Heat treatment line for a hot strip

Abstract

The invention relates to an annealing device (1), in particular an annealing furnace, for the oxidation-free heat treatment of a hot-rolled steel strip (3), which is provided for the production of an electric strip and / or stainless steel strip, a treatment 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

[0001] Heat treatment line for hot strip

[0002] The present invention relates to an annealing device, in particular an annealing furnace, for the oxidation-free heat treatment of a hot-rolled steel strip intended for the production of electrical steel strip and / or stainless steel strip, a treatment line for the continuous pickling and oxidation-free annealing of a hot-rolled steel strip, and a method for the continuous pickling and oxidation-free annealing of a hot-rolled steel strip.

[0003] Electrical steel is one of the most important soft magnetic materials for magnetic cores and is typically made of an iron-silicon alloy. It is currently divided into two different grades. Non-grain-oriented electrical steel is equally magnetizable in all directions and is primarily used in rotating electrical machines. In contrast, grain-oriented electrical steel exhibits a preferred direction of magnetization and is typically used in power transformers, distribution transformers, and high-performance small transformers.

[0004] The production of electrical steel strip, as disclosed, for example, in US 2017 / 0283903 A1, is usually carried out by casting a specific metallic steel composition, which typically contains (in wt. %) 2.5 to 4.0% Si, 0.010 to 0.100% C, up to 0.150% Mn, up to 0.065% Al and up to 0.0150% N, and optionally 0.010 to 0.3% Cu, up to 0.060% S, up to 0.100% P, up to 0.2% each of As, Sn, Sb, Te and Bi, the remainder being iron and unavoidable impurities, into a starting material, such as a slab, thin slab or a cast strip, and then hot-rolling it directly into a so-called hot strip. The hot-rolled steel strip is then subjected to an annealing treatment and, in a further step, cold-rolled into a so-called cold-rolled strip. To achieve the advantageous magnetic properties, the cold-rolled strip is then recrystallized in a continuous annealing and coating line and subsequently coated with an insulating coating.

[0005] For the annealing treatment of hot-rolled steel strip, the existing scale layer on the surface is usually tolerated, as further oxidation in the open-heated annealing furnaces and thus further scale buildup (so-called glow primer) is unavoidable. In the current state of the art, the hot-rolled steel strip is therefore first subjected to an annealing treatment followed by a descaling process to prepare a scale-free hot strip for the subsequent cold rolling process. The combination of annealing and pickling is known as an annealing-pickling line. In line with English usage, such a line is also referred to as an "APL" (annealing pickling line).

[0006] The descaling process initially involves mechanical pre-descaling, which is then followed by a chemical pickling process. Mechanical descaling is typically performed using a blasting device, which roughens the surface of the hot-rolled strip to such an extent that the resulting roughness is largely retained after cold rolling and subsequently impairs the magnetic properties of the grain-oriented or non-oriented electrical steel strip.

[0007] Annealing furnaces known from the prior art consist of a heating and holding section, followed by a cooling section comprising an air cooling and a water cooling section. In the heating section, the hot strip is openly heated by gas burners using fossil fuels, which results in high CO2 emissions. Such an annealing device is known, for example, from US Pat. No. 5,472,528, which also teaches the use of induction devices arranged either upstream or downstream of at least one traditional heating device to improve the inertia of traditional heating means. In the holding section, the hot strip is then electrically heated in a nitrogen atmosphere. In the subsequent air cooling section, the hot strip is first subjected to slow cooling and then to more intensive water cooling. During slow cooling, the hot strip is further oxidized.The scale particles formed during this process are carried away with the exhaust air, requiring extensive filtering. During the more intensive water cooling process, additional scale is also produced, which must be removed from the cooling water, usually via scale settling tanks.

[0008] There is therefore still a desire among experts to improve such procedures.

[0009] Against this background, the present invention is based on the object of providing a device for the oxidation-free heat treatment of a hot-rolled steel strip intended for the production of electrical steel strip and / or stainless steel strip, which allows for improved process control compared to the prior art. Furthermore, the present invention is based on the object of providing a method for the continuous pickling and oxidation-free annealing of a hot-rolled steel strip intended for the production of electrical steel strip and / or stainless steel strip, which method is improved compared to the prior art.

