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CN-117396625-B - Steel sheet pile and method for manufacturing same

CN117396625BCN 117396625 BCN117396625 BCN 117396625BCN-117396625-B

Abstract

The present invention provides a steel sheet pile with high strength and high toughness with stability and high productivity. The steel sheet pile has a microstructure having a ferrite area fraction of 70% or more and an island-like martensite area fraction of 1.0% or less, a V carbon nitride compound, a Nb carbon nitride compound, and a V and Nb composite carbon nitride compound each having a particle diameter of 10nm or less, a total area fraction of 2.6% or more and a V carbon nitride compound, a Nb carbon nitride compound, and an area fraction of 0.3% or more each having a predetermined particle diameter d (nm), and an average particle diameter of 15 [ mu ] m or less and a maximum particle diameter of 40 [ mu ] m or less.

Inventors

  • ASAHI KENTA
  • ANDO KEISUKE
  • Daping hawkwin

Assignees

  • 杰富意钢铁株式会社

Dates

Publication Date
20260508
Application Date
20220323
Priority Date
20210610

Claims (3)

  1. 1. A steel sheet pile having the following composition and microstructure, The composition of the components contains, in mass%, the components satisfying the following formula (1): C:0.05~0.18%、 Si:0.05~0.55%、 Mn:1.00~1.65%、 sol.Al below 0.080%, V:0.005~0.250%、 0.005 To less than 0.030 percent of Nb and 0.0010 to 0.0060 percent of N, The balance being Fe and unavoidable impurities, P, S and B being P0.025% or less, S0.020% or less and B0.0003% or less, The microstructure is a ferrite having a surface area fraction of 70% or more and an island-like martensite having an area fraction of 1.0% or less, and a total area fraction of V carbon nitrogen compound, nb carbon nitrogen compound and V and Nb composite carbon nitrogen compound having a particle diameter of 10nm or less is 2.6% or more, and a total area fraction of V carbon nitrogen compound, nb carbon nitrogen compound and V and Nb composite carbon nitrogen compound having a particle diameter d satisfying the following formula (2) is 0.30% or more, the unit of the particle diameter d is nm, The average grain size of the ferrite is 15 μm or less and the maximum grain size is 40 μm or less, The steel sheet pile has a yield strength of 440MPa or more and a fracture transition temperature of-10 ℃ or less at a ductility section ratio of 50%, -0.010≤[%Nb]-0.1[%V]≤0.020 (1) Wherein, [%V ], [%Nb ] are the contents of V and Nb in the steel in mass percent respectively, d≥5[(Ae 3 －Ar 3 ）／Ae 3 ] －0.63 (2), Wherein Ae 3 is the ferrite transformation starting temperature at the time of equilibrium transformation, the unit is the temperature, Ar 3 ferrite transformation starting temperature during cooling, and the unit is DEG C.
  2. 2. The steel sheet pile according to claim 1, wherein the composition further contains 1 or 2 or more of 0.50% or less of Cu, 0.50% or less of Ni, 0.50% or less of Cr, 0.30% or less of Mo, 0.0050% or less of Ca, 0.025% or less of Ti, and 0.005% or less of REM in mass%.
  3. 3. A method for producing a steel sheet pile according to claim 1 or 2, wherein a steel blank having the composition is heated to 1200 ℃ to 1350 ℃, and hot rolling including rough rolling, intermediate rolling and finish rolling is performed under conditions in which the cumulative reduction of 900 ℃ to 1000 ℃ is 20% or more, the reduction of an austenite unrecrystallized temperature region is 10% or more and less than 20%, and the finishing temperature of the intermediate rolling is 650 ℃ to 900 ℃.

Description

Steel sheet pile and method for manufacturing same Technical Field The present invention relates to a steel sheet pile suitable for use in a permanent structure or a temporary installation structure in the field of civil engineering and construction, and a method for manufacturing the same. Background Steel sheet piles are subjected to high loads when used for shovels and earth barriers, and therefore require high strength and toughness. For example, a steel sheet pile having a yield strength (hereinafter referred to as YP) of 290MPa or more, and further 390MPa or more can be used. Further, in a more severe environment, steel sheet piles having strength of YP440MPa or more are sometimes required. In the production of high strength and high toughness steel products, it is common practice to add alloying elements or to roll in the austenite non-recrystallization temperature region. However, in the production of steel sheet piles having a complicated shape, rolling and forming at high temperature with less deformation resistance is desired from the viewpoint of formability, and alloys capable of increasing the deformation resistance are limited. In JIS Specifications (SYW) of steel sheet piles, although the specification is made for the charpy absorption energy at 0 ℃, steel sheet piles are used even in environments below 0 ℃ such as the cold weather in japan, and therefore, steel sheet piles with higher toughness are expected to be required later. Under the above circumstances, research and development of steel sheet piles having high strength and high toughness are underway. That is, patent document 1 proposes a steel sheet pile having a composition in which Nb exceeding 0.05% is added, thereby achieving high toughness with YP440MPa or more. Patent document 2 proposes a steel sheet pile in which a composition of 0.030% or more of Nb is added together with V, a rolling reduction of 1000 ℃ or less is controlled, and an average grain size of ferrite, an area ratio of island-like martensite, and a number density of precipitates are optimized to achieve high toughness of YP440MPa or more. Patent document 3 proposes a steel sheet pile having a composition in which Nb and B are added to a low carbon steel having 0.005 to 0.030% of C, and which has high strength, high toughness, and excellent weldability in water. Patent document 4 proposes a steel sheet pile having a composition in which 1 or 2 kinds of V or Nb are added, and in which the rolling reduction in the non-recrystallization temperature range of 900 ℃ or less is controlled, and after the rolling is completed, the steel sheet pile is cooled with acceleration to achieve high toughness. On the other hand, patent document 5 proposes a steel sheet pile in which Nb in unavoidable impurities is limited to 0.005% or less, thereby realizing YP340MPa or more and high toughness. Patent documents 6 and 7 propose steel sheet piles in which YP440MPa or more and vTrs is-10 ℃ or less are achieved by water-cooling a predetermined position during or after the completion of hot rolling. Prior art literature Patent literature Patent document 1 Japanese patent application laid-open No. 2018-83963 Patent document 2 Japanese patent application laid-open No. 2018-90845 Patent document 3 Japanese patent application laid-open No. 2000-17378 Patent document 4 Japanese patent laid-open No. 2006-249513 Patent document 5 Japanese patent laid-open publication No. 2002-294392 Patent document 6 Japanese patent laid-open No. 2007-332414 Patent document 7 Japanese patent laid-open No. 2008-221318 Disclosure of Invention The techniques described in patent documents 1 and 2 are to obtain a steel sheet pile having high strength and high toughness by adding 0.030% or more of Nb in a composition, but Nb tends to increase deformation resistance during hot rolling in both solid solution and precipitation states, and therefore, shape control during hot rolling is required to be strictly performed. In the technique described in patent document 3, since the C content is a component composition of less than 0.005 to 0.030%, the decarburization step at the time of melting the steel becomes long, and there is a problem that the productivity in the refining process is low. In addition, in the technique described in patent document 4, in order to obtain a steel sheet pile with high toughness, it is necessary to set the rolling reduction in the unrecrystallized temperature region to 20% or more, and it is necessary to strictly control the shape at the time of hot rolling, and it is necessary to accelerate cooling of a predetermined portion after the completion of rolling, so that the problem of shape change such as bending and warping cannot be avoided. On the other hand, in the technique described in patent document 5, there is proposed a steel sheet pile in which the rolling temperature and the reduction ratio in the final pass are limited to promote complete recrystallization of austenite and obtain a