JP5114746B2 - Method for producing hot-dip aluminized steel sheet with pear skin surface - Google Patents

Description

  The present invention relates to a method for producing a hot-dip aluminized steel sheet having a pear skin pattern.

  Specifically, the present invention relates to a method for producing a hot-dip aluminized steel sheet having a pear skin pattern on the entire surface of the hot-dip aluminum-plated steel sheet, which has no uneven plating and does not generate spangles after pressing.

  Conventionally, various proposals have been made regarding a method for producing a hot-dip aluminized steel sheet having a small spangle pattern.

For example, in Japanese Patent Laid-Open No. 61-147906 (Patent Document 1), the maximum height (μRmax) of a hot-dip plated steel sheet in a continuous hot-dip aluminum plating line is disclosed.
Applying temper rolling with a unit width rolling load of 250 to 450 kgf / mm by a multi-skin pass mill with a roll roll of 450 mm or more having a surface roughness of 10 to 30 and a peak number (PPI) of 100 to 125 as a work roll A characteristic method for improving the surface skin of a hot dip galvanized steel sheet is described, and there is a disclosure that a dull roll is used for the No. 1 stand and a bright roll is used for the No. 2 stand.

  However, according to the method of Patent Document 1, in order to erase the spangle pattern, the spangle does not disappear unless the maximum height (μRmax) is 10 μm to 30 μm and the roughness is large, and a glossy steel plate is produced. In order to obtain a dull appearance, there is a limit to the size of the pear skin (lower limit), and spangles remain when trying to produce fine pear skin. there were.

  Furthermore, the phenomenon that the spangle pattern that should have disappeared after the press working emerged again was observed.

  JP-A-63-153255 (Patent Document 2) and JP-A-10-158807 (Patent Document 3) suppress the spangle pattern by spraying a powder made of a metal oxide powder on the plating surface. A method for producing a hot-dip galvanized steel sheet is described.

  However, in the methods of Patent Document 2 and Patent Document 3, there is a case where the powder contact method becomes non-uniform due to powder clogging or accumulation, and there is a problem of stability because the suitable range of the plate temperature is narrow. In particular, when the plate speed changes during operation, if the temperature range is out of the range, the surface may be uneven and the appearance may be impaired.

  JP-A-59-145770 (Patent Document 4) discloses that forced cooling is performed by spraying water or an aqueous solution when the surface of the plated metal is still in a molten state, and then normal cooling is performed. A single-sided molten metal plating method characterized by sequentially performing non-plated surface polishing and skin pass rolling is described.

However, the method described in Patent Document 4 may cause a mist particle to bind to increase the particle diameter, resulting in a spot-like surface defect. In addition, the appropriate range of plate temperature is narrow and there is a problem of stability. In particular, when the size of the spangle was made to be 1.5 mm or less, irregularities were generated on the surface and the appearance was impaired.
JP-A-61-147906 JP 63-153255 A JP-A-10-158807 JP 59-145770 A

  Therefore, the present invention solves the problems of the prior art as described above, and has an excellent appearance in which there is no uneven plating over the entire surface of the hot-dip aluminized steel sheet surface with a pear skin pattern and no spangles are raised after pressing. It is an object of the present invention to provide a method for producing a hot-dip aluminized steel sheet capable of obtaining the above.

