Device and method for applying a layer to a flat steel product

Abstract

The invention relates to a device (150) for applying a layer (10) to a front and / or rear side of a flat steel product (100), comprising: a zinc-alloy melt pool (11) with an inlet side (E) and an outlet side (A); a stripping nozzle device (14) with at least one gas nozzle (15) for blowing off the front or rear side of the flat steel product (100) with gas (G), wherein the stripping nozzle device (14) is arranged in the region of the outlet side (A); a water vapour device (50) which is designed to output gaseous water vapour and to provide a controlled water vapour atmosphere in the proximity (NB) of the front and / or rear side of the flat steel product (100), wherein the controlled water vapour atmosphere has an absolute local humidity that is greater than 1 g / m³ and lower than 300 g / m³.

Claims

Claims 1. Device (150) for applying a layer (10) to a front and / or back of a flat steel product (100), comprising: - a zinc alloy melt bath (11) (ZnAl; ZnAlMg) with an inlet side (E) and an outlet side (A), - a wiping nozzle device (14) with at least one gas nozzle (15) for blowing the front or back of the flat steel product (100) with gas (G), wherein the wiping nozzle device (14) is arranged in the region of the outlet side (A), a steam device (50) which is designed to release gaseous steam and to provide a controlled steam atmosphere in the vicinity (NB) of the front and / or back of the flat steel product (100), wherein the controlled steam atmosphere has an absolute local humidity (f) which is greater than 1 g / m 3 and is less than 300 g / m 3, the absolute local humidity (f) preferably being in the range 2.71 g / m 3 up to 50 g / m 3 lies.

2. Device (150) according to claim 1, characterized in that for applying the layer (10), system parameters and process parameters of the device (150) are set such that the layer (10) can be blown off with the wiping nozzle device (14) according to a predetermined specification, wherein the system parameters and process parameters define a wiping efficiency factor (AWZ) which is substantially constant during the application of the layer (10).

3. Device (150) according to claim 2, characterized in that the stripping efficiency (AWZ) is defined either as follows: h EEZ = 24.61 ■ 3639 ■ - - 45.42 , v or is defined as follows: where: d is the thickness (d) of a nozzle lip gap (17), in mm, of the at least one gas nozzle (15) of the wiping nozzle device (14) D is the effective flow rate (D) of the gas (G) across the band width (w) per side of the flat steel product (100) in Nm 3 / hk is a unitless proportionality factor w is the bandwidth of the steel compartment product (100) in mm 2b is the half-width of the pressure distribution of the gas (G) on the steel compartment product (100) in mm v is the belt speed in m / min with which the steel compartment product (100) is moved along the wiping nozzle device (14) and through the near area (NB).

4. Method according to one of claims 1 to 3, characterized in that the following definitions apply to the half-width (b) and the proportionality factor (k) using the ratio of the distance (Z) to the thickness (d) of the nozzle lip gap (17): k = - Q 4 ■ 6.05 ■ 10“4 + Q 3 ■ 2.2 ■ IO“ 2 - ( ) 2 ■ 2.89 ■ 10“ 1 + ) ■ 1.55 - 1.9 Case 1.3: - d > 10 -> b = 0.125 Z and k = 6.5 -~ Z 5. Method according to one of claims 1 to 3, characterized in that when determining the values ​​for the half-width (b) and the proportionality factor (k) using the ratio of the distance (Z) to the thickness (d) of the nozzle lip gap (17), the following simplified definitions apply: Case 2.1 : - d < 7.6 b = l.9 -~ 2 and k = l Case 2.2: - d > 7.6 b = 0.125 Z and k = 6.S - ~ Z 6. Device (150) according to claim 3, characterized in that - the thickness (d) of the nozzle lip gap (17) is in a range between 0.5 mm and 10 mm, preferably between 0.8 mm and 2.0 mm, and / or - the flow rate (D) in the range from 200 to 8000 Nm 3 per hour, and / or - the distance (Z) between the nozzle lip gap (17) and the front or rear side of the flat steel product (100) is in a range between 2 mm and 15 mm, preferably between 3 mm and 12 mm, and / or - the belt speed (v) is in a range between 50 m / min and 200 m / min, preferably between 70 m / min and 150 m / min, and / or - the near field (NB) is a volume in a range of 1 m 3 up to 10 m 3 and preferably a volume of at least 2 m 3 has.

7. Device (150) according to one of claims 1 to 5, characterized in that the absolute local air humidity (f) applies in a virtual cylinder volume, which is delimited on the one hand by a virtual cylinder surface and on the other hand by two virtual planes running parallel to the steel flat product (100) on both sides of the steel flat product (100) and at a distance (s) from the steel flat product (100), wherein the cylinder volume has a volume in a range of 1 m 3 up to 10 m 3 and preferably a volume of at least 2 m 3 wherein the measurement of the absolute local humidity (f) is carried out directly or indirectly.

8. Device (150) according to one of claims 2 to 7, characterized in that it comprises a controller (250) designed to regulate the controlled water vapor atmosphere in order to adjust the absolute humidity (f) so that during the application and blow-off of the layer (10) the following inequality is satisfied: f > AWZ.

