CN110643917B

CN110643917B - Production method of continuous hot-dip galvanizing aluminum magnesium, air knife device and air knife system

Info

Publication number: CN110643917B
Application number: CN201911103569.XA
Authority: CN
Inventors: 杜昕; 董世文; 王海; 张国堂; 赵小龙; 王瑾; 赵永科; 孙朝勇
Original assignee: Gansu Jiu Steel Group Hongxing Iron and Steel Co Ltd
Current assignee: Gansu Jiu Steel Group Hongxing Iron and Steel Co Ltd
Priority date: 2019-11-13
Filing date: 2019-11-13
Publication date: 2021-07-30
Anticipated expiration: 2039-11-13
Also published as: CN110643917A

Abstract

The invention provides a production method of continuous hot-dip galvanizing aluminum magnesium, an air knife device and an air knife system, and relates to the technical field of continuous hot-dip galvanizing production. It includes main air knife and slope cooling device, main air knife is including last sword lip and the lower sword lip of mutually supporting, it has first inclined plane to go up the sword lip outside, slope cooling device includes from down first cooling zone and the second cooling zone that up links to each other in proper order, first cooling zone is connected with first inclined plane cooperation, first cooling zone has the second inclined plane, it has first cooling gas export to open on the second inclined plane, open on the surface of second cooling zone has second cooling gas export, and the jet-propelled direction slope of first cooling gas export and second cooling gas export is upwards. The combined air knife of the air knife and the cooling device can cool strip steel as soon as possible and control the cooling rate of the coating.

Description

Production method of continuous hot-dip galvanizing aluminum magnesium, air knife device and air knife system

Technical Field

The invention relates to the technical field of continuous hot-dip production, in particular to a production method of continuous hot-dip galvanized aluminum magnesium, an air knife device and an air knife system.

Background

At present, the air knife used in the continuous hot galvanizing production line is mainly used for controlling the galvanized coating, and the working principle of the air knife is that air knife using gas as medium is used for controlling the coating, and the weight of the coating and the additional cooling of the coating are carried out by the pressure of the air knife blown by the air knife. After the strip steel is coated, the strip steel is cooled by an air knife and a special cooling air box, the cooling of the strip steel and the size of spangles are controlled, and the tear marks generated by thick coating layers of products such as zinc-aluminum-magnesium, aluminum-zinc, zinc-aluminum and the like are difficult to control, which is also a difficulty of continuous hot-dip coating products.

The surface quality of the product is related to factors such as the cooling rate after plating, the production line speed, the cooling position, the tear trace lines, the coating thickness and the like, wherein the surface of the product with the tear trace lines is uneven, the poor surface quality of the product can bring great harm to subsequent production, the service life of working rolls of a withdrawal and straightening machine, a finishing machine and a roller coater is seriously threatened, and in addition, the abrasion of a wringing roll and a compression roll is easily increased due to the defect of the tear trace lines.

In view of this, the invention is particularly proposed.

Disclosure of Invention

The invention aims to provide a production method of continuous hot-dip galvanizing aluminum magnesium, an air knife device and an air knife system to solve the technical problems.

The invention is realized by the following steps:

the utility model provides an air knife device of continuous hot dipping production zinc-aluminum magnesium, it includes main air knife and slope cooling device, main air knife is including the last sword lip and the lower sword lip of mutually supporting, it has first inclined plane to go up the sword lip outside, slope cooling device includes from down up consecutive first cooling zone and second cooling zone, first cooling zone is connected with the cooperation of first inclined plane, first cooling zone has the second inclined plane, it has first cooling gas export to open on the second inclined plane, open on the surface of second cooling zone has second cooling gas export, and the jet-propelled direction slope of first cooling gas export and second cooling gas export is upwards.

