CN114729439A

CN114729439A - Hot-dip coated steel sheet

Info

Publication number: CN114729439A
Application number: CN202080080805.5A
Authority: CN
Inventors: 鸟羽哲也; 金藤泰平; 东新邦彦; 森下敦司; 桥本茂; 安井裕人; 中川雄策; 小东勇亮
Original assignee: Nippon Steel and Sumitomo Metal Corp
Current assignee: Nippon Steel Corp
Priority date: 2019-11-29
Filing date: 2020-07-02
Publication date: 2022-07-08
Anticipated expiration: 2040-07-02
Also published as: TWI813903B; TW202120713A; WO2021106259A1; CN114729439B; KR20220084134A

Abstract

A hot-dip plated steel sheet is provided with a steel sheet and a hot-dip plating layer formed on the surface of the steel sheet, wherein the hot-dip plating layer contains 0-90 mass% of Al and 0-10 mass% of Mg in terms of average composition, and the balance contains Zn and impurities, the hot-dip plating layer contains a pattern portion and a non-pattern portion arranged in a predetermined shape, the pattern portion and the non-pattern portion respectively contain 1 or 2 of a 1 st region and a 2 nd region determined by any one of determination methods 1-5, and the absolute value of the difference between the area ratio of the 1 st region in the pattern portion and the area ratio of the 1 st region in the non-pattern portion is 30% or more.

Description

Hot-dip coated steel sheet

Technical Field

The present invention relates to a hot-dip coated steel sheet.

The present application claims priority based on patent application nos. 2019-216681, 2019-216682, 2019-216683 and 2019-216684 filed in japan on 11/29 of 2019, the contents of which are incorporated herein by reference.

Background

The hot dip plated steel sheet is excellent in corrosion resistance, and particularly excellent in corrosion resistance is provided by a Zn-Al-Mg system hot dip plated steel sheet. Such a hot-dip plated steel sheet is widely used in various manufacturing industries such as building materials, home appliances, and automobile fields, and the amount of use thereof has been increasing in recent years.

For the purpose of displaying characters, patterns, design drawings and the like on the surface of the hot-dip plated steel sheet, the characters, patterns, design drawings and the like may be displayed on the surface of the hot-dip plated layer by performing a printing and/or coating process or the like on the hot-dip plated layer.

However, if a step such as printing and/or coating is performed on the hot-dip plated layer, there is a problem that the cost and time for performing characters, design, and the like increase. Further, when characters, designs, and the like are expressed on the surface of the plating layer by printing and/or painting, not only the metallic glossy appearance that is regarded as important by consumers is lost, but also the durability is poor due to the problems of the deterioration of the coating film itself with time and the deterioration of the adhesion of the coating film with time, and there is a possibility that the characters, designs, and the like disappear with time. In addition, when characters, designs, and the like are expressed on the surface of the plating layer by printing ink, although the cost and time are relatively suppressed, there is a possibility that the corrosion resistance of the hot-dip plating layer may be lowered by the ink. Further, when design and the like are exhibited by grinding of the hot-dip plated layer, although durability such as design and the like is excellent, corrosion resistance is inevitably lowered by a large reduction in the thickness of the hot-dip plated layer at the ground portion, and plating characteristics may be lowered.

As shown in the following patent documents, various techniques have been developed for Zn — Al — Mg hot-dip plated steel sheets, but no technique is known for improving the durability of the plated steel sheets when characters, designs, and the like appear on the surfaces of the plated steel sheets.

There is a conventional technique for a Zn — Al — Mg hot-dip coated steel sheet for the purpose of making a translucent coating layer appearing on the Zn — Al — Mg hot-dip coated steel sheet more beautiful in appearance.

For example, patent document 1 describes a Zn — Al — Mg hot dip coated steel sheet having a translucent appearance with a fine texture and a large number of smooth glossy portions, that is, a Zn — Al — Mg hot dip coated steel sheet having a large number of white portions per unit area and a large area ratio of glossy portions and a good translucent appearance. Further, patent document 1 describes that the poor translucency is a state in which irregular white portions and circular glossy portions are mixed and appear to spread on the surface.

Patent document 2 describes a Zn — Al — Mg-based plated steel sheet in which, in a cross section in the thickness direction of a plating layer, a portion where no Al crystal exists between the interface of the plating layer and base iron and a plating surface layer occupies 10% to 50% of the length in the width direction of the cross section, thereby improving the appearance of the plating layer.

Patent document 3 describes a hot-dip galvanized steel sheet having excellent formability, in which the center line average roughness Ra of the surface of the galvanized steel sheet is 0.5 to 1.5 μm, PPI (the number of peaks having a size of 1.27 μm or more per 1 inch (2.54 cm)) is 150 to 300, and Pc (the number of peaks having a size of 0.5 μm or more per 1 cm) is Pc ≥ PPI/2.54+ 10.

Further, patent document 4 describes a highly corrosion-resistant hot-dip galvanized steel sheet obtained by forming Al/MgZn₂the/Zn ternary eutectic structure is refined, so that the glossiness of the plating layer is increased as a whole, and the appearance uniformity is improved.

However, when characters or the like are displayed on the surface of the plating layer, a technique for improving the durability thereof without lowering the corrosion resistance has not been known.

Documents of the prior art

Patent document 1: japanese patent No. 5043234

Patent document 2: japanese patent No. 5141899

Patent document 3: japanese patent No. 3600804

Patent document 4: international publication No. 2013/002358

Disclosure of Invention

The present invention has been made in view of the above circumstances, and an object thereof is to provide a hot-dip plated steel sheet which can make characters, designs, and the like appear on the surface of a plating layer, and which is excellent in durability and corrosion resistance.

The gist of the present invention is as follows.

[1] A hot-dip coated steel sheet characterized in that,

comprising a steel sheet and a hot-dip coating layer formed on the surface of the steel sheet,

the hot-dip coating contains 0-90 mass% of Al and 0-10 mass% of Mg in terms of average composition, and the balance of Zn and impurities,

the hot-dip coating layer includes a pattern portion and a non-pattern portion arranged in a predetermined shape,

when the 1 st region and the 2 nd region are determined by any one of the following determination methods 1 to 5, the pattern portion and the non-pattern portion are respectively composed of 1 or 2 of the 1 st region and the 2 nd region, and an absolute value of a difference between an area ratio of the 1 st region in the pattern portion and an area ratio of the 1 st region in the non-pattern portion is 30% or more.

[ determination method 1]

Virtual grid lines are drawn on the surface of the hot-dip plated layer at intervals of 0.5mm, and the inside of a circle having a diameter of 0.5mm and centered on the center of gravity of each region is defined as a measurement region a in each of a plurality of regions defined by the virtual grid lines, and the L value in each measurement region a is measured. When 50 points are selected from the obtained L values and the average value of 50 points of the obtained L values is set as a reference L value, a region where the L value is not less than the reference L value is set as a 1 st region and a region where the L value is less than the reference L value is set as a 2 nd region.

[ determination method 2]

Virtual grid lines are drawn on the surface of the hot dip plating layer at intervals of 0.5mm, the inside of a circle having a diameter of 0.5mm and centered on the center of gravity of each region is defined as a measurement region A in each of a plurality of regions defined by the virtual grid lines, the L value in each measurement region A is measured, a region having a L value of 45 or more is defined as a 1 st region, and a region having a L value of less than 45 is defined as a 2 nd region.

[ determination method 3]

Virtual grid lines are drawn at intervals of 0.5mm on the surface of the hot-dip plated layer, and arithmetic average surface roughness Sa is measured in each of a plurality of areas demarcated by the virtual grid lines. The region having a Sa of 1 μm or more was defined as the 1 st region, and the region having a Sa of less than 1 μm was defined as the 2 nd region.

[ determination method 4]

Drawing virtual grid lines on the surface of the hot dip coating layer at intervals of 1mm or 10mm, making X-rays incident on each of a plurality of regions partitioned by the virtual grid lines by an X-ray diffraction method, and measuring the diffraction peak intensity of the (0002) plane of the Zn phase for each of the regionsI₀₀₀₂And diffraction peak intensity I of (10-11) plane of Zn phase_10-11The intensity ratio (I) of them₀₀₀₂/I_10-11) As the orientation ratio. The region having the orientation ratio of 3.5 or more is defined as a 1 st region, and the region having the orientation ratio of less than 3.5 is defined as a 2 nd region.

[ determination method 5]

Virtual grid lines are drawn on the surface of the hot-dip plated layer at intervals of 1mm, and then a circle S is drawn for each of a plurality of regions divided by the virtual grid lines, centering on the center of gravity G of each region. The circle S has a diameter R set such that the total length of surface boundary lines of the hot-dip coating layers contained in the circle S is 10 mm. An average value of a maximum diameter Rmax and a minimum diameter Rmin among diameters R of circles S of the plurality of regions is set as a reference diameter Rave, a region having a circle S with a diameter R smaller than the reference diameter Rave is set as a 1 st region, and a region having a circle S with a diameter R equal to or larger than the reference diameter Rave is set as a 2 nd region.

[2] The hot-dip coated steel sheet according to [1], wherein the hot-dip coating layer contains 4 to 22 mass% of Al and 1 to 10 mass% of Mg in terms of average composition, and the balance is Zn and impurities.

[3] The hot-dip coated steel sheet according to [1] or [2], wherein the hot-dip coating layer further contains 0.0001 to 2 mass% of Si in terms of average composition.

[4] The hot-dip coated steel sheet according to any one of [1] to [3], wherein the hot-dip coating layer further contains, in an average composition, 0.0001 to 2 mass% in total of 1 or 2 or more of Ni, Ti, Zr, Sr, Fe, Sb, Pb, Sn, Ca, Co, Mn, P, B, Bi, Cr, Sc, Y, REM, Hf, and C.

[5] The hot-dip coated steel sheet according to any one of [1] to [4], wherein the pattern portion is arranged in any one of 1 shape of a straight portion, a curved portion, a dot portion, a figure, a numeral, a symbol, a pattern, and a character, or a combination of 2 or more thereof.

[6] The hot dip coated steel sheet according to any one of [1] to [5], characterized in that the pattern portion is intentionally formed.

[7]According to [1]～[6]The hot-dip coated steel sheet according to any one of the preceding claims, wherein the total adhesion amount of the hot-dip coated layers on both surfaces of the steel sheet is 30 to 600g/m²。

[8] A hot-dip plated steel sheet comprising a steel sheet and a hot-dip plating layer formed on the surface of the steel sheet,

the hot-dip plating layer includes a pattern portion and a non-pattern portion arranged in a predetermined shape,

the pattern portion and the non-pattern portion include 1 or 2 of a 1 st region and a 2 nd region determined by any one of the following determination methods 1 to 5, respectively, and an absolute value of a difference between an area ratio of the 1 st region in the pattern portion and an area ratio of the 1 st region in the non-pattern portion is 30% or more.

[ determination method 1]

Virtual grid lines are drawn on the surface of the hot-dip plated layer at intervals of 0.5mm, and the inside of a circle having a diameter of 0.5mm and centered on the center of gravity of each region is defined as a measurement region a in each of a plurality of regions defined by the virtual grid lines, and the L value in each measurement region a is measured. When 50 points are selected from the obtained L values and the average value of 50 points of the obtained L values is set as a reference L value, a region where the L value is equal to or greater than the reference L value is set as a 1 st region and a region where the L value is less than the reference L value is set as a 2 nd region.

[ determination method 2]

[ determination method 3]

[ determination method 4]

Drawing virtual grid lines on the surface of the hot dip coating layer at intervals of 1mm or 10mm, making X-rays incident on each of a plurality of regions partitioned by the virtual grid lines by an X-ray diffraction method, and measuring the diffraction peak intensity I of the (0002) plane of the Zn phase for each of the regions₀₀₀₂And diffraction peak intensity I of (10-11) plane of Zn phase_10-11The intensity ratio (I) of them₀₀₀₂/I_10-11) As the orientation ratio. The region having the orientation ratio of 3.5 or more is defined as a 1 st region, and the region having the orientation ratio of less than 3.5 is defined as a 2 nd region.

[ determination method 5]

Virtual grid lines are drawn on the surface of the hot-dip plated layer at intervals of 1mm, and then a circle S is drawn for each of a plurality of regions divided by the virtual grid lines, centering on the center of gravity G of each region. The diameter R of the circle S is set so that the total length of surface boundary lines of the hot-dip coating layer contained in the circle S is 10 mm. An average value of a maximum diameter Rmax and a minimum diameter Rmin among diameters R of circles S of the plurality of regions is set as a reference diameter Rave, a region having a circle S with a diameter R smaller than the reference diameter Rave is set as a 1 st region, and a region having a circle S with a diameter R equal to or larger than the reference diameter Rave is set as a 2 nd region.

According to the hot-dip coated steel sheet of the present invention in which the 1 st region and the 2 nd region are determined by the determination methods 1 to 4, the pattern portion and the non-pattern portion can be recognized by setting the absolute value of the difference between the area ratio of the 1 st region in the pattern portion and the area ratio of the 1 st region in the non-pattern portion to 30% or more. Thus, it is possible to provide a hot-dip plated steel sheet having excellent durability and excellent corrosion resistance when characters, designs, and the like are displayed on the surface of the hot-dip plated layer.

In addition, according to the hot-dip coated steel sheet of the present invention in which the 1 st region and the 2 nd region are determined by the determination method 5, the hot-dip coated layer surface is divided into the 1 st region included in a portion where the density of the boundary line appearing on the hot-dip coated layer surface is relatively high and the 2 nd region included in a portion where the density of the boundary line appearing on the hot-dip coated layer surface is relatively low, and the absolute value of the difference between the area ratio of the 1 st region in the pattern portion and the area ratio of the 1 st region in the non-pattern portion is 30% or more, whereby the pattern portion and the non-pattern portion can be identified from the difference in the density of the boundary lines. Thus, it is possible to provide a hot-dip plated steel sheet having excellent durability and excellent corrosion resistance when characters, designs, and the like are displayed on the surface of the hot-dip plated layer.

