CN104364405A - Ultrahigh-tensile-strength steel plate for welding - Google Patents

Ultrahigh-tensile-strength steel plate for welding Download PDF

Info

Publication number
CN104364405A
CN104364405A CN201380028579.6A CN201380028579A CN104364405A CN 104364405 A CN104364405 A CN 104364405A CN 201380028579 A CN201380028579 A CN 201380028579A CN 104364405 A CN104364405 A CN 104364405A
Authority
CN
China
Prior art keywords
formula
steel
steel plate
less
toughness
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.)
Granted
Application number
CN201380028579.6A
Other languages
Chinese (zh)
Other versions
CN104364405B (en
Inventor
渡部义之
原卓也
藤冈政昭
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.)
Nippon Steel Corp
Original Assignee
Nippon Steel Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Nippon Steel Corp filed Critical Nippon Steel Corp
Publication of CN104364405A publication Critical patent/CN104364405A/en
Application granted granted Critical
Publication of CN104364405B publication Critical patent/CN104364405B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/16—Controlling or regulating processes or operations
    • B22D11/22—Controlling or regulating processes or operations for cooling cast stock or mould
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C21D1/25—Hardening, combined with annealing between 300 degrees Celsius and 600 degrees Celsius, i.e. heat refining ("Vergüten")
    • 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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/50—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for welded joints
    • 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
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • 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
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
    • 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
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • 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
    • C22C38/16—Ferrous alloys, e.g. steel alloys containing 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
    • C22C38/42—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
    • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
    • 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
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • 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
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
    • 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
    • C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
    • 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
    • C21D2211/004—Dispersions; Precipitations

Landscapes

  • 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)
  • Continuous Casting (AREA)
  • Treatment Of Steel In Its Molten State (AREA)

Abstract

This steel plate has a chemical composition that contains, in terms of mass%, 0.015-0.045% C, 1.80-2.20% Mn, 0.40-0.70% Cu, 0.80-1.80% Ni, 0.005-0.015% Nb, 0.05-0.25% Mo, 0.005-0.015% Ti, 0.0004-0.0020% B, 0.0020-0.0060% N, and 0.0015-0.0035% O. In the plate-thickness-direction central part of a thickness-direction cross-section of the steel plate, the number of oxide grains having an equivalent-circle diameter of 2 [mu]m or larger is 20 or less per mm2 and the number of Ti oxide grains having an equivalent-circle diameter of 0.05-0.5 [mu]m is 1.0103-1.0105 per mm2.

