[Name of Document] DESCRIPTION [Title of the Invention! HOT-DIP PLATED HIGH-STRENGTH STEEL SHKHT FOR PRESSWORK EXCELLENT IN LOW-TEMPKRAfURE TOUGHNESS AMD CORROSION RESISTANCE AND 5 MANUf ACTIJRTNG METHOD THEREOF [Technical Field 1 [0001] The present invention relates to a hot-dip plated high-strength steel sheet for presswork applied to fields of automobiles, home electric appliances and the like and a manufacturing method thereof, and particularly 10 relates to a hot-dip plated high-strength steel sheet for presswork excellent in low-lemperature toughness and corrosion resistance and suitable for a ftiel tank of an automobile and a manufacturing method thereof. [Background Art] [0002] 1" recent years, for the purpose of improving fuel economy by ] 5 reducing a weight of vehicle body, a strengtli of a steel sheet for automobile has been increased. Similarly, also in a sled sheet for fuel tank, because of a reduction in weight of a tank, a complication of design of a vehicle body, and further, in terms of a place where the fuel tank is housed and installed, a shape of the fuel tank becomes complicated, and accordingly, the steel sheet for fuel 20 lank has been required to have excellent formability and high strength. [0003] In order lo satisfy the requirements of realizing both of ihe excellent formability and the high strength, there has been developed a high-strength IF sted being an IF (Interstitial Free) steel made by adding carbon ilride forming elements such as Ti and Nb to an ultralow carbon steel, 25 to which solid-solution strengthening elements such as P, Si, Mn and the like are further added. J [0004] However, when a conventional high-strength steel sheet is used in a fuel lank, there is a problem that a tensile strength of a coach peel seam weld zone at low temperature is low. Specifically, there is a problem that even if a strength of steel sheet is increased, a strength of welded joint is not increased in accordance with the high-strengthening of the steel sheet. [0005] A fliel tank is manufactured by performing seam welding on two upper and lower cup-shaped parts at flange portions, in which a scam weld zone of the iuel tank has a coach peel shape (which indicates a shape of mutually welded flanges welded in such a manner that palms are folded to pray, and is described as "coach peel seam weld zone" or "coach peel weld zone31, hereinafter), as shown in FIG 6, and in particular, when a high-strength steel sheet is used, a stress is easily concentrated on a weld zone, compared to a normal cold-rolled steel sheet, and as a result of this, there is a tendency that a toughness is lowered and a tensile strength is lowered. [0006] Further, the TF steel fixes C, N and the like as a carbide or a nitride of Nb or Ti, so that a crystal grain boundary becomes very clean, and after forming, a secondary work low-temperature embrittlement easily occurs due to a grain boundary fracture, which is a problem. Particularly, when a high-strength IF steel is used, an inside of grain is strengthened by a sol id-solution strengthening clement, and a lowering oT relative grain boundary strength becomes obvious, and the secondary work low-tcmperaturc embrittlement is Facilitated, which is a problem. [0007] These become concerns regarding a fracture resistance of a fuel tank being an important safety related part when the fiiei tank receives Impact due to collision particularly in a low-temperature region, [0008] Further, it has been conventionally proposed to use various types 3 of alloy plated steel sheets formed by performing Pb-Sn. alloy plating, Al-Si alloy plating, Sn-/n alloy plating, or Zn-Al alloy plating on surfaces of steel sheets, in which the steel sheets are required to have good plating properties when being coaled with the above alloy plating through hot-dipping. 5 [0009] Regarding these problems, some methods for avoiding the occurrence of secondary work embritdement have been proposed (refer to Patent Documents 1 and 2, for example). In Patent Document 1, there is proposed a technique in which in a Ti-added IF steel, an amount of P is reduced as much as possible and large amounts of Mn and Si are added by the 10 amount of reduced P, to obtain a high-tensile steel sheet excellent in secondary work britlleneKS resistance, in order to avoid the secondary work embrittlemenl caused by grain boundary segregation. [0010] In Patent Document 2, there is proposed a technique in which not only Ti and Nb but also 13 is added to an ultralow carbon steel sheet to ]5 increase a grain boundary strength and to enhance the secondary work britlienoss resistance. In the technique described in Patent Document 2, an amount of B is optimized for the purpose of improving the secondary work brittleness resistance ^nd preventing an increase in load during hot rolling in accordance with a delay of recrystallization of austemte grains. 20 [0011] Further, some propositions have been made for the purpose of improving a weldabllity (refer to Patent Documents 3 to 5 and Non-Patent Document 1? for example). [0012] A technique described in Patent Document 3 is a technique in which an ultralow carbon steel sheet to which Ti and/or Mb are (is) added is 25 earburi/.ed during annealing, and structures of martensite and bainitc are formed on a surface layer, to thereby improve a spot weldability. A 4 technique described in Patent Document 4 is a technique in which Cu is added to an uitraiow carbon steel to enlarge a heat-affected zone during welding, tlierehy increasing a strength of a spot-welded joint. [0013] A technique described in Patent Document 5 is a technique in 5 wliich a grain refining of structures of a weld zone and a heat-affeeted zone is performed by utilizing a pinning effect of Mg oxide and/or Mg sulfide to prevent a deterioration of fatigue strength. Non-Patent Document ! discloses a technique in which TiN is finely dispersed in a thick steel sheet to improve a toughness of a weld zone and a heat-affected zone. 10 [0014] Further, some techniques of improving a hot-dip platability of a high-strength steel sheet have been proposed (refer to Patent Documents 6 and 7; for example). [0015j In a hot-dip galvanised high-strength cold-rolled steel sheet described in Patent Document 6, a content of S which hinders a hot-dip 13 platability is limited to 0.0!? mass% or less, and a content of P is limited to 0.01 to 0.12 mass%, and Mn and Cr are added as strengthening elements. In a high-tensile alloyed galvanized steel sheet described in Patent Document 7, a mutual relationship between Si and Mn is defined to improve a hot-dip alloy 7xi platability, 20 [0016J There has been disclosed a steel sheet excellent in strength and secondary work brittleness resistance in which B is added and a balance of addition of Mn and F is optimized to improve the secondary work brittleness resistance (refer to Patent Document 8, for example). Tuitlier, there has also been disclosed a technique of adding H, Ti3 and Nb for improving the 25 secondary work brittleness resistance (refer to Patent Document 9, for example), 5 [0017J Further, a technique of improving a tensile strength oT a coach pee^ weld zone peculiar lo a fuel tank (refer to Patent Document 10, for exampic)? and a technique related to a high-strength steel sheet for deep drawing or presswork (refer to Patent Documents 11 to 15, for example) have 5 been disclosed. [Prior An Document] [Patent 1 >ocumentj [0018] Patent Document 1: Japanese Laid-open Patent Publication No. 115-59491 10 Patcnl Document 2: Japanese Laid-open Patent Publication No. 116-57373 Patent Document 3: Japanese Laid-open Patent Publication No. 117-188777 Patent Document 4: Japanese Laid-open Patent Publication No. 15 118-291364 Patent Document 5: Japanese Laid-open Patent Publication No. 2001-288534 Patent Document 6: Japanese Laid-open Patent Publication No. H5-255 807 20 Patent Document 7: Japanese Laid-open Patent Publication No. H7-278745 Patent Document 8: Japanese Laid-open Patent Publication No. 2000-192188 Patent Document 9: Japanese Laid-open Patent Publication No. 25 H6-256900 Patent Document 10: Japanese Laid-open Patent Publication No. 6 2007-119808 Patent Document 11: Japanese Laid-open Patent Publication No. 2007-169739 Patent Document 12: Japanese Laid-open Patent Publication No, 5 2007-169738 Patent Document 13: Japanese Laid-open Patent Publication No. 2007-277713 Patent Document 14: Japanese Laid-open Patent Publication No, 2007-277714 i 0 Patent Document 15: J apanesc Unexamined Patent Appli cation Publication No. 200R-126945 [Non-Patent Document] [003 91 Non-Patent Document 1: Iron and Steel, Vol, 65 (1979), No. 8? page 1232 15 [Summary of the Invention] [Problems to Be Solved by (he Invention] [0020] However, the above-described conventional techniques have the following problems. The sice! sheets manufactured through the methods described in Patent Documents 1 and 2 have problems such that although the 20 workability is good, when press forming is conducted under severe conditions such as working conditions of a complicated fuel tank shape in particular, the secondary work briuleness resistance is insufficient, and further, the strength of the coach peel weld zoneof Ihe welded joint is low. f0021 ] The method of performing carburization during annealing 25 described in Patent Document 3 has a problem that it is