JP2002275645A - Surface treated steel sheet having excellent workability and corrosion resistance in worked part and production method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain excellent workability, corrosion resistance in the worked part and roll formability in a surface treated steel sheet using a hot dip Al-Zn based plated steel sheet in which the content of Al in a plating film is 20 to 95 mass% as a base steel sheet. SOLUTION: The face of the plating film is provided with a chemical conversion coating film obtained by performing chromate treatment under specified conditions, and containing a prescribed amount of Cr and a thermosetting resin. The plating film is preferably obtained through heat histeresis at least in the following (a) and (b). (a) Heat histeresis in which the average cooling rate for 10 sec directly after the discharge of the steel sheet from a hot dip plating bath is <11 deg.C/sec. (b) Heat histeresis in which, after the solidification of plating metals applied for hot dip plating, heating is performed so that the temperature is increased to T( deg.C) in the range from 130 to 300 deg.C, and after that, the average cooling rate in the range from the temperature T( deg.C) to 100 deg.C satisfies C( deg.C/hr) shown in the following formula (1) or lower, or/and heat histeresis in which the average cooling rate from the temperature T( deg.C) in the range from 130 to 300 deg.C after the solidification of the plating metals applied for hot dip plating to 100 deg.C satisfies C( deg.C/hr) shown in the following formula (1) or lower: C=(T-100)/2...(1).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for producing A
The present invention relates to a surface-treated steel sheet using a hot-dip Al-Zn-based plated steel sheet having an l content of 20 to 95 mass% as a base steel sheet and a method for producing the same.

[0002]

2. Description of the Related Art Al in a plating film is 20 to 95 mass%.
The hot-dip Al-Zn plated steel sheet contained is
As shown in No. 7161, since it exhibits superior corrosion resistance as compared with hot-dip galvanized steel sheet, in recent years, demand has been increasing mainly in the field of building materials. The plated steel sheet is produced as follows in a continuous hot-dip plating facility using a hot-rolled steel sheet subjected to pickling descaling or a cold-rolled steel sheet obtained by further cold-rolling the hot-rolled steel sheet as a base steel sheet.

In a continuous hot-dip plating apparatus, a base steel sheet is heated to a predetermined temperature in an annealing furnace maintained in a reducing atmosphere to remove rolling oil and the like adhering to the steel sheet surface simultaneously with annealing.
After the oxide film is reduced and removed, the lower end is immersed in a hot-dip galvanizing bath containing a predetermined concentration of Al through a snout immersed in the plating bath. After the steel sheet immersed in the plating bath is lifted above the plating bath via the sink roll, by injecting pressurized gas toward the surface of the steel plate from the gas wiping nozzle arranged on the plating bath The coating weight was adjusted, and then cooled by a cooling device to form a molten Al-
A Zn-based plated steel sheet is obtained.

The operating conditions such as the heat treatment conditions and atmosphere conditions of the annealing furnace in the continuous hot-dip plating equipment, the plating bath composition, and the cooling rate after plating are controlled within predetermined control ranges in order to ensure desired plating quality and material. Well managed. The plating film of the plated steel sheet manufactured as described above is mainly composed of a portion where Al containing Zn in supersaturation is dendrite solidified and a portion of the remaining dendrite gap, and the dendrite is in the thickness direction of the plating film. Laminated. With such a characteristic film structure, molten Al-
Zn-based plated steel sheets exhibit excellent corrosion resistance.

[0005] In addition, usually about 1.5 mass% of Si is added to the plating bath, and the action of the Si suppresses the growth of the alloy phase at the interface between the plating film and the base steel sheet in the molten Al-Zn-based plated steel sheet. And the alloy phase thickness is about 1 to 2 μm. The thinner the alloy phase, the greater the number of characteristic film structures exhibiting excellent corrosion resistance. Therefore, suppressing the growth of the alloy phase contributes to the improvement of the corrosion resistance. Further, since the alloy phase is harder than the plating film and acts as a starting point of cracks during processing, suppressing the growth of the alloy phase reduces the occurrence of cracks and has an effect of improving workability. In addition, since the cracked portion is inferior in corrosion resistance because the base steel sheet is exposed, reducing the occurrence of cracks also improves the corrosion resistance of the processed portion.

[0006] Usually, the plating bath contains unavoidable impurities, Fe eluted from a steel plate or equipment in the plating bath, and Si for suppressing an alloy phase. These elements are present in the alloy phase or plating film in the form of an alloy or a simple substance. In addition, hot-dip Al-Zn-based coated steel sheets are rarely used as they are when they are put to practical use, and are usually used as surface-treated steel sheets that have been subjected to chemical conversion treatment or painting on the surface of the coated steel sheets. You.

[0007]

SUMMARY OF THE INVENTION Molten Al as described above
-There is a problem that the plating film of a Zn-based plated steel sheet is liable to be "galling" when it is slid by contact with a mold during roll forming, and the appearance quality is likely to be deteriorated. This is because, from the viewpoint of rationalization, when performing molding without oiling or processing without coolant, the temperature rise of the mold due to continuous processing acts as a more severe condition for processing. It is considered to be. In order to enhance roll forming properties, Japanese Patent Publication No. Hei 4-2672 proposes a method of coating a plating surface with a film containing an organic resin. However, according to this method, although the roll forming property is improved to some extent, the effect of the improvement is that a good appearance quality without "galling" can be obtained even under severe processing conditions in which the temperature of the mold is increased by the processing. Not that.

[0008] Further, when the above-described hot-dip Al-Zn-based plated steel sheet is subjected to processing such as bending, cracks occur in the plated film of the processed portion depending on the degree of processing. In this plated steel sheet, about 1
Since the alloy phase with a thickness of ~ 2 µm becomes the starting point of cracks and the dendrite gap of the plating film becomes the propagation path of cracks, even when the same processing is performed, compared with the hot-dip galvanized steel sheet with the same plating film thickness Cracks tend to open relatively large. For this reason, there is a problem that the crack is visually recognized depending on the degree of processing and the appearance is impaired. Furthermore, as described above, the hot-dip Al-Zn coated steel sheet exhibits superior corrosion resistance as compared with a hot-dip galvanized steel sheet having the same plating film thickness, but the exposed cracked portion of the base steel sheet is compared with a crack-free portion. Therefore, there is also a problem that the corrosion resistance is significantly reduced.

