TW201213550A - High strength steel sheet and method for preparing the same - Google Patents

Abstract

The present invention provides a high strength steel sheet having excellent chemical conversion treatability and corrosion resistance of post-electrodeposition coating even though the content of Si is high, and also provides a method for preparing the same. In this preparation method, the steel sheet containing, in terms of mass%, C of 0.01 to 0.18%, Si of 0.4 to 2.0%, Mn of 1.0 to 3.0%, Al of 0.001 to 1.0%, P of 0.005 to 0.060%, S of 0.01 or less and the remainder comprising Fe and unavoidable impurities is treated by a continuous annealing process, during which the temperature region of greater than 750 DEG C inside an annealing furnace is controlled to have a dew point of lower than -40 DEG Cin the atmosphere.

Description

201213550 6. OBJECT OF THE INVENTION: The present invention relates to a high-strength steel sheet having excellent chemical conversion treatability and durability after electrocoating even when Si content is large. Production method. [Prior Art] In recent years, from the viewpoint of improving the fuel cost of automobiles and improving the safety of conflicts between automobiles, the use of the strength of the vehicle body material has been sought to reduce the thickness of the vehicle body, and the weight of the vehicle body itself has been increased. The demand is increasing. Therefore, the application of high-strength steel sheets to automobiles is being promoted. In general, a steel sheet for automobiles is used for coating, and as a treatment before the coating, a chemical conversion treatment called phosphate treatment is performed. The formation of steel sheets is one of the important treatments to ensure the resistance to surnames after painting. In order to increase the strength and ductility of the steel plate, the addition of Si is effective. However, in the case of continuous annealing, even in the case where the oxidation of Fe does not occur (reduction of Fe oxide) in a reductive N2+H2 gas atmosphere, si is oxidized, and Si oxide is formed on the outermost layer of the steel sheet. (Si〇2). Since the si 〇 2 hinders the formation reaction of the skin sputum in the chemical conversion treatment, micro-dipoles (hereinafter also referred to as pores) which are not formed into the film are formed, and the chemical conversion treatment property is lowered. As a conventional technique for improving the chemical conversion treatment property of a high-Si steel sheet, Patent Document 1 discloses a method of forming an iron coating layer of 20 to 1500 mg/m2 on a steel sheet by an electric boat method. However, there is a need to add additional electric forging equipment, and there are 099133254 3 201213550 steps to increase and the cost is also increased. Further, in Patent Document 2, the Mn/Si ratio is specified, and in Patent Document 3, the addition of Ni improves the phosphoric acid treatability. However, the effect depends on the Si content in the steel sheet, and further improvement is required for a steel sheet having a high Si content. Further, Patent Document 4 discloses a method of forming an internal oxide layer composed of a Si-containing oxide by setting a dew point during annealing to -25 to (TC, within a depth of 1 μm from the surface of the steel sheet substrate. The ratio of the Si-containing oxide in the surface length of the steel sheet is 80% or less. However, in the case of the method described in Patent Document 1, the area where the dew point is controlled is assumed to be the entire furnace, and therefore the controllability of the dew point is difficult. It is difficult to carry out stable operation. Moreover, in the distribution state of the internal oxide formed in the steel sheet by the annealing of the unstable Lu Shihuan base, it is observed that the deviation 'will be processed in the longitudinal direction or the width direction of the steel sheet. In addition, in the case of the improvement of the processability, since the chemical conversion treatment film has yttrium oxide, it has a problem of good durability after electrocoating. Patent Document 5 describes a method of forming an oxide film on the surface of a steel sheet in an oxidizing atmosphere, and then reducing the temperature of the steel sheet to a temperature of recrystallization and cooling. However, in this method, the oxidation method is different in the thickness of the oxide film formed on the surface of the steel sheet, and the oxidation may not be sufficiently performed, or the oxide film may become too thick, and it may be in the annealing in the environment of 099133254 201213550. Before the film is peeled off or peeled off, the condition deteriorates. In the examples, although it is described that oxygen = technology is carried out in the atmosphere, there is a problem that the oxidation in the atmosphere is thick to form a thick oxide, and the reduction is difficult, or the reduction environment of high hydrogen inversion is required. Further, Patent Document 6 describes a method in which a cold-coated steel sheet containing & 0.1% or more and/or Mnl._ is contained in a mass%, and the steel sheet temperature / 〇CΜ is in an oxidizing atmosphere of iron. An oxide film is formed on the surface of the steel sheet, and then the oxide film on the surface of the steel sheet is reduced in a county environment of iron. Specifically, it is 40 (TC or more, and the Fe on the surface of the steel sheet is oxidized by a direct-fired furnace having an air ratio of 〇93 or more and I·10 or less, and then annealed in a gas atmosphere in which the Fe oxide is reduced. A method of forming an oxide layer of Fe on the outermost surface by oxidizing Si〇2 which deteriorates the processability to the outermost surface. Patent Document 6 does not specifically describe the heating temperature of the direct fire furnace, but contains a large amount of Si (about In the case of 0.6% or more, the amount of oxidation of the oxide which is more easily oxidized than Fe is increased, the oxidation of Fe is suppressed, or the oxidation itself becomes too small. As a result, there is a surface Fe reduced layer after reduction. In the case where the shape of the steel sheet is insufficient, or the surface of the steel sheet after the reduction is present, Si 2 is formed, and the pores of the film are formed. [Prior Art] [Patent Document 1] Patent Document 1 (Japanese Patent Application Laid-Open No. Hei 5-320952) (Patent Document 2) Japanese Patent Laid-Open No. Hei. No. 2004-323969 (Patent Document 3) Japanese Patent Laid-Open No. Hei 6-10096 (Patent Document 4). Document 5) 曰本专利专开昭55-1451 SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to provide a lithium even in the case of Si. In the case of 'high-strength steel sheet having excellent chemical conversion treatment and insect-repellent resistance after electrocoating, and a method for producing the same. (Means for solving the problem) In the prior art, oxidizing properties such as Si and Μ are contained. The steel sheet of the element actively oxidizes the inside of the steel sheet for the purpose of improving the processability. However, the durability of the steel sheet after electroforming is also deteriorated. Therefore, the present inventors have not adopted the concept of the prior art. A new method was adopted to review the method for solving the problem. As a result, it was found that by appropriately controlling the environment and temperature of the annealing step, the formation of internal oxides in the surface portion of the steel sheet can be suppressed, and excellent chemical processing properties and higher can be obtained. Specifically, the temperature in the annealing furnace is 750 C or more, and the temperature is controlled by the dew point in the environment: 4 〇 ^ or less. The temperature region in the annealing furnace is 750 Ϊ ^ is the dew point in the environment: book c or less, the oxygen potential of the interface between the steel plate and the ring brother is lowered, and the internal oxide can be controlled without forming an internal oxide. Selective surface diffusion, oxidation (hereinafter referred to as surface desertification). 099133254 201213550 Document 1 (7th International Conference on Zinc and Zinc Alloy Coated Steel Sheet Galvatech 2007, Proceedings p404) reveals the thermodynamics of oxidation reaction from Si and Μη In the data, the oxygen level energy is converted to the dew point, and in the presence of 800 ° C and N 2 -5% H 2 , oxidation is not prevented if Si is not below -80 ° C and Μη is not below the dew point of -60 C. Therefore, when the high-strength steel sheet containing Si or Μη is annealed, it is considered that even if the hydrogen concentration is increased, if the dew point is at least less than -80 °C, the surface concentration cannot be prevented. Therefore, conventional techniques have never attempted to carry out a chemical conversion treatment after annealing at a dew point of _4 〇 to -7 °C. Fig. 1 is a literature 2 (metal physical chemistry p72~73, May 20, 曰fs_4亍's published by the Institute of Metals). The thermodynamic data of the oxidation reaction from Si and Μη is calculated as follows. The relationship between the redox balance and the dew point and shows a graph of the relationship.

