JP3287351B2 - Hot-dip Zn-Al-based alloy plated steel sheet excellent in workability and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to molten Zn-Al having excellent workability, which is suitable as a material for automobiles, home appliances, building materials and the like.
The present invention relates to a system alloy-plated steel sheet and a method for producing the same. More specifically, a molten Zn-A having a plating film excellent in crack resistance, adhesion and design, and also excellent in economic efficiency.
The present invention relates to an l-based alloy-plated steel sheet and a method for producing the same.

[0002]

2. Description of the Related Art Zn-based plated steel sheets are widely used as materials for automobiles, home appliances, building materials, and the like because they have good corrosion resistance, are inexpensive, and are economical. Among them, molten Zn-Al
Alloy-plated steel sheets have better corrosion resistance and excellent heat resistance, so in addition to building materials such as roofs and wall materials, civil engineering products such as guardrails, wiring piping and soundproof walls, etc., heat shield plates for automobiles, electric washing machines , And is rapidly spreading to home appliances such as microwave ovens.

Further, when the Al content is 3.5% by mass%,
A molten Zn—Al alloy that is 6.5% (hereinafter, chemical composition% means mass%) has a solidification point of a eutectic point of Zn and Al (382 ° C.), and thus is higher than that of pure Zn. It has a low melting point and can be hot-dipped at relatively low temperatures. Generally, at the time of hot-dip Zn plating, there is a problem that an alloy layer develops at the interface between the plating film and the base material, the adhesion of the plating film is reduced, and the workability of the plated steel sheet is impaired. It is known that alloy plating has a low plating temperature, so that the development of an alloy layer is small, and therefore, the workability of a plated steel sheet is superior to other hot-dip products.

As described above, steel sheets used for various applications are required to have not only corrosion resistance but also excellent workability and design. It is known that a plating film in which a Zn-Al alloy contains several percent of Mg is effective for improving corrosion resistance (for example, “Materials and Processes”, Vol. 12 (1999), P554). This Zn-Al alloy containing Mg (hereinafter also referred to as Zn-Al-based alloy) enables stable hot-dip plating, and has been put to practical use to utilize the effect of improving corrosion resistance.

Conventionally, a hot-dip coated steel sheet has been characterized by a large spangle of the plating film and rich in metallic luster. However, recently, depending on the application, it has a low metallic luster and has a so-called matte appearance, which is free from glare. steel sheet,
That is, there is a need for a steel sheet having a good design.

In order to reduce the metallic luster of a hot-dip galvanized steel sheet and to provide a steel sheet with a high designability, water or a chemical solution is applied to the hot-dip galvanized steel sheet when the coating layer is in a molten state through a wiping process for adjusting the amount of adhesion after hot-dip coating. There is known a method of performing a so-called steam-water cooling treatment of spraying a plating layer to reduce spangles. The steam-cooled coated steel sheet continues to be
It is a general manufacturing method to cool to a room temperature region by a process such as air cooling or water cooling.

[0007] By the steam-water cooling treatment, the hot-dip coating layer is rapidly cooled to a temperature below the solidification temperature, and a large number of solidification nuclei are generated and rapidly solidified, thereby reducing spangles. Spangles have also been efficiently reduced by mixing a chemical that promotes supercooling in air water.

For example, Japanese Patent Application Laid-Open No. 10-88310 discloses that an element steel plate is immersed in a plating bath, drawn out, gas-wiped, and subsequently, at a plate temperature equal to or higher than the solidification start temperature of the plating layer and an air pressure of 1.0 kgf / cm ^2. A method for producing a hot-dip galvanized steel sheet in which glaze is suppressed by applying the following air-water spray cooling to achieve a glossiness of the plating surface of 100 or less is disclosed.

Japanese Patent Application Laid-Open No. 10-265931 discloses that after plating in a Zn-Al-based alloy plating bath containing 3.1 to 5.5% by mass of Al, water or water is added when the plating layer is in a molten state. The surface roughness of the plating layer was adjusted to 1.5 μm or more by Ra by spraying a chemical solution, and the static friction coefficient μ was 0.2
A plated steel sheet having excellent slip resistance of 3 or more and a method for producing the same are disclosed.

