WO2018066019A1 - Steel for crude oil tanker and crude oil tanker - Google Patents

Steel for crude oil tanker and crude oil tanker Download PDF

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Publication number
WO2018066019A1
WO2018066019A1 PCT/JP2016/004508 JP2016004508W WO2018066019A1 WO 2018066019 A1 WO2018066019 A1 WO 2018066019A1 JP 2016004508 W JP2016004508 W JP 2016004508W WO 2018066019 A1 WO2018066019 A1 WO 2018066019A1
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Prior art keywords
crude oil
less
steel
steel material
resistance
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PCT/JP2016/004508
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French (fr)
Japanese (ja)
Inventor
至 寒澤
塩谷　和彦
博司 池田
慶一郎 岸
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Ｊｆｅスチール株式会社
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Application filed by Ｊｆｅスチール株式会社 filed Critical Ｊｆｅスチール株式会社
Priority to KR1020197012152A priority Critical patent/KR102259444B1/en
Priority to CN201680089864.2A priority patent/CN109844153B/en
Priority to PCT/JP2016/004508 priority patent/WO2018066019A1/en
Priority to JP2017548311A priority patent/JP6260756B1/en
Priority to TW106129672A priority patent/TWI654316B/en
Publication of WO2018066019A1 publication Critical patent/WO2018066019A1/en
Priority to PH12019500756A priority patent/PH12019500756A1/en

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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
    • B65D88/00—Large containers
    • B65D88/02—Large containers rigid
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur

Definitions

  • a crude oil tank (oil tank part) of a crude oil tanker formed by welding steel materials, in particular, an upper deck back surface (ceiling part) and an upper side wall where local corrosion occurs, and local corrosion (pitting corrosion) occur.
  • the present invention relates to a steel material for a crude oil tanker that can be suitably used for any bottom plate of an oil tank section and has excellent corrosion resistance and lamellar resistance.
  • the present invention also relates to a crude oil tanker using the above steel material.
  • steel materials such as the bottom plate of a crude oil tank are conventionally considered to be free from corrosion due to the corrosion inhibition effect of the crude oil itself and the corrosion inhibition effect of a protective coat (oil coat) derived from crude oil formed on the inner surface of the crude oil tank. It was. However, recent research has revealed that bowl-shaped local corrosion (pitting corrosion) occurs in the steel plate of the crude oil tank bottom plate.
  • Patent Document 1 “In mass%, C: 0.01 to 0.3%, Si: 0.02 to 1%, Mn: 0.05 to 2%, P: 0.05% or less, S: 0.01% or less, Ni: 0.05 to 3%, Mo: 1% or less, Cu: 1% or less, Cr: 2% or less, W: 1% or less, Ca: 0.01% or less, Ti: 0.1% or less, Nb : 0.1% or less, V: 0.1% or less, B: 0.05% or less, and the steel material for cargo oil tank which consists of remainder Fe and impurities. " Is disclosed.
  • Patent Document 2 “In mass%, C: 0.01 to 0.2%, Si: 0.01 to 1%, Mn: 0.05 to 2%, P: 0.05% or less, S: 0.01% or less, Ni: 0.01-1%, Cu: 0.05-2%, Sn: 0.01-0.2%, Cr: 0.1% or less, Al: 0.1% or less, and the balance Fe And cargo oil tank steel made of impurities. " Is disclosed.
  • a crude oil tank of a crude oil tanker usually welds a bottom plate and a hopper plate, an upper deck back plate and a longi material, and the welded joint receives a tensile stress in the thickness direction.
  • lamellate is a welded joint that receives tensile stress in the thickness direction, such as a cross joint, T joint, and corner joint, and cracks develop in the steel material in the direction parallel to the steel sheet surface due to the tensile stress. Is a phenomenon that occurs.
  • the steel material for crude oil tankers is required to have excellent lamellar tear resistance in addition to the above-mentioned corrosion resistance against the overall corrosion and local corrosion of the crude oil tank.
  • the steel material of the cited reference 1 does not take into consideration any mechanical properties such as lamellar resistance. Further, even in the steel material of Cited Document 2, no consideration is given to the lamellar resistance.
  • the cited references 1 and 2 do not consider the risk of occurrence of lamellar tears in welded joints. Therefore, when the steel materials of the cited references 1 and 2 are used in a crude oil tank of an actual crude oil tanker. There is a concern that lamellar tear may occur in the welded joint.
  • the present invention has been developed in view of the above-described situation, and is excellent in corrosion resistance against the overall corrosion of the upper deck back surface and the upper side of the crude tank inside the crude oil tank and the local corrosion of the bottom plate, and also has a lamellar resistance.
  • the object is to provide an excellent steel material for crude oil tankers.
  • Another object of the present invention is to provide a crude oil tanker using the above steel material for crude oil tankers.
  • the gist configuration of the present invention is as follows. 1. % By mass C: 0.03-0.18% Mn: 0.10 to 2.00% P: 0.030% or less, S: 0.0070% or less, Al: 0.001 to 0.100%, Sn: 0.01 to 0.20% and N: 0.0080% or less, Cu: 0.01-0.50%, Ni: 0.01-0.50%, Sb: 0.01-0.30% W: 0.01-0.50% Mo: 0.01 to 0.50% and Si: 0.01 to 1.50% Containing one or more selected from among the above, the remainder having a component composition consisting of Fe and inevitable impurities, Steel material for crude oil tankers with Sn segregation degree of less than 18.
  • the degree of Sn segregation is defined by the following equation (1).
  • [Sn segregation degree] [Sn concentration in central segregation part] / [Average Sn concentration] --- (1)
  • the component composition is further mass%, Cr: 0.01-0.50% and Co: 0.01-0.50%
  • the component composition is further mass%, Ti: 0.001 to 0.100%, Zr: 0.001 to 0.100%, Nb: 0.001 to 0.100% and V: 0.001 to 0.100% 4.
  • the steel material for a crude oil tanker according to any one of 1 to 3 above, which contains one or more selected from among the above.
  • the component composition is further mass%, Ca: 0.0001 to 0.0100% Mg: 0.0001 to 0.0200% and REM: 0.0002 to 0.2000% 5.
  • the steel material for a crude oil tanker according to any one of 1 to 4 above, which contains one or more selected from among the above.
  • the component composition is further mass%, B: 0.0001-0.0300% 6.
  • B 0.0001-0.0300% 6.
  • a crude oil tanker comprising the steel material for a crude oil tank according to any one of 1 to 6 above.
  • the steel material for crude oil tankers which is excellent in the corrosion resistance in the corrosive environment of the crude oil tank inner surface of a crude oil tanker, ie, both general corrosion resistance and local corrosion resistance, and is excellent also in the lamellar tear resistance. And by using the steel material for crude oil tankers of the present invention for the crude oil tank of the crude oil tanker, it becomes possible to reduce the cost for inspection and painting of the crude oil tank while ensuring high safety.
  • C 0.03-0.18%
  • C is an element necessary for securing the strength of steel.
  • the C content is 0.03% or more.
  • the C content is in the range of 0.03 to 0.18%.
  • they are 0.04% or more and 0.16% or less.
  • Mn 0.10 to 2.00%
  • Mn is an element that increases the strength of steel. In order to obtain such an effect, the Mn content is 0.10% or more. However, if the amount of Mn exceeds 2.00%, the toughness and weldability of the steel will decrease. Further, the lamellar resistance is also lowered by the central segregation of Mn. Therefore, the Mn content is in the range of 0.10 to 2.00%. Preferably they are 0.60% or more and 1.80% or less. More preferably, it is 0.80% or more and 1.60% or less.
  • the P content is 0.030% or less. Preferably it is 0.025% or less. More preferably, it is 0.015% or less.
  • the lower limit is not particularly limited, but is preferably 0.003%.
  • S 0.0070% or less
  • S is an important element involved in local corrosion resistance and lamellar resistance. That is, S is a harmful element that forms MnS, which is a non-metallic inclusion, becomes a starting point of local corrosion, and reduces local corrosion resistance. Therefore, it is desirable to reduce S as much as possible. In particular, when the amount of S exceeds 0.0080%, the local corrosion resistance is significantly reduced. Coarse MnS is the starting point for lamellar tears. In particular, if the amount of S exceeds 0.0070%, the lamellar resistance is greatly reduced. Therefore, from the viewpoint of achieving both local corrosion resistance and lamellar resistance, the S content is 0.0070% or less. Preferably it is 0.0060% or less. More preferably, it is 0.0050% or less. The lower limit is not particularly limited, but is preferably 0.0003%.
  • Al 0.001 to 0.10%
  • Al is an element added as a deoxidizer, and the Al content is 0.001% or more. However, if the Al content exceeds 0.10%, the toughness of the steel decreases. For this reason, the Al content is in the range of 0.001 to 0.10%.
  • Sn 0.01-0.20%
  • Sn is an element necessary for improving local corrosion resistance and overall corrosion resistance, and is an important element involved in lamellar resistance, in other words, improving corrosion resistance while reducing lamellar resistance. It is an element to be made. That, Sn, in strongly acidic local corrosion environments such as the bottom plate of a crude oil tank, to form a poorly soluble film on the surface of the steel, Cl to promote corrosion - inhibiting the diffusion of (chloride ions), thereby , Has the effect of increasing corrosion resistance. In addition, Sn is incorporated into the rust on the steel surface in a mildly acidic overall corrosive environment such as the upper back of a crude oil tank, and suppresses diffusion of anionic species such as SO 4 2- that promotes corrosion.
  • the Sn content is 0.01% or more.
  • the effect of addition of Sn is large.
  • the Sn amount is easily segregated at the center of the steel material, and in such a segregated part, the hardness is remarkably increased, so that the lamellar resistance is deteriorated.
  • the Sn content is 0.20% or less.
  • it is 0.15% or less. More preferably, it is 0.10% or less.
  • N 0.0080% or less Since N is a harmful element that lowers toughness, it is desirable to reduce it as much as possible. In particular, when the N content exceeds 0.0080%, the toughness is greatly reduced. Therefore, the N content is 0.0080% or less. Preferably it is 0.0070%.
  • the lower limit is not particularly limited, but is preferably 0.0005%.
  • Cu 0.01 to 0.50%, Ni: 0.01 to 0.50%, Sb: 0.01 to 0.30%, W: 0.01 to 0.50%, Mo: 0.01 to 0.50%, and Si: 0.01 to 1.50%
  • Species and above Cu, Ni, Sb, W, Mo and Si are elements that improve the corrosion resistance in a full corrosive environment such as the upper deck of a crude oil tank of a crude oil tanker.
  • Sn is an element effective for improving corrosion resistance, but cannot be contained in a large amount from the viewpoint of lamellar resistance.
  • Cu 0.01 to 0.50%
  • Ni 0.01 to 0.50%
  • Sb 0.01 to 0.30%
  • W 0.01
  • Cu, Ni, and Sb are released from the steel surface as Cu 2+ , Ni 2+, and Sb 3+ as corrosion progresses, and are associated with the corrosion factor S 2-, and CuS, NiS, Sb, respectively. 2 S 3 is formed. As a result, permeation of S 2 ⁇ to the steel interface is suppressed.
  • W, Mo, and Si are liberated as WO 4 2 ⁇ , MoO 4 2 ⁇ , and SiO 4 4 ⁇ , respectively, and are taken into rust, imparting cation selective permeability to rust, and SO 4 to the steel interface.
  • Cu content is in the range of 0.01 to 0.50%
  • Ni content is in the range of 0.01 to 0.50%
  • Sb content is in the range of 0.01 to 0.30%
  • W content is in the range of 0.01 to 0.50%
  • Mo content is in the range of 0.01 to 0.50%.
  • the range and Si content should be 0.01 to 1.50%.
  • Cu amount is 0.02% or more and 0.40% or less
  • Ni amount is 0.02% or more and 0.40% or less
  • Sb amount is 0.02% or more and 0.25% or less
  • W amount is 0.02% or more and 0.40% or less
  • Mo amount is 0.02% or more and 0.40% or less
  • Si amount is 0.01% or more and 1.00% or less.
  • the mechanism for decreasing lamellar resistance by Sn is different from the mechanism for decreasing lamellar resistance by S.
  • the reduction of lamellar resistance due to S and Sn acts synergistically.
  • it is preferable that the relationship of the following formula (2) is satisfied with respect to the S and Sn contents. 10000 ⁇ [% S] ⁇ [% Sn] 2 ⁇ 1.40 --- (2)
  • [% S] and [% Sn] are the contents (mass%) of S and Sn in the component composition, respectively.
  • the above equation (2) means that the influence of Sn amount on the lamellar resistance is much larger than the influence of S amount. That is, strictly managing Sn means that it is particularly important in securing the lamellar resistance.
  • 10000 ⁇ [% S] ⁇ [% Sn] 2 is more preferably 1.20 or less.
  • the lower limit of 10000 ⁇ [% S] ⁇ [% Sn] 2 is not particularly limited, but is preferably 0.001. Needless to say, in order to suppress the lamellar tear, it is assumed that both the S amount and the Sn amount are limited to the above-described range.
  • Such an effect is particularly remarkable in a portion that comes into contact with a liquid containing a high concentration of salt separated from a crude oil component, such as a bottom plate of a crude oil tank of a crude oil tanker. That is, when the steel material is subjected to a Zn-containing primer treatment and this steel material is used in a portion that comes into contact with a liquid containing high-concentration salt separated from crude oil, these elements are contained in the steel material containing Cr or Co. Corrosion resistance is greatly improved compared to steel materials that do not contain. Such an effect cannot be sufficiently obtained when the Cr content or the Co content is less than 0.01%. On the other hand, if the Cr content or Co content exceeds 0.50%, the toughness of the welded portion deteriorates.
  • Cr is an element that causes a hydrolysis reaction and lowers the pH in the corroded part. That is, if Cr is added excessively, the total corrosion resistance may be deteriorated. Therefore, when Cr and Co are contained, the amounts are both in the range of 0.01 to 0.50%. Preferably they are 0.02% or more and 0.30% or less. More preferably, it is 0.03% or more and 0.20% or less.
  • Ti, Zr, Nb and V are desired From the viewpoint of securing strength, they can be added alone or in combination. However, if any element is excessively contained, toughness and weldability are deteriorated. For this reason, when Ti, Zr, Nb and V are contained, the amounts are all in the range of 0.001 to 0.100%. Preferably it is 0.005% or more and 0.050% or less.
  • Ca, Mg and REM are used singly or in combination from the viewpoint of improving the toughness of the weld Can be added. However, if any of these elements is excessively contained, the toughness of the weld is deteriorated. Also, the cost increases. Therefore, when Ca, Mg and REM are contained, the Ca amount is in the range of 0.0001 to 0.0100%, the Mg amount is in the range of 0.0001 to 0.0200%, and the REM amount is in the range of 0.0002 to 0.2000%.
  • B 0.0001-0.0300%
  • B is an element that improves the hardenability of the steel material.
  • B can be contained from a viewpoint of ensuring desired intensity
  • Components other than the above are Fe and inevitable impurities.
  • the component composition of the steel for crude oil tankers of the present invention has been described above. However, in the steel for crude oil tankers of the present invention, it is extremely important to control the degree of Sn segregation as follows. Sn segregation degree: less than 18 The central segregation of Sn greatly increases the hardness of the segregated part. And such a segregation part becomes a starting point of lamellar tear generation. In other words, in order to ensure excellent lamellar tear resistance in the component composition containing Sn, it is important to suppress the center segregation of Sn and suppress the increase in hardness of the segregated portion. From such a viewpoint, the Sn segregation degree is set to less than 18. Preferably it is less than 16. More preferably, it is 15 or less. The lower limit is not particularly limited, but is preferably 2.
  • Sn segregation degree here is the average obtained by the line analysis of an electron beam microanalyzer (henceforth EPMA) in the cross section (cross section perpendicular
  • This is the ratio of the Sn concentration in the central segregation part to the Sn concentration.
  • EPMA surface analysis of Sn is performed under the conditions of a beam diameter: 20 ⁇ m and a pitch: 20 ⁇ m.
  • Sn's EPMA surface analysis is performed in three cross-sectional visual fields at positions of 1/4 ⁇ W, 1/2 ⁇ W, and 3/4 ⁇ W.
  • the steel material for a crude oil tanker of the present invention suppresses the center segregation of Sn from the viewpoint of securing excellent lamellar resistance properties, that is, the Sn segregation degree indicating the degree of Sn center segregation is a predetermined value or less. It is extremely important to control it.
  • the degree of Sn segregation varies greatly depending on manufacturing conditions even if the component composition is the same. For this reason, in order to suppress the center segregation of Sn, it is very important to appropriately control the steel material manufacturing method.
  • the suitable manufacturing method of the steel material for crude oil tankers of this invention is demonstrated.
  • the steel material of the present invention is obtained by melting steel adjusted to the above-described component composition using a known refining process such as a converter, electric furnace, vacuum degassing, etc., and continuously casting or ingot-bundling rolling. It can be manufactured by using a steel material (slab) by the method, and then re-heating the steel material as necessary, followed by hot rolling to obtain a steel plate or a shaped steel.
  • the thickness of the steel material is not particularly limited, but is preferably 2 to 100 mm. More preferably, it is 3 to 80 mm. More preferably, it is 4 to 60 mm.
  • the casting speed (drawing speed) is preferably 0.3 to 2.8 m / min.
  • the casting speed is less than 0.3 m / min, the operation efficiency is deteriorated.
  • the casting speed exceeds 2.8 m / min, surface temperature unevenness occurs, and the supply of molten steel to the inside of the slab becomes insufficient, which promotes center segregation of Sn.
  • it is more preferably 0.4 m / min or more and 2.6 m / min or less. More preferably, it is 1.5 m / min or less.
  • a light reduction method in which an end-solidified slab having an unsolidified layer is cast while being gradually reduced by a reduction roll group at a reduction amount and a reduction speed corresponding to the sum of the solidification shrinkage and the heat shrinkage. It is preferable to carry out.
  • the steel material when the steel material is hot-rolled to a desired size and shape, it is preferably heated to a temperature of 900 ° C. to 1350 ° C.
  • the heating temperature is less than 900 ° C., the deformation resistance is large and hot rolling becomes difficult.
  • the heating temperature exceeds 1350 ° C., surface marks are generated, scale loss and fuel consumption increase.
  • the higher the heating temperature the more the diffusion of Sn in the central segregation part is promoted, which is advantageous from the viewpoint of securing the lamellar resistance.
  • the heating temperature is more preferably 1030 ° C. or higher.
  • the holding time at the heating temperature is preferably 60 min or longer. Thereby, the diffusion of Sn in the central segregation part is sufficiently promoted. More preferably, it is 150 min or more.
  • the upper limit is not particularly limited, but is preferably 1000 min.
  • the temperature of the steel material is originally in the range of 1030 to 1350 ° C. and is maintained in the temperature range for 60 minutes or more, it may be subjected to hot rolling without being heated. Further, the hot-rolled sheet obtained after hot rolling may be subjected to reheating treatment, acidity, and cold rolling to obtain a cold-rolled sheet having a predetermined thickness.
  • the finish rolling finish temperature is 650 ° C. or higher. When the finish rolling finish temperature is less than 650 ° C., the rolling load increases due to an increase in deformation resistance, making it difficult to perform the rolling.
  • Cooling after hot rolling may be either air cooling or accelerated cooling, but accelerated cooling is preferred when higher strength is desired.
  • the cooling rate exceeds 100 ° C./s and / or the cooling stop temperature is less than 400 ° C., the toughness of the steel material may be reduced, or the shape of the steel material may be distorted. However, this is not the case when heat treatment is performed in the subsequent process.
  • each of the above No.1 to 58 steel plates is 25mm wide x 60mm long x thick from the position of 1mm surface. A 5 mm long rectangular piece was cut out and the surface was polished with 600th emery paper.
  • This corrosion test apparatus includes a corrosion test tank 2 and a temperature control plate 3. Water 6 having a temperature maintained at 30 ° C. is injected into the corrosion test tank 2, and 13 vol% CO 2 , 4 vol% O 2 , 0.01 vol are introduced into the water 6 through the introduction gas pipe 4. % SO 2 , 0.05vol% H 2 S, and the balance N 2 are introduced. By this, the corrosion test tank 2 is filled with supersaturated steam, and the corrosive environment behind the upper deck of the crude oil tank Is reproduced.
  • a test piece 1 is set on the upper and rear surfaces of the corrosion test tank 2, and 25 ° C. ⁇ 1.5 hours + 50 ° C. ⁇ 22.5 hours are applied to the test piece 1 through a temperature control plate 3 incorporating a heater and a cooling device.
  • symbol 5 shows the exhaust gas pipe
  • the test piece was subjected to a corrosion test in which it was immersed in a 2 L test solution for 168 hours.
  • the test solution was preheated and maintained at 30 ° C. and replaced with a new test solution every 24 hours.
  • the apparatus used for the corrosion test is shown in FIG.
  • This corrosion test apparatus is a dual structure apparatus consisting of a corrosion test tank 8 and a constant temperature bath 9, and the test solution 10 is put in the corrosion test tank 8, and the test piece 7 is suspended and immersed in the teg 11 therein. Has been.
  • the temperature of the test solution 10 is maintained by adjusting the temperature of the water 12 placed in the thermostatic chamber 9.
  • the lamellar tear resistance was evaluated in the following manner. (3) Evaluation of lamellar tear resistance No. 1 to 58 steel plates obtained as described above according to the ClassNK Steel Ship Rules and Inspection Procedures (Part K, Chapter 2) Tensile test in the direction (Z direction) was performed, and the aperture value (RA) was calculated. Based on the calculated aperture value (RA), the lamellar resistance was evaluated according to the following criteria. ⁇ (pass, especially excellent): 70 or more ⁇ (pass): 35 or more and less than 70 ⁇ (failure): 25 or more and less than 35 ⁇ (failure): less than 25
  • Table 2 shows the evaluation results of (1) to (3).
  • the overall evaluation in Table 2 is “Pass” when all of the evaluations (1) to (3) above are “ ⁇ ” or “ ⁇ ”, and one evaluation in the evaluations from (1) to (3).
  • ⁇ or “ ⁇ ” is present is regarded as “fail”.
  • Comparative Examples No. 42, 48, and 52 since the amount of S exceeds the upper limit, sufficient characteristics are not obtained with respect to local corrosion resistance and lamellar resistance.
  • the Sn amount exceeds the upper limit, so that sufficient characteristics for lamellar resistance are not obtained.
  • the amount of S exceeds the upper limit and does not contain the prescribed amount of Cu, Ni, Sb, W, Mo and Si, so it has general corrosion resistance, local corrosion resistance and lamellar resistance. However, sufficient characteristics have not been obtained.
  • Comparative Example No. 45 the Sn amount is below the lower limit, so that sufficient characteristics are not obtained with respect to general corrosion resistance and local corrosion resistance. In Comparative Example No.
  • Comparative Example No. 49 does not contain a predetermined amount of Cu, Ni, Sb, W, Mo, and Si, sufficient characteristics are not obtained for the general corrosion resistance.
  • Comparative Example No. 51 the amount of S exceeds the upper limit and the amount of Sn is lower than the lower limit, so that sufficient characteristics are not obtained with respect to general corrosion resistance, local corrosion resistance, and lamellar resistance.
  • Comparative Examples Nos. 53 to 56 the Sn segregation degree exceeds the upper limit, so that sufficient characteristics are not obtained for the lamellar resistance.