The redox balance of Si in a hydrogen-nitrogen environment is represented by the following formula. Si02(solid)+2H2(gas)=Si+2H20(gas) (1) The equilibrium constant K of the 5 hai reaction is 1 as the activity of Si, as described below. K = (square of H2 〇 partial pressure) / (square of partial pressure of 3⁄4) (7) Further, the standard free energy AG (1) is R: gas constant, T: temperature, as shown below. AG(l)=-RTlnK (3) where, 099133254 7 201213550 H2(gas)=l/202(gas)=H2〇(gas) (4)

The standard free energy AG(4) and AG(5) of each reaction formula of Si(solid)+02(gas)=Si〇2(solid)(5) are expressed as follows as a function of τ.

AG(4)=-246000+54.8T

AG(5)=-902100+174T Therefore, from 2χ(4)-(5), it becomes AG(l)=4l0100-64.4T (6), and by (3)=(6), it becomes K=exp{( l/R) (64.4-410100/T)} (7). Further, from (2) = (7), Η? partial pressure = 0.1 air pressure (in the case of 10%), the Ηβ partial pressure at each temperature T is obtained, and this is converted into a dew point, and Fig. 1 can be obtained. Similarly, for Μη, the redox balance of Μη in a hydrogen-nitrogen environment is expressed by the following formula.

MnO(solid)+H2(gas)=Mn+H20(gas) (8) The equilibrium constant K of the reaction is as follows. Κ=(Η20 partial pressure)/(H2 partial pressure) (9) Further, the standard free energy AG(8) is R: gas constant, τ: temperature is as follows. △G(8)=-RTlnK (10) where H2(gas)=l/202(gas)=H20(gas) (11)

Mn(solid)+l/2〇2(gas)=MnO(solid), (12) The standard free energy ΔΟ(11) and AG(12) of each reaction formula are as τ; 099133254 8 201213550 and below Said.

