JP5354600B2 - High-strength galvanized DP steel sheet with excellent mechanical properties and surface quality and method for producing the same - Google Patents

Description

The present invention relates to a high strength DP (Dual Phase) steel having excellent mechanical properties and surface quality, which is mainly used for interior, exterior and structure of a vehicle, and more specifically, manufactured from a conventional high strength DP steel. The present invention relates to a high-strength galvanized DP steel sheet having a superior surface quality and mechanical properties, and a method for producing the same.

  Due to the tendency of recent automotive molded products to become complicated and integrated, automotive steel sheets are required to have higher formability. On the other hand, as is well known, a steel sheet for automobiles must be excellent in work brittleness and fatigue properties of welds in order to improve the usefulness of automobiles. Furthermore, the steel sheet for automobiles must have a plated surface that is satisfactory even in beauty.

  In general, in order to increase the formability and strength of a steel sheet, the material strengthening component such as silicon (Si), manganese (Mn), titanium (Ti), niobium (Nb), aluminum (Al) is used to manufacture the steel sheet Add. However, most of these components are components having a stronger oxygen affinity than iron (Fe), and thus cause surface concentration of the oxide during the cold rolling annealing process.

  Such surface concentration of the oxide may cause deterioration in plating quality such as plating peeling. In addition, if the surface concentrate is rough, it may adhere to the hearth roll of the continuous annealing furnace and cause defects such as dents on the surface of the plated steel sheet.

In order to improve the above-mentioned problem of plating defects, Japanese blast furnace companies have developed a known technique for manufacturing a thin steel sheet for deep processing.

  In summary, methods for improving plating performance by adding specific components such as chromium (Cr), antimony (Sb), and tin (Sn) are disclosed (for example, Patent Document 1 and Patent Document 1). 2, see Patent Document 3, Patent Document 4, and Patent Document 5). Alternatively, a method of preventing the formation of a surface concentrate in the cold rolling annealing process by pre-oxidizing the hot rolled coil before the cold rolling process has been shown (for example, see Patent Document 6). However, in these methods, the effect of adding specific components is not clear, and the metallurgical behavior of the added components is not clearly verified. For this reason, it was thought that this manufacturing method was insufficient and lacked processability.

  Furthermore, since some of the above-mentioned conventional techniques are manufacturing methods that cannot be carried out with the current general hot-rolling-cold-rolling-continuous annealing equipment, there is no actual commercial production.

JP 2002-146477 A JP 2001-64750 A JP 2002-29497A JP 2002-155317 A Korean Application No. 2005-0128666 Specification JP 2001-288550 A

The present invention has been made to improve the conventional problems. The object of the present invention is to control the alloy components and the coiling temperature of the hot rolling process appropriately, thereby improving the mechanical performance and surface. An object of the present invention is to provide a method for establishing a method for producing a high-strength galvanized DP steel sheet having quality more easily than conventional high-strength DP steel.

The high-strength galvanized DP steel sheet having excellent mechanical properties and surface quality according to the present invention for achieving the above-mentioned problems is carbon (C) 0.01 to 0.2%, silicon (Si) by weight%. 0.01 to 1.5%, manganese (Mn) 0.2 to 4.0%, phosphorus (P) 0.001 to 0.1%, sulfur (S) 0.03% or less, aluminum (Al) 0 0.01 to 1.5%, nitrogen (N) 0.001 to 0.03%, and antimony (Sb) 0.005 to 0.1% , and boron (B) 0.0002 to 0.00% selectively. Including at least one of 005%, chromium (Cr) 0.01 to 2.0%, and molybdenum (Mo) 0.005 to 0.5%, with the balance of iron (Fe) and other inevitable Having a composition consisting of impurities,
The composition satisfies the relationship of the following formula (1),
In addition, an oxide layer having a thickness of 1 μm or less is provided on the surface.