The inclined cooling device comprises a first cooling section and a second cooling section which are sequentially connected from bottom to top, and a cooling gas outlet is arranged on a second inclined plane of the first cooling section, so that the cooling gas outlet sprays upward gas, the coating liquid which is not solidified is prevented from flowing downwards, and the generation of tear marks is reduced or stopped. And a second cooling gas outlet is formed in the surface of the second cooling section, so that cooling gas is sprayed out from the second cooling gas outlet in an inclined upward direction, the coating liquid on the surface of the strip steel is further cooled, and the generation of tear marks is reduced.

In a preferred embodiment of the present invention, an inclined air inlet pipe of the cooling device is disposed at a top end of the second cooling section, and the second cooling section is communicated with the internal cavity of the first cooling section.

The inner cavities of the first cooling section and the second cooling section are communicated, air is fed from the upper side of the second cooling section, the gas pressure of the first cooling section is controlled to be lower than that of the second cooling section, and the phenomenon that the thickness of a coating cannot be accurately controlled due to the fact that the gas pressure close to the knife lip of the main air knife is too large is prevented.

In a preferred embodiment of the present invention, an included angle between the gas spraying direction of the first cooling gas outlet and the horizontal plane is greater than an included angle between the gas spraying direction of the second cooling gas outlet and the horizontal plane.

The arrangement is that when the strip steel is initially cooled, more unset coating liquid exists, and in order to inhibit the generation of tear marks, an oblique upward cooling air flow with a larger inclination angle needs to be provided to accelerate the cooling of the coating liquid, so that the generation of the tear marks is inhibited. After the coating liquid is cooled by the first cooling section, the coating liquid is basically in a solidification state, and at the moment, an obliquely upward cooling air flow with a lower inclination angle is provided, so that the coating liquid is solidified fully and uniformly.

In a preferred embodiment of the present invention, an included angle between the first inclined surface and the horizontal plane is an included angle a, an included angle between the second inclined surface and the first inclined surface is an included angle b, and a sum of the included angle a and the included angle b is less than 90 °;

preferably, the angle of angle a is greater than the angle of angle b.

Because the air flow of the main air knife is smaller than that of the air flow during inclined cooling, the included angle a is larger than the included angle b, so that the air can be prevented from being interfered by the air flow of the inclined cooling device when being sprayed out of the knife lip of the air knife, and the control of a coating is facilitated. Further, if the sum of the included angle a and the included angle b is larger than 90 °, the flow rate and the flow velocity are reduced, and the cooling control of the plating layer cannot be realized.

In a preferred embodiment of the present invention, the number of the first cooling gas outlets and the second cooling gas outlets is at least 2; the first cooling gas outlets are arrayed on the second inclined surface, and the second cooling gas outlets are arrayed on the surface of the second cooling section;

preferably, the first cooling gas outlet and the second cooling gas outlet are arranged in at least one of a horizontal array, a spaced array and a crossed array.

The cooling gas outlets are arranged in an array manner, so that the surface of the strip steel can be uniformly cooled, tear marks are reduced, and the quality of a strip steel coating is improved.

In a preferred embodiment of the present invention, the first cooling gas outlet and the second cooling gas outlet are cooling nozzles or cooling gas holes;

preferably, the shape of the cooling air holes is a round hole or a polygonal hole;

preferably, the cooling air nozzle is a slit nozzle, a circular hole nozzle or a polygonal nozzle.

The shape of the cooling air nozzles or cooling air holes can be adjusted according to needs, and the round hole nozzles are preferred.

In a preferred embodiment of the present invention, the length of the main air knife is less than or equal to the width of the inclined cooling device, and the width of the inclined cooling device is 1.5-1.7 times of the maximum width of the strip steel to be cooled.

The length of the main air knife is less than or equal to the width of the inclined cooling device, and the width of the inclined cooling device is 1.5-1.7 times of the maximum width of the strip steel to be cooled, so that the strip steel sprayed with a coating can be fully cooled without dead angles on the surface, and tear marks are reduced.

