Hot-based zinc-aluminum-magnesium steel sheet and method for manufacturing the same

Abstract

The application discloses a hot-based zinc-aluminum-magnesium steel plate and a preparation method thereof, and belongs to the technical field of hot galvanizing coating. The preparation method comprises the following steps: placing a strip steel base material into a direct combustion furnace for heating, controlling the hydrogen content in a cold area of the direct combustion furnace to be between 15-25%, controlling the temperature in the direct combustion furnace to be between 1250-1325 DEG C, and controlling the temperature of the strip steel base material to be between 660-720 DEG C; and placing the heated strip steel base material into a main pot filled with an aluminum-zinc-magnesium plating solution for hot plating, so as to obtain the aluminum-zinc-magnesium plated steel plate. According to mass percentage, the Al content in the aluminum-zinc-magnesium plating solution is 6.0-7.0%, the Mg content is 2.0-3.0%, and the rest is zinc and other inevitable impurities. The preparation method can effectively improve the problem of the thickening of the edge of the zinc-aluminum-magnesium plated steel plate by changing the aluminum-zinc-magnesium plating solution composition and related process parameters.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hot-dip galvanizing coating technology, and particularly relates to a hot-based zinc-aluminum-magnesium steel plate and a preparation method thereof. BACKGROUND

[0002] Galvanizing aluminum magnesium on the surface of the strip steel is the most important production process of hot-dip galvanizing aluminum magnesium production line, and the uniformity of the coating directly affects the delicacy and dimensional accuracy of the surface of the strip steel.

[0003] In the coating process, due to the characteristics of hot-dip galvanizing process and air knife blowing, even if the process parameters are normal, the edge thickening phenomenon may occur. The main reason is that the edge effect of the strip steel leads to the divergence of the airflow at the edge of the strip steel, and the zinc scraping ability decreases. Moreover, due to the surface tension of the zinc liquid on the surface of the strip steel, the zinc liquid is more likely to gather at the edge. The thickness of the general hot-dip galvanizing product is between 0.3-2.5mm, and the thickness of the hot-based zinc-aluminum-magnesium product can be up to 6mm. The running speed of the strip steel in the continuous galvanizing production line of thick-gauge products is low, and the heat loss at the edge is more serious, so the viscosity of the zinc liquid is larger, and the zinc liquid scraped at the edge is less than that at the middle, further aggravating the edge thickening defect of the strip steel, and in severe cases, even after leveling or coiling, the wave-shaped defect may be produced.

[0004] Therefore, a method for controlling the edge thickening of a thick-gauge hot-based zinc-aluminum-magnesium steel plate is needed, so as to obtain an excellent product with uniform zinc layer, edge quality and surface quality meeting the requirements of customers. SUMMARY

[0005] In view of the above problems, the present application is proposed to provide a hot-based zinc-aluminum-magnesium steel plate and a preparation method thereof which can overcome the above problems or at least partially solve the above problems.

[0006] In a first aspect, a preparation method of a hot-based zinc-aluminum-magnesium steel plate is provided, and the preparation method comprises:

[0007] putting a strip steel substrate into a direct-fired furnace for heating, controlling the hydrogen content in the cold zone of the direct-fired furnace to be between 15-25%, and controlling the temperature in the direct-fired furnace to be between 1250-1325℃, so that the temperature of the strip steel substrate is between 660-720℃;

[0008] putting the heated strip steel substrate into a main pot containing an aluminum-zinc-magnesium plating liquid for hot-dip galvanizing, to obtain an aluminum-zinc-magnesium plated steel plate;

[0009] wherein, in terms of mass percentage, the Al content in the aluminum-zinc-magnesium plating liquid is 6.0-7.0%, the Mg content is 2.0-3.0%, and the balance is zinc and other unavoidable impurities.

[0010] Optionally, in the process of placing the heated strip substrate into the main pot filled with the aluminum-zinc-magnesium plating solution for hot plating, the strip substrate has the same temperature as the aluminum-zinc-magnesium plating solution.

[0011] Optionally, in the process of placing the heated strip substrate into the main pot filled with the aluminum-zinc-magnesium plating solution for hot plating, the temperature of the aluminum-zinc-magnesium plating solution is 420-450 DEG C.