difficult to stably manufacture the steel sheet because, in an actual manufacturing facility, a 7 sheet passage speed, an atmosphere gas composition, and a temperature are not constant, and a earrmri/athm amount is changed. [0022] The method described in Patent Document 4 has a problem that a surface defect occurs due to the addition of Cu, and a yield is lowered. The 5 methods described in Patent Document 5 and Non-Patent Document 1 have a problem that, although there is an effect in an arc welding and the like in which a cooling rate after welding is relatively slow, there is no effect in a seam welding and the like in which the cooling rate is fast [0023J further, the thick steel sheet described in Patent Document 5 and EO Non-Patent Document 1 has components different from those of a thin stcci sheet for fuel tank, and further, il has a different shape of weld zone, so that it cannot be immediately applied to the fuel tank. The steel sheets described in Patent Documents 6 and 7 have a problem that although the hot-dip galvanizing property is good, the weldabllity and the secondary work 15 brittleness resistance are insufficient [0024 J The steel sheet described in Patent Document 8 has a disadvantageous point that the sufficient low-temperature toughness Js not achieved since a large amount of P is contained for securing the strength, and the balance of P and B is not optimum from a point of view of the 20 low-temperature toughness. [0025] The technique described in Patent Document 9 has a problem that the sufficient strength and toughness of the weld zone cannot be secured since a large amount of Ti is used from a point of view of the improvement of formabiiity, and further, the sufficient workability cannot be secured since the 25 amount ot'Nb is small, even with the appropriate amount of addition of Ti. [0026] The technique using the laser welding described in Patent s Document 10 is difficult to be applied to the seam welding of the fuel lank. Further, Patent Document 10 discloses no technique of improving properties of weld zone by improving properties of base material. The techniques of improving the properties of base material described in Patent Documents 11 and 12 h^vo problems that the corrosion resistance and the workability of the base material are low, and in addition to that, the toughness of the coach peel seam weld xone is low depending on the welding conditions. [0027] The techniques described in Patent Documents 13 ami 14 have a problem Ihal the toughness of the coach peel seam weld zone is low depending on the welding conditions, Turther, the technique described in Patent Document 13 also has a problem that the lowering of workability is caused. [0028] The technique described in Patent Document 15 has a problem that a scale layer lends to be solidly generated on a surface of the steel sheet di.Ee lo a large Si amount contained in the steel sheet, and in order to remove the scale layer, it is often the case thai conditions of decreasing and pickiing treatment have to be strictly controlled or a surface grinding treatment has to be performed by u brush Tor heavy duty grinding, and thus it is difficult to stably manufacture a hot-dip plated steel sheet having excellent corrosion resistance under usual degreasing and pickling conditions. [0029J As described above, the conventional findings include a (mding of increasing the secondary work briltleness resistance, and a finding of improving the toughness of weld zone in a field of thick steel sheets. However, since manufacturing steps of a fuel tank Include a working step {pressing, for example), and a heat-affect step (seam welding, for example), so that not only the properties of base material, but also the properties after 9 the working and (lie properties after the heat-affect arc also important. [0030] Specifically, when a high-strength steel sheet is used for a fuel tank, since llic toughness is generally lowered, the secondary work briUleness resistance and the toughness of weld zone become important properties, and 5 further, since the plating is performed on tbe suiTa.ce of the sleei sheet, the platability and the corrosion resistance also become important properties. [00311 However, there is no technique, in the conventional techniques, that provides a high-strength steel sheet excellent in press formabihty, in which all of excellent secondary work briltleness resistance and toughness of 10 coach peel scam weld zone at low temperature, and excellent platubility and corrosion resistance are improved. [0032J The prcsenl invention is made hi view of such problems, and an object thereof is to provide a hot-dip plated high-strength steel sheet for prcsswork having a tensile strength of 340 MPa or more and less than 540 !5 MPa, a press fbrmability capable of being applied to a field of automobile, particularly a fuel lank, excellent secondary work briUleness resistance and excellent toughness of coach peel weld zone at low temperature, and excellent corrosion resistance, and a manufacturing method thereof. [Means for Solving the Problems] 20 [0033] The present invention is made, lor solving the above-described problems, based on a result of studies regarding an influence of Ti, B, V and Al on a toughness of eoach peel seam weld zone peculiar to a fuel tank and a secondary work briUleness resistance, and an influence of Si on a corrosion resistance, and a gist thereof is as follows. 25 [00341 (1) A hot dtp plated high-strength steel sheet for prcsswork excellent in m low-temperature toughness and corrosion resistance is characterized in that it includes a high-strength steel sheet having a hot-dip plated layer on a surface of a cold-rolled steel sheet, in which the above-described cold-rolled steel sheet contains, by mass%, C: 0,0005 to 0.0050%, Si: 0,30% or less, Mn: 0.70 5 to 3.00%, P: 0,05% or less, Ti: 0.01 to 0,05%, Nb: 0.01 to 0.04%, B: 0.0005 to 0.0030%, S: 0.01% or less, Al: 0.01 In 0.30%, N: 0.0005 to 0.010%, and a balance composed of Fe and inevitable impurities, when the Ti content (%) is set to [Ti], the B content (%) is set to [B], and the P content (%) is set to flJ~|, TB* defined by the following expression is 0.03 to 0.06, and [Bj and [PJ 10 satisfy the following expression . TB*-(0.11 - | T i j ) / ( l n ( | B j x 10000)) - [PJ ^ i 0 x [ B ] i 0.03 - [00351 P) The hot-dip plaleu1 high-strength steel sheet for presswork excellent in 15 low-temperature toughness and corrosion resistance according to the above-described (l), is characterized in that the above-described cold-roiled steel sheet further contains, by inass%, one or two or more of Cu: 0.005 to 1%, Ni: 0.005 to 1%, Or: 0.005 to 1%, and Mo: 0,0005 to 1%. [0036] (3) 20 The hot-dip plated high-strength steel sheet for presswork excellent in low-temperature toughness and corrosion resistance according to the above-described (1) or (2), is characterised in that the above-described hot-dip plated layer is made of Zn of 1.0 to 8.8 mass%5 and a balance composed of Sn and inevitable impurities, and a plating deposition amount is 25 10 to 150 g/m? per one side. [0037] (4) ft The hot-dip plated high-strength steel sheet for presswork excellent in low-temperature toughness and corrosion resistance according lo any one nT the above-described (3) to (3), is characterised in that a secondary work britlleness resistance temperature after performing working on the 5 above-described high-strength steel sheet at a drawing ratio of 1.9 is -50°C or less. [0038] (5) The hot-dip plated high-strength steel sheet for presswork excellent in low-leraperalurc toughness and corrosion resistance according to any one of 10 the above-described (1) to (4), is characterised in that a ductile-brittle transition temperature of a coach peel seam weld zone of the above-described high-strength steel sheet is -40°C or less, [00391 (6) A manufacturing method of a hot-dip plated high-strength steel sheet 15 for presswork excellent In low-temperature toughness and corrosion resistance is characterised in that it includes, in a manufacturing method of manufacturing the hot-dip plated Jiigh-strength steel sheet for presswork excellent in low-temperature toughness and corrosion resistance according to any one of the above-described (1) to (5), a step of obtaining a slab by making 20 a molten steel having a chemical composition same as a chemical composition of the cold-rolled steel sheet according to the above-described (1) or (2) lo be subjected to continuous casting, a step of obtaining a hot rolled coil by heating the above-described slab at 1050 to 1245"C for a period of lime within 5 hours, completing, after the healing, hoi rolling at a 25 finishing temperature of Ar$ lo 910°C lo produce a hot roiled steel sheet, and then coiling the hot rolled steel sheet at a temperature of750°C or less, a step 12 of performing cold rolling on the above-described hot-rolled steel sheet at a cold-rolling ralio of 50% or more In produce a cold-rolled steel sheet, and then obtaining a cold-rolled coil, and a step of performing annealing on the abovc-described cold-rolled steel sheet at it temperature of recryslalli/alion 5 temperature or more, and then performing hot-dipping. [00401 (7) It is characterized in that in the manufacturing method of the hot-dip plated high-strength steel sheet for presswork excellent in low-temperature