EP3206808B1 - Installation and method for producing heavy plate - Google Patents

Description

The invention is directed to a process for the production of heavy plates made of a steel alloy and formed directly from the casting heat of a continuous caster as an endless flat material to the dimensions of heavy plate, comprising the continuous casting of a steel melt and primary shaping of a cast strand obtained into a slab with subsequent shaping or hot rolling of the slab from the casting heat in several forming steps to a desired heavy plate dimension and an immediately subsequent heat treatment of the heavy plate causing targeted cooling of the heavy plate obtained, the heavy plate being cut in the production direction before or after its heat treatment to a desired individual plate length.

Furthermore, the invention is directed to a device for carrying out such a method for the production of heavy plates made of a steel alloy that are formed directly from the casting heat of a continuous caster as an endless flat material on heavy plate dimensions and that have a system that is used for the immediate consecutive processing and / or machining of a Steel melt a casting plant in which the steel melt can be poured continuously, a primary forming plant in which a cast strand cast from the steel melt can be shaped into a slab, a forming plant or rolling plant in which the slab is converted from the casting heat in several forming steps into a heavy plate with the desired heavy plate size can be rolled, and which comprises a heat treatment plant and a heavy plate cutting device arranged in front of or behind the heat treatment plant in the production direction.

In the production of hot strip in the single coil, semi-endless or endless process, it is common for a slab produced in the continuous casting process to be fed directly from the casting heat to a reheating or equalizing furnace in which the desired temperature for the subsequent finish rolling is set. In the finishing mill, the slab is rolled out to the desired final thickness in several passes.

One method of making sheet steel is from US Pat EP 0 415 987 B1 known. In this process, a slab is produced by means of a continuous casting process, which is then heated in a furnace after passing through a first forming stage to reduce the slab thickness before it enters a finishing rolling mill in which the slab is rolled into the steel sheet or strip steel. In the rolling mill, which comprises several forming steps, the steel strip is subjected to a treatment consisting of a combination of targeted forming steps and targeted cooling and heating steps. Here, the desired mechanical properties of the steel strip are set by this combination of deformation at specifically set temperatures, the degrees of deformation carried out specifically at a certain temperature and the deformation speeds. After passing through the finishing mill, the desired sheet lengths are separated from the finish-rolled steel sheet and stacked. No specific heat treatment is carried out on the steel sheet produced after it has passed through the finishing train.

From the WO 2006/106376 A1 a method is known for the production of metal sheets with a thickness of 10-100 mm, which are made from a continuously cast cast strand with subsequent hot rolling. The hot rolling can be combined with cooling devices arranged between the individual roll stands and a cooling of the rolled steel sheet that can be brought about therewith. After passing through the rolling train, the steel sheet is passed through a heat treatment system in the form of a cooling system and then sheet steel plates are cut to the desired length.

The problem with these methods known from the prior art is that grain-refining processes take place very quickly due to the rapid recrystallization of steels in the temperature range above 1,100 ° C., and that in practice there is always a temperature field in a slab which after every grain-refining forming step leads to grain growth following the local temperature. As a result of the locally different grain growth, a different structure is formed at least over the width of the sheet rolled from the slab, which manifests itself in the finished sheet as an inhomogeneous mechanical property that is formed by the respective strength value and / or the respective toughness value. With the methods and devices known from the prior art, it is therefore not reliably possible to produce metal sheets, in particular heavy plates, which meet high toughness requirements with constant quality. It is also not possible with the methods and devices previously disclosed in the prior art for the production of heavy plate, which only comprise a combination of forming / heating / cooling with a subsequent cooling, to produce plates in the delivery condition + QT (tempered). Even steels, which in their delivery standards must be subjected to targeted heat treatment, normalization or tempering, cannot be produced on the known systems either.

From the WO 95/02706 A1 a method and a system for producing stainless steel blanks are known, a band being continuously cast from a steel melt by means of a band casting system and being originally formed into the band. The strip is then hot-rolled and passes through a cooling system and an annealing furnace before it is then descaled and cut to the desired individual sheet length. Here, a heat treatment is carried out in the form of a combination of targeted cooling of the strip from the rolling heat to a desired first temperature with immediately subsequent heating of the strip to a desired second temperature.

