Heat treatment lines for hot strip

Abstract

The present application relates to an annealing installation (1), in particular an annealing furnace, for the oxidation-free heat treatment of a hot-rolled steel strip (3) intended for producing an electrical steel strip and / or a stainless steel strip, a process line (2) for the continuous pickling and oxidation-free annealing of a hot-rolled steel strip (3) and a method for the continuous pickling and oxidation-free annealing of a hot-rolled steel strip (3).

Description

[Technical field]

[0001] The present invention relates to an annealing installation, in particular an annealing furnace, for the oxidation-free heat treatment of hot-rolled steel strip intended for the production of electrical steel strip and / or stainless steel strip, a process line for the continuous pickling and oxidation-free annealing of hot-rolled steel strip and a method for the continuous pickling and oxidation-free annealing of hot-rolled steel strip. [Background technology]

[0002] Electrical steel strip is one of the most important soft magnetic materials for cores and usually consists of an iron-silicon alloy. Currently, a distinction is made between two different electrical steel strip grades: the so-called non-oriented electrical steel strip is magnetizable uniformly in all directions and is mainly used in rotating electrical machines; the so-called oriented electrical steel strip, on the other hand, has an easy direction of magnetization and is generally used in power transformers, distribution transformers and high-quality small transformers.

[0003] The production of electrical steel strip, as disclosed for example in US20170283903, is usually carried out by casting a special metallic steel compound with, in weight percent, 2.5-4.0% Si, 0.010-0.100% C, max. 0.150% Mn, max. 0.065% Al and max. 0.0150% N, respectively, and optionally 0.010-0.3% Cu, max. 0.060% S, max. 0.100% P, max. 0.2% As, Sn, Sb, Te and Bi, respectively, with the balance being iron and unavoidable impurities, into an initial material such as a slab, thin slab or cast piece, which is then directly hot rolled into a so-called hot strip. The hot rolled steel strip is then subjected to an annealing treatment and, in a separate step, cold rolled into a so-called cold strip. To achieve advantageous magnetic properties, the cold strip is subsequently annealed to recrystallize in a continuous annealing and coating line and then coated with an insulating coating.

[0004] For the annealing treatment of hot-rolled strip, a scale layer present on the surface is usually tolerated, since further oxidation in the open-fired annealing furnace and thus further scale build-up (so-called annealing scale) is unavoidable. Therefore, in the prior art, the hot-rolled strip is first subjected to an annealing treatment and then to a descaling process in order to provide a scale-free hot strip for the subsequent cold rolling process. The combination of annealing and pickling is known as the so-called annealing and pickling line. Using English, such a line is also called the so-called "APL" (annealing and pickling line).

[0005] The descaling process begins with a mechanical pre-descaling which is then supplemented by a chemical pickling process. Mechanical descaling is usually performed by a sandblasting device, whereby the surface of the hot strip is roughened in such a way that the resulting roughness remains for the most part after cold rolling and further affects the magnetic properties of oriented or non-oriented electrical steel strip.

[0006] Annealing furnaces known from the prior art consist of a heating section as well as a holding section followed by a cooling section with an air-cooling section and a water-cooling section. In the heating section, the hot strip is directly heated via gas burners with fossil fuels, which results in high CO2 emissions. Such an annealing apparatus is known, for example, from US Pat. No. 5,472,528, which also teaches the use of an induction device arranged either upstream or downstream of at least one conventional heating device in order to improve the inertia of the conventional heating device. In the holding section, the hot strip is electrically heated in a nitrogen atmosphere. In the subsequent air-cooling section, the hot strip is first subjected to slow cooling and then to intensive water cooling. During slow cooling, the hot strip is further oxidized. The scale particles formed here are discharged by the exhaust, which must be filtered at great expense. During intensive water cooling, additional scale also forms, which must be removed from the cooling water, usually via a scale settling tank.

[0007] Thus, there remains a desire among professionals to improve such processes. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] US Patent Publication No. 20170283903 [Patent Document 2] U.S. Pat. No. 5,472,528 Summary of the Invention [Problem to be solved by the invention]

[0009] Against this background, the problem underlying the present invention is to provide an apparatus for the oxidation-free heat treatment of hot-rolled steel strip intended for producing electrical and / or stainless steel strip, which allows improved process control compared to the prior art.