Drawings

Fig. 1 is a schematic diagram illustrating a method (determination method 5) for determining the 1 st zone and the 2 nd zone in a hot-dip coated steel sheet as an example of the present embodiment.

Fig. 2 is a schematic diagram illustrating a method of determining the 1 st zone and the 2 nd zone in a hot-dip coated steel sheet as an example of the present embodiment.

FIG. 3 is an enlarged photograph of a scanning electron microscope of region 1 of example No. 1-1.

FIG. 4 is an enlarged photograph of a scanning electron microscope of region 2 of example No. 1-1.

FIG. 5 is an enlarged plan view showing the surface of a hot-dip galvanized steel sheet in example 1.

FIG. 6 is an enlarged photograph of the scanning electron microscope of region 1 of example No. 2-1.

FIG. 7 is an enlarged photograph of a scanning electron microscope of region 2 of example No. 2-1.

FIG. 8 is an enlarged plan view showing the surface of a hot-dip galvanized steel sheet in example 2.

FIG. 9 is an enlarged photograph taken by a scanning electron microscope of the pattern portion of example No. 3-1.

FIG. 10 is an enlarged photograph taken by a scanning electron microscope of a non-pattern portion of example No. 3-1.

FIG. 11 is an enlarged plan view showing the surface of a hot-dip galvanized steel sheet in example 3.

FIG. 12 is a schematic view showing a boundary line obtained by binarizing captured data on the surface of the hot dip coating layer of example No. 4-1.

FIG. 13 is an enlarged photograph of a scanning electron microscope of region 1 of example No. 4-1.

FIG. 14 is an enlarged photograph of a scanning electron microscope of region 2 of example No. 4-1.

FIG. 15 is an enlarged plan view showing the surface of a hot-dip galvanized steel sheet in example 4.

Detailed Description

Hereinafter, a hot-dip coated steel sheet according to an embodiment of the present invention will be described.

In the present specification, the numerical range expressed by the term "to" means a range including numerical values before and after the term "to" as a lower limit value and an upper limit value.

(outline of Hot-dipped Steel sheet in the present embodiment)

The hot-dip plated steel sheet according to the present embodiment includes a steel sheet and a hot-dip plating layer formed on a surface of the steel sheet, the hot-dip plating layer containing 0 to 90 mass% of Al and 0 to 10 mass% of Mg in terms of average composition, and the balance containing Zn and impurities, the hot-dip plating layer including a pattern portion and a non-pattern portion arranged in a predetermined shape, and when the 1 st region and the 2 nd region are determined by any of the following determination methods 1 to 5, the pattern portion and the non-pattern portion are respectively composed of 1 or 2 of the 1 st region and the 2 nd region, and an absolute value of a difference between an area ratio of the 1 st region in the pattern portion and an area ratio of the 1 st region in the non-pattern portion is 30% or more.

In the hot dip plated layer of the hot dip plated steel sheet, when the 1 st region and the 2 nd region are determined by any one of the following determination methods 1 to 5, the pattern portion and the non-pattern portion are respectively composed of 1 or 2 types of the 1 st region and the 2 nd region.

That is, the 1 st and 2 nd regions in the pattern portion and the 1 st and 2 nd regions in the non-pattern portion are defined by the same determination method. For example, in the case where the 1 st and 2 nd regions of the pattern portion are defined by the determination method 1, the 1 st and 2 nd regions of the non-pattern portion are defined by the determination method 1.

The hot-dip coated steel sheet according to the present embodiment may be: the hot dip coating comprises a steel sheet and a hot dip coating layer formed on the surface of the steel sheet, wherein the hot dip coating layer contains 0-90 mass% of Al and 0-10 mass% of Mg in terms of average composition, and the balance contains Zn and impurities, the hot dip coating layer comprises a pattern part and a non-pattern part which are arranged in a predetermined shape, the pattern part and the non-pattern part respectively comprise 1 or 2 of a 1 st region and a 2 nd region determined by any one of the following determination methods 1-5, and the absolute value of the difference between the area ratio of the 1 st region in the pattern part and the area ratio of the 1 st region in the non-pattern part is 30% or more.

In the hot dip coating layer, the pattern portion and the non-pattern portion include 1 or 2 kinds of the 1 st region and the 2 nd region determined by any one of the following determination methods 1 to 5, respectively.

That is, in the present invention, the method of specifying the 1 st area and the 2 nd area is 5 of the specifying methods 1 to 5, the method of specifying the 1 st area of the pattern portion and the method of specifying the 2 nd area of the pattern portion in the hot-dip plating layer may be the same specifying method, or the method of specifying the 1 st area of the pattern portion and the method of specifying the 2 nd area of the pattern portion may be different specifying methods. Similarly, the method of determining the 1 st region of the non-pattern portion and the method of determining the 2 nd region of the non-pattern portion may be the same or different.

The method of determining the 1 st region of the pattern portion and the method of determining the 1 st region of the non-pattern portion may be the same or different. Similarly, the method of determining the 2 nd region of the pattern portion and the method of determining the 2 nd region of the non-pattern portion may be the same or different.

Further, the same determination method may be employed to define the 1 st and 2 nd regions in the pattern portion and the 1 st and 2 nd regions in the non-pattern portion. For example, in the case where the 1 st and 2 nd regions of the pattern portion are defined by the determination method 1, the 1 st and 2 nd regions of the non-pattern portion may be defined by the determination method 1.

In the surface of the hot dip plated layer of the present embodiment, the 1 st region and the 2 nd region are preferably determined by the same determination method. Further, it is more preferable that the determination method of the 1 st region and the determination method of the 2 nd region are the same in both the pattern portion and the non-pattern portion. That is, it is more preferable that the 1 st region and the 2 nd region of the pattern portion and the 1 st region and the 2 nd region of the non-pattern portion are all distinguished by the same specifying method. For example, when the 1 st region and the 2 nd region of the pattern portion are defined by the determination method 1, it is more preferable that the 1 st region and the 2 nd region are defined by the determination method 1 in the non-pattern portion as well.

[ determination method 1]

[ determination method 2]

[ determination method 3]

[ determination method 4]

Drawing virtual grid lines on the surface of the hot dip coating at intervals of 1mm or 10mm, and making X-rays enter the virtual grid lines by adopting an X-ray diffraction methodIn each of a plurality of regions divided by pseudo grid lines, the diffraction peak intensity I of the (0002) plane of the Zn phase was measured for each of the regions₀₀₀₂And diffraction peak intensity I of (10-11) plane of Zn phase_10-11The intensity ratio (I) of them₀₀₀₂/I_10-11) As the orientation ratio. The region having the orientation ratio of 3.5 or more is defined as a 1 st region, and the region having the orientation ratio of less than 3.5 is defined as a 2 nd region.

[ determination method 5]

(description of determination methods 1 and 2)

Determination method 1 is as follows. Virtual grid lines are drawn on the surface of the hot-dip plated layer at intervals of 0.5mm, and the inside of a circle having a diameter of 0.5mm and centered on the center of gravity of each region is defined as a measurement region a in each of a plurality of regions defined by the virtual grid lines, and the L value in each measurement region a is measured. Any 50 points are selected from the obtained L values, and the average value of the 50 points is set as a reference L value.

In the determination method 2, the reference L value in the determination method 1 is set to 45. Except for this, the determination method 2 is the same as the determination method 1.

In the hot-dip plated steel sheet of the present embodiment, when virtual grid lines are drawn on the surface of the hot-dip plated layer at intervals of 0.5mm, each of the plurality of regions divided by the virtual grid lines is divided into any one of the 1 st region and the 2 nd region according to the value of L ×.

The 1 st region is a region in which L is equal to or greater than the reference L. On the other hand, the 2 nd region is a region having a L value smaller than the reference L value. Since L x of the 1 st region is large, a portion including the 1 st region in the hot-dip plated layer looks relatively white or nearly white when observed with the naked eye or under a microscope compared with a portion including the 2 nd region. Since the value of L x in the 2 nd region is small, the hot-dip plated layer including a large number of the 2 nd regions and a small number of the 1 st regions has a metallic luster or a dark appearance compared to the hot-dip plated layer including a large number of the 1 st regions. In addition, the part where the 1 st region and the 2 nd region are mixed and the area ratio of the 1 st region is 30-70%, the appearance is relatively semitransparent.

(description of determination method 3)

The determination method 3 is as follows. Virtual grid lines are drawn at intervals of 0.5mm on the surface of the hot-dip plated layer, and the arithmetic average surface roughness Sa is measured in each of a plurality of areas divided by the virtual grid lines.

In the hot-dip coated steel sheet of the present embodiment, when virtual grid lines are drawn on the surface of the hot-dip coated layer at intervals of 0.5mm, each of a plurality of regions divided by the virtual grid lines is divided into any one of the 1 st region and the 2 nd region according to the arithmetic average surface roughness Sa.

The 1 st region is a region having an arithmetic average surface roughness Sa of 1 μm or more. On the other hand, the 2 nd region is a region where the arithmetic average surface roughness Sa is less than 1 μm. Since the arithmetic average surface roughness Sa of the 1 st region is large, a portion including a large number of the 1 st regions in the hot-dip plated layer looks relatively white or nearly white in color when observed with the naked eye or under a microscope compared with a portion including a large number of the 2 nd regions. Since the arithmetic average surface roughness Sa of the 2 nd region is small, a portion including a large number of the 2 nd region and a small number of the 1 st region in the hot-dip plated layer looks relatively metallic when observed with naked eyes or a microscope, compared with a portion including a large number of the 1 st region. In addition, the part where the 1 st region and the 2 nd region are mixed and the area ratio of the 1 st region is 30 to 70% looks relatively semitransparent.

(description of determination method 4)

The determination method 4 is as follows. At 1mmDrawing virtual grid lines on the surface of the hot-dip plating layer at intervals of 10mm, making X-rays incident on each of a plurality of regions defined by the virtual grid lines by X-ray diffraction, and measuring the diffraction peak intensity I of the (0002) plane of the Zn phase for each region₀₀₀₂And diffraction peak intensity I of (10-11) plane of Zn phase_10-11The intensity ratio (I) of them₀₀₀₂/I_10-11) As the orientation ratio. "1" in (10-11) means that a bar is attached to "1".

In the hot-dip coated steel sheet of the present embodiment, when virtual grid lines are drawn on the surface of the hot-dip coated layer at intervals of 1mm or at intervals of 10mm, each of a plurality of regions divided by the virtual grid lines depends on the orientation ratio (I)₀₀₀₂/I_10-11) Is divided into any one of the 1 st area and the 2 nd area.

The present inventors measured the orientation ratio by performing X-ray diffraction measurement for each region divided by the virtual grid lines, examined the relationship between the appearance and the orientation ratio of each region, and found that the higher the orientation ratio, the more white the appearance color of the region becomes, and the lower the orientation ratio, the more metallic the appearance of the region appears. The relationship between the orientation ratio and the appearance is between Al phase and MgZn₂The phases were not confirmed, and could be confirmed in the case of the Zn phase.

The 1 st region is a region having an orientation ratio of 3.5 or more. On the other hand, the 2 nd region is a region having an orientation ratio of less than 3.5. Since the orientation ratio of the 1 st region is high, the hot-dip plated layer including the 1 st region is seen to be relatively white or nearly white in color when observed with the naked eye or under a microscope compared with the hot-dip plated layer including the 2 nd region. Since the orientation ratio of the 2 nd region is low, the hot-dip plated layer including a large number of the 2 nd region and a small number of the 1 st region looks relatively metallic with naked eyes or under a microscope compared with the portion including a large number of the 1 st region. In addition, the part where the 1 st region and the 2 nd region are mixed and the area ratio of the 1 st region is 30-70%, the appearance is relatively semitransparent.

(description of determination method 5)

The determination method 5 is as follows. Virtual grid lines are drawn on the surface of the hot-dip plated layer at intervals of 1mm, and then a circle S is drawn for each of a plurality of regions divided by the virtual grid lines, centering on the gravity center point G of each region. The diameter R of the circle S is set so that the total length of the surface boundary lines of the hot-dip plated layer contained in the circle S is 10 mm. An average value of a maximum diameter Rmax and a minimum diameter Rmin among diameters R of circles S of the plurality of regions is set as a reference diameter Rave, a region having a circle S with a diameter R smaller than the reference diameter Rave is set as a 1 st region, and a region having a circle S with a diameter R equal to or larger than the reference diameter Rave is set as a 2 nd region.

The boundary line appearing on the hot-dip plated layer may be, for example, a crystal grain boundary appearing on the plated layer surface, or a boundary between a portion with high brightness and a portion with low brightness on the plated layer surface.

If the region included in the portion having a high grain boundary density appearing on the surface of the plating layer or the region included in the portion having a low grain boundary density is arranged in a shape such as a straight portion or a letter on the surface of the plating layer, it is considered that the straight portion or the letter is present on the surface of the plating layer.

Similarly, if a region included in a portion of the plating surface where the density of the bright-dark boundary is high or a region included in a portion of the plating surface where the density of the bright-dark boundary is low is arranged in a shape such as a straight portion or a letter on the plating surface, it is considered that the straight portion or the letter is present on the plating surface.

Therefore, the present inventors tried to divide the surface region of the hot-dip coating into the 1 st region and the 2 nd region according to the density of the boundary line appearing at the surface of the coating.

