MX2007013675A

MX2007013675A - Cold rolled steel sheet having high yield ratio and less anisotropy, process for producing the same.

Info

Publication number: MX2007013675A
Application number: MX2007013675A
Authority: MX
Inventors: Jeong-Bong Yoon; Sang-Ho Han; Sung-Il Kim; Kwang-Geun Chin; Ho-Seok Kim; Jin-Hee Chung
Original assignee: Posco
Priority date: 2005-05-03
Filing date: 2006-05-03
Publication date: 2008-01-28
Also published as: KR20060115313A; KR100723160B1; KR20060115317A; KR20060115629A; KR100742943B1; KR100742950B1; KR100742926B1; KR100742941B1; KR100742927B1; KR100742819B1; KR20060115623A; KR100723182B1; KR100742932B1; JP4954981B2; KR20060115636A; JP4964870B2; KR20060115314A; KR100723165B1; KR20060115627A; KR20060115309A

Abstract

Disclosed herein is a Nb-Ti composite IF steel in which fine precipitates, such as CuS precipitates, having a size of 0.2 ??mum or less are distributed. The distribution of fine precipitates in the Nb-Ti composite IF steel enhances the yield strength and lowers the in-plane anisotropy index. The nanometer-sized precipitates allow the formation of minute crystal grains. As a result, dissolved carbon is present in a larger amount in the crystal grain boundaries than within the crystal grains, which is advantageous in terms of room-temperature non-aging properties and bake hardenability.

Description

LAMINATED STEEL SHEET IN FRIÓ THAT HAS A HIGH RELATION OF DEFORMATION AND LESS ANISOTROPY, PROCESS TO PRODUCE IT [Technical Field] The present invention relates to steel foils laminated in interiospheric (IF) free trio based on niob or (Nb) that are used as materials for automobiles, domestic electronic devices, etc. More particularly, the present invention relates to trio II-rolled steel sheets with high deformation ratio whose anisotropy in the plane is decreased due to the distribution of fine precipitates, and a method for producing such steel sheets. ] In general, cold-rolled steel sheets for use in automobiles and home electronics are required because they are resistant to aging at excellent room temperature and oven hardness, with high strength and superior formability. It is a phenomenon of aging by deformation that arises from the hardening caused by loose elements, such as C and N, fixed to dislocations.Since the aging causes defect, called "superficial deformation", it is important to ensure the resistance to aging at temperature excellent atmosphere.

The bake hardening means increases in strength due to the presence of dissolved charcoal after the press formation, followed by painting and drying, by leaving a slight amount of carbon in a solid solution state. The steel sheets with excellent bake hardenability can overcome the difficulties of form in the press resulting from the high resistance. Resistance to aging at room temperature and oven hardenability can be imparted to aluminum-calmed steels (Al) by batch-picking steels that are quenched with it. However, the extended time of batching causes low productivity of steel steeped with Al and severe variations in steel materials at different sites. In addition, the steels calmed with it have an oven hardening value (Bll) (a difference in the deformation resistance before and after painting) of 10-20 MPa, which shows that an increase in the strength of formation is to. Under such circumstances, interstitial free steels (LF) with resistance to aging at room temperature and excellent baking hardening have been developed by adding carbide and nitride-forming elements, such as Ti and Nb, followed by continuous annealing. .

For example, Japanese Unexamined Patent Publication No. Sho 57-041349 describes an increase in the strength of a Ti-based 1L steel by adding 0.4-0.8% manganese (Mn) and 0.04-0.12% phosphorus (P) . In very high carbon IF steel, however, P causes the problem of secondary work embrittlement due to segregation in grain boundaries. Japanese Unexamined Patent Publication No. Hei 5-078784 discloses an increase in strength by the addition of Mn as a solid solution reinforcing element in an amount exceeding 0.9% and not exceeding 3.0%. Korean patent open to the public No. 2003-0052248 describes an improvement in the embrittlement strength of secondary work as well as strength and work capacity by the addition of 0.5-2.0% Mn instead of P, with aluminum only (? l) and boron (B). Japanese Unexamined Patent Application No. Hei 10-158783 discloses an increase in strength by reducing the content of P and using Mn and S i as solid solution reinforcing elements. According to this publication, Mn is used in an amount of up to 0.5%, Al as a deoxidizing agent is used in an amount of 0.1%, and nitrogen (N) as an impurity is limited to 0.01% or less. If the content of Mn increases, the characteristics of enamel become worse.

Japanese Unexamined Patent Publication No. Hei 6-057336 discloses an increase in the strength of an IF steel by adding 0.5-2.5% copper (Cu) to form precipitates of ..- Cu. The high strength of the IF steel is achieved due to the presence of e-Cu precipitates, but the working capacity of the steel II 'worsens. Japanese Unexamined Patent Publications Nos. Hei 9-227951 and Hei 10-265900 suggest technologies ciated with the improvement in working capacity or surface defects due to carbides by the use of Cu as a core for the precipitation of carbides. According to the first publication, 0.005-0.1% of Cu is added to precipitate the CuS during the annealing by rolling of an IF steel, and the CuS precipitates are used as cores to form Cu-Ti-CS precipitates during the lamination hot In addition, the first publication states that the number of cores that form a plane. { 111.}. parallel to The surface of a plate increases in the vicinity of the precipitates of Cu-Ti-C-S during the reclfication, which contributes to an improvement in the working capacity. According to the last publication, 0.01-0.05% of Cu is added to an IF steel to obtain CuS precipitates and then the CuS precipitates are used as a nucleus for the precipitation of carbides to reduce the quantity of dissolved carbon (C), driving to an improvement e The defects of the surface. According to the prior art, since the CuS precipitates are used during the production of cold-rolled steel sheets, the carbides remain in the final products. Further, since the emulsifying elements, such as Ti and R, are added in an amount greater than the amount of sulfur (S) in an atomic weight ratio, a major portion of the sulfur (S) reacts with Ti or Zr before Cu. On the other hand, Japanese Unexamined Patent Publications Nos. Hei 6-240365 and Hei 7-216340 disclose the addition of a combination of Cu and P to improve the corrosion resistance of the IF-type steels for oven curing. According to these publications, the Cu is added in an amount of 0.05-1.0% to ensure improved corrosion resistance. However, at present, Cu is added in an excessively large amount of 0.2% or more. Japanese Unexamined Patent Application Publications Nos. Hei 10-280048 and Hei 10-287954 suggest the dissolution of carbosulfide (based on Ti-CS) on a carbide at the time of recovery and annealing to obtain a solid solution in the limits of the crystal degree, thus achieving a furnace hardening value (BU) (a lerenc a in the resistance of deformation before and after baking) of 30 MPa or more. According to the publications mentioned in the above, the resistance is increased by hardening the solid solution or using e-Cu precipitates. Cu is used to form e-Cu precipitates and improves corrosion resistance. In addition, Cu is used as a nucleus for the precipitation of carbides. No mention is made in these publications of an increase in the high strain ratio (ie, strain resistance / tensile strength) and a reduction in the anisotropy index in the plane. If the ratio of tensile strength to deformation strength (i.e. deformation ratio) of an IF steel sheet is high, the thickness of the LF steel sheet can be reduced, which is effective in reducing weight. In addition, if the amsoLropLa index in the plane of an IF steel sheet is low, few creases and wavy edges occur during processing and after processing, respectively. [Describing] [Technical Problem] One objective of certain embodiments of the invention is to provide Nb based cold-rolled steel sheets based on Nb and a method for producing such steel sheets which are capable of achieving a high deformation ratio and a index of anisotrop a in the low plane.

