WO2022149365A1 - Palplanche en acier et son procédé de fabrication - Google Patents

Palplanche en acier et son procédé de fabrication Download PDF

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Publication number
WO2022149365A1
WO2022149365A1 PCT/JP2021/043278 JP2021043278W WO2022149365A1 WO 2022149365 A1 WO2022149365 A1 WO 2022149365A1 JP 2021043278 W JP2021043278 W JP 2021043278W WO 2022149365 A1 WO2022149365 A1 WO 2022149365A1
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less
rolling
steel sheet
sheet pile
ferrite
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PCT/JP2021/043278
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English (en)
Japanese (ja)
Inventor
健太 朝日
浩文 大坪
佳祐 安藤
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Ｊｆｅスチール株式会社
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Priority to KR1020237019193A priority Critical patent/KR20230098874A/ko
Priority to CN202180086274.5A priority patent/CN116670305A/zh
Priority to JP2022511394A priority patent/JP7323056B2/ja
Publication of WO2022149365A1 publication Critical patent/WO2022149365A1/fr

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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
    • 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 applied as a permanent structure or a temporary structure in the field of civil engineering and construction, and a method for manufacturing the same.
  • Steel sheet piles are required to have strength and toughness because they are subject to high loads when used for quays and earth retaining.
  • a steel sheet pile having a yield strength (hereinafter referred to as YP) of 290 MPa or more or 390 MPa or more is used.
  • YP440 MPa or more may be indispensable.
  • the addition of alloying elements and rolling of austenite in the unrecrystallized region are common methods.
  • rolling and forming at a high temperature having a smaller deformation resistance is aimed at from the viewpoint of formability, and the addition of an alloy capable of increasing the deformation resistance may be limited.
  • the JIS standard (SYW) for steel sheet piles stipulates the Charpy absorption energy at 0 ° C. However, since steel sheet piles are used even in environments below 0 ° C, such as during the cold season in Japan, it is expected that steel sheet piles with even higher toughness will be required in the future.
  • Patent Document 1 proposes a steel sheet pile having a YP of 440 MPa or more and high toughness by using a component composition to which Nb is added.
  • the average particle size of ferrite, the area ratio of island-shaped martensite, and the number density of precipitates are controlled by controlling the reduction rate at 1000 ° C. or lower by using a component composition in which both Nb and V are added.
  • a steel sheet pile that has a YP of 440 MPa or more and high toughness.
  • the component composition is such that both Nb and V are added as in Patent Document 2, the cumulative reduction rate at 900 ° C. or lower is 90% or more, and the average particle size of ferrite and the number density of precipitates are optimized.
  • a steel sheet pile having a YP of 460 MPa or more and high toughness has been proposed.
  • Patent Document 4 proposes a steel sheet pile having a YP of 340 MPa or more and high toughness by limiting Nb in unavoidable impurities to 0.005% or less.
  • Patent Document 5 or 6 proposes a steel sheet pile having a YP of 440 MPa or more and a vTrs of ⁇ 10 ° C. or less by cooling a predetermined portion with water during hot rolling or after rolling.
  • Patent Documents 1, 2 and 3 are steel sheet piles having high strength and high toughness by having a component composition to which Nb is added.
  • Nb tends to increase the deformation resistance during hot rolling regardless of the solid solution or precipitation state, and it is necessary to strictly control the shape during hot rolling.
  • the grain size of ferrite is defined as an average value.
  • Nb suppresses the recrystallization of austenite, and the precipitation state may vary, resulting in a mixture of ferrite grains having different diameters. Therefore, it is also required to stably obtain high toughness.
  • Patent Document 4 a steel sheet pile having a YP of 340 MPa or more and high toughness is obtained by limiting the rolling temperature and the rolling reduction of the final pass to promote complete recrystallization of austenite and obtaining a uniform structure.
  • the YP is less than 440 MPa, and further improvement of the YP is required.