An air knife system for continuous hot-dip production comprises at least two air knife devices which are symmetrically arranged on two sides of a strip steel.

The air knife devices arranged on the two sides of the strip steel can realize uniform stress when the strip steel is cooled and plated, and can also eliminate tear marks on the two sides of the strip steel.

The air knife device or the air knife system can be applied to the production of continuous hot-dip galvanizing aluminum, hot-dip galvanizing aluminum zinc, hot-dip galvanizing pure zinc or hot-dip galvanizing aluminum magnesium.

The air knife device or the air knife system provided by the invention can be widely applied to the production of continuous hot-dip galvanizing aluminum, hot-dip galvanizing aluminum zinc, hot-dip galvanizing pure zinc or hot galvanizing aluminum magnesium.

A method for continuous hot-dip production of strip steel by using an air knife device comprises the step of enabling the strip steel to sequentially pass through a lower knife lip, an upper knife lip, a first cooling section and a second cooling section.

The strip steel is cooled from bottom to top, the downward gravity of the coating liquid attached to the strip steel and the airflow cooling pressure counteract the downward trend of the coating liquid, and the coating liquid which is not solidified is prevented from flowing downwards, so that the generation of tear marks is reduced or avoided.

Compared with the prior art, the invention has the beneficial effects that:

the invention provides a production method of continuous hot-dip galvanizing aluminum magnesium, an air knife device and an air knife system, wherein the oblique upward blowing force of a first cooling gas outlet of a first cooling section acts on strip steel to be cooled, the downward trend of coating liquid is counteracted by the cooling pressure of air flow and the downward gravity of the unsolidified coating liquid attached to the strip steel, the downward flow of the unsolidified coating liquid is prevented, so that the generation of tear marks is reduced or avoided, the cooling pressure borne by a coating layer is increased along with the increase of the thickness of the coating layer, the pressure and the cooling speed of the air flow sprayed to the strip steel are greater than the downward trend of the unsolidified coating liquid, and the defect of the tear marks is basically eliminated. After the first cooling section is cooled, cooling gas is sprayed out from a second cooling gas outlet of the second cooling section in an inclined upward manner to cool the strip steel again, so that the uniformity of a coating is improved, the strip steel is fully cooled, and the surface quality of a product is improved. The thickness of the coating is accurately controlled by arranging the upper knife lip and the lower knife lip. The air knife device or the air knife system provided by the invention can be widely used for hot galvanizing aluminum magnesium production, and the production method is simple and easy to popularize.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.

FIG. 1 is a front view of a cooling air knife of the present invention;

FIG. 2 is a top view of a cooling gas knife according to the present invention;

FIG. 3 is a side view of a cooling air knife of the present invention;

FIG. 4 is an isometric view of a cooling air knife of the present invention;

FIG. 5 is a schematic gas flow diagram of a cooling gas knife in accordance with the present invention;

FIG. 6 is a cross-sectional view of a cooling air knife of the present invention;

FIG. 7 is an enlarged partial view of a cross-sectional view of a cooling air knife in accordance with the present invention;

FIG. 8 is an enlarged view of a portion of the present invention;

FIG. 9 is a schematic view of a primary air knife and an inclined cooling of a cooling air knife according to the present invention;

FIG. 10 is an exemplary schematic view of a primary air knife and an inclined cooling type of a cooling air knife according to the present invention;

FIG. 11 is a schematic view of an angle between a primary air knife and an inclined cooling of a cooling air knife according to the present invention;

FIG. 12 is a schematic view of a thick plated tear striation defect;

FIG. 13 is a schematic view of an optimized thick coating tear cross-striation defect with a cooling air knife in accordance with the present invention;

FIG. 14 is a graph showing the analysis of the flowing stress of the zinc liquid of the thick plating layer according to the present invention.

