CN114672733B - 690 MPa-grade steel plate capable of being welded under high heat input and production method thereof - Google Patents

690 MPa-grade steel plate capable of being welded under high heat input and production method thereof Download PDF

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CN114672733B
CN114672733B CN202210329144.6A CN202210329144A CN114672733B CN 114672733 B CN114672733 B CN 114672733B CN 202210329144 A CN202210329144 A CN 202210329144A CN 114672733 B CN114672733 B CN 114672733B
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steel plate
equal
heat input
high heat
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CN114672733A (en
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麻晗
杨浩
武凤娟
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Jiangsu Shagang Steel Co ltd
Jiangsu Shagang Group Co Ltd
Jiangsu Shagang Iron and Steel Research Institute Co Ltd
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Jiangsu Shagang Group Co Ltd
Zhangjiagang Hongchang Steel Plate Co Ltd
Jiangsu Shagang Iron and Steel Research Institute Co Ltd
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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
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/0006—Adding metallic additives
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/06—Deoxidising, e.g. killing
    • 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
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0242—Flattening; Dressing; Flexing
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    • 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
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/04—Making ferrous alloys by melting
    • C22C33/06—Making ferrous alloys by melting using master alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/002—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
    • C22C38/04—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
    • C22C38/46—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
    • 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
    • C21D2211/002—Bainite
    • 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
    • C21D2211/008—Martensite

Abstract

The invention discloses a 690 MPa-grade steel plate capable of being welded under high heat input and a production method thereof. The steel plate comprises: 0.04 to 0.07 percent of C, 0.15 to 0.2 percent of Si, 1.35 to 1.5 percent of Mn, 0.45 to 0.55 percent of Cr, 1.1 to 1.3 percent of Ni, 0.3 to 0.4 percent of Mo, 0.9 to 1 percent of Cu, 0.04 to 0.06 percent of Nb, 0.01 to 0.04 percent of V, 0.02 to 0.05 percent of Ti, 0.0005 to 0.002 percent of Mg, 0.0005 to 0.002 percent of B, 0.0015 to 0.0035 percent of O, more than or equal to 20 percent of Ti/Mg and less than or equal to 50 percent, and the balance of Fe and impurities, less than or equal to 0.004 percent of Al and less than or equal to 0.005 percent of N. The impact energy of the steel plate at the welding heat affected zone of minus 60 ℃ is more than or equal to 140J under the heat input welding condition of 50-200 kJ/cm.

Description

690 MPa-grade steel plate capable of being welded under high heat input and production method thereof
Technical Field
The invention belongs to the technical field of steel, and relates to a 690 MPa-grade steel plate capable of being welded under high heat input and a production method of the 690 MPa-grade steel plate capable of being welded under high heat input.
Background
In recent years, the large heat input welding technology based on oxide metallurgy is rapidly developed, and the method has a wide application prospect in the fields of ships, maritime works, buildings, containers, bridges, energy sources and the like. The large heat input welding is carried out by electroslag welding, electrogas welding, multi-wire submerged arc welding and other methods, so that the welding efficiency can be greatly improved, the manufacturing cost of the whole process can be reduced, and the structure safety can be improved.
High strength is a permanent theme of steel research and development and application, and in the last decade, 690MPa grade high strength steel is gradually applied in the fields of maritime work, ships, bridges and the like. However, the high-strength steel has high alloy content and high welding difficulty, and under the condition of high heat input welding, the temperature near a welding seam can exceed 1400 ℃, so that austenite grains are obviously grown, and grain boundary ferrite, M/A islands, wei-King structures and the like are formed in the subsequent cooling process, so that the low-temperature toughness of the welded steel is reduced.
Disclosure of Invention
In order to solve the existing problems, the invention aims to provide a 690 MPa-grade steel plate capable of being welded under high heat input and a production method of the 690 MPa-grade steel plate capable of being welded under high heat input, wherein the steel plate has high strength and can ensure excellent low-temperature toughness under the condition of heat input welding.