Another object of certain embodiments of the invention is to provide a method for producing such steel sheets. [Technical Solution] According to the present invention, there is provided a cold rolled steel sheet with high deformation ratio and anisotropy index in the plane, the cold rolled steel sheet having a composition comprising 0.01% or less of C, 0.01 to 0.2% of Cu, 0.005 to 0.08% of S, 0.1% or less of? l, 0.004% or less of N, 0.2% or less of P, 0.001-0.002% of B, 0.002 to 0.04% of Nb, by weight, and the rest of Fe and other non-avoidable impurities, wherein the composition satisfies the following ratio: 1 < (Cu / 63.5) / (S / 32) < 30 and the steel sheet comprises CuS precipitates having an average size of 0.2 μm or less. In one embodiment of the present invention, there is provided a sheet of cold rolled steel having a composition comprising 0.01% or less of C, 0.01 to 0.2% of Cu, 0.01 to 0.3% of Mn, 0.00 to 0.08% of S , 0.1% or less of Al, 0.004% or less of N, 0.2% or less of P, 0.001 to 0.002% of B, 0.002 to 0.04 of Nb, by weight, and the rest of Fe and other non-avoidable impurities, in where the composition satisfies the following relationship: 1 < (Mn / 55 t Cu / 63.5) / (S / 32) < 30 and the steel sheet comprises precipitates of (Mn, Cu) S which has an average size of 0.2 μm or less. In another embodiment of the present invention, the cold-rolled steel sheet has a composition comprising 0.01% or less of C, 0.01 to 0.2% Cu, 0.005 to 0.08% of S, 0.1% or less of it, 0.004 or less of N, 0.2% or less of P, 0.001 to 0.002% of B, 0.002 to 0.04% of Nb, by weight, and the rest of Fe and other non-avoidable impurities, where the composition satisfies the following relationships: 1 = (Cu / 63.5) / (S / 32) < 30, 1 < (Al / 27) / (N / 14) < 10, and the steel sheet comprises precipitates of (Mn, Cu) S having an average size of 0.2 μm or less. In yet another embodiment of the present invention, the cold rolled steel sheet has a composition comprising 0.01% or less of C, 0.01 to 0.2% of Cu, 0.01 to 0.3% of Mn, 0.00 to 0.08% of S, 0.1% or less of Al, 0.004 to 0.02% of N, 0.2% or less of P, 0.001 to 0.002% of B, 0.002 to 0.04% of Nb, by weight, and the rest of Fe and other non-avoidable impurities, in where the composition satisfies the following relationships: 1 < (Mn / 55 i Cu / 63.5) / (S / 32) < 30, 1 < (Al / 27) / (N / l) < 10, and the steel sheet comprises precipitates of (Mn, Cu) S and? 1N having an average size of 0.2 μm or less. According to another aspect of the present invention, there is provided a cold rolled steel sheet with high deformation ratio and anisotropy index in the low plane, the cold rolled sheet having a composition comprising: 0.01% or less of C, 0.08% or less of S, 0.1% or less of? l, 0.004% or less of N, 0.2% of P, 0.0001 to 0.002% of B, 0.002 to 0.04% of Nb, at least one class selected from 0.01 to 0.2% of Cu, 0.01 to 0.3% of Mn and 0.004 to 0.2% of N, by weight, and the rest of Fe and other non-avoidable impurities, wherein the composition satisfies the following ratios: 1 < (Mn / bb i Cu / 63.) / (S / 32) < 30, 1 < (Al / 27) / (N / 14) < 10, wherein the content N is 0.004% or more, and the steel sheet comprises at least one selected class of precipitates of (Nn, Cu) S and 1 1N having an average size of 0.2 μm or less. For the non-aging properties at room temperature, the contents of C and Nb satisfy a ratio, by weight: 0.8 < (Nb / 93) / (C / 12) < 5.0. In addition, for oven hardening, the solute carbon (Cs) is from 5 to 30, where Cs = (C-Nbxl2 / 93) x 10,000. Depending on the design of the compositions, the cold-rolled steel sheets of the present invention have characteristics of smooth cold-rolled steel sheets in the order of 280 MPa and high-strength cold-rolled steel sheets in the order of 340 MPa or plus. When the content of P in the compositions of the present invention is 0.015% or less, the cold rolled steel sheets are smooth in the order of 280 MPa. produced. When the soft cold-rolled steel sheets further contain at least one solid solution reinforcing element selected from Si and Cr, or the P content is in the range of 0.015-0.2%, a high strength of 340 MPa is achieved. or more. The content of P in high strength steels containing P alone are preferable in the range of 0.03% to 0.2%. Si content in high strength steels is preferably in the range of 0.1 to 0.8%. The Cr content in the high strength steels is preferably in the range of 0.2 to 1.2. In the case where the cold-rolled steel sheets of the present invention contain at least one element selected from Si and Cr, the content of P can be freely designated in an amount of 0.2% or less. For better workability, the cold rolled steel sheets of the present invention may contain 0.01 to 0.2% by weight Mo. According to yet another aspect of the present invention, there is provided a process for producing the cold-rolled steel sheets, the method comprising the steps of reheating a slab to meet one of the compositions at a temperature of 1,100 ° C or higher, heat-laminate the superheated coarse sheet at a lamination temperature terminated from the transformation point? r3 or higher to provide a sheet of hot-rolled steel, cooling the hot-rolled steel sheet in a ratio of 300 ° C / min., winding the cooled steel sheet to 700 ° C or more, cold rolling the rolled steel sheet, and continuously annealing the cold rolled steel sheet. [Best Mode] The present invention will be described in detail below. Fine precipitates having a size of 0.2 μm or less are distributed in the cold-rolled steel sheets of the present invention. Examples of such precipitates include precipitates of MnS, precipitates of CuS, and precipitates composed of MnS and CuS. These precipitates are simply referred to as "(Mn, Cu) S". The present inventors have found that when the fine precipitates are distributed in the IF steels based on Nb, the deformation resistance of the steels IF is increased and the anisotropy index in the plane of the steels Í T is diminished, thus driving to an improvement in work capacity. The present invention has been achieved based on this invention. The precipitates used in the present invention have little related stress in conventional 1L steels. Particularly, the precipitates have not been used actively from the point of view of deformation resistance and index of anisotropy in the plane. The regulation of the components in the Ti-based IF steels is required to obtain precipitates of (Mn, Cu) S and / or precipitates of? 1N. If the steels IF contain Ti, Nb, Zr and other elements, S react preferentially with Ti and Zr. Since the cold-rolled steel sheets of the present invention are IF steels added with Nb, S for the precipitates of (Mn, Cu) S through the regulation of the content of Cu and Mn. N is precipitated in the AlN through the content regulation of Al and N. The fine precipitates thus obtained allow the formation of tiny crystal grains. The smallness in the size of the crystal grains relatively increases the proportion of crystal grain boundaries. Accordingly, loose carbon is present in a larger amount within the limits of the crystal grain than within the crystal grains, thereby achieving excellent non-aging properties at room temperature. Since the loose carbon present inside the crystal grains can migrate more freely, it joins the movable dislocations, thus affecting the aging properties at room temperature. In contrast, the dissolved carbon segregated in the stable positions, such as in the limits of the crystal grain and in the vicinity of the precipitates, is activated at a high temperature, example, a temperature for the treatment of painting / baking, thus affecting the hardenability in the oven. The fine precipitates distributed in the steel sheets of the present invention have a positive influence on the increase in the deformation resistance that increases the precipitation, improves the resistance-ductility balance, index of anisotropy in the plane, and anotropy of plasticity. For this purpose, fine (Mn, Cu) S precipitates and AlN precipitates should be distributed evenly. According to the cold-rolled steel sheets of the present invention, the contents of the components that affect the precipitation, the composition between the components, the production conditions, and particularly the cooling ratio after the hot rolling, t They have a greater influence on the distribution of fine precipitates. The constituent components of the cold rolled steel sheets according to the present invention will be explained. The content of carbon (C) is preferably limited to 0.01% or less. The carbon (C) affects the resistance to aging at room temperature and the oven hardenability of the cold rolled steel sheets. When the The carbon content exceeds 0.01%, the addition of expensive agents Nb and Ti is required to remove the remaining carbon which is economically disadvantageous and undesirable in terms of formab 1. When it is proposed to achieve resistance to aging at room temperature only, it is preferred to keep the carbon content at a low level, which allows the reduction of the amount of the expensive Nb and Ti agents added. When it is proposed to ensure the desired bake hardenability, the coal is preferably added in an amount of 0.001% or more, and more preferably 0.005% to 0.01%. When the carbon content is less than 0.00%, the resistance to aging at room temperature can be ensured without increasing the amounts of Nb and Ti. The copper (Cu) content is preferably in the range of 0.01 to 0.2%. Copper serves to form fine CuS precipitates, which make fine cpstal grains. Copper decreases the amsotrop a rate in the plane of the Trio laminated steel sheets and increases the deformation strength of the cold rolled steel sheets by promoting precipitation. ? In order to form fine precipitates, the Cu content must be 0.01% or more. When the content of Cu is more than 0.2%, the coarse precipitates are obtained. Cl content of Cu is more preferably in the range of 0.03 to 0.2%. The manganese content (Mn) is preferably in the range of 0.01 to 0.3%. Cl manganese serves to precipitate sulfur in a solid state solution in steels such as MnS precipitates, thereby preventing the occurrence of hot brittleness caused by dissolved sulfur, or is known as a solid solution reinforcing element. From such a technical point of view, manganese is generally added in a large amount. The present inventors have found that when the manganese content is reduced and the sulfur content is optimized, very fine MnS precipitates are obtained. Based on this invention, the manganese content is limited to 0.3% or less. In order to ensure this characteristic, the manganese content must be 0.01% or more. When the manganese content is less than 0.01%, ie the content of a / f re that remains in a solid state solution is high, hot brittleness can occur. When the manganese content is greater than 0.3%, the coarse MnS precipitates are formed, thus making it difficult to achieve the desired strength.