Description

Welding super high tensile steel plate
Technical field
The present invention relates to and require the weldability of large welded structures thing purposes of high security, the super high tensile steel plate of the tenacity excellent of welding heat affected zone as marine structure etc.
Background technology
In recent years, the energy demand vigorous with the whole world is echoed mutually, and the exploitation of the oceanic resources such as oil and natural gas enlivens.Meanwhile, due to excavation, the efficient activity of production and harshization etc. of development environment, point to the maximization of marine structure, thickization, high strength are required to steel.And the marine structure that ocean is arranged also requires the high security for destroying, excellent weldability, the toughness of welding heat affected zone are required for steel plate.
Generally speaking, there is steel plate thick, high strength, more disadvantageous tendency in the weldability of steel plate, the toughness of welding heat affected zone.This is because guaranteeing in intensity, the alloying element of the toughness of infringement welding heat affected zone must added in a large number.So-called weldability has wide in range implication, represents hardening and the welding cold crack sensitivity of welding heat affected zone in the narrow sense, how to form P by various carbon equivalent Ceq and welding crack sensibility cMrepresent Deng composition parameter.High alloy composition, these indexs are higher, and hardening and the welding cold crack sensitivity of welding heat affected zone are higher, it is generally acknowledged that weldability is poor.The size of the index of the toughness of welding heat affected zone and these weldabilities may not be completely the same, but it is known for there is high dependency.
As mentioned above, usually, thickization of steel plate and/or high strength contrary with the directivity of the toughness of raising weldability, welding heat affected zone, Composition Design, manufacturing technology that the steel plate characteristic making these contrary is taken into account become problem.
As not damaging weldability, do not need chemical composition to be increased to necessary amount in other words and realize thickization of steel plate and/or the means of high strength with Shangdi, there is processing and heat treatment, i.e. TMCP (Thermo-Mechanical Control Process, thermomechanical Controlling Technology) and add B (boron) quenching and tempering (quenching-temper), this is known to those skilled in the art, even if do not carry out technology here openly.But even if also insufficient by these means, this is also true.
TMCP is the technique controlled the steel manufacturing process entirety reaching heating-rolling-cooling, and when thick material, after rolling, the water-cooling process being also referred to as accelerating cooling or controlled cooling model is effective for high strength.But, cool the physical phenomenon owing to being heat transfer, even if the thickness of slab central part of thick material also cannot obtain sufficient speed of cooling by water-cooled, be difficult to guarantee thick and high strength with low composition.
On the other hand, the B (boron) used in high-strength hardened and tempered steel is by sentencing solid solution condition segregation at original austenite crystal prevention, even the denier of ppm grade, also can significantly improve the hardenability of steel, this is known, is effective for high strength.But this also significantly improves the hardening of welding heat affected zone simultaneously.When requiring the marine structure of extra high security (the high destruction toughness of welding heat affected zone), weld heat input during construction is limited lower, and its hardening improves further.The hardening of welding heat affected zone also has high dependency with the toughness of welding cold crack sensitivity and welding heat affected zone as mentioned above, unconditionally use B (boron) in have problems.In addition, when using the high hardenability of B (boron), its effect just plays after B (boron) exists with solid solution condition, therefore, the composition, the technology controlling and process that control the precipitation of boron compound are integral, when the combination with TMCP, the knowledge existed in modifier treatment cannot direct applied situation.Thus, the technique of being undertaken by modifier treatment, i.e. quenching-temper manufacturing, in heat treated duration and cost, is disadvantageous compared with TMCP.And then in recent years, save from the view point of carrying capacity of environment, energy, it is truth that Micro Alloying and TMCPization constantly become social requirement.
Wherein, as the marine structure steel of crack tip opening displacement CTOD excellent of welded-joint with the thickness of slab equal with the major objective of the present application described later, yield strength, such as, Patent Document 1 discloses the invention that the Cu related to containing the more Cu of more than 0.8% separates out shaped steel.But, when Cu adds separately in a large number, when heating or hot rolling time produce Cu crackle, there is the problem becoming and be difficult to manufacture.
Prior art document
Patent documentation
Patent documentation 1: Japanese Laid-Open 2011-1625 publication
Summary of the invention
The problem solved is wanted in invention
The present invention is in view of above-mentioned truth, and object is that being provided as marine structure etc. requires the weldability of large welded structures thing purposes of high security, the super high tensile steel plate of the tenacity excellent of welding heat affected zone.
Main target has the marine structure steel plate that thickness of slab is 50 ~ 100mm, tensile strength is 600 ~ 700MPa, yield strength is 500 ~ 690MPa, the minimum CTOD value of the crack tip opening displacement of welding heat affected zone is the characteristic of more than 0.25mm, purposes requires crack tip opening displacement CTOD (the Crack-Tip Opening Displacement) characteristic of welded-joint.In addition, in order to ensure the sufficient security for destruction, preferred minimum CTOD value is high.Purposes is not particularly limited, and as the toughness evaluation of welding heat affected zone, compared with Xia Shi impact characteristics, thinks that CTOD characteristic is stricter evaluation assessment, using marine structure steel plate as main target.Therefore, the present invention obviously can apply as welded structure steel plates such as boats and ships, steelframe, bridge, various tanks widely.
For solving the means of problem
In order to solve various problem points, the problem of indication in background technology, to effectively using the method for B (boron) to carry out further investigation, research under TMCP prerequisite, find the best means do not damaged weldability, the toughness of welding heat affected zone is improved.Main point is: the balance optimization that (a) makes the B-N-Ti in order to ensure solid solution B (boron) measure, (b) are in order to relax the indurative extremely low Cization of the welding heat affected zone caused by (solid solution) B, (c) in order to ensure the P of the toughness of intensity and weldability, welding heat affected zone cMoptimization, (d) in order to ensure the Ti deoxygenated without Al of the toughness of welding heat affected zone, (e) in order to suppress changing without the low O (oxygen) when Al of thick oxide compound.These points are not independent phenomenon, but have mutually close relationship, are therefore not easy to realize simultaneously, and the present inventor by system and careful experiment realize first, and complete the present invention.
Main idea of the present invention is as described below.
(1) chemical constitution of the steel plate of the 1st aspect of the present invention is: in mass %, C:0.015% ~ 0.045%, Mn:1.80% ~ 2.20%, Cu:0.40% ~ 0.70%, Ni:0.80% ~ 1.80%, Nb:0.005% ~ 0.015%, Mo:0.05% ~ 0.25%, Ti:0.005% ~ 0.015%, B:0.0004% ~ 0.0020%, N:0.0020% ~ 0.0060%, O:0.0015% ~ 0.0035%, Si:0% ~ 0.40%, below P:0.008%, below S:0.005%, Al:0% ~ 0.004%, Cr:0% ~ 0.30%, V:0% ~ 0.06%, Mg:0% ~ 0.0050%, remainder: iron and impurity, value represented by following formula 1 is more than 2.0, value represented by following formula 2 is more than 0%, FB represented by following formula 3 is more than 0.0003%, welding crack sensibility index represented by following formula 4 and P cMvalue is more than 0.18% and less than 0.23%, and at the thickness of slab central part in cross section, thickness of slab direction, diameter of equivalent circle is the oxide particle of more than 2 μm is 20/mm 2below, and the Ti oxide compound that diameter of equivalent circle is 0.05 ~ 0.5 μm is 1.0 × 10 3~ 1.0 × 10 5individual/mm 2.