[0012] Optionally, the preparation method further comprises:

[0013] In the process of placing the heated strip substrate into the main pot filled with the aluminum-zinc-magnesium plating solution for hot plating, a gas knife is used to blow the plating layer.

[0014] Optionally, the opening degree of the gas knife adopts a stepped transition form from the center to the edge, and the opening degree of the gas knife is 1.0-1.5 mm.

[0015] Optionally, the baffle thickness of the gas knife is 6-8 mm, and the lower end of the baffle of the gas knife is an isosceles triangle structure.

[0016] Optionally, the running speed of the strip substrate is 30-45 m / min, the upper gas knife angle of the gas knife is 0-0.2 DEG, the lower gas knife angle is 0-0.2 DEG, the height of the gas knife is 160-200 mm, the air pressure of the gas knife is 60-90 mbar, and the distance between the gas knife and the strip substrate is 30-60 mm.

[0017] Optionally, the strip substrate is a hot-rolled strip substrate.

[0018] Optionally, the thickness of the aluminum-zinc-magnesium plated steel plate is greater than or equal to 4.0 mm.

[0019] In a second aspect, a hot-based zinc-aluminum-magnesium steel plate prepared by the preparation method of the first aspect is provided.

[0020] The technical scheme provided in the embodiments of the present application has at least the following technical effects or advantages:

[0021] The hot-based zinc-aluminum-magnesium steel plate and the preparation method thereof provided in the embodiments of the present application can ensure the characteristics of the zinc-aluminum-magnesium plating layer by changing the composition of the aluminum-zinc-magnesium plating solution, so that the zinc-aluminum-magnesium plating layer maintains a certain viscosity to meet the production requirements of thick zinc layers. At the same time, by changing the relevant process parameters, the iron oxide on the surface of the strip substrate can be fully reduced to form an active surface suitable for hot galvanizing zinc-aluminum-magnesium, thereby effectively improving the problem of thickening of the edge of the galvanized zinc-aluminum-magnesium steel plate, and having good popularization value.

[0022] The above description is only a summary of the technical solutions of the present application. In order to enable one skilled in the art to better understand the technical means of the present application and to implement the same according to the contents of the description, and in order to enable the above and other purposes, features and advantages of the present application to be more apparent and understandable, the following specific embodiments of the present application are described. BRIEF DESCRIPTION OF DRAWINGS

[0023] Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The accompanying drawings are intended to further aid the understanding of the preferred embodiments, and are not intended to limit the present application thereto. Like reference numerals denote like elements throughout the drawings.

[0024] In the drawings:

[0025] Figure 1 is a flow chart of a preparation method of a hot-based zinc-aluminum-magnesium steel plate provided by an embodiment of the present application;

[0026] Figure 2 is a structural schematic diagram of an opening degree of an air knife provided by an embodiment of the present application;

[0027] Figure 3 is a structural schematic diagram of an air knife provided by an embodiment of the present application;

[0028] Figure 4 is a schematic diagram of A of Figure 3 DETAILED DESCRIPTION

[0029] Exemplary embodiments of the present disclosure will be described more fully hereinafter with reference to the accompanying drawings.

[0030] Various structural schematic diagrams according to embodiments of the present disclosure are shown in the drawings. These diagrams are not drawn to scale, in which certain details are exaggerated for the purpose of clarity and can omit certain details. The shapes of various regions, layers shown in the diagrams, and their relative sizes and positional relationships can deviate in actuality due to manufacturing tolerances or technical limitations, and regions / layers with different shapes, sizes, relative positions can be additionally designed by those skilled in the art according to actual needs.

[0031] In the context of the present disclosure, when a layer / element is referred to as being located "on" another layer / element, the layer / element can be directly located on the other layer / element, or there can be an intermediate layer / element between them. In addition, if a layer / element is located "on" another layer / element in one orientation, it can be located "under" the other layer / element when the orientation is reversed. In the context of the present disclosure, similar or identical parts can be denoted by the same or similar reference numerals.