toughness and corrosion resistance according to the above-described (6), 10 hot-dipping containing Zn of 1.0 to 8.8 mass% and a balance composed of Sn and inevitable impurities, and whose plating deposition amount is 10 to 150 g/m2 per one side is performed in the step of performing the hot-dipping. [004 ij (8) Tl is characterized in that In the manufacturing method of the hot-dip 15 plated high-strength steel sheet for presswork excellent in low-temperature toughness and corrosion resistance according to the above-described (6) or (7), prc-plating of Ke-Ni is performed before performing the hot-dipping In the step of performing the hot-dipping. [Jiffccl of the Invention] 20 [0042] According to the present invention, it is possible to provide a hot-dip plated high-strength steel sheet for presswork having a tensile strength of 340 MPa or more and less (ban 540 MPa3 a press formability capable of being applied to a field of automobile, particularly a fuel tank, excellent secondary work brillleness resistance and toughness of coach peel weld zone 25 at low temperature, and excellent corrosion resistance. [Brief Description of the Drawings] 13 [0043J [FIGS. 11 FTGS. 1 are diagrams showing an appearance of a surface of base steel sheet after being subjected to annealing, and a spectrum of composite oxide remained on the surface, in which FIG 1(a) shows a photograph of scanning electron microscope (SEM) of the surface oTihe base 5 steel sheet, and FIG 1(b) shows an energy dispersive X-ray (EDX) analysis result of the composite oxide remained on the surface of the base steel sheet positioned at a pointed tip of arrow mark shown hi FIG 1(a); [FTGS. 2J FIGS. 2 are diagrams showing an appearance of a surface of base steel sheet after being subjected to pickling after hot rolling, and a spectrum 10 of oxide remained on the surface, in which FIG 2(a) shows a photograph of scanning electron microscope (SEM) of the surface of the base steel sheet, and FIG 2(b) shows an energy dispersive X-ray (EDX) analysts result of the composiie oxide remained on the surface of the base steel sheet positioned at a pointed tip of arrow mark shown in FTG 2(a); 15 [FIGS. 3] FIGS. 3 are diagrams showing an appearance of a surface of base steel sheet after degreasing and pickling and right before plating, and a spectrum of composite oxide remained on the surface, in which FIG 3(a) shows a photograph of scanning electron microscope (SEM) oi the surface of the base sleel sheet, and FIG 3(b) shows an energy dispersive X-ray (EDX) 20 analysis result of the composite oxide remained on the surface of the base steel sheet positioned at a pointed lip of anew mark shown in FIG 3(a); [FIG, 4] I'lG 4 is a diagram showing a relationship between "Si content in steel sheet" and "area ralie- of oxide remained on surface of steel sheet after degreasing and pickling, and right before plating11; 25 [FIG 5j FIG 5 is a diagram showing a relationship between "area ratio o^ oxide" and "SST red rust generation ratio"; 14 [FIG. 6j FIG. 6 is a diagram showing a cross section of lest piece having a coach peel seam weld zone; [FIG. 7] FIG. 7 is a diagram showing an influence of Ti amount and 11 amount on a ductile-brittle transition temperature of the coach peel seam weld zone; 5 [FIGS. 81 i'lGS. 8 are diagrams showing one example of a Fracture surface when a fracture occurs by giving an impact after a heat treatment test in which a weld beal-affceled /one is simulated, in which FTG 8(a) shows a SEM photograph of the fracture surface, and FIG. 8(b) shows an enlarged SliM photograph of a pari surrounded by a quadrangular frame in FIG. 8(a); 10 [FIG 9J FIG. 9 is a diagram showing a test method of evaluating a secondary work brillleness resistance; and [FIG. 10) FIG. 10 is a diagram showing an influence of P amount and H amount on the secondary work brittleness resistance. [Mode for Carrying out the Invention! 15 [0044] The present inventor conducted earnest studies regarding a method of solving (he problems which are difficult lo be solved by the conventional techniques, such that "a hot-dip plated high-strength steel sheet for prcsswork having excellent press formability, excellent secondary work brittleness resistance and toughness of coach peel wcid zone at low 20 lemperalure, and excellent corrosion resistance is obtained". [0045] As a result of this, the present inventor found out that by regulating respective amounts of Ti, B, P, Al and Si to fall within specific ranges, it Is possible lo realize a hot-dip plated high-strength steel sheet for presswork having a tensile strength of 340 MPa or more and less than 540 25 MPa, a press formabiHly capable of being applied lo a field of automobile, particularly a fuel tank, excellent secondaiy work brittleness resistance and 15 toughness of coach peel weld zone at low temperature, and excellent corrosion resistance. [0046] A hol-dip plated high-strength steel sheet for prcsswork excellent in low-temperature toughness and corrosion resistance of the present invention (which is sometimes referred to as "steel sheet of the present invention", hereinafter) is made based on the above-described findings, and is characterized in that in a high-strcngih steel sheet having a hot-dip plated layer on a surface of a cold-rolled steel sheet, the above-described cold-rolled steel sheet contains, by mass%, C: 0.0005 to 0.0050%, Si: 0.30% or less, Mn: 0.70 to 3.00%, P: 0.0.5% or less, Ti: 0.01 to 0.05%, Nb: 0,01 to 0.04%, B: 0.0005 to 0.0030%, S: 0,01% or less, Al: 0.01 to 0.30%, N; 0.0005 to 0,010%, and a balance composed of Fe and inevitable impurities, in which when the Ti content (%) is set to [Ti], the B content (%) Is set to [B], and the P content (%) is set to [PJ, T13* defined by the following expression is 0,03 to 0.06, and [B] and [P] satisfy the following expression , TB* = ( 0 J l - i T i ] ) / ( i n ( | _ R ] x 10000)) ••• [P] < 10 x [Bl I 0,03 - [0047] Hrst, reasons for limiting a chemical composition ol" the steel sheet of the present invention will be described. Hereinafter, % indicated in the chemical composition means mass%. [0048] C: 0.0005 to 0.0050% C is an important element that couples with Nb and Ti to form carbides, and contributes to an Improvement oT strength. liven if a C amount is small, the strength can be compensated by another strengthening method, but, when the C amount Is less than 0.0005%, it Is difficult to secure the strength, and further, a decarburization cost during steel making is increased, !6 so that a lower limit oT the C amount is set to 0.0005%. The lower limit is preferably 0.0010% or more. [0049] On the other hand, iT the C content exceeds 0.0050%, even if'fi and Nb fixing C are added, a workability is lowered, and a toughness of a coach peel seam weld zone is lowered, so that an upper limil of the C content is set to 0.0050%. When extremely high workability and toughness of weld zone are required, the C content is preferably set to 0,0030% or less. [0050J Si: 0.30% or less Si is an element that contributes to an improvement of strength through sol id-solution strengthening, and the present inventor conducted a salt spray Lest (SST) conducted under a severe environment compared to an actual environment of fuel lank, and set an upper limit of a content of Si based on a result of the test. [0051] The prevent inventor conducted earnest studies regarding a mechanism in which a red rust is generated on a surface of steel sheet, based on the result of the salt spray test (SST). As a result of this, the present inventor found out that on the surface of steel sheet, there exists "fine oxide31 estimated to be remained alter degreasing and pickling right before plating, in a deep portion of very small plating defect estimated to deteriorate the corrosion resistance. [0052J Here, FIGS. 3 show an appearance of a surface of base steel sheet aHer degreasing and pickling and right before plating, and a spectrum of composite oxide remained on the surface. FIG. 3(a) shows a photograph of scanning electron microscope (SFM) of the surface of the base steel sheet, and FIG. 3(b) shows an energy dispersive X-ray (FDX) analysis result of the composite oxide remained on the surface of the base steel sheet positioned at 17 a pointed tip of arrow mark shown io FIG. 3(a). The composite oxide remained on the surface of the base steel sheet in FIG 3(a) Includes one having a size of about 2 mil. [00531 Further, FIGS. 1 show an appearance of a surface of base steel 5 sheet at a processing stage before conducting Ihe degreasing and [he pickling applied io the base steel sheet in FIGS. 3, and after performing annealing, and a spectrum of composite oxide remained on Ihe surface. FIG. 1(a) shows a photograph of scanning election microscope (SliM) of the surface of the base steel sheet, and MG 1(b) shows an energy dispersive X-ray (EDX) analysis 10 result of the composite oxide remained on the surface of the base steel sheet positioned at a pointed lip of arrow mark shown in FTG 1(a). [0054J As a comparison, FIGS. 2 show an appearance ofa surface ofbase steel sheet at a processing stage before performing the annealing on the base steel sheet in FIGS, i and after pickling is conducted after hot rolling, and a 35 spectrum of oxide remained on the surface. FIG 2(a) shows a photograph of scanning electron microscope (SliM) of the surface of ihe base steel sheet, and FIG 2(b) shows an energy dispersive X-ray (EDX) analysis result of the composite oxide remained on Ihe surface of the base steel sheet positioned at a pointed lip o farrow mark shown in FIG. 2(a). 