KR101143189B1 - Steel sheet for hot dip galvanizng with precoating layer having excellent coatability and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a steel plate; An Fe-rich precoat layer directly formed on the steel sheet; And a Mn-rich precoat layer formed directly on the Fe-rich precoat layer. The present invention also provides a steel sheet for hot-dip coating excellent in galvanizing property. The present invention also provides a method of producing a steel sheet for hot-dip galvanizing comprising the steps of immersing the steel sheet in an Fe-Mn-S aqueous solution or spraying a Fe-Mn-S aqueous solution on the steel sheet to form a precoat layer on the surface of the steel sheet ; And annealing the steel sheet on which the precoat layer is formed.

Hot-dip coating, Pre-coating, Lead plating, Plating

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a steel sheet for precoating, which is excellent in galvanizing ability,

The present invention relates to a steel sheet for hot-dip galvanizing which is used as a vehicle material and a method of manufacturing the steel sheet.

Recently, as the regulations on environmental pollution become more strict, there is a demand for improvement of fuel efficiency of automobiles, and a lot of efforts have been made to reduce the weight of automobile body to solve this problem. There is a need for a method capable of securing stability.

To solve this problem, a hot-dip galvanized steel sheet has emerged as a high-strength steel sheet for an automobile body. Of these, Dual Phase Steel, TRIP (Transformation Induced Plasticity Steel), CP Steel (Comlex Phase Steel) and TWIP Steel (Twinning Induced Plasticity Steel) are commercially available. However, such a high-strength steel contains a large amount of strong oxidizing and rust-inhibiting elements such as silicon, manganese and aluminum, and thus has a problem of poor plating ability. The annealing process, which is one of the manufacturing processes of the hot dip galvanized steel sheet, is performed in a reducing atmosphere containing 5% or more of hydrogen and the remaining nitrogen and at a high temperature of about 800 ° C. During the heat treatment process, silicon, manganese, Is diffused and reacts with oxygen and moisture present in the annealing furnace, and SiO ₂ , MnO, Al ₂ O ₃ and composite oxides thereof are accumulated on the surface of the steel sheet, thereby significantly reducing the wettability with molten zinc. As a result, it becomes difficult to secure the plating property, so that bare spots are generated, and even if the plating is performed by hot-dip coating, the adhesion of the plating is seriously deteriorated and plating peeling occurs during processing.

In order to solve such a problem, there has been proposed a technique of forming a Fe-line plating layer on the surface of a steel sheet before the hot dip galvanizing process. Among these techniques, Japanese Patent Application Laid-Open Nos. 1980-146229, 1981-201780, Patent Publication No. 1982-002813 and the like. As another technique, a technique of forming a pre-plating layer containing boron, carbon, nitrogen and sulfur in iron has been proposed, and among these techniques, JP-A-1991-328353 and the like can be mentioned. However, such an Fe-based electroplating method mainly uses electroplating to conduct electroplating, which requires expensive plating equipment and raises the process unit price. In addition, the lead plating by the electroplating method requires a plating adhesion amount of about 10 g / m < 2 > or more in order to prevent unplated plating, but it is often difficult to completely prevent unplated plating even if the plating amount is plated.

The present invention intends to provide a steel sheet for pre-coating and hot-dip galvanizing steel which can improve the wettability of a steel sheet and a molten steel amount without using an additional electroplating facility, thereby ensuring stable and superior plating quality.

In one embodiment, the present invention provides a steel plate comprising: a steel plate; An Fe-rich precoat layer directly formed on the steel sheet; And a Mn-rich precoat layer formed directly on the Fe-rich precoat layer. The present invention also provides a precoating hot-dip coating steel sheet excellent in platability.

The sum of the thicknesses of the Fe-rich precoat layer and the Mn-rich precoat layer is preferably 50 to 800 nm.

The thickness of the Mn-rich precoat layer is preferably 10 to 50% of the total thickness of the precoat layer.

The steel sheet may include one or more of O (oxygen), Si, Mn and Al.

The steel sheet may be one of Dual Phase Steel, TRIP (Transformation Induced Plasticity Steel), CP Steel (Comlex Phase Steel), and TWIP Steel (Twinning Induced Plasticity Steel).

According to another embodiment of the present invention, there is provided a method of manufacturing a steel sheet for hot-dip galvanizing, comprising the steps of immersing the steel sheet in an Fe-Mn-S aqueous solution or spraying a Fe-Mn- ; And annealing the steel sheet on which the precoat layer has been formed by annealing. The present invention also provides a method for producing a precoated hot-dip galvanizing steel sheet.

