JP4087800B2 - Method for producing molten Al-Zn plated steel sheet - Google Patents

Description

  The present invention relates to a method for producing a molten Al—Zn-based plated steel sheet having an Al content in a plating film of 20 to 95 mass%.

A hot-dip Al—Zn plated steel sheet (hereinafter referred to as “55% Al—Zn plated steel sheet”) containing 20 to 95 mass% Al in the plating film, represented by 55% Al—Zn plated steel sheet, will be described as an example. ) Shows excellent corrosion resistance as compared with hot dip galvanized steel sheet as shown in Japanese Examined Patent Publication No. 46-7161, and in recent years, demand is increasing mainly in the building material field.
This 55% Al-Zn-based plated steel sheet is a hot-rolled steel sheet that has been pickled and descaled or a cold-rolled steel sheet obtained by further cold rolling the base steel sheet. Manufactured.

  In the continuous hot dip plating facility, the base steel sheet was heated to a predetermined temperature in an annealing furnace maintained in a reducing atmosphere, and simultaneously with the annealing, the rolling oil adhered to the steel sheet surface was removed, and the oxide film was reduced and removed. Thereafter, the lower end passes through a snout immersed in the plating bath and is immersed in a hot dip galvanizing bath containing a predetermined concentration of Al. After the steel plate immersed in the plating bath is pulled up above the plating bath via the sink roll, a pressurized gas is sprayed from the gas wiping nozzle arranged on the plating bath toward the surface of the steel plate. The plating adhesion amount is adjusted, and then cooled by a cooling device to obtain a 55% Al—Zn-based plated steel sheet on which a predetermined plating film is formed.

Operating conditions such as annealing furnace heat treatment and atmosphere conditions, plating bath composition and cooling rate after plating in continuous hot dip plating equipment are accurately controlled within a prescribed control range to ensure the desired plating quality and material. The
The plating film of the 55% Al—Zn-plated steel sheet produced as described above mainly consists of a portion where Al containing Zn in supersaturation is dendrite solidified and a portion of the remaining dendrite gap. They are stacked in the film thickness direction. With such a characteristic film structure, the 55% Al—Zn-based plated steel sheet exhibits excellent corrosion resistance.

In addition, Si of about 1.5 mass% is usually added to the plating bath, but due to the action of this Si, 55% Al—Zn-based plated steel sheet suppresses alloy phase growth at the plating film / underlying steel sheet interface, The alloy phase thickness is about 1-2 μm. The thinner the alloy phase is, the more portions of the characteristic film structure exhibiting excellent corrosion resistance. Therefore, the suppression of the growth of the alloy phase contributes to the improvement of the corrosion resistance.
Usually, the plating bath contains unavoidable impurities, Fe eluted from the steel plate and equipment in the plating bath, Si for alloy phase suppression, but some elements may be added in addition to them, In the alloy phase and the plating film, these elements exist in the form of an alloy or a simple substance.

  As described above, the 55% Al—Zn-based plated steel sheet has excellent corrosion resistance, while the mechanical properties, in particular the elongation characteristics, are other plated steel plates, for example, a molten Al—Zn-based alloy containing about 5 mass% of Al in the plating film. There is a tendency to be inferior to a plated steel sheet (hereinafter referred to as “5% Al—Zn-based plated steel sheet”), which makes it difficult to use for strict processing. On the other hand, although 5% Al—Zn-based plated steel sheet has excellent elongation characteristics and is easy to process, it is inferior in corrosion resistance to 55% Al—Zn-based plated steel sheet. Replacement to a Zn-based plated steel sheet is being performed.

  As described above, the 55% Al—Zn-based plated steel sheet has a small elongation characteristic value, so that even when the same degree of processing is performed, the workability is inferior compared to the 5% Al—Zn-based plated steel sheet having the same plating film thickness. Tend. For this reason, when processing such as bending is performed, a crack may occur in the plated steel plate portion of the processed portion depending on the degree of processing, which may be a major problem in use.

