CN117396616A

CN117396616A - Device and method for producing wire-shaped and/or strip-shaped steel

Info

Publication number: CN117396616A
Application number: CN202280038165.0A
Authority: CN
Inventors: M·克贝里克; T·道贝; T·尼扎克; N·雷多尔菲
Original assignee: SMS Group GmbH
Current assignee: SMS Group GmbH
Priority date: 2021-05-28
Filing date: 2022-03-29
Publication date: 2024-01-12
Also published as: DE102021205429A1; EP4347905A1; KR20240004700A; WO2022248102A1

Abstract

The present application relates to a plant (1) and a method for thermo-mechanically rolling long steel semifinished products (2), said plant comprising: a first rolling device (5); a second rolling device (7) arranged downstream of the first rolling device (5) in the conveying direction; a first cooling device (6) optionally arranged between the first rolling device (5) and the second rolling device (7); a first thermo-mechanical reducing and sizing rolling zone (11) arranged downstream of the second rolling device (7) in the conveying direction; a second cooling device (9) arranged between the second rolling device (7) and the first thermo-mechanical reducing and sizing rolling zone (11, 11.1); a cooling bed device, a ring placement device and/or a coil winding device (16) arranged downstream of the first thermo-mechanical reducing and sizing rolling zone (11) in the conveying direction; a third cooling device (14) arranged between the first thermo-mechanical reducing and sizing rolling zone (11) and the cooling bed device, the ring placement device and/or the coil winding device (16); and a structure sensor device (17) arranged between the first thermomechanically reducing and sizing rolling zone (11) and the cooling bed device, the ring placement device and/or the coil winding device (16), by means of which the martensite content, in particular in area percent (A-%) of the martensite structure in the thermomechanically rolled long steel semifinished product or in the linear and/or strip-shaped steel (3) can be determined directly in the ongoing process.

Description

Device and method for producing wire-shaped and/or strip-shaped steel

Technical Field

The present invention relates to: an apparatus for thermo-mechanically rolling long steel semi-finished products; method for producing a linear and/or bar-shaped steel, preferably a structural steel, from a long steel semifinished product, the linear and/or bar-shaped steel having in particular a yield strength of at least 300MPa, preferably a yield strength of at least 400 MPa; and wire-shaped and/or bar-shaped steel products, which are preferably obtainable by the method according to the invention.

Background

The thermo-mechanical rolling process, which was originally developed for the production of high-quality steel, is now increasingly used for the production of steel bars, since the use of the thermo-mechanical rolling process, in addition to significantly improving the important properties, in particular the elongation properties, of structural steels, allows at the same time a reduction in alloying costs and operating costs. In this context, the ductility is of critical importance in order to minimize the risk of structural failure, especially in areas with frequent earthquakes.

To obtain a batch of structural building material, structural steel must meet certain specifications. For this purpose, the specifications, namely yield and tensile strength, ductility, elongation at break a, reduction of area Z, notched impact energy K, welding properties, which are mainly given in terms of carbon equivalent (Ceq), and fatigue resistance, are mainly included.

Using the thermomechanical methods known from the prior art for producing linear and/or bar-shaped structural steels, a substantially pure ferrite-pearlite microstructure can be achieved over the entire cross-section, so that the structural steel products produced in this way have the desired ductility properties in addition to high strength values. Since the entire cooling process is not stable with respect to the respective target temperatures, it is often the case that an unidentified martensitic structure is formed suddenly in the edge region of the linear and/or strip-shaped structural steel during the process control, which can have a negative effect on the desired expansion properties.

Disclosure of Invention

The object of the present invention is therefore to provide a device for the thermomechanical rolling of long steel semifinished products and a method for producing linear and/or bar-shaped steel, in particular structural steel, with which linear and/or bar-shaped steel, in particular structural steel, can be produced which is consistent in terms of its structure and mechanical properties.

According to the invention, this object is achieved by a device having the features of claim 1 and by a method having the features of claim 8.

