Process for operating a thermal treatment line for the flexible thermal treatment of metal pre-products

Abstract

The invention relates to a process for operating a thermal treatment line for the flexible thermal treatment of metal pre-products, to a thermal treatment line configured and suitable for carrying out the process, and to a casting-rolling mill and a process for operating a casting-rolling mill having a thermal treatment line according to the invention. In comparison with previous thermal treatment lines and processes for operating said thermal treatment lines, the thermal treatment line according to the invention allows flexible operation. Emissions and production costs in the process are thereby reduced.

Description

[0001] Method for operating a heat treatment line for the flexible heat treatment of metallic precursors

[0002] Area:

[0003] The invention relates to a method for operating a heat treatment line for the flexible heat treatment of metallic precursors, a heat treatment line equipped and suitable for carrying out the method, and a casting and rolling plant and a method for operating a casting and rolling plant comprising a heat treatment line according to the invention.

[0004] State of the art:

[0005] The feedstock in rolling mills is conventionally heated to process temperature in gas-fired reheating furnaces. Typically, the previously formed feedstock, for example, from continuous casting, is cooled on cooling beds and fed to a cold storage area. The cold feedstock is then removed from the storage area and fed to a gas-fired reheating furnace. This process route is referred to as cold charging.

[0006] An alternative to this is hot charging. In hot charging, the preformed feedstock, coming from continuous casting, is fed to the reheating furnace via roller conveyors, cranes, and / or other conveying equipment, with only minimal cooling, and heated to process temperature. For small-format precursor material, so-called billets, continuous induction furnaces are used to raise the temperature to the required rolling temperature.

[0007] Page 1 This heating process using induction furnaces is, however, limited to small square, rectangular or round feed materials and is sometimes used in conjunction with a combustion furnace as hybrid heating.

[0008] The gas-fired preheating furnace has the disadvantage that it causes unwanted emissions such as CO, CO2, NO X etc. When using natural gas, the resource consumption of fossil fuels is added, as are the high operating costs, which are heavily dependent on the gas price. A preheating furnace cannot simply be switched on and off; instead, it must be ramped up and down slowly, which causes additional gas consumption and emissions. Regular ramping up and down reduces the service life of the refractory lining, which in turn leads to unwanted downtime and increases furnace maintenance costs.

[0009] The use of pure induction furnaces for heating to rolling temperature is limited to the small formats mentioned above, and heating from ambient temperature to rolling temperature is not possible or only possible with insufficient throughput (e.g., in so-called shuttle operation). In the event of a malfunction in the rolling mill or the induction furnace, the hot feedstock could no longer be fed to the rolling mill, so it would have to be cooled down before being processed as scrap in the steelworks.

[0010] The heating process is limited to one or a few heating routes and has only limited flexibility to respond to possible disturbances.

[0011] Object of the invention:

[0012] The object of the invention is to further develop a known heat treatment line, a known casting and rolling plant with a heat treatment line and the known methods for operating the two devices in such a way that they can be operated more flexibly and at the same time emissions and production costs are reduced.

[0013] Page 2 Invention:

[0014] The object of the invention is achieved by a method for operating a heat treatment section having the features of claim 1, a heat treatment section having the features of claim 8, a casting and rolling plant comprising a heat treatment section according to the invention having the features of claim 15 and a method for operating a casting and rolling plant having the features of claim 16.

[0015] A flexible heat treatment line comprises at least one loading bed for introducing hot or cold metallic precursors into the heat treatment line; an unloading bed for discharging hot or cold metallic precursors from the heat treatment line; at least one first heating device for heat-treating the metallic precursor; at least one second heating device for heat-treating the metallic precursor, in particular for heating the metallic precursor to a forming temperature; at least three transport devices for transporting and / or temporarily storing the metallic precursor and at least two transfer points for transferring the metallic precursor between the transport devices, wherein the first transport device connects the loading bed at least to the first heating device and the first transfer point.and the second transport device connects the first heating device and the first transfer point to the second heating device and the second transfer point; and the third transport device connects the second heating device and the second transfer point to the unloading bed.;

[0016] In the method for operating a heat treatment line for the flexible heat treatment of metallic precursors, at least the following work steps can be carried out:

[0017] - Introducing hot or cold metallic precursors into the heat treatment section;

[0018] Page 3 - Intermediate storage and / or transport of the metallic pre-product by means of the first transport device from the loading bed to the first transfer point or the first heating device;

[0019] - heat-treating the metallic precursor in the first heating device, wherein after the heat-treatment of the metallic precursor in the first heating device, the metallic precursor is transferred to the second transport device or transferring the metallic precursor from the first transport device to the second transport device;

[0020] - intermediate storage and / or transport of the metallic precursor product by means of the second transport device to the second transfer point or the second heating device;

[0021] - heat-treating the metallic precursor in the second heating device, wherein after the heat-treatment of the metallic precursor in the second heating device, the metallic precursor is transferred to the third transport device or transferring the metallic precursor from the second transport device to the third transport device;

[0022] - Intermediate storage and / or transport of the metallic pre-product by means of the third transport device to the unloading bed;

[0023] - Ejection of hot or cold metallic pre-products from the heat treatment line.

