WO2022259697A1 - 鋼矢板及びその製造方法 - Google Patents

鋼矢板及びその製造方法 Download PDF

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WO2022259697A1
WO2022259697A1 PCT/JP2022/013720 JP2022013720W WO2022259697A1 WO 2022259697 A1 WO2022259697 A1 WO 2022259697A1 JP 2022013720 W JP2022013720 W JP 2022013720W WO 2022259697 A1 WO2022259697 A1 WO 2022259697A1
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steel sheet
rolling
sheet pile
ferrite
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PCT/JP2022/013720
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English (en)
French (fr)
Japanese (ja)
Inventor
健太 朝日
佳祐 安藤
浩文 大坪
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Ｊｆｅスチール株式会社
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Priority to CN202280039177.5A priority Critical patent/CN117396625A/zh
Priority to JP2022541707A priority patent/JP7201136B1/ja
Priority to KR1020237039794A priority patent/KR20230173169A/ko
Publication of WO2022259697A1 publication Critical patent/WO2022259697A1/ja

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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
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/08—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling structural sections, i.e. work of special cross-section, e.g. angle steel
    • B21B1/082—Piling sections having lateral edges specially adapted for interlocking with each other in order to build a wall
    • 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
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • 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
    • 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
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • 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
    • 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
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0231—Warm rolling
    • 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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • 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
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • 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
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • 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
    • 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
    • C21D2211/005—Ferrite

Definitions

  • the present invention relates to a steel sheet pile that is applied to permanent or temporary structures in the fields of civil engineering and construction, and a method for manufacturing the same.
  • Steel sheet piles are required to have high strength and toughness because they are subjected to high loads when used for quays and earth retaining walls.
  • a steel sheet pile having a yield strength (hereinafter referred to as YP) of 290 MPa or more, and further 390 MPa or more is used.
  • Steel sheet piles having a strength of YP440 MPa or more may be essential under even more severe environments.
  • Patent Document 1 proposes a steel sheet pile having a YP of 440 MPa or more and high toughness by adding more than 0.05% of Nb to the composition.
  • the component composition is such that 0.030% or more of Nb is added together with V, and the rolling reduction at 1000° C. or less is controlled to reduce the average grain size of ferrite, the area ratio of island-shaped martensite, and the precipitates.
  • Proposals have been made for steel sheet piles having a YP of 440 MPa or more and high toughness by optimizing the number density.
  • Patent Document 3 proposes a steel sheet pile having a chemical composition in which Nb and B are added to a low carbon steel containing 0.005 to 0.030% C, and which has high strength, high toughness, and excellent underwater weldability. .
  • Patent Document 4 a component composition in which one or two types of V or Nb are added is used, the reduction ratio in the non-recrystallization temperature range is controlled at 900 ° C. or less, and accelerated cooling is performed after the completion of rolling to achieve high toughness. Steel sheet piles have been proposed.
  • Patent Document 5 proposes a steel sheet pile with a YP of 340 MPa or more and high toughness by limiting Nb in the inevitable impurities to 0.005% or less.
  • Patent Documents 6 and 7 propose a steel sheet pile having a YP of 440 MPa or more and a vTrs of -10°C or less by water-cooling a predetermined portion during or after hot rolling.
  • steel sheet piles having high strength and high toughness are obtained by adding 0.030% or more of Nb to the composition. It tends to increase the deformation resistance during hot rolling, so it is necessary to strictly control the shape during hot rolling.
  • the amount of C is as low as 0.005 to 0.030%, so the decarburization process during steel smelting takes a long time, and the productivity in the refining process is low. There's a problem.
  • Patent Document 5 promotes complete recrystallization of austenite by limiting the rolling temperature and the rolling reduction of the final pass, and by obtaining a uniform structure, a YP of 340 MPa or more and high toughness.
  • the YP is less than 440 MPa, and further improvement of YP is required.
  • the present invention aims to solve the above-mentioned problems, and aims to provide steel sheet piles with high strength and high toughness stably and with high productivity.
  • high strength means that YP is 440 MPa or more
  • high toughness means that the fracture surface transition temperature (hereinafter referred to as vTrs) at which the ductile fracture surface ratio becomes 50% is -10°C or less.