[Ni]/[Cu] formula 1
[N]-[Ti]/3.4 formula 2
FB=[B]-0.77 × ([N]-0.29 × ([Ti]-2 × ([O]-0.89 × [Al]))) formula 3
P cM=[C]+[Si]/30+ [Mn]/20+ [Cu]/20+ [Ni]/60+ [Cr]/20+ [Mo]/15+ [V]/10+5 [B] formula 4
Here, [C], [Si], [Mn], [Cu], [Ni], [Cr], [Mo], [V], [Ti], [B], [N], [O], [Al] refer to the content represented with quality % of C, Si, Mn, Cu, Ni, Cr, Mo, V, Ti, B, N, O, Al respectively.
Wherein, in above-mentioned formula 3, when the item of ([O]-0.89 × [Al]) is less than 0, the item of ([O]-0.89 × [Al]) in above-mentioned formula 3 is set to 0 to calculate above-mentioned FB, in addition, in above-mentioned formula 3, when the item of ([Ti]-2 × ([O]-0.89 × [Al])) is less than 0, the item of ([Ti]-2 × ([O]-0.89 × [Al])) in above-mentioned formula 3 is set to 0 to calculate above-mentioned FB, and then, in above-mentioned formula 3, when the item of ([N]-0.29 × ([Ti]-2 × ([O]-0.89 × [Al]))) is less than 0, the item of ([N]-0.29 × ([Ti]-2 × ([O]-0.89 × [Al]))) in above-mentioned formula 3 is set to 0 to calculate above-mentioned FB, and then, when FB≤0, if FB=0.
(2) in the steel plate described in above-mentioned (1), and then the Bp represented by following formula 5 can be more than 0.09% and less than 0.30%.
Bp=(884 × [C] × (1-0.3 × [C] 2)+294) × FB formula 5
(3) in above-mentioned (1) or the steel plate described in (2), and then, in above-mentioned chemical constitution, in mass %, Si can be limited in less than 0.15%.
(4) in the steel plate described in any one in above-mentioned (1) ~ (3), and then, in above-mentioned chemical constitution, in mass %, Mg can be limited in lower than 0.0003%.
(5), in the steel plate according to any one of above-mentioned (1) ~ (4), thickness of slab can be more than 50mm and below 100mm, tensile strength can for more than 500MPa and below 690MPa for more than 600MPa and below 700MPa, yield strength.
Invention effect
According to the present invention, the extra-high tension steel of the tenacity excellent of weldability, welding heat affected zone can be provided at an easy rate, while the maximization of the welded structures such as marine structure, security can be improved further.
Embodiment
The present invention is described in detail below.
To be provided as marine structure etc., the present invention requires that for the purpose of the extra-high tension steel of the weldability of large welded structures thing purposes of high security, the tenacity excellent of welding heat affected zone, the steel plate of the characteristic that thickness of slab is 50 ~ 100mm, tensile strength is 600 ~ 700MPa, yield strength is 500 ~ 690MPa to have, the minimum CTOD value of the crack tip opening displacement of welding heat affected zone is more than 0.25mm is main target.
First, the limited range of the composition of steel of extra-high tension steel of the present invention and reason are described.Here the % recorded refers to quality %.
C：0.015％～0.045％
In the present invention of high hardenability using B, in order to suppress the hardening of the surplus of welding heat affected zone, C needs to suppress lower.But, when C amount is too low, in order to compensation intensity (tensile strength), alloying element amount must be increased, infringement economy.In order to suppress cost of alloy and stably to obtain as yield strength in the thick material as target of the present invention be 500 ~ 560MPa level steel (is the strength grade of steel grade, the scope of actual yield strength) intensity, be limited to more than 0.015% in the present invention.From the view point of economy, its lower limit can be set to 0.018%, 0.020%, 0.023% or 0.025%.In addition, when more than 0.045%, work mutually with B effect, the hardening of welding heat affected zone becomes superfluous, makes the toughness deterioration of welding heat affected zone, therefore, using 0.045% as the upper limit.In order to make the hardening of welding heat affected zone reduce, its upper limit can be set to 0.042%, 0.040%, 0.037% or 0.035%.
Below Si:0% ~ 0.40%
Si inevitably contains in steel, in welding heat affected zone, particularly encourage hard and crisp MA (Martensite-Austenite, martensite-austenite) generation of composition (hereinafter referred to as MA), make the toughness deterioration of welding heat affected zone.Therefore, Si is more low more preferred.C amount be limited in the present invention of lower scope, if contain till 0.40%, then MA growing amount is few, can allow from the viewpoint of the toughness of welding heat affected zone.But, when considering the various welding conditions as welded structure steel, obviously preferably less, its upper limit can be set to less than 0.30%, 0.25%, 0.20%, 0.15% or 0.10%.Do not need the lower limit of regulation Si, its lower limit is 0%.In order to improve the base metal tenacity of steel plate or carry out deoxidation, can Si be contained, as required, its lower limit can be set to 0.01%, 0.02% or 0.03%.
Mn：1.80％～2.20％
Mn is less expensive element, but strength-enhancing effect is large, also less to the detrimentally affect of the toughness of mother metal and welding heat affected zone.Be set in the present invention without the Ti deoxidation of Al, in order to make the toughness of welding heat affected zone improve, in welding heat affected zone with Ti oxide compound etc. for the generation of the Intragranular Acicular Ferrite of core becomes important, but now, Mn also plays an important role.It separates out MnS to Ti oxide compound, forms the thinning area of Mn in its vicinity, increases with matrix phase than transformation temperature, encourage and promote ferrite transformation.Consider the toughness and then cost of alloy etc. of the intensity of mother metal, toughness, welding heat affected zone, in the present invention, Mn is limited to more than 1.80%.For this lower limit, there is no metallurgical upper, technical critical meaning, embodying in the scope of the present invention as the excellent specific property of object, limit in order to the feature of clear and definite composition.In order to improve characteristic, its lower limit can be set to 1.85% or 1.90%.Mn is also cheap element, ites is desirable to do one's utmost to use Mn.But when Mn amount is too much, the center segregation of growth encourage continuous casting plate blank and microsegregation, form the embrittlement region of local thus the possibility of the toughness of infringement mother metal or welding heat affected zone increases, and therefore, is limited in less than 2.20%.In order to improve the toughness of mother metal or welding heat affected zone, its upper limit can be set to 2.15% or 2.10%.
Below P:0.008%, below S:0.005%
P, S contain as inevitable impurity, and from base metal tenacity, HAZ toughness, both all a small amount of situations are better, but, also there is the restriction in industrial production, respectively using 0.008%, 0.005% as the upper limit.In order to obtain better HAZ toughness, respectively the upper limit of P can be set to 0.006%, 0.005% or 0.004%, the upper limit of S is set to 0.004%, 0.003% or 0.002%.P, S are inevitable impurity, do not need the lower limit of regulation P, S.If necessary, also the lower limit of P, S can be set to 0%.
Cu：0.40％～0.70％
Cu makes the intensity of mother metal improve, and on the other hand, the degradation of the toughness of mother metal and welding heat affected zone is less, is therefore useful element.In the extra-high tension steel of the present invention as target, preferably add more than 0.40%.In order to improve the intensity of mother metal, its lower limit can be set to 0.45%, 0.50% or 0.55%.When Cu is more than 0.70%, demonstrate precipitation-hardening phenomenon, the material of steel, particularly intensity significantly change discontinuously.Therefore, in the present invention, as the scope that Strength Changes easily controls continuously, be limited to less than 0.70%.By Cu amount is limited to less than 0.7%, measures with Ni described later and mutually work, the effect that the danger that Cu crackle when having hot rolling occurs almost disappears.As required, its upper limit can be set to 0.65%, 0.60% or 0.55%.
Ni：0.80％～1.80％
[Ni]/[Cu] > 2.0 formula 1