  • Patent Document 5 or 6 a predetermined portion of water cooling is indispensable in order to obtain a steel sheet pile having a YP of 440 MPa or more and a vTrs of ⁇ 10 ° C. or less. Therefore, the problem is that shape changes such as bending and warping are inevitable.
  • the present invention solves the above-mentioned problems, and an object of the present invention is to provide a steel sheet pile having high strength and high toughness in a stable manner and with high productivity.
  • high strength means, for example, YP of 440 MPa or more
  • high toughness means that vTrs is ⁇ 10 ° C. or less.
  • vTrs is a fracture surface transition temperature (a temperature at which the ductile fracture surface ratio is 50%) measured by a Charpy impact test based on JIS Z2242, and hereinafter, also referred to as a fracture surface transition temperature having a ductile fracture surface ratio of 50%.
  • the present inventors use V as an essential component without using Nb, and not only control the temperature during hot rolling and control the cumulative reduction rate. Focusing on the average rolling reduction rate per pass in the high temperature range, we conducted a diligent study. As a result, the structure is uniformly refined by optimizing the rolling conditions, and by utilizing the dispersion strengthening by V precipitates, the strength is as high as YP 440 MPa or more and the vTrs is as high as -10 ° C or less. I found a way to provide a steel sheet pile.
  • the gist of the present invention is as follows. 1. 1. By mass%, C: 0.05 to 0.18%, Si: 0.05-0.55%, Mn: 1.00 to 1.65%, sol. Al: 0.080% or less, V: 0.050 to 0.300% and N: 0.0010 to 0.0060% The balance is Fe and unavoidable impurities, and P, S and B as the unavoidable impurities are P: 0.025% or less, S: 0.020% or less and B: 0.0003% or less.
  • Has a component composition that is The microstructure is a ferrite-based structure, the average grain size of ferrite is 15 ⁇ m or less and the maximum grain size is 40 ⁇ m or less, and the area ratio of island-shaped martensite in the microstructure is 1.0% or less.
  • a steel sheet pile having a yield strength of 440 MPa or more and vTrs of ⁇ 10 ° C. or less.
  • composition of the components is further increased by 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
  • Nb 0.005% or less
  • the microstructure is a ferrite-based structure, the average grain size of ferrite is 15 ⁇ m or less and the maximum grain size is 40 ⁇ m or less, the area ratio of island-shaped martensite in the microstructure is 1.0% or less, and yielding.
  • a steel material having a component composition of is heated to 1200 ° C to 1350 ° C.
  • the steel material is hot-rolled, and in the hot-rolling,
  • the average reduction rate per pass at 900 ° C to 1150 ° C is 10% or more.
  • the cumulative rolling reduction at 800 ° C to 1150 ° C is 60% or more, and the end temperature of intermediate rolling is 650 ° C to 900 ° C.
  • intermediate rolling refers to rolling from after rough rolling to before finish rolling, and in intermediate rolling, the thickness is adjusted by rolling down a portion mainly to be a web in the thickness direction.
  • composition of the components is further increased by 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
  • Nb 0.005% or less
  • a steel sheet pile having high strength and high toughness having a YP of 440 MPa or more and a vTrs of ⁇ 10 ° C. or less can be provided stably and with high productivity, which is very useful industrially.
  • C 0.05 to 0.18% C is an element that is indispensable for stably ensuring the strength of the base metal as V (C, N) by binding to V and N in steel, and needs to be added in an amount of 0.05% or more.
  • the C content exceeds 0.18%, bainite containing island-like martensite is generated, and the toughness is greatly reduced by increasing the island-like martensite. In addition, the precipitate becomes excessive and the toughness is further lowered. Therefore, the C content is set to 0.05 to 0.18%. Further, the C content is preferably 0.10% or more. 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 metal by strengthening the solid solution, and must be contained in an amount of 0.05% or more.
