JP2003306757A - HOT DIP Al-Zn ALLOY-COATED STEEL SHEET AND METHOD OF PRODUCING THE SAME - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a hot dip Al-Zn alloy-coated steel sheet having an excellent surface appearance by imparting a uniform unevenness on a plated surface and a method of producing the same, and to obtain a hot dip Al-Zn alloy-coated steel sheet having an excellent surface appearance by preventing the formation of a spangle pattern capable of being visually recognized or by preventing the emboss of the spangle pattern after being coated and a method of producing the same. <P>SOLUTION: The method for producing the hot dip Al-Zn alloy-coated steel sheet includes a process for subjecting a steel sheet to hot dip Al-Zn alloy coating by dipping it in a hot dip Al-Zn alloy coating bath and passing it through the bath, a process for controlling the plated coating weight after pulling up the steel sheet from the hot dip Al-Zn alloy coating bath and cooling the pulled steel sheet to a temperature not higher than the solidifying point of the plated metal, and a surface control process for controlling the surface morphology of the hot dip Al-Zn alloy-coated steel sheet by projecting solid particles onto the surface of the hot dip Al-Zn alloy coated-steel sheet being cooled to a temperature not higher than the solidifying point of the plated metal. In the surface control process, the average roughness Ra of the surface of the steel sheet is controlled to be ≤3 μm. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a hot-dip Al—Zn alloy plated steel sheet and a method for producing the same.

[0002]

2. Description of the Related Art Normally, hot-dip Al-Zn alloy plated steel sheet is
The annealed steel sheet is immersed in a plating bath in which an Al-Zn alloy has been melted, passed through the plating bath, and then pulled up from the plating bath to control the coating weight, and then cooled to below the solidification temperature of the plating metal. To be done. In the process, a pattern called spangle (also called solidified structure or spangle pattern) is formed on the plated surface.

The surface with a spangle pattern is beautiful,
There are uses that are favored in terms of design. On the other hand, there are applications where spangle patterns are not preferred. For example, since a spangle pattern has good light reflection characteristics, it is necessary to impart irregularities to the surface to make the spangle pattern visually invisible in applications where antiglare properties are required. In addition, in the application for coating, there is a problem that the appearance of spangle patterns appears to be raised after coating and the uniformity of the appearance is impaired.

The following techniques are available as methods for dealing with the above-mentioned problems. For example, when the steel plate is pulled up from the plating bath, and when the plating metal is in a molten state, water is sprayed from the spray nozzle to rapidly cool the plating surface to a temperature below the freezing point of the plating metal, thereby preventing the growth of spangle patterns. At the same time, there is a technique for giving unevenness to the surface. In this technique, indentations of sprayed water are likely to remain on the plating surface, and since it is necessary to spray water at a position where the steel plate temperature is near the freezing point of the plating metal, the steel plate size,
When the speed, the amount of plating deposit, etc. change, it is difficult to adjust the position of the spray nozzle to an appropriate position accordingly, and the unevenness on the surface is uneven due to temperature unevenness in the width direction of the steel strip. The surface appearance tends to be non-uniform, and it is difficult to surely make the spangle pattern invisible.

Conventionally, there has been a means of temper rolling in order to make the surface appearance uniform, and the unevenness (dull) on the surface of the rolling roll is imparted to the steel sheet while imparting plastic elongation of about 0.5 to 2.0% to the steel sheet. By transferring to the surface and imparting microscopic unevenness to the surface of the steel sheet, the appearance of the steel sheet surface can be made uniform.

As a method for imparting microscopic unevenness to the surface of the temper rolling roll, various processing methods such as shot blast processing, electric discharge processing, laser processing and electron beam processing are used. For example, Japanese Patent Laid-Open No. 7-136701
Japanese Patent Laid-Open No. 6-75728 discloses means for using a temper rolling roll subjected to laser dull processing.
No. 6 discloses that a temper rolling roll whose surface is processed by electron beam processing is used. The form of microscopic unevenness formed on the surface of the steel sheet depends on the shape of the unevenness imparted to the surface of the rolling roll.When temper rolling is performed on the molten Al-Zn alloy plated steel sheet, the following problems occur. is there. That is, since the grain boundary portion of the spangle is concave with respect to the inside of the grain, a difference in the transfer rate of the unevenness of the rolling roll between the grain boundary portion and the inside of the grain causes a spangle pattern to be raised, and the surface of the plated steel sheet. The appearance is impaired. In the grain boundary part,
Since the light-reflecting property is good, there is a problem in use in applications where antiglare properties are required.