[0010]

If a plated film is damaged when a plated steel sheet is processed into a structural member or the like (for example, cracks are generated in the plated film), the appearance of the product is impaired, and the corrosion resistance of the portion is also impaired. . Therefore, the plating film of the plated steel sheet used for processing applications needs to have excellent workability that does not cause film damage such as peeling or cracking of the plating film.

Even in the case of Zn-Al hot-dip plating containing Mg, the surface appearance of the minimum spangle specification with good design can be easily obtained by applying the steam-water cooling treatment known for hot-dip Zn plating. . However, the resulting plated steel sheet has a problem in that the workability of the plating film is significantly reduced as compared with the usual plated steel sheet having a large spangle obtained when the air-water cooling and quenching treatment is not performed.

[0012] In a hot-dip Zn-Al alloy-plated steel sheet containing no Mg, large cracks that adversely affect the corrosion resistance do not occur in the plating film even when bending is performed. However, the plating film contains Mg,
And molten Zn- produced by steam-water cooling after hot-dip plating
In the case of Al-based alloy-plated steel sheets, many large cracks occur in the plating film in the parts subjected to severe processing, corrosion progresses from those parts, and although the flat part has excellent corrosion resistance, its commercial value as a structural component The problem arises that the image is damaged early.

The object of the present invention is to solve these problems,
An object of the present invention is to provide a hot-dip Al-Zn-based alloy plated steel sheet having excellent corrosion resistance and design properties, having a plating film that can withstand severe processing, and having excellent workability that can be economically manufactured, and a method for manufacturing the same. .

[0014]

Means for Solving the Problems The inventors of the present invention have made Al produced by hot-water cooling after hot-dip plating 3.5 to 15 mm.
As a result of various studies on the relationship between the workability of the plating film of the hot-dip Zn-Al-based alloy-plated steel sheet containing 0.1% and the hot-dip plating conditions, the following new findings were found.

In a Zn-Al alloy-plated steel sheet containing no Mg, cracks due to bending were suppressed even when steam-water cooling treatment was performed after hot-dip plating. However, in a Zn-Al-based alloy-plated steel sheet containing Mg, when steam-water cooling treatment was performed after hot-dip plating, a large number of cracks were observed in the plating film in the bent portion when the bending process was performed. As a result of microscopic observation of the cross section of the plating film at the bent portion, the crack was found to be a eutectic part in which a Zn phase and an Al-enriched phase crystallized in a lamellar shape from the molten metal, or the eutectic part and the primary βZn phase It was recognized that the occurrence occurred at the boundary of.

[0016] The Zn-
The workability of the Al-based alloy plating film is such that a short-time heat treatment (hereinafter simply referred to as “post-heat treatment”) is performed by holding the plating film subjected to steam cooling in a temperature range of 130 ° C. or higher and lower than the melting point of the plating film for about 1 minute. ) Can be greatly improved.

The reason is not clear, but is presumed as follows. In general, when the molten Zn plating layer is cooled, the Zn parallel to the plating surface is increased as the cooling rate increases.
It is also known that the X-ray peak intensity of the (00 · 2) plane increases (for example, Zinc-Based Steel).
coating Systems, The Mine
rals, Metals Society, 1998,
p261. ), It is known that the Zn (00 · 2) plane is preferentially oriented parallel to the plating surface in the crystal structure of Zn. This phenomenon is obtained even if the chemical composition of the plating film contains a large amount of Al, by promoting steam nucleation by subjecting the hot-dip coated surface to steam-water cooling treatment or Hearty treatment of spraying Zn powder. The same applies to a plated film.

The ductility of the Zn phase is improved by reducing the orientation of the Zn (00 · 2) plane. this is,
It is presumed that when the orientation of the Zn (00 · 2) plane is reduced, twin sliding deformation easily occurs in the plating film during processing.

The orientation of the Zn (00 · 2) plane is determined by applying a short-time heat treatment to the plating film cooled by steam and water for about 1 minute in a temperature range of 130 ° C. or more and lower than the melting point of the plating film (that is, Heat treatment) can be easily randomized. This is because Al and Mg are supersaturated in the plating film solidified by rapid cooling from the molten state, and large internal stress is generated inside the coating. By applying
It was speculated that the promotion of diffusion of solid solution atoms and the release of internal stress were promoted, and the recrystallization of the plating film was easily generated by using these as driving sources. Further, it is considered that the improvement of the workability of the plating film also contributes to the effect of eliminating the supersaturated solid solution state by the post-heat treatment and the effect of improving the ductility by releasing the residual stress.