The gist of the present invention is the following contents as described in the claims.
(1) Si: 3 to 15% by mass, and the balance is adjusted to 0.1 to 10 mm on the surface of the steel plate subjected to hot dip aluminum plating consisting of Al and inevitable impurities, and then No. 1 of the skin pass rolling mill The surface is characterized by performing skin pass rolling with roll roughness Ra2 of the stand No.2: 1.5 μm to 4.0 μm after the skin pass rolling with the roll roughness Ra1 of the stand: 0.1 μm to 0.5 μm. Manufacturing method of hot-dip aluminized steel sheet with pear skin pattern.
(2) The method for producing a hot-dip aluminized steel sheet having a pear-skin surface as described in (1), wherein the spangle diameter before the skin pass rolling is 0.1 mm to 2 mm.
(3) The method of adjusting the spangle diameter before the skin pass rolling is characterized in that powder is sprayed on the surface of the steel sheet after the basis weight of the plating is adjusted by a wiping nozzle provided on the outlet side of the immersion pot for hot dip aluminum plating. The method for producing a hot-dip aluminized steel sheet having a pear skin pattern as described in (1) or (2).
(4) The method for producing a hot-dip aluminized steel sheet having a pear-skin surface as described in (3), wherein the temperature of the steel sheet when spraying the powder is 580 to 600 ° C.
(5) The powder is a metal powder or a metal oxide powder, and the content of the metal oxide per steel plate surface area is 0.1 to 20 mg / m2, (3) or (4) A method for producing a hot-dip aluminized steel sheet having a pear skin pattern as described in 1.
(6) The method according to (5), wherein the metal oxide powder or the metal oxide powder has a particle size of 2 to 100 μm, and the surface is a pear-skinned hot-dip aluminized steel sheet.
(7) The metal oxide powder or the spraying speed of the metal oxide powder is 10 to 80 m / sec on the plating surface, and the surface is a pear-skinned molten aluminum as described in (5) or (6) Manufacturing method of plated steel sheet.
(8) The method of adjusting the spangle diameter before the skin pass rolling is to spray mist on the surface of the steel sheet after adjusting the plating weight with a wiping nozzle installed on the outlet side of the immersion pot for hot-dip aluminum plating. A method for producing a hot-dip aluminized steel sheet having a pear-skin surface as described in (1) or (2).
(9) The method for producing a hot-dip aluminized steel sheet having a pear-skinned surface as described in (8), wherein the steel sheet temperature when spraying the mist is 575 ° C. to 615 ° C.
(10) The method of adjusting the spangle diameter before skin pass rolling is to blow the air on the steel sheet surface after adjusting the plating weight with a wiping nozzle provided on the outlet side of the immersion pot for hot dip aluminum plating. The method for producing a hot dip galvanized steel sheet having a pear skin pattern as described in (1) or (2), wherein cooling or natural cooling is performed.
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According to the invention of (1), after adjusting the spangle diameter of the surface of the steel plate on which the molten aluminum plating is made of Al and inevitable impurities including Si: 3 to 15% by mass to 0.1 mm to 10 mm, the skin pass By performing skin pass rolling with the roll roughness Ra1 of the No. 1 stand of the rolling mill being 0.1 μm to 0.5 μm and then performing skin pass rolling with the roll roughness Ra2 of the No. 2 stand being 1.5 μm to 4.0 μm By skin pass rolling with bright rolls with low roll roughness, the hardness difference on the surface of the Al plating layer is made uniform, and the boundary of spangles on the steel sheet surface is filled and pressed, and then skin pass rolling with dull rolls with high roll roughness by performing the surface becomes possible to produce a molten aluminum-plated steel sheet Nashihada pattern, after pressing spangle It is possible to prevent the occurrence of the raised.
According to the invention of (2), by setting the spangle diameter before the skin pass rolling to 0.1 mm to 2 mm, it is possible to produce an aluminized steel sheet having a finer surface.
According to the invention of (3), the spangle diameter before the skin pass rolling can be obtained by spraying powder onto the steel sheet surface after adjusting the coating weight with a wiping nozzle provided on the outlet side of the immersion pot for hot-dip aluminum plating. Can be adjusted, and unevenness can be eliminated by a skin pass, and a pear skin-patterned aluminum-plated steel sheet having a fine surface and no unevenness can be produced.
According to invention of (4), by adjusting the steel plate temperature at the time of spraying the said powder to 580 degreeC-600 degreeC, while adjusting the spangle diameter before the said skin pass rolling, it can perform effectively and with a skin pass. Unevenness can be eliminated, and a pear skin-patterned aluminum-plated steel sheet having a fine surface and no unevenness can be produced.
According to the invention of (5), the powder is a metal acid powder or metal oxide powder, and the content of the metal acid powder or metal oxide powder per steel plate surface area is 0.1 to 20 mg / m 2. Further, the spangle diameter before the skin pass rolling can be adjusted effectively, and unevenness can be eliminated by the skin pass, and a surface-finished aluminum-plated steel sheet having a fine and uniform surface can be produced.
According to the invention of (6), by adjusting the particle size of the metal acid powder or metal oxide powder to 2 to 100 μm, it is possible to more effectively adjust the spangle diameter before the skin pass rolling, Unevenness can be eliminated with a skin pass, and a pear skin-patterned aluminum-plated steel sheet having a fine surface and no unevenness can be produced.
According to the invention of (7), by adjusting the spraying speed of the metal acid powder or metal oxide powder to 10 to 80 m / sec on the plating surface, the spangle diameter before the skin pass rolling is adjusted more effectively. In addition, it is possible to eliminate the unevenness by the skin pass, and to produce a pear skin-patterned aluminum-plated steel sheet having a fine surface and no unevenness.
According to the invention of (8), the spangle before the skin pass rolling can be obtained by spraying mist on the surface of the steel plate after adjusting the coating weight with a wiping nozzle installed on the exit side of the immersion pot for hot-dip aluminum plating. The diameter can be adjusted, and unevenness can be eliminated by a skin pass, and a pear skin-patterned aluminum-plated steel sheet having a fine surface and no unevenness can be produced.
According to the invention of (9), by adjusting the steel plate temperature when spraying the mist to 575 ° C. to 615 ° C., the spangle diameter before the skin pass rolling can be adjusted more effectively, and the skin pass Thus, it is possible to eliminate the unevenness, and it is possible to produce an aluminized steel sheet with a pear skin pattern that has a fine surface and no unevenness.
According to the invention of (10), the surface of the steel sheet after adjusting the basis weight of the plating with a wiping nozzle provided on the exit side of the immersion pot for hot dip aluminum plating is cooled by air or cooled naturally. As a result, the spangle diameter before the skin pass rolling can be adjusted to be large, and unevenness can be eliminated by the skin pass, and a pear skin-patterned aluminum plated steel sheet having a fine surface and no unevenness can be produced.