20 [00551 Although the reason why the line oxide remains even if the degreasing and the pickling are conducted before plating is not clear, on a surface of steel sheet aEler being subjected to annealing in a CAPL (continuous annealing and processing line), a composite oxide containing Si and Mn is remained, as shown in FIGS. 1. FIGS. 2 show, as a comparison, 25 an oxide remained on a surface of steel sheet afler being subjected to pickling after hot rolling, in which the oxide is an oxide containing only Si. IK [0056] As described above, the oxide remained on the surface of steel shcel after being subjected to the annealing in the CAVI, (continuous annealing and processing line) is complicated by being affected by an atmosphere. Therefore, even if the degreasing and the pickling are 5 performed on the surface of steel sheet, it is not possible to complelely remove the oxide iiom the surface of steel sheet, and thus the line oxide remains, [0057] The present inventor further conducted earnest studies, and as a result of this? it was found out that if an area ratio of oxide remained on the !0 surface of steel sheet is 3% or less in the entire surface, a size of each oxide becomes very small, and hot-dipping is performed on a surface of base steel sheet with this surface state, resulting in that a surface detect is decreased, and a corrosion resistance as a hot-dip plated steel sheet is remarkably improved. Further, it was found out that in order to set the area ratio of oxide to 3% or 15 less, it is required to set the content of Si to 0,3% or less. [005SJ Next, the present inventor examined a relationship between "Si content in steel sheet" and "area ratio of oxide remained on surface of steel sheet after degreusing and pickling and right before plating3', and a relationship between "area ratio of oxide" and "SST red rust generation ratio". 20 [0059] MO, 4 shows the relationship between the ,cSi content in steel sheet" and the "area ratio of oxide remained on surface of steel sheet after degreasing and piclcling and right before plating". bIG 5 shows the relationship between the "area ratio of oxide" and the "SST red rust generation ratio". Note that the chemical composition of the steel sheet used 25 in FIG. 4 and 11G 5 is as follows, C: 0.0005 to 0.0050%, Si: 1.5% or less, Mn: 0.70 to 3.00%, P: 0.05% or less, Ti; 0.01 to 0.05%, Nb: 0.01 to 0.04%, B: \9 0,0005 to 0,0030%, S; 0.01% or less, AI: 0.01 to 0.30%, N: 0.0005 to 0.010%, and a balance composed of Fe and inevitable impurities. [0060] From FIG 4, it can be understood that if the "Si content in steel sheet" is 0.30% or less, the "area ratio of oxide remained on surface of steel 5 sheet afler degreasing and pickling and right before plating" can be maintained to 3% or less. Further, from FKJ. 5, it can be understood that if the above-described "area ratio of oxide" is 3% or less, the "SST red rust generation ratio" can be maintained to less than 10%, Specifically, by selling the "Si eonlent in steel sheet" to 0.30% or less, the corrosion resistance 10 of the surface of the hot-dip plated steel sheet is remarkably improved, [0061] Rased on the above-described findings, an upper limit of the content of Si is set to 0.30%. The upper limit is preferably 0*25% or less. When the content of Si is 0.25% or less, the above-described "area ratio of oxide" can be reduced to 2% or less (refer to FIG 4), and Ihe "SS'l' red rust 15 generation ratio" can be reduced to less than 6% (refer to FKJ. 5). The upper limit of the content of Si is more preferably 0.20% or less. [0062] By setting the content of SI to 0.30% or less, it becomes possible to remove ihe scale (oxide) generated on the surface of Ihe base steel sheet without performing grinding with the use of a brush for heavy duty grinding, 20 which is normally conducted in a hot-dip galvanized steel sheet, resulting in that the corrosion resistance is improved. A bio fuel has a strong eorrosiveness, so that a hot-dip galvanized steel sheet containing SI of 0.30% or less is suitable for a steel sheet for a tank for biofuel. Note thai a lower limit of the content of Si is preferably set to 0.01%, and is mote preferably set 2.5 to 0.02%5 from a point of view of an improvement of strength through solid-solution strengthening and an improvement of workability. ?0 [00631 Mn: 0.70 to 3.00% Mn is an element that contributes to an improvement of strength through solid-solution strengthening and/or refining of structures, similar to Si, and is an important element tor increasing the strength of the steel sheet of 5 the present invention for the purpose of improving the secondary work brittleness resistance, the toughness of weld zone, and the hot-dip platability. [0064] If a Mn content is less than 0,70%, an effect of improving the strength cannot be obtained, and further, when die effect of improving the strength is tried lo be supplemented by adding another element, it is not 10 possible to obtain target secondary work brittleness resistance, target toughness of weld /.one, and target hot-dip platabilily (plating wettability with respect to the surface of steel sheet), so that a lower limit of the Mn content is set to 0.70%, and is preferably set lo 1.00% or more. If the Mn conlent is i.00% or more, structures of the steel sheet can be controlled even if a 15 hot-rolling finishing temperature is towered to 910I:'C or less, and as a result of this, it is possible lo improve Ihe low-temperature toughness, [0065J On the other hand, if the Mn content exceeds 3.00%, an In-plane anisolropy of r value being an index of deep drawabilily becomes large, resulting in that the press formabihty is impaired, and die hot-dip piatability is 20 impaired due to a generation of Mn oxide on the surface of sleel sheet, so thai an upper limit of the Mn content is set to 3.00%, and is preferably set to 2.50% or less. 10006] P: 0.05% or less P is an element which hardly causes the deterioration of workability, 25 and contributes lo an improvement of strength through solid-solution strengthening, but, it is also an element that deteriorates the secondary work 21 brittieness resistance by being segregated at a grain boundary, and deteriorate the toughness of the coach peel seam weld /one by solidifying and segregating at the weld zone. [0067] further, P is -an element which is segregated at the surface of steel 5 sheet due to a thermal history up to when the hot-dipping is conducted, to thereby deteriorate the hot-dip platability. If a P content exceeds 0.05%, these segregations are caused, so thai an upper limit of the P content is set to 0.05%, preferably set to 0.04% or less, and more preferably wet to 0.035% or less. 10 L0068) Although there is no need to particularly define a lower limit of the P content, if the P content is reduced to less than 0.005%, a refining cost is increased, so that the P content is preferably 0.005% or more. Further, the P content is preferably 0.02% or more in terms of seeurement of strength. [00691 Ti: 0.01 to 0.05% 15 Ti is an element which has a strong affinity with C and N, and forms carbonitrides during solidification or during hot rolling to reduee C and N solid-solved in the steel, Ihereby contributing to an improvement of workability. If a Ti content is less than 0.01%, an effect of adding Ti cannot be achieved, so that a lower limit of the Ti content is set to 0.01%, and is 20 preferably set to 0.015% or more. [0070] On the other hand, if the Ti content exceeds 0.05%, the toughness of weld zone of welded joint, namely, the toughness of the coach peel seam weld /.one deteriorates, so that an upper limit of the Ti content is set to 0.05%, and is preferably set to 0,04% or less. 25 [00711 Nb:(UH to 0.04% Nb is, similar 1o Ti, an element which has a strong affinity with C and 22 N, and forms earbo nitrides during solidification or during hoi rolling to reduce C and N solid-solved in Ihe steel, thereby contributing to an improvemenl of workability. If a Nb content is loss than 0.01%, an effect of adding Nb cannot bo achieved, so thai a lower limit of the Nb content is set to 5 0.01%, and is preferably set to 0.02% or more 10072J On ihe other hand, if the Nb content exceeds 0.04%5 a recrystallization temperature becomes high, high-temperature annealing has to be conducted, and the toughness of weld zone of welded joint, namely, the toughness of coach peel scam weld zone deteriorates, so that an upper limit of 10 the Nb content is set to 0.04%, and is preferably set to 0.035% or less. [0073] B: 0.0005 to 0.0030% B is an element that contributes to the improvement of secondary work brtttleness resistance by being segregated at a grain boundary to increase the grain boundary strength. If a B content is less than 0.0005%, an 15 effect of adding B cannot be achieved, so that a lower limit of the B content is set to 0.0005%, preferably set to 0.0008% or more, and more preferably set to 0.0010% or more. [0074] On the other hand, if the B content exceeds 0.0030%, B Is segregated at y grain boundary during welding to suppress a ferriie 20 transformation, structures of tlie weld /one and the heat-aflected zone become structures generated by low-temperature transformation, and Ihe weld /one and the heat-affected /.one are hardened and the toughness deteriorates, resulting in that the toughness of the coach peel seam weld /one deteriorates, so that an upper limit of Ihe B content is set to 0.0030%. 