In the hot-dip coated steel sheet of the present embodiment, when virtual grid lines are drawn on the surface of the hot-dip coating layer at intervals of 1mm, each of a plurality of regions divided by virtual grid lines is divided into any of the 1 st region and the 2 nd region according to the density of the surface boundary line of the hot-dip coating layer in the vicinity around each divided region.

The 1 st region is a region included in a portion where the density of the boundary line appearing on the surface of the hot-dip plated layer is high. The 2 nd region is a region included in a portion where the density of the boundary line appearing on the surface of the hot-dip plated layer is low. In the hot dip coating, the boundary line density of the portion where the 1 st zone gathers and the portion where the 2 nd zone gathers is different, and therefore, the 1 st zone and the 2 nd zone look relatively different.

(in the hot-dip coated steel sheet of the present embodiment, the difference between the area ratio of the 1 st region in the pattern portion and the area ratio of the 1 st region in the non-pattern portion is 30% or more in absolute value.)

As described above, in the determination methods 1 to 4, the surface of the hot-dip plating layer appears to be relatively white or nearly white in color, metallic luster, or low brightness or translucent in accordance with the area ratio of the 1 st region.

In addition, in the determination method 5, the 1 st zone is a zone included in a portion where the density of the boundary line appearing on the surface of the hot-dip plated layer is high, and the 2 nd zone is a zone included in a portion where the density of the boundary line appearing on the surface of the hot-dip plated layer is low, so that the density of the boundary line of the 1 st zone gathered is different from that of the 2 nd zone gathered in the hot-dip plated layer, and the 1 st zone and the 2 nd zone look relatively different.

Here, in order to visually confirm characters, figures, lines, dots, patterns, and the like on the surface of the hot-dip plated layer, the pattern portion constituting the characters, and the like and the other non-pattern portion may be recognized. For this reason, it is sufficient if the area ratio of the 1 st region in the pattern portion is different from the area ratio of the 1 st region in the non-pattern portion.

Specifically, the difference between the area ratio of the 1 st region in the pattern portion and the area ratio of the 1 st region in the non-pattern portion may be 30% or more in absolute value. As a result, the pattern portion and the non-pattern portion can be recognized.

In the determination methods 1 to 4, for example, when the area ratio of the 1 st region of the pattern part is 75%, the pattern part appears to be relatively white or nearly white in color. When the area ratio of the 1 st region in the non-pattern portion is 45% or less, the pattern looks relatively translucent or metallic. In addition, in the case of the determination methods 1 and 2, a color with relatively low luminance may be observed. When the difference in area ratio between the 1 st region in the pattern portion and the non-pattern portion is 30% or more, the pattern portion and the non-pattern portion can be distinguished from each other by the difference in appearance.

When the area ratio of the 1 st region of the pattern portion is about 65% and the area ratio of the 1 st region of the non-pattern portion is about 35%, both the pattern portion and the non-pattern portion relatively look translucent, but the area ratio of the 1 st region in the pattern portion is large, and therefore the pattern portion presents a relatively whiter appearance with respect to the non-pattern portion. When the difference in area ratio between the 1 st region in the pattern portion and the non-pattern portion is 30% or more, the pattern portion and the non-pattern portion can be distinguished from each other by the difference in appearance.

Further, in the case where the 1 st region of the pattern part is 50%, the pattern part appears to be relatively translucent. When the area ratio of the 1 st region in the non-pattern portion is 20% or less, it appears to be a relatively metallic luster or a low-lightness color. When the difference in area ratio between the 1 st region in the pattern portion and the non-pattern portion is 30% or more, the pattern portion and the non-pattern portion can be distinguished from each other by the difference in appearance.

In the determination method 5, for example, when the pattern portion includes a large number of the 1 st regions, a large number of boundary lines are visible in the pattern portion. In this case, the area ratio of the 1 st region in the non-pattern portion is reduced. Since the area ratio of the 1 st region of the non-pattern portion is small, the area ratio of the 2 nd region is relatively high, and thus the boundary line of the non-pattern portion appears to be small. This makes it possible to distinguish, with the naked eye, under a magnifying glass, or under a microscope, a pattern portion where the boundary line appears much and a non-pattern portion where the boundary line appears little.

In addition, when the pattern portion includes a large number of 2 nd regions, the borderline in the pattern portion appears to be small. In this case, the area ratio of the 2 nd region in the non-pattern portion is reduced, and the area ratio of the 1 st region is increased. Since the area ratio of the 1 st region of the non-pattern portion is large, the boundary line of the non-pattern portion appears to be large. This makes it possible to distinguish, with the naked eye, under a magnifying glass, or under a microscope, a pattern portion where the boundary line appears less and a non-pattern portion where the boundary line appears more.

As described above, in the determination methods 1 to 5, when the difference between the area ratio of the 1 st region in the pattern portion and the area ratio of the 1 st region in the non-pattern portion is 30% or more in absolute value, the appearance of the pattern portion and the non-pattern portion is relatively different, and therefore, the pattern portion can be clearly recognized. That is, in the visible light image on the surface of the plating layer, the difference in relative hue, lightness, chroma, and the like between the pattern portion and the non-pattern portion becomes large, and thus the pattern portion and the non-pattern portion can be recognized.

On the other hand, if the difference in absolute value between the area ratio of the 1 st region in the pattern portion and the area ratio of the 1 st region in the non-pattern portion is less than 30%, the difference in relative appearance between the pattern portion and the non-pattern portion disappears, and the pattern portion cannot be clearly recognized. That is, in the visible light image on the surface of the plating layer, the difference in relative hue, lightness, chroma, and the like between the pattern portion and the non-pattern portion becomes small, and thus the pattern portion and the non-pattern portion cannot be recognized.

As described above, although the example of the existence ratio of the 1 st region in the pattern portion and the non-pattern portion is shown, the difference between the area ratio of the 1 st region in the pattern portion and the area ratio of the 1 st region in the non-pattern portion may be 30% or more in absolute value, and the existence ratio of the 1 st region in each of the pattern portion and the non-pattern portion is not necessarily limited.

(Steel plate)

The steel sheet to be a base of the hot-dip coating layer is not particularly limited in material. As will be described in detail later, as the material, ordinary steel or the like may be used without particular limitation, Al-killed steel or partially high alloy steel may be used, and the shape is not also particularly limited. The hot dip coating layer of the present embodiment is formed by applying a hot dip coating method described later to a steel sheet.

(chemical composition of Hot Dip coating)

Next, the chemical composition of the hot-dip coating layer will be described.

The hot-dip coating layer contains 0-90 mass% of Al and 0-10 mass% of Mg in terms of average composition, and contains Zn and impurities as the balance. More preferably, the alloy contains 4 to 22 mass% of Al and 1 to 10 mass% of Mg in terms of the average composition, and the balance being Zn and impurities. Further preferably, the alloy contains 4 to 22 mass% of Al and 1 to 10 mass% of Mg in terms of an average composition, and the balance is Zn and impurities. The hot-dip coating layer may contain 0.0001 to 2 mass% of Si in terms of the average composition. The hot-dip coating layer may contain 0.0001 to 2 mass% in total of 1 or 2 or more of Ni, Ti, Zr, Sr, Fe, Sb, Pb, Sn, Ca, Co, Mn, P, B, Bi, Cr, Sc, Y, REM, Hf, and C in terms of the average composition.

The Al content is preferably in the range of 0 to 90 mass%, and more preferably 4 to 22 mass%, based on the average composition. Al may be contained to ensure corrosion resistance. When the Al content in the hot-dip plated layer is 4 mass% or more, the effect of improving the corrosion resistance is further improved. If the content is 90% or less, the plating layer can be formed stably. Further, if the Al content exceeds 90%, it takes a long time to impart design, and it may be difficult to produce the steel in reality. Further, if the Al content exceeds 90%, the amount of Zn present decreases, and the 1 st region and the 2 nd region cannot be clearly identified. In addition, if the Al content exceeds 22 mass%, the effect of improving the corrosion resistance is saturated. From the viewpoint of corrosion resistance, it is preferably 5 to 18% by mass. More preferably 6 to 16 mass%.

The Mg content is preferably in the range of 0 to 10 mass%, more preferably 1 to 10 mass% in terms of the average composition. Mg may be contained for the purpose of improving corrosion resistance. When the Mg content in the hot-dip coating layer is 1 mass% or more, the effect of improving the corrosion resistance is further improved. If the amount exceeds 10 mass%, generation of dross in the plating bath becomes remarkable, and it becomes difficult to stably produce a hot-dip plated steel sheet. From the viewpoint of balance between corrosion resistance and dross generation, the amount of the metal oxide is preferably 1.5 to 6% by mass. More preferably 2 to 5 mass%.

Al and Mg may be 0%, respectively. That is, the hot-dip coating layer of the hot-dip coated steel sheet according to the present embodiment is not limited to the Zn — Al — Mg system hot-dip coating layer, and may be a Zn — Al system hot-dip coating layer, a hot-dip galvanized layer, or an alloyed hot-dip galvanized layer.

The hot-dip coating layer may contain Si in an amount of 0.0001 to 2 mass%.

Si may be contained because it improves the adhesion of the hot-dip coating layer. Since the effect of improving the adhesion is exhibited by containing 0.0001 mass% or more of Si, it is preferable to contain 0.0001 mass% or more of Si. On the other hand, even if the content exceeds 2 mass%, the effect of improving the adhesion of the plating layer is saturated, and therefore the Si content is 2 mass% or less. From the viewpoint of coating adhesion, the content of the metal oxide may be 0.001 to 1 mass%, or may be 0.01 to 0.8 mass%.

The hot-dip coating layer may contain 1 or 2 or more of Ni, Ti, Zr, Sr, Fe, Sb, Pb, Sn, Ca, Co, Mn, P, B, Bi, Cr, Sc, Y, REM, Hf, and C in a total amount of 0.001 to 2 mass% in terms of average composition. By containing these elements, the corrosion resistance can be further improved. REM is 1 or more than 2 of rare earth elements with atomic numbers of 57-71 in the periodic table. The total content of these elements may be 0.0001 to 2% by mass.

The balance of the chemical composition of the hot dip coating is zinc and impurities. The hot-dip coating layer necessarily contains Zn. The impurities include substances inevitably contained in the base metal other than zinc, and substances contained in the plating bath due to melting of steel.

The average composition of the hot-dip coating layer can be measured by the following method. First, a coating film is removed from the surface layer by a coating film remover (for example, NEOREVER SP-751 available from Sanko chemical industries, Ltd.) which does not corrode the coating film, and then the hot-dip coating film is dissolved in a hydrochloric acid containing an inhibitor (for example, HIBIRON available from Semanura chemical industries, Ltd.), and the obtained solution is subjected to Inductively Coupled Plasma (ICP) emission spectrum analysis, whereby the coating film can be obtained. In addition, when the top coat film is not provided, the operation of removing the top coat film can be omitted.

(Hot-dip plated Metal Structure)

Next, the structure of the hot-dip plated layer will be described. The structure described below is a structure in which the hot-dip coating layer contains 4 to 22 mass% of Al, 1 to 10 mass% of Mg, and 0 to 2 mass% of Si in terms of average composition.

The hot dip coating containing Al, Mg and Zn contains [ Al phase ]]And [ Al/Zn/MgZn ]₂Ternary eutectic structure of]. Having an [ Al phase ]]Is contained in [ Al/Zn/MgZn ]₂Three elements ofCrystal structure]The morphology in the matrix of (1). Furthermore, in [ Al/Zn/MgZn ]₂Ternary eutectic structure of]May also contain [ MgZn ] in the matrix₂Phase (C)]And [ Zn phase ]]. In addition, when Si is added, [ Al/Zn/MgZn ] may be added₂Ternary eutectic structure of]Contains [ Mg ] in the matrix₂Phase of Si]。

Here, [ Al/Zn/MgZn ]₂Ternary eutectic structure of]Is Al phase, Zn phase and intermetallic compound MgZn₂Ternary eutectic structure of phase, forming [ Al/Zn/MgZn ]₂Ternary eutectic structure of]The Al phase (B) corresponds to, for example, an "Al" phase (Al solid solution in which Zn is dissolved, and a small amount of Mg is contained) at a high temperature in a ternary equilibrium diagram of Al-Zn-Mg. The Al "phase at high temperature generally appears as a fine Al phase and a fine Zn phase separated at normal temperature. Further, [ Al/Zn/MgZn ]₂Ternary eutectic structure of]The Zn phase in the alloy is a Zn solid solution in which a small amount of Al is dissolved in a solid solution and, in some cases, a small amount of Mg is also dissolved in a solid solution. [ Al/Zn/MgZn ]₂Ternary eutectic structure of]MgZn in (1)₂The phase is an intermetallic compound phase in which Zn is present in the vicinity of about 84 mass% in a binary equilibrium diagram of Zn-Mg. From the state diagram, it is considered that other additive elements are not dissolved in the respective phases or the amount of the additive elements is very small even if the additive elements are dissolved in the respective phases, but the amounts thereof cannot be clearly distinguished in the normal analysis, and therefore, the ternary eutectic structure composed of these 3 phases is represented as [ Al/Zn/MgZn ] in the present specification₂Ternary eutectic structure of]。

In addition, the so-called [ Al phase ]]Is in [ Al/Zn/MgZn ]₂Ternary eutectic structure of]Has a clear boundary and appears as an island-like phase, which corresponds to, for example, an "Al" phase (Al solid solution of solid solution Zn, containing a small amount of Mg) at high temperature in the ternary system equilibrium diagram of Al — Zn — Mg.

