JP2003213395A - Surface-treated steel plate with excellent machinability and corrosion resistance of machined part, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-chromate surface-treated steel plate with excellent machinability and corrosion resistance of machined part in which an Al-Zn hot-dipped steel plate with 20 to 95% Al contained in a plating film constitutes a base steel plate. <P>SOLUTION: The plating film is obtained through (a) a heat history in which the mean cooling rate of the steel plate for 10 seconds immediately after the steel plate leaves a hot-dipping bath is <11°C/sec, (b) a heat history in which a hot-dipping metal is solidified, and heated to a temperature T(°C) in a range between 130 and 300°C, and the mean cooling rate from the temperature T(°C) to 100°C is ≤C(°C/hr) expressed by the formula C=(T-100)/2 (1), and/or a heat history in which the mean cooling rate from the temperature T(°C) in a range between 130 and 300°C to 100°C after the hot-dipping metal is solidified is ≤C(°C/hr) expressed by the formula (1). A specified non-chromate coating layer is provided on the surface of the plating film. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to A in a plating film.
The present invention relates to a surface-treated steel sheet using a hot-dip Al-Zn-based plated steel sheet having an I 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 20 to 95 mass% Al in a plating film
The hot-dip Al-Zn-based plated steel sheet contains Japanese Patent Publication No. 46-
As shown in No. 7161, it shows excellent corrosion resistance as compared with hot-dip galvanized steel sheet, and thus, in recent years, demand has been growing mainly in the field of building materials. This galvanized steel sheet is produced as follows in a continuous hot dip galvanizing facility using a hot-rolled steel sheet that has been pickled and descaled or a cold-rolled steel sheet obtained by further cold rolling the same as a base steel sheet.

In continuous hot dip coating equipment, 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 passed through the snout immersed in the plating bath and immersed in a hot dip galvanizing bath containing Al of a predetermined concentration. The steel plate immersed in the plating bath is pulled up above the plating bath via a sink roll, and then a pressurized gas is jetted toward the surface of the steel plate from a gas wiping nozzle arranged on the plating bath. Molten Al- on which the amount of plating adhered is adjusted and then cooled by a cooling device to form a predetermined plating film
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 coating equipment, the plating bath composition and the cooling rate after plating are accurate within a predetermined control range in order to ensure the desired plating quality and material. Well managed. The plating film of the plated steel sheet produced as described above is mainly composed of a portion where Al containing Zn in a supersaturated state is dendrite solidified and a remaining dendrite gap portion, and the dendrite is in the thickness direction of the plating film. They are stacked. Due to such a characteristic film structure, molten Al-
The Zn-based plated steel sheet exhibits excellent corrosion resistance.

Further, although about 1.5 mass% of Si is usually added to the plating bath, the function of this Si suppresses the alloy phase growth at the interface of the coating film / base steel sheet in the molten Al-Zn system steel sheet. The alloy phase thickness is about 1 to 2 μm. Since the thinner the alloy phase, the more the portion of the characteristic film structure showing the excellent corrosion resistance, the inhibition of 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 brings an effect of improving workability. Further, since the base steel sheet is exposed at the crack portion and the corrosion resistance is poor, reducing the occurrence of cracks also improves the corrosion resistance at the worked portion.

Usually, the plating bath contains unavoidable impurities, Fe leaching from the steel plate or equipment in the plating bath, and Si for suppressing alloy phase. However, in addition to these, some element is added. Therefore, these elements exist in the form of alloy or simple substance in the alloy phase and the plating film. In addition, the hot-dip Al-Zn plated steel sheet is rarely used as it is in hot practical use, and it is usually used as a surface-treated steel sheet whose surface is subjected to chemical conversion treatment or coating. It

[0007]

When a hot-dip Al—Zn-based plated steel sheet is subjected to processing such as bending, cracks are generated in the plating film of the processed portion depending on the degree of processing. With this plated steel sheet, there is approximately 1
The alloy phase with a thickness of ~ 2 μm serves as the starting point for cracks, and the dendrite gaps in the plating film serve as the propagation paths for cracks. Cracks tend to open relatively large. Therefore, depending on the degree of processing, there is a problem that cracks are visually recognized and the appearance is impaired. Further, as described above, the hot dip Al-Zn-based plated steel sheet exhibits excellent corrosion resistance as compared with the 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 non-cracked portion. There is also a problem that the corrosion resistance is significantly reduced.

For such a problem, for example, Japanese Patent Publication No. 6
Japanese Patent Laid-Open No. 1-28748 discloses a method of improving the ductility of a plated steel sheet by subjecting a molten Al-Zn system 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. In addition, as described above, molten Al-Z
The n-based plated steel sheet is usually used as a chemical conversion treated steel sheet whose surface is subjected to a chemical conversion treatment or a coated coated steel sheet. And, from the viewpoint of suppressing the occurrence of cracks in the processed portion simply by processing such as bending, even if the ductility of the plating film is improved to some extent as in the above-mentioned conventional technique, the performance as a product that is practically used, that is, the chemical conversion treatment It does not immediately improve the workability of the surface-treated steel sheet that has been painted or coated and the corrosion resistance of the machined part.