[0010] Furthermore, the problem underlying the present invention is to provide an improved method compared to the prior art for the continuous pickling and oxidation-free annealing of hot-rolled steel strip intended for producing electrical and / or stainless steel strip. [Means for solving the problem]

[0011] According to the invention the problem is solved by an annealing installation, in particular an annealing furnace, for the oxidation-free heat treatment of hot-rolled steel strip having the features of claim 1, a process line for continuous pickling and oxidation-free annealing of hot-rolled steel strip having the features of claim 9 and a method for continuous pickling and oxidation-free annealing of hot-rolled steel strip having the features of claim 10.

[0012] The annealing apparatus according to the invention, in particular an annealing furnace, for the oxidation-free heat treatment of hot-rolled steel strip intended for producing electrical and / or stainless steel strip has a closed furnace chamber, which comprises a heating section, a holding section optionally following the heating section, and a cooling section optionally following the holding section, the heating section comprising a plurality of inductors connected in series, the cooling section comprising a cooling device, via which a reducing shielding gas can be introduced into the cooling section in order to cool the hot-rolled steel strip.

[0013] A treatment line according to the invention for continuous pickling and oxidation-free annealing of hot-rolled steel strip intended for producing electrical steel strip and / or stainless steel strip comprises a pre-treatment device capable of pickling the hot-rolled steel strip and an annealing device according to the invention arranged downstream of the pre-treatment device in the direction of strip travel.

[0014] According to the method according to the invention for continuous pickling and oxidation-free annealing of a hot-rolled steel strip intended for producing an electrical steel strip and / or a stainless steel strip, the hot-rolled steel strip, optionally after an unwinding step, is first fed to a pre-treatment device, pickled in the pre-treatment device and then fed as pickled steel strip to an annealing device, where it is first induction heated to the annealing temperature via a number of inductors connected in series under a reducing shielding gas atmosphere, thereafter annealed and then quenched and / or cooled under the use of a reducing shielding gas.

[0015] As steel strip for manufacturing electrical steel strip, preferably a steel is used which comprises, in weight percent, typically 2.5-4.0% Si, 0.010-0.100% C, max 0.150% Mn, max 0.065% Al and max 0.0150% N, and optionally 0.010-0.3% Cu, max 0.060% S, max 0.100% P, max 0.2% As, Sn, Sb, Te and Bi, respectively, with the balance being Fe and unavoidable impurities.

[0016] The annealing apparatus according to the invention allows a complete heat treatment under a reducing shielding gas atmosphere, which acts reductively on the hot strip used and thus allows an oxidation-free strip surface. Via the inductor, very high power densities can be achieved, so that the heating section can be significantly shortened compared to annealing furnaces known from the prior art. Conventional gas burners or radiant heating elements are therefore not provided. This likewise allows an economical operation of the annealing apparatus under a reducing shielding gas atmosphere. Furthermore, a reducing shielding gas, for example hydrogen, provides an improved convective heat transfer compared to atmospheric air, so that high cooling rates, for example up to 50 K / s, can be achieved in the cooling section. These either act advantageously, for example for non-oriented electrical steel strip, in order to obtain a shorter overall length of the annealing apparatus according to the invention, or act particularly advantageously for quality reasons, for example for achieving intensive cooling of grain-oriented electrical steel strip or stainless steel.

[0017] In this respect, the annealing device according to the invention allows a pickling treatment to be carried out before the heat treatment, which has a particularly advantageous effect on the heat treatment process of the hot strip, since the use of scale breakers and / or sandblasting devices can be omitted. This allows shorter pickling times to be selected, which in turn increases the yield. In addition, the surface roughness can be reduced, which improves the magnetic properties of the electrical steel strip.

[0018] Another advantage of the present invention is that a) Avoided CO2 emissions; b) Oxidation-free heat treatment; c) shorter overall length of the annealing equipment; d) Avoidance of open cooling water; e) Reduction of dust emissions It is.

[0019] Further advantageous configurations of the invention are set forth in the dependent claims. The features recited individually in the dependent claims can be combined with one another in a technically meaningful manner to define further configurations of the invention. Furthermore, the features recited in the claims will be specified and explained in more detail in this specification, which will show further preferred configurations of the invention.

