JPH02118086A - Hot-dip galvanized alloyed steel sheet excellent in workability and coating property and production thereof - Google Patents

Abstract

PURPOSE:To simply and easily produce the title steel sheet excellent in corrosion resistance, powdering resistance and cratering resistance by hot-dip galvanizing the steel sheet and smoothening the surface and thereafter performing Fe-B alloy plating thereon and then heat-treating this plated steel sheet. CONSTITUTION:A steel sheet on which ordinary pretreatment has been performed is immersed in a hot-dip galvanizing bath contg. 0.05-0.3wt.% Al and <=0.2wt.% Pb to perform galvanizing of 30-90g/m<2>. Spangle is made fine by mist spray while the galvanized film is kept in a molten state. After the film is solidified, the surface of the film is smoothened by skin pass treatment. Fe-B alloy plating which consists of Fe not less than 97.0% and less than 100% and B not less than 0.001% and less than 3% is performed at 0. 5-10g/m<2> on the single face or double faces of this steel sheet by an electroplating method. Then the above-mentioned plated steel sheet is produced by heating this steel sheet at the temp. not lower than 320 deg.C and not higher than m.p. of Zn for 10min-50 hours in an open-coil state in a batch type annealing furnace of the nonoxidative or reductive atmosphere. The internal layer is constituted of delta1 phase and xsi phase excepting the boundary phase for the basis material having 0.5mum thickness and Fe is uniformly distributed in the facial direction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a Fe-Zn alloy plated steel sheet used for automobiles, home appliances, building materials, etc.

[Prior art] Galvanized steel sheets are widely used as materials that are inexpensive and have excellent corrosion resistance and strength.In addition to corrosion resistance, galvanized steel sheets are also used for the interior and exterior panels of automobiles. Used in large quantities. Generally speaking, there are two methods for mass production of galvanized steel sheets: electroplating and hot-dip plating.Since electroplating is processed at low temperatures, there is no phase change due to heat effects, and it is easy to control the composition of the plating film. In order to increase the amount of deposited metal, it is necessary to increase the processing time.On the other hand, with the hot-dip plating method, the amount of deposited material can be easily increased without increasing the processing time. −Z r+ alloy can be made.

However, the control of the plating film composition and the generated phases requires -3 degrees. 5 of the most used automatic machines in recent years! -1 number,
A higher degree of military resistance is required due to measures such as dealing with salt damage, etc., and in response to this, we are developing coating compositions mainly based on hot-dip galvanizing, which can easily secure 1-inch coverage and is economical. There is a need for a plated steel sheet that has excellent phase control, high corrosion resistance, and has good workability and paintability.

The most important issue in processability is powdering resistance.
An issue with paintability is crater link resistance. Powdering is a phenomenon in which a plating film becomes powdery and falls off during press molding, and cratering is a phenomenon in which the plating film becomes powdery and falls off. Cratering is a phenomenon in which the plating film is subjected to a chemical conversion treatment and then visually visible in the electro-deposition coating process. (crater) is a phenomenon that occurs.

The previous row shows a phase with a high iron content (Fe3) in the plating film.
Zn, o, Fe2O ~ 28 wt%) is generated, which occurs because it is hard and brittle, and the latter occurs due to non-uniformity of the plating film surface (surface shape, oxide film, plating film phase structure, etc.).

Conventionally, the alloying mass 1 galvanized steel sheets used for automobiles are alloyed after hot dipping until the average iron content of the gold plating film reaches around 10 wt%, and the Fe is diffused to the plating surface. It has improved raw corrosion resistance, especially corrosion resistance after painting.

