KR20100001330A - Ultra high-strength hot- dip galvanized steel sheet having excellent formability and galvanizing property, and method for producing the same - Google Patents

Abstract

PURPOSE: An ultra high-strength hot-dip galvanized steel sheet and a method for producing the same are provided to obtain a hot-dip galvanized steel sheet having excellent elongation ratio. CONSTITUTION: A method for manufacturing an ultra high-strength hot-dip galvanized steel sheet is as follows. Steel is subject to equalizing at 1200°C or higher and then hot rolling at 850~950. The treated steel is wound at 500~700°C. The cooled steel is subjected to cold rolling at a cold-rolling ratio of 50%, annealing, hot-dip galvanizing, and then alloying hot-dip galvanizing.

Description

Ultra high-strength hot-dip galvanized steel sheet having excellent formability and galvanizing property, and method for producing the same

The present invention relates to an ultra-high strength hot-dip galvanized steel sheet excellent in formability and plating property, and a method of manufacturing the same. More particularly, the present invention relates to excellent formability and plating property and excellent moldability and plating property which can satisfy tensile strength of 980 MPa or more. It relates to an ultra high strength hot dip galvanized steel sheet and a method of manufacturing the same.

Recently, as the interest in environmental regulations and passenger safety increases, the ratio of use of high strength steel to car bodies is rapidly increasing. In particular, the use of high-strength steel of 590 MPa or more is occupied most of the time, and among them, a very high tensile steel sheet of 780 to 1180 MPa is composed of a dual phase (DP), mainly composed of ferrite and martensite. D. Abbreviated name) As a steel sheet, it is widely used because of its excellent strength and ductility.It is easier to manufacture than other types of high tensile steel, has excellent price competitiveness, and complicated parts can be formed due to the development of press technology. Doing.

On the other hand, automotive steel sheets also require excellent corrosion resistance (corrosion) characteristics, and thus alloyed and molten galvanized steel sheets having a composite structure and alloyed hot dip galvanized steel sheets having a composite structure as steel sheets having both formability and corrosion resistance characteristics. Galvanized steel sheet is being developed. For example, Japanese Patent Application No. 1989-198459, Japanese Patent Application No. 199-105960, Japanese Patent Application No. 1999-193419, and the like use a steel whose composition is controlled to produce a manufacturing condition in a continuous hot dip galvanizing line. By making it suitable, the high strength hot dip galvanized steel sheet excellent in moldability is produced. In addition, non-patent literature, such as Satoshi Hironaka and three others, published in GALVATECH 07 in November 2007, "DEVELOPMENT OF Si BEARING HIGH STRENGTH GALVANNEALED STEEL SHEETS WITH SUPERIOR FORMABILITY". The steel sheet was developed, and the contents of producing alloyed molten zinc steel sheet having excellent moldability by controlling alloying elements such as C, Mn, and Si and manufacturing conditions are disclosed. However, when the Si content is more than 1.2%, it is possible to produce a steel plate with a good balance between strength and ductility, but as the actual Si content increases, the plating property drops sharply. However, the solution for this problem is not accurately represented. It is a common situation to keep as little as possible. Therefore, the present invention finds a method to control the microstructure by adding Al, Cr and the like to reduce the Si content at the same time as possible to solve this problem to balance the strength and ductility GA steel sheet having excellent formability and plating properties than conventional steel sheet I wanted to develop.

Two-phase tissue steels are quenched in the austenite and ferrite two-phase regions to produce about 10-30% (volume fraction) of martensite. Compared with precipitation hardened steel, it has excellent ductility and elongation processability, and is applied to impact bars and bumpers due to its high impact energy absorption capacity.

Since most automotive parts are molded into a desired shape through press working, excellent press formability (molding) is required for steel sheets. In order to increase the press formability, first, a method of improving the elongation must be sought. In addition, it should not be overlooked that the shape should be frozen. For this reason, there is a demand for the development of materials capable of realizing excellent elongation and resistance ratio that can be used for automotive parts. In addition, development of materials that can be applied to parts requiring high corrosion resistance is also required. In particular, the development of high strength hot-dip galvanized steel sheets with excellent elongation and yield ratio is a requirement of the times.

