JP2002173754A - Hot-dip galvanized steel sheet and method for producing the same - Google Patents

Abstract

(57) [Problem] To provide a hot-dip galvanized steel sheet excellent in both spot weldability and plating adhesion and a method for producing the same. SOLUTION: B is 1 to 20 massppm and / or P is
A steel sheet containing 0.010 to 0.050 mass% has a hot-dip galvanized layer on at least one surface, and / or the total amount of Al in the plated layer: X (g / m ² ), and Fe—
Hot-dip galvanized steel sheet whose Al content in Al intermetallic compound: Y (g / m ² ) and coating weight: W (g / m ² ) satisfy the following formulas (1) and (2): Manufacturing method of galvanized steel sheet. Y / (X−0.0012W) ≦ 0.90 ... (1), 0.10 ≦ X−0.0012
W… (2)

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot-dip galvanized steel sheet used for automobiles and the like, and more particularly to a hot-dip galvanized steel sheet excellent in spot weldability and plating adhesion and a method for producing the same.

[0002]

2. Description of the Related Art Galvanized steel sheets have been put to practical use in Japan and overseas as rust-resistant steel sheets for automobiles because of their excellent sacrificial corrosion resistance. Among them, hot-dip galvanized steel sheets and alloyed hot-dip galvanized steel sheets are currently the mainstream of rust-preventive steel sheets for automobiles because of their low production cost and high corrosion resistance.

[0003] One of the performances of galvanized steel sheet which is a problem in the automobile manufacturing process is spot weldability. As is well known, the weldability is closely related to the coating weight, and the weldability is improved by reducing the coating weight. However, if an attempt is made to provide a coating weight necessary for ensuring sufficient corrosion resistance as a steel sheet for automobiles, the spot weldability of a galvanized steel sheet is inferior to that of a cold-rolled steel sheet without plating.

[0004] With respect to the improvement of spot weldability of galvanized steel sheets, several proposals as described below have hitherto been made. For example, JP-A-63-230861 and the like disclose a technique for improving spot weldability by providing an oxide film mainly composed of ZnO on the surface of a galvanized steel sheet. Many proposals have been disclosed for improving spot weldability by providing an oxide film on the surface layer of zinc-based plating.

[0005] Recently, the amount of metal Zn in the outermost layer of the plating,
JP-A-10-330902, which defines the amount of Al ₂ O _3, and JP-A-2000-73183, which defines the amount of the oxide film and the ratio of the amount of the Zn oxide film in the oxide film to the amount of the Al oxide film, are disclosed. It has been disclosed. However, the above technique is a technique mainly for an alloyed hot-dip galvanized steel sheet.

[0006] That is, even in the same hot-dip galvanized steel sheet, a hot-dip galvanized steel sheet (non-alloyed hot-dip galvanized steel sheet) in which the coating layer is mainly a pure zinc layer and a hot-dip galvanized steel sheet
The welding behavior at the time of spot welding is fundamentally different from the alloyed hot-dip galvanized steel sheet made of Zn-Fe intermetallic compound, and the weldability of the hot-dip galvanized steel sheet is significantly higher than that of the galvannealed steel sheet. There is a problem of inferiority.

[0007] Regarding the relationship between the spot weldability of hot-dip galvanized steel sheet and the properties of the coating layer, several reports have been reported on the relationship between the Al content during plating and the spot weldability. Has a close relationship with the amount of Al in the plating, and it has been reported that the spot weldability deteriorates when the amount of Al increases. On the other hand, in recent years, the problem of appearance quality of hot-dip galvanized steel sheets based on dross adhesion, which was a conventional problem, is being solved. Therefore, the momentum for adopting hot-dip galvanized steel sheets (non-alloyed hot-dip galvanized steel sheets) as rust-preventive steel sheets for automobiles has been increasing.

[0008] Hot-dip galvanized steel sheets are advantageous in terms of production cost because they are not subjected to alloying treatment, and demand for anticorrosion steel sheets for automobiles is expected to grow in the future. Therefore, improvement of spot weldability of hot-dip galvanized steel sheet is strongly desired as a performance problem. As described above, the spot weldability of a hot-dip galvanized steel sheet can be improved by reducing the amount of Al during plating.

