Apparatus and method for the treatment of a flat steel product, taking place in throughput

Abstract

An apparatus and a method for the treatment of a flat steel product, taking place in throughput. The apparatus includes an indirectly heated annealing furnace chamber, a conveyor device for continuously conveying the flat steel product over a conveyor path leading from an entry to an exit of the annealing furnace chamber, and nozzle arrangements for feeding atmosphere gas, which is reactive in relation to the flat steel product, into the annealing furnace chamber. A controlled treatment of the flat steel product includes a first nozzle arrangement, from which a gas jet induces a first gas flow towards the entry of the annealing furnace chamber and sweeping over the surface of flat steel product to be treated. A second nozzle arrangement includes a gas jet which induces a second gas flow directed towards the exit of the annealing furnace chamber and sweeping over the surface of flat steel product.

Claims

1. An apparatus for the treatment of a flat steel product, taking place in throughput, comprising: an indirectly heated annealing furnace chamber, having a conveyor device for continuously conveying the flat steel product over a conveyor path leading from an entry of the annealing furnace chamber to an exit of the annealing furnace chamber, and having nozzle arrangements for feeding atmosphere gas, which is reactive in relation to the flat steel product, into the annealing furnace chamber, wherein the nozzle arrangements include a first nozzle arrangement, from which a gas jet, which induces a first gas flow directed towards the entry of the annealing furnace chamber and sweeping over the surface of flat steel product to be treated, emerges during the treatment, and a second nozzle arrangement, from which a gas jet, which induces a second gas flow directed towards the exit of the annealing furnace chamber and sweeping over the surface of flat steel product to be treated, emerges during the treatment, and wherein the first and second nozzle arrangements are provided in the annealing furnace chamber and at least one of the nozzles of one of the nozzle arrangements emits a gas jet which is directed towards the lower side of the flat steel product to be treated, while at least one of the nozzles of one of the nozzle arrangements emits a gas jet which is directed towards the upper side of the flat steel product to be treated.

2. The apparatus according to claim 1, further comprising a control device is provided, which controls the delivery of atmosphere gas to the annealing furnace chamber in such a way that a positive pressure of at least 0.001 bar relative to the ambient pressure is maintained in the annealing furnace chamber during the treatment operation.

3. The apparatus according to claim 1, wherein the nozzle arrangements respectively comprise at least one nozzle and an incidence angle of the gas jet emerging from the at least one nozzle of a nozzle arrangement is varied in the range of from 0 to 90.

4. The apparatus according to claim 1, wherein the orientation of the at least one nozzle is adjustable.

5. The apparatus according to claim 1, wherein the at least one nozzle of the nozzle arrangements is connected to an N.sub.2 supply and an O.sub.2 supply.

6. The apparatus according to claim 5, wherein the N.sub.2 or O.sub.2 gas flow flowing into the respective nozzle is adjustable.

7. The apparatus according to claim 1, wherein the longitudinal side surfaces of the annealing furnace chamber are curved concavely as seen in cross section.

8. The apparatus according to claim 1, wherein the annealing furnace chamber is connected to at least one second annealing furnace chamber, in which the flat steel product to be treated undergoes a further treatment in an atmosphere which differs from the atmosphere of the first annealing furnace chamber.

9. A method for treating a flat steel product comprising: conveying the flat steel product in continuous throughput through an indirectly heated annealing furnace chamber from its entry to its exit; and introducing an atmosphere which is reactive in relation to the flat steel product into the annealing furnace chamber through nozzle arrangements, being maintained in the annealing furnace chamber, wherein a first gas flow, directed towards the entry of the annealing furnace chamber and sweeping over the surface of the flat steel product to be treated is generated by one of the nozzle arrangements, and in that a second gas flow directed towards the exit of the annealing furnace chamber and sweeping over the surface of the flat steel product to be treated, is generated by a second nozzle arrangement, and wherein the first and second nozzle arrangements are provided in the annealing furnace chamber and gas flows travel spirally around the flat steel product to be treated.