Abstract

Provided is steel for a crude oil tanker for which excellent uniform corrosion resistance and excellent local corrosion resistance together with excellent lamellar tear resistance have been established as a result of the steel having a specified component composition and an Sn segregation of less than 18.

Description

原油タンカー用鋼材および原油タンカーCrude oil tanker steel and crude oil tanker
　本発明は、鋼材を溶接して形成される原油タンカーの原油タンク（油槽部）、特には全面腐食が発生する上甲板裏面（天井部）や側壁上部、および局部腐食（孔食）が発生する油槽部の底板のいずれにも好適に用いることができる、耐食性および耐ラメラテア性に優れる原油タンカー用鋼材に関するものである。
　また、本発明は、上記の鋼材を用いてなる原油タンカーに関するものである。 In the present invention, a crude oil tank (oil tank part) of a crude oil tanker formed by welding steel materials, in particular, an upper deck back surface (ceiling part) and an upper side wall where local corrosion occurs, and local corrosion (pitting corrosion) occur. The present invention relates to a steel material for a crude oil tanker that can be suitably used for any bottom plate of an oil tank section and has excellent corrosion resistance and lamellar resistance.
The present invention also relates to a crude oil tanker using the above steel material.
　原油タンカーの原油タンク内面、特に上甲板裏面および側壁上部に用いられる鋼材には、全面腐食が生じることが知られている。 It is known that the steel used for the inner surface of a crude oil tank of a crude oil tanker, particularly the back of the upper deck and the upper part of the side wall, is totally corroded.
　この全面腐食が起こる原因としては、
（１）昼夜の温度差による鋼板表面への結露と乾燥（乾湿）の繰り返し、
（２）原油タンク内に防爆用に封入されるイナートガス（O2：約４vol％、CO2：約13vol％、SO2：約0.01vol％、残部N2を代表組成とするボイラあるいはエンジンの排ガス等）に含まれるO2，CO2，SO2の結露水への溶け込み、
（３）原油から揮発するH2S等の腐食性ガスの結露水への溶け込み、
（４）原油タンクの洗浄に使用された海水の残留
などが挙げられる。これらは、通常、2.5年毎に行われる実船のドック検査で、強酸性の結露水中に、硫酸イオンや塩化物イオンが検出されていることからも窺い知ることができる。 As a cause of this total corrosion,
(1) Repeated condensation and drying (wet and dry) on the steel sheet surface due to temperature difference between day and night,
(2) Inert gas enclosed in crude oil tanks for explosion protection (O 2 : about 4 vol%, CO 2 : about 13 vol%, SO 2 : about 0.01 vol%, boiler or engine exhaust gas with a balance of N 2 as a representative composition) Etc.) O 2 , CO 2 , SO 2 contained in condensed water,
(3) Dissolution of corrosive gas such as H 2 S volatilized from crude oil into condensed water,
(4) Residual seawater used for cleaning crude oil tanks. These can be recognized from the fact that sulfate ions and chloride ions are detected in strongly acidic condensed water during dock inspections of actual ships that are usually conducted every 2.5 years.
　また、腐食によって生成した鉄錆を触媒としてH2Sが酸化されると、固体Ｓが鉄錆中に層状に生成する。かような固体Ｓが層状に生成した鉄錆は、容易に剥離して脱落し、原油タンクの底部に堆積する。そのため、原油タンカーのドック検査では、多大な費用をかけて、原油タンク上部の補修やタンク底部の堆積物の回収を行っているのが現状である。 Further, when H 2 S is oxidized using iron rust generated by corrosion as a catalyst, solid S is formed in layers in the iron rust. The iron rust produced by forming such solid S in layers is easily peeled off and deposited, and is deposited on the bottom of the crude oil tank. For this reason, in the dock inspection of crude oil tankers, the current situation is that the cost of repairing the upper part of the crude oil tank and the collection of deposits at the bottom of the tank are being increased.
　一方、原油タンク底板などの鋼材では、従来、原油そのものの腐食抑制作用や原油タンク内面に形成される原油由来の保護性コート（オイルコート）の腐食抑制作用により、腐食は生じないものと考えられていた。
　しかしながら、最近の研究によって、原油タンク底板の鋼材では、お椀型の局部腐食（孔食）が発生することが明らかになった。 On the other hand, steel materials such as the bottom plate of a crude oil tank are conventionally considered to be free from corrosion due to the corrosion inhibition effect of the crude oil itself and the corrosion inhibition effect of a protective coat (oil coat) derived from crude oil formed on the inner surface of the crude oil tank. It was.
However, recent research has revealed that bowl-shaped local corrosion (pitting corrosion) occurs in the steel plate of the crude oil tank bottom plate.
　かような局部腐食が起こる原因としては、
（１）塩化ナトリウムを代表とする塩類が高濃度に溶解した凝集水の存在、
（２）過剰な洗浄によるオイルコートの離脱、
（３）原油中に含まれる硫化物の高濃度化、
（４）結露水に溶け込んだ防爆用イナートガス中のO2、CO2、SO2等の高濃度化、
などが挙げられる。実際、実船のドック検査時に、原油タンク内に滞留した水を分析した結果では、高濃度の塩化物イオンと硫酸イオンが検出されている。 As a cause of such local corrosion,
(1) presence of condensed water in which salts represented by sodium chloride are dissolved at a high concentration;
(2) Oil coat detachment due to excessive cleaning,
(3) High concentration of sulfides contained in crude oil,
(4) Increasing concentrations of O 2 , CO 2 , SO 2, etc. in the inert gas for explosion protection dissolved in condensed water,
Etc. Actually, when the water stayed in the crude oil tank was analyzed during the dock inspection of the actual ship, high concentrations of chloride ions and sulfate ions were detected.
　上記した原油タンク内面の全面腐食や局部腐食の防止には、鋼材表面に塗装を施し、鋼材を腐食環境から遮断することが有効である。
　しかしながら、原油タンクの塗装作業は、その塗布面積が膨大であり、また塗膜の劣化により約10年に一度は塗り替えが必要となる。このため、原油タンクの塗装作業には、検査や塗装に膨大な費用が発生する。さらに、塗膜が損傷を受けると、かような損傷部では、原油タンクの腐食環境下でかえって腐食が助長されることが指摘されている。 In order to prevent the above-described overall corrosion and local corrosion of the crude oil tank inner surface, it is effective to coat the steel material surface to shield the steel material from the corrosive environment.
However, the painting operation of the crude oil tank has an enormous application area, and it is necessary to repaint it about once every 10 years due to deterioration of the coating film. For this reason, huge costs are incurred for inspection and painting in the painting operation of the crude oil tank. Furthermore, it has been pointed out that when the coating film is damaged, corrosion is promoted in such a damaged portion in the corrosive environment of the crude oil tank.
　そこで、塗装を施さなくとも、原油タンク内面の全面腐食や局部腐食を防止することのできる鋼材の開発が望まれている。 Therefore, it is desired to develop a steel material that can prevent the overall corrosion and local corrosion of the inner surface of the crude oil tank without painting.
　このような鋼材として、例えば特許文献１には、
「質量％で、Ｃ：０．０１～０．３％、Ｓｉ：０．０２～１％、Ｍｎ：０．０５～２％、Ｐ：０．０５％以下、Ｓ：０．０１％以下、Ｎｉ：０．０５～３％、Ｍｏ：１％以下、Ｃｕ：１％以下、Ｃｒ：２％以下、Ｗ：１％以下、Ｃａ：０．０１％以下、Ｔｉ：０．１％以下、Ｎｂ：０．１％以下、Ｖ：０．１％以下、Ｂ：０．０５％以下を含有し、残部Ｆｅ及び不純物からなるカーゴオイルタンク用鋼材。」
が開示されている。 As such a steel material, for example, in Patent Document 1,
“In mass%, C: 0.01 to 0.3%, Si: 0.02 to 1%, Mn: 0.05 to 2%, P: 0.05% or less, S: 0.01% or less, Ni: 0.05 to 3%, Mo: 1% or less, Cu: 1% or less, Cr: 2% or less, W: 1% or less, Ca: 0.01% or less, Ti: 0.1% or less, Nb : 0.1% or less, V: 0.1% or less, B: 0.05% or less, and the steel material for cargo oil tank which consists of remainder Fe and impurities. "
Is disclosed.
　また、特許文献２には、
「質量％で、Ｃ：０．０１～０．２％、Ｓｉ：０．０１～１％、Ｍｎ：０．０５～２％、Ｐ：０．０５％以下、Ｓ：０．０１％以下、Ｎｉ：０．０１～１％、Ｃｕ：０．０５～２％、Ｓｎ：０．０１～０．２％、Ｃｒ：０．１％以下、Ａｌ：０．１％以下を含有し、残部Ｆｅ及び不純物からなるカーゴオイルタンク用鋼材。」
が開示されている。 In addition, in Patent Document 2,
“In mass%, C: 0.01 to 0.2%, Si: 0.01 to 1%, Mn: 0.05 to 2%, P: 0.05% or less, S: 0.01% or less, Ni: 0.01-1%, Cu: 0.05-2%, Sn: 0.01-0.2%, Cr: 0.1% or less, Al: 0.1% or less, and the balance Fe And cargo oil tank steel made of impurities. "
Is disclosed.
特開2003-82435号公報Japanese Patent Laid-Open No. 2003-82435 特開2007-270196号公報JP 2007-270196 A
　ところで、原油タンカーの原油タンクは、通常、底板とホッパープレート、上甲板裏板とロンジ材等を溶接しており、その溶接継手では、板厚方向に引張応力を受ける。かような溶接継手では、ラメラテアが生じる危険性があることが最近明らかとなってきた。ここで、ラメラテアとは、十字継手、Ｔ継手、角継手などの板厚方向に引張応力を受ける溶接継手において、引張応力によって鋼板表面に平行な方向に、鋼材内部においてき裂が進展し、割れが発生する現象である。
　このため、原油タンカー用鋼材には、上記した原油タンク内面の全面腐食や局部腐食に対する耐食性に加え、耐ラメラテア性にも優れていることが要求される。 By the way, a crude oil tank of a crude oil tanker usually welds a bottom plate and a hopper plate, an upper deck back plate and a longi material, and the welded joint receives a tensile stress in the thickness direction. It has recently become apparent that such welded joints have a risk of lamellar tearing. Here, lamellate is a welded joint that receives tensile stress in the thickness direction, such as a cross joint, T joint, and corner joint, and cracks develop in the steel material in the direction parallel to the steel sheet surface due to the tensile stress. Is a phenomenon that occurs.
For this reason, the steel material for crude oil tankers is required to have excellent lamellar tear resistance in addition to the above-mentioned corrosion resistance against the overall corrosion and local corrosion of the crude oil tank.
　この点、引用文献１の鋼材では、耐ラメラテア性などの機械的特性については何ら考慮されていない。また、引用文献２の鋼材でも、やはり耐ラメラテア性については何ら考慮されていない。 In this respect, the steel material of the cited reference 1 does not take into consideration any mechanical properties such as lamellar resistance. Further, even in the steel material of Cited Document 2, no consideration is given to the lamellar resistance.
　このように、引用文献１および２では、溶接継手においてラメラテアが発生するリスクを全く考慮しておらず、このため、引用文献１および２の鋼材を実際の原油タンカーの原油タンクに使用した場合には、溶接継手においてラメラテアが発生することが懸念される。 As described above, the cited references 1 and 2 do not consider the risk of occurrence of lamellar tears in welded joints. Therefore, when the steel materials of the cited references 1 and 2 are used in a crude oil tank of an actual crude oil tanker. There is a concern that lamellar tear may occur in the welded joint.
　本発明は、上記の現状に鑑み開発されたものであって、原油タンカーの原油タンク内面の上甲板裏面や側壁上部における全面腐食、および底板における局部腐食に対する耐食性に優れ、かつ耐ラメラテア性にも優れる原油タンカー用鋼材を提供することを目的とする。
　また、本発明は、上記の原油タンカー用鋼材を用いてなる原油タンカーを提供することを目的とする。 The present invention has been developed in view of the above-described situation, and is excellent in corrosion resistance against the overall corrosion of the upper deck back surface and the upper side of the crude tank inside the crude oil tank and the local corrosion of the bottom plate, and also has a lamellar resistance. The object is to provide an excellent steel material for crude oil tankers.
Another object of the present invention is to provide a crude oil tanker using the above steel material for crude oil tankers.
　さて、発明者らは、上記課題の解決に向けて鋭意研究を重ね、以下の知見を得た。
（１）原油タンカーの原油タンクの底板における局部腐食環境、すなわち孔食環境における耐食性（以下、耐局部腐食性ともいう）の向上には、Snの添加とＳの低減が有効である。
（２）原油タンカーの原油タンクの上甲板裏面や側壁上部における全面腐食環境での耐食性（以下、耐全面腐食性ともいう）の向上には、Snとともに、Cu、Ni、Sb、Ｗ、MoおよびSiのうちから選んだ１種または２種以上を複合添加することが有効である。
（３）一方、耐ラメラテア性の観点からは、鋼中のＳ量を低減するとともに、Snを低減することが有効である。 Now, the inventors have conducted intensive research to solve the above problems, and have obtained the following knowledge.
(1) Addition of Sn and reduction of S are effective in improving the local corrosion environment in the bottom plate of a crude oil tank of a crude oil tanker, that is, the corrosion resistance in a pitting environment (hereinafter also referred to as local corrosion resistance).
(2) In addition to Sn, Cu, Ni, Sb, W, Mo, and Sn can be used to improve the corrosion resistance of the crude oil tanker in the entire corrosive environment on the back of the upper deck and the upper part of the side wall of the crude oil tank. It is effective to add one or more selected from Si in combination.
(3) On the other hand, from the viewpoint of lamellar resistance, it is effective to reduce Sn while reducing the amount of S in steel.
