THERMAL TREATMENT DEVICE, METHOD AND USE

Description

The invention relates to a thermal treatment device, to a method and to a use.

In the prior art, a slab is heated using a furnace before being hot formed, in particular hot rolled. The slab can first be heated to a temperature of greater than or equal to the temperature of the carbonitride precipitation and/or the dissolution of nitrite precipitations of the steel composition of the slab, in particular to an average temperature of the slab, which, depending on the alloy composition, is between 950° C. and 1,280° C.

The object of the invention is that of providing an improvement over or an alternative to the prior art.

According to a first aspect of the invention, the object is achieved by a thermal treatment device for heating and treating a metal product comprising:

• • a heating device having a nominal power density into the metal product of greater than or equal to 5·10⁵ W/m², preferably greater than or equal to 1·10⁶ W/m², more preferably greater than or equal to 5·10⁶ W/m² and particularly preferably greater than or equal to 2·10⁷ W/m², in particular a first heating device;
  • a homogenizing device, in particular a first homogenizing device, the homogenizing device being designed to reduce a temperature difference between a surface temperature of the metal product and a core temperature of the metal product to less than or equal to 50° C., preferably to less than or equal to 20° C. and particularly preferably to less than or equal to 10° C.;
  • a treatment device for treating the metal product; and
  • a conveying device for conveying the metal product from the heating device toward the treatment device.

In this regard, the following is explained conceptually:

First of all, it should be expressly pointed out that in the context of the present patent application indefinite articles and numerical indications such as “one”, “two”, etc. are as a rule to be understood as “at least” indications, i.e. as “at least one . . . ” , “at least two . . . ” , etc., unless it is expressly clear from the respective context or it is obvious or technically imperative to a person skilled in the art that only “exactly one . . . ” , “exactly two . . . ” , etc. can be meant there.

In the context of the present patent application, the expression “in particular” should always be understood as introducing an optional, preferred feature. The expression should not be understood to mean “specifically” or “namely.”

A “metal product” is understood to mean a semi-finished product which consists of at least one metal or which has a metal content of greater than or equal to 90 wt %, preferably a metal content of greater than or equal to 95 wt % and particularly preferably a metal content of greater than or equal to 98 wt %.

The metal product has a thickness, a width and a length, wherein the metal product can alternatively also have an endless length. The metal product further comprises a surface and a core region, wherein a temperature, in particular an averaged temperature, of a metal product at the surface may differ from a temperature in the core region. Accordingly, a surface temperature of the metal product may deviate from a core temperature of the metal product, in particular due to a thermal flow from the surroundings of the metal product into the metal product and/or due to a thermal flow from the metal product to the surroundings of the metal product.

A metal product can be a billet, with a billet having a thickness that corresponds substantially to the width of the billet. In other words, a billet has a substantially square cross-sectional area. Preferably, the thickness of a billet is greater than or equal to 0.9 widths of the billet and less than or equal to 1.1 widths of the billet, preferably the thickness of a billet is greater than or equal to 0.95 widths of the billet and less than or equal to 1.05 widths of the billet and particularly preferably the thickness of a billet is greater than or equal to 0.975 widths of the billet and less than or equal to 1.025 widths of the billet.

A metal product can be a bloom. Preferably, the width of a bloom is less than or equal to 1.4 thicknesses of the bloom, preferably less than or equal to 1.3 thicknesses of the bloom and particularly preferably less than or equal to 1.2 thicknesses of the bloom. Furthermore preferably, the width of a bloom is greater than or equal to 1.1 thicknesses of the bloom, preferably greater than or equal to 1.15 thicknesses of the bloom and particularly preferably greater than or equal to 1.2 thicknesses of the bloom.

A metal product can be a slab. Preferably, the width of a slab is less than or equal to 35 thicknesses of the slab, preferably less than or equal to 30 thicknesses of the slab and particularly preferably less than or equal to 20 thicknesses of the slab. Furthermore preferably, the width of a slab is greater than or equal to 1.5 thicknesses of the slab, preferably greater than or equal to 1.6 thicknesses of the slab and particularly preferably greater than or equal to 2 thicknesses of the slab.

A slab is also referred to as a thick slab if it has a thickness of greater than or equal to 150 mm, preferably a thickness of greater than or equal to 180 mm and particularly preferably a thickness of greater than or equal to 220 mm.

A slab is also referred to as a thin slab if it has a thickness of less than or equal to 150 mm, preferably a thickness of less than or equal to 135 mm and particularly preferably a thickness of less than or equal to 120 mm.

Preferably, a slab has a length of greater than or equal to 1.2 m, preferably greater than or equal to 1.5 m, further preferably greater than or equal to 1.8 m and particularly preferably greater than or equal to 2 m. Furthermore preferably, a slab has a length of greater than or equal to 4 m, preferably greater than or equal to 5 m, further preferably greater than or equal to 10 m and particularly preferably greater than or equal to 12 m.