The Fe-Mn-S aqueous solution preferably contains 70 to 85% of Fe, 15 to 30% of Mn, residual moisture, moisture and other unavoidable impurities, and further contains 0.5% or less of a wetting agent More preferable.

In the annealing heat treatment step, the precoat layer is separated into an Fe-rich precoat layer and a Mn-rich precoat layer. An Fe-rich precoat layer is formed directly on the steel sheet, and a Mn-rich precoat layer It is preferable that a coating layer is formed.

According to the present invention, it is possible to provide a steel sheet for hot-dip coating that is excellent in platability, alloyability, and dent resistance.

In the case of high-strength steels containing a lot of high-oxidation elements such as silicon and manganese, silicon or manganese diffuses to the surface of the steel sheet during the annealing process before plating and reacts with oxygen or moisture to form an oxide layer on the surface of the steel sheet . 590 TRIP steel, a kind of high-strength steel, was annealed in a reducing atmosphere of 5% hydrogen and the remainder nitrogen under the conditions of a roots -40 ° C, a soaking temperature of 800 ° C and a soaking time of 60 seconds, An oxide layer 2 is formed on the substrate 1. Here, the Pt protection layer 3 is a layer formed on the uppermost layer to prevent damage to the oxide layer 2 during processing of the sample for analysis. 2 is a graph showing the results of analysis using a glow discharge spectrometer (GDS) in order to confirm the compositional change of the steel sheet at different depths. The silicon and manganese were diffused on the surface of the steel sheet to form an oxide layer Can be confirmed. The steel sheet was subjected to alloying and hot dip galvanizing under the conditions of a plating bath temperature of 460 캜 and an aluminum concentration of 0.13%, and the surface appearance of the steel sheet was shown in Fig. 3. The area of about 80% It can be confirmed that the sex is poor.

The oxide layer is formed to a thickness of several tens of nanometers and is a single or composite oxide of silicon and manganese, which is a factor that greatly reduces the wettability of the steel sheet and molten zinc. In particular, the silicon oxide forms a very stable oxide of an amorphous type, and thus the plating ability is greatly deteriorated.

In order to solve this problem, the inventors of the present invention have found that a steel sheet is immersed in an Fe-Mn-S aqueous solution before the annealing heat treatment step or at the beginning of the annealing heat treatment step (steel sheet temperature: 150 DEG C or lower) A method of spraying an Fe-Mn-S aqueous solution onto the surface of a substrate and then forming a precoat layer having a structure in which the coating material is separated into two or more layers in annealing heat treatment, Thereby completing a method for producing a gold steel sheet.

In the present invention, the Fe-Mn-S aqueous solution is not necessarily limited in its content, but may be variously used depending on the type of steel sheet, the composition of the plating bath, and the like. Preferably, the Fe-Mn-S aqueous solution is prepared by mixing Fe oxide, Mn oxide and sulfuric acid as main components and adjusting the pH to 1 to 2. The Fe-Mn-S aqueous solution contains 70 to 85% Fe, 15 to 30% Other moisture, oxygen and unavoidable impurities. It is more preferable to add not more than 0.5% of a water-soluble ester wetting agent containing no Si and an anionic surfactant to the aqueous solution having the above composition.

In the case of forming the precoat layer of the present invention, since the dense oxide layer causing the delay in the alloying rate and the outburst and causing the dent defect to adhere to the Hearth Roll is reduced or prevented, Alloying reactivity and anti-dent are simultaneously improved.

The present invention is characterized in that the steel sheet is immersed in the Fe-Mn-S aqueous solution using a conventional immersion apparatus to coat the surface of the steel sheet or the Fe-Mn-S aqueous solution is coated on the surface of the steel sheet using a conventional spraying apparatus And the surface of the steel sheet is coated. Such a precoating process can be carried out before the annealing heat treatment step, and the same effect can be obtained even when the above coating apparatus (immersion or spraying) is provided in the annealing furnace and the annealing is performed at the initial stage of annealing heat treatment .

By this annealing heat treatment step, the precoat layer formed on the surface of the steel sheet is separated into two or more precoat layers. The annealing heat treatment method is not particularly limited. However, since the remaining coating layer may be incidental or may not be generated in some cases, only two layers will be described below. The moisture contained in the precoat layer is evaporated by the heat and hydrogen gas provided in the annealing heat treatment process, and the precoat layer is separated into the Fe-rich precoat layer and the Mn-rich precoat layer. At this time, even if some unreacted oxygen remains in the components of the coating layer, the same effect can be obtained.