[0020] It is pointed out here that the annealing plant according to the invention is not intended for or suitable for hot strip galvanizing plants (also called pickling and galvanizing lines (PGL)).

[0021] In this respect, it is advantageously provided that the annealing device is of horizontal design, and it is furthermore preferably provided that the cooling zone and / or the exit gate of the annealing device do not reach the coating device.

[0022] In an advantageous implementation variant of the method, the pickled steel strip is first heated in a heating section of an annealing plant to an annealing temperature of at least 800° C. at a heating rate of at least 20 K / s, more preferably at least 25 K / s, even more preferably at least 30 K / s, with the proviso that the heating rate must not exceed a maximum value of 60 K / s, more preferably 55 K / s, most preferably 50 K / s.

[0023] Here, it is advantageously provided that the pickled and thus completely descaled steel strip is heated in two separate stages in the heating section. In this respect, the annealing apparatus preferably has a first stage with a number of longitudinal inductors connected in series, in which the pickled steel strip is first heated to a temperature of at least 650° C. In contrast, the annealing apparatus has a second stage with a number of transverse inductors connected in series, by means of which the steel strip is subsequently heated to an annealing temperature of at least 800° C.

[0024] The number of inductors in the annealing apparatus, each capable of achieving a heating rate of typically up to 100 K / (s*mm strip thickness), depends on the total power required and can therefore vary between 1 and 20.

[0025] In order to obtain a good coupling of the magnetic field, the passage gap for the strip must not be too large, so that in the heating section the passage gap advantageously has a vertical extent of less than 300 mm, more preferably a vertical extent of less than 250 mm, most preferably a vertical extent of less than 200 mm.

[0026] In order to keep heat losses in the heating section as low as possible, another advantageous implementation variant provides for the passage gap to be limited by an insulating layer arranged below and above the steel strip passage level and provided with an airtight cover on the outside.

[0027] If the hot rolled steel strip is further intended for producing oriented as well as non-oriented electrical steel strip, the steel strip is preferably annealed in a holding zone following the heating zone at a temperature in the range of 800-1200°C for at least 60 seconds.

[0028] The annealing apparatus can thus comprise a holding section in a preferred embodiment variant, which particularly preferably comprises three individual holding section stages. The first holding section stage follows directly after the heating section, the second holding section stage is connected immediately before the cooling section. Both holding section stages have on the one hand conventional electric heating elements, which can be arranged below the steel strip passing level. Furthermore, both holding section stages contain conventional airflow cooling nozzles, which can be arranged, for example, above the steel strip passing level. The third holding section stage is arranged in the holding section between the first and second holding section stages and, in contrast to these, does not comprise cooling nozzles but only electric heating elements.

[0029] After the annealing treatment, the steel strip is quenched and / or cooled under reducing shielding gas. In an advantageous embodiment of the method, the annealed steel strip can be cooled in a cooling section of the annealing apparatus, which directly follows the heating section, at an initial cooling rate of at least 15 K / s. The annealing apparatus in this embodiment therefore only has a heating section and a cooling section.

[0030] In another advantageous embodiment of the method, the annealed steel sheet can be cooled in a cooling section of the annealing apparatus which directly follows the holding section, the formal cooling rate being at least 40 K / s.

[0031] For this purpose, the cooling device preferably has at least one nozzle, through which the reducing shielding gas can be sprayed onto the strip. However, it is more preferably provided that the cooling device has at least one nozzle arranged above the strip passing level and at least one nozzle arranged below the strip passing level. The at least one nozzle can be designed as a slit nozzle extending transversely to the conveying direction of the strip in the cooling section. In another advantageous embodiment, the cooling device can have at least one distributor arranged above and below the strip passing level, which distributor has a plurality of hole nozzles. Each nozzle is preferably designed in such a way that an outlet velocity of the reducing shielding gas of 50 to 150 m / s is achievable.

[0032] It is furthermore advantageously provided that the cooling device has at least one blower, via which the reducing shielding gas can be supplied to the at least one nozzle and, if necessary, to the at least one distributor, and the cooling device can furthermore have at least one heat exchanger, via which the reducing shielding gas blown into the cooling section can be cooled.