Ni is known as high malleableize element, and the deterioration of the toughness of welding heat affected zone is few, have make mother metal intensity, toughness improve effect.Therefore, Ni is exceedingly useful element in the such extra-high tension steel of the present invention.Particularly in the chemical composition of the such pole low-carbon (LC) of the present invention, need to utilize alloying element compensation intensity, at least need the Ni containing more than 0.80%.In order to improve the toughness of welding heat affected zone, its lower limit can be set to 0.90%, 1.00%, 1.05% or 1.10%.On the other hand, Ni is also the alloy of high price, and content is preferably limited to the irreducible minimum that can obtain the necessary characteristic such as intensity, toughness.When considering as the intensity of target of the present invention and maximum thickness of slab (100mm), maximum demand is 1.80%, is set to the upper limit, but, obviously not the upper limit of characteristic or metallurgical aspect.As required, can by its ceiling restriction 1.75%, 1.70%, 1.65%, 1.60%, 1.55% or 1.50%.In addition, as mentioned above, in the steel of the present invention containing slightly many Cu, in order to suppress the Cu crackle of strand, it is effective that Ni contains more than 2.0 times of Cu amount, in claim 1, is defined as [Ni]/[Cu] > 2.0.
Nb：0.005％～0.015％
Austenite non-recrystallization temperature province in rolling process is expanded to high-temperature area, is enjoying useful element in the miniaturization effective controlled rolling effect to tissue by Nb.The miniaturization of tissue be make intensity, effective means that toughness all improves.Reliably enjoy this effect in, need at least containing 0.005%.As required, its lower limit can be set to 0.006%, 0.007% or 0.008%.The Nb manifesting such effect exceedingly useful to mother metal also makes hardening increase in welding heat affected zone, encourages MA and generates, be harmful to its toughness.Therefore, the upper limit must be suppressed 0.015%.In order to improve the toughness of welding heat affected zone, also its upper limit can be set to 0.013%, 0.011% or 0.010%.
Mo：0.05％～0.25％
Mo is extremely effective from the viewpoint of the intensity improving mother metal, is indispensable element in the thick high tensile steel plate that the present invention is such.Particularly in the present invention using B, by simultaneously containing both, show further hardenability and improve effect.In order to enjoy the effect of the excellence of such Mo, at least need containing 0.05%.Improving effect to reliably play this hardenability, its lower limit can be set to 0.07%, 0.09%, 0.11% or 0.13%.But because effect is large, thus too much interpolation makes hardening significantly improve, also significantly encourage MA and generate, therefore, need to be limited in less than 0.25%.In order to suppress MA to generate, also its upper limit can be set to 0.23%, 0.21%, 0.19% or 0.17%.
Ti：0.005％～0.015％
[N]-[Ti]/3.4 >=0% formula 2
The present invention is the Ti deoxidized steel without Al.In order to the necessity in the deoxidation of steel, and in order to make Ti oxide compound generate, in welding heat affected zone with it for core makes Intragranular Acicular Ferrite generate, make microstructure miniaturization, at least need containing Ti:0.005%.In order to improve the toughness of welding heat affected zone, also its lower limit can be set to 0.006% or 0.007%.But content increases, when stoichiometry becomes surplus relative to N, the Ti of the surplus after nitride is formed generates TiC, and the possibility of the toughness deterioration of welding heat affected zone is increased, therefore using 0.015% as the upper limit.In addition, meanwhile, from the view point of doing one's utmost to prevent TiC from generating, in claim 1, as the stoichiometric relation with N, [N]-[Ti]/3.4 >=0% representing N surplus (Ti is not enough) are defined as.In addition, accurately, the consumption of the Ti that deoxidation causes also should be considered, but, avoid numerous and diverse, experimentally confirm there is no in fact large impact simultaneously.In order to formula 2 is set to more than 0%, also the upper limit of Ti can be set to 0.013%, 0.012%, 0.011% or 0.010%.
B：0.0004％～0.0020％
FB=[B]-0.77 × ([N]-0.29 × ([Ti]-2 × ([O]-0.89 × [Al]))) >=0.0003% formula 3
B is one of important element in the present invention.The hardenability of B improves effect greatly, by using B, significantly can suppress alloying element.The content of B for this reason at least needs 0.0004%.As required, also its lower limit can be set to 0.0005%, 0.0006% or 0.0007%.But, be insufficient by means of only regulation B content.This is because in order to use the hardenability of B, need to make it exist with solid solution condition.B easily forms nitride, also becomes important with the stoichiometric balance of N.But, because the nitride Forming ability of Ti is higher than B, therefore also this point is considered, in claim 1, FB=[B]-0.77 × ([N]-0.29 × ([Ti]-2 × ([O]-0.89 × [Al]))) >=0.0003% is defined as.About the upper limit, even if containing more than requirement, effect is also saturated, and therefore, contriver, as not producing the characteristic of steel in the scope confirmed through experimentally of dysgenic scope, is set to 0.0020%, but, critical meaning may not be had.As required, also its upper limit can be set to 0.0018%, 0.0016%, 0.0015% or 0.0014%.
In order to ensure in steel with solid solution condition exist B (effective B), find need by above-mentioned formula 3 definition the effective B of expression measure parameter and above-mentioned FB be limited in more than 0.0003%.In order to more effectively use B, also above-mentioned FB can be set to more than 0.0004% or 0.0005%.
The upper limit of FB=[B]-0.77 × ([N]-0.29 × ([Ti]-2 × ([O]-0.89 × [Al]))) is not particularly limited, but, naturally limit by the limited range of each element.
Wherein, in above-mentioned formula 3, when the item of ([O]-0.89 × [Al]) is less than 0, the item of ([O]-0.89 × [Al]) in above-mentioned formula 3 is set to 0 to calculate above-mentioned FB.
In addition, in above-mentioned formula 3, when the item of ([Ti]-2 × ([O]-0.89 × [Al])) is less than 0, the item of ([Ti]-2 × ([O]-0.89 × [Al])) in above-mentioned formula 3 is set to 0 to calculate above-mentioned FB.
And then, in above-mentioned formula 3, when the item of ([N]-0.29 × ([Ti]-2 × ([O]-0.89 × [Al]))) is less than 0, the item of ([N]-0.29 × ([Ti]-2 × ([O]-0.89 × [Al]))) in above-mentioned formula 3 is set to 0 to calculate above-mentioned FB.
And then, when FB≤0, if FB=0.
In addition, above-mentioned formula 3 asks the solid solution B in the steel obtained to measure (effective B amount by stoichiometric ratio on the basis of the intensity considering the bonding force between each element; FB) formula.Although do not need the upper limit specifying above-mentioned FB especially, also can 0.0010% be set to.
Find after further research, as the parameter that the HAZ hardness avoiding being caused by B rises, preferably the B parameter Bp of definition in formula 5 is set to 0.09% ~ 0.30%.
Bp=(884 × [C] × (1-0.3 × [C] 2)+294) × FB formula 5
In addition, Bp is the empirical formula that the parsing in being tested by the molten steel in a large amount of laboratories is derived, and has carried out parametrization by (maximum hardness by the anticipation of C amount) × (contribution of FB).FB is more, and HAZ hardness more easily increases, and particularly has large impact to this CTOD characteristic.When Bp is more than 0.30%, sometimes there is significant hardness in welding penetration line (FL) portion and rise, finding the target value in order to meet CTOD characteristic and more than 0.25mm, being preferably limited to less than 0.30%.As required, also the upper limit of Bp can be set to 0.27% or 0.25%.In the welding steel that embodiment relates to, when FB is more than 0.0003%, Bp must be more than 0.09%, therefore, Bp is the region of the effect of the solid solution B of the target that cannot obtain as welding steel of the present embodiment lower than 0.09%, thus, also Bp can be set to more than 0.09%.As required, also the lower limit of Bp can be set to 0.12% or 0.15%.
N：0.0020％～0.0060％
N is the element inevitably contained in steel-making, and when being reduced to more than necessary amount, steel-making load is high, not preferred in industrial production.N forms nitride by adding Ti, and this nitride is at high temperature stablized, therefore have the effect of the growth coarsening pinning of the austenite crystal of the welding heat affected zone left a little during heating before the hot rolling of steel or from welding molten thread, thus, preferably containing more than 0.0020%.But time too much, as mentioned above, be combined the possibility forming nitride increase with B, the hardenability that can weaken B improves effect.From absolute magnitude and the stoichiometric relation of above-mentioned B, Ti, the upper limit is restricted naturally, but, in addition, when more than 0.0060%, produce surface spots when steel billet manufactures, therefore, the upper limit is set to 0.0060%.Be preferably less than 0.0055%, be more preferably less than 0.005%.
O：0.0015％～0.0035％