As an embodiment of the present invention, 590 TRIP steels were subjected to annealing in a reducing atmosphere of 5% hydrogen and the balance of nitrogen under the conditions of a roots -40 ° C, a soaking temperature of 800 ° C and a soaking time of 60 seconds, A slight oxide layer 5 is formed on the steel sheet 4 and an Fe-rich precoat layer 6 and a Mn-rich precoat layer 7 are formed on the oxide layer 5. Here, the Pt protection layer 8 is a layer formed on the uppermost layer in order to prevent damage to the oxide layer 5 and the precoat layers 6 and 7 during processing of the sample for analysis. FIG. 5 is a graph showing the results of analysis using a glow discharge spectrometer (GDS) in order to confirm the compositional change of the steel sheet at different depths. The Fe-rich precoat layer 6 and the Mn- It can be confirmed that the coating layer 7 is formed and the Si-based oxide is greatly reduced on the extreme surface of the steel sheet. The steel sheet was subjected to alloying and hot-dip galvanizing under the conditions of a plating bath temperature of 460 ° C and an aluminum concentration of 0.13%, and the surface appearance of the steel sheet was shown in Fig. 6, and there was almost no plated portion, Can be confirmed.

Since the Mn-rich precoat layer of the present invention is not a complete metallic crystal and is mainly a particle type or a porous oxide, it readily undergoes a substitution reaction with aluminum, which is one component of the plating bath, and zinc, which is one component of the plating bath, The wettability can be secured and the formation of oxides can be prevented. The Fe-rich precoat layer is formed below the Mn-rich precoat layer and prevents diffusion of elements such as silicon and manganese present in the steel sheet to the surface, thereby reducing the diffusion rate.

The thickness of the precoat layer of the present invention is preferably limited to a range of 50 to 800 nm in order to provide excellent plating ability. When the thickness of the precoat layer is less than 50 nm, the separated Mn-rich precoat layer is not formed, and since the precoat layer is not uniform throughout, the effect of suppressing the diffusion of the oxidizing elements in the steel to the surface of the steel sheet is reduced When the hot-dip coating is carried out, the plating property becomes poor. On the other hand, when the thickness of the precoat layer exceeds 800 nm, there is an effect of inhibiting the diffusion of oxidizing elements from the steel to the surface of the steel sheet, but the effect is saturated, meaning less and also alloying and denting properties are somewhat reduced . In addition, since it is very difficult to secure the thickness of the precoat layer by the dipping or spraying method without performing the electroplating in excess of 800 nm, the precoating treatment time and the solution concentration are out of the range that can be worked in a normal hot- .

The Fe-rich precoat layer of the present invention preferably contains Fe in an amount of 50 wt% or more, and the remainder may include manganese, oxides, and the like. The Mn-rich precoat layer preferably contains Mn in an amount of 10 wt% or more, and the content is a high manganese content to the manganese content in the steel sheet.

Also, it is preferable that the Mn-rich precoat layer in the thickness ratio is in the range of 10 to 50% of the total precoat layer. When the Mn-rich precoat layer is less than 10%, the effect of suppressing the diffusion of the oxidizing elements in the steel to the surface of the steel sheet is reduced, so that when the hot-dip coating is performed, the plating ability is poor. On the other hand, when the Mn-rich precoat layer is more than 50%, the Fe-rich precoat layer is not properly formed and it is difficult to prevent diffusion of strong oxidizing elements present in the steel sheet.

As described above, according to the present invention, it is possible to provide a steel sheet for hot-dip coating that prevents the diffusion of a strong oxidizing element present in a steel sheet and improves the diffusion of zinc upon hot-dipping to provide a steel sheet having excellent plating ability, alloyability and dent resistance .

Hereinafter, the present invention will be described in detail by way of examples.