That is, after pre-treating the steel plate (including heat treatment) continuously to adjust the material, it is plated by immersing it in a plating bath containing molten zinc, and then this plated steel plate is alloyed in a furnace for 5 minutes.
Rapidly raise the temperature from 00℃ to 700℃ for a short period of time (1
0 to 30 seconds) to reduce the iron content of the plating film to 10%.
The front and back are alloyed. However, since the alloyed hot-dip galvanized steel sheets produced in this way are heated to high temperatures due to rapid temperature rise, the iron content in the plating film tends to vary depending on the location, and the iron content in the plating film tends to vary in the surface direction and depth direction. In addition to this, the iron concentration gradient within the plating film increases, and in order to secure the iron content in the surface layer, the iron content at the interface with the steel base increases and the r-phase is formed. Furthermore, high temperature treatment and rapid cooling generate thermal stress in the plating film.

On the other hand, a method has been proposed in which the alloying treatment is divided into two steps, primary and secondary. For example, Tokuko Sho 59-1454
In No. 1, in the secondary heating, rapid temperature rise and high temperature heating is performed to remelt the Zn plating film in order to obtain smoothness of the plating film. In this heating, the iron content is 2.2 to 5.5 wt.
Therefore, depending on the result of this secondary heating, secondary heating is performed over a period of time at a low temperature below the melting point of zinc, and the iron content is kept within a range of 6 to 13 wt%. . It is also disclosed that by this method, it is possible to obtain an alloyed hot-dip galvanized film with a smooth surface, excellent appearance, and no peeling or powdering during processing.

On the other hand, it has also been proposed to improve cratering resistance by increasing the iron content only in the surface layer of the plating film. for example,
The proposal of Japanese Patent Publication No. 58-15554 is a plated steel sheet with a corrosion-resistant metal layer as an inner layer and a Fe--Zn alloy coating layer with a high iron content attached thereon to improve cationic electrodeposition coating properties. This proposal discloses an alloyed hot-dip galvanized layer that is formed into an Fe-Zn alloy by heat treatment after hot-dip galvanizing as the corrosion-resistant metal layer that is the inner layer.

[Problems to be Solved by the Invention] However, the above-mentioned Japanese Patent Publication No. 59-14541 does not satisfy the cratering resistance. Regarding cratering resistance, the iron content on the surface is insufficient, and regarding powdering resistance, the alloying reaction is uneven because the alloying treatment is performed by rapid heating at high temperature after hot-dip galvanizing. As a result, a single layer with poor processability grows. Further, in some cases, unalloyed portions and highly alloyed portions coexist, resulting in a so-called uneven burning phenomenon.

As described above, secondary heating tends to be non-uniform, so secondary heating conditions based on the results of secondary heating become extremely complicated, and implementation thereof is very difficult in actual operation.

In Japanese Patent Publication No. 58-15554, the iron content of the plating surface was dramatically increased to 3 degrees, improving the cratering resistance, but since the alloying was completed by heat treatment after hot-dip galvanizing, As with Publication No. 5914541, there is the problem of non-uniform alloying, and in addition, the iron concentration gradient within the plating film becomes large, and at the interface with the steel base where the iron concentration becomes high, "phases grow." Further, thermal stress caused by rapid heating and cooling is also unfavorable for powdering resistance.

As described above, efforts have been made to satisfy powdering resistance and cratering resistance, but a hot-dip galvanized steel sheet that satisfies both properties has not yet been obtained.

In order to solve this problem, the present invention was made, and an object thereof is to provide a plated steel sheet that satisfies not only corrosion resistance but also powdering resistance and cratering resistance, and a method for manufacturing the same. .

[Means and effects for solving the problem] The means for achieving this object is to coat at least one side of the steel plate with a first layer formed by hot-dip galvanizing and a Fe layer of 97% on top of the first layer. It has a plating film formed by heat treatment of 1 to 10% Owt%, and the surface layer is Fe-B alloy plating having the Fe content of the second layer, and the inner layer has a thickness of 0.5 μm. An alloyed galvanized coating consisting of a δ1 phase and a ζ phase, excluding the boundary layer with the steel substrate, which has excellent workability and paintability, with iron content uniformly distributed in the surface direction. It is a steel plate.