A chromium compound is added to the conventional chemical conversion coatings and coatings of surface-treated steel sheets for the purpose of improving corrosion resistance, but in recent years, from the viewpoint of environmental protection, non-chromate containing no chromium compound has been added. Film formation has become an important issue. However, such a non-chromate coating has low corrosion resistance, and it is particularly difficult to improve the corrosion resistance of the hot-dip Al—Zn-based plated steel sheet to a level satisfying the corrosion resistance. Therefore, an object of the present invention is to provide a non-chromate surface treatment that uses a hot-dip Al-Zn-based plated steel sheet having an Al content in the plating film of 20 to 95 mass% as a base steel sheet and that has excellent workability and corrosion resistance of the processed portion which have not been obtained in the past. It is to provide a steel sheet and a manufacturing method thereof.

[0010]

In order to solve the above problems, the inventors of the present invention have a viewpoint of the performance as a practical product, that is, a surface-treated steel sheet in which a coating layer such as a chemical conversion treatment is formed on a molten Al-Zn system plated steel sheet. And determined the optimum composition of the plating film and the coating layer to improve the workability and the corrosion resistance of the processed part. As a result, the hot-dip Al—Zn-based plated steel sheet was subjected to a specific heat history, and a specific non-chromate coating layer was formed on the surface of the plated film, which was extremely excellent in the past and could not be achieved. It has been found that workability and corrosion resistance of the processed part can be obtained.

The present invention has been made on the basis of such findings, and its features are as follows. [1] A surface-treated steel sheet having a coating layer on the surface of a molten Al—Zn-based plated steel sheet having an Al content of 20 to 95 mass% in the plating film, wherein the plating film is at least the following:
(a) and the following (b) is a plating film obtained through the thermal history, the coating layer is a single-layer or multi-layer coating containing an organic resin and an inorganic component and containing no chromium, the coating A surface-treated steel sheet excellent in workability and corrosion resistance in a worked part, characterized in that an adhesion amount is 0.1 g / m ² or more and less than 5 g / m ² . (a) A thermal history in which the steel plate has an average cooling rate of less than 11 ° C./sec for 10 seconds immediately after leaving the hot dip bath (b) 130% after the hot dip plated metal has solidified
Up to a temperature T (° C.) in the range of 300 ° C., and then the average cooling rate from the temperature T (° C.) to 100 ° C. satisfies C (° C./hr) or less shown in the following formula (1). Thermal history and / or 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 formula (1)
Thermal history satisfying the following C = (T-100) / 2 (1)

[2] In the surface-treated steel sheet according to the above [1], the coating layer has an inorganic component such as phosphoric acid, phosphate, silica, silane coupling agent, Ca, Mn, Mg, Ni, Co,
Fe, Ca-based compounds, Mn-based compounds, Mg-based compounds, N
A surface-treated steel sheet having excellent workability and corrosion resistance in a worked part, which contains one or more selected from i-based compounds, Co-based compounds, and Fe-based compounds. [3] In the surface-treated steel sheet according to the above [1] or [2], the temperature T (° C.) of the heat history of (b) is in the range of 130 to 200 ° C. Excellent surface-treated steel sheet. [4] In the surface-treated steel sheet according to any one of the above [1] to [3],
A surface-treated steel sheet having excellent workability and corrosion resistance in a worked part, wherein the plating film contains 0.01 to 10 mass% in total of one kind or two kinds or more selected from Mg, V, and Mn.

[5] The surface-treated steel sheet according to any one of the above [1] to [4], characterized in that the coating layer is a single-layer coating and is excellent in workability and corrosion resistance in the processed portion. [6] In the surface-treated steel sheet according to any one of the above [1] to [4],
A surface-treated steel sheet having excellent workability and corrosion resistance in a processed part, characterized in that the coating layer is composed of multiple layers, the lower layer contains an inorganic component, and the upper layer contains an organic resin. [7] A coated steel sheet having a single-layer or multi-layer coating film formed on the surface of the surface-treated steel sheet according to any one of the above [1] to [6].

[8] The Al content in the plating film is 20 to 9
A method for producing a surface-treated steel sheet having a coating layer on the surface of a 5 mass% hot-dip Al-Zn-based plated steel sheet, the method comprising:
(a) and (b) the process of imparting heat history, and (a) the average cooling rate for 10 seconds immediately after the steel sheet leaves the hot dip bath is 11 ° C.
Heat history of less than / sec (b) After the hot dip plated metal has solidified, the temperature T in the range of 130 to 300 ° C.
The temperature is raised to (° C.) and then heated from the temperature T (° C.) to 10
The average cooling rate up to 0 ° C is C (° C / h
r) The heat history satisfying the following conditions, and / or the average cooling rate from the temperature T (° C) in the range of 130 to 300 ° C to 100 ° C after the hot dip plated metal is solidified is as follows.
Thermal history C = (T-100) / 2 satisfying C (° C / hr) or less shown in the formula (1) (1) The surface of the plated steel sheet contains an organic resin and an inorganic component and contains chromium. A single layer or a multi-layer, which has a step of forming a coating layer having a coating amount of 0.1 g / m ² or more and less than 5 g / m ² and is excellent in workability and corrosion resistance of a processed portion. Method for manufacturing surface-treated steel sheet.