A metal product can be a sheet plate. Preferably, a sheet plate has a thickness of less than or equal to 100 mm, preferably a thickness of less than or equal to 80 mm and particularly preferably a thickness of less than or equal to 50 mm. Furthermore preferably, the width of a sheet plate is greater than or equal to 30 thicknesses of the sheet plate, preferably greater than or equal to 50 thicknesses of the sheet plate and particularly preferably greater than or equal to 100 thicknesses of the sheet plate.

A “heating device”, in particular a first heating device and/or a second heating device, is understood to mean a device which is designed to increase the average temperature in a metal product, in particular starting from an averaged starting temperature to an averaged final temperature. A heating device may be in primary operative connection to one or more surfaces of the metal product. Preferably, a heating device acts primarily on the surface of the top side and the surface of the bottom side of the metal product.

A “power density” is understood to mean a surface power density with unit W/m², wherein the power density refers to the distribution of a power of a heating device over a surface of the metal product, in particular the surface of the top side of the metal product and the surface of the bottom side of the metal product. A “nominal power density” is understood to mean the maximum achievable power density of a heating device during designated operation. A heating device having a nominal power density of greater than or equal to 5·10⁵ W/m² is therefore designed to deliver a power of greater than or equal to 5·10⁵ W to one square meter of the surface of the metal product. In some cases where the edges of the metal product are specifically heated separately, the surface of the metal product relevant for determining the power density may also extend to the side surface of the metal product extending beyond the top side and bottom side of the metal product and heated by an edge heater.

Preferably, the heating device has a nominal power density of greater than or equal to 9·10⁵ W/m², further preferably of greater than or equal to 1·10⁶ W/m², preferably of greater than or equal to 2·10⁶ W/m² and particularly preferably of greater than or equal to 3.5·10⁶ W/m². Furthermore preferably, the heating device has a nominal power density of greater than or equal to 7·10⁶ W/m², preferably of greater than or equal to 8.5·10⁶ W/m² and particularly preferably of greater than or equal to 1·10⁷ W/m².

The actual power density introduced into the metal product by the heating device can be limited, in particular by controlling and/or regulating the heating device, if there is a risk of exceeding a surface temperature of 1300° C., or even exceeding a surface temperature of 1380° C., depending on the alloy composition. This can prevent melting of the surface of the metal product.

An “inductor” is understood to mean a device designed to increase the temperature of a metal product using a magnetic field. An inductor has at least one inductor coil which, in operative connection with at least one capacitor, forms an oscillating circuit. Said oscillating circuit can be supplied with electrical energy using a power supply device. The power supply device can comprise an inverter, which preferably is or can be connected to a DC intermediate circuit.

An inductor can have a nominal power density of greater than or equal to 1·10⁶ W/m², preferably of greater than or equal to 8.5·10⁶ W/m² and particularly preferably of greater than or equal to 1·10⁷W/m².

The use of an inductor as a heating device has the advantage that the nominal power density is independent of the ambient temperature of the metal product. This is particularly advantageous for heating the metal product at high averaged final temperatures.

Preferably, an inductor has two inductor coils. They can be designed to generate a transverse field and/or a longitudinal field with respect to the metal product.

During designated operation, an inductor has, starting from a surface of the metal product to be heated, which surface faces an inductor coil, a heat development layer which extends substantially over a penetration depth into the metal product to be heated. The penetration depth of the heat development layer also depends on the frequency of an oscillating circuit with which an inductor coil is excited. However, the penetration depth of the heat development layer also depends on the temperature of the metal product in the region of the heat development layer.

If the temperature of the product to be heated in the region of the heat development layer is lower than the Curie temperature for the material of the metal product, the heat development layer can have a penetration depth of less than or equal to 4 mm, preferably less than or equal to 3 mm and particularly preferably less than or equal to 2 mm.

If the temperature of the product to be heated in the region of the heat development layer is greater than or equal to the Curie temperature, the heat development layer can have a penetration depth of less than or equal to 25 mm, preferably less than or equal to 20 mm and particularly preferably less than or equal to 15 mm. Furthermore, at a temperature of the product to be heated in the region of the heat development layer of greater than or equal to the Curie temperature, the heat development layer can have a penetration depth of greater than or equal to 5 mm, preferably greater than or equal to 7 mm and particularly preferably greater than or equal to 10 mm.

A heating device may comprise a plurality of inductors, in particular two inductors, three inductors, four inductors, five inductors or more than five inductors. This plurality of inductors can be arranged in a common inductor housing. Alternatively, the plurality of inductors may have separate inductor housings, which may be arranged in a sequence relative to one another in the designated conveying direction of the metal product.

A “DFI module” is understood to mean a heating device designed to use a direct flame impingement (DFI) process to heat the metal product. The DFI process is also known as oxy-fuel process. In the DFI process, at least one oxyacetylene flame or one oxygen flame heats the metal product directly, in particular by direct action on the metal product. The nominal power density achievable with the DFI process can be up to ten times higher than that of conventional fuel-fired furnaces. A nominal power density of a DFI module can reach 1·10⁶W/m².

