TW201125988A - Hot rolled steel sheet, cold rolled steel sheet and fabricating methods thereof - Google Patents

Abstract

A hot rolled steel sheet, a cold rolled steel sheet without cracked edges and with a thickness of 0.2 mm or below, and fabricating methods thereof are provided. The hot rolled steel sheet contains 0.001 to 0.10 mass% of carbon, 0.005 to 0.8 mass% of silicon, 0.01 to 2.0 mass% of manganese, 0.001 to 0.40 mass% of phosphorus, 0.1 mass% of sulfur or below, 0.001 to 0.10 mass% of aluminum, 0.020 mass% of nitrogen or below, the residues containing iron, and inevitable impurities. The main phase structures of the hot rolled steel sheet is ferrite. The average crystalline grain size of the ferrite is 10 to 25 μ m. The aspect ratio of the ferrite Nx/Ny is 0.70 to 1.00. The cold rolled steel sheet is obtained by cold rolling the hot rolled steel sheet, and the thickness is 0.2 mm or below.

Description

[Technical Field] The present invention relates to a cracked edge hot rolling which is excellent in edge properties even in cold rolling when used in building materials, household appliances, and the like; Cold rolled steel sheet and its manufacturing method. [Prior Art] When the final product is manufactured by hot rolling or cold rolling from the slab, the width of the sheet is adjusted in accordance with the size ordered by the customer, and the hot rolled steel sheet is subjected to the following In the following (referred to as tnmming treatment), the both ends of the steel plate are cut by a trimmer. Further, it is widely known that if the above-mentioned sheared steel sheet is rolled by a cold rolling mill, a small number of cracks called rims are formed on the cut surface. The cracked edge is a portion in which the shape of both ends of the steel plate is a mineral tooth shape, and the coiled pipe (eGil) is broken during the cold rolling, or the shape is deteriorated after becoming a product, and becomes a defective product in order to form a product. Wei Xingshang, and then cut again, once again to repair the side to the two steel plates to Jing. However, if it is re-paste, the ruler will be shorter than the index. Therefore, it is virtually impossible to re-process the money. Therefore, in this case, it must be remanufactured. In addition, there is also the following re-cutting after cold rolling, 'reducing the trimming of hot-rolled steel sheets'. After the V-drawing, the trimming area is used to trim the width of the product. When the electric power treatment or the immersion treatment is carried out, it is easy to cause a shape defect when the coil is called edge buildup. Further, in the case where the customer performs the Wei treatment or the heat treatment, the edge is excessively plated, and the yield is lowered due to excessive plating, and the original unit price is increased. As a method of controlling the edge layering, for example, Patent Document 1 discloses a method for preventing edge layering of a plated steel sheet by using a masher roll after plating the steel sheet. The thick plating portion at the edge portion of the steel sheet is flattened, and the plating deposit protruding from the edge end surface is removed by the mechanical unit. Further, Patent Document 2 discloses a method for preventing a crack in a cold-rolled line with a steel sheet, which is a method of trimming an edge portion of a hot-rolled steel sheet. Heat to 450 ° C ~ 900 ° C. Further, Patent Document 3 discloses a method and apparatus for preventing cracking in cold rolling with a steel sheet, and as a method of trimming the edge portion in the pre-cold rolling step, a two-stage trimming method has been disclosed. . In the case of the crack prevention method of the electromagnetic steel sheet, Patent Document 4 discloses a method for producing a non-cleavable directional electrical steel sheet. According to this method, it has been revealed that in order to prevent cracking during hot rolling and to maintain good magnetic properties, a portion f within 10 mm from the surface of the plate is left in the temperature region from the solidification temperature to 1 WC at the time of casting. The time to regulate 'by this' can * produce cracks while maintaining magnetic properties. In the case of Patent Document 1 to Patent Document 4, it is necessary to introduce a new one. Also, it is necessary to carry out the details matching the steel type, and it is necessary to accumulate a large amount of technology (kn〇wh〇w). (4) The problem of the edge layer at the time of trimming after not being ======================================================================================== A technique for generating a micro-suppression such as a crack on a sheared section to form such a crack is disclosed in Patent Document 5. According to Patent Document 5, in order to suppress cracking and crusting, according to the point of re-crystallization, the re-crystallization of the body, the source of the sore, the mouth, the day, the dish, and the Ar3 change. The expansion of the temperature difference between the bundles and the dishes becomes important, and as the method, it has been revealed that

