[Technical Field of the Invention] [000 I] The present invention relates to a steel H-shape for low temperature service used as a structural member or the like of a building used in a low-temperature environment, and a manufacturing method therefor_ Priority is claimed on Japanese Patent Application No. 2016-039957, filed on March 02, 2016, the content of which is incorporated herein by reference. !Related Art l [0002] Recently, construction of related facilities entailing resource development in cold regions is increasing. It is necessary for structures built in such cold regions to use a steel H -shape having excellent low temperature toughness. [0003] In response to such a demand, for example, in Patent Documents 1 to 3, a method in which toughness of a steel H -shape is enhanced by refining a metallographic structure has been proposed. In the method. oxides which become a nucleation site of ferrite are utilized, and accelerated cooling is performed after hot rolling in order to suppress grain growth of ferrite. According to Patent Documents 1 to 3, it is possible to obtain a steel H-shape exhibiting excellent Charpy absorbed energy at -5'C or -IO'C. However, recently. lovv temperature toughness (for example, toughness at AO'C) required to steel Hshapes used a cold region has not been sufficient. - 1 - [0004] In addition, for example, Patent Document 4 has proposed a steel H-shape having the Charpy absorbed energy equal to or greater than 27 J at -40°C and excellent low temperature toughness_ In Patent Document 4, the C content or the nitrogen content (amount of solute N), which is solid-solubilized in a steeL is reduced without adding Nb, V, or the like, and the low temperature toughness of a steel II-shape is improved by applying accelerated cooling. However, in Patent Document 4, although toughness of a base metal is evaluated, low temperature toughness of a welded heat-affected zone is not taken into consideration. In Patent Document 4, N is fixed by Ti, TiN is generated, and the amount of solute N is reduced. However, if a steel is heated to 1 ,400°C or higher through welding, TIN is solid-solubilized in the steeL As a result, it is concern that a coarse structure is generated in a heat affected zone, particularly in the vicinity of a fusion line (FL)_ That is, in a case where TiN is formed and the amount of solute N is reduced as in Patent Document 4, although there is a certain effect of improving toughness of a base metal, there is a concern that low temperature toughness is degraded in a welded heat-affected zone (HAZ)_ [Prior Art Document] [Patent Document] [0005] [Patent Document 1] Japanese Unexamined Patent Application, First Publication No. HS-263182 [Patent Document 2] Japanese Unexamined Patent Application, First Publication No. HS-271754 [Patent Document 3] Japanese Unexamined Patent Application, First 2 Publication No. H7-216498 [Patent Documenl4] Japanese Unexamined PatenlAppl.ication, hrst Publication No. 2006-249475 [Disclosure of the Invention] [Problems to be Solved by the Invention] [0006] The present invention has been made in consideration of the foregoing circumstances, and an object thereof is to provide a steel I-l-shape for low temperature service, in which while strength required for a structural member is ensured, low temperature toughness of not only a base metal but also a welded heat-affected zone is improved, and a manufacturing method therefor. [Means fO< Solving the Problem] [0007] Nb is an element generating precipitates, such as carbides and nitrides, and is an element which adversely affects toughness in general and of which the amount is thereby limited as in Patent Document 4. However, Nb is an element suppressing recrystallization and contributing to grain refinement and is an element useful for an enhancement of strength_ Therefore, the inventors have attempted to ensure strength and toughness of a steel H-shape by containing Kb and applying accelerated cooling. [0008] As a result of investigation, the inventors have found that in a case where Nb is contained, low temperature toughness can be ensured by increasing a cooling rate of the accelerated cooling and promoting refinement of a structure. In addition, it has been found that the amount of an alloying element for enhancing hardenability can be reduced by performing the accelerated cooling so that, as a result generation of a hard 3 phase can be suppressed and low