KR20130071208A - High strength steel sheet with excellent coatability and method for manufacturing the same - Google Patents

Abstract

PURPOSE: A high strength steel plate with excellent plating and a manufacturing method thereof are provided to include the tensile strength which is over 780 MPa and a TS×E1 value which is over 15000 MPa %. CONSTITUTION: A high strength steel plate with excellent plating is comprised of 0.07-0.10 % of carbon, 0.1-0.3 % of silicone, 2.0-2.5 % of manganese, 0.05-0.25 % of aluminum, 0.1-0.3 % of copper, 0.01-0.03 % of niobium, below 0.007 % of phosphorus, below 0.005 % of sulfur, residue Fe, and the other unavoidable impurity on the weight%. A tissue of the steel plate is comprised of ferrite of 85-95 % and martensite of 5-15 %. A minute precipitation Cu particle of a particle diameter of 1-100 nm is dispersed and is extracted from the tissues.

Description

High strength steel plate with excellent plating property and manufacturing method {HIGH STRENGTH STEEL SHEET WITH EXCELLENT COATABILITY AND METHOD FOR MANUFACTURING THE SAME}

The present invention relates to a high strength steel sheet excellent in plating properties used as a plate for automobiles and a method of manufacturing the same.

In recent years, the automotive industry has focused on high strength and light weight to meet the demands of the times such as exhaustion of resources, rapid progress in global warming, and high oil prices. Therefore, the improvement of workability and plating characteristics is attracting attention as an important technology.

As such high-strength automotive materials, precipitation hardening steel, hardening hardening steel, solid solution hardening steel, transformation hardening steel and the like are used. Dual Phase Steel (DP Steel) and Transformation Induced Plasticity (TRIP Steel), which are dual transformation steels, are made of manganese (Mn), silicon (Si), and niobium (Mn) to improve the strength and formability of steel sheets. Nb) and aluminum (Al), etc. are added to the alloying elements, these alloying elements are concentrated on the surface of the steel sheet during the cold rolling process to reduce the plating characteristics. Accordingly, there is a problem that a bare spot layer is generated or a defect such as microdents is generated.

In order to solve the problem, Patent Documents 1, 2, 3, and 4 disclose techniques for improving plating characteristics by adding specific elements such as chromium (Cr), antimony (Sb), and tin (Sn). However, the consideration of the addition effect and metallurgical behavior of the specific element is not clear, so the manufacturing method is insufficient, and the workability is deteriorated.

On the other hand, it has been recognized that conventional tramp elements such as copper (Cu) have a great influence on the deterioration of the steel sheet, so that it is desirable not to add them. However, in recent years, from the viewpoint of resource recycling, the molten iron ratio (HMR) is reduced, and as the amount of scrap is increased, low scrap steel having a high copper content is inevitably used in large quantities.

Therefore, there is a growing need to reversely utilize tramp elements, such as non-removable copper (Cu).

Japanese Patent Application Laid-Open No. 2002-146477 Japanese Laid-Open Patent Publication No. 2001-064750 Japanese Laid-Open Patent Publication No. 2002-294397 Japanese Laid-Open Patent Publication No. 2002-155317

The present invention is to solve the above problems of the prior art, to provide a high-strength steel sheet having excellent plating properties and a method for manufacturing the same, an object thereof.

The present invention is in weight%, carbon (C): 0.07 to 0.10%, silicon (Si): 0.1 to 0.3%, manganese (Mn): 2.0 to 2.5%, aluminum (Al): 0.05 to 0.25%, copper (Cu ): 0.1 to 0.3%, niobium (Nb): 0.01 to 0.03%, phosphorus (P): 0.007% or less, sulfur (S): 0.005% or less, residual iron (Fe) and other unavoidable impurities. It is composed of 85 to 95% of ferrite and 5 to 15% of martensite in area fraction, and microprecipitated Cu particles having a particle size of 1 to 100 nm are dispersed in each of the structures. It provides a high strength steel sheet excellent in plating properties.