[0010] Description of the invention

[0011] According to the invention, the object is achieved by an annealing device, in particular by an annealing furnace, for the oxidation-free heat treatment of a hot-rolled steel strip having the features of patent claim 1, by a treatment line for the continuous pickling and oxidation-free annealing of a hot-rolled steel strip having the

[0012] Features of claim 9, as well as by a process for the continuous pickling and oxidation-free annealing of a hot-rolled steel strip with the

[0013] Features of patent claim 10.

[0014] The annealing device according to the invention, in particular an annealing furnace, for the oxidation-free heat treatment of a hot-rolled steel strip, which is intended for the production of electrical steel strip and / or stainless steel strip, comprises a hermetically sealed furnace chamber which has a heating section, optionally a holding section adjoining the heating section, and a cooling section adjoining the heating section, optionally a holding section, wherein the heating section has a plurality of inductors connected in series, and wherein the cooling section comprises a cooling device via which a reducing protective gas for cooling the hot-rolled steel strip can be introduced into the cooling section.

[0015] The treatment line according to the invention for the continuous pickling and oxidation-free annealing of a hot-rolled steel strip, which is intended for the production of electrical steel strip and / or stainless steel strip, comprises a pretreatment device in which the hot-rolled steel strip can be pickled, as well as the annealing device according to the invention arranged behind the pretreatment device in the strip travel direction.

[0016] According to the method according to the invention for the continuous pickling and oxidation-free annealing of a hot-rolled steel strip intended for the production of electrical steel strip and / or stainless steel strip, the hot-rolled steel strip, optionally after an uncoiling step, is first fed to a pretreatment device and pickled therein; and then, as pickled steel strip, is fed to an annealing device and, under a reducing protective gas atmosphere, is first inductively heated to an annealing temperature via a plurality of inductors connected in series, then annealed, and subsequently quenched and / or cooled using a reducing protective gas.

[0017] The steel strip used for the production of electrical steel strip is preferably a steel which typically contains (in wt.%) 2.5 to 4.0% Si, 0.010 to 0.100% C, up to 0.150% Mn, up to 0.065% Al and up to 0.0150% N, and optionally 0.010 to 0.3% Cu, up to 0.060% S, up to 0.100% P, up to 0.2% each of As, Sn, Sb, Te and Bi, the remainder being iron and unavoidable impurities.

[0018] The annealing device according to the invention enables complete heat treatment under a reducing protective gas atmosphere, which has a reducing effect on the hot strip used, thus enabling an oxide-free steel strip surface. A very high power density can be achieved via the inductors, which allows the heating section to be significantly shortened compared to prior art annealing furnaces. Conventional gas burners or radiant heating elements are therefore not required. This also enables economical operation of the annealing device under a reducing protective gas atmosphere. Furthermore, a reducing protective gas, such as hydrogen, exhibits improved convective heat transfer compared to atmospheric air, enabling high cooling rates, for example, of up to 50 K / s, to be achieved within the cooling section.These either have the effect of shortening the overall length of the annealing device according to the invention, for example for non-grain-oriented electrical steel, or are particularly advantageous for qualitative reasons, for example to achieve intensive cooling of grain-oriented electrical steel or stainless steel.

[0019] In this respect, the annealing device according to the invention enables a pickling treatment to be carried out prior to heat treatment, which has a particularly advantageous effect on the heat treatment process of the hot strip, as the use of scale breakers and / or blasting equipment can be dispensed with. This allows for shorter pickling times and thus increased yield. Furthermore, surface roughness can be reduced, thereby improving the magnetic properties of the electrical steel strip.

[0020] Further advantages of the invention are: a) avoidance of CO2 emissions; b) oxidation-free heat treatment; c) shorter length of the annealing device; d) avoidance of open cooling water; e) reduction of dust emissions.

[0021] Further advantageous embodiments of the invention are specified in the dependent claims. The features listed individually in the dependent claims can be combined with one another in a technologically expedient manner and can define further embodiments of the invention. Furthermore, the features specified in the claims are further specified and explained in the description, where further preferred embodiments of the invention are presented.

[0022] At this point, it should be noted that the annealing device according to the invention is neither intended for nor suitable for a hot strip galvanizing line (also referred to as a pickling and galvanizing line (PGL)).

[0023] In this respect, it is advantageously provided that the annealing device is designed horizontally. Furthermore, it is preferably provided that the cooling section and / or the exit lock of the annealing device do not open into a coating device.