In response to such a problem, for example,
JP-A-28748 discloses a method of improving the ductility of a plated steel sheet by subjecting a hot-dip Al-Zn-based plated steel sheet to a predetermined heat treatment. However, it is difficult to sufficiently improve the ductility of the plating film only by such a conventional heat treatment. Further, as described above, the molten Al-Z
The n-type plated steel sheet is usually used as a chemical conversion treated steel sheet whose surface has been subjected to a chemical conversion treatment or as a painted steel sheet. From the viewpoint of suppressing cracking in a processed portion by simply bending or the like, even if the ductility of the plating film is improved to some extent as in the above-described conventional technology, the performance as a product to be practically used, that is, It does not immediately improve the workability as a coated surface-treated steel sheet or the corrosion resistance of the processed part.

[0010] Accordingly, an object of the present invention is to use a hot-dip Al-Zn plated steel sheet having an Al content of 20 to 95 mass% in a plating film as a base steel sheet, and to provide unprecedented excellent workability, corrosion resistance in a processed portion, and roll forming property. And to provide a method for producing the same.

[0011]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have determined the viewpoint of the performance as a practical product, that is, a surface-treated steel sheet obtained by subjecting a hot-dip Al-Zn-based plated steel sheet to a chemical conversion treatment. In order to improve the properties such as corrosion resistance, corrosion resistance of the processed part, roll forming property, etc., the intensive study was carried out on the optimal composition of the plating film and the chemical conversion treatment film. As a result, by forming a specific chemical conversion treatment film on the plating film surface of the hot-dip Al-Zn-based plated steel sheet, more preferably by making the plating film have passed a specific heat history, it was not possible to achieve conventionally. It has been found that extremely excellent workability, corrosion resistance in a processed portion, and roll forming property can be obtained.

The present invention has been made based on such findings, and the features thereof are as follows. [1] A surface-treated steel sheet having a chemical conversion coating film on the surface of a hot-dip Al-Zn-based coated steel sheet having an Al content of 20 to 95 mass% in the plating film, wherein the chemical conversion coating film is made of chromic acid or chromate After applying a chromate treatment liquid containing at least one compound selected from a compound and a chromic acid compound obtained by partially reducing chromic acid and a thermosetting organic resin,
A film obtained by drying at a temperature of from about 300 ° C. to a mass ratio (A) / (B) of the amount of organic resin (A) contained in the film and the amount of Cr (B) in terms of metallic chromium Is 1 or more and 200
A surface-treated steel sheet having excellent workability and corrosion resistance in a processed portion, comprising a film having a Cr content of less than 0.1 mg / m ^{2 and} less than 100 mg / m ^{2 in} terms of chromium metal.

[2] The Al content in the plating film is 20 to 9
A surface-treated steel sheet having a chemical conversion coating on the surface of a 5 mass% hot-dip Al-Zn-based plated steel sheet, wherein the chemical conversion coating is a chromate coating formed on a plating coating surface and a coating formed thereon. Then, after applying a chromate treatment solution containing at least one selected from chromic acid, a chromate compound, and a chromic acid compound obtained by partially reducing chromic acid, and a thermosetting organic resin, The mass ratio (A) / (B) of the amount (A) of the organic resin contained in the film obtained by drying at a temperature of 300 ° C. and the amount of Cr (B) in terms of metallic chromium is 1 or more and less than 200 , excellent surface-treated steel sheet in workability and the processing unit corrosion, characterized in that the Cr content of the metal chromium conversion is composed of a 0.1 mg / ^{m 2} or more 100 mg / ^{m 2} less than a is film.

[3] The surface-treated steel sheet according to [1] or [2], wherein the plating film is a plating film obtained through at least the following thermal histories (a) and (b). Surface treated steel sheet with excellent workability and corrosion resistance. (a) Heat history in which the average cooling rate for 10 seconds immediately after the steel sheet leaves the hot-dip bath is less than 11 ° C./sec. (b) After the hot-dip plated metal solidifies,
The temperature is raised to a temperature T (° C.) in the range of −300 ° C., and thereafter, the average cooling rate from the temperature T (° C.) to 100 ° C. satisfies C (° C./hr) or less represented by the following formula (1). Heat history,
And / or from a temperature T (° C.) in the range of 130 to 300 ° C. after solidification of the hot-dip plated metal to 100 ° C.
The average cooling rate up to C (° C / hr) shown in the following equation (1)
Heat history that satisfies the following: C = (T-100) / 2 (1)

[4] In the surface-treated steel sheet according to any one of [1] to [3], the temperature T (° C.) of the heat history of (b) is 130 to 2
A surface-treated steel sheet having excellent workability and corrosion resistance in a processed portion, which is characterized by being in the range of 00 ° C. [5] A coated steel sheet comprising a surface-treated steel sheet according to any one of the above [1] to [5], wherein a single-layer or multiple-layer coating film is formed on the surface.

[6] The Al content in the plating film is 20 to 9
A method for producing a surface-treated steel sheet having a chemical conversion coating film on the surface of a 5 mass% hot-dip Al-Zn-based coated steel sheet, wherein at least the following (a) and (b) And (a) heat history in which the average cooling rate for 10 seconds immediately after the steel sheet leaves the hot-dip bath is less than 11 ° C./sec. (B) hot-dip plated metal solidifies After that, 130
The temperature is raised to a temperature T (° C.) in the range of −300 ° C., and thereafter, the average cooling rate from the temperature T (° C.) to 100 ° C. satisfies C (° C./hr) or less represented by the following formula (1). Heat history,
And / or from a temperature T (° C.) in the range of 130 to 300 ° C. after solidification of the hot-dip plated metal to 100 ° C.
The average cooling rate up to C (° C / hr) shown in the following equation (1)
Thermal history that satisfies the following: C = (T-100) / 2 (1) The surface of the plated steel sheet is selected from chromate, a chromate compound, and a chromate compound in which a part of the chromate is reduced. A film obtained by applying a chromate treatment liquid containing at least one kind of thermosetting organic resin and drying at a plate temperature of 130 to 300 ° C., wherein the amount of organic resin contained in the film (A ) and the amount of Cr reckoned as metal chromium weight ratio of (B) (a) / ( B) is less than 200 1 or more, Cr content of the metal chromium conversion is less than 0.1 mg / ^{m 2} or more 100 mg / ^{m 2} Chemical A method for producing a surface-treated steel sheet having excellent workability and corrosion resistance in a processed portion, comprising a step of forming a treated film.