Conventional Japanese Patent Application Laid-open No. Hei 8-134591 has a high-strength alloyed hot-dip galvanized steel sheet having a resistive ratio and excellent press formability. In addition, the technique mentioned in Japanese Patent JP-B-35900 requires a cooling rate of 100 ° C./s or more in order to obtain high strength, and thus has a problem in that it is difficult to implement the gas jet cooling method.

Conventional US Patent US 2003 / 0129444A1 realizes 780 MPa by controlling the content of vanadium (V), but vanadium is expensive, so it is difficult to add a relatively large amount, and also satisfactory weldability because the content of silicon (Si) is high. There is a problem that can not.

The present invention is to meet the requirements as described above and to solve the conventional problems, the object of the present invention is to have excellent elongation and resistive ratio, excellent moldability and to satisfy the tensile strength of 980 MPa or more while improving the plating property. It is to provide an ultra-high strength hot-dip galvanized steel sheet excellent in formability and plating properties, and a method of manufacturing the same.

In addition, another object of the present invention is to remove the expensive component content of the ultra-high-strength hot-dip galvanized steel sheet excellent in formability and plating properties to reduce the manufacturing cost and to balance the strength and ductility by controlling the alloying elements in a small amount and a method of manufacturing the same To provide.

The present invention reduces the content of carbon (C) and silicon (Si), which are the major constituents of the steel, and instead increases manganese (and optionally copper) to improve the insufficient strength. And elongation is improved by adding chromium in order to achieve a resistive ratio. In addition, in order to secure excellent plating characteristics, silicon (Si) content is minimized, and niobium and titanium are added to maximize grain refinement to improve plating and elongation, and addition of trace boron (B: boron) to bainite or pearlite It does not cause transformation, refines grains and reduces material deviation.

Specifically, the component composition of the present invention is 0.1% to 0.18% of carbon (C), 0.1 to 0.3% of silicon (Si), 2.0 to 3.0% of manganese (Mn), 0.2 to 0.5% of aluminum (Al), and chromium ( Cr) 0.1-0.5%, phosphorus (P) 0.01% or less, sulfur (S) 0.001% or less, nitrogen (N) 0.006% or less and boron (B: boron) as a trace component, and the remaining iron (Fe) Has an alloy composition of.

The boron (B: boron) is contained in the range of 0.001% to 0.0025%.

The component may further contain at least one of niobium (Nb) and titanium (Ti). The content of boron (B: boron), niobium (Nb), and titanium (Ti) is in a range satisfying the formula of (B + Nb + Ti) ≤ 0.15%.

The component may further contain up to 0.3% copper (Cu).

In the production method of the present invention, carbon (C) 0.12 to 0.18%, silicon (Si) 0.1 to 0.3%, manganese (Mn) 2.0 to 3.0%, aluminum (Al) 0.2 to 0.5%, chromium (Cr) by weight% 0.1-0.5%, phosphorus (P) 0.01% or less, sulfur (S) 0.001% or less, nitrogen (N) 0.006% or less and boron (B: boron) as a trace component, and the remaining iron (Fe) alloy The steel with composition is homogenized at 1200 ° C or higher, hot rolled at 850 ~ 950 ° C, wound up at 500 ~ 700 ° C, cold rolled at 50% or more of cold rolling ratio, and then annealed After plating treatment, alloying hot dip galvanizing treatment is performed.

The hot dip galvanizing treatment and alloying hot dip galvanizing treatment is a hot dip galvanizing treatment after the cold rolling to maintain a predetermined time at a temperature of Ar1 (A1 transformation point) or more than Ar3 (A3 transformation point) or less and then quench. It is made by reheating to a temperature range of 450 to 550 ° C. to perform alloying hot dip galvanizing and then quenching.

Through the process of component control and heat treatment of the alloying element of the present invention, the average grain size of the microstructure is 5 to 20㎛, the phase is formed to 50 to 60% and the second phase (including martensite) to 40 to 50%. It is formed, and the strength and ductility are balanced, and the super-strength hot-dip galvanized steel sheet of 980 MPa or more which is excellent in moldability and plating property is manufactured.