  For such a problem, for example, Patent Document 1 discloses a method for improving ductility of a 55% Al—Zn-based plated steel sheet by subjecting it to a predetermined heat treatment. However, according to what the present inventors have confirmed through experiments and the like, when such heat treatment is performed on a plated steel sheet coil by batch processing, seizure (adhesion) is caused between the steel sheets in the coil during the heat treatment. As a result, it has been found that the beautiful surface appearance of the plated steel sheet as a product is significantly impaired.

Patent Document 2 discloses a method of preventing seizure between steel sheets by making the heating atmosphere slightly oxidizable when heating an alloyed hot-dip galvanized steel sheet to 400 to 480 ° C. by batch annealing. However, if batch heating of the 55% Al—Zn-based plated steel sheet is performed within the above temperature range, the occurrence of baking between the steel sheets is inevitable.
Japanese Patent Publication No. 61-28748 Japanese Patent Publication No.53-9176

  Therefore, an object of the present invention is a molten Al-Zn-based plated steel sheet represented by 55% Al-Zn-based plated steel sheet, wherein the Al content in the plating film is 20 to 95 mass%, and has excellent elongation characteristics. It is providing the manufacturing method of the fusion | melting Al-Zn type plated steel plate which can manufacture stably the plated steel plate which has a beautiful surface appearance.

In order to solve the above problems, the present inventors have improved the elongation characteristics of 55% Al—Zn-based plated steel sheet and have a beautiful plated surface appearance from the viewpoint of securing an excellent plated surface appearance as a practical product. We have intensively studied the optimum manufacturing method for obtaining the above. As a result, when a 55% Al—Zn-based plated steel sheet was produced on a continuous hot dipping line, a plating film having a plating surface roughness Ra of 0.20 μm or more was formed, and this plated steel sheet was then used as a continuous hot dipping line. The coil is continuously heated to a temperature of less than 300 ° C. immediately before the coiling device and wound at a coil winding tension of 3.0 kg / mm ² or less. By heating and holding at a temperature of less than 300 ° C., the elongation characteristics can be appropriately improved by the heat treatment, and the seizure between the plated steel sheets in the coil is appropriately prevented, and the surface appearance is excellent in elongation characteristics and beautiful. It was found that a 55% Al—Zn-based plated steel sheet having the following can be produced.

That is, the manufacturing method of the molten Al—Zn-based plated steel sheet of the present invention has the following characteristics.
[1] A method for producing a molten Al—Zn-based plated steel sheet having an Al content in a plating film of 20 to 95 mass%, wherein the molten Al—Zn-based plated steel sheet is solidified after the plated metal has solidified. In the method of improving the elongation characteristics by
A hot-dip Al-Zn-based plated steel sheet on which a plating film having a plating surface roughness Ra of 0.20 μm or more and 2.0 μm or less is formed at a temperature of 100 ° C. or more and less than 300 ° C. immediately before the winding device of the continuous hot dipping plating line. continuously heating, heat retaining coil winding tension 0.3 kg / mm ² or more 3.0 kg / mm ² or less, after winding of a steel plate heating temperature minus 10 to 20 ° C. (sheet temperature), by the potential heat of the coil A method for producing a molten Al—Zn-plated steel sheet, wherein self- heating is carried out at a starting plate temperature of 100 ° C. or higher and a steel plate heating temperature in the continuous heating of −50 ° C. or higher .

[2] A method for producing a molten Al-Zn-based plated steel sheet having an Al content of 20 to 95 mass% in the plating film, wherein the molten Al-Zn-based plated steel sheet after the plating metal has solidified is heat-treated. In the method of improving the elongation characteristics by
A hot-dip Al-Zn-based plated steel sheet on which a plating film having a plating surface roughness Ra of 0.20 μm or more and 2.0 μm or less is formed at a temperature of 100 ° C. or more and less than 300 ° C. immediately before the winding device of the continuous hot dipping plating line. continuously heating, coil winding tension 0.3 kg / mm ² or more 3.0 kg / mm ² or less, after winding of a steel plate heating temperature minus 10 to 20 ° C. (sheet temperature), the coil maximum temperature in a heating furnace to the coil Heating and holding under such conditions that the plate temperature of the part is 100 ° C. or higher and lower than 300 ° C., the plate temperature at the start of heating and holding is 100 ° C. or higher, and the steel plate heating temperature in the continuous heating is −50 ° C. or higher. The manufacturing method of the fusion | melting Al-Zn type plated steel plate characterized by these.