  According to the present invention, it is possible to provide a method for producing a hot dip galvanized steel sheet capable of obtaining an excellent satin appearance with no uneven plating over the entire surface of the hot dip galvanized steel sheet and without occurrence of spangles after pressing. It has a remarkable effect that is industrially useful.

  The best mode for carrying out the present invention will be described with reference to FIGS.

  FIG. 1 is a diagram illustrating a hot-dip aluminum plating line to which the present invention is applied.

  In FIG. 1, 1 is a redox furnace, 2 is a molten Al pot, 3 is metal oxidation, or a mist spraying device (zero appearance device), 4 is a skin pass rolling machine, and 5 is a wiping nozzle.

  The steel plate heat-treated in the oxidation-reduction furnace 1 is immersed in a molten Al pot 2, and after being subjected to molten aluminum plating containing Si: 3 to 15% by mass and the balance of Al and inevitable impurities, After adjusting the plating weight with the wiping nozzle 5 provided on the outlet side of the molten Al pot, the spangle diameter of the steel sheet surface is adjusted by the zero appearance device 3, and then the yield point elongation is adjusted by the skin pass rolling machine 4. Is eliminated and the shape is corrected.

  FIG. 2 is a diagram illustrating an embodiment of the present invention, and FIG. 3 is a diagram illustrating a comparative example.

  After normal immersion cooling in the aluminum plating bath, a spangle pattern of about 3 to 10 mm can be formed on the steel plate surface.

As shown by the ▲ mark in FIG. 4, even if the dull skin pass rolling of about 1.5% with high roughness is continued after plating on the aluminum-plated steel sheet having the spangle pattern, a portion that is not rolled by the dull roll remains. The spangles may appear after pressing.
Assuming this cause, the hot-dip aluminum plating spangle is that the primary crystal of aluminum develops in a dendritic shape parallel to the surface of the steel sheet, but when there are many crystal nuclei, the dendritic crystal grows as a result. It is thought that the part which collides with the dendritic crystal and the crystal orientation is different becomes visible as a grain boundary, and the connection of this grain boundary is recognized as spangle.

  In FIG. 6, the example which measured the aluminum plating steel plate surface with the white interferometer is shown. FIG. 5A is an example in which the spangle diameter is 1 mm, and FIG. 5B is an example in which the spangle diameter is 2.8 mm, but the dendritic primary crystal of aluminum appears on the surface as a streak, and the streak looks like that. It was confirmed that a spangle boundary appeared when the dendritic crystal collided with an adjacent dendritic crystal in a different direction.