Even when temper-rolling is performed on a plated steel sheet whose surface is made uneven by water spraying, the problem of unevenness of unevenness made by water spraying cannot be solved.

Further, the unevenness imparted by temper rolling has the following problems. In the roll bite in temper rolling, the contact pressure between the rolling roll and the steel sheet is very large,
The microscopic irregularities on the surface of the rolling roll change over time due to wear, and it is difficult to keep the shape of the microscopic irregularities transferred to the steel plate surface constant, that is, it is difficult to prevent changes in the surface roughness. is there.

For example, when a rolling roll having an average surface roughness Ra of 3.5 μm is used, temper rolling with a rolling length of about 6 km reduces the average surface roughness Ra of the rolling roll surface to about 3.0 μm. Along with this, the average roughness Ra of the surface of the molten Al—Zn alloy plated steel sheet decreases from 1.5 μm to 1.3 μm. The effect of such abrasion on the surface of the rolling roll becomes more remarkable as the rolling length increases, and the surface roughness changes due to the change in the microscopic ruggedness of the surface of each product. By changing the degree of emergence of
The problem arises that the quality cannot be constant.

By using a roll having a large surface roughness Ra as the rolling roll, it is possible to reduce the conspicuousness of the dent at the grain boundary portion of the spangle.
In addition to the effect of aging due to wear of the rolling roll surface becoming more prominent, Al-based and Zn-based powder peeled from the steel plate adheres to the recesses on the surface of the rolling roll, and the apparent roll surface due to so-called clogging. The decrease in roughness further increases the change over time in the surface roughness Ra of the manufactured molten Al—Zn alloy plated steel sheet. On the other hand, if the surface roughness of the rolling roll is too large, the plating appearance after temper rolling will be rough and the uniformity of the appearance will be reduced, such being undesirable.

Further, when the hardness of the base material differs due to the difference in the steel type of the steel plate as the plating material, it is difficult to obtain the same level of surface roughness for the soft material and the hard material. .

Therefore, in order to stabilize the quality of the steel sheet, it is necessary to manufacture the rolling rolls while the rolling rolls are reassembled before the surface of the rolling rolls is worn so much. Results in reduced efficiency.

[0013]

SUMMARY OF THE INVENTION An object of the present invention is to provide a hot-dip Al-Zn alloy-plated steel sheet having an excellent surface appearance by providing uniform unevenness on the plating surface and a method for producing the same. .

Another object of the present invention is to prevent the appearance of a spangle pattern by visual observation, or prevent the spangle pattern from rising after painting, and a hot-dip Al-Zn alloy-plated steel sheet excellent in surface appearance and its production. Is to provide a method.

Another object of the present invention is to provide a hot-dip Al-Zn alloy-plated steel sheet and a method for producing the same, which can reduce variations in surface roughness of the steel sheet.

Further, the object of the present invention is that the present invention does not have a problem of a decrease in production efficiency due to frequent roll rearrangement, which is a problem when imparting roughness in temper rolling, and further has a surface roughness adjusting range. It is an object of the present invention to provide a hot-dip Al-Zn alloy plated steel sheet that can be expanded and a method for manufacturing the same.

[0017]

Means for solving the above problems according to the present invention are as follows. (1) a step of dipping the steel sheet in a molten Al-Zn alloy plating bath to perform molten Al-Zn alloy plating, and the steel sheet to the molten Al-
After pulling up from the Zn-based alloy plating bath, adjusting the amount of plating adhered, and further cooling to below the freezing point of the plating metal, and the temperature of the molten Al-Z below the freezing temperature of the plating metal.
and a surface adjustment step of adjusting the surface morphology of the steel sheet by projecting solid particles onto the surface of the n-based alloy plated steel sheet.

(2) Hot-dip Al-Zn alloy-plated steel sheet characterized by having a surface conditioning step of projecting solid particles onto the surface of the hot-dip Al-Zn alloy-plated steel sheet to adjust the surface morphology of the steel sheet. Manufacturing method.

(3) In the surface adjusting step, the average roughness Ra of the steel sheet surface is adjusted to 3 μm or less.
Alternatively, the method for producing the hot dip Al-Zn alloy plated steel sheet according to (2).