In addition, the present invention is a weight%, carbon (C): 0.07-0.10%, silicon (Si): 0.1-0.3%, manganese (Mn): 2.0-2.5%, aluminum (Al): 0.05-0.25%, copper (Cu): 0.1-0.3%, niobium (Nb): 0.01-0.03%, phosphorus (P): 0.007% or less, sulfur (S): 0.005% or less, steel composed of residual iron (Fe) and other unavoidable impurities Finishing slab at 880 to 920 ° C., wound at 580 to 620 ° C., followed by cold rolling at a reduction ratio of 50 to 90%, followed by recrystallization annealing heat treatment at 770 to 810 ° C. for 10 to 120 seconds. Provided is a method for producing a high strength steel sheet having excellent plating properties.

According to the present invention, it is possible to provide a high strength steel sheet having excellent plating property having a tensile strength of 780 MPa or more and a TS × E1 value of 15000 MPa% or more.

Hereinafter, embodiments of the high-strength steel sheet having excellent plating properties and a method for manufacturing the same according to the present invention will be described in detail, but the present invention is not limited to the following examples. Therefore, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Hereinafter, the present invention will be described in detail.

High-strength steel sheet excellent in plating properties according to the present invention by weight%, carbon (C): 0.07 ~ 0.10%, silicon (Si): 0.1 ~ 0.3%, manganese (Mn): 2.0 ~ 2.5%, aluminum (Al): 0.05 to 0.25%, copper (Cu): 0.1 to 0.3%, niobium (Nb): 0.01 to 0.03%, phosphorus (P): 0.007% or less, sulfur (S): 0.005% or less, balance iron (Fe) and others It is a steel sheet composed of inevitable impurities, and the structure of the steel sheet is composed of 85 to 95% of ferrite (Ferrite) and 5 to 15% of martensite (area fraction), and each particle size of 1-100 nm in size. The fine precipitated Cu particles are dispersedly precipitated.

At this time, the composition of the steel sheet in the group consisting of chromium (Cr): 0.1 ~ 0.4%, boron (B): 0.0005 ~ 0.0015%, antimony (Sb): 0.02 ~ 0.04% and nickel (Ni): 0.06 ~ 0.10% It may further comprise one or more selected.

Hereinafter, the reason for limiting the components in the high strength steel sheet of the present invention will be described in detail.

At this time, the content of the component element means all weight%.

C: 0.07 ~ 0.10%

Carbon (C) is an essential element to improve the strength of the steel sheet, and when added in a small amount, not only the strength is low, but also the austenite is transformed into ferrite, making it difficult to secure the martensite fraction. Therefore, it is preferable to add at least 0.07% to secure the strength of the material. If the content of C is less than 0.07%, it is difficult to secure adequate strength because it does not secure stable austenite in the critical temperature range, and hence an appropriate fraction of martensite is not produced after cooling, whereas when the content exceeds 0.10%, It is difficult to secure ductility and deteriorates weldability, so the content is limited to 0.07 ~ 0.10%.

Si: 0.1 to 0.3%

Silicon (Si) is a useful element that can improve the strength without lowering the ductility of the steel sheet. Si contributes to strength as a ferrite stabilizing element to be dissolved in ferrite, and promotes martensite formation by encouraging carbon enrichment with unmodified austenite. If Si is added less than 0.1%, it is difficult to secure the martensite fraction, whereas if it is added in excess, the upper limit is 0.3% because it causes surface defects due to plating property and red scale and degrades the plating adhesion. It is preferable to limit to.

Mn: 2.0 ~ 2.5%

Manganese (Mn) is an austenite stabilizing element. Mn delays the decomposition of austenite to pearlite during cooling to 300 ~ 580 ° C. after annealing, but forms stable martensite tissues at low temperature during cooling to room temperature. In addition, there is an effect of improving the strength by strengthening the solid solution, it is very effective to prevent the hot crack of the slab (Slab) by forming MnS inclusions in combination with sulfur (S) in the steel. If the Mn content is less than 2.0%, it is difficult to delay the decomposition of the austenite to the pearlite phase, whereas if the content is more than 2.5%, it not only leads to a significant increase in the slab cost but also to deterioration of weldability and formability. do. Therefore, the content of Mn in the present invention is preferably limited to 2.0 ~ 2.5%.