According to the present invention, an ultra-high strength hot-dip galvanized steel sheet having excellent formability (press workability) and plating property and having tensile strength of 980 Mpa or more and excellent elongation can be obtained. In other words, it has excellent elongation characteristics with a resistive ratio, excellent moldability (processability), excellent plating properties, and a proper combination of ferrite and martensite ratios to balance strength and ductility, and satisfy tensile strength of 980 MPa or more. Ultra high strength hot dip galvanized steel sheet can be obtained.

Hereinafter, a preferred embodiment of the ultra-high strength hot-dip galvanized steel sheet excellent in formability and plating property according to the present invention and a method of manufacturing the same will be described in detail.

Ultra high strength hot-dip galvanized steel sheet of the present invention, by weight% of carbon (C) 0.12-0.18%, silicon (Si) 0.1-0.3%, manganese (Mn) 2.0-3.0%, aluminum (Al) 0.2-0.5%, 0.1 to 0.5% of chromium (Cr), 0.01% or less of phosphorus (P), 0.001% or less of sulfur (S), 0.006% or less of nitrogen (N), and boron (B: boron) as a trace component, and the remaining iron ( It is made of steel having an alloy composition of Fe).

Ultra high strength hot dip galvanized steel sheet according to the present invention of such a composition, to reduce the content of carbon (C) and silicon (Si), instead increase the manganese in order to improve the insufficient strength. And elongation is improved by adding chromium in order to achieve a resistive ratio. In addition, the silicon (Si) content is minimized to secure excellent plating characteristics.

The boron (B: boron) is contained in the range of 0.001 ~ 0.0025%, so that bainite and pearlite transformation does not occur, the crystal grains are refined and the material deviation is reduced.

The component may further contain at least one of niobium (Nb) and titanium (Ti). The niobium (Nb) and titanium (Ti) maximize the grain refinement to improve plating and elongation.

The content of boron (B: boron), niobium (Nb) and titanium (Ti) is within the range of satisfying the formula of (B + Nb + Ti) ≤ 0.15%, balance of strength and ductility through precipitation and grain refinement Allow this to be adjusted.

The component may further contain 0.3% or less (preferably 0.1% to 0.3%) of copper (Cu). The copper (Cu), like manganese (Mn) improves the insufficient strength by reducing the content of carbon (C) and silicon (Si).

Hereinafter, the function and content of the alloying elements of the present invention will be described in detail.

Carbon (C): 0.12-0.18 wt%

Carbon (C) is an indispensable element for reinforcing steel sheets, and is added in an amount of 0.12 wt% or more to obtain a desired strength. However, if it exceeds 0.18 wt%, spot weldability will fall, so the upper limit is made 0.18 wt%.

Silicon (Si): 0.1-0.3 wt%

Silicon (Si) is a ferrite stabilizing element employed in ferrite and contributes to strength, and is usually added as a deoxidizer. Silicon promotes austenite-ferrite transformation upon cooling in composite steel, increasing ferrite fraction. However, it is preferable to add as little as possible because excessively acting reduces the plating properties. In the present invention, the upper limit thereof is 0.3 wt%. In addition, when the content is less than 0.1 wt%, the strength of the ferrite decreases and the carbide inhibiting effect decreases, so 0.1 wt% or more is added.

Manganese (Mn): 2.0-3.0 wt%

Manganese (Mn) is an austenite stabilizing element that increases strength through the effect of strengthening solid solution and improving hardenability. In the present invention, rather than reducing Mn, instead of improving the spot weldability by decreasing C. If the content of C is not reduced, excellent spot weldability and material stability cannot be obtained. Therefore, in view of these matters, the Mn content is added to 2.0% or more as possible as C is reduced. When excessively adding Mn, weldability and plating property are reduced, hydrogen organic brittleness is caused by inclusion formation, and segregation zone is formed at the center of the sheet during hot rolling, so it is limited to 3.0 wt% or less.

Sulfur (S): 0.001 wt% or less

If sulfur (S) exceeds 0.001 wt%, it will form an emulsion-based inclusion and cause cracks and the like. In particular, in the present invention, since a large amount of Mn is added, the amount of S is better, and the upper limit thereof is 0.001 wt%.

Phosphorus (P): 0.01 wt% or less

Phosphorus (P) is an element useful for securing the strength of the material. However, when added in a large amount, not only the workability decreases but also the weldability decreases, so the upper limit thereof is limited to 0.01 wt%.