  According to the method of the present invention, it is a molten Al-Zn-based plated steel sheet represented by 55% Al-Zn-based plated steel sheet and having an Al content of 20 to 95 mass% in a plating film, and has excellent elongation characteristics. A plated steel sheet having a beautiful plated surface appearance can be stably produced.

The plated steel sheet to be manufactured by the present invention is a molten Al—Zn-based plated steel sheet containing 20 to 95 mass% of Al in the plated film, and a more preferable component composition of the plated film is Al: 45 to 65 mass. %, Si: 0.7 to 2.0 mass%, Fe: less than 10 mass%, the balance being substantial Zn containing inevitable impurities, and particularly excellent corrosion resistance is exhibited in such a composition.
Moreover, the amount of plating adhesion of the molten Al—Zn-based plated steel sheet is not particularly limited, but generally about 30 to 120 g / m ² per side is appropriate.

In the first method of the present invention, in a continuous hot dipping line, while forming a hot Al—Zn plating film having a plating surface roughness Ra of 0.20 μm or more on the steel plate surface, The coil is continuously heated to a temperature of less than 300 ° C. just before the winding device of the continuous hot dipping line, wound at a coil winding tension of 3.0 kg / mm ² or less, and then the coil is subjected to a heat treatment (self-maintaining) by its retained heat. heat.

Here, the plating surface roughness Ra of the molten Al—Zn-based plated steel sheet is 0.20 μm or more. When the plating surface roughness Ra is less than 0.20 μm, when the plated steel sheet is wound around a coil, the plated steel sheets are separated from each other. This is because the contact area becomes large, seizure occurs between the plated steel sheets during coil heat retention, and a plated surface appearance that can withstand use as a product cannot be obtained.
However, if the value of the plating surface roughness Ra is too large, the surface roughness of the plating surface increases and the appearance of the plating surface tends to deteriorate. Therefore, the plating surface roughness Ra is preferably 2.0 μm or less.

  Factors governing the plating surface roughness Ra include the penetration temperature of the steel sheet into the plating bath, the plating bath temperature, the plating bath composition, and the cooling rate after plating for plated steel sheets that form spangles. In the case of a plated steel sheet that makes the spangle pattern inconspicuous, conditions for temper rolling after plating, etc. can be mentioned. Therefore, by appropriately adjusting these, a plating film having a plating surface roughness Ra of 0.20 μm or more Can be obtained.

  In this method, in order to heat-treat the plated steel sheet, the plated steel sheet immediately before the winding device of the continuous hot dipping plating line (of course, the plated metal of the plated steel sheet is solidified) is less than 300 ° C, preferably 250 ° C. Continuously heated to the following temperatures, but the plated steel sheets that are continuously passed through in this way were heated because the heating temperature was low in the coil inside and outside, in the coil thickness direction, and in the plate width direction. While it tends to be uniform and the heating time becomes longer, the continuous heating of the plated steel sheet to be passed allows uniform heating in the plate longitudinal direction and width direction. This is because it can be narrowed. As a result, it is possible to obtain a product of uniform quality by reducing temperature variations in the coil. Further, the heating temperature raising time can be remarkably shortened as compared with batch heating, and the production efficiency can be improved by shortening the heat treatment time.

There is no particular restriction on the heating method of continuous heating of the plated steel sheet to be passed, and an appropriate heating method such as a gas heating method, an electric heater method, an induction heating method, a steam heating method can be adopted, but among these, The induction heating method is suitable for performing uniform heating in the steel plate width direction.
The heating temperature of the plated steel sheet immediately before the winding device of this continuous hot dipping line is less than 300 ° C., when the heating temperature is 300 ° C. or more, the viscosity of the plating surface decreases, and after winding on the coil, This is because seizure occurs between the plated steel sheets during heat retention, and a plated surface appearance that can withstand use as a product cannot be obtained. From such a viewpoint, the heating temperature is more preferably 250 ° C. or lower.
Moreover, about the minimum of heating temperature, it is appropriate to set it as 100 degreeC, Preferably it is 150 degreeC. If the heating temperature is less than 100 ° C., the effect of improving the elongation characteristics by heating cannot be sufficiently obtained.