A plant for the production of hot strip from austenitic, stainless steels, which is rolled and heat-treated without cooling to room temperature, so that the end product is already solution-annealed and quenched, is disclosed in WO 03/064069 A1 . The plant comprises a continuous caster, the cast strand being cut into slabs in front of a roller hearth furnace or preheating furnace, which are then heated a first time in the furnace before rolling, then rolled, then heated again and then rolled into hot strip in a hot rolling mill.

The closest prior art is the US 2011/012938 A1 from which the production of steel sheets from steel alloys with a bainite structure on the route - continuous casting - hot rolling - heat treatment - is known. Slabs are rolled from the casting heat and then immediately subjected to a heat treatment that includes the steps of cooling, heating and re-cooling. In this case, a slab is separated from the cast strand and, after the separation, rolled into a sheet which is then heat-treated. The US 2011/012938 A1 discloses a batch process in which the material is processed in sections and in separate process steps independently of the original casting speed.

The invention is based on the object of providing a solution for the production of heavy plate which does not have the disadvantages mentioned above and enables the flexible production of different heavy plate qualities.

This object is achieved by a method according to claim 1 and a device according to claim 10.

In the case of the method described in detail at the beginning for the production of heavy plates directly from the casting heat of a continuous caster as an endless flat material to the dimensions of heavy plate, the object of this method is achieved in that the heat treatment in the temperature range of 150 ° C - 1,100 ° C as a combination of a targeted cooling of the obtained heavy plate from the rolling heat to a desired first temperature with an immediately subsequent targeted heating of the heavy plate to a desired second temperature and an immediately subsequent cooling of the heavy plate to a desired third temperature.

In the case of a device of the type described in more detail at the outset for the production of heavy plates which are shaped and formed directly from the casting heat of a continuous caster as continuous flat material to the dimensions of heavy plate, the object for carrying out this production method is achieved in that the heat treatment system comprises at least one cooling device and at least one heating device which are designed in such a way that a heat treatment of the heavy plate in the temperature range of 150 ° C - 1,100 ° C in the form of a combination of targeted cooling of the obtained heavy plate from the rolling heat to a desired first temperature with an immediately subsequent targeted heating of the heavy plate to a desired second temperature and an immediately subsequent cooling of the heavy plate to a desired third temperature can be carried out.

Since it is provided according to the invention that immediately after the rolling process has been carried out and thus after the slab has been rolled out to the plate size, a heat treatment is carried out which includes targeted cooling, targeted reheating and, in turn, targeted cooling of the heavy plate in several steps finished heavy plate a uniform temperature field over the width with a resulting uniform structure in the finished heavy plate, so that the heavy plate has a homogeneous mechanical property, ie a homogeneous strength and / or toughness distribution. It is also possible with the method according to the invention and the device according to the invention, both heavy plates in the normalized state, ie To produce steels with high toughness, as well as in the quenched and tempered condition, ie steels with high strength, as well as special steels in the tempered condition, ie steels subjected to a tempering treatment.

In the context of this application, heavy plate is understood to mean a flat product that is defined as heavy plate in accordance with standard EN 10029. The process can be used to produce a wide variety of grades, such as those designated with abbreviations in the standard EN 10025-2: 2004. Heavy plate "as rolled" (abbreviation + AR), but also normalized heavy plate (abbreviation + N) or thermomechanically rolled heavy plate (abbreviation + M) and tempered heavy plate (abbreviation + QT) can be produced. And all of this with one and the same device or system.

An advantageous procedure for producing a normalized heavy plate can, according to an embodiment of the invention, include the measure that the heavy plate is cooled to the first desired temperature, which is below the complete transformation temperature of γ-iron, in the immediately following heat treatment from the rolling heat, after the forming or hot rolling (γ mixed crystal; austenite) in α-iron (α mixed crystal; ferrite), is then heated to the desired second temperature, which is the normal annealing temperature above the complete transformation temperature from γ-iron to α-iron, the Ac ₃ temperature , is in the range of homogeneous austenite, and is finally cooled to ambient temperature as the desired third temperature.