  • precipitation dispersion strengthening by precipitates is one of the effective means. become conspicuous.
  • precipitates with a certain grain size or more are necessary, while fine precipitates are effective in ensuring high strength. These two are in an antinomic relationship, and conventionally it has been difficult to achieve both high strength and high toughness by utilizing precipitates.
  • One way to solve this problem is to lower the ferrite transformation starting temperature by accelerated cooling, but this is not preferable because it may cause bending or warping.
  • positive rolling in the non-recrystallization temperature range is one of the effective means, but it is necessary to strictly control the shape.
  • V precipitates in austenite as V carbonitride in a relatively high temperature range and has a coherent interface with ferrite, so it is characterized in that it greatly contributes to the formation of ferrite nuclei.
  • Nb finely precipitates in austenite as Nb carbonitrides with grain sizes on the order of several nanometers mainly due to strain induction, dispersion strengthening by the precipitates is expected.
  • the present inventors considered the component composition in which V and Nb are added in combination, and studied the component composition ratio of V and Nb in order to control precipitates.
  • the components of V and Nb it was found that there is an appropriate range for the composition ratio.
  • V precipitates In order to effectively improve the strength and toughness of V precipitates, Nb precipitates, and composite precipitates thereof, the present inventors have found that fine particle size precipitates that can contribute to an increase in strength It has been found that a certain or more area ratio is required for precipitates with coarse grains that can contribute to the formation of ferrite nuclei.
  • the gist of the present invention is as follows.
  • Ar 3 910-310[%C]-80[%Mn]-20[%Cu]-15[%Cr]-55[%Ni]-80[%Mo] (4)
  • [%C], [%Si], [%Mn], [%Cu], [%Cr], [%Ni] and [%Mo] are respectively C, Si, Mn, Cu , Cr, Ni and Mo contents (% by mass).
  • the component composition is further mass %, Cu: 0.50% or less, Ni: 0.50% or less, Cr: 0.50% or less, Mo: 0.30% or less, Ca: 0.0050% or less, 2.
  • a steel material having the chemical composition described in 1 or 2 above is heated to 1200° C. to 1350° C. and subjected to hot rolling including rough rolling, intermediate rolling and finish rolling at a cumulative rolling reduction of 20% at 900° C. to 1000° C.
  • the rolling reduction in the austenite non-recrystallization temperature range is 10% or more and less than 20%
  • the end temperature of the intermediate rolling is 650 ° C. to 900 ° C.
  • the yield strength is 440 MPa or more
  • vTrs is -10 ° C. or less.
  • high-strength and high-toughness steel sheet piles with a YP of 440 MPa or more and a vTrs of -10°C or less can be stably provided with high productivity, which is very useful industrially.
  • FIG. 3 is a diagram showing a typical caliber in a hot rolling process of a hat-shaped steel sheet pile.
  • 4 is a graph showing the relationship between the area ratio of precipitates satisfying formula (2) and vTrs. 4 is a graph showing the relationship between the area ratio of precipitates having a size of 10 nm or less and yield strength.
  • the hat-shaped steel sheet pile 1 shown in FIG. 1(a) is a typical example, and there is also the straight steel sheet pile 9 shown in FIG. The final shape is given through a mold. This form and manufacturing procedure will be described later in detail.
  • ⁇ Steel sheet pile> The chemical composition and microstructure of the steel sheet pile of the present invention will be described in detail below. [Composition] First, the reason for limiting the chemical composition of the steel sheet pile of the present invention will be described. In the following description, "%" of the content of each element means “% by mass” unless otherwise specified.
  • V carbonitride is "V precipitate” or “V (C, N)”
  • Nb carbonitride is “Nb precipitate” or “Nb (C, N)”
  • V and Nb composite Carbonitrides are also referred to as “(their) composite precipitates” or "(V,Nb)(C,N)”.
  • C 0.05-0.18% C combines with V, Nb and N in steel, precipitates as carbonitrides such as V(C,N), Nb(C,N) or (V,Nb)(C,N), and increases the strength of the base material.
  • Ni is an essential element for stably securing toughness and must be added in an amount of 0.05% or more.