[0024] In an advantageous embodiment of the process, the pickled steel strip is first heated in a heating section of the annealing device to an annealing temperature of at least 800 °C at a heating rate of at least 20 K / s, more preferably at a heating rate of at least 25 K / s, and even more preferably at a heating rate of at least 30 K / s. However, the heating rate should not exceed a maximum value of 60 K / s, more preferably 55 K / s, and most preferably 50 K / s.

[0025] Advantageously, the pickled and thus completely scale-free steel strip is heated within the heating section in two separate stages. For this purpose, the annealing device preferably comprises a first stage with a plurality of series-connected longitudinal-field inductors, in which the pickled steel strip is initially heated to a temperature of at least 650 °C. In contrast, the annealing device has a plurality of series-connected transverse-field inductors in the second stage, by means of which the steel strip is then heated to the annealing temperature of at least 800 °C.

[0026] The respective number of inductors, with which heating rates of up to 100 K / (s*mm strip thickness) can usually be achieved, within the annealing device depends on the required total power and can therefore vary between 1 and 20.

[0027] To ensure good coupling of the magnetic field, the passage gap for the steel strip should not be too large. Therefore, in the heating section, it is advantageously < 300 mm vertically, more preferably < 250 mm vertically, and most preferably < 200 mm vertically.

[0028] In order to keep the heat losses within the heating section as low as possible, a further advantageous embodiment provides that the passage gap is limited by a thermal insulation layer which is arranged below and above the steel strip feedthrough level and is provided with a gas-tight casing on the outside.

[0029] If the hot-rolled steel strip is further intended for the production of a grain-oriented and a non-grain-oriented electrical steel strip, it is preferably annealed in a holding section following the heating section at a temperature in the range of 800 - 1200 °C for at least 60 s.

[0030] In a preferred embodiment, the annealing device can therefore have a holding section, which particularly preferably comprises three individual holding section stages. The first holding section stage is directly adjacent to the heating section, with the second holding section stage being arranged directly upstream of the cooling section. Both holding section stages comprise, on the one hand, conventional electrical heating elements, which can be arranged below the steel strip feed-through level. Furthermore, the two holding section stages comprise conventional air-flow cooling jet pipes, which can be arranged, for example, above the steel strip feed-through level. The third holding section stage is arranged within the holding section between the first and second holding section stages and, in contrast to these, does not have any cooling jet pipes, but only the electrical heating elements.

[0031] After the annealing treatment, the steel strip is quenched and / or cooled using a reducing protective gas. In an advantageous embodiment of the process, the annealed steel strip can be cooled in a cooling section of the annealing device directly following the heating section, with an initial cooling rate of at least 15 K / s. In this embodiment, the annealing device therefore comprises only a heating section and a cooling section.

[0032] In a further advantageous embodiment of the process, the annealed steel strip can be cooled in a cooling section of the annealing device directly adjacent to the holding section. In this case, the initial cooling rates are at least 40 K / s.

[0033] For this purpose, the cooling device advantageously comprises at least one nozzle through which the reducing protective gas can be blown onto the steel strip. More preferably, however, the cooling device comprises at least one nozzle arranged above and at least one nozzle below a steel strip feed-through plane. The at least one nozzle can be designed as a slot nozzle that extends within the cooling section transversely to a transport direction of the steel strip. In a further advantageous embodiment, the cooling device can have at least one distributor arranged above and below a steel strip feed-through plane, which distributor comprises a plurality of perforated nozzles. The respective nozzle is advantageously designed such that an exit velocity of the reducing protective gas of 50 to 150 m / s can be achieved.

[0034] Furthermore, it is advantageously provided that the cooling device comprises at least one blower device, via which the reducing protective gas can be supplied to the at least one nozzle, optionally to the at least one distributor. Furthermore, the cooling device can comprise at least one heat exchanger, via which the reducing protective gas blown into the cooling section can be cooled.

[0035] In a particularly advantageous embodiment, the cooling device comprises a circulation system in which the at least one nozzle and / or the at least one distributor and nozzles, the at least one blower device, and the at least one heat exchanger are interconnected, particularly preferably in such a way that the reducing protective gas is blown into the cooling section, most preferably onto the steel strip, via the at least one blower device and the at least one nozzle and / or the at least one distributor and nozzles, and is extracted again via the at least one blower device and cooled by means of the at least one heat exchanger. Such a cooling device, using the reducing protective gas, enables convective heat transfer of 500 to 800 W / m², based on the steel strip surface. 2 K, which enables high cooling rates of > 40 K / s to be achieved.