Al: 0.05 ~ 0.25%

Aluminum (Al) combines with nitrogen in the steel to form AlN to refine the structure, and removes oxygen in the steel as a deoxidizer to prevent cracking during slab manufacturing.

In the present invention, as the content of silicon (Si) having an elongation improving effect is controlled low, Al is added to compensate for this, so it is preferably added at 0.05% or more. However, when excessively added, the action as a deoxidizer is saturated, carbon diffusion is promoted in the ferrite and austenite phases and the strength is lowered. Therefore, the upper limit is preferably limited to 0.25%.

Cu: 0.1 ~ 0.3%

Copper (Cu) is a very important element in the present invention, an element that is very effective in improving the ductility, and the strength-ductile balance of the material is improved as the amount of Cu added increases. If the added amount is less than 0.1%, the amount of Cu to be precipitated is insufficient, so that it is difficult to obtain a desired ductility improving effect. If the added amount is more than 0.3%, it becomes saturated. Therefore, the content of Cu is preferably limited to 0.1 to 0.3%. For the above reason, not only does not adversely affect the physical properties of the steel sheet, but can also expect improved plating properties.

In addition, when the grain size of the precipitated Cu particles is too small or too coarse, the precipitation strengthening ability becomes insufficient, so that the grain size of the precipitated Cu particles is 1 to 100 nm.

Nb: 0.01 ~ 0.03%

Niobium (Nb) combines with N or C to form NbN or NbC precipitates, or improve the strength of the steel sheet through solid solution strengthening in iron. If the content is added less than 0.01%, the precipitation amount of NbC precipitates is small, and it is difficult to expect the effect of strength improvement due to precipitation strengthening.However, if it is added in excess of 0.03%, the Nb is dissolved and the value of r decreases and yields. Increasing the strength weakens the formability.

P: 0.007% or less

Phosphorus (P) is an element useful for securing the strength of the material. However, when a large amount is added, not only the workability is lowered but also the weldability is lowered, so the upper limit is preferably limited to 0.007%.

S: not more than 0.005%

Sulfur (S) inhibits toughness and weldability, increases MnS non-metallic inclusions, and causes cracks during processing of steel, and particularly when excessively added, increases coarse inclusions to deteriorate fatigue properties, so it is preferable to add sulfur (S). In the present invention, since a large amount of manganese is added, the content of sulfur is preferably kept as low as possible. Therefore, the upper limit of the S content is limited to 0.005%.

In addition to the above composition, the steel sheet according to the present invention preferably further comprises a component satisfying the following conditions.

Cr: 0.1-0.4%

Chromium (Cr) is a very effective element for stable formation of low temperature transformation phase by improving hardenability, which leads to miniaturization of carbides, delays spheroidization rate, inhibits grain refinement and grain growth, and strengthens ferrite. It is an element to say. In addition, since the effect of suppressing the softening of the heat affected zone (HAZ) during welding is preferably added at 0.1% or more. If the Cr content is less than 0.1%, it is difficult to obtain sufficient strength, whereas if the content of Cr exceeds 0.4%, there is a problem that the balance between strength and ductility is broken. Therefore, it is preferable to limit the content of Cr to 0.1 to 0.4%.

B: 0.0005-0.0015%

Boron (B) is a grain boundary strengthening element, which improves the fatigue characteristics of welds, prevents grain brittleness of phosphorus (P), and improves high temperature ductility in steels with high content of aluminum (Al) and silicon (Si). have. In addition, boron increases the quenching of the steel, and diffuses into the grain boundary during heat treatment, thereby delaying the pearlite transformation of austenite and the ferrite reverse transformation of martensite. However, when it is added in excess, the solid solution boron increases and the elongation decreases, and since boron can diffuse on the surface and reduce plating property, it is preferable to limit the upper limit to 0.0015%. However, it is preferable to add at least 0.0005% or more in order to obtain the above-mentioned effect.