The plant according to the invention for thermo-mechanically rolling long steel semi-finished products into linear and/or strip steel comprises: a first rolling device; a second rolling device arranged downstream of the first rolling device in the conveying direction; a first cooling device arranged between the first rolling device and the second rolling device if necessary; a first thermo-mechanical reducing and sizing rolling zone arranged downstream of the second rolling device in the direction of conveyance; a second cooling device arranged between the second rolling device and the first thermo-mechanical reducing and sizing mill; a cooling bed device, an annular placement device and/or a coil winding device arranged downstream of the first thermo-mechanical reducing and sizing rolling zone in the conveying direction; a third cooling device arranged between the first thermo-mechanical reducing and sizing rolling zone and the cooling bed device, the annular placement device and/or the coil winding device; and a structure sensor device arranged between the first thermomechanically reducing and sizing rolling zone and the cooling bed device, the ring placement device and/or the coil winding device, by means of which the martensite content, in particular in area percent (a-%) of the martensite structure in the thermomechanically rolled long steel semifinished product or the linear and/or strip steel, can be determined directly in the ongoing process.

The invention likewise relates to a method for producing a linear and/or bar-shaped steel from a long steel semifinished product, in particular having a yield strength of at least 300MPa, preferably having a yield strength of at least 400MPa, even more preferably having a yield strength of at least 500MPa, and most preferably having a yield strength of at least 600MPa, wherein the long steel semifinished product, which is optionally heated to a temperature of at least 900 ℃, preferably to a temperature of at least 950 ℃, is first roughed in a first rolling device and optionally cooled in a subsequent first cooling device; then, a subsequent rolling is carried out in a second rolling device arranged downstream of the first rolling device in the conveying direction and cooled to a temperature of at least 850 ℃ in a subsequent second cooling device; then finish-rolling into wire-shaped and/or strip-shaped steel in a first thermo-mechanical reducing and sizing rolling zone arranged downstream of the second cooling device in the conveying direction, the wire-shaped and/or strip-shaped steel being cooled to a temperature in the range of 400 ℃ to 850 ℃ in a third cooling device following the first thermo-mechanical reducing and sizing rolling zone; then, the hot-rolled long steel semifinished product or the martensitic structure possibly present in the linear and/or strip steel is directly determined in the continuous process by means of a structure sensor device arranged in the section between the first thermo-mechanical reducing and sizing rolling zone and the cold-bed device, the annular placing device and/or the coil winding device.

By introducing a structure-sensor device, by means of which the martensite structure possibly present in the thermomechanically finish-rolled wire-like and/or strip-like steel, in particular the martensite content in terms of area percent, can be continuously determined, the production process can be designed significantly more efficiently, since by recognizing the martensite structure on-line, the corresponding process parameters can be directly influenced, for example, by: the temperature in the respective cooling device, the rolling temperature in the respective rolling unit and/or the reduction can be adjusted.

This results in a linear and/or bar-shaped steel, in particular a structural steel, which has a quality which is almost uniform in terms of its structure and free of martensite. In addition, in the case of defective and/or disadvantageous cooling temperatures in the respective cooling device, the reject rate can be detected in time by the on-line sensor device and corrected directly.

Further advantageous embodiments of the invention are given in the dependent claims. The features listed in the dependent claims can be combined with each other in a technically reasonable manner and can define further embodiments of the invention. Furthermore, the features which are specified in the claims are explained and explained in more detail in the description, wherein further preferred embodiments of the invention are presented.

It should be noted that the temperatures mentioned herein are average temperatures along the cross section of the product and thus cannot be equated with surface temperatures.

In the sense of the present invention, the term "long steel semifinished product" is understood to mean a steel semifinished product suitable for producing a linear and/or bar-shaped steel or steel product, in particular a structural steel, according to the invention. Such long steel semi-finished products are also called billets and generally have a square or rectangular cross-section.

The term "wire-shaped and/or strip-shaped steel or steel product" is understood in the sense of the present invention to mean a steel product, in particular a structural steel. Preferably having a circular cross-section with raised striations and/or a smooth surface. However, in alternative embodiments, it may also have a square, rectangular or hexagonal cross section.

The wire-like steel product may have a diameter in the range of 4.5mm to 29mm, preferably in the range of 5.5mm to 16mm, in the sense of the invention and is sent to an annular placement device, in particular a laying head (winduslteger), at the end of the manufacturing unit. The wire-like steel product is formed into coils of a desired size by an endless placement device or laying head, then unrolled for placement on a roller table for uniform cooling, and then concentrated in a baling chamber for use as a coil.