The present invention has been completed on the basis of these new findings, and the gist of the present invention is to provide a Zn-Al-based alloy-coated steel sheet excellent in workability described in (1) below and (2), ( The method is described in 3).

(1) At least one surface of the base steel sheet is molten Z
A steel sheet provided with an n-Al-based alloy plating film, wherein the plating film has a chemical composition in mass% of Al: 3.5 to 15
%, Mg: 0.5 to 3.5%, balance being Zn and unavoidable impurities, Fe content as unavoidable impurities of 0.5 g / m ² or less, content of Pb, Sn, Cd and Bi Is 200 ppm or less in total, the average diameter of the spangle is 2 mm or less, and Zn (0
A hot-dip Zn-Al-based alloy-plated steel sheet excellent in workability, characterized in that the orientation index of the (0.2) plane is 3.5 or less.

(2) The base material steel plate is Al: 3.5% by mass.
-15%, Mg: 0.5-3.5%, the balance being Zn
And Pb, Sn, Cd and Bi as inevitable impurities have a total content of 200
After immersing in a hot-dip plating bath with a concentration of less than 1 ppm and lifting it up, gas wiping is performed, and water or a mixture of water and a chemical solution is sprayed onto the plating layer in a molten state to cool and solidify the plating layer, followed by plating. Below the solidification temperature of the layer,
(1) The method for producing a hot-dip Zn-Al-based alloy-plated steel sheet having excellent workability according to the above (1), wherein the steel sheet is kept at a temperature of 130 ° C. or more for 10 seconds or more and then cooled to room temperature.

(3) The base material steel plate is Al: 3.5% by mass.
-15%, Mg: 0.5-3.5%, the balance being Zn
And Pb, Sn, Cd and Bi as inevitable impurities have a total content of 200
After immersion in a hot-dip plating bath having a concentration of not more than 1 ppm and pulling up, gas wiping is performed, and water or a mixture of water and a chemical solution is sprayed onto the molten plating layer to cool and solidify the plating layer. ℃ below, then 1
The molten Zn— excellent in processability according to the above (1), characterized in that it is heated to a temperature range of 30 ° C. or higher and lower than the melting temperature of the plating layer, kept at the temperature range for 10 seconds or more, and then cooled to room temperature. A method for producing an Al-based alloy plated steel sheet.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in detail. Chemical composition of plating film: The plating film defined by the present invention contains 3.5% or more and 15% or less of Al and 0.5% of Mg.
% Or more and 3.5% or less, with the balance having a chemical composition consisting of Zn and unavoidable impurities.

Although Al has an effect of improving the corrosion resistance of the plating film, it is necessary to contain 3.5% or more in order to obtain the effect. Therefore, the Al content is set to 3.5% or more. Preferably it is 4.0% or more. Al content is 15
%, The melting point of the plating bath rises, a Zn-Al alloy layer develops at the interface with the base material, and impairs the workability and adhesion of the plating film. In order to avoid this, the Al content is 15
% Or less. Preferably it is 13% or less. Since Al is an expensive element, if importance is placed on economics,
The content is preferably set to 5.5% or less.

Mg has the effect of improving the corrosion resistance of the Zn—Al alloy plating film.
% Or more. Therefore, the Mg content is set to 0.5% or more. It is preferably at least 1.0%.
If the Mg content exceeds 3.5%, the corrosion resistance saturates, and adding more than this only impairs economic efficiency, so the Mg content is set to 3.5% or less. The content of Mg is 3.0% to suppress the generation of oxides on the bath surface to obtain a beautiful plating film.
It is desirable to do the following.