If, on the other hand, a high-strength heavy plate is to be produced, the embodiment of the invention provides the measures that, after the forming or hot rolling, the heavy plate is cooled from the rolling heat to the first desired temperature, which is below the bainite formation temperature, in the immediately following heat treatment Heating is kept at a temperature lying in the range of the bainite transformation as the desired second temperature and is finally cooled to ambient temperature as the desired third temperature.

It is also possible to use the method according to the invention to produce sheets of highest strength. In this case, the invention is characterized in an embodiment by the measures that the heavy plate after the forming or hot rolling in the immediately subsequent heat treatment from the rolling heat is cooled to the first desired temperature, which is below the martensite formation temperature, then by heating to a temperature below the tempering temperature lying next to the transformation temperature of γ-iron into α-iron, the A _c1 temperature, is heated as the desired second temperature and is finally cooled to ambient temperature as the desired third temperature.

In an advantageous and expedient manner, the heat treatment provided comprises cooling to room temperature. The invention therefore also provides that the final cooling to ambient temperature as the desired third temperature is carried out as air cooling.

Forced cooling is useful for cooling the heavy plate from the rolling heat. In an embodiment, the invention therefore also provides that the cooling of the heavy plate from the rolling heat is carried out in the heat treatment immediately following the forming or hot rolling of the heavy plate to the first desired temperature by means of strong water or air cooling.

However, it is also possible to carry out a part or further cooling and / or heating steps on the manufactured or produced heavy plate only then or even then when it has already passed through a straightening system or a straightening device. In this respect, the invention also provides in a further development that part of the heat treatment, in particular comprising further cooling and / or heating steps, is carried out after the heavy plate has passed through a straightening system and before it is stacked.

It is also advantageous and expedient if the heavy plate, after it has been heated to the desired second temperature, is then stacked, which the invention also provides.

The method can be carried out particularly expediently with a heavy plate, so that the invention is further characterized in that, in the several forming steps, a heavy plate with a thickness of more than 8 mm, in particular a thickness of 40 mm-400 mm, and a width of more than 1,200 mm is produced.

To carry out the method according to the invention, the device according to the invention is distinguished in an expedient and advantageous embodiment in that the cooling of the heavy plate to the desired third temperature takes place at least partially outside the heat treatment system.

In order to be able to carry out the method according to the invention for the production of normalized sheet metal advantageously, the device is characterized in that the heat treatment system is designed in such a way that the heavy plate is removed from the rolling heat in an immediately subsequent heat treatment by means of the cooling device after the forming or hot rolling the first desired temperature, which is below the complete transformation temperature from γ-iron (γ-mixed crystal; austenite) to α-iron (a-mixed crystal; ferrite), can be cooled so that the heavy plate is then brought to the desired second temperature by means of the heating device, the normal annealing temperature above the complete transformation temperature from γ-iron to α-iron, the A _c3 temperature, is in the range of homogeneous austenite, can be heated and that the heavy plate can finally be cooled to ambient temperature as the desired third temperature.

In order to be able to use the method according to the invention for producing a high-strength sheet, which has its properties in the bainitic state of the structure, the device according to the invention is further characterized in that the heat treatment system is designed in such a way that the heavy plate after forming or hot rolling in a immediately subsequent heat treatment by means of the cooling device from the rolling heat to the first desired temperature, which is below the bainite formation temperature, can be cooled so that the heavy plate can then be kept by means of the heating device by heating to a temperature in the range of the bainite transformation as the desired second temperature and, that the heavy plate can finally be cooled to ambient temperature as the desired third temperature.

A particularly expedient embodiment of the device for carrying out the method according to the invention for the production of sheet metal with the highest strength is characterized in that the heavy plate after forming or hot rolling in an immediately subsequent heat treatment by means of the cooling device from the rolling heat to the first desired temperature, which is below the martensite formation temperature, can be cooled, that the heavy plate can then be heated by means of the heating device by heating to a tempering temperature below the transformation temperature of γ-iron to α-iron, the A _c1 temperature, as the desired second temperature, and that the heavy plate can finally be cooled to ambient temperature as the desired third temperature.

Advantageously, the device is designed so that it is designed to produce a heavy plate with a thickness of more than 8 mm, in particular a thickness of 40 mm - 400 mm, and a width of more than 1,200 mm in the several forming steps of the rolling plant and is formed, which the invention also provides.