On the other hand, the strip steel product may have a diameter in the range of 8.0mm to 60.0mm or in the range of 6.0mm to 50.0 mm. If long steel semifinished products are to be processed into steel bars with a finished length of up to 12m, the steel bar products have a diameter in the range of 8.0mm to 60.0mm and will be sent to the cooling bed at the end of the manufacturing unit. If the long steel semifinished product is to be processed into coiled steel strips, the strip steel product has a diameter in the range of 6.0mm to 50mm, preferably in the range of 6.0mm to 32mm, and is then fed to the coil coiling device at the end of the manufacturing unit.

The first rolling device may be formed from a plurality of frameless rolling stands in which the long steel semifinished product has been pre-heated to a temperature of at least 900 ℃, preferably at least 950 ℃. Advantageously, the first rolling device comprises at least six, more preferably at least eight, even more preferably at least ten, and most preferably twelve such frameless rolling stands.

If the temperature of the rough-rolled long steel semifinished product has to be regulated, a first cooling device can be arranged downstream of the first rolling device in the conveying direction. The first cooling device comprises one or two water tanks which are arranged spaced apart from each other in a first section between the first rolling device and the second rolling device.

The rough rolled long steel semifinished product is then subjected to subsequent rolling in a second rolling device. The second rolling device advantageously comprises at least two, more preferably at least four, and most preferably six frameless rolling stands.

Additionally or alternatively, the first rolling device and/or the second rolling device may comprise hydraulically adjustable rolling stands instead of frameless rolling stands.

In a further advantageous embodiment, the long steel semifinished product which has been finish-rolled in the second rolling device can be separated by forming in the last rolling stand in the conveying direction into two individual strands which can be finish-rolled in a further process into linear and/or strip-shaped steel products in a thermo-mechanical reducing-sizing rolling zone arranged parallel to one another.

After the second rolling device in the conveying direction, a second cooling device is arranged in the second section. The second cooling device advantageously comprises at least two, more preferably at least three or four water tanks, which are arranged spaced apart from one another in the second section in order to achieve a temperature reduction in the rolling stock before the thermo-mechanical rolling step.

The first and second sections are preferably selected such that the product has sufficient time to adequately temperature equalize across the section. Temperature equalization within the product is performed by conduction from the core to the surface. In order to achieve a temperature which is as uniform as possible over the entire cross section of the rolling stock, it is particularly preferably provided that a temperature gradient of at most 100 ℃, more preferably at most 80 ℃, even more preferably at most 60 ℃ and most preferably at most 50 ℃ is provided. The homogenization of the section temperature can be controlled indirectly between the respective stations by measuring the surface temperature of the rolled long steel semifinished product. In addition, a corresponding process model can also be used.

Thus, the first interval between the first rolling device and the second rolling device advantageously has a length of 40m to 80m, more preferably 45m to 60 m. The second section between the second rolling device and the first thermo-mechanical rolling zone advantageously has a length of 100m to 140m, more preferably 115m to 130m.

The rolled long steel semifinished product cooled to a temperature of at least 850 ℃ in the second cooling device is then sent to a first thermo-mechanical reducing rolling zone, where the long steel semifinished product is finish rolled to a desired or predetermined final diameter.

In a particularly advantageous embodiment variant, it is provided that the rolled long steel semifinished product is fed to the first thermomechanical reducing rolling zone at a temperature in the range of 700 ℃, preferably at a temperature of at least 730 ℃, more preferably at a temperature of at least 750 ℃, even more preferably at a temperature of at least 760 ℃, and most preferably at a temperature of at least 770 ℃. However, the temperature of the rolled long steel semifinished product should not be too high, since otherwise the minimum possible temperature gradient between the surface temperature and the core temperature, which is required for the metallurgical recrystallization process and the grain refining effect associated therewith, cannot be set. The temperature at which the rolled long steel semi-finished product is fed to the first thermo-mechanical reducing rolling zone is therefore limited to 850 ℃, preferably to 840 ℃, more preferably to 820 ℃ and most preferably to 800 ℃. It is particularly preferred to feed the rolled long steel semifinished product to the first thermo-mechanical reducing rolling zone at a temperature of 780 ℃.

A maximum deformation or maximum reduction, which may preferably be 30% to 80%, is achieved in the thermo-mechanical reducing rolling zone. The thermo-mechanical reducing mill section may be configured with one stand, preferably two stands, more preferably four stands, even more preferably six stands, and most preferably eight stands.