In addition, the method for producing a high-strength galvanized DP steel sheet having excellent mechanical properties and surface quality according to the present invention includes carbon (C) 0.01 to 0.2%, silicon (Si) 0.01% by weight. To 1.5%, manganese (Mn) 0.2 to 4.0%, phosphorus (P) 0.001 to 0.1%, sulfur (S) 0.03% or less, aluminum (Al) 0.01 to 1.5%, nitrogen (N) 0.001 to 0.03%, and antimony (Sb) 0.005 to 0.1%, optionally boron (B) 0.0002 to 0.005%, A composition comprising at least one of chromium (Cr) 0.01 to 2.0% and molybdenum (Mo) 0.005 to 0.5%, the balance being iron (Fe) and other inevitable impurities And a steel slab whose composition satisfies the following formula (1): 1100 ° C. to 1250 A step of re-heating to,
Hot rolling the steel slab;
Winding temperature (CT) satisfying the following formula (2) winding within a temperature range of ± 20 ° C.,
Carrying out pickling and cold rolling;
Annealing at 700 ° C. to 860 ° C .;
It is characterized by including.

  According to the present invention, it is possible to produce a high-strength DP steel having excellent surface properties and excellent mechanical properties.

It is a photograph which shows the shape of the oxide of this invention steel and comparative example steel by the presence or absence of antimony (Sb) addition. FIG. 1A is a comparative steel 16, and FIG. 1B is an inventive steel 11. It is a graph showing the size distribution of the oxide formed in the surface of the steel of this invention.

Hereinafter, embodiments of the present invention will be described in detail.
The present inventors have studied a method for producing high-strength DP steel that is easier to manufacture than conventional high-strength DP steel and has excellent mechanical properties and surface quality. In the research process, researchers can control the increase in the diameter of oxide particles on the steel sheet surface by appropriately controlling the alloy composition of the steel and the hot rolling coiling temperature, It has been found that it can guarantee excellent surface quality and improve mechanical properties.

Hereinafter, the component composition range of the steel according to the present invention will be described.
The carbon (C) content is preferably in the range of 0.01 to 0.2%.
Carbon (C) is a very important component for increasing the strength of the steel sheet and securing a composite structure composed of ferrite and martensite. When the carbon (C) content is less than 0.01%, the target strength in the present invention cannot be ensured. On the other hand, if the carbon (C) content exceeds 0.2%, the tensile strength and weldability are likely to be reduced. Therefore, carbon (C) is preferably added in an amount of 0.01 to 0.2%.

The silicon (Si) content is preferably in the range of 0.01 to 1.5%.
Silicon (Si) is a useful component that can ensure strength without reducing the ductility of the steel sheet. Silicon (Si) forms ferrite and promotes the formation of martensite by increasing the carbon (C) concentration in untransformed austenite. When the content of silicon (Si) is less than 0.01%, the above effect is not exhibited. On the other hand, silicon (Si) added in an amount of 1.5% or more increases the possibility that the surface characteristics and weldability will deteriorate. Therefore, it is preferable to add 0.01 to 1.5% of silicon (Si).

The content of manganese (Mn) is preferably in the range of 0.2 to 4.0%.
Manganese (Mn) has a great effect of strengthening the solid solution and promotes the formation of a composite structure composed of ferrite and martensite. When the addition amount of manganese (Mn) is less than 0.2%, the effect of realizing high strength is not sufficient. On the other hand, manganese (Mn) added in an amount of 4.0% or more increases the possibility of reducing weldability and hot rollability. Therefore, it is preferable to add 0.2 to 4% of manganese (Mn).

The phosphorus (P) content is preferably in the range of 0.001 to 0.1%.
Phosphorus (P) is a typical component added with manganese (Mn) to increase the strength of the solid solution. If the amount of phosphorus (P) added is less than 0.001%, a predetermined effect cannot be obtained. On the other hand, phosphorus (P) added in an amount of 0.1% or more reduces weldability and causes a large difference in the properties of steel due to central segregation that occurs during continuous casting. Accordingly, the P content is preferably limited to 0.001 to 0.1%.

The content of sulfur (S) is preferably 0.03% or less.
Since sulfur (S) is a component inevitably contained during the production of steel, it is preferable to limit the upper limit to 0.03% or less.