The following methods are available for forming the above-mentioned alloyed hot-dip galvanized steel sheet.

One method is as follows: (a) A steel plate subjected to normal pretreatment is subjected to Aft. 05wt%
More than 0.3wt. % or less and Pb0.2wt% or less by immersion in a hot dip galvanizing bath containing 30g7m2 or more9
A step of applying a first layer plating of 0 g/m" or less, (1) a step of applying spangle refinement treatment while the plating film is in a molten state, (c) a skin pass treatment after the plating film has solidified,
A step of smoothing the surface of the hot-dip galvanized film, (2) applying zero,
Fe of 5 g/m" or more and Log/m" or less is 97. Ol
, 11t% or more and less than 1' OOwt%, B is O,001
A step of applying a second layer of Fe-B alloy plating with a content of not less than 3 wt%; 1 in the temperature range of 320℃ or higher and lower than the melting point of zinc.
This method includes a step of heating from 0 minutes to 50 hours.

Another method is to coat one or both sides of the steel plate with an Fc of 97% after the hot-dip galvanizing step (a) above, while the plating film is still in a molten state.
0w4% or more and less than 100wt%, B is 0.001wt%
It includes a step of spraying less than 3 wt% of Fe-B alloy powder to apply a second layer plating of 0.5 g/rn2 or more and 10 g/m2 or less, and then the steps (c), (d), and (e) above. This is a method that includes

The above means will be described in detail below, including their effects.

First, the steel plate for plating may be a cold-rolled steel plate or a hot-rolled steel plate, and may be subjected to surface conditioning and annealing treatment as a normal pretreatment.

When the iron content of the surface layer of the plating film is 97W% or more,
Prevents cratering from occurring during electrodeposition coating.

In other words, alloyed hot-dip galvanized steel sheets are subjected to cationic electrodeposition coating after phosphate treatment on the plated surface, but phosphophyllite [Zn2] containing Fe is added to the phosphate crystals produced by this chemical conversion treatment. Granular and dense crystals called Fe (PO4)2 ・4)(20] and hopite' [
There are coarse needle-like crystals called Z n3(P 04)2 .4 H20].

One of the causes of crater formation is thought to be localized current concentration in the defective areas of the chemical conversion coating, but the coating formed with phosphophyllite is denser than that of hopite and has fewer defects.
Therefore, if enough Fe is supplied on the plating surface to facilitate the formation of phosphophyllite, craters will be less likely to occur. Further, if the surface layer of the plating film contains boron, the dissolution of Fe during the chemical conversion treatment is promoted, and the formation of the phosphophyllite is facilitated. At this time, if the B content in the plating film is less than 0.001 wt.%, the effect of promoting dissolution of Fe will not be exhibited, and if it exceeds 3 wt.%, the dissolution promoting effect will be saturated. The surface layer of the plating film of the alloyed hot-dip galvanized steel sheet of this invention has an iron content of Fe.
97.0wt% or more 100wt, less than %, B content is 0
．． 001wt% or more and 3w11%, Fe is smoothly supplied and a dense and uniform chemical conversion film is formed. As a result, the occurrence of clay tag) is significantly reduced.

In the case of alloyed hot-dip galvanized steel sheets, the corrosion resistance is mostly determined by the coating weight and the iron content in the coating. Therefore, the inner layer also needs to be alloyed, but it does not need to have a high iron content like the surface layer, and about 5 wt% to 20 wt% is sufficient. Furthermore, the processing characteristics of this inner layer are extremely important. The "phase" is formed at the boundary between the inner layer and the steel base, but the plating film in which no phase is detected has good powdering resistance.
It is difficult to detect unless it has grown to a thickness greater than that. The inner layer, which accounts for most of the plating film of the alloyed hot-dip galvanized steel sheet of this invention, contains a hard and brittle "δ1 phase and a ζ phase, which are distinct from each other, except for the 0.5 μm thick boundary layer with the steel substrate. During processing, there are no defects and powdering is extremely unlikely to occur, and the distribution of iron content is uniform in the surface direction, which has a very positive effect on improving workability. The boundary between the inner layer and the steel base is formed into an integral structure by mutual thermal diffusion, and the plating film, which is formed into an integral structure by thermal diffusion, has a state in which the iron concentration changes continuously. Due to the structure of the inner layer, the mechanical properties and electrochemical properties of the plating film do not differ significantly between adjacent parts, and the plating film has excellent workability and corrosion resistance.