(4) The solid particles of the molten Al-Zn alloy plated steel sheet according to any one of (1) to (3), wherein the solid particles have an average particle diameter of 10 to 300 μm. Production method.

(5) The method for producing a hot dip Al-Zn alloy plated steel sheet according to any one of (1) to (4), wherein the solid particles are a metallic material.

(6) The molten Al according to (4) or (5), wherein the solid particles have a substantially spherical shape.
-Method of manufacturing Zn-based alloy plated steel sheet.

(7) A hot-dip Al—Zn alloy-plated steel sheet manufactured by the method described in any one of (1) to (6) above.

(8) The hot dip Al-Zn alloy plated steel sheet according to (7), wherein the plated surface has a dimple-like surface formed by projecting solid particles.

(9) The hot dip Al-Zn alloy plated steel sheet is A
l: 3 to 15 mass% and misch metal: 0.01 to 0.02 mass%
The molten Al-Zn according to (7) or (8), characterized in that the balance has a plating film consisting essentially of Zn.
System alloy plated steel sheet.

(10) The hot dip Al-Zn alloy plated steel sheet is A
l: 3 to 15 mass% and Mg: 0.01 to 10 mass%, the balance having a plating film consisting essentially of Zn, the molten Al-Zn according to (7) or (8) System alloy plated steel sheet.

(11) The hot dip Al-Zn alloy plated steel sheet is A
l: 20 to 95% by mass, Si: 3% by mass or less, the balance having a plating film consisting essentially of Zn, the molten Al-Zn system according to (7) or (8) Alloy plated steel sheet.

(12) The hot dip Al-Zn alloy plated steel sheet is A
l: 20-95% by mass, Si: 3% by mass or less, and further contains one or more of Mg, V, and Mn in a total amount of 0.01 to 10% by mass,
The hot-dip Al-Zn alloy plated steel sheet according to (7) or (8) above, characterized in that the balance has a plating film consisting essentially of Zn.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. Hot-dip Al-Zn alloy plated steel sheet, the steel sheet is immersed in a plating bath in which the Al-Zn alloy is molten, and then passed through the plating bath to control the coating weight by pulling it up from the plating bath. It is manufactured by cooling to the following. A spangle pattern is formed on the plating surface during the cooling process.

In the present invention, the temperature is below the solidification temperature of the plating metal, and a spun pattern is formed on the molten Al-Z.
A characteristic is that solid particles are projected onto the surface of the n-based alloy plated steel sheet to adjust the surface morphology of the steel sheet.

The individual solid particles projected on the surface of the molten Al-Zn alloy plated steel sheet collide with the molten Al-Zn alloy plated coating on the surface of the steel sheet to form indentations on the coating surface. By colliding a large number of solid particles with the molten Al-Zn alloy plated steel sheet, a large number of irregularities are formed on the surface,
A certain form of microscopic irregularities will be imparted. The depth and size of the unevenness, the pitch of the adjacent unevenness, and the like are determined according to the kinetic energy of the solid particles, the particle diameter, the projected amount per unit area, and the hardness of the molten Al—Zn alloy plating film. Therefore, it is possible to control these factors and adjust the surface morphology. Even if the steel plate size, speed, coating weight, etc. are changed, by controlling the above factors, it is possible to impart unevenness with excellent uniformity to the plated surface, so that an excellent surface appearance can be obtained.

The morphological features of the microscopic asperities formed by projecting solid particles onto the hot dip Al-Zn alloy plated steel sheet are mainly indented depressions on the surface of the hot Al-Zn alloy plated steel sheet. It is the point that is formed.

On the other hand, in the temper rolling method which is a conventional technique, in order to impart a concave shape to the surface of the molten Al-Zn alloy plated steel sheet, a microscopic convex portion is formed on the surface of the rolling roll. It is necessary to give the surface morphology as the main constituent. However, it is difficult to precisely process microscopic protrusions on the surface of the rolling roll.
Generally, it is difficult to perform shot blasting, electric discharge machining, laser machining, electron beam machining on the surface of rolling rolls.
In principle, it is unavoidable to mainly give the surface of the rolling roll a concave shape.