The amount of Zn and the amount of Mg dissolved in the Al' phase at high temperature vary depending on the Al and Mg concentrations in the plating bath. The Al "phase at high temperature is usually separated into a fine Al phase and a fine Zn phase at normal temperature, but the island-like shape observed at normal temperature can be regarded as a skeleton in which the Al" phase at high temperature is retained. From the state diagram, it is considered that other additive elements are not dissolved in the phase or are extremely trace even if dissolved in the phaseSince it cannot be clearly distinguished in a normal analysis, in the present specification, the phase derived from the Al "phase at a high temperature and having the Al" phase retained in shape is referred to as "Al phase]. The [ Al phase ]]With formation of [ Al/Zn/MgZn ]₂Ternary eutectic structure of]The Al phase (2) can be clearly distinguished under microscopic observation.

In addition, the so-called [ Zn phase ]]Is in [ Al/Zn/MgZn ]₂Ternary eutectic structure of]The matrix of (2) has a clear boundary and appears as an island-like phase, and actually a small amount of Al and a small amount of Mg are sometimes solid-dissolved. From the state diagram, it is considered that other additive elements are not dissolved in the phase or are extremely small in amount even if dissolved in the phase. The [ Zn phase ]]With formation of [ Al/Zn/MgZn ]₂Ternary eutectic structure of]Can be clearly distinguished under microscopic observation. The hot-dip coating layer of the present invention may contain [ Zn phase ] depending on production conditions]However, in the experiment, the influence on the improvement of the corrosion resistance of the processed part is hardly observed, and therefore, even if the plating layer contains [ Zn phase ]]There is no particular problem.

In addition, the term "MgZn")₂Phase(s)]Is in [ Al/Zn/MgZn ]₂Ternary eutectic structure of]The matrix of (2) has a clear boundary and appears as an island-like phase, and actually a small amount of Al is sometimes solid-dissolved. From the state diagram, it is considered that other additive elements are not dissolved in the phase or are extremely small in amount even if dissolved in the phase. The [ MgZn ]₂Phase (C)]And formation of [ Al/Zn/MgZn ]₂Ternary eutectic structure of]MgZn of₂The phases can be clearly distinguished under microscopic observation. The plating layer of the present invention may not contain [ MgZn ] depending on the production conditions₂Phase (C)]But is included in the coating under most manufacturing conditions.

In addition, the term "Mg₂Phase of Si]The phase is a phase which appears as an island shape with a clear boundary in the solidification structure of the Si-added plating layer. From the state diagram, it is considered that Zn, Al and other additive elements are not dissolved in a solid solution or are present in a very small amount even in a solid solution. The [ Mg ]₂Phase of Si]Clearly distinguishable in the coating under microscopic observation.

(for pattern part and non-pattern part)

Next, the pattern portion and the non-pattern portion on the surface of the hot dip coating layer will be described.

The hot-dip plated surface of the present embodiment includes a pattern portion and a non-pattern portion arranged in a predetermined shape. The pattern portion is preferably arranged in any 1 shape of a straight portion, a curved portion, a dot portion, a figure, a numeral, a symbol, a pattern, and a character, or in a combination of 2 or more thereof. The non-pattern portion is a region other than the pattern portion. Further, even if the shape of the pattern portion is partially missing such as a missing dot, the shape is allowed as long as the entire pattern portion can be recognized. The non-pattern portion may have a shape in which the boundary of the pattern portion is bordered. The area ratio of the pattern portion to the non-pattern portion in the hot-dip plating layer is not particularly limited.

When any 1 shape of straight line portion, curved line portion, dot portion, pattern, numeral, symbol, pattern and character, or a combination of 2 or more thereof is disposed on the surface of the hot-dip plated layer, these regions may be regarded as pattern portions, and the other regions may be regarded as non-pattern portions. The boundary between the pattern portion and the non-pattern portion can be grasped with the naked eye. The boundary between the pattern portion and the non-pattern portion can be grasped by an enlarged image of an optical microscope, a magnifying glass, or the like.

The pattern part may be formed in a size capable of recognizing the degree of the presence of the pattern part under the naked eye, a magnifying glass, or a microscope. The non-pattern portion is a region occupying most of the hot-dip plated layer (hot-dip plated layer surface), and the pattern portion may be disposed in the non-pattern portion.

The pattern portion is arranged in a predetermined shape in the non-pattern portion. Specifically, the pattern portion is arranged in the non-pattern portion in any 1 shape or a combination of 2 or more shapes of a straight portion, a curved portion, a figure, a dot portion, a figure, a numeral, a symbol, a pattern, and a character. By adjusting the shape of the pattern part, 1 or 2 or more combined shapes of straight line parts, curved line parts, figures, point parts, figures, numbers, symbols, patterns and characters are displayed on the surface of the hot-dip coating layer. For example, a character string, a number string, a symbol, a mark, a line drawing, a design drawing, or a combination thereof, which is composed of a pattern portion, appears on the surface of the hot-dip plated layer. This shape is intentionally or artificially formed by a manufacturing method described later, and is not naturally formed.

In this way, the pattern portion and the non-pattern portion are regions formed on the surface of the hot-dip plated layer. In addition, the pattern portion and the non-pattern portion include 1 kind or 2 kinds of the 1 st region and the 2 nd region, respectively. The pattern portion and the non-pattern portion may be constituted by 1 or 2 kinds of the 1 st region and the 2 nd region, respectively.

(regarding the 1 st region and the 2 nd region)

Next, the 1 st region and the 2 nd region in the determination methods 1 to 5 will be described.

(determination of 1 st and 2 nd regions in methods 1 and 2)

The 1 st region in the determination method 1 is a region including the measurement region a having L value obtained by the following determination method 1 as a reference L value or more. The 2 nd region is a region including the measurement region a having a value L smaller than the reference value L obtained by the determination method 1.

In the hot-dip coating, the 1 st region appears to be relatively white or nearly white in color. On the other hand, in the hot-dip coating, the 2 nd area is relatively metallic or looks dark. The 1 st region and the 2 nd region are respectively dispersed and gathered, and the part with the area ratio of the 1 st region of 30-70% looks like a semi-transparent state relatively.

The 1 st area and the 2 nd area may be specified by a specifying method 2 described later.

Next, determination methods 1 and 2 will be described.

In the determination method 1, virtual grid lines are drawn on the surface of the hot-dip plated layer at intervals of 0.5mm, and the inside of a circle having a diameter of 0.5mm and centered on the center of gravity of each region is defined as a measurement region a in each of a plurality of regions partitioned by the virtual grid lines, and the L value in each measurement region a is measured.

In the determination method 1, virtual grid lines are drawn on the surface of the hot-dip coating layer at intervals of 0.5mm, and a plurality of regions divided by the virtual grid lines are set. The shape of each region was a square with a side of 0.5 mm. Here, the set region is either the 1 st region or the 2 nd region. The L value in each measurement area a was measured using a circle having a diameter of 0.5mm centered on the center of gravity of each area divided by the virtual grid lines as the measurement area a.

Next, a reference L value is obtained. The reference L value is an average value of L values of 50 regions arbitrarily selected from the plurality of regions divided by the virtual grid line. The arbitrary measurement point 50 for measuring the reference L value is selected as follows, for example. First, 1 region among a plurality of regions divided by the virtual grid line is selected. Next, with these 1 region as a starting point, 50 points in total of 10 regions in the vertical direction × 5 regions in the horizontal direction (50mm × 25mm) are selected at 10 intervals. The region of the total 50 points thus selected is set as arbitrary measurement points 50 for measuring the reference L x value.

Then, of the regions divided by the virtual grid lines, a region including the measurement region a whose L value is equal to or greater than the reference L value is set as a 1 st region, and a region including the measurement region a whose L value is smaller than the reference L value is set as a 2 nd region.

In addition, in the determination method 2, the 1 st region and the 2 nd region are determined by using L ═ 45 instead of the reference L value. That is, virtual grid lines are drawn at intervals of 0.5mm on the surface of the hot-dip plated layer, and a plurality of regions defined by the virtual grid lines are set. The shape of each region was a square with a side of 0.5 mm. The region set here is the 1 st region or the 2 nd region. The center of gravity point marked off by the virtual grid line is selected. Then, a circle having a diameter of 0.5mm and centered on the center of gravity was used as a measurement area a, and the L value in each measurement area a was measured.

In the above-described fields, a field including a measurement field a having a L value of 45 or more is defined as a 1 st field, and a field including a measurement field a having a L value of less than 45 is defined as a 2 nd field.

In the above determination methods 1 and 2, L value was measured in accordance with JIS K5600-4-5. In the present embodiment, L × values representing luminance among parameters of a color space represented by L × a × b color system are used. The L value is measured by irradiating irradiation light from a halogen lamp as a light source at an angle of 45 ° with respect to the vertical direction (direction of 90 °) of the hot-dip coating surface and receiving reflected light reflected in the vertical direction (direction of 90 °) of the hot-dip coating surface by a light receiver. The measurement device for L value may use a micro-spectrocolorimeter (VSS 7700, manufactured by japan electro-chromo industries co., ltd.). The measurement wavelength range is 380nm to 780nm, and the intensity in the wavelength range is measured at intervals of 5nm and converted into L x value.

(determination of 1 st and 2 nd regions in method 3)

Since the 1 st region in the determination method 3 is a region having an arithmetic average surface roughness Sa of 1 μm or more, a region having a large number of the 1 st regions in the hot-dip coating layer looks relatively white or nearly white. On the other hand, the hot-dip plated layer appears to have a relatively metallic luster in the region with the larger number of 2 nd regions. The 1 st region and the 2 nd region are respectively dispersed and gathered, and the part with the area ratio of the 1 st region of 30-70% looks like a semi-transparent state relatively.

Since the 1 st region is a region having an arithmetic average surface roughness Sa of 1 μm or more, a part of the hot-dip plated layer having a large number of the 1 st regions looks relatively white or nearly white. On the other hand, the hot-dip plated layer appears to have a relatively metallic luster in the region with the larger number of 2 nd regions. The 1 st region and the 2 nd region are respectively dispersed and gathered, and the part with the area ratio of the 1 st region of 30-70% looks like a semi-transparent state relatively.

Next, a method of measuring the arithmetic average area roughness Sa will be described.

First, virtual grid lines were drawn at intervals of 0.5mm on the surface of the hot-dip plated layer, and the arithmetic average surface roughness Sa of each region was measured for each of a plurality of regions partitioned by the virtual grid lines.

A region having an arithmetic average surface roughness Sa of 1 μm or more is referred to as a 1 st region, and a region having an arithmetic average surface roughness Sa of less than 1 μm is referred to as a 2 nd region.

In determination method 3, the arithmetic average surface roughness Sa was measured using a 3D laser microscope (manufactured by kynshi corporation). In the present embodiment, the height Z in the region was measured at measurement intervals of 50 μm in each of a plurality of regions divided by virtual grid lines using a standard lens of 20 times. When the measurement is performed on a grid, 100 measurement points are obtained in the region. When the obtained height Z100 point is defined as height Z1 to height Z100, Sa is calculated using the following expression. Zave is the average of the Z100 height points.

Sa 1/100 × Σ [ x 1 → 100] (| height Zx-Zave |)

(determination of 1 st and 2 nd regions in method 4)

The region 1 in the determination method 4 is a region having an orientation ratio of 3.5 or more. In the hot-dip coating, the 1 st region appears to be relatively white or nearly white in color. On the other hand, the 2 nd region is a region having an orientation ratio of less than 3.5. In the hot dip coating, the 2 nd region is relatively seen as metallic luster to the naked eye. The 1 st region and the 2 nd region are dispersed and gathered, and the portion of the 1 st region with the area ratio of 30-70% looks relatively semitransparent.

Next, a method of measuring the orientation ratio will be described.

First, virtual grid lines are drawn on the surface of the hot-dip plated layer at intervals of 1mm or 10 mm. Next, X-rays are incident on each of the regions divided by the virtual grid lines by X-ray diffraction, and the intensity I of the diffraction peak of the (0002) plane of the Zn phase is measured for each region, with the center of gravity of each region being the center₀₀₀₂And diffraction peak intensity I of (10-11) plane of Zn phase_10-11. Then, the intensity ratio (I) of them was measured₀₀₀₂/I_10-11) As the orientation ratio.

Further, the intensity of Zn phase measured by X-ray diffraction method is the composition [ Al/Zn/MgZn ]₂Ternary eutectic structure of]Zn phase of (2) constituting [ Zn phase]And constituent of [ Al phase ]]The sum of the strengths of the fine Zn phases. Wherein the contribution to the orientation ratio is made by the composition [ Al/Zn/MgZn ]₂Ternary eutectic structure of]Zn phase of (2) constituting [ Zn phase]Is dominant in the Zn phase of (1).

X-ray diffraction measurements Co tube spheres were used as the X-ray source. Diffraction Peak intensity I of (0002) plane of Zn phase₀₀₀₂Is the intensity of the (0002) plane diffraction peak of the Zn phase appearing in the range of 42.41 ° ± 0.5 ° in the 2 θ range. Diffraction Peak intensity I of (10-11) plane of Zn phase_10-11Is in the 2 theta rangeNow the intensity of the diffraction peak of the (10-11) plane of the Zn phase in the range of 50.66 DEG + -0.5 deg. It is preferable that: the step is 0.02 deg., the scanning speed is preferably 5 deg./min, and the detector uses a high-speed semiconductor two-dimensional detector.

When the interval between the virtual grid lines is 1mm, it is preferable that the X-ray emitted from the X-ray source is condensed by a condenser tube. The irradiation range of the condensed X-ray is preferably within an elliptical range having a major axis of 1mm and a minor axis of 0.75 mm. In this way, by irradiating X-rays with a reduced irradiation range for each region divided by the virtual grid lines at intervals of 1mm, it is possible to perform X-ray diffraction measurement for each region. In this case, an X-ray diffraction device for measuring a minute area is preferably used for the X-ray diffraction measurement.