A more preferable Mn content is within the range of 0.01 to 0.12%. The sulfur content (S) is preferably limited to 0.08% or less.

Cl sulfur (S) reacts with Cu and / or Mn to form precipitates of CuS and MnS, respectively. When the sulfur content is greater than 0.08%, the proportion of dissolved sulfur increases. increase in dissolved sulfur greatly deteriorates the ductility and formability of the steel sheets and increases the risk of brittleness in the street. ? In order to obtain as many CuS and / or MnS precipitates as possible, a sulfur content of 0.005% or more is preferred. The aluminum content (Al) is preferably limited to 0.1% or less. Gl to Lumin or reacts with nitrogen (N) to form fine 1N precipitates, thereby completely preventing aging by dissolved nitrogen. When the nitrogen content is 0.004% or more, the AlN precipitates are formed sufficiently. The distribution of the fine AlN precipitates in the steel sheets allows the formation of tiny crystal grains and increases the deformation resistance of the steel sheets by increasing precipitation. A more preferable content is in the range of 0.01 to 0.1%. The nitrogen (N) content is preferably limited to 0.02% or less. When it is proposed to use AlN precipitates, the nitrogen is added in an amount of up to 0.02%. Of other Thus, the nitrogen content is controlled at 0.004% or less. When the nitrogen content is less than 0.004%, the number of? 1N precipitates is small, and therefore, the effects of the smallness of the crystal grains and the effects of increased precipitation are negligible. In contrast, when the nitrogen content is greater than 0.02%, it is difficult to guarantee the aging properties through the use of dissolved nitrogen. The phosphorus content (p) is preferably limited to 0.2% or less. Cl phosphor is an element that has excellent solid solution reinforcing effects while allowing a slight 1 reduction in the r value. r.l phosphor guarantees high resistance of the steel sheets of the present invention in which the precipitates are controlled. It is desirable that the phosphorus content in steels requiring a strength of the order of 280 MPa is defined as 0.015% or less. It is desirable that the phosphorus content in high strength steels in the order of 340 MPa be limited to a range exceeding 0.015% and not exceeding 0.2%. A phosphorus content exceeding 0.2% can lead to a reduction in ductility in the steel sheets. Accordingly, the phosphorus content is preferably limited to a maximum of 0.2%. When the Si and Cr are added in the present invention, the phosphorus content it can be appropriately controlled to be 0.2% or less to achieve the desired strength. The boron content (B) is preferably in the range of 0.0001 to 0.002%. TI boron is added to prevent the occurrence of secondary work. For purpose, a preferable boron content is 0.0001% or more. When the boron content exceeds 0.002%, the deep drawing capacity of the steel sheets can deteriorate markedly. The niobium content (Nb) is preferably in the range of 0.002 to 0.04%. The niobium is added for the purpose of ensuring the non-aging properties and improving the formability of the steel sheets. Cl Nb, which is an element that forms potent carbide, is added to steels to form NbC precipitates in steels. In addition, the NbC precipitates allow the steel sheets to be well textured during the annealing, thereby greatly enhancing the deep stiffness of the steel sheets. When the added Nb content is not greater than 0.002%, the NbC precipitates are obtained in very small amounts. Consequently, the steel sheets are not well textupsed and thus there is little improvement in the deep drawing capacity of the steel sheets. In contrast, When the Nb content exceeds 0.04%, the NbC precipitates are obtained in very large amounts. Consequently, the deep stretchability and the elongation of the steel sheets are reduced, and thus the formability of the steel sheets can deteriorate markedly. To obtain the precipitates of (Mn, Cu) S and AlN, the contents of Mn, Cu, S, Al, and N are adjusted within the ranges defined by the following ratios. The respective components indicated in the following ratios are expressed as percentages by weight. 1 < (Cu / 63.5) / (S / 32) < 30 (1) Ratio 1 is associated with the formation of (Mn, Cu) S precipitates. To obtain fine CuS precipitates, it is preferred that the value of Rection 1 be equal to or greater than 1. If the value of ratio 1 is greater than 30, the coarse CuS precipitates are distributed, which is undesirable. To stably obtain CuS precipitates having a size of 0.2 μm or less, the Lor va of ratio 1 is preferably in the range of 1 to 9 and most preferably 1 to 6. The reason for this limitation is to obtain precipitates of (Mn, Cu) S fine. 1 < (Mn / b5 i Cu / 63.5) / (S / 32) < 30 (2) Ratio 2 is associated with the formation of precipitates of (Mn, Cu) S, and is obtained by adding a content of Mn to ratio 1. To obtain precipitates from (Mn, Cu) S effective, the value of ratio 2 must be 1 or greater. When the value of the ratio 2 is greater than 30, the precipitates of (Mn, Cu) S coarse are obtained. To stably obtain precipitates of (Mn, Cu) having a size of 0.2 μm or less, the value of the ratio 2 is preferably preferably in the range of 1 to 20, more preferably 1 to 9, and most preferably of 1 to 6. 1 < (? l / 27) / (N / 14) < 10 (3) Relationship 3 is associated with the formation of AlN precipitates. When the value of ratio 13 is less than 1, aging can take due to dissolved N. When the value of ratio 3 is greater than 10, the coarse? 