Sb: 0.02-0.04%

Antimony (Sb) is an element added to prevent the presence of manganese (Mn) and silicon (Si) in the form of oxide on the surface of the steel sheet. Sb does not form an oxide film on its own at high temperatures, but is concentrated at the steel plate surface and the grain interface to suppress the diffusion of manganese and silicon in the steel sheet to control oxide formation. Such Sb is effective in suppressing the formation of oxide during the annealing process to improve the plating characteristics and suppress the dent bond on the surface of the plating material. Therefore, in order to obtain the above-mentioned effect, it is preferable to add at 0.02% or more. However, when added excessively, the ductility decreases and the material properties of the steel sheet tend to be deteriorated. Therefore, the upper limit is preferably limited to 0.04%.

Ni: 0.06 ~ 0.10%

Nickel (Ni) is an element that is added to prevent the red heat brittleness caused by the addition of copper (Cu), it is known that the effect is good when added to the ratio of Cu: Ni = 1: 1 to 2 usually Cu. Ni also improves plating properties when added with Cu in an appropriate amount. Therefore, in order to obtain the above-mentioned effect, Ni is preferably added at least 0.06%, but when added in excess of 0.1%, since it is disadvantageous in terms of economics, the content is limited to 0.06 to 0.10% in accordance with the amount of Cu added. It is preferable.

As a steel plate which satisfies the above-described component system, it is necessary to limit the microstructure of the steel sheet to preferable conditions for becoming a high strength steel sheet having excellent plating properties.

The microstructure of the steel sheet having the above-described component system is characterized by having an area fraction of 85% to 95% ferrite and 5% to 15% martensite.

The present invention is manufactured so that the microstructure of the steel is composed of two phases including ferrite and martensite by controlling the cooling rate and the cooling end temperature in the cooling process after the heat treatment and the alloy composition described above. In steel sheet, the ductility increases as the fraction of martensite increases, and the ductility increases as the fraction of ferrite increases. This will be lowered. Therefore, the microstructure of the steel sheet is preferably controlled to include 85 to 95% of ferrite having an average grain size of 2 to 10 µm, and 5 to 15% of martensite. Thus, by constructing the tissue in two phases, it is possible to balance strength and ductility.

In addition, it is preferable that fine precipitated Cu particles having a particle size of 1 to 100 nm are dispersed and precipitated in the above-described structures. This is because the grain size of the precipitated Cu particles is too small or too coarse, so that the precipitation strengthening ability is insufficient, so that the grain size is 1 to 100 nm.

The steel sheet that satisfies the above-described component system and internal structure is a steel sheet that satisfies all properties desired in the present invention by having a tensile strength of 780 MPa or more and a TS × E1 value of 15000 MPa% or more.

As described above, by controlling the component system and the microstructure of the steel sheet, it is possible to provide a high strength steel sheet having excellent plating properties by controlling the dispersion precipitation through the fine precipitated Cu particles in the steel sheet.

The present invention includes a steel sheet (plated steel sheet) having a hot dip galvanized layer or an alloyed hot dip galvanized layer on the surface of the above steel sheet.

Hereinafter, the manufacturing method of the high strength steel plate which satisfy | fills the above-mentioned steel component is demonstrated in detail.

The following manufacturing method shows a preferred example of producing a high strength steel sheet according to the present invention, but is not limited thereto.

First, in weight percent, carbon (C): 0.07 to 0.10%, silicon (Si): 0.1 to 0.3%, manganese (Mn): 2.0 to 2.5%, aluminum (Al): 0.05 to 0.25%, copper (Cu) : 0.1 to 0.3%, niobium (Nb): 0.01 to 0.03%, phosphorus (P): 0.007% or less, sulfur (S): 0.005% or less, steel slab composed of residual iron (Fe) and other unavoidable impurities Finish rolling at 920 ° C., winding at 580 ° C. to 620 ° C., cold rolling at a reduction ratio of 50 to 90%, and then performing recrystallization annealing heat treatment at 770 ° C. to 810 ° C. for 10 to 120 seconds.