Depending on the application, the alloyed hot-dip galvanized steel sheet of this invention may not require corrosion resistance, workability, paintability, appearance, smoothness, etc. on both sides at the same time, and in such cases, the other side may not have a plating film. Alternatively, other plating films may be applied.

Below, a method for manufacturing an alloyed hot-dip galvanized steel sheet according to the present invention will be described.

A hot-dip galvanizing bath usually contains around 0.2% Af to suppress the Fe-Zn alloy reaction and smooth the plated surface, and also contains PB to adjust the spangle.

Among these, Aρ has the effect of suppressing alloying, so 0.05w
F, e − after adding t% or more and immersing in a hot-dip galvanizing bath
Prevents partial and non-uniform formation of Zn alloy.

It is important not to produce a Fe-Zn alloy non-uniformly in this process, and once it becomes unrestricted, it cannot be corrected in a later process. The amount of AfI added was too large and 0.
If it exceeds 3 wt%, the effect of suppressing alloying becomes excessive, and the subsequent alloying treatment takes too much time, making it unsuitable for industrial use. Although PB does not directly participate in the Alloy 1 reaction, a large amount of PB reduces powdering resistance, so 0.2wt.
Must be limited to no more than %.

For the first layer, a coating weight of 30 g/m'' to 90 g/m'' is suitable for high corrosion resistance.

In addition, if it exceeds 90 g/m2, not only will the quality be excessive, but also a long time will be required in the alloying treatment performed at a low temperature in the subsequent process, resulting in a decrease in productivity. Additionally, when the plating film becomes thick, the film may break or peel during processing, and powdering is likely to occur in the case of alloyed hot-dip galvanized steel sheets.

While the first layer of hot-dip galvanized film is in a molten state, the spangles are made finer, and after the plating film has solidified, a skin pass treatment is performed to obtain a smooth galvanized surface. - The coverage of B plating is improved. As a result, the cratering resistance can be efficiently improved, and the image clarity after painting can also be improved. If the skin bath is performed at an elongation rate of 03% or more, the plated surface will be smooth, but if the elongation rate is too high, it will be 5%.
If it exceeds -, there is a possibility that the workability of the steel plate for inner-shell thin plates will be affected.

The Fe-n alloy plating with an iron content of 97w% or more in the second layer ensures cratering resistance, and in the subsequent heat treatment, the first hot-dip galvanized layer is applied to the steel substrate. As a result, the iron concentration gradient in the inner layer of the plating film is kept small.

The processing method for the above alloy plating is electroplating, vapor deposition plating, unless processing at a temperature higher than the melting point of zinc.
When performing this alloy plating treatment by spraying alloy powder, spangles will be made finer at the same time if the previous hot-dip galvanized layer is in a molten state. It can be omitted.

The second layer needs to have a coating weight of 0.5 g/m" to 10 g/rl. If it is less than 0.5 g/m", Fe cannot be sufficiently supplied over the entire plating surface, and If it adheres in excess of Log/m2, the effect will be saturated, which will not only be disadvantageous in terms of cost, but also increase the likelihood of red rust occurring in terms of corrosion resistance after painting.

