JPH11222658A - Method for regulating spangle in hot dip zinc-aluminum series plated steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the objective spangle grain size in a hot dip Zn-Al series steel sheet without deteriorating its workability and corrosion resistance with the conventional continuous hot dip plating equipment utilized. SOLUTION: The compsn. of a plating film is composed of, by weight, 0.05 to 70% Al, 0 to 7.0% Si, and the balance zinc with inevitable intruded impurity elements. At the time of hot dip plating, the difference between the grain size of spangles formed on the surface of the plating film and the objective grain size is obtd., and in the case the difference lies within a prescribed range, the production continues as it is, and in the case the difference exceeds this prescribed range, the producing conditions are changed, which is reflected in the objective spangle grain size.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a spangled pattern of a hot-dip Zn or Zn-Al alloy-plated steel sheet, which is suitable for use in building materials, home appliances, automobiles, and the like.

[0002]

2. Description of the Related Art Hot-dip Zn-Al-based plating is performed to improve the corrosion resistance and weather resistance of a steel sheet, but its application has increased in recent years. A typical example is hot-dip galvanizing (Al <
0.2%), Zn-5% Al alloy plating, Zn-55% Al alloy plating and the like. Hereinafter, these are also collectively referred to as hot-dip Zn-Al-based alloy plating including the hot-dip galvanizing.

[0003] In particular, Zn-55% Al alloy-plated steel sheet is a high-performance plated steel sheet having both the durability, heat resistance, heat reflection property of aluminum and the sacrificial corrosion resistance of zinc. Widely used for automotive parts. Such plated steel sheets typically contain Al:
It is manufactured using a hot-dip plating bath consisting of 55%, Zn: 43.4%, and Si: 1.6%. The ratio of Al and Zn is determined in consideration of corrosion resistance, and Si is added to suppress an alloy reaction with a steel substrate that inhibits plating adhesion.

[0004] Unlike other Zn-Al alloy-plated steel sheets having a low Al content, this Zn-55% Al alloy-plated steel sheet has a characteristic silver-white spangle pattern on the plating surface, and is made of a fabric due to its design. As it is, it is widely used for roofs and walls of commercial and industrial buildings and general-purpose buildings, and for fixtures.

[0005] The particle diameter of spangles on the plating surface of a Zn-55% Al alloy-plated steel sheet varies depending on the hot-dip plating conditions, particularly the solidification rate after hot-dip plating, but is generally about 0.8 on average.
mm or more, and the spangle pattern can be visually identified.

[0006] In particular, in recent years, a melt having a spangle pattern
Zn-Al-based alloy-plated steel sheets tend to be used for outer panels, etc., and many of them are easily accessible to the public.Therefore, there is an increasing need to control the size of spangle patterns when delivering products. That is the current situation.

In general, the spangle diameter of a hot-dip Zn—Al-based alloy-coated steel sheet decreases when the cooling rate (hence, the solidification rate of the plating film) is increased by increasing the air volume during forced cooling after hot-dip coating, and conversely. It is known that the air volume increases when the air volume decreases. However, only cooling by air has a limited effect on the spangle particle size, and there is no other way to control the particle size beyond or below it by another means. In particular, the following methods are generally known for reducing the spangle particle size.

[0008] Regarding the spangle of hot-dip coated steel sheet,
It has also been practiced to eliminate the spangle pattern by performing skin pass reduction after the plating film has solidified. However, if this method alone is used to eliminate the spangle, the appearance deterioration due to the remaining spangle and the uneven appearance after painting are likely to occur. Also,
There is also a problem that flaws are likely to occur when the plating film is picked up by the skin pass roll, and a spangle pattern tends to emerge during press working by the user.

Further, fine particles of solid or liquid are sprayed on the unsolidified plating surface of the hot-dip coated steel sheet immediately after plating, so that a large number of solidification nuclei are uniformly generated and rapidly cooled, so that the spangle pattern is refined. Various technologies have been proposed (for hot-dip aluminum-coated steel sheets,
See, for example, JP-A-50-38638, JP-A-63-143249, and JP-A-63-153255.