From the generative nature of the Ti oxide compound as Intragranular Acicular Ferrite product nucleus in welding heat affected zone, O is necessary for more than 0.0015%.But when O is too much, the site of oxide compound and number become excessive, the possibility that the generation starting point as brittle rupture works improves, and as a result, makes toughness deterioration, therefore, needs ceiling restriction 0.0035%.In order to obtain the toughness of stable welding heat affected zone more well, being preferably set to less than 0.0030%, being more preferably set to less than 0.0028% or less than 0.0025%.
Al：0％～0.004％
In the present invention of the Ti deoxidation without Al, Al is one of inevitable impurity.In claim 1, although still limiting the upper limit is due to inevitable, when content is more than 0.004%, the composition change of oxide compound, the possibility that cannot work as the core of Intragranular Acicular Ferrite improves, and therefore, is limited to less than 0.004%.As required, also its upper limit can be set to 0.003% or 0.002%.Do not need the lower limit that special stipulation Al measures, its lower limit is 0%.But, in the refining process of steel, be sometimes mixed into Al, also its lower limit can be set to 0.0001% or 0.0003%.
In steel of the present embodiment, except mentioned component, remainder comprises iron (Fe) and impurity.Here, impurity refers to, when industrially manufacturing steel, the composition be inevitably mixed into because of the raw material of ore or waste material etc. or the various factors of manufacturing process, not producing the composition allowed in dysgenic scope to the present invention.
In steel plate of the present embodiment, except mentioned component, also can one kind or two or more further containing in Cr, V, Ca, Mg and REM.The lower limit of these compositions does not need to specify especially, and its lower limit is 0%.In addition, even if these alloying elements add wittingly, or being mixed into the form of impurity, as long as its content is within the scope of the claims, these steel are just interpreted as in right of the present invention.
Cr：0％～0.30％
Cr, in order to reduce the CTOD characteristic of welding heat affected zone, is set to less than 0.30%.In order to improve this CTOD characteristic, also its upper limit can be set to 0.20%, 0.15%, 0.10% or 0.05%.Do not need the lower limit of regulation Cr amount especially, its lower limit is 0%.But, also have situation about being mixed into as impurity, also its lower limit can be set to 0.001%.
V：0％～0.06％
V is the effective element of raising for strength of parent.But during more than 0.06%, infringement CTOD characteristic, therefore, as the scope significantly can not damaging CTOD characteristic, is set to less than 0.06% by the upper limit.In order to ensure more excellent CTOD characteristic, also its upper limit can be set to 0.04%, 0.02% or 0.01%.Do not need the lower limit of the content of regulation V, its lower limit is 0%.Also there is situation about being mixed into as impurity, also its lower limit can be set to 0.001%.
Mg：0％～0.0050％
Mg can contain as required.During containing Mg, generate the fine oxide compound containing Mg, therefore, the miniaturization for γ particle diameter is effective.But when the content of Mg is more than 0.0050%, oxide compound becomes too much, sometimes causes ductility to reduce, therefore, its upper limit is set to 0.0050%.Also can be 0.0030%, 0.0020%, 0.0010% or 0.0003% by its ceiling restriction.Do not need the lower limit of the content of regulation Mg, its lower limit is 0%.
In welding steel of the present embodiment, except mentioned component, in order to improve the intensity, toughness etc. of steel self further, or as the impurity from auxiliary materials such as waste materials, can containing following alloying element.
Ca is mixed into as impurity sometimes, therefore, its upper limit can be set to 0.0010%, 0.0005% or 0.0003%.
REM (Rare Earth Metal) is mixed into as impurity sometimes, therefore, also its upper limit can be set to 0.0010%, 0.0005% or 0.0003%.Here, REM is that 15 kinds of elements of lanthanon add Y and Sc and the general name of the 17 kinds of elements obtained.
Sb damages the toughness of HAZ, therefore, also the upper limit of the content of Sb can be set to 0.03%.In order to make HAZ toughness improve, also the upper limit of the content of Sb can be set to 0.01%, 0.005%, 0.003% or 0.001%.
Because As and Sn damages the toughness of HAZ, therefore, also the upper limit of the content of As and Sn can be set to 0.02%.As required, also the upper limit of the content of As and Sn can be set to 0.005%, 0.003% or 0.001%.In addition, do not need the lower limit of regulation Ca, REM, Sb, As, Sn especially, its lower limit is 0%.
In addition, in order to improve intensity and toughness, also Pb, Zr, Zn and W can be set to less than less than 0.1%, 0.01% or 0.005% respectively.Not needing the lower limit determining them especially, is 0%.
Co contains as impurity sometimes in Ni.Co damages HAZ toughness, therefore, also the upper limit of the content of Co can be set to 0.05% or 0.002%.Do not need to determine its lower limit especially, its lower limit is 0%.
On the basis defining various element as mentioned above, need the P of the following formula 4 by also can be described as overall control further cMbe limited in suitable scope.In addition, following formula 4 is as welding crack sensibility index (P cM) known formula.Even if this is because each element is all limited range, when be all lower limit or the upper limit, hardenability becomes not enough or superfluous, in the former case, high strength cannot be realized when Plate Steel, in the latter case, the hardening of welding heat affected zone, MA generate and become superfluous, cannot guarantee toughness.In order to stably guarantee intensity and stably guarantee the toughness of welding heat affected zone under the thickness of slab of the present invention as target, need P cMbe set to 0.18 ~ 0.23%.
P cM=[C]+[Si]/30+ [Mn]/20+ [Cu]/20+ [Ni]/60+ [Cr]/20+ [Mo]/15+ [V]/10+5 [B] formula 4
Here, each element is quality % contained in steel.
And then, known in order to meet CTOD characteristic, make the number counting the oxide compound of more than 2 μm with diameter of equivalent circle be 20/mm 2below and have 1.0 × 10 as the Ti oxide compound that phase change core counts 0.05 ~ 0.5 μm with diameter of equivalent circle in steel 3~ 1.0 × 10 5individual/mm 2important.Diameter of equivalent circle is that the oxide compound number of more than 2 μm is more than 20/mm 2time, this oxide compound becomes the starting point destroyed and occur, CTOD deterioration in characteristics.In addition, diameter of equivalent circle is that the Ti oxide compound of 0.05 ~ 0.5 μm is lower than 1.0 × 10 3individual/mm 2time, the Ti oxide compound number as the ferritic product nucleus of intracrystalline phase transformation becomes insufficient, more than 1.0 × 10 5individual/mm 2time, Ti oxide compound becomes the starting point destroyed and occur, and in any one situation, CTOD characteristic is all deteriorated.
Limiting on the basis of composition of steel as mentioned above, in order to the high tensile steel plate that stably industrial production is thick, also need to limit manufacture method.
Then, for the manufacture method of welding with extra-high tension steel, an example is described.
Steel of the present invention is industrially preferably by Continuous casting process manufacture.Its reason is, the solidification cooling of molten steel is fast, can generate fine Ti oxide compound and Ti nitride in a large number in slab.In the manufacture method of welding steel of the present embodiment, be preferably set to more than 5 DEG C/min by near zero pour to the average cooling rate of the central part of the strand of 800 DEG C.Its reason is, obtains 20/mm in steel 2following counts the number of the oxide compound of more than 2 μm with diameter of equivalent circle and obtains 1.0 × 10 3~ 1.0 × 10 5individual/mm 2the Ti oxide compound counting 0.05 ~ 0.5 μm with diameter of equivalent circle.When the speed of cooling of strand is lower than 5 DEG C/min, be difficult to obtain fine oxide compound, thick oxide compound increases.On the other hand, even if average cooling rate is more than 50 DEG C/min, the quantity of fine Ti oxide compound also can not significantly increase, and even makes manufacturing cost increase, and therefore, also average cooling rate can be set to less than 50 DEG C/min.
In addition, the average cooling rate of the central part of strand by measuring the speed of cooling of casting billet surface, can be obtained by Calculation of Heat Transfer.In addition, average cooling rate, by measuring casting temp or cooling water inflow etc., is obtained by Calculation of Heat Transfer.