[0036] As reducing protective gas, a hydrogen-rich gas is preferably used which has a hydrogen content of at least 30 vol%, more preferably a hydrogen content of at least 50 vol%, even more preferably a hydrogen content of at least 75 vol%.

[0037] The reducing protective gas can, in principle, be supplied to the furnace chamber at various points in the annealing system. However, it is preferred that the reducing protective gas be supplied to the holding section in order to achieve the maximum reduction effect at maximum strip temperature. In another preferred embodiment, the reducing protective gas can be supplied to the cooling section to increase heat transfer.

[0038] Figure name

[0039] The invention and the technical environment are explained in more detail below with reference to the figures. It should be noted that the invention is not intended to be limited by the exemplary embodiments shown. In particular, unless explicitly stated otherwise, it is also possible to extract partial aspects of the facts explained in the figures and combine them with other components and findings from the present description and / or figures. In particular, it should be noted that the figures and in particular the illustrated proportions are only schematic. The same reference numerals denote the same objects, so that explanations from other figures can be used as a supplement if necessary. They show:

[0040] Fig. 1 shows an embodiment of the annealing device according to the invention,

[0041] Fig. 2 shows an embodiment of the treatment line according to the invention,

[0042] Fig. 3 shows a heat treatment temperature profile for a grain-oriented and a non-grain-oriented electrical steel strip, and

[0043] Fig. 4 a heat treatment temperature profile for a stainless steel strip.

[0044] Figure 1 shows a variant of the annealing device 1 according to the invention, which is intended for use in a treatment line 2 for the continuous pickling and oxidation-free annealing of a hot-rolled steel strip 3 (see Figure 2). Such steel strips 3 are used for the production of electrical steel strip and / or stainless steel strip and are typically subjected to a cold rolling process after the annealing or heat treatment.

[0045] The annealing device 1 shown in the present embodiment comprises a hermetically sealed furnace chamber 4, which is operated under a reducing protective gas atmosphere. The reducing protective gas can be supplied to the furnace chamber 4 at various locations, as illustrated by reference numeral 100.

[0046] The furnace chamber 4 comprises an inlet lock 5, through which the hot-rolled steel strip 3 enters the furnace chamber 4, and an outlet lock 6, through which the subsequently heat-treated steel strip 3 leaves the furnace chamber 4. Adjacent to the inlet lock 5, the annealing device 1 initially has a heating section 7, which comprises a plurality of inductors 8, 9, 10, 11 connected in series, wherein the inductors 8, 9 form a first stage 12 and the two inductors 10, 11 form a second stage 13 of the heating section 7.

[0047] The inductors 8, 9 are designed as longitudinal-field inductors and have corresponding longitudinal-field inductor coils 14. In contrast, the inductors 10, 11 are designed as transverse-field inductors and have corresponding transverse-field inductor coils 15. Furthermore, each of the inductors 8, 9, 10, 11 has a thermal insulation layer 17, 18 arranged below and above a steel strip feedthrough plane 16, which is provided on the outside with a gas-tight casing 19. As can be seen from the illustration, a passage gap 20 is created in each of the inductors 8, 9, 10, 11 through the thermal insulation layers 17, 18. In the present embodiment, this passage gap has a vertical extension of 150 mm to ensure good coupling of the magnetic field. Furthermore, roller stands 21 are arranged between the individual inductors 8, 9, 10, 11, by means of which the strip sag of the steel strip 3 is limited.In the present embodiment, the roller stands 21 are also provided with a thermal insulation layer 17, 18 arranged below and above the steel strip feedthrough level 16, which is sealed from the atmosphere on the outside by the gas-tight casing 19.