If this method is adopted, it is possible to make the average spangle diameter of the plating surface of the Zn-55% Al alloy plated steel sheet smaller than 0.8 mm. Problems such as aging deterioration of the base material itself cannot be solved yet. In addition, this method requires the addition of a fine particle spraying device to a conventional hot-dip plating facility,
Increases cost. Conversely, in order to increase the spangle particle size, it is necessary to replace the spraying device with the air cooling zone, which causes a large loss in time.

Japanese Unexamined Patent Publication No. 59-56570 discloses that molten zinc having a very fine spangle and excellent corrosion resistance, which comprises adding 3 to 15 wt% of Si and 3 to 20 wt% of Mg in a plating bath. -Al-based alloy plated steel sheet is described. But,
Since a relatively large amount of Si and Mg coexist in the plating film, this plated steel sheet has a problem that the workability is deteriorated due to the precipitation of Si and Mg in the film. Conversely, increasing the spangle particle size requires a reduction in the Mg concentration in the bath, resulting in a time loss and a loss in production volume.

[0012]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for forming a target spangle grain by a simple means without the presence of other elements such as Mg in the plating film and without spraying fine particles. An object of the present invention is to provide a spangle particle size control method capable of obtaining a diameter. Another object of the present invention is to provide a method for controlling a spangle particle size of a hot-dip Zn-Al-based alloy-plated steel sheet that enables automation.

[0013]

In order to achieve the above object, the present inventor always measures the spangle particle size after plating at an on-line or off-line position and determines the result. Focusing on the fact that the spangle particle size can be brought close to the target particle size in a short time by feeding back to the condition changing system, the manufacturing conditions that contribute to the spangle particle size other than air cooling were studied.

By the way, hot-dip Zn-Al alloy-plated steel sheets are generally manufactured by a conventional continuous hot-dip galvanizing equipment as used for hot-dip galvanizing. In a typical continuous hot-dip coating equipment, a base material steel sheet (cold-rolled steel sheet or hot-rolled steel sheet) annealed in a continuous annealing furnace is immersed in a hot-dip plating bath via a snout without exposure to the atmosphere, and then exits the plating bath. Immediately afterward, control the desired amount of plating by gas wiping,
Temperature at which solidification is completed in the cooling zone (usually air cooling) (Zn-55%
After cooling to about 370 ° C. or less for Al alloy plating), if necessary, lightly roll it down with a leveler or skin pass roll and wind it up.

The present inventors have conducted intensive studies on means for controlling the spangle pattern of a hot-dip Zn—Al alloy plating film by using such conventional plating equipment as it is,
In particular, the composition of the plating film is as follows: Al: 0.05 to 70%, Si: 0 to 7.0
% And the balance of Zn, feedback control is performed if the spangle particle size is measured immediately after the plated steel sheet passes through the cooling zone by means of online image processing as shown in Japanese Patent Application No. 9-252515. However, the time lag is as small as possible and virtually negligible, and as a result,
It has been found that not only the cooling rate of the cooling zone, but also the cooling start point, that is, the distance between the cooling device and the plating bath surface, and the intruded material temperature can be used as control factors, and the spangle particle size between them. The cooling rate, the distance between the cooling device and the plating bath surface,
It has been found that the temperature decreases in the order of the intruding material temperature, and it has been found that by combining these controls, a plating film having a desired average spangle particle size can be formed, and the present invention has been completed.

[0016] In spite of the conventional spangle pattern, it is possible to check the spangle pattern before winding when winding the steel sheet after plating, and then change the cooling condition of the air cooling zone after plating. Is being done. However, in such a conventional method, there is a large time lag in adjusting the spangle pattern, and there is a risk of producing a large amount of spangle patterns that largely deviate from the target, and air cooling that can adjust the spangle pattern in a relatively short time. Since the use of only the band is limited, the adjustment width of the spangle pattern becomes very small. In fact, it cannot be said that the spangle pattern is controlled.

Here, the present invention relates to Al: 0.05 to 70 wt%,
i: Generated on the surface of the plating film when the steel sheet is continuously intruded into a hot-dip Zn-Al alloy-based plating bath having a composition consisting of 0 to 7.0 wt%, the balance being zinc and unavoidable impurity elements, and performing hot-dip plating. The difference between the spangle particle size and the target particle size is obtained, and when the difference is within a predetermined range, the production is continued as it is, and when the difference exceeds the predetermined range, the manufacturing conditions are changed to obtain the target spangle particle size. This is a spangle adjustment method to be reflected on the data.