When the rolling of slab, it reheats temperature and is preferably set to 1000 ~ 1100 DEG C.This is because when reheating temperature more than 1100 DEG C, Ti nitride coarsening, the toughness deterioration of mother metal maybe cannot expect that HAZ toughness improves effect.In addition, when lower than 1000 DEG C reheat temperature, rolling reactive force increase, rolling load improve, hinder productivity.
After reheating, need to be manufactured by TMCP.First, the rolling that accumulation draught is more than 30% is carried out at the temperature more than 950 DEG C.Rolling in high-temperature area is in order to by the overall grain refined of thick austenite through heating condition, and accumulation draught is more high more preferred, but, be subject to slab thickness and subsequent rolling condition restricts.In fact the rolling structure of the condition of high temperature cannot be held, but, confirm in the factory and laboratory experiment of the present inventor, when accumulation draught is more than 30%, as long as rolling-cooling conditions is after this in suitable scope, then stability of characteristics.
Then, at the temperature of 720 ~ 950 DEG C, accumulation draught is more than 40%, and accumulation total reduction is more than 60%, at the temperature of 700 ~ 750 DEG C, terminate rolling.These temperature provinces are probably austenitic non-recrystallization temperature province.But when thick material, have temperature distribution in thickness of slab direction, the temperature near thickness of slab central part is high, therefore, the rolling of non-recrystallization temperature province is insufficient sometimes.Therefore, the present invention's limiting temperature, accumulation draught in two stages.The austenite non-recrystallization amount of rolling that the minimum of accumulation draught to be the rolling of more than 40% be from table back surface layer to roughly thickness of slab 1/4 needs at the temperature of 720 ~ 950 DEG C.And then accumulation total reduction being set to more than 60%, terminating rolling at the temperature of 700 ~ 750 DEG C is in order to also can carry out organizing the degree of miniaturization to give pressure in austenite non-recrystallization region at thickness of slab central part.Although the draught of thickness of slab central part relatively in austenite non-recrystallization region is less, but, work mutually with the suitable pressure under the lower Heating temperature limited in the present invention, high-temperature area, can so that good intensity can be guaranteed, the degree of tough sexual balance will organize miniaturization.Under the rolling condition departing from these limited ranges, confirm the degraded toughness of thickness of slab central part especially experimentally.
And then the cooling after rolling needs to start water-cooled within 80 seconds after the end of rolling, and is cooled to less than 280 DEG C.Water-cooled is started rapidly after preferred rolling, but, in large-scale actual production equipment, need time of delivery to be to a certain degree inevitable from milling train end to cooling apparatus.Under these circumstances, the period ferrite of letting cool to cooling after rolling is separated out, and this is preferred in intensity, and due to the precipitation in letting cool, the thick possibility of this ferrite is high, and this is also not preferred in toughness.Therefore, need to start water-cooled within 80 seconds after the end of rolling.Be preferably within 60 seconds.Even if water-cooled needs to be cooled to till the thickness of slab central part becoming heat transfer speed limit also terminates phase transformation completely, therefore, need to be cooled to less than 280 DEG C.In addition, even if in order to also enjoy accelerating cooling effect in the present invention as the thickness of slab central part of the thick material of target, preferably with roughly 1.2m 3/ m 2/ point more than water yield density cool.
After cooling, tempering must be carried out further in the temperature range of 400 ~ 550 DEG C.By carrying out temper, the intensity of mother metal, tough sexual balance can not only be improved, can also stably control accurately.And then also can relax unhomogeneity during cooling, the elimination for the residual stress in steel is also effective, and the change in shape during cut-out caused by them is also inhibited.Lower than tempering at 400 DEG C when, these effects are little, and when the tempering more than 550 DEG C, intensity reduces large, is difficult to guarantee the high strength of the present invention as target.
In addition, above-mentioned temperature is all steel surface temperature.
As mentioned above, weldability, after the steel billet or strand with the composition of steel recorded in above-mentioned (1) are such as heated to the temperature of 1000 ~ 1100 DEG C by the manufacture method of the welding extra-high tension steel of the tenacity excellent of welding heat affected zone, accumulation draught at temperature more than 950 DEG C is set to more than 30%, accumulation draught at the temperature of 720 ~ 950 DEG C is set to more than 40%, accumulation total reduction is set to more than 60%, rolling is terminated at the temperature of 700 ~ 750 DEG C, water-cooled is started after the end of rolling within 80 seconds, be cooled to less than 280 DEG C, then, tempering under the temperature range of 400 ~ 550 DEG C further.
Embodiment
Below, based on example and comparative example, the present invention will be described.
Manufactured the Plate Steel of various composition of steel by converter, continuous casting, slab operation, have rated the toughness of mother metal characteristic and welding heat affected zone.
Welding is set to: by submerged arc welding (submerged arcwelding) method that uses usually used as test welding, to become the multilayer welding that vertical mode is 4.5kJ/mm at " レ " type groove place weld heat input according to welding penetration line (FL).About the toughness evaluation of welding heat affected zone, the CTOD carried out according to API (American Petroleum Institute) standard RP 2Z and BS (BritishStandards) standard 7448 tests.Gap position is being called as the welding molten thread place of CGHAZ (Coarse grainHAZ), implements 6 tests at test temperature-10 DEG C respectively.
The chemical composition of steel shown in table 1-1 ~ table 1-4, shows the toughness (CTOD characteristic) of oxide compound number in manufacturing condition, steel shown in 2-1 ~ table 2-4 and mother metal characteristic, welding heat affected zone.Steel plate (the steel of the present invention: composition of steel No.1 ~ 15 manufactured in the present invention, 29 ~ 51 and the present invention example No.A1 ~ L2) in, yield strength (YS) is shown as 526 ~ 611Mpa in the position of steel plate 1/4 thickness, 516 ~ 594Mpa is shown as in the position of steel plate 1/2 thickness, tensile strength (TS) is shown as 616 ~ 680Mpa in the position of steel plate 1/4 thickness, 604 ~ 656Mpa is shown as in the position of steel plate 1/2 thickness, fracture transition (vTrs) test-results about base metal tenacity is shown as-48 ~-81 DEG C in the position of steel plate 1/4 thickness,-40 ~-68 DEG C are shown as in the position of steel plate 1/2 thickness, the minimum CTOD value of-10 DEG C is shown as the good destruction toughness of 0.29 ~ 0.94mm.In addition, from the P of steel of the present invention cMvalue, CTOD value show good weldability.
In contrast, depart from the comparative example of limited range of the present invention steel plate (comparative steel: composition of steel No.16 ~ 28,52 ~ 62 and comparative example No.a ~ x) strength of parent low, or base metal tenacity is poor, or the poor toughness of welding heat affected zone.
That is, the composition of steel of comparative example a ~ c, comparative example e ~ o, comparative example q ~ v is outside the scope of the invention, is not the steel meeting above-mentioned mechanical properties.Particularly the comparative example f of composition of steel No.21 does not meet Ni/Cu > 2.0, therefore, cracks when hot rolling, manufactures and becomes difficulty.And then, composition of steel within the scope of the present invention, FB or P cMvalue comparative example d, w, x outside the scope of the invention do not meet FB>=0.0003% or P cMvalue is more than 0.18% and less than 0.23%, and therefore, strength of parent is low or high, or base metal tenacity is poor, or the poor toughness of welding heat affected zone.
Table 1-2
Table 1-4
Table 2-1
Table 2-2
Table 2-3
Table 2-4
Utilizability in industry
According to the present invention, the extra-high tension steel of the tenacity excellent of weldability, welding heat affected zone can be provided at an easy rate, while the maximization of the welded structures such as marine structure, security can be improved further.