At this time, the composition of the steel slab is made of chromium (Cr): 0.1 ~ 0.4%, boron (B): 0.0005 ~ 0.0015%, antimony (Sb): 0.02 ~ 0.04% and nickel (Ni): 0.06 ~ 0.10% It may further comprise one or two or more selected from.

Hereinafter, detailed conditions for each step will be described.

The slab having the composition as described above is obtained in the slab through the ingot or continuous casting process after obtaining the molten steel through the steelmaking process, and here it is manufactured in the form of steel sheet through hot rolling, cold rolling, annealing, the surface of the steel sheet The hot dip galvanizing is subjected to the following process.

Hot rolling process

In hot rolling the steel slab, the hot rolling finish temperature is 880 ~ 920 ℃, and after the finish rolling to adjust the cooling so that the hot rolled structure becomes fine. At this time, when the hot rolling finish temperature is less than 880 ° C, excessive dislocations are introduced into the ferrite during rolling to form coarse crystal grains on the surface during cooling or winding, and when it is higher than 920 ° C, the ferrite grain size increases to decrease the strength.

Winding process

In winding the hot rolled steel sheet, the coiling temperature is 580 to 620 ° C. to smoothly form carbides in the wound state, thereby minimizing solid solution carbon and maximizing AlN to minimize formation of solid nitrogen in steel. Let's do it. At this time, the winding temperature is a temperature for obtaining a structure that can ensure the optimum mechanical properties after cold rolling and recrystallization heat treatment, when the winding temperature is less than 580 ℃ cold rolling is difficult due to the formation of bainite or martensite structure When the temperature exceeds 620 ° C., the final microstructure becomes coarse, making it difficult to manufacture a steel sheet having sufficient strength.

Cold rolling process

In cold rolling after pickling the wound hot rolled steel sheet, it is preferable to set the cold reduction rate to 50 to 90%. Cold rolling deforms the hot rolled tissue, where the strain energy that deforms the tissue becomes the energy of the recrystallization process. If the cold reduction rate is less than 50%, the tissue deformation effect is small. On the other hand, cold rolling of more than 90% of the cold rolling rate is difficult to roll in reality, and complex precipitates in the hot rolled steel are decomposed during rolling to develop (100) texture in the early stage of recrystallization, thus degrading drawing property and There is a high probability of cracking and breaking into the plate.

Continuous Annealing Process

In the continuous annealing of the cold rolled steel sheet, the continuous annealing is preferably carried out for 10 to 120 seconds in the temperature range of 770 to 810 ° C. In the continuous annealing process, it is important to cool the austenite phase produced in the two phase region at a sufficient cooling rate so that the austenite phase is not transformed into pearlite or bainite. In the temperature range of 770 to 810 ° C., the austenite phase is not sufficiently formed during heating, so that an appropriate amount of martensite fraction cannot be obtained. On the other hand, if it is maintained for more than 120 seconds, the productivity decreases, which is not preferable.

Hot dip galvanizing and alloying heat treatment process

The present invention includes a hot dip galvanizing process or a hot dip galvanizing and alloying heat treatment process if necessary.

In hot dip galvanizing of the continuously annealed steel sheet, after quenching to 400 ~ 480 ℃ at a cooling rate of 5 ~ 50 ℃ / sec is carried out hot dip galvanizing. If the quench end temperature exceeds 480 ° C, the ductility decreases because it is transformed into the bainite phase, while if it is less than 400 ° C, the ductility decreases with the rapid increase in strength, thereby decreasing workability. Therefore, it is preferable to control quenching end temperature to 400-480 degreeC.

After hot-dip galvanizing is completed, the conventional method is used for stable growth of the plating layer. The alloy is heat treated by reheating until the temperature reaches 480 ~ 520 ℃.

Then, it is cooled to a temperature range of 250 ~ 350 ℃ at a cooling rate of 5 ~ 50 ℃ / sec or more by the usual method.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are only examples for describing the present invention in more detail, and do not limit the scope of the present invention.

< Example >

In order to confirm the effect of the composition and the manufacturing method of the steel sheet according to the present invention, a high strength steel sheet was prepared under the conditions shown in Table 2 below for the composition shown in Table 1.