[0024] In a first operating mode, a hot metallic precursor product is transported from the loading bed to the unloading bed by means of the at least three transport devices without heat treatment.

[0025] In a second operating mode, a hot or cold metallic precursor is transported to the second heating device by means of the first two transport devices, and in the second heating device, the metallic precursor undergoes a heat treatment. By means of the third

[0026] Page 4 The metallic pre-product is transported from the second heating device to the unloading bed via the transport device.

[0027] In a third operating mode, a hot or cold metallic precursor is transported to the first heating device by means of the first transport device, and the metallic precursor undergoes heat treatment in the first heating device. The metallic precursor is transported to the second heating device by means of the second transport device, and the metallic precursor undergoes heat treatment in the second heating device. The metallic precursor is transported from the second heating device to the discharge bed by means of the third transport device.

[0028] In a fourth operating mode, a hot or cold metallic precursor is transported to the first heating device by means of the first transport device, and the metallic precursor undergoes heat treatment in the first heating device. The metallic precursor is transported from the first heating device to the discharge bed by means of the second and third transport devices.

[0029] A hot metallic precursor within the meaning of the invention has a temperature above 200°C, preferably above 500°C, even more preferably above the material-specific austenitizing temperature. The temperature is considered to be the average temperature of the metallic precursor. This temperature may differ from the surface temperature of the metallic precursor and can either be derived from empirical values ​​by a person skilled in the art based on the surface temperature or can be determined using appropriate process models.

[0030] A cold metallic precursor has a temperature below 200°C. Typically, the temperature of a cold metallic precursor corresponds to the ambient temperature.

[0031] Page 5 Heat treatment, within the meaning of the invention, includes all process steps that specifically change, maintain, or equalize the temperature of the metallic precursor. This particularly includes process steps that equalize the temperature of the core and surface, or process steps in which the microstructure of the precursor is specifically adjusted.

[0032] A controller selects the operating modes depending on process parameters, in particular the material, material flow, temperature of the metallic precursor on the loading bed, target temperature of the metallic precursor on the unloading bed, energy availability, and / or energy costs. By selecting an operating mode for each metallic precursor, the controller optimizes at least the total energy consumption of the heat treatment line.

[0033] The loading and unloading devices are designed as interfaces according to the invention and are suitable for enabling material exchange with upstream or downstream systems. These interfaces are freely dimensioned, provided the device fulfills its interface function according to the invention. Particularly when transferring a cold metallic precursor into or out of the system, they can interact with external transport means, such as a crane or industrial truck.

[0034] Further advantageous embodiments of the method are listed in the dependent claims 2 to 8. At least one transport device is preferably designed at least partially as a cooling section and / or cooling bed, and the metallic precursor product is preferably cooled in a targeted manner during transport by the transport device.

[0035] The second heating device is preferably designed as an induction furnace and preferably heats the metallic precursor inductively.

[0036] Page 6 The first heating device is preferably designed as a gas-fired furnace, and the metallic precursor is preferably heated by means of an exothermic gas conversion. Gases that can be used include natural gas, hydrogen, biogas, coke oven gas, or mixtures thereof. These can act directly via a burner flame or indirectly via radiant heating tubes.

[0037] A heating device preferably combines different heating methods, more preferably induction with combustion of gas, when heating a metallic precursor.

[0038] A separating device is preferably present in the heat treatment section and the metallic pre-product is divided into smaller units by the separating device.

[0039] A connecting device is preferably present in the heat treatment section and the metallic pre-product is connected to larger units by the connecting device.

[0040] Furthermore, the object of the invention is achieved by a heat treatment line for the flexible heat treatment of metallic precursors with the features of claim 8, which is designed and suitable for carrying out the method according to one of claims 1 to 7.