The balance is Zn and unavoidable impurities,
The smaller the inevitable impurities, the better. Among them, the Fe content in the plating film is set to 0.5 g / m ² or less. Fe in the plating film increases with the growth of the alloy layer formed at the steel sheet / plating interface. When this alloy layer develops and the Fe content exceeds 0.5 g / m ² , the workability of the plating film is impaired, which is not preferable. Preferably 0.2 g / m ²
It is as follows. Most of the Fe in the plating film is eluted from the steel sheet, and it is preferable that the temperature of the plating bath, the temperature of the base material entering the plating tank, and the like do not become excessively high. F
In order to make the e content 0.5 g / m ² or less, it is preferable to limit the plating bath temperature to 460 ° C. or less and the base material infiltration temperature to the plating bath to 490 ° C. or less, for example.

Pb, Sn, Bi as unavoidable impurities
When quenching treatment such as air-water cooling is performed, Cd segregates at grain boundaries and causes intergranular corrosion. In order to prevent this, the contents of Pb, Sn, Bi and Cd are desirably 200 ppm or less in total. More preferably, it is 100 ppm or less. Usually, these impurities are mixed in from a raw material when preparing a plating bath. Therefore, it is preferable to remove these impurities at a raw material stage.

The size of the spangle of the plating film: When the size of the spangle exceeds 2 mm in average diameter, the difference in luster between the adjacent steel plates is conspicuous, and the color tone greatly differs depending on the production chance depending on the angle at which the plating film is viewed. Impairs design. In order to prevent this, the size of the spangle is limited to 2 mm or less in average diameter. Further, it is preferable that the thickness be 1.5 mm or less in an application part where importance is placed on design.

Orientation of Zn (00 · 2) plane: plating film
Is calculated by the following formula.
Orientation index (hereinafter, “I_aTo 3.5 or less
You. I _aIs calculated based on the (hk · l) crystal plane of the plating film.
X-ray diffraction intensity was measured using a Co tube at an accelerating voltage of 30 kv and a current of
Measured under the condition of 100 mA, and from the result,
Use the calculated value.

[0031]

(Equation 1)

Here, I _(XX · _X) : integrated intensity of (XX · X) plane in X-ray diffraction, _{IF (XX} · _X) : integrated intensity ratio of (XX · X) plane in X-ray diffraction, I _{FR (XX}・_X) : A
It represents the intensity ratio in the X-ray diffraction of the (XX.X) plane described in the STM card.

When the orientation index of the Zn (00 · 2) plane exceeds 3.5, the deformability of the Zn phase dispersed in the plating film is poor, the crack in the bent portion becomes large, and the corrosion resistance in a corrosive environment. Is significantly reduced. Therefore, the orientation index is set to 3.5 or less. Preferably it is 2.5 or less.

The method for producing the steel sheet of the present invention: In the steel sheet of the present invention, the base steel sheet is prepared by adding Al of 3.5% or more and 15% or less,
g of not less than 0.5% and not more than 3.5%, the balance being composed of Zn and unavoidable impurities, and having a total content of Pb, Sn, Cd and Bi as unavoidable impurities of 200 p.
immersed in a hot-dip plating bath that is not more than pm and then lifted up, gas-wiped, and dipped in a hot-dip plating bath that sprays water or a chemical solution onto the plating layer in a molten state to perform hot-dip plating. While in the molten state, water or a chemical is sprayed onto the surface of the plating layer to cool and solidify the plating layer. Subsequently, the solidification temperature of the plating layer is kept below 130 ° C. for 10 seconds or more, and then cooled to room temperature. Or by cooling and solidifying the plating layer.
It is preferable to cool to below 130 ° C., then heat to a temperature range of 130 ° C. or higher and lower than the melting temperature of the plating layer, hold in this temperature range for 10 seconds or more, and then cool to room temperature.

As the base material, either a hot rolled plate or a cold rolled plate may be used. When using a cold rolled sheet as the base material,
It is economical and preferable to use one that has not been annealed,
Annealed ones may be used.

The content of Al, Mg and the like in the plating film is almost equal to the concentration of each element in the plating bath. Therefore, the chemical composition of the plating bath is as follows: Al: 3.5 to 15%, Mg:
0.5 to 3.5%, with the balance being Zn and unavoidable impurities, the total content of Pb, Sn, Cd and Bi as unavoidable impurities is 200 ppm or less.