In a further advantageous embodiment, the device can comprise a second thermo-mechanical reducing mill between the first thermo-mechanical reducing mill and the third cooling device, which can likewise be configured with one stand, preferably two stands, more preferably four stands, even more preferably six stands, and most preferably eight stands. In this connection, it is particularly preferred to provide an intermediate cooling device between the two thermo-mechanical reducing rolling zones, which comprises one or two water tanks spaced apart from one another. Thus, for example, in a first advantageous embodiment, the first thermo-mechanical reducing mill section can be configured with four stands and the second thermo-mechanical reducing mill section can be configured with two stands. In a further advantageous embodiment, the first thermo-mechanical reducing mill section can be configured, for example, with four stands, and the second thermo-mechanical reducing mill section can likewise be configured with four stands. Any other combination of the aforementioned divisions of the stand with respect to the two thermo-mechanical reducing mill sections is possible and conceivable.

The thermomechanical reducing mill section constructed in the basic embodiment, for example, is thus constructed as a six-stand thermomechanical reducing mill section, can also be divided into six single-stand thermomechanical reducing mill sections, wherein an intermediate cooling device with at least one water tank is provided in each case between two of the six single-stand thermomechanical reducing mill sections, for example, within the entire cascade of six single-stand thermomechanical reducing mill sections.

Thermomechanical reducing mill sections are well known and are known by the applicant under the trade nameAnd (5) selling.

In this case, a third cooling device is arranged in the third section after the first and optionally after the second thermomechanical reducing rolling section in the conveying direction, in which third cooling device the long steel semifinished product which has been finish-rolled into a wire-shaped and/or strip-shaped steel is cooled in order to prevent further grain growth. The third cooling means comprise at least one, preferably at least two, more preferably at least three, even more preferably at least four, and most preferably at least five water tanks through which the wire-like and/or strip-like steel is cooled in order to ensure a temperature equalization on the one hand and to prevent the formation of hardened tissue structures in the form of martensite or bainite on the other hand.

The third cooling means particularly advantageously comprise between two and twelve water tanks, more preferably between four and ten water tanks.

The cooling power of the respective water tank of each cooling device can be adjusted specifically by the volume flow of the cooling water, the number of effective cooling pipes of each water tank, the cooling pipe diameter and/or the cooling water pressure and, if appropriate, the cooling water temperature. The predefined parameters can typically be predefined by means of a specific process model and are set by online adjustment.

The exemplary water tank may have a tank length of 6500mm and include six cooling tubes of a length of 750mm, respectively. At this time, such a tank usually has 230m ³ Maximum cooling water quantity per h, and an adjustable cooling water pressure range of 1.5bar to 6.0 bar.

The third section extending between the first or second thermomechanical reducing mill and the cooling bed device, ring placement device or coil winding device is also preferably selected as such, i.e. such that the rolled product has sufficient time to undergo a sufficient temperature equalization in cross section. It is therefore preferred that in the long steel semifinished product finish rolled into wire-like and/or strip-like steel a temperature gradient of maximally 100 ℃, more preferably a temperature gradient of maximally 80 ℃, even more preferably a temperature gradient of maximally 60 ℃ and most preferably a temperature gradient of maximally 50 ℃ is provided. Thus, the third interval advantageously has a conveying length of 110m to 150m, more preferably a conveying length of 110m to 130m. In this connection, it has been shown to be particularly preferred that the cooling which takes place as soon as possible after the last pass, i.e. after the first or the second thermo-mechanical reducing mill, is decisive for the control of the recrystallization process and for a high level of fine grain size, preferably having an average grain diameter of less than 12.0 μm, even more preferably having an average grain diameter of less than 10.0 μm.

It is therefore advantageously provided that the wire-shaped and/or strip-shaped steel, after the last pass, having a temperature in the range of 700 ℃ to 1100 ℃, is fed to the third cooling device, in particular to the first water tank of the third cooling device, after a maximum of 300ms, preferably after a maximum of 200ms, even more preferably after a maximum of 100ms, even more preferably after a maximum of 90ms, and most preferably after a maximum of 80 ms.