[0041] Advantageous embodiments of the heat treatment line are listed in the dependent claims 9 to 14. At least one transport device preferably has means, preferably driven rollers, conveyor chains, and / or sliders, for moving the metallic precursor in different directions on the transport bed, preferably longitudinally and transversely to a main conveyor line. According to the invention, the main conveyor line is the line that exhibits the lowest energy loss combined with the highest throughput. Energy loss is the energy required to heat or maintain the precursor to a process temperature.

[0042] Page 7 A connecting device, preferably a driven roller table, is preferably arranged in the heat treatment section for connecting the various loading and unloading devices, transport devices, heating devices and / or separating devices.

[0043] The connecting device is preferably at least partially insulated.

[0044] At least one transport device is preferably designed to be at least partially insulated.

[0045] The heat treatment section preferably has a cooling section and / or a cooling bed for the targeted cooling of a metallic precursor product, and the cooling section and / or the cooling bed is connected to the transport devices, heating devices and / or the loading or unloading bed.

[0046] The object of the invention is further achieved by a casting-rolling plant with the features of claim 15. The casting-rolling plant comprises a series of units for casting and rolling a metallic precursor into a semi-finished or finished product and a heat treatment line for the flexible heat treatment of metallic precursors according to one of claims 8 to 14, wherein the heat treatment line is arranged at least between a casting plant and a first rolling stand. Furthermore, the casting-rolling plant comprises a higher-level control system for controlling the production process steps taking place on the units and the heat treatment line.

[0047] The object of the invention is further achieved by a method for operating a casting and rolling plant with the features of claim 16. In the method for operating a casting and rolling plant according to claim 15, the higher-level control of the casting and rolling plant monitors the material flow through the casting and rolling plant and, in the event of a planned or unplanned deviation from the mass flow through the

[0048] Page 8 Between the casting plant and the mass flow through the rolling mill, the higher-level control system uses the heat treatment section as a buffer for metallic precursors or feeds metallic precursors in or out. Planned or unplanned deviations can result, for example, from a plant malfunction or material / dimension-related differences between the casting speed and the rolling speed.

[0049] The higher-level control system optimizes the material flow through the casting-rolling plant with regard to the availability of cold precursors, furnace emissions, costs, material yield, and / or quality. Furthermore, the higher-level control system optimizes at least the casting speed, the cooling water quantity, and the process parameters of the heat treatment line with regard to the total emissions of the casting-rolling plant and the overall production costs.

[0050] The following two figures are attached to the description of the invention:

[0051] Fig. 1 : Possible process routes of the operating modes of the

[0052] Heat treatment line

[0053] Fig. 2: Material flow through the heat treatment section

[0054] The invention is described in detail below with reference to the figures mentioned in the form of exemplary embodiments. In all figures, identical technical elements are designated by identical reference numerals.

[0055] Figure 1 shows a flowchart of the possible process routes within the heat treatment section. A cold or hot precursor can be fed into the heat treatment section. In the case shown here, a hot precursor originates from a continuous casting plant 2. Alternatively, precursors can also be fed in hot from, for example, an insulation hood or other devices for controlled cooling from the casting process.

[0056] Page 9 The preliminary product is fed to the heat treatment section via the loading bed 3. For this purpose, the loading bed 3 can be connected to the continuous casting 2, for example, via roller conveyors. For cold feed from a cold storage area 1, the loading bed 3 is loaded, for example, by a crane. The loading bed 3 can also have devices that allow preliminary products to be separated or combined.

[0057] The loading bed 3 is connected to a first transport bed 6, so that the precursor product can be transported from the loading bed 3 to a first transfer point 18 or the first gas furnace 7. The first gas furnace 7 can specifically heat-treat the precursor product, for example, heating it and holding it at a temperature at which the precursor product has a substantially austenitic structure.

[0058] The first transfer point 18 connects the first transport bed 6 to the second transport bed 8. This allows the pre-product to reach the second transport bed 8 without passing through the first gas furnace 7. The second transport bed 8 can also receive the pre-product from the first gas furnace 7. The second transport bed 8 is suitable for transporting the pre-product to a second transfer point 19 or for transferring it to a second furnace 9, for example, an induction furnace. In the second furnace 9, the surface of the pre-product can be heated to the target temperature in a short time.

[0059] Both the second transfer point 19 and the second furnace 9 can transfer the pre-product to a third transport bed 10. The third transport bed 10 has an integrated cooling section 11. The cooling section 11 can be used to specifically cool the pre-product. The cooling section 11 is not necessarily in operation during every transport process through the third transport bed 10.

[0060] The third transport bed 10 transfers the pre-product to an unloading bed 12. The unloading bed 12 can also be designed as a direct feed to a first rolling stand 14 or a scale washer 13. Furthermore, by means of the

[0061] Page 10 A pre-product can also be discharged from the unloading bed 12. The unloading bed 12 can also contain means that allow pre-products to be separated or combined.