Aluminum (Al) is preferably in the range of 0.01 to 1.5%.
Aluminum (Al) is generally added for deoxidation of steel, but in the present invention, it is added for improving extensibility. Aluminum (Al) also suppresses the formation of carbides formed during austempering and increases strength. Further, when the amount of aluminum (Al) is less than 0.01%, the effect cannot be sufficiently obtained. On the other hand, aluminum (Al) added in an amount of 1.5% or more hinders alloying of the GA-plated layer in order to accelerate internal oxidation that occurs during annealing in the cold rolling process of steel, resulting in high alloying. Temperature requires. Therefore, it is preferable to add 0.01% to 1.5% of aluminum (Al).

Nitrogen (N) is preferably in the range of 0.001 to 0.03%.
N is an effective component for stabilizing austenite. Nitrogen (N) added less than 0.001% does not provide such an effect. On the other hand, nitrogen (N) added in an amount of 0.03% or more may combine with Al to produce coarse AlN, thereby reducing mechanical properties. Therefore, it is preferable that the nitrogen (N) content does not exceed 0.03%.

The boron (B) content is preferably in the range of 0.0002 to 0.005%.
Boron (B) is a grain boundary strengthening component, and has the effect of improving fatigue characteristics of spot welds and preventing phosphorus (P) grain boundary brittleness. Boron (B) has the effect of improving high-temperature extensibility in the production of steel with a high Al and Si content. In addition, boron (B) delays the transformation of austenite to pearlite during the cooling process during annealing. When boron (B) is added in an amount exceeding 0.005%, excess boron (B) is concentrated on the surface of the steel, thereby reducing the adhesion of the plating. Therefore, in order to obtain a desired effect, boron (B) must be added in an amount of 0.0002% or more. However, if it exceeds 0.005%, boron (B) rapidly deteriorates workability and plating. Deteriorate the surface properties of the steel sheet. Therefore, it is preferable to add 0.0002 to 0.005% of boron (B).

The chromium (Cr) content is preferably in the range of 0.01 to 2.0%.
Chromium (Cr) is a component added to improve the hardness of the steel and ensure the strength. When the chromium (Cr) content is less than 0.01%, it is difficult to ensure the above effect. On the other hand, if the chromium (Cr) content exceeds 2.0%, no further effect can be obtained, and the ductility is likely to deteriorate. Therefore, the chromium (Cr) content is preferably 0.01 to 2.0%.

The molybdenum (Mo) content is preferably in the range of 0.005 to 0.5%.
Molybdenum (Mo) is added to improve work brittleness and plating properties. However, when the molybdenum (Mo) content is less than 0.005%, the predetermined effect cannot be obtained. On the other hand, when the amount of molybdenum (Mo) exceeds 0.5%, a large improvement effect cannot be obtained, which is disadvantageous economically. Therefore, the content of molybdenum (Mo) is preferably 0.005 to 0.5%.

The content of antimony (Sb) is preferably in the range of 0.005 to 0.1%.
Antimony (Sb) itself does not form an oxide film at a high temperature, but is concentrated on the surface and grain boundaries of the steel and suppresses diffusion of components to the surface. As a result, the formation of oxides is suppressed. Moreover, antimony (Sb) has a remarkable effect in suppressing the selective oxidation which grows along the crystal grain boundary of the thin steel plate. Since antimony (Sb) contains a large amount of silicon (Si), manganese (Mn), and aluminum (Al), it penetrates various oxides generated along the grain boundaries on the surface of the steel sheet in the hot rolling process. Added to suppress.

  When the grain boundary oxide depth of the hot-rolled thin steel sheet exceeds 1 μm, the oxide remains inside the metal even after pickling, thereby causing defects of various scales in the subsequent cold rolling process. Cause. Therefore, it is important to control the depth of the grain boundary oxide of the hot-rolled steel sheet to 1 μm or less. Antimony (Sb) added in order to effectively suppress the selective selective oxidation of the crystal grain boundaries of the hot-rolled steel sheet has a remarkable effect on the suppression of defects due to scale. Antimony (Sb) is added to prevent the formation of oxides during annealing caused by the addition of large amounts of silicon (Si), manganese (Mn), and aluminum (Al), and promotes plating properties. In particular, antimony (Sb) effectively suppresses the coarsening of the surface oxide layer when added in combination with manganese (Mn) and boron (B).

