JP3282482B2 - Alloyed hot-dip galvanized steel sheet with excellent lubricity and chemical conversion properties - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a galvannealed steel sheet having excellent lubricity and chemical conversion property.

[0002]

2. Description of the Related Art In recent years, the use of surface-treated steel sheets in which the surface of a steel sheet is plated is increasing. Among them, alloyed hot-dip galvanized steel sheets are not only resistant to corrosion after coating, but also have good adhesion to coatings. Due to its excellent weldability, economy, etc., the demand for surface-treated steel sheets for automobiles is rapidly growing. However, in places where press molding is severe, galling between the plating and the dies occurs, causing a problem that the lubricity of the press is reduced. Therefore, an improvement is demanded from an automobile manufacturer.

Therefore, various proposals have been made as a method for improving the press formability. For example, Japanese Patent Application Laid-Open No. 62-192597 discloses a galvanized steel sheet in which a hard galvannealed steel sheet is provided with a hard electric zinc-iron alloy plating layer, and a smoothing action accompanying the formation of the plated layer is disclosed. Thus, the unevenness on the surface of the lower plating is made uniform to improve the powdering resistance. Japanese Patent Publication No. 7-13308 discloses a steel sheet in which the surface of a zinc-based plated steel sheet is coated with each oxide of Zn, Mn, and P, and one or more oxides of Mo, W, and V. Have been. This is based on the point that a method of forming a hard coating on the surface of a plated steel sheet is effective in improving lubricity during press forming. The purpose of the present invention is to achieve the object by selecting a material that can form a chemical conversion treatment film and that does not adversely affect the chemical conversion treatment property even when the film components are dissolved in the chemical conversion treatment solution. However, even with these methods, there is no lubricating property-enhancing effect sufficient to satisfy the characteristics required by the manufacturer, and there is a problem that the manufacturing cost increases.

Japanese Patent Application Laid-Open No. 1-136952 discloses Fe
A method is disclosed in which a lubricant is applied to the surface of a plating layer having a specified concentration or the like to reduce the frictional resistance between the plating layer surface and a die. Although the plated steel sheet containing such a lubricant contributes to the improvement of the lubricating action, the lubricant cannot be removed even if the degreasing step is performed before the chemical conversion step performed by the automobile manufacturer, so that the chemical conversion treatment is not performed. There is a problem that it is difficult to form a phosphate film at the time.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a novel alloyed molten zinc having improved press lubricity and excellent chemical conversion treatment. It is to provide a plated steel sheet.

[0006]

The alloyed hot-dip galvanized steel sheet of the present invention which can solve the above-mentioned problems has a surface roughness of 0.5 to 1.5 μm in center line average roughness Ra. 75 to 30 at PPI (cut-off value: 1.25 μm)
The surface of the alloyed hot-dip galvanized steel sheet, which is 0, is coated with a silicic acid or silicate-containing coating, and the silicic acid or silicate in the coating is converted to a dry SiO ₂ weight of 1 to 1
200 mg / m ² or the coating rate of the coating is 1
It has a gist where it is set to ６０60%.

The type of silicate used in the present invention is preferably Na ₂ O.nSiO ₂ , K ₂ O.nSiO ₂ or Li ₂ O.nSiO ₂ (n: an integer of 3 or more). In addition, in the galvanized steel sheet of the present invention, for the purpose of further improving lubricity, one containing 7 to 15% by weight of Fe in a plating layer or one containing water-dispersible wax particles in a coating film. Is a preferred embodiment of the present invention.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS When a galvannealed steel sheet is pressed, galling of the plating and the dies occurs in a severely processed part. One of the causes is that the sliding applied to the surface layer of the plating during the pressing is performed. Large dynamic deformation resistance is mentioned.

Therefore, a method of forming a hard coating on the surface of a plated steel sheet has been proposed for the purpose of improving press formability by reducing the sliding deformation resistance and improving the slidability. As mentioned above, Tokuhei 7-13
No. 308 discloses a method in which an oxide film such as Mn is selected as a hard film which does not adversely affect the chemical conversion property, and the oxide film is formed on a plating surface.
However, at present, even the oxide film exemplified in this publication has not yet satisfied the severe demands of users for improving lubricity.

