TW201333219A - High strength steel plate having excellent brittle crack arrestability and method for manufacturing same - Google Patents
High strength steel plate having excellent brittle crack arrestability and method for manufacturing same Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
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- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
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- C21D8/0226—Hot rolling
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- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
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- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2201/00—Treatment for obtaining particular effects
- C21D2201/05—Grain orientation
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/002—Bainite
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Abstract
Description
本發明係關於一種使用於船舶、海洋結構物、低溫儲料罐、建築/土木結構物等大型結構物中之較佳地作為板厚超過50 mm之厚鋼板的脆性龜裂傳播停止特性(brittle crack arrestability)優異之高強度厚鋼板(high strength steel plate)及其製造方法。 The present invention relates to a brittle crack propagation stop characteristic (brittle) which is preferably used as a thick steel plate having a thickness of more than 50 mm in a large structure such as a ship, a marine structure, a low temperature storage tank, or a building/civil structure. Crack arrestability) A high strength steel plate and a method for producing the same.
於船舶、海洋結構物、低溫儲料罐、建築/土木結構物等大型結構物中,由於伴隨脆性破裂(brittle fracture)之事故對經濟及環境造成之影響較大,因此,始終要求提高安全性,而對所使用之鋼材要求使用溫度下之韌性(toughness)或脆性龜裂傳播停止特性。 In large structures such as ships, marine structures, cryogenic storage tanks, and construction/civil structures, safety and environmental impact are always required due to the economic and environmental impacts of accidents involving brittle fractures. For the steel used, it is required to use the toughness or brittle crack propagation stop characteristic at the temperature.
集裝箱船或散裝貨船(bulk carrier)等船舶係於其結構上對船體外板(outer plate of ship's hull)使用高強度之厚壁材料,但最近隨著船體之大型化而推進進一步之高強度厚壁化,一般而言,鋼板之脆性龜裂傳播停止特性存在越高強度或越厚壁材料則越劣化之傾向,故而對脆性龜裂傳播停止特性之要求亦更加高度化。 Ships such as container ships or bulk carriers use high-strength thick-walled materials for the outer plate of ship's hull in their structure, but recently they have advanced further strength with the enlargement of the hull. In the case of thickening, in general, the brittle crack propagation stop characteristic of the steel sheet tends to be higher, and the thicker the wall material tends to deteriorate. Therefore, the requirements for the brittle crack propagation stop characteristics are further increased.
作為提高鋼材之脆性龜裂傳播停止特性之方法,自先前以來已知有增加Ni含量之方法,於液化天然氣(LNG:Liquefied Natural Gas)之儲料罐中,以商業規模使用有9%Ni鋼。 As a method for improving the brittle crack propagation characteristics of steel, a method of increasing the Ni content has been known from the prior, and in a storage tank of a liquefied natural gas (LNG: Liquefied Natural Gas), a commercial scale of 9% Ni steel is used. .
然而,由於Ni量之增加迫使成本大幅上升,故而難以應用於LNG儲料罐以外之用途。 However, since the increase in the amount of Ni forces the cost to rise significantly, it is difficult to apply to applications other than LNG storage tanks.
另一方面,對於未達到如LNG般之極低溫(cryogenic temperature)之船舶或管線(line pipe)中所使用的板厚未達50 mm之相對較薄之鋼材,可藉由熱機控制製程(TMCP,Thermo-Mechanical Control Process)法而實現細粒化,提高低溫韌性,並賦予優異之脆性龜裂傳播停止特性。 On the other hand, for relatively thin steels with a thickness of less than 50 mm used in ships or line pipes that do not reach the cryogenic temperature of LNG, the heat exchanger control process (TMCP) can be used. The "Thermo-Mechanical Control Process" method achieves fine granulation, improves low temperature toughness, and imparts excellent brittle crack propagation stop characteristics.
又,於專利文獻1中提出有如下鋼材:使表層部之組織超微細化(ultrafine-grained),以便不使合金成本上升而提高脆性龜裂傳播停止特性。 Further, Patent Document 1 proposes a steel material in which the microstructure of the surface layer portion is ultrafine-grained so as to improve the brittle crack propagation stop characteristics without increasing the alloy cost.
專利文獻1所記載之脆性龜裂傳播停止特性優異之鋼材之特徵在於:著眼於當脆性龜裂傳播時產生於鋼材表層部之剪切唇(塑性變形區域shear-lips)對提高脆性龜裂傳播停止特性有效之情況,而使剪切唇部分之晶粒微細化,從而吸收傳播之脆性龜裂具有之傳播能量。 The steel material excellent in the brittle crack propagation stop characteristic described in Patent Document 1 is characterized in that the shear lip (plastic deformation region shear-lips) which is generated in the surface layer portion of the steel material when the brittle crack propagates is focused on the improvement of the brittle crack propagation. When the stopping characteristic is effective, the crystal grains of the shear lip portion are made fine, thereby absorbing the propagation energy of the propagated brittle crack.
作為製造方法,記載有:反覆進行1次以上之藉由熱軋後之控制冷卻(controlled cooling)而將表層部分冷卻至Ar3變態點(Ar3 temperature)以下,其後停止控制冷卻並使表層部分重熱(reheat)至變態點以上的步驟,在此期間對鋼材施加軋縮,藉此,使其反覆變態或加工再結晶,從而於表層部分生成超微細之肥粒鐵組織(ferrite structure)或變韌鐵組織(bainite structure)。 As a manufacturing method, it is described that the surface layer portion is cooled to an Ar 3 transformation point (Ar 3 temperature) or less by controlled cooling after one or more times, and then the controlled cooling is stopped and the surface layer is stopped. Partially reheating to a step above the metamorphic point, during which the steel is subjected to rolling and shrinking, thereby causing it to be metamorphosed or processed to recrystallize, thereby generating an ultrafine ferrite structure in the surface layer. Or toughen iron structure (bainite structure).
進而,於專利文獻2中記載有:為了於設為以肥粒鐵-波來鐵(pearlite)為主體之微組織的鋼材中提高脆性龜裂傳播停止特性,而使鋼材之兩表面部由具有50%以上之肥粒鐵組織之層構成,該肥粒鐵組織具有近似圓的粒徑(average grain diameter equivalent to a circle)為5 μm以下、縱橫比(aspect ratio of the grains)為2以上之肥粒鐵粒,且抑制肥粒鐵粒徑之不均較為重要,作為抑制不均之方法,將精軋中之平均1道次之最大軋縮率(rolling reduction ratio)設為12%以下而抑制局部之再結晶現象。 Further, in Patent Document 2, in order to improve the brittle crack propagation stop characteristic in a steel material which is a microstructure mainly composed of ferrite iron-pearlite, the two surface portions of the steel material are provided. 50% or more of a layer of ferrite-grained iron structure having an average grain diameter equivalent to a circle of 5 μm or less and an aspect ratio of the grains of 2 or more. It is important to suppress the unevenness of the iron particle size of the ferrite grains, and as a method of suppressing unevenness, the average rolling reduction ratio of the average one pass in the finish rolling is set to 12% or less. Inhibit local recrystallization.
然而,專利文獻1、2中記載之脆性龜裂傳播停止特性優異之鋼材係於僅將鋼材表層部暫時冷卻後使其重熱且於重熱中施加加工,藉此獲得特定之組織者,於實際生產規模中難以控制,尤其是板厚超過50 mm之厚壁材料時軋壓成為對冷卻設備之負載較大之製程。 However, the steel materials excellent in the brittle crack propagation stop characteristics described in Patent Documents 1 and 2 are obtained by temporarily cooling the surface layer portion of the steel material and reheating it, and applying it to the reheating, thereby obtaining a specific organizer. It is difficult to control in the production scale, especially when the thick-walled material with a thickness of more than 50 mm becomes a process with a large load on the cooling equipment.