Aluminum (Al): 0.2-0.5 wt%

Aluminum (Al) is an element mainly used as a deoxidizer, and it has to be added more than 0.2 wt% to compensate for this, because it reduces the amount of silicon that improves elongation. However, when a large amount is added, the effect as a deoxidizer is saturated and economically effective. It does not cause plating defects and promotes C diffusion in ferrite and austenite phases, so it should be added at 0.5 wt% or less.

Chromium (Cr): 0.1-0.5 wt%

Chromium (Cr) is a ferrite-forming element that delays the transformation of austenite into pearlite or bainite, and has an effect of transforming austenite into martensite at room temperature after abnormal reverse annealing and serves to improve strength. When chromium is added in an amount less than 0.1 wt%, it is difficult to obtain sufficient strength, and when it is added in an amount of 0.5 wt% or more, a problem arises that the balance between strength and ductility is broken, so the upper limit is limited to 0.5 wt% or less.

Copper (Cu): 0.1-0.3 wt%

Copper (Cu) has the effect of improving strength, but there is a problem that may cause hot brittleness, so it should be added in an appropriate amount. If it contains more than 0.3%, expensive nickel must be added in a 1: 1 ratio, so it is limited to 0.1 ~ 0.3 wt%. It is desirable to.

Titanium (Ti): 0.02 ~ 0.1 wt%

Titanium (Ti) is an element that improves strength, and helps austenite to transform into martensite. Carbide of Ti plays an important role in promoting ferrite grain refinement to achieve the desired grain size. If the added amount of Ti is less than 0.02 wt%, the amount of finely dispersed composite carbide cannot be sufficiently exhibited. If the added amount of Ti exceeds 0.05 wt%, the composite carbide coarsens and lowers the strength.

Niobium (Nb): 0.01 to 0.05 wt%

Niobium (Nb) forms Nb (CN) and NbC precipitates to prevent grain boundary growth during hot rolling and anomalous reverse annealing to form fine grain size. As an employment element, Nb acts as a strength enhancer and prevents austenite from transforming to pearlite or bainite. When Nb is added at 0.05 wt% or more, there is a problem that the ductility is reduced and the yield strength is increased, and when it is added at less than 0.01 wt%, the reinforcing effect cannot be exerted.

Boron (B: Boron): 0.001 to 0.0025 wt% or less

Boron (B) is an element that improves the hardenability of steel and is an element that can reduce material variation. It increases the hardenability (quenchability) of steel and diffuses into grain boundary during heat treatment, which delays the perlite transformation of austenite and the ferrite reverse transformation of martensite. However, it is preferable to limit the upper limit to 0.0025 wt% or less since the elongation decreases due to the increase of the solid solution boron, and the boron may diffuse on the surface and degrade the plating property.

Nitrogen (N): 0.006 wt% or less

Nitrogen (N) increases austenite formation when the trace amount is added, and increases the strength by forming aluminum nitride (AlN) or titanium nitride (TiN), it is advantageous to keep the addition amount as low as possible. In particular, nitrogen is preferably limited to the range of 0.006 wt% or less because it reduces elongation at the time of excessive addition and inhibits workability.

The steel sheet of the present invention contains the above components, and the balance is substantially iron (Fe) and unavoidable impurities, and incorporation of 0.01 wt% or less of unavoidable impurities is allowed as elements to be entered depending on the situation of raw materials, materials, manufacturing facilities, and the like. .

The slabs having the composition as described above are obtained from molten steel through a steelmaking process and then made into slabs through an ingot or continuous casting process, and then hot rolled by a conventionally known method and cold rolled again to produce a steel sheet. After the annealing, the surface of the steel sheet undergoes a hot dip galvanizing treatment and an alloyed hot dip galvanizing treatment.

The cold rolled steel sheet was heated to an ideal temperature range for 5 to 120 seconds, then rapidly cooled to a temperature of 500 ° C. or lower at a rate of 5 ° C./s, followed by hot dip galvanizing and a temperature of 450 to 550 ° C. After reheating to the area, the hot dip galvanized film is alloyed, and then quenched to 300 ° C. at a cooling rate of 5 ° C./s or more. The ductility increases as the martensite fraction increases and the ductility increases as the ferrite fraction increases. However, when the martensite fraction is too large to increase the strength, the ferrite ratio decreases and the ductility decreases. Therefore, the appropriate combination of ferrite and martensite ratios balances strength and ductility.