　このように、原油タンカーの原油タンク内面の腐食環境における耐食性（耐全面腐食性および耐局部腐食性）の向上の観点からはSnの添加が有効であるものの、耐ラメラテア性の観点からは、Snを低減することが有効である。そこで、発明者らは、上記の知見を基に、さらに耐食性と耐ラメラテア性とを両立すべく検討を重ねた。 Thus, although addition of Sn is effective from the viewpoint of improving the corrosion resistance (total corrosion resistance and local corrosion resistance) in the corrosive environment of the crude oil tank inner surface of the crude oil tanker, from the viewpoint of lamellar resistance, Sn It is effective to reduce. Therefore, the inventors have repeatedly studied to achieve both corrosion resistance and lamellar resistance, based on the above findings.
　その結果、
（４）Snの中心偏析を抑制して、Snを鋼材全体に極力拡散させてやれば、Snを所定量含有していても優れた耐ラメラテア性が得られる、すなわち、Sn量を適正に調整しつつ、Snの中心偏析を抑制して、Snを鋼材全体に拡散させてやれば、原油タンカーの原油タンク内面の腐食環境における耐食性と耐ラメラテア性とを両立することできる、
との知見を得た。
　また、
（５）Ｓ量に応じてSn量を厳密に制御することで、一層、耐ラメラテア性が向上する、
との知見を得た。
　本発明は、上記の知見に基づき、さらに検討を重ねて完成させたものである。 as a result,
(4) By suppressing the center segregation of Sn and diffusing Sn throughout the steel as much as possible, excellent lamellar resistance can be obtained even if a predetermined amount of Sn is contained, that is, the Sn amount is adjusted appropriately. However, if the central segregation of Sn is suppressed and Sn is diffused throughout the steel material, both corrosion resistance and lamellar resistance in the corrosive environment of the crude oil tank inner surface of the crude oil tanker can be achieved.
And gained knowledge.
Also,
(5) By strictly controlling the Sn amount according to the S amount, the lamellar resistance is further improved.
And gained knowledge.
The present invention has been completed through further studies based on the above findings.
　すなわち、本発明の要旨構成は次のとおりである。
１．質量％で、
　　Ｃ：0.03～0.18％、
　　Mn：0.10～2.00％、
　　Ｐ：0.030％以下、
　　Ｓ：0.0070％以下、
　　Al：0.001～0.100％、
　　Sn：0.01～0.20％および
　　Ｎ：0.0080％以下
を含有するとともに、
　　Cu：0.01～0.50％、
　　Ni：0.01～0.50％、
　　Sb：0.01～0.30％、
　　Ｗ：0.01～0.50％、
　　Mo：0.01～0.50％および
　　Si：0.01～1.50％
のうちから選んだ１種または２種以上を含有し、残部がFe及び不可避的不純物からなる成分組成を有し、
　Sn偏析度が18未満である、原油タンカー用鋼材。
　ここで、Sn偏析度は、次式(1)により定義される。
　［Sn偏析度］＝［中心偏析部のSn濃度］／［平均のSn濃度］--- (1) That is, the gist configuration of the present invention is as follows.
1. % By mass
C: 0.03-0.18%
Mn: 0.10 to 2.00%
P: 0.030% or less,
S: 0.0070% or less,
Al: 0.001 to 0.100%,
Sn: 0.01 to 0.20% and N: 0.0080% or less,
Cu: 0.01-0.50%,
Ni: 0.01-0.50%,
Sb: 0.01-0.30%
W: 0.01-0.50%
Mo: 0.01 to 0.50% and Si: 0.01 to 1.50%
Containing one or more selected from among the above, the remainder having a component composition consisting of Fe and inevitable impurities,
Steel material for crude oil tankers with Sn segregation degree of less than 18.
Here, the degree of Sn segregation is defined by the following equation (1).
[Sn segregation degree] = [Sn concentration in central segregation part] / [Average Sn concentration] --- (1)
２．前記成分組成におけるＳ含有量とSn含有量とが、次式(2)の関係を満足する、前記１に記載の原油タンカー用鋼材。
　　10000×[％S]×[％Sn]2 ≦ 1.40 --- (2)
　ここで、[％S]および[％Sn]はそれぞれ、成分組成におけるＳおよびSnの含有量（質量％）である。 2. 2. The steel material for a crude oil tanker according to 1, wherein the S content and the Sn content in the component composition satisfy the relationship of the following formula (2).
10000 × [% S] × [% Sn] 2 ≤ 1.40 --- (2)
Here, [% S] and [% Sn] are the contents (mass%) of S and Sn in the component composition, respectively.
３．前記成分組成が、さらに質量％で、
　　Cr：0.01～0.50％および
　　Co：0.01～0.50％
のうちから選んだ１種または２種を含有する、前記１または２に記載の原油タンカー用鋼材。 3. The component composition is further mass%,
Cr: 0.01-0.50% and Co: 0.01-0.50%
The steel material for crude oil tankers according to 1 or 2 above, which contains one or two selected from among the above.
４．前記成分組成が、さらに質量％で、
　　Ti：0.001～0.100％、
　　Zr：0.001～0.100％、
　　Nb：0.001～0.100％および
　　Ｖ：0.001～0.100％
のうちから選んだ１種または２種以上を含有する、前記１～３のいずれかに記載の原油タンカー用鋼材。 4). The component composition is further mass%,
Ti: 0.001 to 0.100%,
Zr: 0.001 to 0.100%,
Nb: 0.001 to 0.100% and V: 0.001 to 0.100%
4. The steel material for a crude oil tanker according to any one of 1 to 3 above, which contains one or more selected from among the above.
５．前記成分組成が、さらに質量％で、
　　Ca：0.0001～0.0100％、
　　Mg：0.0001～0.0200％および
　　REM：0.0002～0.2000％
のうちから選んだ１種または２種以上を含有する、前記１～４のいずれかに記載の原油タンカー用鋼材。 5). The component composition is further mass%,
Ca: 0.0001 to 0.0100%
Mg: 0.0001 to 0.0200% and REM: 0.0002 to 0.2000%
5. The steel material for a crude oil tanker according to any one of 1 to 4 above, which contains one or more selected from among the above.
６．前記成分組成が、さらに質量％で、
　　Ｂ：0.0001～0.0300％
を含有する、前記１～５のいずれかに記載の原油タンカー用鋼材。 6). The component composition is further mass%,
B: 0.0001-0.0300%
6. The steel material for a crude oil tanker according to any one of 1 to 5 above, which contains
７．前記１～６のいずれかに記載の原油タンク用鋼材を用いてなる原油タンカー。 7). A crude oil tanker comprising the steel material for a crude oil tank according to any one of 1 to 6 above.
　本発明によれば、原油タンカーの原油タンク内面の腐食環境における耐食性、すなわち耐全面腐食性および耐局部腐食性のいずれにも優れ、かつ耐ラメラテア性にも優れる原油タンカー用鋼材が得られる。
　そして、本発明の原油タンカー用鋼材を原油タンカーの原油タンクに用いることで、高い安全性を確保しながら、原油タンクの検査や塗装にかかる費用を低減することが可能となる。 ADVANTAGE OF THE INVENTION According to this invention, the steel material for crude oil tankers which is excellent in the corrosion resistance in the corrosive environment of the crude oil tank inner surface of a crude oil tanker, ie, both general corrosion resistance and local corrosion resistance, and is excellent also in the lamellar tear resistance.
And by using the steel material for crude oil tankers of the present invention for the crude oil tank of the crude oil tanker, it becomes possible to reduce the cost for inspection and painting of the crude oil tank while ensuring high safety.
全面腐食試験（結露試験）に用いた試験装置の概略図である。It is the schematic of the test apparatus used for the general corrosion test (condensation test). 局部腐食試験（耐酸試験）に用いた試験装置の概略図である。It is the schematic of the test apparatus used for the local corrosion test (acid resistance test).
　以下、本発明を具体的に説明する。まず、本発明において鋼の成分組成を前記の範囲に限定した理由について説明する。なお、鋼の成分組成における元素の含有量の単位はいずれも「質量％」であるが、以下、特に断らない限り単に「％」で示す。 Hereinafter, the present invention will be specifically described. First, the reason why the composition of steel is limited to the above range in the present invention will be described. In addition, although the unit of element content in the component composition of steel is “mass%”, hereinafter, it is simply indicated by “%” unless otherwise specified.
Ｃ：0.03～0.18％
　Ｃは、鋼の強度確保に必要な元素である。このような効果を得るため、Ｃ量は0.03％以上とする。しかし、Ｃ量が0.18％を超えると、溶接性および溶接熱影響部の靭性が低下する。従って、Ｃ量は0.03～0.18％の範囲とする。好ましくは0.04％以上、0.16％以下である。 C: 0.03-0.18%
C is an element necessary for securing the strength of steel. In order to obtain such an effect, the C content is 0.03% or more. However, when the C content exceeds 0.18%, the weldability and the toughness of the weld heat affected zone are deteriorated. Therefore, the C content is in the range of 0.03 to 0.18%. Preferably they are 0.04% or more and 0.16% or less.
Mn：0.10～2.00％
　Mnは、鋼の強度を高める元素である。このような効果を得るため、Mn量は0.10％以上とする。しかし、Mn量が2.00％を超えると、鋼の靭性および溶接性が低下する。また、Mnの中心偏析によって、耐ラメラテア性も低下する。従って、Mn量は0.10～2.00％の範囲とする。好ましくは0.60％以上、1.80％以下である。より好ましくは、0.80％以上、1.60％以下である。 Mn: 0.10 to 2.00%
Mn is an element that increases the strength of steel. In order to obtain such an effect, the Mn content is 0.10% or more. However, if the amount of Mn exceeds 2.00%, the toughness and weldability of the steel will decrease. Further, the lamellar resistance is also lowered by the central segregation of Mn. Therefore, the Mn content is in the range of 0.10 to 2.00%. Preferably they are 0.60% or more and 1.80% or less. More preferably, it is 0.80% or more and 1.60% or less.
Ｐ：0.030％以下
　Ｐは、靭性及び溶接性を劣化させる。このため、Ｐ量は0.030％以下とする。好ましくは0.025％以下である。より好ましくは0.015％以下である。なお、下限については特に限定されないが、0.003％とすることが好ましい。 P: 0.030% or less P deteriorates toughness and weldability. Therefore, the P content is 0.030% or less. Preferably it is 0.025% or less. More preferably, it is 0.015% or less. The lower limit is not particularly limited, but is preferably 0.003%.
Ｓ：0.0070％以下
　Ｓは、耐局部腐食性と耐ラメラテア性に関与する重要な元素である。すなわち、Ｓは、非金属介在物であるMnSを形成して局部腐食の起点となり、耐局部腐食性を低下させる有害な元素である。よって、Ｓは極力低減させることが望ましい。特に、Ｓ量が0.0080％を超えると、耐局部腐食性の顕著な低下を招く。また、粗大なMnSは、ラメラテアの起点となる。特に、Ｓ量が0.0070％を超えると、耐ラメラテア性の大幅な低下を招く。従って、耐局部腐食性と耐ラメラテア性を両立する観点から、Ｓ量は0.0070％以下とする。好ましくは0.0060％以下である。より好ましくは0.0050％以下である。なお、下限については特に限定されないが、0.0003％とすることが好ましい。 S: 0.0070% or less S is an important element involved in local corrosion resistance and lamellar resistance. That is, S is a harmful element that forms MnS, which is a non-metallic inclusion, becomes a starting point of local corrosion, and reduces local corrosion resistance. Therefore, it is desirable to reduce S as much as possible. In particular, when the amount of S exceeds 0.0080%, the local corrosion resistance is significantly reduced. Coarse MnS is the starting point for lamellar tears. In particular, if the amount of S exceeds 0.0070%, the lamellar resistance is greatly reduced. Therefore, from the viewpoint of achieving both local corrosion resistance and lamellar resistance, the S content is 0.0070% or less. Preferably it is 0.0060% or less. More preferably, it is 0.0050% or less. The lower limit is not particularly limited, but is preferably 0.0003%.
Al：0.001～0.10％
　Alは、脱酸剤として添加される元素であり、Al量は0.001％以上とする。しかし、Al量が0.10％を超えると、鋼の靭性が低下する。このため、Al量は0.001～0.10％の範囲とする。 Al: 0.001 to 0.10%
Al is an element added as a deoxidizer, and the Al content is 0.001% or more. However, if the Al content exceeds 0.10%, the toughness of the steel decreases. For this reason, the Al content is in the range of 0.001 to 0.10%.
Sn：0.01～0.20％
　Snは、耐局部腐食性と耐全面腐食性を向上させるために必要な元素であるとともに、耐ラメラテア性に関与する重要な元素、換言すれば、耐食性を向上させる一方で、耐ラメラテア性を低下させる元素である。
　すなわち、Snは、原油タンクの底板などの強酸性の局部腐食環境において、鋼の表面に難溶性被膜を形成して、腐食を促進させるCl-（塩化物イオン）の拡散を抑制し、これにより、耐食性を高める効果がある。また、Snは、原油タンクの上甲板裏面などの弱酸性の全面腐食環境において、鋼の表面の錆中に取り込まれ、腐食を促進させるSO4 2-等のアニオン種の拡散を抑制し、これにより、耐食性を高める効果がある。これらの効果はSn量を0.01％以上とすることで発現する。また、特に、上甲板裏面などの全面腐食環境においては、Snの添加効果が大きく、Sn量を0.05％以上とすることにより、後述するCu、Ni、Sb、Ｗ、MoおよびSiのうち、Cu、Ni、Sb、Ｗ、およびMoを添加しなくとも、良好な耐食性を発現させることが可能となる。
　一方で、Snは鋼材中心部に偏析し易く、かような偏析部では、硬度が著しく増大するために、耐ラメラテア性が劣化する。特に、Sn量が0.20％を超えると、耐ラメラテア性が大きく劣化する。従って、耐ラメラテア性の確保の観点から、Sn量は0.20％以下とする。好ましくは0.15％以下である。より好ましくは0.10％以下である。 Sn: 0.01-0.20%
Sn is an element necessary for improving local corrosion resistance and overall corrosion resistance, and is an important element involved in lamellar resistance, in other words, improving corrosion resistance while reducing lamellar resistance. It is an element to be made.
That, Sn, in strongly acidic local corrosion environments such as the bottom plate of a crude oil tank, to form a poorly soluble film on the surface of the steel, Cl to promote corrosion - inhibiting the diffusion of (chloride ions), thereby , Has the effect of increasing corrosion resistance. In addition, Sn is incorporated into the rust on the steel surface in a mildly acidic overall corrosive environment such as the upper back of a crude oil tank, and suppresses diffusion of anionic species such as SO 4 2- that promotes corrosion. Thus, there is an effect of improving the corrosion resistance. These effects are manifested when the Sn content is 0.01% or more. In particular, in the entire corrosive environment such as the back of the upper deck, the effect of addition of Sn is large. By setting the Sn amount to 0.05% or more, among Cu, Ni, Sb, W, Mo and Si described later, Cu Even without adding Ni, Sb, W, and Mo, good corrosion resistance can be expressed.