[7] The Al content in the plating film is 20 to 9
5 mass% hot-dip Al-Zn coated steel sheet
A method for producing a surface-treated steel sheet having a
At least the plating film of the steel sheet that has left the plating bath
(A) a step of imparting the heat history of (a) and (b), and
(B) After the hot-dip plating metal solidifies, the heat history is less than 11 ° C / sec.
And heated to a temperature T (° C.) in the range of
After that, the average cooling rate from temperature T (° C) to 100 ° C decreases
Thermal history satisfying C (° C./hr) or less shown in the expression (1);
And / or after the hot-dip plated metal solidifies
A temperature T (° C.) in the range of 130 to 300 ° C. to 100 ° C.
The average cooling rate up to C (° C / hr) shown in the following equation (1)
Thermal history satisfying the following: C = (T-100) / 2 (1) A chromate film is formed on the surface of the plated steel sheet.
Chromic acid, chromic acid
Salt compounds, chromic acid compounds that have partially reduced chromic acid
Containing at least one selected from the group consisting of a thermosetting organic resin and
After applying the romate treatment liquid, the plate temperature is 130 to 300 ° C.
A film obtained by drying at a temperature, which is contained in the film.
Of organic resin (A) and Cr in terms of chromium metal
(B) mass ratio (A) / (B) of 1 to less than 200, gold
0.1mg / m Cr content of genus chromium ²More than 100m
g / m²Of a chemical conversion coating to form a coating that is less than
Processability and process part resistance characterized by having a forming step
A method for producing surface-treated steel sheets with excellent corrosion properties.

[8] In the method of the above-mentioned [6] or [7],
(b) A method for producing a surface-treated steel sheet having excellent workability and corrosion resistance in a processed portion, wherein the temperature T (° C.) of the heat history is in the range of 130 to 200 ° C. [9] In the manufacturing method according to any one of [6] to [8], the heat history of (b) is applied to the plating film in at least one of the following steps (1) to (4). A method for producing a surface-treated steel sheet having excellent workability and corrosion resistance in a processed portion. (1) Before the formation of the chemical conversion coating (2) During the chemical conversion coating drying process (3) After the formation of the chemical conversion coating (4) Cooling process after the hot-dip plated metal solidified [10] The above [6] ] To [9], further comprising a step of applying one or more coats to the surface of the chemical conversion coating film, in addition to the steps of any one of the manufacturing methods of [9].

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The surface treated steel sheet of the present invention has a molten Al-Z containing 20 to 95 mass% of Al in a plating film.
The n-based plated steel sheet is used as a base steel sheet. Further, from the viewpoint of corrosion resistance and the like, a more preferable range than the amount of Al in the plating film is 45 to 45.
It is 65 mass%. Further, particularly preferred component compositions of the plating film are: Al: 45 to 65 mass%, Si: 0.7 to
2.0 mass%, Fe: less than 10 mass%, and the balance being substantially Zn containing unavoidable impurities. In such a composition, particularly excellent corrosion resistance is exhibited. However, this molten Al
-Zn-based plated steel sheet, it is difficult to obtain high corrosion resistance in the processed part only by its plating composition, by combining with the upper chemical conversion treatment film, more preferably by combining the application of heat history to the plating film described later For the first time, excellent corrosion resistance in the processed part can be obtained. In addition, the molten Al-Zn
Although there is no particular limitation on the coating weight of the system-coated steel sheet, it is generally appropriate to set it to about 30 to 120 g / m ² per one surface.

In the surface-treated steel sheet of the present invention, the chemical conversion film formed on the plating film surface is at least one selected from the group consisting of chromic acid, a chromate compound, and a chromic acid compound obtained by partially reducing chromic acid. And a thermosetting organic resin, followed by drying at a plate temperature of 130 to 300 ° C., the amount of the organic resin contained in the film (A) The mass ratio (A) / (B) of the Cr amount (B) in terms of metallic chromium is 1 or more and less than 200, preferably 50 or more and 150 or less, and the Cr amount in terms of metallic chromium is 0.1 mg / m ² or more and 100 mg / m. It is necessary that the chemical conversion coating be less than ² , preferably 5 mg / m ² or more and 40 mg / m ² or less.

If the Cr content in terms of metallic chromium in the chemical conversion treatment film is less than 0.1 mg / m ² , the corrosion resistance of the processed part is not sufficiently improved, while if the Cr content is 100 mg / m ² or more, the effect of improving the corrosion resistance of the processed part is reduced. Not only saturates, but also lowers the Cr fixation rate due to an increase in the amount of Cr, thereby impairing environmental harmony.

In the present invention, an organic resin is incorporated into the chemical conversion coating for the purpose of improving the corrosion resistance of the processed portion, and the organic resin needs to be a thermosetting organic resin. When continuous roll forming is performed on a surface-treated steel sheet, the roll temperature rises significantly, and when the organic resin contained in the chemical conversion coating is a normal thermoplastic resin or a general emulsion resin, the roll temperature is increased. The rise causes scratches on the film and deteriorates the appearance after processing. Therefore, as a result of studying to solve such a problem, the use of a thermosetting resin as a resin to be blended in the film dramatically improves the scratch resistance at high temperatures, and as a result,
It was found that there was no problem in appearance after processing even in continuous roll forming processing.

Here, the thermosetting resin refers to an addition or condensation reaction between functional side chains of an organic polymer or between an organic polymer and a curing agent, or a main chain or a side chain, when heated during film formation. A resin that undergoes a cross-linking reaction such as radical polymerization utilizing a chain double bond. Examples of the thermosetting resin include alkyd resins, polyester resins, polyurethane resins, acrylic resins, epoxy resins, styrene resins, and modifications thereof. One or more kinds of resins and the like can be used. Among these, polyester resin, polyurethane resin and acrylic resin are particularly desirable from the viewpoint of workability. Further, the above-mentioned thermosetting resins include an aqueous dispersion type and a solvent type, and any of them may be used.

The amount of the organic resin in the chemical conversion coating (A)
And mass ratio (A) of Cr amount (B) in terms of metallic chromium (A) /
When (B) is less than 1, the effect of improving the corrosion resistance of the processed portion by the organic resin cannot be sufficiently obtained. On the other hand, the mass ratio (A) /
(B) If it is 200 or more, the effect of improving the corrosion resistance of the processed portion by Cr cannot be sufficiently obtained. In addition, when the drying temperature after applying the chromate treatment liquid at the time of forming the chemical conversion treatment film is less than 130 ° C. at the plate temperature, an appropriate chemical conversion treatment film is not formed because the temperature is low. The organic resin is liable to be thermally degraded, and further heat is applied to the plating film, so that the alloying reaction is accelerated, and the workability may be reduced.

In the surface-treated steel sheet of the present invention, a general chromate film may be formed on the plating film surface, and the above-mentioned specific chemical conversion film may be formed thereon. In this case, the chemical conversion film is composed of two layers. It will be composed of a film,
Further improvement in corrosion resistance can be expected. In this case, the composition of the chromate film formed on the lower layer side is not particularly limited, and may be a known composition usually applied to a plated steel sheet. It is optional to add an organic resin to the chromate film, but usually it does not contain an organic resin.