temperature toughness of a base metal can be ensured. [0009] Moreover, the inventors have found that the structure in the vicinity ofFL is refined and low temperature toughness of a HAZ is improved by causing Ti oxide (generic name for TiO, Ti02, and Tb03, and is sometimes called TiOx), which becomes a nucleation site for intragranular ferrite in a steeL to precipitate. Specifically, it has heen found that since TiOx refines coarse austenite in the vicinity of FL by generating intragranular ferrite~ generation of intergranular fenite or coarse bainite is suppressed and low temperature toughness of the HAZ is improved. [0010] On the other hand, it has been found that in a case where TiOx is utilized, TiN in a steel is reduced and initial austenite is likely to be coarse, thereby resulting in a problem of degradation of toughness of a base metal due to the formed coarse structure_ In regard to this problem, the inventors have newly found that low temperature toughness of a base metal can be ensured by strictly controlling conditions for accelerated cooling after hot rolling. [0011] The present invention has heen made based on the knowledge described above, and the gist thereof is as follows. [0012] (l) According to an aspect of the present invention, there is provided a steel I-1-shape for low temperature service including, by mass%, C: 0.03% to 0.!3%, Mn: 0.80% to 2.00%, Nb: 0.005% to 0.060%, Ti: 0.005% to 0.025%, 0: 0.0005% to 0.0100%, V: 0% to 0.08%, Cu: 0% to 0.40%, Ni: 0% to 0.70%, Mo: 0% to 0.10%, Cr: 0% to 0.20%, Si: limited to 0.50% or less, A!: limited to 0.008% or less, Ca: limited to - 4 - 0.0010% or less, REM: limited to O.OOJ 0% orless, Mg: limited to O.OOJ 0% or less, N: limited to 0.0120% or less, and a remainder including ofPe and impurities. A CEV obtained by the following Expression (a) is 0.40 or less. The sum of an area ratio of one or both of ferrite and bainite at a 1/4 position from an outer side across a thickness of a flange and a l/6 position from an outer side across a flange width is 90% or more, and the area ratio of a hard phase is 10% or less. The effective grain size is 20.0 rtm or less. and the grain size of the hard phase is 10.0 fll11 or less. 30 pieces/mm2 or more Ti oxides having an equivalent circle diameter ranging from 0.01 to 3.0 fUll are included. The thickness of the flange is 12 to 50 mm. CEV=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/l5 ... (a) here, C. Mn, Cr, Mo, V, Ni, and Cu each indicate an amount of the element by mass%. (2) The steel H-shape for low temperature service according to (1) may include, by mass%, one or two or more selected from the group consisting of V: 0.01% to 0.08%, Cu: 0.01% to 0.40%, Ni: 0.01% to 0.70%, Mo: 0.01% to 0.10%, and Cr: 0.01% to 0.20%. (3) According to another aspect of the present invention, there is provided a method of manufacturing the steel H-shape for low temperature service according to (l) or (2). The method of manufacturing the steel H-shape for low temperature service includes melting a steel including the same chemical composition as that of the steel H-shape for low temperature service according to (l) or (2), casting the steel obtained through the melting to obtain a slab, heating the slab to a temperature ranging from 1,1 OO'C to l,350'C, and then performing hot rolling at a finishing temperature ranging from (An-30)'C to 900°C to obtain a steel H-shape, performing an accelerated cooling of the steel H-shape, in which inner and outer surfaces of a fld tbe welded heat-affected zone at -:zooc is 0.40 mm or greater, and it is more preferable tbat a brittle fracture such as pop-in is not generated. The toughness oftbe welded heat-affected zone is evaluated while setting a fusion line (FL) at which the welded heat-affected zone is heated to tbe highest temperature and becomes coarse grains, as a notch position. As an index indicating toughness of a steel, the Charpy absorbed energy and a CTOD value indicate tendencies similar to each otber. However, the correlation ship therebetween is not clear, and even if the Charpy absorbed energy satisfies the target value, it is not possible to mention tbat the CTDD value satisfies the target value. It is determined that the steel H-shape for low temperature service according lo the present embodiment has excellent low temperature toughness in the case where both the Charpy absorbed energy and the CTOD value satisfy the target value. [0045] ="ext, a