△G(l 1)=-246000+54.8T AG(12)=-384700+72.8T Therefore 'from (11)-(12), becomes ag(8)=138700-18.0T (13), by (10) )=(13) ' Become K=exp{(i/R)(i8.0-138700/T)} (14). In addition, '(9)=(14), Η: partial pressure = 〇·ι pressure (in the case of 1〇%), the HA partial pressure at each temperature T is obtained, and it is converted into the dew point' to obtain the graph i. . From Fig. 1, at 8 〇〇 aC of the standard annealing temperature, Si is in the dew point _8 (the above rc is in an oxidized state, and in order to make it a reduced state, it must be less than _8 (rc. Μη is also the same, It is understood that it will not be in a reduced state unless it is not full. This result is consistent with the result of Document 1. In addition, it is necessary to heat from room temperature to 8 〇〇 < t at the time of annealing. Further, as shown in Fig. 1 and Document 1 As a result, the lower the temperature is, the lower the dew point of Si is in the reduced state. From room temperature to 8 〇 (between rc, a very low dew point of less than -10 °C is required, strongly suggesting that the industry On the one hand, while preventing

The oxidation of Si and Μη is not possible in an annealing environment where heating to the annealing temperature is achieved. The technical common sense that can be easily derived from thermodynamic data well known to those skilled in the art is also a technical common sense that attempts to anneal the dew point of -40 to -7 G °C which should be selectively oxidized by S i and η η. 35. According to the present invention, the dew point of _4〇~_7〇ΐ which is originally thought to occur on the surface of Si and Μη is concentrated, although it is a dew point region where oxidation occurs, but when 099133254 9 201213550 Short-term reduction in the case of continuous annealing. ^In terms of speed theory, there should be no possibility of greatly reducing the surface concentration of the treatment. Therefore, its review was carried out. As a result, the present invention of the following features was completed. The present invention is characterized in that, in the annealing of the steel sheet, the temperature in the annealing furnace: 750 ° C or higher is the dew point in the environment: _4 〇 < 3 c or less. Usually, the dew point of the annealing environment of the steel sheet is _3〇ΐ or more. Therefore, in order to become the dew point of -40C or less, it is necessary to remove the moisture in the annealing environment, and it is necessary to make the equipment cost of the annealing furnace become _4GC'. And operating costs. However, in the present invention, the temperature in the annealing furnace is only 75 Torr. 〇The above limits The dew point HC is below the 疋 area, so it has the feature of reducing equipment costs and operating costs. In addition, the control in a limited area of 7 or more thieves can be used to fully obtain the desired characteristics. In addition, if you want to make _. (: The above temperature range becomes the dew point in the environment: 4 (The method of TC or less is given (4), and annealing and chemical conversion treatment are performed, and better chemical conversion treatment property can be obtained. If the temperature is 75 〇〇c or more or 600 ° C or higher, The area becomes the dew point in the ring brother: _45. 〇 below, better processing properties can be obtained. By controlling the dew point in the environment only in the thus defined area, no internal oxide is formed, which can suppress the surface as much as possible. When it is concentrated, it is possible to obtain a high-strength steel sheet which has no voids, is not uniform in processing property, and is excellent in chemical properties. Moreover, it is excellent in chemical conversion property, and it means that there is no void after treatment, and the uneven appearance is 0. 099133254 201213550 In addition, the high-strength steel sheet obtained by the above method is used to suppress one of P, B, Nb, Ti, Cr, Mo, Cu, and Ni selected from the surface of the steel sheet from the surface of the steel sheet. In the formation of the above-mentioned oxides (except for Fe), the amount of formation is suppressed to 0.060 g/m or less per one surface in total, whereby the chemical conversion property is excellent, and the corrosion resistance after electrocoating can be remarkably improved.The present invention is characterized by the above findings, and is characterized as follows: [1] A method for producing a strength-strength steel sheet, which comprises c: 0.01 to 0.18% by mass, Si: 0.4 to 2.0%, Μικί.ο~3.0%, and AliO. .OOl~1.0%, P: 0.005~0.060%, SS0.01%, and the rest of the steel sheet composed of Fe and unavoidable impurities is subjected to continuous annealing, and the temperature in the annealing furnace is 750 ° C or higher. The dew point in the environment: -40 ° C or less. [2] The method of producing a high-strength steel sheet according to the above [1], wherein the component composition of the steel sheet further contains one or more selected from the following elements in mass% Element; Β: 0·〇〇ΐ~0.005%, Nb: 〇.〇〇5~0.05%, Ti: 0.005-0.05%, CnO.OOl~ι.〇〇/0,

Cu: 0.05 to 1.0%, Ni: 0.05 to 1.0% 〇 [3] The method for producing a high-strength steel sheet according to the above [1] or [2], wherein the continuous annealing is performed in an aqueous solution containing sulfuric acid Electrolytic pickling. [4] A strength-strength steel plate manufactured by the method of the above-mentioned item [1] to [3], which is produced from the surface layer of the steel sheet from the surface of the steel sheet to 099133254 201213550. One or more oxides selected from the group consisting of Si, Μη, A1, P, B, Nb, Ti, Cr, Mo, Cu, and Ni are 0.060 g/m 2 or less per one side. Further, in the present invention, high strength means that the tensile strength TS is 340 MPa or more. (Effect of the Invention) According to the present invention, even when the Si content is large, a high-strength steel sheet having excellent chemical conversion treatment properties and corrosion resistance after electrocoating can be obtained. [Embodiment] Hereinafter, the present invention will be specifically described. In the following description, the content unit of each element of the steel component composition is "mass 妒", and unless otherwise specified, it is expressed by "%". First, the annealing environment conditions for determining the surface structure of the steel sheet, which are the most important requirements of the present invention, will be described. In the high-strength steel sheet in which a large amount of Si and Mn are added to the steel, the internal oxidation of the surface layer of the steel sheet which may become the starting point of the rot # is extremely reduced in order to satisfy the requirement of (8). And, in terms of promoting the internal oxidation of Si and Μη,