When the interval between the virtual grid lines is 10mm, it is preferable to condense the X-rays emitted from the X-ray light source by a usual means. The irradiation range of the condensed X-ray is preferably within a rectangular range having a length of 10mm and a width of 10 mm. In this way, by irradiating X-rays with a reduced irradiation range for each region divided by virtual grid lines at intervals of 10mm, X-ray diffraction measurement can be performed for each region. In this case, a normal X-ray diffraction apparatus is preferably used for the X-ray diffraction measurement.

The intervals of the virtual grid lines may be set as appropriate according to the size of the pattern portion and the size of the hot-dip coating layer. When the pattern portion representing the straight line portion, the character, or the like is relatively small, if the interval of the virtual grid lines is set to 10mm, the region divided by the virtual grid lines may straddle the positions of both the pattern portion and the non-pattern portion. Therefore, when the minimum width of the pattern portion is less than 10mm, the interval between the virtual grid lines is preferably 1mm or less. On the other hand, when the minimum width of the pattern portion exceeds 10mm, the interval between the virtual grid lines may be 10mm or 1 mm.

(determination of 1 st and 2 nd regions in method 5)

The 1 st region in the determination method 5 is a region included in a portion where the density of the boundary line appearing on the surface of the hot dip coating layer is high. The 2 nd region is a region included in a portion where the density of the boundary line appearing on the surface of the hot-dip coating layer is low. The density of the boundary line of the 1 st region-gathered portion and the 2 nd region-gathered portion in the hot dip coating layer is different, and thus it can be recognized.

Next, a method of determining the 1 st area and the 2 nd area will be described with reference to fig. 1.

As shown in fig. 1, virtual grid lines K are drawn at intervals of 1mm on the surface of the hot-dip plated layer. In fig. 1, virtual grid lines are indicated by dot-dash lines. In fig. 1, the boundary line where the hot-dip coating layer appears is not shown. Next, a plurality of regions M divided by the virtual grid lines K are set. The shape of each region M was a square with a side of 1 mm. Here, the set region is either the 1 st region or the 2 nd region. Next, for each of the plurality of regions M divided by the virtual grid line K, the center of gravity G of each region is set. Then, a circle S is drawn with the center of gravity G as the center. The diameter R of the circle S is set so that the total length of the surface boundary lines of the hot-dip plated layer contained in the circle S becomes 10 mm.

Fig. 2(a) and 2(b) show a circle S corresponding to an arbitrary region M. In fig. 2(a) and 2(b), a boundary line appearing on the surface of the hot-dip plated layer is shown. The boundary lines shown in FIG. 2(a) and FIG. 2(b) each have a total length of 10 mm. In the present embodiment, the diameter of the circle S is adjusted so that the total length of the boundary lines L included in the inside of the circle S is 10 mm. Therefore, as shown in fig. 2(a), in the case where many boundary lines L exist in the region M and the vicinity thereof, the diameter R of the circle S becomes relatively small. On the other hand, as shown in fig. 2(b), when the boundary line L between the region M and the vicinity thereof is relatively small, the diameter R of the circle S becomes relatively large. Circles S are drawn for all regions, and the diameter R of each circle S is determined.

Then, the average value of the maximum diameter Rmax and the minimum diameter Rmin among the circles S of the plurality of regions M is set as a reference diameter Rave, a region having a circle S with a diameter R smaller than the reference diameter Rave is set as a 1 st region, and a region having a circle S with a diameter R equal to or larger than the reference diameter Rave is set as a 2 nd region. The 1 st region is a region included in a portion where many boundary lines L exist as shown in fig. 2(a), and the 2 nd region is a region included in a portion where few boundary lines L exist as shown in fig. 2 (b).

The boundary line appearing on the hot-dip plated layer includes, for example, a grain boundary appearing on the surface of the plated layer and a boundary between a portion with high brightness and a portion with low brightness on the surface of the plated layer. The boundary between the high-luminance portion and the low-luminance portion may be a boundary line obtained by binarizing the image of the plating surface.

(regarding the 1 st area and the 2 nd area in the pattern part and the non-pattern part in the determination methods 1 to 5.)

The pattern portion includes a plurality of regions divided by virtual grid lines, and each region is classified into either a 1 st region or a 2 nd region. The non-pattern portion also includes a plurality of regions divided by the virtual grid lines, and each region is classified as either the 1 st region or the 2 nd region. That is, the pattern portion may include only one of the 1 st region and the 2 nd region, or may include 2 kinds of the 1 st region and the 2 nd region. Similarly, the non-pattern portion may include only one of the 1 st region and the 2 nd region, or may include 2 types of the 1 st region and the 2 nd region.

Here, in the pattern portion, the area ratio of each of the 1 st region and the 2 nd region can be determined.

In the determination methods 1 to 4, when the area fraction of the 1 st region exceeds 70%, the color of the pattern part looks relatively white or close to white. When the area fraction of the 1 st region is 30% or more and 70% or less, the pattern portion looks relatively translucent. In addition, in the case where the area fraction of the 1 st region is less than 30%, the pattern portion relatively has a metallic luster or looks dark.

In the determination method 5, if the area fraction of the 1 st region is high, a relatively large number of boundary lines are included in the pattern portion. On the other hand, if the area fraction of the 2 nd region in the pattern portion becomes high, relatively few boundary lines are included in the pattern portion.

Thus, the appearance of the pattern part depends on the area fraction of the 1 st region.

On the other hand, even in the non-pattern portion, the area ratio of each of the 1 st region and the 2 nd region can be obtained. Like the pattern portion, the appearance of the non-pattern portion depends on the area fraction of the 1 st region.

In addition, when the difference between the area ratio of the 1 st region in the pattern portion and the area ratio of the 1 st region in the non-pattern portion is 30% or more in absolute value, the pattern portion and the non-pattern portion can be recognized. When the difference in area ratio is less than 30%, the difference between the area ratio of the 1 st region in the pattern portion and the area ratio of the 1 st region in the non-pattern portion is small, and the appearance of the pattern portion and the non-pattern portion is similar, making it difficult to recognize the pattern portion. The larger the difference in area ratio, the better, the more preferably 40% or more, and the more preferably 60% or more.

The pattern part and the non-pattern part can be identified by naked eyes or under a magnifying glass or a microscope. The shape of the pattern portion can be recognized under a magnifying glass or a microscope, and for example, the shape of the pattern portion can be recognized in a field of view of 50 times or less. If the field of view is 50 times or less, the pattern portion and the non-pattern portion can be recognized by a relative difference in appearance. The pattern portion and the non-pattern portion are preferably distinguishable by a factor of 20 or less, more preferably by a factor of 10 or less, and still more preferably by a factor of 5 or less.

(chemical conversion coating layer, coating film layer)

The hot-dip coated steel sheet according to the present embodiment may have a chemical conversion coating film layer or a coating film layer on the surface of the hot-dip coating layer. Here, the type of the chemical conversion coating layer and the coating layer is not particularly limited, and a known chemical conversion coating layer or coating layer may be used.

(method for producing Hot-dipped Steel sheet)

Next, a method for producing a hot-dip plated steel sheet according to the present embodiment will be described.

The hot dip coated steel sheet according to the present embodiment is a steel sheet produced through steel making, casting, and hot rolling, and is hot dip coated. In the production of the steel sheet, pickling, hot-rolled sheet annealing, cold-rolled sheet annealing, and cold-rolled sheet annealing may be further performed. The hot dip coating may be a continuous hot dip coating method in which a steel sheet is continuously passed through a hot dip coating bath, or may be a tank coating method in which a steel material processed into a predetermined shape from a steel sheet or the steel sheet itself is immersed in a hot dip coating bath and then pulled up.

The hot-dip plating bath preferably contains 0 to 90 mass% of Al and 0 to 10 mass% of Mg, and the balance being Zn and impurities. The hot-dip plating bath may contain 4 to 22 mass% of Al and 1 to 10 mass% of Mg, with the remainder containing Zn and impurities. The hot-dip plating bath may contain 0.0001 to 2 mass% of Si. The hot-dip plating bath may contain 0.0001 to 2 mass% in total of 1 or 2 or more of Ni, Ti, Zr, Sr, Fe, Sb, Pb, Sn, Ca, Co, Mn, P, B, Bi, Cr, Sc, Y, REM, Hf, and C. The average composition of the hot-dip coating layer of the present embodiment is substantially the same as the composition of the hot-dip coating bath.

The temperature of the hot-dip plating bath varies depending on the composition, and is preferably in the range of 400 to 500 ℃. When the temperature of the hot-dip plating bath is within this range, a desired hot-dip plating layer can be formed.

The amount of the hot dip coating deposited may be adjusted by means of gas wiping or the like for the steel sheet drawn out of the hot dip coating bath. The amount of the hot-dip coating is preferably adjusted so that the total amount of the hot-dip coating on both surfaces of the steel sheet is 30 to 600g/m²The range of (1). The adhering amount is less than 30g/m²In the case of (3), the corrosion resistance of the hot-dip plated steel sheet is undesirably lowered. The adhesion amount exceeds 600g/m²In the case of (3), the molten metal adhering to the steel sheet droops, and the surface of the hot-dip plated layer cannot be smoothed, which is not preferable.

After the amount of the hot-dip coating was adjusted, the steel sheet was cooled. The cooling conditions are not particularly limited when the hot-dip coated steel sheets in the 1 st zone and the 2 nd zone are determined by the determination methods 1 to 3. On the other hand, in the case where the 1 st and 2 nd zones of the hot dip coated steel sheet are determined by the determination method 4 or 5, the cooling conditions need to be defined. Hereinafter, the description will be divided into cases of the determination methods 1 to 5.

(method for producing Hot Dip coated Steel sheet in which the 1 st region and the 2 nd region were determined by the determination methods 1-2)

In the case of methods 1 to 2, the steel sheet is cooled after the amount of adhesion of the hot-dip coating layer is adjusted as described above. The cooling conditions need not be particularly limited.

After the thermal immersion plating layer is formed, formation of a pattern portion and a non-pattern portion is performed. The pattern part and the non-pattern part are formed by attaching an acidic solution to the surface of the hot-dip coated layer of the hot-dip coated steel sheet at 60-200 ℃. More specifically, an acidic solution may be prepared and attached to the surface of the hot-dip coating layer by printing means. As the printing means, a general printing method such as a printing method using various plates (gravure printing, flexographic printing, offset printing, screen printing, and the like), an ink jet method, and the like can be used.

As an example of a printing method using a plate, a rubber roller or a rubber stamp having a printing pattern formed on the circumferential surface thereof may be pressed against the surface of the hot-dip plated layer while an acidic solution is attached thereto, and the acidic solution may be attached thereto by transferring the acidic solution. According to this method, the acidic solution can be effectively adhered to the continuously passing steel sheet.

At the portion where the acidic solution is attached, the extreme surface of the hot-dip plated layer dissolves (i.e., the uppermost surface layer of the upper portion of the hot-dip plated layer dissolves extremely thinly), and the surface of the hot-dip plated layer changes from the original state of the plated layer. As a result, the appearance of the portion to which the acidic solution is attached changes compared to the portion to which the acidic solution is not attached. Thus, it is estimated that the difference between the area ratio of the 1 st region in the pattern portion and the area ratio of the 1 st region in the non-pattern portion becomes large, and the pattern portion and the non-pattern portion can be recognized. Although the reason is not clear, this method does not affect the corrosion resistance unlike grinding. The reason for this is considered to be that the reduction in thickness of the hot-dip plated layer is very small, and the change in structure of the plated layer due to the adhesion of acid.

The range of the acidic solution to be attached may be a region corresponding to the pattern portion or a region corresponding to the non-pattern portion.

As the acidic solution, inorganic acids such as hydrochloric acid, nitric acid, and sulfuric acid are preferably used. The acid concentration in the acidic solution is preferably 0.1 to 10 mass%. The temperature of the steel sheet to which the acidic solution is applied may be 60 to 200 ℃, preferably 50 to 80 ℃. By adjusting the type and concentration of the acidic solution, the area fractions of the 1 st region and the 2 nd region on the surface of the hot dip coating layer can be adjusted at the portion where the acidic solution adheres.

When the surface temperature of the hot-dip plated layer at the time of adhesion of the acid solution is less than 60 ℃, it takes time to form a pattern portion or a non-pattern portion, which is not preferable, and if the surface temperature of the hot-dip plated layer exceeds 200 ℃, the acid solution is immediately volatilized, and the pattern portion or the non-pattern portion cannot be formed, which is not preferable.

The acidic solution is washed with water within 1 to 10 seconds after the adhesion.

(method of manufacturing Hot Dip coated Steel sheet in which the 1 st region and the 2 nd region were determined by the determination method 3)

In the case of determination method 3, the steel sheet is cooled after the adhesion amount of the hot-dip coating is adjusted as described above. The cooling conditions need not be particularly limited.

After the thermal immersion plating layer is formed, formation of a pattern portion and a non-pattern portion is performed. The formation of the pattern portion and the non-pattern portion is performed by pressing a roll having a partially increased surface roughness to the surface of the hot-dip plating layer and transferring the surface shape of the roll to the hot-dip plating layer. For example, in order to form a pattern portion on the surface of the hot-dip plated layer, a portion of the roll surface corresponding to the pattern portion has a larger roughness than other portions, and thus a pattern portion including a large number of 1 st regions having a large surface roughness can be formed. Conversely, a roller may be used in which the roughness of the portion corresponding to the pattern portion is smaller than that of the other portions. The roughness (arithmetic average surface roughness, Sa (μm)) of the roll surface may be in the range of 0.6 to 3.0 μm, preferably 1.2 to 3.0 μm, at the portion where the roughness is improved. The roughness of the portions where the roughness is reduced may be in the range of 0.05 to 1.0 μm, preferably 0.05 to 0.8. mu.m. The surface temperature of the hot dip coating can be in the range of 100-300 ℃ for transfer printing. The difference between the roughness at the portion where the roughness is increased and the roughness at the portion where the roughness is decreased exceeds 0.2 μm, preferably 0.3 μm or more in terms of the arithmetic average surface roughness Sa. If the difference in roughness is reduced, it is difficult to recognize the pattern portion and the non-pattern portion.