[9] In the manufacturing method of the above-mentioned [8], the coating layer has an inorganic component such as phosphoric acid, phosphate, silica, a silane coupling agent, Ca, Mn, Mg, Ni, Co, F.
e, Ca-based compound, Mn-based compound, Mg-based compound, Ni
A method for producing a surface-treated steel sheet having excellent workability and corrosion resistance in a worked part, which comprises one or more selected from a group-based compound, a Co-based compound, and a Fe-based compound. [10] In the manufacturing method of the above [8] or [9], the heat history temperature T (° C) of (b) is in the range of 130 to 200 ° C, which is excellent in workability and corrosion resistance of the processed portion. Method for manufacturing surface-treated steel sheet. [11] In the manufacturing method according to any one of the above [8] to [10], the plating film is one or two selected from Mg, V, and Mn.
A method for producing a surface-treated steel sheet excellent in workability and corrosion resistance of a worked part, characterized by containing 0.01 to 10 mass in total of at least one kind.

[12] In the manufacturing method according to any one of the above [8] to [11], the heat history of (b) is applied to the plating film,
A method for producing a surface-treated steel sheet excellent in workability and corrosion resistance of a worked part, which is carried out in at least one of the following (1) to (4). (1) Before coating layer formation (2) During coating layer drying process (3) After coating layer formation (4) Cooling process after solidification of hot-dip plated metal [13] Above [8] ~ [ 12] In the manufacturing method according to any one of [12], the step of forming the coating layer on the surface of the plating film includes the step of forming a single-layer chemical conversion treatment film, which has excellent workability and corrosion resistance in the processed part. Method for manufacturing treated steel sheet.

[14] In the manufacturing method according to any one of the above [8] to [12], the step of forming a coating layer on the surface of the plating film forms at least a film containing an inorganic component on the surface of the plating film. And a step of forming a film containing an organic resin on the upper layer thereof, the method for producing a surface-treated steel sheet excellent in workability and corrosion resistance of a worked portion. [15] Manufacture of a coated steel sheet, characterized in that, in addition to the steps of the manufacturing method according to any one of [8] to [14], the method further comprises a step of applying one coat or two or more coats to the coating layer surface. Method.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The surface-treated steel sheet of the present invention is a molten Al-Z containing 20 to 95 mass% of Al in the plating film.
The n-based plated steel sheet is used as the base steel sheet. From the viewpoint of corrosion resistance and the like, the more preferable range of the amount of Al in the plating film is 45.
~ 65 mass%. In addition, a particularly preferable component composition of the plating film is Al: 45 to 65 mass%, Si: 0.7 to
2.0 mass%, Fe: less than 10 mass%, the balance being substantially Zn containing unavoidable impurities, and particularly such a composition exhibits excellent corrosion resistance.

Further, one or two or more kinds selected from Mg, V and Mn are added to the plating film in a total amount of 0.01 to.
By containing 10 mass%, the corrosion resistance and workability can be further improved. If the total content of these elements is less than 0.01 mass%, a sufficient effect cannot be obtained. On the other hand, if the total content exceeds 10 mass%, the corrosion resistance improving effect is saturated, and the coating becomes hard, so that the workability is deteriorated.

However, it is difficult to obtain a high corrosion resistance of the worked part only by the plating composition of the above-mentioned hot-dip Al—Zn plated steel sheet, and it is necessary to undergo the heat history described later and to combine it with the upper coating layer. For the first time, excellent corrosion resistance of the processed part can be obtained. Further, the coating amount of the molten Al—Zn based plated steel sheet is not particularly limited, but it is generally suitable that the coating amount is about 30 to 200 g / m ² per one surface.

Further, the plating film of the hot dip Al-Zn system plated steel sheet needs to be a plating film obtained through at least the following heat history (a) and (b). (a) Thermal history in which the average cooling rate for the first 10 seconds immediately after the steel sheet leaves the hot dip coating bath is less than 11 ° C./sec (b) After the hot dip plated metal has solidified, 130
Up to a temperature T (° C.) in the range of 300 ° C., and then the average cooling rate from the temperature T (° C.) to 100 ° C. satisfies C (° C./hr) or less shown in the following formula (1). Thermal history and / or 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 formula (1)
Thermal history satisfying the following: C = (T-100) / 2 (1) Further, in the thermal history of (b) above, the more preferable range of the temperature T (° C) is 130 to 200 ° C. Where above
The formula (1) is a detailed study based on experiments by the present inventors on the effect that the heating and heating conditions of the plating film and the subsequent cooling conditions and the cooling conditions after the solidification of the plated metal of the hot-dip plated film affect the plating film. This is a derived empirical formula.