10. The method according to claim 9, wherein in relation to the longitudinal extent of the annealing furnace chamber, the gas flow directed towards the entry and the gas flow directed towards the exit respectively have their origin in the middle of the annealing furnace chamber.

11. The method according to claim 9, wherein the gas jet respectively emerging from the nozzles of the nozzle arrangements is an N.sub.2/O.sub.2 mixture, the O.sub.2 fraction of which is 0.01-20 vol. %.

12. The method according to claim 9, wherein the flow rate of the gas jets respectively emerging from the nozzle arrangements is 60-180 m/s.

13. The method according to claim 9, wherein the temperature of the flat steel product to be treated is 450-950 C.

14. The method according to claim 9, wherein the temperature of the gas jets introduced into the annealing furnace chamber is 100-1050 C.

15. The method according to claim 9, wherein a positive pressure of the reactive atmosphere of at least 0.001 bar relative to the ambient pressure is maintained in the annealing furnace chamber during the treatment.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be explained in more detail below with the aid of exemplary embodiments.

(2) FIG. 1 schematically shows an apparatus for the treatment a flat steel product (S), taking place in throughput, in plan view;

(3) FIG. 2 schematically shows the apparatus according to FIG. 1 in a section along the section line X-X indicated in FIG. 1.

DESCRIPTION OF THE INVENTION

(4) The apparatus V for the treatment of the flat steel product S in the form of a cold- or hot-rolled steel strip, taking place in throughput, comprises a first annealing furnace chamber 1, in which the flat steel product S is subjected to an oxidation treatment, a second annealing chamber 2a arranged immediately before the annealing furnace chamber 1 and a second annealing furnace chamber 2b connected to the annealing furnace chamber 1. In the annealing furnace chambers 2a, 2b, the flat steel product S is subjected to a reduction treatment. The annealing furnace chambers 1, 2a, 2b are part of an indirectly heated annealing furnace 3 of the RTF type, in the middle of which the annealing furnace chamber 1 is located.

(5) The flat steel product S respectively to be treated is transported through the annealing furnace 3 in a conventional way by means of a conveyor device (not represented here for the sake of clarity) on a linearly horizontally extending conveyor path 4 through the annealing furnace chambers 1, 2a, 2b, and in this case enters the annealing furnace chamber 1 through an entry 5, formed on an end side of the annealing furnace chamber 1, in a conveyor direction F coming from the annealing furnace chamber 2a. Through the exit 6 arranged on the opposite end side of the annealing furnace chamber 1, the flat steel product S leaves the annealing furnace chamber 1 and enters the chamber 2b, following directly thereon, of the annealing furnace 3. The entry 5 of the annealing furnace chamber 1 thus forms the exit of the annealing furnace chamber 2a preceding it. Likewise, the exit 6 of the annealing furnace chamber 1 simultaneously forms the entry of the annealing furnace chamber 2b subsequently passed through.

(6) The inner surfaces 7, 8 of the longitudinal walls 9, 10 of the annealing furnace chamber 1 are concavely curved inward with a uniform curvature as seen from its interior.

(7) Nozzle arrangements D1, D2, distributed in the conveyor direction F along the conveyor path 4, are provided in the annealing furnace chamber 1. The first nozzle arrangement D1 in this case comprises six individual nozzles 11-16, while the second nozzle arrangement D2 comprises five individual nozzles 17-21.

(8) The nozzles 11-16 of the nozzle arrangement D1 are positioned along the conveyor path 4 in such a way that the first nozzle 11 is positioned in immediate proximity to the entry 5, the sixth nozzle 16 is positioned in immediate proximity to the exit 6 of the annealing furnace chamber 1 and the remaining four nozzles 12-15 are positioned between the nozzles 11 and 16, while being distributed from one another at regular distances.