Therefore, the molten Al-Z obtained according to the present invention
n-based alloy plated steel sheet, when using the average roughness Ra, which is a parameter representing the morphology of the microscopic unevenness of the surface as an index, even if the value is the same as the molten Al-Zn alloy plated steel sheet according to the prior art However, even if it is, it will exhibit more excellent uniformity. In that respect, it is an essentially different means from the surface adjustment method of hot-rolled hot-dip Al-Zn alloy plated steel sheet by temper rolling, and the term "surface morphology" also means hot-dip Al-Zn-based alloy plating. Average roughness Ra of the steel plate surface,
It is used as a broad concept including the individual shapes and depths of the recesses, the intervals between adjacent recesses, and the like.

In the present invention, the surface morphology imparted by the projection of the solid particles is not different between the grain boundary portion and the inside of the spangle pattern, so that the appearance of the molten Al-Zn alloy plated steel sheet is improved. Excellent effect to give a uniform surface appearance with no visible spangle pattern.

The average roughness Ra defined in JIS-B0601 is usually used as an index showing the microscopic unevenness of the steel sheet surface. However, parameters such as the maximum height Rmax and the ten-point average roughness Rz may be used as other indexes.

Also in the present invention, various surface conditions to be adjusted can be considered as described above and are not particularly limited, but the surface morphology to be adjusted can be the average roughness Ra. The surface morphology imparted by the projection of solid particles has the effect of improving the uniformity of the appearance of the molten Al-Zn alloy plated steel sheet itself, but in order to ensure product quality control and stability. This is because it is necessary to use a certain index.

In the present invention, when the average roughness Ra of the surface of the hot dip Al-Zn alloy plated steel sheet exceeds 3 μm, the microscopic unevenness is too large to give a rough appearance and impair the uniformity of the appearance. Therefore, the average roughness Ra is preferably adjusted to 3 μm or less. The average roughness Ra is the center line average roughness specified in JIS-B0601.

The molten Al produced by the conventional technique is used.
-Zn alloy plated steel sheet surface average roughness Ra is usually 1.2 μm
Melted Al-Zn produced according to the invention to a degree
Compared with the conventional hot-dip Al-Zn alloy-plated steel sheet, the alloy-plated steel sheet shows excellent uniformity of appearance even if the average roughness Ra of the surface is the same. Even if the average roughness is adjusted, it is possible to obtain characteristics equal to or higher than the conventional one.

Further, in the present invention, it is possible to control the surface morphology formed on the surface of the molten Al—Zn alloy plated steel sheet by changing the projection conditions of the solid particles. For example, by changing the material of the solid particles, the average particle size, the particle size distribution, the shape and density of each particle, or the projection speed of the solid particles, the projection density (the weight of the solid particles projected per unit area), It is possible to change the form of microscopic unevenness formed on the surface of the molten Al-Zn alloy plated steel sheet. That is, it is easy to adjust the optimum surface morphology according to the specifications and application of the molten Al—Zn alloy plated steel sheet. Further, since there is no problem of change in surface morphology due to wear of the surface of the temper rolling roll in the prior art, there is a feature that a constant surface morphology can be stably obtained without depending on a manufacturing opportunity.

On the other hand, since the indentation formed by the collision of the solid particles is limited to the vicinity of the molten Al-Zn alloy coating layer, it has a characteristic that it is not significantly affected by the hardness of the base steel. Therefore, the size of the recess formed on the surface of the coating mainly depends on the hardness of the coating and not so much on the type of base steel. Therefore, there was a problem in the conventional technique of transferring the surface roughness of the rolling roll by temper rolling, "with the same rolling roll, within the range of elongation rate limited by the material, different steel types as the base material To melt
The problem that "the same surface roughness cannot be imparted to the Al-Zn alloy plated steel sheet" does not occur.

In the present invention, solid particles having an average particle diameter of 10 to 300 μm are preferably used as the solid particles projected onto the surface of the hot dip Al—Zn alloy plated steel sheet.

The indentation formed on the surface of the molten Al—Zn alloy plated steel sheet becomes larger as the average particle diameter of the solid particles becomes larger. When the average particle size exceeds 300 μm, the recesses formed on the surface of the molten Al-Zn alloy plated steel sheet become large,
It becomes impossible to provide dense microscopic unevenness, and the uniformity of the appearance deteriorates.

Therefore, the average particle size of the solid particles used in the present invention is 300 μm or less. More preferably, the average particle size is 200 μm or less.