25 [0075] Further, if a large amount of B is added, a Territe transformation during hot rolling is also suppressed, resulting in that a high-strength 23 hot-rolled steel sheet having a structure generated by low-temperature trans formation is produced, and a load during cold rolling becomes high, so thai from this point as well, the upper limit of" the B content is set to 0,0030%. £0076] Further, if the B content exceeds 0,0030%, the recry s tail i/ati on 5 temperature becomes high, and annealing at high temperature has to be conducted, which increases manufacturing costs, and al ihe same lime, the in-plane anisotropy of r value being the index of deep drawability becomes large, and the press formability deteriorates, so thai from this point as well, the upper limit of the B content is set to 0.0030%, and is preferably sel to 10 0,0025% or less. L0077J S: 0.01% or less S, being an inevitably mixed impurily, couples wilh Mn and Ti to form precipitates to deteriorate the workability, so that a content of S is regulated to 0.01% or 3ess, and is preferably sel to 0.005% or less. Although a lower 15 limit of S content includes 0%, if the S content is reduced to less ihan 0.0001%, a manufacturing cost is increased, so that the S content is preferably 0.0001% or more, and is more preferably set to 0.001% or more. [0078] Al:0.01 to 0.30% Ai is an element used as adeoxidizcr at a lime of refining steel, but, it 20 is also an element which worsens the low-temperature toughness of the weM zone and the secondary work brittlcncss resistance if a content thereof is too much. Accordingly, in the present invention, it is important 1o regulate the Al content. If the Ai content is less than 0.01%, an effect of deoxidation cannot be achieved, so that a lower limit of the Al content is set to 0.01%, and 25 is preferably set to 0,03% or more. On the other hand, if the Al content exceeds 0.30%, the toughness of the coach peel seam weld /.one is lowered, 24 and further, the workability is lowered, so that an upper limit of the Al content is set io 0.30%, preferably 0.20% or less, more preferably less than 0.10%, and an optimum value thereof is 0,075% or less. r0079] N; 0.0005 to 0.010% N, being an element inevitably mixed at a time of refining steel, forms nitrides with Ti, Al and Nb, and although it does not exert adverse effect on the workability, it deteriorates the toughness of the weld zone, so thai a content oTN is regulated to 0.010% or less, and is preferably set to 0.007% or Jess. On the other hand, if the N content is reduced to less than 0,0005%, a manufacturing cost is increased, so that a lower limit of the N content is set to 0.0005%, and is preferably set to 0.0010% or more [0080] TR*: 0.03 to 0.06 TJ3* = (0.11 - fTil) / (In (rill x 10000)) ••• The present inventor found out that if TB* (index of strength of coach peel seam weld /one) defined by the above-described expression in which the content of Ti and the content of B which exert an influence on the toughness of the coach peei seam weld /.one are set to [Ti] and [BJ, respectively, becomes small, a tensile strength of the eoaeh peel scam weld zone is lowered. [0081J When the TB* is less than 0.03, a tensile strength at low temperature is significantly lowered. This is because a brittle fracture easily occurs due to the reduction in K>w-temperature toughness. [0082] Hereinafter, a test from which the present inventor obtained this finding will be described. [0083] Steels in which compositions were changed in ranges of C: 0.0005 to 0,0050%, Si: 0.30% or less, Mm 0.70 to 3.00%, P: 0.05% or less, Ti: 0.09% 25 or less, Nb: 0.01 to 0.04%, B: 0.03% or less, S: 0.01% or less, Al: 0.01 to 030%, and N: 0.0005 lo 0.010%, were produced in a vacuum melting furnace. [0084J liach oflhe produced steels was heated at 1200°C for 3 hour, the resultant was then subjected to hot rolling, and the hot rolling was completed at a finishing temperature of 880 to 9I0°C, thereby obtaining a hot-rolled sheet with a thickness of 3.7 mm. This hot-rolled sheet was pickled, and then subjected to cold rolling, thereby obtaining a cold-rolled sheet with a thickness of 1.2 mm. This cold-rolled sheet was subjected to annealing at 800°C for 60 seconds, the resultant was then subjected to be-Ni plafing of I g/m , and then subjected to Sn-/.nplating using a Mux method. [0085] AstheFe-Ni plating bath, a Watts bath of Ni plating to which 100 g/L of iron sulfate was added, was used. As a flux, an aqueous solution of ZnC^-NTijC.l was applied by a roll. The plating was conducted in a Sn-Zn plating bath containing Xn of 7 wl%. A bath temperature was set to 280"C, and after the plating, a plating deposition amount was adjusted by gas wiping. [0086J Turther, the steel sheet after being subjected to the hot-dipping was subjected to treatment in which Cr was mainly used, thereby obtaining a hot-dip plated steel sheet. By using the hot-dip plated steel sheet, the toughness of the coach peel seam weld zone was evaluated. The evaluation was conducted in the following manner. [0087] As illustrated in MG 6, hot-dip plated steel sheets la, lb after being subjected to bending were faced each other in a coach peel configuration and seam-welded, to thereby produce a test piece having a weld /.one 2 (coach peel scam weld zone). Horizontal parts of the hot-dip plated steel sheets 1 a3 1 b were fixed by a chuck, a tensile force was applied (pec! test 26 was conducted) at a rate of 200 inm/min under various temperatures, and after a fracture occurred, a fracture surface was examined. In the fracture surface, a temperature at which a percentage of brittle fracture surface and that of ductile fracture surface became 50% and 50%, was set to a ductile brittle transition temperature (°C). [0088] FIG 7 shows an influence of Ti amount and B amount on the ductile-brittle transition temperature of the coach peel seam wekl zone, in which a horizontal axis indicates the B amount (ppm), and a vertical axis indicates the Ti amount (%), Ihe ductile-brittle transition temperature is preferably in a temperature range in which a temperature corresponding to the lowest temperature (-40°C) in a cold district in which an automobile is used is set lo an upper limit, namely, it is preferably -40UC or less, and is more preferably -50°C or less. [0089] As illustrated in FIG. 7? if TI3* defined by the following expression is 0.03 or more, the ductile-brittle transition temperature can be set to -40°C or less, and if the TB* is 0.035 or more, the ductile-brittle transition temperature can be set to -50°C or less. TB* = (0.11 - [Til) / (in (fBl x 10000)) ••• [0090"| Based on the above-described test results, it is possible to make a deduction as follows. [0091 ] (i) When the Ti amount is large, TIN is generated, which becomes a starting point of fracture. FTGS. 8 show an example of fracture surface when a cold-rolled steel sheet in which a Ti amount is 0.1% and thus exceeds 0.05%, and Ihe other components fall within the range of the present invention is manufactured;, the steel sheet is subjected to a heat treatment test in which a welding is simulated, and the steel sheet is fractured after an 27 Impact is given thereto (FIG. ft(a) shows a. fracture surface when the fracture occurs, and FTG. 8(b) shows an enlarged fracture surface of a pait surrounded by a quadrangular frame in FIG 8(a)), in which it can be considered that when the Ti amount is large, TIN of about 2 to 3 \im Is generated, which becomes a 5 stalling point of fracture. [0092] (ii) When the B amount is large, the hardness of the weld/one and the hcat-affectcd /.one is increased, or the hardened region is enlarged, resulting Jn that when a tensile force acts on the coach peel seam weld /one (refer to FIG, 6), the coach peel seam weld zone is difficult to be deformed. 10 Therefore, it can be considered that the stress concentrates in one part to be locally Increased, resulting in that the toughness is lowered. It can be considered that since the influences of (i) and (ii) coexist, even if the contents of Ti and B are within the above-described ranges, the low-temperature toughness deteriorates when the TB* is less than its lower IS limit value (0.03). [0093J Based on the above-described test results and deduction, the TB* is set to 0.03 or more. The TB* is preferably 0.035 or more. An upper limit of the TB* is 0.06 based on the ranges of the Ti amount and the B amount. 20 T0094J pJl == 10x[B] + 0.03 The present invenlor found out that if the V content ([?]) and the B content ([B]) are controlled to maintain a relationship defined by the following expression , the secondary work brillleness resistance is improved. 25 |P1 ^ K)x[B] + 0I}3 .