[0032] ​In order to better understand the above technical solutions, the above technical solutions will be described in detail below in combination with specific embodiments. It should be understood that the embodiments of the present disclosure and the specific features in the embodiments are detailed descriptions of the technical solutions of the present application, rather than limitations of the technical solutions of the present application. In the case of no conflict, the technical features in the embodiments of the present application and the embodiments can be combined with each other.

[0033] Figure 1 A flow chart of a preparation method of a hot-based zinc-aluminum-magnesium steel plate provided by an embodiment of the present application is shown in FIG. 1, and the preparation method comprises the following steps. Figure 1

[0034] In step S101, the strip steel substrate is placed into a direct-fired furnace for heating, the hydrogen content in the cold zone of the direct-fired furnace is controlled to be between 15-25%, and the temperature in the direct-fired furnace is controlled to be between 1250-1325℃, so that the temperature of the strip steel substrate is between 660-720℃.

[0035] In the present embodiment, the strip steel substrate is a hot-rolled strip steel substrate. The hydrogen content in the cold zone of the direct-fired furnace is a volume percentage.

[0036] By controlling the hydrogen content in the furnace, the iron oxide scale on the surface of the hot-based steel plate is fully reduced to form an active surface suitable for hot-dip galvanizing aluminum-magnesium.

[0037] It should be noted that before step S101 is performed, the preparation method can further comprise the following steps.

[0038] The strip steel substrate is cleaned.

[0039] In an implementation manner of the present embodiment, the hot-based zinc-aluminum-magnesium can be produced by a modified Sendzimir method.

[0040] In step S102, the heated strip steel substrate is placed into a main pot containing an aluminum-zinc-magnesium plating solution for hot-dip plating to obtain an aluminum-zinc-magnesium plated steel plate. In the aluminum-zinc-magnesium plating solution, the Al content is 6.0-7.0% by mass, the Mg content is 2.0-3.0% by mass, and the balance is zinc and other unavoidable impurities.

[0041] In the present embodiment, by changing the composition of the aluminum-zinc-magnesium plating solution, the zinc-aluminum-magnesium plated layer can maintain a certain viscosity under the premise of ensuring the characteristics of the zinc-aluminum-magnesium plated layer to meet the production requirements of thick zinc layer.

[0042] In the present embodiment, the thickness of the obtained aluminum-zinc-magnesium plated steel plate is greater than or equal to 4.0mm.

[0043] In the process of performing step S102, the strip steel substrate has the same temperature as the temperature of the aluminum-zinc-magnesium plating solution when entering the pot, which can effectively eliminate the core heat and further improve the fluidity of the zinc liquid to obtain a more uniform zinc layer. ​

[0044] In one implementation of the embodiment, the temperature of the aluminum-zinc-magnesium plating solution is 420-450℃. Alternatively, the entry temperature of the strip steel substrate into the pot is 420-460℃.

[0045] Optionally, in the process of performing step S102, the preparation method further comprises:

[0046] A gas knife is used to blow the plating layer.

[0047] The zinc scraping ability of the gas knife is related to the momentum of the gas flow of the gas knife, and the momentum I of the gas flow has the following relationship with the pressure P of the gas knife and the opening degree b of the gas knife:

[0048] I=Pb2

[0049] Therefore, by increasing the width of the gap of the gas knife, the zinc scraping ability of the edge part can be increased, so as to obtain a uniform zinc layer, improve the edge thickening, and produce 4.0mm and above hot base zinc-aluminum-magnesium plate.

[0050] Figure 2 is a structural diagram of the opening degree of a gas knife provided by the embodiment of the present application, as shown in Figure 2 The opening degree of the gas knife adopts a stepped transition form from the center to the edge, that is, different slopes are adopted at different positions, and the opening degree of the gas knife is 1.0-1.5mm.

[0051] Figure 3 is a structural diagram of a gas knife provided by the embodiment of the present application, Figure 4 is Figure 3 the A direction schematic view of Figure 3 and Figure 4 As shown in , the thickness of the baffle 200 of the gas knife is 6-8mm, and the lower end of the baffle 200 of the gas knife is an isosceles triangle structure to maximize the improvement of the edge airflow.

