EP2042616B1 - Gewalzte platte aus nichtrostendem austenitstahl mit einer dicke von 100 mm oder mehr und herstellungsverfahren dafür - Google Patents

Gewalzte platte aus nichtrostendem austenitstahl mit einer dicke von 100 mm oder mehr und herstellungsverfahren dafür Download PDF

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EP2042616B1
EP2042616B1 EP07767966.0A EP07767966A EP2042616B1 EP 2042616 B1 EP2042616 B1 EP 2042616B1 EP 07767966 A EP07767966 A EP 07767966A EP 2042616 B1 EP2042616 B1 EP 2042616B1
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Prior art keywords
thickness
reduction ratio
forging
rolling
steel
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French (fr)
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EP2042616A4 (de
EP2042616A1 (de
Inventor
Yutaka Tadokoro
Shinji Tsuge
Kazuhiro Suetsugu
Yoichi Yamamoto
Toshinori Ohtsubo
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Nippon Steel Stainless Steel Corp
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Nippon Steel and Sumikin Stainless Steel Corp
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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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • 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
    • B21B1/02—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 heavy work, e.g. ingots, slabs, blooms, or billets, in which the cross-sectional form is unimportant ; Rolling combined with forging or pressing
    • B21B1/026—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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
    • 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
    • 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
    • C21D8/021—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips involving a particular fabrication or treatment of ingot or slab
    • 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
    • C21D8/0247—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
    • 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
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • 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
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • 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
    • C22C38/52—Ferrous alloys, e.g. steel alloys containing chromium with nickel with cobalt
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B3/00—Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences ; Rolling of aluminium, copper, zinc or other non-ferrous metals
    • B21B3/02—Rolling special iron alloys, e.g. stainless steel
    • 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
    • C21D2211/001—Austenite

Definitions

  • the present invention relates to extremely low temperature use austenitic stainless rolled steel plate useful at 150K or less used for superconductive coils of thermonuclear reactors and structural materials for LNG (liquefied natural gas).
  • it relates to rolled steel plate of a thickness of 100 mm or more which conventionally could not be produced.
  • thermonuclear reactors promising as a next generation energy source are required to be nonmagnetic and at the same time high in strength properties at the extremely low temperature region of the superconductivity temperature. Further, superconductive coils are expected to become massive apparatuses, so as structural material, thick-gauge plate will be essential.
  • JIS G4304 has provisions on hot-rolled stainless steel plate and steel strip.
  • a yield strength of 245 N/mm 2 or more, a tensile strength of 550 N/mm 2 , and an elongation of 40 or more are defined.
  • Japanese Patent Publication ( A) No. 60-13063 discloses austenitic stainless steel for extremely low temperature structures with high N and Mn, but does not disclose stainless steel of a thickness of 100 mm or more.
  • Japanese Patent Publication ( A) No. 61-52351 discloses austenitic stainless steel high in N, Mn, and Al and superior in extremely low temperature yield strength and toughness, which is used as structural materials, but does not disclose stainless steel of a thickness of 100 mm or more.
  • Japanese Patent Publication ( A) No. 2-57668 discloses austenitic stainless steel containing Nb, high in Mn, and superior in reheating resistance property, which is used at extremely low temperature, but does not disclose stainless steel of a thickness of 100 mm or more.
  • Japanese Patent Publication ( A) No. 7-316653 discloses a method of production of stainless steel plate of 100 mm or more superior in properties at extremely low temperature, but does not disclose the addition of Cu or Ti to the stainless steel.
  • the above publication discloses a method of working and heat treatment for obtaining a uniform granular structure over the entire cross-section, but does not disclose homogenization by increasing the fineness of the solidified structure.
  • Japanese Patent Publication ( A) No. 7-310120 discloses a method of hot-rolling austenitic stainless thick-gauge steel plates of 50 mm thickness and 100 mm thickness, but does not disclose the compositions of the stainless steel.
  • Japanese Patent Publication ( A) No. 8-104920 discloses a method of production of high strength austenitic stainless steel plate (containing Ti).
  • Ti is added to increase the fineness of the solidified structure and prevent the occurrence of surface defects at the time of rolling.
  • the solution treatment is omitted.
  • the above publication does not disclose stainless steel plate of a thickness of 100 mm or more.
  • Japanese Patent Publication ( A) No. 11-131138 discloses the method of production of very thick steel plate of stainless steel of 97 mm thickness comprising using forging to eliminate porosity without causing cracks in the surface of the continuously cast slab.