另一方面,於專利文獻3中記載有如下處於TMCP之延長上之技術:不僅著眼於肥粒鐵晶粒之微細化,而且著眼於形成於肥粒鐵晶粒內之次晶粒(subgrain),從而提高脆性龜裂傳播停止特性。 On the other hand, Patent Document 3 describes the following technique for extending the TMCP: focusing not only on the miniaturization of the ferrite grains, but also on the subgrains formed in the ferrite grains. , thereby improving the brittle crack propagation stop characteristics.
具體而言,於板厚30~40 mm時,無需鋼板表層之冷卻及重熱等複雜之溫度控制,而是藉由如下條件提高脆性龜裂傳播停止特性,即,(a)確保微細之肥粒鐵晶粒之軋壓條件、(b)於鋼材板厚之5%以上之部分生成微細肥粒鐵組織之軋 壓條件、(c)於微細肥粒鐵上使集合組織(texture)發達並且利用熱能重新配置因加工(軋壓)而導入之位錯(dislocation)並形成次晶粒的軋壓條件、(d)抑制所形成之微細之肥粒鐵晶粒與微細之次晶粒之粗大化的冷卻條件。 Specifically, when the thickness is 30 to 40 mm, complicated temperature control such as cooling and reheating of the surface layer of the steel sheet is not required, but the brittle crack propagation stop characteristic is improved by the following conditions, that is, (a) ensuring fine fertilizer The rolling conditions of the granular iron grains and (b) the rolling of the fine ferrite iron structure in the part of the steel plate thickness of 5% or more The pressure condition, (c) the development of the texture on the fine ferrite iron, and the dislocation of the dislocation introduced by the processing (rolling) by thermal energy and the formation of the secondary grain rolling conditions, (d) The cooling condition for suppressing the coarsening of the fine ferrite grains and fine crystal grains formed.
又,於控制軋壓中,亦已知有如下方法:藉由對變態之肥粒鐵施加軋縮使集合組織發達,而提高脆性龜裂傳播停止特性。於鋼材之破裂面上於與板面平行之方向上產生裂口(separation),而緩和脆性龜裂前端之應力,藉此,提高對脆性破裂之阻抗。 Further, in controlling the rolling, a method is also known in which the aggregate structure is developed by applying a shrinkage to the metamorphic ferrite, thereby improving the brittle crack propagation stop characteristic. A crack is formed in the direction parallel to the plate surface on the rupture surface of the steel, and the stress at the front end of the brittle crack is moderated, thereby improving the impedance against brittle fracture.
例如,於專利文獻4中記載有:藉由控制軋壓將(110)面X射線強度比(X-ray diffraction intensity according to(110)plane)設為2以上,且將相當於圓的直徑(average grain diameter equivalent to a circle)為20 μm以上之粗大粒設為10%以下,藉此,提高耐脆性破裂特性。 For example, Patent Document 4 describes that the (110) plane X-ray intensity ratio (X-ray diffraction intensity according to (110) plane) is set to 2 or more by controlling the rolling pressure, and corresponds to the diameter of the circle ( The coarse grain size of 20 μm or more is set to 10% or less, thereby improving the brittle fracture resistance.
於專利文獻5中,作為接頭部之脆性龜裂傳播停止性能優異之焊接結構用鋼,揭示有如下鋼板,其特徵在於板厚內部之軋壓面上之(100)面之X射線面強度比具有1.5以上,且記載有藉由該集合組織發達所致之應力負載方向與龜裂傳播方向之角度的偏差而使脆性龜裂傳播停止特性優異。進而,於專利文獻6~9中記載有藉由規定控制軋壓中之平均軋縮率而於板厚方向之各部(板厚之1/4部、板厚中央部等)中使集合組織發達的脆性龜裂傳播停止性能優異之焊接結 構用鋼之製造方法。 In Patent Document 5, a steel for welded structure excellent in brittle crack propagation resistance of a joint portion is disclosed as a steel sheet characterized by an X-ray plane strength ratio of a (100) plane on a rolling surface inside the sheet thickness. It is 1.5 or more, and it is described that the brittle crack propagation stop characteristic is excellent by the deviation of the angle of the stress load direction and the crack propagation direction by the development of the aggregate structure. Further, in Patent Documents 6 to 9, it is described that the collective structure is developed in each of the thickness direction (1/4 portion of the thickness, the center portion of the thickness, and the like) by controlling the average rolling reduction ratio in the rolling. Brittle crack propagation stop welding joint with excellent performance The method of manufacturing steel is used.
專利文獻1:日本專利特公平7-100814號公報 Patent Document 1: Japanese Patent Special Publication No. 7-100814
專利文獻2:日本專利特開2002-256375號公報 Patent Document 2: Japanese Patent Laid-Open Publication No. 2002-256375
專利文獻3:日本專利第3467767號公報 Patent Document 3: Japanese Patent No. 3467767
專利文獻4:日本專利第3548349號公報 Patent Document 4: Japanese Patent No. 3548349
專利文獻5:日本專利第2659661號公報 Patent Document 5: Japanese Patent No. 2659661
專利文獻6:日本專利特開2008-214652號公報 Patent Document 6: Japanese Patent Laid-Open Publication No. 2008-214652
專利文獻7:日本專利特開2010-047805號公報 Patent Document 7: Japanese Patent Laid-Open Publication No. 2010-047805
專利文獻8:日本專利特開2009-221585號公報 Patent Document 8: Japanese Patent Laid-Open Publication No. 2009-221585
專利文獻9:日本專利特開2010-202931號公報 Patent Document 9: Japanese Patent Laid-Open Publication No. 2010-202931
非專利文獻 Non-patent literature
非專利文獻1:井上等人:厚造船用鋼中之長大脆性龜裂傳播行為,日本船舶海洋工學會演講論文集第3號,2006,pp359-362 Non-Patent Document 1: Inoue et al.: Long-term brittle crack propagation behavior in thick shipbuilding steel, Nippon Marine Engineering Society Speech Paper No. 3, 2006, pp359-362
然而,最近,於超過6,000 20呎標準貨櫃(TEU,Twenty-foot Equivalent Unit)之大型集裝箱船中使用板厚超過50 mm之厚鋼板,井上等人於厚造船用鋼中之長大脆性龜裂傳播行為、日本船舶海洋工學會演講會論文集第3號、2006、 pp359-362中對板厚65 mm之鋼板之脆性龜裂傳播停止性能進行了評價,且報告有母材之大型脆性龜裂傳播停止試驗中脆性龜裂未停止之結果。 Recently, however, thick steel plates with a thickness of more than 50 mm have been used in large container ships of more than 6,000 20 Twenty-foot Equivalent Units, and the growth of brittle cracks in the shipbuilding steel by Inoue et al. Behavior, Proceedings of the Japan Society of Marine and Ocean Engineering Lectures No. 3, 2006, In pp359-362, the brittle crack propagation resistance of the steel plate with a thickness of 65 mm was evaluated, and the results of the brittle cracking in the large brittle crack propagation stop test of the base material were reported.