1N precipitates are obtained, and thus sufficient strength is not obtained. Preferably, the value of the ratio 3 is in the range of 1 to 5. The components of the cold-rolled steel sheets according to the present invention can be combined in various ways according to the kind of precipitates to be obtained. For example, the present invention provides a cold rolled steel sheet with deformation ratio and amasotropy index in the flat ba, having a composition comprising 0.01% or less of C, 0.08% or less of S, 0.1% or less than?, 0.004% or less of N, 0.2% or less of P, 0.001 to 0.002% of B, 0.002 to 0.04% of Nb, at least a selected class of 0.01 to 0.2% of Cu, 0.01 to 0.3% of Mn and 0.004-0.2% of N, by weight, and the rest of FE and other non-avoidable impurities where the composition satisfies the following relationships: 1 < (Mn / 5b + Cu / 63.5) / (S / 32) < 30, 1 < (Al / 27) / (N / 14) < 10, where the content of N is 0.004% or more. Then, the steel sheets comprise at least one selected class of CuS precipitates, precipitates composed of MnS and CuS, and AlN precipitates having an average size of 0.2 μm or less. That is, one or more classes selected from the group consisting of 0.01 to 0.2% Cu, 0.01 to 0.3% Mn, and 0.004-0.2% N lead to various combinations of precipitates of (Mn, Cu) S and AlN that It has a size no greater than 0.2 μmm. In the steel sheets of the present invention, the carbon is precipitated in the NbC and TiC forms. Therefore, the resistance to aging at room temperature and the bake hardening of the steel sheets are affected depending on the conditions of the dissolved carbon or on which the NbC and TiC precipitates are not obtained. Taking these requirements into account, it is much more preferred that the contents of Ti and C satisfy the following relationships. 0.8 < (l'i 748) / (C / l?) < 5.0 (4) Ratio 5 is associated with the formation of NbC precipitates to remove carbon in a solution of solid state, in this way achieving non-aging properties at room temperature. When the value of the ratio 4 is less than 0.8, it is difficult to ensure the properties of non-aging at room temperature. In contrast, when the value of the ratio 4 is greater than 5, the amounts of Nb that remain in a solid state solution in the steels are large, which deteriorates the durability of the steels. When it is proposed to achieve non-aging properties at room temperature without insuring the hardenability in a furnace, it is preferred to limit the carbon content to 0.005% or less. Although the carbon content is more than 0.005%, the non-aging properties at room temperature can be achieved when the ratio 4 is satisfied is satisfied by the amounts of the TiC precipitates are increased, thus deteriorating the working capacity of the steel sheets. Cs (solute carbon): 5-30, where Cs = (C-Nbxl2 / 93) x 10,000 (5) The relationship b is associated with the achievement of oven hardenability. Ll Cs, which represents the dissolved carbon content and is expressed in ppm. In order to achieve a high furnace hardening value, the value of Cs must be bppm or more. If the value of Cs exceeds 30 ppm, the content of the dissolved carbon increases, making it difficult to achieve properties of non-aging at temperature ambient . It is advantageous if the fine precipitates are evenly distributed in the compositions of the present invention. It is preferable that the precipitates have an average size of 0.2 μm or less. According to a study conducted by the present inventors, when the precipitates have an average size greater than 0.2 μm, the steel sheets have poor strength and anisotropy index in the low plane. In addition, large amounts of precipitates having a size of 0.2 μm or less are distributed to the compositions of the present invention. While the number of distributed precipitates is not particularly limited, it is more advantageous with the higher number of precipitates. The number of the distributed precipitates is preferably 1 x lOVmm2 or more, more preferably 1 x 10c / mrrr or more, and most preferably 1 x 107 / mm2 or more. The plasticity anisotropy index is increased and the amsotropy index in the plane decreases with the increase in the number of precipitates, and as a result, the work capacity is greatly improved. It is commonly known that there is a limitation in the increase in work capacity due to the fact that the index of anisotropy in the plane increases with the anisotropy index of plasticity. No SLrve anything that the number of precipitates distributed in the sheets of The steel of the present invention is increased, the anisotropy index of plasticity of the steel sheets is increased and the amsotropy index in the plane of the steel sheets is decreased. The steel sheets of the present invention in which the fine precipitates are formed satisfy a deformation ratio (deformation resistance / tensile strength) of 0.58 or higher. When the steel sheets of the present invention are applied to the high strength steel sheets in the order of 340MPa, they can contain Clonally at least one solution reinforcing element selected from P, Si and Cr. The effects of the addition of P have been previously described, and thus their explanation is omitted. The content of silicon (Si) is preferably in the range of 0.1 to 0.8%. If it is an element that has solid solution strengthening effects and shows a slight reduction in elongation. If it guarantees high strength of the steel sheets of the present invention in which the precipitates are controlled. Only when the Si content is 0.1% or more can the high strength be assured. However, when Si content is more than 0.8%, the ductility of steel sheets deteriorates. The content of chromium (Cr) is preferably in the range of 0.2 to 1.2%.

Cr is an element having solid solution reinforcement effects, the secondary work embrittlement temperature decreases, and the aging index decreases due to the formation of Cr carbides. Cr guarantees high strength of the steel sheets of the present invention in which the precipitates are controlled and serve to decrease the rate of amsotropy in the plane of the steel sheets. Only when the Cr content is 0.2% or more, the high strength can be assured. However, when the Cr content exceeds 1.2%, the ductility of the steel sheets deteriorates. The cold-rolled steel bars of the present invention may additionally contain molybdenum (Mo). The content of molybdenum (Mo) in the cold-rolled steel sheets of the present invention is preferably in the range of 0.01 to 0.2%. Mo is added as an element that increases the anisotropy index of plasticity of the steel sheets. Only when the molybdenum content is not less than 0.01%, the plasticity amsotropy index of the steel sheets increases. However, when the molybdenum content exceeds 0.2%, the plasticity anisotropy index does not increase adi ciently 1 and there is a danger of hot brittleness.