In the surface-treated steel sheet of the present invention, when a heat treatment is performed after the formation of the chemical conversion coating in order to impart a specific thermal history to the plating coating, the properties of the organic resin contained in the chemical conversion coating may be impaired. In some cases, it is effective to add an inorganic additive (fine particles) to the chemical conversion coating. As inorganic additives, silica,
Phosphoric acid compounds, silicate compounds (for example, Ca salt, Mg
Salt) or the like.

In the surface-treated steel sheet of the present invention, the molten Al-Z
The plating film of the n-based plated steel sheet is preferably a plating film obtained through the heat history of at least the following (a) and (b), and the plating film having passed the heat history of such (a) and (b) By forming the above-mentioned specific chemical conversion coating on the surface of the coating, particularly excellent workability and corrosion resistance of the processed portion can be obtained. (a) Thermal history in which the average cooling rate during the first 10 seconds immediately after the steel sheet leaves the hot-dip bath is less than 11 ° C./sec. (b) After the hot-dip plated metal solidifies,
The temperature is raised to a temperature T (° C.) in the range of −300 ° C., and thereafter, the average cooling rate from the temperature T (° C.) to 100 ° C. satisfies C (° C./hr) or less represented by the following formula (1). Heat history,
And / or from a temperature T (° C.) in the range of 130 to 300 ° C. after solidification of the hot-dip plated metal to 100 ° C.
The average cooling rate up to C (° C / hr) shown in the following equation (1)
Heat history that satisfies the following: C = (T-100) / 2 (1)

In the thermal history of the above (b), the temperature T
A more preferable range of (° C) is 130 to 200 ° C.
Here, the above-mentioned formula (1) is based on experiments by the present inventors to examine in detail the effects of the heating conditions of the plating film and the subsequent cooling conditions and the cooling conditions after the solidification of the hot-dip plated metal on the plating film based on experiments. And the empirical formula derived as a result.

By forming the plating film through the thermal histories of (a) and (b) above, the workability (crack resistance and the like) is remarkably improved while being a molten Al-Zn plating film. . It is considered that the workability of the plating film is remarkably improved by passing through the heat histories (a) and (b) for the following reasons. First, immediately after the steel sheet has left the hot-dip plating bath, the heat history of the above (a), that is, a heat history in which the average cooling rate for 10 seconds immediately after leaving the hot-dip bath has been sufficiently slowed down, gives a hot-dip coating film. Solidification is closer to an equilibrium state than solidification by a normal cooling process, and diffusion in a semi-molten state promotes two-phase separation of Al and Zn, and as a result, the plating film is softened. Then, the plating film having undergone such a heat history is further heated to a temperature range of 130 to 300 ° C. (preferably 130 to 200 ° C.) after the heat history of the above (b), and then gradually cooled under specific conditions. Heat history or / and 130 to 300 ° C. after the solidification of the plating film (preferably 130 to 2 ° C.)
Through the thermal history of slow cooling from the temperature range of (00 ° C.) under specific conditions, the strain accumulated in the plating film at the time of solidification is released, and solid diffusion occurs in the plating film. A) in the plating film caused by the thermal history
The two-phase separation of 1 and Zn is further effectively promoted. As a result, it is considered that the plating film is remarkably softened and its workability is remarkably improved.

Therefore, the softening of the plating film and the remarkable improvement of the workability accompanying the softening of the plating film can be achieved by the above-mentioned (a) and (b).
This is due to the combined action of the heat histories of the two, and it is difficult to achieve only one of them.

The details of the heat histories (a) and (b) will be described below. First, regarding the heat history of the above (a), the average cooling rate of the plating film for the first 10 seconds immediately after the steel sheet exits the hot-dip plating bath is set to less than 11 ° C./sec. Because the solidification of the film is closer to the equilibrium state than the solidification by the normal cooling process,
The two-phase separation of Al and Zn is promoted by diffusion in a semi-molten state, whereby the plating film is softened. If the average cooling rate in the first 10 seconds immediately after the steel sheet leaves the hot-dip plating bath is 11 ° C./sec or more, the solidification rate is too high, so that the solidification of the hot-dip coating proceeds in a non-equilibrium state, Since the certain time is short, the two-phase separation between Al and Zn is not sufficiently promoted, and the softening of the plating film due to the combination with the heat history of (b) cannot be sufficiently achieved.

FIG. 1 shows the effect of the average cooling rate of the plating film on the workability of the surface-treated steel sheet for the first 10 seconds immediately after the steel sheet leaves the hot-dip bath. The results were obtained. Each of the test materials is a surface-treated steel sheet in which a chemical conversion treatment film satisfying the conditions of the present invention is formed on a plated steel sheet whose plating film has been manufactured through the thermal history of the above (b). In addition,
The evaluation of the workability in this test was performed in accordance with the evaluation of the workability in Examples described later. As shown in FIG. 1, when the average cooling rate of the plating film in the first 10 seconds immediately after the steel sheet leaves the hot-dip plating bath is 11 ° C./sec or more, the workability score in the 0T bending is 2 or less. It is. On the contrary,
When the average cooling rate of the plating film was less than 11 ° C./sec, the workability score was 4 or more, indicating that the workability was significantly improved.

In order for the coating film to have undergone the thermal history described in (a) above, the temperature must be maintained between the hot-dip bath surface of the continuous hot-dip coating equipment and the roll where the steel sheet that has exited the hot-dip coating bath first contacts. It is necessary to provide an adjusting device and control the cooling rate of the plating film by the temperature adjusting device. It is preferable that the temperature control device be provided with a heating or heat retaining means and, if necessary, a cooling means. The cooling means cools the plated steel sheet, whose cooling rate of the plating film is controlled by the heating or heat retaining means, before it comes into contact with the first roll (such as a top roll), and generates pickup on the roll surface. It is for the purpose of preventing, for example. For example, an induction heater or a gas heating furnace can be used as a heating or heat retaining means of the temperature adjusting device, and a gas blowing device or the like can be used as a cooling means. However, there is no special restriction on the method, shape, scale, etc. of the heating or heat retaining means and cooling means of the temperature control device, and any point that the heat history of (a) can be imparted to the plating film. Good.

Next, regarding the heat history of the above (b),
(a) the heat-treated plating film (plating film after solidification of hot-dip plated metal) is 130 to 300
C, preferably a temperature T (C) in the range of 130 to 200C.
The temperature is then raised and then cooled so that the average cooling rate from the temperature T (° C.) to 100 ° C. satisfies C (° C./hr) or less in the above equation (1), or The average cooling rate from the temperature T (° C.) in the range of 130 to 300 ° C., which is the cooling process, to 100 ° C., which is the cooling process of the plated film after the solidified plated metal solidifies, is represented by the above formula (1).
By cooling so as to satisfy (° C./hr) or less, the strain accumulated in the plating film is released as described above, and solid diffusion occurs in the plating film.
Al and Zn in the plating film generated by the thermal history of (a)
Is more effectively promoted. Then, due to the combined action of such heat history and the heat history of the above (a), the plating film is remarkably softened, and its workability is remarkably improved.