  • bainite containing island-shaped martensite is generated, and the increase in island-shaped martensite significantly reduces the toughness, and excessive precipitates reduce the toughness. Therefore, in the present invention, the C content is made 0.05 to 0.18%. Furthermore, the C content is preferably 0.10% or more. Also, the C content is preferably 0.16% or less.
  • Si 0.05-0.55% Si is an element that enhances the strength of the base material by solid solution strengthening, and should be contained in an amount of 0.05% or more. On the other hand, if the Si content is excessive, it promotes the formation of island-shaped martensite that reduces the toughness, so the Si content is made 0.55% or less. Therefore, the Si content should be 0.05 to 0.55%. Furthermore, the Si content is preferably 0.10% or more. Also, the Si content is preferably 0.50% or less.
  • Mn 1.00-1.65%
  • Mn is a relatively inexpensive element that has the effect of increasing the strength of steel, so it is an element necessary for increasing the strength.
  • the Mn content is set to 1.00 to 1.65%.
  • the Mn content is preferably 1.10% or more.
  • the Mn content is preferably 1.60% or less.
  • sol. Al 0.080% or less
  • Al is an element added as a deoxidizing agent.
  • the effect of Al as a deoxidizing agent is sol. Since it is saturated when it exceeds 0.080% as Al, sol. Al is set to 0.080% or less.
  • the lower limit is not particularly limited, it is preferably 0.001% or more for deoxidation. More preferably, it is 0.003% or more. Moreover, it is preferable that it is 0.060% or less.
  • V 0.005-0.250%
  • V precipitates in austenite as V (C, N) or (V, Nb) (C, N) during rolling or cooling, contributes as a ferrite nucleation site, and has the effect of refining crystal grains. is an important element possessing
  • V has a role of increasing the strength of the base material by dispersion strengthening as a precipitate, and is an essential element for ensuring strength and toughness.
  • the V content must be 0.005% or more.
  • the V content is set to 0.005 to 0.250%.
  • the V content is preferably 0.075% or more. More preferably, it exceeds 0.080%.
  • the V content is preferably 0.200% or less.
  • Nb 0.005% or more and less than 0.030%
  • Nb is mainly strain-induced precipitation during rolling to form Nb (C, N) or (V, Nb) (C, N) in austenite with a size on the order of several nm. It has the effect of suppressing recrystallization of austenite and refining crystal grains.
  • Nb has a role of increasing the strength of the base material by dispersion strengthening as a precipitate, and is an essential element for ensuring strength and toughness.
  • the Nb content must be 0.005% or more. Preferably, it is 0.010% or more.
  • Nb increases hot deformation resistance and, if the content is 0.030% or more, precipitation embrittlement tends to reduce toughness, so the Nb content is set to less than 0.030%. Preferably, it is 0.025% or less.
  • N 0.0010 to 0.0060%
  • N combines with V, Nb and C in steel, and forms V(C,N), Nb(C,N) or (V,Nb)(C,N) to improve base material strength and toughness.
  • Ni is a useful element and should be contained in an amount of 0.0010% or more.
  • the N content is made 0.0010 to 0.0060%.
  • the N content is preferably 0.0015% or more.
  • the N content is preferably 0.0055% or less.
  • V and Nb contents (% by mass) of V and Nb are respectively [%V] and [%Nb], It is important to satisfy the relationship of the following formula (1). ⁇ 0.010 ⁇ [%Nb] ⁇ 0.1[%V] ⁇ 0.020 (1)
  • V contributes as a ferrite nucleation site and uniformly refines the structure.
  • V contributes as a ferrite nucleation site and uniformly refines the structure.
  • V contributes as a ferrite nucleation site and uniformly refines the structure.
  • it is possible to secure a sufficient size and amount of precipitates V (C, N) or (V, Nb) (C, N) that contribute to the improvement of toughness, and a sufficient amount that contributes to the increase in strength.
  • Finely precipitated Nb(C,N) or (V,Nb)(C,N) can be secured.
  • the value calculated by [%Nb]-0.1[%V] is in the range of -0.010 to 0.020.
  • the value calculated by the above formula is preferably -0.005 or more. Moreover, it is preferable that it is 0.015 or less.
  • the balance other than the above elements is Fe and unavoidable impurities.
  • the upper limit of the content of P, S, and B is set as shown below.