  • the above publication does not disclose stainless steel plate of a thickness of 100 mm or more and compositions of the stainless steel plate.
  • the limitations on thickness of the material due to the forging machine are smaller than with a rolling machine, the reduction ratio can be increased, and working is possible even in the direction of increase of the plate thickness, so it is possible to introduce work strain over the entire cross-section even in thick-gauge products and as a result it is easy to obtain a fine recrystallized structure over the entire cross-section.
  • JP H08 269564 (A ) discloses a production method of an austenitic steel having a thickness of 50 mm or more and a magnetic permeability of 1.05 or less.
  • the present invention relates to a structural material for a superconductive coil of a thermonuclear reactor, a structural material for LNG (liquefied natural gas), and other materials used at extremely low temperatures, in particular relates to extremely thick stainless steel plate of 100 mm or more, and has as its object the provision of a rolled product superior in mechanical properties over its entire cross-section and a method of production for obtaining the same.
  • LNG liquefied natural gas
  • the locations of 1/4 of plate thickness to 3/4 of plate thickness from the surface layer are locations resistant to work strain by forging or rolling. At those locations, it is difficult to secure strength and ductility.
  • the inventors investigated in detail various alloys and first obtained the discovery that by defining the composition, it is possible to secure the lowest required strength and ductility even at an extremely low temperature.
  • the inventors obtained the discovery that if suitably combining the forging and rolling processes to crush the cast structure of a steel ingot over its entire cross-section and introduce hot rolling strain to the entire cross-section, the recrystallization is promoted and a uniform recrystallized structure is obtained.
  • the present invention was made based on this discovery and has as its gist the following.
  • the "forging” here is free-forging using a press, but sometimes the press process is performed divided into several operations at the same surface and same direction of the steel ingot until the steel ingot as a whole reaches the predetermined cross-sectional shape.
  • the series of press operations by a press at the same surface and same direction until the steel ingot as a whole reaches the predetermined cross-sectional shape is defined as a "single forging process”.
  • the austenitic stainless rolled steel plate of the present invention can be applied as a structural material for superconductive coils for thermonuclear reactors (ITER) expected to serve as a next generation energy source.
  • the austenitic stainless steel plate of the present invention can be applied for increasingly larger superconductive equipment, for structures for LNG (liquefied natural gas), etc. and is expected to contribute greatly to the future energy industry and other various industrial fields.
  • the present invention therefore has a great industrial and social effect.
  • the present invention by forging a steel ingot defined in composition effective for improvement of the strength in the first half of the process and rolling it in the second half of the process, it is possible to produce austenitic stainless rolled steel plate of a thickness of 100 mm or more superior in strength and ductility.
  • N is an element extremely effective for stabilizing the austenite phase and securing the strength at an extremely low temperature. However, if less than 0.10%, the effect is small, while if over 0.22%, the weldability remarkably deteriorates and weld cracks and blow holes frequently occur, so the N content was made 0.10 to 0.22%.
  • the strength at an extremely low temperature is correlated with the amount of (C+N) in the steel.
  • C and N the range of content for each is defined, so C+N was made 0.12% or more.
  • Si if less than 0.01%, results in a poor cleanliness of the steel and deteriorated toughness, while if over 2.0%, the hot workability deteriorates and production of thick-gauge plate becomes difficult, so the Si content was made 0.01 to 2.0%.
  • Mn also, if less than 0.1%, results in poor cleanliness of the steel, while if over 2.0%, the hot workability deteriorates, so the Mn content was made 0.1 to 2.0%.
  • Cr is required to be 15% or more to secure corrosion resistance at the time of working the member, but if over 27%, a brittle ⁇ -phase is formed and the toughness deteriorates, so the Cr content was made 15 to 27%.
  • Ni is an element stabilizing the austenite phase and improving the strength, toughness, and ductility at an extremely low temperature, but if less than 8%, the effect of stabilization of the austenite phase is insufficient, so 8% was made the lower limit. However, this is an extremely expensive element, so from the viewpoint of cost, 20%, where the austenite stabilization effect is stabilized, was made the upper limit.
  • Co when mixed in as an impurity element, radiates and is harmful. To reduce the radiation, the Co content was made 0.1% or less.
  • Cu is an element increasing the corrosion resistance, so is deliberately added. If less than 0.1%, there is no such effect, while if over 3%, the hot workability is impeded, so the Cu content was made 0.1% to 3%.
  • Al is an element improving the cleanliness of the steel as a deoxidizing material. However, if less than 0.001%, there is no such effect, while if over 0.10%, the hot workability deteriorates, so the Al content was made 0.001 to 0.10%.
