Hood-type annealing furnace, and method for operating a hood-type annealing furnace

Abstract

The invention relates to a hood-type annealing furnace with a hood cover which has an insulating layer with a heating element arranged on the inner side, and with an inductor, and to a method for operating a hood-type annealing furnace. The problem addressed by the invention is to provide a novel hood-type annealing furnace which has a lower energy consumption, can be controlled more simply with regard to the cooling and has a shorter process time. The solution to this problem arises from a hood-type annealing furnace with a hood cover which has an insulating layer with a heating element arranged on the inner side, and with an inductor, wherein the hood cover is formed from an inductor arranged on the outside of the insulating layer and a heating element arranged on the inner side, wherein there is a means for cooling between the insulating layer and the heating element which at the same time also acts as an inert gas hood.

Description

[0001] Hood annealing furnace and method for operating a hood annealing furnace

[0002] The invention relates firstly to a hood annealing furnace with a hood cover which has an insulating layer with a heating element arranged on the inside and with an inductor.

[0003] Such a bell annealing furnace is known from the prior art from CN-Y 2709905, in particular from Figure 2 and the associated description.

[0004] Such bell annealing furnaces are often used to heat (approx. 600 - 700°C) metallic products, such as rolled sheets rolled up as coils, so that the material properties change in a predetermined way.

[0005] The heat treatment, which can last up to 100 hours, eliminates inhomogeneities with regard to strength that may have arisen during production.

[0006] In addition, heat treatment makes it possible to achieve the desired strength in the rolled sheets.

[0007] In this context, it is also important that the heat treatment is preceded by an atmosphere exchange inside the bell annealing furnace, whereby protective gases (nitrogen, hydrogen) are introduced into the bell annealing furnace instead of ambient air, so that oxidation processes on the product to be heated are prevented during heating.

[0008] The aforementioned prior art has the disadvantage that the overall process length of the controlled heating and subsequent cooling of the heat-treated metallic product is considered in need of improvement. Furthermore, it is considered disadvantageous that the cooling process in the prior art can only be controlled by using a special cooling hood, and that the overall energy consumption of the bell-type annealing furnace is excessive.

[0009] The object of the invention is therefore to create a new bell annealing furnace which has lower energy consumption, is easier to control with regard to cooling and has a shorter process time.

[0010] The solution to this problem results from a bell annealing furnace with the following features of claim 1 :

[0011] Hood annealing furnace with a hood cover which has an insulating layer with a heating element arranged on the inside and with an inductor, characterized in that the hood cover is formed from an inductor arranged on the outside of the insulating layer and a heating element arranged on the inside, wherein a device for cooling is provided between the insulating layer and the heating element, which simultaneously also functions as a protective gas hood.

[0012] The bell annealing furnace according to the invention has the significant advantage that the energy consumption for heating and subsequent cooling is significantly lower than that of the prior art.

[0013] Furthermore, it is possible to cool the product without changing the hood in a very effective manner and even shortly after the heat treatment of the heat-treated product by means of the cooling system according to the invention, which is arranged between the insulation layer and the heating element.

[0014] Ultimately, the process is simplified simply by the fact that the hood cover of the hood annealing furnace according to the invention has the three functions of protective gas hood, heating hood and cooling hood.

[0015] The fact that the hood change is not necessary also eliminates work processes that are problematic from a safety perspective.

[0016] In an advantageous embodiment of the invention, the cooling device is formed by a plurality of channels incorporated into the interior of the insulation layer, through which a gaseous coolant is passed. This design of the cooling device allows for the heating element and the heated product to be cooled very simply, effectively, and quickly immediately after the heat treatment.

[0017] In the above-mentioned embodiment, in a further embodiment, the channels in the upper and lower regions are at least partially connected to one another via distributors.

[0018] A further embodiment of the invention is characterized in that the cooling device is formed by a pyramid-shaped inner surface of the insulation layer, through which a gaseous coolant is passed. This significantly reduces the cost of manufacturing the flow channels required for cooling.

[0019] The aforementioned embodiments of the cooling devices according to the invention can further be designed during the heating phase in such a way that a closure means prevents a gaseous volume flow in the channels so that no uncontrolled heat losses occur.

[0020] In principle, it is conceivable that the closure means could be formed by a rotating shutter on the base of the bell-type annealing furnace, which closes the channels during the heating phase. Advantageously, the rotating shutter could be used to briefly open all channels after the heating phase simply by turning it. This would ensure that a large gaseous volume flow allows for cooling of the bell-type annealing furnace.

[0021] Advantageously, the gaseous volume flow flowing through the cooling device can be increased by an overpressure or underpressure generator arranged at the top and / or bottom in the region of at least one distributor of the cooling device.