  • an excessive Si content promotes the formation of islet martensite, which reduces toughness. Therefore, the Si content is set to 0.55% or less. Therefore, the Si content is set to 0.05 to 0.55%. Further, the Si content is preferably 0.10% or more. The Si content is preferably 0.50% or less.
  • Mn 1.00 to 1.65% Like Si, Mn is a relatively inexpensive element that has the effect of increasing the strength of steel, and is an element necessary for increasing the strength. However, when the Mn content is less than 1.00%, the effect becomes small. On the other hand, when the Mn content exceeds 1.65%, the formation of upper bainite containing island-like martensite is promoted, and the toughness is greatly impaired. Therefore, the Mn content is set to 1.00 to 1.65%. Further, 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. However, the effect of Al as a deoxidizing agent is sol. When it exceeds 0.080% as Al, it is saturated. Therefore, sol. Al was contained in an amount of 0.080% or less. sol. Al is preferably contained in an amount of 0.060% or less. sol. The lower limit of Al is not particularly limited, but for deoxidation, sol. It is preferable to contain Al in an amount of 0.001% or more. sol. Al is more preferably contained in an amount of 0.003% or more.
  • V 0.050 to 0.300%
  • V is an important element that precipitates as V (C, N) in austenite during rolling or cooling and contributes as a ferrite nucleation site, and has an effect of refining crystal grains.
  • V has a role of increasing the strength of the base metal by strengthening the dispersion as a precipitate, and is an essential element for ensuring the strength and toughness.
  • the V content needs to be 0.050% or more.
  • the V content is set to 0.050 to 0.300%.
  • the V content is preferably 0.075% or more.
  • the V content is more preferably more than 0.080%.
  • the V content is preferably 0.200% or less.
  • N 0.0010 to 0.0060%
  • N is an element that binds to V and C in steel and is useful as V (C, N) to improve the strength of the base metal, and requires a content of 0.0010% or more.
  • the N content is set to 0.0010 to 0.0060%.
  • the N content is preferably 0.0015% or more.
  • the N content is preferably 0.0055% or less.
  • Cu 0.50% or less
  • Cu is an element that can further increase the strength of steel by solid solution strengthening. In order to obtain such an effect, it is preferable that Cu is contained in an amount of 0.01% or more. However, if the Cu content exceeds 0.50%, Cu cracking is likely to occur. Therefore, when Cu is contained as the component composition of steel, the Cu content is preferably 0.50% or less.
  • Ni 0.50% or less
  • Ni like Cu, is an element that can be dissolved in steel to increase the strength of steel without deteriorating ductility and toughness. In order to obtain such an effect, it is preferable that Ni is contained in an amount of 0.01% or more. In particular, Ni suppresses Cu cracking by adding it in combination with Cu. Therefore, it is preferable to add Ni in combination with Cu. On the other hand, an excessive Ni content promotes the formation of island-like martensite. Also, Ni is an expensive element. Therefore, the Ni content is preferably 0.50% or less.
  • Cr 0.50% or less
  • Cr is an element that can further increase the strength of steel by solid solution strengthening. In order to obtain such an effect, it is preferable that Cr is contained in an amount of 0.01% or more. On the other hand, an excessive Cr content promotes the formation of island-like martensite. Therefore, the Cr content is preferably 0.50% or less.
  • Mo 0.30% or less
  • Mo is an element that can further increase the strength of steel by solid solution strengthening. In order to obtain such an effect, it is preferable that Mo is contained in an amount of 0.01% or more. On the other hand, an excessive Mo content promotes the formation of island-like martensite. Therefore, the Mo content is preferably 0.30% or less.
  • Ca 0.0050% or less Ca combines with S and O to reduce MnS in steel. This makes it possible to improve the toughness and ductility of the steel. In order to obtain such an effect, it is preferable that Ca is contained in an amount of 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. Therefore, the Ca content is preferably 0.0050% or less.