Claims (5)

1. a steel plate, is characterized in that, its chemical constitution is: in mass %,
C：0.015％～0.045％、
Mn：1.80％～2.20％、
Cu：0.40％～0.70％、
Ni：0.80％～1.80％、
Nb：0.005％～0.015％、
Mo：0.05％～0.25％、
Ti：0.005％～0.015％、
B：0.0004％～0.0020％、
N：0.0020％～0.0060％、
O：0.0015％～0.0035％、
Si：0％～0.40％、
Below P:0.008%,
Below S:0.005%,
Al：0％～0.004％、
Cr：0％～0.30％、
V：0％～0.06％、
Mg：0％～0.0050％、
Remainder: iron and impurity,
Value represented by following formula 1 more than 2.0,
Value represented by following formula 2 is more than 0%,
FB represented by following formula 3 is more than 0.0003%,
Welding crack sensibility index represented by following formula 4 and P cMvalue is more than 0.18% and less than 0.23%,
At the thickness of slab central part in cross section, thickness of slab direction, diameter of equivalent circle is the oxide particle of more than 2 μm is 20/mm 2below, and the Ti oxide compound that diameter of equivalent circle is 0.05 ~ 0.5 μm is 1.0 × 10 3~ 1.0 × 10 5individual/mm 2,
[Ni]/[Cu] formula 1
[N]-[Ti]/3.4 formula 2
FB=[B]-0.77 × ([N]-0.29 × ([Ti]-2 × ([O]-0.89 × [Al]))) formula 3
P cM=[C]+[Si]/30+ [Mn]/20+ [Cu]/20+ [Ni]/60+ [Cr]/20+ [Mo]/15+ [V]/10+5 [B] formula 4
Here, [C], [Si], [Mn], [Cu], [Ni], [Cr], [Mo], [V], [Ti], [B], [N], [O], [Al] refer to the content represented with quality % of C, Si, Mn, Cu, Ni, Cr, Mo, V, Ti, B, N, O, Al respectively
Wherein, in described formula 3, when the item of ([O]-0.89 × [Al]) is less than 0, the item of ([O]-0.89 × [Al]) in described formula 3 is set to 0 to calculate described FB,
In addition, in described formula 3, when the item of ([Ti]-2 × ([O]-0.89 × [Al])) is less than 0, the item of ([Ti]-2 × ([O]-0.89 × [Al])) in described formula 3 is set to 0 to calculate described FB
And then, in described formula 3, when the item of ([N]-0.29 × ([Ti]-2 × ([O]-0.89 × [Al]))) is less than 0, the item of ([N]-0.29 × ([Ti]-2 × ([O]-0.89 × [Al]))) in described formula 3 is set to 0 to calculate described FB, and then, when FB≤0, if FB=0.
2. steel plate according to claim 1, is characterized in that, and then the Bp represented by following formula 5 is more than 0.09% and less than 0.30%,
Bp=(884 × [C] × (1-0.3 × [C] 2)+294) × FB formula 5.
3. steel plate according to claim 1 and 2, is characterized in that, and then in described chemical constitution, in mass %, Si is limited in less than 0.15%.
4. the steel plate according to any one of claims 1 to 3, is characterized in that, and then in described chemical constitution, in mass %, Mg is limited in lower than 0.0003%.
5. the steel plate according to any one of Claims 1 to 4, is characterized in that, thickness of slab is more than 50mm and below 100mm, and tensile strength is more than 600MPa and below 700MPa, and yield strength is more than 500MPa and below 690MPa.
CN201380028579.6A 2013-06-13 2013-06-13 Welding super high tensile steel plate Active CN104364405B (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/JP2013/066349 WO2014199488A1 (en) 2013-06-13 2013-06-13 Ultrahigh-tensile-strength steel plate for welding