metbod of manufacturing a steel H-shape for low temperature service - 20 - ----;-,---- according lo the present embodiment will be described. The sled H-shape for low temperature service according to fhe present embodiment is manufactnred as follows. A slab obtained by casting a molten steel, which is melted to have a predetermined chemical composition, through continuous casting or the like is heated in a healing furnace as shown in FIG 5. Hot rolling including rough rolling, intermediate rolling. and finish rolling is performed by using a roughing milL an intermediate rolling mill, and a finishing milL Then, accelerated cooling is performed by using a full face water cooling device. In the hot rolling, fhe rough rolling may be performed as necessary. and the rough rolling may be omitted. Hereinafter, each step will be described. [0046] (Oxygen content in molten steel immediately before Ti is added: 0.0015% to 0.0110%) In a melting step and a casting step (not shown), fhe chemical composition of a steel (molten steel) is adjusted to fhe above-described range by any method, and a slab is obtained. However, in a case where fhe steel H-shape for low temperature service according to the present embodiment is obtained, in order to form Ti oxides in the steel, there is a need lo control the oxygen content included in the molten steel immediately before Ti is added, when fhe component is adjusted. In order to ensure a sufficient amount for forming Ti oxides, the oxygen content in the molten steel is set to 0.0015% or more. The oxygen content is preferably 0.0025% or more. Mearwhile. in order to ensure low temperature toughness, there is a need lo suppress generation of cmu·se - 21 - oxides. Therefore, the oxygen content in the molten steel (oxygen concentration) is limited to O.Cll 10% or less. The oxygen content is preferably 0.0090% or less and is more preferably 0.0080% or less. TI1cn Ti is added, and casting is performed after the chemical composition of the molten steel is adjusted as necessary, thereby obtaining a slab. ]n regard to casting, frm11 a viewpoint of productivity, continuous casting is preferably performed. In addition, from a viewpoint of productivity, the thickness of the slab is preferably set to 200 mm or more. In consideration of reduction of segregation, homogeneity of the heating temperature in hot rolling, and the like, the thickness thereof is preferably 350 rrun or less. [0047] Next, the slab is heated by using a heating furnace, and hoi rolling is performed. The hot rolling includes rough rolling performed by using a roughing mill, intermediate rolling performed by using an intermediate rolling mill, and finish rolling performed by using a finishing milL The rough rolling is a step performed as necessary before the intermediate rolling and is performed in accordance with the thickness of the slab and the thickness of a product In addition. as the intermediate rolling, interpass water cooling rolling may be performed by using an intermediate universal rolling mill (intermediate rolling mill) and a water cooling device (not shown). [00481 (Heating temperature of slab: l.lOO'C to 1 ,350'C) The heating temperature of the slab subjected to hot rolling is set to range from L 100°C to 1,350'C. If the heating temperature is low. deformation resistance mcreases. Accordingly, in order to ensure plasticity in the hot rolling, the heating 22 temperature is sello l,l 00°C or more. In order to sufficiently solid-solubilize an element such as Nb which forms precipitates. the heating temperature of the slab is preferably set to J J50'C or more. Particularly, in the case where the thickness of a product is small, since cumulative rolling reduction becomes significant large, the heating temperature of the slab is preferably set to L200°C or higher. Meanwhile, if the heating temperature of the slab exceeds L350°C, oxides on the surface of the slab (material) arc fused and the inside of the heating furnace is damaged sometimes. Therefore, the heating temperature is set to l,350°C or lower. In order to have a fine structure, the heating temperature of the slab is preferably set to 1,300°C or lower. [0049] ln the intermediate rolling of hot rolling, controlled rolling may be performed. The controlled rolling is a rolling method performed by controlling a rolling temperature and the rolling reduction. In the intermediate rolling of hot rolling, interpass water