However, the addition of Al to the plating bath is originally performed to ensure the adhesion of the plating, and reducing the amount of Al in the plating to a predetermined level or less may deteriorate the adhesion of the plating. May invite. That is, when the Fe-Al intermetallic compound is present, the formation of the Fe-Zn alloy layer is suppressed, and good plating adhesion is ensured, but the plating is so performed that the formation of the Fe-Al intermetallic compound is insufficient. When the Al concentration in the layer decreases, the Fe-Zn alloying reaction proceeds, and the plating adhesion deteriorates.

Therefore, it is a contradictory problem to improve spot weldability and ensure plating adhesion in a hot-dip galvanized steel sheet. Conventionally, it has been technically required to improve spot weldability while maintaining good plating adhesion. Was difficult.

[0011]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, and provides a hot-dip galvanized steel sheet excellent in both spot weldability and plating adhesion, and a method of manufacturing the same. Aim.

[0012]

Means for Solving the Problems The present inventors have conducted intensive studies on the improvement of the spot weldability of the hot-dip galvanized steel sheet, and as a result, have found the following findings (1), (2) and (3). Reached. (1) In case of hot-dip galvanizing, 1-20 mass ppm of B
Or the addition of 0.010 to 0.050 mass% of P can significantly improve the continuous hitting property.

(2) Total amount of Al in the plating layer per unit area of plating adhesion: X and amount of Al in the Fe-Al intermetallic compound present at the plating / steel interface per unit area of plating adhesion:
By defining the relationship between Y and the plating adhesion amount per plating adhesion unit area: W, spot weldability can be improved in a state where good plating adhesion is secured.

(3) The hot-dip galvanized steel sheet described above has a plating bath temperature: Tb and a sheet temperature entering the plating bath: Te.
It can be manufactured by defining the relationship with the Al concentration in the plating bath: N _Al . That is, in the first invention, B is 1 to 20 mass ppm and / or P is 0.010 to 0.2.
A hot-dip galvanized steel sheet having a hot-dip galvanized layer on at least one side of a steel sheet containing 050 mass%.

[0015] The second invention is directed to a method of manufacturing a semiconductor device, wherein at least one side of a steel sheet has a total Al
Amount: X (g / m ² ), Amount of Al in Fe / Al intermetallic compound present at plating / steel interface at plating adhesion unit area: Y (g / m 2)
² ), and the amount of plating per unit area of plating:
A hot-dip galvanized steel sheet having a hot-dip galvanized layer whose W (g / m ² ) satisfies the following formulas (1) and (2).

Y / (X−0.0012 W) ≦ 0.90 (1) 0.10 ≦ X−0.0012 W (2) According to the third invention, B is 1 to 20 mass ppm and / or Alternatively, on at least one side of a steel sheet containing P from 0.01 to 0.050 mass%, the total Al in the plating layer per unit area of plating adhesion
Amount: X (g / m ² ), Amount of Al in Fe / Al intermetallic compound present at plating / steel interface at plating adhesion unit area: Y (g / m 2)
² ), and the amount of plating per unit area of plating:
A hot-dip galvanized steel sheet having a hot-dip galvanized layer whose W (g / m ² ) satisfies the following formulas (1) and (2).

Y / (X−0.0012 W) ≦ 0.90 (1) 0.10 ≦ X−0.0012 W (2) Further, the fourth invention is to provide a steel sheet in a hot-dip galvanizing bath. In the method for producing a hot-dip galvanized steel sheet that is dipped and then plated by plating, the bath temperature of the plating bath: Tb (° C.), the temperature of the plate entering the plating bath: Te (° C.), and the Al concentration in the plating bath: N _Al
A hot-dip galvanized steel sheet is manufactured by subjecting a steel sheet to hot-dip galvanizing under a condition where (mass%) satisfies all of the following formulas (3) to (5).