In addition, when winding a plated steel sheet around a coil in a continuous hot dipping line, the coil winding tension is set to 3.0 kg / mm ² or less when the winding tension exceeds 3.0 kg / mm ² in the coil. This is because the contact force between the plated steel sheets increases, seizure occurs between the plated steel sheets during coil heat retention, and a plated surface appearance that can withstand use as a product cannot be obtained. However, when the coil winding tension is too low, the force for holding the coil is weakened, and the coil is likely to be deformed or crushed. For this reason, the coil winding tension is preferably 0.3 kg / mm ² or more.

The coil of the plated steel sheet taken out from the continuous hot dipping line is immediately heat-treated by the retained heat. The coil may be self-heated in the atmosphere without being stored in a heat-retaining container, but if it is stored in a heat-retaining container with a lid and heat-retained, heat retention time can be ensured and efficient self-heating. Heat insulation can be performed.
In general, a plated steel sheet that is continuously heated immediately before the winding device is heated immediately after winding is completed at a steel sheet heating temperature of minus 10 to 20 ° C. (sheet temperature). It is preferable that the temperature is at least 150 ° C., preferably at least 150 ° C., and [steel plate heating temperature−50] ° C. or more. If the heat retention start temperature is less than [steel plate heating temperature−50] ° C., a sufficient effect of improving elongation characteristics cannot be obtained.

This coercive heat treatment is preferably performed for 5 minutes or longer. If the heat retention time is less than 5 minutes, the effect of improving the elongation characteristics due to heat retention cannot be sufficiently obtained. In addition, since the coil heated to a temperature of less than 300 ° C. normally reaches room temperature in about 24 hours after the start of heat retention, the heat retention may be performed for about 24 hours.
FIG. 1 and FIG. 2 show typical temperature rising / holding / cooling temperature patterns of the heat treatment performed by this method. Of these, FIG. 1 shows each temperature pattern when the coil is kept in the atmosphere without being housed in the heat retaining container, and FIG. 2 shows each temperature pattern when the coil is housed in the heat retaining container with a lid and kept warm. .

FIG. 4 schematically shows the state of implementation of the first method of the present invention, and A is a continuous hot dipping line (a line configuration from the annealing furnace to the delivery side winding device). In this continuous hot dip plating line A, the steel plate exiting the annealing furnace 1 is led into the hot dip plating pot 2 and hot dip plated, and then the amount of plating is adjusted by the gas wiping nozzle 3 and subsequently cooled in a cooling zone (not shown). As a result, the plated metal is completely solidified. This plated steel sheet is subjected to temper rolling and the like, if necessary, continuously guided to the heating device 4 and continuously heated to a temperature of less than 300 ° C., and then immediately coiled by the winding device 5 with a coil winding tension of 3.0 kg / It is wound up on the coil x at mm ² or less. Then, the coil x is taken out of the line, put into the heat insulating container 6 as necessary, and immediately subjected to heat retention by the retained heat.

In the second method of the present invention, the coil is heated and held in a heating furnace, while the first method described above retains the coil by its own retained heat.
That is, in the second method of the present invention, in a continuous hot dipping line, a hot Al—Zn plating film having a plating surface roughness Ra of 0.20 μm or more is formed on the steel plate surface, and this hot Al—Zn plating is performed. The steel sheet is continuously heated to a temperature of less than 300 ° C. just before the winding device of the continuous hot dipping line, and wound at a coil winding tension of 3.0 kg / mm ² or less. The plate temperature is kept under heating so as to be less than 300 ° C.
Here, the reason why the plating surface roughness Ra of the molten Al—Zn-based plated steel sheet is 0.20 μm or more and the preferable upper limit of the plating surface roughness Ra are the same as in the first method described above.