[0033] In a particularly advantageous embodiment variant, it is provided here that the cooling device comprises a circulation system in which at least one nozzle and / or at least one distributor, at least one blower and at least one heat exchanger are connected to one another, and particularly preferably, whereby the reducing shielding gas is blown onto the cooling section, particularly preferably onto the steel strip, via at least one blower and at least one nozzle and / or via a nozzle and at least one distributor, sucked out again via the at least one blower and cooled by means of at least one heat exchanger.

[0034] Such cooling devices can provide a heat flux of 500 to 800 W / m2 to the steel strip surface when using reducing shielding gas. 2 This allows for convective heat transfer of K, making high cooling rates of >40 K / s achievable.

[0035] As reducing shielding gas preferably a hydrogen-rich gas is used having a hydrogen content of at least 30% by volume, more preferably at least 50% by volume, even more preferably at least 75% by volume.

[0036] The supply of the reducing shielding gas into the furnace chamber can in principle take place at different points in the annealing apparatus. However, it is preferably provided that the reducing shielding gas is supplied to the holding section in order to achieve the maximum reducing effect at the highest strip temperature. In another preferred embodiment, the reducing shielding gas can be supplied to the cooling section in order to increase the heat transfer.

[0037] The present invention and technical environment are described in detail below with the drawings. It is pointed out that the present invention should not be limited by the illustrated embodiments. In particular, unless otherwise specified, it is also possible to extract partial aspects of the matters described in the drawings and combine them with other components and findings from this specification and / or the drawings. In particular, it is pointed out that the drawings, and in particular the illustrated size ratios, are only approximate. The same reference numerals indicate the same objects, so that descriptions from other drawings can be used supplementarily if necessary. [Brief description of the drawings]

[0038] [Figure 1] One embodiment of the annealing device according to the invention [Diagram 2] One embodiment of the processing line according to the invention [Diagram 3] Heat treatment temperature profile for oriented and non-oriented electrical steel strip [Figure 4] Heat treatment temperature profile for stainless steel strip DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] Figure 1 shows one embodiment variant of an annealing installation 1 according to the invention, which is intended for use in a process line 2 for the continuous pickling and oxidation-free annealing of a hot-rolled steel strip 3 (see Figure 2). Such a steel strip 3 is used for producing electrical and / or stainless steel strip and is usually fed to a cold rolling process after carrying out an annealing or heat treatment.

[0040] The annealing apparatus 1 shown in this embodiment variant has a closed furnace chamber 4 which is operated under a reducing shielding gas atmosphere. The supply of the reducing shielding gas into the furnace chamber 4 can take place at different points, as exemplarily indicated with the reference number 100.

[0041] The furnace chamber 4 has an entrance gate 5 through which the hot rolled strip 3 enters the furnace chamber 4 and an exit gate 6 through which the heat treated strip 3 leaves the furnace chamber 4 again. Adjacent to the entrance gate 5 the annealing device 1 firstly comprises a heating section 7 which comprises a number of inductors 8, 9, 10, 11 connected in series, the inductors 8, 9 constituting a first stage 12 and both inductors 10, 11 constituting a second stage 13 of the heating section 7.

[0042] Here, the inductors 8, 9 are formed as longitudinal inductors and therefore have corresponding longitudinal inductor coils 14. In contrast, the inductors 10, 11 are formed as transverse inductors with corresponding transverse inductor coils 15. Furthermore, each inductor 8, 9, 10, 11 has a respective insulation layer 17, 18 arranged below and above the strip passage level 16, which insulation layer has an airtight cover 19 on the outside. As can be seen from the figure, in each inductor 8, 9, 10, 11, respectively, a passage gap 20 is formed by the insulation layers 17, 18, which passage gap has a vertical extent of 150 mm in this embodiment variant in order to obtain a good coupling of the magnetic fields. Furthermore, roller tracks 21 are arranged between the individual inductors 8, 9, 10, 11, by means of which the strip sagging of the strip 3 is limited. In this embodiment variant, the roller track 21 also has one insulation layer 17, 18 arranged below and above the steel strip passing level 16, respectively, which insulation layer is sealed against the atmosphere on the outside via an airtight cover 19.