It is treated as It', but this method relatively brings about deterioration of age resistance, promotes S rationality, and does not require internal oxidization to maintain good internal emulsification and improve corrosion resistance. As a result of the review, the present invention ensures that the formation of impurities is reduced, and the oxygen level energy is lowered in the annealing step, and the Si and 易η of the easily emulsifiable element are reduced in the surface layer of the base iron by 099133254 12 201213550. In addition, these elements are suppressed and handled. In addition, it is formed in the surface of the steel sheet to be oxidized, and as a result, the chemical conversion can be improved, and the internal oxidation of the slave/slave after the electrocoating is also suppressed, and the effect can be suppressed by the environment in the temperature region above the resignation. : It is obtained by controlling the temperature in the annealing furnace. By turning back = _4G. (3) The way below ^ The temperature inside the person: 750. (The above temperature is controlled by the oxygen potential energy at the interface where the dew point in the % is _, which can reduce the steel plate and the environment ^ '. Selective surface diffusion and surface concentration of Si, Μ, etc. In addition, the red radish is treated with no porosity or unevenness, and the corrosion resistance after electrocoating is improved. The reason for controlling the dew point temperature region 7 〇Λ疋 750 C or more is as follows. In the temperature zone, 'easy to cause holes and uneven hair

Surface concentration and internal oxidation to the extent of problems such as deterioration of resistance. Since the temperature is 75 (rc or more) in the temperature range in which the effect of the present invention can be exhibited, if the temperature region of the tantalum defect is set to 6 〇〇〇c or more, the surface concentration and internal oxidation can be further stabilized and controlled. The control dew point is _4 (the upper limit of the temperature range below TC is not specifically set. ..., and ' § exceeds the case'. Although the effect of the present invention is not problematic, it is disadvantageous from the viewpoint of cost increase. Preferably, it is 9 (8). The following is given. The dew point is set to -4 (the reason for the TC or less is as follows. It can be confirmed that the surface is concentrated.

The effect of the suppression effect is H Hachi. The lower limit of the dew point is not specifically set. 099133254 S 201213550 However, the effect is saturated with less than -70 C, which is disadvantageous in terms of cost, so it is preferably -70 ° C or higher. Next, the steel composition of the high-strength steel sheet according to the present invention is described as 0 C : 0.01 to 0.18%. C is a steel structure to form a granulated iron or the like, thereby improving workability. Therefore, 0.01% or more is required. On the other hand, when it exceeds 0.18%, the elongation is lowered, the material is deteriorated, and the weldability is deteriorated. Therefore, the amount of C is set to be 0.01% or more and 0.18% or less.

Si : 0.4-2.0%

The Si system strengthens the steel and increases the elongation, and is used to obtain an effective element of a good material, and 0.4% or more is required in order to obtain the strength of the object of the present invention. If Si is less than 0, 4%, the strength of the application range of the present invention cannot be obtained, and the chemical conversion process is not a problem. On the other hand, if it exceeds 2.0%, the steel strengthening ability and the elongation improving effect are saturated. Therefore, the amount of Si is set to be 0.4% or more and 2.0% or less. Μη : 1.0~3.0% 有效η steel is an effective element for high strength. In order to ensure mechanical properties and strength, it must be 1.0% or more. On the other hand, when it exceeds 3.0%, it is difficult to ensure the weldability or the mineral adhesion, or it is difficult to ensure the balance between strength and ductility. Therefore, the amount of Μη is set to be 1.0% or more and 3.0% or less. Α1 : 0.001 ～1.0% 099133254 14 201213550 A1 is added for the purpose of deacidification of marrying steel. If the content is less than 〇〇 1%, this cannot be achieved. The deacidification effect of the molten steel can be obtained by 0.001% or more. On the other hand, if it exceeds 1.0%, it will lead to an increase in cost. In addition, the surface of the crucible 1 will become more and more difficult to be processed. Therefore, the amount of Α1 is 0.001% or more and 1.0% or less. Ρ : 0.005~〇.06〇% The following is one of the elements that are inevitably contained in the system. If you want to make it less than 0005%, there is a concern that the cost increases. Therefore, it is set to 0.005% or more. On the other hand, if the niobium content exceeds 0.060%, the weldability may deteriorate. Further, deterioration in chemical conversion treatability is fierce, and even with the present invention, it is difficult to improve the processability. Therefore, the amount of ρ is set to be 0.005% or more and 0.060% or less. S^O.Ol% S is one of the elements inevitably contained. The lower limit is not specified, and if it is contained in a large amount, the weldability and corrosion resistance are deteriorated, so it is determined to be 1%. In addition, 'in order to control the balance between strength and ductility' can also be added from Β··0.001 to 0.005%, Nb:〇.〇〇5 to 0.05%, Ti:〇.〇〇5 to 0 05〇/〇, Cr One or more elements selected from the group consisting of 0.001 to 1.0%, Mo: 0.05 to 1.0%, Cu: 0.05 to 1.0%, and Ni: 0.05 to 10%. The reason for the appropriate addition amount in the case of adding these elements is as follows. B : 0.001 to 0.005% B If it is less than 0.001%, it is difficult to obtain a quenching promoting effect. On the other hand, when the content is more than 0.005%, the chemical conversion property is deteriorated. Therefore, when the content is 099133254 or c 201213550, the amount of B is 0.001% or more and 0.005% or less.