The specific spangle adjusting means in the present invention may be performed as follows. (1) The spangle diameter of the obtained plated steel sheet is S ₁ m
m, and the target spangle particle size is Smm, if K ₁ ≧ | S−S ₁ |, the production conditions are the same. If K ₁ <| S−S ₁ |, the cooling device and bath after plating K ₁ ≧ | S−S ₁ | by changing at least one manufacturing condition of the surface distance and the temperature of the material entering the plating bath of the steel sheet.
So that

(2) Assuming that the resulting plated steel sheet has a spangle particle size of S ₁ mm and a target spangle particle size of S mm, in the case of K ₁ ≧ | S−S ₁ | ₁ + K ₂ <| S−S ₁ | (where 0 <K ₂ <
K ₁ ) In addition to the cooling rate after plating, the distance between the cooling device after plating and the bath surface is changed so that K ₁ ≧ | S−S ₁ |.

(3) Assuming that the obtained plated steel sheet has a spangle particle size of S ₁ mm and a target spangle particle size of S mm, in the case of K ₁ ≧ | S−S ₁ | ₁ + K ₃ <| S−S ₁ | (where 0 <K ₃ <
K ₁ ) In addition to the cooling rate after the plating, the temperature of the material entering the plating bath of the steel sheet is changed so that K ₁ ≧ | S−S ₁ |.

According to another aspect of the present invention, the spangle diameter is measured immediately after cooling, for example, immediately after passing through a cooling zone, the cooling rate after plating, the distance between the cooling device and the bath surface after plating, and The target spangle particle size may be obtained by adjusting the temperature of the material entering the plating bath of the steel sheet.

The specific spangle adjusting means in this embodiment may be performed as follows. (1) The spangle diameter of the obtained plated steel sheet is S ₁ m
m, if the target spangle particle size is Smm, if K ₁ ≧ | SS ₁ |, the manufacturing conditions are the same. If K ₁ <| SS ₁ |, the cooling rate after plating, plating At least one manufacturing condition such as the distance between the cooling device and the bath surface and the temperature of the material entering the steel sheet into the plating bath is changed so that K ₁ ≧ | S−S ₁ |.

(2) Assuming that the spangled grain size of the obtained plated steel sheet is S ₁ mm and the target spangled grain size is Smm, in the case of K ₁ ≧ | S−S ₁ | ₁ + K ₂ <| S−S ₁ | (where 0 <K ₂ <
K ₁ ) In addition to the cooling rate after plating, the distance between the cooling device after plating and the bath surface is changed so that K ₁ ≧ | S−S ₁ |.

(3) Assuming that a spangle particle size of the obtained plated steel sheet is S ₁ mm and a target spangle particle size is S mm, when K ₁ ≧ | S−S ₁ | ₁ + K ₃ <| S−S ₁ | (where 0 <K ₃ <
K ₁ ) In addition to the cooling rate after the plating, the temperature of the material entering the plating bath of the steel sheet is changed so that K ₁ ≧ | S−S ₁ |.

Here, assuming that the target spangle particle size is, for example, an average particle size of 0.8 mm, K ₁ is 0.3 mm and K ₂ is
0.2 mm, and K ₃ may be 0.15 mm.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. In the following description,% is wt% unless otherwise specified.

FIG. 1 is a schematic explanatory view of a plating line for implementing the spangle adjusting method according to the present invention. In FIG. 1, a steel sheet (strip) preheated in an annealing furnace 10 enters a plating bath, is pulled up around an immersion roll, and is sent to a cooling zone equipped with a cooling device, where a plating film is formed. It is cooled, forms a predetermined spangle pattern, and is sent to a subsequent winding step to be wound.

According to a preferred embodiment of the present invention, the spangle particle size is measured offline or online immediately after cooling, for example, immediately after leaving the cooling zone. The data at this time is sent to a computer and compared with data such as the target spangle particle diameter which has been input in advance, and based on the result, the capacity of the cooling device, that is, the cooling speed, the cooling start time, that is, the plating If necessary, one or more of the position of the cooling device from the bath surface and the intruding material temperature, that is, the heating temperature of the annealing furnace, are changed to change the manufacturing conditions so as to obtain the target spangle particle size.