Accordingly, the present inventors have conducted intensive studies with the aim of further improving lubricity. As a result, the surface of a galvanized steel sheet is coated with a silicic acid or silicate-containing coating,
By controlling the surface roughness of the plated steel sheet to a specific range, it has been found that lubricity can be remarkably improved without lowering the chemical conversion property, and the present invention has been completed.

More specifically, the galvannealed steel sheet of the present invention comprises: (1) a zinc-coated steel sheet having a surface coated with a silicic acid or silicate-containing coating, and (1-a) the coating. The silicic acid or silicate therein is converted to 1 to 200 mg / m ² in terms of the weight of dried SiO ₂ , or (1-b
) The coating rate of the coating is set to 1 to 60%, and (2) the surface roughness of the galvanized steel sheet is measured by the center line average roughness R.
a (JIS B0601 standard) 0.5-1.5 μm and PPI (cut-off value: 1.25 μm, SAE J
911 standard).

In the present invention, the term "PPI" refers to the number of peaks having a size of 1.25 μm or more per inch in length. This 1.25 μm is called a cut-off value or a peak count level. If the cut-off value is reduced, the PPI value naturally increases, but in the present invention, the cut-off value is determined in consideration of the simplicity and reproducibility of measurement. The off value is usually 1.25 μm, which is most commonly used.
I decided to adopt. First, the silicic acid or silicate-containing coating that is coated on the surface of a galvanized steel sheet will be described.

This coating is a strong hard coating composed of fine silica particles. By forming such a coating, it is possible to reduce the sliding deformation resistance applied to the plating surface layer during press working. it can. In addition, silicic acid and silicate are inexpensive, and have the advantage that the production cost is low.

The silicate used in the present invention is a salt composed of silicon dioxide and a metal oxide, and has a general formula xM ₂ O.
Any substance may be used as long as it is represented by ySiO ₂ , but preferred are sodium silicate represented by Na ₂ O · nSiO ₂ (n: an integer), potassium silicate represented by K ₂ O · nSiO ₂ , lithium silicate represented by li ₂ O · nSiO _2. Here, it is preferable that n is in the range of 3 or more. If n is less than 3, the phosphatability deteriorates, the hygroscopicity increases, and the water resistance after coating deteriorates. The larger n is, the more the performance such as lubricity is improved, and the one where n is infinitely large is considered to be silicic acid.

As described above, in order to incorporate such silicic acid or silicate (hereinafter, sometimes referred to as silicate) into the coating film to effectively exert the above-described coating effect, as described above, 1-a) The content in the coating is converted to 1 to _{2 by} weight of SiO ₂ after drying (may be simply abbreviated as SiO ₂ ).
It is necessary that the coating rate be 200 mg / m ² or (1-b) the coverage of the coating be 1 to 60%. The reasons for determining these numerical values will be described with reference to FIGS.

FIG. 1 shows that a galvannealed steel sheet is made of Na
It is an examination of the relationship between the content of SiO ₂ and the lubricity and chemical conversion property when ₂ O · 5SiO ₂ is applied (the surface roughness of a galvanized steel sheet is 1.0 in Ra).
150 μm and PPI). The coefficient of friction was used as an index of lubricity, and the chemical conversion treatment was represented by phosphate treatment.

Among them, the friction coefficient was measured by a flat sliding test described below. [Sample size]: 40 × 300 mm [Tool]: Flat tool (18 × 20 mm) [Pressing force]: 5 kg / mm ² [Sliding speed]: 300 mm / min [Sliding length]: 150 mm [oiling] : Knoxlast 550 (manufactured by Parker Kosan), 2 g / m ² Specifically, the pulling load was measured, and the friction coefficient was calculated from the surface pressure and the pulling load.

The phosphatability was evaluated by the following method. [Phosphate treatment liquid]: SD5000 (manufactured by Nippon Paint Co., Ltd.) [Step]: Degreasing → washing with water → surface adjustment → phosphate treatment [Determination of phosphate coating]: Observation of coating by SEM,
Classification was performed according to the following evaluation criteria. ：: Uniform film formation △: Partial film formation ×: No film formation

As is clear from FIG. 1, 1 mg of SiO ₂
/ M ² or more, the coefficient of friction is remarkably reduced and the lubricity is improved. However, when SiO ₂ is 200
When the amount exceeds mg / m ₂ , the lubricity is good, but the phosphatability is significantly deteriorated.
^{And 2} . A preferred lower limit is 10 mg / m ² , more preferred is 20 mg / m ² , while a preferred upper limit is 100 mg / m ² , more preferred is 60 mg / m ^2.
It is.