The plated steel sheet that has gone through the two plating processes described above is heat treated, and this is to achieve high corrosion resistance after painting by alloying the first layer of zinc with Fe. The iron content of the inner layer does not need to be as high as that of the surface layer, and good post-painting corrosion resistance can be obtained within the range of 5 wt% to 20 wt%.

The purpose of performing the annealing in a non-oxidizing or reducing atmosphere is to prevent surface oxidation and to prevent the chemical conversion coating crystals from becoming non-uniform during the chemical conversion treatment before painting. This is because it is processed by multiplying. The purpose of heating with an oven coil is to prevent unevenness in alloying by uniformly heating, and at the same time to prevent the plating surfaces from adhering to each other and causing defects. In a tight coil state, the temperature distribution becomes uneven,
There will be parts where the alloying rate is high and parts where the alloying rate is low. In particular, this non-uniformity occurs in the longitudinal direction of the steel plate, making it difficult to obtain a high quality product. Heating is done at low temperature, 320℃
A temperature higher than that is necessary. If the temperature is lower than 320°C, it takes too much time to obtain a degree of alloying sufficient to ensure corrosion resistance after painting.

When the temperature is made higher than the melting point of zinc (419.5℃),
There appears a point where alloying progresses rapidly, and the formation of F phase cannot be ignored. Furthermore, there is a risk that the spacer inserted between the steel plates of the open coil may leave marks on the plating surface. 1st
The figure shows the conditions under which both powdering and cratering do not occur within the above temperature range.The horizontal axis is the heating time, and the vertical axis is the heating temperature. The range surrounded by the connecting line is the preferred range of conditions for actual operation that does not cause powdering or cratering, and the heating time is from the time coordinate of point a to the time coordinate of point 0, that is, 1
0 minutes or more and 50 hours or less. When heat treatment is performed under the above heating conditions, Fe diffuses from the steel base side and from the second layer plating side, so proper alloying is achieved without creating a large Fe concentration gradient on the steel base side. . As a result, a plating film consisting only of the δ1 phase and ζ phase is obtained, with virtually no phase formation.And since rapid high-temperature heating is avoided, this plating film is uniform even along the surface. In addition, the iron content falls within the range of 5wt% to 20wt%.However, considering the variations in conditions that tend to occur during actual operation, it is particularly preferable to increase the heating temperature from 320°C to 380°C. The time is from 30 minutes to 10 hours.In this case, the iron content of the plating film falls within the range of 5vt% to 14wt%.Furthermore, by this heat treatment, the first layer and the second layer are formed into an integral structure by thermal diffusion of Fe. becomes.

[Example] Two types of steel sheets were used and the galvannealed steel sheets of 17 examples (Examples) were treated with different hot-dip galvanizing conditions, second layer plating conditions, and alloying treatment conditions. The iron content inside was investigated and evaluated by performing a powdering test and a cratering test. For comparison,
Details of the 0 condition, which was similarly investigated for six cases (comparative examples) processed under conditions outside the scope of this invention and three cases according to the prior art (conventional examples), are as follows.

The steel plate used is a cold-rolled steel plate with a thickness of 0.81, and it contains low carbon A1 quilt (material A) for thin sheets, which is commonly used, and ultra-low carbon titanium, which is said to easily cause powdering for high processing purposes! 1 (Material B).

Table 1 shows each component.

Table 1 (% by weight) Hot-dip galvanizing is carried out in a continuous plating facility equipped with a non-oxidizing furnace and a reduction heating furnace. The spangles were thinned by spraying, and after the plating layer was cooled, a skin pass was performed at an elongation rate of 1.5% to smooth the surface.

Electroplating, plasma spraying, or powder spraying was used for Fe-B alloy plating, and each treatment was performed under the following conditions. In the case of powder spray plating, spangles were made finer by spray plating, and mist spraying was not performed.

(1) Electroplating FeSO4+ (NH4)2 S04 ・6H20:
350g/, QC406H6 (Starstone'!!ff)
: 3.5g/ , Q(NF(4) 2 B4O7・
4 H20: 1 to 100 g/Ωp)l: 2.5° Bath temperature: 60°C.