  In this method, in order to heat-treat the plated steel sheet, the plated steel sheet immediately before the winding device of the continuous hot dipping plating line (of course, the plated metal of the plated steel sheet is solidified) is less than 300 ° C, preferably 250 ° C. Continuously heated to the following temperatures, but the plated steel sheets that are continuously passed through in this way were heated because the heating temperature was low in the coil inside and outside, in the coil thickness direction, and in the plate width direction. While it tends to be uniform and the heating time becomes longer, the continuous heating of the plated steel sheet to be passed allows uniform heating in the plate longitudinal direction and width direction. This is because it can be narrowed. As a result, it is possible to obtain a product of uniform quality by reducing temperature variations in the coil. Further, the heating temperature raising time can be remarkably shortened as compared with batch heating, and the production efficiency can be improved by shortening the heat treatment time.

There is no particular restriction on the heating method of continuous heating of the plated steel sheet to be passed, and an appropriate heating method such as a gas heating method, an electric heater method, an induction heating method, a steam heating method can be adopted, but among these, The induction heating method is suitable for performing uniform heating in the steel plate width direction.
The heating temperature of the plated steel sheet immediately before the winding device of this continuous hot dipping line is less than 300 ° C., when the heating temperature is 300 ° C. or more, the viscosity of the plating surface decreases, and after winding on the coil, This is because seizure occurs between the plated steel sheets during heat retention, and a plated surface appearance that can withstand use as a product cannot be obtained. From such a viewpoint, the heating temperature is more preferably 250 ° C. or lower.
Moreover, about the minimum of heating temperature, it is appropriate to set it as 100 degreeC, Preferably it is 150 degreeC. If the heating temperature is less than 100 ° C., the effect of improving the elongation characteristics by heating cannot be sufficiently obtained.

In addition, when winding a plated steel sheet around a coil in a continuous hot dipping line, the coil winding tension is set to 3.0 kg / mm ² or less when the winding tension exceeds 3.0 kg / mm ² in the coil. This is because the contact force between the plated steel sheets increases, seizure occurs between the plated steel sheets during coil heat retention, and a plated surface appearance that can withstand use as a product cannot be obtained. However, when the coil winding tension is too low, the force for holding the coil is weakened, and the coil is likely to be deformed or crushed. For this reason, the coil winding tension is preferably 0.3 kg / mm ² or more.

  After the coil of the plated steel sheet is taken out from the continuous hot dipping line, it is immediately heated and maintained in a heating furnace under the condition that the plate temperature of the coil maximum temperature portion is less than 300 ° C. In the method of keeping the coil by its own retained heat as in the first method of the present invention described above, the temperature is likely to decrease at the inner and outer periphery of the coil and the coil edge, and there is a risk that the heating of the portion will be insufficient. However, according to this method, the heat treatment can be performed without causing the temperature in the coil to be non-uniform.

The heating furnace to be used may be simple, and the heating method is not particularly limited. Therefore, an appropriate heating method such as a gas heating method, an electric heater method, an induction heating method, or a steam heating method can be employed. The heating furnace may be a closed type or an open type.
The plated steel sheet that has been continuously heated immediately before the winding device is generally charged in a heating furnace immediately after completion of winding at a steel sheet heating temperature of minus 10 to 20 ° C. (sheet temperature). The plate temperature at the start of holding is 100 ° C. or higher, preferably 150 ° C. or higher, and [steel plate heating temperature−50] ° C. or higher. If the heat retention start temperature is less than [steel plate heating temperature−50] ° C., a sufficient effect of improving elongation characteristics cannot be obtained.

In the heating and holding in the heating furnace, if the plate temperature of the coil maximum temperature portion is within the range of less than 300 ° C., the coil may be heated or may be held at the heating and holding start temperature. Further, in some cases, the heating and holding may cause a gentle temperature drop.
The heating and holding temperature in the heating furnace is set to a temperature lower than 300 ° C. at the coil maximum temperature portion. When the plate temperature at the coil maximum temperature portion is 300 ° C. or more, the viscosity of the plating surface is lowered, and the heating is held. This is because seizure occurs between the plated steel sheets, and a plated surface appearance that can withstand use as a product cannot be obtained. From such a viewpoint, the plate temperature of the coil maximum temperature portion is more preferably 250 ° C. or less.