0 ≦ Te−Tb ≦ 50 …………… (3) 1000N _Al +300 ≦ Tb ≦ 1000N _Al +350 (4) 0.12 ≦ N _Al …………………… (5) In the fifth invention, a steel sheet containing 1 to 20 mass% of B and / or 0.010 to 0.050 mass% of P is immersed in a hot-dip galvanizing bath, and then pulled up to perform plating. In the method for producing a hot-dip galvanized steel sheet, a plating bath temperature: Tb
(° C.), the temperature of the sheet entering the plating bath: Te (° C.) and the Al concentration in the plating bath: N _Al (mass%) satisfy the following conditions (3) to (5). This is a method for producing a hot-dip galvanized steel sheet, characterized by performing hot-dip galvanizing.

0 ≦ Te−Tb ≦ 50 …………… (3) 1000N _Al +300 ≦ Tb ≦ 1000N _Al +350 (4) 0.12 ≦ N _Al ………………… …………………(Five)

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The present inventors have developed a galvanized steel sheet (: GI, non-alloyed hot-dip galvanized steel sheet) to solve the above-mentioned problems.
As a result of earnestly studying the contradictory issues of improving spot weldability and ensuring plating adhesion, the following findings were found, and the present invention was reached.

That is, as a specific phenomenon at the time of spot welding of a hot-dip galvanized steel sheet, a galvanized layer melted by energization heating generates an electrode and a hot-dip Zn-Cu alloy, which penetrate into a ferrite grain boundary of a base material, It occurs that the electrode is easily welded to the steel plate. In addition, this phenomenon causes a part of the electrode tip to adhere to the steel plate side, resulting in severe electrode wear.

The above-mentioned phenomenon is remarkably exhibited in a hot-dip galvanized steel sheet made of an ultra-low carbon steel sheet developed to realize particularly good workability. The above phenomenon, which is considered to be caused by a kind of liquid metal brittleness, is affected by the cleanliness of the material grain boundaries. It would be more disadvantageous.

According to the present invention, various methods for suppressing the above-mentioned phenomenon of deteriorating the continuous hitting property were examined.
It has been found that the improvement of the weldability without deterioration of the workability of the material can be realized by adding a predetermined amount of grain boundary segregation element to the steel sheet. That is, 1-20 mass ppm of B
It has been clarified that the addition of P in an amount of 0.010 to 0.050 mass% suppresses a decrease in continuous hitting properties due to liquid metal embrittlement, and significantly improves the continuous hitting properties of a galvanized steel sheet. B to be contained is 1 masspp
If it is less than m, the effect of improving the continuous hitting property is insufficient, and if it exceeds 20 massppm, the effect is saturated and the cost is disadvantageous. Further, the content of P is 0.01
If the amount is less than 0 mass%, the effect of improving the continuous hitting point is insufficient, and if the amount exceeds 0.050 mass%, not only the effect is saturated but also it becomes difficult to secure sufficient workability of the material.

[0024] As the material steel plate, B and / or
Or, in addition to P, C: 0.0010 to 0.0050 mass%, Si: 0.00
5 to 0.050 mass%, Mn: 0.01 to 1.0 mass%, Al: 0.02 to
0.05 mass%, Ti: 0.0001-0.10 mass%, Nb: 0.0001-0.
The one containing 0.05 mass% and the balance being iron and unavoidable impurities is preferable. The reason is as follows. C: 0.0010 to 0.0050 mass% The present invention is mainly intended for automobile panels. As is well known, in recent years, panels for automobiles have been required to have good workability, particularly deep drawability for processing even complicated shapes. In order to ensure such workability,
The C content is preferably set to 0.0050 mass% or less. Also,
The lower limit is determined by the relationship between the effect and cost, but 0.0010
It is preferable to be at least mass%.

Si: 0.005 to 0.050 mass% When Si exceeds 0.050 mass%, the plating property tends to deteriorate, and it is preferable that the content be 0.050 mass% or less. Also, the lower limit is determined by the relationship between the effect and cost,
It is preferably at least 005 mass%. Mn: 0.01 to 1.0 mass% Mn is preferably set to 1.0 mass% or less from the viewpoint of a decrease in r value and corrosion resistance. The lower limit is determined by the relationship between the effect and the cost, but is preferably 0.01% by mass or more.