A heating device may comprise a plurality of DFI modules, in particular two DFI modules, three DFI modules, four DFI modules, five DFI modules or more than five DFI modules.

This plurality of DFI modules can be arranged in a common housing. Alternatively, the plurality of DFI modules may have separate housings which are arranged in a sequence relative to one another in the designated conveying direction of the metal product.

A “homogenizing device”, in particular a first homogenizing device and/or a second homogenizing device, is understood to mean a device which is designed to homogenize the temperature profile in a metal product. In other words, a homogenizing device is designed to reduce temperature differences in a metal product.

Heating and/or cooling a metal product can result in large temperature differences within the metal product. When a metal product cools, a core of the metal product cools more slowly than its surface. When heating a metal product, it can also happen that the surface of the metal product heats up faster than its core. Furthermore, temperature differences can also arise from a treatment process of the metal product and/or from a casting process.

When casting a slab using a continuous casting plant, a casting speed at which a cast strand leaves the continuous casting plant can have a value of less than or equal to 0.14 m/s, in particular a value of less than or equal to 0.1 m/s. Accordingly, periods of 2 minutes are usual when casting a slab having a length of 12 m. During this time, a slab head that left the continuous casting plant first cools down faster than a slab end. A temperature difference of a metal product is therefore not to be understood exclusively as a temperature distribution that varies only over the cross-section of the metal product, but rather it can also vary over a longitudinal elongation of the metal product.

Homogenization of a temperature of a metal product can be understood as a reduction of an absolute temperature difference of the metal product when it enters the homogenizing device until the metal product exits the homogenizing device.

If a slab is reheated with an inductor immediately after leaving a continuous casting plant, an absolute temperature difference, in particular between a core of the slab and the surface of the slab, can be greater than or equal to 100° C. In some cases, a temperature difference can also be greater than or equal to 300° C. and, in case of very intensive heating using an inductor, even greater than or equal to 650° C.

If a slab is heated intensively with an inductor starting from room temperature, the temperature difference can be greater than or equal to 1,000° C., and in particular cases greater than or equal to 1,300° C.

A homogenizing device can be designed to reduce the temperature difference of a metal product up to the point when it exits the homogenizing device to less than or equal to 100° C., preferably to less than or equal to 60° C., further preferably to less than or equal to 30° C. and particularly preferably to less than or equal to 15° C.

A homogenizing device can further be designed so that a metal product can leave the homogenizing device at an averaged temperature of greater than or equal to 950° C., preferably at an averaged temperature of greater than or equal to 1,000° C. and particularly preferably at an averaged temperature of greater than or equal to 1,050° C.

A homogenizing device can expediently comprise an active means for heating a metal product, in particular at least one gas burner, preferably in combination with at least one corresponding jet pipe. A homogenizing device can be designed, inter alia, as a walking beam furnace. A homogenizing device can be designed as a roller furnace. A homogenizing device can be designed as a pusher furnace. A nominal power density of a gas burner can reach 1·10⁵ W/m².

Alternatively, a homogenizing device can have at least one heat radiator as an active means for heating a metal product, in particular at least one heat radiator operated with electrical energy, wherein a heat radiator is designed to emit heat radiation to a metal product. An electrically operated heat radiator can achieve a nominal power density of 4·10⁴ W/m².

According to an expedient embodiment, a homogenizing furnace can have a holding furnace as a passive means for homogenizing the temperature distribution of the metal product, which is designed to thermally insulate the metal product from its surroundings.

Particularly preferably in terms of energy, a homogenizing device can comprise only one passive means for homogenizing the temperature distribution of the metal product, in particular an insulation device, preferably a heat hood. In this way, the thermal energy with which the metal product enters the homogenizing device can be used to even out the temperature distribution in the metal product.

A “treatment device” is understood to mean a device with which a metal product can be treated.

According to a further variant, a treatment device can be designed as a pressure forming device, wherein a metal product is formed by compressive forces. A pressure forming device can be a rolling device. Advantageously, a metal product with a starting thickness of greater than or equal to 5 mm is pressure-formed, in particular rolled, preferably with a starting thickness of greater than or equal to 10 mm and particularly preferably with a starting thickness of greater than or equal to 30 mm.

A tensile forming device can also be used as a further variant of a treatment device, wherein the tensile forming device is designed to deform the metal product by tensile forces. A tensile forming device can be a stretching device, in particular a stretching device for improving the flatness of the metal product. Advantageously, a metal product with a starting thickness of less than or equal to 12 mm is pressure-formed, in particular stretched, preferably with a starting thickness of less than or equal to 10 mm and particularly preferably with a starting thickness of less than or equal to 5 mm.