Nb : 0.005~0.05%

If Nb is less than 0.005%, it is difficult to obtain the effect of strength adjustment. On the other hand, if it exceeds 0.05%, it will lead to an increase in cost. Therefore, in the case of inclusion, the amount of Nb is set to be 0.005% or more and 0.05% or less.

Ti : 0.005~0.05%

If Ti is less than 0.005%, it is difficult to obtain the effect of strength adjustment. On the other hand, if it exceeds 0.05%, the chemical conversion treatment property is deteriorated. Therefore, in the case of inclusion, the amount of Ti is set to be 0.005% or more and 0.05% or less.

Cr : 0.001 to 1.0%

If Cr is less than 0.001%, it is difficult to obtain a quenching promoting effect. On the other hand, when it exceeds 1.0%, surface-concentration of Cr will occur, and the weldability will deteriorate. Therefore, in the case of being contained, the amount of Cr is set to be 0.001% or more and 1.0% or less.

Mo: 0.05~1.0%

If Mo is less than 0.05%, it is difficult to obtain the effect of strength adjustment. On the other hand, if it exceeds 1.0%, it will lead to an increase in cost. Therefore, in the case of inclusion, the amount of Mo is set to be 0.05% or more and 1.0% or less.

Cu : 0.05~1.0%

When Cu is less than 0.05%, it is difficult to obtain a residual γ phase formation promoting effect. On the other hand, if it exceeds 1.0%, the cost will increase. Therefore, in the case of inclusion, the amount of Cu is set to be 0.05% or more and 1.0% or less. 099133254 16 201213550

Ni : 0.05~l.o%

If Ni is less than 5%, it is difficult to obtain a residual γ phase formation promoting effect. On the other hand, if it exceeds 1.0%, the cost will increase. Therefore, in the case of inclusion, the amount of Ni is set to be 0.5% or more and 1.0% or less. The rest of the above is Fe and impurities that are not avoided. Next, the method for producing the high-strength steel sheet according to the present invention and the reason for the limitation will be described. For example, after the steel having the above chemical composition is hot rolled, it is subjected to annealing and then annealing is performed in a continuous annealing apparatus. Further, in the case of re-ignition, the temperature in the annealing furnace is 750 in the present invention. (: The above temperature range is defined as the dew point in the ring production: -40 ° C or less. This is the most important requirement in the present invention. In addition, if the temperature range for controlling the dew point is set to 600 ° C or more, then + The above surface is concentrated or controlled by internal oxidation. Further, in the above, there is a case where the cold rolling is performed without performing cold rolling after completion of hot rolling. [Hot rolling] It can be carried out under normal conditions. [Pickling] It is preferable to carry out pickling treatment after hot rolling. The pickling step is used to remove black rust generated on the surface by the pickling step, followed by cold rolling. Further, the pickling conditions are not particularly limited. Rolling] If the rolling reduction ratio is preferably 40% or more and 80% or less, the 099133254 17 201213550 is less than 40%, the recrystallization temperature is lowered, so the mechanical properties are easily deteriorated. When the shrinkage ratio exceeds 80%, it is a high-strength steel sheet, so that not only the rolling cost is increased, but also the surface concentration during annealing is increased, so that the chemical treatment property is deteriorated. For cold-rolled steel sheets or hot rolled The steel plate is annealed and connected In the annealing furnace, a heating step of heating the steel sheet to a predetermined temperature is performed in a heating belt of the preceding stage, and a soaking step of maintaining the tempering zone at a predetermined temperature for a predetermined time in the subsequent stage is performed. It is controlled so that the dew point in the temperature range of the annealing furnace temperature: 750 ° C or higher is -40 ° C or less, and annealing and chemical conversion treatment are performed. Usually, the dew point is higher than -40 ° C, so The dehumidifying device or the absorbent absorbs and removes moisture in the furnace, thereby forming a dew point of -40 ° C or lower. The gas component in the annealing furnace is composed of nitrogen, hydrogen, and unavoidable impurities, as long as the present invention is not impaired. In addition, when the hydrogen concentration is less than 1% by volume, the activation effect by reduction cannot be obtained, and the chemical conversion treatment property is deteriorated. The upper limit is not particularly specified, and if it exceeds 50% by volume, The cost is increased and the effect is saturated. Therefore, the hydrogen concentration is preferably 1% by volume or more and 50% by volume or less, and more preferably 5% by volume or more and 30% by volume or less. After cooling in a temperature range of 750 ° C or higher, quenching and 099133254 18 201213550 tempering may be carried out as needed. The conditions are not particularly limited, but the tempering is preferably carried out at a temperature of 150 to 400 ° C. 15〇t: There is a tendency for the elongation to deteriorate, and if it exceeds 400 °C, the hardness tends to decrease. In the present invention, even if electrolytic pickling is not performed, a good chemical conversion treatment can be ensured. In order to ensure better chemical conversion treatment, electrolytic pickling is preferably performed for the purpose of ensuring better chemical conversion treatment. The conditions of electrolytic pickling are not particularly limited, in order to efficiently It is inevitable that the Si and the oxide are removed after the annealing, and it is preferably an alternating current having a current density of 1 A/dm 2 or more. The reason for the alternating current is that if the steel is kept at the new pole, the riding effect is small. On the contrary, if the steel plate is maintained as the anode, the Fe dissolved during the electrolysis will accumulate in the pickling liquid, and the Fe of the pickling is increased. Large, if the surface of the steel plate on the surface of the steel plate, there will be problems such as drying dirt. Further, the pickling liquid used for the electrolytic pickling is not particularly limited, and the sulphuric acid is more pure to the equipment, and must be paid attention to in handling, and thus is not preferable. Also, hydrochloric acid may generate gas from the cathode, which is preferred. Therefore, if the test is rotted and the environment is used more secretly. The sulfur (tetra) degree is preferably 5 masses ^:: and 2% by mass or less. When the degree is not full, the conductivity is lowered, so the __ division is extinguished during electrolysis (4). The other side is brought about by the effect (": caused by more than 20% by mass, the knowledge of X is too large, there will be problems in cost. 099133254 19 201213550 The temperature of the electrolyte is preferably 40t: the heat caused by the above solution The bath temperature will rise, because it is below j ° C. Since the continuous power is not full, it is difficult to maintain the temperature from the electrolytic cell, and the temperature exceeds 70. (: It is not good. From the viewpoint of longness The high-strength steel sheet of the present invention can be obtained. Further, as described below, the structure of the surface of the steel sheet has characteristics. From the surface of the steel sheet, the steel sheet of 100, m or less is formed from Fe, Si, Mn, A1, p, 1 ° Face shape