On the other hand, it is possible in principle that the smaller the average particle diameter of the solid particles, the more minute the unevenness can be provided on the surface of the molten Al—Zn alloy plated steel sheet. However,
If the average particle diameter is less than 10 μm, the speed of the projected solid particles decreases in the air, so unless the projection speed is made extremely high, the surface roughness cannot be effectively imparted, and Reduces the effect of making the spangle pattern invisible and the effect of preventing the spangle from appearing after painting.

In particular, commercially available solid particles have a uniform particle size distribution, and even if the average particle size is 10 μm, particles ranging from very small particles of several μm or less to particles of about 30 μm are included. Therefore, the small particles have a large deceleration in the air, and the kinetic energy when colliding with the surface of the molten Al—Zn alloy plated steel sheet decreases. Therefore, even if the projection amount is increased, only relatively large particles contribute to the formation of microscopic unevenness on the surface, and small particles do not contribute to the adjustment of the surface morphology. Also, the average particle size is 10 μm
If the following is the case, the price of the particles is high, and it is not economical to use it for the production of hot dip Al-Zn alloy plated steel sheet.

Therefore, although it is desirable to use smaller particles from the viewpoint of providing dense irregularities on the surface of the hot dip Al-Zn alloy plated steel sheet, in the present means,
From a practical and economical point of view, the lower limit of the average particle size is 10μ
Let m.

When the density of the solid particles is small, the mass of the solid particles becomes small, and unless the projection speed is made extremely high, the average roughness Ra of the molten Al-Zn alloy plated steel sheet is set to a certain value or more. Difficult to do. Therefore, plastic-based solid particles are not suitable. Usually, solid particles of a metal material or a ceramic material having a density of 2 g / cm ³ or more are used. Specific examples include steel balls, steel grids, stainless steel, high speed steel, alumina, silicon oxide, diamond, zirconia oxide, and tungsten carbide.

By the way, the solid particles projected on the molten Al—Zn alloy plated steel sheet scatter after forming indentations on the surface, and therefore a system for circulating and collecting the solid particles and projecting them is necessary. At this time, it is necessary that the solid particles have such strength that they will not be crushed even if they collide with the molten Al—Zn alloy plated steel sheet. Therefore, metal-based solid particles are preferable, and materials such as glass beads that are easily crushed are not suitable. In particular,
Among the metallic materials, carbon steel, stainless steel, high speed steel, etc. are suitable, and it has been found that they exhibit better formability than projection using ceramic-based particles such as alumina.

As for the projection of solid particles, shot blast in which the particle shape is substantially spherical or grid blast in which the particle shape is angular is known. The former is generally used to obtain a shot peening effect that hardens the surface of the material to be processed, and the latter is generally used to grind the surface, so-called shot blasting.

In adjusting the surface morphology of the hot dip Al—Zn alloy plated steel sheet targeted by the present invention, it is desirable to use almost spherical shot particles. When substantially spherical particles are used, fine dimples are formed on the surface of the steel sheet as indentations. Here, the "dimple" refers to a form in which the shape of the dent on the surface is mainly composed of a curved surface, and for example, a large number of crater-like dents formed by a spherical object colliding with the surface are formed. The term "dimple-like surface" means that the surface is the surface having the above-mentioned shape.

Further, when the grit-shaped solid particles are used, depending on the projection conditions, there is a case where an action of polishing the coating layer of the molten Al-Zn alloy plated steel sheet occurs.
By using substantially spherical solid particles, such problems do not occur. Therefore, it is preferable that the solid particles have a substantially spherical shape.

In the present invention, "substantially spherical" means
Even if it is not a perfect ball, it is considered to be a ball according to the social convention,
And the difference between the long diameter and the short diameter of the average diameter is
It is meant to include oval spheres within 20%.

In the present invention, temper rolling may be carried out from the viewpoint of material adjustment (reduction of yield point elongation, etc.). In this case, temper rolling is performed before projecting the solid fine particles.

In the present invention, the component composition of the plating film is
Al: 3 to 15% by mass and misch metal: 0.01 to 0.02% by mass, the balance being substantially Zn, Al: 3-1
5% by mass and Mg: 0.01 to 10% by mass, the balance being essentially Zn, Al: 20 to 95% by mass, Si: 3% by mass
The following, with the balance essentially consisting of Zn, Al: 20
~ 95% by mass, Si: 3% by mass or less, out of Mg, V, Mn
One or two or more of them are contained in a total amount of 0.01 to 10% by mass, and the balance is substantially Zn. In the present invention, the plating bath having the above-mentioned composition is used for plating.