Optimization of the etc. The cake as a steel component B, Ti, N However, the increase in the addition of elements will increase the cost of the final product. Moreover, in order to strictly adjust the width of the product, it is efficient in heat cutting in the production steps. Moreover, it is required to be used for mm or less), and the crack of the cold-rolled steel sheet having a 厗 of 0.2 mm or less has not been revealed. CITATION LIST Patent Literature Patent Literature 1: Japanese Patent Laid-Open Publication No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. As described above, if the trimming treatment is performed after cold rolling, when the plating treatment or the hot dip plating treatment is subsequently performed, the edge may be caused by the second method. On the one hand, in order to avoid the problem of edge layering after the 6 201125988 side of the problem. In particular, the edging-free cold-rolled steel sheet having a thickness of not less than 2 mm is produced by the present invention. , Zhang, +, pill ±, bite ~ AM 乳 board and its rolling AM f", the rolled steel plate will be cold after rolling without the need for trimming, even when cold rolling, no Cracks. The following findings: For the hot-rolled steel sheet after the trimming treatment, the treated section is hardened by processing, and the fracture surface, m (burr), etc. are generated. Therefore, the above-mentioned trimming is studied in detail. After f-weaving and the relationship between the cracks after lyophilization, the a-rolling t controls the structure of the hot-rolled steel sheet before the repair process, and even if the V rolling rate is still good, the generation of cracks can be suppressed. It was found that for the microstructure of the hot-rolled steel sheet, the aspect ratio of the ferrite (such as (6), the average crystal grain control, and the ferrite crystal grain is controlled, thereby performing trimming treatment on both ends, followed by cold seam ratio a cold-rolled steel sheet having a thickness of a2 mm or less obtained for 85% of two, The present invention is based on the above findings, and the object thereof is as follows: [1] A hot-rolled steel sheet characterized by having a composition of carbon in a mass percentage (C) : 0_001〇/〇~010%,矽(10):〇〇〇5%~ 〇·80/0 ' Meng (Μη) : 0.01%~2 〇%, constitutive (p) : 〇〇〇1%~ 〇4〇%, sulfur (s). o.ig% below '(10):_1%~Q 1G%, nitrogen (Ν): 〇 2011 201125988 below, the remainder contains iron (Fe) and unavoidable impurities, will be the main The phase structure is set to ferrite, and the average crystal grain size of the ferrite is ίο μπι~25 μπι 'the aspect ratio Nx/Ny of the above ferrite crystal grains is 〇7〇~〗 〇〇. Among them, Nx is JISG0551 : The number of captured crystal grains per 1 mm in the pressure extension direction specified in 2005, and Ny is the number of captured crystal grains per 1 mm in the direction perpendicular to the rolling direction specified by JISG 〇 551 ·· 2〇〇5. [2] The hot-rolled steel sheet according to the above [1], characterized in that, in terms of mass percentage, chromium (α), copper (Cu), and nickel (Ni) are further contained in a total amount of 〇.〇〇1% to 〇1%. Any of the tin (Sn) applications The hot-rolled steel sheet according to the above [1] or [2], characterized in that, in terms of mass percentage, the total is further contained in 〇〇〇1% to 丨〇%. The hot-rolled steel sheet according to any one of the above [1] to [3], characterized in that it is characterized by any one or more of titanium (Ti), vanadium (V), and sharp (Nb). In addition, in terms of a percentage by mass, one or more of the elements (Mo), the initial (c〇), and the crane (W) having a total of 〇〇〇1% to 〇% are contained. [5] The hot-rolled steel sheet according to any one of the above [1] to [4], which is characterized in that it contains 〇._1% to _5% by weight (8). [6] The hot-rolled steel sheet according to any one of [1] to [5], which has a hole expansion ratio of 80% or more. [7] The hot-rolled steel sheet according to any one of [1] to [6] wherein the ratio of the maximum value of the hardness Hv after the trimming treatment to the minimum value Hv-min is 1· ΐ〇The following. [8] A cold-rolled steel sheet having a thickness of G. 2 mm or less, which is any one of the first to seventh inventions according to any one of the above [1] to [7]. The hot rolled steel sheet is obtained by cold rolling. [9] A method for producing a hot-rolled steel sheet, characterized in that a cast slab comprising the component composition according to any one of the above [1] to [5] is cast or temporarily cooled and then heated to llOOt: ~1270 ° C, the rolling reduction rate in the final stand is set to 10% ~ 20%, and the hot rolling finishing temperature is set to 850 ° C ~ lOOOO: for hot rolling, to 600 ° C ~ 700. (: entanglement is performed to form a hot-rolled steel sheet, and then both ends of the hot-rolled steel sheet are subjected to trimming treatment of more than 2 mm and less than 30 mm. [10] - a type of sheet having a thickness of 〇_2 mm or less The method of producing a rolled steel sheet is characterized in that the hot-rolled steel sheet according to the above [9] is cold-rolled at a cold rolling reduction ratio of 85% or more. [Effect of the Invention] According to the present invention, a sheet thickness can be obtained. The cold-rolled steel sheet having a crack-free side of 〇_2 mm or less has excellent edge properties in the cold-rolled steel sheet obtained by the present invention, and since it is not subjected to trimming treatment after cold rolling, it is prevented from being called edge-added layer. When the coil is wound, the shape is poor, and when the plating treatment or the hot dip plating treatment is performed by the customer, the plating is not excessively applied to the edge, and the plating is excessively plated to cause a decrease in yield or an increase in the original unit price. Therefore, it can be preferably used as a material for building materials, household appliances, etc. * The above and other objects, features and advantages of the present invention will become more apparent and obvious. A detailed description will be given below. The present invention will be described in detail. Further, in the specification 201125988 -----χ--, '% of the components of the steel are all percentage by mass. C: 0.001%~0.10% C has solid solution in steel In addition, if the c content exceeds 0.10% of the 'old-axis carbide, the 'cold-rolling during cold rolling is extremely large, and it is difficult to obtain a cold-rolled steel sheet having a thickness of 0.2 mm or less. Therefore, the towel of the present invention From the viewpoint of cold rolling properties, the upper H of the amount of c is 0.10%. Further, considering the secret (4), it is preferable to make C 2 but the significant amount of C is less likely to reduce the strength of the crucible. Steelmaking ^, in order to reduce C and increase the cost by A, it is difficult to provide materials at low cost, 'self-strength securing and cost considerations, and when the amount of C is lower, in the case of both cold rolling and cost. 1 It is better to set the C content to 0.005%~〇.〇7〇/.