In order to achieve the above object, one embodiment provides a 690MPa grade steel sheet that can be welded with high heat input, and the steel sheet comprises the following chemical components by mass percent: 0.04 to 0.07 percent of C, 0.15 to 0.20 percent of Si, 1.35 to 1.5 percent of Mn, 0.45 to 0.55 percent of Cr, 1.1 to 1.3 percent of Ni, 0.3 to 0.4 percent of Mo, 0.9 to 1.0 percent of Cu, 0.04 to 0.06 percent of Nb, 0.01 to 0.04 percent of V, 0.02 to 0.05 percent of Ti, 0.0005 to 0.0020 percent of Mg, 0.0005 to 0.0020 percent of B, 0.0015 to 0.0035 percent of O, more than or equal to 20 percent of Ti/Mg and less than or equal to 50 percent of O, and the balance of Fe and inevitable impurities, wherein the partial impurities are less than or equal to 0.008 percent of P, less than or equal to 0.005 percent of S, less than or equal to 0.004 percent of Al and less than or equal to 0.005 percent of N.
Furthermore, the surface density of D-type spherical inclusions with the diameter of 0.2-5 mu m in the steel plate is more than or equal to 10000/mm 2 。
Furthermore, the content of grain boundary M/A islands of the steel plate is less than or equal to 1 percent.
Further, the D-type spherical inclusion is composed of Mg, ti and Al (Mg, al and Ti) x O composite oxide particles, wherein x is 0.8 to 1.5.
Further, the steel plate has-60 ℃ impact energy A of a welding heat affected zone under the heat input welding condition of 50-200 kJ/cm KV2 The average value is more than or equal to 160J, and the single value is more than or equal to 140J.
Furthermore, the thickness of the steel plate is 15-50 mm, and the yield strength is more than or equal to 700MPa.
In order to achieve the above object, an embodiment further provides a method for producing a 690MPa grade steel sheet that can be welded with a high heat input, including the steps of:
preparing a continuous casting slab of the chemical composition of the steel sheet of claim 1 in the order of molten iron pre-desulfurization, converter smelting, LF refining, RH vacuum refining, alloy wire feeding, and continuous casting;
heating the obtained continuous casting billet, and then performing two-stage rolling to prepare a steel plate; wherein the starting temperature of the first-stage rolling is 1050 +/-50 ℃, and the finishing temperature is more than or equal to 960 ℃; the starting temperature of the second stage rolling is 840 +/-20 ℃, and the finishing temperature is 780 +/-20 ℃;
straightening a steel plate at the temperature of above 720 ℃, and then directly carrying out water cooling, wherein the water outlet temperature of the steel plate is less than or equal to 300 ℃;
the steel plate is subjected to tempering heat treatment in a heating furnace after water is discharged, the temperature of the heating furnace is 450-550 ℃, the time in the furnace is (2.5t + 10-30) min, wherein t is the thickness of the steel plate.
Furthermore, the surface density of D-type spherical inclusions with the diameter of 0.2-5 mu m in the obtained continuous casting billet is more than or equal to 10000/mm 2 (ii) a After tempering heat treatment, the content of grain boundary M/A islands of the obtained steel plate is less than or equal to 1 percent.
Preferably, in the step of preparing a continuous casting slab satisfying the chemical composition of the steel plate in the order of hot metal pre-desulfurization, converter smelting, LF refining, RH vacuum refining, alloy wire feeding, and continuous casting, feSi/SiMn → Ni/FeMo/Cu alloy is added in the converter smelting process, feCr → Nb/V → FeTi alloy is added in the LF refining process, feTi → FeB is added in the RH vacuum refining process, and NiMg alloy wire is added in the alloy wire feeding process after RH refining is finished.
Preferably, the length of the water-cooling roller bed is 24m and the speed is 0.6-2.0 m/s during water-cooling.