As described above, in the present invention, when forming the silicate-containing film, it is necessary that the content of SiO ₂ be within the above range, or alternatively, by controlling the coverage of the film. The intended purpose can be achieved.

Strictly speaking, the surface of the galvannealed steel sheet has fine irregularities, so that the silicate generally tends to adhere to the recesses, especially when the coating amount is small. It is remarkably seen and hardly adheres to the projections. The present inventors have studied and found that the silicate does not necessarily need to be coated on the entire galvanized steel sheet, and for example, even if it is slightly present in the concave portion, the lubricity of the galvanized steel sheet is significantly improved. That is, as a result of examining the relationship between the coating state of the coating and the lubricity of the plated steel sheet in detail,
It was found that the improvement in lubricity depends not only on the amount of silicate deposited but also on the coverage of the coating.

FIG. 2 shows that the alloyed hot-dip galvanized steel sheet
Na ₂ O · in the case of coating ₂ O · 5 SiO ₂
The relationship between the coverage of the 5SiO ₂ -containing coating and the lubricity and chemical conversion treatment was examined. The experimental conditions are shown in FIG.
The results were substantially the same as the conditions used for obtaining the results, and the lubricity and phosphatability were evaluated in the same manner. Here, the coverage means the area ratio of the silicate coating the surface of the alloyed hot-dip galvanized steel sheet. Specifically, the surface of the sample is observed by EPMA, and the Si characteristic X
The Si-enriched portion of the line image was used as the silicate-coated portion, and the area was measured by an image analyzer. The coverage was represented by [silicate coverage area / sample measurement area].

[0023] As is apparent from the results shown in FIG. _2, Na 2 O ·
When the coverage of the 5SiO ₂ -containing coating is 1% or more, the lubricity is significantly improved. However, if the coverage exceeds 60%, the phosphatability will be significantly degraded, so it is necessary to set the upper limit to 60%. The preferred lower limit is 10
%, More preferably 20%, while the preferred upper limit is 50%, more preferably 40%.

Further, in the present invention, the surface roughness of the galvanized steel sheet is 0.5 to 1.5 μm in Ra and 75 to 1.5 in PPI.
By setting it to 300, lubricity is to be significantly improved. The reasons for determining these numerical values will be described with reference to FIGS.

FIG. 3 shows that the alloyed hot-dip galvanized steel sheet
₂ O · 6SiO ₂ are those which examine the relationship between the surface roughness (Ra) and lubricity when coated with (20 mg / m ² as SiO _2), similarly 4 Na ₂ above steel plate
O · 6SiO ₂ in which examined the relationship between the surface roughness (PPI) and the lubricity in the case of applying the (20 mg / m ² as SiO _2). In addition, it measured similarly to the above using a friction coefficient as an index of lubricity.

As is apparent from these figures, even when a silicate-containing coating as defined in the present invention is formed, the surface roughness is less than 0.5 μm in Ra or 7 in PPI.
When it is less than 5, it is understood that the coefficient of friction is high, and the sliding surface of the molded article after molding is seized and the lubricity is reduced. On the other hand, Ra was 1.5 μm and PPI was 3 μm.
If it exceeds 00, problems such as deterioration of sharpness after coating occur. The lower limit is preferably 0.7 μm for Ra and P
120 for PI, more preferably 0.75 μm for Ra,
The PPI is 150, while the upper limit is preferably 1.3 μm for Ra, 250 for PPI, more preferably 1.1 μm for Ra, and 200 for PPI.

As described above, according to the present invention, a coating having a certain specific range of silicate content or coverage is applied to a galvanized steel sheet having a controlled surface roughness. It is possible to improve not only the coefficient of friction but also the anti-galling property, the lubricating property can be remarkably improved, and the chemical conversion property can be improved. When a silicic acid colloid solution is used, the silicic acid is similarly converted to SiO ₂ weight of 1 to 200 mg / m ₂ , or the coverage of the silicic acid-containing coating is set to 1 to 60%. Thereby, the lubricity and chemical conversion treatment property of the galvannealed steel sheet can be improved. In the present invention, the following configuration is recommended for the purpose of further improving these characteristics.