Al: 0.02 to 0.05 mass% Al is preferably added as a deoxidizing agent in an amount of 0.02 mass% or more. If the content is too large, inclusions increase, so that the content is preferably set to 0.05 mass% or less. Ti: 0.0001 to 0.10 mass% Ti is preferably added in an amount of 0.0001 mass% or more to fix N, which is a harmful substance in steel, as TiN. On the other hand, if the content is too large, TiC increases and the workability deteriorates.
% Is preferable.

Nb: 0.0001 to 0.05 mass% Nb is used as NbC to control hot-rolled crystal grains during hot-rolling.
Is preferably added in an amount of 0.0001 mass% or more in order to fix. Further, if added too much, the r value is reduced as fine precipitates, so that the content is preferably 0.05 mass% or less. Furthermore, in the present invention, it has been found that even if the material steel plates are the same, the continuous hitting properties are significantly different if the properties of the plating layers are different. In other words, the phenomenon that molten Zn-Cu penetrates into the grain boundaries of the steel sheet during spot welding of hot-dip galvanized steel sheet,
It was clarified that the higher the Al concentration in the molten zinc, the more pronounced. The Al concentration in this case means the concentration of Al dissolved in the molten zinc.

Further, it is apparent that the above-mentioned adverse effect on the spot weldability is affected not by the total amount of Al in the plating layer but by the amount of Fe-Al intermetallic compound generated at the plating / steel interface during plating. became. In other words, even if the amount of Al in the plating layer is the same, even if the amount of Fe-Al intermetallic compound is large, if the zinc plating layer melts during welding and the temperature rises above the plating bath temperature during hot-dip galvanizing, Since the saturation solubility of the Fe-Al intermetallic compound in the molten zinc increases, the Fe-Al intercalates into the molten zinc and is dissolved in the molten zinc. As a result, the Al concentration in the molten zinc, which adversely affects weldability, is disadvantageously increased.

On the other hand, when the generation amount of the Fe-Al intermetallic compound is reduced, there arises a problem that the plating adhesion is deteriorated. The present inventors have conducted various studies to solve the above-described problems, and as a result, even if the amount of Fe-Al intermetallic compound generated is small as a result, it is preferable that the amount of Al incorporated into the plating layer is large. An important finding that plating adhesion can be ensured has been obtained.

FIG. 1 is a longitudinal sectional view showing a layer structure of a hot-dip galvanized layer during hot-dip galvanizing. In FIG. 1, 1 is a plating layer, 2 is a Fe-Al intermetallic compound (: Fe-Al
Alloy layer), 3 indicates a zinc layer (η phase), 4 indicates a base steel sheet (: material steel sheet), 5 indicates a hot-dip galvanized steel sheet, and 6 indicates an Fe-Zn intermetallic compound (: Fe-Zn alloy layer).

Usually, when the Al concentration in the hot-dip galvanizing bath is high in hot-dip galvanizing, alloying hardly proceeds in the bath at the time of plating, and as shown in FIG. It is composed of almost two layers of an Fe-Al intermetallic compound (: Fe-Al alloy layer) 2 and a zinc layer (η phase) 3 generated at the plating / steel plate interface. On the other hand, under the plating conditions of the present invention described below, even in a plating bath having a high Al concentration, Zn-
The Fe alloying reaction proceeds.

When the Zn—Fe alloying reaction proceeds in the above-mentioned plating bath, Al in the molten zinc reacting with the base steel sheet 4
If the concentration is high, Al is taken into the Zn—Fe alloy layer 6 as shown in FIG. 1 (b), and the Al concentration in the entire plating layer increases. Cause amount plating adhesion is degraded when little Fe-Al intermetallic compound produced during galvanizing, interface gamma phase and gamma _1-phase and Zn-Fe alloy layer and the steel sheet produced in the plating bath It is for generating.

However, when the condition of the Al concentration in the plating bath is sufficiently high, the Zn—Fe alloy layer formed in the plating bath contains a sufficient amount of Al, and the formation of the Γ phase and the Γ ₁ phase is suppressed. As a result, good plating adhesion can be secured. Further, the hot-dip galvanized steel sheet of the present invention to be described later, even if a large amount of Al is contained in the coating layer, is actually redissolved during welding and increases the Al concentration in the molten zinc. Since the generated amount is small, good spot weldability can be secured.