Si : 0.005%~0.80%

Si is an element that effectively increases the strength of steel, and because it contains a large amount of Si, it is not only cold, but also has chemical resistance, chemical conversion treatment, and corrosion resistance. The Si content is set to 〇.8〇% to Μη: 0.01%~2 〇% Μη has a system for suppressing heat generation caused by s. For the purpose, one contains 0.01% or more of Mn, preferably 〇 2% ς = Μη. In addition, adding a large amount of Μη hardens the steel sheet material, and H + . It will also reduce the weld and plating. Set the upper limit of Μη to 2 〇%. Furthermore, in the case of requiring a better shape and the case of 201125988 corrosion resistance, it is preferable that Μ Ρ : 0.001% - 0.40% 1 is also 1·5 /. the following. Ρ has a tendency to make the strength of the steel sheet material strong, and the tendency of precipitation is strong, which causes embrittlement of the welded portion. The limit is set. Light, s is mainly present as inclusions in order to minimize s, but is allowed to exist until::: η. In the present invention, the upper limit of the s content is set to 0, and is 0.05% or less. Furthermore, in order to reduce the s content to 〇卞〇〇1%, the manufacturing cost increases. Also, it is difficult to consider the aspects of self-made steel capacity. In this case, it is preferable to set the lower limit of the S content to about _1%. A1: 0.001 〇 / 〇 〇 〇〇 〇〇 0 0 0 0 0 0 0 A A A A A A A A A A A A A A A A A A A A A A A A , actively add A1. In order to obtain the above effects, the amount of A1 is made 0.001% or more. When the content of A1 is less than 0 001%, the effect of deoxidation is small, and inclusions remain and the formability is lowered. On the other hand, when the A1 content exceeds 0.10%, the production cost rises, so the upper limit of the A1 content is set to 0.10%. Further, from the viewpoint of material stability, it is preferred to set the A1 content to 0.005% to 0.08%. N: 0.020% or less N is solid-dissolved in the steel sheet. If the N content exceeds 0.2% by weight, the steel sheet is remarkably hardened, so that the N content is set to 0 020% or less. Further, 11 201125988 It is preferable to set the lower limit of the N content to about 0.001% in consideration of the steelmaking ability or cost. The component composition of the hot-rolled steel sheet of the present invention is, in addition to the above components, the remainder being Fe and unavoidable impurities. In addition, in the present invention, the above-mentioned component composition may be used as a basic component, and if necessary, a total of 0.001% to 3% by weight of Cr, Cu, or any one or two or more elements may be contained, and the total amount may be contained. 〖%~〗 Any one or two or more elements of Ti, V, and Nb may contain, in total, * 0.001 〇 / 〇 to 1.0% of any one of Mo, Co, and W, or both. It can contain 〇.〇〇〇1%~〇〇〇5% B. A total of 0.001 〇 / 〇 ~ 0.1% of Cr, Cu, Ni, Sn or more than two elements