F in the galvanized steel sheet
e The content is 7 to 15% by weight. If the Fe content is less than 7% by weight, the soft η phase remains to deteriorate the slidability, while if it exceeds 15% by weight, the powdering property deteriorates.
However, even when the Fe content is in the range of 7 to 9%, considering that the soft ζ phase is present, although slightly, and the slidability is slightly reduced, the range may be set to 9 to 14%. Recommended.

Water-dispersible wax particles are contained in the coating. Examples of the water-dispersible wax particles used in the present invention include low softening point water-dispersible wax particles, such as natural waxes such as carnauba wax, line wax, montan wax, and paraffin wax. 506, SL-508, S
L-511 [all manufactured by San Nopco Co., Ltd.], Passrun N
o.52 [Kyoeisha Yushi Kagaku Kogyo Co., Ltd.], Hoechst wax emulsion J-120 [Hoechst Japan K.K.
And the like; high-softening point water-dispersible wax particles include low molecular weight polyethylene wax of synthetic wax, polyethylene oxide, polypropylene oxide and the like, and commercially available products thereof include Dijet E-17 [manufactured by Kyogo Chemical Co., Ltd., KUE- 1,
KUE-5, KUE-7, KUE-8, KUE-11
[The above are manufactured by Sanyo Chemical Industries, Ltd.], Chemipearl W-10
0, W-200, W-300, W-400, W-50
0, WF-640, W-900, W-950 (manufactured by Mitsui Petrochemical Industries, Ltd.), Eponol, Eponol HC-1
And [Elepon E-20] (manufactured by Nichika Chemical Co., Ltd.).

Next, a method for producing the galvannealed steel sheet of the present invention will be described. First, it is preferable that the surface roughness of the galvanized steel sheet serving as the substrate be controlled in a specific range by the roll roughness of the SKP after plating, the SKP rolling reduction, the roughness of the plating base plate, the Al concentration in the bath, and the like.

The surface of the steel sheet whose surface roughness is controlled in this way is coated with a silicate or silicic acid-containing coating. Specifically, it is formed by applying a silicate aqueous solution or a silicate colloid solution to the steel sheet and drying. Examples of the aqueous solution of silicic acid include the above-described sodium silicate, potassium silicate, lithium silicate, and the like, and examples of the colloidal silicate solution include a colloid solution in which fine particles of silicic anhydride are dispersed in water using water as a dispersion medium. And the like.
The colloid solution is commercially available in the form of colloidal silica or colloid sol.
0, Snowtex 40, Snowtex N, Snowtex S, Snowtex K, Lithium silicate 3
5, lithium silicate 45, lithium silicate 7
5. Snowtex XS [all manufactured by Nissan Chemical Industries, Ltd.] and the like can be used.

The method of applying the silicate aqueous solution or the silicate colloid solution to the surface of the galvannealed steel sheet is not particularly limited, but may be immersed in the aqueous solution, applied by a roll coater, or applied by spraying. An ordinary coating method such as a method of performing the coating can be appropriately selected.

In this way, the coating formed by applying and drying a silicate aqueous solution or a silicate colloid solution on the surface of the alloyed hot-dip galvanized steel sheet forms a strong dry gel composed of fine silica particles. And it becomes a hard film, so that an excellent lubricating action can be obtained.

For the purpose of further improving lubricity, it is recommended to add the wax particles to the silicate aqueous solution or the silicate colloid solution. The proportion of the wax added is preferably 1 to 30% by weight in terms of SiO ₂ weight after coating and drying the aqueous silicate solution or a silicic acid colloidal solution. When the addition ratio of the wax is less than 1% by weight, the effect of improving the lubricity cannot be exhibited effectively. On the other hand, when it exceeds 30% by weight, the adhesion between the zinc plating layer and the silicate-containing film is poor. As a result, the coating peels off at the time of press working, resulting in poor appearance of the product due to the blackening phenomenon. Incidentally, as long as the amount of the wax added is within the above range, two or more kinds of the above-mentioned waxes may be added.

Hereinafter, the present invention will be described in detail with reference to examples.
However, the following examples do not limit the present invention,
All modifications and alterations without departing from the spirit of the preceding and following descriptions are included in the technical scope of the present invention.