It is also advantageous if the device according to the invention has a straightening system connected downstream of the heating device in the production direction of the heavy plate, which the invention also provides in a further development.

Finally, the invention is also characterized in that it has one or more further heat treatment system (s) downstream of the straightening system in the production direction of the heavy plate, each of which preferably comprises at least one further cooling device and at least one further heating device. This embodiment of the invention makes it possible to carry out heat treatment processes or heat treatment measures on the rolled heavy plate even after straightening the heavy plate produced.

Figur 1

in schematischer Darstellung im oberen Teilbild eine erfindungsgemäße Vorrichtung zur Herstellung von Endlosgrobblech und im unteren Teilbild in schematischer Darstellung den Temperaturverlauf in dem jeweils erzeugten Flachprodukt über die Länge der Vorrichtung und die einzelnen Anlagenteile der Vorrichtung und in

Figur 2

in schematischer Darstellung im oberen Teilbild eine erfindungsgemäße Vorrichtung zur Herstellung von Einzelgrobblech und im unteren Teilbild in schematischer Darstellung den Temperaturverlauf in dem jeweils erzeugten Flachprodukt über die Länge der Vorrichtung und die einzelnen Anlagenteile der Vorrichtung.

The invention is explained in more detail below with reference to the drawing. This shows in

Figure 1

in a schematic representation in the upper part of a device according to the invention for the production of continuous heavy plate and in the lower part in a schematic representation of the temperature profile in the flat product produced over the length of the device and the individual parts of the device and in

Figure 2

in a schematic representation in the upper part of an apparatus according to the invention for the production of individual heavy plate and in the lower part in a schematic representation of the temperature profile in the respective flat product produced over the length of the device and the individual system parts of the device.

The in the form of a production plant of the Figures 1 and 2 The devices shown and designated as a whole by 1 or 1 'differ only in that in the embodiment according to FIG Figure 1 a separating device 2 in the production direction of the heavy plate 4 indicated by the arrow 3 on the output side behind a heat treatment system 5 and in the embodiment according to FIG Figure 2 Is arranged on the input side in front of a heat treatment system 5. The device 1 according to Figure 1 thus enables the production of heavy plates 4 in the endless operation of the production system, since the flat material produced as endless heavy plate is only separated into individual sheet lengths after a heat treatment carried out in the heat treatment system 5 by means of the cutting device 2. In this case, an endless flat material runs through the individual system parts or system equipment of the device 1, which is designed in the form of a production system, to behind the heat treatment system 5. Then the heavy plates 4 cut to individual sheet lengths then pass through a straightening system 6 and are then stacked in the usual way by means of a discharge unit 7. In the embodiment according to Figure 2 the produced endless flat material is already separated into individual sheet lengths before entering the heat treatment system 5, so that heavy plates 4 already divided into individual sheet lengths pass through the heat treatment system 5 and then subsequently through the straightening system 6 and the discharge unit 7. The production of heavy plate in the single plate operation in the device 1 'after Figure 2 is particularly advantageous for the production and processing of tempered sheet metal with very high shear strengths. Heavy plates with lower strengths, which in contrast have lower strength values after passing through the heat treatment system 5, can be used both with the system after the Figure 2 in single sheet operation as well as with the system after the Figure 1 are manufactured in continuous sheet metal production.

In the devices 1 and 1 ′ according to the invention, in direct consecutive processing and / or machining, a steel melt is continuously cast in a casting system 8 designed as a continuous casting system. The resulting cast strand is formed into a slab in the usual way in a master-forming system 9 assigned to the casting system 8, which then after passing through a descaling device 10 in a rolling system 11 forming a forming system from the casting heat in several forming steps to a heavy plate 4 with the desired Heavy plate dimension is rolled. The primary and reshaped heavy plate 4 then passes through the system after Figure 1 the heat treatment system 5 and is then separated to an individual length by means of the separating device 2, which is a transverse separating device. In the device 1 'after Figure 2 the primary and formed product heavy plate 4 is divided into individual sheet lengths by means of the separating device 2, which is also designed as a transverse separating device, before entering the heat treatment system 5 and passed through the heat treatment system 5 as a single sheet. In both devices 1 and 1 ′, the heat treatment system 5 comprises a cooling device 12 and a heating device 13. The heavy plates 4 then pass through the straightening system 6 and are stacked in the discharge unit 7. In a manner not shown, further heat treatment systems 5 can also be arranged between the straightening system 6 and the discharge unit 7 if this should be necessary for qualities that have to be subjected to a special heat treatment. These systems can also each comprise a cooling device and a heating device, so that with these heat treatment systems a combination of increased air cooling or water cooling with subsequent heating to a tempering temperature can also be carried out.