Icon: 1-cooling the air knife; 101-upper knife lip; 1011-horizontal plane of upper air knife cavity structure; 1012-first inclined plane; 102-lower lip; 1021-main air knife air inlet line; 103-inclined cooling means; 1031-second cooling section nozzle; 1032-first cooling stage nozzle; 1033-inclined cooling inlet line; 1034-second inclined plane; l1-length of the top bevel of the upper lip; l2-oblique cooling of the cooling air knife-the width of the bevel connecting the upper knife lip; a-the included angle between the horizontal plane of the upper air knife cavity structure and the inclined plane; b, an included angle between the inclined surface of the upper air knife cavity structure and the inclined cooling inclined surface; 2-strip steel; 201-steel plate base body; 202-steel plate plating; 203-the coating has lighter tear transverse striations; 2031-the coating has lighter transverse tear lines after improvement; 204-lowest point after the coating flows; 2041-lowest point after coating flow after improvement; 205-plating layer tear cross striation critical point; 2051-hard spot of tear transverse striation of the coating after improvement; s1-distance of the convex high point of zinc; s2-distance of the convex low point of zinc; 3-roller contact surface.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.

Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", "clockwise", "counterclockwise", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings or orientations or positional relationships that the products of the present invention usually place when in use, and are used only for convenience of describing the present invention and simplifying the description, but do not indicate or imply that the devices or elements referred to must have specific orientations, be constructed in specific orientations, and be operated, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," "third," and the like are used solely to distinguish one from another and are not to be construed as indicating or implying relative importance.

Furthermore, the terms "horizontal", "vertical", "overhang" and the like do not imply that the components are required to be absolutely horizontal or overhang, but may be slightly inclined. For example, "horizontal" merely means that the direction is more horizontal than "vertical" and does not mean that the structure must be perfectly horizontal, but may be slightly inclined.

In the description of the present invention, it should also be noted that, unless otherwise explicitly specified or limited, the terms "disposed," "mounted," "connected," and "connected" are to be construed broadly and may, for example, be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

Example 1

The present embodiment provides an air knife apparatus for continuous hot-dip galvanizing of al-mg, and referring to fig. 1 and 4, a cooling air knife 1, i.e. an air knife apparatus, includes a main air knife including an upper knife lip 101 and a lower knife lip 102, and an inclined cooling apparatus 103. The upper knife lip 101 and the lower knife lip 102 are buckled up and down to communicate with the rear cavity.

The length of the main air knife of the cooling air knife 1 is less than or equal to the width of the inclined cooling device 103, and the design width of the inclined cooling device 103 is 1.5-1.7 times of the maximum width of the produced strip steel.

The bottom of the lower knife lip 102 is connected with a main air knife air inlet pipeline 1021, in the embodiment, the main air knife air inlet pipeline 1021 is a multi-hole air supply mode connected by a plurality of groups of air pipelines, so that normal air supply of the main air knife can be ensured, and air can be sprayed out from the knife lip of a cavity formed by the upper knife lip 101 and the lower knife lip 102, so that the coating thickness of the strip steel can be accurately controlled.

Further, as shown in fig. 11, the side surface of the upper lip 101 has a first inclined surface 1012, and the first inclined surface 1012 is fixedly connected to the bottom surface of the inclined cooling device 103.

The inclined cooling device 103 includes a first cooling section and a second cooling section that are sequentially connected from bottom to top, and as shown in fig. 11, the first cooling section has a second inclined surface 1034, and the second inclined surface 1034 is provided with a first cooling gas outlet. In this embodiment, referring to fig. 11 and 4 in particular, the second inclined surface 1034 is provided with a first cooling section nozzle 1032. The first cooling section and the second cooling section are provided with inner chambers, and the inner chambers of the first cooling section and the second cooling section are communicated.

Referring to fig. 2 and 3, a second cooling stage nozzle 1031 is opened on a second cooling stage surface of the inclined cooling device 103. In this embodiment, the second cooling gas outlet is a cooling nozzle, and the second cooling section nozzles 1031 are circular hole nozzles arranged in a horizontal array. In other embodiments, the second cooling gas outlet can be set as a cooling gas hole according to requirements, and the shape of the cooling gas hole is adjusted to be a circular hole or a polygonal hole.