[0043] The annealing apparatus 1 further comprises a holding section 22 following the heating section 7, which comprises three holding section stages 23, 24, 25, each of which comprises an electric heating element 26 arranged below the strip passage level 16. In the embodiment shown here, the two outer holding section stages 23, 25 additionally comprise conventional airflow cooling nozzles 27 arranged above the strip passage level 16. As can also be seen from FIG. 1, the entire holding section 22 also comprises an insulation layer 17, 18 respectively arranged below and above the strip passage level 16, which insulation layer is sealed against the atmosphere on the outside via a gas-tight cover 19. The holding section 22 is further followed by a cooling section 28 with a cooling device 29, which in this embodiment comprises two separate cooling stages 30, 31, via which the annealed strip 3 can be intensively cooled or quenched by a reducing shielding gas, for example hydrogen. For this purpose, each cooling stage 30, 31 comprises a distributor 32, 33 respectively arranged below and above the strip passing level 16, which distributor comprises a number of nozzles (not shown) oriented in the direction of the strip passing level 16. Here, each distributor 32, 33 is fluidly connected via a gas line to a blower 34, 35, e.g. a fan, arranged outside the furnace chamber 4, via which reducing shielding gas can be supplied to the distributor. Furthermore, each of the two separate cooling stages 30, 31 has a heat exchanger 36, 37, also arranged outside the furnace chamber 4, via which the reducing shielding gas blown into the respective cooling stage 30, 31 of the cooling section 28 can be cooled. For this purpose, each cooling stage 30, 31 is fluidly connected via a separate gas line to the respective blower 34, 35.

[0044] 2 exemplarily shows one embodiment variant of a treatment line 2 according to the invention with a pre-treatment device 38 and an annealing device 1 arranged downstream of the pre-treatment device in the strip travel direction. In detail, the treatment line 2 shown has a first reeling device 39, through which a hot strip coil 40 is first unwound. The unwound hot-rolled strip 3 is fed to a first separating device 41 in order to produce a clean edge for the subsequent welding process. After welding in a welding device 42, the strip 3 is fed to a trimming device 43, in which the strip edge of the strip 3 is trimmed. After passing through an inlet store 44, the strip 3 enters the pre-treatment device 38, in which it is pickled, washed and then dried. The pickled steel strip 3 is then fed to the annealing plant 1 where it is first heated to the annealing temperature under a reducing shielding gas atmosphere, annealed, then intensively cooled or quenched, and then recoiled via the outlet store 45.

[0045] FIG. 3 further shows the heat treatment temperature profile for one hot-rolled steel strip 3 intended for the production of grain-oriented and non-oriented electrical steel strips 48, 49 in each case.

[0046] The hot-rolled steel strip 3 intended for the production of the grain-oriented electrical steel strip 48 has, in this example, a width of 1280 mm and a strip thickness of 2300 μm, and is subjected to a non-oxidation heat treatment in the annealing apparatus 1 at a strip speed of 75 m / min. On the other hand, the hot-rolled steel strip 3 intended for the production of the non-oriented electrical steel strip 49 has a width of 1280 mm and a strip thickness of 2600 μm, and is subjected to a non-oxidation heat treatment in the annealing apparatus 1 at a strip speed of 80 m / min.

[0047] For this purpose, each hot-rolled strip 3, previously pickled in a pretreatment device 38, is guided via an inlet gate 5 into a furnace chamber 4, which is provided with a reducing shielding gas atmosphere. A hydrogen-rich gas with a hydrogen content of 75% by volume is used as the reducing shielding gas. Each hot-rolled strip first passes through a heating section 7, where it is heated to a Curie temperature of 700° C. by means of two longitudinal field inductors 8, 9. Above the Curie temperature, the strip typically loses its paramagnetic properties and is therefore heated by two transverse field inductors 10, 11 until it reaches the respective annealing temperature of 1120° C. (grain-oriented magnetic strip 48) or 1050° C. (non-grain-oriented magnetic strip 49).

[0048] The steel strips 3, each heated to the annealing temperature, then pass through a holding section 22, where they are annealed according to a specific heat treatment profile. As can be seen from Figure 3, the grain-oriented electrical steel strip 48 is slowly cooled in the first holding section stage 23 to a temperature of 900°C and then passes through the second and third holding sections 24, 25 at 900°C. On the other hand, the non-oriented electrical steel strip 49 first passes through both holding sections 23, 24 at a preset annealing temperature of 1050°C and is only slowly cooled in the third holding section stage 25 to a temperature of 800°C.