To inhibit grain growth, the wire-shaped and/or strip-shaped steel is cooled until a cooling bed inlet temperature, an inlet temperature into the ring placement device and/or an inlet temperature into the coil winding device is achieved in the range of 400 ℃ to 850 ℃. Particularly advantageous cooling bed inlet temperatures are 550 ℃ to 750 ℃, more preferably 600 ℃ to 650 ℃. However, particularly advantageous inlet temperatures into the web winding device are 450 ℃ to 550 ℃. A particularly advantageous inlet temperature into the ring placement device is 600 to 750 ℃.

The tissue sensor device according to the invention arranged in the third section between the first or second thermo-mechanical reducing mill and the cooling bed device, the ring placement device or the coil winding device can advantageously be arranged immediately before the cooling bed device, the ring placement device and/or the coil winding device in the conveying direction; immediately before the separating device arranged in the conveying direction before the cooling bed device, the ring placement device and/or the web winding device; and/or if necessary immediately after the third cooling device, in particular after the last water tank, in the conveying direction. But may also be arranged between two of the plurality of water tanks in the third cooling device.

In an advantageous embodiment variant, the device comprises a tissue sensor device according to the invention after each of the plurality of water tanks in the third cooling device arranged in the third section. Each of the plurality of water tanks may thus be individually adjusted and the formation of the martensitic structure may be associated with a particular water tank.

The martensitic structure, in particular the martensitic content in percent by area, in the linear and/or strip steel can be detected in an on-line manner by means of a structure sensor device in a continuous process. In principle, all techniques known to the person skilled in the art at the point in time of application can be used as measurement method. However, it is advantageously provided that the tissue sensor device for detecting undesired martensite has an ultrasonic measuring device, an ethical beam measuring device, a radar beam measuring device and/or an electromagnetic measuring device.

The tissue sensor device can advantageously be coupled to a control and/or regulating device, by means of which, if appropriate, an active intervention can be carried out in the respective process step by means of the respective algorithm in order to bring about the desired tissue.

In a further aspect, the present invention also relates to a wire-and/or strip-shaped steel product, preferably manufactured by the method according to the present invention, which wire-and/or strip-shaped steel product has in particular a yield strength of at least 300MPa, more preferably a yield strength of at least 400MPa, even more preferably a yield strength of at least 500MPa, and most preferably a yield strength of at least 600MPa, the wire-and/or strip-shaped steel product having a martensite content of maximally 15.0 a.+ -. Preferably a martensite content of maximally 10.0 a.+ -. More preferably a martensite content of maximally 8.0 a.+ -. Even more preferably a martensite content of maximally 6.0 a.+ -. And most preferably a martensite content of maximally 5.0 a.-%.

Linear and/or strip steel, in particular structural steel, preferably has the following chemical composition in weight percent:

carbon: 0.04 to 0.35 of the total weight of the composition,

silicon: 0.10 to 0.80 of the total weight of the composition,

manganese: from 0.40 to 1.60 a,

phosphorus: at most 0.06 of the total number of the components,

sulfur: at most 0.06 of the total number of the components,

nitrogen: at most 0.012;

the balance being iron, possibly together with other accompanying elements, and unavoidable impurities.

As further accompanying elements, the wire-like and/or strip-like steel may preferably comprise the following elements (in weight percent) alone and/or in combination:

chromium: at most 0.40 of the total number of the components,

molybdenum: at most 0.20 of the total number of the components,

nickel: at most 0.90 of the total number of the components,

copper: 0.65 to 1.0 of the total weight of the composition,

lead: at most 0.25 of the total number of the components,

tin: at most 0.07.

It is particularly preferred to provide that the wire-shaped and/or strip-shaped steel, in particular the structural steel, has a carbon equivalent (Ceq) of 0.60 or less, more preferably a carbon equivalent (Ceq) of 0.50 or less.

Drawings

The invention and the technical field are explained in more detail below with reference to the figures and examples. It should be noted that the invention should not be limited to the embodiments shown. In particular, unless explicitly stated otherwise, some aspects of the facts explained in the figures and/or examples may also be extracted and combined with other components and knowledge from the present description and/or figures. It should be noted in particular that the figures and the proportions shown in particular are merely schematic. Like reference numerals denote like objects, and explanations from other drawings may be used supplementarily as necessary. Wherein:

fig. 1 shows an embodiment variant of the device according to the invention;

fig. 2 shows a temperature distribution of a first embodiment of the method according to the invention;

fig. 3 shows a temperature distribution of a second embodiment of the method according to the invention; and

fig. 4 shows a temperature distribution of a third embodiment of the method according to the invention.