(9) In a comparable way, the nozzles 11-21 of the nozzle arrangement 2 are positioned on the opposite side of the conveyor path 4 in such a way that the first nozzles 17 is positioned next to the entry 5, the fifth nozzle 21 is positioned next to the exit 6 of the annealing furnace chamber 1 and the remaining three nozzles 18-20 are positioned between the nozzles 17 and 21, while being distributed from one another at regular distances. As seen in the conveyor direction F, the nozzles 17-21 in this way each lie in the section of the conveyor path in which there is respectively a free space between nozzles 11-16 of the nozzle arrangement D1.

(10) As shown by way of example in FIG. 1 for the nozzles 17-21 of the nozzle arrangement D2, the nozzles 11-21, formed for example as jet tubes of known design, are respectively connected to an N.sub.2 supply 22 and an O.sub.2 supply 23. The feed of N.sub.2 and O.sub.2 to the nozzles 11-21, and therefore the gas mixture emerging as a concentrated gas jet G from the nozzles 11-21, can in this case be adjusted individually for each nozzle 11-21 by means of valves 24, 25.

(11) Likewise, for each of the nozzles 11-21, both the incidence angle at which the gas jet G delivered by the respective nozzle 11-21 flows onto the flat steel product S to be treated, as seen in plan view (FIG. 1), and the attitude angle at which the gas jet strikes the flat steel product S, as seen in cross section (FIG. 2), can be adjusted individually for each nozzle 11-21.

(12) The incidence angle of the nozzles 11-16, oriented transversely with respect to the conveyor direction F, is varied in magnitude in the angle range of from 30 to 85, the nozzle 11 assigned to the entry 5 being oriented at an incidence angle of about 30 towards the entry 5 and the nozzle 16 assigned to the exit 6 being oriented also at an incidence angle of about 30 towards the exit 6. Likewise, the nozzles 12, 13 following on from the nozzle 11 in the delivery direction F are directed at an incidence angle towards the entry 5, the incidence angle of the nozzle 12 being greater than the incidence angle of the nozzle 11 and the incidence angle of the nozzle 13, at about 85, in turn being greater than the incidence angle of the nozzle 12. The nozzles 14, 15 following on from the nozzle 13 in the conveyor direction F, on the other hand, are oriented like the nozzle 16 towards the exit 6 of the annealing furnace chamber 1. In this case, respectively, the incidence angle of the nozzle 14 in turn corresponds in magnitude to the incidence angle of the nozzle 13 and the incidence angle of the nozzle 15 corresponds to the incidence angle of the nozzle 12.

(13) The incidence angle , likewise respectively relative to a plane oriented transversely with respect to the conveyor direction F, of the nozzles 17-21 is varied in magnitude in the angle range of from 0 to 30, the nozzle 17 assigned to the entry 5 being oriented at an incidence angle of about 30 towards the entry 5 and the nozzle 21 assigned to the exit 6 being oriented in the opposite direction, also at an incidence angle of about 30, towards the exit 6. Likewise, the nozzle 18 following on from the nozzles 17 in the conveyor direction F is directed at an incidence angle towards the entry 5, the incidence angle of the nozzle 18 being greater than the incidence angle of the nozzle 17. The nozzle 20 arranged before the nozzle 21 in the conveyor direction F is oriented in magnitude at the same incidence angle towards the exit 6. The nozzle 19 arranged in the middle of the nozzle arrangement D2, on the other hand, is oriented at an incidence angle of 0 with respect to the conveyor path 4, so that the gas jet G emerging from this nozzle 19 strikes the flat steel product S to be treated at a right angle.

(14) At the same time, the nozzles 11-16 of the nozzle arrangement D1 are directed towards the lower side US of the flat steel product S and the nozzles 17-21 of the nozzle arrangement D2 are directed towards the upper side OS of the flat steel product S.

(15) Owing to this arrangement of the nozzles 11-21, the gas jets G emerging from the nozzles 11-21 together form two gas flows G1, G2, of which one gas flow G1 flows towards the entry 5 in the form of a flow vortex turbulently travelling spirally around the flat steel product S to be treated, and the other gas flow G2 flows to the exit 6 of the annealing furnace chamber in a similar way as the flat steel product S in the manner of a flow vortex turbulently travelling spirally in the opposite direction.