Here, if the heating temperature T of the plating film in the heat history of the above (b) is lower than 130 ° C., the above-mentioned effect cannot be sufficiently obtained.
If the temperature exceeds ℃, the growth of the alloy phase at the interface between the base steel sheet and the plating film is promoted, which adversely affects workability.
Further, from such a viewpoint, the upper limit of the heating temperature T, which is more preferable for improving the workability, is 200 ° C. Also,
From the temperature T (° C.) in the range of 130 to 300 ° C., which is the cooling process after the hot-dip plated metal solidifies,
Also in the case where the cooling is performed under the condition of imparting the heat history of (b), if the temperature T is lower than 130 ° C., the above-mentioned effect cannot be sufficiently obtained.

FIG. 2 (a) shows the effect of the heating temperature of the plating film on the workability of the surface-treated steel sheet when the hot-dip coated steel sheet is heat-treated after solidification of the hot-dip plated metal. In all of the test materials from which this result was obtained, the average cooling rate of the plating film from the heating temperature to the heating temperature of 100 ° C. was within the condition of the heat history of (b) above, and the plating film had the above-mentioned ( This is a surface-treated steel sheet in which a chemical conversion coating satisfying the conditions of the present invention is formed on a plated steel sheet manufactured through the heat history of a). The evaluation of the workability in this test was performed according to the evaluation of the workability in Examples described later.

FIG. 2 (b) shows the average cooling rate (average cooling rate from the heating temperature to 100 ° C.) of the plated film when heat-treating the plated steel sheet after the hot-dip plated metal has solidified. The effect on the workability of the surface-treated steel sheet was investigated, and the test materials from which this result was obtained, the heating temperature of the plating film was within the heat history conditions of (b) above, Further, the coated steel sheet is a surface-treated steel sheet in which a chemical conversion coating is formed on a plated steel sheet manufactured through the thermal history described in (a) above. The evaluation of workability in this test is as follows.
The evaluation was performed according to the evaluation of workability in Examples described later.

As shown in FIGS. 2 (a) and 2 (b), when the heating temperature of the plating film is in the range of 130 to 300 ° C., the workability of the 0T bending is 4 or more, and the preferable conditions are as follows. In the range of 130 to 200 ° C., the workability score was 4 to 5 points. On the other hand, when the heating temperature is 13
Outside the range of 0 to 300 ° C., only three points of workability were obtained. When the difference between the average cooling rate from the heating temperature and the heating temperature to 100 ° C. and “C” in the above equation (1) is zero to minus (within the range of the present invention), the workability of the 0T bending is 4 points. If the difference is plus (outside the scope of the present invention), the workability score is only 3 points.

In order to make the plating film have passed the thermal history of the above (b), a heating or heat retaining device for heat-treating or keeping the plating film inside or outside the continuous hot-dip plating equipment is provided. A predetermined heat treatment or heat retention is performed. For example, a heating mechanism (for example, an induction heater, a gas heating furnace, a hot blast furnace, etc.) may be provided in a continuous hot-dip plating facility to perform continuous heating in-line, or may be performed offline after winding on a coil. It may be performed by batch heating. In addition, a heating mechanism (for example, an induction heater, a gas heating furnace,
The heating may be performed by continuous heating using a hot air oven or the like. Furthermore, after the plated steel sheet continuously heated in the plating line or in the above-described continuous processing equipment is wound around a coil, appropriate heat retention or heat retention may be performed. In addition, a heat retaining device may be provided so that the plating film can be cooled and gradually cooled in a cooling process after the hot-dip plated metal solidifies. However, there is no special restriction on the method, shape, scale, etc. of the heating or heat retaining device, and it is essential that the heat treatment of the above (b) be given to the plating film.

Next, a method for producing the above-mentioned surface-treated steel sheet according to the present invention will be described. The production method of the present invention uses a hot-dip Al-Zn-based coated steel sheet having an Al content of 20 to 95 mass% in a plating film manufactured by a continuous hot-dip plating equipment or the like as a base steel sheet, and forms a chemical conversion coating on the surface thereof. A method of imparting at least the following (a) and (b) thermal histories to a plating film of a steel sheet that has exited a hot dip coating bath, and a specific chemical treatment on the surface of the plated steel sheet. Forming a treatment film. (a) Heat history in which the average cooling rate for 10 seconds immediately after the steel sheet leaves the hot-dip bath is less than 11 ° C./sec. (b) After the hot-dip plated metal solidifies,
The temperature is raised to a temperature T (° C.) in the range of −300 ° C., and thereafter, the average cooling rate from the temperature T (° C.) to 100 ° C. satisfies C (° C./hr) or less represented by the following formula (1). Heat history,
And / or from a temperature T (° C.) in the range of 130 to 300 ° C. after solidification of the hot-dip plated metal to 100 ° C.
The average cooling rate up to C (° C / hr) shown in the following equation (1)
Heat history that satisfies the following: C = (T-100) / 2 (1)

Of the thermal histories (a) and (b) applied to the plating film, the application of the thermal history (a) is performed by controlling the cooling condition of the plating film immediately after plating. In order to impart the heat history of (a) to the plating film, as described above, the temperature is adjusted from the hot-dip bath surface of the continuous hot-dip plating equipment to the roll where the steel sheet that has exited the hot-dip plating bath first contacts. It is necessary to provide a device and control the cooling rate of the plating film by this temperature adjusting device. As described above, the temperature control device is preferably provided with a heating or heat retaining means, and, if necessary, provided with a cooling means,
There is no special limitation on the method, shape, scale, etc. of the heating or heat retaining means and cooling means, and any material may be used as long as it can impart the heat history of (a) to the plating film. For example, an induction heater or a gas heating furnace can be used as a heating or heat retaining means of the temperature adjusting device, and a gas blowing device or the like can be used as a cooling means.

The heat history of (b) may be applied by subjecting the plated steel sheet after the hot-dip plated metal has solidified to a specific heat treatment, or after the hot-dip plated metal has solidified. The cooling of the plating film is controlled by heat retention or the like. In the production method of the present invention, a specific chemical conversion treatment film is formed on the plating film surface of the plated steel sheet, but the heat treatment for imparting the heat history of (b) to the plating film is performed before the formation of the chemical conversion treatment film, During the step of drying the film, the step may be performed at any stage after the formation of the chemical conversion treatment film (after the application of the treatment liquid and the formation of the film by the drying step). Moreover, you may perform in two or more steps of these.