Production of cold-rolled steel sheets. Hereinafter, a process for producing the cold-rolled steel sheets of the present invention will be explained with reference to the preferred embodiments that follow. Various modifications of the embodiments of the present invention can be made, and such modifications are within the scope of the present invention. The process of the present invention is characterized in that a steel satisfying one of the steel compositions defined above is processed through hot rolling and cold rolling to form precipitates having an average size of 0.2. μm or less in a cold-rolled steel sheet. The average size of the precipitates in the cold-rolled plate is affected by the design of the steel composition and the processing conditions, such as preheating temperature and winding temperature. Particularly, the rate of cooling after hot rolling has a direct influence on the average size of the precipitates. Hot Rolling Conditions In the present invention, a steel that satisfies one of the compositions defined in the foregoing is reheats and then undergoes hot rolling. The reheat temperature is preferably 1,100 ° C or higher. When the steel is reheated to a temperature lower than 1,100 ° C, the coarse precipitates formed during continuous emptying do not completely dissolve and remain. The coarse precipitates still remain after hot rolling. It is preferred that hot rolling be performed at a finish rolling temperature not lower than the transformation point of Ar. When the finishing lamination temperature is lower than the transformation point of? R3, laminated grains are created which deteriorate the working capacity and cause poor resistance. The cooling is preferably carried out in a range of 300 ° C / min or higher before winding and after hot rolling. Although the composition of the components is controlled to obtain fine precipitates, the precipitates can have an average size greater than 0.2 μm in a cooling ratio of less than 300 ° C / m? N. This is, as the cooling rate increases, many sc-cores thus create the size of the precipitates become finer and finer. Since the size of the precipitates decreases with the increase in the cooling rate, it is not necessary to define the upper limit of the cooling rate. When the cooling ratio cs higher than 1, 000 ° C / mm. , however, a significant improvement in the effects of the reduction in size of the precipitates is not shown further. Therefore, the cooling rate is preferably in the range of 300-1000 ° C / m? N. Winding conditions After hot rolling, winding is carried out at a temperature no higher than 700 ° C. When the winding temperature is higher than 700 ° C, the precipitates develop very thickly, in this way making it difficult to ensure high resistance. Cold rolling conditions Cl steel is cold rolled at a reduction ratio of 90-90%. Since a cold reduction ratio lower than b0% leads to the creation of a small amount of nuclei in the recltalization of annealing, the crystal grains develop excessively in the annealing, thus thickening the recrystalline crystal grains i / through the recoction, which results in the reduction of the resistance and ormabilidad. A cold reduction ratio greater than 90% leads to increased formability, while creating an excessively large amount of minerals so that the recrystallized crystal grains raised through the annealing reach be very thin, thus deteriorating the ductility of steel. Continuous collection The continuous collection temperature plays an important role in determining the mechanical properties of the final product. According to the present invention, continuous co-operation is preferably carried out at a temperature of 700 to 900 ° C. When continuous annealing is carried out at a temperature lower than 700 ° C, the recharge is not compelled and thus a desired ductility can not be ensured. In contrast, when the continuous annealing is carried out at a temperature higher than 900 ° C, the grafted grains become thick and so the strength of the steel deteriorates. The continuous annealing is maintained until the steel recrystallizes completely. The recrystallization of the steel can be completed for approximately 10 seconds or more. The continuous annealing is preferably carried out for 10 seconds to 30 minutes. [Mode for the Invention] The present invention will now be described in greater detail with reference to the following examples. The mechanical properties of the steel sheets produced in the following examples were valued according to the ASTM C-8 standard test methods. Specifically, each of the steel sheets was machined to obtain standard samples. The deformation resistance, tensile strength, elongation, plasticity anisotropy index (r value, ") and anisotropy index in the plane (value? R), and aging index were measured using a resistance tester to the tension (available from TNSTRON Company, Model 602b). The plasticity anisotropy index rm and the anisotropy index in the plane (value? R) were calculated by the following equations: rm = (r0 i 2r45 i rq0) / 4 and r r (r0 - 2r45 + r90) / 2, respectively. The steel sheet aging index is defined as a strain point elongation measured by annealing each of the samples, followed by the rolling and thermal pass rolling process of 1.0% at 100 ° C for 2 hours. . The oven hardness value (BH) of the standard samples were measured by the following procedure. After a deformation of 2% was applied to each of the samples, the deformed sample was annealed at 170 ° C for 20 minutes. The deformation strength of the annealed sample was measured. The Bll value was calculated by subtracting the strain resistance measured before the annealing of the strain resistance value measured after the annealing. Example 1 First, the thick steel sheets were prepared according to the compositions shown in the following tables. The thick steel sheets were reheated and hot-rolled finished to provide hot-rolled steel sheets. The hot-rolled steel sheets were cooled at a rate of 400 ° C / min., Rolled at 650 ° C, cold rolled at a 75% reduction rate, followed by continuous annealing to produce laminated steel sheets cold At this time, the finishing laminating was carried out at 910 ° C, which is above the control point of Ar3, and the continuous annealing was carried out by heating the hot-rolled steel sheets in a proportion of 10 °. C / second at 830 ° C for 40 seconds to produce the final cold-rolled steel sheets. TABLE 1 Table 2 shows the Nupw'io of the precipitates of No. (Cu / 63.5) (Nb / 93) / (C / l precipitates of CuS (um) CuS (/? M? 2) / (S / 32) 2) TABLE 3 * Note: YS = Deformation resistance, TS = Stress Resistance, Cl = Elongation, rm = Plasticity Anisotropy index,? R = Amsotropy index in the Plane, AI = Aging index, SWC = Capacity Pragilization Secondary Work, 1S = Inventive Steel, CS = Comparative Steel Example 2 First, the thick steel sheets were prepared according to the compositions shown in the following tables. The thick steel sheets were reheated and hot-rolled finished to provide hot-rolled steel sheets. The hot-rolled steel sheets were cooled at a rate of 400 ° C / min., Rolled at 6 ° C, cold rolled at a reduction ratio of 75%, followed by continuous annealing to produce sheets of cold rolled steel. At this time, the hot finish lamination was carried out at 910 ° C, which is above the transformation point of Ar3, and the continuous recollection is made by heating the hot-rolled steel sheets in a proportion of 10 ° C / second at 830 ° C for 40 seconds to produce the final cold-rolled steel sheets.

TABLE 4 TABLE 5 -or TABLE 6 Do not . Pi-opiedade i > I Ice, in íc-is Observations YS TS Kl? R? L C4) SWE (MPa) (MFa) (%) (DBTT- * C) * Note: YS = Deformation resistance, TS = Stress Resistance, El = Elongation, rm = Plasticity Anisotropy index,? R = Anisotropy index in the Plane, AI = Aging index, SWE = Capacity Fragilization Secondary Work, IS =? Zero Inventive, CS = Comparative Steel Example 3 First, the thick steel sheets were prepared according to the compositions shown in the following tables. The thick steel sheets were reheated and Laminated in hot finish to provide hot rolled steel sheets. The hot-rolled steel sheets were cooled at a rate of 400 ° C / min., Rolled at 650 ° C, cold rolled at a 75% reduction rate, followed by continuous annealing to produce laminated steel sheets cold At this time, the hot rolling of the finishing was carried out at 910 ° C, which is above the transformation point of Ar3, and the continuous annealing was carried out when heating the hot-rolled steel sheets in a proportion of 10 ° C / second at 830 ° C for 40 seconds to produce the final cold-rolled steel sheets. TABLE 7 TABLE 8 TABLE 9 * Note: YS = deformation resistance, TS = tensile strength, el = elongation, rm = index of plasticity anisotropy,? R = index of nisotropy in the plane, AI = index of aging, SW1 = fragility of work Secondary, TS =? Zero Inventive, CS =? Comparative zero Example 4 First, the thick steel sheets were prepared according to the compositions shown in the following tables. The thick steel sheets were reheated and hot-rolled finished to provide hot-rolled steel sheets. The hot-rolled steel sheets were cooled at a rate of 400 ° C / min., Rolled at 6 ° -0 ° C, cold-rolled at a reduction ratio of 75%, followed by continuous annealing to produce sheets of cold rolled steel. At this time, the hot-rolled finish was reacted at 910 ° C, which is above the transformation point of? R3, and the continuous annealing was performed by heating the hot-rolled steel sheets at a ratio of 10 °. C / second at 830 ° C for 40 seconds to produce the final cold-rolled steel sheets is.