cooling rolling processing is preferably executed 1 pass or more. The interpass water cooling rolling processing is a method of rolling in which a temperature difference is caused between the surface layer area and the inside of the flange by performing water cooling between rolling passes. In the interpass water cooling rolling processing, for example, after the flange surface is water-cooled to a temperature of 700°C or lower in the water cooling between the rolling passes, rolling is performed in a recuperating process. [0050] In a case where the interpass water cooling rolling processing is performed, water cooling between the rolling passes is preferably performed by using water cooling devices (not shown) provided in front of and behind the intermediate universal rolling mill, and it is preferable that spray cooling on the outer surface of the flange by the water cooling devices and revc·rse rolling are repetitively performed_ In the interpass water cooling rolling processing, even in a case where the rolling reduction is small, processing strain can be introduced to the inside across the thickness. In addition, productivity is also improved by decreasing the rolling temperature in a short period of time in water cooling. [0051] (Finishing temperature of the hot rolling: (An-30)'C to 900°C) The finishing temperature of the hot rolling is set to range from (An-30)°C to 900'C If the finishing temperature exceeds 900°C, coarse austenite remains after rolling. If this coarse austenite is transformed into coarse bainite after cooling, the coarse bainite becomes an origin of a brittle fracture, so that toughness is degraded. The finishing temperature is preferably set to 850°C or lower. In consideratiou of the shape acwracy and the like of the steel H-shape, the finishing temperature of the hot rolling is set to be equal to or higher than (An-30)'C which is a start temperature of fenite transformation. Ars can be obtained by the following Expression (2). In the following Expression (2), C, Si, Mn, Ni, Cu, Cr, and Mo each indicate an amount of the element by mass%. In a case where the elements are not contained, Ar3 is obtained hy setting the amounts thereof to zero. [0052] Ar3=868-396xC+24.6xSi-68.1 xMn-36.lxNi-20.7xCu-24.8xCr+29.6xMo _ (2) [0053] In addition, as hot rolling, a manufacturing process in which hot rolling (primary rolling) is performed by heating a slab to a temperature ranging from l ,1 oooc to J ,350°C, and after being cooled to 500°C ot·Iower, hot rolling (secondary rolling) is - 24 - performed by heating the slab to a temperature ranging from Ll00°C lo 1,350°C again. that is, so-called double heat rolling may be employed. In the double heat rolling, since the amount of plastic deformation per time in the hot rolling is small and the decrease in temperature in the rolling step also becomes small, the heating temperature can be lowered. [0054] <:Accelerated cooling step> After the hoi rolling ends, the inner surface and the outer surface of the flange of the as rolled steel are subjected to the accelerated cooling by the water cooling device (full face water cooling device) provided on tbe output side of the finishing milL Air cooling is pe1formed within a section from the finishing mill to the fuU face water cooling device. However, even if the start temperature of ihe accelerated cooling is equal to or slight! y lower than tbe finishing temperature of ihe hot rolling, the characteristics are seldom affected. In addition, since the inner surface and the outer surface of tbe flange are subjected to the accelerated cooling, the cooling rate of ihe inner and outer surfaces of the flange becomes uniform, so that tbe material and the shape accuracy can be improved. On ihe upper surface of the web, the upper surface side is cooled by cooling water sprayed onto ihe inner surface of the !lange. In order to suppress ihe warpage ofihe web, the web may be cooled from the lower surface side. [0055] (Cooling rate of accelerated cooling: faster than 15 'C/sec) For example, tbe accelerated cooling of both the outer surface and ihe inner surface of a flange 2 of a steel H-shape 1 is performed through spray cooling by a water cooling device shown in FIG 1 (cooling performed by cooling water 5 from a spray nozzle 4). In order to suppress coarsening of the effective grain size and 25 generation of a hard phase constituted of one or both of pseudo-pearlite and MA. to improve