Further, the steel plate has-60 ℃ impact energy A of a welding heat affected zone under the heat input welding condition of 50-200 kJ/cm KV2 The single value is more than or equal to 145J; the thickness of the steel plate is 15-50 mm, and the yield strength is 740-820 MPa.
Compared with the prior art, the beneficial effects of one embodiment include:
(1) High-density oxide particles with high melting point (namely good thermal stability) are formed by controlling a strong deoxidizer Mg, and austenite crystal grains can be restrained from growing under the high-temperature condition of large heat input welding, brittle tissues in the phase transformation process are reduced, and fine tissues are promoted to be formed in the crystal grains, so that coarsening of the heat affected zone tissues caused by large heat input is reduced, and the problem of welding embrittlement is solved;
(2) The hardenability of the steel plate is improved by adding elements such as Cr, mo and B, so that the content of M/A island in the grain boundary of the steel plate is less than or equal to 1 percent, and the strength and the low-temperature toughness of the steel plate are improved; meanwhile, the comprehensive control of elements such as Cr, mo, B, ni, cu and the like is combined, so that the adverse effect that the low-temperature toughness is reduced in conventional cognition on the elements is avoided under the condition of ensuring the strength improvement of the steel plate;
(3) Through the content control of Cu, the combination of high-temperature water inlet cooling and low-temperature water outlet after high-temperature straightening improves the strength of the steel plate, more importantly, the combination of the cooling mode and subsequent tempering heat treatment can promote the existence of Cu elements in the steel plate in a fine and dispersed form, thereby improving the strength of Cu content improvement, reducing the adverse effect of low-temperature toughness reduction caused by the increase of Cu content, and further ensuring that the strength of the steel plate and the low-temperature toughness under the condition of large heat input welding are improved.
Drawings
FIG. 1 is a metallographic structure diagram of a steel sheet according to example 1 of the present invention;
FIG. 2 is a metallographic structure drawing of a steel sheet according to example 2 of the invention.
Detailed Description
The technical solution of the present invention is further described below with reference to specific embodiments, but the scope of protection claimed is not limited to the description.
The invention provides a 690 MPa-grade steel plate which comprises the following chemical components in percentage by mass: 0.04 to 0.07 percent of C, 0.15 to 0.20 percent of Si, 1.35 to 1.5 percent of Mn, 0.45 to 0.55 percent of Cr, 1.1 to 1.3 percent of Ni, 0.3 to 0.4 percent of Mo, 0.9 to 1.0 percent of Cu, 0.04 to 0.06 percent of Nb, 0.01 to 0.04 percent of V, 0.02 to 0.05 percent of Ti, 0.0005 to 0.0020 percent of Mg, 0.0005 to 0.0020 percent of B, 0.0015 to 0.0035 percent of O, more than or equal to 20 percent of Ti/Mg and less than or equal to 50 percent of O, and the balance of Fe and inevitable impurities, wherein the partial impurities are less than or equal to 0.008 percent of P, less than or equal to 0.005 percent of S, less than or equal to 0.004 percent of Al and less than or equal to 0.005 percent of N.
The chemical elements in the steel sheet will be described in detail below.
C: the steel contains the cheapest strengthening elements and has good solid solution strengthening effect, but the welding performance and low-temperature toughness of the steel plate are greatly damaged by increasing the content of C, and in the embodiment, the content of C is controlled to be 0.04-0.07 percent by mass percent.
Si: ferrite strengthening elements, but the olivine is easily formed on the surface of the steel plate due to the excessively high content of Si element, so that the descaling is difficult, and the surface quality of the steel plate is reduced; in addition, under the high heat input welding conditions, the Si element promotes the formation of large-sized M/a islands to seriously deteriorate the low-temperature toughness of the steel sheet, and in the present embodiment, si is controlled to 0.15 to 0.20% by mass.