Detailed Description

Fig. 1 shows a schematic block diagram of an embodiment variant of an apparatus 1 according to the invention for the thermomechanical rolling of long steel semifinished products 2. Such long steel semifinished products 2 which are thermomechanically rolled into wire-like and/or strip-like steel 3 in the apparatus 1 may have a quadrangular (square) cross section with dimensions 165x165 mm. The respective finish-rolled wire-shaped and/or strip-shaped steel 3 may have a diameter (wire-shaped steel) in the range of 4.5mm to 29mm or a diameter (strip-shaped steel) in the range of 8.0mm to 60.0mm or in the range of 6.0mm to 50.0 mm.

In order to produce the respective wire-shaped and/or strip-shaped steel 3, the long steel semifinished product 2 is first fed to a regenerator 4 in which the long steel semifinished product 2 to be rolled is heated to a temperature of 900 ℃ to 1000 ℃.

The heated long steel semifinished product 2 is then fed to a first rolling device 5, in which it is to be roughed in a cascade of twelve frameless rolling stands (not shown). In this case, a reduction of 20% to 40% per pass is achieved in the respective rolling stand. The average temperature of the rolled stock in the first rolling device 5 is 900 to 1100 ℃.

A first cooling device 6 can be arranged downstream of the first rolling device 5 in the conveying direction, which first cooling device has one or two water tanks in order to be able to subsequently adjust the temperature of the rough-rolled long steel semifinished product 2 before it is fed to the second rolling device 7. The first cooling device 6 is arranged here in a first section 8 between the first rolling device 5 and the second rolling device 7, which is selected such that the rolled product has sufficient time to perform a sufficient temperature equalization between the two rolling processes. The first interval 8 may have a length of 45m to 60 m.

In the second rolling device 7, the rough-rolled long steel semifinished product 2 is then subsequently rolled in a cascade of six frameless rolling stands (not shown), wherein a reduction of 20% to 30% per pass is achieved in the respective rolling stands. The average temperature of the rolled stock in the second rolling device 7 is 800 ℃ to 1000 ℃.

After the second rolling device 7 in the conveying direction, a second cooling device 9 is arranged in the second section 10, which currently comprises three water tanks (not shown) spaced apart from each other in order to achieve a cooling of the hot rolled piece of 800 to 1000 ℃ before the subsequent thermo-mechanical rolling step. Furthermore, the second section 10 is selected such that the rolled stock, in addition to being cooled down, has sufficient time to perform a sufficient temperature equalization over its cross-section. Thus, the second interval may currently have a length of 115m to 130m.

The subsequently rolled and cooled long steel semifinished product 2, now with a circular and/or oval cross section, is then fed to the first thermo-mechanical reducing rolling zone 11 at a temperature in the range 740 ℃ to 800 ℃ and finish rolled to a desired or predetermined final diameter, which may be 8mm, 18mm or 25mm, for example. For this purpose, in an embodiment variant, the first thermo-mechanical reducing rolling zone 11 can be configured with six stands, wherein a reduction of approximately 22% to 27% per pass can be achieved in the respective stands.

In a further embodiment variant, the first thermo-mechanical reducing mill 11/11.1 can be supplemented by a second thermo-mechanical reducing mill 11.2, which can likewise be configured with a plurality of stands. In this embodiment variant, an intermediate cooling device 13 with at least one water tank (not shown) is provided in the intermediate section 12 formed between the two thermo-mechanical reducing mill sections 11.1, 11.2. The intermediate section 12 likewise has a specific section of, for example, 30m, in order to achieve a sufficient time for the rolled product to undergo a sufficient temperature equalization over its cross-section.