In (3), the content of Al is set to 3 to 15% by mass. When 3 to 15% by mass of Al is contained, a eutectic structure develops and spangle grows, and the spangle pattern on the plating surface is particularly conspicuous. This is because the effect of the present invention that the spangle pattern is made invisible is easily exhibited.

The content of 0.01 to 0.02% by mass of misch metal and the content of 0.01 to 10% by mass of Mg are defined as the above-mentioned components are components necessary for preventing non-plating and improving adhesion of the plating film. This is because the effect of preventing non-plating and the effect of improving adhesion are excellent in the above range.

In addition, in 20% to 95% by mass of Al
Specified in, when containing 20 to 95 mass% of Al, dendrite growth of Al occurs, spangle grows, the spangle pattern on the plating surface is particularly noticeable, and the effect of the present invention that the spangle pattern is invisible Is played particularly remarkably.

In Al-Zn alloy plating containing 20 to 95 mass% of Al, the Fe-Al alloy layer grows due to the Fe-Al alloy reaction during plating. If this alloy layer becomes too thick, the workability of the plating film will deteriorate. The inclusion of Si in the plating bath has the effect of suppressing the growth of a thick Fe-Al alloy layer. When the Si content exceeds 3% by mass, not only the above-mentioned action is saturated, but also the workability of the plating film is deteriorated due to the large amount of Si present in the plating film. for that reason,,
In the above, Si is specified to be 3 mass% or less.

In, one of Mg, V, Mn or
It is specified that the total content of two or more kinds is 0.01 to 10% by mass.These components are components useful for preventing non-plating and improving adhesion. This is because the effect is excellent.

[0061]

[Example] (Example 1) A steel plate having a thickness of 0.35 mm and a width of 914 mm
Means (9) or (10) is soaked in the plating bath of the component composition and then pulled up from the plating bath, and the coating weight is approximately 100 g on one side.
/ m ² (corresponding to the adhesion amount code Y18), cooled (air cooling), and temper-rolled at an elongation of 2.0% to produce hot-dip Al-Zn alloy plated steel sheets (No. 1 to 16). . Molten A produced above
The l-Zn alloy plated steel sheet had a spangle pattern. Furthermore, regarding some of the steel plates (No. 3 to 16) produced above,
Using a pneumatic projection device, solid particles were projected onto the surface to adjust the surface morphology of the steel sheet.

As the solid particles, granular high speed steels having different average particle diameters were used. The projection pressure was 0.5 MPa, the distance from the nozzle tip to the steel plate surface: 100 mm, the projection time: 0.03 to 10 seconds, the projection density (the surface of the steel plate surface). the weight of the solid particles to be projected per unit area): 0.4~86kg / m ^2, and mainly projected under the condition of 20 kg / m ^2.

The appearance uniformity of the steel sheet obtained above was evaluated.
The appearance uniformity was evaluated as follows by visually observing the degree of spangle remaining and the surface irregularity state. (Amount of remaining spangle) ○: No spangle is observed. Δ: Some spangles remained. X: Spangles clearly remained. (Surface irregularity state) ○: The surface irregularity is uniform and has no roughness. X: The unevenness of the surface is non-uniform and the surface is rough.

Particle diameter of projected solid particles, plating film component composition of plated steel sheet, average roughness of surface after surface morphology adjustment
Table 1 shows the evaluation results of Ra and appearance uniformity.

[0065]

【table 1】

Compared to the comparative example, the present invention example has less spangle remaining. Among the examples of the present invention, those having a particle size of 10 μm or more do not show spangles. Also, the average roughness
When Ra is 3.0 μm or less, a good appearance with no rough surface is obtained. When the average roughness Ra is 3.0 μm or less and the particle size is 10 μm or more, the surface does not have a rough feeling, spangles are not recognized, and a further excellent surface appearance is obtained.