Cr, Cu, Ni, and Sn are for the purpose of solid solution strengthening, and may be any of the above-mentioned Cr, Cu, and Ni. On the other hand, if adding a total of more than 〇 1% of Cr, cu,

In the case of Ni and Sn, the steel sheet is remarkably hardened, which is detrimental to the cold-worked field. When Cr, Cu, Ni, and Sn are contained, the upper limit of the content of Cr and Cu is 〇1%. And n totals 0.001% to 1.0% of two or more kinds of Ti, v, and Nb, or two or more V, and b is a carbide which is mainly formed into a carbide or a nitride to increase the strength of the steel sheet. Prime. In order to obtain the above effects, any one or two or more of & V and Nb are used in accordance with the above-mentioned effects; on the other hand, Tl, v, Nb, ^^; 12 201125988 is significant. Since the ground is hard and the cold workability is impaired, the upper limit of the content of 'Ti, V, and Nb in the case of containing Ti, V, and Nb is 1.0% in total. A total of 0.001% to 1.0% of any one of Mo, Co, and W, or two or more elements

Mo, Co, and W are mainly used as a strengthening element, and may contain any one or two or more of Mo, Co, and W in total o.oop/o or more. On the other hand, if a total of more than 1.0% of Mo, Co, and W is added in a large amount, the steel sheet is remarkably hardened, thereby impairing cold workability, and therefore, contains

In the case of Mo, Co, and W, the upper limit of the contents of Mo, Co, and W is 1.0% in total.