The microstructure of the steel sheet produced by the present invention is composed of a second phase including the ferrite and martensite as described above, the grain size is 5 ~ 20㎛ ferrite 50 to 60% phase is formed and the second phase (martensite 40-50%), which balances strength and ductility. If the ferrite phase is formed to 50% or less, the ductility and formability (press workability) is lowered, and if the ferrite phase is formed to 60% or more, it is difficult to secure the strength.

On the other hand, after forming austenite in the rolling process, it controls the cooling rate and the cooling end temperature during the cooling process to form ferrite and martensite at room temperature, and relatively small amount of alloying element added to the weldability and excellent strength. It is important to control the cooling conditions in order to improve the elongation, and in order to obtain ferrite through air cooling during cooling, it is necessary to optimize the cooling pattern and optimize the components. To this end, in the present invention, as shown in the additive element, manganese, aluminum, chromium, and the like are added, and microelements such as niobium (Nb), titanium (Ti), and boron (B: boron) are added to finely grains. do.

Hereinafter, the manufacturing method of the steel sheet produced by the present invention for each step will be described in more detail.

-Furnace process;

The slab of the present invention is reheated at 1200 ° C. or higher (more preferably 1230 ° C. or higher) and maintained for 2 to 3 hours to homogenize in order to reclaim segregated components during casting. If the reheating temperature is low, the segregated components are not reusable. If the reheating temperature is excessively high, the austenite grain size increases and the ferrite grains are coarsened, so the reheating temperature is preferably set at 1200 to 1300 ° C. Of course, the reheat temperature holding time can be adjusted according to the slab thickness. The thicker the thickness, the longer the reheating holding time is. The thinner the thickness, the shorter the reheating temperature holding time.

In addition, it is more economical to maintain the homogenization treatment time is not economically useful, and if it is short, it may be a problem that the quality of the material is inferior and product quality may be degraded.

- hot / cold rolling process;

The homogenized slab in the furnace is hot rolled at 850 ~ 950 ℃ to produce a single-phase hot rolled coil. The coiling temperature is finished at a coiling temperature (CT) of 500 to 700 ° C., preferably 550 to 620 ° C. to facilitate cold rolling, and then the furnace is cold-treated to room temperature, followed by a pickling treatment of the wound hot rolled steel sheet. Cold rolling is performed at the above reduction ratio.

Here, when the finish hot rolling temperature is less than 850 ° C, excessive dislocations are introduced into the ferrite during rolling to form coarse grains on the surface during cooling or winding, and when the finish hot rolling temperature exceeds 950 ° C, the ferrite grain size increases to decrease the strength.

In addition, when the coiling temperature is less than 500 ° C, a second phase having high strength is generated in the hot rolled steel sheet to increase the strength of the hot rolled sheet, and the shape of the steel sheet worsens after hot rolling, and thus cold rolling is difficult. Since coarse pearlite is formed in the annealing process, re-dissolution does not occur well, so that an annealing steel sheet having a uniform structure cannot be obtained.

Annealing process;

Annealing is performed to obtain the final desired material. To control the fraction of martensite and ferrite, the cold rolled steel sheet is maintained at an Ar1 temperature or more than an Ar3 temperature for 5 to 120 seconds and then a cooling rate of 5 to 50 ° C / s or more. After quenching and annealing to 460 ℃.

During this process, it is important to cool the austenite phase produced in the two-phase region at a sufficient cooling rate to prevent transformation into pearlite or bainite. If the temperature is kept below 5 seconds in the region above Ar1 temperature or below Ar3 temperature, the austenite phase is not sufficiently formed during heating, so that an appropriate amount of martensite fraction cannot be obtained, and when it exceeds 120 seconds, the productivity decreases. It is preferable to hold for ˜120 seconds.

After the above process, a hot dip galvanizing process and an alloying hot dip galvanizing process are further performed.