When the surface temperature of the hot-dip plated layer at the time of roll transfer is less than 100 ℃, the hot-dip plated layer is not softened and a clear pattern portion is difficult to form, which is not preferable. Further, if the surface temperature of the hot-dip plated layer exceeds 300 ℃, the roll transfer is performed in a state where the hot-dip plated layer is greatly softened, and there is a fear that the pattern portion and the non-pattern portion cannot be clearly recognized, which is not preferable.

(method of manufacturing Hot Dip coated Steel sheet in which the 1 st area and the 2 nd area were determined by the determination method 4)

In the case of determination method 4, the non-oxidizing gas is locally blown onto the molten metal through the gas nozzle to the steel sheet or steel material which has been lifted from the hot-dip plating bath and whose adhesion amount has been adjusted. As the non-oxidizing gas, nitrogen and argon can be used.

The optimum temperature range differs depending on the composition, but when the temperature of the molten metal is in the range of (final solidification temperature-5) ° c to (final solidification temperature +5) ° c, the non-oxidizing gas may be blown. Furthermore, the temperature of the non-oxidizing gas is below the final solidification temperature.

When the hot-dip plating layer is in the temperature range, the non-oxidizing gas is blown to the portion, and the cooling rate of the molten metal increases, whereby the orientation ratio of the solidified hot-dip plating layer increases. On the other hand, at the portion where the non-oxidizing gas is not blown, the cooling rate of the molten metal is reduced, and thereby the orientation ratio of the hot-dip coating layer after solidification is lowered. Therefore, by adjusting the blowing range of the non-oxidizing gas, the appearance positions of the high orientation ratio region and the low orientation ratio region can be intentionally or arbitrarily adjusted.

This allows the shapes of the pattern portion and the non-pattern portion to be arbitrarily adjusted, and allows the pattern portion and the non-pattern portion to be recognized. The orientation ratio is higher as the temperature of the blown gas is lower, and therefore the orientation ratio can be adjusted according to the temperature of the blown gas. The gas temperature is preferably lower than the final solidification temperature, and for example, the gas temperature may be adjusted to 25 to 250 ℃.

(method of manufacturing Hot Dip coated Steel sheet in which the 1 st area and the 2 nd area were determined by the determination method 5)

In the case of determination method 5, a non-oxidizing gas having a temperature equal to or higher than the final solidification temperature of the plating layer is locally blown onto the molten metal through a gas nozzle to the steel sheet or steel material just after the steel sheet or steel material is lifted from the hot-dip plating bath and the deposition amount thereof is adjusted. As the non-oxidizing gas, nitrogen and argon can be used.

The optimum temperature range differs depending on the composition, but when the temperature of the molten metal is in the range of (final solidification temperature-5) ° c to (final solidification temperature +5) ° c, the non-oxidizing gas may be blown.

The temperature of the non-oxidizing gas is preferably equal to or higher than the final solidification temperature. For example, in a plating composition in which Al is 11% and Mg is 3%, the blowing of the non-oxidizing gas may be performed at a gas temperature of not less than the final solidification temperature when the temperature of the molten metal is 330 to 340 ℃.

In the vicinity of the blowing of the non-oxidizing gas, the cooling rate of the molten metal is reduced, and thereby the boundaries appearing on the surface or the crystal grain boundaries become coarse. Therefore, by adjusting the blowing amount and range of the non-oxidizing gas, the size of the boundary or grain boundary appearing on the surface can be arbitrarily adjusted.

Thus, the shapes of the pattern portion and the non-pattern portion can be arbitrarily adjusted, and the pattern portion and the non-pattern portion can be recognized with the naked eye, under a magnifying glass, or under a microscope.

The above-described manufacturing methods may be combined to form a pattern portion and a non-pattern portion. The surface appearance of the hot-dip plated layer was different depending on the production method, and it was confirmed that in methods 1 to 4, the region having a large number of the 1 st region appeared to be relatively white or nearly white in color, and the 2 nd region appeared to have a metallic luster with the naked eye. Therefore, for example, even if the pattern portion uses "the method for producing hot-dip coated steel sheets in the 1 st and 2 nd regions specified by the specifying methods 1 to 2", and the non-pattern portion uses "the method for producing hot-dip coated steel sheets in the 1 st and 2 nd regions specified by the specifying method 3", if the absolute value of the difference between the area ratios of the pattern portion and the non-pattern portion is specified as 30% or more, the pattern portion and the non-pattern portion can be recognized.

(chemical conversion treatment layer and coating layer)

In the case where the chemical conversion treatment layer is formed on the surface of the hot-dip plated layer, the chemical conversion treatment is performed on the hot-dip plated steel sheet after the hot-dip plated layer is formed. The type of the chemical conversion treatment is not particularly limited, and a known chemical conversion treatment can be used.

In addition, when a coating film layer is formed on the surface of the hot-dip plated layer or the surface of the chemical conversion layer, the hot-dip plated steel sheet after the hot-dip plated layer or the chemical conversion layer is formed is subjected to a coating process. The type of the coating treatment is not particularly limited, and a known coating treatment can be used.

As described above, in the hot-dip coated steel sheet according to the present embodiment, the absolute value of the difference between the area ratio of the 1 st region in the pattern portion and the area ratio of the 1 st region in the non-pattern portion in the 1 st region and the 2 nd region is 30% or more, whereby the pattern portion and the non-pattern portion can be distinguished. Since the formed pattern portion and non-pattern portion are not formed by printing or coating, the durability is improved. Further, since the pattern portion and the non-pattern portion are not formed by printing or coating, the corrosion resistance to the hot-dip plating layer is not affected. Further, the patterned portion and the non-patterned portion are not formed into the hot-dip plated layer surface by grinding or the like. Therefore, the thickness of the hot-dip plated layer in the pattern portion is reduced to such an extent that the corrosion resistance is not deteriorated as compared with the thickness of the hot-dip plated layer in the non-pattern portion. Therefore, the hot-dip plated steel sheet of the present embodiment is excellent in corrosion resistance.

According to the present embodiment, it is possible to provide a hot-dip plated steel sheet having high durability of a pattern portion formed into a predetermined shape and having suitable plating characteristics such as corrosion resistance.

In particular, in the case of hot-dip plated steel sheets of the 1 st zone and the 2 nd zone identified by the identifying methods 1 and 2, the acid solution is allowed to adhere to the surface of the hot-dip plated layer in an arbitrary pattern, whereby the range of the pattern portion or the non-pattern portion can be formed into an intentional or artificial shape, and the pattern portion can be arranged so as to be formed into any 1 shape of a straight line portion, a curved line portion, a dot portion, a figure, a numeral, a symbol, a pattern, and a character, or a shape in which 2 or more kinds of these are combined.

In addition, in the case where the hot-dip plated steel sheets in the 1 st zone and the 2 nd zone are determined by the determination method 3, the surface shape of the roll is transferred onto the hot-dip plated layer by pressing the roll having a partially different roughness on the surface of the hot-dip plated layer, whereby the range of the pattern portion or the non-pattern portion can be formed into an intentional or artificial shape, and the pattern portion can be arranged so as to have any 1 shape of a straight portion, a curved portion, a dot portion, a figure, a numeral, a symbol, a pattern, and a character, or a shape composed of 2 or more of them.

In the case of the hot-dip plated steel sheets of the 1 st and 2 nd zones identified by the identifying method 4, when the temperature of the molten metal after lifting up from the plating bath is in the range of (final solidification temperature-5) ° c to (final solidification temperature +5) ° c, the orientation ratio of the hot-dip plated layer after solidification can be increased by locally blowing a non-oxidizing gas onto the surface of the hot-dip plated layer with a gas nozzle, the pattern part or the range of the pattern part or the non-pattern part can be formed into an intentional or artificial shape, and the pattern part can be arranged so as to have any 1 shape of a straight line part, a curved line part, a dot part, a figure, a numeral, a symbol, a pattern, and characters, or a shape in which 2 or more of these are combined.

Further, in the case of the hot dip plated steel sheet of the 1 st zone and the 2 nd zone specified by the specifying method 5, when the temperature of the molten metal after being lifted up from the plating bath is in the range of (final solidification temperature-5) ° c to (final solidification temperature +5) ° c, the size of the boundary or crystal grain boundary appearing on the surface of the hot dip plated layer after solidification can be arbitrarily adjusted by locally blowing a non-oxidizing gas to the surface of the hot dip plated layer with a gas nozzle, the range of the pattern portion or the non-pattern portion can be formed into an intentional or artificial shape, and the pattern portion can be arranged so as to be any 1 shape or a combination of 2 or more shapes among a straight portion, a curved portion, a dot portion, a figure, a symbol, a pattern, and characters.

In the hot-dip coated steel sheet of the present embodiment, various design designs, trademarks, and other identifying marks can be displayed on the surface of the hot-dip coated layer without printing or coating, and the visibility and design of the origin of the steel sheet can be improved. Further, the pattern portion can also provide information necessary for process management, stock management, and the like, and arbitrary information required by a user to the hot-dip coated steel sheet. This also contributes to improvement in productivity of the hot-dip plated steel sheet.

Examples

Next, an embodiment of the present invention will be described.

(example 1)

No.1-1 to No.1-32 hot-dip coated steel sheets shown in Table 2 were produced by degreasing and washing the steel sheets, followed by reduction annealing, dipping in a plating bath, controlling the amount of deposit, and cooling. Next, an acidic solution containing the components shown in table 1 was attached to a rubber plate having convex portions or concave portions of a square pattern with a side length of 50mm, and the rubber plate was pressed against the surface of the hot-dip plated layer, whereby the acidic solution was attached to the steel sheet, and a square pattern portion was formed. The surface temperature of the hot-dip coating layer of the hot-dip coated steel sheet to which the acidic solution is attached is in the range of 60 to 200 ℃. The non-pattern portion is a portion other than the square pattern portion. Among them, Nos. 1 to 30 adhered the acidic solution when the surface temperature of the hot-dip plated layer exceeded 200 ℃.

Further, a Zn-Al-Mg-based hot-dip coated steel sheet was produced in the same manner as described above. Then, a square pattern having a side length of 50mm was printed on the surface of the hot-dip plated layer by a spray method. The results are shown in Table 2 as Nos. 1 to 33.

Further, a Zn-Al-Mg-based hot-dip coated steel sheet was produced in the same manner as described above. Then, a square pattern having a side length of 50mm was produced by printing ink on the surface of the hot-dip plated layer. The results are shown in Table 2 as Nos. 1 to 34.

Area ratios of the 1 st region and the 2 nd region included in the pattern portion and the non-pattern portion were determined for the obtained hot-dip coated steel sheet. First, the boundary between the pattern portion and the non-pattern portion is determined by observing the hot-dip plated surface with the naked eye. In the case where the boundary under the naked eye is difficult to determine, a magnified image using a magnifying glass or an optical microscope is used. In the example in which the boundary was difficult to be recognized, the pattern portion and the non-pattern portion were determined based on the adhesion range of the acidic solution, and the area ratios of the 1 st region and the 2 nd region were evaluated.

Next, as the area ratios of the 1 st region included in the pattern portion and the non-pattern portion, hot-dip galvanized steel sheets other than Nos. 1 to 7 were obtained by the determination method 1. That is, virtual grid lines were drawn on the surface of the hot-dip plated layer at intervals of 0.5mm, and the inside of a circle having a diameter of 0.5mm centered on the center of gravity of each region was defined as a measurement region a in each of a plurality of regions defined by the virtual grid lines, and the L value in each measurement region a was measured. Any 50 points are selected from the obtained L values, and the average of the 50 points is set as a reference L value.

Specific selection of the arbitrary measurement point 50 for measuring the reference L value is selected as follows. First, 1 region among a plurality of regions divided by virtual grid lines is selected. Next, with these 1 region as a starting point, 50 points in total of 10 regions long by 5 regions wide (50mm by 25mm) were selected at 10 intervals. These total 50 points are set as arbitrary measurement points 50 points for measurement of the reference L x value.

Then, of the regions including the measurement region a, a region having an L value equal to or greater than a reference L value is identified as a 1 st region, and a region having an L value smaller than the reference L value is identified as a 2 nd region.

Then, the area ratios of the 1 st region in the pattern portion and the non-pattern portion were obtained. Further, the difference between the area ratio of the 1 st region in the pattern portion and the area ratio of the 2 nd region in the non-pattern portion is obtained.

The area ratios of the 1 st region included in the pattern portion and the non-pattern portion in the hot-dip galvanized steel sheets of nos. 1 to 7 were determined by the determination method 2, and the difference between the area ratios of the 1 st region of the pattern portion and the non-pattern portion was determined from the results.

The L value is measured by irradiating irradiation light from a halogen lamp (12V, 20W) as a light source at an angle of 45 ° with respect to the vertical direction (direction of 90 °) of the surface of the hot-dip coating layer and receiving reflected light reflected in the vertical direction (direction of 90 °) of the surface of the hot-dip coating layer by a light receiver. The measuring device of L value is a micro-surface spectrocolorimeter (VSS 7700, manufactured by Nippon Denshoku industries Co., Ltd.), the measuring wavelength range is 380nm to 780nm, the intensity in the wavelength range is measured at intervals of 5nm, and the value is converted into L value.

[ identifiability ]

The test panels in the initial state immediately after manufacture and the test panels in the aged state exposed outdoors for 6 months, of the test panels having the square pattern portions, were subjected to visual evaluation based on the following criteria. In both the initial state and the aged state, A to C were accepted as passed.