[0062] Figure 2 shows the schematic structure of an apparatus according to the invention for carrying out the method. A main conveying direction 15 allows the precursors to pass along the shortest route from the continuous casting 2 to a scale washer 13 and the first rolling stand 14, undergoing heat treatment only in the second furnace 9. This enables a continuous casting and rolling process with minimal use of additional energy from a furnace.

[0063] A connecting device 4 is arranged between the loading bed 3 and the first transport bed 6. This connecting device 4 can be designed, for example, as an insulated roller conveyor. This allows the distance between the continuous casting 2 and the separating device 5 to be bridged without significant temperature loss. The separating device 5 can separate the previously continuous strand from the continuous casting 2 into individual sections.

[0064] Parallel to this main conveyor direction 15, another conveyor direction 16 is arranged. This connects the cold storage area 1 with the scale washer 13 and the first rolling stand 14 via the shortest route. This route passes through the first furnace 7 and, if necessary, uses a cooling section 11 arranged in the third conveyor bed 10. In addition to their transport function, the conveyor beds 6, 8, and 10 can each perform a parallel shift between these two conveyor directions 15, 16 or discharge the precursor (17).

[0065] Page 11 Number Description

[0066] 1 cold storage

[0067] 2 continuous casting

[0068] 3 loading bed

[0069] 4 Connecting device

[0070] 5 Separator

[0071] 6 First transport bed

[0072] 7 First heating device / first furnace

[0073] 8 Second transport bed

[0074] 9 Second heating device / second furnace

[0075] 10 Third transport bed

[0076] 11 Cooling section

[0077] 12 unloading bed

[0078] 13 tinder washers

[0079] 14 First rolling stand

[0080] 15 Main conveying direction

[0081] 16 Parallel conveying direction

[0082] 17 discharge to cold storage

[0083] 18 First handover point

[0084] 19 Second handover point

[0085] 20 rolling mill

[0086] Page 12

Claims

Patent claims:

1. Method for operating a heat treatment line for the flexible heat treatment of metallic precursors, wherein the heat treatment line comprises at least - a loading bed (3) for introducing hot or cold metallic precursors into the heat treatment section; - a discharge bed (12) for discharging hot or cold metallic precursors from the heat treatment section; - at least one first heating device (7) for heat-treating the metallic precursor; - at least one second heating device (9) for heat-treating the metallic precursor, in particular for heating it to a forming temperature; - at least three transport devices (6, 8, 10) for transporting and / or temporarily storing the metallic precursor and at least two transfer points (18, 19) for transferring the metallic precursor between the transport devices (6, 8, 10), wherein i. the first transport device (6) connects the loading bed (3) at least to the first heating device (7) and the first transfer point (18); and ii. the second transport device (8) connects the first heating device (7) and the first transfer point (18) to the second heating device (9) and the second transfer point (19); and iii. the third transport device (10) connects the second heating device (9) and the second transfer point (19) to the unloading bed (12), and Page 13 at least the following steps can be carried out: - Introducing hot or cold metallic precursors into the heat treatment section; - intermediate storage and / or transport of the metallic precursor product by means of the first transport device (6) from the loading bed (3) to the first transfer point (18) or the first heating device (7); - heat-treating the metallic precursor in the first heating device (7), wherein after the heat-treatment of the metallic precursor in the first heating device (7), the metallic precursor is transferred to the second transport device (8) or transferring the metallic precursor from the first transport device (6) to the second transport device (8); - intermediate storage and / or transport of the metallic precursor product by means of the second transport device (8) to the second transfer point (19) or the second heating device (9); - heat-treating the metallic precursor in the second heating device (9), wherein after the heat treatment of the metallic precursor in the second heating device (9), the metallic precursor is transferred to the third transport device (10) or transferring the metallic precursor from the second transport device (8) to the third transport device (10); - intermediate storage and / or transport of the metallic precursor product by means of the third transport device (10) to the unloading bed (12); - discharging hot or cold metallic precursors from the heat treatment section; characterized in that - in a first operating mode, a hot metallic precursor is transported by means of the at least three transport devices (6, 8, 10) from Page 14 loading bed (3) to the unloading bed (12) without heat treatment; or - in a second operating mode, a hot or cold metallic precursor is transported to the second heating device by means of the first two transport devices, the metallic precursor undergoes a heat treatment in the second heating device, and the metallic precursor is transported from the second heating device to the discharge bed by means of the third transport device; or - in a third operating mode, a hot or cold metallic Pre-product is transported by means of the first transport device (6) to the first heating device (7), in the first Heating device (7) the metallic precursor a undergoes heat treatment; by means of the second transport device (8), the metallic precursor is transported to the second heating device (9), in the second heating device (9) the metallic precursor undergoes heat treatment and by means of the third transport device (10) the metallic precursor is transported from the second heating device (9) to the unloading bed (12); or - in a fourth operating mode, a hot or cold metallic Pre-product is transported by means of the first transport device (6) to the first heating device (7), in the first Heating device (7) the metallic precursor a undergoes heat treatment and the metallic precursor is transported from the first heating device (7) to the unloading bed (12) by means of the second and third transport device (8, 10); and Page 15 - a controller that selects the operating modes depending on process parameters, in particular material, material flow, temperature of the metallic precursor on the loading bed (3), target temperature of the metallic precursor on the unloading bed (12), energy availability, energy costs; and - the control by selecting an operating mode for each metallic precursor which at least optimizes the total energy consumption of the process. Process according to claim 1, characterized in that - at least one transport device (6, 8, 10) is at least partially designed as a cooling section (11) and / or cooling bed; and - the metallic precursor is cooled in a targeted manner during transport by the transport device (6, 8, 10). Process according to one of the preceding claims, characterized in that - the second heating device (9) is designed as an induction furnace; and - the metallic precursor is heated inductively. Process according to one of the preceding claims, characterized in that - the first heating device (7) is designed as a gas-operated furnace; and - the metallic precursor is heated by means of an exothermic gas conversion. Process according to one of the preceding claims, characterized in that Page 16 a heating device (6, 7) various Heating methods, preferably induction with gas combustion, combined to heat a metallic precursor.