[0048] The annealing device 1 further comprises a holding section 22 adjoining the heating section 7, which has three holding section stages 23, 24, 25, each of these holding section stages 23, 24, 25 being provided with electrical heating elements 26 arranged below the steel strip feedthrough level 16. In the presently illustrated embodiment, the two outer holding section stages 23, 25 additionally comprise conventional air-flow cooling jet pipes 27 arranged above the steel strip feedthrough level 16. As can also be seen from Figure 1, the entire holding section 22 is also provided with a thermal insulation layer 17, 18 arranged below and above the steel strip feedthrough level 16, which is sealed from the atmosphere on the outside by the gas-tight enclosure 19. The holding section 22 is then followed by a cooling section 28 which comprises a cooling device 29.In the present embodiment, the cooling device 29 has two separate cooling stages 30, 31, via which the annealed steel strip 3 can be intensively cooled or quenched with a reducing protective gas, such as hydrogen. For this purpose, each of the two cooling stages 30, 31 has a distributor 32, 33 arranged below and one above the steel strip feed-through plane 16, each of which is provided with a plurality of nozzles (not shown) directed in the direction of the steel strip feed-through plane 16. Each of the distributors 32, 33 is fluidly connected via a gas line to a blower device 34, 35, for example a fan, arranged outside the furnace chamber 4, via which the reducing protective gas can then be supplied to them.Furthermore, each of the two separate cooling stages 30, 31 comprises a heat exchanger 36, 37, also located outside the furnace chamber 4, through which the reducing protective gas blown into the respective cooling stage 30, 31 of the cooling section 28 can be cooled. For this purpose, the respective cooling stage 30, 31 is fluidly connected to the respective blower device 34, 35 via a further gas line.

[0049] Figure 2 shows an example of an embodiment of the treatment line 2 according to the invention, which comprises a pretreatment device 38 and the annealing device 1 arranged downstream in the strip travel direction. In detail, the treatment line 2 shown comprises a first coiling device 39, over which a hot-rolled strip coil 40 is first unwound. The then unwound hot-rolled steel strip 3 is fed to a first cutting device 41 in order to produce a clean edge for a subsequent welding process. After welding in a welding device 42, the steel strip 3 is fed to a trimming device 43, in which the strip edges of the steel strip 3 are trimmed. After passing through an inlet accumulator 44, the steel strip 3 enters the pretreatment device 38, where it is pickled, rinsed, and then dried.As pickled steel strip 3, it is then fed to the annealing device 1 and, in this device, is first heated to an annealing temperature under a reducing protective gas atmosphere, annealed and then intensively cooled or quenched before it is subsequently reeled off again via a discharge storage device 45.

[0050] Figure 3 shows a heat treatment temperature profile for a hot-rolled steel strip 3, which is further intended for the production of a grain-oriented and a non-grain-oriented electrical steel strip 48, 49.

[0051] In the present exemplary embodiment, the hot-rolled steel strip 3 intended for the production of the grain-oriented electrical steel strip 48 has a width of 1280 mm and a strip thickness of 2300 μm and is subjected to an oxidation-free heat treatment in the annealing device 1 at a strip speed of 75 m / min. The hot-rolled steel strip 3 intended for the production of the non-grain-oriented electrical steel strip 49, on the other hand, has a width of 1280 mm and a strip thickness of 2600 μm and is subjected to an oxidation-free heat treatment in the annealing device 1 at a strip speed of 80 m / min.

[0052] For this purpose, the respective hot-rolled steel strip 3, previously pickled in the pretreatment facility 38, is fed through the inlet lock 5 into the furnace chamber 4, which has a reducing protective gas atmosphere. A hydrogen-rich gas with a hydrogen content of 75 vol% is used as the reducing protective gas. The respective hot-rolled steel strip first passes through the heating section 7, where it is heated to the Curie temperature of 700 °C by means of the two longitudinal field inductors 8, 9. Above the Curie temperature, the steel strip typically loses its paramagnetic properties and is therefore heated by means of the two transverse field inductors 10, 11 until the respective annealing temperature of 1120 °C (grain-oriented electrical steel strip 48) or the annealing temperature of 1050 °C (non-grain-oriented electrical steel strip 49) is reached.

[0053] Subsequently, the respective steel strip 3, heated to the annealing temperature, passes through the holding section 22, where it is 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 to a temperature of 900°C in the first holding section stage 23 before then passing through the second and third holding section stages 24, 25 at 900°C. The non-grain-oriented electrical steel strip 49, on the other hand, first passes through the two holding section stages 23, 24 at the previously set annealing temperature of 1050°C and is only slowly cooled to a temperature of 800°C in the third holding section stage 25.