(Example 1)

(1.5% by weight of Si, 1.6% by weight of Mn, 0.08% by weight of C, 0.02% by weight of Sb, and the balance of Fe and other alloying elements) of 1.095 mm in thickness and 590 MPa in tensile strength. Full Hard Hard Steel Sheets: F / H) were immersed in an Fe-Mn-S aqueous solution to control the precoat thickness as shown in the following Table 1 in a reducing atmosphere of 5% hydrogen and the remainder nitrogen in a reducing atmosphere at a temperature of -40 ° C, 60 seconds and a heat treatment cycle of a conventional 590 TRIP steel. The steel sheet was plated with a hot dip galvanizing bath (Al concentration: 0.13%) at 460 ° C. and then alloyed to form a galvannealed steel sheet : GA). Anti-dent was evaluated for the annealed specimens, and the remainder was subjected to alloying hot dip galvanizing to evaluate the wettability and the alloying reactivity. The results are shown in the following Table 1 Respectively. In this case, the composition of the Fe-Mn-S precoat solution was composed of 80% Fe, 19.9% Mn and 0.1% wetting agent based on the ratio of the solid content corresponding to each component. S was controlled by adding sulfuric acid to the range of pH 2.

Hereinafter, methods and criteria for evaluating the plating quality (plating ability, alloyability and dent resistance) in the examples are as follows.

* Wettability: In the present embodiment, the appearance of the coated steel sheet was observed with naked eyes, and the evaluation criteria were as follows.

Grade 1: no bare spot, level for car exterior

Grade 2 (Grade 2): Micro-plating microscopic observation, level for automobile inner panel

Grade 3 (Grade 3): uncoated slightly observed, general purpose level

Grade 4 (Grade 4): uncoated somewhat observable, no product level

Grade 5 (Grade 5): Unplated large quantities, no product level

** Alloying reactivity: When the hot-dip galvanized steel sheet is rapidly reheated, the appearance of the coated steel sheet is visually observed to the extent that the Fe of the base material diffuses into the galvanized layer to form the Fe-Zn alloy plating layer uniformly. Is as follows.

Grade 1: very uniform alloy layer surface, level for automotive shell plating

Grade 2: uniform surface of alloy layer, level for automobile inner plate

Grade 3: The surface of the alloy layer is relatively uniform,

Grade 4 (Grade 4): alloy layer surface is relatively uneven, not product level

Grade 5 (Grade 5): Unevenness of alloy layer surface, product not level

*** Anti-dent: It is a property that the annealed oxide is not picked up on the surface of the hearth roll of the annealing apparatus. In the annealing apparatus, in the process of heat treatment of the steel sheet at a high temperature, Si, When the annealed oxide formed by diffusing Mn, Al or the like into the surface of the steel sheet is picked up on the surface of the hurt roll, a dent defect is caused in the steel sheet. Therefore, the dent resistance is excellent as the coverage percentage of the annealed oxide formed by diffusing on the surface of the steel sheet is small. The coating rate of the annealed oxide was measured at 30,000 times using a polarization scanning electron microscope (SEM) and then the coating rate was measured using a particle analyzer (Image Analyzer). The thickness of the annealed oxide film was also measured by reference to the evaluation using a GDS (Glow Discharge Spectrometer). The evaluation criteria are as follows.

Grade 1: Coating rate of annealed oxide: 5% or less

Grade 2 (Grade 2): Coating rate of annealed oxide is 20% or less

Grade 3: Coating rate of annealed oxide is 35% or less

Grade 4 (Grade 4): Coating rate of annealed oxide is 45% or less

Grade 5 (Grade 5): Over 45% of annealed oxide

division Precoat layer
Thickness (nm) Plating quality * Plating Properties ** Alloyability ** Na dent castle Comparative Example 1 0 5 5 5 Comparative Example 2 40 4 4 3 Inventory 1 50 3 3 3 Inventory 2 100 2 2 2 Inventory 3 300 One One One Honorable 4 500 One One One Inventory 5 800 One One One Comparative Example 3 900 One 2 2 Comparative Example 4 1200 3 3 3

As shown in Table 1, Inventive Examples 1 to 5 satisfying the conditions of the present invention all exhibited plating qualities of 1 to 3 grades and exhibited sufficient quality for use as a plating product. In particular, when the thickness of the precoat layer of Inventive Examples 3 to 5 was in the range of 300 to 800, the best plating quality was exhibited. On the other hand, Comparative Example 1, in which no precoating was applied, and Comparative Example 2 in which the thickness of the precoat layer was not sufficient, was inferior in quality to at least one of plating quality, alloyability and dent resistance, Respectively. On the other hand, in the case of Comparative Examples 3 and 4 in which the thickness of the precoat layer exceeds 800 nm, the quality characteristic is not at an inferior level of the product, but it is difficult to actually realize it in operation and even if the thickness of the precoat layer is increased, There is no meaning.