The component □ containing 0.0001% to 0.005% of B B 疋 which effectively enhances the grain boundary ′ exhibits the above effects when the b content is 0.0001% or more. On the other hand, when B is added in a large amount of more than 0.005%, the steel sheet is remarkably hardened and the cold workability is impaired. Therefore, when B is contained, the upper limit of the B content is 0.005%. Next, the structure of the hot rolled steel sheet will be described. In the present invention, the both ends of the hot-rolled steel sheet are subjected to trimming treatment, and in order to suppress cracking of the cold-rolled steel sheet after cold rolling, the phase of the main phase structure of the hot-rolled steel sheet, that is, the largest area ratio, is set to ferrite. body. Further, specifically, the area ratio of the ferrite is 80% or more. Other tissues may contain one or less of ceminite, carbide (disperse iron (_caffeine), varnish (bainite), residue:) s (austenite) or More than two substances. 13 201125988 pieces ~m The rate is obtained by using an optical microscope, 200:: factory etched liquid (nitai) narration (-g), and according to the cutting method or image analysis, etc. For the present hot-rolled steel sheet, Wei_ is ΙΟμιη~25μιη. If the crystal grain size is less than 1G μηη, the steel plate will be significantly ntn-added to the cold, so the average crystal grain size is called. On the other hand, when cold rolling is performed on a field having an average crystal grain size of more than 25, surface wrinkles are generated, and the shape is lowered, and the % is easily formed as a concave extension or an upwardly convex shape. Therefore, the upper limit of the average crystal grain size is set. It is 25 μπι. Further, the average crystal grain size is a particle diameter obtained from the group «seven ϋβ: : TISG0551 = 2005 "Microscopic test method for steel-crystal grain size" observed by the above method. For the present hot-rolled steel sheet, the aspect ratio Nx/Ny of the ferrite crystal grains is ojoh 〇〇. When the right aspect ratio is smaller than 〇.7〇, it becomes a structure that remarkably extends along the rolling direction. When such a structure is subjected to a pressure delay, the steel sheet is remarkably hardened, so that it is drawn in cold workability. On the other hand, in the usual calendering, the number of particles per unit length of the calendering in the right angle direction is not smaller than the number of particles per unit length in the calendering (length) direction, i.e., the aspect ratio is not more than 1.0. Further, according to the structure observed by the above method and according to the microscope test method of "Glass-Crystal Grain Size" of the ISG 0551.2005, the Nx described in the JIS "4 mark" in the above 201125988 is set in the direction of the pressure extension. For the number of captures per i mm, Ny is set to the number of captures per 1 mm in the direction perpendicular to the calender, and the aspect ratio is calculated using the ratio of Nx to Ny (Nx/Ny). Further, in the case of performing a hole expansion test on a hot-rolled steel sheet, it is preferable to have a hole expansion ratio of 80% or more. The hole expansion test is known as an index for evaluating the stretch flangeability of a steel sheet. A hot-rolled steel sheet having a thickness of 2 mm to 3 mm manufactured according to various conditions (c: 0.003% to 0.25%, Si: 0.012%, Mn: 0.01% to 2.5%, P: 〇·〇1〇/0) , S : 0.014%, A1 : 0.044%, N: 0.003%), and a hole expansion test was carried out. The measurement method and the calculation of the hole expansion ratio are based on the JFS Τ10〇Μ996 specification. Further, various hot-rolled steel sheets were cold-rolled to 0.2 mm, and the amount of cracks (edge crack depth) was measured. Regarding the amount of cracking, the sample is magnified 5 to 100 times by an optical microscope or the like, and the amount of cut (edge crack depth) is measured by a vernier caliper or the like, and if the measured edge crack depth is less than 0.100 In the case of mm, there is no problem with the substantial final product. In the present invention, the case where the edge crack depth is less than 0.100 mm is judged as "no cracking". The results obtained by examining the relationship between the hole expansion ratio and the amount of cracking of the cold-rolled steel sheet are shown in Fig. 1. According to the figure, if the reaming rate is above, the money will not crack. Therefore, it is preferable that it is 80% or more. Further, in the hot-rolled steel sheet according to the present invention, the comparison between the maximum value Hv-max and the minimum value Hv-min of the surface hardness Hv after the trimming treatment is preferably U0 or less. Fig. 2 is a schematic view showing a cross-section of the both ends of the hot-rolled steel sheet: 15 201125988. As shown in Fig. 2, in the cross section after the trimming treatment, a sag angle is generated at the upper portion of the fracture surface and the fracture surface and the shear surface, and a burr (also referred to as a burr) is generated at the lower portion of the fracture surface. The hardness Hv of the cross section was measured. A hot-rolled steel sheet having a thickness of 2 mm to 3 mm manufactured according to various conditions was used (C: 0.003% to 0.25%, Si: 0.012%, Μη: 0.01% to 2.5%, Ρ: 0.01%, S: 0.014%, Α1 : 0.044%, Ν : 0.003%) 'The section hardness was measured after trimming treatment with various trimming conditions (ciearance, overlap amount). The method of measuring the hardness was carried out in accordance with the JIS Z 2244 Vickers hardness test. The measurement of the amount of crack (edge crack depth) was carried out in the same manner as in Fig. 1. The relationship between the maximum value Hv-max and the minimum value Hv_min (Hv-max/Hv-min) of the table hardness in FIG. 3 and the edge amount (edge crack depth) of the cold-rolled steel sheet having a thickness of 〇.2 mm or less . As can be seen from Fig. 3, if the above-described ratio (Hv-max/Hv-min) is L10 or less, a crack-free cold air flip cup can be obtained. Next, a method of producing the hot-rolled steel sheet of the present invention will be described. The cast plate chain adjusted to the above chemical composition range is temporarily cooled, and then heated to. ◦ ~ (2) 叱, the final pressure table = dry shrinkage rate is set to 10% ~ ·, and hot rolling is added to I temperature. : 热 进行 进行 进行 进行 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热The crack is then subjected to a non-cracked cold-rolled steel sheet having a one-side end = 85% 16 201125988 m or less at both ends of the hot-dry steel sheet. First, in the method for producing a hot-rolled steel sheet according to the present invention, or temporarily cooled, and then heated to = high, and the shape = temperature is below the war, the rolling load at the time of hot rolling is entangled or difficult. Guardian temperature is used for manufacturing. The heating temperature was set to 1100. 〇 Above. On the other hand, tlTe)1,2 produces thick yttrium oxide on the entire surface of the plate: the loss of the scale causes the surface properties to deteriorate or the yield to decrease. Thus, the upper limit of the heating temperature is set to 12,703⁄4.