By subjecting the plating film to the heat history of the above (a) and (b), the workability (crack resistance etc.) of the molten Al-Zn system coating is remarkably improved. . It is considered that the workability of the plating film is remarkably improved by passing through the thermal history of the above (a) and (b) for the following reasons. First, immediately after the steel sheet exits the hot dip coating bath, the thermal history of (a) above, that is, the heat history of sufficiently slowing the average cooling rate for 10 seconds immediately after leaving the hot dip coating bath, results in the hot dip coating Is closer to the equilibrium state than the solidification in the normal cooling process, diffusion in the semi-molten state promotes two-phase separation of Al and Zn, and as a result, the plating film is softened. Then, the plating film that has undergone such heat history is further heated to the heat history of (b) above, that is, in the temperature range of 130 to 300 ° C. (preferably 130 to 200 ° C.), and then slowly cooled under specific conditions. Heat history, or / and 130 to 300 ° C. (preferably 130 to 2) after solidification of the plating film
By passing through a thermal history of being gradually cooled from a 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 heat history of
The two-phase separation of 1 and Zn is promoted more effectively. As a result of these, it is considered that the plating film is remarkably softened and the workability thereof is remarkably improved.

Therefore, such a softening of the plating film and a conspicuous improvement in workability associated therewith are caused by the above (a) and (b).
This is due to the combined action of the heat history of, and it is difficult to achieve by only one heat history.

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

FIG. 1 shows the results obtained by investigating the influence of the average cooling rate of the plating film for the first 10 seconds immediately after the steel sheet leaves the hot dip coating bath on the workability of the surface-treated steel sheet. Each of the test materials is a surface-treated steel sheet in which a coating layer satisfying the conditions of the present invention is formed on a plated steel sheet whose plating film has undergone the heat history of (b) above. The evaluation of the workability in this test was carried out according to the evaluation of the workability of 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 0T bending is 2 points or less. Is. On the other hand, when the average cooling rate of the plating film is less than 11 ° C./sec, the workability score is 4 or more, which shows that the workability is remarkably improved.

In order to obtain a plating film that has undergone the heat history of (a) above, the temperature between the hot dip bath surface of the continuous hot dip galvanizing equipment and the roll that comes out of the hot dip bath first comes into contact with the steel sheet. It is necessary to provide an adjusting device and control the cooling rate of the plating film by this temperature adjusting device. It is preferable that the temperature adjusting device is provided with a heating or heat retaining means and, if necessary, a cooling means. This 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 (top roll, etc.) and picks up on the roll surface. The purpose is to prevent An induction heater, a gas heating furnace, or the like can be used as the heating or heat retaining means of the temperature adjusting device, and a gas spraying device or the like can be used as the cooling means. However, there is no special limitation on the method, shape, scale, etc. of the heating or heat retaining means or cooling means included in the temperature adjusting device, as long as it can impart the thermal history of (a) to the plating film. Good.

Next, regarding the thermal history of (b) above,
130-300 the plating film that has undergone the heat history of (a) (the plating film after the hot-dip plated metal has solidified)
° C, preferably temperature T (° C) in the range of 130-200 ° C
Or by hot-dip heating, and then cooling so that the average cooling rate from temperature T (° C) to 100 ° C is equal to or lower than C (° C / hr) shown in the above formula (1), or hot dip plating is performed. The average cooling rate from the temperature T (° C.) in the range of 130 to 300 ° C. to 100 ° C., which is the cooling process of the plated film after solidification of the plated metal, is C shown in 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 caused by the thermal history of (a)
The two-phase separation of is more effectively promoted. The combined action of such a heat history and the heat history of (a) above makes the plating film extremely soft and the workability thereof is significantly improved.

When the heating temperature T for heating the plating film in the heat history of (b) above is less than 130 ° C., the above-mentioned action cannot be sufficiently obtained, while the heating temperature T for heating is 300.
Above ℃, it promotes the growth of the alloy phase at the interface between the base steel sheet and the plating film, which adversely affects the workability.
From this point of view, the upper limit of the heating temperature T that 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 is solidified,
Also in the case where the cooling is performed under the condition that the thermal history of (b) is given, if the temperature T is lower than 130 ° C., the above-described action cannot be sufficiently obtained.

FIG. 2 (a) is a graph showing the effect of the heating temperature of the plating film on the workability of the surface-treated steel sheet when the plated steel sheet after the hot-dip galvanized metal is solidified is heat-treated. In each of the test materials from which this result was obtained, the average cooling rate of the plating film from the elevated heating temperature to 100 ° C. was within the thermal history condition of (b) above, and the plating film was above ( It is a surface-treated steel sheet in which a coating layer satisfying the conditions of the present invention is formed on a plated steel sheet produced through the heat history of a). The evaluation of the workability in this test was carried out according to the evaluation of the workability of Examples described later.