又,於供試材之ESSO試驗(ESSO test compliant with the guide line for brittle crack arrest design(2009,CLASS NK))中顯示使用溫度-10℃時之Kca之值未達3000 N/mm3/2之結果,暗示於應用有超過50 mm之板厚之鋼板的船體結構之情形時,安全性確保成為課題。 In addition, in the ESSO test compliant with the guide line for brittle crack arrest design (2009, CLASS NK), the value of Kca at a temperature of -10 ° C is less than 3000 N/mm 3/2. As a result, it is suggested that safety is ensured as a problem when a hull structure of a steel sheet having a thickness of more than 50 mm is applied.
上述專利文獻1~5中記載之脆性龜裂傳播停止特性優異之鋼板係根據製造條件或所揭示之實驗資料而以板厚50 mm左右為主要對象,於應用於超過50 mm之厚壁材料之情形時,能否獲得特定之特性並不明確,且完全未對船體結構中針對所需之板厚方向之龜裂傳播的特性進行驗證。 The steel sheets having excellent brittle crack propagation stop characteristics described in the above Patent Documents 1 to 5 are mainly used for a thick wall material of more than 50 mm, depending on the production conditions or the experimental data disclosed, with a thickness of about 50 mm. In the case, it is not clear whether the specific characteristics can be obtained, and the characteristics of the hull structure for the crack propagation in the required thickness direction are not verified at all.
又,於專利文獻6~9中,為了使板厚中央部之集合組織發達,而於軋壓時必需較高地設定平均1道次之軋縮率,因此,於製造條件或鋼板尺寸等方面產生各種制約,從而謀求其改善。 Further, in Patent Documents 6 to 9, in order to develop the aggregate structure at the center portion of the thickness of the sheet, it is necessary to set the rolling reduction ratio of one pass at a high level during the rolling, so that it is produced in terms of production conditions, steel sheet size, and the like. Various constraints to seek for improvement.
因此,本發明之目的在於提供一種即便於板厚超過50 mm之厚壁鋼板中,亦能夠以使軋壓條件最佳化且控制板厚方向上之集合組織之工業上極其簡易之製程穩定地製造的脆性龜裂傳播停止特性優異之高強度厚鋼板及其製造方法。 Accordingly, it is an object of the present invention to provide an industrially extremely simple process which is capable of optimizing the rolling conditions and controlling the assembly in the thickness direction even in a thick-walled steel sheet having a thickness of more than 50 mm. A high-strength thick steel plate having excellent brittle crack propagation resistance characteristics and a method for producing the same.
本發明者等人對即便為板厚超過50 mm之厚壁鋼板亦具有優異之脆性龜裂傳播停止特性的高強度厚鋼板及穩定地獲得該鋼板之製造方法反覆進行了銳意研究,並對厚鋼板中集合組織對脆性龜裂傳播停止特性造成之影響進行了詳細調查,結果獲得了如下見解:具有與鋼板表面平行之面上之(211)面X射線強度比為1.0以上之集合組織的區域存在於包含板厚中心部在內之板厚總厚之1/3以上之區域內,藉此,可獲得優異之脆性龜裂傳播停止特性。而且,亦瞭解到:為了獲得此種厚鋼板,較佳為將特定範圍之化學成分與特定範圍之製造條件、尤其是板厚中央部之軋壓/冷卻條件加以組合進行製造。 The inventors of the present invention have conducted intensive studies on the high-strength thick steel plate having excellent brittle crack propagation stop characteristics even for a thick-walled steel sheet having a thickness of more than 50 mm and the method for stably obtaining the steel sheet. The influence of the aggregate structure in the steel plate on the propagation characteristics of the brittle crack propagation was investigated in detail. As a result, the following findings were obtained: a region having a (211) plane X-ray intensity ratio of 1.0 or more on a plane parallel to the surface of the steel sheet It is present in a region of 1/3 or more of the total thickness of the plate thickness including the center portion of the plate thickness, whereby excellent brittle crack propagation stop characteristics can be obtained. Further, it is also known that in order to obtain such a thick steel plate, it is preferable to combine a chemical component of a specific range with a production condition of a specific range, in particular, a rolling/cooling condition at a central portion of the thickness.
本發明係對所獲得之見解進而加以研究而成者,即,本發明係: The present invention is based on the insights obtained, that is, the present invention is:
1.一種脆性龜裂傳播停止特性優異之高強度厚鋼板,其特徵在於:於包含板厚中心部在內之板厚總厚之1/3以上之區域內,具有與鋼板表面平行之面上之(211)面X射線強度比為1.0以上之集合組織,板厚之中央部中之變韌鐵分率為80%以上,且板厚之1/4位置上之夏比斷裂轉變溫度(fracture transition temperature)為-40℃以下。 A high-strength thick steel plate excellent in brittle crack propagation stop characteristics, characterized in that it has a surface parallel to the surface of the steel sheet in a region of 1/3 or more of the total thickness of the plate thickness including the center portion of the plate thickness The (211) plane X-ray intensity ratio is 1.0 or more, and the toughness iron fraction in the central portion of the sheet thickness is 80% or more, and the Charpy break transition temperature at the 1/4 position of the sheet thickness (fracture) The transition temperature) is below -40 °C.
2.如1之脆性龜裂傳播停止特性優異之高強度厚鋼板,其中,鋼之化學成分係以質量%計,C:0.03~0.20%、Si:0.03~0.50%、Mn:0.50~2.20%、P:0.030%以下、S:0.010% 以下、Al:0.005~0.08%、N:0.0045%以下,且以下述(1)式所表示之碳當量(Ceq)為0.34%以上且0.49%以下,剩餘部分包含Fe及不可避免之雜質。 2. A high-strength thick steel plate having excellent brittle crack propagation resistance characteristics, wherein the chemical composition of the steel is in mass%, C: 0.03 to 0.20%, Si: 0.03 to 0.50%, and Mn: 0.50 to 2.20%. , P: 0.030% or less, S: 0.010% In the following, Al: 0.005 to 0.08%, N: 0.0045% or less, and the carbon equivalent (Ceq) expressed by the following formula (1) is 0.34% or more and 0.49% or less, and the remainder contains Fe and unavoidable impurities.
Ceq=C+Mn/6+(Cu+Ni)/15+(V+Mo+Cr)/5 (1) Ceq=C+Mn/6+(Cu+Ni)/15+(V+Mo+Cr)/5 (1)
其中,各元素符號表示各成分之含量(質量%)。 Here, each element symbol indicates the content (% by mass) of each component.
3.如2之脆性龜裂傳播停止特性優異之高強度厚鋼板,其中,鋼之化學成分進而以質量%計,含有選自Ti:0.005~0.030%、Nb:0.005~0.050%,Cu:0.01~0.50%、Ni:0.01~1.00%、Cr:0.01~0.50%、Mo:0.01~0.50%、V:0.001~0.10%、B:0.0030%以下、Ca:0.0050%以下、REM:0.010%以下中之1種或2種以上。 3. A high-strength thick steel plate having excellent brittle crack propagation resistance characteristics, wherein the chemical composition of the steel is further selected from the group consisting of Ti: 0.005 to 0.030%, Nb: 0.005 to 0.050%, and Cu: 0.01. ~0.50%, Ni: 0.01 to 1.00%, Cr: 0.01 to 0.50%, Mo: 0.01 to 0.50%, V: 0.001 to 0.10%, B: 0.0030% or less, Ca: 0.0050% or less, and REM: 0.010% or less One or two or more.