  • Ti is added to increase the fineness of the solidified structure and more stably improve the strength and elongation. If less than 0.010%, there is no effect of addition, while if over 0.030%, coarse nitrides precipitate and the toughness deteriorates, so the Ti content was made 0.010% to 0.030%.
  • S included as an unavoidable impurity is an element causing a drop in the hot workability and toughness and is preferably reduced to 0.003% or less.
  • P included as an unavoidable impurity is an element harmful to the corrosion resistance and is preferably reduced to 0.040% or less.
  • the amount of ⁇ -ferrite of a large cross-section steel ingot covered by the present invention was confirmed by a sampling investigation to give a value of about -0, +8% from the amount of precipitation of ⁇ -ferrite predicted by this calculation formula.
  • ⁇ -ferrite appears at the time of solidification, there is an effect in increasing the fineness of the austenitic solidified structure. Further, if the ⁇ -ferrite is finely dispersed in the steel plate, the coarsening of the crystal grains during heating is suppressed.
  • the directions of elongation of the steel plate include the width direction, length direction, and thickness direction, that is, three directions, but considering actual use, the elongations in the width direction and length direction were defined. If the elongation is 30% or more at any location in the thickness direction at a temperature of ordinary temperature to 4K, there is no practical problem, so the elongation was made 30% or more.
  • the elongation is preferably 40% or more.
  • the covered steel ingots considering the thickness of the product, are limited to steel ingots of a thickness of 650 mm or more.
  • the area reduction ratio of the forging able to impart a large strain locally as much as possible. Further, if considering the restrictions on plate thickness in rolling machines and introduction of sufficient work strain in the cast structure over the entire cross-section, the area reduction ratio was made 0.5 or more.
  • the hot rolling is a process performed after the forging until obtaining the product thickness. To increase the reduction ratio as much as possible, introduce strain over the entire cross-section, and obtain a uniform recrystallized structure after solution heat treatment, the reduction ratio of the hot rolling was made 1.5 or more.
  • the solution heat treatment is performed for the purpose of obtaining sufficient values for the strength and elongation and other mechanical properties and the corrosion resistance by dissolving the component elements and making the metal structure crystal grain size uniform.
  • the solution heat treatment is performed in accordance with the alloy composition and production process at 920 to 1200°C. The steel is rapidly cooled from that temperature.
  • the area reduction ratio (C) of forging in the direction of decrease or increase of the thickness is defined as follows:
  • the area reduction ratio per operation in the forging in the direction where the thickness is increased is less than 0.15, the effect is small. At 0.15 or more, a uniform structure was obtained, so the area reduction ratio was made 0.15 or more. Further, the area reduction ratio per operation in the forging in the direction where the thickness is decreased should be 0.3 or more.
  • the restriction on the thickness of the steel ingot at the start is eased to 500 mm or more. Further, after forging, the ingot is hot rolled by a reduction ratio of 1.5 or more, then treated by solution heat treatment. This point is the same as with the method explained above.
  • the steels shown in Table 1 and Table 4 were cast into ingots, forged by reduction ratios of 1.5, 2.0, and 2.5, then hot rolled by reduction ratios of 1.4 to 3.7 to produce thick-gauge plates of thicknesses of 100 to 250 mm.
  • the production conditions and production results of the steel shown in Table 1 are shown in Table 2 and Table 3.
  • Table 5 No Content (mass%) ⁇ cal % C Si Mn P S Cr Ni Mo Co Cu N Al Ca Ti C+N Inv.
  • Thick-gauge plates forged and rolled by the production conditions shown in Table 2 were treated by solution heat treatment by the method of heating to 1100°C, then water cooling.
  • test pieces JIS Z 2201 No. 14A test pieces (diameter of 6 mm, reference point distance of 30 mm, total length of 110 mm) were used.
  • test pieces were cut out from near the end in the longitudinal direction of the product plate (location corresponding to 100 to 200 mm from top of steel ingot) at the center in the width direction (location corresponding to center in width direction of steel ingot) at five places: the product surface layer (location 10 mm from surface), location 1/4 of plate thickness from surface layer, location 1/2 of plate thickness from surface layer, location of 3/4 of plate thickness, and back surface layer. Note that the strength was evaluated by a tensile test.
  • Table 2 and Table 3 show the 0.2% yield strength, tensile strength, and elongation for representative invention steels.
  • the elongation is shown by the value in the width direction and length direction of the thick-gauge plate from the cross-sectional location.