[0049] The respective annealed steel strip 3 then passes through the cooling section 28 where it is quenched by a reducing shielding gas. Here, the grain-oriented electrical steel strip 48 is cooled at an initial cooling rate of 40 K / s to a temperature of 420° C. and then at a cooling rate of less than 20 K / s to an outlet temperature of 130° C., whereas the non-oriented electrical steel strip 49 is cooled constantly at a cooling rate of 25 K / s to an outlet temperature of 130° C.

[0050] FIG. 4 further illustrates a heat treatment temperature profile for hot rolled steel strip 3 intended to produce stainless steel strip 50.

[0051] The hot-rolled strip 3 of austenitic AISI 300 intended for the production of stainless steel strip 50, in this example with a width of 1280 mm and a strip thickness of 2600 μm, is subjected to an oxidation-free heat treatment in an annealing plant 1 at a strip speed of 80 m / min. In contrast to the annealing plant 1 shown in FIG. 1, the furnace chamber 4 consists of a heating zone 7 as well as a cooling zone 28, the heating zone 7 furthermore only comprising a series of transverse magnetic field inductors 10, 11. The hot-rolled strip 3, previously pickled in a pretreatment device 38, is also introduced via the inlet gate 5 into the furnace chamber 4, which is provided with a reducing shielding gas atmosphere with a hydrogen content of 75% by volume. The hot-rolled strip 3 first passes through the heating zone 7, where it is heated to the annealing temperature of 1050 ° C by the transverse magnetic field inductors 10, 11. The briefly annealed strip 3 then passes through a cooling section 28 where it is cooled by reducing shielding gas at a constant cooling rate of 18 K / s to an exit temperature of 80° C. [Explanation of symbols]

[0052] 1 Annealing equipment / annealing furnace 2 Processing Line 3. Hot rolled steel strip / hot strip 4 Furnace room 5. Entrance Gate 6 Exit Gate 7 Heating Section 8 Inductors / Vertical Magnetic Field Inductors 9 Inductors / Vertical Magnetic Field Inductors 10 Inductors / Transverse Magnetic Field Inductors 11 Inductors / Transverse Magnetic Field Inductors 12 First Section 13 Second Stage 14 Vertical magnetic field inductor coil 15 Transverse magnetic field inductor coil 16 Steel strip passing level 17 Thermal insulation layer 18 Thermal insulation layer 19 Airtight cover 20 Passage gap 21 Rolla Track 22 Holding Section 23 First holding section 24 Second holding section 25 Third holding section 26 heating elements 27 Cooling nozzle 28 Cooling Section 29 Cooling device 30 First cooling stage 31 Second cooling stage 32 Distributor 33 Distributor 34 Blower / Fan 35 Blower / Fan 36 Heat exchanger 37 Heat exchanger 38 Pretreatment Equipment 39 First reel device 40 Hot strip coil 41 First Separator 42 Welding equipment 43 Trimming equipment 44 Inlet reservoir 45 Outlet reservoir 46 Second Separator 47 Second reel device 48 Annealing of Grain-Oriented Electrical Steel Strip 49 Annealing treatment of non-oriented electrical steel strip 50 Annealing treatment of stainless steel strip 100 Shielding gas supply

Claims

1. An annealing installation (1), in particular an annealing furnace, for use in a process line (2) for the non-oxidizing heat treatment of a hot-rolled steel strip (3), preferably for the continuous pickling and non-oxidizing annealing of a hot-rolled steel strip (3) intended for producing an electrical steel strip and / or a stainless steel strip, comprising: The furnace has a closed furnace chamber (4), which comprises a heating section (7), optionally a holding section (22) following the heating section (7), and optionally a cooling section (28) following the heating section (7) and optionally following the holding section (22), 1. An annealing apparatus (1), characterized in that the heating section (7) comprises a plurality of inductors (8, 9, 10, 11) connected in series, and the cooling section (28) has a cooling device (29) via which a reducing shielding gas can be introduced into the cooling section (28) for cooling the hot rolled steel strip (3).

2. 2. The annealing apparatus (1) according to claim 1, characterized in that the cooling device (29) has at least one nozzle, via which a reducing shielding gas can be sprayed onto the steel strip (3).

3. 3. The annealing apparatus (1) according to claim 1 or 2, characterized in that the cooling device (29) has at least one blower device (34, 35) via which a reducing shielding gas can be supplied, preferably to at least one nozzle.

