EP1031636B1 - Heavy wall steel material having superior weldability and method for producing the same - Google Patents

Heavy wall steel material having superior weldability and method for producing the same Download PDF

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Publication number
EP1031636B1
EP1031636B1 EP00301481A EP00301481A EP1031636B1 EP 1031636 B1 EP1031636 B1 EP 1031636B1 EP 00301481 A EP00301481 A EP 00301481A EP 00301481 A EP00301481 A EP 00301481A EP 1031636 B1 EP1031636 B1 EP 1031636B1
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EP
European Patent Office
Prior art keywords
steel material
less
heavy wall
wall steel
diameter
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP00301481A
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German (de)
English (en)
French (fr)
Other versions
EP1031636A3 (en
EP1031636A2 (en
Inventor
Hiroshi Nakajima
Shiro Torizuka
Kaneaki Tsuzaki
Kotobu Nagai
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Mitsubishi Heavy Industries Ltd
National Research Institute for Metals
Original Assignee
Mitsubishi Heavy Industries Ltd
National Research Institute for Metals
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Filing date
Publication date
Application filed by Mitsubishi Heavy Industries Ltd, National Research Institute for Metals filed Critical Mitsubishi Heavy Industries Ltd
Publication of EP1031636A2 publication Critical patent/EP1031636A2/en
Publication of EP1031636A3 publication Critical patent/EP1031636A3/en
Application granted granted Critical
Publication of EP1031636B1 publication Critical patent/EP1031636B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • 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
    • C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/10—Alloys containing non-metals
    • C22C1/1094—Alloys containing non-metals comprising an after-treatment
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C32/00—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ
    • C22C32/001—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with only oxides
    • C22C32/0015—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with only oxides with only single oxides as main non-metallic constituents
    • C22C32/0026—Matrix based on Ni, Co, Cr or alloys thereof
    • 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
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy

Definitions

  • the invention of the present application relates to a heavy wall steel material having superior weldability and to a method for producing the same.
  • the invention of the present application relates to a highly tough high strength heavy wall steel material having superior weldability and to a method for producing the same.
  • JP-A 09 003 590 discloses an oxide dispersion strengthened steel sheet in which Ta-base or Nb-base oxides having 0.002 to 3 ⁇ m average grain size are dispersed with a density of 0.01 to 10/ ⁇ m 2 .
  • an object of the invention according to the present application is to provide the novel type of heavy wall steel material above, having increased strength and toughness and still improved in weldability.
  • Another object of the present invention is to provide a method for producing the same.
  • a heavy wall steel material having superior weldability which is a steel material having in a plane making a right angle with respect to the rolling direction a diameter or a short side 5 mm or more in length and which comprises oxides 1 ⁇ m or less in grain diameter homogeneously dispersed at a dispersion density in a range of from 10,000 to 100,000 particles/mm 2 and uniform ferrite grains 2 ⁇ m or less in grain diameter formed over the entire plane making a right angle with respect to the rolling direction (Claim 1).
  • a method for producing a heavy wall steel material having superior weldability which comprises allowing oxide crystals 1 ⁇ m or less in grain diameter to form in the texture and uniformly dispersing them at a dispersion density of from 10,000 to 100,000 particles/mm 2 , rolling the resulting steel material through a hole profile in the temperature range of 400 °C or higher but not higher than the Ac3 transformation point, and subjecting it to a recrystallization treatment to form uniform ferrite grains 2 ⁇ m or less in grain diameter over the plane making a right angle with respect to the rolling direction, thereby obtaining a heavy wall steel material having superior weldability and having a diameter or a short side 5 mm or more in length in a plane making a right angle with respect to the rolling direction (Claim 2).
  • the method for producing a heavy wall steel material having superior weldability comprises undercooling a molten steel by placing it inside an oxide slag, thereby allowing oxide crystals 1 ⁇ m or less in grain diameter to form in the texture and uniformly dispersing them at a dispersion density of from 10,000 to 100,000 particles/mm 2 (Claim 3), and wherein the molten steel contains:
  • the heavy wall steel material according to the application of the present invention is a steel material which is characterized by its heavy wall and its plane making a right angle with respect to the rolling direction, said plane having a diameter or a short side 5 mm or more in length and comprising ferrite grains 2 ⁇ m or less in diameter uniformly dispersed over the entire plane, and characterized by being produced by hot rolling using a series of profile molds and recrystallization treatment.
  • This material is available in various forms, such as a rod, a wire, a profile, etc.
  • the heavy wall steel material having superior weldability according to the invention of the present application comprises oxides 1 ⁇ m or less in grain diameter homogeneously dispersed at a dispersion density in a range of from 10,000 to 100,000 grains/mm 2 .
  • These oxides 1 ⁇ m or less in grain diameter increase the internal strain which generates during rolling of the material, and thereby divide the recrystallized ferrite grains into finer grains 2 ⁇ m or less in grain diameter.
  • the strength and the toughness of the heavy wall steel material can be further increased.
  • a heavy wall steel material having a tensile strength of 660 MPa or higher can be realized.
  • the grain diameter of the oxides is confined to 1 ⁇ m or less by taking the strength and the toughness of the heavy wall steel material into account. If the grain diameter of the oxides should exceed 1 ⁇ m, on the other hand, the strength and the toughness of the heavy wall steel material suffer unfavorable influences.
  • the oxides 1 ⁇ m or less in grain diameter are uniformly dispersed in the texture at a dispersion density in a range of from 10,000 to 100,000 particles/mm 2 , the oxides dispersed in the heat affected zone (HAZ) during welding function as nuclei to accelerate the generation of ferrites, and prevent the coarsening of crystal grains from occurring.
  • the generation of coarse acicular Widmanstatten ferrites can be suppressed to improve the toughness at the HAZ.
  • the heavy wall steel material having superior weldability according to the invention of the present application exhibits a further improved strength and toughness as compared with the conventional products, and yet, has excellent weldability.
  • Such superior characteristics are enabled by uniformly dispersing the oxides at a predetermined grain diameter and at a particular dispersion density and by the ferrite grains of predetermined grain diameter formed over the entire plane making a right angle with respect to the rolling direction, but not by the conventionally employed means, i.e., the addition of a particular alloying element such as nickel (Ni).
  • the heavy wall steel material having superior weldability according to the invention of the present application can be produced in the following manner.
  • the process comprises allowing oxide crystals 1 ⁇ m or less in grain diameter to form in the texture and uniformly dispersing them at a dispersion density of from 10,000 to 100,000 particles/mm 2 , rolling the resulting steel material through a hole profile in the temperature range of 400 °C or higher but not higher than the Ac3 transformation point, and subjecting it to a recrystallization treatment to form uniform ferrite grains 2 ⁇ m or less in grain diameter over the plane making a right angle with respect to the rolling direction.
  • a heavy wall steal material having superior weldability and having a diameter or a side 5 mm or more in length can be obtained.
  • Profile rolling using a hole mold is effective for the formation of fine textures in the material, because the steel material can be processed from multiple directions, i.e., the material can be processed multiaxially, such as in the case of grooved roll processing. At the same time, the process steps for producing fine textures can be simplified.
  • the process temperature for profile rolling is in a range of 400 °C or higher but not higher than the Ac3 transformation point. If the temperature should be lower than 400 °C, the texture turns into a simple ferrite texture elongated along a single direction and would not form an isometric texture. This results in a strength showing anisotropy. If the temperature exceeds the Ac3 transformation point, on the other hand, the rate of grain growth becomes too high as to coarsen the texture, and this impairs the strength and the toughness of the material.
  • Uniform ferrite grains 2 ⁇ m or less in grain diameter are available over the entire plane making a right angle with respect to the rolling direction by performing the profile rolling and the recrystallization treatment subsequent thereto.
  • oxide crystals 1 ⁇ m or less in grain diameter are formed in the texture and are uniformly dispersed at a dispersion density of from 10,000 to 100,000 particles/mm 2 prior to the sequential profile rolling and recrystallization treatment.