4.一種脆性龜裂傳播停止特性優異之高強度厚鋼板之製造方法,其特徵在於:將具有如2或3之化學成分之鋼素材加熱至900~1200℃之溫度,且於進行如下軋壓後,以4.0℃/s以上之冷卻速度冷卻至450℃以下為止,上述軋壓係於熱軋中之板厚中央部之溫度處於(Ar3點+100)℃以上之溫度區域內時累積軋縮率為30%以上,於板厚中央部之溫度處於(Ar3點+60)℃以下且Ar3點以上之溫度區域內時累積軋縮率為50%以上,且平均1道次之軋縮率之平均值為6.0%以上,且各道次之軋縮率範圍為5.0~20.0%。 A method for producing a high-strength thick steel plate excellent in brittle crack propagation stop characteristics, characterized in that a steel material having a chemical composition such as 2 or 3 is heated to a temperature of 900 to 1200 ° C, and is subjected to the following rolling After that, it is cooled to 450 ° C or lower at a cooling rate of 4.0 ° C / s or more, and the rolling is accumulated in a temperature region at a central portion of the thickness of the hot rolling at a temperature range of (Ar 3 point + 100) ° C or more. The shrinkage is 30% or more, and when the temperature in the central portion of the thickness is at (Ar 3 + 60) ° C or lower and the temperature is within Ar 3 or more, the cumulative reduction ratio is 50% or more, and the average rolling is 1 pass. The average shrinkage ratio is 6.0% or more, and the rolling reduction ratio of each pass is 5.0 to 20.0%.
藉由本發明而獲得之厚鋼板係即便板厚為50 mm以上, 亦根據板厚方向之各位置適當地控制集合組織,因此,脆性龜裂傳播停止特性優異。將本發明應用於板厚50 mm以上、較佳為板厚超過50 mm、更佳為板厚55 mm以上、進而較佳為板厚60 mm以上之鋼板時,相對於先前技術之鋼發揮更顯著之優越性,故而有效。其中作為船舶用之結構構件,例如,藉由在集裝箱船或散裝貨船等之強力甲板部結構中對接合於艙口邊緣圍板(hatch side coaming)之甲板構件應用本發明,而有助於提高船舶之安全性,於工業上極其有用。 The thick steel plate obtained by the present invention has a plate thickness of 50 mm or more, Since the aggregate structure is appropriately controlled according to each position in the thickness direction, the brittle crack propagation stop characteristic is excellent. When the present invention is applied to a steel sheet having a thickness of 50 mm or more, preferably a thickness of more than 50 mm, more preferably a thickness of 55 mm or more, and more preferably a thickness of 60 mm or more, it is more effective than the steel of the prior art. Significant superiority, so effective. Among them, as a structural member for a ship, for example, by applying the present invention to a deck member joined to a hatch side coaming in a strong deck structure of a container ship or a bulk cargo ship, it is helpful to improve The safety of the ship is extremely useful in industry.
於本發明中,規定1.鋼板內部之集合組織、2.板厚中央部之微組織、3.母材韌性。 In the present invention, the assembly structure inside the steel sheet, the microstructure of the center portion of the sheet thickness, and the toughness of the base material are defined.
1.鋼板內部之集合組織 1. The organization of the inside of the steel plate
於本發明中,為了對於在軋壓方向或軋壓直角方向等與板面平行之方向上傳播之龜裂提高龜裂傳播停止特性,而於與鋼板表面平行之面上、即與軋壓面平行地使(211)面發達。若於板厚中央部於與鋼板表面平行之面上使(211)面發達,則會於龜裂進展之前產生微觀之裂痕(crack),從而成為龜裂進展之阻抗。 In the present invention, in order to improve the crack propagation stop characteristic for the crack propagated in the direction parallel to the plate surface in the direction of the rolling direction or the direction perpendicular to the rolling direction, the surface parallel to the surface of the steel sheet, that is, the rolling surface is formed. The (211) surface is developed in parallel. When the (211) surface is developed on the surface parallel to the surface of the steel sheet at the center portion of the sheet thickness, a micro crack is generated before the crack progresses, and the crack progresses.
由於在龜裂進展之前產生微觀之裂痕,故而於包含板厚中心部在內之板厚總厚之1/3以上之區域內,具有與鋼板表面平行之面上之(211)面X射線強度比為1.0以上之集合組織。上述於龜裂進展之前產生微觀之裂痕而成為龜裂進展之 阻抗的作用效果係只要具有該集合組織之區域為包含板厚中心部在內之板厚總厚之1/3以上之區域則可獲得,因此,上限並未特別規定。若具有該集合組織之區域增多,則進一步發揮上述作用效果,但即便使該區域增多至超過板厚總厚之3/4,上述作用效果之增加亦會飽和,故而無需使具有該集合組織之區域多至超過板厚總厚之3/4。然而,當然即便板厚總厚為該集合組織亦發揮上述作用效果。 Since the microscopic crack is generated before the crack progresses, the (211) plane X-ray intensity on the surface parallel to the surface of the steel sheet is in the region of more than 1/3 of the total thickness of the plate thickness including the center portion of the plate thickness. A collection organization with a ratio of 1.0 or more. The above-mentioned micro cracks occur before the crack progresses, and the crack progresses. The effect of the impedance is obtained as long as the region having the aggregated structure is one-third or more of the total thickness of the plate thickness including the center portion of the plate thickness. Therefore, the upper limit is not particularly specified. If the area having the aggregate structure is increased, the above-described effects are further exerted. However, even if the area is increased to more than 3/4 of the total thickness of the plate thickness, the increase in the effect is saturated, so that it is not necessary to have the assembly. The area is up to 3/4 of the total thickness of the board. However, of course, even if the total thickness of the plate is the aggregate structure, the above effects are exerted.
此處,所謂(211)面X射線強度比係指表示對象材料之(211)結晶面之積體度(X-ray diffraction intensity ratio of texture)之數值,且係指對象材料之(211)反射之X射線繞射強度(I(211))、與無集合組織之無規則之標準試樣的(211)反射之X射線繞射強度(I0(211))之比(I(211)/I0(211))。 Here, the (211) plane X-ray intensity ratio refers to a value indicating the (X-ray diffraction intensity ratio of texture) of the target material, and refers to the (211) reflection of the target material. the X-ray diffraction intensity (I (211)), ( 211) X -ray diffraction intensity of the reflection (I 0 (211)) and the ratio of the non-random texture of the standard sample (I (211) / I 0 (211) ).
2.板厚中央部之微組織 2. Microstructure in the central part of the plate thickness
為了獲得上述板厚中央部中之較佳之集合組織,而將與軋壓方向平行之剖面之板厚之中央部中之變韌鐵分率設為至少80%。變韌鐵分率係設為以面積分率表示。 In order to obtain a preferred aggregate structure in the central portion of the thickness of the sheet, the tough iron fraction in the central portion of the thickness of the cross section parallel to the rolling direction is set to be at least 80%. The toughened iron fraction is set to be expressed by area fraction.
與鋼板表面平行之面上之(211)面係藉由軋壓時進行加工之沃斯田鐵(austenite)組織變態為肥粒鐵或變韌鐵組織而發達者。於肥粒鐵-雪明碳鐵(cementite)組織之情形時,由於存在恢復等之影響,故而該集合組織不會於板厚方向之較廣範圍內發達。藉由使變態後之組織變態為變韌鐵組織而可於廣泛範圍內保持最高之(211)面X射線強度比。於本發明中所 謂板厚中央部之微組織,意指包含板厚中心部之至少板厚之1/3部分之區域之微組織。本發明包含板厚方向之整個剖面為該微組織之鋼板。 The (211) plane on the surface parallel to the surface of the steel sheet is developed by the austenite structure which is processed at the time of rolling and is transformed into a ferrite iron or a toughened iron structure. In the case of the fermented iron-cementite carbonite (cementite) structure, the aggregated structure is not developed in a wide range in the thickness direction due to the influence of recovery or the like. The highest (211) plane X-ray intensity ratio can be maintained over a wide range by metamorphizing the transformed tissue into a toughened iron structure. In the present invention The microstructure of the central portion of the plate thickness means the microstructure of the region including at least 1/3 of the thickness of the center portion of the plate thickness. The present invention includes a steel sheet having a whole cross section in the thickness direction of the microstructure.