(Example 2)

The thickness of the precoat layer was uniformly coated to 300 nm, and the ratio of the thickness of the Mn-rich precoat layer was measured as shown in Table 2 below Respectively. Plating properties, alloyability and dent resistance were evaluated in the same manner as in the evaluation method of Example 1, and the results are shown in Table 2 below.

division Mn-rich coating layer thickness /
Total Precoat Layer Thickness (%) Plating quality * Plating Properties ** Alloyability *** My Dent Castle Comparative Example 5 0 5 5 5 Comparative Example 6 5 4 3 3 Inventory 6 10 3 2 2 Honorable 7 20 One One One Honors 8 30 One One One Proposition 9 50 3 3 One Comparative Example 7 60 4 3 One Comparative Example 8 70 5 5 2

As shown in Table 2, it can be seen that the plating quality is influenced by the ratio of the thickness of the Mn-rich precoat layer and the Fe-rich precoat layer forming the precoat layer. In this case, the optimum thickness ratio of the Mn- Is in the range of 10 to 50% of the total thickness of the precoat layer. If it is out of the optimum thickness range, one or more of the quality characteristics shows that the product is in an inapplicable level.

(Example 3)

The components of the precoat layer were controlled and controlled in the order shown in Table 3. Other conditions were precoating, annealing heat treatment, and galvanneal zinc plating under the manufacturing conditions of Example 1. The thickness of the precoat layer was 300 nm The positions of the Mn-rich precoat layer, the Fe-rich precoat layer and the steel sheet were controlled in the order shown in Table 3 below. The plating ability, the alloyability and the dent resistance were evaluated in the same manner as the evaluation method of Example 1, and the results are shown in Table 3 below.

division Precoat layer and steel plate sequence Plating quality * Plating Properties ** Alloyability *** My Dent Castle Inventory 10 Mn / Fe / Sub One One One Comparative Example 9 Fe / Mn / Sub 4 3 3 Comparative Example 10 FeMn / Sub 4 3 3

However, the notation of the precoat layer forming structure is as follows.

a) Mn / Fe / Sub: Mn-rich Underneath the precoat layer Fe-rich precoat layer Underneath the steel plate

b) Fe / Mn / Sub: Underneath the Fe-rich precoat layer, Mn-rich precoat layer

c) FeMn / Sub: Mutual mixing of Mn and Fe Precoat layer and order

As shown in Table 3, it can be seen that the plating quality is influenced by the structure of the precoat layer, and the Fe-rich precoat layer directly under the Mn-rich precoat layer and the plating quality It is the only structure that can be secured.

(Example 4)

The steel grades shown in Table 4 were pre-coated, annealed and galvannealed under the manufacturing conditions of Example 1, and the precoat layer was uniformly coated at a thickness of 300 nm. The plating performance, alloyability and dent resistance were evaluated in the same manner as in the evaluation method of Example 1, and the results are shown in Table 4 below.

division Grade / Tensile Strength
(MPa) Precoat layer thickness (nm) Plating quality * Plating Properties ** Alloyability *** My Dent Castle Exhibit 11 TRIP / 780 300 One One 2 Inventory 12 DP / 590 300 One 2 One Inventory 13 DP / 1180 300 One 2 2 Inventory 14 TWIP / 980 300 3 3 3 Comparative Example 11 TRIP / 780 0 3 4 4 Comparative Example 12 DP / 590 0 3 3 4 Comparative Example 13 DP / 1180 0 3 4 4 Comparative Example 14 TWIP / 980 0 5 5 5

As shown in Table 4, when the precoating treatment of the present invention was applied to the high-strength steel (Examples 11 to 14) and the conventional cases (Comparative Examples 11 to 14) were compared, While the plating quality is all within the grade 3, the comparative example shows one or more quality characteristics of the grade 4 or higher, which is not available. As a result, it can be seen that the plating quality is greatly improved when the technique of the present invention is applied regardless of the type of high strength steel.