The hot-dip plating is preferably performed on both sides of the base material, but may be performed on only one side. After adjusting the coating weight by a known method such as a gas wiping method, so that the size of the spangle of the plating film is 2 mm or less in average diameter,
While the plating layer is in a molten state, a spangle adjusting process of spraying water or a chemical on the surface of the plating layer is performed. This method may be a known method, and in a temperature range in which the plating layer is in a molten state, the plating layer is solidified by spraying an aqueous solution containing water and a sublimable agent such as ammonium phosphate.

Thereafter, at a temperature below the solidification temperature of the plating layer, 130 ° C.
A post-heat treatment is performed for 10 seconds or more in the above region. Thereafter, by heat treatment, the supersaturated state of Al or Mg is eliminated by promoting diffusion between Zn-Al or Zn-Mg, and Zn (00) is passed through recrystallization promoted by the presence of internal stress.
(2) The orientation index of the plane can be 3.5 or less.

If the post heat treatment temperature is less than 130 ° C. or the holding time in the above temperature range is less than 10 seconds, recrystallization is not sufficient, and the orientation index of Zn (00 · 2) plane is 3. 5 or less, and the workability of the plating film is not improved. 15 to increase the controllability of orientation
It is desirable that the temperature be 0 ° C. or more or the holding time be 20 seconds or more.

If the post heat treatment temperature exceeds the solidification temperature of the plating layer, the spangles will again sublimate, and the design may deteriorate. Therefore, the upper limit of the post heat treatment temperature is the solidification temperature of the plating layer. Although the solidification temperature is affected by the Mg content, it is generally around 380 ° C.

The upper limit of the holding time in the post-heat treatment temperature range is not particularly limited, but the effect as the post-heat treatment is saturated even if the holding time is longer than 5 minutes even in a low temperature range, and the economical efficiency is increased. Therefore, the holding time is preferably 5 minutes or less at most. When the holding temperature is in a high temperature range, the holding time on the short side is preferably set within the above range.

The timing of the post-heat treatment may be such that the same effect can be obtained by cooling once to 130 ° C. or less after the air-water cooling treatment and then re-heating the above-mentioned temperature range. In addition, the said holding time means the time which a steel plate stays in the said temperature range.

The holding method in the post heat treatment temperature range may be performed by preventing cooling of the steel sheet,
Known heating means such as gas combustion heating and electric heating may be used in combination. In addition, the same heating method as described above may be used in the case of once cooling to 130 ° C. or lower, reheating, and performing post-heat treatment.

The manufacturing method other than the above is arbitrary and may be a known method. A preferred example is as follows. In order to make the surface suitable for hot-dip plating, the base steel sheet is subjected to a pretreatment of washing with an alkaline aqueous solution or the like or grinding the surface with a nylon brush or the like. Next, after heating in a reducing atmosphere to a temperature of at least 600 ° C. or a temperature of at least the recrystallization temperature and holding it for a required time, it is cooled to near the plating bath temperature. The reducing atmosphere may be a commonly used atmosphere, for example, an atmosphere in which hydrogen is 5 to 30% by volume, the balance is nitrogen, and the dew point is −60 ° C. or more and −10 ° C. or less.

Thereafter, it is immersed in a plating bath having the above-mentioned chemical composition to adjust the amount of plating to a desired amount. The temperature of the plating bath is 30 to 60 times lower than the melting point of the alloy of the plating film composition.
It is preferable to increase the temperature by ℃. If the temperature is higher than 60 ° C., the development of the alloy layer when immersed in the plating bath becomes remarkable, which is not preferable. The adhesion amount of the plating film is optional, but in order to secure appropriate operation efficiency, 40 to 150 per side is required.
A range of g / m ² is preferred. A gas wiping method (gas squeezing method) is preferable for adjusting the plating adhesion amount, but other methods may be used.

After adjusting the amount of plating, the spangle is preferably adjusted by air-water cooling treatment. However, the spangle is adjusted by another method, for example, the so-called Hearty method of spraying a metal powder serving as a solidification nucleus of a hot-dip layer. Is also good.

After the post heat treatment, the molten Z
The steel sheet may be an n-Al alloy plated steel sheet, but may be subjected to post-treatments such as rust preventive oil, lubricating rust preventive oil, chromate, resin coating, and chromate / resin coating.