In a manner not shown, the forming plant or rolling plant 11 is equipped in the usual way with devices for adjusting the profile and flatness and with devices for controlling the surface temperature of the rolling stock.

The embodiment of the device 1 according to Figure 1 is suitable for heavy plates with low thicknesses and low shear strengths, where high shear rates can be achieved. With the embodiment of the device 1 'according to Figure 2 Heavy plates with the highest strength values can also be produced, since the cutting in the cutting device 2 in the production direction 3 takes place immediately after leaving the rolling plant 11 from the rolling heat and thus in a high temperature range. At these temperatures, the materials usually processed into heavy plate still have low shear strengths.

With those in the Figures 1 and 2 The devices 1 and 1 'shown and described above can be used to produce heavy plates directly from the casting heat of a continuous caster. There is no cooling to room temperature for more than five minutes. The cast slabs have a thickness of at least 40 mm, the maximum possible slab thickness being limited by the design and the technical conditions of the downstream forming plant and rolling plant 11 and the required or desired thickness of the heavy plate 4 at their outlet. The slab width is not particularly limited but corresponds to the slab widths usually achievable with such systems according to the prior art. The continuous caster can be an arch system, a vertical bending system, a vertical system or a horizontal continuous caster. A thickness reduction of the cast strand by deformation with a liquid core (Liquid Core Reduction) or a slight deformation in the area of final solidification of the cast strand (Dynamic Soft Reduction) is not necessary for the implementation of the method according to the invention, but can be carried out if desired.

The continuously cast cast strand leaves the exit area of the primary forming system 9 with an average temperature of 1,150 ° C to 1,300 ° C and a solid core. Steel qualities or materials that have a strong tendency to form scale are then descaled in the descaling device 10. In the case of high-alloy materials, this process step can be omitted, but with these materials it is advisable to clean the surface after a first forming step in the subsequent forming plant or rolling plant 11. Likewise, materials or steel grades with a higher tendency to form scale are cleaned in the usual way before the first forming step in the forming plant or rolling plant 11, which is usually done with pressurized water or steam, although alternative methods such as cleaning with dry ice or water are mixed with abrasive ingredients are also possible. When descaling with pressurized water, it is advantageous to use rotating systems.

The forming process carried out in the casting system 8 and the primary forming system 9 is then followed by a forming or a forming process in the forming system or rolling system 11, which comprises at least two forming steps with an accumulated logarithmic degree of deformation of more than 0.7. This leads to the cast structure of the slab being converted into a deformed structure, thus achieving a basic toughness of the steel material used and closing any core porosities. Depending on the required final thickness, more than two stands, which carry out at least two forming steps, can be part of the rolling plant 11, so that further forming steps can follow depending on the required final thickness of the heavy plate. The heavy plate 4, which has been reshaped and rolled to the desired plate dimensions after passing through the rolling installation 11, exits the rolling installation 11 at a temperature in the range from 950.degree. C. to 1,100.degree. The heavy plate 4 thus has a temperature at this point which is above a temperature which is optimal for normalizing rolling. In order to still be able to set the desired end properties of the heavy plates 4 or the respective heavy plate 4, the rolling heat is followed immediately by a heat treatment by means of the heat treatment system 5, to which the heavy plate 4 is fed directly after the forming and rolling. For this purpose, the rolling stock, ie the heavy plate 4, remains in the production plant or the device 1 or 1 '.

In the lower images of the Figures 1 and 2 the temperature curves (T) of a flat product produced in the respective device 1 or 1 'over the system length (I) and thus the respective production time (s) are shown. By means of the heat treatment system 5, heavy plates 4, which up to then have passed through the same temperature and cooling process, can be treated differently, so that different qualities and strength values can be produced.