On the other hand, Sn is easily segregated at the center of the steel material, and in such a segregated part, the hardness is remarkably increased, so that the lamellar resistance is deteriorated. In particular, when the Sn content exceeds 0.20%, the lamellar resistance is greatly deteriorated. Therefore, from the viewpoint of ensuring the lamellar resistance, the Sn content is 0.20% or less. Preferably it is 0.15% or less. More preferably, it is 0.10% or less.
Ｎ：0.0080％以下
　Ｎは、靭性を低下させる有害な元素であるので、極力低減させることが望ましい。特に、Ｎ量が0.0080％を超えると、靭性の低下が大きくなる。従って、Ｎ量は0.0080％以下とする。好ましくは0.0070％である。なお、下限については特に限定されないが、0.0005％とすることが好ましい。 N: 0.0080% or less Since N is a harmful element that lowers toughness, it is desirable to reduce it as much as possible. In particular, when the N content exceeds 0.0080%, the toughness is greatly reduced. Therefore, the N content is 0.0080% or less. Preferably it is 0.0070%. The lower limit is not particularly limited, but is preferably 0.0005%.
Cu：0.01～0.50％、Ni：0.01～0.50％、Sb：0.01～0.30％、Ｗ：0.01～0.50％、Mo：0.01～0.50％およびSi：0.01～1.50％のうちから選んだ１種または２種以上
　Cu、Ni、Sb、W、MoおよびSiは、原油タンカーの原油タンクの上甲板などの全面腐食環境での耐食性を向上させる元素である。
　上述したように、Snは耐食性の向上に有効な元素であるものの、耐ラメラテア性の観点から多量には含有させることができない。そのため、原油タンカーの原油タンクの上甲板などの全面腐食環境での優れた耐食性を得るためには、Cu：0.01～0.50％、Ni：0.01～0.50％、Sb：0.01～0.30％、Ｗ：0.01～0.50％、Mo：0.01～0.50％およびSi：0.01～1.50％のうちから選んだ１種または２種以上を含有させることが必要である。
　ここで、Cu、NiおよびSbはそれぞれ、腐食の進行に伴い、鋼材表面からCu2+、Ni2+およびSb3+として遊離し、腐食因子であるS2-と結びつき、CuS、NiS、Sb2S3を形成する。その結果、鋼界面へのS2-の透過を抑制する。また、Ｗ、MoおよびSiはそれぞれ、WO4 2-、MoO4 2-およびSiO4 4-として遊離し、錆中に取り込まれ、錆にカチオン選択透過性を付与し、鋼界面へのSO4 2-やS2-等の腐食性アニオンの透過を電気的に抑制する。
　これらの効果は、上述のSnの防食作用が共存した場合において顕在化し、Cu、Ni、Sb、Ｗ、MoおよびSi量がそれぞれ0.01％以上で発現する。しかし、いずれの元素も多く含有させると、溶接性や靱性を劣化させ、コストの観点からも不利になる。
　従って、Cu量は0.01～0.50％の範囲、Ni量は0.01～0.50％の範囲、Sb量は0.01～0.30％の範囲、Ｗ量は0.01～0.50％の範囲、Mo量は0.01～0.50％の範囲、Si量は0.01～1.50％の範囲とする。
　好ましくは、Cu量は0.02％以上、0.40％以下、Ni量は0.02％以上、0.40％以下、Sb量は0.02％以上、0.25％以下、Ｗ量は0.02％以上、0.40％以下、Mo量は0.02％以上、0.40％以下、Si量は0.01％以上、1.00％以下である。 One or two selected from Cu: 0.01 to 0.50%, Ni: 0.01 to 0.50%, Sb: 0.01 to 0.30%, W: 0.01 to 0.50%, Mo: 0.01 to 0.50%, and Si: 0.01 to 1.50% Species and above Cu, Ni, Sb, W, Mo and Si are elements that improve the corrosion resistance in a full corrosive environment such as the upper deck of a crude oil tank of a crude oil tanker.
As described above, Sn is an element effective for improving corrosion resistance, but cannot be contained in a large amount from the viewpoint of lamellar resistance. Therefore, in order to obtain excellent corrosion resistance in the entire corrosive environment such as the upper deck of crude oil tanks of crude oil tankers, Cu: 0.01 to 0.50%, Ni: 0.01 to 0.50%, Sb: 0.01 to 0.30%, W: 0.01 It is necessary to contain one or more selected from ˜0.50%, Mo: 0.01 to 0.50%, and Si: 0.01 to 1.50%.
Here, Cu, Ni, and Sb are released from the steel surface as Cu 2+ , Ni 2+, and Sb 3+ as corrosion progresses, and are associated with the corrosion factor S 2-, and CuS, NiS, Sb, respectively. 2 S 3 is formed. As a result, permeation of S 2− to the steel interface is suppressed. W, Mo, and Si are liberated as WO 4 2− , MoO 4 2−, and SiO 4 4− , respectively, and are taken into rust, imparting cation selective permeability to rust, and SO 4 to the steel interface. Electrically inhibits permeation of corrosive anions such as 2- and S 2- .
These effects become apparent when the above-described anticorrosive action of Sn coexists, and are manifested when the amounts of Cu, Ni, Sb, W, Mo, and Si are each 0.01% or more. However, if any element is contained in a large amount, the weldability and toughness are deteriorated, which is disadvantageous from the viewpoint of cost.
Therefore, Cu content is in the range of 0.01 to 0.50%, Ni content is in the range of 0.01 to 0.50%, Sb content is in the range of 0.01 to 0.30%, W content is in the range of 0.01 to 0.50%, Mo content is in the range of 0.01 to 0.50%. The range and Si content should be 0.01 to 1.50%.
Preferably, Cu amount is 0.02% or more and 0.40% or less, Ni amount is 0.02% or more and 0.40% or less, Sb amount is 0.02% or more and 0.25% or less, W amount is 0.02% or more and 0.40% or less, Mo amount is 0.02% or more and 0.40% or less, and Si amount is 0.01% or more and 1.00% or less.
　また、上述したように、Snによる耐ラメラテア性の低下機構は、Ｓによる耐ラメラテア性の低下機構とは異なっている。しかし、ＳとSnによる耐ラメラテア性の低下は互いに相乗して作用する。このため、耐ラメラテア性を一層向上させる観点からは、ＳおよびSnの含有量について、次式(2)の関係を満足させることが好適である。
　　10000×[％S]×[％Sn]2 ≦ 1.40 --- (2)
　ここで、[％S]および[％Sn]はそれぞれ、成分組成におけるＳおよびSnの含有量（質量％）である。 Further, as described above, the mechanism for decreasing lamellar resistance by Sn is different from the mechanism for decreasing lamellar resistance by S. However, the reduction of lamellar resistance due to S and Sn acts synergistically. For this reason, from the viewpoint of further improving the lamellar resistance, it is preferable that the relationship of the following formula (2) is satisfied with respect to the S and Sn contents.
10000 × [% S] × [% Sn] 2 ≤ 1.40 --- (2)
Here, [% S] and [% Sn] are the contents (mass%) of S and Sn in the component composition, respectively.
　上掲(2)式は、耐ラメラテア性に対するSn量の影響がＳ量の影響に比べて非常に大きいことを意味している。すなわち、Snを厳密に管理することが、耐ラメラテア性を確保するうえで特に重要であることを意味している。
　ここで、10000×[％S]×[％Sn]2は、1.20以下とすることがより好ましい。10000×[％S]×[％Sn]2の下限については特に限定されるものではないが、0.001とすることが好ましい。
　なお、ラメラテアを抑制するにあたっては、Ｓ量とSn量をともに上記した範囲に限定することが前提となることは言うまでもない。 The above equation (2) means that the influence of Sn amount on the lamellar resistance is much larger than the influence of S amount. That is, strictly managing Sn means that it is particularly important in securing the lamellar resistance.
Here, 10000 × [% S] × [% Sn] 2 is more preferably 1.20 or less. The lower limit of 10000 × [% S] × [% Sn] 2 is not particularly limited, but is preferably 0.001.
Needless to say, in order to suppress the lamellar tear, it is assumed that both the S amount and the Sn amount are limited to the above-described range.
　以上、基本成分について説明したが、本発明の原油タンカー用鋼材では、以下に述べる元素を適宜含有させることができる。
Cr：0.01～0.50％およびCo：0.01～0.50％のうちから選んだ１種または２種
　CrおよびCoは、腐食の進行に伴って錆層中に移行し、Cl-の錆層への侵入を遮断することで、錆層と地鉄の界面へのCl-の濃縮を抑制し、これによって耐食性の向上に寄与する。また、Zn含有プライマーを鋼材表面に塗布したときには、CrおよびCoは、Feを中心としてZnなどと複合酸化物を形成して、長期間にわたり鋼板表面にZnを存続させることを可能とし、これにより一層耐食性を向上させる。このような効果は、特に原油タンカーの原油タンクの底板のように、原油油分から分離された高濃度の塩分を含む液と接触する部分において特に顕著となる。すなわち、鋼材にZn含有プライマー処理を施して、この鋼材を、原油油分から分離された高濃度の塩分を含む液と接触する部分に使用する場合、CrやCoを含有した鋼材では、これらの元素を含有しない鋼材と比較して、耐食性が大きく向上する。
　このような効果は、Cr量またはCo量が0.01％未満では十分には得られない。一方、Cr量またはCo量が0.50％を超えると、溶接部の靭性を劣化させる。また、Crについては、加水分解反応を生じる元素であり、腐食部でのpHを低下させる。すなわち、Crを過剰に添加すると、トータルでの耐食性を劣化させるおそれもある。
　従って、CrおよびCoを含有させる場合、その量はいずれも0.01～0.50％の範囲とする。好ましくは0.02％以上、0.30％以下である。より好ましくは0.03％以上、0.20％以下である。 The basic components have been described above, but the elements described below can be appropriately contained in the steel for crude oil tankers of the present invention.
Cr: 0.01 ~ 0.50% and Co: 0.01 1 kind or two kinds Cr and Co chose from among to 0.50 percent, with the progress of corrosion proceeds to rust layer, Cl - of entry into rust layer By blocking, the concentration of Cl- at the interface between the rust layer and the ground iron is suppressed, thereby contributing to the improvement of corrosion resistance. In addition, when a Zn-containing primer is applied to the steel surface, Cr and Co form a composite oxide with Zn, etc., centered on Fe, making it possible to keep Zn on the steel sheet surface for a long period of time. Further improve corrosion resistance. Such an effect is particularly remarkable in a portion that comes into contact with a liquid containing a high concentration of salt separated from a crude oil component, such as a bottom plate of a crude oil tank of a crude oil tanker. That is, when the steel material is subjected to a Zn-containing primer treatment and this steel material is used in a portion that comes into contact with a liquid containing high-concentration salt separated from crude oil, these elements are contained in the steel material containing Cr or Co. Corrosion resistance is greatly improved compared to steel materials that do not contain.
Such an effect cannot be sufficiently obtained when the Cr content or the Co content is less than 0.01%. On the other hand, if the Cr content or Co content exceeds 0.50%, the toughness of the welded portion deteriorates. Cr is an element that causes a hydrolysis reaction and lowers the pH in the corroded part. That is, if Cr is added excessively, the total corrosion resistance may be deteriorated.
Therefore, when Cr and Co are contained, the amounts are both in the range of 0.01 to 0.50%. Preferably they are 0.02% or more and 0.30% or less. More preferably, it is 0.03% or more and 0.20% or less.
Ti：0.001～0.100％、Zr：0.001～0.100％、Nb：0.001～0.100％およびＶ：0.001～0.100％のうちから選んだ１種または２種以上
　Ti、Zr、NbおよびＶは、所望とする強度を確保する観点から、単独または複合して添加することができる。しかし、いずれの元素も過剰に含有させると、靱性および溶接性を劣化させる。このため、Ti、Zr、NbおよびＶを含有させる場合、その量はいずれも0.001～0.100％の範囲とする。好ましくは0.005％以上、0.050％以下である。 One or more selected from Ti: 0.001 to 0.100%, Zr: 0.001 to 0.100%, Nb: 0.001 to 0.100% and V: 0.001 to 0.100% Ti, Zr, Nb and V are desired From the viewpoint of securing strength, they can be added alone or in combination. However, if any element is excessively contained, toughness and weldability are deteriorated. For this reason, when Ti, Zr, Nb and V are contained, the amounts are all in the range of 0.001 to 0.100%. Preferably it is 0.005% or more and 0.050% or less.
Ca：0.0001～0.0100％、Mg：0.0001～0.0200％およびREM：0.0002～0.2000％のうちから選んだ１種または２種以上
　Ca、MgおよびREMは溶接部の靱性を向上させる観点から、単独または複合して添加することができる。しかし、いずれの元素も過剰に含有させると、却って溶接部の靱性劣化を招く。また、コストも増加する。従って、Ca、MgおよびREMを含有させる場合、Ca量は0.0001～0.0100％、Mg量は0.0001～0.0200％、REM量は0.0002～0.2000％の範囲とする。 One or more selected from Ca: 0.0001 to 0.0100%, Mg: 0.0001 to 0.0200%, and REM: 0.0002 to 0.2000% Ca, Mg and REM are used singly or in combination from the viewpoint of improving the toughness of the weld Can be added. However, if any of these elements is excessively contained, the toughness of the weld is deteriorated. Also, the cost increases. Therefore, when Ca, Mg and REM are contained, the Ca amount is in the range of 0.0001 to 0.0100%, the Mg amount is in the range of 0.0001 to 0.0200%, and the REM amount is in the range of 0.0002 to 0.2000%.
Ｂ：0.0001～0.0300％
　Ｂは、鋼材の焼入性を向上させる元素である。また、所望の強度を確保する観点から、Ｂを含有させることができる。このような観点からは、Ｂ量を0.0001％以上とすることが有効である。しかし、Ｂを過剰に含有させる、特にＢ量が0.0300％を超えると、靱性の大幅な劣化を招く。従って、Ｂを含有させる場合には、その量は0.0001～0.0300％の範囲とする。 B: 0.0001-0.0300%
B is an element that improves the hardenability of the steel material. Moreover, B can be contained from a viewpoint of ensuring desired intensity | strength. From such a viewpoint, it is effective to set the B amount to 0.0001% or more. However, when B is contained excessively, especially when the amount of B exceeds 0.0300%, the toughness is greatly deteriorated. Therefore, when B is contained, the amount is in the range of 0.0001 to 0.0300%.