4. The annealing apparatus (1) according to any one of claims 1 to 3, characterized in that the cooling device (29) has at least one heat exchanger (36, 37) via which the reducing shielding gas blown into the cooling section (28) can be cooled.

5. 5. The annealing apparatus (1) according to claim 2, wherein the cooling device (29) comprises a circulation system in which at least one nozzle, at least one blower (34, 35) and at least one heat exchanger (36, 37) are connected to one another, preferably so that a reducing shielding gas is blown via the at least one blower (34, 35) and the at least one nozzle onto the cooling section (28), in particular onto the steel strip (3), and is sucked out again via the at least one blower (34, 35) and cooled by the at least one heat exchanger (36, 37).

6. The annealing device (1) according to any one of claims 1 to 5, characterized in that the heating section (7) comprises a first stage (12) having a number of longitudinal magnetic field inductors (8, 9) connected in series and a second stage (13) having a number of transverse magnetic field inductors (10, 11) connected in series.

7. 7. The annealing device (1) according to claim 1, characterized in that the heating section (7) comprises a passage gap (20) for the steel strip (3), which is limited by thermal insulation layers (17, 18).

8. Annealing device (1) according to claim 7, characterised in that the passage gap (20) has a vertical extent of less than or equal to 300 mm, preferably less than or equal to 250 mm.

9. A process line (2) for continuous pickling and oxidation-free annealing of a hot-rolled steel strip (3) intended for producing an electrical steel strip and / or a stainless steel strip, characterized in that it comprises a pre-treatment device (38) capable of pickling the hot-rolled steel strip (3) and an annealing device (1) according to any one of claims 1 to 8, which is arranged downstream of the pre-treatment device in the strip travel direction.

10. A method for continuous pickling and oxidation-free annealing of a hot-rolled steel strip (3) intended for producing an electrical steel strip and / or a stainless steel strip, characterized in that the hot-rolled steel strip (3), optionally after an unwinding step, is first fed to a pre-treatment device (38), where it is pickled and then fed as the pickled steel strip (3) to an annealing device (1), where it is first inductively heated to an annealing temperature via a number of inductors (8, 9, 10, 11) connected in series under a reducing shielding gas atmosphere, thereafter annealed and then quenched and / or cooled under the use of a reducing shielding gas.

11. 11. The method according to claim 10, characterized in that the pickled steel strip (3) is first heated in a heating section (7) of the annealing plant (1) to an annealing temperature of at least 800 ° C with a heating rate of at least 20 K / s.

12. 12. The method according to claim 11, characterized in that the pickled steel strip (3) is annealed in a holding section (22) of the annealing device (1) following the heating section (7) at a temperature in the range of 800 to 1200 °C for at least 60 seconds.

13. 13. The method according to claim 11 or 12, characterized in that the annealed steel strip (3) is cooled in a cooling section (28) of the annealing plant (1), which follows the heating section (7) and optionally a holding section (22), with an initial cooling rate of at least 15 K / s.

14. The method according to any one of claims 10 to 13, characterized in that the pickled steel strip (3) is preferably heated in two stages (12, 13) in the heating section (7), by firstly heating the pickled steel strip (3) in a first stage (12) to a temperature of at least 650 °C and then in a second stage (13) to an annealing temperature of at least 800 °C.

15. 15. The method according to claim 14, characterized in that the pickled steel strip (3) is heated in a first stage (12) via a number of longitudinal magnetic field inductors (8, 9) connected in series and in a second stage (13) via a number of transverse magnetic field inductors (10, 11) connected in series.

16. 16. The method according to claim 10, characterized in that the annealed steel strip (3) is cooled in the cooling section (28) of the annealing apparatus (1) by the cooling device (29) in such a way that a reducing shielding gas is blown onto the annealed steel strip (3) via the cooling device (29), the reducing shielding gas being sucked out of the cooling section (28) via blowers (34, 35) and, if necessary, cooled via heat exchangers (36, 37).

17. 17. The method according to any one of claims 10 to 16, characterized in that the reducing shielding gas is a hydrogen-rich gas, preferably with a hydrogen content of at least 30% by volume, preferably with a hydrogen content of at least 50% by volume, more preferably with a hydrogen content of at least 75% by volume.

Images