One of Cu and Ni selected is B HG'Mo and 0.060 W or less. The total amount of oxides is suppressed by adding a large amount of Si and Mn to the steel, and it is necessary to reduce the amount of the steel in the steel sheet to meet the oxidation. The inner surface of the surface of the steel plate with the surface of the scale is firstly used to ensure the reduction of the oxygen level in order to ensure the formation of impurities, thereby reducing the activity of the surface layer which is an easily oxidized element. In addition, inhibition of external oxidation of these elements: η improves chemical conversion treatability. , ~ fruit 匕 开 open / into the surface of the slave internal oxidative Μ to inhibition, and change. This effect is made from the steel plate that is started from the surface of the steel plate (4).

The total amount of formation of at least one type of oxide selected in Cu and N1 is suppressed by o'_gW or less. If the amount of oxide formation is equal to 099133254 20 201213550, the internal oxidation amount exceeds 0.060 g/m 2 , and the properties are deteriorated. Further, even if the internal oxidation amount is suppressed to less than 0.0001 g / m2, the corrosion resistance improving effect is still sufficient, so the lower limit of the internal oxidation amount is preferably 0.0001 g/m2 or more. [Example 1] Hereinafter, the present invention will be specifically described based on examples. The hot-rolled steel sheet having the steel composition shown in Table 1 was pickled to remove black rust, and then cold-rolled to obtain a cold-rolled steel sheet having a thickness of 1.0 mm. Further, some of them were not subjected to cold rolling, and were also prepared to remove hot-rolled steel sheets (thickness 2.0 mm) after black rust. 099133254 21 201213550

[II m

O ΓΟ inch 0.0 a sod !00·0 sod

OS (Nld ΙΓΟ 5 τι εοο.ο Ιο.οd

Inch 0·0 IV

6·ΙI

Id1^1 inch 0.0οι

V εοο.ο inch ε εοο.ο εοο.ο sod id sod inch 000 0000.ο id εοο.ο εοο.ο εοο·ο sod εοο·ο £00·0sod no-0 id inch ood inch 00.0 idl Ι0·0 Lod Ι0·0 Ιο.ο Ι0·0 Ιο.ο Ι0·0 90·0 Ι0·0 100 Ι0·0 10.ο Ι0·0 lod 10,0 IQ.Qlod so lod 10.0lod inch 0.0 0·(Ν εο .ο εο·ο

Icsi 60·0 υ εο·ο sd εο·ο sd S6.0 inch 0.0 εο.ο sd inch 00 εο.ο >〇0·0 εο·ο inch 00 inch Qdεο·ο inch 0·0εο·οFTT inch 〇 ·〇寸0·0 ooi 6·Ι ι·(Ν 00·ζ 0·(Ν