A “conveying device” is understood to mean any system which is designed to transport a metal product, in particular to transport slabs. A conveying device preferably has a roller table, in particular an electrically driven roller table.

A conveying device can have several different segments, in particular a first segment between a heating device and a homogenizing device and a second segment between a homogenizing device and a treatment device or a final-stage heating device. It shall be understood that a conveying device can also have additional segments between plant components of the thermal treatment device. However, this does not explicitly exclude the possibility that a thermal treatment device may have a plurality of conveying devices, in particular a first conveying device between a heating device and a homogenizing device and a second conveying device between a homogenizing device and a treatment device or a final-stage heating device.

Furthermore, a conveying device can be designed to convey a metal product from a homogenizing device to a heating device, in particular from a homogenizing device which is operatively connected to a continuous casting machine and which can be designed to at least partially receive the cast strand, to a heating device, in particular a first heating device.

A “thermal treatment device” is understood to mean a device and/or a system which is designed to heat a metal product from an average starting temperature of a metal product upon reaching a heating device to an average final temperature of a metal product upon leaving a heating device and/or a homogenizing device and to treat, in particular roll, the metal product in a treatment device, wherein the thermal treatment device has at least one conveying device which is designed to convey the metal product toward the treatment device.

The thermal treatment device can be designed so that a metal product has an average temperature of greater than or equal to 1,050° C. upon reaching the treatment device, preferably of greater than or equal to 1,100° C. and particularly preferably of greater than or equal to 1,200° C. Furthermore advantageously, the thermal treatment device can be designed so that a metal product has an average temperature of greater than or equal to 950° C. upon reaching the treatment device, preferably of greater than or equal to 1,050° C. and particularly preferably of greater than or equal to 1,250° C.

The thermal treatment device can be designed so that a metal product, upon reaching a heating device, in particular the first heating device, has an average temperature of less than or equal to 250° C., preferably of less than or equal to 200° C. and particularly preferably of less than or equal to 150° C. Furthermore advantageously, the thermal treatment device can be designed so that a metal product, upon reaching a heating device, in particular the first heating device, has an average temperature of less than or equal to 100° C., preferably of less than or equal to 50° C. and particularly preferably of less than or equal to 35° C. In that case, one could also say that the metal product is being introduced as a cold charge into the thermal treatment device.

The thermal treatment device can be expediently designed so that a metal product, upon reaching a heating device, in particular the first heating device, has an average temperature of less than or equal to 650° C., preferably of less than or equal to 550° C. and particularly preferably of less than or equal to 450° C. In that case, one could also say that the metal product is being introduced as a hot charge into the thermal treatment device. Furthermore, the thermal treatment device for a hot charge can be designed so that a metal product, upon reaching a heating device, in particular the first heating device, has an average temperature of greater than or equal to 200° C., preferably of greater than or equal to 250° C. and particularly preferably of greater than or equal to 300° C.

According to a particularly preferred embodiment, the thermal treatment device can be designed so that a metal product, upon reaching a heating device, in particular the first heating device, has an average temperature of greater than or equal to 600° C., preferably of greater than or equal to 700° C. and particularly preferably of greater than or equal to 800° C. If the starting temperature of the metal product is in one of the above ranges, it could also be said that the metal product is being introduced as a direct charge.

Particularly preferably, the thermal treatment device can be designed to combine the above-mentioned “cold charge” and/or “hot charge” and/or “direct charge” scenarios. It is conceivable, among other things, that the thermal treatment device is arranged corresponding to one or more casting machines and/or to a hot storage facility for a metal product and/or to a cold storage facility for a metal product. The thermal treatment device can be used alternately or in any sequence with a metal product of different temperature. A thermal treatment device can be designed to operate in any sequence with metal products at different temperatures.

The average temperature of a metal product can be understood to mean a volume-averaged average temperature of the metal product.

In particular, improving the energetic process efficiency of a thermal treatment device and/or reducing the carbon dioxide emissions released by a thermal treatment device by using low-carbon energy sources can advantageously be achieved by means of a heating device having a nominal power density into the metal product of greater than or equal to 5·10⁵W/m² , preferably of greater than or equal to 1·10⁶W/m².

Heating devices having such a high nominal power density can advantageously be implemented for energy efficiency with a compact length and thus a short throughput time, since the power required for the temperature increase can be transferred to the metal product in a comparatively compact design. This can have a particularly beneficial effect on the energy efficiency of the process, in particular by reducing heat losses. Moreover, the thermal treatment device proposed herein can be designed more compactly overall.

However, heating devices having a correspondingly high nominal power density, in particular an inductor and/or a DFI module, physically require a limited direct penetration depth of the heat across the surface of the metal product. This means that a temperature above the melting point of the material can be reached on the surface of the metal product, while the core temperature of the metal product can still be at room temperature. Over time, temperature differences can even out, but heat is released into the environment of the metal product.