  • the 0.2% yield strength, tensile strength, and elongation were lowest at the locations of 1/4 of plate thickness to 3/4 of plate thickness. The surface layer never gave the lowest values.
  • Invention Steel No. 14 was forged, by a forging process before rolling, in the width direction of the steel ingot by an area reduction ratio of 0.25 to increase the thickness from 730 mm to 900 mm, then was forged in the thickness direction by an area reduction ratio of 0.6, then was rolled by a reduction ratio of 1.8 to obtain a product of a thickness of 200 mm.
  • Invention Steel No. 15 was forged, by a forging process before rolling, in the longitudinal direction of the steel ingot, by an area reduction ratio of 0.15 to increase the thickness from 730 mm to 900 mm, then was forged in the thickness direction by an area reduction ratio of 0.6, then was rolled by a reduction ratio of 1.8 to obtain a product of a thickness of 200 mm.
  • Invention Steel No. 16 was forged, by a forging process before rolling, in the width direction of the steel ingot, by an area reduction ratio of 0.25 to increase the thickness from 500 mm to 614 mm, then was forged in the thickness direction by an area reduction ratio of 0.6, then was rolled by a reduction ratio of 1.8 to obtain a product of a thickness of 137 mm.
  • Invention Steel No. 17 was forged, by a forging process before rolling, in the thickness direction of the steel ingot by an area reduction ratio of 0.30 to decrease the thickness from 730 mm to 510 mm, then was forged in the width direction by an area reduction ratio of 0.15 to increase the thickness to 600 mm, then was forged in the thickness direction by an area reduction ratio of 0.30 to decrease the thickness to 358 mm, then was rolled by a reduction ratio of 1.8 to obtain a product of a thickness of 200 mm.
  • Invention Steel No. 18 was forged, by a forging process before rolling, in the width direction of the steel ingot, was forged by an area reduction ratio of 0.25 to increase the thickness from 500 mm to 614 mm, then was forged in the thickness direction by an area reduction ratio of 0.6 to decrease the thickness to 430 mm, then was forged in the width direction by an area reduction ratio of 0.25 to increase the thickness to 471 mm, then was forged in the thickness direction by an area reduction ratio of 0.6 to decrease the thickness to 330 mm, then was rolled by a reduction ratio of 1.8 to obtain a product of a thickness of 184 mm.
  • Comparative Steel No. 12 for comparison of the difference of strength due to differences in the forging area reduction ratio with Example 14, was forged, by a forging process before rolling, in the width direction of the steel ingot by an area reduction ratio of 0.10 to increase the thickness from 730 mm to 832 mm, then was forged in the thickness direction by an area reduction ratio of 0.57 to decrease the thickness to 358 mm, then was rolled by a reduction ratio of 1.8 to obtain a product of a thickness of 200 mm.
  • Comparative Steel No. 13 for comparison of the difference of strength due to differences in the forging area reduction ratio with Example 18, was forged, by a forging process before rolling, in the width direction of the steel ingot by an area reduction ratio of 0.23 to increase the thickness from 500 mm to 631 mm, then was forged in the thickness direction by an area reduction ratio of 0.29 to decrease the thickness to 448 mm, then was rolled in the width direction by an area reduction ratio of 0.13 to increase the thickness to 502 mm, then was forged in the thickness direction by an area reduction ratio of 0.29 to decrease the thickness to 356 mm, then were rolled by a reduction ratio of 1.8 to obtain a product of a thickness of 199 mm.
  • Thick-gauge plate forged and rolled by the above production conditions were treated by solution heat treatment by the method of heating to 1100°C then water cooling.
  • the coarse grain structure partially remained, so even if a high strength could be obtained, a high elongation could not be obtained.
  • the austenitic stainless steel plate of the present invention can be used as a structural material of a superconductive coil for a thermonuclear reactor (ITER) promising as a next generation energy source.
  • ITER thermonuclear reactor
  • the austenitic stainless steel plate of the present invention can be applied for increasing larger superconductive equipment, for structures for LNG (liquefied natural gas), etc. and are expected to greatly contribute to the future energy industry and other various industrial fields.
  • the present invention will have a great industrial and social effect.