Further, referring to fig. 3, an inclined cooling air inlet pipeline 1033 is arranged at the top end of the second cooling section of the inclined cooling device 103, and the inclined cooling air inlet pipeline 1033 is mainly used for supplying air to the internal chamber of the inclined cooling device 103, so that the chamber is filled with gas with pressure and flow, and the gas is sprayed out from the

nozzles

1031 and 1032 of the second cooling section to cool the coating on the surface of the strip steel 2. In use, gas enters the second cooling section from the inclined cooling inlet line 1033 at the top of the inclined cooling device 103, and flows from top to bottom. The pressure and flow rate of the gas ejected from the second cooling stage nozzles 1031 approaching the inclined cooling intake pipe 1033 are greater than those ejected from the first cooling stage nozzles 1032.

Referring to fig. 4, the first cooling stage nozzle 1032 is installed in a chamber structure having a cross-sectional shape similar to a triangle, and is formed to face the strip 2 at one side of the formed triangle. By adopting the cavity mechanism, the pressure of the nozzle close to the gap between the upper knife lip 101 and the lower knife lip 102 of the main air knife is lower, and the pressure of the nozzle far away from the gap between the upper knife lip 101 and the lower knife lip 102 of the main air knife is higher. The arrangement can avoid the gas ejected from the gap between the upper knife lip 101 and the lower knife lip 102 of the main air knife from being disturbed, and the accurate control of the main air knife on the coating can be influenced.

In use, the airflow first enters the top chamber (i.e. the second cooling section) of the tilted cooling device 103 through the tilted cooling air inlet pipe 1033, and the cavity of the tilted cooling device 103 is divided into two chambers, the second cooling section and the first cooling section. The air current supplies air to the main chamber through the input mode of porous reposition of redundant personnel, flows out through second cooling segment nozzle 1031 and first cooling segment nozzle 1032 and acts on belted steel 2, cools the belted steel.

The second cooling section nozzle 1031 and the first cooling section nozzle 1032 are both mounted to the inclined cooling device 103 surface having a sealed cavity. The second cooling zone nozzles 1031 and the first cooling zone nozzles 1032 are each held at an angle of 0 to 85 ° with respect to the vertically upward running strip 2. The air flow ejected at the angle is sprayed on the strip steel 2, and provides an oblique upward thrust to the coating, thereby offsetting the downward flowing force of the zinc liquid of part of the coating, preventing the downward flowing of the zinc liquid and reducing tear marks.

Referring to fig. 5, it can be seen from fig. 5 that the strip 2 moves upward, the gas flow forms a certain angle along the moving direction of the strip 2, the downward flow speed of the zinc liquid in the coating is delayed or stopped, and the coating is cooled by the second cooling section nozzle 1031 and the first cooling section nozzle 1032. When the adhesion force of the unset zinc liquid overcomes the gravity acceleration, the zinc liquid does not flow downwards any more, and the aim of reducing the tear mark defect is fulfilled.

The first inclined surface 1012 of the upper lip 101 of the cooling air knife 1 is an inclined surface having a constant slope. The first cooling section is fixedly connected to the first inclined surface, the cooling air nozzles of the porous structure are arranged on the second inclined surface of the first cooling section, and the air of the first cooling section is blown and applied to the strip steel 2 which runs upwards. At the moment, the strip steel 2 vertically upwards runs, after the thickness of the coating is controlled to reach a target coating, the zinc liquid is attached to the strip steel by virtue of the adhesive force and simultaneously upwards runs along with the strip steel, and the air flow cooling pressure is offset with the downward gravity of the zinc liquid on the strip steel 2, so that the descending trend of the zinc liquid is inhibited, the unset zinc liquid is prevented from downwards flowing, and the generation of tear marks is reduced or avoided. As the thickness of the coating increases, the cooling pressure increases, the pressure and cooling speed of the air flow sprayed to the strip steel 2 are higher than the descending trend of the unsolidified zinc liquid, and thus the defect of tear marks is basically eliminated.