TABLE 10 TABLE 11 TABLE 12 * Note: YS = Deformation resistance, TS = Stress Resistance, El = Elongation, rm = Plasticity Anisotropy Index,? R = Amsotropy index in the Plane, AI = Aging index, SWE = Work fragmentation Secondary, 1S = Nventive steel, CS =? Comparative zero Example 5 First, the thick steel sheets were prepared according to the compositions shown in the following tables. The thick steel sheets were reheated and hot-rolled to finish provide hot-rolled steel sheets. The hot-rolled steel sheets were cooled at a rate of 400 ° C / min., Rolled at 650 ° C, cold rolled at a reduction ratio of 75%, followed by continuous annealing to produce sheets of cold rolled steel. During this time, the hot-finished lamination was carried out at 910 ° C, which is above the transformation point of? R3, and the continuous annealing was carried out by heating the rolled steel sheets in a ratio of 10 ° C. / second at 830 ° C for 40 seconds to produce the final cold-rolled steel sheets. TABLE 13 TABLE 14 TABLE 15 * Note: YS = deformation resistance, TS = tensile strength, el = elongation, rra = plasticity anisotropy index,? R = index of nisotropy in the plane, AI = index of aging, SWE = fragmentation Secondary work, 1S =? zero Inventive, CS =? Comparative zero Example 6 First, the thick steel sheets were prepared according to the compositions shown in the following tables. The thick steel sheets were reheated and hot-rolled finished to provide hot-rolled steel sheets. The hot-rolled steel sheets were cooled at a rate of 400 ° C / m n., Rolled at 650 ° C, cold rolled at a reduction ratio of 75%, followed by continuous annealing to produce steel sheets. cold rolled. At this time, the finishing laminating was carried out at 910 ° C, which is above the transformation point of? R3, and the continuous annealing was carried out by heating the hot-rolled steel sheets in a proportion of 10 ° C. / second at 830 ° C for 40 seconds to produce the thin cold-rolled steel sheets.

TABLE 16 TABLE 17 TABLE 18 * Note: YS = deformation resistance, TS = tensile strength, el = elongation, rm = plasticity anisotropy index,? R = index of nisotropy in the plane, Al = aging index, SWL = Fraga li of Secondary work, 1S = Inventive Steel, CS = Comparative Steel Example 7 First, the thick steel sheets were prepared according to the compositions shown in the following tables. The thick steel sheets were reheated and hot-rolled finished to provide hot-rolled steel sheets. The laminated steel sheets when hot they were cooled at a rate of 400 ° C / m. n., rolled at 650 ° C, cold rolled at a reduction ratio of 75%, followed by continuous annealing to produce cold-rolled steel sheets. At this time, the hot rolling of finishing was carried out at 910 ° C, which is above the transformation point of Ar, and the continuous annealing was carried out when heating the hot-rolled steel sheets in a proportion of 10 ° C / second at 830 ° C for 40 seconds to produce the final cold-rolled steel sheets.

TABLE 19 TABLE 20 TABLE 21 * Note YS = Deformation resistance, TS = Stress resistance, El = Enlargement, rm = Plasticity Anisotropy index,? R = Amsotropy index in the plane, AI = Aging index, SWt = Secondary work fragility, 1S = Inventive Steel, CS = Comparative Steel Example 8 First, the thick steel sheets were prepared according to the compositions shown in the following tables. The thick steel sheets were reheated and hot-rolled finished to provide hot-rolled steel sheets. The laminated steel sheets were cooled at a rate of 400 ° C / min., Rolled at 650 ° C, cold rolled at a reduction ratio of 75%, followed by continuous annealing to produce sheets of cold rolled steel. At this time, the finished lime mill lamination was carried out at 910 ° C, which is above the transformation point of Ar, and the continuous annealing was carried out by heating the laminated steel sheets in a ratio of 10 ° C / second at 830 ° C for 40 seconds to produce the final cold-rolled steel sheets.

TABLE 22 TABLE 23 TABLE 24 * Note: YS = deformation resistance, TS = tensile strength, el = elongation, r, "= index of plasticity nisotropy, r = index of Amsotropia in the plane, AI = index of aging, SWE = Secondary labor release, IS = Inventive steel, CS =? Comparative zero Example 9 First, the thick steel sheets were prepared according to the compositions shown in the following tables. The thick steel sheets were reheated and hot-rolled finished to provide sheets of hot rolled steel. The hot-rolled steel sheets were cooled at a rate of 400 ° C / min., Rolled at 650 ° C, cold rolled at a 75% reduction rate, followed by continuous annealing to produce laminated steel sheets cold During this time, the hot-finish lamination was carried out at 910 ° C, which is above the transformation point of Ar3, and the continuous annealing was carried out by heating the rolled steel sheets at a rate of 10 ° C / second at 830 ° C for 40 seconds to produce the final cold-rolled steel sheets. TABLE 25 TABLE 26 -13 TABLE 27 * Note: YS = deformation resistance, TS = tensile strength, el = elongation, rm = plasticity anisotropy index,? R = index of nisotropy in the plane, AI = index of aging, SWE = fragmentation of Secondary work, TS =? zero Inventive, CS =? Comparative zero Example 10 First, the thick steel sheets were prepared according to the compositions shown in the following tables. The thick steel sheets were reheated and hot-rolled finished to provide sheets of hot rolled steel. The hot-rolled steel sheets were cooled at a rate of 400 ° C / min., Rolled at 650 ° C, cold rolled at a reduction ratio of 75%, followed by continuous annealing to produce sheets of cold rolled steel. At this time, the hot-finish lamination was carried out at 910 ° C, which is above the transformation point of Ar, and the continuous annealing was performed by heating the hot-rolled steel sheets at a rate of 10 ° C / second at 830 ° C for 40 seconds to produce the final cold-rolled steel sheets. TABLE 28 No. Components O i nucos (t? Peso) c P s? l Cu Nb B N Ottos . • .. ".