- hot-dip galvanizing process and galvannealed process;

The annealed steel sheet is quenched to 460 ° C. at a cooling rate of 5 to 50 ° C./s, plated, reheated to 450 to 550 ° C., alloyed, and cooled to 250 ° C. or more at a cooling rate of 5 ° C./s or more. .

Hereinafter, the embodiments of the ultra-high strength hot-dip galvanized steel sheet and its manufacturing method will be described by comparing the present invention with comparative examples, tables, and graphs.

Table 1 shows the component ratio of the invention example and comparative example of this invention.

division Chemical composition (wt%) Remarks C Si Mn P (max) S (max) Al Cr Cu B Nb Ti Ni N One 0.15 0.25 2.5 0.01 0.001 0.2 0.25 - 0.0015 0.04 0.02 - 0.006 Inventive Example 2 0.20 0.25 2.5 0.01 0.001 0.2 0.25 - 0.0015 0.04 0.02 - 0.006 Comparative example 3 0.15 0.25 2.2 0.01 0.001 0.2 0.25 - 0.0015 0.04 0.02 - 0.006 Inventive Example 4 0.17 0.25 2.2 0.01 0.001 0.2 0.25 - 0.0015 0.04 0.02 - 0.006 Inventive Example 5 0.15 0.25 2.8 0.01 0.001 0.2 0.25 - 0.0015 0.04 0.02 - 0.006 Inventive Example 6 0.15 0.25 3.1 0.01 0.001 0.2 - - 0.0015 0.04 0.02 - 0.006 Comparative example 7 0.15 0.25 2.5 0.01 0.001 0.2 0.25 - 0.0015 0.06 0.02 - 0.006 Comparative example 8 0.15 0.25 2.5 0.01 0.001 0.2 0.4 - 0.0015 0.04 0.02 - 0.006 Inventive Example 9 0.15 0.25 2.5 0.01 0.001 0.2 0.25 - 0.0015 0.05 0.02 - 0.006 Inventive Example 10 0.15 0.25 2.5 0.01 0.001 0.05 0.25 0.2 0.0015 0.04 0.02 0.1 0.006 Inventive Example 11 0.15 0.25 2.5 0.01 0.001 0.05 0.25 0.2 0.0015 0.04 - 0.1 0.006 Inventive Example 12 0.15 0.48 2.5 0.01 0.001 0.05 0.25 - 0.0015 0.04 0.02 0.006 Inventive Example

Figure 1 is a slab of the composition of Table 1 heated at 1250 ℃ for 2 hours to homogenize treatment, after finishing hot rolling at 850 ~ 900 ℃, then quenched to 550 ~ 580 ℃ and maintained for about 1 hour to cool the furnace hot After rolling, pickling and cold rolling at 50% reduction, followed by annealing at 800 to 860 ° C, quenching to 460 ° C, immersing in plating bath, and then alloying at 490 to 520 ° C. Is shown in the graph. AT in the graph represents the annealing temperature. And, Table 2 is a table showing the mechanical properties of the alloyed hot-dip galvanized steel sheet prepared according to the process of FIG.

division Annealing Temperature (℃) Remarks  800 830 860 YP TS EL Plating YP TS EL Plating YP TS EL Plating One 657 1101 13.6 ○ 882 1171 8.6 ○ 694 1214 8.4 ○ Inventive Example 2 756 1237 9.5 × 772 1275 8.6 × 788 1297 8.4 × Comparative example 3 464 985 17.3 ○ 598 1006 12.8 ○ 617 1055 10.9 ○ Inventive Example 4 521 1103 13.0 ○ 573 1148 12.1 ○ 579 1159 11.9 ○ Inventive Example 5 704 1289 10.3 ○ 802 1337 8.8 ○ 887 1356 7.8 ○ Inventive Example 6 811 1312 8.1 × 839 1332 7.9 × 847 1333 7.6 × Comparative example 7 754 1199 11.1 ○ 759 1211 10.1 ○ 766 1222 9.4 ○ Comparative example 8 580 1076 13.9 ○ 637 1124 11.0 ○ 588 1173 10.3 ○ Inventive Example 9 671 1202 13.1 ○ 723 1161 10.8 ○ 716 1218 10.3 ○ Inventive Example 10 687 1178 10.5 ○ 769 1231 10.2 ○ 833 1287 10.1 ○ Inventive Example 11 638 1171 13.1 ○ 672 1139 11.3 ○ 575 1142 10.8 ○ Inventive Example 12 665 1190 12.2 ○ 724 1210 11.2 ○ 736 1276 9.4 ○ Inventive Example