3.母材韌性 3. Base metal toughness
關於母材韌性,具有良好之特性成為抑制脆性龜裂之進展之前提,因此,於本發明之鋼板中,規定利用自作為代表鋼板之材質之位置的板厚之1/4位置提取之夏比試驗片之夏比衝擊試驗中之夏比斷裂轉變溫度。 In the steel sheet of the present invention, it is prescribed that the ratio of the thickness of the base material is 1/4 of the thickness of the steel sheet. The Charpy break transition temperature in the Charpy impact test of the test piece.
為了以板厚50 mm以上之厚壁材料獲得於確保結構安全性方面被視為目標之Kca(-10℃)≧7000 N/mm3/2之脆性龜裂傳播停止特性,而將利用自板厚之1/4位置提取之試驗片之夏比衝擊試驗中之夏比斷裂轉變溫度規定為-40℃以下。 In order to obtain a brittle crack propagation stop characteristic of Kca (-10 ° C) ≧ 7000 N/mm 3/2 which is regarded as a target in terms of structural safety, a thick-walled material having a thickness of 50 mm or more is used. The Charpy break transition temperature in the Charpy impact test of the test piece extracted at a quarter of the thickness was specified to be -40 ° C or less.
對具備上述集合組織與母材韌性之鋼板而言較佳之鋼之化學成分與製造條件如下。以下,於化學成分之說明中%係設為質量%。 The chemical composition and manufacturing conditions of steel which is preferable for the steel sheet having the above-mentioned aggregate structure and base material toughness are as follows. Hereinafter, % of the description of the chemical components is made by mass%.
C:0.03~0.20% C: 0.03~0.20%
C係提高鋼之強度之元素,於本發明中,為了確保所需之強度而必需含有0.03%以上,但若超過0.20%,則不僅焊接性劣化而且亦會對韌性造成不良影響。因此,C較佳為規定為0.03~0.20%之範圍。再者,更佳為0.05~0.15%。 In the present invention, it is necessary to contain 0.03% or more in order to secure the required strength. However, if it exceeds 0.20%, not only the weldability is deteriorated but also the toughness is adversely affected. Therefore, C is preferably specified to be in the range of 0.03 to 0.20%. Further, it is preferably 0.05 to 0.15%.
Si:0.03~0.50% Si: 0.03~0.50%
Si作為去氧元素有效,又,作為鋼之強化元素有效,但 於含量未達0.03%時無該效果。另一方面,若超過0.50%,則不僅會損及鋼之表面性狀而且韌性會極端地劣化。因此,較佳為將其含量設為0.03%以上且0.50%以下。更佳為0.05~0.45%。 Si is effective as a deoxidizing element, and is effective as a strengthening element of steel, but This effect is not obtained when the content is less than 0.03%. On the other hand, when it exceeds 0.50%, not only the surface property of steel but also the toughness will be extremely deteriorated. Therefore, the content thereof is preferably set to 0.03% or more and 0.50% or less. More preferably, it is 0.05 to 0.45%.
Mn:0.50~2.20% Mn: 0.50~2.20%
Mn可作為強化元素而含有。若少於0.50%則其效果不充分,若超過2.20%則母材之韌性或焊接性會劣化,且鋼材成本亦上升,故而較佳為設為0.50%以上且2.20%以下。更佳為0.60~2.15%。 Mn can be contained as a strengthening element. When the amount is less than 0.50%, the effect is insufficient. When the amount exceeds 2.20%, the toughness or weldability of the base material is deteriorated, and the cost of the steel material also increases. Therefore, it is preferably 0.50% or more and 2.20% or less. More preferably, it is 0.60 to 2.15%.
P、S P, S
P、S係鋼中之不可避免之雜質,但若P超過0.030%、S超過0.010%則韌性會劣化,故而分別較理想為0.030%以下、0.010%以下,分別更理想為0.020%以下、0.005%以下。 P, S, and the inevitable impurities in the S-based steel. However, if P exceeds 0.030% and S exceeds 0.010%, the toughness deteriorates. Therefore, it is preferably 0.030% or less and 0.010% or less, and more preferably 0.020% or less and 0.005, respectively. %the following.
Al:0.005~0.08% Al: 0.005~0.08%
Al係作為去氧劑而發揮作用,為此較佳為含有0.005%以上。然而,若含有超過0.08%,則會使韌性下降,並且於焊接之情形時使焊接金屬部之韌性下降。因此,Al較佳為規定為0.005~0.08%之範圍。再者,更佳為0.02~0.04%。 Al acts as an oxygen scavenger, and is preferably contained in an amount of 0.005% or more. However, if it is more than 0.08%, the toughness is lowered, and the toughness of the welded metal portion is lowered in the case of welding. Therefore, Al is preferably in the range of 0.005 to 0.08%. Furthermore, it is more preferably 0.02 to 0.04%.
N:0.0045%以下 N: 0.0045% or less
N係與鋼中之Al結合,調整軋壓加工時之結晶粒徑並強化鋼。然而,若超過0.0045%則韌性會劣化,故而較佳為設為0.0045%以下。更佳為0.0040%以下。 The N system is combined with Al in the steel to adjust the crystal grain size during the rolling process and to strengthen the steel. However, if it exceeds 0.0045%, the toughness deteriorates, so it is preferably 0.0045% or less. More preferably, it is 0.0040% or less.
碳當量(carbon equivalent)(Ceq):0.34%以上且0.49%以下 Carbon equivalent (Ceq): 0.34% or more and 0.49% or less
碳當量成為用以預測組織之強度、變態行為等之重要指標。若碳當量未達0.34%則於板厚中心部難以獲得上述變韌鐵分率。又,若超過0.49%則韌性劣化,故而較佳為設為0.34%以上且0.49%以下。更佳為0.35~0.48%。 Carbon equivalent is an important indicator for predicting the strength and abnormal behavior of tissues. If the carbon equivalent is less than 0.34%, it is difficult to obtain the above-mentioned tough iron fraction in the center portion of the sheet thickness. Moreover, when it exceeds 0.49%, since toughness deteriorates, it is preferable to set it as 0.34 % or more and 0.49% or less. More preferably, it is 0.35 to 0.48%.
再者,碳當量(Ceq)係設為藉由以下所示之式而獲得者。 Further, the carbon equivalent (Ceq) is obtained by the formula shown below.
Ceq=C+Mn/6+(Cu+Ni)/15+(V+Mo+Cr)/5 Ceq=C+Mn/6+(Cu+Ni)/15+(V+Mo+Cr)/5
各元素符號係設為含量(質量%),於未含有之情形時設為0。 Each element symbol is a content (% by mass), and is set to 0 when it is not contained.
以上為本發明中之較佳之基本成分組成且剩餘部分Fe及不可避免之雜質。作為不可避免之雜質,例如只要O為0.0050%以下則容許。 The above is a preferred basic component composition of the present invention and the remaining part of Fe and unavoidable impurities. As an unavoidable impurity, for example, O is allowed to be 0.0050% or less.