This heating and holding is preferably performed for 5 minutes or more and within 24 hours. If the heating and holding time is less than 5 minutes, a sufficient effect of improving the elongation characteristics cannot be obtained. On the other hand, if it exceeds 24 hours, seizure between the plated steel sheets tends to occur, and the productivity also decreases.
FIG. 3 shows a typical temperature rise / hold / cooling temperature pattern of the heat treatment performed by this method.

FIG. 5 schematically shows the implementation status of the second method of the present invention. In this method, in the continuous hot dipping line A, after the steel plate exiting the annealing furnace 1 is led into the hot dipping pot 2 and hot dipped, the amount of plating is adjusted by the gas wiping nozzle 3, and the cooling not shown is continued. The plated metal is completely solidified by being cooled in the strip. The plated steel sheet is subjected to temper rolling and the like as necessary, and is subsequently guided to the heating device 4 and continuously heated to a temperature of less than 300 ° C., and immediately thereafter, the coil winding tension is 3.0 kg / mm by the winding device 5. ^It is wound around the coil x at ² or less. The coil x is taken out of the line and inserted into the heating furnace 9, and is heated and held under such a condition that the plate temperature of the coil maximum temperature portion is less than 300 ° C.

In the plated steel sheet produced by the method of the present invention, spangles may be formed on the plating surface, or the spangle pattern may be made inconspicuous. In general, a plated steel sheet having spangles on the plating surface is suitable for a bare use because of its appearance, and a plated steel sheet having a spangle pattern on the plating surface made inconspicuous is suitable for a coating base application.
In order to make the spangle pattern on the plating surface inconspicuous, temper rolling or the like may be performed after plating according to a conventional method.

[Example 1]
A cold-rolled steel sheet (thickness 0.5 mm) manufactured by a conventional method is passed through a continuous hot-dip plating facility, hot-dip plated using a 55 mass% Al-1.5 mass% Si-Zn plating bath, and molten Al- A Zn-based plated steel sheet was produced. In a continuous hot dip plating facility, a plated steel sheet with solidified plating metal was continuously heated by a heating device (induction heating method) immediately before the winding device, and then wound on a coil. Next, this coil was heat-treated in the atmosphere for a predetermined time to obtain a product of a molten Al—Zn-based plated steel sheet.
The line speed of the hot dipping line was 160 m / sec, and the amount of single-sided plating was such that the variation between the plated steel sheets was within the range of 75 to 90 g / m ² .

About the obtained product, the presence or absence of baking, the appearance of the plating surface, and the elongation characteristics were evaluated based on the following methods. The results are shown in Table 1 and Table 2 together with the hot-dip plating conditions, the heat retention conditions, and the structure of the plating film.
In addition, in each Example (invention example and comparative example) shown in Table 1, a plated steel sheet in which the spangle pattern on the plating surface is made inconspicuous by performing temper rolling before the heat treatment is also shown in Table 2. In each example (invention example and comparative example), a plated steel sheet having spangles on the plating surface was produced.
(1) Presence or absence of seizure The presence or absence of seizure was evaluated according to the presence or absence of sound generated when the plated steel sheets peeled off during coil rewinding after heat treatment.
None: No buzzing sound is generated when the coil is rewound.
Generation: A buzzing sound is generated when the coil is rewound.

(2) Plating surface appearance The surface appearance of the plated steel sheet after the heat treatment was visually observed and evaluated as follows.
Good: The plated surface is the same as before the heat treatment and has a beautiful plated surface appearance.
Poor: Plating peeling or welding due to baking between plated steel sheets occurs in a portion of 1% or more of the total coil area, resulting in a poor plated surface appearance.

(3) Elongation characteristics Using the No. 5 test piece defined in JIS Z 2201 (1998) metal material tensile test piece, the test was conducted by JIS Z 2241 (1998) metal material tensile test method, and the total elongation at break evaluated. As a specific evaluation method, evaluation was performed by an increase amount (%) of the total elongation at break relative to the total elongation at the time of plating fracture of the steel plate before the heat treatment.