A combination of a heating device having a high nominal power density and a homogenizing device is proposed herein, wherein the homogenizing device is designed to reduce temperature differences in the metal product which have been caused by heating using the heating device having a high nominal power density.

The combination of heating device and homogenizing device can advantageously enable energy-efficient and/or low-carbon heating of a metal product to a high average temperature with small local temperature differences. The metal product tempered in this way can advantageously be treated, in particular rolled, by the subsequent treatment device.

In the course of modernizing existing thermal treatment devices having a heating device with a nominal power density of less than or equal to 1·10⁵ W/m² it is also planned to continue using an existing heating device as a homogenizing device and to advantageously install upstream thereof a modern heating device having a nominal power density of greater than or equal to 5·10⁵W/m², preferably greater than or equal to 1·10⁶W/m². This allows energy efficiency to be improved and/or carbon dioxide emissions to be reduced by moderate intervention in the existing thermal treatment device.

According to an optional embodiment, the metal product has a thickness of greater than or equal to 50 mm, preferably a thickness of greater than or equal to 150 mm and particularly preferably a thickness of greater than or equal to 200 mm.

In particular, the combination of heating device and homogenizing device can have a particularly advantageous effect on the treatment of the metal product from a thickness of the metal product of greater than or equal to 20 mm, preferably from a thickness of greater than or equal to 35 mm, further preferably from a thickness of greater than or equal to 50 mm and particularly preferably from a thickness of greater than or equal to 75 mm. Furthermore advantageously, the combination of heating device and homogenizing device proposed herein can have a particularly advantageous effect on the treatment of the metal product from a thickness of the metal product of greater than or equal to 100 mm, preferably from a thickness of greater than or equal to 135 mm, further preferably from a thickness of greater than or equal to 180 mm and particularly preferably from a thickness of greater than or equal to 250 mm.

It shall be understood that the above-specified values for the thickness of the metal product may interact with the penetration depth of the heating device having high nominal power density and thus the need to homogenize temperature differences in the metal product.

Optionally, the metal product has a ratio of a width of the metal product to a thickness of the metal product of greater than or equal to 1.1, preferably of greater than or equal to 1.5, further preferably of greater than or equal to 5 and particularly preferably of greater than or equal to 10.

Furthermore advantageously, the metal product has a ratio of a width of the metal product to a thickness of the metal product of greater than or equal to 1.25, preferably of greater than or equal to 2.5, further preferably of greater than or equal to 8 and particularly preferably of greater than or equal to 16.

Heating devices having a comparatively high nominal power density benefit from a high ratio of the width of the metal product to the thickness of the metal product. In particular, with larger width-to-thickness ratios, a higher proportion of a cross-sectional area of the metal product can be achieved via the direct penetration depth of the heat from the heating device having high nominal power density, whereby the effort for homogenizing temperature differences in the metal product can be reduced.

In contrast, heating devices having low nominal power density, in particular classic furnaces having a gas burner, can benefit from a higher ratio of the surface of the metal product to the volume of the metal product, which can be achieved by a particularly small ratio of width to thickness of the metal product.

According to an expedient embodiment, the metal product has a ratio of a circumference of the metal product to a cross-sectional area of the metal product of less than or equal to 3.25 1/mm, preferably of less than or equal to 2.5 1/mm, further preferably of less than or equal to 2.3 1/mm and particularly preferably of less than or equal to 2.1 1/mm.

According to a further expedient embodiment, the metal product has a ratio of a circumference of the metal product to a cross-sectional area of the metal product of less than or equal to 3 1/mm, preferably of less than or equal to 2.75 1/mm, further preferably of less than or equal to 2.4 1/mm and particularly preferably of less than or equal to 2.2 1/mm.

It has been shown that a small ratio of circumference to cross-sectional area is advantageous for tempering the metal product with a heating device having a nominal power density of greater than or equal to 5·10⁵ W/m², preferably of greater than or equal to 1·10⁶ W/m², so that an energy-efficient and/or low-carbon dioxide emission thermal treatment of the metal product can be achieved with the thermal treatment device proposed herein.

Optionally, the conveying device is designed to convey the metal product from the heating device toward the homogenizing device.

The conveying device is expediently designed to convey the metal product from the homogenizing device toward the treatment device.

According to a preferred embodiment, the thermal treatment device has at least two heating devices and at least two homogenizing devices, in particular a first heating device, a first homogenizing device, a second heating device and a second homogenizing device, wherein the conveying device is designed to convey the metal product from the first heating device toward the first homogenizing device, from the first homogenizing device toward the second heating device, from the second heating device toward the second homogenizing device and from the second homogenizing device toward the treatment device.

Furthermore preferably, the thermal treatment device has at least three heating devices and at least three homogenizing devices, in particular a first heating device, a first homogenizing device, a second heating device, a second homogenizing device, a third heating device and a third homogenizing device, wherein the conveying device is designed to convey the metal product from the first heating device toward the first homogenizing device, from the first homogenizing device toward the second heating device, from the second heating device toward the second homogenizing device, from the second homogenizing device toward the third heating device, from the third heating device toward the third homogenizing device and from the third homogenizing device toward the treatment device.