為了進一步提高特性,可含有選自Ti、Nb、Cu、Ni、Cr、Mo、V、B、Ca、REM中之一種或兩種以上。 In order to further improve the characteristics, one or two or more selected from the group consisting of Ti, Nb, Cu, Ni, Cr, Mo, V, B, Ca, and REM may be contained.
Ti:0.005~0.030% Ti: 0.005~0.030%
Ti係藉由含有微量而形成氮化物、碳化物或碳氮化物,具有使晶粒微細化而提高母材韌性之效果。該效果係藉由含有0.005%以上而獲得,但若含有超過0.030%則會使母材及焊接熱影響部之韌性下降,故而於含有Ti之情形時,較佳為設為0.005~0.030%之範圍。更佳為0.008~0.028%。 Ti forms a nitride, a carbide, or a carbonitride by containing a trace amount, and has an effect of refining crystal grains and improving the toughness of the base material. This effect is obtained by containing 0.005% or more. However, if the content exceeds 0.030%, the toughness of the base material and the heat-affected zone of the weld is lowered. Therefore, when Ti is contained, it is preferably 0.005 to 0.030%. range. More preferably, it is 0.008 to 0.028%.
Nb:0.005~0.050% Nb: 0.005~0.050%
Nb係以NbC之形式於肥粒鐵變態時或再加熱時析出,有 助於高強度化。又,於沃斯田鐵區域之軋壓中具有擴大未再結晶區域之效果,且有助於肥粒鐵之細粒化,故而亦對韌性之改善有效。該效果係藉由含有0.005%以上而獲得,但若含有超過0.050%,則析出粗大之NbC,反而會導致韌性下降,故而於含有Nb之情形時,其上限較佳為設為0.050%。更佳為0.008~0.040%。 Nb is precipitated in the form of NbC when the ferrite is metamorphosed or reheated. Helps to increase strength. Further, in the rolling of the Worthite iron region, the effect of expanding the non-recrystallized region is promoted, and the fine graining of the ferrite iron is facilitated, so that the improvement of the toughness is also effective. This effect is obtained by containing 0.005% or more. However, when the content exceeds 0.050%, coarse NbC is precipitated, which in turn causes a decrease in toughness. Therefore, when Nb is contained, the upper limit is preferably set to 0.050%. More preferably, it is 0.008 to 0.040%.
Cu、Ni、Cr、Mo Cu, Ni, Cr, Mo
Cu、Ni、Cr、Mo中之任一者均為提高鋼之淬火性之元素。直接有助於提高軋壓後之強度,並且可為了提高韌性、高溫強度、或耐候性等功能而含有,但過量含有會使韌性或焊接性劣化,故而於含有Cu、Ni、Cr、Mo之情形時,較佳為分別將Cu之上限設為0.50%,Ni之上限設為1.00%,Cr之上限設為0.50%,Mo之上限設為0.50%。更佳為分別將Cu之上限設為0.45%,Ni之上限設為0.95%,Cr之上限設為0.45%,Mo之上限設為0.45%。另一方面,若各元素之含量未達0.01%則其效果不會顯現,故而於含有之情形時,關於各元素較佳為設為含有0.01%以上。 Any of Cu, Ni, Cr, and Mo is an element that improves the hardenability of steel. It directly contributes to the improvement of the strength after rolling, and can be contained in order to improve functions such as toughness, high-temperature strength, and weather resistance. However, excessive inclusion may deteriorate toughness or weldability, so it contains Cu, Ni, Cr, and Mo. In the case, it is preferable to set the upper limit of Cu to 0.50%, the upper limit of Ni to 1.00%, the upper limit of Cr to 0.50%, and the upper limit of Mo to 0.50%. More preferably, the upper limit of Cu is set to 0.45%, the upper limit of Ni is set to 0.95%, the upper limit of Cr is set to 0.45%, and the upper limit of Mo is set to 0.45%. On the other hand, if the content of each element is less than 0.01%, the effect does not appear. Therefore, when it is contained, it is preferable to contain 0.01% or more with respect to each element.
V:0.001~0.10% V: 0.001~0.10%
V係藉由以V(CN)之形式之析出強化而提高鋼之強度之元素,為了發揮該效果,亦可含有0.001%以上。然而,若含有超過0.10%,則使韌性下降。因此,於含有V之情形時,較佳為設為0.001~0.10%之範圍之含有。更佳為0.008~ 0.095%。 V is an element which increases the strength of steel by precipitation strengthening in the form of V (CN), and may contain 0.001% or more in order to exhibit this effect. However, if it contains more than 0.10%, the toughness will fall. Therefore, in the case where V is contained, it is preferably contained in the range of 0.001 to 0.10%. More preferably 0.008~ 0.095%.
B:0.0030%以下 B: 0.0030% or less
B係以微量提高鋼之淬火性之元素,其效果係藉由含有0.0006%以上而發揮。然而,若含有超過0.0030%則會使焊接部之韌性下降,故而於含有B之情形時,較佳為設為0.0030%以下。更佳為0.0028%以下。 B is an element which slightly increases the hardenability of steel, and its effect is exhibited by containing 0.0006% or more. However, when the content exceeds 0.0030%, the toughness of the welded portion is lowered. Therefore, when B is contained, it is preferably 0.0030% or less. More preferably, it is 0.0028% or less.
Ca:0.005%以下、REM:0.01%以下 Ca: 0.005% or less, REM: 0.01% or less
Ca、REM使焊接熱影響部之組織微細化且提高韌性,即便含有亦不會損及本發明之效果,故而視需要亦可含有。然而,若過量含有則會形成粗大之中介物而使母材之韌性劣化,故而於含有Ca、REM之情形時,較佳為將其量之上限分別設為0.005%、0.01%。 Ca and REM make the structure of the welded heat-affected zone finer and improve the toughness, and even if it is contained, the effect of the present invention is not impaired, and may be contained as needed. However, when it is contained in a large amount, a coarse intermediate is formed and the toughness of the base material is deteriorated. Therefore, when Ca or REM is contained, the upper limit of the amount is preferably made 0.005% or 0.01%.
以下,對本發明中之較佳之製造條件進行說明。 Hereinafter, preferred manufacturing conditions in the present invention will be described.
製造條件較佳為規定鋼坯加熱條件、熱軋條件及熱軋後之冷卻條件。 The production conditions are preferably slab heating conditions, hot rolling conditions, and cooling conditions after hot rolling.
較佳為將上述組成之鋼液以轉爐等熔化,並藉由連續鑄造等製成鋼素材(鋼坯),於加熱至900~1200℃後進行熱軋。 It is preferable to melt the molten steel of the above composition in a converter or the like, and to form a steel material (steel billet) by continuous casting or the like, and to perform hot rolling after heating to 900 to 1200 °C.
若加熱溫度未達900℃,則無法充分地確保進行沃斯田鐵再結晶溫度區域內之軋壓之時間,又,若超過1200℃,則沃斯田鐵粒粗大化,不僅導致韌性下降,而且氧化損耗顯著,從而使良率下降,故而加熱溫度設為900~1200℃。就 韌性之觀點而言較佳之加熱溫度之範圍為1000~1150℃,更佳為1000~1050℃。 When the heating temperature is less than 900 ° C, the rolling time in the recrystallization temperature region of the Worthite iron cannot be sufficiently ensured, and if it exceeds 1200 ° C, the Worthite iron particles are coarsened, which not only causes a decrease in toughness. Further, the oxidation loss is remarkable, so that the yield is lowered, so the heating temperature is set to 900 to 1200 °C. on The preferred heating temperature range from 1000 to 1150 ° C, more preferably from 1000 to 1050 ° C.