- [0095] Hereinafter, a test from which the present inventor obtained this 28 finding and results thereof will be described. [0096] The present inventor produced steels in which compositions were changed in ranges of C: 0.0005 to 0.0050%, Si: 0.30% or less, Mn: 0.70 to 3.00%: P: 0.09% or less, Ti: 0.01 lo 0.05%, Nb: 0.01 to 0.04%, B: 0.0030% or 5 less, S: 0.01% or less, Al: 0.01 to 0.30%, and N: 0.0005 to 0.010%, in a vacuum melting furnace. [00971 Haeh of Ihe produced steels was heated al 1200°C for 1 hour, the resultant was then subjected to hot rolling, and the hot rolling was completed al a finishing temperature of 880 lo 910°C, thereby obtaining a hot-rolled ]<) sheet with a thickness of 3.7 mm. This hot-roiled sheet was pickled, and then subjected to cold rolling, thereby obtaining a cold-rolled sheei with a thickness of 1.2 mm. This cold-rolled sheet was subjected to annealing at 800°C for 60 seconds, the resultant was then subjected lo Fe-Ni plating of 1 g/m , and then subjected to Sn-Zn plating using a flux melhod. 15 [00981 As the Fe-Ni plaling bath, a Watts bath ofNi plating to which 100 g/L of iron sulfate was added, was used. As a (lux, an aqueous solution of ZnCl?-NH4Cl was applied by a roll. The plating was conducted In a Sn-Zn plating bath containing Zn of 7 wt%. A bath temperature was set lo 2R0°C3 and after the plating, a plating deposition amount was adjusted by gas wiping. 20 [00991 1'uriher, the sleel sheet after being subjected lo the hot-dipping was subjected to treatment in which Cr 4 was mainly used, thereby obtaining a hoi-dip plated steel sheet. By using the hot-dip plated steel sheet, the secondary work britticness resistance temperature was examined. The examination was conducted in the following manner. 25 [0100] A blank material with a diameter of 95 mm was collected from the hot-dip plated steel sheet, and a cylindrical drawing with a drawing ratio of 29 1.9 was performed using a punch with an outside diameter of 50 mm, to thereby manufacture a drawn cup, TIG 9 shows a test method of evaluating the secondary work brittleness resistance. As shown in FIG. 9, a drawn cup 3 was placed upside down on a truncated cone 4 with a base angle of 30°, a weight 5 having a weight of 5 kg was dropped from a position of a height of 1 m under various temperature conditions, and die Jowesl temperature at which no crack occurred on the drawn cup (secondary work brittlcness resistance temperature) was ex am in ed. [0101] Results thereof are presented in FIG. 10, as an influence of P amount (%) and H amount (ppm) on the secondary work briltleness resistance. The working of the steel sheet for fuel tank is normally conducted with a drawing ratio corresponding U> 1.9 or less, so that the secondaiy work brittleness resistance temperature after performing the forming work at a drawing ratio o\' 1.9 is preferably in a temperature range In which a temperature corresponding to the lowest temperature (-40°C) in a cold district in which an automobile is used is set to an upper limit, namely, it is preferably -40°C or less, and is more preferably -50°C or less. [01021 As shown in FIG. 10, if the P amount (%) ([PJ) and the B amount (%) ([Bj) satisfy the following expression , the secondary work brittleness resistance temperature after performing the forming work at the drawing ratio of 1,9 can be set to -50°C or less. [P] < 10 x [Bj-t-0,03 - [0103] One or two or more of Cu: 0.005 to 1%, Ni: 0.005 to 1%, Cr: 0.005 to 1%, and Mo: 0.0005 to 1% The present inventor found out that by further adding Cu, Ni, Cr and Mo, in addition Lo the above-described basic composition, it is possible to 30 lower the yield strength (YP) and to secure the workability while securing the tensile strength* For ibis reason, in the present invention, it is set that Cu, Ni, Or and Mo are appropriately contained according to need. f0104] Bach content of Cu, Ni and Cr is preferably set lo 0.005% or more 5 by which an effect of adding the element can be achieved, and is more preferably set lo 0.01% or more. A content of Mo is set to 0.0005% or more by which an effect of adding Mo can be achieved, anil is preferably sel lo 0.001% ormore. [0105J On the other hand, if each content of Cu, Ni, Cr and Mo exceeds 10 1%: tbe secondary work brittleness resistance and the toughness of the coach peel seam weld zone are lowered, and an alloy cost is increased, so that each content oi^ Cu, Ni, Cr and Mo is set to 1% or less, preferably set to 0.5% or less, and more preferably, each content of Cu and Mo is set lo 0.75% or less, and each content of Ni and Cr Is set to 0.4% or less. 15 [0106] Note thai tbe balance of Ihe sleel sheet of the present invention is composed of Fe and inevitable impurities. [01071 fhe sleel sheet of the present invention has the above-described chemical composition, so that it has a tensile strength of 340 MPa or more and less lhan 540 MPa, and a press form-ability capable of being applied to a 20 field of automobile, particularly a fuel tank, and in addition lo that, it is excellent in low-temperature toughness. Therefore, according to the steel sheet of the present invention, El becomes possible lo improve a fuel economy by reducing a weight of vehicle body of an automobile, and in particular, it becomes possible to realize a reduction in weight and a complicated shape of 25 a hiel tank. This effect is an extremely large effect from industrial point of view, 33 |"GI08j Next, a manufacturing method oT the steel slice! of ihe present invention will he described. [01091 A raw material in which amounts of respective elements are adjusted to achieve the above-described chemical composition, is put in a converter or an electric furnace, and a vacuum degassing treatment is conducted, to thereby manufacture a slab. Ihe slab is heated at 1050 to 1245°C for a period of time within 5 hours, hot rolling is completed at a finishing temperature of Ai\ to 910°C to produce a hot-rolled steel sheet, and thereafter, the bet-rolled steel sheet is coiled at a coiling temperature of 750':C or less, to thereby obtain a hot-rolled coil. [0110] A heating temperature of the slab is required to be 1050°C or more for securing a rolling temperature, and in order to suppress the generation of coarse ThN which causes the reduction in toughness, to suppress the growth of coarse austemte grains, and farther, to suppress a heating cost, ihe heating temperature of ihe slab is set to i245°C or less, and a heating time is set to 5 hours or less. 101II] In particular, the coarse TiN reduces the toughness of the coach peel seam weld zone, so that heating conditions, in addition to the restriction of TB*5 are important requirements. Although the technique described in Patent Documents 13 and 14 is a technique of improving ihe properties of base material, the toughness of the coach peel seam weld zone is lowered depending on (he heating conditions and conditions regarding the TBS. TO 112] Tithe finishing temperature in ihe hoi rolling is less than Ar3, the workability of steel sheet is impaired, so that the finishing temperature is set to A^ or more. Hy setting the finishing temperature in die hot rolling to 910"C or less, it is possible to control structures of the steel sheet to improve 32 the low-temperature toughness. Further, if the coiling temperature after the hot roiling exceeds 750°C, the strength of steel sheet after cold rolling and annealing is lowered, so that the coiling temperature is set to 750°C or less. [0113] The hot-rolled steel sheet produced in the above-described method 5 is subjected to descaling, according to need, and then subjected to cold rolling at a rolling ratio of" 50% or more, thereby obtaining a cold-rolled steel sheet with a predetermined sheet thickness. If the rolling ratio is less than 50%, the strength of sleel sheet after annealing is lowered, and a deep drawability deteriorates. Note that the rolling ratio is preferably 65 to 80%, and at the 10 rolling ratio, it is possible to obtain a hot-dip plated steel sheet with further excellent strength and deep drawability. [0114] After that, the cold-rolled steel sheet is subjected to annealing at a temperature of equal to or more than a recry si alligation temperature. If the annealing temperature is less than the recrystaliization temperature, a good 15 texture is not developed, and the deep drawability deteriorates. The annealing temperature is preferably equal to or more than "recrystaliization temperature H- 20°C". On the other hand, if the annealing temperature becomes high, the strength of steel sheet is lowered, so that the annealing temperature is set to 850°C or less, preferably set to 840°C or less, and more 20 preferably set to 83(TC or less. [0115] Tn order to suppress an oxidation at the time of annealing, the annealing is preferably conducted in an atmosphere in which hydrogen of 20% or less is mixed in nitrogen, and a dew point is -60 to 0C'C. if an operation load is also taken into consideration, an atmosphere in which 25 hydrogen of 2 to 8% is mixed In nitrogen, and a dew point is -50 to -10°C is more preferable. 33 [01161 I lot-dipping is performed on a surface of the cold-roiled steel sheet, to thereby produce a hot-dip plated steel sheet. The hot-dipping may be conducted in the middle oT cooling after die annealing, and further, it may also be conducted by performing reheating after the annealing. 