Fig. 6 is a cross-sectional view of a top view of the cooling air knife of fig. 2, from which it can be seen that the supply air to the cooling air knife 1 is divided into two parts, an inclined cooling air inlet line 1033 and a main air knife inlet line 1021.

The inclined cooling air inlet pipeline 1033 is arranged above the inclined cooling device 103, the pipeline arrangement is parallel to the strip steel 2, the arrangement is favorable for installation of occupied space in the production process, and the inclined cooling air inlet pipeline 1033 is arranged on the transmission side of the air knife overall air supply. The main air knife air inlet pipeline 1021 is arranged below the cavity of the lower knife lip 102, and is also of a porous structure, and the porous structure is beneficial to stabilizing the uniformity of flow and pressure inside the air knife.

Referring to fig. 5, the strip 2 is cooled from the first cooling zone nozzle 1032 of the cooling air knife 1 and from the position closest to the position of the knife lip, that is, the strip 2 is immediately cooled after being controlled by the coating.

The strip 2 is cooled by the inclined cooling device 103 in the shortest time after passing through the cooling air knife 1, and the effective length of the coating and the strip cooling is increased.

The cooling from the upper part of the knife lip of the main air knife is also a main characteristic of the invention, and the rapid cooling or the slow cooling gives longer cooling time, increases the cooling effect and is beneficial to better controlling the cooling length.

Fig. 7 to 8 are a side view and a partially enlarged view of the cooling air-knife 1, and for convenience of viewing the connection portion between the main air-knife and the inclined cooling device 103, the length of the first inclined surface 1012 of the common sidewall defining the connection portion between the inside of the main air-knife and the inclined cooling device 103 is L1 (i.e., the length of the inclined surface at the top of the upper lip is L1), and the inclined surface width of the second inclined surface of the first cooling stage is L2 (i.e., the inclined surface width of the inclined cooling portion of the cooling air-knife connected to the upper lip is L2). Referring to fig. 9 and 11 in particular, the combination of the upper knife lip 101 and the lower knife lip 102 constitutes a main air knife, the middle gasket constitutes a cavity of the air knife, and the air is collected in the cavity of the air knife and ejected from the knife lip of the air knife (i.e. the middle gap between the upper knife lip 101 and the lower knife lip 102).

Each face of going up sword lip 101 is formed and is equivalent to triangle-shaped, first inclined plane 1012 is equivalent to the hypotenuse, go up sword lip bottom and is equivalent to horizontal right-angle side, the contained angle of first inclined plane 1012 and last sword lip bottom is contained angle a (being the horizontal plane of last air knife cavity structure and the contained angle an of inclined plane), the contained angle that L1 and L2 are formed is contained angle b (being the contained angle b of last air knife cavity structure inclined plane and slope cooling inclined plane promptly), contained angle a and contained angle b sum are less than 90, preferred, the angle of contained angle a is greater than the angle of contained angle b.

In order to obtain the desired coating thickness uniformity and good surface quality, it is also necessary that the air knife have a certain flow rate and additional cooling capacity. In order to better use the air knife and reduce the generation of tear mark defects, the strip steel is firstly cooled at the tail end (namely a first cooling section) of an air knife lip nozzle of the inclined cooling device at a small flow and a small pressure, the tail end of the air knife lip is closest to the strip steel, the cooling effect of the air knife is better, and tear mark defects are also easily generated after the strip steel 2 passes through the air knife lip, and the tear mark defects are better as the tear mark defects are earlier from the cooling start of the air knife lip. The larger the air knife pressure of the first cooling section of the inclined cooling device 103 is, the farther the air knife pressure is from the strip steel 2, and the control principle of controlling tear cross-striation defects is met.