Therefore, the application of the thermal history of (b) to the plating film can be performed in at least one of the following steps (1) to (4). (1) Before forming chemical conversion coating (2) During drying process of chemical conversion coating (3) After formation of chemical conversion coating (4) Cooling process after solidification of hot-dip plated metal Among the methods, the method has the advantage that each condition of the heat treatment step and the chemical treatment step can be independently optimized, and the method of and is suitable for performing all the processing in the continuous hot-dip plating equipment. . In addition, since the heat treatment is carried out by utilizing the heating in the drying step of the chemical conversion treatment, the method is particularly economical.

The heat treatment or heat retention for imparting the heat history of the above (b) is performed by a heating or heat retention device provided inside or outside the continuous hot-dip plating equipment. A heating mechanism (e.g., induction heater, hot blast stove, etc.) may be provided in the continuous hot-dip plating equipment to perform continuous heating in-line, or to perform batch heating offline after winding on a coil. Is also good. Further, the heating may be performed by continuous heating using a heating mechanism (for example, an induction heater or a hot blast stove) in a continuous processing facility outside the plating line. Furthermore, after the plated steel sheet continuously heated in the plating line or in the above-described continuous processing equipment is wound around a coil, appropriate heat retention or heat retention may be performed. Also,
In the cooling process after the hot-dip-plated metal is solidified, a heat retaining device may be provided so as to keep the plating film heated and gradually cooled. However, there is no special restriction on the method, shape, scale, etc. of the heating or heat retaining device, and it is essential that the heat treatment of the above (b) be given to the plating film. In addition, the preferable plating composition of the hot-dip Al-Zn-based plated steel sheet, the coating weight, the reasons for limiting the heat history of the above (a) and (b), the obtained effects, and the like are as described above.

In the production method of the present invention, at least one selected from chromic acid, a chromate compound, and a chromic acid compound in which a part of chromic acid is reduced is coated with a thermosetting organic compound on a plating film surface of a plated steel sheet. After applying the chromate treatment liquid containing the resin, the mass of the amount of the organic resin (A) contained in the film and the amount of Cr (B) in terms of metallic chromium by drying at a plate temperature of 130 to 300 ° C. the ratio (a) / (B) is less than 200 1 or more, preferably 50 or more 150 or less, Cr of the metal chromium conversion is 0.1 mg / ^{m 2} or more 100 mg / m
A chemical conversion coating of less than ² , preferably 5 mg / m ² or more and 40 mg / m ² or less is formed. In this chromate treatment, a chromate treatment solution is applied to the plated steel sheet surface, and usually,
Dry without washing.

The reasons for limiting the coating composition and the drying temperature of the chemical conversion coating film, the relationship between the step of forming the chemical conversion coating film and the step (b) of imparting the heat history, and the like are as described above. . In the production method of the present invention, it is also possible to apply a general chromate treatment to the plating film surface and then form a film by the above-mentioned specific chromate treatment on the upper layer. A treatment film is formed. In this case, the lower layer side chromate treatment may be performed under a known treatment condition that is usually applied to a plated steel sheet.

[0047]

[Example 1] A cold-rolled steel sheet (sheet thickness: 0.5 mm) manufactured by a conventional method was passed through a continuous hot-dip plating facility, and 55%
Hot-dip plating was performed using an Al-1.5% Si-Zn plating bath. The line speed was 160 m / sec, and the single-side plating adhesion amount was 75 g / m ² .

In the manufacturing process of the plated steel sheet, a heat history is given to the plated film at an average cooling rate of 15 ° C./sec for 10 seconds immediately after the steel sheet leaves the plating bath, and the plated film surface is A chemical conversion treatment was performed. The following were used as the organic resin for chemical conversion treatment film addition. (a) Thermosetting resin (main resin: polyester urethane emulsion resin, curing agent: isocyanate curing agent) (b) Thermosetting resin (main resin: acrylic emulsion resin having tertiary amino group and carboxyl group, cured Agent: epoxy silane compound having both alkoxysilyl group and epoxy group) (c) Thermoplastic resin (MMA-MA acrylic emulsion resin) (d) Thermoplastic resin (polyester urethane emulsion resin)

A treatment solution obtained by mixing any one of the above organic resins and chromic acid at a predetermined ratio is applied to a surface of a plated steel sheet with a predetermined Cr content.
Coating was carried out so as to obtain an adhesion amount, and drying treatment was performed at a maximum reached plate temperature of 160 ° C. With respect to the surface-treated steel sheet manufactured as described above, the corrosion resistance of the processed portion, the roll forming property, and the Cr fixing rate were evaluated by the following methods. Table 1 shows the results together with the chemical conversion treatment conditions.

(1) Corrosion Resistance of Processed Section After the surface-treated steel sheet was bent by 5T, it was inserted into a salt spray tester, and the state of rust generation from the bent section after 500 hours had passed was observed and evaluated according to the following criteria. ◎: No abnormality (Rust generation area rate less than 10%) ○: Mild white rust or black rust generation (Rust generation area rate 10%)
Δ: less than 25%) Δ: White rust and black rust occurred (rust generation area ratio 25% or more: 8)
X: Significant white rust and black rust occurred (rust generation area ratio 80%)
that's all)

(2) Roll forming workability A 30 mm × 300 mm surface-treated steel sheet was subjected to a flat plate sliding test using a draw bead tester at a mold temperature of 80 ° C. and a bead pressing load of 100 kg, and the appearance after drawing was visually observed. And evaluated according to the following criteria. ◎: The blackened area is less than 10% and there is no adhesion of the film peeling to the mold. ○: The blackening area is 10% or more and less than 25%, or the adhesion of the film peeling to the mold is insufficient. Slightly present △: Blackening area is 25% or more and less than 50%, or there is remarkable adhesion of a film exfoliated substance to a mold ×: Blackening area is 50% or more, or remarkable on the surface of a plated steel sheet There is "biting"

(3) Cr fixation rate The surface-treated steel sheet was immersed in boiling water for 30 minutes, and the amount of deposited Cr before and after the treatment was measured by X-ray fluorescence.
Was measured as a Cr fixing rate, and evaluated according to the following criteria. ◎: Cr residual rate of 95% or more ：: Cr residual rate of 85% or more and less than 95% Δ: Cr residual rate of 75% or more and less than 85% ×: Cr residual rate of less than 75%

[0053]

[Table 1]

Example 2 A cold-rolled steel sheet (sheet thickness: 0.5 mm) manufactured by a usual method was passed through a continuous hot-dip plating apparatus,
% Al-1.5% Si-Zn plating bath (N in Tables 2 to 5)
o. 1 to No. 11, No. 14-No. 25), 40
% Al-1.0% Si-Zn plating bath (No. 12 in Tables 2 and 3) and 70% Al-1.8% Si-Zn plating bath (No. 13 in Tables 2 and 3). Hot-dip plating. The line speed was 160 m / sec, and the single-side plating adhesion amount was 75 g / m ² .