[TS (MPa): Tensile Strength, YS (MPa): Yield Strength, EL (%): Elongation]

As shown in Table 1 and Table 2, boron (B: boron) is added, and an appropriate amount of chromium (Cr) and niobium (Nb) is added to prepare according to the manufacturing method of the present invention. It can be seen that an alloyed hot-dip galvanized steel sheet having tensile strength and high elongation at high tensile strength can be obtained.

1 is a graph showing a method of manufacturing an ultra-high strength hot-dip galvanized steel sheet according to an embodiment of the present invention.

Claims (9)

By weight%, carbon (C) 0.12 ~ 0.18%, silicon (Si) 0.1 ~ 0.3%, manganese (Mn) 2.0 ~ 3.0%, aluminum (Al) 0.2 ~ 0.5%, chromium (Cr) 0.1 ~ 0.5%, phosphorus ( P) 0.01% or less, sulfur (S) 0.001% or less, nitrogen (N) 0.006% or less, boron (B: boron) is contained as a trace component, and has an alloy composition of the remaining iron (Fe), Ultra-high strength hot-dip galvanized steel sheet having excellent formability and plating property, characterized in that the grain size is 5-20 μm, the ferrite is formed at 50-60%, and the second phase (including martensite) is formed at 40-50%. The method according to claim 1, The boron (B: boron) is ultra-high strength hot dip galvanized steel sheet excellent in formability and plating properties, characterized in that it is contained in the range of 0.001 ~ 0.0025 wt%. The method according to claim 2, At least one of niobium (Nb) and titanium (Ti) is further contained in said component, The ultra-high strength hot-dip galvanized steel sheet excellent in moldability and plating property characterized by the above-mentioned. The method according to claim 3, The boron (B: boron), niobium (Nb), titanium (Ti) content is contained in a range that satisfies the formula (B + Nb + Ti) ≤ 0.15 wt% Excellent ultra high strength hot dip galvanized steel sheet. The method according to any one of claims 1 to 4, An ultra-high strength hot dip galvanized steel sheet excellent in formability and plating property, further comprising 0.3 wt% or less of copper (Cu). By weight%, carbon (C) 0.12 ~ 0.18%, silicon (Si) 0.1 ~ 0.3%, manganese (Mn) 2.0 ~ 3.0%, aluminum (Al) 0.2 ~ 0.5%, chromium (Cr) 0.1 ~ 0.5%, phosphorus ( P) 0.01% or less, sulfur (S) 0.001% or less, nitrogen (N) 0.006% or less, boron (B: boron) is contained as a trace component, and steel having an alloy composition of the remaining iron (Fe), Homogenizing treatment at 1200 ℃ or higher, hot rolling finished at 850 ~ 950 ℃, coiled at 500 ~ 700 ℃, cold rolled at 50% or more of cold reduction rate, and then hot dip galvanized after annealing A method for producing an ultra-high strength hot-dip galvanized steel sheet excellent in formability and plating property, characterized by performing an alloying hot dip galvanizing treatment. The method according to claim 6,  The hot dip galvanizing and alloying hot dip galvanizing treatment, after the cold rolling is maintained at a temperature of Ar1 (A1 transformation point) or more than Ar3 (A3 transformation point) for a predetermined time, and then quenched and hot dip galvanized , The method of manufacturing a super high strength hot-dip galvanized steel sheet excellent in formability and plating property, characterized in that by the re-heating to a temperature range of 450 ~ 550 ℃ and quenching after the alloying hot dip galvanizing treatment. The method according to claim 7, Method for producing a super-high strength hot-dip galvanized steel sheet excellent in formability and plating properties, characterized in that the last step of the annealing is maintained for 5 to 120 seconds in the Ar1 point to Ar3 point temperature range. The method according to claim 7, The quenching treatment after the alloyed hot dip galvanizing treatment is cooled to 250 ° C. at a cooling rate of 5 ° C./s or more, characterized in that the super high strength hot dip galvanized steel sheet having excellent moldability and plating property.

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