  • Nb 0.005% or less Nb is precipitated in austenite as Nb (C, N) during rolling, has the effect of suppressing recrystallization of austenite and refining the crystal grains.
  • Nb is contained in an amount of 0.001% or more.
  • Nb tends to increase the deformation resistance during hot rolling regardless of the solid solution or precipitation state.
  • the average reduction rate per pass in the recrystallization temperature range is 10% or more, it is advantageous to set the Nb content to 0.005% or less. Therefore, when Nb is contained as the component composition of the steel, the Nb content is preferably 0.005% or less.
  • Ti 0.025% or less Ti has the effect of precipitating in austenite as TiN and refining the crystal grains. In order to obtain such an effect, it is preferable that Ti is contained in an amount of 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, so that the toughness tends to decrease. Therefore, the Ti content is preferably 0.025% or less.
  • REM 0.005% or less REM (rare earth element) can be combined with S and O to reduce MnS in the steel in the same manner as Ca, thereby improving the toughness and ductility of the steel.
  • REM is contained in an amount of 0.001% or more.
  • the REM content is preferably 0.005% or less.
  • the balance other than the above elements is Fe and unavoidable impurities. If the content of the element related to the above-mentioned optional additive component is less than each suitable lower limit value, the element is treated as an unavoidable impurity (included as an unavoidable impurity).
  • the total amount of unavoidable impurities is such that it is unavoidably mixed in steel by a general manufacturing method, for example, preferably 0.050% or less, more preferably 0.040% or less.
  • the upper limit of the content of P, S and B is set as shown below.
  • P 0.025% or less P is present in steel as an unavoidable impurity. However, if the P content is excessive, the toughness of the steel is lowered, so the P content is set to 0.025% or less. The smaller the P content is, the more preferable it is, and it may be 0%, but an excessive reduction in the P content causes a decrease in productivity due to a long refining process. Therefore, the P content is more preferably 0.005% or more.
  • S 0.020% or less S is contained as an unavoidable impurity in steel like P, and is present as an A-based inclusion.
  • the S content is set to 0.020% or less. The smaller the S content is, the more preferable it is, and it may be 0%, but an excessive reduction in the S content causes a decrease in productivity due to a long refining process. Therefore, the content of S is more preferably 0.002% or more.
  • B 0.0003% or less B is an element that segregates at the grain boundaries in steel and has the effect of increasing the 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 is increased, which promotes the formation of island-shaped martensite and lowers the toughness. Therefore, the B content is set to 0.0003% or less. Further, the B content is preferably 0.0002% or less. The smaller the B content is, the more preferable it is, and it may be 0%.
  • the microstructure of the steel sheet pile according to one embodiment of the present invention defines the web of the steel sheet pile as a representative site.
  • the web has the lowest degree of processing among the parts of the steel sheet pile, and the structure is coarse, making it the most difficult to secure strength and toughness. Therefore, the microstructure is defined with the web as the representative site. Since the characteristics targeted by the present application can be obtained if the microstructure of the web satisfies the conditions described below, the steel sheet pile according to the embodiment of the present invention is not particularly limited to the microstructure of the portion other than the web. Further, if the microstructure of the web satisfies the conditions described below, it can be said that it is highly probable that the same microstructure is obtained in a part other than the web.
  • the area ratio of ferrite, the average particle size and the maximum particle size, and the area ratio of island-shaped martensite satisfy the following conditions.
  • the microstructure of the steel sheet pile shall be a ferrite-based structure.
  • the ferrite-based structure refers to a structure in which the area ratio of ferrite is 70% or more. If the area ratio of ferrite 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 residual structure other than ferrite is not particularly limited, and examples thereof include bainite structure including pearlite and island-like martensite and martensite.
  • the total area ratio of the residual structure other than ferrite is preferably 30% or less. Further, the total area ratio of the residual structure other than ferrite is preferably more than 10%. However, the area ratio of island-shaped martensite needs to be limited as described later.