FIG. 2 (b) shows the average cooling rate of the plating film (average cooling rate from the heating temperature to 100 ° C.) when the plated steel sheet after the hot-dip galvanized metal is solidified is heat-treated. Is to investigate the influence on the workability of the surface-treated steel sheet, the test material obtained this result, the heating temperature of the plating film is within the conditions of the thermal history of the above (b), Further, it is a surface-treated steel sheet in which a coating layer is formed on a plated steel sheet whose plating film has undergone the thermal history of (a) above. The evaluation of the workability in this test was carried out according to the evaluation of the workability of Examples described later.

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

In order to make the plating film pass through the heat history of the above (b), a heating or heat-retaining device for heat-treating or heat-retaining the plating film is provided inside or outside the continuous hot dip plating equipment. Then, 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-air stove, etc.) may be provided in the continuous hot dip galvanizing equipment to perform continuous in-line heating, or offline after winding the coil. It may be carried out by heating in batch. Further, in a continuous processing facility outside the plating line, a heating mechanism (for example, an induction heater, a gas heating furnace,
It may be performed by continuous heating with a hot air oven or the like). Further, appropriate heat retention or heat retention may be carried out after winding the coated steel sheet which has been continuously heated in the plating line or in the above-mentioned continuous treatment equipment on a coil. In addition, a heat retaining device may be provided so that the plating film can be retained and gradually cooled in the cooling process after the hot-dip plated metal is solidified. However, there is no particular limitation on the method, shape, scale, etc. of the heating or heat retaining device, and any method may be used as long as it can impart the thermal history of (b) to the plating film.

By forming a specific non-chromate coating layer on the surface of the plating film that has undergone the heat history of (a) and (b) as described above, this surface-treated steel sheet has extremely excellent workability and corrosion resistance in the worked portion. Indicates.

The surface-treated steel sheet of the present invention has a specific coating layer on the surface of the plating film described above. This coating layer is a single-layer or multi-layer coating containing an organic resin and an inorganic component and containing no chromium. The organic resin contained in the coating layer has an effect of improving both processability and processed portion corrosion resistance. The type of organic resin is not particularly limited, but for example, acrylic resin, urethane resin, olefin resin, epoxy resin, etc. can be used.

The inorganic component contained in the coating layer has the effect of improving corrosion resistance. The above-mentioned organic resin alone is insufficient in corrosion resistance in the coating layer, and the desired corrosion resistance can be obtained by adding this inorganic component. As the inorganic component, phosphoric acid, phosphate (eg, zinc phosphate, aluminum phosphate, magnesium phosphate, calcium phosphate, etc.), silica, silane coupling agent (eg, aminosilane-based, isocyanate-based, mercapto-based, epoxy-based) , Vinyl-based, methacryloxy-based silane coupling agents), Ca, Mn, Mg, Ni, Co,
Fe, Ca-based compounds (eg calcium silicate, calcium carbonate etc.), Mn-based compounds (eg manganese nitrate etc.), Mg-based compounds (eg magnesium nitrate, magnesium acetate etc.), Ni-based compounds (eg nickel acetate) , Nickel nitrate, etc.), Co-based compounds (eg, cobalt acetate, cobalt nitrate, etc.), Fe-based compounds (eg, iron nitrate, etc.), and the like, and one or more of these can be used. By dissolving or dispersing these inorganic components in the treatment liquid for forming a film (for metals, dissolving or dispersing in the form of metal ions or fine powder),
It can be a coating component.

The coating layer may be a single layer or multiple layers (plural layers), but the organic resin and the inorganic component may be contained in one coating film (layer), or may be contained in separate coating films (layers). You may make it contain each. That is, when the coating layer is a single layer, the organic resin and the inorganic component are contained in the coating, while when the coating layer is a multilayer, for example, the inorganic coating is contained in the lower layer (or It is also possible to form a film made of the above-mentioned inorganic component) and to add an organic resin to the film above it (or make it a film made of the above-mentioned organic resin). Further, an organic resin and an inorganic component may be contained in at least one of the multi-layer coatings.

Adhesion amount of coating layer (when the coating layer is a multilayer
Is its total adhesion amount) is 0.1 g / m ^Two5g / m or more^TwoNot yet
Full, preferably 1.0 g / m^Two5g / m or more^TwoIs less than
It Adhesion amount is 0.1g / m^TwoBelow, sufficient corrosion resistance is obtained
Not possible, while 5g / m^TwoWith the above, the film is peeled off by processing
It becomes easy to separate. In addition, the workability and corrosion resistance of the processed part are particularly good.
To be preferable, the solid content of the organic resin and the above-mentioned inorganic components in the coating layer
The mass ratio of the components is [organic resin]: [inorganic component] = 100:
1 to 100, more preferably 100: 1 to 50
Is good. The ratio of the inorganic component to 100 parts of the organic resin is 1
If the amount is less than the range, sufficient corrosion resistance cannot be obtained. Also, organic resin
When the ratio of the inorganic component exceeds 100 parts with respect to 100 parts
The coating makes the coating easier to peel off.