Next, in the method for producing a hot-rolled steel sheet according to the present invention, the rolling in the final press is set to 1 G% to 2% by weight, and the fineness is added to the fourth. π is the hot rolling finishing temperature: 850 ° C to 100 CTC. If the finishing temperature during hot rolling is less than 850 ° C, a non-recrystallized structure is formed on the surface layer of the hot rolled steel sheet, or a coarse structure is formed, and cold rolling is performed. At the time, the shape of the surface layer is likely to be poor. Therefore, the finishing temperature is set to 850 ° C or higher. On the other hand, if the finishing temperature is too high, the structure in the hot-rolled steel sheet becomes coarse, resulting in a poor shape of the surface after cold rolling. Therefore, the upper limit of the finishing temperature is set to l〇〇〇〇C. The reduction ratio in the final press: 10% to 20% If the rolling reduction ratio in the final press of the hot rolling is less than 1 〇〇 / 0, the sheet thickness accuracy of the hot-rolled steel sheet may be lowered or the shape may be poor. Therefore, the rolling reduction ratio of the final press table is set to 10% or more. On the other hand, if the rolling reduction ratio exceeds 20%, 17 201125988 forms a non-recrystallized structure in the hot dry steel sheet, resulting in poor shape or poor surface properties during cold drying. Therefore, the upper limit of the (four) rate is 20%. Further, in the method for producing a hot-rolled steel sheet according to the present invention, hot rolling is carried out under the above conditions, and 60 (TC to 70 (TC is wound. Winding temperature: 600. 〇~7 〇〇 °c) is used. The crystal grains of the rolled steel sheet are homogenized, and the winding temperature is set to 600 c or more. In addition, if the winding temperature is increased, the thickness is increased, and the scale is peeled off, and the surface of the scale is deteriorated. Producing a larger second phase 'to perform a cold material filament surface defect. Therefore, the upper limit of the winding temperature is set to 7 〇〇. 接着. Next, both ends of the hot-rolled steel sheet are more than 2 mm and = Trimming treatment of the foot 3 _ to produce the non-cracked hot-milk steel sheet of the present invention. The trimming of the both ends of the hot-rolled steel sheet is a step necessary to strictly adjust the b-degree of the final product. However, a large trimming will reduce the yield' and thus set it to less than 30 mm. On the other hand, if the repair is too wide, too little, it is difficult to strictly carry out the width of the product, so that the final product needs to be repaired. Processing side by side. Therefore, set the trimming width to coffee. The method of the trimming treatment is not particularly limited as long as the sheet width of the final product is adjusted, and examples thereof include a method of mechanically cutting the sheet, etc. i. The method for producing a cold-rolled steel sheet according to the present invention is The hot-rolled steel sheet produced by the above method is cold-rolled at a coldness of 85% or more. 18 201125988 In order to make the thickness of the final product 〇 2 mm or less, the cold rolling reduction ratio is set to 85% or more. The thickness of the sheet during rolling is reduced, whereby the cold rolling reduction can be reduced. However, if the sheet thickness during hot rolling is too thin, it is difficult to set the finishing temperature to 850 ° C or higher. Further, shape defects are likely to occur. Therefore, the cold rolling reduction ratio is set to 85% or more. ° Thereby, a non-cracked cold-rolled steel sheet having a thickness of 〇.2 mm or less is produced. Further, in the present invention, "no cracking" is used. It means that there is no edge crack. Specifically, when the edge portion is observed by an optical microscope at a magnification of 5 〜 to 1 〇〇, if the edge crack depth is less than 〇〇1 〇〇 mm, the substantial final product does not exist. Problem 'Therefore, in the towel of the present invention, the edge crack depth is less than 0.100 mm. It is judged as "no cracking". Example 1 Steel A to steel j containing the composition shown in Table 1 was melted to form a sheet, and then the obtained sheet was produced under the manufacturing conditions shown in Table 2.叮 叮 ' 获得 获得 获得 获得 获得 获得 获得 获得 获得 获得 获得 获得 获得 获得 获得 获得 获得 获得 获得 获得 获得 获得 获得 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热 热^Measure the average crystal grain size (1, the aspect ratio of the ferrite crystal grains, the hole expansion ratio (%), and the cross-sectional hardness ratio) by taking out the '% of the structure and ferrite ratio') and the average crystal grain size of the ferrite. t = The thickness of the plate was G.15 mm, and the cold-rolled steel plate was obtained. For the cold-rolled steel sheet obtained by this, the edge crack was investigated. Details of each investigation method are as follows. The microstructure of the hot-rolled steel sheet was observed from the hot-rolled steel sheet, and the sheet thickness profile (L-section) of the rolled and rolled line 201125988 was etched using a Scanning Electron Microscope (SEM). The imaging is performed on three or more fields of view at a magnification of one, and then the measurement is performed by a method such as image analysis. Further, the average crystal grain size of the ferrite was determined in accordance with JIS G0551 "Microscopy test method for steel_crystal grain size". The aspect ratio is based on JIS G0551 "Microscopic test method for steel-crystal grain size", and Nx described in "4. Symbol" is set to the number of traps per imm in the direction of the pressure extension direction, and Ny is set in the direction perpendicular to the rolling direction. When the number of 丨mm is captured, the aspect ratio is calculated by the ratio of Nx to Ny (Nx/Ny). Hole expansion ratio The hole expansion ratio was determined in accordance with the Japan Iron and Steel Federation specification JFS T1001-1996. Vickers hardness (hardness ratio) The measurement was carried out in accordance with the regulations of TIS Z 2244. Furthermore, the test force was set to 2.94 N (0.3 kgf). Also on the maximum value Hv-inax and the minimum