(Plating Film and Bath Composition) According to the present invention, the plating bath composition is made of Al: 0.05 to 70% and Si: 0 to 7.0.
%. The balance of the plating bath is zinc and unavoidable impurities. The composition of the plating film is substantially the same as the composition of the plating bath.

Al: The Al content is 0.05 to 70%, preferably 0.1%.
10 to 0.20% or 40 to 60%. If the Al content is less than 0.05%, Zn in the Fe plating bath of the base steel sheet tends to alloy in hot-dip galvanizing, and the workability deteriorates. On the other hand, when the Al content exceeds 70%, the Al-rich phase increases, so that the sacrificial corrosion resistance of Zn decreases, and the corrosion resistance decreases again.

Si: Si has been conventionally used to suppress the development of a brittle Fe-Al alloy layer formed at the plating film-base metal interface.
-Al-based alloy plating bath has been added. As mentioned above, the hot-dip plating of Zn-55% Al alloy has 1.6%
It was common to include some Si. In the present invention,
For the following reasons, the Si content is suppressed to 0 to 7.0%, preferably 0 to 5.0%.

In hot-dip Zn plating, Si is not necessary because Al suppresses the development of the Fe—Zn alloy layer. Conversely, when Si is added, since the bath temperature is lower than in the case of Zn-55% Al alloy plating, it causes plating defects such as non-plating. On the other hand, in Zn-Al based alloy plating containing high Al,
It is appropriate to mix the Si concentration by 2.0 to 7.0% by weight with Al. In other words, in Zn-55% Al-based alloy plating
An appropriate amount of Si is 2 to 4%. If less than 2%
As described above, the brittle Fe-Al alloy layer abnormally develops and adversely affects workability. On the other hand, if it exceeds 4%, the alloy layer becomes extremely thin, and moreover, a large amount of Si needle-like precipitates precipitate in the plating film, thereby deteriorating workability. In the present invention, in the case of hot dip Zn plating, the content of Si is desirably inevitably mixed, and in the case of high Al-Zn alloy plating, the Al concentration is 2.0 to 3.
5% is desirable.

(Method for measuring spangle particle size) Al content is 40
The spangle that appears on the surface of the Zn—Al-based alloy plating film of about 70% is a region surrounded by Al-rich primary dendrite crystals (Al primary dendrite crystals) extending from the nucleus. Therefore, the diameter of this region is the spangle particle size. The secondary dendrite crystal extends from the primary dendrite crystal.

The measurement of the spangle particle size in the present invention is as follows.
Off-line measurement is performed by measuring the number of spangles over a certain distance (for example, 100 mm) using, for example, a magnified photograph (for example, 3 times magnification) or an enlarged image of a plated steel sheet. The average spangle particle size is calculated from the “number”.

When the measurement is performed on-line, the measurement may be performed, for example, by using an average image diameter of a spangle surrounded by the dendrite structure by an optical image processing device. The measurement position may be fixed at a certain width position in the plate width direction or scanned, and in the case of the steel plate length direction, it can be measured between the time the plating solidifies and the time it is wound It is. Desirably, the closer to the solidification position of the plating film, the faster the feedback to the change of the operating conditions is effective. Therefore, in the preferred embodiment of the present invention, the measurement is performed immediately after the plated steel sheet passes through the cooling zone.

The spangle particle size obtained during the operation is input to an operation system or the like, and the operating conditions are automatically changed based on the difference from the target spangle diameter to converge on the target spangle particle size. .

In the present invention, there are various production conditions to be adjusted on the basis of the difference from the target spangle particle size. Change the distance between the equipment and the plating bath surface and the penetration temperature of the steel plate.

In the present invention, the closer to the measurement point of the spangle particle size, the smaller the time lag in the feedback control. Therefore, the first control factor is the cooling rate of the cooling zone. Therefore, in the preferred embodiment of the present invention, the first control is to control the cooling rate of the cooling zone, and when the spangle particle size is still outside the allowable range, the distance between the cooling device of the cooling zone and the plating bath surface is changed. If the spangle particle size is still outside the allowable range, the temperature of the intruding plate material is changed. In other words, for example, when the target spangle particle size is 0.8 mm, if the difference from the actually measured value is a fluctuation of about ± 0.3 mm, it can be brought close to the target value by changing the cooling rate. The difference is ± 0.3mm + ± 0.2m
When the distance is about m, change the distance between the cooling device and the plating bath surface in addition to the cooling rate. Such a difference is ± 0.
When 3 mm + ± 0.2 mm + ± 0.15 mm is reached, the target spangle particle size is changed by changing the cooling rate, the distance between the cooling device and the plating bath surface, and the temperature of the plate that enters the plating bath. The diameter can always be realized.