  • the area ratio of each phase can be measured according to the measuring method described in Examples described later.
  • the average particle size of ferrite is 15 ⁇ m or less, and the maximum particle size is 40 ⁇ m or less
  • the average particle size of ferrite is 15 ⁇ m or less, and the maximum particle size is 40 ⁇ m or less.
  • the average particle size of ferrite is 12 ⁇ m or less and the maximum particle size is 30 ⁇ m or less.
  • the average particle size of ferrite is 10 ⁇ m or less and the maximum particle size is 25 ⁇ m or less.
  • the lower limits of the average particle size and the maximum particle size of ferrite are not particularly limited. Further, the average particle size and the maximum particle size of ferrite can be measured according to the measuring method described in Examples described later.
  • the area ratio of island-shaped martensite shall be 1.0% or less. If the area ratio of island-shaped martensite is more than 1.0%, it becomes difficult to secure toughness. In order to obtain better toughness, it is desirable that the area ratio of island-shaped martensite is 0.5% or less. The smaller the area ratio of the island-shaped martensite is, the more preferable it is, and 0% may be used. Therefore, no lower limit is set.
  • the area ratio of island-shaped martensite can be measured according to the measuring method described in Examples described later.
  • FIG. 1A shows a hat-shaped steel sheet pile 1, which is a typical example of a steel sheet pile.
  • the hat-shaped steel sheet pile 1 extends parallel to the web 2 from the web 2, a pair of flanges 3 and 4 inclined from both ends of the web 2, and sides of both flanges 3 and 4 opposite to the web 2. It has existing arms 5 and 6 and claws 7 and 8 at both ends of the arms 5 and 6.
  • this hat-shaped steel sheet pile after heating the steel material, it is finally formed by passing through a hole mold 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 first rough rolling, it finally passes through the hole mold 13 to form a rough shape of the steel sheet pile. In the subsequent intermediate rolling, the thickness of the portion to be the web 2, the flanges 3 and 4, the arm portions 5 and 6, and the claw portions 7 and 8 is adjusted, and finally passes through the hole mold 14. Further, in the finish rolling, shape control including mainly claw bending molding is performed, and finally the shape is passed through the hole mold 15 to obtain the final product shape.
  • hot rolling includes rough rolling, intermediate rolling and finish rolling.
  • rough rolling the approximate shape of the steel sheet pile is given.
  • Intermediate rolling refers to rolling from after rough rolling to before finish rolling (in the above example, claw bending forming (rolling)), and in intermediate rolling, mainly the part that becomes the web is rolled down in the thickness direction. Adjust the thickness.
  • finish rolling final shape control is performed, and in the above example, claw bending molding is included.
  • steel sheet piles other than the hat-shaped steel sheet piles shown above for example, steel sheet piles having differences in the web thickness and the product shape including the claws, such as the linear steel sheet pile 9 shown in FIG. 1 (b), may be used.
  • steel sheet piles having differences in the web thickness and the product shape including the claws, such as the linear steel sheet pile 9 shown in FIG. 1 (b)
  • there may be differences in the number of rolling passes and rolling temperature in hot rolling there is no fundamental difference in the production by rough rolling, intermediate rolling and finish rolling (including claw bending forming), and all of them are books. It is included in the method for manufacturing a steel sheet pile according to an embodiment of the invention.
  • the straight portion located between the left and right claw portions 11 and 12 is referred to as a web 10.
  • the steel material In hot rolling, the steel material is heated to 1200 ° C to 1350 ° C, and the average reduction rate per pass at 900 ° C to 1150 ° C is 10% or more, and the cumulative reduction rate at 800 ° C to 1150 ° C. It is important that the temperature is 60% or more and the finishing temperature of the intermediate rolling is 650 ° C to 900 ° C. All of the following temperature regulations are based on the surface temperature of the steel material and the material to be rolled. The temperature of the steel material and the material to be rolled can be measured by a radiation thermometer.