In the temperature and process sequence shown by the solid line 14, a normalized heavy plate 4 is produced. For this purpose, the rolled heavy plate 4 in the heat treatment system 5 is fed to the cooling device 12 and is cooled here to a temperature (T) at which the conversion of γ-iron, ie the γ-mixed crystal or austenite that forms, into α-iron, ie the forming α mixed crystal or ferrite has completely expired. The heavy plate 4 is therefore cooled to a temperature which is below the temperature line 15, which represents the lower end temperature of the conversion range from γ-iron to α-iron. The cooling speeds are measured in such a way that no components of hard structures such as martensite or bainite arise. The heavy plate 4 cooled in this way is then subjected to normal annealing, for which purpose the temperature of the heavy plate 4 is increased above the A _C3 temperature of the respective material and held there for a short time. This takes place by means of the heating device 13, which the heavy plate 4 passes through in the production direction 3 after it has passed through the cooling device 12. In the heating device 13, the desired heating of the heavy plate 4 to a temperature above the A _C3 temperature by means of a conventional roller hearth furnace with open gas firing or radiant tube heating, by means of induction heating or by using what is known as "direct flame inpingement" or a combination of all of these Firing options or heating device options take place. The heating device 13 is designed such that it can be operated in a temperature range from 150.degree. C. to 1,100.degree. The heavy plate 4 produced is then cooled in air to ambient temperature, which is usually carried out after the heavy plate 4 has left the heat treatment installation 5. The method characterized by the course of curve 14 and described above, in particular Heat treatment process, is suitable for all types of sheet metal that should have the quality status + N "normalized".

The course of the dotted cooling curve and heat treatment line 16 shows the temperature course in the production of high-strength metal sheets which have usage properties that are characterized by a bainitic structure. To produce such qualities, the rolled heavy plate 4 is cooled in the heat treatment plant 5 by means of the cooling device 12 to temperatures between the temperature line 17, which characterizes the beginning of the bainite transformation, and the temperature line 18, which characterizes the beginning of the transformation of the structure into a martensite structure. By means of the heating device 13, into which the heavy plate 4 enters after passing through the cooling device 12 in the production direction 3, the heavy plate 4 is then also held within the heat treatment system 5 in this area between the temperature lines 17 and 18, so that the transformation of the structure into a bainite structure continues to run. With this process, in particular heat treatment processes, high-strength and ultra-high-strength heavy plates 4 with good deformation and wear properties and heavy plates 4 with defined contents of retained austenite can be produced. After leaving the heat treatment plant 5, the heavy plate 4 produced by the method or the course of the temperature line 16 also cools in air to ambient temperature.

The other, in the lower partial images of the Figures 1 and 2 The temperature profile curve 19 shown in dashed lines represents the cooling and heating profile of a heavy plate 4 when a heavy plate 4 of the highest strength is to be produced. For this purpose, the rolled heavy plate 4 is cooled relatively strongly in the cooling device 12 of the heat treatment plant 5 to temperatures which are below the temperature line 18 which characterizes the start of the martensite transformation. Thereafter, the heavy plate 4 is tempered in the heating device 13 to a temperature below the A _C1 temperature of the respective material and thus below the temperature limiting the end of the conversion range from γ-iron to α-iron. Subsequently and finally, the heavy plate 4 after leaving the Heat treatment system 5 is again cooled in air to ambient temperature.

In addition to the heat treatment methods described above, other combinations of cooling and heating, i.e. H. of cooling stop temperatures and tempering and annealing temperatures, are carried out in the devices 1 and 1 'according to the invention. For example, it is possible to carry out a solution heat treatment of high-alloy steels or a precipitation hardening of previously quenched heavy plates 4 in the devices 1 and 1 ′. It is also possible here for further, possibly multi-stage treatments of a heavy plate 4 to be carried out in corresponding heat treatment systems between the respective straightening system 6 and the discharge unit 7 that feeds the heavy plates 4 to a stack. In this case, these heat treatment systems also advantageously have a cooling device with a heating device following in the production direction 3.