0.CN Γ(Ν 61 0·(Ν οτ 6·Ι 6·Ι

ι·3 "5T

IT MM W TT Γ ει·ο 60·0 80·0 110 ΖΓΟ ΖΓΟ π·ο (ΝΓΟ csro CNI.0 CNI.0 ΖΙ.Ο (ΝΓΟ

QsCNIro ICNro Ι(Ν1Γ0 ΖΙΌ ΖΓΟ ΖΓΟ α Η ο Ί

PM 3⁄4 ο d ΊΚ Η Τ Η Η KZS660 201213550 The cold-rolled steel is short-lived and smoothed. The continuous annealing zone is set to the temperature of the exposed area as shown in the figure. 'Control the 7 muscles in the annealing furnace to 3 sails (10) seconds; ^ Read After the quenching, the material is carried out. Receiver, in the 40 〇C, 5 皙 〇 〇 / 士 政 政 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Electrolytic pickling was carried out in the order of the anode and the cathode in alternating current of 3 seconds to obtain a sample. In addition, this. In addition, the dew point of the ring furnace is based on _35. 0 - the gas component of the ride is composed of gas and hydrogen and inevitable impurities, and the point f is to dehumidify the water in the environment. The concentration of hydrogen removed in the control of the incoming light is based on volume %. The sample of the two 'π' was sampled according to JIS Z 2241 metal material tensile test method, and the obtained sample was investigated for processability and durability. The oxide (internal oxidation amount) of the surface layer portion of the steel sheet which was present immediately below the surface layer of the steel sheet and cut (4) was measured. The measurement method and evaluation criteria are as follows. (Chemical Processing Property) The evaluation method of the chemical conversion property is described below. In the chemical conversion treatment liquid (Parbond L3080 (registered trademark)) manufactured by PAR本 PARKERIZING Co., Ltd., the chemical conversion treatment was carried out in the following manner. After degreasing with the degreasing liquid Fine Cleaner (registered trademark) manufactured by Japan PARKERIZING Co., Ltd., it was washed with water, and then subjected to surface conditioning of Prepan Z (registered trademark) manufactured by Japan PARKERIZING Co., Ltd. for 30 seconds at 43°. After being immersed in the chemical conversion solution of C (Parbond L3080) for 120 seconds, 099133254 23 201213550 was washed with water and dried with warm air. After the chemical conversion treatment, the sample was evaluated by a broom-type electron microscope (SEM) at a magnification of 500 times - 5 fields of view were observed, and the cell area ratio of the chemical conversion film was measured by image processing. The following evaluation was performed using the cell area ratio. 〇 is a qualified grade. 〇: 10% or less X: more than 10% (corrosion resistance after electrocoating) A test piece having a size of 70 inm×150 mm was cut out from the chemically treated sample obtained by the above method, and PN-150G manufactured by Nippon Paint Co., Ltd. (registered trademark) Conductive electrocoating (hardening conditions: 170 C 20 knives '貘25#m). Thereafter, the end portion was sealed with the surface UAI tape on the side where the evaluation was not performed, and the cutter was transversely cut to reach the base iron (cross-cut angle 60) as a sample. Next, the sample was subjected to a tape _ in a 5 mass% NaC1 aqueous solution (55 immersed in a crucible for 10 hours, and then taken a 'water-washed and then money'), and the tape width was measured. The peeling width was measured, and the following evaluation was carried out. : The peeling width is less than 2.5 mm on one side. • The peeling width is 2.5 mm or more on one side (processability). The workability is JIS No. 5 tensile test piece from the sample in the direction of 9 相对 with respect to the rolling direction, according to JIS Z2241. The stipulation is to carry out the tensile test by measuring the tensile strength (TS/MPa) and the elongation (El%) by the crosshead (four) can (four) 099133254 24 201213550 fixed l〇mm/min, when the TS is less than 650MPa, TSxElk22000 is good for 'TSxEl < 22000. When ts is 650 MPa or more and 900 MPa, 'TSXE12 20000 is good, tsxEI < 20000 is bad. When TS is 900 MPa or more, TSxElg 18000 is good. The TSxElC 18000 is defective. (The amount of internal oxidation in the area of the steel sheet surface ΙΟΟμιη) The internal oxidation amount is measured by the "pulse furnace melting-infrared absorption method". In the present invention, the surface layer portions of both surfaces of the high-strength steel sheet after continuous annealing are polished to 100 μm or more, and the oxygen concentration in the steel is measured, and the measured value is used as the measured value. The amount of oxygen contained in the material was 0 Η, and the oxygen concentration in the steel in the thickness direction of the high-strength steel sheet after continuous annealing was measured, and the measured value was taken as the amount of oxygen 内部1 after internal oxidation. The high-strength steel sheet thus obtained was used. The amount of oxygen contained in the oxygen oxidized 01 and the material after the internal oxidation is calculated as the difference between 01 and ( (=〇Ι-〇Η), and further converted into a value of a single-sided unit area (that is, lm2) ( g/m2) as the internal oxidation amount. The results obtained above are shown in Table 2 together with the production conditions. 099133254 25 201213550 [(Nl 1 good 1 invention example 1 good invention example good invention example good invention example good invention example good invention example) Liangzhu 1 invention example 1 1 good invention example good invention example poor comparison example 1 £ s 1 κ* •^srr •g £ $ s ί % £ -C& fSxEl |Processability 丨Remarks | 1 I $ I 1 i Good invention example good invention example GENERAL EMBODIMENT EXAMPLES GENERAL EMBODIMENT EMBODIMENT EMBODIMENT EMBODIMENT EMBODIMENT EMBODIMENT EMBODIMENT EMBODIMENT EMBODIMENT EMBODIMENT EMBODIMENT EMBODIMENT EMBODIMENT 1 皋 皋 丨 丨 丨 丨 丨 良好 良好 良好 良好 良好 良好 Φ Φ 21 21 21 21 20683 20338 21058 20754 20800 20547 20577 21025 19087 21269 22506 23288 , 20208 I 21213 22069 1 23681 I 21216 20902 19969 21796 21910 1 22186 I 21226 1 21165 17443 .19800 1 16464 5 22079 6 21167 7 \ 22273 m 20.6 : 20.0 : 19.4 20.1 20.6 S 20.1 19.9 21.4 20.9 17.9 19.7 19.9 20.1 26.4 (N 22.0 22.5 1 19.6 19.9 20.8 1 20.7 20.4 〇〇\ (N 20.4 20.6 26.4 20.1 13.8 in vg ) 14; οό vr> 〇0 MPa 1066 : 1031 : 1034 1020 1033 1035 1029 1022 Os ms 1162 1043 1034 1046 3 1008 1023 1035 〇1066 1061 1 1144 1040 1061 1051 1033 1074 1077 s 00 1053 1264 1200 U2C δ t—^ ΓΟ BT—^ Electro-coating 1 唆Tactile XX 〇 〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇 X 〇X turns into a 丨. Rational h XXX 〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇X 〇XX 〇(4) 1 1 1 1 1 1 1 1 1 1 1 1 〇1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 II 1 1 Electrolytic pickling 1 with or without 4: m 4ί 4: mm Disc 41 φΗ I Life i 0.221 0.143 0.074 0.056 I 0.016 1 0.042 0.009 1 0.005 1 0.010 1 0.012 I 1 0.025 1 丨0.013 I 0.012 I 0.012 I 0.005 0.009 I 0.011 0-030 丨0.039 | | 0.021 1 0.051 I 0.022 0.015 0.016 0.013 I 0.014 I 0.016 1 0.015 1 0.013 I 0.017 0.019 0.052 0.016 0.051 i 0.033 0.020 ! np ss ο «/ί 00 o in 00 o in 00 00 ο 00 ο IT) 00 ο 00 00 8 1 § o \n 00 ο 00 〇ΙΛ 00 00 〇00 〇00 〇 〇00 00 00 I 850 〇»〇00 〇〇yn 00 00 00 00 00 〇〇ο v-) 00 Ο \Τί 00 Ο \η 00 ο ID 00 00 I yn m 00 CO 1 ? (S 卜卜卜卜守守丝750 〇C ^ΜΚ°0 in in m 1 \n in 9 in 1 in f? IT) 1 in in yn yn 1 in U-) mmm 9 1 9 1 κη V) V) cn 1 cold-rolled ML cold-rolled 1 cold-rolled cold-rolled 1 cold-rolled cold-rolled Τ Μ · 戚 cold-rolled 1 cold-rolled 1 cold lucky n cold-rolled cold-rolled cold-rolled i 丨 cold mess;丨Cold rolling 1 cold rolling cold rolling cold rolling|cold rolling cold rolling cold rolling cold rolling cold rolling cold rolling cold L 1 cold rolling cold cold rolling cold rolling cold rolling cold rolling cold rolling l cold rolling ^ m ^13⁄4 S s 〇 \ Cs Η 〇〇Η 〇\ η Os σ\ Η C\ 2 众<ξ mm g CO cn rO ro ΓΟ Γ〇cn cn ΓΟ ro CO CO CO 〇\ 卜 fO ΓΟ cn ro ΓΟ ΓΟ ΓΟ ΓΛ ΓΟ rn η ρη ΓΛ ro Rm mm QQQQQQ o Q ooo QQQ < UW Ρη ο ffi HH »—> Ο α, 〇Oil 001 Η PI >1 — (S m Ό 卜 00 Os o cs 2 2 v〇〇〇〇\ < N <N m (N CN a CN m in 201213550) It can be seen from Table 2 that the high-strength steel sheet produced by the method of the present invention is a high-strength steel sheet containing a large amount of easily oxidizable elements such as Si or Mn, but is chemically processed. Sexuality, electric painting, and good fortune. On the other hand, in the comparative example, the chemical conversion treatment property, the corrosion resistance after the electrocoating, and the workability are not preferable. (Industrial Applicability) The high-strength system of the present invention can be used to treat the steel sheet in a lightweight and high-strength manner for the 7-vehicle body itself. In addition to the air car, it can also be used as a surface-treated steel plate with rust-proof properties. A broad understanding of the materials [Simplified diagram] Figure 1 is a graph showing the relationship between the redox balance of Si and Μη and the dew point. 099133254 27