  • Heating temperature of steel material 1200 ° C to 1350 ° C
  • the heating temperature is set to 1200 ° C to 1350 ° C.
  • the heating temperature of the steel material is preferably 1250 ° C to 1350 ° C.
  • Average reduction rate per pass from 900 ° C to 1150 ° C is 10% or more
  • the average reduction rate per pass (hereinafter, also simply referred to as the average reduction rate) at 900 ° C to 1150 ° C is 10% or more.
  • the average reduction rate is preferably 12% or more.
  • the average reduction rate can be calculated by the following equation (1).
  • R 100 ⁇ 1- (T f / T s ) 1 / n ⁇ ⁇ ⁇ ⁇ (1)
  • R is the average rolling reduction (%)
  • T f and T s are the plate thicknesses (mm) of the material to be rolled (position corresponding to the web) at 900 ° C. and 1150 ° C., respectively
  • n is 900.
  • the number of rolling passes at ° C to 1150 ° C.
  • the number of rolling passes counts the number of rolling passes in which at least one of the rolling start temperature and the rolling end temperature is in the range of 900 ° C to 1150 ° C.
  • a rolling pass having a rolling start temperature of 1160 ° C. and a rolling end temperature of 1100 ° C. is regarded as one pass and counted in the number of rolling passes.
  • the plate thickness can be controlled by the roll gap of the rolling mill.
  • the average reduction rate is preferably 20% or less from the viewpoint of shape control. Further, when the average reduction rate is less than 10%, recovery of austenite or partial recrystallization becomes remarkable, and the crystal grains are coarse and mixed, so that it may be difficult to secure toughness.
  • [Cumulative reduction rate from 800 ° C to 1150 ° C is 60% or more]
  • the cumulative reduction rate at 800 ° C to 1150 ° C (hereinafter, also simply referred to as the cumulative reduction rate) is 60% or more.
  • the cumulative reduction rate is preferably 70% or more.
  • the cumulative reduction rate is preferably 90% or less from the viewpoint of the risk of circumcision of the roll.
  • the cumulative reduction rate can be calculated by the following equation (2).
  • R' 100 ⁇ 1- ( TL / T s ) ⁇ ⁇ ⁇ ⁇ (2)
  • R' is the cumulative rolling reduction rate (%)
  • TL and T s are the plate thicknesses (mm) of the material to be rolled (position corresponding to the web) at 800 ° C. and 1150 ° C., respectively.
  • End temperature of intermediate rolling is 650 ° C to 900 ° C
  • the end temperature of the above intermediate rolling for forming the web and the flange is 650 ° C to 900 ° C.
  • the end temperature of intermediate rolling exceeds 900 ° C. It becomes difficult to satisfy any of the above two rolling conditions, and finally the average particle size of ferrite in the microstructure may be larger than 15 ⁇ m or the maximum particle size may be larger than 40 ⁇ m, making it difficult to secure toughness. ..
  • the end temperature of the intermediate rolling is less than 650 ° C., the rolling load in the intermediate rolling becomes high and the risk of rolling roll breakage in the intermediate rolling mill increases.
  • intermediate rolling refers to rolling from after rough rolling to before finish rolling (in the above example, claw bending forming (rolling)). Then, in the intermediate rolling, the portion mainly to be the web is pressed down in the thickness direction to adjust the thickness. Further, in finish rolling, final shape control is performed. That is, finish rolling is not intended only for the final path of hot rolling, but refers to a rolling process in which the shape is finally adjusted after intermediate rolling. Finish rolling is performed from the viewpoint of formability and cannot have a significant effect on the characteristics, so the conditions for finish rolling are not specified.