The present invention provides a hot-dip galvanized steel sheet excellent in both spot weldability and plating adhesion based on the above-described principle found by the present inventors, and a method for producing the same. That is, the hot-dip galvanized steel sheet of the present invention is a hot-dip galvanized steel sheet that is excellent in both spot weldability and plating adhesion that satisfy the following formulas (1) and (2) with respect to the properties of the coating layer.

Y / (X−0.0012 W) ≦ 0.90 (1) 0.10 ≦ X−0.0012 W (2) In the above formulas (1) and (2), X: Total amount of Al in plating layer per unit area of plating adhesion (g
/ m ² ) Y: Plating per unit area of plating adhesion / Amount of Al in Fe-Al intermetallic compound present at steel plate interface (g / m ² ) W: Amount of plating adhesion per unit area of plating adhesion (g / m ² ) ² ) is shown.

As described above, in order to ensure good spot weldability, it is important where Al is taken in the plating layer. That is, the above η
Hot-dip galvanizing with good spot weldability, in which the amount of Al taken in the Fe-Al intermetallic compound is small, but the Zn-Fe alloying reaction is not suppressed during welding It becomes a steel plate.

According to the present invention, with respect to the properties of the plating layer, the amount of Al contained in other than the η phase satisfies the above formula (2), and the amount of Al in the Fe-Al intermetallic compound and the other than the η phase. It has been clarified that a galvanized steel sheet excellent in both plating adhesion and spot weldability can be obtained if the plating satisfies the above formula (1) with respect to the amount of Al contained.

That is, ΔY /
When the value of (X−0.0012 W)｝ exceeds 0.90, the effect of improving spot weldability cannot be obtained, and the above-mentioned formula (2)
If the value of {X-0.0012W} is less than 0.10, it will be difficult to ensure plating adhesion. In the present invention, the property of the plating layer is the following formula (6),
It is more preferable that the condition (7) is satisfied.

0.10 ≦ Y / (X−0.0012 W) ≦ 0.90 (6) 0.10 ≦ X−0.0012 W ≦ 0.50 (7) In the above formulas (6) and (7) X: Total amount of Al in the plating layer per unit area of plating adhesion (g
/ m ² ) Y: Plating per unit area of plating adhesion / Amount of Al in Fe-Al intermetallic compound present at steel plate interface (g / m ² ) W: Amount of plating adhesion per unit area of plating adhesion (g / m ² ) ² ) is shown.

This is because ΔY / (X−
When the value of 12 is less than 0.10, the amount of Fe dissolved from the steel sheet at the time of hot-dip galvanizing becomes excessive, leading to the generation of a large amount of dross. If the value of 0.0012 W｝ exceeds 0.50, the absolute amount of Al in the plating layer becomes too large, and the weldability deteriorates.

The coating weight of the hot-dip galvanized steel sheet of the present invention can be determined in accordance with the required corrosion resistance, and is not particularly limited. Per 20 ~
It is preferably 300 g / m ² , more preferably 20 to 100 g / m ²
Is more preferable. This means that the plating weight is 20
If it is less than g / m ² , the corrosion resistance will be reduced, and if it exceeds 300 g / m ² , the effect of improving corrosion resistance will be practically saturated and not economical.

The manufacturing method for obtaining the hot-dip galvanized steel sheet of the present invention in which the Zn-Fe alloy layer having a high Al concentration is formed and the amount of Al in the Fe-Al intermetallic compound is regulated is as follows.
It is necessary to satisfy the following conditions. That is, in order for the Al concentration of the plating bath to be in a state high enough to secure plating adhesion and for the Zn-Fe alloying reaction to proceed in the bath,
First, the plating bath temperature must be equal to or higher than the temperature at which alloying occurs, that is, the bath temperature must be equal to or higher than a predetermined temperature.