Further, FIG. 7 shows an example in which the spangle diameter and the dent depth at the spangle boundary are measured. FIG. 7 was measured using white light interferometry. As shown in FIG. 7, when the spangle diameter is increased up to 6 mm, the dent depth increases. On the other hand, it was found that when the spangle diameter exceeds 6 mm, the dent depth of the spangle boundary portion is reversed and becomes smaller.
These crystal grain boundaries are thought to have microscopic voids, and may be raised during pressing only by rolling. That is, the grain boundary at the boundary between the crystal grain and the spangle is considered to have different hardness, so even if rolling using a high-roughness dull roll, the hardness difference does not decrease, It is considered that the grain boundary is mechanically opened at the convex part of the dull roll, or the hardness difference is given microscopically by the protrusion of the dull roll, and the spangle pattern is raised during pressing.

  On the other hand, in the present invention, as shown in FIG. 2, after hot-dip aluminum plating, skin pass rolling is performed with a smooth bright roll to first uniform the hardness of the steel sheet surface and fill the boundary of the spangle. And then press-bonding, followed by skin pass rolling using a dull roll, a beautiful dull appearance having a fine satin appearance can be obtained.

Here, the beautiful dull appearance having a fine satin appearance is 1) pear skin obtained by rolling with a bridal roll and then rolling with a dull roll having a Ra of about 4 μm or less, or a Rmax of 9 μm or less. There is no extremely deep part, and the steel sheet has a pear skin surface property with no unevenness. The surface roughness of the steel sheet is about Ra of about 3 μm or less and Rmax of about 7 μm or less,
And 2) a steel plate having a surface on which the skin pass pattern does not appear after press forming.

The mechanism by which the spangle pattern by bright skin pass rolling is reduced and a beautiful dull appearance having a fine satin appearance can be obtained as follows.

  As shown schematically in FIG. 2, the grain boundaries of the spangles of the Al plating layer are generally recessed, and whether or not the spangles emerge after pressing depends on whether or not a bright roll is used for the No. 1 stand. On the other hand, whether or not the unevenness disappears depends on the roughness of the No. 2 stand dull roll.

  If a bright roll is used for the No. 1 stand, the spangles can be prevented from coming out after pressing because the plated metal fills and crimps the grain boundaries of the spangles.

The product roughness PPI depends on the roll roughness of the No. 2 stand. The initial roughness of the hot-dip aluminized steel sheet without the skin pass is about 0.6 μm in Ra, and there is also unevenness, which remains even after rolling on a No. 1 stand with a bright roll. However, even after rolling on a No. 1 stand with a bright roll, the surface is soft and the transfer rate is as high as 50-70%, so the PPI of product roughness does not vary much, and it depends on the roughness of the original plate before skin pass It depends on the roughness of the skin pass roll.
Therefore, unevenness is eliminated by providing irregularities on the surface by dull roll rolling. The unevenness mentioned here mainly refers to irregularities generated in a substantially circular shape of about 1 mm to 5 mm generated by metal oxide spraying or mist spraying after hot dipping.
In addition, since rolls are rolled on the No. 1 stand with bright rolls, dull roll irregularities can be added regardless of the spangle pattern, so that the spangle pattern can be adjusted so that it cannot be seen.

  Therefore, in the present invention, the roll roughness Ra1 of the No. 1 stand of the skin pass rolling mill is set to 0.1 μm to 0.5 μm and then subjected to skin pass rolling, and then the roll roughness Ra2 of the No. 2 stand: 1.5 μm to 4. Skin pass rolling is performed at 0 μm.

  If the roll roughness Ra1 of the No. 1 stand of the skin pass rolling mill is less than 0.1 μm, rolling is not possible because it falls below the slip limit during rolling. On the other hand, if the roughness Ra1 exceeds 0.5 μm, the roll surface irregularities This is because the vertical streaks remain after being transferred to.

  Also, if the roll roughness Ra2 of the No.2 stand is less than 1.5 μm, the plating unevenness will not disappear completely. On the other hand, if the roll roughness Ra2 exceeds 4.0 μm, the steel sheet surface will become rough and the appearance will be fine. It is because it does not become.

  In particular, since the surface hardness is made uniform in the first skin pass, the spangle pattern does not appear after pressing.

  For the zero appearance device 3 shown in FIG. 1, the following mist cooling, powder spraying of metal oxide, natural cooling, or air cooling at a cooling rate close to natural cooling can be applied.