Yin 8i! Current density +1OA/dm".

f21 flame spraying Plasma gas: Ar.

Thermal spraying heat input: 20KW.

Thermal spraying distance: 100 degrees Average powder particle size: approximately 5μm Powder feeding distance: 5 g/miO・dm”.

(3) Powder spray Average powder particle size: approximately 5 μm.

Unsupplied speed: 3g/m stone/dm”.

The iron content in the surface layer of the plating film and the inner layer of the plating film is
They were investigated by Auger electron spectroscopy and Grimglow discharge emission spectroscopy, respectively.

Powdering resistance is determined by bending the material at 90 degrees with a radius of curvature of 2, applying adhesive tape to the inside of the bend, and peeling it off.
The adhesion of the powder to this adhesive tape was visually observed and evaluated by giving a score.

The grading criteria are as follows: 1: No adhesion at all, 2: Very little adhesion, 3: Slight adhesion, 4: Slight adhesion, and 5: Considerable adhesion.

Cratering resistance was evaluated by applying a chemical conversion treatment to the plated surface, followed by electrodeposition coating, and evaluating the number of craters generated at this time. A commercially available dipping type phosphate treatment agent was used for the chemical conversion treatment. For electrodeposition coating, a commercially available cationic electrodeposition paint was used, but after preparation, it was stirred for one week and electrodeposition was carried out by instantaneously applying an electrodeposition voltage of 300 V with an inter-electrode distance of 4Ω.

The processing conditions and investigation results for each of these examples are shown in Table 2.

In the examples, there was no inferiority in powdering resistance even with material B, and slight powdering was observed in Example No. 6 with the limit adhesion amount and Example No. 017 near the limit heating time, but in practical terms In terms of cratering resistance, two small cracks were found in one inner layer in Example No. 013 where the amount of plating on the second layer was at the lower limit, but this also poses no problem in practice.

In this way, all the alloyed hot-dip galvanized steel sheets in the examples have both powdering resistance and cratering resistance. In addition, the iron content in the inner layer ranges from 6wt% to 13wt.
%, which ensures sufficient corrosion resistance after painting.

On the other hand, in the comparative examples treated under conditions outside the scope of the invention, Comparative Example Na 1 without AI in the bath + Comparative Example N[L2 with excessive heating time, Comparative Example Na 3 with a large amount of PB in the bath, and Comparative Example Na 3 with a large amount of adhesion. Comparative example Na 4 which is too high, Comparative example N [L5 where the second layer is not plated, Comparative example Nα where the heating temperature is too high
There is a problem with either powdering resistance or cratering resistance.

In the conventional example, the conventional example NIL1 was alloyed only by rapid heating and high temperature heating, and there were problems in both properties, and the conventional example NIL
L 2 is alloyed at a low temperature after rapid heating at high temperatures and has inferior cratering resistance, while conventional examples No. 3 are alloyed through rapid heating at high temperatures and have an iron content of 80% without boron. It has Fe-Zn alloy plating and has poor powdering resistance. In this way, both characteristics are not satisfied at the same time.

In addition, in Example N (L 14), regarding the direction of the alloyed hot dip galvanized coil ('b 1800 mm),
The iron content of the inner plating layer was examined at intervals of 00 rhymes.

In this case, comparison was made with conventional example No. 2. This result is shown in Figure 2. In Figure 0, the horizontal axis is the distance from the left end of the coil, the vertical axis is the iron content, the O mark is the plot of Example No. 14, and the mark is the conventional example No. As is clear from Figure 0, which is a plot of [L 2 , N[Ll
The average iron content of No. 4 was 8.1 wt%, and the iron content at all measurement points was distributed between 7.9 ivj% and 8.3 wt%. On the other hand, the iron content of conventional example No. 2 is -8.3w
t%, and all measurement points range from 8.0wt% to 9.0w
It was distributed between t% and had a large variation.