[0048]

EXAMPLES (Example 1) C: 0.04%, Mn: 0.2
A test piece having a width of 100 mm and a length of 200 mm was sampled from an unannealed low-carbon steel cold-rolled sheet having a thickness of 0.7 mm containing 5%, and the test piece was degreased with a 10% aqueous NaOH solution at 75 ° C. The substrate was washed and subjected to recrystallization annealing using a hot-dip galvanizing simulator apparatus, heating to 800 ° C. in an atmosphere having a dew point of −40 ° C. with hydrogen: 20% by volume and the balance being nitrogen, and holding for 60 seconds. Al: 3-18 as hot-dip plating bath
%, Mg: 0 to 15%, and a Zn-Al-based hot-dip bath adjusted to a melting point of + 40 ° C is prepared, and the recrystallized and annealed base material is cooled to a temperature close to the hot-dip bath temperature. The base material was immersed, pulled up and subjected to gas wiping, and hot-dip plating was performed on both surfaces of the base material so that the amount of adhesion per one surface was 100 g / m ² . Then, air-water cooling was performed to adjust the spangle particle size. As a comparative example, one in which spangles were adjusted by spraying only compressed air (Test No. 33) and one in which spangles were not adjusted (Test No. 34) were also produced.

These test pieces were then cooled at a cooling rate of 20 ° C./sec to various post-heat treatment temperatures, kept for various times, and then water-cooled to room temperature. A test piece having a post-treatment temperature of 200 ° C. or 130 ° C. and a comparative example of 120 ° C. was also prepared.

As another example, after the steam-water cooling treatment, the cooling was performed between 300 and 200 ° C. for 30 seconds, followed by water cooling to room temperature (Test No. 21). After cooling to a normal temperature once at a cooling rate of 50 ° C./sec, it was charged into an atmosphere furnace heated to 200 ° C.
A sample which was kept for 0 second and then cooled with water to room temperature (Test No. 22) was also prepared.

The chemical composition of the plating film of the obtained steel sheet was analyzed, and the spangle diameter, the orientation index of the Zn (00 · 2) plane,
Performance such as workability was evaluated by the following method. Spangle diameter: 20 places were randomly selected from the plating film surface, and the average value of the major axis and minor axis of the spangle at that location was determined.
The average value of the pieces was taken as the average diameter.

The orientation index of the Zn (11.2) plane: The X-ray diffraction intensity of the plating film was measured using a Co tube at an accelerating voltage of 30 kv.
The measurement was performed under the conditions of a current of 100 mA, and the orientation index (I _a ) was calculated from the results according to the above equations (1) and (2).

Bending workability: width: 70 mm, length: 150
A bending test piece with the length direction of mm as the rolling direction was sampled,
Bending (1t bending, t is a plate thickness) with an inner radius of 0.35 mm was performed, the appearance of the bent portion was observed with a microscope, and the occurrence of cracks in the plating film was evaluated according to the following five grades. A: No crack is observed. ：: Small cracks are partially observed. Δ: Small cracks are observed on the entire surface. X: Large and small cracks are mixed and observed on the entire surface. XX: Large cracks are observed on the entire surface.

Corrosion resistance: width: 70 mm, length: 150 m
The end face of the test piece of m was sealed with a tape, subjected to a 2t bending process, subjected to a cyclic corrosion test, and the number of days until red rust was generated in the flat plate portion and the bent portion was obtained. One cycle of the corrosion test cycle is salt spray (35 ° C. × 6 hours) → drying (60 ° C. × 12 hours) → wet (50 ° C. × 6 hours). The corrosion resistance was evaluated as good when red rust did not occur for the flat part for 50 days or more and for the bent part for 30 days or more.

Removability with time: width: 25 mm, length: 100
After performing a corrosion test in which a test piece having a length of 80 mm is stored for 240 hours in a high-temperature and high-humidity state at a temperature of 80 ° C. and a relative humidity of 95%, a 2t bending process is performed, and an adhesive tape is applied to the bent portion and peeled off. The state of peeling of the plating film by the adhesive tape was visually observed, and the results were evaluated according to the following criteria. A: No peeling was observed at all. ：: Slight peeling is observed at the edge portion △: Peeling is observed linearly in the width direction of the bent portion ×: Peeling is observed over the entire bent portion Design property: 20-degree specular glossiness described in JIS-Z8741 It was evaluated by the measurement method. Suga U as a measuring device
Using GV-4D, the case where the obtained result was in the range of 20 to 40 was judged to be good. ：: 21 to 40 Δ: 41 to 60 ×: 61 to Table 1 shows the chemical composition of the plating film and the performance evaluation results of the obtained steel sheet.