Here, the reason for changing such manufacturing conditions in the present invention will be further described. (Cooling rate after plating) The spangle diameter is controlled by changing the cooling rate after plating.In the case of the present invention, the spangle diameter of the plated steel sheet immediately after leaving the cooling zone is measured. It is distinguished from the prior art in that: In the present invention, a generally used forced air cooling zone is used as it is. Therefore, in order to increase the cooling rate after plating, the amount of air in the forced cooling zone should be increased, and in order to decrease the cooling rate, the amount of air should be reduced. The cooling capacity of the forced cooling zone depends on the blowing capacity of the cooling equipment,
It depends on the distance, length, etc. from the steel sheet, and depends on the temperature, thickness, and speed of the passing steel sheet. During the operation, since the conditions such as the thickness of the steel sheet and the passing speed are apt to change, it is desirable to provide a facility capable of obtaining a cooling rate of about 30 ° C./s within the operable range. However, if the cooling rate after plating exceeds 25 ° C / s, it becomes difficult to reduce the diameter of the spangle (see Fig. 2 described later). It also causes bloat and cost increase. Therefore, the capacity of the forced cooling zone is desirably 25 ° C / s or less.

In such a cooling rate range, the spangle particle size capable of rapidly and effectively changing the spangle particle size is approximately ± 0.3 mm with respect to a target (for example, an average particle size: 0.8 mm). . Therefore, within ± 0.3 mm of the target spangle particle size, the spangle particle size control by adjusting the air volume in the forced cooling zone, which can quickly and effectively change the spangle particle size, becomes effective.

(Distance Between Forced Cooling Device and Bath Surface) The distance between the forced cooling device and the bath surface is a factor that changes the cooling start temperature after plating. The relationship between the control means and the spangle particle size control is first discovered and used in the present invention, and in that case, the measurement time of the spangle particle size is not limited.

When the cooling start temperature after plating is high, that is, when the distance between the cooling device and the bath surface is short, the plating on the surface of the base steel sheet has not yet been in the solidification stage. The spangle diameter is reduced due to increased nucleation and refinement of the crystal structure. on the other hand,
When the distance between the forced cooling device and the bath surface is long, the plating on the surface of the base steel sheet is in the solidification temperature range, so that some nucleation and crystal growth from it have occurred. When cooling is started, crystal growth occurs preferentially over nucleation, which promotes crystal growth and results in an increase in spangle particle size.

By adjusting the distance between the cooling device and the bath surface, in the present invention, the target (for example, the average particle size: 0.8 m
m), the spangle particle size can be changed by about ± 0.2mm.

When the cooling start temperature is kept constant, the distance between the forced cooling device and the bath surface is determined by the thickness of the base steel sheet, the plating bath temperature,
In order to change depending on the temperature of the material entering the plating bath of the base steel sheet, the passing speed, and the like, the standard appropriate distance under each condition is determined in advance.

(Plating Bath Penetration Material Temperature) The penetration material temperature of the steel sheet into the plating bath is rapidly and effectively forced cooling zone is not effective for spangle particle size, but effective operating conditions affecting spangle particle size. It is one of the factors. Also in this case, similarly to the case where the distance between the forced cooling device and the bath surface is controlled, the timing of measuring the spangle particle size is not limited.

It was found that, as the temperature of the material entering the steel sheet into the plating bath becomes higher with respect to the plating bath temperature, the spangle particle size decreases as the temperature decreases, and as the temperature becomes lower, the spangle particle size increases (see FIG. 3 described later). ). The reason for this is that the amount of reaction increases at the steel sheet-plating interface, and as a result, the alloy layer tends to grow partially unevenly, so that the projections of the alloy layer hinder crystal growth and increase nucleation. Combined with this, it is estimated that the spangle particle size decreases. In the case of the present invention, by adjusting the plating bath intruding material temperature, it is possible to change the spangle particle size of about ± 0.15 mm with respect to a target (for example, an average particle size: 0.8 mm).