Mn: the strength of the steel plate can be effectively improved, but when the content of Mn is too high, mn is easy to segregate in the process of molten steel solidification, the low-temperature toughness of the steel plate is reduced, cracks are easy to occur in a steel plate welding joint, and in the embodiment, mn is controlled to be 1.35-1.5% in percentage by mass.
Cr: the steel sheet can be improved in hardenability and is advantageous for improving the strength of the steel sheet, but is disadvantageous for the low-temperature toughness of the steel sheet, and in the present embodiment, cr is controlled to 0.45 to 0.55% by mass.
Ni: the Ni is an austenite stabilizing element, reduces the transformation temperature from austenite to ferrite, refines the steel plate structure, and can effectively improve the low-temperature toughness of the steel plate and a welding joint, and in the embodiment, the Ni is controlled to be 1.1 to 1.3 percent by mass percent.
Mo: the hardenability of the steel sheet can be effectively improved, which is advantageous for improving the strength of the thick gauge steel sheet, but is disadvantageous for the low temperature toughness of the steel sheet, and in the present embodiment, mo is controlled to 0.3 to 0.4% by mass%.
Cu: although the copper alloy has a function of precipitation strengthening, the low-temperature toughness of large heat input welding deteriorates when the content is too high, and in the present embodiment, cu is controlled to 0.9 to 1.0% by mass.
Nb: the steel sheet has the effects of fine grain strengthening and precipitation strengthening, and is beneficial to improving the strength of the steel sheet, but when the content of Nb is too high, the welded joint is easy to generate large-sized carbon nitride and nitrogen carbide precipitates of NbTi under the condition of high heat input welding, and the low-temperature toughness is reduced, and in the embodiment, the content of Nb is controlled to be 0.04-0.06 percent by mass percent.
V: has the functions of fine grain strengthening and precipitation strengthening, can improve the strength of the steel plate, and in addition, the carbonitride of V is beneficial to ferrite crystal inner nucleation, but the content of V is too high, so that precipitates with larger sizes can be formed, and the low-temperature toughness is reduced, and in the embodiment, the content of V is controlled to be 0.01 to 0.04 percent by weight.
Ti: however, when the content of Ti element is too high, N preferentially bonds to Ti, and therefore the content of BN in the steel is reduced, and when B exists in the form of BN, the low-temperature toughness of the steel sheet is improved, and in the present embodiment, ti is controlled to 0.02 to 0.05% by mass.
Mg: the element is an oxide forming element, and can form fine and dispersed oxide particles in molten steel, and inhibit austenite grains from growing during the heating of the steel plate, thereby improving the low-temperature toughness of the steel plate under the condition of large heat input welding, and in the embodiment, mg is controlled to be 0.0005-0.0020 percent by mass percent.
B: the steel plate is an element with hardenability, and the strength of the steel plate can be effectively improved; in addition, in the large heat input welding process, BN particles existing in the steel easily promote ferrite nucleation in austenite crystal, refine the welded joint structure, and improve the welding performance, in the present embodiment, B is controlled to 0.0005 to 0.0020% by mass.
O: can form fine oxide particles with Mg element, inhibit austenite grain growth and improve the welding performance of the steel plate, but the content of large-size inclusions is increased due to the over-high content of O, which affects the quality of the steel plate, and in the embodiment, the content of O is controlled to be 0.0015 to 0.0035 percent by mass percent.
Al: the reaction of the strong deoxidizer Mg and the molten steel can be interfered, the content of oxide particles is influenced, in the embodiment, al deoxidation is not adopted, namely Al alloy is not added in the steelmaking process, and Al exists in the steel plate as impurity elements and is controlled to be less than or equal to 0.004%.
S, P, N: in the present embodiment, the content of S element is not more than 0.005%, the content of P element is not more than 0.008%, and the content of N element is not more than 0.005%.