toughness. and to enhance strength due to the effect of quenching. the cooling rate of the accelerated cooling is set to be faster than 15 "C/sec. \Vhen the accelerated cooling is executed at the cooling rate faster than 15 °C/sec and the structure is refined. even if Nb of 0.005% or more is contained, low temperature toughness can be ensured. On the other hand. since TiOx is generated in the steel H-shape for low temperature service according to the present embodiment, TiN in the steel is reduced and initial austenite is likely to be coarse. Therefore. if the accelerated cooling rate is 15 °C/sec or slower, degradation of toughness due to generation of a coarse structure becomes remarkable. The cooling rate of the accelerated cooling is preferably set to 18 °C/sec or faster and is more preferably set to 20 °C/sec or faster. The upper limit for the cooling rate of the accelerated cooling is not limited. However. in consideration of the shape accuracy, the upper limit is preferably 50 °C/sec or slower. In the present embodiment, as shown in FIG 7, the cooling rate of the accelerated cooling is calculated by dividing a temperature difference (LIT) between the surface temperature when the accelerated cooling starts and the surface temperature after recuperating by a water cooling time (Lih). A time U'-tz) from the end of water cooling to the completion of recuperating is not considered. [0056] (Cooling stop temperature: 300°C or lower) The accelerated cooling is performed until the surface temperature of the steel H-shape becomes 300°C or lower. lfthe surface temperature of the steel H-shape when cooling stops (when water cooling ends) exceeds 300"C. toughness is degraded due to an increase in hard phase or coarsening of the stmcture. [0057] - 26 - (Highest temperature in recuperating: 350°C to 700"C) The temperature of the surface of the steel H-shape decreases fast through the accelerated cooling compared to the temperature of the inside. However. after the accelerated cooling stops, the temperature rises due to thermal conduction from the inside, thereby being equal to the internal temperature. In the present embodiment, the accelerated cooling is performed such that the maximum temperature to which the surface temperature reaches after such recuperating is controlled to a temperature within a certain range. Specifically, the accelerated cooling is performed such that the highest temperature on the surface at the l/6 position from the outer side across the flange width after recuperating r-anges from 350°C to 700°C. If the highest temperature in recuperating exceeds 700°C, toughness is degraded due to coarsening of the effective grain sizeor·an increase in hard phase (mainly pseudo-pearlite). Meanwhile, if the highest temperature becomes lower than 350°C, low temperature toughness is degraded due to an enhancement of strength or an increase in hard phase (mainly MA). As shown in FIG 3, low temperature toughness of the steel H-shape (base metal) is improved when the recuperated temperature after the accelerated cooling is 350°C to 700°C of, so that the low temperature toughness becomes equal to or greater than 60 J which is the target [0058] After the accelerated cooling. heat treatment may he executed in order to adjust strength and toughness. This heat treatment may be performed at a temperature (Acr) or less at which transformation to austenite stmis and is preferably performed within a range from 1 oooc to 700°C. More preferably, the lower limit is set to 300°C and the upper limit is sello 650°C. Stillmore preferably, the lower limit - 27 - is set to 400°C aJJd the upper limit is set lo 600"C [Examples] [0059] Next, Example of the present invention will be described. The conditions for Example are examples of conditions employed to check the feasibility and the effect of the present invention. and the present invention is not limited to the examples of conditions. The present invention caJJ employ various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention. [0060] Steels having the compositions shown in Table 1 and 2 were melted, and slabs having a thickness ranging from 240 to 300 mm were manufactured through continuous casting. The steels were melted by using a converter, and the amount of dissolved oxygen was adjusted. Thereafter, the component was adjusted by adding an alloy including Ti, and vacuum degassing was performed as necessary. The obtained slabs