Optionally, the three heating devices and the three homogenizing devices can be arranged in blocks one behind the other and connected to each other by conveying devices.

It shall be understood that a heating device having a nominal power density of greater than or equal to 5·10⁵ W/m², preferably greater than or equal to 1·10⁶ W/m² , can only transfer so much power to the metal product that an edge of the metal product and/or a surface of the metal product is just not yet melted. In particular in case of larger absolute thicknesses of the product to be heated and/or high final temperatures and/or low temperatures when charging the metal product into the first heating device, the heating required for the treatment device may not be achieved with a first heating device without intermediate homogenization of the temperature differences.

The heating of the metal product required for the treatment device can be advantageously achieved with the cascade of heating devices and homogenizing devices proposed herein.

Furthermore preferably, the thermal treatment device has a final-stage heating device, in particular a final-stage heating device having a nominal power density into the metal product of greater than or equal to 5·10⁵ W/m², preferably greater than or equal to 1·10⁶ W/m², preferably greater than or equal to 5·10⁶ W/m² and particularly preferably greater than or equal to 2·10⁷W/m², wherein the conveying device is designed to convey the metal product from a homogenizing device toward the final-stage heating device and from the final-stage heating device toward the treatment device.

In this regard, the following is explained conceptually:

A “final-stage heating device” is understood to mean a heating device having a nominal power density of greater than or equal to 5·10⁵ W/m², preferably greater than or equal to 1·10⁶ W/m², which is located directly in front of the treatment device.

Some materials of metal products are preferably treated, in particular rolled, at a higher average temperature. To increase flexibility for different materials, it is therefore proposed that the thermal treatment device can have a final-stage heating device which only reheats the materials with a specifically increased optimal treatment temperature and does not have to influence other materials, but can do so in advantageous cases.

To increase energy efficiency and/or reduce carbon dioxide emissions, it is therefore proposed to design the final-stage heating device with a nominal power density of greater than or equal to 5·10⁵ W/m² into the metal product, preferably greater than or equal to 1·10⁶ W/m², in particular as a DFI module and/or as an inductor, since these designs can be used as needed without any preheating time.

Preferably, the final-stage heating device has a nominal power density of greater than or equal to 9·10⁵ W/m², preferably of greater than or equal to 2·10⁶ W/m² and particularly preferably of greater than or equal to 3.5·10⁶ W/m². Furthermore preferably, the final-stage heating device has a nominal power density of greater than or equal to 7·10⁶ W/m², preferably of greater than or equal to 8.5·10⁶ W/m² and particularly preferably of greater than or equal to 1·10⁷ W/m².

A final-stage heating device may comprise a plurality of inductors, in particular two inductors, three inductors, four inductors, five inductors or more than five inductors. A final-stage heating device may comprise a plurality of DFI modules, in particular two DFI modules, three DFI modules, four DFI modules, five DFI modules or more than five DFI modules.

Furthermore, it is proposed that a final-stage heating device be arranged after the treatment device. In this way, the temperature of the metal product can be increased again after treatment. One option here is to treat it by descaling.

The final-stage heating device is expediently designed to heat the metal product to an average temperature of greater than or equal to 1,125° C., preferably of greater than or equal to 1,175° C. and particularly preferably of greater than or equal to 1,225° C.

According to a particularly preferred embodiment, a heating device, in particular the first heating device and/or the second heating device and/or the final-stage heating device, consists of an inductor and/or comprises at least one inductor.

Preferably, a heating device, in particular the first heating device and/or the second heating device and/or the final-stage heating device, consists of a DFI module and/or comprises at least one DFI module.

According to an expedient embodiment, a heating device, in particular the first heating device and/or the second heating device and/or the final-stage heating device, has a longitudinal elongation of less than or equal to 1 length of the metal product, preferably of less than or equal to 0.7 lengths of the metal product and particularly preferably of less than or equal to 0.5 lengths of the metal product.

Furthermore expediently, a heating device has a longitudinal elongation of less than or equal to 0.85 lengths of the metal product, preferably of less than or equal to 0.6 lengths of the metal product and particularly preferably of less than or equal to 0.4 lengths of the metal product.

Particularly preferably, a heating device, in particular the first heating device and/or the second heating device and/or the final-stage heating device, has a longitudinal elongation of greater than or equal to 0.2 lengths of the metal product, preferably of greater than or equal to 0.3 lengths of the metal product and particularly preferably of greater than or equal to 0.4 lengths of the metal product.

Tests have shown that particularly economical heating of the metal product can be achieved with the values described above for the longitudinal elongation of the heating device.

