the primary data P for the metal strip. or calculated in front of the reel device 12. With the help of measuring elements, which can be arranged, for example, in a finishing line upstream of the cooling zone 5 (not shown in the drawing) and / or with the aid of a measuring element 6 at the entrance of the cooling zone 5, measured values are obtained in a second step detected and fed to the computing device 3. The measurement values are recorded while the metal 1 passes through the plant for producing a metal 1.

With the aid of the measured value or values, the cooling section model 7 determines at least at the end of the cooling section 5 at least one phase component Pi of the metal 1 to be expected. The expected phase component Pi calculated in the second step is compared with the phase component Pi calculated in the first step on the basis of the primary data P. This comparison is used to adapt at least one manipulated variable S of the cooling section 5. According to FIG. 3, the cooling section controller 8 adjusts at least one manipulated variable S of the cooling section 5. A relatively simple way of realizing such a cooling distance controller is such that manipulated variables S of actuators 2 are adapted as far as possible at the end of the first cooling section I.

According to FIG. 4, the computing device 3 has a cooling section module 7, a cooling section controller 8 and a phase component controller 11. In terms of control technology, the phase proportion controller 11 is superimposed on the cooling section controller 8. For example, the P-hash component controller 11 specifies at least one desired value, for example T _H or t _H , on the cooling section controller 8 on the basis of the comparison of the phase component Pi calculated in the first step and the expected phase component Pi calculated in the second step. In the case of a cooling process with a plurality of cooling sections I, II, III or cooling phases, as is shown, for example, in FIG. 2, the phase proportion controller 11 preferably specifies a holding time t _H and / or a holding temperature T _H for the cooling section controller 8. The cooling section controller 8 adjusts the manipulated variables S of the cooling section 5, taking into account the target specifications of the Ptiasen fraction controller 11.

Both control systems, that is to say both the control system according to FIG. 3 and the control system according to FIG. 4, preferably work such that the second step is carried out iteratively online, ie in real time during the production of the metal 1.

In both the first step and the second step, the phase component Pi is determined in the same way, i.e. calculated using the same calculation methods or models. The calculation in the two steps differs, however, with regard to the data on which the calculation is based, in particular with regard to the input data for the calculation.

As an alternative to the phase component Pi calculated on the basis of the primary data P in the first step, a phase component Pi, for example given by an operator in a first step, can also be compared in the second step with the expected phase component Pi calculated in the second step. In order to ensure a consistently high quality of the metal 1 at the end of the cooling section 5, at least one phase component P of the metal 1 at the end of the cooling section is calculated.

Alternatively or additionally, at least one phase component P of the metal 1 can be calculated at at least one other point on the cooling section 5. If, for example, it is not expedient to measure at the end of the cooling section 5, at least one phase component P of the metal 1 can be calculated at another point in the cooling section 5 both in the first and in the second step of the method, e.g. at a point where it is assumed that the essential part of the phase conversion within the cooling section 5 has already been completed.

The computing device 3 or the cooling section model 7 preferably have a temperature model 9 which calculates the temperature profile of the metal 1 in the cooling section 5 over time t or over the strip running direction x. The temperature model 9 is advantageously adapted with the aid of at least one measured value. The at least one measured value is preferably a measured value for the temperature TUR of the metal 1, which is detected by means of a measuring element 6, 6 at the entrance or at the end of the cooling section 5. As an alternative or in addition, the measured value acquisition can also take place at another point of the cooling section 5. A conversion model 10 is preferably present, which calculates the course of the at least one phase component Pi of the metal 1 in the cooling section 5 over the time t and / or the strip running direction x. As an alternative and / or in addition to the temperature T, the cooling section model 7 and / or the temperature model 9 can also use or calculate the enthalpy or another quantity describing the energy content.

A conversion model 10 is not shown in more detail in FIG. 4 for the sake of clarity, but is also expedient in the exemplary embodiment according to FIG. 4. Provide a conversion model 10 uss at least the phase component Pi of the metal 1 at at least one point of the cooling section 5, preferably at the end of the cooling section 5.

Via the manipulated variables S for the actuators 2 of the cooling section 5, e.g. the position of valves for coolant or the coolant flow in the cooling section 5 is regulated. Such local manipulated variables S, i.e. Actuating variables which have no effects on upstream system parts on the cooling section 5 can, however, also be the speed v of the metal 1 in the cooling section and a idle time of the metal 1 in the production of heavy plate.

The idea of the invention can essentially be summarized as follows:

In the production of steel, an LT conversion model 10 is used for the cooling section 5, with the aid of which the phase components Pi along the steel strip are also calculated in real time in addition to the temperature T of the steel. A control system is implemented which keeps the phase components Pi of the steel strip wound on a reel device 12 constant holds. This is done in the following steps: In a first step, the degree of conversion, in the case of multiphase steels, for example the ferrite content, is determined from data which are given from the primary data P of the steel strip. In a second step, when the strip enters the cooling section 5, one or more parameters of the cooling strategy, ie manipulated variables S, are adjusted online in the sense of a regulation in such a way that the ferrite content of the cooled steel on the coiler device 12 is kept constant. When cooling with several cooling sections, the holding temperature T _{H can be} modified. Raising the holding temperature T _H reduces the ferrite content, lowering the holding temperature T _H increases it.