More specifically, after maintaining the slab having the alloy composition of Table 1 in the heating furnace of 1250 ℃ for 2 hours, the hot rolling is finished at 880 ~ 920 ℃ according to the manufacturing conditions shown in Table 2, the temperature of 580 ~ 620 ℃ After cooling, the product was wound up and cold rolled at a reduction ratio of 50 to 90% after pickling. Thereafter, the cold rolled steel sheet was annealed at 770 to 810 ° C., quenched to 460 ° C. to perform hot dip galvanizing, and alloyed heat treatment was performed at 490 to 520 ° C. to prepare a specimen.

Thereafter, the mechanical properties of the prepared specimens were measured and shown in Table 2.

division C Si Mn Al P S Cu Cr Sb Ni B * Nb Inventory 1 0.07 0.11 2.1 0.11 0.0069 0.0047 0.12 0.12 0.02 0.06 13 0.01 Inventive Example 2 0.09 0.16 2.4 0.07 0.0038 0.0042 0.15 0.17 0.03 0.08 12 0.01 Inventory 3 0.09 0.17 2.2 0.13 0.0049 0.0035 0.18 0.34 0.04 0.07 5 0.02 Honorable 4 0.10 0.23 2.4 0.09 0.0047 0.0041 0.14 0.19 0.03 0.07 8 0.01 Inventory 5 0.08 0.22 2.5 0.06 0.0056 0.0037 0.29 0.22 0.04 0.08 9 0.03 Inventory 6 0.08 0.29 2.3 0.06 0.0063 0.0036 0.27 0.12 0.04 0.06 6 0.02 Honorable 7 0.07 0.17 2.2 0.08 0.0039 0.0049 0.21 0.17 0.02 0.08 7 0.01 Inventive Example 8 0.10 0.14 2.3 0.05 0.0047 0.0044 0.24 0.16 0.04 0.08 6 0.02 Proposition 9 0.08 0.19 2.3 0.12 0.0039 0.0029 0.29 0.29 0.03 0.07 4 0.03 Inventory 10 0.08 0.15 2.5 0.09 0.0059 0.0032 0.17 0.18 0.02 0.08 15 0.01 Exhibit 11 0.07 0.14 2.2 0.13 0.0049 0.0039 0.18 0.39 0.04 0.09 7 0.03 Inventory 12 0.07 0.20 2.5 0.08 0.0051 0.0035 0.28 0.34 0.04 0.08 14 0.01 Inventory 13 0.10 0.18 2.3 0.14 0.0058 0.0047 0.19 0.37 0.03 0.07 11 0.01 Inventive Example 14 0.08 0.13 2.4 0.08 0.0047 0.0031 0.26 0.28 0.04 0.07 10 0.02 Honorable Mention 15 0.10 0.28 2.5 0.15 0.0056 0.0047 0.16 0.22 0.03 0.08 9 0.02 Comparative Example 1 0.07 0.28 2.7 0.01 0.0071 0.0031 - 0.17 - - - - Comparative Example 2 0.09 0.16 2.7 0.02 0.0056 0.0042 - 0.21 - - - - Comparative Example 3 0.09 0.20 2.8 0.04 0.0048 0.0042 - 0.27 - - - - Comparative Example 4 0.10 0.29 2.6 0.02 0.0049 0.0057 - 0.37 - - - - Comparative Example 5 0.08 0.20 2.9 0.04 0.0065 0.0031 - - 0.02 - - - Comparative Example 6 0.08 0.18 2.4 0.03 0.0056 0.0052 - - 0.03 - - - Comparative Example 7 0.07 0.23 2.2 0.03 0.0068 0.0048 - - 0.03 - - - Comparative Example 8 0.10 0.14 2.1 0.06 0.0053 0.0037 - - 0.04 - - - Comparative Example 9 0.08 0.23 2.5 0.05 0.0057 0.0031 - - - 0.07 - - Comparative Example 10 0.08 0.16 2.1 0.02 0.0049 0.0031 - - - 0.08 - - Comparative Example 11 0.07 0.17 2.2 0.07 0.0056 0.0033 - - - 0.09 - - Comparative Example 12 0.07 0.20 2.1 0.01 0.0075 0.0031 - - - 0.08 - - Comparative Example 13 0.10 0.33 2.5 0.02 0.0063 0.0026 - - - - 6 - Comparative Example 14 0.08 0.41 2.4 0.03 0.0056 0.0042 - - - - 9 - Comparative Example 15 0.10 0.47 2.2 0.03 0.0074 0.0037 - - - - 12 -