[0054] The respective annealed steel strip 3 then passes through the cooling section 28, where it is quenched using the reducing protective gas. 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 subsequently at a cooling rate of less than 20 K / s to an exit temperature of 130 °C. The non-grain-oriented electrical steel strip 49, on the other hand, is cooled at a constant cooling rate of 25 K / s to an exit temperature of 130 °C.

[0055] Figure 4 shows a heat treatment temperature profile for a hot-rolled steel strip 3, which is further intended for the production of a stainless steel strip 50.

[0056] The hot-rolled steel strip 3 of an austenitic grade AISI 300 intended for the production of the stainless steel strip 50 has, in the present exemplary embodiment, a width of 1280 mm and a strip thickness of 2600 μm and is subjected to an oxidation-free heat treatment in an annealing device 1 at a strip speed of 80 m / min. In contrast to the annealing device 1 shown in Figure 1, the furnace chamber 4 is formed from the heating section 7 and the cooling section 28, wherein the heating section 7 also has only one row of transverse field inductors 10, 11. The hot-rolled steel strip 3, previously pickled in the pretreatment device 38, is also fed through the inlet lock 5 into the furnace chamber 4, which has a reducing protective gas atmosphere with a hydrogen content of 75 vol%. The hot-rolled steel strip 3 first passes through the heating section 7, where it is heated to the annealing temperature of 1050 °C by means of the transverse field inductors 10, 11.The briefly annealed steel strip 3 then passes through the cooling section 28, where it is cooled by means of the reducing protective gas at a constant cooling rate of 18 K / s to an exit temperature of 80 °C. Reference symbol.

[0057] 1 annealing device I annealing furnace

[0058] 2nd treatment line

[0059] 3 hot-rolled steel strip / hot-rolled strip

[0060] 4 oven room

[0061] 5 Entrance lock

[0062] 6 Exit gate

[0063] 7 Heating section

[0064] 8 Inductor / Longitudinal field inductor

[0065] 9 Inductor / Longitudinal field inductor

[0066] 10 Inductor / Cross-field inductor

[0067] 11 Inductor / Cross-field inductor

[0068] 12 first stage

[0069] 13 second stage

[0070] 14 Longitudinal field inductor coil

[0071] 15 Cross-field inductor coil

[0072] 16 steel strip feedthrough level

[0073] 17 Thermal insulation layer

[0074] 18 Thermal insulation layer

[0075] 19 gas-tight enclosure

[0076] 20 Passage gap

[0077] 21 Roll stand

[0078] 22 Holding section

[0079] 23 first holding section level

[0080] 24 second holding section level

[0081] 25 third holding section level

[0082] 26 heating elements

[0083] 27 Cooling jet pipe

[0084] 28 Cooling section

[0085] 29 Cooling device

[0086] 30 first cooling stage

[0087] 31 second cooling stage 32 distributor

[0088] 33 distributors

[0089] 34 Blower unit / fan

[0090] 35 Blower device / fan

[0091] 36 heat exchangers

[0092] 37 heat exchangers

[0093] 38 Pretreatment facility

[0094] 39 first reel device

[0095] 40 Warm band coil

[0096] 41 first separating device

[0097] 42 Welding device

[0098] 43 Trimming device

[0099] 44 inlet storage tanks

[0100] 45 discharge storage

[0101] 46 second separating device

[0102] 47 second reel device

[0103] 48 Annealing of grain-oriented electrical steel

[0104] 49 Annealing treatment of non-grain-oriented electrical steel

[0105] 50 Annealing treatment of stainless steel strip

[0106] 100 protective gas supply

Claims

Patent claims 1. Annealing device (1), in particular an annealing furnace, for the oxidation-free heat treatment of a hot-rolled steel strip (3), preferably for use in a treatment line (2) for the continuous pickling and oxidation-free annealing of a hot-rolled steel strip (3), which is intended for the production of electrical steel strip and / or stainless steel strip, comprising a hermetically sealed furnace chamber (4) which has a heating section (7), optionally a holding section (22) adjoining the heating section (7), and a cooling section (28) adjoining the heating section (7), optionally a holding section (22), wherein the heating section (7) has a plurality of inductors (8, 9, 10, 11) connected in series, and the cooling section (28) comprises a cooling device (29) through which a reducing protective gas is supplied for cooling the hot-rolled steel strip (3). can be inserted into the cooling section (28).