Furthermore, to determine whether or not the r-phase exists at the bottom of the plating film, approximately two-thirds of the upper layer of the plating film was removed and X-ray diffraction was performed on samples subjected to alloyed hot-dip galvanizing treatments from Examples NIL1 to Nα17. As a result, no phase was detected for any of the samples.

[Effects of the Invention] The plated steel sheet of the present invention has substantially no phase in the plating film, has a high iron content, a boron-containing surface layer and an inner layer that have an integral structure, and has a low alloy composition. Since it has a film with uniform distribution in the surface direction, it has not only sufficient corrosion resistance but also excellent powdering resistance and cratering resistance.

Furthermore, the method of the present invention allows the above-mentioned plated steel sheet to be easily manufactured through simple steps, and is thus an invention that is highly effective industrially.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between heat treatment conditions and appropriate characteristics for detailed explanation of the present invention, and FIG. 2 is a diagram showing the distribution of iron content in one embodiment of the present invention.

Claims (3)

[Claims] (1) At least one side of the steel plate has a first layer formed by hot-dip galvanizing, and the Fe content on the first layer is 97.0 wt% or more and 100 wt%.
% and the remainder is boron. The inner layer is an alloyed galvanized plating consisting of δ_1 phase and ζ phase except for the boundary layer with the steel substrate with a thickness of 0.5 μm, and is characterized by a uniform distribution of iron content in the surface direction. Alloyed hot-dip galvanized steel sheet with excellent workability and paintability. (2) A method for producing an alloyed hot-dip galvanized steel sheet with excellent workability and paintability, the method comprising the following steps. (b) Steel plate subjected to normal pretreatment with Al0.05wt%
30g/m^2 or more by immersion in a hot-dip galvanizing bath containing 0.3wt% or less and 0.2wt% or less of Pb9
A step of applying a first layer plating of 0 g/m^2 or less, (b) a step of performing spangle refinement treatment while the plating film is in a molten state, (c) a skin pass treatment after the plating film has solidified. ,
A step of smoothing the surface of the hot-dip galvanized film, (d) applying 0.5% on one or both sides of this hot-dip galvanized steel sheet.
Fe of g/m^2 or more and 10g/m^2 or less is 97.0w
A step of applying a second layer of Fe-B alloy plating containing t% or more and less than 100wt% and B of 0.001wt% or more and less than 3wt%, (e) Placing the plated steel sheet in the above step in a non-oxidizing or reducing atmosphere 1 in a temperature range of 320℃ or higher and lower than the melting point of zinc in an open coil state in a batch type annealing furnace maintained at
A process of heating from 0 minutes to 50 hours. (3) A method for producing an alloyed hot-dip galvanized steel sheet with excellent workability and paintability, the method comprising the following steps. (b) Steel plate subjected to normal pretreatment with Al0.05wt%
30g/m^2 or more by immersion in a hot-dip galvanizing bath containing 0.3wt% or less and 0.2wt% or less of Pb9
A step of applying a first layer plating of 0 g/m^2 or less, (b) Fe content of 97.0 wt% or more and less than 100 wt% on one or both sides of the steel plate while the plating film is in a molten state;
Spray Fe-B alloy powder with B of 0.001 wt% or more and less than 3 wt% to produce 0.5 g/m^2 or more and 10 g/m
A step of applying a second layer plating of ^2 or less, (c) a step of smoothing the surface of the hot-dip galvanized film by performing skin pass treatment after the plating film has solidified, (d) a step of smoothing the surface of the galvanized film smoothed in the above step. A process of heating a steel plate with an open coil in a batch type annealing furnace maintained in a non-oxidizing or reducing atmosphere at a temperature range of 320° C. or higher and lower than the melting point of zinc for 10 minutes to 50 hours.