Publications (2)

Publication Number Publication Date
CN104364405A true CN104364405A (en) 2015-02-18
CN104364405B CN104364405B (en) 2016-12-07

Family

ID=50614404

Family Applications (1)

Application Number Title Priority Date Filing Date
CN201380028579.6A Active CN104364405B (en) 2013-06-13 2013-06-13 Welding super high tensile steel plate

Country Status (5)

Country Link
EP (1) EP2843073B1 (en)
JP (1) JP5445723B1 (en)
KR (1) KR101679498B1 (en)
CN (1) CN104364405B (en)
WO (1) WO2014199488A1 (en)

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP6672620B2 (en) * 2015-06-29 2020-03-25 日本製鉄株式会社 Stainless steel for oil well and stainless steel tube for oil well
JP6665658B2 (en) * 2016-04-21 2020-03-13 日本製鉄株式会社 High strength steel plate
EP3447162B1 (en) * 2016-04-21 2020-12-30 Nippon Steel Corporation Thick steel plate
JP6753204B2 (en) * 2016-08-09 2020-09-09 日本製鉄株式会社 Steel plate and steel plate manufacturing method
JP6753203B2 (en) * 2016-08-09 2020-09-09 日本製鉄株式会社 Steel plate and manufacturing method of the steel plate
KR102045641B1 (en) * 2017-12-22 2019-11-15 주식회사 포스코 High strength steel for arctic environment having excellent resistance to fracture in low temperature, and method for manufacturing the same
KR102357082B1 (en) 2019-12-20 2022-02-03 주식회사 포스코 High strength steel sheet having excellent heat affected zone toughness and method for manufacturing the same

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101165202A (en) * 2006-10-19 2008-04-23 鞍钢股份有限公司 High-strength steel with high toughness of welding heat affected zone and manufacturing method thereof
WO2013077022A1 (en) * 2011-11-25 2013-05-30 新日鐵住金株式会社 Steel material for welding

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP4066897B2 (en) * 2002-07-17 2008-03-26 住友金属工業株式会社 Steel for construction used after thickening
JP4660250B2 (en) * 2004-04-07 2011-03-30 新日本製鐵株式会社 Thick high-strength steel sheet with excellent low-temperature toughness in the heat affected zone by high heat input welding
JP4311740B2 (en) * 2004-10-27 2009-08-12 株式会社神戸製鋼所 Thick steel plate with high heat input welded joint toughness
JP4901262B2 (en) * 2006-03-29 2012-03-21 新日本製鐵株式会社 Thick steel plate with excellent toughness of heat affected zone
JP5233867B2 (en) 2009-06-22 2013-07-10 新日鐵住金株式会社 High strength steel and offshore structures with excellent corrosion resistance and weld toughness
JP5741378B2 (en) * 2011-10-28 2015-07-01 新日鐵住金株式会社 High tensile steel plate with excellent toughness and method for producing the same
JP5741379B2 (en) * 2011-10-28 2015-07-01 新日鐵住金株式会社 High tensile steel plate with excellent toughness and method for producing the same

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101165202A (en) * 2006-10-19 2008-04-23 鞍钢股份有限公司 High-strength steel with high toughness of welding heat affected zone and manufacturing method thereof
WO2013077022A1 (en) * 2011-11-25 2013-05-30 新日鐵住金株式会社 Steel material for welding

Also Published As

Publication number Publication date
JPWO2014199488A1 (en) 2017-02-23
KR20150020181A (en) 2015-02-25
CN104364405B (en) 2016-12-07
JP5445723B1 (en) 2014-03-19
WO2014199488A1 (en) 2014-12-18
KR101679498B1 (en) 2016-11-24
EP2843073B1 (en) 2017-08-02
EP2843073A4 (en) 2016-01-06
EP2843073A1 (en) 2015-03-04

Similar Documents

Publication Publication Date Title
CN105463324B (en) A kind of thick-specification high-tenacity pipe line steel and its manufacture method
JP5924058B2 (en) High tensile strength steel sheet with excellent low temperature toughness of weld heat affected zone and method for producing the same
CN101289728B (en) Low-yield ratio, high heat input welding, high-strength and high ductility steel plate and method of manufacture
CN104364405B (en) Welding super high tensile steel plate
KR20140117560A (en) High tensile steel plate having excellent low-temperature toughness in weld heat-affected zones, and method for producing same
EP2385149B1 (en) Steel material for welding and method for producing same
KR101142185B1 (en) Steel being excellent in ctod characteristic in welding heat affected zone and a method of producing the same
CN103952643A (en) Low-yield ratio steel plate with yield strength of 690MPa and preparation method of steel plate
KR20150029758A (en) Thick-walled, high tensile strength steel with excellent ctod characteristics of the weld heat-affected zone, and manufacturing method thereof
JP4705696B2 (en) Steel for welding and method for manufacturing the same
JP2010202931A (en) High-strength thick steel plate for structure excellent in brittle crack propagation arrest property, and method for producing the same
CN102732797B (en) 800MPa grade low welding crack sensitivity steel plate and its manufacturing method
JP6245352B2 (en) High-tensile steel plate and manufacturing method thereof
CN105750760B (en) Steel material for welding
CN106086650B (en) It is a kind of can Large Heat Input Welding polar region ship plate and preparation method thereof
CN103998636B (en) Steel material for welding
JP5708349B2 (en) Steel with excellent weld heat affected zone toughness
JP2009132995A (en) High strength thick steel plate for structural use having excellent brittle crack propagation arrest property, and method for producing the same
JP5949113B2 (en) Structural high-strength thick steel plate with excellent brittle crack propagation stopping characteristics and method for producing the same
JP2013129885A (en) Method of producing high-strength thick steel plate excellent in brittle crack propagation arrest property
CN102747284A (en) High-strength high-tenacity steel for ship structure
JP5949114B2 (en) Manufacturing method of structural high strength thick steel plate with excellent brittle crack propagation stopping characteristics
JP5811044B2 (en) Thick high-strength steel sheet excellent in weldability and weld heat-affected zone toughness and method for producing the same
CN115976408A (en) Low-alloy corrosion-resistant anti-seismic reinforcing steel bar and production method thereof
CN107699792A (en) A kind of low temperature resistant micro alloyed steel and production technology

Legal Events

Date Code Title Description
C06 Publication
PB01 Publication
C10 Entry into substantive examination
SE01 Entry into force of request for substantive examination
C14 Grant of patent or utility model
GR01 Patent grant
CP01 Change in the name or title of a patent holder
CP01 Change in the name or title of a patent holder

Address after: Tokyo, Japan

Patentee after: Nippon Iron & Steel Corporation

Address before: Tokyo, Japan

Patentee before: Nippon Steel Corporation