  • the method for manufacturing a steel sheet pile according to an embodiment of the present invention includes hot rolling during hot rolling (rough rolling, intermediate rolling and finish rolling) and hot rolling (finish rolling (claw bending rolling)) for the purpose of improving strength and toughness. )) No subsequent accelerated cooling is required. That is, accelerated cooling is not preferable in terms of production because it causes shape changes such as bending and warping. Therefore, it is desirable to cool the air after hot rolling (finish rolling (claw bending rolling)). From the viewpoint of shape control during rolling, cooling such as water inevitably applied or mist water in the cooling bed does not affect the characteristics of the steel sheet pile.
  • the composition, rolling and cooling By adjusting the composition, rolling and cooling according to the above conditions, it is possible to obtain excellent mechanical properties of a steel sheet pile having a high strength of YP 440 MPa or more and a vTrs of -10 ° C or less.
  • the production conditions other than the above are not particularly limited, and the conventional method may be followed.
  • the number of rolling passes for rough rolling, intermediate rolling and finish rolling is 5 to 20 passes, 1 to 5 passes and 1 to 3 passes, respectively.
  • the rolling paths at 900 ° C. to 1150 ° C. include, for example, rolling passes by rough rolling and intermediate rolling.
  • the steel sheet pile according to the embodiment of the present invention includes, for example, a rolling pass by rough rolling and intermediate rolling, and may optionally include a rolling pass by finish rolling.
  • the finish rolling end temperature is preferably 550 to 700 ° C.
  • the steel sheet pile according to the embodiment of the present invention includes a hat shape, a U shape, a combination thereof, a linear shape and the like regardless of the cross-sectional shape, and the web thickness and the shape of the claw portion are not particularly limited. do not have.
  • the present invention is not limited by the following examples, and can be appropriately modified within a range that can be adapted to the gist of the present invention, all of which are included in the technical scope of the present invention. ..
  • a steel material having the steel composition shown in Table 1 (the balance is Fe and unavoidable impurities) was prepared, heated and hot-rolled under the conditions shown in Table 2, and the web shown in FIG. 1 was formed. 2 and a pair of flanges 3 and 4 inclined and extended from both ends of the web 2 are located at the arms 5 and 6 extending in a direction extending in parallel to the left and right of the web 2 and at both ends of the arms 5 and 6.
  • a hat-shaped steel sheet pile having claws 7 and 8 was manufactured.
  • the cooling after hot rolling was performed by air cooling.
  • conditions other than the above shall be in accordance with the conventional law.
  • Specimens were collected from the web thickness 1/4 position of the steel sheet pile web and used for microstructure observation. The surface of the test piece collected here was polished and corroded with nital prior to observation. Then, using an optical microscope, the type of tissue was identified by observing the thickness of the web 100 times, and ferrite, pearlite, and bainite and martensite were analyzed in a field of 800 ⁇ m ⁇ 600 ⁇ m by image analysis using the diversion ridge algorithm. A process of converting each into three gradations of white, black, and gray was performed to distinguish them, and the area ratio of each structure was obtained.
  • the average grain size of ferrite For the average grain size of ferrite, the area of each crystal grain of ferrite in the above-mentioned visual field is calculated by the same image analysis by the diversion ridge algorithm, and the equivalent circle diameter of each crystal grain is defined as the grain size of ferrite in the above-mentioned visual field. The average value was calculated. The maximum particle size of ferrite was set to the maximum value among the diameters equivalent to circles in the above field of view. The average grain size of ferrite was calculated using only crystal grains having a diameter equivalent to a circle and a grain size of 3 ⁇ m or more that can be confirmed in the above field of view.
  • ⁇ Tensile test> From the web thickness 1/4 position of the web of the steel sheet pile, the JIS1A tensile test piece specified in JIS Z2201 is collected so that the tensile direction is the longitudinal direction, and the tensile test is performed in accordance with JIS Z2241 to perform the yield point. (YP) and tensile strength (TS) were determined.