This is because the reaction rate of Zn—Fe alloying between the molten zinc and the steel sheet is higher as the plating bath temperature is higher, and furthermore, the production amount of the Fe—Al intermetallic compound is higher at the same Al concentration. This is because the higher the bath temperature, the smaller the bath temperature.
However, the important gist of the present invention is "Zn generated in a bath.
− From the viewpoint of `` securing the Al concentration in the Fe alloy layer '', it is not merely that the bath temperature is simply increased, but the plating bath temperature and the Al concentration in the plating bath are expressed by the following formula (4) and
(5) must be satisfied.

The _{1000N Al +300 ≦ Tb ≦ 1000N Al} +350 ...... (4) 0.12 ≦ N Al ............................................. (5) The above equation (4), (5) Medium, Tb: plating bath temperature (° C.) N _Al : Al concentration in plating bath (mass%).

That is, in the production method of the present invention,
Plating bath temperature: Tb needs to be equal to or more than {1000N _Al +300}. This is because if the Al concentration in the plating bath increases, the amount of the Fe-Al intermetallic compound increases and the amount of the Zn-Fe alloy layer decreases unless the bath temperature is raised accordingly. ) And (2) cannot be produced.

On the other hand, the plating bath temperature: Tb is ｛1000 N _Al +
It must be less than 350 mm. This is because if the plating bath temperature is too high, the amount of iron eluted from the steel sheet increases, and a problem arises that the amount of dross generated in the bath increases significantly. In the production method of the present invention, the Al concentration in the plating bath: N _Al must be 0.12 mass% or more.

This is because the Al concentration in the plating bath: N _Al is 0.12 ma.
If the content is less than ss%, it is not possible to secure the amount of Al taken in other than the η phase for maintaining the good plating adhesion described above. The Al concentration in the plating bath: N _Al is more preferably 0.5% by mass or less from the viewpoint of preventing weldability from being deteriorated due to incorporation of a necessary amount or more of Al into the plating layer.

In the present invention, the Al concentration in the plating bath is as follows:
N _Al (mass%) indicates the amount of Al (: Al concentration) actually dissolved at the bath temperature in the molten zinc of the plating bath, and is present in the bath as an Fe-Al intermetallic compound This is the value excluding the dross. Further, in the production method of the present invention, the plating bath temperature and the plate temperature entering the plating bath need to satisfy the following expression (3).

0 ≦ Te−Tb ≦ 50 (3) In the above formula (3), Tb: plating bath temperature (° C.) Te: plate temperature entering the plating bath (° C.)

That is, in the production method of the present invention,
The difference between the temperature of the sheet entering the plating bath and the temperature of the plating bath ｛Te -T
b｝ must be 0 ° C or higher and 50 ° C or lower. More preferably, it is 30 ° C. or more and 50 ° C. or less. This is because if the invading plate temperature is lower than the bath temperature, the bath temperature near the invading portion of the plate decreases, and the effect of raising the bath temperature to a certain temperature or higher is lost. This is because there is a problem that the amount of dross significantly increases due to the same reason as described above.

In the hot-dip galvanized steel sheet of the present invention, the Fe content in the coating layer is preferably 5 mass% or less, more preferably 2 mass% or less, in view of the non-alloyed hot-dip galvanized steel sheet (GI). More preferably, the content is 1 mass% or less. As described above, the present invention has been described.
The hot-dip galvanized steel sheet of the present invention contains one or more elements selected from the group consisting of Mg, Cr, Mn, Co, and Ni, for example, added for the purpose of improving the corrosion resistance of the hot-dip galvanized steel sheet. The hot-dip galvanized steel sheet containing these elements in the coating layer is also included in the hot-dip galvanized steel sheet of the present invention.

Further, in the production of a hot-dip galvanized steel sheet, in order to ensure the wettability of the plating, P
Elements such as b, Sb, Bi, As, Cd and Sn may be added, but in the method for producing a hot-dip galvanized steel sheet of the present invention, one kind selected from these elements is added in a hot-dip galvanizing bath. Or you may contain 2 or more types. Further, in the present invention, the steel type of the material steel sheet is not particularly limited, and a cold-rolled steel sheet used as a steel sheet for automobiles,
A hot-rolled steel sheet or the like may be used, and the mechanical properties of the raw steel sheet, the components in the steel, and the production method are not particularly limited.