  When the annealing oxide grows coarsely, the oxide is repeatedly laminated on a roll, and a dent is generated on the surface of the cold-rolled steel sheet and the plated steel sheet. Here, the suppression of the surface oxide by the addition of antimony (Sb) is very effective in suppressing the dent defect. Antimony (Sb) added in an appropriate amount increases the strength and ductility of the steel material, thereby improving the mechanical properties of the steel material.

  In addition to antimony (Sb), components such as tin (Sn), selenium (Se), and yttrium (Y) may have similar effects, but Sn is a grain of hot-rolled steel sheets. There is little effect to suppress the oxidation of the boundary. In addition, selenium (Se) and yttrium (Y) are more likely to be concentrated on the surface of the steel sheet than other components, and these oxides are formed under SiO2 and Al2O3 formed on the surface of the steel sheet. There is a high possibility of coarsening.

Therefore, the added antimony (Sb) exhibits an excellent effect of suppressing the surface concentration of MnO, SiO ₂ and Al ₂ O ₃ during the annealing of the cold-rolled steel sheet, and enhances the mechanical properties. Antimony (Sb) is required to be at least 0.005% or more, but when it is added in excess of a specific limit, an improved effect cannot be obtained. Therefore, it is preferable that the amount of antimony (Sb) does not exceed 0.1%.

When designing an alloy of a steel sheet having the component content range, it is preferable to satisfy the following formula (1).

  Manganese (Mn), silicon (Si), aluminum (Al), and boron (B) have the property of forming a concentrate on the surface of the steel sheet in the annealing process. If the amount of the concentrate of these components is increased, the plating characteristics are degraded. On the other hand, carbon (C), phosphorus (P), and antimony (Sb) tend to be unevenly distributed at the grain boundaries. Due to the uneven distribution of components such as carbon (C), phosphorus (P), and antimony (Sb), the concentrated components are manganese (Mn), silicon (Si), aluminum (Al), And hinders the diffusion of boron (B) and contributes to the surface properties.

  However, when an excessive amount of components are unevenly distributed at the grain boundaries, material properties such as elongation are deteriorated. On the other hand, when an excessive amount of components is concentrated on the surface, the surface characteristics are deteriorated, so it is necessary to control the amount to an appropriate amount. The above formula (1) is an empirical value that can prevent deterioration of the properties of the steel sheet, and an empirical value that can guarantee the surface quality, depending on the behavior that each component concentrates on the surface and the uneven distribution behavior. Present a numerical value. For example, in an example in which the value calculated by the formula (1) has a value smaller than 5, the mechanical properties of the steel sheet are deteriorated. On the other hand, in an example in which the value calculated by equation (1) has a value greater than 18, the steel sheet cannot obtain the desired surface quality.

  According to the present invention, the steel sheet containing the above components further comprises cobalt (Co) 0.01 to 1.0%, zirconium (Zr) 0.001 to 0.1%, titanium (Ti) 0.001 to 0.1%, niobium (Nb) 0.001 to 0.1%, lanthanum (La) 0.0005 to 0.040%, cerium (Ce) 0.0005 to 0.040%, and calcium (Ca) 005 Or one or more components selected from 0.030%.

The Co content is preferably in the range of 0.01 to 1.0%.
Cobalt (Co) is added to improve the strength of the steel. Cobalt (Co) can suppress the formation of oxides during high temperature annealing, thereby improving the wettability of the hot dip galvanized steel sheet during hot dip plating. In order to ensure the above effect, cobalt (Co) must be added at least 0.01% or more. On the other hand, when added above a specific limit, the elongation of steel is greatly reduced. Therefore, the amount of cobalt (Co) is preferably 1.0% or less.