[0036]

【Example】

Example 1 In this example, the effect of silicate or silicic acid adhesion amount on lubricity and chemical conversion treatment properties was examined. A solution containing a predetermined amount of various silicates or silicic acids (SiO ₂ colloid solutions) shown in Tables 1 and 2 on an alloyed hot-dip galvanized steel sheet (coating weight: 60 g / m ² ) is drawn with a squeezing roll. Applied. The SiO ₂ weights after coating and drying are also shown in Tables 1 and 2. After the application, the coating was dried at 80 ° C. to form a hard SiO ₂ coating.

The thus obtained galvanized steel sheets having various silicate or silicate-containing coatings were evaluated for lubricity (coefficient of friction and mold galling resistance) and phosphatability. Among them, the coefficient of friction and the phosphatability were evaluated in the same manner as in the above-mentioned experimental method, and the mold resistance was measured as follows.

That is, a single-shot press test was carried out using an 80-ton crank press device, and the molded product was visually observed for the galling resistance on the sliding surface, and classified according to the following criteria. ◎: no galling ○: almost no galling △: little galling ×: large galling These results are also shown in Tables 1 and 2.

[0039]

[Table 1]

[0040]

[Table 2]

From the results in the table, the following can be considered. No. 1 to No. 41 are galvanized steel sheets satisfying all the constituent requirements of the present invention, and showed good values in both lubricity and phosphatability. On the other hand, Nos. 42 to 50 that do not satisfy any of the constituent requirements of the present invention have the following problems.

Since No. 42 had no silicate-containing coating, it had a high coefficient of friction and poor anti-galling properties, and when viewed comprehensively, had extremely poor lubricity. No. 43 is an example in which the amount of adhered SiO ₂ is out of the lower limit specified in the present invention, and the friction coefficient was large and the anti-galling property was slightly poor.

No. 44 is an example in which the amount of adhered SiO ₂ exceeds the upper limit specified in the present invention. Although the coefficient of friction and the galling resistance were good, the phosphatability was reduced. No.
Nos. 45 and 46 are examples in which the surface roughness (Ra or PPI) of the plated steel sheet is lower than the constitutional requirements of the present invention, and both have good phosphatability but reduced lubricity.

Nos. 47 to 50 are comparative examples in which a coating containing Mn oxide and phosphoric acid was formed instead of the silicate coating specified in the present invention. As is clear from the results in the table,
In the case where either or both of Ra and PPI are less than the requirements of the present invention (Nos. 47 to 49), the lubricity is reduced, and even if Ra and PPI are within the range of the present invention (No. 50) No improvement in sex was seen.

Example 2 In this example, the effect of the water-dispersed wax added to the silicate or silicic acid in Example 1 was examined. Specifically, a galvannealed steel sheet (coating weight: 6
0 g / m ² ), a solution containing a predetermined amount of various silicates or silicic acid (SiO ₂ colloid solution) shown in Table 3 was applied by a squeezing roll, and a hard film was formed in the same manner as in Example 1. Formed. About the galvanized steel sheet on which various silicate or silicic acid containing coatings obtained in this way are formed,
Lubricity and phosphatability were evaluated in the same manner as in Example 1. Table 3 also shows these results.

[0046]

[Table 3]

From the results in the table, the following can be considered. Nos. 51 to 63 correspond to the above No. 1 (examples of the present invention).
In the examples in which various waxes were added, it was found that the lubricating properties were remarkably improved as compared with No. 1 because the added amounts of the waxes were all within the preferable ranges specified in the present invention. No. 64 and No. 6 with different silicate types
5, and Nos. 66 to 69 using silicic acid,
Similarly, it can be seen that it shows very excellent lubricity.

On the other hand, in Nos. 70 and 71 in which the amount of wax added exceeds the preferred upper limit of the present invention, the lubricity and phosphatability were extremely reduced. No. 7 in which the amount of wax added is below the preferred lower limit of the present invention.
In Nos. 2 and 73, the coefficient of friction was slightly reduced.

Example 3 In this example, the effect of the coverage of a silicate or silicic acid-containing coating on lubricity and chemical conversion treatment was examined. Alloyed hot-dip galvanized steel sheet (coating weight: 60 g / m ² )
Then, solutions containing predetermined amounts of various silicates or silicic acids (SiO ₂ colloid solutions) shown in Table 4 were applied by a squeezing roll. Table 4 shows the silicate or silicate coverage after coating and drying.
It is described together. After the application, a hard coating was formed in the same manner as in Example 1.