9. Device (150) according to one of claims 1 to 7, characterized in that the steam device (50) at least partially encloses the front and / or back of the flat steel product (100) with a housing (52) in order to be able to specify the controlled steam atmosphere as a quasi-static ambient condition in a close range (NB) in the interior of the housing (52).

10. Device (150) according to claim 9, characterized in that the absolute local humidity (f) is measurable in the vicinity (NB) of the housing (52), wherein the measurement of the absolute local humidity (f) is carried out directly or indirectly.

11. Device (150) according to claim 9 or 10, characterized in that the near area (NB) of the housing (52) has a volume in a range of 1 m 3 up to 10 m 3 and preferably a volume of at least 2 m 3 has.

12. Device (150) according to one of claims 2 - 11, characterized in that the predetermined specification determines the coating application of the layer (10) and / or the desired thickness of the layer (10) and that the layer (10) to be applied meets the following specification: - Coating layer (10) on each side of the flat steel product (100) in the range of 20 g / m 2 up to 200 g / m 2 , preferably range 30 g / m 2up to 100 g / m 2 , lies, and / or - Target thickness of the layer (10) on each side of the flat steel product (100), which is in the range 3 μm to 30 μm, preferably in the range 4.5 μm to 15 μm.

13. Device (150) according to one of claims 1 - 12, characterized in that the controlled water vapor atmosphere for a given stripping efficiency (AWZ) provides a sufficiently high absolute local air humidity (f) in the near field (NB) in order to prevent marbling and / or the formation of toothpick defects on the layer (10).

14. Device (150) according to one of claims 1 - 12, characterized in that - at least one humidity sensor (51) is arranged in the near area (NB) of the water vapor device (50) in order to be able to directly measure the absolute local air humidity (f) in the near area (NB), and / or - at least one humidity sensor (56) is provided in order to be able to directly measure the absolute local air humidity (ZUG) in the environment of the device (150).

15. Device (150) according to one of claims 1 - 14, characterized in that it comprises at least one steam generator (DG) in order to be able to adjust the absolute local air humidity (f) in an automated manner such that the absolute local air humidity (f) is greater than the stripping efficiency factor (AWZ).

16. Method for applying a layer (10) according to a target specification to at least one side of a flat steel product (100), by moving the flat steel product (100) through a zinc alloy molten bath (11) (ZnAl; ZnAlMg) and, on the outlet side (A) of the molten bath, stripping gas (G) exits through a nozzle lip gap (17) of at least one gas nozzle (15) in the direction of the flat steel product (100) in order to blow off the layer (10) according to the target specification, wherein a stripping efficiency factor (AWZ) is defined by the following parameters: d thickness (d) of the nozzle lip gap (17) of the gas nozzle (15) of the stripping nozzle device (14), D across the bandwidth (w) effective flow (quantity) (D) of the gas (G) per side of the flat steel product (100) in Nm 3 / h, w bandwidth of the steel compartment product (100) in mm, 2b half-width of the pressure distribution of the gas (G) on the steel compartment product (100) in mm, v Belt speed in m / min at which the steel product (100) is moved along the wiping nozzle device (14), the method comprising the following steps: - determining the absolute local humidity (f) in a controlled water vapor atmosphere in a close range (NB) at the front and / or back of the flat steel product (100) and / or the ambient air humidity (ZUG) before carrying out the method and / or during the method, - Relating the measured moisture content (f, ZUG) to the stripping efficiency factor (AWZ) to determine whether the condition f > AWZ or ZUG > AWZ is met, - if the condition is met, initiating or continuing the process for applying the layer (10), or if the condition is not met, increasing the absolute local humidity (f) in the controlled water vapor atmosphere by using a water vapor device (50) designed to release gaseous water vapor in order to achieve the fulfillment of the condition f > MNZ, in order to then initialize or continue the process for applying the layer.

17. Method according to claim 16, characterized in that the Stripping efficiency factor (AWZ) is defined either as follows: n 2 .ih AWZ = 24.61 ■ , , + 3639 ■ - - 45.42 , w z -d z -bv or as follows: where: d is the thickness (d) of a nozzle lip gap (17), in mm, of a Gas nozzle (15) of the wiping nozzle device (14) D is the effective flow rate (D) of the gas (G) across the band width (w) per side of the flat steel product (100) in Nm 3 / hk is a unitless proportionality factor w is the bandwidth of the steel compartment product (100) in mm 2b is the half-width of the pressure distribution of the gas (G) on the steel compartment product (100) in mm v is the belt speed in m / min with which the steel compartment product (100) is moved along the wiping nozzle device (14) and through the near area (NB).

18. Method according to one of claims 16 or 17, characterized in that the absolute local humidity (f) of the controlled water vapor atmosphere is determined on the front and / or back of the flat steel product (100) at a distance of more than 20 cm from the front and / or back.

19. Method according to one of claims 16 to 18, characterized in that a controller (250) is used which is designed to regulate the controlled water vapor atmosphere in order to adjust the absolute humidity (f) such that during the application and blow-off of the layer (10) the condition is met: f > AWZ.

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