According to a particularly preferred embodiment, a homogenizing device, in particular the first homogenizing device and/or the second homogenizing device, has a longitudinal elongation in the conveying direction of less than or equal to 2.7 lengths of the metal product, preferably of less than or equal to 2.6 lengths of the metal product and particularly preferably of less than or equal to 2.5 lengths of the metal product.

Tests have shown that particularly economical homogenization of the metal product can be achieved with the values described above for the longitudinal elongation of the homogenizing device.

Expediently, a homogenizing device, in particular the first homogenizing device and/or the second homogenizing device consists of an insulating holding furnace and/or comprises at least one insulating holding furnace.

Optionally, a homogenizing device, in particular the first homogenizing device and/or the second homogenizing device, has at least one gas burner, in particular at least one gas burner in a jet pipe.

Furthermore optionally, a homogenizing device, in particular the first homogenizing device and/or the second homogenizing device, has at least one electric heat radiator.

According to an optional embodiment, the treatment device comprises a pressure forming device for pressure forming the metal product, in particular a rolling device for rolling the metal product.

According to a further optional embodiment, the treatment device comprises a tensile forming device for tensile forming the metal product, in particular a stretching device for stretch-straightening the metal product.

According to a second aspect of the invention, the object is achieved by a method for heating and treating a metal product with a thermal treatment device according to the first aspect of the invention, wherein a metal product having an average temperature of less than or equal to 700° C., preferably having an average temperature of less than or equal to 800° C. and particularly preferably having an average temperature of less than or equal to 950° C., is fed to the thermal treatment device.

In particular, a mixed use of the thermal treatment device can be advantageously established in this way, wherein a cold charge and/or a hot charge and/or a direct charge can advantageously be combined with one another in a thermal treatment device.

Expediently, a metal product having an average temperature of less than or equal to 400° C., preferably having an average temperature of less than or equal to 500° C. and particularly preferably having an average temperature of less than or equal to 600° C., is fed to the thermal treatment device.

With the above temperature values, a hot charge process can be used advantageously and energy consumption and emissions can be reduced.

Optionally, a metal product having an average temperature of less than or equal to 100° C., preferably having an average temperature of less than or equal to 200° C. and particularly preferably having an average temperature of less than or equal to 300° C., is fed to the thermal treatment device.

In this way, the thermal treatment device can also be advantageously used for cold charge.

Particularly expediently, a metal product having an average temperature of greater than or equal to 600° C., preferably having an average temperature of greater than or equal to 700° C. and particularly preferably having an average temperature of greater than or equal to 800° C., is fed to the thermal treatment device.

This makes it possible to advantageously implement a particularly energy-efficient direct charge process, in particular directly from a continuous casting plant, so that carbon dioxide emissions can be reduced.

It should be expressly noted that the subject matter of the second aspect can advantageously be combined with the subject matter of the preceding aspect of the invention, both individually or cumulatively in any combination.

According to a third aspect of the invention, the object is achieved by using a thermal treatment device according to the first aspect of the invention and/or by applying a method according to the second aspect of the invention.

It shall be understood that the advantages of a thermal treatment device according to the first aspect of the invention and/or of a method according to the second aspect of the invention extend directly to using a thermal treatment device according to the first aspect of the invention and/or a method according to the second aspect of the invention.

It should be expressly noted that the subject matter of the third aspect can advantageously be combined with the subject-matter of the preceding aspects of the invention, both individually and cumulatively in any combination.

Further advantages, details, and features of the invention can be found below in the described exemplary embodiments. In the figures, in detail:

FIG. 1 schematically shows a sectional view of a metal product with an inhomogeneous temperature distribution in the cross section;

FIG. 2 schematically shows a first embodiment of a thermal treatment device and an associated temperature profile of the average temperature of a metal product in the thermal treatment device;

FIG. 3 schematically shows a second embodiment of a thermal treatment device and an associated temperature profile of the average temperature of a metal product in the thermal treatment device; and

FIG. 4 schematically shows a third embodiment of a thermal treatment device and an associated temperature profile of the average temperature of a metal product in the thermal treatment device.

In the following description, the same reference signs denote the same components or features; in the interest of avoiding repetition, a description of a component made with reference to one drawing also applies to the other drawings. Furthermore, individual features that have been described in connection with one embodiment can also be used separately in other embodiments.

FIG. 1 schematically shows a sectional view of a metal product 10 with an inhomogeneous temperature profile along a cross section of the metal product 10. The core temperature T_K of the metal product can be greater or smaller than the surface temperature T_O of the metal product. The temperature profile of the core temperature can range from a plurality of temperatures T_i to the surface temperature T_O.

A first embodiment of a thermal treatment device 20 according to FIG. 2 consists substantially of a heating device 30, a homogenizing device 40, a conveying device 60, and a treatment device 50. The conveying device 60 can convey the metal product 10 from the heating device 30 toward the treatment device 50. In the first embodiment described herein, the metal product 10 is transferred directly from the heating device 30 to the homogenizing device 40. Optionally, the first embodiment described herein could also be modified such that the metal product 10 is conveyed from the heating device 30 to the homogenizing device 40 by means of a further conveying device (not shown).