  • This can be realized by various ways, and preferably exemplified among them is the method using undercooling.
  • undercooling is effected by placing the molten steel inside slag of oxides.
  • Undercooling is a state in which the melt is held at a temperature not higher than the melting point.
  • the maximum degree of undercooling is one-fifth of the melting point.
  • the solidification rate of the molten steel to be undercoolod is not only higher than that of rapid solidification, but also a rate non-achievable by rapid solidification.
  • the increase in particle diameter of the oxide can also be suppressed.
  • the generation of further finer oxides is promoted, and these oxides can bo dispersed at a higher density.
  • the dispersion density of the resulting oxides attain twice or more of that achieved in rapid solidification.
  • the undercooling above can be realized, more specifically, by covering the molten steel with the slag, or by flowing the molten steel into the slag.
  • the content of the components is confined in the range above based on the fact as follows.
  • C carbon
  • carbides such as cementite accounts for 20 % by volume or more of the material
  • toughness there occurs a drop in toughness. Accordingly, it is preferred that C is incorporated in the material at a quantity as such that the carbide accounts for 20 % by volume or less in the material.
  • the content of silicon (Si) is present at an amount exceeding 0.8 % by weight, the steel becomes extremely brittle.
  • manganese (Mn) should be present at an amount of 0.05 % by weight or more.
  • Mn manganese
  • the content of Mn is preferably in a range of from 0.05 to 3.0 % by weight.
  • An element which produces oxides i.e., titanium (Ti), magnesium (Mg), or aluminum (Al) is incorporated at a concentration of 0.3 % by weight or less, which corresponds to an amount for the case it is present as oxide grains 1 ⁇ m or less in diameter dispersed in the texture at a dispersion density of 100,000 grains/mm 2 .
  • the molten steel may contain other alloying elements which impart other characteristics to the steel material.
  • their addition must be made by taking into consideration that it may not impair the particle diameter and the dispersion density, or the roll processability.
  • a molten steel containing Ti as the oxide generating element was covered with a slag containing a plurality of oxides, and was undercooled by a degrees of 90 K to suppress the generation of nuclei from the surface of molten steel.
  • Ti oxide which is one of the secondary deoxidized products, was dispersed as particles 1 ⁇ m or less in diameter and at a dispersion density of 50,000 grains/mm 2 or higher.
  • the heavy wall steel material having excellent weldability according to the present invention and the method for producing the same is described in further detail below by making reference to examples.
  • a steel having the chemical composition given in Table 1 below was buried in a mixed oxide powder or granules comprising SiO 2 , Al 2 O 3 , and Na 2 O, and was molten in an induction furnace or by resistance heating under a non-oxidizing atmosphere.
  • the resulting molten steel was covered with a slag of glassy mixed oxides, and was heated to a temperature 50 K or higher than the liquidus temperature.
  • the molten steel was allowed to stand still until the primary deoxidized products were adsorbed by the slag.
  • Chemical composition (% by weight) C Sl Mn P S Ti 0.15 0.19 1.51 0.019 0.02 0.08
  • the molten steel allowed to stand still was undercooled, and the solidification thereof was initiated at a temperature 60 K lower than the solidus temperature to prepare a cast specimen 40 mm in diameter and 60 mm in length.
  • the cast specimen was reheated to 1,200 °C, and was processed into a 30 ⁇ 30 ⁇ 85 mm specimen by forging.
  • the forged specimen was recrystallized by water-cooling, followed by holding it in the furnace at a temperature of 640 °C for a duration of 300 seconds. Subsequently, the specimen was subjected to grooved rolling at a draught of about 10 % per single pass to perform hole profile rolling. The specimen was subjected to repeated hole profile rolling and the subsequent recrystallization treatment until a total area reduction of 90 % was achieved, and was then water-cooled.
  • FIG. 1 is a micrograph obtained with a scanning electron microscopy showing the texture of the steel rod material thus obtained in Example 1.
  • the micrograph of FIG. 1 shows the image of the C-cross section, i.e., the cross section vertical to the rolling direction.
  • the white colored portion shows the oxides
  • the black colored portion shows the texture of mixed ferrite and carbide.
  • the oxides are the Ti-Mn-Si complex oxides, and are dispersed at a density of 54,000 particles/mm 2 . From FIG . 1, it is confirmed that the texture of mixed ferrite and carbide has an average diameter of 0.75 ⁇ m, and that it is uniformly distributed from the surface layer to the center of the specimen.
  • the rod material thus obtained was subjected to the measurement of tensile strength (TS), lower yield strength (LYS), uniform elongation (U.EL), and the total elongation (T.EL).
  • TS tensile strength
  • LYS lower yield strength
  • U.EL uniform elongation
  • T.EL total elongation
  • Example 1 Comparative Ex. 1 Dispersion density of oxides (particles/mm 2 ) 54,000 Several hundreds Diameter of oxides ( ⁇ m) ⁇ 1 ⁇ 5 Draught (%) 90 90 Ferrite grain diameter ( ⁇ m) 0.75 0.79 TS (MPa) 775 724 LYS (MPa) 754 685 U.EL (%) 3.58 7.30 T. EL (%) 13.44 14.10
  • Example 1 yields a tensile strength (TS) and a lower yield strength (LYS) of 700 MPa or higher, showing that the strength is higher than that of the steel rod material of Comparative Example 1, which contains less oxides dispersed therein. Furthermore, the steel rod material according to Example 1 yields a uniform elongation (U. EL) and a total elongation (T. EL) both at a value of 10 % or higher, and is therefore confirmed that this material exhibits sufficiently high toughness.
  • TS tensile strength
  • LES lower yield strength
  • Example 1 The steel rod materials of Example 1 and Comparative Example 1 were compared with each other for their weldability.
  • the rod materials were each heated to 1,400 °C at a heating rate of 100 K/s, and were then cooled therefrom to 900 °C at a cooling rate of 50 K/s, followed by further cooling to 300 °C at a cooling rate of 10 K/s, to thereby reproduce the heat affected zone (HAZ) which form at welding.
  • HAZ heat affected zone
  • the invention according to the present application provides a heavy wall steel material in various shapes such as a rod, a wire, a profile, etc., comprising fine oxides uniformly dispersed at a high density and thereby having superior strength as well as toughness, and furthermore improved in weldability.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Heat Treatment Of Steel (AREA)
  • Superconductors And Manufacturing Methods Therefor (AREA)
EP00301481A 1999-02-25 2000-02-24 Heavy wall steel material having superior weldability and method for producing the same Expired - Lifetime EP1031636B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP04896299A JP3538613B2 (ja) 1999-02-25 1999-02-25 溶接性に優れた鋼製厚肉材料とその製造方法
JP4896299 1999-02-25