Next, a method of manufacturing the surface-treated steel sheet according to the present invention will be described. In the production method of the present invention, a molten Al—Zn-based plated steel sheet having an Al content in the plating film produced by a continuous hot dip coating facility or the like of 20 to 95 mass% is used as a base steel sheet, and a coating layer is formed on the surface thereof. It is a method for producing a surface-treated steel sheet, the plating film of the steel sheet leaving the hot dip plating bath, at least a step of applying a thermal history of the following (a) and (b), a specific coating layer on the surface of the plated steel sheet And a step of forming. (a) A thermal history in which the steel plate has an average cooling rate of less than 11 ° C./sec for 10 seconds immediately after leaving the hot dip bath (b) 130% after the hot dip plated metal has solidified
Up to a temperature T (° C.) in the range of 300 ° C., and then the average cooling rate from the temperature T (° C.) to 100 ° C. satisfies C (° C./hr) or less shown in the following formula (1). Thermal history and / or 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 formula (1)
Thermal history satisfying the following C = (T-100) / 2 (1)

Of the thermal histories (a) and (b) given to the plating film, the thermal history (a) is given by controlling the cooling conditions of the plating film immediately after plating. In order to impart this heat history of (a) to the plating film, as described above, temperature adjustment is performed from the hot dip bath surface of the continuous hot dip galvanizing equipment to the roll that the steel plate that leaves the hot dip 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, it is preferable that the temperature adjusting device is provided with heating or heat retaining means and, if necessary, with cooling means.
There is no particular limitation on the method, shape, scale, etc. of the heating or heat retaining means or the cooling means, and any method may be used as long as it can impart the heat history of (a) to the plating film. An induction heater, a gas heating furnace, or the like can be used as the heating or heat retaining means of the temperature adjusting device, and a gas spraying device or the like can be used as the cooling means.

Further, the heat history of (b) is given by performing a specific heat treatment on the plated steel sheet after the hot dip plated metal is solidified or after the hot dip plated metal is solidified. This is done by controlling the cooling of the plating film by heat retention. In the production method of the present invention, a specific coating layer is formed on the plating film surface of the plated steel sheet, but the heat treatment for imparting the thermal history of (b) to the plating film is performed before forming the coating layer and drying the coating layer. During the process
It may be carried out at any stage after the formation of the coating layer (after the coating of the treatment liquid and the formation of the film by the drying step thereof). 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 (1) to (4). (1) Before forming the coating layer (2) During the drying step of the coating layer (3) After forming the coating layer (4) Cooling process after the hot-dip galvanized metal is solidified. The method (1) has an advantage that each condition of the heat treatment step and the coating layer forming step can be optimized independently, and the method (2) is suitable for performing all the treatments in the continuous hot dip plating equipment.
Further, the method (2) is particularly economical because the heat treatment is performed by utilizing the heating in the drying step for forming the coating layer.

The heat treatment or heat retention for imparting the heat history of the above (b) is performed by a heating or heat retaining device provided inside or outside the continuous hot dip plating equipment. A continuous heating system (for example, an induction heater, a hot air oven, etc.) may be installed in the continuous hot dip galvanizing facility to continuously heat the product in-line, or the coil may be wound into a coil and then batch-heated offline. Good. Alternatively, continuous heating may be performed by a heating mechanism (for example, an induction heater, a hot air oven, etc.) in a continuous processing facility outside the plating line. Further, appropriate heat retention or heat retention may be carried out after winding the coated steel sheet which has been continuously heated in the plating line or in the above-mentioned continuous treatment equipment on a coil. Also,
A heat retention device may be provided so that the plating film can be heated and gradually cooled in the cooling process after the hot-dip plated metal is solidified. However, there is no particular limitation on the method, shape, scale, etc. of the heating or heat retaining device, and any method may be used as long as it can impart the thermal history of (b) to the plating film. The preferable plating composition of the manufactured molten Al—Zn-based plated steel sheet, the coating amount, the reasons for limiting the thermal history of the above (a) and (b), and the obtained effect and the like are as described above.

In the step of forming a specific coating layer on the surface of the plated steel sheet, the surface of the plated steel sheet is a single layer or a multi-layer containing an organic resin and an inorganic component and containing no chromium, and the amount of coating adhered is A coating layer of 0.1 g / m ² or more and less than 5 g / m ² is formed. The step of forming this coating layer and the above
The context of the step (b) of applying the heat history is as described above. The types of the organic resin and the inorganic components are as described above, and the treatment liquid in which these are dissolved or dispersed (for metals, dissolved or dispersed in the form of metal ions or fine powder) is applied to the plated steel plate surface, The coating layer can be formed by drying. Usually after applying the treatment liquid,
Drying is performed at 80 to 300 ° C. without washing with water.

As described above, the coating layer may be a single layer or multiple layers (plural layers). Therefore, a single-layer coating layer containing the organic resin and the inorganic component may be formed on the surface of the plating film, or when the coating layer is a multilayer,
It is also possible to form a film containing the above-mentioned inorganic component (or a film consisting of the above-mentioned inorganic component) on the surface of the plating film, and form a film containing an organic resin (or a film consisting of the above-mentioned organic resin) on the upper layer. Further, an organic resin and an inorganic component may be contained in at least one of the multi-layer coatings.