[0047]

[Example 1] [Example 1] In this example, a strip was introduced and immersed in a molten 55% Al-Zn bath, and a cooling zone after plating was placed in a continuous hot-dip plating line installed at a passing position of a steel plate after plating. after the single-side coating weight was subjected to hot-dip plating of 75 mg / m ^2, the steel strip line speed 90m / min by the cooling zone the cooling rate of 15
Change at ~ 25 ° C / s, target spangle particle size S ₁ mm
(0.8 mm) was controlled and adjusted based on information on the spangle particle size measured immediately after the plated steel sheet exited the cooling zone. In this case, the spangle particle size obtained is K ₁ ≦ | S−S ₁ | (K ₁ =
0.3 mm).

The results are collectively shown in FIG. 2. As can be seen from the results, the target spangle particle size S ₁ mm can be obtained by controlling the cooling zone as compared with the case where the cooling zone is not controlled.

Example 2 In this example, a strip was introduced and immersed in a molten 55% Al-Zn bath, and a cooling zone after plating was placed at a passing position of a steel plate after plating. after the single-sided coating weight was subjected to hot-dip plating of 75 mg / m ^2, cooling the steel strip line speed 90m / min in a cooling zone rate 15
~ 25 ° C / s, the distance between the cooling device and the bath surface after plating was changed, and the spangle particle size measured immediately after the plated steel sheet exited the cooling zone to the target spangle particle size S ₁ mm (0.8 mm) The control was adjusted from the information of In this case, it is assumed that the obtained spangle diameter is K ₁ + K ₂ ≦ | S−S ₁ |. However, K ₁ = 0.3 mm and K ₂ = 0.2 mm.

The results are shown in FIG. 3. As can be seen from the figure, as compared with the case where the cooling zone is not controlled, the target spangle particle size K ₁ ≦ | S−S ₁ | mm can be obtained by controlling the cooling zone. It became. In this example, the same control was performed by measuring the spangle particle size during winding of the plated steel sheet, but in this case, the same result was obtained.

Example 3 In this example, a strip was introduced and immersed in a molten 55% Al-Zn bath, and a cooling zone after plating was placed at a passing position of a steel plate after plating. after the single-sided coating weight was subjected to hot-dip plating of 75 mg / m ^2, cooling the steel strip line speed 90m / min in a cooling zone rate 15
~ 25 ° C / s, changing the temperature of the material entering the plating bath of the steel sheet to the target spangle diameter S ₁ mm, and controlling and controlling it from the information of the spangle diameter measured immediately after the plated steel sheet exits the cooling zone. did. In this case, the obtained spangle particle size is K ₁
It is assumed that + K ₃ ≦ | S−S ₁ |. Where K ₁
= 0.3mm, and K ₃ = 0.15mm.

The results are shown in FIG. 4. As can be seen, it is possible to obtain the target spangle particle size K ₁ ≦ | S−S ₁ | mm when controlled, as compared with the case where the cooling zone is not controlled. It became. In this example, the same control was performed by measuring the spangle particle size during winding of the plated steel sheet, but in this case, the same result was obtained.

[0053]

According to the present invention, the conventional continuous hot-dip galvanizing equipment can be used without modification, without deteriorating the workability and corrosion resistance, and the spangles of the hot-dip Zn-Al-based alloy-plated steel sheet targeted at the time of production. It becomes possible to obtain a pattern.

This plated steel sheet has excellent corrosion resistance typified by a Zn-55% Al-based alloy-plated steel sheet, good workability to withstand severe bending, and has an appearance with high designability. Therefore, it can be used for building materials, home appliances, and other objects without being painted. Further, since the spangle pattern is uniform, it is most suitable for exterior panels such as building materials and home appliances without any painting.

[Brief description of the drawings]

FIG. 1 is a skeleton diagram of a continuous hot-dip plating line to which the present invention is applied.

FIG. 2 is a graph showing a spangle control effect according to an example together with a comparative example.

FIG. 3 is a graph showing a spangle control effect according to an example together with a comparative example.

FIG. 4 is a graph showing a spangle control effect according to an example together with a comparative example.