　上記以外の成分は、Ｆｅおよび不可避的不純物である。 Components other than the above are Fe and inevitable impurities.
　以上、本発明の原油タンカー用鋼材の成分組成について説明したが、本発明の原油タンカー用鋼材では、Sn偏析度を次のように制御することが極めて重要である。
Sn偏析度：18未満
　Snの中心偏析によって、偏析部の硬度は大きく増加する。そして、このような偏析部がラメラテア発生の起点となる。すなわち、Snを含有する成分組成において優れた耐ラメラテア特性を確保するには、Snの中心偏析を抑制して偏析部の硬度増加を抑制することが重要である。このような観点から、Sn偏析度は18未満とする。好ましくは16未満である。より好ましくは15以下である。下限については特に限定されるものではないが、2とすることが好ましい。 The component composition of the steel for crude oil tankers of the present invention has been described above. However, in the steel for crude oil tankers of the present invention, it is extremely important to control the degree of Sn segregation as follows.
Sn segregation degree: less than 18 The central segregation of Sn greatly increases the hardness of the segregated part. And such a segregation part becomes a starting point of lamellar tear generation. In other words, in order to ensure excellent lamellar tear resistance in the component composition containing Sn, it is important to suppress the center segregation of Sn and suppress the increase in hardness of the segregated portion. From such a viewpoint, the Sn segregation degree is set to less than 18. Preferably it is less than 16. More preferably, it is 15 or less. The lower limit is not particularly limited, but is preferably 2.
　なお、ここでいうSn偏析度とは、鋼材の圧延方向と平行に切断した断面（鋼材表面に垂直な断面）において、電子線マイクロアナライザ（以下、EPMAと示す）の線分析により得られる平均のSn濃度に対する中心偏析部のSn濃度の比である。
　具体的には、鋼材の厚さをｔ（mm）、幅（鋼材の圧延方向および厚さ方向と直角の方向）をＷ（mm）としたとき、まず、鋼材の圧延方向と平行に切断した断面（鋼材表面に垂直な断面）の鋼材の厚さ方向：(0.5±0.1)×ｔ、圧延方向：15mmの面領域（すなわち、鋼材の厚さ方向の中心位置を包含する面領域）において、ビーム径：20μｍ、ピッチ：20μｍの条件で、SnのEPMA面分析を実施する。なお、SnのEPMA面分析は、１／４×Ｗ、１／２×Ｗおよび３／４×Ｗの位置の３つの断面視野にて実施する。
　ついで、上記EPMA面分析から各断面視野においてSn濃度が最も高い位置を選択し、当該位置においてそれぞれ、鋼材の厚さ方向にビーム径：５μｍ、ピッチ：５μｍの条件で、SnのEPMA線分析を実施する。なお、EPMA線分析の実施にあたっては、鋼材の表裏面からそれぞれ25μmまでの領域は除外する。
　そして、測定ラインごとにSn濃度（質量濃度）の最大値を求め、これらの平均値を中心偏析部のSn濃度（質量濃度）とし、この中心偏析部のSn濃度を、測定ラインの全測定値の算術平均値である平均のSn濃度（質量濃度）で除した値を、Sn偏析度とする。
　すなわち、
　［Sn偏析度］＝［中心偏析部のSn濃度］／［平均のSn濃度］
　である。 In addition, Sn segregation degree here is the average obtained by the line analysis of an electron beam microanalyzer (henceforth EPMA) in the cross section (cross section perpendicular | vertical to the steel material surface) cut | disconnected in parallel with the rolling direction of steel materials. This is the ratio of the Sn concentration in the central segregation part to the Sn concentration.
Specifically, when the thickness of the steel material is t (mm) and the width (the rolling direction of the steel material and the direction perpendicular to the thickness direction) is W (mm), the steel material is first cut parallel to the rolling direction of the steel material. In the thickness direction of the steel material of the cross section (cross section perpendicular to the steel material surface): (0.5 ± 0.1) × t, rolling direction: 15 mm surface area (that is, the surface area including the center position in the thickness direction of the steel material) EPMA surface analysis of Sn is performed under the conditions of a beam diameter: 20 μm and a pitch: 20 μm. In addition, Sn's EPMA surface analysis is performed in three cross-sectional visual fields at positions of 1/4 × W, 1/2 × W, and 3/4 × W.
Next, select the position where the Sn concentration is the highest in each cross-sectional view from the above EPMA surface analysis, and perform the EPMA line analysis of Sn under the conditions of beam diameter: 5 μm and pitch: 5 μm in the thickness direction of the steel at each position. carry out. In conducting the EPMA line analysis, the area from the front and back surfaces of the steel material to 25 μm is excluded.
Then, the maximum value of the Sn concentration (mass concentration) is obtained for each measurement line, and the average value of these values is taken as the Sn concentration (mass concentration) of the central segregation part. The value obtained by dividing by the average Sn concentration (mass concentration), which is the arithmetic average value, is the Sn segregation degree.
That is,
[Sn segregation degree] = [Sn concentration in central segregation part] / [Average Sn concentration]
It is.
　上述したように、本発明の原油タンカー用鋼材は、優れた耐ラメラテア特性を確保する観点から、Snの中心偏析を抑制する、すなわち、Snの中心偏析の度合いを示すSn偏析度を所定値以下に制御することが極めて重要である。ここで、Sn偏析度は、成分組成が同じであっても、製造条件によって大きく変化する。このため、Snの中心偏析を抑制するには、鋼材の製造方法を適切に制御することが非常に重要である。
　以下、本発明の原油タンカー用鋼材の好適製造方法について説明する。 As described above, the steel material for a crude oil tanker of the present invention suppresses the center segregation of Sn from the viewpoint of securing excellent lamellar resistance properties, that is, the Sn segregation degree indicating the degree of Sn center segregation is a predetermined value or less. It is extremely important to control it. Here, the degree of Sn segregation varies greatly depending on manufacturing conditions even if the component composition is the same. For this reason, in order to suppress the center segregation of Sn, it is very important to appropriately control the steel material manufacturing method.
Hereinafter, the suitable manufacturing method of the steel material for crude oil tankers of this invention is demonstrated.
　すなわち、本発明の鋼材は、上記した成分組成に調整した鋼を、転炉や電気炉、真空脱ガス等、公知の精錬プロセスを用いて溶製し、連続鋳造法あるいは造塊－分塊圧延法で鋼素材（スラブ）とし、ついでこの鋼素材を必要に応じて再加熱してから熱間圧延することにより、鋼板または形鋼等とすることで製造することができる。なお、鋼材の厚さは特に限定されるものではないが、好ましくは2～100mmである。より好ましくは3～80mmである。さらに好ましくは4～60mmである。
　ここで、連続鋳造の場合、鋳造速度（引抜速度）を0.3～2.8m/minとすることが好ましい。鋳造速度が0.3m/min未満では、操業効率が悪くなる。一方、鋳造速度が2.8m/minを超えると、表面温度ムラが生じ、また鋳片内部への溶鋼供給が不十分になって、Snの中心偏析が促される。Snの中心偏析を抑制する観点からは、より好ましくは0.4m/min以上、2.6m/min以下である。さらに好ましくは1.5m/min以下である。
　また、未凝固層を有する凝固末期の鋳片を、凝固収縮量と熱収縮量との和に相当する程度の圧下総量及び圧下速度で、圧下ロール群によって徐々に圧下しながら鋳造する軽圧下法を行うことが好ましい。 That is, the steel material of the present invention is obtained by melting steel adjusted to the above-described component composition using a known refining process such as a converter, electric furnace, vacuum degassing, etc., and continuously casting or ingot-bundling rolling. It can be manufactured by using a steel material (slab) by the method, and then re-heating the steel material as necessary, followed by hot rolling to obtain a steel plate or a shaped steel. The thickness of the steel material is not particularly limited, but is preferably 2 to 100 mm. More preferably, it is 3 to 80 mm. More preferably, it is 4 to 60 mm.
Here, in the case of continuous casting, the casting speed (drawing speed) is preferably 0.3 to 2.8 m / min. When the casting speed is less than 0.3 m / min, the operation efficiency is deteriorated. On the other hand, when the casting speed exceeds 2.8 m / min, surface temperature unevenness occurs, and the supply of molten steel to the inside of the slab becomes insufficient, which promotes center segregation of Sn. From the viewpoint of suppressing the center segregation of Sn, it is more preferably 0.4 m / min or more and 2.6 m / min or less. More preferably, it is 1.5 m / min or less.
In addition, a light reduction method in which an end-solidified slab having an unsolidified layer is cast while being gradually reduced by a reduction roll group at a reduction amount and a reduction speed corresponding to the sum of the solidification shrinkage and the heat shrinkage. It is preferable to carry out.
　次に、上記の鋼素材を所望の寸法形状に熱間圧延する際には、900℃～1350℃の温度に加熱することが好ましい。加熱温度が900℃未満では変形抵抗が大きく、熱間圧延が難しくなる。一方、加熱温度が1350℃を超えると、表面痕が発生したり、スケールロスや燃料原単位が増加したりする。
　また、特に、加熱温度が高いほど中心偏析部のSnの拡散が促されるため、耐ラメラテア性を確保する観点からは有利となる。このような観点から、加熱温度は1030℃以上とすることがより好ましい。
　さらに、上記加熱温度における保持時間は、60min以上とすることが好ましい。これにより、中心偏析部におけるSnの拡散が十分に促される。より好ましくは150min以上である。なお、上限については特に限定されるものではないが、1000minとすることが好ましい。 Next, when the steel material is hot-rolled to a desired size and shape, it is preferably heated to a temperature of 900 ° C. to 1350 ° C. When the heating temperature is less than 900 ° C., the deformation resistance is large and hot rolling becomes difficult. On the other hand, when the heating temperature exceeds 1350 ° C., surface marks are generated, scale loss and fuel consumption increase.
In particular, the higher the heating temperature, the more the diffusion of Sn in the central segregation part is promoted, which is advantageous from the viewpoint of securing the lamellar resistance. From such a viewpoint, the heating temperature is more preferably 1030 ° C. or higher.
Further, the holding time at the heating temperature is preferably 60 min or longer. Thereby, the diffusion of Sn in the central segregation part is sufficiently promoted. More preferably, it is 150 min or more. The upper limit is not particularly limited, but is preferably 1000 min.
　なお、鋼素材の温度が、もともと1030～1350℃の範囲の場合でかつ、その温度範囲に60min以上保持されていた場合には、加熱せずに、そのまま熱間圧延に供してもよい。また、熱間圧延後に得られた熱延板に、再加熱処理、酸性、冷間圧延を施し、所定板厚の冷延板としてもよい。
　熱間圧延では、仕上圧延終了温度を650℃以上とすることが好ましい。仕上圧延終了温度が650℃未満では、変形抵抗の増大により圧延荷重が増加し、圧延の実施が困難となる。 In the case where the temperature of the steel material is originally in the range of 1030 to 1350 ° C. and is maintained in the temperature range for 60 minutes or more, it may be subjected to hot rolling without being heated. Further, the hot-rolled sheet obtained after hot rolling may be subjected to reheating treatment, acidity, and cold rolling to obtain a cold-rolled sheet having a predetermined thickness.
In hot rolling, it is preferable that the finish rolling finish temperature is 650 ° C. or higher. When the finish rolling finish temperature is less than 650 ° C., the rolling load increases due to an increase in deformation resistance, making it difficult to perform the rolling.
　熱間圧延後の冷却は、空冷、加速冷却のいずれの方法でもよいが、より高い強度を得たい場合には、加速冷却を行うことが好ましい。
　ここで、加速冷却を行う場合には、冷却速度を２～100℃/ｓ、冷却停止温度を700～400℃とするのが好ましい。すなわち、冷却速度が２℃/ｓ未満、および／または冷却停止温度が700℃超では、加速冷却の効果が小さく、十分な高強度化が達成されない場合がある。一方、冷却速度が100℃/ｓ超、および／または冷却停止温度が400℃未満では、鋼材の靭性が低下したり、鋼材の形状に歪が発生する場合がある。ただし、後工程において熱処理を施す場合はその限りではない。 Cooling after hot rolling may be either air cooling or accelerated cooling, but accelerated cooling is preferred when higher strength is desired.
Here, when performing accelerated cooling, it is preferable to set the cooling rate to 2 to 100 ° C./s and the cooling stop temperature to 700 to 400 ° C. That is, when the cooling rate is less than 2 ° C./s and / or the cooling stop temperature exceeds 700 ° C., the effect of accelerated cooling is small, and sufficient strength may not be achieved. On the other hand, if the cooling rate exceeds 100 ° C./s and / or the cooling stop temperature is less than 400 ° C., the toughness of the steel material may be reduced, or the shape of the steel material may be distorted. However, this is not the case when heat treatment is performed in the subsequent process.
　表１に示す成分組成になる鋼（残部はＦｅおよび不可避的不純物である）を、転炉で溶製して、表２に示す条件の連続鋳造により鋼スラブとした。これらの鋼スラブを1150℃に再加熱後、表２に示す条件で保持し、仕上圧延終了温度：800℃の熱間圧延を施し、板厚：40mmの鋼板を得た。なお、熱間圧延後の冷却は、冷却速度：10℃/ｓ、冷却停止温度：550℃の水冷（加速冷却）とした。