(Example 2) A molten Al-Zn alloy plated steel sheet obtained by projecting solid particles in Example 1 was coated with a polyester resin-based coating material to give a dry coating film of 4 μm Was coated with 13 μm to produce a coated steel sheet. The appearance uniformity of the coated steel sheet obtained above was evaluated. The appearance uniformity was evaluated as follows by visually observing the degree of protrusion of spangle grain boundaries and the state of surface irregularities. (Protrusion of spangle grain boundaries) ○: Spangle grain boundaries do not appear on the coating film. Δ: Spangle grain boundaries slightly appearing on the coating film. X: Spangle grain boundaries clearly appearing on the coating film. (Surface irregularity state) ○: The surface irregularity is uniform and has no roughness. X: The unevenness of the surface is non-uniform and the surface is rough.

The evaluation results are shown in Table 2. No. 2 in Table 2
Corresponds to the steel plate of the same No. in Table 1.

[0069]

[Table 2]

Compared with the comparative example, in the example of the present invention, spangle grain boundaries were less likely to appear on the coating film. Among the examples of the present invention, in the case of particles having a particle size of 10 μm or more, the spangle grain boundaries did not float above the coating film. Also, the average roughness Ra is 3.
Those having a thickness of 0 μm or less have a good appearance with no roughness on the coated surface. When the average roughness Ra is 3.0 μm or less and the particle size is 10 μm or more, the coated surface has no roughness and spangle grain boundaries are not raised, and a more excellent surface appearance is obtained.

(Example 3) A steel plate having a thickness of 0.35 mm and a width of 914 mm was immersed in a plating bath having the component composition of the means (11) or (12) and then pulled up from the plating bath to reduce the amount of coating adhered on one side. 80
After adjusting to g / m ² (equivalent to adhesion amount code AZ150), cooling (air cooling)
Then, the molten Al—Zn alloy plated steel sheet (No. 1 to 16) was manufactured. The hot-dip Al-Zn alloy plated steel sheet produced above has Al
There was a clear spangle pattern due to the dendrite growth. Furthermore, regarding the steel plates of Nos. 3 to 16, solid particles were projected onto the surface of the steel plate using an air projection device to adjust the surface morphology of the steel plate.

As the solid particles, granular high speed steels having different average particle diameters were used, the projection pressure was 0.5 MPa, the distance from the nozzle tip to the steel plate surface: 100 mm, the projection time: 0.03 to 10 seconds, the projection density (the surface of the steel plate surface). the weight of the solid particles to be projected per unit area): 0.4~86kg / m ^2, and mainly projected under the condition of 20 kg / m ^2.

The appearance uniformity of the steel sheet obtained above was measured according to Example 1
It evaluated similarly to. Table 3 shows the evaluation results of the particle diameter of the projected solid particles, the plating film component composition of the plated steel sheet, the average surface roughness Ra after the surface morphology adjustment, and the appearance uniformity.

[0074]

[Table 3]

Compared with the comparative example, the present invention example has less spangle remaining. Among the examples of the present invention, the average particle size is 10μ
Spangles are not allowed for items over m. Further, when the average roughness Ra is 3.0 μm or less, the surface is not rough and a good appearance is obtained. When the average roughness Ra is 3.0 μm or less and the particle size is 10 μm or more, the surface does not have a rough feeling, spangles are not recognized, and a further excellent surface appearance is obtained.

Example 4 On a molten Al-Zn alloy plated steel sheet obtained by projecting solid particles in Example 3, a polyester resin-based coating was used to undercoat a dry film having a thickness of 4 μm. Was coated with 13 μm to produce a coated steel sheet. The appearance uniformity of the coated steel sheet obtained above was evaluated in the same manner as in Example 2.

The evaluation results are shown in Table 4. In addition, Table 4 No.
Corresponds to the steel plate of the same No. in Table 3.

[0078]

[Table 4]

Compared with the comparative example, in the example of the present invention, the spangle grain boundaries were less likely to float on the coating film. Among the examples of the present invention, in the case of particles having a particle size of 10 μm or more, the spangle grain boundaries did not float above the coating film. Also, the average roughness Ra is 3.
Those having a thickness of 0 μm or less have a good appearance with no roughness on the coated surface. When the average roughness Ra is 3.0 μm or less and the particle size is 10 μm or more, the coated surface has no roughness and spangle grain boundaries are not raised, and a more excellent surface appearance is obtained.

[0080]

EFFECTS OF THE INVENTION According to the present invention, a hot-dip Al-Zn alloy-plated steel sheet is obtained which has no spangle pattern visually, is uniformly provided with irregularities on the surface, and has a good surface appearance.