Claims (1)

201213550 VII. Patent application scope: 1. A method for manufacturing high-strength steel sheets, which contains c: 0.01 to 0.18%, Si: 0.4 to 2.0%, Mn: 1.0 to 3.0%, and Α1: 0.001 to 1.0 in mass%. %, Ρ: 0.005~0.060%, SS0.01%, and the rest of the steel sheet composed of Fe and unavoidable impurities is subjected to continuous annealing, and the dew point in the environment of the temperature range of the annealing furnace: 750 ° C or higher : -40 ° C or less. 2. The method for producing a high-strength steel sheet according to the first aspect of the invention, wherein the component composition of the steel sheet further contains one or more elements selected from the following elements in mass%; B: 0.001 to 0.005%, Nb: 0.005-0.05%, Ti: 0.005 to 0.05%, Cr: 0.001-1.0%, Mo: 0.05 to 1.0%, Cu: 0.05 to 1.0%, and Ni: 0.05 to 1.0%. 3. The method for producing a high-strength steel sheet according to claim 1 or 2, wherein after the continuous annealing, electrolytic pickling is carried out in an aqueous solution containing sulfuric acid. A high-strength steel sheet produced by the manufacturing method according to any one of claims 1 to 3, wherein the surface layer of the steel sheet from the surface of the steel sheet is formed from Fe, Si, Μ, Al, One or more oxides selected from the group consisting of ruthenium, osmium, Nb, Ti, Cr, Mo, Cu, and Ni are 0.060 g/m 2 or less per one side. 099133254 28