Thus, the steel sheet of the present embodiment has a high yield strength of 690MPa or more, for example, a thickness of 15 to 50mm and a yield strength of 700MPa or more; meanwhile, the alloy also has excellent low-temperature toughness under the condition of large heat input welding, in particular, the impact energy A of a welding heat affected zone at minus 60 ℃ under the condition of 50-200 kJ/cm heat input welding KV2 The average value is more than or equal to 160J, and the single value is more than or equal to 140J.
Specifically, the steel sheet of the present embodiment is designed to have the following chemical composition:
(1) High-density oxide particles with high melting point (i.e. good thermal stability) are formed by controlling a strong deoxidizer MgThe surface density of D-type spherical inclusion with the diameter of 0.2-5 mu m is more than or equal to 10000/mm 2 The D-type spherical inclusion with the diameter of 0.2-5 mu m is specifically composed of Mg, ti and Al (Mg, al and Ti) x The value of x of the O composite oxide particles is 0.8-1.5, so that austenite grains can be restrained from growing under the high-temperature condition of large heat input welding, brittle tissues in the phase transformation process are reduced, and fine tissues are promoted to form inside the grains, so that coarsening of heat affected zone tissues caused by large heat input is reduced, and the problem of welding embrittlement is solved;
(2) The hardenability of the steel plate is improved by adding elements such as Cr, mo and B, so that the content of M/A island in the grain boundary of the steel plate is less than or equal to 1 percent, and the strength and the low-temperature toughness of the steel plate are improved; meanwhile, by combining the comprehensive control of elements such as Cr, mo, B, ni, cu and the like, under the condition of ensuring the strength improvement of the steel plate, the adverse effect of the elements on the reduction of low-temperature toughness in the conventional cognition is avoided, for example, the content control of Ni compensates the deterioration of the toughness adverse elements on the low-temperature toughness of the final steel plate, and for example, the content control of Cu enables Cu in the steel plate to exist in a fine and dispersed form, so that the adverse effect degree of Cu on the low-temperature toughness is reduced, and the strength of the final steel plate and the low-temperature toughness under the large heat input welding condition are comprehensively improved;
(3) By finely controlling the elements Ti, B, and V, a sufficient amount of N-carbides (e.g., V-carbonitrides, B-nitrides) are formed and precipitated in the steel, so that ferrite grain nucleation is promoted under the high heat input welding conditions, formation of grain boundary ferrite in the heat affected zone is suppressed, and low temperature toughness of the steel sheet under the high heat input welding conditions is improved.
Further, an embodiment of the present application also provides a preferable production method of the above-mentioned 690MPa grade steel sheet, and of course, the production method of the above-mentioned steel sheet is not limited thereto. The production method provided by the embodiment can further optimize the performance of the steel plate on the basis of the design of the chemical components.
Specifically, the production method comprises the steps of:
preparing a continuous casting billet which meets the chemical components of the steel plate according to the sequence of molten iron pre-desulfurization, converter smelting, LF refining, RH vacuum refining, alloy wire feeding and continuous casting, namely, the chemical components of the obtained continuous casting billet are the same as those of the steel plate; wherein, the thickness of the continuous casting slab is preferably 320mm, but not limited to;
heating the obtained continuous casting billet, and then performing two-stage rolling to prepare a steel plate; wherein the starting temperature of the first-stage rolling is 1050 +/-50 ℃, and the finishing temperature is more than or equal to 960 ℃; the starting temperature of the second stage rolling is 840 +/-20 ℃, and the finishing temperature is 780 +/-20 ℃;
straightening a steel plate at the temperature of above 720 ℃, and then directly carrying out water cooling, wherein the water outlet temperature of the steel plate is less than or equal to 300 ℃;
after the steel plate is watered, tempering heat treatment is carried out in a heating furnace, the temperature of the heating furnace is 450-550 ℃, the time of the furnace is (2.5t + 10-30) min, wherein t is the thickness of the steel plate, for example, the time of the furnace is (2.5 + 20+ 10-30) min, namely 60-80 min, when the thickness of the steel plate is 20 mm.