A coated steel sheet can be obtained by forming a single-layer or multi-layer coating film on the surface of the surface-treated steel sheet of the present invention described above. Examples of the coating film include a polyester resin coating film, an epoxy resin coating film, an acrylic resin coating film, a urethane resin coating film, and a fluororesin coating film.
Further, for example, an epoxy resin-modified polyester resin-based coating film obtained by modifying a part of the above resin with another resin can also be applied. Further, a curing agent, a curing catalyst, a pigment, an additive and the like can be added to the above resin as needed. The coating method for forming a coating film on the surface of the surface-treated steel sheet is not particularly specified, but examples of the coating method include roll coater coating, curtain flow coating and spray coating. After coating the paint, it is generally heated and dried by means of hot air drying, infrared heating, induction heating or the like to form a coating film.

[0046]

[Example] [Example 1] A cold-rolled steel sheet (sheet thickness: 0.5 mm) produced by a conventional method was passed through a continuous hot dip galvanizing facility, and
Hot-dip plating was performed using various hot-dip Al-Zn based plating baths having bath compositions equivalent to the plating film compositions shown in Table 6. The line speed was set to 160 m / sec, and the amount of coating on one side was set so that the variation between the steel plates was within the range of 75 to 90 g / m ² .

In the manufacturing process of this plated steel sheet, the thermal history (I) and (II) shown in Tables 1 to 6 were applied to the plating film and a coating layer was formed on the surface of the plating film. In forming the coating layer, a treatment liquid in which an organic resin and an inorganic component were dissolved or dispersed was applied to the plated steel plate surface and heated and dried at 150 ° C. Moreover, about some Examples (No. 11, No. 12), after applying the processing liquid which melt | dissolved the metal ion to the plated steel plate surface and heat-drying at 120 degreeC, the organic resin and the inorganic component were made to the upper layer. The treatment liquid in which was dissolved or dispersed was applied, and dried by heating at 150 ° C. The surface-treated steel sheet thus manufactured was evaluated for workability and processed portion corrosion resistance by the following methods. The results are shown in Tables 1 to 6.

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

(2) Corrosion resistance of the processed part After the surface-treated steel plate was bent by 3T, it was placed in a wet tester at 50 ° C. and 98% RH or more, and the state of rust generation from the bent part after 1000 hours was observed, The following criteria were evaluated. 5: No abnormality 4: Light white rust and black rust occurred on part 3: Light white rust and black rust occurred on the entire surface 2: Significant white rust and black rust occurred on the entire surface 1: Red rust occurred Yes

[0050]

[Table 1]

[0051]

[Table 2]

[0052]

[Table 3]

[0053]

[Table 4]

[0054]

[Table 5]

[0055]

[Table 6]

[0056]

As described above, the surface-treated steel sheet of the present invention uses a molten Al-Zn-based plated steel sheet having an Al content in the plating film of 20 to 95 mass% as a base steel sheet and further has a non-chromate coating layer. Despite being a surface-treated steel sheet, it has extremely excellent workability and corrosion resistance in the processed part. Further, according to the manufacturing method of the present invention, such a surface-treated steel sheet can be stably manufactured with high productivity.

[Brief description of drawings]

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

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

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C23C 22/22 C23C 22/22 28/00 28/00 C (72) Inventor Toshihiko Oi Chiyoda-ku, Tokyo Marunouchi 1-2, Nihon Steel Pipe Co., Ltd. (72) Inventor Keiji Yoshida 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Pipe Co., Ltd. (72) Junichi Inagaki, Marunouchi, Chiyoda-ku, Tokyo 1st and 2nd Nihon Steel Pipe Co., Ltd. (72) Inventor Masaaki Yamashita 1st and 2nd Marunouchi, Chiyoda-ku, Tokyo 1st Nihon Steel Pipe Co., Ltd. (72) Inventor Yasuhiro Majima Mizue Kawasaki-ku, Kawasaki-shi, Kanagawa 6-1 NK NK Steel Plate Co., Ltd. (72) Inventor Nobuyuki Ishida 6-1 Mizue-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa NKK Steel Plate Co., Ltd. (72) Inventor Yu Fukushima F-term in NK Steel Sheet Co., Ltd. 6-1 Mizue-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture (reference) 4K026 AA02 AA13 BA03 BA05 BA12 BB08 BB09 CA16 CA18 CA23 4K027 AA05 AA22 AB05 AB26 AB44 AB48 AC76 AE03 AE12 AE18 4K044 AA02 BA10 BA10 BA21 BC02 BC05 CA11 CA16 CA53

Claims (15)