In this case, the third cooling device 14 is arranged in the third section 15 downstream of the first thermomechanical reducing mill 11.1 or the second thermomechanical reducing mill 11.2 in the conveying direction. In this third cooling device, the long steel semifinished product 2, which has been finish-rolled into a wire-shaped and/or strip-shaped steel 3, at a temperature of 700 ℃ to 1050 ℃, is cooled by four or five successive spaced-apart water tanks in cascade to inhibit further grain growth and to prevent the formation of hardened microstructure in the form of martensite or bainite. For this purpose, it is necessary to cool as quickly as possible immediately after the last pass in order to be able to control the recrystallization process and to achieve a high level of fine particle size with an average particle diameter in the range of 6.0 μm to 10.0 μm. The third section 15 is likewise selected with a corresponding length in order to allow the rolled product sufficient time to undergo a sufficient temperature equalization in its cross section on its way to the last work station. The length of the third interval section may be, for example, 110m to 130m.

According to an embodiment variant, the strip steel 3 is then sent to the cooling bed device 16 at an inlet temperature of 550 ℃ to 750 ℃, to the laying head 16 at an inlet temperature of 600 ℃ to 750 ℃, or to the coil winding device 16 at a coil winding temperature of 450 ℃ to 550 ℃.

Since the entire cooling process is not stable with respect to the respective target temperature and, as a result, abrupt formation of the martensitic structure may occur in the context of process control, the apparatus 1 further comprises a structure sensor device 17, which is arranged in the third interval 15.

The formation of the martensitic structure, in particular the martensitic content in percentage by area, in the linear and/or strip steel 3 can be detected in an on-line manner by means of the structure sensor device 17 in a continuous process.

For identifying undesired martensite, the tissue sensor means 17 may comprise, for example, ultrasonic measuring means, rennet-ray measuring means, radar beam measuring means and/or electromagnetic measuring means.

The possible positions of the tissue sensor device 17 in the third section 15 are shown by dashed lines. Thus, the tissue sensor device may be arranged, for example, in the conveying direction before the third cooling device 14 or immediately before the cooling bed device, the ring placement device or the web winding device 16. But may also be arranged between the water tanks of the plurality of water tanks in the third cooling device 14 or in the intermediate section 12.

Fig. 2 to 4 each show three different temperature profiles (average temperatures) 18, 19, 20 of three different diameter bars 3 produced according to an embodiment variant of the method according to the invention. For this purpose, a HRB 400 quality billet having a quadrangular (square) cross-section and a cross-sectional dimension of 165x165mm is thermo-mechanically rolled in an apparatus 1 comprising a regenerator 4, a first rolling device 5 having twelve frameless rolling stands (not shown), a first cooling device 6 having two water tanks, a second rolling device 7 having six frameless rolling stands (not shown), a second cooling device 9 having three water tanks, a six-frame reduced diameter rolling zone 11, a third cooling device 14 having five water tanks, and a cooling bed device 16 to a bar 3 having an 8mm diameter (fig. 2), an 18mm diameter (fig. 3) and a 25mm diameter (fig. 4).

List of reference numerals

1. Apparatus and method for controlling the operation of a device

2. Long steel semi-finished product

3 Linear/strip Steel

4. Furnace with a heat exchanger

5. First rolling device

6. First cooling device

7. Second rolling device

8. A first interval section

9. Second cooling device

10. A second interval section

11. First reducing sizing rolling zone

11.1 First reducing sizing rolling zone

11.2 Second reducing sizing rolling zone

12. Intermediate section

13. Intercooler device

14. Third cooling device

15. Third interval section

16 cooling bed device/coiled material winding device/annular placement device

17. Tissue sensor device

18. Temperature distribution

19. Temperature distribution

20. Temperature distribution.

Claims

1. Device (1) for thermomechanically rolling long steel semifinished products (2) into linear and/or strip-shaped steel (3), comprising: a first rolling device (5); a second rolling device (7) arranged downstream of the first rolling device (5) in the conveying direction; -first cooling means (6) arranged, if necessary, between said first rolling means (5) and said second rolling means (7); -a first thermo-mechanical reducing and sizing rolling zone (11) arranged downstream of the second rolling device (7) in the conveying direction; -a second cooling device (9) arranged between the second rolling device (7) and the first thermo-mechanical reducing rolling zone (11, 11.1); a cooling bed device, a ring placement device and/or a coil winding device (16) arranged downstream of the first thermo-mechanical reducing and sizing rolling zone (11) in the conveying direction; -third cooling means (14) arranged between said first thermo-mechanical reducing and sizing rolling zone (11) and said cooling bed means, ring placement means and/or coil winding means (16); and a structure sensor device (17) arranged between the first thermomechanically reducing and sizing rolling zone (11) and the cooling bed device, ring placement device and/or coil winding device (16), by means of which the martensite content, in particular in area percent (A-%) in the thermomechanically rolled long steel semifinished product (2) or in the wire-shaped and/or strip-shaped steel (3), can be determined directly in a continuous process.