　そして、上記した方法により、得られた鋼板におけるSn偏析度を求めた。結果を表２に併記する。 Steel having the component composition shown in Table 1 (the balance being Fe and inevitable impurities) was melted in a converter and made into a steel slab by continuous casting under the conditions shown in Table 2. These steel slabs were reheated to 1150 ° C. and then held under the conditions shown in Table 2, followed by hot rolling at a finish rolling finish temperature of 800 ° C. to obtain a steel plate having a plate thickness of 40 mm. The cooling after hot rolling was water cooling (accelerated cooling) at a cooling rate of 10 ° C./s and a cooling stop temperature of 550 ° C.
And the Sn segregation degree in the obtained steel plate was calculated | required by the above-mentioned method. The results are also shown in Table 2.
　また、上記のようにして得られた鋼板について、以下の要領で、原油タンカーの原油タンクの上甲板裏面環境を模擬した全面腐食試験（結露試験）と底板環境を模擬した局部腐食試験（耐酸試験）をそれぞれ行った。
（１）全面腐食試験（結露試験）
　原油タンカーの原油タンクの上甲板裏面における全面腐食に対する耐食性（耐全面腐食性）を評価するため、上記No.1～58の鋼板それぞれについて、表面１mmの位置から、幅25mm×長さ60mm×厚さ５mmの矩形の小片を切り出し、その表面を600番手のエメリー紙で研磨した。ついで、裏面および端面は腐食しないようにテープでシールして試験片１を準備し、図１に示す腐食試験装置を用いて全面腐食試験を行った。この腐食試験装置は、腐食試験槽２と温度制御プレート３とから構成されている。腐食試験槽２には温度が30℃に保持された水６が注入されており、またその水６中には、導入ガス管４を介して、13vol％CO2、４vol％O2、0.01vol％SO2、0.05vol％H2S、残部N2からなる混合ガスを導入しており、これにより、腐食試験槽２内を過飽和の水蒸気で充満させて、原油タンクの上甲板裏の腐食環境を再現している。そして、この腐食試験槽２の上裏面に試験片１をセットし、この試験片１に対して、ヒーターと冷却装置を内蔵した温度制御プレート３を介して25℃×1.5時間＋50℃×22.5時間を１サイクルとする温度変化を21、49、77および98日間繰り返して付与し、試験片１の表面に結露水を生じさせて、全面腐食が生じるようにした。なお、図１中、符号５は試験槽からの排出ガス管を示す。
　上記の腐食試験後、各試験片表面の錆を除去し、試験前後の質量変化から腐食による質量減を求め、この値から１年当たりの板厚減少量（片面の腐食速度）に換算した。そして、４試験期間の値から25年後の予測損耗量を求め、腐食量が2.0mm以下の場合には耐全面腐食性が良好（○）、2.0mm超の場合には耐全面腐食性が不良（×）と評価した。 In addition, for the steel plates obtained as described above, a full corrosion test (condensation test) simulating the environment of the upper deck of a crude oil tank of a crude oil tanker and a local corrosion test (acid resistance test) simulating the bottom plate environment in the following manner. ).
(1) Overall corrosion test (condensation test)
In order to evaluate the corrosion resistance (total corrosion resistance) against the overall corrosion of the upper tank back surface of the crude oil tank of the crude oil tanker, each of the above No.1 to 58 steel plates is 25mm wide x 60mm long x thick from the position of 1mm surface. A 5 mm long rectangular piece was cut out and the surface was polished with 600th emery paper. Next, the back surface and the end surface were sealed with tape so as not to corrode, and a test piece 1 was prepared, and a full surface corrosion test was performed using the corrosion test apparatus shown in FIG. This corrosion test apparatus includes a corrosion test tank 2 and a temperature control plate 3. Water 6 having a temperature maintained at 30 ° C. is injected into the corrosion test tank 2, and 13 vol% CO 2 , 4 vol% O 2 , 0.01 vol are introduced into the water 6 through the introduction gas pipe 4. % SO 2 , 0.05vol% H 2 S, and the balance N 2 are introduced. By this, the corrosion test tank 2 is filled with supersaturated steam, and the corrosive environment behind the upper deck of the crude oil tank Is reproduced. Then, a test piece 1 is set on the upper and rear surfaces of the corrosion test tank 2, and 25 ° C. × 1.5 hours + 50 ° C. × 22.5 hours are applied to the test piece 1 through a temperature control plate 3 incorporating a heater and a cooling device. Was repeatedly applied for 21, 49, 77, and 98 days to generate condensed water on the surface of the test piece 1 to cause general corrosion. In addition, the code | symbol 5 shows the exhaust gas pipe | tube from a test tank in FIG.
After the above corrosion test, the rust on the surface of each test piece was removed, the mass loss due to corrosion was determined from the mass change before and after the test, and this value was converted into a reduction in plate thickness per year (corrosion rate on one side). The predicted amount of wear after 25 years is calculated from the values of the four test periods. When the corrosion amount is 2.0 mm or less, the general corrosion resistance is good (○), and when it exceeds 2.0 mm, the general corrosion resistance is good. It was evaluated as defective (x).
（２）局部腐食試験（耐酸試験）
　原油タンカーの原油タンクの底板における局部腐食環境（孔食）における耐食性（耐局部腐食性）を評価するため、上記No.1～58の鋼板についてそれぞれ、表面１mmの位置から、幅25mm×長さ60mm×厚さ５mmの矩形の小片を切り出し、その表面を600番手のエメリー紙で研磨し、試験片を準備した。
　ついで、10質量％NaCl水溶液を、濃塩酸を用いてClイオン濃度：10質量％、pH：0.85に調製した試験溶液を作製し、試験片の上部に開けた３mmφの孔にテグスを通して吊るし、各試験片について２Ｌの試験溶液中に168時間浸漬する腐食試験を行った。なお、試験溶液は、予め30℃に加温・保持し、24時間毎に新しい試験溶液と交換した。
　上記腐食試験に用いた装置を図２に示す。この腐食試験装置は、腐食試験槽８、恒温槽９の二重構造の装置で、腐食試験槽８には上記試験溶液10が入れられ、その中に試験片７がテグス11で吊るされて浸漬されている。試験溶液10の温度は、恒温槽９に入れた水12の温度を調整することで保持している。
　上記の腐食試験後、試験片表面に生成した錆を除去した後、試験前後の質量差を求め、この差を全表面積で割り戻し、１年当たりの板厚減少量（両面の腐食速度）を求めた。その結果、腐食速度が1.0mm/y以下の場合を耐局部腐食性が良好（○）、腐食速度が1.0mm/y超の場合を耐局部腐食性が不良（×）と評価した。 (2) Local corrosion test (acid resistance test)
In order to evaluate the corrosion resistance (local corrosion resistance) in the local corrosive environment (pitting corrosion) on the bottom plate of the crude oil tank of the crude oil tanker, each of the steel plates No. 1 to 58 above, from the position of 1 mm surface, 25 mm width x length A 60 mm × 5 mm thick rectangular piece was cut out and its surface was polished with 600th emery paper to prepare a test piece.
Next, a 10% by mass NaCl aqueous solution was prepared using concentrated hydrochloric acid to prepare a Cl ion concentration: 10% by mass, pH: 0.85, and suspended through 3mmφ holes in the upper part of the test piece. The test piece was subjected to a corrosion test in which it was immersed in a 2 L test solution for 168 hours. The test solution was preheated and maintained at 30 ° C. and replaced with a new test solution every 24 hours.
The apparatus used for the corrosion test is shown in FIG. This corrosion test apparatus is a dual structure apparatus consisting of a corrosion test tank 8 and a constant temperature bath 9, and the test solution 10 is put in the corrosion test tank 8, and the test piece 7 is suspended and immersed in the teg 11 therein. Has been. The temperature of the test solution 10 is maintained by adjusting the temperature of the water 12 placed in the thermostatic chamber 9.
After removing the rust generated on the surface of the test piece after the above corrosion test, obtain the mass difference before and after the test, divide this difference by the total surface area, and calculate the reduction in thickness (corrosion rate on both sides) per year. Asked. As a result, when the corrosion rate was 1.0 mm / y or less, the local corrosion resistance was evaluated as good (◯), and when the corrosion rate was higher than 1.0 mm / y, the local corrosion resistance was evaluated as poor (×).
　さらに、以下の要領で、耐ラメラテア性の評価を行った。
（３）耐ラメラテア性の評価
　ClassNK 鋼船規則・同検査要領（K編、第2章）に準拠して、上記のようにして得られたNo.1～58の鋼板について、鋼板の板厚方向（Z方向）の引張試験を実施し、絞り値（RA）を算出た。そして、算出した絞り値（RA）に基づき、以下の基準で耐ラメラテア性を評価した。
　◎（合格、特に優れる）：70以上
　○（合格）：35以上70未満
　△（不合格）：25以上35未満
　×（不合格）：25未満 Furthermore, the lamellar tear resistance was evaluated in the following manner.
(3) Evaluation of lamellar tear resistance No. 1 to 58 steel plates obtained as described above according to the ClassNK Steel Ship Rules and Inspection Procedures (Part K, Chapter 2) Tensile test in the direction (Z direction) was performed, and the aperture value (RA) was calculated. Based on the calculated aperture value (RA), the lamellar resistance was evaluated according to the following criteria.
◎ (pass, especially excellent): 70 or more ○ (pass): 35 or more and less than 70 △ (failure): 25 or more and less than 35 × (failure): less than 25
　（１）～（３）の評価結果を表２に併記する。なお、表２中の総合評価は、上記した（１）～（３）の評価が全て「○」または「◎」の場合を「合格」、（１）～（３）までの評価において１つでも「△」または「×」がある場合を「不合格」としている。 Table 2 shows the evaluation results of (1) to (3). In addition, the overall evaluation in Table 2 is “Pass” when all of the evaluations (1) to (3) above are “◯” or “◎”, and one evaluation in the evaluations from (1) to (3). However, a case where “△” or “×” is present is regarded as “fail”.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-I000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-I000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　表２に示したとおり、発明例はいずれも、優れた耐全面腐食性と耐局部腐食性、さらには優れた耐ラメラテア性を兼ね備えている。
　これに対し、比較例では、耐全面腐食性、耐局部腐食性および耐ラメラテア性の少なくとも１つについて、十分な特性が得られていない。 As shown in Table 2, all of the inventive examples have excellent overall corrosion resistance and local corrosion resistance, as well as excellent lamellar resistance.
On the other hand, in the comparative example, sufficient characteristics are not obtained for at least one of the general corrosion resistance, the local corrosion resistance, and the lamellar resistance.
　すなわち、比較例No.42、48、52はS量が上限を超えているため、耐局部腐食性および耐ラメラテア性について、十分な特性が得られていない。
　また、比較例No.43、47、50はSn量が上限を超えているため、耐ラメラテア性について、十分な特性が得られていない。
　比較例No.44はS量が上限を超えており、また所定量のCu、Ni、Sb、W、MoおよびSiが含有されていないため、耐全面腐食性、耐局部腐食性および耐ラメラテア性について、十分な特性が得られていない。
　比較例No.45はSn量が下限を下回っているため、耐全面腐食性と耐局部腐食性について、十分な特性が得られていない。
　比較例No.46はS量およびSn量が上限を超えているため、耐局部腐食性および耐ラメラテア性について、十分な特性が得られていない。
　比較例No.49は所定量のCu、Ni、Sb、W、MoおよびSiが含有されていないため、耐全面腐食性について、十分な特性が得られていない。
　比較例No.51はS量が上限を超えており、またSn量が下限を下回っているため、耐全面腐食性、耐局部腐食性および耐ラメラテア性について、十分な特性が得られていない。
　比較例No.53～56はSn偏析度が上限を超えているため、耐ラメラテア性について、十分な特性が得られていない。 That is, in Comparative Examples No. 42, 48, and 52, since the amount of S exceeds the upper limit, sufficient characteristics are not obtained with respect to local corrosion resistance and lamellar resistance.
In Comparative Examples No. 43, 47, and 50, the Sn amount exceeds the upper limit, so that sufficient characteristics for lamellar resistance are not obtained.
In Comparative Example No. 44, the amount of S exceeds the upper limit and does not contain the prescribed amount of Cu, Ni, Sb, W, Mo and Si, so it has general corrosion resistance, local corrosion resistance and lamellar resistance. However, sufficient characteristics have not been obtained.
In Comparative Example No. 45, the Sn amount is below the lower limit, so that sufficient characteristics are not obtained with respect to general corrosion resistance and local corrosion resistance.
In Comparative Example No. 46, the amount of S and the amount of Sn exceeded the upper limit, so that sufficient characteristics were not obtained for local corrosion resistance and lamellar resistance.
Since Comparative Example No. 49 does not contain a predetermined amount of Cu, Ni, Sb, W, Mo, and Si, sufficient characteristics are not obtained for the general corrosion resistance.
In Comparative Example No. 51, the amount of S exceeds the upper limit and the amount of Sn is lower than the lower limit, so that sufficient characteristics are not obtained with respect to general corrosion resistance, local corrosion resistance, and lamellar resistance.
In Comparative Examples Nos. 53 to 56, the Sn segregation degree exceeds the upper limit, so that sufficient characteristics are not obtained for the lamellar resistance.
　１，７　試験片
　２，８　腐食試験槽
　３　温度制御プレート
　４　導入ガス管
　５　排出ガス管
　６，12　水
　９　恒温槽
　10　試験溶液
　11　テグス DESCRIPTION OF SYMBOLS 1,7 Test piece 2,8 Corrosion test tank 3 Temperature control plate 4 Introducing gas pipe 5 Exhaust gas pipe 6,12 Water 9 Thermostatic bath 10 Test solution 11 Tegs