TABLE 29 Cs = (C-Nbxl 2/93) xl 0000 TABLE 30 * Note: YS = Deformation resistance, TS = Stress Resistance, Cl = Lengthening, Rra = Plasticity Anisotropy index,? R = Anisotropy index in the Plane, Al = Aging Index, SWE = Fragilization of Secondary work, IS = Inventive Steel, CS = Comparative Steel Example 11 First, the thick steel sheets were prepared according to the compositions shown in the following tables. The thick steel sheets were reheated and hot-rolled finished to provide hot-rolled steel sheets. The hot-rolled steel sheets were cooled at a rate of 400 ° C / min., Rolled at 650 ° C, cold rolled at a 75% reduction ratio, followed by continuous annealing to produce sheets of cold rolled steel. At this time, the hot rolling of the finishing was carried out at 910 ° C, which is above the transformation point of Ar3, and the continuous annealing was carried out when heating the hot-rolled steel sheets in a proportion of 10 ° C / second at 830 ° C for 40 seconds to produce the final cold-rolled steel sheets. TABLE 31 TABLE 32 TABLE 33 * Note: YS = deformation resistance, TS = Stress Resistance, El = Enlargement, rm = Plasticity Anisotropy index,? R = Index of nisotropy in the Plane, AI = Aging index, SWC = Fragile 1 Secondary Workplace, IS = Inventive Steel, CS = Comparative Steel Example 12 First, the thick steel sheets were prepared according to the compositions shown in the following tables. The thick steel sheets were reheated and hot-rolled finished to provide sheets of 5') hot rolled steel. The hot-rolled steel sheets were cooled at a rate of 400 ° C / min., Rolled at 650 ° C, cold rolled at a 75% reduction rate, followed by continuous annealing to produce laminated steel sheets cold At this time, the hot-finish lamination was carried out at 910 ° C, which is above the transformation point of Ar3, and the continuous annealing was carried out by heating the rolled steel sheets at a rate of 10 ° C. / second at 830 ° C for 40 seconds to produce the final cold-rolled steel sheets. TABLE 34 TABLE 35 TABLE 36 * Note: YS = Deformation resistance, TS = Stress Resistance, Ll = A load, rm = Plasticity Anisotropy index,? R = Amsotropy index in the Plane, AI = Aging index, SWE = Fragilization Secondary work, 1S = Inventive Steel, CS = Comparative Steel Example 13 First, the thick steel sheets were prepared according to the compositions shown in the following tables. The thick steel sheets were reheated and hot-rolled finished to provide hot-rolled steel sheets. The hot-rolled steel sheets were cooled at a rate of 400 ° C / min., Rolled at 650 ° C, cold rolled at a reduction ratio of 75%, followed by continuous annealing to produce sheets of cold rolled steel. At this time, the hot-finished lamination was carried out at 910 ° C, which is above the transformation point of Ar3, and the continuous annealing was carried out by heating the rolled steel sheets at a rate of 10 ° C / second at 830 ° C for 40 seconds to produce the final cold-rolled steel sheets.

TABLE 37 TABLE 38 TABLE 39 * Note: YS = deformation resistance, 1S = Stress Resistance, El = Lengthening, rm = Plasticity Anisotropy index,? R = Nisotropy Index in the Plane, AI = Aging index, SWE = Eragí Secondary work, ES =? zero Inventive, CS = Comparative Steel Example 14 First, the thick steel sheets were prepared according to the compositions shown in the following tables. The thick steel sheets were reheated and hot-rolled finished to provide sheets of hot rolled steel. The laminated steel sheets were cooled at a rate of 400 ° C / min., Rolled at 650 ° C, cold rolled at a reduction ratio of 75%, followed by continuous annealing to produce sheets of Cold rolled steel. At this time, the hot-finish lamination was carried out at 910 ° C, which is above the point of formation of Ar 3, and the continuous annealing was carried out by heating the steel sheets laminated in heat in a proportion of 10%. ° C / second at 830 ° C for 40 seconds to produce the final cold-rolled steel sheets. TABLE 40 TABLE 41 TABLE 42 * Note: YS = Deformation resistance, TS = Stress Resistance, El = Elongation, r ", = End-.ee of Plasticity Anisotropy,? R = Index of Nisotropy in the Plane, AI = Aging index, SWE = Secondary Work Eragi lication, IS =? Zero Inventive, CS = Comparative Steel The preferred embodiments illustrated in the present invention do not serve to limit the present invention, but are set forth for illustrative purposes. Any embodiment having substantially the same constitution in the same operative effects thereof as the technical spirit of the present invention as defined in the appended claims is encompassed within the technical scope of the present invention. As is clear from the above description, according to the cold-rolled steel sheets of the present invention, the distribution of the fine precipitates in the Nb-based F steels allows the formation of minuscule crystal grains, and as a result , the anisotropy index in the plane is decreased and the deformation resistance is increased by increasing precipitation.