  • P 0.025% or less
  • P is present as an unavoidable impurity in steel, but if the P content is excessive, the toughness of the steel is lowered, so P is made 0.025% or less.
  • the P content is preferably as small as possible, and may be 0%, but an excessive reduction in the P content leads to a decrease in productivity due to a prolonged refining process, so the P content is 0.005%. It is preferable to set it as above.
  • S 0.020% or less S, like P, is contained in steel as an unavoidable impurity and also exists as A-based inclusions. If the S content is excessive, the amount of A-based inclusions increases excessively and the toughness of the steel deteriorates, so the S content is made 0.020% or less.
  • the S content is preferably as small as possible, and may even be 0%. It is preferable to set it as above.
  • B 0.0003% or less B is an element that segregates at grain boundaries in steel and has the effect of increasing grain boundary strength.
  • the steel may contain more than 0.0003% of B. In this case, coarse grain boundary precipitates are formed, and the hardenability increases, which promotes the formation of island-shaped martensite and lowers the toughness. Furthermore, it is preferable to make it 0.0002% or less.
  • Cu 0.50% or less
  • Ni 0.50% or less
  • Cr 0.50% or less
  • Mo 0.30% or less
  • Ca 0.0050% or less
  • Ti 0.025% or less
  • REM 0.005% or less
  • Cu 0.50% or less
  • Cu is an element capable of further increasing the strength of steel through solid-solution strengthening.
  • it is preferable that the Cu content is 0.01% or more.
  • the content is preferably 0.50% or less.
  • Ni 0.50% or less
  • Ni is an element that dissolves in the steel and increases the strength of the steel without degrading the ductility and toughness.
  • the Ni content is 0.01% or more.
  • an excessive Ni content promotes the formation of island-shaped martensite, and Ni is an expensive element. From these points of view, the Ni content is set to 0.50% or less. is preferred.
  • Cr 0.50% or less
  • Cr is an element capable of further increasing the strength of steel through solid-solution strengthening. In order to obtain such effects, it is preferable that the Cr content is 0.01% or more. On the other hand, an excessive Cr content promotes the formation of island martensite, so the Cr content is preferably 0.50% or less.
  • Mo 0.30% or less
  • Mo is an element capable of further increasing the strength of steel through solid-solution strengthening.
  • the Mo content is preferably 0.01% or more.
  • an excessive Mo content promotes the formation of island-shaped martensite, so the Mo content is preferably 0.30% or less.
  • Ca 0.0050% or less Ca combines with S and O to reduce MnS in the steel, thereby improving the toughness and ductility of the steel. In order to obtain such effects, it is preferable that the Ca content is 0.0005% or more. On the other hand, if the Ca content exceeds 0.0050%, the cleanliness tends to decrease and the toughness tends to decrease, so the Ca content is preferably 0.0050% or less.
  • Ti 0.025% or less Ti precipitates as TiN in austenite and has the effect of refining crystal grains. In order to obtain such effects, it is preferable that the Ti content is 0.001% or more. On the other hand, if the Ti content is excessive, the precipitated TiN becomes coarse and the crystal grains become coarse, which tends to lower the toughness. Therefore, it is preferable to set the Ti content to 0.025% or less.
  • REM 0.005% or less
  • REM rare earth element
  • the REM content is 0.001% or more.
  • the Ca content exceeds 0.005%, the cleanliness tends to decrease and the toughness tends to decrease, so the REM content is preferably 0.005% or less.
  • the microstructure of the steel sheet pile in the present invention will be explained.
  • the microstructure of the web portion of the steel sheet pile may be defined. This is because the web portion has the lowest working degree and coarse structure, making it the most difficult to secure strength and toughness. will fulfill.
  • the microstructure has an area fraction of ferrite of 70% or more, an area fraction of island martensite of 1.0% or less, an average grain size of ferrite of 15 ⁇ m or less, and a maximum grain size of 40 ⁇ m or less. is essential.
  • a ferrite-based structure refers to a structure in which the area ratio of ferrite is 70% or more. If the ferrite area ratio is less than 70%, the hard phase may increase and the toughness may decrease. The upper limit of the area ratio of ferrite is preferably less than 90% from the viewpoint of ensuring strength.
  • the second phase is not particularly limited, examples thereof include pearlite, bainite structure including island-shaped martensite, and martensite. However, the area ratio of island-shaped martensite will be limited later.