However, in Table 1, the content units of the elements marked with * are ppm, and the content units of the remaining elements are wt%.

division FDT CT Cold rolling Annealing Temperature Bera
It Marten
site Cu
particle TS Hand TS X El TS, El evaluation Plating property Synthesis ℃ ℃ % ℃ % % nm MPa % MPa% Inventory 1 885 580 55 770 87 13 7 810 19 15390 ○ ○ ◎ Inventive Example 2 885 590 55 780 85 15 15 837 18 15066 ○ ○ ◎ Inventory 3 890 600 65 790 95 5 11 780 20 15600 ○ ○ ◎ Honorable 4 890 610 65 810 86 14 71 836 18 15048 ○ ○ ◎ Inventory 5 895 620 70 770 92 8 34 793 19 15067 ○ ○ ◎ Inventory 6 895 580 70 780 91 9 76 791 19 15029 ○ ○ ◎ Honorable 7 900 590 75 790 90 10 30 790 20 15800 ○ ○ ◎ Inventive Example 8 900 600 75 810 89 11 94 792 19 15048 ○ ○ ◎ Proposition 9 905 610 80 770 87 13 78 791 19 15029 ○ ○ ◎ Inventory 10 905 620 80 780 94 6 46 780 21 16380 ○ ○ ◎ Exhibit 11 910 580 85 790 92 8 50 794 20 15880 ○ ○ ◎ Inventory 12 910 590 85 810 88 12 45 802 19 15238 ○ ○ ◎ Inventory 13 915 600 90 770 87 13 62 804 19 15276 ○ ○ ◎ Inventive Example 14 915 610 90 780 89 11 25 800 19 15200 ○ ○ ◎ Honorable Mention 15 915 620 90 790 90 10 85 799 19 15181 ○ ○ ◎ Comparative Example 1 885 580 55 810 82 18 radish 785 19 14915 △ △ △ Comparative Example 2 885 590 55 770 79 21 radish 794 19 15086 ○ △ △ Comparative Example 3 890 600 65 780 77 23 0.5 827 18 14886 △ △ △ Comparative Example 4 890 610 65 790 75 25 radish 822 18 14796 △ △ △ Comparative Example 5 895 620 70 810 74 26 - 842 16 13472 × ○ △ Comparative Example 6 895 580 70 770 71 29 radish 854 16 13664 × ○ △ Comparative Example 7 900 590 75 780 77 23 radish 829 17 14093 △ ○ △ Comparative Example 8 900 600 75 790 79 21 0.7 827 18 14886 △ ○ △ Comparative Example 9 905 610 80 810 69 31 0.5 857 16 13712 × ○ △ Comparative Example 10 905 620 80 770 72 28 radish 848 17 14416 △ ○ △ Comparative Example 11 910 580 85 780 88 12 0.4 802 18 14436 △ ○ △ Comparative Example 12 910 590 85 770 89 11 radish 821 18 14778 △ ○ △ Comparative Example 13 915 600 90 780 91 9 radish 825 18 14850 △ × × Comparative Example 14 915 610 90 790 84 16 radish 832 18 14976 △ × × Comparative Example 15 915 620 90 810 82 18 radish 847 17 14399 △ × ×

Here, TS * El represents 15000 MPa% or more (circle), and 14000-15000 MPa% represents (triangle | delta) and 14000 MPa% or less as x. In addition, plating property evaluation was measured by external appearance evaluation, and was expressed by (circle) in case of favorable, (triangle | delta) in normal case, and x in case of defect.