(Example 5)

In order to control the component system of the precoat layer, a precoat layer was formed using an Fe-Mn-S aqueous solution shown in Table 5 below. Otherwise, the precoating, annealing heat treatment, and galvanneal zinc plating were performed under the manufacturing conditions of Example 1, and the precoat layer was uniformly coated at a thickness of 300 nm. The composition of the precoat solution was controlled based on the solid content ratio of each component. The plating performance, alloyability and dent resistance were evaluated in the same manner as in the evaluation method of Example 1, and the results are shown in Table 5 below.

division Preparation of pre-coating liquid Plating quality Fe (%) Mn (%) Wetting agent (%) * Plating Properties ** Alloyability *** My Dent Castle Comparative Example 15 95 5 0 4 3 3 Honorable Mention 15 85 15 0 2 One One Inventory 16 80 20 0 2 One One Inventory 17 70 30 0 2 One 2 Comparative Example 16 60 40 0 4 4 4 Inventory 18 80 19.95 0.05 One One One Evidence 19 80 19.5 0.5 One One One Comparative Example 17 80 19 1.0 2 One One

As shown in Table 5, it can be seen that the coating quality is influenced by the composition ratio of the pre-coating solution. In this case, the optimum composition of the pre-coating solution is 70 ~ 85% Fe and 30 ~ 15% , And more preferably 0.5% or less by weight of the wetting agent. If it is out of the optimal composition range, one or more of the quality characteristics shows that the product is in an inadequate level. On the other hand, in the case of the wetting agent, it is possible to dispense with the addition, but when the addition is carried out (Examples 18 and 19), the plating ability is improved more than the solution of the same condition. When the weighting agent exceeds 0.5% (Comparative Example 17), precipitation of the solution occurs or the plating property is deteriorated.

FIG. 1 is a photograph of a cross-sectional structure of an oxide layer of a steel sheet produced by a conventional technique by an electric field transmission electron microscope (FE-TEM).

FIG. 2 is a graph showing a change in composition of a steel sheet manufactured by a conventional technique with depth by a glow discharge spectrometer (GDS).

3 is a photograph of the surface appearance of the galvannealed steel sheet produced by the prior art.

Fig. 4 is a photograph of the cross-sectional structure of the oxide layer of the steel sheet subjected to the pre-coating and the annealing heat treatment produced by the present invention with an electric field transmission electron microscope.

Fig. 5 is a photograph of the distribution of the cross section of the oxide layer in the precoated and annealed steel sheet produced by the present invention by field emission transmission electron microscopy. Fig.

Fig. 6 is a front surface photograph of a steel sheet subjected to precoating, annealing heat treatment and galvannealed galvanized steel sheet according to the present invention.

DESCRIPTION OF THE RELATED ART [0002]

1. steel plate, 2. oxide layer

3. Pt protective layer, 4. Steel plate

5. oxide layer, 6. Fe-rich precoat layer

7. Mn rich precoat layer, 8. Pt protective layer

(1 to 3: steel sheet according to the prior art, 4 to 8: steel sheet according to the present invention)

Claims (9)

Steel plate; An Fe-rich precoat layer directly formed on the steel sheet; And a Mn-rich precoat layer formed directly on the Fe-rich precoat layer. The pre-coating hot-dip coating steel plate according to claim 1, wherein the sum of the thicknesses of the Fe-rich precoat layer and the Mn-rich precoat layer is 50 to 800 nm. The pre-coating hot-dip coating steel plate according to claim 1, wherein the thickness of the Mn-rich precoat layer is 10 to 50% of the total precoat layer thickness. The pre-coated hot-dip galvanized steel sheet according to claim 1, wherein the steel sheet comprises one or more of O (oxygen), Si, Mn and Al. The plating apparatus according to claim 1, wherein the steel sheet is one of Dual Phase Steel, TRIP (Transformation Induced Plasticity Steel), CP Steel (Compex Phase Steel) and TWIP Steel (Twinning Induced Plasticity Steel) Precoated steel sheet for hot-dip galvanizing with excellent properties. A method for producing a steel sheet for hot dip galvanizing, Immersing the steel sheet in an Fe-Mn-S aqueous solution or spraying a Fe-Mn-S aqueous solution on the steel sheet to form a precoat layer on the surface of the steel sheet; And And annealing the steel sheet on which the precoat layer is formed, The precoat layer is separated into an Fe-rich precoat layer and an Mn-rich precoat layer, and a Fe-rich precoat layer is formed on the steel sheet. An Mn-rich Wherein a precoat layer is formed on the surface of the precoat layer. The method of claim 6, wherein the Fe-Mn-S aqueous solution contains 70 to 85% of Fe, 15 to 30% of Mn, and other moisture, oxygen and unavoidable impurities. A method for manufacturing a steel sheet for plating. 8. The method of claim 7, wherein the Fe-Mn-S aqueous solution further comprises 0.5% or less of a wetting agent. delete

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