The lubricating properties and phosphatability of the thus obtained galvanized steel sheets having various silicate or silicate-containing coatings were evaluated in the same manner as in Example 1. Table 4 also shows these results.

[0051]

[Table 4]

From the results in the table, the following can be considered. Nos. 74 to 112 are galvanized steel sheets satisfying all the constituent requirements of the present invention, and showed good values in both lubricity and phosphatability. On the other hand, Nos. 113 to 11 that do not satisfy any of the constituent requirements of the present invention
No. 7 has the following problems.

Since No. 113 had no silicate-containing coating, it had a high coefficient of friction and poor anti-galling properties, and when viewed comprehensively, had extremely poor lubricity. No. 114 is an example in which the coverage of the coating film falls outside the lower limit specified in the present invention, and the coefficient of friction was large and the anti-galling property was slightly poor.

No. 115 is an example in which the coverage exceeds the upper limit specified in the present invention, and although the coefficient of friction and the galling resistance are good, the phosphatability is reduced. No. 116
And 117 indicate the surface roughness (Ra or P
PI) is less than the requirements of the present invention. In each case, the phosphatability was good, but the lubricity was reduced.

Example 4 In this example, the effect of the water-dispersible wax added to silicate or silicic acid in Example 3 was examined. Specifically, a galvannealed steel sheet (coating weight: 6
0 g / m ² ), a solution containing a predetermined amount of various silicates or silicic acids (SiO ₂ colloid solution) shown in Table 5 was applied by a squeeze roll, and a hard film was formed in the same manner as in Example 1. Formed. The lubricating properties and the phosphating properties of the galvanized steel sheets having various silicate or silicate-containing coatings thus obtained were evaluated in the same manner as in Example 1. Table 5 also shows these results.

[0056]

[Table 5]

From the results in the table, the following can be considered. Nos. 118 to 130 are examples in which various waxes were added to the aforementioned No. 77 (Example of the present invention). However, since the amount of the wax added is within the preferable range specified in the present invention, No. It was found that the lubricity was significantly improved as compared with .77. No.131 which changed the kind of silicate
No. 132, and No. 133-using silica.
136 also shows very good lubricity.

On the other hand, Nos. 137 and 138 in which the added amount of the wax exceeds the preferred upper limit of the present invention are:
Lubricity and phosphatability were significantly reduced. Also,
If the amount of wax added falls below the preferred lower limit of the present invention,
Nos. 139 and 140 had slightly reduced friction coefficients.

[0059]

Since the galvannealed steel sheet of the present invention is constituted as described above, not only the coefficient of friction but also the mold resistance is good, and the lubricity of the galvanized steel sheet is significantly improved. As well as excellent chemical conversion properties. In addition, since low-cost silicic acid or silicate salt is used, there are advantages that the production cost can be reduced and the productivity can be improved.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the amount of deposited SiO ₂ and the lubricity and phosphatability.

FIG. 2 is a graph showing the relationship between the coverage of a sodium silicate-containing coating and lubricity and phosphatability.

FIG. 3 is a graph showing the relationship between surface roughness Ra and lubricity of an alloyed hot-dip galvanized steel sheet.

FIG. 4 is a graph showing the relationship between the surface roughness PPI of an alloyed hot-dip galvanized steel sheet and lubricity.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C23C 28/00 C23C 2/28 C23C 22/53

Claims (4)

(57) [Claims] The surface roughness is set to a center line average roughness Ra of 0.
5-1.5 μm and PPI (cut-off value: 1.25
The surface of the alloyed hot-dip galvanized steel sheet having a thickness of 75 to 300 μm is coated with a silicic acid or silicate-containing coating, and the silicic acid or silicate in the coating is dried with SiO _2.
An alloyed hot-dip galvanized steel sheet having excellent lubricity and chemical conversion property, wherein the weight is 1 to 200 mg / m ² in terms of weight or the coating rate of the coating is 1 to 60%. 2. The galvannealed steel sheet according to claim 1, wherein the Fe content in the galvanized steel sheet is 7 to 15% by weight. 3. The method according to claim 1, wherein the silicate is Na_Two On SiOn
_Two , K_Two On SiOn _Two Or Li_Two On SiOn_Two 
(N: an integer of 3 or more).
Alloyed hot-dip galvanized steel sheet. 4. The galvannealed steel sheet according to claim 1, wherein the coating contains water-dispersed wax particles.