Claims

CLAIMS 1. A cold rolled steel sheet with high deformity ratio and low anisotropy index in the plane, the cold rolled steel sheet characterized in that it has a composition comprising 0.01% or less of C, 0.01 to 0.2% of Cu, 0.005 to 0.08% of S, 0.1% or less of Al, 0.004% or less of N, 0.2% or less of P, 0.001 to 0.002% of B, 0.002 to 0.04% of Nb, by weight, and the rest of Fe and other non-preventable impurities, wherein the composition satisfies the following relationship: 1 < (Cu / 63.5) / (S / 32) < 30, and wherein the steel sheet comprises CuS precipitates having an average size of 0.2 μm or less. 2. The cold-rolled steel sheet according to claim 1, characterized in that the composition further comprises 0.01 to 0.3% of Mn, and satisfies the following ratio: 1 < (Mn / 55 + Cu / 63.5) / (S / 32) < 30, and the steel sheet comprises precipitates of (Mn, Cu) S of 0.2 μm or less. 3. The cold-rolled steel sheet according to claim 1, characterized in that the content of N is 0.004 to 0.02%, and the composition satisfies the following ratio: 1 < (Al / 27) / (N / 14) < 10, and the steel sheet comprises AlN precipitates having an average size of 0.2 μm or less. 4. The cold-rolled steel sheet according to claim 1, characterized in that the composition further comprises 0.01 to 0.3% of Mn, and 0.004 to 0.02% of N, and satisfies the following ratios: 1 < (Mn / 55 + Cu / 63.5) / (S / 32) < 30, 1 < (Al / 27) / (N / 1) < 10, and the steel sheet comprises precipitates of (Mn, Cu) S and AlN precipitates having an average size of 0.2 μm or less. 5. The cold rolled steel sheet with high deformity ratio and anisotropy index in the low plane, the cold rolled steel sheet characterized in that it has a composition comprising 0.01% or less of C, 0.08% or less of S , 0.1% or less of Al, 0.004% or less of N, 0.2% or less of P, 0.0001 to 0.002% of B, 0.002 to 0.04% of Nb, at least one selected class of 0.01 to 0.2% Cu, 0.01 to 0.3% of Mn and 0.004 to 0.2% of N, by weight, and the rest of Fe and other non-avoidable impurities, where the composition satisfies the following relationships: 1 < (Mn / 55 + Cu / 63.5) / (S / 32) < 30, 1 < (Al / 27) / (N / 14) < 10, wherein the content of N is 0.004% or more, and wherein the steel sheet comprises at least one selected class of precipitates of (Mn, Cu) S and AlN precipitates having an average size of 0.2 μm or less . 6. The cold-rolled steel sheet of according to claim 1 or 5, characterized in that the contents of C, and Nb satisfy the following ratio: 0.8 << (Ti * / 48) / (C / 12) < 5.0. 7. The cold rolled steel sheet according to claim 6, characterized in that the content of C is 0.005% or less. 8. The cold-rolled steel sheet according to claim 1 or 5, characterized in that the soluble carbon (Cs) is from 5 to 30, where Cs = (C-Nbxl2 / 93) x 10,000. 9. The cold-rolled steel sheet according to claim 8, characterized in that the content of C is 0.001 to 0.01%. The cold rolled steel sheet according to one of claims 1 to 5, characterized in that the cold rolled steel sheet satisfies a deformation ratio (deformation resistance / tensile strength) of 0.58 or higher . The cold-rolled steel sheet according to one of claims 1 to 5, characterized in that the number of precipitates is 1 x 106 / mm2 or more. 12. The cold rolled steel sheet according to claim 1 or 5, characterized in that the P content is 0.015% or less. 13. The cold rolled steel sheet according to claim 1 or 5, characterized in that the content of P is from 0.03% to 0.2%. 14. The cold rolled steel sheet according to claim 1 or 5, characterized in that the composition further comprises at least one class of 0.1 to 0.8% Si and 0.2 to 1.2% Cr. 15. The cold rolled steel sheet according to claim 1 or 5, characterized in that the composition also it comprises 0.01 to 0.2% of Mo. 16. The cold rolled steel sheet according to claim 14, characterized in that the composition further comprises 0.01 to 0.2% Mo. 17. The cold-rolled steel sheet according to claims 2, 4 or 5, characterized in that the sum of Mn and Cu is 0.08% to 0.4%. 18. The cold-rolled steel sheet according to claims 2, 4 or 5, characterized in that the content of Mn is 0.01 to 0.12%. 19. The cold-rolled steel sheet according to claim 2, 4 or 5, characterized in that the value of (Mn / 55 + Cu / 63.5) / (S / 32) is from 1 to 9. The sheet of cold rolled steel according to claim 3, 4 or 5, characterized in that the value of (Al / 27) / (N / 14) is from 1 to 5. 21. A method for producing a cold-rolled steel sheet with high deformation ratio and anisotropy index in the low plane, the method characterized in that it comprises the steps of: reheating a thick film at a temperature of 1,100 ° C or higher, the thick sheet having a composition comprising 0.01% or less of C, 0.01 to 0.2% Cu, 0.005 to 0.08% S, 0.1% or less of Al, 0.004% or less of N , 0.2% or less of P, 0.001-0.002% of B, 0.002 to 0.04% of Nb, by weight, and the rest of Fe and other non-avoidable impurities, the composition that satisfies the following relationship: 1 = (Cu / 63.5 ) / (S / 32) = 30; hot rolling the hot sheet heated to a finishing lamination temperature of the transformation point Ar3 or higher to provide a hot rolled steel sheet; cooling the hot-rolled steel sheet in a proportion of 300 ° C / min or higher; roll the steel sheet cooled to 700 ° C or lower; cold rolling the rolled steel sheet; and continuously reheating the cold-rolled steel sheet, the steel sheet comprising CuS precipitates having an average size of 0.2 μm or less. 22. The method of compliance with the claim 21, characterized in that the composition also comprises 0.01 to 0.3% of Mn, and satisfies the following ratios: 1 = (Mn / 55 + Cu / 63.5) / (S / 32) < 30, and the steel sheet comprises precipitates of (Mn, Cu) S having an average size of 0.2 μm or less. 23. The method according to claim 21, characterized in that the content of N is from 0.004 to 0.02%, and the composition satisfies the following relationship: 1 < (Al / 27) / (N / 14) < 10, and the steel sheet comprises AlN precipitates having an average size of 0.2 μm or less. 24. The method according to claim 21, characterized in that the composition further comprises 0.01 to 0.3% Mn and 0.004 to 0.02% N, and satisfies the following ratios: 1 < (Mn / 55 + Cu / 63.5) / (S / 32) < 30, 1 < (Al / 27) / (N / 14) < 10, and the metal sheet comprises precipitates of (Mn, Cu) S and AlN precipitates having an average size of 0.2 μm or less. 25. A method for producing a cold rolled steel sheet with high deformation ratio and anisotropy index in the low plane, the method characterized in that it comprises the steps of; reheat a thick film at a temperature of 1,100 ° C or higher, the thick sheet having a composition comprising 0.01% or less of C, 0.08% or less of S, 0.1% or less of Al, 0.004% or less of N, 0.2% or less of P, 0.0001 to 0.002% of B, 0.002 to 0.04% of Nb, at least one selected class of 0.01 to 0.2% of Cu, 0.01 to 0.3% of Mn and 0.004-0.2% of N, by weight, and the rest of Fe and other non-avoidable impurities, the composition satisfying the following relationships: 1 < (Mn / 55 + Cu / 63.5) / (S / 32) < 30, 1 < (Al / 27) / (N / 14) < 10, where the content of N is 0.004% or more; hot rolling the hot sheet heated at a finishing lamination temperature of the transformation point Ar3 or higher to provide a hot rolled steel sheet - cooling the hot rolled steel sheet at a rate of 300 ° C / min or highest; roll the steel sheet cooled to 700 ° C or lower; cold rolling the rolled steel sheet; and continuously annealing cold rolled steel sheet, cold rolled steel sheet comprising at least one selected class of (Mn, Cu) S precipitates and AlN precipitates having an average size of 0.2 μm or less. 26. The method of compliance with the claim 21 or 25, characterized in that the contents of C and Nb satisfy the following ratio, by weight: 0.8 < (Nb / 93) / (C / 12) < 5.0. 27. The method according to claim 26, characterized in that the content of C is 0.005% or less. 28. The cold rolled steel sheet according to claim 21 or 25, characterized the solute carbon (Cs) is from 5 to 30, where Cs = (C - Nbxl2 / 93) x 10,000. 29. The method according to claim 28, characterized in that the content of C is 0.001 to 0.01%. 30. The method according to any one of claims 21 to 25, characterized in that the cold-rolled steel sheet satisfies a deformation ratio (strain resistance / tensile strength) of 0.58 or higher. 31. The method according to any of claims 21 to 25, characterized in that the number of precipitates is 1 x 106 / mm2 or more. 32. The method according to claim 21 or 25, characterized in that the content of P is 0.015% or less. 33. The method according to claim 21 or 25, characterized in that the content of P is 0.03% to 0.2%. 3 . The method in accordance with the claim 21 or 25, characterized in that the composition further comprises at least one class or 0.1 to 0.8% Si and 0.2 to 1.2% Cr. 35. The method according to claim 21 or 25, characterized in that the composition further comprises 0.01 to 0.2% of Mo. 36. The method according to claim 34, characterized in that the composition further comprises 0.01 to 0.2% Mo. 37. The method according to claim 22, 24 or 25, characterized in that the sum of MN and Cu is 0. 08% to 0.4%. 38. The method according to claim 22, 22 or 25, characterized in that the content of Mn is 0.01 to 0.12%. 39. The method of compliance with the claim 22, 24 or 25, characterized in that the value of (Mn / 55 + Cu / 63.5) / (S / 32) is from 1 to 9. 40. The method according to the claim 23, 24 or 25, characterized in that the value of (Al / 27) / (N / 14) is from 1 to 5.