Fig. 10 shows a combination of five structures (1), (2), (3), (4), and (5), and in another embodiment, any of the cooling control methods shown in fig. 10 may be used.

In the cavity formed by the horizontal plane 1011 of the upper air knife cavity structure and the upper air knife in fig. 11, the length of L2 is greater than or equal to the length of the first inclined planes 1012 and L1. The larger the length of L2 compared with L1, the larger the inner space of the cavity structure, the larger the cooling capacity of the coating and the strip steel is, and the effective cooling length is increased. The smaller the length of L2 compared to L1, the smaller the internal space of the chamber structure obtained, and the reduced cooling capacity of the coating and strip. In actual production, the length ratio of L1 and L2 can be adjusted and optimized according to different production conditions, production line speeds and different types of plating solutions, and a good tear striation defect control effect is obtained.

FIG. 12 is a schematic view showing tear-line defects in a thick coating of a strip, and FIG. 12 shows only the form of the coating on one side of the strip and the substrate, while the other side is omitted. After the strip steel 2 is galvanized to obtain the coating weight meeting the production requirement, the zinc liquid which does not start to solidify starts to flow downwards under the action of the blowing pressure of the air knife lip, and the moving direction of the strip steel 2 which runs upwards is opposite to that of the zinc liquid.

The steel plate coating 202 is attached to the steel plate base body 201, the zinc liquid flows downwards to generate excessive zinc liquid aggregation to form tear line defects, and fig. 12 shows that in the prior art, the coating tear line serious points 205, the coating tear line lighter points 203 and the coating flowing rear lowest points 204 only show the tear line defects of the local part of the strip steel and represent the approximate appearance of the tear line defects generated by the zinc liquid flowing on the whole plate surface.

The raised points of zinc which the roller contact surface 3 first contacts the highest point after contacting the strip 2 are supported, and the distance S1 between the raised high points of zinc and the distance S2 between the raised low points of zinc represent two local high points which cannot be reached. The coating layer 205 with severe tear cross striations is thick due to the zinc flow accumulation, and the required cooling amount is large; the minimum point 204 is thinner after the coating has flowed, requiring a small amount of cooling. Therefore, the difference of the thickness of the coating makes the difference of the cooling temperature needed by the same cooling air volume at the high point and the low point larger, which causes the stress concentration generated in the cooling process and after the cooling of the coating and the strip steel, and finally directly influences the subsequent surface treatment and the stability of the performance.

The point 205 that the focus is tightened to the high point cladding material tear transverse striation cladding material is thicker, the coating flows back minimum 204 cladding material is thinner, make product surface unevenness, the high point contacts with roller surface in the production process, the lighter point 203 of cladding material tear transverse striation and the coating flow back minimum 204 are in unsettled state, the zinc of high point department can lead to the wearing and tearing of roller surface inhomogeneous, the frictional force of belted steel and roller has been reduced, lead to the roughness of roller surface to reduce too fast when serious, the life-span of roller reduces, local high point moves unstably, the high point receives the influence of the gravity and the tensile of belted steel, make the high point receive the extrusion and drop, and the zinc adhesion that drops can produce the secondary influence to the quality of product again on the surface of roller.

As shown in fig. 13, 2-1 is a schematic diagram of optimized thick coating lachrymal striation defects of the cooling air knife of the present invention, after the cooling air knife 1 is used, the lachrymal striation defects of the improved coating are significantly reduced from the lighter point 2031, the lowest point 2041 and the severe point 2051 after the coating flows, as compared with fig. 12. The uniform coating can be obtained after the defects of the high-point tear marks are reduced or eliminated, so that the loss of the high-point tear mark defects to the roller surface is reduced, the reduction probability of the roughness of the roller surface of the roller is slowed down, and the service life of the roller is prolonged. The cooling uniformity of the strip steel and the coating is correspondingly improved, and the product performance and the appearance quality are remarkably improved.