  • the average grain size of ferrite is 15 ⁇ m or less and the maximum grain size is 40 ⁇ m or less
  • ferrite has an average grain size of 15 ⁇ m or less and a maximum grain size of 40 ⁇ m or less. If the average grain size of ferrite is larger than 15 ⁇ m or the maximum grain size is larger than 40 ⁇ m, YP will decrease and it will be difficult to ensure toughness. In order to obtain even higher strength and toughness, it is desirable that the ferrite has an average grain size of 12 ⁇ m or less and a maximum grain size of 30 ⁇ m or less.
  • the average grain size and maximum grain size of ferrite can be measured according to the measuring method described in Examples below.
  • the lower limit of the average grain size of ferrite is not particularly limited, it is preferably 5 ⁇ m or more, more preferably 10 ⁇ m or more, from the viewpoint of ensuring tensile strength.
  • the lower limit of the maximum grain size of ferrite is not particularly limited, but is preferably 20 ⁇ m or more, more preferably 25 ⁇ m or more, from the viewpoint of securing tensile strength.
  • the area ratio of island-shaped martensite is set to 1.0% or less. If the area ratio of island-shaped martensite is more than 1.0%, it becomes difficult to ensure toughness. In order to obtain higher toughness, it is desirable to set the area ratio of island martensite to 0.5% or less. The smaller the area ratio of island-shaped martensite, the better.
  • the area ratio of island-shaped martensite can be measured according to the measuring method described in Examples below.
  • vTrs fracture surface transition temperature
  • the measurement result of vTrs is shown in FIG. 3 as a relationship with the area ratio of the precipitates.
  • the precipitates can be arranged according to the following formula (2).
  • d, Ae 3 and Ar 3 are the grain size (nm) of the precipitate, the ferrite transformation start temperature (°C) during equilibrium transformation, and the ferrite transformation start temperature (°C) during air cooling, respectively.
  • Ae 3 and Ar 3 are determined by the following equations (3) and (4), respectively.
  • Ar 3 910-310[%C]-80[%Mn]-20[%Cu]-15[%Cr]-55[%Ni]-80[%Mo] (4)
  • [%C], [%Si], [%Mn], [%Cu], [%Cr], [%Ni] and [%Mo] are respectively C, Si, Mn, Cu , Cr, Ni and Mo contents (% by mass).
  • FIG. 3 shows the area ratio of V carbonitrides, Nb carbonitrides and their composite precipitates having a precipitate grain size that satisfies the formula (2) and the fracture surface transition temperature (° C.) (hereinafter “vTrs”). Show relationship. It can be seen that when the total area ratio of V carbonitride, Nb carbonitride and their composite precipitates having a precipitate grain size that satisfies formula (2) is 0.30% or more, vTrs-10 ° C. or less. .
  • the total area ratio is preferably 0.35% or more.
  • the upper limit of the total area ratio is not particularly limited, it is preferably 1.00% or less from the viewpoint of suppressing excessive precipitation embrittlement.
  • YP tensile test pieces were taken from each steel sheet pile to determine YP (0.2% yield strength).
  • YP was measured according to the method described in Examples below.
  • the reason for focusing on the area ratio of V carbonitrides, Nb carbonitrides and their composite precipitates having a grain size of 10 nm or less is that the Orowan stress related to precipitation strengthening is inversely proportional to the grain size of the precipitates.
  • the YP is 440 MPa or more when the total area ratio of V carbonitrides, Nb carbonitrides and their composite precipitates with grain sizes of 10 nm or less is 2.6% or more.
  • the total area ratio is preferably 4.0% or more.
  • the upper limit of the total area ratio is not particularly limited, it is preferably 10.0% or less from the viewpoint of suppressing excessive precipitation embrittlement.
  • FIG. 1(a) shows a hat-shaped steel sheet pile 1, which is a typical example of steel sheet piles.
  • a hat-shaped steel sheet pile 1 includes a web 2, a pair of flanges 3 and 4 extending obliquely from both ends of the web 2, and extending parallel to the web 2 from opposite sides of the flanges 3 and 4. It has arms 5 and 6 that are present and claws 7 and 8 that are at the ends of arms 5 and 6 .