As shown in Table 2, Inventive Examples 1 to 15 control the particle size of the steel component, the structure and the precipitated Cu within the range proposed by the present invention, and have a high tensile strength of more than 780 MPa and a TS × El value of 15000. A steel sheet having good workability exceeding MPa% can be produced. In addition, it can be seen that Inventive Examples 1 to 15 are all excellent in plating properties.

On the contrary, it can be seen that the steel sheet of Comparative Examples 13 to 15 in which the content of silicon (Si) was added in excess of the upper limit of the present invention and copper (Cu) was not added is reduced in plating properties. In addition, in the case of Comparative Examples 1 to 4 in which the content of manganese (Mn) was added in excess of the upper limit of the present invention, and copper (Cu) was not added, the plating characteristics were lowered.

Although copper (Cu) was not added, Comparative Examples 5 to 12, in which antimony or nickel elements were added, showed that the plating characteristics were improved, but the workability was not good.

In addition, it can be seen that even if chromium (Cr) is added instead of expensive molybdenum (Mo), high elongation and high tensile strength can be secured.

Therefore, it is a high strength steel sheet that has a tensile strength of 780 MPa or more and excellent elongation and plating properties by lowering the carbon content, increasing the silicon, manganese, aluminum content, and adding an alloy such as copper, nickel, and antimony. Can be prepared.

Claims (6)

By weight%, carbon (C): 0.07 to 0.10%, silicon (Si): 0.1 to 0.3%, manganese (Mn): 2.0 to 2.5%, aluminum (Al): 0.05 to 0.25%, copper (Cu): 0.1 0.3%, niobium (Nb): 0.01-0.03%, phosphorus (P): 0.007% or less, sulfur (S): 0.005% or less, residual iron (Fe) and other unavoidable impurities Plating property, consisting of 85% to 95% ferrite and 5% to 15% martensite, and microprecipitated Cu particles having a particle size of 1 to 100 nm are dispersed and deposited in the respective structures. This excellent high strength steel sheet.
According to claim 1, wherein the high-strength steel sheet by weight, chromium (Cr): 0.1 ~ 0.4%, boron (B): 0.0005 ~ 0.0015%, antimony (Sb): 0.02 ~ 0.04% and nickel (Ni): 0.06 High-strength steel plate with excellent plating properties, characterized in that it further comprises one or two or more selected from the group consisting of ~ 0.10%.
The high strength steel sheet according to claim 1 or 2, wherein the high strength steel sheet has a tensile strength of 780 MPa or more and a TS × El value of 15000 MPa% or more.
By weight%, carbon (C): 0.07 to 0.10%, silicon (Si): 0.1 to 0.3%, manganese (Mn): 2.0 to 2.5%, aluminum (Al): 0.05 to 0.25%, copper (Cu): 0.1 0.3%, niobium (Nb): 0.01-0.03%, phosphorus (P): 0.007% or less, sulfur (S): 0.005% or less, steel slabs composed of residual iron (Fe) and other unavoidable impurities 880-920 Plating is performed by finishing rolling at 캜, winding at 580 to 620 캜, cold rolling at a reduction ratio of 50 to 90%, and then performing recrystallization annealing heat treatment at 770 to 810 캜 for 10 to 120 seconds. Excellent method for producing high strength steel sheet.
The method of claim 4, wherein the steel slab is chromium (Cr): 0.1 ~ 0.4%, boron (B): 0.0005 ~ 0.0015%, antimony (Sb): 0.02 ~ 0.04% and nickel (Ni): 0.06 ~ 0.10% Method for producing a high strength steel sheet having excellent plating properties, characterized in that it further comprises one or two or more selected from the group consisting of.
The alloy annealing heat treatment according to claim 4 or 5, wherein the annealing heat-treated steel sheet is quenched to 400 to 480 ° C. at a cooling rate of 5 to 50 ° C./sec to hot dip zinc plated, and then reheated to a temperature range of 480 to 520 ° C. The method for producing a high strength steel sheet having excellent plating property, characterized in that cooling to 250 to 350 ° C. at a cooling rate of 5 to 50 ° C./sec.