were heated under the conditions shown in Tables 3 and 4, hot rolling was performed, and accelerated cooling was executed. TI1e recuperated temperatures in Tables 3 and 4 denote the highest temperature in recuperating after the accelerated cooling has stopped. In the hot rolling, subsequent to rough rolling, spray cooling and reverse rolling were performed with respect to the outer surface of the flange by using an intermediate universal rolling mill and water cooling devices provided in front of and behind the intermediate universal rolling milL The components shown in Table 1 and Table 2 were obtained by performing chemical analysis of samples collected from the manufactured steel H-shapes.In addition, the samples were collected from the position at which the test pieces used for measuring the mechanical characteristics were collected. The metallographic structure in a region \Vithin a rectangle of 500 Jlm (longitudinal direction) x 400 Jlm (thickness direction of the flange) was observed by using an optical microscope. Then. the sum of the area ratio of one or both of ferrite and bainite, and the area ratio of the hard phase and the grain size were measured. It was also checked that the remainder was pearlite by observing the metaUographic structure. The effective grain size was measured by the EBSD. The number ofTi oxides having an equivalent circle diameter ranging from 0.01 to 3.0 Jlm was measured in a region of 4 mnl or greater using samples collected from a portion similar to that in the evaluation of the metallographic structure, preparing extraction replicas, and using the TEM. claims. l. A steel H-shape for low temperature service, the steel comptising, by C: 0.03% to 0.13%, Mn: 0.80% to 2.00%, Nb: 0.005% to 0.060%, Ti: 0.005% to 0.025%, 0:0.0005% to 0.0100%, V: 0% to 0.08%, Cu: 0% to 0.40%, Ni: 0% to 0.70%, Mo: 0% to 0.10%, Cr: 0% to 0.20%, Si: limited to 0.50% or less, AI: limited to 0.008% or less, Ca: limited to 0. 0010% or less, REM: limited to 0.0010% or Jess, Mg: limited to 0.0010% or less, N: limited to 0.0120% or less, and a remainder including of Fe and impurities, wherein a CEV obtained by lhe following Expression (1) is 0.40 or less, wherein at a 1/4 position from an outer side across a thickness of a flange and a 1/6 position from an outer side across a flange width, a sun1 of an area ratio of one or both of ferrite and bainite is 90% or more, and an area ratio of a hard phase is 10% or less, wherein an effective grain size is 20.0 f!m or less, and a grain size of the hard phase is 10.0 11m orless. wherein 30 pieces/mm2 or more Ti oxides having an equivalent circle diameter ranging from 0.01 to 3.0 fllll are included, and wherein a thickness of the !lange is 12 to 50 rnm, CEV=C+Mni6-t-(Cr+Mo+V)/5+(Ni+Cu)/l5 ... (1) where, C, Mn, Cr, Mo. V, Ni, and Cu each indicate an amount of the element by mass%. 2. The steel H-shape for low temperature service according to Claim 1, comprising, by mass%, one or two or more selected from the group consisting of V: 0.01% to 0.08%, Cu: 0.01% to 0.40%, Ni: 0.01% to 0.70%, Mo: 0.01% to 0.10%, and Cr: 0.01% to 0.20%. 3. A method of manufacturing the steel H-shape for low temperature service according to Claim 1 or 2. the method comprising: melting a steel including the same chemical composition as that of the steel H-shape for low temperature service according to Claim 1 or 2; casting the steel obtained through the melting to obtain a slab; heating the slab to a temperature ranging from l,lOO'C to 1,350'C, and then performing hol rolling at a finishing temperature ranging heating the slab to a temperature ranging from l,lOO'C to 1,350'C, and then performing hol rolling at a finishing temperature ranging from (An-30)"C to 900°C to - 40 - obtain a steel H-shape; and performing an accelerated cooling of the steel H-shape, in which inner and outer surfaces of a flange are subjected to water cooling at a cooling rate exceeding 15 °C/sec, wherein in the melting, Ti is added after oxygen concentration of a molten steel immediately before addition of the Ti is adjusted to a range from 0,()015 to 0_0110 n1asso/o, and wherein in the accelerated cooling, the water cooling is performed such that a cooling stop temperature at a l/6 position from an outer side across a flange width of the steel H-shape is 300°C or lower at a surface temperature, and a maximum temperature of the surface temperature after recuperating is 350°C to 700°C