In the manufacturing process of the plated steel sheet, the heat history shown in Tables 2 and 4 is imparted to the plating film,
A chemical conversion treatment was applied to the plating film surface. The same organic resin as in Example 1 was used as the organic resin for chemical conversion coating addition. A treatment liquid in which an organic resin and chromic acid were mixed at a predetermined ratio was applied to the surface of the plated steel sheet so as to have a predetermined Cr adhesion amount, and was dried at a maximum temperature of 160 ° C. With respect to the surface-treated steel sheet thus manufactured, the roll forming property and the Cr fixing rate were evaluated by the same method as in Example 1, and the workability and the corrosion resistance of the processed portion were evaluated by the following methods. The results are shown in Tables 2 to 5 together with the thermal history and chemical conversion treatment conditions applied to the plating film.

(1) Workability The surface-treated steel sheet was bent by 0T, cracks at the tip of the 0T bending were observed, and evaluated according to the following criteria. No cracks were observed even when observed with a 5:20 loupe. 4: No crack is observed when visually observed, but 20
Cracks are observed when observed with a double magnifier. 3: Cracks are observed by visual observation. 2: A large opening crack is observed by visual observation. 1: A crack accompanied by peeling has occurred.

(2) Corrosion resistance of the processed part After the surface-treated steel sheet was bent by 3T, it was inserted into a salt spray tester, and after 500 hours, the state of rust generation from the bent part was observed and evaluated according to the following criteria. 5: No abnormalities 4: Slight white rust and black rust occurred on part 3: Slight white rust and black rust occurred on the entire surface 2: Remarkable white rust and black rust occurred on the entire surface 1: Red rust occurred Yes

[0058]

[Table 2]

[0059]

[Table 3]

[0060]

[Table 4]

[0061]

[Table 5]

[Example 3] A cold-rolled steel sheet (sheet thickness 0.5 mm) manufactured by a conventional method was passed through a continuous hot-dip plating apparatus, and 55
Hot-dip plating was performed using a 1.5% Al-1.5% Si-Zn plating bath. The line speed was 160 m / sec, and the single-side plating adhesion amount was 75 g / m ² .

In the manufacturing process of the plated steel sheet, a heat history shown in Table 6 was imparted to the plating film, and a chemical conversion treatment was applied to the plating film surface. The chemical conversion treatment conditions were as follows: the resin (b) used in Example 1 (10 parts by weight of a curing agent was added to 100 parts by weight of the base resin) and chromic acid were an organic resin / Cr = 1.
/ 100 is applied to the coated steel sheet surface
r The coating amount was 20 mg / m ^2, and the coating was dried at a maximum temperature of 160 ° C. The workability (crack resistance) and the corrosion resistance of the processed portion of the surface-treated steel sheet manufactured as described above were evaluated in the same manner as in Example 2. Table 6 shows the results together with the thermal history applied to the plating film.

[0064]

[Table 6]

[0065]

As described above, the surface-treated steel sheet of the invention according to claims 1 and 2 of the present application is characterized in that A
Although it is a surface-treated steel sheet using a hot-dip Al-Zn plated steel sheet having an l content of 20 to 95 mass% as a base steel sheet, it has extremely excellent corrosion resistance and roll forming properties in a processed part.
Further, the surface-treated steel sheet of the invention according to claims 3 and 4 of the present application has excellent workability and roll forming property, and particularly has excellent corrosion resistance in a processed portion. Also,
According to the manufacturing method of the present invention, such a surface-treated steel sheet can be manufactured stably and with high productivity.

[Brief description of the drawings]

FIG. 1 is a graph showing the effect of the average cooling rate of a plating film on the workability of a surface-treated steel sheet for the first 10 seconds immediately after the steel sheet leaves a hot-dip bath.

FIG. 2 (a) is a graph showing the effect of increasing the heating temperature of a plating film on the workability of a surface-treated steel sheet when a plated steel sheet after solidification of a hot-dip plated metal is heat-treated. FIG. 2 (b) shows the average cooling rate of the plating film (from the heating temperature to the heating temperature of 1%) when the plated steel sheet after the hot-dip plating metal was solidified was heat-treated.
Graph showing the effect of average cooling rate to 00 ° C) on the workability of surface-treated steel sheet

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C23C 2/12 C23C 2/12 2/28 2/28 2/40 2/40 22/77 22/77 28/00 28 / 00 C (72) Inventor Toshihiko Oi 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Keiji Yoshida 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Stock Within the company (72) Inventor Junichi Inagaki 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Japan Pipe Co., Ltd. (72) Inventor Masaaki Yamashita 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Japan Pipe Co., Ltd. (72) Inventor Yasuhiro Majima 6-1 Mikae-cho, Kawasaki-ku, Kawasaki-city, Kanagawa Prefecture, Japan (72) Inventor Nobuyuki Ishida 6-1 Mizue-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa NKK Steel Co., Ltd. (72) Inventor Yuichi Fukushima 6-1 Mizue-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa F-term (reference) in NKK Steel Sheet Co., Ltd. 4D075 A E03 BB18Y BB23Y BB24Z BB26Z BB74Y BB87X BB91X BB91Y BB92Z BB93Y BB93Z BB95Y CA09 CA33 DA06 DB05 DB07 DC01 EA06 EA07 EA13 EA19 EB14 EB22 EB32 EB33 EB35 EB36 EB38 EB45 EB56 EC01 EC15 EC54 4F100 AA22C AB03A AB10B AB18B AB31B AK01C AK25 AK51 AK53 BA03 BA07 BA10A BA10C EH71B EJ68C GB07 JB02 JB13C JL01 YY00C 4K026 AA02 AA07 AA09 AA13 AA22 BA06 BA12 BB08 BB09 CA16 CA19 CA22 CA39 DA02 DA11 DA15 DA16 EB08 EB11 4K027 AA02 AA05 AA22 AB02 AB05 AB44 AB03 AC02 A02 BB04 CA11 CA16 CA53 CA62

Claims (10)