Publications (3)

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EP1031636A2 EP1031636A2 (en) 2000-08-30
EP1031636A3 EP1031636A3 (en) 2002-04-03
EP1031636B1 true EP1031636B1 (en) 2004-10-13

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US (5) US20020026969A1 (ko)
EP (1) EP1031636B1 (ko)
JP (1) JP3538613B2 (ko)
KR (1) KR100628795B1 (ko)
CN (1) CN1144884C (ko)
AT (1) ATE279543T1 (ko)
DE (1) DE60014726T2 (ko)

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JP3944579B2 (ja) * 2003-05-20 2007-07-11 独立行政法人物質・材料研究機構 角型及びオーバルの孔型ロールを用いた多パス温間制御圧延方法
JP4714828B2 (ja) * 2004-08-06 2011-06-29 独立行政法人物質・材料研究機構 温間制御圧延により大ひずみが導入された金属線材、およびその製造方法と製造装置
DE102008053676B4 (de) * 2008-10-29 2013-03-28 Ab Skf Wasserstoffbeständiges Stahlbauteil
IT1399625B1 (it) * 2010-04-19 2013-04-26 Archimede Solar Energy Srl Perfezionamenti nei collettori solari tubolari.
JP2011246804A (ja) * 2010-04-30 2011-12-08 Nippon Steel Corp 電子ビーム溶接継手及び電子ビーム溶接用鋼材とその製造方法
JP5606985B2 (ja) * 2011-04-08 2014-10-15 株式会社神戸製鋼所 耐水素脆化感受性に優れた溶接金属
CN102628141A (zh) * 2012-05-09 2012-08-08 武汉钢铁(集团)公司 一种抗拉强度500MPa级低成本高延性冷弯成型用钢及其制造方法
CN109665714B (zh) * 2019-02-28 2021-06-29 成都光明光电股份有限公司 光学玻璃、玻璃预制件、光学元件及光学仪器

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JPH05185273A (ja) * 1992-01-13 1993-07-27 Tanaka Kikinzoku Kogyo Kk 酸化物分散強化白金及び白金合金の接合構造
JP3852118B2 (ja) * 1994-04-15 2006-11-29 住友金属工業株式会社 溶接熱影響部靱性の優れた鋼材
JPH093590A (ja) * 1995-06-21 1997-01-07 Nippon Steel Corp 酸化物分散強化フェライト系耐熱鋼板及びその製造方法
JP3464567B2 (ja) * 1995-06-23 2003-11-10 新日本製鐵株式会社 溶接熱影響部靱性の優れた溶接構造用鋼材
US5743972A (en) * 1995-08-29 1998-04-28 Kawasaki Steel Corporation Heavy-wall structural steel and method
KR100340640B1 (ko) * 1997-12-16 2002-07-18 이구택 고강도내열스테인레스강의서버머지드아크용접용플럭스
JP4171779B2 (ja) * 1998-03-04 2008-10-29 独立行政法人物質・材料研究機構 酸化物分散鋼の製造方法
EP1068915A4 (en) * 1998-03-26 2004-12-01 Jp Nat Res Inst For Metals HIGH-STRENGTH METAL-BASED SOLIDIFIED MATERIAL, ACID STEEL AND METHODS OF MANUFACTURE THEREOF
JP2000080445A (ja) * 1998-09-02 2000-03-21 Natl Res Inst For Metals 酸化物分散鋼とその製造方法

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Publication number Publication date
US20110083775A1 (en) 2011-04-14
US20030145917A1 (en) 2003-08-07
US20070119527A1 (en) 2007-05-31
KR100628795B1 (ko) 2006-09-27
CN1297063A (zh) 2001-05-30
DE60014726T2 (de) 2006-03-09
KR20000058123A (ko) 2000-09-25
US20020026969A1 (en) 2002-03-07
CN1144884C (zh) 2004-04-07
US20050178482A1 (en) 2005-08-18
EP1031636A3 (en) 2002-04-03
DE60014726D1 (de) 2004-11-18
ATE279543T1 (de) 2004-10-15
JP2000239781A (ja) 2000-09-05
JP3538613B2 (ja) 2004-06-14
EP1031636A2 (en) 2000-08-30

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