6. Method according to one of the preceding claims, characterized in that - a separating device (5) is provided in the heat treatment section; and - the metallic precursor is cut into smaller units.

7. Method according to one of the preceding claims, characterized in that - a connecting device (6) is present in the heat treatment section; and - the metallic pre-product is joined to form larger units by the joining device.

8. Heat treatment line for the flexible heat treatment of metallic Precursors, arranged and suitable for carrying out the method according to one of claims 1 to 7.

9. Heat treatment line according to claim 8, characterized in that at least one transport device (6, 8, 10) has means, preferably driven rollers, conveyor chains and / or sliders, for moving the metallic precursor product in different directions on the transport bed, preferably longitudinally and transversely to a main conveyor line (15).

10. Heat treatment section according to one of claims 8 or 9, Page 17 characterized in that a connecting device (4), preferably a driven roller table, is arranged in the heat treatment section for connecting the various loading and unloading beds, transport devices, heating device and / or separating devices. Heat treatment section according to claim 10, characterized in that the connecting device (4) is designed to be at least partially insulated. Heat treatment section according to one of claims 8 to 11, characterized in that at least one transport device (6, 8, 10) is designed to be at least partially insulated. Heat treatment section according to one of claims 8 to 12, characterized in that - the heat treatment section has a, preferably integrated, cooling section (11) and / or a, preferably integrated, cooling bed for the targeted cooling of a metallic precursor; and - the cooling section (11) and / or the cooling bed is connected to the transport devices (6, 8, 10), heating devices (7, 9) and / or the loading or unloading bed (3, 12). Heat treatment section according to one of claims 8 to 13, characterized in that the transport device (6, 8, 10) has a loading and / or unloading device. Page 18 - a series of units for casting and rolling a metallic precursor into a semi-finished or finished product and a heat treatment line for the flexible heat treatment of metallic precursors according to one of claims 8 to 14, wherein - the heat treatment section is arranged at least between a casting plant (2) and a first rolling stand (14); and - a higher-level control system for controlling the production process steps on the units and the heat treatment line. Method for operating a casting-rolling plant according to claim 15, characterized in that - the higher-level control system of the casting-rolling plant (2) monitors the material flow through the casting-rolling plant; and - in the event of a planned or unplanned deviation from the mass flow through the casting plant (2) to the mass flow through the rolling mill, the higher-level control system uses the heat treatment section as an intermediate storage facility for metallic precursors or feeds metallic precursors in or out, whereby the higher-level control system optimises the material flow through the casting-rolling plant with regard to the availability of cold precursors, furnace emissions, costs, material yield and / or quality; and - the higher-level control system optimizes at least the casting speed, the cooling water quantity and the process parameters of the heat treatment section with regard to the total emissions of the casting and rolling plant and the total production costs. Page 19

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