[0053]

EXAMPLES The present invention will be described below more specifically based on examples. (Examples 1 to 17, Comparative Examples 1 to 5) An ultra-low carbon cold rolled steel sheet having the composition shown in Table 1 was used as a material, and hot-dip galvanizing was performed in a continuous hot-dip galvanizing line under the plating conditions shown in Table 2.

Next, with respect to the plating layer of the obtained hot-dip galvanized steel sheet, the plating layer was replaced with SbCl ₃ as an inhibitor.
Was dissolved in 5 mass% hydrochloric acid to which was added, and the solution was analyzed using an inductively coupled plasma emission spectrometer (ICP), and the total amount of Al and the total amount of Fe in the plating layer per unit area of plating adhesion (Fe content) ) And the amount of plating per unit area of plating.

Further, the plated steel sheet is immersed in fuming nitric acid,
After dissolving the pure zinc layer and the Zn-Fe alloy layer to leave only the Fe-Al intermetallic compound present at the plating / steel plate interface, the Fe-Al intermetallic compound was 5 mass% in the same manner as described above.
The solution was dissolved in hydrochloric acid, and the solution was analyzed by ICP to determine the amount of Al in the Fe-Al intermetallic compound per unit area of plating adhesion.

Table 1 shows the measurement results of the properties of the plating layer obtained above. In addition, the obtained hot-dip galvanized steel sheet was examined for the number of continuous spots during spot welding under the following welding conditions. In addition, the welding current value in the investigation of the number of continuous hit points is such that the current value: I ₁ (kA) at which a nugget diameter represented by 4 × (t ^1/2 ) is obtained with respect to the plate thickness: t (mm) and the welding The minimum current value that occurred: the average value of I ₂ (kA) was used.

(Spot welding conditions :) Electrode; DR type, tip diameter: 6.0 mmφ, radius of curvature: 40 mm, outer diameter: 16 mmφ, material: Cu-Cr welding conditions; energizing time: 10 cycles, pressing force: 1960 N (20
0kgf) Pressurization condition; 30 cycles before energization, 7 cycles after energization No up slope, no down slope Continuous spot welding speed: 1 point / 2 seconds Table 2 shows the results of the spot weldability survey obtained above. Show.

Further, the obtained hot-dip galvanized steel sheet was subjected to a DuPont impact test under the following conditions to evaluate the plating adhesion. (Plating adhesion evaluation method :) DuPont impact test conditions; Load: 9.8 N (1 kgf), Dropping height: 100 cm, Punch diameter:
After the DuPont impact test on the 6.35 mm (1/4 inch) hot-dip galvanized steel sheet, cellophane tape peeling was performed on the convex portions, and the scores were 1 to 5 according to the amount of plating peeling.

The evaluation method was as follows. For the plating layer peeled off by the tape, the fluorescent X-ray count of zinc per 100 mm ² area was measured, and the count number (cps) was less than 100.
100 or more, less than 200 score 4, 200 or more, less than 300 score 3, 300 or more, less than 400 score 2, 400 or more score 1
And In other words, those without plating peeling were rated 5,
As the score becomes 1, the amount of plating peeling increases.

Table 2 shows the evaluation results of the plating adhesion obtained above. (Comparative Examples 6 to 8) An alloyed hot-dip galvanized steel sheet made of an ultra-low carbon cold-rolled steel sheet having the composition shown in Table 1 and electric Zn-Ni
The spot weldability and plating adhesion were evaluated in the same manner as described above for the alloy plated steel sheet and the electric Zn-Fe alloy plated steel sheet.

Table 3 shows the obtained evaluation results. As shown in Tables 2 and 3, a steel sheet containing a predetermined amount of B and / or P was used, and further, the total amount of Al in the plating layer per unit area of plating adhesion, and the amount of Fe− per unit area of plating adhesion.
The hot-dip galvanized steel sheet of the present invention, which defines the three factors of the amount of Al in the Al intermetallic compound and the amount of plating per unit area of plating, has superior spot weldability and plating adhesion compared to conventional hot-dip galvanized steel sheet. Having.