A: the pattern portion can be seen even from a distance of 5 meters.

B: the pattern portion was not visible from a distance of 5m, but the visibility was high from a distance of 3 m.

C: the pattern portion was not visible from a distance of 3m, but the visibility was high from a distance of 1 m.

D: the pattern portion was not visible from a distance of 1 meter.

[ Corrosion resistance ]

The test plate was cut into 150X 70mm, and after 30 cycles of corrosion promotion test CCT according to JASO-M609, the state of rust was investigated and evaluated based on the following criteria. A to C are qualified.

A: the rust was not generated, and both the pattern portion and the non-pattern portion maintained a beautiful design appearance.

B: although no rust was generated, a very small change in design appearance was observed in the pattern portion and the non-pattern portion.

C: although the design appearance is slightly impaired, the pattern portion and the non-pattern portion can be viewed with the eye.

D: the appearance quality of the pattern portion and the non-pattern portion is remarkably reduced and cannot be distinguished visually.

As shown in Table 2, the hot dip coated steel sheets of Nos. 1-1 to 1-29 according to the examples of the present invention are excellent in both visibility and corrosion resistance. FIG. 3 shows the observation result of the scanning electron microscope of the 1 st region mainly constituting the pattern portion of No.1-1, and FIG. 4 shows the observation result of the scanning electron microscope of the 2 nd region mainly constituting the non-pattern portion of No. 1-1. It is found that the pattern portion has a relatively large metallic luster area compared with the non-pattern portion, and the pattern portion and the non-pattern portion can be distinguished from each other.

In nos. 1 to 30, the temperature of the hot-dip plating layer was too high at the time of adhesion of the acidic solution, and therefore the difference between the area ratio of the 1 st region in the pattern portion and the area ratio of the 1 st region in the non-pattern portion was less than 30%, and the visibility of the pattern portion was lowered.

In addition, the compositions of the hot dip coatings of Nos. 1 to 31 and 1 to 32 deviate from the scope of the present invention, and the recognizability after 6 months of outdoor exposure is lowered.

On the other hand, in the case of nos. 1 to 33 in which the square pattern portions were printed by the ink jet method, the pattern portions became thinner by 6 months of outdoor exposure, and the visibility was lowered. In addition, the corrosion resistance of Nos. 1 to 34, in which square pattern portions were formed by ink stamping, was significantly reduced, and it was difficult to visually distinguish the pattern portions from the non-pattern portions.

Furthermore, the hot-dip coating layers of Nos. 1-1 to 1-6, 1-10 to 1-30, and 1-32 to 1-34 contain an [ Al phase ]]And [ Al/Zn/MgZn ]₂Ternary eutectic structure of]。

FIG. 5 shows the surface of a hot-dip coated steel sheet in which a character string (letter sequence) is shown in a figure by applying an acidic solution to a Zn-Al-Mg-based hot-dip coating layer.

According to the present invention, a pattern portion including characters, marks, or the like can be remarkably shown on the surface of the hot-dip coated steel sheet.

TABLE 1

(example 2)

Hot dip plated steel sheets of Nos. 2-1 to 2-32 shown in tables 4 and 5 were produced by degreasing and washing the steel sheets, followed by reduction annealing, dipping in a plating bath, controlling the amount of deposit, and cooling. Then, a roller having a square pattern with a side length of 50mm is pressed against the surface of the hot-dip plated layer in a state where the surface temperature of the hot-dip plated layer is set to 100 to 300 ℃. The roughness of the square pattern and the roughness of the roll surface excluding the square pattern (arithmetic average surface roughness, Sa (μm)) are shown in table 3. The square pattern portion is defined as a pattern portion, and the portions other than the square pattern portion are defined as non-pattern portions.

Further, a Zn-Al-Mg-based hot-dip coated steel sheet was produced in the same manner as described above. Then, a square pattern having a side length of 50mm was printed on the surface of the hot-dip plated layer by a spray method. The results are shown in tables 4 and 5 as Nos. 2 to 33.

Further, a Zn-Al-Mg-based hot-dip coated steel sheet was produced in the same manner as described above. Then, the surface of the hot-dip plated layer was ground to form a square pattern having a side length of 50 mm. The results are shown in tables 4 and 5 as Nos. 2 to 34.

The area ratios of the 1 st region and the 2 nd region included in the pattern portion and the non-pattern portion were determined for the hot-dip coated steel sheet obtained. First, the boundary between the pattern portion and the non-pattern portion is determined by observing the surface of the hot-dip plated layer with the naked eye. In the case where the boundary under the naked eye is difficult to determine, a magnified image using a magnifying glass or an optical microscope is used. In an example in which the boundary is difficult to distinguish, the area ratios of the 1 st region and the 2 nd region were evaluated as the pattern portion corresponding to the square pattern of the roller surface.

Next, the area ratio of each region included in the pattern portion and the non-pattern portion is obtained by the measurement method described below. That is, virtual grid lines are drawn at intervals of 0.5mm on the surface of the hot-dip plated layer, a plurality of regions divided by the virtual grid lines are set, and the arithmetic average surface roughness Sa is calculated.

Then, a region having an arithmetic average surface roughness Sa of 1 μm or more is determined as a 1 st region, and a region having an arithmetic average surface roughness Sa of less than 1 μm is determined as a 2 nd region.

Then, the area ratios of the 1 st region in the pattern portion and the non-pattern portion were obtained. Further, the difference between the area ratio of the 1 st region in the pattern portion and the area ratio of the 1 st region in the non-pattern portion is obtained.

In the above measurement method, the arithmetic mean surface roughness Sa was measured using a 3D laser microscope (VK-9710, Kinzhi, K.K.). The height Z in the area was measured at measurement intervals of 50 μm in each of a plurality of areas divided by virtual grid lines using a standard lens of 20 times. Using the obtained height Z100 points as the height Z1 to the height Z100, Sa was calculated using the following formula. Zave is the average of the Z100 height points.

Sa 1/100 × Σ [ x ═ 1 → 100] (| height Zx-Zave |)

[ identifiability ]

The test panels in the initial state immediately after the manufacture of the test panels having the square pattern portions and the test panels in the aged state exposed outdoors for 6 months were subjected to visual evaluation based on the criteria for determination. In both the initial state and the aged state, A to C were accepted as passed. The determination criterion is the same as in example 1.

[ Corrosion resistance ]

The test plate was subjected to a corrosion resistance test under the same conditions as in example 1, and then the rust state was examined and evaluated based on the judgment standards. And taking A to C as qualified. The determination criterion is the same as in example 1.

As shown in tables 4 and 5, the Zn-Al-Mg-based hot-dip coated steel sheets of Nos. 2-1 to 2-29 according to the examples of the present invention are excellent in both visibility and corrosion resistance. FIG. 6 shows the observation result of the scanning electron microscope in the 1 st region of No.2-1, and FIG. 7 shows the observation result of the scanning electron microscope in the 2 nd region of No. 2-1. It is understood that the arithmetic mean surface roughness is significantly larger in the 1 st region shown in fig. 6 than in the 2 nd region shown in fig. 7.

In nos. 2 to 30, the difference between the thickness of the square pattern in the roll and the thickness of the other portions was insufficient, and therefore the difference between the area ratio of the 1 st region in the pattern portion and the area ratio of the 1 st region in the non-pattern portion was less than 30%, and the visibility of the pattern portion was degraded.

In addition, in Nos. 2-31 and 2-32, the composition of the hot-dip coating layer deviated from the range of the present invention, and the recognizability after 6 months of outdoor exposure was lowered.

In Nos. 2 to 33 in which square pattern portions were printed by the ink jet method, the pattern portions became thinner due to 6 months of outdoor exposure, and the visibility was lowered.

In addition, in Nos. 2 to 34 in which the square pattern was formed by grinding, the thickness of the plating layer at the grinding site was reduced, and the corrosion resistance of the grinding site was reduced.

Further, the plating layers of Nos. 2-1 to 2-6, 2-10 to 2-30, and 2-32 to 2-34 contain an [ Al phase ]]And [ Al/Zn/MgZn ]₂Ternary eutectic structure of]。

Fig. 8 shows the surface of a hot-dip coated steel sheet in which the shape of the surface of a roll is transferred to a Zn — Al — Mg hot-dip coating layer to show a character string (letter sequence) in a figure portion.

According to the present invention, a pattern portion formed of characters, symbols, or the like can be remarkably shown on the surface of a hot-dip coated steel sheet.

TABLE 3

TABLE 4

TABLE 5

(example 3)

Hot dip plated steel sheets of Nos. 3-1 to 3-32 shown in tables 7 and 8 were produced by degreasing and washing the steel sheets, followed by reduction annealing, dipping in a plating bath, controlling the amount of deposit, and cooling. When the steel sheet is lifted up from the plating bath, nitrogen gas, which is one of non-oxidizing gases, is blown to the molten metal on the surface of the steel sheet by a gas nozzle when the temperature of the molten metal is in the range of (final solidification temperature-5) DEG C to (final solidification temperature +5) ° C. The blowing conditions of nitrogen gas are shown in Table 6. The gas temperatures shown in table 6 are all below the final freezing temperature. Then, cooling is performed to completely solidify the molten metal. The control was performed by blowing nitrogen gas so as to appear a square pattern having a side of 50 mm. Among them, in the case of Nos. 3 to 30, when the temperature of the molten metal was lower than the range of (final solidification temperature-5) ° C to (final solidification temperature +5) ° C, nitrogen gas was blown through the gas nozzle.

Further, a hot-dip Zn-Al-Mg-based steel sheet was produced in the same manner as described above. Then, a square pattern having a side length of 50mm was printed on the surface of the hot-dip plated layer by a spray method. The results are shown in tables 7 and 8 as Nos. 3 to 33.

Further, a Zn-Al-Mg-based hot-dip coated steel sheet was produced in the same manner as described above. Then, the surface of the hot-dip plated layer was ground to form a square pattern having a side length of 50 mm. The results are shown in tables 7 and 8 as Nos. 3 to 34.

The area ratios of the 1 st region and the 2 nd region included in the pattern portion and the non-pattern portion were determined for the hot-dip coated steel sheet obtained. First, the boundary between the pattern part and the non-pattern part is determined by observing the surface of the hot-dip plated layer with the naked eye. In the case where the boundary under the naked eye is difficult to determine, a magnified image using a magnifying glass or an optical microscope is used. In the example in which the boundary was difficult to be discriminated, the boundary was set based on the blowing range of the nitrogen gas, and the area ratios of the 1 st zone and the 2 nd zone were evaluated.

Next, the orientation ratios of the respective regions included in the square pattern (indicated as a pattern portion in table 7) and the other regions (indicated as a non-pattern portion in table 7) were determined by the measurement method described below. That is, virtual grid lines were drawn on the surface of the hot-dip plated layer at intervals of 1 mm. Subsequently, the diffraction peak intensity I of the (0002) plane of the Zn phase was measured for each region by an X-ray diffraction method in which X-rays were incident on each of a plurality of regions divided by virtual grid lines₀₀₀₂And diffraction peak intensity I of (10-11) plane of Zn phase_10-11. Then, the intensity ratio (I) of them was determined₀₀₀₂/I_10-11) This was taken as the orientation ratio.

X-ray diffraction measurements Co tube spheres were used as the X-ray source. Diffraction Peak intensity I of (0002) plane of Zn phase₀₀₀₂Is the intensity of the (0002) plane diffraction peak of the Zn phase appearing in the range of 42.41 ° ± 0.5 ° in the 2 θ range. Diffraction Peak intensity I of (10-11) plane of Zn phase_10-11Is the intensity of the diffraction peak of the (10-11) plane of the Zn phase appearing in the range of 50.66 DEG + -0.5 DEG in the 2 theta range. The stepping is 0.02 degree, the scanning speed is 5 degree/min, and the detector adopts a high-speed semiconductor two-dimensional detector.

In this embodiment, the side length of the square pattern is 10mm or more, and the interval between the virtual grid lines is 1 mm. Therefore, the X-ray emitted from the X-ray light source is condensed by the condenser tube. The irradiation range of the condensed X-ray is a circle having a diameter of 1 mm. In the X-ray diffraction measurement in which the X-rays having the irradiation range thus narrowed are irradiated to each region divided by the virtual grid lines at intervals of 1mm, an X-ray diffraction apparatus for measuring a minute region is used.

Then, a region having an orientation ratio of 3.5 or more was determined as a 1 st region, and a region having an orientation ratio of less than 3.5 was determined as a 2 nd region.

Then, the area ratios of the 1 st region in the square pattern and the other portions are obtained, and the absolute value of the difference between the area ratios of the 1 st region is obtained.

[ identifiability ]

The test panels in the initial state immediately after manufacture and the test panels in the aged state exposed outdoors for 6 months were subjected to visual evaluation based on the criteria for determination. In both the initial state and the aged state, A to C were accepted as passed. The judgment criterion is the same as in example 1.

[ Corrosion resistance ]

The test plate was subjected to a corrosion resistance test under the same conditions as in example 1, and then the rust state was examined and evaluated based on the judgment standard. And taking A to C as qualified. The determination criterion is the same as in example 1.

As shown in tables 7 and 8, the Zn-Al-Mg-based hot-dip coated steel sheets of Nos. 3-1 to 3-29 according to the examples of the present invention are excellent in both visibility and corrosion resistance. FIG. 9 shows the observation result of the No.3-1 pattern portion by the scanning electron microscope, and FIG. 10 shows the observation result of the No.3-1 non-pattern portion by the scanning electron microscope. It is found that the area ratios of the 1 st region are greatly different between the pattern portion and the non-pattern portion, and the pattern portion and the non-pattern portion can be distinguished.