較佳為規定熱軋中之板厚中央部之溫度(成為板厚之1/2之位置上之溫度,以下相同)為(Ar3點+100)℃以上時之累積軋縮率、(Ar3點+60)℃以下且Ar3點以上之累積軋縮率、(Ar3點+60)℃以下且Ar3點以上中之平均1道次之軋縮率之平均值、及(Ar3點+60)℃以下且Ar3點以上中之平均1道次之軋縮率之範圍。 It is preferable that the temperature at the central portion of the thickness of the sheet during hot rolling (the temperature at a position equal to 1/2 of the sheet thickness, the same applies hereinafter) is the cumulative rolling reduction ratio (Ar 3 point + 100) ° C or more, (Ar 3 points + 60) °C or less and the cumulative rolling reduction ratio of Ar 3 or more, (Ar 3 + 60) ° C or less, and the average of 1 rolling pass of Ar 3 points or more, and (Ar 3 The range of the rolling reduction ratio of the average one pass of the point +60) ° C or less and the Ar 3 point or more.
熱軋係首先在板厚中央部之溫度為(Ar3點+100)℃以上時進行累積軋縮率為30%以上之軋壓,使沃斯田鐵細粒化,藉此,實現最終之微組織之細粒化,提高母材韌性。該溫度區域內之累積軋縮率進而較佳為35%以上。於本發明中以下式求出Ar3點(℃)。 In the hot rolling system, when the temperature in the central portion of the thickness is (Ar 3 + 100) ° C or more, the rolling reduction is 30% or more, and the Worthite iron is finely granulated, thereby achieving the final result. Fine granulation of the microstructure to improve the toughness of the base metal. The cumulative rolling reduction ratio in this temperature region is further preferably 35% or more. In the present invention, the Ar 3 point (°C) is obtained by the following formula.
Ar3點=910-273C-74Mn-57Ni-16Cr-9Mo-5Cu Ar 3 point = 910-273C-74Mn-57Ni-16Cr-9Mo-5Cu
於式中各元素符號係鋼中含量(質量%),未含有之情形時設為0。 In the formula, the content of each element symbol steel (% by mass) is set to 0 when it is not contained.
其次,於板厚中央部之溫度處於(Ar3點+60)℃以下且Ar3點以上之溫度區域內時,進行累積軋縮率50%以上且平均1道次之軋縮率之平均值為6.0%以上之軋壓。若該溫度區域內之累積軋縮率未達50%,則鋼板之韌性劣化。又,由於將(211)面X射線強度比設為1.0以上,故而於作為未再結晶 沃斯田鐵區域之(Ar3點+60)℃以下且Ar3點以上之溫度區域內將累積軋縮率設為50%以上。該溫度區域內之累積軋縮率進而較佳為55%以上。 Next, when the temperature in the central portion of the plate thickness is within a temperature range of (Ar 3 + 60) ° C or less and Ar 3 or more, the cumulative rolling reduction ratio is 50% or more and the average value of the rolling reduction is 1 pass. It is a rolling pressure of 6.0% or more. If the cumulative rolling reduction ratio in this temperature region is less than 50%, the toughness of the steel sheet is deteriorated. In addition, since the (211) plane X-ray intensity ratio is 1.0 or more, cumulative rolling is performed in a temperature range of (Ar 3 point + 60) ° C or less and Ar 3 point or more in the non-recrystallized Worstian iron region. The shrinkage ratio is set to 50% or more. The cumulative rolling reduction ratio in this temperature region is further preferably 55% or more.
於厚壁材料之精軋中,通常成為小軋縮多道次軋壓,故而有如下傾向:與鋼板表面平行之面上之(211)面X射線強度比為1.0以上之區域變窄。因此,於本發明中,將板厚中央部之溫度處於(Ar3點+60)℃以下且Ar3點以上之溫度區域內之平均1道次之軋縮率之平均值規定為6.0%以上,且將各道次之軋縮率範圍規定為5.0~20.0%。藉此,可將(211)面X射線強度比為1.0以上之區域設為包含板厚中心在內之板厚總厚之1/3以上之區域。於平均1道次之軋縮率之平均值未達6.0%之情形時,或者於各道次軋縮率之最小值未達5.0%之情形時,韌性會下降,且無法將(211)面X射線強度比為1.0以上之區域設為包含板厚中心在內之板厚總厚之1/3以上之區域。另一方面,若各道次軋縮率之最大值超過20.0%,則因加工應變之影響,反而導致韌性劣化。該溫度區域內之平均1道次之軋縮率之平均值進而較佳為6.5%以上,又,各道次之軋縮率範圍進而較佳為5.5~18.0%。再者,於熱軋中亦可實施規定之溫度區域外之軋壓。只要於上述規定之溫度區域內進行包含上述規定之累積軋縮率之軋壓即可。 In the finish rolling of the thick-walled material, the rolling is usually performed by a small rolling and multi-pass rolling. Therefore, there is a tendency that the area of the (211) plane X-ray intensity ratio which is parallel to the surface of the steel sheet is 1.0 or more. Therefore, in the present invention, the average value of the rolling rate of the average one pass in the temperature range of (Ar 3 point + 60) ° C or less and Ar 3 point or more is set to 6.0% or more. And the range of rolling reduction of each pass is specified as 5.0~20.0%. Thereby, the region in which the (211) plane X-ray intensity ratio is 1.0 or more can be set to a region of 1/3 or more of the total thickness of the plate thickness including the center of the plate thickness. When the average value of the average rolling reduction is less than 6.0%, or when the minimum value of each pass is less than 5.0%, the toughness will decrease and the (211) surface will not be able to be used. A region in which the X-ray intensity ratio is 1.0 or more is set to a region of 1/3 or more of the total thickness of the plate including the center of the plate thickness. On the other hand, if the maximum value of the rolling reduction ratio of each pass exceeds 20.0%, the toughness is deteriorated due to the influence of the processing strain. The average value of the average rolling reduction ratio in the temperature region is further preferably 6.5% or more, and the rolling reduction ratio of each pass is further preferably 5.5 to 18.0%. Further, in the hot rolling, the rolling pressure outside the predetermined temperature range can also be performed. The rolling pressure including the above-described predetermined rolling reduction ratio may be performed in the temperature range specified above.
軋壓結束後之鋼板係以4.0℃/s以上之冷卻速度冷卻至 450℃以下為止。若冷卻速度未達4.0℃/s,則不會充分地進行向變韌鐵之變態,故而無法將(211)面X射線強度比為1.0以上之區域設為包含板厚中心在內之板厚總厚之1/3以上,進而亦無法獲得所需之微組織、即板厚之中央部中之變韌鐵分率為80%以上之組織。又,若冷卻停止溫度超過450℃,則不會充分地進行向變韌鐵之變態,故而仍然無法獲得所需之微組織。作為冷卻方式,可使用水冷、氣體冷卻等方式。 After the rolling is completed, the steel plate is cooled to a cooling rate of 4.0 ° C / s or more to Below 450 °C. If the cooling rate is less than 4.0 ° C / s, the transformation to the toughened iron will not be sufficiently performed. Therefore, the region where the (211) plane X-ray intensity ratio is 1.0 or more cannot be set to the thickness including the center of the plate thickness. More than 1/3 of the total thickness, and thus the desired microstructure, that is, the structure in which the toughness iron fraction in the central portion of the plate thickness is 80% or more is not obtained. Further, when the cooling stop temperature exceeds 450 ° C, the transformation to the toughened iron is not sufficiently performed, and thus the desired microstructure is still not obtained. As the cooling method, water cooling, gas cooling, or the like can be used.