[0056]

[Table 1]

As can be seen from Table 1, Test Nos. 1 to 22 satisfying the conditions specified by the present invention all exhibited excellent bending workability, corrosion resistance, peelability with time and design.
On the other hand, in Test Nos. 23 to 28 in which the chemical composition of the plating film did not satisfy the conditions specified by the present invention, any of the steel sheet performances was inferior. In Test No. 29, Mg was excessive, the cost was high, and the economy was not good. In Test No. 30 in which the post-heat treatment temperature was too low and in Test No. 31 in which the post-heat treatment time was too short, the desired Zn (00 · 2) plane orientation was not obtained, and the bending workability was not good. Test No. 32, in which post heat treatment was performed at 400 ° C., was Zn (00
2) The orientation of the surface was large, and the spangles sublimated again, resulting in poor design. Test No. 33 in which only high-pressure air was blown after gas wiping and Test No. 34 in which no air-water cooling treatment was performed were not good in design because spangles were too large.

[0058]

The hot-dip Zn—Al-based alloy-coated steel sheet of the present invention has excellent corrosion resistance in the flat portion, good workability of the plating film, and no damage to the plating film in the processed portion. Is also excellent. Therefore, if the steel sheet of the present invention is used, the life of structural members such as automobiles, home appliances, and building materials can be prolonged, and thus the steel sheet of the present invention is an extremely useful steel sheet. Further, the steel sheet of the present invention is stable and easily manufactured without using special equipment, and thus is an economical steel sheet.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-182260 (JP, A) JP-A-58-177446 (JP, A) JP-A-6-158257 (JP, A) (58) Field (Int. Cl. ⁷ , DB name) C23C 2/00-2/40

Claims (3)

(57) [Claims] 1. At least one surface of a base steel sheet is made of molten Zn-
A steel sheet provided with an Al-based alloy plating film, wherein the plating film has a chemical composition in mass% of Al: 3.5 to 15%,
Mg: 0.5 to 3.5%, balance being Zn and unavoidable impurities, Fe content as unavoidable impurities of 0.5 g / m ² or less, and total content of Pb, Sn, Cd and Bi And the average diameter of spangles is 2 mm or less, and Zn (00
-2) A hot-dip Zn-Al-based alloy-plated steel sheet having excellent workability, wherein the plane has an orientation index of 3.5 or less. 2. The base steel sheet is prepared by adding Al: 3.5 to 1 by mass%.
5%, Mg: 0.5-3.5%, the balance being Zn and unavoidable impurities, and P as unavoidable impurities.
The content of b, Sn, Cd and Bi is 200 pp in total
m and dipped in a hot-dip plating bath, and then gas-wiped, sprayed with water or a mixture of water and a chemical solution onto the plating layer in a molten state to cool and solidify the plating layer. 2. The molten Zn-Al-based alloy excellent in processability according to claim 1, wherein the alloy is cooled to a region having a solidification temperature of 130 ° C. or lower, a temperature of 130 ° C. or higher, and a temperature of at least 10 seconds. Manufacturing method of plated steel sheet. 3. The base steel sheet is made of Al: 3.5 to 1 by mass%.
5%, Mg: 0.5-3.5%, the balance being Zn and unavoidable impurities, and P as unavoidable impurities.
The content of b, Sn, Cd and Bi is 200 pp in total
immersed in a hot-dip plating bath of not more than 100 m and lifted up, followed by gas wiping, spraying water or a mixture of water and a chemical solution onto the molten plating layer to cool and solidify the plating layer. ℃ below, then 130
The molten Z having excellent workability according to claim 1, wherein the molten Z is heated to a temperature range of not less than 0 ° C and less than a melting temperature of the plating layer, kept at the temperature range for 10 seconds or more, and then cooled to room temperature.
A method for producing an n-Al alloy plated steel sheet.