5 [OH 7] As the hot-dip plated sleeE sheel, one obtained by forming a hot-dip plated layer of Zn, Zn alloy, Ai, Al alloy, Sn-Zn or the like on a surFace oi' sleel slieet, can be cited, and when the corrosion resistance is considered as important, a Sn-Zn hot-dip plated steel sheet having a hot-dip plated layer made of Zn of 1.0 to 8.8 mass%: and a balance composed of Sn 10 and inevitable impurities, arid whose plating deposition amount is 10 to 150 g/m2 per one side, is preferable. [0118] A chemical composition of the hot-dip plated layer is limited based on a balance between a corrosion resistance of an inner suilace and that of an outer surface of a fuel tanks I be outer surface of the fuel lank requires ]5 a perfect rust prevention performance, so that coating is performed after the forming, A thickness of coaling determines the rust prevention performance, and In the steel sheet, the generation of red rust is prevented by a corrosion prevention performance of the hot-dip plated layer. Tn a portion which is not coated enough, ihs corrosion prevention performance of the hot-dip pialed 20 layer is extremely important. [0119] 13y adding Z.n to Sn-based plating, an electric potential of plating layer is lowered, resulting in that a sacrificial corrosion prevention performance is given. In order 1o achieve this, ii is preferable lo add Zn of 1.0 mass% or more to the plating layer, and it is more preferable to add Zn of 25 3.0 mass% or more lo the plating layer. [0120J However, if Zn exceeding 8.8 mass%, which corresponds to a 34 binary Sn-Zn euteelie point, is added, a melting point is increased to facilitate the growth of coarse Zn crystal, and further, an excessive growth of inlermelaMic compound layer below the pialing (so-called alloy layer) is facilitated, so that the content of Zn is set to 8.8 mass% or- less, and is preferably set to 8.0 mass% or less, [0121] A deposition amount of Sn-Zn plating is preferably set to 10 to 150 g/m2 per one side. If the above-described deposition amount is Jess than 10 g/m per one side, good corrosion resistance cannot be secured, antl further, if the above-described deposition amount exceeds 150 g/m , a cost of plating is increased, and in addition to that, a layer thickness becomes non-uniform, resulting in that the plating layer exhibits a mottled appearance (defect), and further, Ihc weldabiMty is lowered. Therefore, the deposition amount of Sn-Zn plating is preferably set to 10 to 150 g/m per one stde? and is more preferably set lo 20 to 130 g/m per one side, [0122j In order to improve the platability of Sn-Zn plating, it is preferable to perform, before the plating, pre-plating of Fe-Ni. The pre-plating of Fe-Ni is effective to increase the wettability of Sn-Zn plating, and to improve the corrosion resistance by relming primary eryslal Sn. [0123] The pre-pJaiing of Fe-Ni is an important technique for effectively using Si and Mn which deteriorate the platability (plating wettability with respect to steel sheet), for increasing the slrenglh, and is one of characteristics of the present invention. Note that the Fe-Ni pre-plating also exhibits an effect of improving the plating wettability when hol-dipping of Zn3 Zn alloy, Al, Al alloy or the like, other than the Sn-Zn plating, Is employed. [0124] Tn the pre-plating of Fe-Ni, a deposition amount per one side is preferably 0.2 g/m or more from a point of view of the plating wettability, 35 and a proportion of Ni is preferably 10 to 70 mass% from a point of view of refining of primary crystal Sn. [0325] In the hot-dip plated steel sheet of the present invention manufactured through the above-described method, it is also possible to 5 further provide an electroplated layer on the surface of the hot-dip plated layer according to need. [Examples) [0126] Hereinafter, the feasibility and the effect of the steel sheet of the present invention will be described based on invention examples and 10 comparative examples, in which Invention examples 1 to 20 are examples adopted for confirming the feasibility and the effect of the present invention, and the present invention is not limited to these invention examples 1 to 20. The present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the gist of the present 15 invention, [0127] (Examples) Steel slabs having chemical compositions presented in Table 1 and Table 2 (continued from fable 1} were produced, the sleel slabs were subjected to slab healing at temperatures and for periods of time presented in 20 Table 3, hot roiling was then completed at finishing temperatures presented in Table 3, and coiling was conducted at coiling temperatures presented in fable 3, thereby obtaining hot-rolled sheets each having a thickness of 3,6 mm. Note that balances of the chemical compositions presented in Tabic 1 and Tabic 2 are composed of Fe and inevitable impurities. An underline in Tabic 25 1 and Table 2 indicates a value which is out of the present invention. ' J l o "3 . ~1 Id _ = =? J n " i H ,- " I H £« u i £ =. c e a i s & ft _ £ •^ o 3 K a " o X COMPARATIVE EXAMPLE P A $ ™ P P * S * r5 p a* U S p £ 5 L ; - P ^ -.e _ P r-j m " J a i~i P !_• | b ! C i 1 1 " r j ? O 1 C S("S ft !_i p P U o a a -1 u 1 iLLi j i 1 i _ £ *J c ". ( j o » >•. »-J »; - i " .- hi _ J— i / p ! e , — 5 ' H c • - Ci ! i i i P i P c : c - ! - • = i = ft p & '.& J= & H ' - I O I C ^ ^ | p C (5 • e o ;C i n'-K fc<* o ; o- >-, J •-, * P ^ L'J c * £ o " £ •_! X ft K> • " I M -•"i - • • ,_J P " % ro P r-o I f r p a a f£ 3 Ss o c? L c c !-• ft " i Y o i ^ ^ •-• o t b * > * s CJ * C ^ i ^ i a 1 c o c — K UJ 1 IT ] I -, £ is " o c p & l—n "" •"I -1 P K ^ r- ?- r* -> « m c __ r-. K a b fc -^ ^ i - i ^ o j i r-i p| n W " S VK ' - I ^ s " ^ i~. ^ ^ im ^ ' - i C5 w ^ •-• fe is ^ o u, Q ^ U •-v nc P •>; P P u c "Ir f 1= ? ,_ u c 1 ^ g •5 g 5 INV1-NTI0K EXAMPL ^ r-i O ? ^ - i g. P o g 1 s ? .1 a *< n * •a 3 r> b •^ - • • - • i i W = i t*i n 5 n ^ a n S< " S " ^ P t rj o o p i n ^ ^ ,_ & ^ « d : ~ O * t r, ^ CG « ^ «c : r - g •5 s ^ ? •JD Cl « * a o 4 e * ,v" p iK - x I", Co i-i _ - i a ,-rf ' i s y i I-I X n *i ^ • 1 ~ l r o 1 o - i o a C-5 r-i - J <"i o S o i*3 O i D o 5 |-> COMPARATIVE EXAMPLE £ 1 wo i - . o | J Si1 g ; i i 1 i i i & • "o ' I M i ' i : 1 '• i i ! \P 1 1 i l l 1 1 ! 1 r | CO =• o I D (-) ! i : I • I P ? U l n - i ? - - L 1 • - I a M 1 1 1 • - i Cl | T J i " o OS J .-. c o :r, h i n * iZ. ^ 5 - J r-r CI n o -*z i ^ ft r o i -i ? ^ £ 1 •"-• £? O C M O i n o W I'-I o ' - I (Jl o o .--- 1 l - l n o t o o o ( j i 1*1 3 i " E 1 I I I o ? —1 .-> ~> f•rt, r o 1 1 o £ " a J - , -s J O I 1 ^ 1 1 r i 1 1 1 1 1 f i P P R*ft o -" i 1 ] | • a o to CJ 1 1 1 " r o O CJ <-* O • - > n o • -• s a i ' i o 40 m 'D n r o <-• o i-i Ol n £ j • ^ c j * 7 ] r n < j r i £ „ hO r* C= r-- o Lv Tr- - ^ 1 g ro |-J t a 1 1 r l ft i_i '•h o Ul d 1 1 • ~ l Ni J - C r o —i R r i O W •Ji o •-1 1 1 1 -"1 ' 1 cs u J » o s r r i> ^ - i __ j i p • " . L-l f i ^ 5 V. INVENTION EXAMPLE u o ru 1 I o 1 o O ! ro i i 1 o - -1 t-1 ; W 1 ° 'is i i i O | Cf t o s i i f • c^ l" 1 CJ w _. l - i • -1 1 1 a ' - i u> ' ' o a 1 1 n M 3 J * ^ ^ r • i > 4 i t c [?- .& a o 1 r-. t o -»• r1' O o i CC -J 1 o o r-, i -l 1 • " ' ^ o 4 i I 1 1 O Ul ' - I o I-I-^ ' 1 1? en 1 o" o ' o 38 [0130] [Table 3j c > -1 X w < o V l h h l 1 2 3 A 5 6 7 a 9 10 17 13 re 15 IB 17 • a 21 p? 2 i 24 2S ?6 2? 23 30 3E a? 33 34 M.'NI II 'i HRATSNG 11 h^HI 17 Aiia:"- IlPl bCOfl 1P30 11M 1245 USD 1200 HOU 1245 IZUU 11150 1230 1230 USD 1245 1150 17QO i i o o i ? « i 1220 1200 1?30 1MK) 1050 12G0 lira i sso 1P30 1201] 1P?0 TO.IF 3 2 4 1 4 3 * & J 4 1 2 i 4 2 5 3 3 ? i 3 2 3 4 3 3 7 1 4 5 3 "LMKtNCi I IIMIIJKIN-LIS 1111 L" 111.11 ttOLLSNG Mi 1 hHI'hS An?R5- . M . 69G Ettlfl E1ITO y i o 50? 3B& 863 3132 era 8G? 394 803 324 3S7 000 373 373 0(?5 390 DOG BOO m5 057 373 eoo H03 002 SD7 300 SGS 904 UlO A*. POi>ir m vo r 737 eso 037 7 M 330 7/a 025 003 72G 030 J t i i 030 JV4 R3fi 7GU 731 731 340 fl70 790 B3ft 700 7bfl 744 E27 703 B^Li 001 791 CDILIIXi ThMPhJi All'M-. 0P5 6UQ 0P4 &15 50S 634 653 650 07H e l l 705 GB3 30? em 649 322 760 G73 57B GSfl 625 633 572 •aa 621 G3B 500 (Ml 635 600 SOS B is 753 357 KLIi I.I If 1 b l_ COLLI 1_IIE_L1 IU1I 1 ENir 1-L.lllLi (10 B a t 60.4 OEM fiB.rft 69 4 03 4 69.4 09 J 69 4 09 4 09 4 Q9 4 60 4 69 4 034 no 4 00 4 6D.4 60 4 60 4 30.4 60.4 30.4 BS\A 09 3 fl'Jii 69.4 G94 09 4 694 hi)-! L'ibELU ANNE, TEMPEb 1" •LVllLaE. IfcG ILKCTH A J l i t i I t . 8D3) 793 774 7E5 330 015 302 770 ?93 B?4 a 13 79P tiOb 30D aro 733 aao 77ft no 004 m'J ?n V32 30fi 3 f3 709 -no BOO 7S5 623 7J3 OH EI-JLi ^LING JbL'URE • El R7ST i l : . I'.l N nu TTAFflli! riHUt) fi!16 761 7 !2 636 730 772 7D6 726 701 732 1?? 676 74? 702 &3R 3flJ 7RP 6^3 74 j £9* 746 770 701 631 70? m 730 tiGl 315 706 747 726 706 722 CONE}] [IONS O l ' E1U"] -DEPP1NU I'l i\ i I A H ; 1 iP,1l1")Sll lOrt Sn-liMA-.-.%Zn Gn 7"A';';%Zi> S n - a « A ' ; ' ; 5 i ^ j , Gn- 4 j i A i i % Z i i Sfi-£MASs%Zn Sn^ OMA'.'.SbZii Sn-yfL"^J%Zr> Sn 7'iA,\\%Zr> Sn-6MASS%Zn Sn-4KLA^%Zn Kn-5fciAYi%2it S n - - 7 M . ^ 9 6 Zn ! i n - 7 ' i ' " % Z n S n - 7 " A « W Z n K n - 7 " ^ " ' * & 7 f i K n - S S»ti--^%Zn S n - 7 . M A i i « 2 j i E>j.-GMUi%7n ! i r i - 6 " A i ; ? S i Z j i S H - 7 M A S S % 7 H S J V ' 7 M A ^ % Z I > 7n £ n - 0 . 4 M < ^ % Zn Sn •10KIAiS"h7^ Gn 7ii^ss%Zn S r i - 7 m " ' % Z " G n - 7 M ' i ' 9 l i Zn S»-7M.vss5t,?p Sn -"^MASS'Wiln yy. A"i IMCI lH'I'OSl IS(h>J A.MOIPNT (P&EONl:iEDE> 3 0 & / n i ' 3 0 n / m ! S O E W 4oa . / | 1 1 J 5 0 j ; / m ? a i i f i / m * 7 0 F / m ? 0 5 a / w a ^Og/m^ 8 D f i / m a 6 0 g ' r n ? 3 0 e / r t i* ! 2 0 e / m v « f t / m * 1 3 0 e W 4 0 g ' m ^ O i i K / i r , ' ? 3 g / m J 47K/mT 30K/rriT 23U(-/m? 