FIG. 14 is a graph showing the analysis of the flowing stress of the zinc liquid of the thick plating layer according to the present invention. F is the surface tension borne by the upward running coating of the strip steel 2, F1 is the adhesion force between the coating and the strip steel, G is the gravity borne by the coating, F3 is the cooling pressure of the cooling air knife 1, F2 is the magnitude of the adhesion force for overcoming the coating and the strip steel, and the oblique upward cooling thrust F3 given by the cooling air knife 1 counteracts the downward flowing gravity G and the adhesion force F1 of the zinc liquid, so that a stable and effective overcoming force is obtained. After the zinc liquid is cooled to a certain temperature and the adhesion is overcome enough, F2 is greater than F1, the zinc liquid can not flow downwards to pile up to form tear mark defects.

The invention also provides an air knife system for producing the zinc-aluminum-magnesium by continuous hot dipping, which comprises a front cooling air knife 1 and a rear cooling air knife 1, wherein the front cooling air knife 1 and the rear cooling air knife 1 have the same structure and cooling control mode and are symmetrically arranged at two sides of the strip steel 2.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. The air knife device for producing the zinc-aluminum-magnesium by the continuous hot plating is characterized by comprising a main air knife and an inclined cooling device, wherein the main air knife comprises an upper knife lip and a lower knife lip which are matched with each other, a first inclined plane is arranged on the outer side of the upper knife lip, the inclined cooling device comprises a first cooling section and a second cooling section which are sequentially connected from bottom to top, the first cooling section is matched and connected with the first inclined plane, the first cooling section is provided with a second inclined plane, a first cooling gas outlet is formed in the second inclined plane, a second cooling gas outlet is formed in the surface of the second cooling section, and the air spraying directions of the first cooling gas outlet and the second cooling gas outlet are inclined upwards; the included angle between the first inclined plane and the horizontal plane is an included angle a, the included angle between the second inclined plane and the first inclined plane is an included angle b, and the sum of the included angle a and the included angle b is smaller than 90 degrees; the angle of the included angle a is larger than that of the included angle b.

2. The air knife apparatus of claim 1, wherein a top end of the second cooling section is provided with an inclined cooling apparatus inlet pipe, and the second cooling section is in communication with the first cooling section internal chamber.

3. The gas knife apparatus of claim 1, wherein a gas jet direction of the first cooling gas outlet is at a greater angle to a horizontal plane than a gas jet direction of the second cooling gas outlet.

4. The gas knife apparatus of claim 1, wherein the number of the first cooling gas outlets and the second cooling gas outlets is at least 2; the first cooling gas outlets are arrayed on the second inclined surface, and the second cooling gas outlets are arrayed on the surface of the second cooling section.

5. The gas knife apparatus of claim 4, wherein the first cooling gas outlets and the second cooling gas outlets are arranged in at least one of a horizontal array, a spaced array, and a crossed array.

6. The gas knife apparatus of claim 4, wherein the first cooling gas outlet and the second cooling gas outlet are cooling gas nozzles or cooling gas holes;

the cooling air holes are round holes or polygonal holes;

the cooling air faucet is a slit nozzle, a round hole nozzle or a polygonal nozzle.

7. An air knife apparatus according to claim 1, wherein the length of the main air knife is less than or equal to the width of the inclined cooling means, which is 1.5-1.7 times the maximum width of the strip to be cooled.

8. An air knife system for producing zinc-aluminum-magnesium by continuous hot dipping, which is characterized by comprising at least two air knife devices according to any one of claims 1 to 7 and is used for being symmetrically arranged on two sides of a strip steel.

9. A method for continuous hot-dip production of a steel strip using the air knife device of claim 1, comprising passing the steel strip through a lower knife lip, an upper knife lip, a first cooling zone and a second cooling zone in this order.