If the mist is positively cooled after wiping, a fine spangle is formed as a whole, and the difference in hardness is reduced.
The best method is to spray metal oxide after wiping. In this case, since a finer spangle is formed as compared with mist cooling, the difference in hardness is further reduced, and the spangle pattern does not appear at all after pressing. However, in the method of spraying the metal oxide, unevenness may occur on the surface, and skin pass rolling using a bright roll and the subsequent dull roll is also effective for this adjustment.

  The powder spraying temperature of the method of spraying the metal oxide is good between the primary crystal temperature and the eutectic temperature of the molten aluminum plating liquid, and is optimally 580 to 600 ° C.

If there is little metal oxide powder, the crystal of aluminum will become large and sufficient spangle cannot be erased. If the amount is too large, there is no problem from the viewpoint of removing spangles, but since the powder adheres to the roll and the appearance of the steel plate deteriorates, the content of the metal oxide per steel plate surface area should be 0.1-20 mg / m2. preferable.

  If the particle size of the metal oxide powder is small, the spangle will not disappear because it is difficult to form aluminum crystal nuclei. On the other hand, if the size is too large, the number of particles is reduced and the crystal of aluminum becomes large. Therefore, the particle size of the metal oxide powder is preferably in the range of 2 to 10 μm.

If the spraying speed of the metal oxide powder is too slow, it will not become enough crystal nuclei, so the crystals will become large, and if it is too fast, the metal oxide powder will scatter and adhere to rolls, etc. It is preferable that the spraying speed of the powder is 10 to 80 m / sec on the plating surface.
In the case of mist cooling, it is the same as that of metal oxide spraying, but since it solidifies immediately after spraying, it is slightly wider than that of metal oxide spraying and is preferably 575 ° C to 615 ° C. Any general two-fluid nozzle can be used for the amount, particle diameter, spraying speed, etc. of the mist.

  In order to reduce the micro hardness difference on the surface of the hot-dip plated steel sheet, air cooling may be performed after wiping at a natural cooling rate or a cooling rate close to natural cooling. Furthermore, when air cooling is performed at a natural cooling rate or at a cooling rate close to natural cooling, the spangle diameter increases beyond 6 mm, and when this diameter exceeds 6 mm, the spangle boundary recess depth decreases. In addition, when air cooling is performed at a natural cooling rate or a cooling rate close to natural cooling, the unevenness of the dendritic primary crystal of aluminum is small as in the example where the spangle diameter is 7 mm shown in FIG. Since the surface becomes smooth as a whole, the surface becomes very uniform after rolling with No. 1 stand with bright roll, so by using skin pass rolling with subsequent No. 2 stand dull roll, A beautiful dull appearance with a satin appearance can be obtained.

  4 and 5 are diagrams showing an embodiment of the present invention.

  The horizontal axis of FIG. 4 indicates the spangle diameter, and the vertical axis indicates the appearance score after skin pass rolling. The higher the score, the worse the appearance.

  As shown in FIG. 4, there is a correlation between the spangle diameter and the appearance score, and in the roll of dull roll (Ra = 4 μm, Rmax = 9 μm), the appearance score after the skin pass is 2 μm even if the spangle diameter is 2 μm. 3 is inferior.

  On the other hand, the steel sheet which was reduced by 1% by bright roll (Ra = 0.4 μm, Rmax = 0.9 μm) and then reduced by 0.5% by dull roll (Ra = 4 μm, Rmax = 9 μm) is equivalent spangle 2 μm, Appearance score after skin pass is 2 and good.

  Thus, when the spangle diameter is reduced, the appearance score after the skin pass is further improved, and this effect is considered to decrease the hardness difference microscopically when the spangle is reduced.

The horizontal axis in FIG. 5 shows the roughness of the dull roll of the NO. 2 stand, and the vertical axis shows the appearance score after skin pass rolling. The higher the score, the better the appearance.
The reason why the score in FIG. 5 is different from that in FIG. 4 is the result of further detailed analysis of the surface appearance score. Score 1 in FIG. 4 corresponds to score 5 in FIG. 5, and score 2 in FIG. Corresponds to a rating of 5.

  The roughness of the NO.2 stand dull roll is related to the rolling force, but it is 2 μm or more, and the score is 4 or more, which is even better.

  Although not shown, when air cooling is performed at a natural cooling rate or a cooling rate close to natural cooling, the spangle diameter exceeds 6 mm. In this case as well, the rating is 2 or less in FIG. A good pear skin score of 2 or higher was obtained.