As described above, in the present embodiment, in addition to the design of the chemical components, the production method includes:
(1) The first stage is rolling in a complete recrystallization region through temperature control in the first stage rolling, more distortion energy is stored in a rolled steel plate, further growth of an austenite structure after recrystallization is avoided, and meanwhile, more deformation structures and dislocation are reserved through temperature control in the second stage rolling, more nucleation points are provided for phase transformation, the structure is refined, and the strength and the low-temperature toughness of the steel plate are improved;
(2) On the other hand, after high-temperature straightening, high-temperature water inlet cooling and low-temperature water outlet are carried out, so that the structure of the steel plate is a bainite + martensite structure, wherein the proportion of the martensite structure is more than or equal to 60%, and bainite is a lath-shaped bainite structure as a main part, the strength of the steel plate is improved, more importantly, the cooling mode is combined with subsequent tempering heat treatment, so that the Cu element in the steel plate can be promoted to exist in a fine and dispersed form, the adverse effect of low-temperature toughness reduction caused by the increase of the Cu content, which is considered traditionally, is reduced while the strength is improved, and the strength of the steel plate and the low-temperature toughness under the condition of high-heat input welding are improved.
Wherein, in the production method of the present embodiment, the surface density of D-type spherical inclusions having a diameter of 0.2 to 5 μm in the obtained continuous casting slab is not less than 10000 inclusions/mm corresponding to the steel sheet structure described above 2 (ii) a After tempering heat treatment, the content of grain boundary M/A islands of the obtained steel plate is less than or equal to 1 percent.
Based on the chemical components, the steel plate obtained by the production method has more excellent strength and low-temperature toughness, and specifically, the impact energy A of a welding heat affected zone at minus 60 ℃ is measured under the condition of 50-200 kJ/cm heat input welding KV2 The single value is more than or equal to 145J; the thickness of the steel plate is 15-50 mm, and the yield strength is 740-820 MPa.
Further, in a preferred embodiment, in the step of "preparing a continuous casting slab satisfying the chemical composition of the above steel sheet in the order of hot metal pre-desulfurization, converter smelting, LF refining, RH vacuum refining, alloy wire feeding, and continuous casting", feSi/SiMn → Ni/FeMo/Cu alloy is added in the converter smelting process, feCr → Nb/V → FeTi alloy is added in the LF refining process, feTi → FeB is added in the RH vacuum refining process, and NiMg alloy wire is added in the alloy wire feeding process after RH refining is finished. Thus, by controlling the adding time of each alloy, particularly adding Mg in an alloy wire feeding mode after RH vacuum refining, high-density high-melting-point oxide particles can be further formed in molten steel and continuous casting billets, the surface density of D-type spherical inclusions with the diameter of 0.2-5 mu m in the continuous casting billets is increased, and the low-temperature toughness of the final steel plate under the condition of high-heat input welding is further ensured.
Preferably, during water cooling, the length of the water cooling roller way is 24m, and the speed is 0.6-2.0 m/s, so as to further optimize the cooling rate and improve the strength and low-temperature toughness of the steel plate.
The following provides 2 preferred embodiments of the present invention to further illustrate the technical solution of the present invention. Of course, these 2 examples are only preferred implementations of the many variations that are encompassed by this embodiment, and not all.
Example 1
The embodiment provides a steel plate, which comprises the following chemical components in percentage by mass: 0.05% of C, 0.15% of Si, 1.5% of Mn, 0.50% of Cr, 1.1% of Ni, 0.3% of Mo, 0.9% of Cu, 0.04% of Nb, 0.02% of V, 0.03% of Ti, 0.0010% of Mg, 0.0010% of B, 0.0025% of O, and the balance of Fe and inevitable impurities, wherein the impurities comprise 0.007% of P, 0.003% of S, 0.003% of Al and 0.003% of N in part.