Further, according to the present invention, the conventional problem of surface roughness imparting by temper rolling is that the surface roughness changes over time, resulting in a large variation in surface roughness and the result thereof. It is possible to solve the problem of reduction in production efficiency due to necessary frequent roll replacement, prevent changes in surface roughness, and eliminate the above-described problem of reduction in productivity.

Further, according to the present invention, the required surface roughness can be surely imparted without being affected by the base steel type and the elongation rate of temper rolling.

Further, according to the present invention, since the range of adjusting the surface roughness can be expanded, it is possible to provide a hot-dip Al-Zn alloy plated steel sheet having various surface roughness and excellent surface appearance. Will be possible.

The hot-dip Al—Zn alloy plated steel sheet of the present invention is
Even after coating, the spangle grain boundaries do not rise, and the surface is evenly textured, resulting in an excellent surface appearance, which is suitable for use in coating applications.

The hot-dip Al—Zn alloy plated steel sheet of the present invention is
There is no spangle protrusion, and the surface is provided with uniform unevenness, and it can be used for applications requiring antiglare properties.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masaaki Yamashita             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. (72) Inventor Masayasu Ueno             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. (72) Inventor Yukio Kimura             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. F-term (reference) 4K027 AA05 AA22 AB14 AB15 AB44                       AB48 AC72 AC86 AE03 AE25

Claims (12)

[Claims] [Claim 1] A step of dipping a steel sheet in a molten Al-Zn-based alloy plating bath to perform molten Al-Zn-based alloy plating, and pulling the steel sheet from the molten Al-Zn-based alloy plating bath, followed by plating Adjusting the amount of adhesion, a step of further cooling to below the freezing point of the plating metal, the surface of the molten Al-Zn alloy plated steel sheet whose temperature is below the solidification temperature of the plating metal, projecting solid particles, the steel sheet And a surface adjustment step of adjusting the surface morphology of the above. A method for producing a hot dip Al-Zn alloy plated steel sheet. 2. A molten Al-Zn alloy-plated steel sheet having a surface adjusting step of projecting solid particles onto the surface of the molten Al-Zn alloy-plated steel sheet to adjust the surface morphology of the steel sheet. Production method. 3. The method for producing a molten Al—Zn alloy plated steel sheet according to claim 1, wherein the surface adjusting step adjusts the average roughness Ra of the steel sheet surface to 3 μm or less. 4. The method for manufacturing a molten Al—Zn alloy plated steel sheet according to claim 1, wherein the solid particles have an average particle diameter of 10 to 300 μm. 5. The molten Al according to claim 1, wherein the solid particles are metallic materials.
-Method of manufacturing Zn-based alloy plated steel sheet. 6. The molten Al-Zn according to claim 4 or 5, wherein the solid particles have a substantially spherical shape.
Method for producing base alloy plated steel sheet. 7. A hot-dip Al—Zn alloy-plated steel sheet manufactured by the method according to any one of claims 1 to 6. 8. The hot dip Al-Zn alloy plated steel sheet according to claim 7, wherein the plated surface has a dimple-like surface formed by projecting solid particles. 9. The molten Al—Zn alloy plated steel sheet is made of Al:
The molten Al-Zn alloy plated steel sheet according to claim 7 or 8, characterized in that it has a plating film containing 3 to 15% by mass and misch metal: 0.01 to 0.02% by mass, and the balance is substantially Zn. . 10. The molten Al—Zn alloy plated steel sheet is A
l: 3 to 15% by mass and Mg: 0.01 to 10% by mass, the balance having a plating film consisting essentially of Zn, hot-dip Al-Zn alloy plating according to claim 7 or 8. steel sheet. 11. The molten Al—Zn alloy plated steel sheet is A
l: 20 to 95% by mass, Si: 3% by mass or less, and the balance has a plating film consisting essentially of Zn. The hot dip Al-Zn alloy plated steel sheet according to claim 7 or 8. . 12. The molten Al—Zn alloy plated steel sheet is A
l: 20 to 95% by mass, Si: 3% by mass or less, and further contains one or more of Mg, V, and Mn in a total amount of 0.01 to 10% by mass,
9. The hot-dip Al—Zn alloy-plated steel sheet according to claim 7 or 8, characterized in that the balance has a plating film consisting essentially of Zn.