The method according to the invention and the device according to the invention make it possible to save energy in the production of heavy plates, which otherwise require a subsequent heat treatment not directly integrated into the production process of a respective heavy plate in individual lengths during production according to the methods known from the prior art. With the devices 1 and 1 'according to the invention, heavy plates 4 in the normalized state, for example quality S355J2 + N, as well as tempered heavy plates, for example quality S355 + QT, a steel brand or steel quality, can be produced in one casting sequence. I.e. Heavy plates 4 can be produced from molten steel in a casting sequence in the plant, the chemical composition or basic composition of which is the same, but whose heat treatment is different. In the methods that can be carried out with the devices 1 and 1 'according to the invention, the cooling of the slab produced to room temperature, its reheating before hot rolling and, in addition, the cooling and heating before a heat treatment, are dispensed with compared to the prior art. Another advantage of the inventive devices 1 and 1 'consists in the fact that it is possible to use these heavy plates 4 to produce high-strength steels with a bainitic structure by annealing in the bainite stage.

List of reference symbols

1, 1 '

contraption

2

Heavy plate cutting device

3

Production direction

4th

Heavy plate

5

Heat treatment plant

6

Straightening system

8th

Casting plant

9

Molding line

12th

Cooling device

13

Heater

Claims (17)

1. Method of producing heavy plates (4) from a steel alloy, which are primarily shaped and reshaped to heavy plate size, as endless flat material directly from the casting heat of a continuous casting plant, comprising continuous casting of a steel melt and primary shaping of an obtained cast strip to form a slab with subsequent reshaping or hot-rolling of the slab from the casting heat in a plurality of reshaping steps to a desired heavy plate size and a directly succeeding thermal treatment, which causes selective cooling of the obtained heavy plate (4), of the heavy plate (4), wherein the heavy plate (4) is cut to a desired individual plate length before or after the thermal treatment thereof in production direction (3),
   wherein the heat treatment is carried out in a temperature range of 150° C to 1,100° C as a combination of a selective cooling of the obtained heavy plate (4) from the rolling heat to a desired first temperature with a directly succeeding selective heating of the heavy plate (4) to a desired second temperature and a directly succeeding cooling of the heavy plate (4) to a desired third temperature.
2. Method according to claim 1, characterised in that the heavy plate (4) after the reshaping or hot-rolling is cooled in the directly succeeding thermal treatment from the rolling heat to the first desired temperature, which lies below the complete conversion temperature from γ iron (y mixed crystal; austenite) into a iron (a mixed crystal; ferrite), is subsequently heated to the desired second temperature, which as normal annealing temperature lies above the complete conversion temperature from y iron into a iron, i.e. the A_c3 temperature, in the region of homogenous austenite, and is subsequently cooled to ambient temperature as the desired third temperature.
3. Method according to claim 1, characterised in that the heavy plate (4) after the reshaping or hot-rolling is cooled in the directly succeeding thermal treatment from the rolling heat to the first desired temperature, which lies below the bainite formation temperature, is subsequently held by heating at a temperature, which lies in the region of bainite conversion, as the desired second temperature and is subsequently cooled to ambient temperature as the desired third temperature.
4. Method according to claim 1, characterised in that the heavy plate (4) after the reshaping or hot-rolling is cooled in the directly succeeding thermal treatment from the rolling heat to the first desired temperature, which lies below the martensite formation temperature, is subsequently heated by heating to a tempering temperature, which lies below the conversion temperature of γ iron into a iron, i.e. the A_c1 temperature, as the desired second temperature and is subsequently cooled to ambient temperature as the desired third temperature.
5. Method according to any one of the preceding claims, characterised in that the subsequent cooling to ambient temperature as the desired third temperature is carried out as air cooling.
6. Method according to any one of the preceding claims, characterised in that the cooling of the heavy plate (4) from the rolling heat in the thermal treatment, which directly succeeds the reshaping or hot-rolling of the heavy plate (4), to the first desired temperature is carried out by means of a strong water cooling or air cooling.
7. Method according to any one of the preceding claims, characterised in that a part of the thermal treatment, which particularly comprises further cooling and/or heating steps, is carried out after the heavy plate (4) has run through a straightening installation (6) and before it is stacked.
8. Method according to any one of the preceding claims, characterised in that the heavy plate (4) after heating thereof to the desired second temperature is straightened and subsequently stacked.