[Claims] An aluminum content in a plating film is 20 to 95.
What is claimed is: 1. A surface-treated steel sheet having a chemical conversion treatment film on the surface of a hot-dip Al-Zn-based plated steel sheet of mass%, wherein the chemical conversion treatment film is a chromic acid, a chromate compound, and a chromate compound in which a part of the chromic acid is reduced. A film obtained by applying a chromate treatment solution containing at least one selected from among the above and a thermosetting organic resin, and then drying the plate at a temperature of 130 to 300 ° C., which is contained in the film. The mass ratio (A) / (B) of the amount of organic resin (A) and the amount of Cr (B) in terms of chromium metal is 1 or more and less than 200, and the amount of Cr in terms of chromium metal is 0.1 mg / m ² or more and 100 mg / excellent surface treated steel sheet in workability and the processing unit corrosion resistance characterized by comprising the film is less than m ^2. 2. An aluminum content in a plating film of 20 to 95.
A surface-treated steel sheet having a chemical conversion coating on the surface of a hot-dip Al-Zn-based plated steel sheet of mass%, wherein the chemical conversion coating is a chromate coating formed on a plating coating surface and a coating formed thereon. Then, after applying a chromate treatment liquid containing at least one selected from chromic acid, a chromate compound, and a chromic acid compound obtained by partially reducing chromic acid, and a thermosetting organic resin,
The mass ratio (A) / (B) of the amount of organic resin (A) obtained by drying at a temperature of 0 to 300 ° C. and contained in the film and the amount of Cr (B) in terms of metallic chromium is 1 or more and 200 Less than 0.1mg / m ² Cr 100mm
A surface-treated steel sheet having excellent workability and corrosion resistance in a processed portion, comprising a film having a g / m ^{2 or} less. 3. The workability and the corrosion resistance of a processed part according to claim 1, wherein the plating film is a plating film obtained through at least the following thermal histories (a) and (b). Excellent surface treated steel sheet. (a) Heat history in which the average cooling rate for 10 seconds immediately after the steel sheet leaves the hot-dip bath is less than 11 ° C./sec. (b) After the hot-dip plated metal solidifies,
The temperature is raised to a temperature T (° C.) in the range of −300 ° C., and thereafter, the average cooling rate from the temperature T (° C.) to 100 ° C. satisfies C (° C./hr) or less represented by the following formula (1). Heat history, and / or temperature T (° C.) in the range of 130 to 300 ° C. after solidification of hot-dip plated metal to 100 ° C.
The average cooling rate up to C (° C / hr) shown in the following equation (1)
Heat history that satisfies the following: C = (T-100) / 2 (1) 4. The heat history temperature T (° C.) of (b) is 130 to
The surface-treated steel sheet having excellent workability and corrosion resistance of a processed portion according to claim 1, wherein the temperature is in a range of 200 ° C. 5. A coated steel sheet comprising a surface-treated steel sheet according to claim 1, wherein a single-layer or multi-layer coating film is formed on the surface thereof. 6. An Al content in a plating film of 20 to 95.
A method for producing a surface-treated steel sheet having a chemical conversion coating film on the surface of a hot-dip Al-Zn-based coated steel sheet having a mass%, wherein at least the following (a) and (b) And (a) heat history in which the average cooling rate for 10 seconds immediately after the steel sheet leaves the hot-dip bath is less than 11 ° C./sec. (B) hot-dip plated metal solidifies After that, 130
The temperature is raised to a temperature T (° C.) in the range of −300 ° C., and thereafter, the average cooling rate from the temperature T (° C.) to 100 ° C. satisfies C (° C./hr) or less represented by the following formula (1). Heat history, and / or temperature T (° C.) in the range of 130 to 300 ° C. after solidification of hot-dip plated metal to 100 ° C.
The average cooling rate up to C (° C / hr) shown in the following equation (1)
Thermal history that satisfies the following: C = (T-100) / 2 (1) The surface of the plated steel sheet is selected from chromate, a chromate compound, and a chromate compound in which a part of the chromate is reduced. A film obtained by applying a chromate treatment liquid containing at least one kind of thermosetting organic resin and drying at a plate temperature of 130 to 300 ° C., wherein the amount of the organic resin contained in the film (A ) And a Cr content (B) in terms of metallic chromium (B) in a mass ratio (A) / (B) of 1 or more and less than 200, and a Cr content in metallic chromium equivalent of 0.1 mg / m ² or more and less than 100 mg / m ^2. A method for producing a surface-treated steel sheet having excellent workability and corrosion resistance in a processed portion, comprising a step of forming a treated film. 7. An aluminum content in a plating film of 20 to 95.
Chemical conversion treatment on the surface of mass% hot-dip Al-Zn plated steel sheet
A method for producing a surface-treated steel sheet having a coating, the method comprising:
Both (a) and (b) the steps of imparting the thermal history described below, and (a) the average cooling for 10 seconds immediately after the steel sheet has left the hot-dip plating bath.
(B) After the hot-dip plating metal solidifies, the heat history is less than 11 ° C / sec.
And heated to a temperature T (° C.) in the range of
After that, the average cooling rate from temperature T (° C) to 100 ° C decreases
Thermal history that satisfies C (° C./hr) or less shown in equation (1), and / or after the hot-dip plated metal solidifies
A temperature T (° C.) in the range of 130 to 300 ° C. to 100 ° C.
The average cooling rate up to C (° C / hr) shown in the following equation (1)
Thermal history satisfying the following: C = (T-100) / 2 (1) A chromate film is formed on the surface of the plated steel sheet.
Chromic acid, chromic acid
Salt compounds, chromic acid compounds that have partially reduced chromic acid
Containing at least one selected from the group consisting of a thermosetting organic resin and
After applying the romate treatment liquid, the plate temperature is 130 to 300 ° C.
A film obtained by drying at a temperature, which is contained in the film.
Of organic resin (A) and Cr in terms of chromium metal
(B) mass ratio (A) / (B) of 1 to less than 200, gold
0.1mg / m Cr content of genus chromium ²More than 100m
g / m²Of a chemical conversion coating to form a coating that is less than
Processability and process part resistance characterized by having a forming step
A method for producing surface-treated steel sheets with excellent corrosion properties. 8. The temperature T (° C.) of the heat history of (b) is 130 to
8. The temperature range of 200 [deg.] C.
3. A method for producing a surface-treated steel sheet having excellent workability and corrosion resistance in a processed part according to the above. 9. The method according to claim 6, wherein the application of the thermal history of (b) to the plating film is performed in at least one of the following steps (1) to (4). A method for producing surface-treated steel sheets with excellent workability and corrosion resistance in the processed part. (1) Before chemical conversion coating formation (2) During chemical conversion coating drying process (3) After chemical conversion coating formation (4) Cooling process after solidification of hot-dip plated metal 10. The method according to claim 6, further comprising the step of applying one or more coats to the surface of the chemical conversion coating. Manufacturing method of painted steel sheet.