Claims (7)

  1. 　質量％で、
    　　Ｃ：0.03～0.18％、
    　　Mn：0.10～2.00％、
    　　Ｐ：0.030％以下、
    　　Ｓ：0.0070％以下、
    　　Al：0.001～0.100％、
    　　Sn：0.01～0.20％および
    　　Ｎ：0.0080％以下
    を含有するとともに、
    　　Cu：0.01～0.50％、
    　　Ni：0.01～0.50％、
    　　Sb：0.01～0.30％、
    　　Ｗ：0.01～0.50％、
    　　Mo：0.01～0.50％および
    　　Si：0.01～1.50％
    のうちから選んだ１種または２種以上を含有し、残部がFe及び不可避的不純物からなる成分組成を有し、
    　Sn偏析度が18未満である、原油タンカー用鋼材。
    　ここで、Sn偏析度は、次式(1)により定義される。
    　［Sn偏析度］＝［中心偏析部のSn濃度］／［平均のSn濃度］--- (1)     % By mass
    C: 0.03-0.18%
    Mn: 0.10 to 2.00%
    P: 0.030% or less,
    S: 0.0070% or less,
    Al: 0.001 to 0.100%,
    Sn: 0.01 to 0.20% and N: 0.0080% or less,
    Cu: 0.01-0.50%,
    Ni: 0.01-0.50%,
    Sb: 0.01-0.30%
    W: 0.01-0.50%
    Mo: 0.01 to 0.50% and Si: 0.01 to 1.50%
    Containing one or more selected from among the above, the remainder having a component composition consisting of Fe and inevitable impurities,
    Steel material for crude oil tankers with Sn segregation degree of less than 18.
    Here, the degree of Sn segregation is defined by the following equation (1).
    [Sn segregation degree] = [Sn concentration in central segregation part] / [Average Sn concentration] --- (1)
  2. 　前記成分組成におけるＳ含有量とSn含有量とが、次式(2)の関係を満足する、請求項１に記載の原油タンカー用鋼材。
    　　10000×[％S]×[％Sn]2 ≦ 1.40 --- (2)
    　ここで、[％S]および[％Sn]はそれぞれ、成分組成におけるＳおよびSnの含有量（質量％）である。     The steel material for crude oil tankers according to claim 1, wherein the S content and the Sn content in the component composition satisfy the relationship of the following formula (2).
    10000 × [% S] × [% Sn] 2 ≤ 1.40 --- (2)
    Here, [% S] and [% Sn] are the contents (mass%) of S and Sn in the component composition, respectively.
  3. 　前記成分組成が、さらに質量％で、
    　　Cr：0.01～0.50％および
    　　Co：0.01～0.50％
    のうちから選んだ１種または２種を含有する、請求項１または２に記載の原油タンカー用鋼材。     The component composition is further mass%,
    Cr: 0.01-0.50% and Co: 0.01-0.50%
    The steel material for crude oil tankers according to claim 1 or 2, comprising one or two selected from among them.
  4. 　前記成分組成が、さらに質量％で、
    　　Ti：0.001～0.100％、
    　　Zr：0.001～0.100％、
    　　Nb：0.001～0.100％および
    　　Ｖ：0.001～0.100％
    のうちから選んだ１種または２種以上を含有する、請求項１～３のいずれかに記載の原油タンカー用鋼材。     The component composition is further mass%,
    Ti: 0.001 to 0.100%,
    Zr: 0.001 to 0.100%,
    Nb: 0.001 to 0.100% and V: 0.001 to 0.100%
    The steel material for a crude oil tanker according to any one of claims 1 to 3, comprising one or more selected from among the above.
  5. 　前記成分組成が、さらに質量％で、
    　　Ca：0.0001～0.0100％、
    　　Mg：0.0001～0.0200％および
    　　REM：0.0002～0.2000％
    のうちから選んだ１種または２種以上を含有する、請求項１～４のいずれかに記載の原油タンカー用鋼材。     The component composition is further mass%,
    Ca: 0.0001 to 0.0100%
    Mg: 0.0001 to 0.0200% and REM: 0.0002 to 0.2000%
    The steel material for a crude oil tanker according to any one of claims 1 to 4, comprising one or more selected from among the above.
  6. 　前記成分組成が、さらに質量％で、
    　　Ｂ：0.0001～0.0300％
    を含有する、請求項１～５のいずれかに記載の原油タンカー用鋼材。     The component composition is further mass%,
    B: 0.0001-0.0300%
    The steel material for a crude oil tanker according to any one of claims 1 to 5, comprising:
  7. 　請求項１～６のいずれかに記載の原油タンク用鋼材を用いてなる原油タンカー。 A crude oil tanker using the steel material for a crude oil tank according to any one of claims 1 to 6.
PCT/JP2016/004508 2016-10-06 2016-10-06 Steel for crude oil tanker and crude oil tanker WO2018066019A1 (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2020070465A (en) * 2018-10-31 2020-05-07 日本製鉄株式会社 Corrosion-resistant steel for hold of coal carrying vessel or coal/ore carrying vessel
JP2022511465A (en) * 2018-11-30 2022-01-31 ポスコ Steel sheet having corrosion resistance in a combined condensation environment of sulfuric acid and sulfuric acid / hydrochloric acid and its manufacturing method