  • this hat-shaped steel sheet pile As an example, after the steel material is heated, it is finally formed by passing through a groove as shown in Fig. 2 in each of rough rolling, intermediate rolling and finish rolling. Specifically, after the steel material is rolled a plurality of times in the initial rough rolling, it finally passes through the caliber 13 to form the rough shape of the steel sheet pile. In subsequent intermediate rolling, the web 2, the flanges 3 and 4, the arms 5 and 6, and the claws 7 and 8 are adjusted in thickness while finally passing through the groove 14. Furthermore, in the finish rolling, shape control including mainly claw bending forming is performed, and finally it passes through the caliber 15 to obtain the final product shape.
  • hot rolling is performed at a cumulative rolling reduction of 20% or more at 900 ° C. to 1000 ° C., and a rolling reduction in the non-recrystallized austenite region (hereinafter also referred to as CR rate ) is 10% or more and less than 20% and the finishing temperature of intermediate rolling is 650°C to 900°C.
  • CR rate rolling reduction in the non-recrystallized austenite region
  • Heating temperature of steel material 1200°C to 1350°C
  • the heating temperature of the steel material is set to 1200°C to 1350°C. Preferably, it is 1250° C. or higher.
  • [Cumulative rolling reduction at 900°C to 1000°C is 20% or more] It is important that the cumulative rolling reduction at 900°C to 1000°C is 20% or more.
  • the reduction rate just above the non-recrystallization temperature range is 20% or more.
  • Nb carbonitrides or composite precipitates of Nb and V of several nm order are precipitated in austenite due to strain induction, and YP is significantly improved. do.
  • it is 25% or more.
  • the upper limit is not particularly limited, but is preferably 30% or less from the viewpoint of manufacturability.
  • CR rate is 10% or more and less than 20%
  • the CR rate is 10% or more.
  • the grain size in the microstructure eventually becomes coarse, and the average grain size of ferrite becomes larger than 15 ⁇ m or the maximum grain size becomes larger than 40 ⁇ m, making it difficult to secure toughness.
  • the CR ratio is set to less than 20%. Preferably, it is 13% or more and 18% or less.
  • the CR rate can be adjusted by increasing or decreasing the roll gap during feeding.
  • End temperature of intermediate rolling is 650°C to 900°C
  • the end temperature of the intermediate rolling for forming the web and flanges is 650°C to 900°C. If the temperature exceeds 900°C, it becomes difficult to satisfy either of the above two rolling conditions, and finally the average grain size of ferrite in the microstructure becomes larger than 15 ⁇ m or the maximum grain size becomes larger than 40 ⁇ m, and toughness cannot be secured. Difficulties can arise. It is preferably 850° C. or less. On the other hand, if the temperature is lower than 650° C., the rolling load in the intermediate rolling increases, and the risk of roll breakage in the intermediate rolling mill increases. Preferably, it is 700°C or higher.
  • intermediate rolling refers to rolling from rough rolling that gives the outline of the steel sheet pile to nail bending rolling, and mainly the portion that will become the web is rolled down in the thickness direction. It is about rolling.
  • the steel sheet pile of the present invention does not require accelerated cooling during rolling or after nail bending rolling for the purpose of improving strength and toughness. Accelerated cooling is not preferable in terms of production because it causes shape changes such as bending and warping. Therefore, air cooling is desirable after nail bending rolling. From the viewpoint of shape control during rolling, water that is unavoidably applied and cooling such as mist water in the cooling bed do not affect the characteristics of the steel sheet pile of the present invention.
  • steel sheet piles By performing component adjustment, rolling and cooling according to the above conditions, steel sheet piles can have excellent mechanical properties such as high strength of YP 440 MPa or more and vTrs of -10°C or less. It should be noted that the steel sheet piles targeted by the present invention include hat-shaped, U-shaped, combinations thereof, straight-line, etc. regardless of the cross-sectional shape, and the thickness of the web and the shape of the claw portion are not particularly limited. .
  • test piece was taken from the 1/4 position of the web thickness of the steel sheet pile web and used for observation of the microstructure. Prior to observation, the test pieces collected here were surface-polished and corroded with nital. Then, using an optical microscope, the cross section in the thickness direction of the web was observed at a magnification of 100 to identify the type of structure. Processing for conversion into three gradations of black and gray was performed for discrimination, and the area ratio of each tissue was obtained. Also, the average grain size of ferrite is obtained by calculating the area of each crystal grain of ferrite in the field of view by image analysis using the same watershed algorithm. It was obtained as an average value.