[0052] When passing through the welding seam, the number of millimeters that the gas knife baffle opens in advance is automatically determined according to the front and rear strip steel width, the strip steel running speed and the baffle running speed program, solving the problem of edge thickening at the head and tail positions of the strip steel.

[0053] S=

V*(d1-d2) / 2v

[0054] S: the distance from the opening of the gas knife baffle to the next welding seam, m;

[0055] V: the running speed of the strip steel, m / min;

[0056] d1: the width of the next coil of strip steel, m;

[0057] d2: the width of the current coil of strip steel, m;

[0058] v: the running speed of the baffle is 40mm / s.

[0059] Optionally, in the continuous galvanizing production line, the running speed of the strip substrate is 30-45 m / min, the upper air knife angle of the air knife is 0-0.2°, the lower air knife angle is 0-0.2°, the height of the air knife is 160-200 mm; the air pressure of the air knife is 60-90 mbar, and the distance between the air knife and the strip substrate is 30-60 mm. The air knife parameter control method provided by the application is simple to operate, and the operator can quickly adjust the desired zinc layer according to the specifications of the produced strip, the zinc layer and the production line speed.

[0060] In order to better understand the application, the following describes the case of the aluminum-zinc-magnesium plated steel plate prepared by the preparation method of the application in combination with several examples:

[0061] Example 1:

[0062] When producing a hot-based zinc-aluminum-magnesium product with a strip thickness of 4.0 mm and a width of 1250 mm and a coating requirement of 275 g / m 2 , the running speed of the strip substrate in the continuous galvanizing production line is 45 m / min, the opening degree of the air knife is 1.0-1.5 mm, the height of the air knife is 160 mm, the air knife pressure is 90 mbar, the distance between the air knife and the strip substrate is 40 mm, and the coating deviation between the edge and the middle of the produced hot-based zinc-aluminum-magnesium product is 18 g / m 2 , which is well controlled.

[0063] Example 2

[0064] When producing a hot-based zinc-aluminum-magnesium product with a strip thickness of 4.0 mm and a width of 1250 mm and a coating requirement of 450 g / m 2 , the running speed of the strip substrate in the continuous galvanizing production line is 45 m / min, the opening degree of the air knife is 1.0-1.5 mm, the height of the air knife is 180 mm, the air knife pressure is 80 mbar, the distance between the air knife and the strip substrate is 60 mm, and the coating deviation between the edge and the middle of the produced hot-based zinc-aluminum-magnesium product is 24 g / m 2 , which is well controlled.

[0065] Example 3

[0066] When producing a hot-based zinc-aluminum-magnesium product with a strip thickness of 5.0 mm and a width of 1250 mm and a coating requirement of 275 g / m 2 , the running speed of the strip substrate in the continuous galvanizing production line is 35 m / min, the opening degree of the air knife is 1.0-1.5 mm, the height of the air knife is 180 mm, the air knife pressure is 70 mbar, the distance between the air knife and the strip substrate is 50 mm, and the coating deviation between the edge and the middle of the produced hot-based zinc-aluminum-magnesium product is 20 g / m 2 , which is well controlled.

[0067] Example 4

[0068] A hot-based zinc-aluminum-magnesium product with a strip thickness of 5.0 mm, a width of 1250 mm, and a coating requirement of 350 g / m 2 is produced, the running speed of the strip substrate of the continuous galvanizing production line is 35 m / min, the opening degree of the air knife is 1.0-1.5 mm, the height of the air knife is 180 mm, the pressure of the air knife is 70 mbar, the distance between the air knife and the strip substrate is 60 mm, and the coating deviation between the edge and the middle of the produced hot-based zinc-aluminum-magnesium product is 26 g / m 2 , which is well controlled.

[0069] Example 5

[0070] A hot-based zinc-aluminum-magnesium product with a strip thickness of 6.0 mm, a width of 1250 mm, and a coating requirement of 275 g / m 2 is produced, the running speed of the strip substrate of the continuous galvanizing production line is 30 m / min, the opening degree of the air knife is 1.0-1.5 mm, the height of the air knife is 200 mm, the pressure of the air knife is 60 mbar, the distance between the air knife and the strip substrate is 60 mm, and the coating deviation between the edge and the middle of the produced hot-based zinc-aluminum-magnesium product is 28 g / m 2 , which is well controlled.