2. Annealing device (1) according to claim 1, wherein the cooling device (29) comprises at least one nozzle through which the reducing protective gas can be blown onto the steel strip (3).

3. Annealing device (1) according to claim 1 or 2, wherein the cooling device (29) comprises at least one blower device (34, 35) via which the reducing protective gas can preferably be supplied to the at least one nozzle.

4. Annealing device (1) according to one of the preceding claims, wherein the cooling device (29) comprises at least one heat exchanger (36, 37) via which the reducing protective gas blown into the cooling section (28) can be cooled.

5. Annealing device (1) according to one of the preceding claims 2 to 4, wherein the cooling device (29) has a circulating system in which the at least one nozzle, the at least one blower device (34, 35) and the at least one heat exchanger (36, 37) are interconnected, preferably such that the reducing protective gas is supplied via the at least one blower device (34, 35) and the at least one nozzle to the cooling section (28), particularly preferably to the A steel strip (3) is blown in and extracted again via the at least one blower device (34, 35) and cooled by means of the at least one heat exchanger (36, 37). An annealing device (1) according to one of the preceding claims, wherein the heating section (7) has a first stage (12) with a plurality of longitudinal field inductors (8, 9) connected in series, and a second stage (13) with a plurality of transverse field inductors (10, 11) connected in series. An annealing device (1) according to one of the preceding claims, wherein the heating section (7) has a passage gap (20) for the steel strip (3) which is limited by a thermal barrier layer (17, 18). An annealing device (1) according to claim 7, wherein the passage gap (20) has a vertical extent of < 300 mm, preferably < 250 mm.Treatment line (2) for the continuous pickling and oxidation-free annealing of a hot-rolled steel strip (3), which is intended for the production of electrical steel strip and / or stainless steel strip, comprising a pretreatment unit (38) in which the hot-rolled steel strip (3) can be pickled, and an annealing unit (1) arranged downstream in the strip travel direction according to one of the preceding claims. Method for the continuous pickling and oxidation-free annealing of a hot-rolled steel strip (3), which is intended for the production of electrical steel strip and / or stainless steel strip, wherein the hot-rolled steel strip (3), optionallyAfter an unwinding step, the steel strip (3) is first fed to a pretreatment unit (38) and pickled therein; and subsequently fed as a pickled steel strip (3) to an annealing unit (1) and heated therein under a reducing protective gas atmosphere, first inductively via a plurality of inductors (8, 9, 10, 11) connected in series, to an annealing temperature, then annealed, and subsequently quenched and / or cooled using a reducing protective gas. Method according to claim 10, wherein the pickled steel strip (3) is first heated in a heating section (7) of the annealing unit (1) to an annealing temperature of at least 800 °C with a heating rate of at least 20 K / s. Method according to claim 11, wherein the pickled steel strip (3) is heated in a heating section (7) of the annealing unit (1) adapted to the... The annealed steel strip (3) is annealed at a temperature in the range of 800–1200 °C for at least 60 s in a holding section (22) of the annealing device (1) following the heating section (7). The method according to claim 11 or 12, wherein the annealed steel strip (3) is cooled in a cooling section (28) of the annealing device (1) following the heating section (7), optionally following the holding section (22), with an initial cooling rate of at least 15 K / s. Method according to any one of the preceding claims 10 to 13, wherein the pickled steel strip (3) is heated in the heating section (7) over two stages (12, 13), preferably by first 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 the annealing temperature of at least 800 °C.A method according to claim 14, wherein the pickled steel strip (3) is heated in the first stage (12) via a plurality of longitudinal field inductors (8, 9) connected in series and in the second stage (13) via a plurality of transverse field inductors (10, 11) connected in series. A method according to any one of the preceding claims 10 to 15, wherein the annealed steel strip (3) is cooled in the cooling section (28) of the annealing unit (1) by means of a cooling device (29), whereby the reducing protective gas is blown onto the annealed steel strip (3) via the cooling device, and the reducing protective gas is extracted from the cooling section (28) via a blower device (34, 35) and optionally cooled via a heat exchanger (36, 37).Method according to any one of the preceding claims 10 to 16, wherein the reducing protective gas is a hydrogen-rich gas which preferably has a hydrogen content of at least 30 vol%, more preferably a hydrogen content of at least 50 vol%, more preferably a hydrogen content of at least 75 vol%.

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