  • the maximum grain size of ferrite was the maximum value among the circle-equivalent diameters within the field of view. Furthermore, regarding the observation of martensite islands, the cementite was dissolved by subjecting the same test piece as above to two-step etching treatment of electrolytic corrosion and nital, and a scanning electron microscope (SEM) was used at a magnification of about 1000 times. 10 or more fields of view were observed at random, and the area ratio of martensite islands was obtained by the same image analysis as described above.
  • SEM scanning electron microscope
  • ⁇ Tensile test> A JIS No. 1A tensile test piece specified in JIS Z2241 is taken from the 1/4 position of the web thickness of the steel sheet pile web so that the tensile direction is the longitudinal direction, and a tensile test is performed in accordance with JIS Z2241 to yield. Points (YP) and tensile strength (TS) were determined.
  • V notch depth 2 mm V-notch Charpy impact test piece (V notch depth 2 mm) specified in JIS Z2242 was taken from the web thickness 1/4 position of the steel sheet pile web, and a Charpy impact test was performed according to JIS Z2242. The impact test was conducted in a temperature range of -80 to 40°C, and the absorbed energy (vE 0 ) at 0°C and the fracture surface transition temperature (vTrs) at a ductile fracture surface ratio of 50% were determined.
  • Tables 2-1 and 2-2 also show the results of the above survey.
  • Test results (No. 1 to 17 in Table 2-1) of steel sheet piles produced by the manufacturing method according to the present invention using compatible steel satisfying the chemical composition according to the present invention are all the desired properties (yield strength YP: 440 MPa or more and a fracture surface transition temperature vTrs with a ductile fracture surface ratio of 50%: ⁇ 10° C. or less) were satisfied.
  • the steel composition of the steel sheet pile does not satisfy the conditions of the present invention, or does not satisfy the conditions of the manufacturing method of the present invention, or does not satisfy any of the above.
  • Nos. 18 to 38, 41) do not satisfy the required properties in either the yield strength or the fracture surface transition temperature (vTrs) at a ductile fracture surface ratio of 50%.

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JPH101721A (ja) * 1996-06-11 1998-01-06 Nkk Corp 水中溶接性と靱性に優れた鋼矢板の製造方法
JP2002294392A (ja) * 2001-03-29 2002-10-09 Kawasaki Steel Corp ウェブ厚が１５ｍｍ以上の高靭性鋼矢板及びその製造方法
JP2008221318A (ja) * 2007-03-15 2008-09-25 Jfe Steel Kk 鋼矢板の製造方法
JP2018090845A (ja) * 2016-11-30 2018-06-14 Ｊｆｅスチール株式会社 鋼矢板およびその製造方法
CN111187981A (zh) * 2020-02-13 2020-05-22 辽宁科技大学 一种含Nb高强度高韧性热轧钢板桩的生产工艺

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US10540717B2 (en) 2014-06-24 2020-01-21 Hitachi, Ltd. Financial products trading system and financial products trading control method
KR102540731B1 (ko) 2015-12-02 2023-06-05 이네오스 스티롤루션 그룹 게엠베하 개선된 특성을 갖는 abs 플라스틱을 생산하는 방법

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Publication number Priority date Publication date Assignee Title
JPH101721A (ja) * 1996-06-11 1998-01-06 Nkk Corp 水中溶接性と靱性に優れた鋼矢板の製造方法
JP2002294392A (ja) * 2001-03-29 2002-10-09 Kawasaki Steel Corp ウェブ厚が１５ｍｍ以上の高靭性鋼矢板及びその製造方法
JP2008221318A (ja) * 2007-03-15 2008-09-25 Jfe Steel Kk 鋼矢板の製造方法
JP2018090845A (ja) * 2016-11-30 2018-06-14 Ｊｆｅスチール株式会社 鋼矢板およびその製造方法
CN111187981A (zh) * 2020-02-13 2020-05-22 辽宁科技大学 一种含Nb高强度高韧性热轧钢板桩的生产工艺

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