[Example 2]
A cold-rolled steel sheet (thickness 0.5 mm) manufactured by a conventional method is passed through a continuous hot-dip plating facility, hot-dip plated using a 55 mass% Al-1.5 mass% Si-Zn plating bath, and molten Al- A Zn-based plated steel sheet was produced. In a continuous hot dip plating facility, a plated steel sheet with solidified plating metal was continuously heated by a heating device (induction heating method) immediately before the winding device, and then wound on a coil. Next, this coil was heated and held for a predetermined time in a simple heating furnace (electric heater system) to obtain a product of a molten Al—Zn-based plated steel sheet.
The line speed of the hot dipping line was 160 m / sec, and the amount of single-sided plating was such that the variation between the plated steel sheets was within the range of 75 to 90 g / m ² .

About the obtained product, the presence or absence of baking, surface appearance, and elongation characteristics were evaluated based on the same method as in [Example 1]. The results are shown in Tables 3 and 4 together with the hot dipping conditions, tight coil heat treatment conditions, and the configuration of the plating film.
In addition, in each Example (invention example and comparative example) shown in Table 3, a plated steel sheet in which spangles on the plating surface are made inconspicuous by performing temper rolling before heat treatment is shown in Table 4. In each example (invention example and comparative example), a plated steel sheet having spangles on the plating surface was produced.

Explanatory drawing which shows the typical temperature rising / holding / cooling temperature pattern of the heat treatment performed by the first method of the present invention. Explanatory drawing which shows the typical temperature rising / holding / cooling temperature pattern of the heat treatment performed by the first method of the present invention. Explanatory drawing which shows the typical temperature rising / holding / cooling temperature pattern of the heat treatment performed by the second method of the present invention. Explanatory drawing which shows typically the implementation condition of the 1st method of this invention Explanatory drawing which shows typically the implementation condition of the 2nd method of this invention

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Annealing furnace, 2 ... Hot-dipping pot, 3 ... Gas wiping nozzle, 4 ... Heating device, 5 ... Winding device, 6 ... Thermal insulation container, 9 ... Heating furnace, A ... Continuous hot-dipping line, B ... Continuous treatment Facility,

Claims (2)

It is a manufacturing method of the fusion | melting Al-Zn type plated steel plate whose Al content in a plating film is 20-95 mass%, Comprising: Elongation characteristics by heat-processing the molten Al-Zn type plated steel plate after a metal plating solidifies In the method of improving
A hot-dip Al-Zn-based plated steel sheet on which a plating film having a plating surface roughness Ra of 0.20 μm or more and 2.0 μm or less is formed at a temperature of 100 ° C. or more and less than 300 ° C. immediately before the winding device of the continuous hot dipping plating line. continuously heating, heat retaining coil winding tension 0.3 kg / mm ² or more 3.0 kg / mm ² or less, after winding of a steel plate heating temperature minus 10 to 20 ° C. (sheet temperature), by the potential heat of the coil A method for producing a molten Al—Zn-plated steel sheet, wherein self- heating is carried out at a starting plate temperature of 100 ° C. or higher and a steel plate heating temperature in the continuous heating of −50 ° C. or higher . It is a manufacturing method of the fusion | melting Al-Zn type plated steel plate whose Al content in a plating film is 20-95 mass%, Comprising: Elongation characteristics by heat-processing the molten Al-Zn type plated steel plate after a metal plating solidifies In the method of improving
A hot-dip Al-Zn-based plated steel sheet on which a plating film having a plating surface roughness Ra of 0.20 μm or more and 2.0 μm or less is formed at a temperature of 100 ° C. or more and less than 300 ° C. immediately before the winding device of the continuous hot dipping plating line. continuously heating, coil winding tension 0.3 kg / mm ² or more 3.0 kg / mm ² or less, after winding of a steel plate heating temperature minus 10 to 20 ° C. (sheet temperature), the coil maximum temperature in a heating furnace to the coil Heating and holding under such conditions that the plate temperature of the part is 100 ° C. or higher and lower than 300 ° C., the plate temperature at the start of heating and holding is 100 ° C. or higher, and the steel plate heating temperature in the continuous heating is −50 ° C. or higher. The manufacturing method of the fusion | melting Al-Zn type plated steel plate characterized by these.

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