Deviations from the target structure are already discovered online in accordance with the method according to the invention and are not only discovered after measurements of the structure components in the laboratory (cuts) or during tensile tests.

In the case of previously known methods, the constancy of the structural components along the strip was usually assessed by quality assurance in the steelworks only on the basis of the temperature records for the intermediate temperature and the reel temperature. By contrast, the method according to the invention enables the phase components P on the reel device 12 to be kept largely constant along the metal strip, even in the case of fluctuating production conditions and fluctuating speed v of the metal strip. Deviations between different metal strips with the same primary data P are largely eliminated because the fluctuations in the system are not included in the initial determination of the degree of reference conversion and due to the later

Regulation on the degree of reference conversion, the fluctuations of the system are largely compensated. The first determination of the degree of reference conversion or at least one phase component Pi depends only on the primary data P. The subsequent determinations of the degree of conversion or a phase component Pi take into account the fluctuations in manufacture. In this way, steel or metal 1 can remain the same Quality are produced and the requirements for the material properties of metal 1 or steel are met much more reliably than before.

Claims

claims

1. A method for producing a metal (1), the thermoformed metal (1) being cooled in a cooling section (5), wherein in a first step with the aid of primary data (P) for the metal (1) by means of a cooling section model (7 ) the temperature (T) and at least one phase component (P _x ) of the metal (1) is calculated at at least one point on the cooling section (7), characterized in that in a second step

- at least one measured value is recorded during the manufacture of the metal (1),

at least one phase component (P _x ) of the metal (1) to be expected is calculated with the aid of the at least one measured value by means of the cooling section model (7) at the at least one point of the cooling section (5),

- The expected phase component (Pj.) is compared with the phase component (P _x ) calculated in the first step and

- This comparison is used to adapt at least one manipulated variable (S) of the cooling section (5).

2. The method as claimed in claim 1, so that the at least one point at which at least one phase component (P of the metal (1) is calculated in the first and second step) is located at the end of the cooling section (5).

3. The method according to claim 1 or 2, characterized in that in the second step is compared anticipated phase fraction (P _x) with a predetermined phase fraction (P _x).

4. The method according to any one of claims 1 to 3, characterized in that the second step is carried out iteratively online.

5. The method according to any one of claims 1 to 4, so that in the second step a cooling section controller (8) adjusts at least one manipulated variable (S) of the cooling section (5) in accordance with the comparison.

6. The method according to any one of claims 1 to 4, characterized in that in the second step - a phase proportion controller (11) adjusts at least one setpoint for a cooling section controller (8) in accordance with the comparison and - the cooling section controller (8) taking into account setpoint values given to it adapts at least one manipulated variable (S) to the cooling section (5).

7. The method as claimed in one of claims 1 to 6, that a temperature model (9) is used in at least one of the two steps, which calculates the temperature profile of the metal (1) in the cooling section (5).

8. The method as claimed in claim 7, so that the temperature model (9) is adapted with the aid of the at least one measured value.

9. The method according to claim 1, wherein a conversion model (10) is used that calculates the course of the at least one phase component (Pi) in the cooling section (5).

10. The method according to any one of claims 1 to 9, characterized in that a multi-phase steel is produced.

11. The method according to any one of claims 1 to 10, so that the metal (1) in the cooling section (5) is cooled in at least two cooling sections (1, 11, III).

12. The method according to claim 11, characterized in that a holding time (t _H ) is adjusted.

13. The method according to any one of claims 11 or 12, characterized in that a holding temperature (T _H ) is adjusted.

14. The method according to any one of the preceding claims, that at least one manipulated variable (S) for coolant actuators is adapted.

15. The method according to any one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that at least one manipulated variable (S) for the speed (v) of the metal (1) in the cooling section (5) is adapted in the production of heavy plate.

16. The method according to any one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that at least one manipulated variable (S) is adjusted for a lay time of the metal (1) in the production of heavy plate.

17. Computing device (3) for controlling and modeling a cooling section (5), which is programmed to carry out a method according to one of the preceding claims, with at least one cooling section model (7) and at least one cooling section controller (8), the cooling section model (7) has at least one temperature model (9).

18. Computing device (3) for controlling and modeling a cooling section (5), which is programmed to carry out a method according to one of claims 6 to 16, with at least one cooling section model (7) and at least one cooling section controller (8), the cooling section model ( 7) has at least one temperature model (9), a phase component controller (11) being provided for adapting the setpoints of the cooling section controller (8).

19. Plant for producing a metal (1) with a cooling section (5) and with a computing device (3) according to claim 17 or 18, wherein the computing device (3) for controlling and modeling the cooling section (5) via appropriately designed interfaces with Signal transmitters (6, 6 ') and actuators (2) of the cooling section (5) is coupled.

20. metal (1), which was produced on a plant according to claim 19 according to a method according to any one of claims 1 to 16.