  • the present invention has great applicability in industry.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Steel (AREA)
  • Metal Rolling (AREA)

Claims (3)

  1. Austenitisches Edelstahl-Walzstahlblech mit mindestens 100 mm Dicke, dadurch gekennzeichnet, dass es
    in Masse-% enthält:
    höchstens 0,08 % C,
    0,10 % bis 0,22 % N,
    mindestens 0,12 % C+N,
    0,01 % bis 2,0 % Si,
    0,1 % bis 2,0 % Mn,
    15 % bis 27 % Cr,
    8 % bis 20 % Ni,
    höchstens 4 % Mo,
    höchstens 0,1 % Co,
    0,1 % bis 3 % Cu,
    0,001 % bis 0,10 % Al und
    0,0005 % bis 0,01 % Ca,
    optional 0,010 % bis 0,030 % Ti und
    als Rest Eisen und unvermeidliche Verunreinigungen, darunter höchstens 0,003 % S und höchstens 0,040 % P,
    einen Rechenwert der Menge von δ-Ferrit in der Definition durch die folgende (I) Formel (δcal; Vol.-%) von -7 % bis 4 % hat und
    eine Dehnung in Breitenrichtung und Längenrichtung an jeder Stelle in Dickenrichtung von mindestens 30 % hat: δcal Vol . − % = 2 , 9 × Cr + 0 , 3 Si + Mo − 2 , 6 × Ni + 0 , 3 × Mn + 0 , 25 × Cu + 35 × C + 20 × N − 18
    Figure imgb0011
     wobei [Elementabkürzungen] den Gehalt des Elements (Masse-%) bezeichnet und die Dehnung der bei 4K gemessene Wert ist.
  2. Verfahren zur Herstellung von austenitischem Edelstahl-Walzstahlblech mit mindestens 100 mm Dicke nach Anspruch 1, gekennzeichnet durch:
    Schmieden von Stahl mit mindestens 650 mm Dicke mit einem Flächenreduktionsverhältnis von mindestens 0,5,
    Warmwalzen desselben durch ein Reduktionsverhältnis von mindestens 1,5, Behandeln desselben durch Lösungsglühen,
    wobei das Flächenreduktionsverhältnis (A) beim Schmieden wie folgt definiert ist:
    Querschnittfläche des Stahlblocks vor Schmieden (Dicke x Breite): A0
    Querschnittfläche des Stahlblocks nach Schmieden (Dicke x Breite): A1 A = A 0 − A 1 / A 0 ,
    Figure imgb0012
    ferner das Reduktionsverhältnis (R) beim Walzen wie folgt definiert ist:
    Brammendicke vor Walzen: B0
    Brammendicke nach Walzen: B1
    R=B0/B1.
  3. Verfahren zur Herstellung von austenitischem Edelstahl-Walzstahlblech mit mindestens 100 mm Dicke nach Anspruch 1, wobei das Verfahren zur Herstellung von austenitischem Edelstahl-Walzstahlblech mit mindestens 100 mm Dicke gekennzeichnet ist durch:
    mindestens einmaliges abwechselndes Bearbeiten eines Stahlblocks mit mindestens 500 mm Dicke durch Schmieden mit einem Flächenreduktionsverhältnis von mindestens 0,3 in einer Richtung, in der die Dicke abnimmt, und Schmieden mit einem Flächenreduktionsverhältnis von mindestens 0,15 in einer Richtung, in der die Dicke zunimmt,
    Warmwalzen durch ein Reduktionsverhältnis von mindestens 1,5,
    Anwenden von Lösungsglühen,
    wobei das Flächenreduktionsverhältnis (C) beim Schmieden in Abnahme- oder Zunahmerichtung der Dicke wie folgt definiert ist:
    Querschnittfläche des Stahlblocks nach dem n-ten Schmieden (Dicke x Breite): Cn
    Querschnittfläche des Stahlblocks nach dem (n-1)-ten Schmieden (Dicke x Breite): C n − 1 C = C n − 1 − C n / C n − 1 ,
    Figure imgb0013
    ferner das Reduktionsverhältnis (R) beim Walzen wie folgt definiert ist:
    Brammendicke vor Walzen: B0
    Brammendicke nach Walzen: B1
    R=B0/B1.
EP07767966.0A 2006-07-13 2007-06-25 Gewalzte platte aus nichtrostendem austenitstahl mit einer dicke von 100 mm oder mehr und herstellungsverfahren dafür Active EP2042616B1 (de)

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PCT/JP2007/063186 WO2008007572A1 (fr) 2006-07-13 2007-06-25 PLAQUE EN ACIER INOXYDABLE EN AUSTÉNITE ROULÉE AYANT UNE ÉPAISSEUR SUPÉRIEURE OU ÉGALE À 100 mm ET PROCÉDÉ DE PRODUCTION DE CELLE-CI

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