Further, the hot-dip galvanized steel sheet of the present invention has excellent spot weldability and has a galvannealed steel sheet, an electrical Zn—Ni alloy-coated steel sheet, and an electrical Zn—Fe
Has excellent plating adhesion to alloy plated steel sheets.

[0063]

[Table 1]

[0064]

[Table 2]

[0065]

[Table 3]

[0066]

[Table 4]

[0067]

According to the present invention, the problem of spot weldability of a galvanized steel sheet, which has been a problem in the past, is solved.
It has become possible to provide a hot-dip galvanized steel sheet excellent in both spot weldability and plating adhesion.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a layer structure of a hot-dip galvanized layer during hot-dip galvanizing.

[Explanation of symbols]

 Reference Signs List 1 plating layer 2 Fe-Al intermetallic compound (: Fe-Al alloy layer) 3 zinc layer (η phase) 4 base steel sheet (: material steel sheet) 5 hot-dip galvanized steel sheet 6 Fe-Zn intermetallic compound (: Fe-Zn Alloy layer)

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) // C22C 38/14 C22C 38/14 (72) Inventor Chiaki Kato 1 Kawasakicho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Engineering Co., Ltd. (72) Inventor Michimasa Ikeda 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Kawasaki Steel Co., Ltd. Address F-term (reference) in Kawasaki Steel Engineering Laboratory 4K027 AA02 AA05 AA23 AB07 AB13 AB35 AC13 AE02 AE03 AE12 AE23

Claims (5)

[Claims] (1) B is 1 to 20 mass ppm and / or P is
A hot-dip galvanized steel sheet comprising a hot-dip galvanized layer on at least one side of a steel sheet containing 0.010 to 0.050 mass%. 2. At least one surface of the steel sheet has a total amount of Al in the plating layer per unit area of plating adhesion: X (g / m ² ), and Fe—
Hot-dip galvanizing in which the amount of Al in the Al intermetallic compound: Y (g / m ² ) and the amount of plating per unit area of plating: W (g / m ² ) satisfy the following formulas (1) and (2): A hot-dip galvanized steel sheet having a layer. Note Y / (X-0.0012W) ≤ 0.90 (1) 0.10 ≤ X-0.0012W ... (2) 3. B is 1 to 20 mass ppm and / or P is
On at least one side of the steel sheet containing 0.010 to 0.050 mass%, the total amount of Al in the plating layer per unit area of plating adhesion:
X (g / m ² ), amount of plating per unit area of plated coating / Al in Fe-Al intermetallic compound present at steel sheet interface: Y (g / m ² ) and amount of plated coating per unit area of plated coating: W (g / m
² ) A hot-dip galvanized steel sheet having a hot-dip galvanized layer satisfying the following formulas (1) and (2). Note Y / (X-0.0012W) ≤ 0.90 (1) 0.10 ≤ X-0.0012W ... (2) 4. A method of manufacturing a hot-dip galvanized steel sheet in which a steel sheet is immersed in a hot-dip galvanizing bath and then pulled up to perform plating. ) And plating bath Al concentration: N _Al (mass
%), Wherein the steel sheet is hot-dip galvanized under a condition satisfying the following formulas (3) to (5). 0 ≦ Te−Tb ≦ 50 …………… (3) 1000N _Al +300 ≦ Tb ≦ 1000N _Al +350… (4) 0.12 ≦ N _Al …………………………… ……………(Five) 5. B is 1 to 20 mass ppm and / or P is
In a method for producing a hot-dip galvanized steel sheet in which a steel sheet containing 0.010 to 0.050 mass% is immersed in a hot-dip galvanizing bath and then pulled up to perform plating, the bath temperature of the bath is Tb (° C.), and the temperature of the plate entering the bath is Te. Production of a hot-dip galvanized steel sheet characterized by subjecting a steel sheet to hot-dip galvanizing under conditions in which the temperature (° C.) and the Al concentration in the plating bath: N _Al (mass%) satisfy the following expressions (3) to (5). Method. 0 ≦ Te−Tb ≦ 50 …………… (3) 1000N _Al +300 ≦ Tb ≦ 1000N _Al +350… (4) 0.12 ≦ N _Al …………………………… ……………(Five)