  • ⁇ Toughness test> A 2 mm V notch Charpy impact test piece specified in JIS Z2202 was collected from a web thickness 1/4 position of the web of the steel sheet pile, and a Charpy impact test was performed according to JIS Z2242. The impact test was carried out in the temperature range of ⁇ 80 to 40 ° C., and the absorbed energy (vE 0 ) at 0 ° C. and the fracture surface transition temperature (vTrs) having a ductile fracture surface ratio of 50% were determined.
  • Table 2 also shows the results of the above survey.
  • the test results (Nos. 1 to 17 in Table 2) of the steel sheet piles of the invention examples manufactured under the predetermined production conditions using the compatible steel satisfying the predetermined composition are all desired characteristics (yield strength YP :.
  • the fracture surface transition temperature vTrs: ⁇ 10 ° C. or less with a ductile fracture surface ratio of 50% and 440 MPa or more was satisfied. Further, in the examples of the invention, it was confirmed that the shape change such as large bending and warping did not occur in any of the invention examples, and the production could be performed stably and with high productivity.
  • the comparative examples which did not satisfy the predetermined component composition, the predetermined production conditions, or none of the above were the yield strength and the yield strength. Any value of the fracture surface transition temperature (vTrs) with a ductile fracture surface ratio of 50% does not satisfy the required characteristics.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
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  • Metallurgy (AREA)
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  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
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Abstract

Selon la présente invention, une palplanche en acier ayant une résistance élevée et une ténacité élevée est fournie de manière stable avec une productivité élevée. La palplanche en acier a une composition de constituants prédéfinie et présente une structure composée principalement de ferrite en tant que microstructure, la ferrite ayant un diamètre moyen des particules d'au plus 15 µm et un diamètre maximal des particules d'au plus 40 µm, le rapport de surface de la martensite en forme d'îlots dans la microstructure étant d'au plus 1,0 %, et la palplanche en acier ayant une limite d'élasticité d'au moins 440 MPa et une température de transition vTrs d'au plus -10 °C.
PCT/JP2021/043278 2021-01-07 2021-11-25 Palplanche en acier et son procédé de fabrication WO2022149365A1 (fr)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002020835A (ja) * 2000-05-02 2002-01-23 Nippon Steel Corp 脆性き裂伝播停止特性と板厚方向破壊特性の優れた鋼材およびその製造方法
JP2008221318A (ja) * 2007-03-15 2008-09-25 Jfe Steel Kk 鋼矢板の製造方法
JP2016084524A (ja) * 2014-10-27 2016-05-19 新日鐵住金株式会社 低温用ｈ形鋼及びその製造方法
WO2018117228A1 (fr) * 2016-12-21 2018-06-28 新日鐵住金株式会社 Profilé acier en h et procédé pour le fabriquer

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3785940B2 (ja) 2001-03-29 2006-06-14 Ｊｆｅスチール株式会社 ウェブ厚が１５ｍｍ以上の高靭性鋼矢板及びその製造方法
JP2007332414A (ja) 2006-06-14 2007-12-27 Jfe Steel Kk 高強度広幅鋼矢板およびその製造方法
JP5966909B2 (ja) 2012-12-19 2016-08-10 新日鐵住金株式会社 鋼矢板及びその製造方法
JP6720842B2 (ja) 2016-11-22 2020-07-08 日本製鉄株式会社 鋼矢板
JP6610520B2 (ja) 2016-11-30 2019-11-27 Ｊｆｅスチール株式会社 鋼矢板およびその製造方法

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002020835A (ja) * 2000-05-02 2002-01-23 Nippon Steel Corp 脆性き裂伝播停止特性と板厚方向破壊特性の優れた鋼材およびその製造方法
JP2008221318A (ja) * 2007-03-15 2008-09-25 Jfe Steel Kk 鋼矢板の製造方法
JP2016084524A (ja) * 2014-10-27 2016-05-19 新日鐵住金株式会社 低温用ｈ形鋼及びその製造方法
WO2018117228A1 (fr) * 2016-12-21 2018-06-28 新日鐵住金株式会社 Profilé acier en h et procédé pour le fabriquer

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