The zirconium (Zr) content is preferably 0.001 to 0.1%.
Zirconium (Zr) is dissolved in the columnar grain boundaries, increases the melting temperature of the aluminum (Al) concentrate and the low melting point compound, prevents the formation of a liquid film at 1300 ° C. or less, and strengthens the columnar grain boundaries. . Less than 0.001% zirconium (Zr) cannot guarantee such an effect. On the other hand, zirconium (Zr) added in an amount of 0.1% or more cannot obtain further effects. Therefore, it is preferable to add 0.001 to 0.1% of zirconium (Zr).

Titanium (Ti) and niobium (Nb) are each preferably in the range of 0.001 to 0.1%.
Titanium (Ti) and niobium (Nb) are effective in increasing the strength of the steel sheet and obtaining fine crystal grains. When the content of titanium (Ti) and niobium (Nb) is less than 0.001%, it is difficult to obtain such an effect. On the other hand, if the content of titanium (Ti) and niobium (Nb) exceeds 0.1%, the manufacturing cost is increased, and the ferrite ductility is lowered due to excessive precipitates. Therefore, it is preferable that 0.001 to 0.1% of titanium (Ti) and niobium (Nb) can be added respectively.

The contents of lanthanum (La) and cerium (Ce) are each preferably 0.0005 to 0.04%.
Lanthanum (La) and cerium (Ce) reduce the size and amount of columnar grains that cause grain boundary embrittlement, and increase the amount of equiaxed grains with excellent high-temperature ductility. Improves hot workability. Also, lanthanum (La) and cerium (Ce) form a compound with phosphorus (P) and sulfur (S) that are segregated at the grain boundaries and reduce the fracture strength of the crystal grain boundaries, thereby forming phosphorus (P) and sulfur ( It is guaranteed that the adverse effects of S) are almost eliminated. However, when the addition amount of lanthanium (La) and cerium (Ce) is less than 0.0005%, the addition effect is not obtained. On the other hand, when the addition amount of lanthanum (La) and cerium (Ce) exceeds 0.04%, the addition effect is saturated. Therefore, it is preferable to add 0.0005 to 0.04% of lanthanium (La) and cerium (Ce), respectively.

The content of calcium (Ca) is preferably in the range of 0.0005 to 0.03%.
Calcium (Ca) forms a compound with nonmetallic inclusions such as MnO and MnS in molten steel to spheroidize the nonmetallic inclusions. This increases the breaking strength of the columnar grain boundaries, alleviates the occurrence of flange cracks in the steel sheet, and improves the hole expandability of the steel sheet. However, the effect is saturated when the content of calcium (Ca) exceeds 0.03%. Therefore, it is preferable to add 0.0005 to 0.030% of calcium (Ca).

According to the present invention, the balance of the above components is composed of Fe and other inevitable impurities.
According to the present invention, the thickness of the oxide layer on the steel sheet surface is 1 μm or less.

  The oxide layer formed on the metal surface by the annealing process after cold rolling acts as an obstruction between the metal substrate and the plating layer during plating, thereby inhibiting the plating adhesion. When the thickness of the oxide layer exceeds 1 μm, the formation of a dent defect due to the falling off of the oxide and the defect of plating are induced. Therefore, the oxide layer uniformly formed without being too thick by annealing ensures the high quality of the plating layer. According to the present invention, antimony (Sb) added in an amount of 0.005 to 0.1% is not oxidized and is concentrated on the metal surface layer to suppress the oxidation reaction. This reaction ensures that the oxide layer is formed with a uniform thickness of 1 μm or less.

Hereafter, the manufacturing method of the thin-layer steel plate containing the component of said range is described in detail.
First, a steel slab having the above composition is reheated to 1100 to 1250 ° C. At a reheating temperature of less than 1100 ° C., the composition of the steel slab is not uniform, and the remelting of titanium (Ti) and neobium is not sufficient. On the other hand, at a reheating temperature exceeding 1250 ° C., an oxide scale is generated, and a large amount of oxides such as SiO ₂ , MnO, and Al ₂ O ₃ are generated at the interface between the oxide scale and the metal and inside the metal. And thereby reduce the quality of the surface.
Therefore, the reheating temperature is preferably in the range of 1100 to 1250 ° C.