  The present invention is applicable to hot-dip aluminum plating containing Si: 3 to 15% by mass with the balance being Al and inevitable impurities. As the number of crystals increases, it is difficult to achieve uneven appearance. Further, since the amount of primary Al crystal increases and the hard Al—Si eutectic structure decreases, the difference in surface hardness also decreases. By these things, the external appearance after a skin pass becomes favorable.

  Examples of the present invention are shown in Table 1.

  No. 1 to No. 4 are invention examples meeting the conditions of the present invention, there was no plating unevenness, and no spangles were raised after pressing.

  No. 5 to No. 9 are comparative examples, because the conditions of the roll roughness used for skin pass rolling deviate from the scope of the present invention. Uneven plating and / or raised spangles after pressing were observed.

  The effect of the present invention was confirmed by this example.

It is a figure which illustrates the hot-dip aluminum plating line to which this invention is applied. It is a figure which illustrates embodiment of this invention. It is a figure which illustrates the comparative example of this invention. It is a figure which shows the Example of this invention. It is a figure which shows the Example of this invention. It is a figure which shows the surface state of the spangle of this invention. The field of view was measured with a white interferometer at 947 × 710 mm, objective lens: x5. It is the figure which showed the relationship between the dent of the spangle boundary part of this invention, and a spangle diameter. The same measurement method as in FIG. 6 was used.

Explanation of symbols

1 Redox furnace 2 Molten Al pot 3 Metal oxidation or mist spraying device (zero appearance device)
4 Skin pass rolling machine 5 Wiping nozzle

Claims (10)

  No.1 roll of skin pass rolling mill after adjusting the spangle diameter of the steel sheet surface with Si: 3 to 15% by mass, the balance being aluminum and unavoidable impurities to which aluminum plating is applied, to 0.1 mm to 10 mm Roughness Ra1: 0.1 μm to 0.5 μm after skin pass rolling, No.2 stand roll roughness Ra2: 1.5 μm to 4.0 μm, skin pass rolling is performed. Manufacturing method of hot-dip aluminized steel sheet.   The method for producing a hot-dip galvanized steel sheet having a pear-skin surface as claimed in claim 1, wherein the spangle diameter before the skin pass rolling is 0.1 mm to 2 mm.   The method of adjusting the spangle diameter before the skin pass rolling is characterized by spraying powder onto the steel sheet surface after adjusting the plating weight with a wiping nozzle provided on the outlet side of a dipping pot for hot-dip aluminum plating, The manufacturing method of the hot dip galvanized steel plate whose surface of Claim 1 or Claim 2 has a pear skin pattern.   The method for producing a hot-dip galvanized steel sheet having a pear-skin surface as claimed in claim 3, wherein a temperature of the steel sheet when the powder is sprayed is 580C to 600C.   The said powder is a metal powder or a metal oxide powder, and content per steel plate surface area of this metal oxide is 0.1-20 mg / m2, The claim | item 3 or 4 characterized by the above-mentioned. A method for producing a hot-dip aluminized steel sheet having a pear skin surface.   The method for producing a hot-dip galvanized steel sheet having a pear skin pattern according to claim 5, wherein the metal oxide powder or the metal oxide powder has a particle size of 2 to 100 μm.   7. The hot-dip galvanized steel sheet having a pear skin pattern on the surface according to claim 5, wherein a spraying speed of the metal oxide powder or the metal oxide powder is 10 to 80 m / sec on the plating surface. Manufacturing method.   The method of adjusting the spangle diameter before the skin pass rolling is characterized by spraying mist on the surface of the steel sheet after adjusting the plating weight with a wiping nozzle installed on the exit side of the immersion pot for hot-dip aluminum plating. The manufacturing method of the hot dip galvanized steel plate whose surface of Claim 1 or Claim 2 has a pear skin pattern.   The method for producing a hot-dip aluminized steel sheet having a pear skin pattern according to claim 8, wherein the steel sheet temperature when spraying the mist is 575 ° C to 615 ° C.   The method of adjusting the spangle diameter before skin pass rolling is to cool the steel plate surface after adjusting the plating weight with a wiping nozzle provided on the outlet side of the immersion pot for hot-dip aluminum plating, by blowing air or The method for producing a hot-dip aluminized steel sheet having a pear-skin surface as claimed in claim 1 or 2, wherein the surface is naturally cooled.

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