9. Method according to any one of the preceding claims, characterised in that a heavy plate (4) with a thickness of more than 8 mm, particularly a thickness of 40 mm to 400 mm, and a width of more than 1,200 mm is produced in the plurality of reshaping steps.
10. Device (1, 1') for carrying out the method according to any one of claims 1 to 9 for producing heavy plates (4) from a steel alloy, which are primarily shaped and reshaped to heavy plate size, as endless flat material directly from the casting heat of a continuous casting plant, wherein the device (1, 1') comprises a plant which for directly consecutive processing and/or working of a steel melt comprises a casting installation (8), in which the steel melt can be continuously cast, a primary shaping installation (9), in which a cast strip cast from the steel melt can be shaped into a slab, a reshaping installation or rolling installation (11), in which the slab from the casting heat can be rolled in several reshaping steps to form a heavy plate (4) with a desired heavy plate size, and a thermal treatment installation (5) as well as a heavy plate separating device (2) arranged in front of or behind the thermal treatment installation (5) in production direction (3),
    wherein the thermal treatment installation (5) comprises at least one cooling device (12) and at least one heating device (13), which are designed so that a thermal treatment can be carried out by these of the heavy plate (4) in the temperature range of 150° C to 1,100° C in the form of a combination of a selective cooling of the obtained heavy plate (4) from the rolling heat to a desired first temperature with a directly succeeding selective heating of the heavy plate (4) to a desired second temperature and a directly succeeding cooling of the heavy plate (4) to a desired third temperature.
11. Device (1, 1') according to claim 10, characterised in that the cooling of the heavy plate (4) to the desired third temperature is carried out at least partly outside the thermal treatment installation (5).
12. Device (1, 1') according to claim 10 or 11, characterised in that the thermal treatment installation (5) is designed so that the heavy plate (4) after the reshaping or hot-rolling can be cooled in a directly succeeding thermal treatment by means of the cooling device (12) from the rolling heat to the first desired temperature, which lies below the complete conversion temperature from y iron (y mixed crystal; austenite) into a iron (a mixed crystal; ferrite), that the heavy plate (4) can be subsequently heated by means of the heating device (13) to the desired second temperature, which as normal annealing temperature lies above the complete conversion temperature from y iron into a iron, i.e. the A_c3 temperature, in the region of homogenous austenite, and that the heavy plate (4) can be subsequently cooled to ambient temperature as the desired third temperature.
13. Device (1, 1') according to claim 10 or 11, characterised in that the thermal treatment installation (5) is designed so that the heavy plate (4) after the reshaping or hot-rolling can be cooled in a directly succeeding thermal treatment by means of the cooling device (12) from the rolling heat to the first desired temperature, which lies below the Bainite formation temperature, that the heavy plate (4) can be subsequently kept by means of the heating device (13), through heating, at a temperature, which lies in the region of the bainite conversion, as the desired second temperature and that the heavy plate (4) can be subsequently cooled to an ambient temperature as the desired third temperature.
14. Device (1, 1') according to claim 10 or 11, characterised in that the thermal treatment installation (5) is designed so that the heavy plate (4) after the reshaping or hot-rolling can be cooled in a directly succeeding thermal treatment by means of the cooling device (12) from the rolling heat to the first desired temperature, which lies below the martensite formation temperature, that the heavy plate (4) can be subsequently heated by means of the heating device (13) through heating to a tempering temperature, which lies below the conversion temperature from γ iron into a iron, i.e. the A_c1 temperature, as the desired second temperature and that the heavy plate (4) can be subsequently cooled to ambient temperature as the desired third temperature.
15. Device (1, 1') according to any one of claims 10 to 14, characterised in that it is designed and constructed for producing a heavy plate (4) with a thickness of more than 8 mm, particularly a thickness of 40 mm to 400 mm and a width of more than 1,200 mm in the plurality of reshaping steps of the rolling installation (11).
16. Device (1, 1') according to any one of claims 10 to 15, characterised in that it comprises a straightening installation (6) downstream of the heating device (13) in production direction (3) of the heavy plate (4).
17. Device (1, 1') according to claim 16, characterised in that it comprises one or more further thermal treatment installations downstream of the straightening installation (6) in production direction (3) of the heavy plate (4), the further thermal treatment installation or installations preferably each comprising at least one further cooling device and at least one further heating device.

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