Hv-min was measured with a gap of 80 μm for the thickness profile after the trimming treatment, and was set to the maximum value Hv-max and the minimum value Hv-min of the hardness. The presence or absence of cracks (edge cracks) about the cracks (edge cracks) is magnified 50 times to 1 times by an optical microscope, and the amount of cut (edge crack depth) is measured by a vernier caliper or the like. When the measured edge crack depth is less than 〇〇1〇〇mm', there is no problem in the substantial final product. Therefore, in the present invention, the case where the edge crack depth is less than 0.100 mm is judged as "no cracking". The results obtained above are shown together with the conditions in Table 3. 201125988

JU60UC

Steel composition (Wt%) Other 1 Cr/0.05, Ni/0.008 1—H 0 1 soo H Cu/0.03, Ti/0.005, V/0.01 oo 'osso 0 1 sou Cr/0.05, Nb/0.005, Mo/0.007 ,Sn/0.01 C〇/0.01, W/0.03 Mo/0.10, Cr/0.05, Nb/0.005, W/0.02 〇d 'δ g' oo CQ oo OQ oo "osoo ΚΠ 2: 0.003 0.004 0.002 0.005 0.003 0.005 1 : 0.003 0.002 0.004 0.003 0.045 0.034 0.020 0.026 0.052 0.041 0,33 0.028 0.045 0.048 0.012 0.007 0.025 0.023 0.012 1 0.012 0.00S 0.007 0.026 0.007 fx, 0.02 0.08 0.01 0.10 0.28 0.33 0.01 0.08 0.15 0.15 β S 0.20 0.55 0.73 0.17 0.08 0.01 0.22 0.55 yn CN 1.50 w 0.010 0.008 0.010 0.008 0.021 0.025 0.013 0.030 0.150 0.350 U 0.020 0.004 0.002 0.042 0.085 0.065 0.005 0.036 0.051 0.211 Steel mark < CQ u QW o HH 201125988 J-a60uro [<Nd

Remarks Inventive Examples Inventive Examples Inventive Examples Inventive Examples Comparative Examples Comparative Examples Comparative Examples Comparative Examples Manufacturing Methods Cold Rolling Reduction Rate /% 00 00 σ\ 00 Winding Temperature / °c 650 650 650 650 650 600 450 650 660 650 Final Press table reduction ratio /% 〇〇in <n 00 finishing temperature / °c 850 870 870 ! 870 870 780 750 750 880 870 P $ 1250 1230 1250 1220 1250 1220 1200 1250 1230 1240 Steel mark < PQ u Q w Ph a HH ττ 201125988 JU60ue r-le d