An average temperature of a metal product 10 in the thermal treatment device 20 is increased in the region of the heating device 30 from an average starting temperature T_St of the metal product 10 to a first average temperature T1 of the metal product 10 and homogenized in the region of the homogenizing device 40. The metal product 10 is conveyed by the conveying device 60 to the treatment device 50, in particular with the first average temperature T1.

A second embodiment of a thermal treatment device 20 according to FIG. 3 consists substantially of a first heating device 31, a first homogenizing device 41, a second heating device 32, a second homogenizing device 42, a final-stage heating device 70, a conveying device 60 and a treatment device 50. The thermal treatment device can have any number of further nth heating devices 33 and nth homogenizing devices 43 after the second homogenizing device 42 and before the final-stage heating device 70, wherein an nth heating device 33 is always followed by an nth homogenizing device 43. The conveying device 60 can convey the metal product 10 from the first heating device 31 toward the treatment device 50.

In the second embodiment described herein, the metal product 10 is transferred directly from the first heating device 31 to the first homogenizing device 41. Furthermore, the metal product 10 is transferred from the first homogenizing device 41 directly to the second heating device 32 and from there directly to the second homogenizing device 42. The metal product is transferred at least indirectly from the second homogenizing device 42 to the nth heating device 33 and from there directly to the nth homogenizing device 43 and subsequently directly to the final-stage heating device 70. It shall be understood that the second embodiment described herein can also be modified in such a way that a conveying device (not shown) may be arranged between a heating device (30, 31, 32, 33, 70) and a homogenizing device (40, 41, 42, 43), which is designed to forward the metal product 10 to the respective subsequent device (41, 32, 42, 33, 43, 70). Due to the dwell time of the metal product 10 on the conveying device, a thermal flow can be released from the metal product onto a roller of a conveying device and/or the surroundings of the metal product 10. However, this does not lead to complete homogenization; rather, the metal product can cool down in the edge regions. Homogenization of the average temperature therefore takes place in the downstream homogenizing device (40, 41, 42, 43).

An average temperature of a metal product 10 in the thermal treatment device 20 is increased in the region of the first heating device 31 from an average starting temperature T_St of the metal product 10 to a first average temperature T1 of the metal product 10 and homogenized in the region of the first homogenizing device 41. The average temperature of the metal product 10 is increased in the region of the second heating device 32 from a first average temperature T1 to a second average temperature T2 of the metal product 10 and homogenized by a second homogenizing device 42. The average temperature of the metal product 10 is increased from a second average temperature T2 in the region of the final-stage heating device 70 to an average final temperature T_End. The metal product 10 is conveyed by the conveying device 60 to the treatment device 50, in particular with the average final temperature T_End.

Alternatively, the average temperature of the metal product 10 can be increased from the second average temperature T2 in the region of an nth heating device 33 to an nth average temperature T_n of the metal product 10 and homogenized in the region of an nth homogenizing device 43. The average temperature of the metal product 10 can be increased from an nth average temperature T_n in the region of the final-stage heating device 70 to an average final temperature T_End. The metal product 10 is conveyed by the conveying device 60 to the treatment device 50, in particular with the average final temperature T_End.

A third embodiment of a thermal treatment device 20 according to FIG. 4 consists substantially of a first heating device 31, a second heating device 32, a first conveying device 61, a first homogenizing device 41, a third heating device 33, a first thermal treatment device 50, a further conveying device 60, a final-stage heating device 70, a second treatment device 51 and a conveying device 60. The thermal treatment devices 50, 51 can have any number of further nth heating devices (not shown) and nth homogenizing devices (not shown), wherein a first thermal treatment device 50 is always preceded by at least one heating device 31, 32, 33, at least one homogenizing device 41, and a first conveying device 61. The first conveying device 61 can convey the metal product 10 from the first heating device 31 toward the treatment device 50. It can be divided into several individual length segments arranged between the devices.

LIST OF REFERENCE SIGNS

• • 10 Metal product
  • 20 Thermal treatment device
  • 30 Heating device
  • 31 First heating device
  • 32 Second heating device
  • 33 nth heating device; third heating device
  • 40 Homogenization device
  • 41 First homogenization device
  • 42 Second homogenization device
  • 43 nth homogenizing device
  • 50 Treatment device
  • 51 Treatment device
  • 60 Conveying device
  • 61 First conveying device
  • 65 Conveying length
  • 70 Final-stage heating device
  • T_K Core temperature of the metal product
  • T_O Surface temperature of the metal product
  • T_i Internal temperature at point i of the metal product
  • T_St Average starting temperature of a metal product
  • T1 First average temperature of a metal product
  • T2 Second average temperature of a metal product
  • T3 Third average temperature of a metal product
  • T_n nth average temperature of a metal product
  • T_end Average final temperature of a metal product