[Claims] 1. The content of Al in the plating film is 20 to 95.
A surface-treated steel sheet having a coating layer on the surface of a mass% hot-dip Al-Zn-based plated steel sheet, wherein the plating film is a plating film obtained through at least the following thermal history (a) and (b). The coating layer is a single-layer or multi-layer coating containing an organic resin and an inorganic component and containing no chromium, and the coating adhesion amount is 0.1 g / m ² or more and less than 5 g / m ^2. A surface-treated steel sheet with excellent workability and corrosion resistance. (a) A thermal history in which the steel plate has an average cooling rate of less than 11 ° C./sec for 10 seconds immediately after leaving the hot dip bath (b) 130% after the hot dip plated metal has solidified
Up to a temperature T (° C.) in the range of 300 ° C., and then the average cooling rate from the temperature T (° C.) to 100 ° C. satisfies C (° C./hr) or less shown in the following formula (1). Thermal history and / or 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 formula (1)
Thermal history satisfying the following C = (T-100) / 2 (1) 2. The coating layer comprises an inorganic component such as phosphoric acid, a phosphate, silica, a silane coupling agent, Ca, Mn, and M.
g, Ni, Co, Fe, Ca-based compound, Mn-based compound,
The surface excellent in workability and processed portion corrosion resistance according to claim 1, which contains one or more selected from a Mg-based compound, a Ni-based compound, a Co-based compound, and an Fe-based compound. Treated steel plate. 3. The thermal history temperature T (° C.) of (b) is 130 to
It is in the range of 200 ° C. 3.
A surface-treated steel sheet with excellent workability and corrosion resistance in the processed part. 4. The plating film contains 0.01 to 10 mass% in total of one or more selected from Mg, V and Mn.
A surface-treated steel sheet having excellent workability and corrosion resistance in a worked portion according to claim 1, 2 or 3, characterized in that it is contained. 5. The surface-treated steel sheet excellent in workability and corrosion resistance in a worked portion according to claim 1, wherein the coating layer is a single-layer coating. 6. The coating film according to claim 1, 2, 3 or 4, wherein the coating layer is a multi-layer coating, the lower coating contains an inorganic component, and the upper coating contains an organic resin. Surface-treated steel sheet with excellent workability and corrosion resistance in the processed part. 7. A coated steel sheet, wherein a single-layer or multi-layer coating film is formed on the surface of the surface-treated steel sheet according to claim 1, 2, 3, 4, 5 or 6. 8. The content of Al in the plating film is 20 to 95.
A method for producing a surface-treated steel sheet having a coating layer on the surface of a mass% hot-dip Al-Zn-based steel sheet, wherein at least the following (a) and (b) are applied to the plating film of the steel sheet that has left the hot-dip plating bath. And (a) the heat history in which the average cooling rate for 10 seconds immediately after the steel sheet leaves the hot dip coating bath is less than 11 ° C / sec (b) the hot-dipped galvanized metal solidifies After 130
Up to a temperature T (° C.) in the range of 300 ° C., and then the average cooling rate from the temperature T (° C.) to 100 ° C. satisfies C (° C./hr) or less shown in the following formula (1). Thermal history and / or 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 formula (1)
Thermal history satisfying the following: C = (T-100) / 2 (1) A single layer or multiple layers containing an organic resin and an inorganic component and containing no chromium on the surface of the plated steel sheet, and a film is attached. A step of forming a coating layer having an amount of 0.1 g / m ² or more and less than 5 g / m ² and a method for producing a surface-treated steel sheet having excellent workability and corrosion resistance in a processed part. 9. The coating layer comprises phosphoric acid, phosphate, silica, silane coupling agent, Ca, Mn, and M as inorganic components.
g, Ni, Co, Fe, Ca-based compound, Mn-based compound,
The surface excellent in workability and processed part corrosion resistance according to claim 8, containing one or more selected from Mg-based compounds, Ni-based compounds, Co-based compounds, and Fe-based compounds. Method for manufacturing treated steel sheet. 10. The heat history temperature T (° C.) of (b) is 130.
It is a range of -200 degreeC, The manufacturing method of the surface-treated steel sheet excellent in workability and corrosion resistance of a process part of Claim 8 or 9 characterized by the above-mentioned. 11. The process according to claim 8, 9 or 10, wherein the plating film contains 0.01 to 10 mass in total of one or more selected from Mg, V and Mn. Of a surface-treated steel sheet with excellent heat resistance and corrosion resistance in the processed part. 12. The method according to claim 8, wherein 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 worked part as described. (1) Before forming the coating layer (2) During the drying process of the coating layer (3) After forming the coating layer (4) Cooling process after solidification of the hot-dip plated metal 13. The workability according to claim 8, 9, 10, 11 or 12, wherein the step of forming the coating layer on the surface of the plating film comprises the step of forming a single layer film. Processed part: A method for producing a surface-treated steel sheet having excellent corrosion resistance. 14. A step of forming a coating layer on the surface of the plating film, at least a step of forming a film containing an inorganic component on the surface of the plating film, and a step of forming a film containing an organic resin on the upper layer thereof. The method for producing a surface-treated steel sheet having excellent workability and corrosion resistance in a worked portion according to claim 8, 9, 10, 11 or 12. 15. Claims 8, 9, 10, 11, 12, 1
3. A method for producing a coated steel sheet, which comprises, in addition to the steps of the production methods described in 3 and 14, further a step of applying one coat or two or more coats to the coating layer surface.