Remarks Inventive Examples Inventive Examples Inventive Examples Inventive Examples Comparative Examples Comparative Examples Comparative Examples Comparative Examples Cold-rolled sheet properties with or without edge cracks Thermally extended sheet properties Hardness ratio 1.05 1.04 1.06 1.05 1.08 j 1.24 1.65 m rn 1.74 Reaming ratio /% 120 〇110 ο O Aspect ratio 0.82 1 1 0.94 0.91 0.85 0.88 0.46 0.72 0.62 1 0.56 0.46 Ferrite particle size / μπι 18.5 22.4 23.6 17.8 12.6 31.6 inch 〇6 13.9 16.3 Ferrite area ratio /% 00 〇〇〇〇 00 〇l〇S Os Main organization/sub-organization F/Ce (X| &H Εί F/BF/B [X| F/Ce Uh F/M steel mark < CQ UQ ω P-ι Ο X lH

€^®^:s-^^^:aA31H-^d)^^-^:d-ll€^5:a:s:uu*ll^^:J 201125988 According to Table 3, Invention Example A~Inventive Example E has no cracks (edge cracks). On the other hand, it has been confirmed that the F~j of the comparative example has a splitting edge. Although the present invention has been disclosed in the preferred embodiments as above, it is not intended to limit the present invention, and anyone skilled in the art can The scope of protection of the present invention is defined by the scope of the appended claims, and the scope of the invention is defined by the scope of the appended claims. Fig. 2 is a schematic view showing a cross section of the edge of the hot rolled steel sheet after trimming treatment. Fig. 3 is a view showing the maximum value of hardness Hv- A graph showing the relationship between the ratio of max to the minimum value Hv_min (Hv-max/Hv-min) and the amount of cracking (edge crack depth) of a cold-rolled steel sheet having a thickness of 〇2 mm or less. [Explanation of main component symbols] No 24

Claims (1)

201125988 VII. Patent application scope: 1. A hot-rolled steel sheet characterized in that the composition of the composition is C: 0.001%~〇_1〇%, Si: 0.005%~0.80%, Μη: 0 01% 〜2·〇%, Ρ: 0.001%~0.40%, S: 0.10% or less, Α1: 0.001%~0.10%, Ν: 0.020% or less, the remainder contains Fe and unavoidable impurities, and the main phase structure is set to Ferrite, the average crystal grain of the ferrite is expected to be ίο μπι~25 μπι, and the aspect ratio of the ferrite crystal grain (Νχ/Ν3〇 is 0.70 to 1.00, wherein NX is JISG0551: 2005) The number of captured crystal grains per 1 mm in the direction of the pressure extension, Ny is the number of captured crystal grains per 1 mm in the direction perpendicular to the rolling direction specified in JIS G0551: 2005. 2. Hot rolling as described in the scope of claim The steel sheet, in terms of mass percentage, further contains 0.001% to 0.1% of any one of Cr, Cn, Ni, and Sn, or two or more elements. 3. As described in the scope of claim 2 or item 2 Hot-rolled steel plate, "in terms of mass percentage, total of 0.001% ~ 丨〇% Ti, v Any one or two or more of the elements of Nb.) The hot-rolled steel according to any one of items i to 3 of the U-profit range, in terms of the percentage of the shell, is further referred to as (9) to (10). Any one or two or more elements of Co, w. Sword Indium 1 such as heat according to any one of items 1 to 4 of Jr Patent 5, /, in terms of mass percentage, further contains 0.0001 %~0.005% of B. For example, the hot 25 201125988 rolled steel sheet described in any one of the claims-month patent range 帛j to 5 has a hole expansion ratio of 80% or more. The hot-rolled steel sheet according to any one of the items 1 to 6, wherein a ratio of a maximum value Hv-max of the cross-sectional hardness Hv after the trimming treatment to a minimum value Hv-min is 1.1 Å or less. The rolled steel sheet is obtained by cold-rolling a hot-rolled steel sheet according to any one of the above-mentioned items, and has a thickness of 〇2 mm or less. 9. A non-cracked hot rolling A method of producing a steel sheet, comprising: a slab slab comprising the composition of any one of items 1 to 5 of the patent application scope Casting, or temporarily cooling, and then heating to 1100 C~1270 C 'The rolling reduction rate in the final press is set to 1 〇 (^~ 20%, and the hot rolling finishing temperature is set to 85 (TC~lOOOO: The hot rolling is performed by winding at 600 ° C to 700 ° C to form a hot-rolled steel sheet, and then the both ends of the hot-rolled steel sheet are subjected to trimming treatment of more than 2 mm and less than 30 mm. H A method for producing a non-cracked cold-rolled steel sheet having a thickness of 0.2 mm or less, characterized in that the hot-rolled steel sheet according to claim 9 is further cooled by a cold rolling reduction ratio of 85% or more. Rolling. I 26