[0022] In a particularly preferred embodiment, the channels of the cooling device are assigned to different distributors, each of which carries a gaseous volume flow in a countercurrent process. This also advantageously makes it possible to cool the bell-type annealing furnace as evenly as possible.

[0023] In principle, it is possible for the inductor according to the invention to consist of a fluid-flowing copper tube. This has the advantage of targeted cooling of the inductor and thus higher efficiency. The cross-section of the copper tube can advantageously be square.

[0024] Furthermore, the invention also relates to a method for the heat treatment of a hood annealing furnace with a hood cover having an insulating layer with a heating element arranged on the inside and with an inductor.Based on the above-mentioned prior art and the stated problem, the solution to the problem arises from a method for the heat treatment of metallic products, such as rolled sheets (Ci - C3) rolled up as coils, in a bell-type annealing furnace (10), characterized by the following method steps: a) replacement of the air atmosphere by protective gases, such as nitrogen, hydrogen, b) connection of the inductor (16) with its copper tube 17, which acts as a coil on the outer surface of the bell-type annealing furnace 10, to the alternating current, c) induction of a magnetic field inside the bell-type annealing furnace (10), d) generation of eddy currents in the heating element (20), as a result of which the latter heats up considerably, e) transfer of the resulting heat via the protective gas to the coils (Ci - C3) arranged inside the bell-type annealing furnace (10), f) carrying out the heat treatment of the coils (Ci - C3).g) After the long-term heat treatment, the cooling phase begins by disconnecting the inductor 16 from the AC power supply, h) opening the air inlet openings (21).

[0025] For the advantages of the method according to the invention, reference is made to the above statements regarding the advantages of the bell-type annealing furnace according to the invention. Further advantages of the invention will become apparent from the following description of an exemplary embodiment.

[0026] They show:

[0027] Figure 1 is a perspective view of a bell annealing furnace,

[0028] Figure 2 is a front view of the bell annealing furnace according to Figure 1,

[0029] Figure 3 is a sectional view along section line III - III of the bell annealing furnace in Figure 2,

[0030] Figure 4 is a sectional view according to IV - IV of the bell annealing furnace in Figure 2,

[0031] Figure 5 is an enlarged partial view according to circle V in Figure 2 and

[0032] Figure 6 shows a partial view of a pyramidal inner side of the insulation layer.

[0033] In the drawings, a bell annealing furnace is designated overall by reference number 10.

[0034] The hood annealing furnace 10 has a hood cover 11 which is closed on the top and all around and can be placed hermetically on a hood base 12 in the lower area (see Figure 3).

[0035] A coil Ci is positioned on the hood base 12. As shown in Figure 3, two additional coils C2 and C3 are stacked on top of the coil Ci.

[0036] A lifting eyelet 14 is arranged on the cover 13 of the hood cover 11, into which a crane hook (not shown) can engage when the hood cover 11 is to be lifted. A circumferential side surface 15 of the hood cover 11 is at least partially provided with an inductor 16, which is formed from a spirally circumferential hollow copper tube 17 through which water flows for the purpose of cooling.

[0037] In particular, Figure 3 clearly shows the cross-sectional structure of the bell annealing furnace 10.

[0038] On the outside, the hood cover 11 is provided with an insulating layer 18, on which the square hollow copper tube 17 of the inductor 16 is arranged. This insulating layer 18 has, on its inside, as can be seen particularly in Figures 4 and 6, vertical channels 19 incorporated into the material of the insulating layer 18, through which air flows during the cooling phase of the hood annealing furnace 10.

[0039] The cooling channels 19 border on the 5 mm thick heating element 20 made of austenitic stainless steel, which has a significantly greater material thickness in the lid area of ​​the bell annealing furnace 10.

[0040] The previously described cooling channels 19 are connected at the top and bottom by horizontal distributors (not shown), with air inlet openings 21 (see Figure 3) being arranged in the lower area and air outlet openings 22 being arranged in the upper area, each of which has a vacuum generator 23 (see Figure 2).

[0041] In particular, Figure 1 shows a circumferential ring of air inlet openings 21 in the lower region of the bell-type annealing furnace 10, which can be closed by a rotatable shutter 24 during the heating phase. The rotatable shutter 24 has numerous openings 28. If these openings 28 are not at least partially aligned with the air inlet openings 21, the cooling system is blocked.

[0042] The heating phase of the bell-type annealing furnace 10 begins after the air atmosphere has been replaced by protective gas inside the bell-type annealing furnace 10. First, the inductor 16, with its copper tube 17 arranged as a coil on the outer surface of the bell-type annealing furnace 10, is connected to the alternating current, thereby inducing a magnetic field inside the bell-type annealing furnace 10 in the area of ​​the heating element 20.