[0071] As can be seen from the above Examples 1-5, the coating thickness deviation between the edge and the middle of the hot-based zinc-aluminum-magnesium steel plate prepared by the preparation method provided in the Examples is small, and the quality of the strip edge is better.

[0072] The Examples also provide a hot-based zinc-aluminum-magnesium steel plate, which is prepared by the preparation method provided in the above Examples. The specific preparation process can be referred to the related description of the above Examples, which will not be repeated here.

[0073] The hot-based zinc-aluminum-magnesium steel plate and the preparation method thereof provided in the Examples can change the composition of the aluminum-zinc-magnesium plating solution, so that the zinc-aluminum-magnesium coating maintains a certain viscosity under the premise of ensuring the characteristics of the zinc-aluminum-magnesium coating, to meet the production requirements of thick zinc layer. At the same time, by changing the related process parameters, the iron oxide on the surface of the strip substrate can be fully reduced to form an active surface suitable for hot galvanizing zinc-aluminum-magnesium, thereby effectively improving the problem of thickening of the edge of the zinc-aluminum-magnesium plated steel plate, and having good popularization value.

[0074] In the specification provided herein, a large number of specific details are described. However, it can be understood that the embodiments of the present application can be practiced without these specific details. In some examples, well-known methods, structures and techniques are not shown in detail in order not to obscure the understanding of the present specification.

[0075] Similarly, it should be understood that, in order to simplify this disclosure and aid in understanding one or more of the various aspects of the invention, in the above description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof. However, this method of disclosure should not be construed as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as reflected in the following claims, inventive aspects lie in fewer than all features of a single foregoing disclosed embodiment. Therefore, the claims following the detailed description are hereby expressly incorporated into this detailed description, wherein each claim itself is a separate embodiment of the invention.

[0076] It should be noted that the above embodiments are illustrative of the invention and not restrictive of the invention, and that those skilled in the art can devise alternative embodiments without departing from the scope of the appended claims.

Claims

1. A method for preparing a hot-dip zinc-aluminum-magnesium steel plate, characterized in that, The method includes: The strip steel substrate is placed in a direct-fired furnace for heating. The hydrogen content in the cold zone of the direct-fired furnace is controlled between 15-25%, and the temperature in the direct-fired furnace is between 1250-1325℃, so that the temperature of the strip steel substrate is between 660-720℃. The strip steel substrate is a hot-rolled strip steel substrate. The heated steel strip is placed into a main pot containing an aluminum-zinc-magnesium plating solution for hot-dip galvanizing to obtain an aluminum-zinc-magnesium coated steel sheet with a thickness of 4.0 mm or more. The aluminum-zinc-magnesium plating solution contains 6.0% Al and 2.0% Mg by mass percentage, with the remainder being zinc and other unavoidable impurities. The preparation method further includes: During the hot-dip galvanizing process of placing the heated steel strip into a main pot containing an aluminum-zinc-magnesium plating solution, an air knife is used to blow away the coating. The air knife baffle is 6-8 mm thick, and the lower end of the baffle has an isosceles triangular structure. The running speed of the steel strip is 30-45 m / min. The upper air knife angle is 0-0.2°, the lower air knife angle is 0-0.2°, and the height of the air knife is 160-200 mm. The air pressure of the air knife is 60-90 mbar, and the distance between the air knife and the steel strip is 30-60 mm. The opening of the air knife adopts a stepped transition from the center to the edge, and the opening of the air knife is 1.0-1.5 mm.

2. The preparation method according to claim 1, characterized in that, During the process of hot-dip galvanizing the heated steel strip substrate by placing it into a main pot containing an aluminum-zinc-magnesium plating solution, the temperature of the steel strip substrate entering the pot is the same as the temperature of the aluminum-zinc-magnesium plating solution.

3. The preparation method according to claim 2, characterized in that, During the process of hot-dip galvanizing the heated steel strip substrate in a main pot containing an aluminum-zinc-magnesium plating solution, the temperature of the aluminum-zinc-magnesium plating solution is 420-450℃.

4. A hot-dip zinc-aluminum-magnesium steel sheet, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 3.

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