Thereafter, the steel slab is hot-finished in the range of 950 ° C. from the Ar ₃ transformation point. If hot finish rolling is performed at the temperature of the Ar3 transformation point, the resistance to thermal deformation is likely to increase rapidly, and manufacturing problems may occur. On the other hand, in hot finish rolling exceeding 950 ° C., the oxide scale becomes too thick and is likely to become coarse. Therefore, the hot finish rolling temperature is preferably in the range of Ar ₃ transformation point to 950 ° C.

Following hot finish rolling, hot rolling is performed. In the winding operation, the winding must be performed in a temperature range of winding temperature (CT) ± 20 ° C. that satisfies the relationship of the following expression (2).

  According to the present invention, components such as manganese (Mn), silicon (Si), phosphorus (P), chromium (Cr), and Mo are added as alloy components related to the formation of martensite in the microstructure. The However, the higher the coiling temperature, the higher the possibility that segregation will occur. In this case, the added strength of manganese (Mn), silicon (Si), phosphorus (P), chromium (Cr), and molybdenum (Mo) is hardly exhibited and desired strength and workability cannot be ensured.

  The above relational expression has been derived empirically as a method for ensuring desired strength and workability, which is determined by the relationship between the coiling temperature and the amount of alloy components. The above winding method ensures that a better quality steel is obtained.

The hot-rolled sheet produced by the above process is pickled, cold-rolled to a target thickness, and then recrystallized and annealed at a temperature of 700 to 860 ° C. to remove fine structure defects. When the annealing temperature is less than 700 ° C., only a small amount of annealing oxide is generated, and thus the added antimony (Sb) does not have a remarkable effect. On the other hand, in the case of the annealing temperature exceeding 860 ° C., the oxide grows excessively, and therefore surface concentration cannot be sufficiently suppressed.
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  In order to manufacture, the steel slab containing the components shown in Table 1 below was heated in a temperature range of 1200 ° C. Next, the steel slab was hot-rolled, wound at a temperature (+ 20 ° C.) satisfying the formula (2), and cold-rolled to manufacture a cold-rolled thin steel sheet. Thereafter, the cold-rolled thin steel sheet was heat-treated in a nitrogen gas atmosphere containing 10% water vapor at a temperature of 780 to 830 ° C. for 90 seconds at a rate of 3 ° C./sec. Thereafter, the thin steel plate is plated using a zinc (Zn) bath having a bath temperature of 460 ° C. and an aluminum (Al) content of 0.12 to 0.19%, and the plated thin steel plates are 540 to 560. Alloying heat treatment was carried out at 24 ° C. for 24 seconds. Thereafter, in order to confirm the surface quality, the thin-layer steel sheet was observed.

  The classification of the plating appearance in Table 2 below includes ◯ when there is no plating defect and other plating defects, and a defect name when a plating defect occurs. In order to evaluate the plating adhesion, the plated plate was cut into 20 mm × 50 mm, and then a 60 ° bending test was performed. The tape was affixed where it was opened again and bent. The width of the plating layer that peeled off was evaluated according to the following criteria.

A: There is no peeling-off plating, or the width is less than 1 mm. O: The peeling-off plating width is less than 1 to 3 mm. Δ: The peeling-off plating width is less than 3 to 5 mm. that's all

As shown in Table 2, the invention steels satisfying the manufacturing process and component content range according to the present invention (1-7), high with a balance of surface properties and strength elongation excellent plating (TS × El) Strength DP steel can be manufactured.
However, the comparative steels ( 8 to 12 ) that do not satisfy the component range and the production method of the present invention exhibited inferior properties in terms of plating surface properties and strength draw ratio balance.