[0043] Due to the magnetic field, eddy currents are generated in the heating element 20, causing it to heat up considerably and transfer the heat via the protective gas to the coils Ci - C3 arranged inside the bell annealing furnace 10.

[0044] After completion of the sometimes very long heat treatment of the coils Ci - C3 for the purpose of changing the material properties, the inductor 16 is disconnected from the power supply and the cooling phase begins.

[0045] For this purpose, in the present embodiment, the air outlet openings 22 are opened by rotating the cover 24 so that the openings of the cover 24 are aligned with the air inlet openings 21.

[0046] In addition, the 23 vacuum generators begin operation.

[0047] As a result, air flows through the numerous cooling channels 19, cooling the heating element 20 and the internal protective gas atmosphere of the bell-type annealing furnace 10, as well as the coils C1 - C3. Figure 6 shows an alternative embodiment of the cooling device of the bell-type annealing furnace 10, in which an inner side 25 of the insulating layer 18 is pyramidal in shape. Figure 7 shows pyramid tips 26 that rest against the heating element 20 and cooling channels 27 that run from top to bottom between the pyramid tips 26 and are also connected to each other in the transverse direction.

[0048] List of reference symbols

[0049] Bell-type annealing furnace 10

[0050] Hood cover 11

[0051] Hood base 12

[0052] Lid 13

[0053] Transport eyelet 14

[0054] Side surface 15

[0055] Inductor 16

[0056] Copper hollow pipe 17

[0057] Insulation layer 18

[0058] Cooling channels 19

[0059] Heating element 20

[0060] Air inlet openings 21

[0061] Air outlet openings 22

[0062] Vacuum generator 23

[0063] Aperture 24

[0064] Inside page 25

[0065] Pyramid Peak 26

[0066] Cooling channels 27

[0067] Aperture openings 24 28

[0068] Coils C1 - C3

Claims

Claims 1. Hood annealing furnace (10) with a hood cover which has an insulating layer (18) with a heating element (30) arranged on the inside and with an inductor (16), characterized in that the hood cover is formed from an inductor (16) arranged on the outside of the insulating layer (18) and a heating element (20) arranged on the inside, wherein a cooling device is provided between the insulating layer (18) and the heating element (20), which also functions as a protective gas hood.

2. Hood annealing furnace (10) according to claim 1, characterized in that the cooling device is formed from a plurality of channels (19, 27) incorporated into the inside of the insulating layer (18), through which a gaseous coolant is passed.

3. Hood annealing furnace (10) according to claim 2, characterized in that the channels (19, 27) in the upper and lower regions are at least partially connected to one another via distributors.

4. Hood annealing furnace (10) according to claim 1, characterized in that the cooling device is formed by a pyramidal inner side (25) of the insulating layer (18) through which a gaseous coolant is passed.

5. Hood annealing furnace (10) according to one of claims 2 to 4, characterized in that a gaseous volume flow through the cooling device during the heating phase is prevented by a closure means.

6. Hood annealing furnace (10) according to claim 5, characterized in that the closure means consists of a rotatable diaphragm (24) on the hood base (12) of the hood annealing furnace (10), which closes the channels (19, 27) during the heating phase.

7. Hood annealing furnace (10) according to one of the preceding claims 3 to 6, characterized in that at least one overpressure or one underpressure generator (23) is arranged at the top and / or bottom in the region of at least one distributor of the cooling device.

8. Hood annealing furnace (10) according to claim 7, characterized in that the channels (19, 27) are assigned to different distributors and channels (19, 27) assigned to different distributors carry a gaseous volume flow in a countercurrent process.

9. Hood annealing furnace (10) according to any preceding claim, characterized in that the inductor (16) consists of a hollow copper tube through which fluid flows.

10. Hood annealing furnace (10) according to claim 9, characterized in that the cross-section of the hollow copper tube (17) is quadrangular.

11. A method for the heat treatment of metallic products, such as rolled sheets (Ci - C3) rolled up as coils in a bell-type annealing furnace (10), characterized by the following process steps: a) replacing the air atmosphere with protective gases, such as nitrogen, hydrogen, b) connecting the inductor (16) with its copper tube 17, which acts as a coil on the outer surface of the bell-type annealing furnace 10, to the alternating current, c) induction of a magnetic field inside the bell-type annealing furnace (10), d) Generation of eddy currents in the heating element (20), causing it to heat up considerably; e) Dissipation of the resulting heat via the protective gas to the coils (Ci - C3) arranged inside the bell-type annealing furnace (10); f) Heat treatment of the coils (Ci - C3). g) After the long-term heat treatment, the cooling phase begins by disconnecting the inductor 16 from the AC power supply; h) Opening the air inlet openings (21).

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