'JUsh-f? 39 [01311 ^ nc above-described hot-rolled steel sheets were pickled, and then subjected to cold rolling at cold-rolling ratios presented in Table 3, to thereby produce cold-roiled steel sheets each having a thickness of" 1.1 mm. The cold-rolled sheets were subjected to annealing at annealing temperatures 5 presented in Table 3 tor 60 seconds. The annealed steel sheets were subjected to electrolytic degrcasing in a solution of NaOIJ. of 40 g/L at IS^C, electrolytic pickling was then performed in a solution of H2SOJ of 120 g/L at 30"C, next, Fe-Ni plating was performed with a deposition amount oT 1 g/m per one side, and then Sn-Zn plating was performed using a flux method. 10 [0132] As the Fe-Ni alloy plating bath, a Walls bath of Ni plating to which 100 g/L of iron sulfate was added, was used. As a flux, an aqueous solution of ZnCh-NJ £]CI was applied to surfaces oTdic steel sheets by a roll. [0133] Table 3 presents compositions of Sn-Zn plating baths, A bath temperature was set to 280°C, and after the plating, plating deposition 15 amounts (per one side) were adjusted by gas wiping. Tabic 3 also presents the pialing deposition amounts (per one side). [0134J The steel sheets after being subjected to the hot-dipping were subjected to treatment in which Cr" was mainly used, to thereby produce hot-dip Sn-Zn plated steel sheets to be the invention examples and die 20 comparative examples. Hot-dip Zn plating was performed on a part of the steel sheets in the middle of*cooling after the above-described annealing. [0135] Regarding the hot dip plated steel sheets of the invention examples and the comparative examples, the tensile properties, the r value being an Index of deep drawing, the secondary work brittlcncss resistance, the 25 low-temperature toughness of coach peel seam weld zone and the corrosion resistance were evaluated. Methods of evaluation arc as follows. 40 [0136J Regarding the tensile properties, a tensile test was conducted by collecting a JTS No. 5 lest piece, from each oT the hot-dip plated steel sheets, so that a tensile direction became parallel to a rolling direction, and the tensile strength (IS), the yield strength (YP), and elongation (Rl) were evaluated, 5 The steel sheet with the elongation (Ei) of 28% or more was judged as passed. [01371 ^n e r value was measured by collecting JTS No. 5 tensile lest pieces from each of the hot-dip plated steel sheets in three directions of a direction parallel to the rolling direction, a direction inclined by 45° from the roiling direction, and a direction, orthogonal to the rolling direction. The 10 evaluation was conducted based on an average value r ave of r values determined by the following expression ? in which an r value parallel to the rolling direction was set to r0, an v value in the 45" direction was set to r4^ and an r value in Ijie orthogonal direction was set to r4<>. The steel sheet whose rave was 3.10 or more was judged as passed. 15 r ave = (r(f + 2 x r45 + r 9 0}/ 4 - O [0138J The secondary work brittleness resistance was evaluated in a manner that a drawn cup manufactured by collecting a blank materia! with a diameter of 95 nun from each of the hot-dip plated steel sheets, and performing a cylindrical drawing using a punch with an outside diameter of 20 50 mm, was placed upside down on a truncated cone with a base angle of 30°, a weight having a weight of 5 kg was dropped from a position of a height of 1 m under various temperature conditions, as shown in FIG, 9, and the lowest temperature at which no crack occurred on the drawn cup (secondary work britUeuess resistance temperature) was determined. 25 [0339] Although the secondary work brittleness resistance temperature changes depending on a sheet thickness of steel sheet and a method of test, in 4! the present examples in which the sheet thickness of each of the cold-rolled steel sheets was 1.1 mm? the temperature of -5U°C or less was judged as passed. [0140J The toughness of the coach peel seam weld zone was evaluated in a manner that a lest piece shown in FIG. 6 was produced, horizontal paits of hot-dip plated steel sheets la, ib were fixed by a chuck, a tensile force wan applied at a rale of 200 mm/min under various temperatures, a fracture surface after the occurrence of fracture was examined, and a temperature at which a percentage of brittle fracture surface arid that of ductile fracture surface became 50% and 50%, was determined as a duclile-briule transition temperature (°C). The steel sheet in which the temperature became -40°C or less was judged as passed, [0141J The corrosion resistance was evaluated by conducting a salt spray tesl (SSI) being a test under a severe environment compared to an actual environment of fuel tank based on J1S Z 2371. The steel sheet in which Ihe red rust generation ratio after 1000 hours was 10% or less was judged as passed. [0142] Results of the above-described evaluation are presented in Table 4. 42 [0I43J [Tabic 41 IKVEXT10N" EXAMPLE a? 2- < —i > < P. O u STEEL t 2 3 ft 5 6 7 8 3 SO SI !2 13 14 35 10 17 IB 19 7U 23 ?2 23 24 25" 26 ?? 23 30 si 32 S3 3-1 ILNSLLLl'KOI'Ll VEMII 1 nnsiih ^TFFfjTH 1 ^lEFHlTTH If.1 I'll 1 If.iHjl 301 [ 4GI 237 [ 397 ?S3 [ 4?3 323 j 493 dm | 403 202 | 362 ?0rt | 306 205 1 420 W4 j 394 255 ?3l 227 221 040 343 2^0 240 ?fift 229 326 305 317 351 264 204 214 26b 233 273 244 300 171 320 354 4J0 391 J07 39 k 500 SOB •100 400 426 309 436 405 477 551! 424 391 374 416 143 433 #14 4130 307 407 632 11LS GlffllGATJQU H ... -30 3 36 9 29-0 30-9 435 A24 307 42 1 03.0 4 (2 42.5 ZfU 2B.3 mo 3B.0 :i6.B 415 29.6 P4.3 29.7 £3,4 36.3 Vtttt 27.4 2b I 34 3 2.7.9 3«5 31.9 ?3J 27.0 ? J j l ',- 1.35 1 77 1 60 1 20 1311 1 93 1.01 1.59 1.36 l.fih 1.31 IK4 133 1 f3 l . t l i 76 170 I5U 103 1.13 1.24 O.'JV 3.59 i 02 309 1P_& 1.47 1.09 T i l l 1 30 1.IIJ 3,09 j . 03 "iH(J*JUAK7VfllKt. t IfII E-Efe 1—IJKI 1 E1 2 RE^IST/LHCE: TEhlT[?A"rcjREOrCQACII ILMPISAIURL f HJL.\LAhlWILUZLh\L -50 [ -00 "70 j -GO 60 •so - 70 -40 -HO I -40 -BO is 0.03 to 0.06, and fB] and [F] satisfy the following expression . T B * - ( 0 J 1 [Tl])/(ln([B]x 10000)) - [P] ^ 10 x [B] + 0.03 *» [Claim 2] The hot-dip plated high-strength steel sheet for presswork 25 excellent in low-temperature toughness and corrosion resistance according to claim 1, wherein the cold-rolled steel sheet further contains, hy mass%> one or two or more of Cu: 0.005 to 1%, Ni: 0,005 to i%5 5 Cr: 0.005 to l%,and Mo: 0.0005 to 1%. [Claim 3J The hot-dip plated high-strength steel sheet for presswork excellent in low-temperature toughness and corrosion resistance according to claim i or 2, wherein 10 Uie hot-dip plated layer is made of Zn of 1.0 to 8.8 mass%> and a balance composed of Sn and inevitable impurities, and a plating deposition amount is 10 to 150 g/m? per one side. [Claim 4] The hot-dip plated high-strength stcci sheel for presswork excellent in low-temperature toughness and corrosion resistance according to 15 any one of claims i to 35 wherein a secondary work biittleness resistance temperature after performing working on the high-slrengili steel sheet at a drawing ratio of 13 is -50°C or less. f Claim 5} The hot-dip plated high-strength steel sheet for presswork 20 excellent In low temperature toughness and corrosion resistance according to any one ofdaims 1 to 4, wherein a ductile-brittle transition temperature of a eoaeh peel seam weld /one of the high-strength steel sheet is -40°C or less. [Claim 0J A manufacturing method of a hot-dip plated high-strength steel 25 sheet ihr presswork excellent in low-temperature toughness and corrosion resistance comprising: in a manufacturing method of manufacturing the 0 hot-dip plated high-strength steel sheet for press work excellent in low-tciiipcrature loughnesy and corrosion resistance according to any one of claims 1 to 5, a step of obtaining a slab by making a molten steel having a chemical 5 composition same as a chemical composition of the cold-rolled steel sheet according to claim 1 to 2 to be subjected to continuous casting; a step of obtaining a hot-rolled coii by heating the slab at 1050 to 3 245°C for a period of time within 5 hours, completing, after the heating, hot rolling at a finishing temperature of Ar^ to 910UC to produce a hot-roiled steel !0 sheet, and then coiling the hot-rolled steel sheet at a temperature of 750°C or less; a step of performing cold rolling on the hot-rolled steel sheet at a cold-roiling ratio of 50% or more to produce a cold-rolled steel sheet, and then obtaining a cold-rolled coll; and 15 a step of performing annealing on the cold-rolled steel sheet at a temperature of recrystalhzation temperature or more, and then performing hot-dipping. [Claim 7J The manufacturing method of the hot-dip plated high-strength sleel sheet for presswork excellent in low-temperature toughness and 20 corrosion resistance according to claim 6, wherein hot-dipping containing Zn o(" 1.0 to 8.8 mass% and a balance composed of Sn and inevitable impurities, and whose plating deposition amount is 10 to 150 g/m per one side is performed in the step of performing the hot-dipping, 25 [Claim 8] The manufacturing method of the hot dip plated high-strength steel sheet for presswork excellent in low-temperature toughness and < > • coirosion resistance according to claim 6 or 7, wherein pro-pjtiling of l?e-Ni is performed betbie performing the hol-dipping in ihestep of performing the hot-dipping.