Claims (8)

[Claims] (1) Al: 0.05 to 70 wt%, Si: 0 to 7.0 wt%,
A method for producing a plated steel sheet by continuously intruding a steel sheet into a hot-dip Zn-Al-based plating bath having a composition consisting of a balance of zinc and unavoidable impurity elements, and performing hot-dip coating, thereby producing a coated steel sheet. The resulting spangle particle size and the step of obtaining a difference between the target particle size, and when the difference is within a predetermined range, continue manufacturing the plated steel sheet as it is, and when the difference exceeds the predetermined range, A spangle adjusting method for a hot-dip Zn-Al-based coated steel sheet, comprising a step of changing manufacturing conditions of a coated steel sheet so that a difference between a target particle diameter and a spangle particle diameter falls within the predetermined range. 2. Assuming that the obtained coated steel sheet has a spangle particle size of S ₁ mm and a target spangle particle size of S mm, in the case of K ₁ ≧ | S−S ₁ | _{In the case of 1} <| S−S ₁ |, K ₁ ≧ | S−S by changing at least one manufacturing condition of the distance between the cooling device and the bath surface after plating and the temperature of the material entering the plating bath of the steel sheet. ₁ ｜
The spangle adjusting method according to claim 1, wherein 3. A resulting spangle particle diameter S ₁ mm of plated steel and the spangle grain size of the target and _{Smm, K 1 ≧ | S-} S 1 | case, production conditions as is K ₁ + K ₂ <| S−S ₁ | (where 0 <K ₂ <
3. The spangle adjusting method according to claim 2, wherein, in addition to K ₁ ) and the cooling rate after plating, the distance between the cooling device after plating and the bath surface is changed so that K ₁ ≧ | S−S ₁ |. . 4. A resulting spangle particle diameter S ₁ mm of plated steel and the spangle grain size of the target and _{Smm, K 1 ≧ | S-} S 1 | case, production conditions as is K ₁ + K ₃ <| S−S ₁ | (where 0 <K ₃ <
3. The spangle adjusting method according to claim 2, wherein in addition to K ₁ ) and the cooling rate after the plating, the temperature of the material entering the plating bath of the steel sheet is changed so that K ₁ ≧ | S−S ₁ |. 5. Al: 0.05-70 wt%, Si: 0-7.0 wt%,
A method for producing a plated steel sheet by continuously intruding a steel sheet into a hot-dip Zn-Al-based plating bath having a composition consisting of a balance of zinc and unavoidable impurity elements, and performing hot-dip coating, thereby producing a coated steel sheet. Measuring the spangle particle diameter generated as soon as possible after cooling, determining the difference between the spangle particle diameter measured in this way and the target particle diameter, and the difference being within a predetermined range. When it is within, the production of the plated steel sheet is continued as it is, and when the difference exceeds the predetermined range, the production conditions of the plated steel sheet are adjusted so that the difference between the target particle size and the spangle particle size falls within the predetermined range. Melting, comprising the step of changing
Spangle adjustment method for Zn-Al-based plated steel sheet. 6. When the spangle particle size of the obtained plated steel sheet is S ₁ mm and the target spangle particle size is S mm, in the case of K ₁ ≧ | S−S ₁ | _{In the case of 1} <| S−S ₁ |, at least one manufacturing condition of the cooling rate after plating, the distance between the cooling device after plating and the bath surface, and the temperature of the material entering the steel sheet into the plating bath is changed to obtain a K value. 6. The spangle adjusting method according to claim 5, wherein ₁ ≧ | S−S ₁ |. 7. obtained spangle particle diameter S ₁ mm of plated steel and the spangle grain size of the target and _{Smm, K 1 ≧ | S-} S 1 | case, production conditions as is K ₁ + K ₂ <| S−S ₁ | (where 0 <K ₂ <
7. The spangle adjusting method according to claim 6, wherein in addition to K ₁ ) and the cooling rate after plating, the distance between the cooling device after plating and the bath surface is changed so that K ₁ ≧ | S−S ₁ |. . 8. obtained spangle particle diameter S ₁ mm of plated steel and the spangle grain size of the target and _{Smm, K 1 ≧ | S-} S 1 | case, production conditions as is K ₁ + K ₃ <| S−S ₁ | (where 0 <K ₃ <
7. The spangle adjusting method according to claim 6, wherein in addition to K ₁ ) and the cooling rate after the plating, the temperature of the material entering the plating bath of the steel sheet is changed so that K ₁ ≧ | S−S ₁ |.