Furthermore, FIG. 1 is a photograph showing the shapes of oxides of the steel of the present invention and the comparative steel with and without antimony (Sb) addition. FIG. 1 (a) is a comparative steel, and FIG. 1 (b) is an invented steel . As shown in FIG. 1, in the case of the inventive steel, the particle size of the oxide is remarkably small. That is, oxide formation was suppressed by adding antimony (Sb).

  FIG. 2 is a graph showing the size distribution of the oxide formed on the surface of the steel of the present invention. In the steel of the present invention, the size distribution of the oxide formed on the metal surface in the annealing process shows a stable probability distribution at 1 μm or less. That is, it can be seen that the uniform distribution of fine oxides helps to produce a more uniform plating layer.

Claims (6)

By weight percent, carbon (C) 0.01 to 0.2%, silicon (Si) 0.01 to 1.5%, manganese (Mn) 0.2 to 4.0%, phosphorus (P) 0.001 To 0.1%, sulfur (S) 0.03% or less, aluminum (Al) 0.01 to 1.5%, nitrogen (N) 0.001 to 0.03%, and antimony (Sb) 0.005. To 0.1%, selectively boron (B) 0.0002 to 0.005%, chromium (Cr) 0.01 to 2.0%, and molybdenum (Mo) 0.005 to 0.5% Including one or more of the above, the balance consisting of iron (Fe) and other inevitable impurities,
The composition satisfies the relationship of the following formula (1),
A high-strength galvanized DP steel sheet excellent in mechanical properties and surface quality, characterized by having an oxide layer having a thickness of 1 μm or less on the surface.

The high-strength galvanized DP steel sheet excellent in mechanical properties and surface quality according to claim 1, wherein the critical thickness of the oxide layer in the hot rolling step of the steel sheet is 1 µm or less. The high-strength galvanized DP steel sheet having excellent mechanical properties and surface quality according to claim 1, wherein the oxide layer is formed in an annealing process after the cold rolling process. Further, the steel sheet further includes, by weight, cobalt (Co) 0.01 to 1.0%, zirconium (Zr) 0.001 to 0.1%, titanium (Ti) 0.001 to 0.1%, Niobium (Nb) 0.001-0.1%, Lanthanum (La) 0.0005-0.040%, Cerium (Ce) 0.0005-0.040%, and Calcium (Ca) 0.0005-0. The high-strength galvanized DP steel sheet excellent in mechanical properties and surface quality according to claim 1, comprising at least one component selected from 030%. By weight percent, carbon (C) 0.01 to 0.2%, silicon (Si) 0.01 to 1.5%, manganese (Mn) 0.2 to 4.0%, phosphorus (P) 0.001 To 0.1%, sulfur (S) 0.03% or less, aluminum (Al) 0.01 to 1.5%, nitrogen (N) 0.001 to 0.03%, and antimony (Sb) 0.005. To 0.1%, selectively boron (B) 0.0002 to 0.005%, chromium (Cr) 0.01 to 2.0%, and molybdenum (Mo) 0.005 to 0.5% A steel slab containing one or more of the above, having the balance of iron (Fe) and other inevitable impurities, and having the composition satisfying the following formula (1) is returned to 1100 ° C. to 1250 ° C. Heating, and
Hot rolling the steel slab;
Winding temperature (CT) satisfying the following formula (2) winding within a temperature range of ± 20 ° C.,
Carrying out pickling and cold rolling;
Annealing at 700 ° C. to 860 ° C .;
A method for producing a high-strength galvanized DP steel sheet excellent in mechanical properties and surface quality, characterized by comprising:

The steel sheet is further comprised of, by weight, cobalt (Co) 0.01 to 1.0%, zirconium (Zr) 0.001 to 0.1%, titanium (Ti) 0.001 to 0.1%, niobium. (Nb) 0.001 to 0.1%, lanthanum (La) 0.0005 to 0.040%, cerium (Ce) 0.0005 to 0.040%, and calcium (Ca) 0.0005 to 0.030 The method for producing a high-strength galvanized DP steel sheet excellent in mechanical properties and surface quality according to claim 5, comprising at least one component selected from the group consisting of:

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