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2019244320A1 (en) * 2018-06-21 2019-12-26 日本製鉄株式会社 Steel sheet
WO2021100336A1 (en) * 2019-11-22 2021-05-27 Ｊｆｅスチール株式会社 Steel material for liquid ammonia transport and storage, and manufacturing method for steel material for liquid ammonia transport and storage

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001026844A (en) * 1999-07-16 2001-01-30 Sumitomo Metal Ind Ltd Steel for structural purpose excellent in lamellar tearability and its production
JP2012125824A (en) * 2010-12-17 2012-07-05 Sumitomo Metal Ind Ltd Continuously cast slab for high strength steel plate, continuous casting method therefor, and high strength steel plate
JP2012255184A (en) * 2011-06-08 2012-12-27 Nippon Steel & Sumitomo Metal Corp Steel material excellent in corrosion resistance

Family Cites Families (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5845360A (en) * 1981-09-10 1983-03-16 Toshiba Corp Low alloy steel with temper embrittlement resistance
JP3753088B2 (en) 2001-07-04 2006-03-08 住友金属工業株式会社 Steel material for cargo oil tanks
JP2007270196A (en) 2006-03-30 2007-10-18 Sumitomo Metal Ind Ltd Steel material for cargo oil tank
JP2010064110A (en) * 2008-09-11 2010-03-25 Sumitomo Metal Ind Ltd Welded joint for hold of ore/coal carrier
JP5586279B2 (en) * 2010-03-15 2014-09-10 新日鐵住金ステンレス株式会社 Ferritic stainless steel for automotive exhaust system parts
JP5836619B2 (en) * 2011-03-28 2015-12-24 新日鐵住金ステンレス株式会社 Duplex stainless steel with good acid resistance
CN102274937B (en) * 2011-08-18 2013-05-08 东北大学 Method for preparing ferrite stainless steel thin tape containing inversion segregation stannum
US20150004050A1 (en) * 2012-01-18 2015-01-01 Jfe Steel Corporation Steel strip for coiled tubing and method of manufacturing the same
CN102796943B (en) * 2012-08-31 2014-07-23 宝山钢铁股份有限公司 Thin strip steel for thin-wall oil drum and manufacturing method of thin strip steel
CN103866194B (en) * 2014-03-21 2015-11-04 东北大学 Stanniferous low gap ferritic stainless steel of a kind of unusual segregation and preparation method thereof
JP6331881B2 (en) * 2014-08-27 2018-05-30 新日鐵住金株式会社 Cu-Sn coexisting steel and method for producing the same
CN104195461A (en) * 2014-09-10 2014-12-10 首钢总公司 Corrosion-resistant steel capable of being used on upper deck and inner bottom plate for cargo oil tank of crude oil tanker simultaneously

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001026844A (en) * 1999-07-16 2001-01-30 Sumitomo Metal Ind Ltd Steel for structural purpose excellent in lamellar tearability and its production
JP2012125824A (en) * 2010-12-17 2012-07-05 Sumitomo Metal Ind Ltd Continuously cast slab for high strength steel plate, continuous casting method therefor, and high strength steel plate
JP2012255184A (en) * 2011-06-08 2012-12-27 Nippon Steel & Sumitomo Metal Corp Steel material excellent in corrosion resistance

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2020070465A (en) * 2018-10-31 2020-05-07 日本製鉄株式会社 Corrosion-resistant steel for hold of coal carrying vessel or coal/ore carrying vessel
JP7196539B2 (en) 2018-10-31 2022-12-27 日本製鉄株式会社 Corrosion resistant steel for hold of coal carrier or coal carrier
JP2022511465A (en) * 2018-11-30 2022-01-31 ポスコ Steel sheet having corrosion resistance in a combined condensation environment of sulfuric acid and sulfuric acid / hydrochloric acid and its manufacturing method
JP7333399B2 (en) 2018-11-30 2023-08-24 ポスコ カンパニー リミテッド Steel sheet having corrosion resistance in sulfuric acid and sulfuric acid/hydrochloric acid complex condensed environment and method for manufacturing the same

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