(16) The origin of the gas flows G1, G2 in this case lies approximately in the middle of the length of the conveyor path 4 in the region of the nozzle 19, the gas jet G of which, emitted transversely with respect to the conveyor path 4 is divided into two partial flows flowing in opposite directions, from which the gas flows G1, G2 are formed, owing to the impulse caused by the gas jets G of the opposition arranged nozzles 13, 14 respectively directed towards the entry 5 and the exit 6.

(17) Owing to each of the gas jets G emerging from the nozzles 13, 18, 12, 17 and 11, the gas flow G1 receives new impulse and additional volume flow, so that its profile travelling spirally around the conveyor path 4 and the flat steel product S transported thereon is maintained with a high concentration as far as the entry 5.

(18) Likewise, the gas jets G of the gas flow G2, which emerge from the nozzles 14, 20, 15, 21 and 16, supply new flow energy and additional volume, so that the gas flow G2 likewise travelling spirally around the conveyor path 4 and the flat steel product S transported thereon reaches the exit 6 of the annealing furnace chamber 1 with high flow energy.

(19) The gas feed to the annealing furnace chamber 1 is controlled overall in such a way that a positive pressure of at least 0.001 relative to the ambient pressure U is constantly maintained in the annealing furnace chamber 1.

(20) Effective sealing of the annealing furnace chamber 1 in relation to the reduction atmosphere R1, R2, respectively containing H.sub.2, present in the annealing furnace chambers 2a, 2b respectively arranged before and after the first annealing furnace chamber in the conveyor direction, is furthermore achieved by virtue of the fact that, in particular, the gas jets G emitted from the nozzles 11, 12 placed closest to the entry 5 displace the reduction atmosphere R1 of the annealing furnace chamber 2a approaching the entry 5 away from the annealing furnace chamber 1, and the gas jets G emitted from the displacing nozzles 16, 21 next to the exit 6 displace the H.sub.2-containing reduction gas atmosphere R2 of the annealing furnace chamber 2b away from the annealing furnace chamber 1. Furthermore, the O.sub.2-containing gas jets G of the nozzles 16, 21 or the gas flow G2 flowing out of the exit 6 form H.sub.2O in a controlled way by reaction of H.sub.2 and O.sub.2 outside the annealing furnace chamber 1, so that reduction atmosphere R1, R2 reaching the respective gas jet G or the gas flow G2 is also reliably prevented from entering the annealing furnace chamber 1.

LIST OF REFERENCES

(21) 1 annealing furnace chamber (oxidation annealing furnace chamber) 2a annealing furnace chamber (reduction annealing furnace chamber) arranged before the annealing furnace chamber 1 in the conveyor direction F 2b annealing furnace chamber (reduction annealing furnace chamber) arranged after the annealing furnace chamber 1 in the conveyor direction F 3 annealing furnace 4 linear conveyor path through the annealing furnace chambers 1, 2 5 entry of the annealing furnace chamber 1 6 exit of the annealing furnace chamber 1 7, 8 inner surfaces of the longitudinal walls 9, 10 9, 10 longitudinal walls of the annealing furnace chamber 1 11-16 individual nozzles of the nozzle arrangement D1 17-21 individual nozzles of the nozzle arrangement D2 22 N.sub.2 supply 23 O.sub.2 supply 24, 25 valves incidence angle attitude angle D1, D2 nozzle arrangements F conveyor direction of the flat steel, product S G gas jets G1, G2 gas flows OS upper side of the flat steel product S R1 reduction atmosphere of the annealing furnace chamber 2a R2 reduction atmosphere of the annealing furnace chamber 2b S flat steel product U surrounding atmosphere US lower side of the flat steel product S V apparatus for the treatment of a flat steel product S in the form of a cold- or hot-rolled steel strip, taking place in throughput.