In the case of sample No.3-30, when the temperature of the molten metal was lower than the range of (final solidification temperature-5) DEG C to (final solidification temperature +5) DEG C, nitrogen gas was blown through the gas nozzle, and therefore the difference between the area ratio of the 1 st region in the pattern portion and the area ratio of the 1 st region in the non-pattern portion was less than 30%, and the visibility of the pattern portion was lowered.

In addition, in Nos. 3-31 and 3-32, the composition of the hot-dip coating layer deviated from the range of the present invention, and the recognizability after 6 months of outdoor exposure was lowered.

In Nos. 3 to 33 in which square pattern portions were printed by an ink jet method, the pattern portions became thinner in a state of passage after 6 months of outdoor exposure, and visibility was lowered.

Further, by grinding No.3-34 in which the square pattern portion was formed, the plating thickness at the ground portion was reduced, and the corrosion resistance at the ground portion was reduced.

Further, the plating layers of Nos. 3-1 to 3-6, 3-10 to 3-30, and 3-32 to 3-34 contain an [ Al phase ]]And [ Al/Zn/MgZn ]₂Ternary eutectic structure of]。

FIG. 11 shows the surface of a hot-dip coated steel sheet in which a character string (letter sequence) is shown in a figure by blowing nitrogen gas to a Zn-Al-Mg-based hot-dip coating layer.

TABLE 6

Mark	Blowing conditions of nitrogen gas
		A	Gas temperature: 25 deg.C
B	Gas temperature: 150 ℃ C
		C	Gas temperature: 250 deg.C

TABLE 7

TABLE 8

(example 4)

No.4-1 to 4-32 Zn-Al-Mg hot dip coated steel sheets shown in Table 10 were produced by degreasing and washing steel sheets, followed by reduction annealing, dipping in a plating bath, controlling the amount of deposit, and cooling. When the steel sheet is lifted from the plating bath, if the temperature of the molten metal is in the range of (final solidification temperature-5) DEG C to (final solidification temperature +5) DEG C, nitrogen gas, which is one of non-oxidizing gases, is blown onto the molten metal on the surface of the steel sheet from a gas nozzle in a heated state. The blowing conditions of nitrogen gas are shown in table 9. The gas temperatures shown in table 9 are all above the final freezing temperature. Then, cooling is performed to completely solidify the molten metal. The control was performed by blowing nitrogen gas so as to appear a square pattern having a side of 50 mm. Among them, in the case of No.4-30, when the temperature of the molten metal was in a range of higher than the range of (final solidification temperature-5) DEG C to (final solidification temperature +5) DEGC, nitrogen gas was blown through the gas nozzle.

Further, a Zn-Al-Mg-based hot-dip coated steel sheet was produced in the same manner as described above. Then, a square pattern having a side length of 50mm was printed on the surface of the hot-dip plated layer by a spray method. The results are shown in Table 10 as Nos. 4 to 33.

Further, a Zn-Al-Mg-based hot-dip coated steel sheet was produced in the same manner as described above. Then, the surface of the hot-dip plated layer was ground to form a square pattern having a side length of 50 mm. The results are shown in Table 10 as Nos. 4 to 34.

The area ratios of the 1 st region and the 2 nd region included in the pattern portion and the non-pattern portion were determined for the hot-dip coated steel sheet obtained. First, the boundary between the pattern portion and the non-pattern portion is determined by observing the surface of the hot-dip plated layer with the naked eye. In the case where the boundary under the naked eye is difficult to determine, a magnified image using a magnifying glass or an optical microscope is used. In the example in which the boundary was difficult to be discriminated, the boundary was set based on the blowing range of the nitrogen gas, and the area ratios of the 1 st zone and the 2 nd zone were evaluated.

Next, the area ratio of each region included in the square pattern (indicated as a pattern portion in table 10) and the other regions (indicated as a non-pattern portion in table 10) was determined by the following determination method.

As shown in fig. 1, virtual grid lines K are drawn on the surface of the hot-dip plated layer at intervals of 1 mm. In fig. 1, the boundary line where the hot-dip coating layer appears is not shown. Next, a plurality of regions M divided by the virtual grid lines K are set. The shape of each region M is a square with a side of 1 mm. Next, for each of the plurality of regions M divided by the virtual grid line K, the center of gravity G of each region is set. Then, a circle S is drawn with the center of gravity G as the center. The diameter R of the circle S is adjusted so that the total length of boundary lines appearing on the surface of the hot-dip coating layer reaches 10 mm.

Then, the average value of the maximum diameter Rmax and the minimum diameter Rmin among the circles S of the plurality of regions M is set as a reference diameter Rave, a region having a circle S with a diameter R smaller than the reference diameter Rave is set as a 1 st region, and a region having a circle S with a diameter R equal to or larger than the reference diameter Rave is set as a 2 nd region.

The boundary line where the hot-dip plating layer appears is the boundary between the high-luminance portion and the low-luminance portion of the plating surface. The boundary is a boundary line obtained by binarizing the brightness value in the imaging data of the plating surface. Fig. 12 shows an example of the boundary line after the binarization process of the hot-dip plated surface.

Then, area ratios of the 1 st region and the 2 nd region in the square pattern and the other portions are obtained, respectively, and an absolute value of a difference between the area ratios of the 1 st region is obtained.

[ identifiability ]

The test panels in the initial state immediately after manufacture and the test panels in the aged state exposed outdoors for 6 months were subjected to visual evaluation based on the criteria for determination. In both the initial state and the aged state, A to C were accepted as passed. The determination criterion is the same as in example 1.

[ Corrosion resistance ]

After the corrosion resistance test was performed on the test plate under the same conditions as in example 1, the state of rust was examined and evaluated based on the criterion. And taking A to C as qualified. The judgment criterion is the same as in example 1.

As shown in Table 10, the Zn-Al-Mg-based hot-dip coated steel sheets of Nos. 4-1 to 4-29 according to the examples of the present invention were excellent in both visibility and corrosion resistance. FIG. 13 shows the observation result of the scanning electron microscope of the pattern portion of No.4-1, and FIG. 14 shows the observation result of the scanning electron microscope of the non-pattern portion of No. 4-1. It was found that the pattern portions and the non-pattern portions were distinguishable from each other by the area ratio of the 1 st region being greatly different from each other.

In sample 4-30, when the temperature of the molten metal was higher than the range of (final solidification temperature-5) ° c to (final solidification temperature +5) ° c, nitrogen gas was blown through the gas nozzle, and therefore, the difference between the area ratio of the 1 st region in the pattern portion and the area ratio of the 1 st region in the non-pattern portion was less than 30%, and the visibility of the pattern portion was degraded.

In addition, the compositions of the hot dip coatings of Nos. 4-31 and 4-32 deviate from the scope of the present invention, and the recognizability after 6 months of outdoor exposure is lowered.

On the other hand, in the case of Nos. 4 to 33 in which the square pattern portions were printed by the ink jet method, the pattern portions became thinner by 6 months of outdoor exposure, and the design was degraded.

Further, by grinding Nos. 4 to 34 in which the checkered pattern was formed, the plating thickness of the ground portion was reduced, and the corrosion resistance of the ground portion was reduced.

Further, the plating layers of Nos. 4-1 to 4-6, 4-10 to 4-30, and 4-32 to 4-34 contain [ Al phase ]]And [ Al/Zn/MgZn ]₂Ternary eutectic structure of]。

FIG. 15 shows the surface of a hot-dip coated steel sheet with character strings (letter sequences) shown by graphic parts.

According to the present invention, a pattern portion including characters, marks, or the like can be arbitrarily shown on the surface of the hot-dip galvanized steel sheet.

TABLE 9

Mark	Blowing conditions of nitrogen gas
		A	Gas temperature: 380 deg.C
B	Gas temperature: 350 deg.C
		C	Gas temperature: 450 deg.C

Industrial applicability

According to the present invention, various design designs, trademarks, and other identification marks can be displayed on the surface of the hot-dip plated layer without printing or coating, and the visibility and designability of the steel sheet can be improved. Further, the pattern portion can also provide information necessary for process management, stock management, and the like, and arbitrary information required by a user to the hot-dip coated steel sheet. This also contributes to improvement in productivity of the hot-dip plated steel sheet. Therefore, the method is sufficiently industrially applicable.

Claims

1. A hot-dip coated steel sheet characterized in that,

when the 1 st region and the 2 nd region are determined by any one of the following determination methods 1 to 5, the pattern portion and the non-pattern portion are respectively composed of 1 or 2 of the 1 st region and the 2 nd region, and an absolute value of a difference between an area ratio of the 1 st region in the pattern portion and an area ratio of the 1 st region in the non-pattern portion is 30% or more,

the determination method 1: drawing virtual grid lines on the surface of the hot-dip plating layer at intervals of 0.5mm, taking the inside of a circle with the diameter of 0.5mm centering on the center of gravity of each region as a measurement region A in each of a plurality of regions divided by the virtual grid lines, measuring the L value in each measurement region A, selecting any 50 points from the obtained L values, taking the average value of the 50 points of the obtained L values as a reference L value, taking a region with the L value being more than or equal to the reference L value as a 1 st region, and taking a region with the L value being less than the reference L value as a 2 nd region;

the determination method 2 comprises the following steps: drawing virtual grid lines on the surface of the hot dip plating layer at intervals of 0.5mm, taking the inside of a circle with the diameter of 0.5mm centering on the gravity center point of each region as a measurement region A in each of a plurality of regions divided by the virtual grid lines, measuring the L value in each measurement region A, taking the region with the L value of more than 45 as a 1 st region, and taking the region with the L value of less than 45 as a 2 nd region;

the determination method 3: drawing virtual grid lines on the surface of the hot-dip plating layer at intervals of 0.5mm, measuring arithmetic mean surface roughness Sa in each of a plurality of regions partitioned by the virtual grid lines, taking a region having a Sa of 1 μm or more as a 1 st region, and taking a region smaller than 1 μm as a 2 nd region;

the determination method 4: drawing virtual grid lines on the surface of the hot dip coating at intervals of 1mm or 10mm, and deriving by adopting X raysThe X-ray is incident on each of a plurality of regions defined by the virtual grid lines, and the diffraction peak intensity I of the (0002) plane of the Zn phase is measured for each of the regions₀₀₀₂And diffraction peak intensity I of (10-11) plane of Zn phase_10-11Their intensities are compared with each other I₀₀₀₂/I_10-11Regarding the orientation ratios, a region having the orientation ratio of 3.5 or more is defined as a 1 st region, and a region having the orientation ratio of less than 3.5 is defined as a 2 nd region;

the determination method 5: drawing virtual grid lines on the surface of the hot-dip coating layer at intervals of 1mm, drawing a circle S centering on a gravity center point G of each of a plurality of regions partitioned by the virtual grid lines, the circle S having a diameter R set such that the total length of surface boundary lines of the hot-dip coating layer contained in the circle S is 10mm, setting an average value of a maximum diameter Rmax and a minimum diameter Rmin among the diameters R of the circles S of the plurality of regions as a reference diameter Rave, setting a region having the circle S with the diameter R smaller than the reference diameter Rave as a 1 st region, and setting a region having the circle S with the diameter R equal to or larger than the reference diameter Rave as a 2 nd region.

2. A hot dip plated steel sheet according to claim 1,

the hot dip coating contains 4-22 mass% of Al and 1-10 mass% of Mg in terms of average composition, and the balance of Zn and impurities.

3. A hot-dip plated steel sheet according to claim 1 or 2,

the hot dip coating layer further contains 0.0001 to 2 mass% of Si in terms of average composition.

4. A hot dip coated steel sheet according to any one of claims 1 to 3,

the hot dip coating layer further contains 0.0001 to 2 mass% in total of 1 or more than 2 of Ni, Ti, Zr, Sr, Fe, Sb, Pb, Sn, Ca, Co, Mn, P, B, Bi, Cr, Sc, Y, REM, Hf, and C in terms of average composition.

5. A hot-dip coated steel sheet according to any one of claims 1 to 4,

the pattern part is configured to be any 1 shape of straight line part, curve part, point part, figure, number, symbol, pattern and character or the shape formed by combining more than 2 of them.

6. A hot dip coated steel sheet according to any one of claims 1 to 5,

the pattern portion is intentionally formed.

7. A hot dip coated steel sheet according to any one of claims 1 to 6,

the total adhesion amount of the hot-dip coating layers on both sides of the steel sheet is 30-600 g/m²。

8. A hot-dip coated steel sheet characterized in that,

the pattern part and the non-pattern part respectively comprise 1 or 2 of a 1 st region and a 2 nd region determined by any one of the following determination methods 1 to 5, and the absolute value of the difference between the area ratio of the 1 st region in the pattern part and the area ratio of the 1 st region in the non-pattern part is 30% or more,

the determination method 3: drawing virtual grid lines on the surface of the hot-dip plated layer at intervals of 0.5mm, measuring an arithmetic average surface roughness (Sa) in each of a plurality of regions partitioned by the virtual grid lines, and regarding a region having a Sa of 1 μm or more as a 1 st region and a region smaller than 1 μm as a 2 nd region;

the determination method 4: drawing virtual grid lines on the surface of the hot dip coating layer at intervals of 1mm or 10mm, making X-rays incident on each of a plurality of regions partitioned by the virtual grid lines by an X-ray diffraction method, and measuring the diffraction peak intensity I of the (0002) plane of the Zn phase for each of the regions₀₀₀₂And diffraction peak intensity I of (10-11) plane of Zn phase_10-11By comparing their intensities I₀₀₀₂/I_10-11Regarding the orientation ratio, a region having the orientation ratio of 3.5 or more is defined as a 1 st region, and a region having the orientation ratio of less than 3.5 is defined as a 2 nd region;