藉由上述製造條件,不僅可獲得所需之集合組織,而且使夏比衝擊試驗中之斷裂單位(fracture facet size)微細化,從而使板厚1/4位置上之夏比斷裂轉變溫度達到-40℃以下。 According to the above manufacturing conditions, not only the desired aggregate structure but also the fracture facet size in the Charpy impact test can be made fine, so that the Charpy break transition temperature at the 1/4 position of the sheet thickness reaches - Below 40 °C.
於以上之說明中,板厚中央部之溫度係根據以放射溫度計測定之板表面溫度,藉由傳熱計算而求出。熱軋後之冷卻中之溫度條件亦設為板厚中央部之溫度。 In the above description, the temperature at the center portion of the thickness is determined by heat transfer calculation based on the surface temperature of the plate measured by a radiation thermometer. The temperature condition during cooling after hot rolling is also set to the temperature at the center of the sheet thickness.
將表1所示之各組成之鋼液(鋼符號A~T)以轉爐熔化,並藉由連續鑄造法製成鋼素材(鋼坯280 mm厚),於熱軋成板厚50~75 mm之後進行冷卻,而獲得No.1~28之供試鋼。於表2中表示熱軋條件與冷卻條件。Ar3點(℃)係藉由下式而計算。 The molten steel (steel symbol A~T) of each composition shown in Table 1 was melted in a converter, and steel material (slab 280 mm thick) was formed by continuous casting, after hot rolling to a thickness of 50 to 75 mm Cooling was carried out to obtain test steel No. 1 to 28. Table 2 shows hot rolling conditions and cooling conditions. Ar 3 point (°C) is calculated by the following formula.
Ar3點=910-273C-74Mn-57Ni-16Cr-9Mo-5Cu Ar 3 point = 910-273C-74Mn-57Ni-16Cr-9Mo-5Cu
其中,各元素符號係鋼中含量(質量%),於未含有之情形時設為0。 Here, the content (% by mass) of each element symbol steel is set to 0 when it is not contained.
對於所獲得之厚鋼板,自板厚1/4部提取將與軋壓方向正交之方向設為長度方向之14之JIS14A號試驗片,進行拉伸試驗,測定降伏強度(YS)、拉伸強度(TS)。 For the obtained thick steel plate, the direction orthogonal to the rolling direction is taken as the length direction from the 1/4 portion of the plate thickness. A test piece of JIS 14A No. 14 was subjected to a tensile test, and the tensile strength (YS) and tensile strength (TS) were measured.
以試驗片之長軸之方向與軋壓方向平行之方式,自板厚之1/4部提取JIS4號衝擊試驗片,進行夏比衝擊試驗(Charpy impact test),從而求出斷裂轉變溫度(vTrs)。將板厚1/4部中之夏比斷裂轉變溫度為-40℃以下者設為本發明範圍內。 The JIS No. 4 impact test piece was taken from the quarter of the plate thickness in the direction of the long axis of the test piece in parallel with the rolling direction, and the Charpy impact test was performed to determine the fracture transition temperature (vTrs). ). It is within the scope of the invention to set the Charpy to break transition temperature in the 1/4 portion of the sheet thickness to -40 °C or less.
關於板厚之中央部中之變韌鐵分率,於對與板厚之中央部之軋壓長度方向平行之板厚剖面進行鏡面研磨後,拍攝藉由蝕刻(etching)而現出之金屬組織之光學顯微鏡照片,並藉由圖像解析(imaging analysis)進行測定。 Regarding the tough iron fraction in the central portion of the plate thickness, the plate thickness of the plate thickness section parallel to the rolling length direction of the central portion of the plate thickness is mirror-polished, and then the metal structure emerging by etching is taken. An optical microscope photograph was taken and determined by imaging analysis.
又,為了評價鋼板之集合組織,而自鋼板之表面向背面以1 mm為單位測定與鋼板表面平行之面上之(211)面X射線強度比,從而求出(211)面X射線強度比為1.0以上之區域。 Further, in order to evaluate the aggregate structure of the steel sheet, the (211) plane X-ray intensity ratio on the surface parallel to the surface of the steel sheet was measured from the surface of the steel sheet to the back surface in units of 1 mm, thereby obtaining a (211) plane X-ray intensity ratio. It is an area of 1.0 or more.
繼而,為了評價脆性龜裂傳播停止特性,而進行溫度梯度型ESSO試驗,從而求出Kca(-10℃)(N/mm3/2)。 Then, in order to evaluate the brittle crack propagation stop characteristic, a temperature gradient type ESSO test was performed to obtain Kca (-10 ° C) (N/mm 3/2 ).
於表3中表示該等之試驗結果。 The results of these tests are shown in Table 3.
再者,關於No.1~28,任一者均係與鋼板表面平行之面上之(211)面X射線強度比於板厚中央部為1.0以上。 Further, in any of Nos. 1 to 28, the (211) plane X-ray intensity on the surface parallel to the surface of the steel sheet is 1.0 or more in the central portion of the sheet thickness.
於板厚1/4部中之夏比衝擊試驗之轉變溫度、板厚中央部之變韌鐵分率及與鋼板表面平行之面上之(211)面X射線強度比為1.0以上之區域為本發明之範圍內的供試鋼板(製造 編號(No.)1~13)之情形時,顯示Kca(-10℃)為7000 N/mm3/2以上之優異之脆性龜裂傳播停止性能。 The transition temperature of the Charpy impact test in the 1/4 portion of the sheet thickness, the toughening iron fraction at the center of the sheet thickness, and the (211) plane X-ray intensity ratio on the surface parallel to the surface of the steel sheet are 1.0 or more. In the case of the test steel sheets (manufactured No. 1 to 13) in the range of the present invention, Kca (-10 ° C) is an excellent brittle crack propagation stop performance of 7000 N/mm 3/2 or more.
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JPH07100814A (en) | 1993-10-04 | 1995-04-18 | Sekisui Chem Co Ltd | Manufacture of cement molded item |
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JP5064150B2 (en) * | 2006-12-14 | 2012-10-31 | 新日本製鐵株式会社 | High strength steel plate with excellent brittle crack propagation stopping performance |
JP4946512B2 (en) | 2007-02-28 | 2012-06-06 | Jfeスチール株式会社 | Structural high-strength thick steel plate with excellent brittle crack propagation stopping characteristics and method for producing the same |
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JP5146033B2 (en) | 2008-03-19 | 2013-02-20 | Jfeスチール株式会社 | High-strength thick steel plate with excellent toughness and brittle crack propagation stopping characteristics for high heat input welds and its manufacturing method |
JP5146198B2 (en) | 2008-08-22 | 2013-02-20 | Jfeスチール株式会社 | High-strength thick steel plate with excellent toughness and brittle crack propagation stopping characteristics for high heat input welds and its manufacturing method |
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JP5434145B2 (en) | 2009-03-04 | 2014-03-05 | Jfeスチール株式会社 | Structural high-strength thick steel plate with excellent brittle crack propagation stopping characteristics and method for producing the same |
JP4897127B2 (en) * | 2010-05-27 | 2012-03-14 | 新日本製鐵株式会社 | Manufacturing method of high strength steel sheet for welded structure |
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TWI504759B (en) | 2015-10-21 |
JPWO2013099179A1 (en) | 2015-04-30 |
KR101681491B1 (en) | 2016-12-01 |
KR20160021912A (en) | 2016-02-26 |
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BR112014015789B1 (en) | 2019-10-29 |
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