2. The device (1) according to claim 1, wherein the tissue sensor means (17) is arranged to: immediately preceding the cooling bed device, ring placement device and/or coil winding device (16) in the conveying direction; immediately before a separating device arranged in the conveying direction before the cooling bed device, ring placement device and/or coil winding device (16); and/or

If necessary, immediately after the third cooling device (14) in the conveying direction.

3. The device (1) according to claim 1 or 2, wherein the tissue sensor means (17) has ultrasound measuring means, x-ray measuring means, radar beam measuring means and/or electromagnetic measuring means.

4. The apparatus (1) according to any one of the preceding claims, wherein the apparatus further comprises a second thermo-mechanical reducing mill (11.2) arranged between the first thermo-mechanical reducing mill (11, 11.1) and the third cooling device (14) and, if necessary, an intermediate cooling device (13) arranged between the two reducing mill (11.1, 11.2).

5. The apparatus (1) according to any one of the preceding claims, wherein the second cooling device (9) and/or the third cooling device (14) comprises at least two water tanks, preferably at least three water tanks, even more preferably at least four water tanks, which are respectively arranged spaced apart from each other.

6. The apparatus (1) according to any one of the preceding claims, wherein each of the thermo-mechanical reducing mill sections (11.1, 11.2) is configured with one stand, two stands, four stands, six stands and/or eight stands.

7. The device (1) according to any one of the preceding claims, wherein the tissue sensor means (17) are coupled with control and/or regulation means in order to regulate the temperature in the cooling means (6, 9, 13, 14) of the device (1), the rolling temperature and/or the rolling speed in the respective rolling unit (5, 7, 11.1, 11.2).

8. Method for producing a linear and/or bar-shaped steel (3) from a long steel semifinished product (2), said steel having in particular a yield strength of at least 300MPa, preferably at least 400MPa, wherein,

firstly rough rolling of the long steel semifinished product (2), optionally heated to a temperature of at least 900 ℃, in a first rolling device (5) and optionally cooling in a subsequent first cooling device (6);

then, a subsequent rolling is carried out in a second rolling device (7) arranged downstream of the first rolling device (5) in the conveying direction and cooled to a temperature of at least 850 ℃ in a subsequent second cooling device (9);

then finish-rolling into wire-shaped and/or strip-shaped steel (3) in a first thermo-mechanical reducing rolling zone (11, 11.1) arranged downstream of the second cooling device (9) in the conveying direction, said wire-shaped and/or strip-shaped steel being cooled to a temperature in the range of 400 ℃ to 850 ℃ in a third cooling device (14) immediately following the first thermo-mechanical reducing rolling zone (11, 11.1);

then, the sheet is fed to a cooling bed device, a ring placement device and/or a coil winding device (16) arranged downstream of the third cooling device (14) in the conveying direction, wherein the martensite structure possibly present in the thermomechanically rolled long steel semifinished product (2) or in the linear and/or strip steel (3) is directly determined in the ongoing process by means of a tissue sensor device (17) arranged in the section between the first thermomechanically reduced diameter rolling zone (11, 11.1) and the cooling bed device, ring placement device and/or coil winding device (16).

9. Wire-and/or strip-shaped steel (3), preferably manufactured by a method according to claim 8, in particular having a yield strength of at least 300MPa, preferably at least 400MPa, having a martensite content of at most 15.0a. -% in area percent.

10. Linear and/or strip steel (3) according to claim 9, comprising the following chemical composition in weight percent:

carbon: 0.04 to 0.35

Silicon: 0.10 to 0.80

Manganese: 0.40 to 1.60

Phosphorus: at most 0.06

Sulfur: at most 0.06

Nitrogen: at most 0.012 of the number of times,

the balance being iron, possibly with additional accompanying elements, and unavoidable impurities.

11. The wire-shaped and/or strip-shaped steel (3) according to claim 9 or 10, wherein the wire-shaped and/or strip-shaped steel has a carbon equivalent (Ceq) of 0.60 or less.