The production process of the steel plate is as follows:
(1) Preparing a continuous casting billet with the thickness of 320mm according to the sequence of molten iron pre-desulfurization, converter smelting, LF refining, RH vacuum refining, alloy wire feeding and continuous casting;
during the period, the types and the sequence of the added alloys are that FeSi/SiMn → Ni/FeMo/Cu alloy is added in the converter smelting process, feCr → Nb/V → FeTi alloy is added in the LF refining process, feTi → FeB is added in the RH vacuum refining process, and NiMg alloy wire is added in the alloy wire feeding process after RH refining is finished;
the sampling detection proves that the chemical components of the continuous casting billet are as described above, and the surface density of the D-type spherical inclusions with the diameters of 0.2-5 mu m in the continuous casting billet is 12000/mm 2 The D-type spherical inclusion is composed of Mg, ti and Al (Mg, al and Ti) x O composite oxide particles, wherein the value of x is 0.9 to 1.2;
(2) Heating the obtained continuous casting slab at 1200 ℃; then, two-stage rolling is carried out to manufacture a steel plate with the thickness of 15 mm;
wherein the starting temperature 1050 ℃ and the ending temperature 960 ℃ of the first-stage rolling are respectively controlled; the starting temperature and the finishing temperature of the second stage rolling are respectively 840 ℃ and 800 ℃;
(3) After the second-stage rolling is finished, straightening the steel plate at 750 ℃, and then directly carrying out water cooling, wherein the length of a water cooling roller way is 24m, the speed is 2.0m/s, and the water outlet temperature of the steel plate is 250 ℃;
(4) Tempering heat treatment is carried out on the steel plate in a heating furnace after water is discharged, the temperature of the heating furnace is 500 ℃, and the furnace time is 50min;
the steel plate of this example was subjected to structural and performance tests to obtain: the steel plate has a structure of 83% of martensite and 17% of lath bainite, has a yield strength of 820MPa, and has a welding heat affected zone with-60 ℃ impact under the condition of 60kJ/cm heat input weldingWork A KV2 221J, 189J and 199J, and the content of grain boundary M/A island is 0.5%.
Example 2
The embodiment provides a steel plate, which comprises the following chemical components in percentage by mass: 0.06% of C, 0.15% of Si, 1.45% of Mn, 0.50% of Cr, 1.2% of Ni, 0.3% of Mo, 0.9% of Cu, 0.05% of Nb, 0.03% of V, 0.04% of Ti, 0.0020% of Mg, 0.0015% of B, 0.0030% of O, and the balance of Fe and inevitable impurities, wherein the impurities comprise 0.006% of P, 0.003% of S, 0.003% of Al and 0.003% of N.
The production process of the steel plate is as follows:
(1) Preparing a continuous casting billet with the thickness of 320mm according to the sequence of molten iron pre-desulfurization, converter smelting, LF refining, RH vacuum refining, alloy wire feeding and continuous casting;
during the period, the types and the sequence of the added alloys are that FeSi/SiMn → Ni/FeMo/Cu alloy is added in the converter smelting process, feCr → Nb/V → FeTi alloy is added in the LF refining process, feTi → FeB is added in the RH vacuum refining process, and NiMg alloy wire is added in the alloy wire feeding process after RH refining is finished;
through sampling detection, the chemical components of the continuous casting billet are as described above, and the surface density of the D-type spherical inclusion with the diameter of 0.2-5 mu m in the continuous casting billet is 20000 pieces/mm 2 The D-type spherical inclusion is composed of Mg, ti and Al (Mg, al and Ti) x O composite oxide particles, wherein the value of x is 0.8 to 1.3;
(2) Heating the obtained continuous casting slab at 1200 ℃; then, two-stage rolling is carried out to manufacture a steel plate with the thickness of 50 mm;
wherein, the starting temperature 1050 ℃ and the ending temperature 970 ℃ of the first-stage rolling are respectively controlled; the starting temperature of the second stage rolling is 820 ℃, and the finishing temperature is 780 ℃;
(3) After the second-stage rolling is finished, straightening the steel plate at 740 ℃, and then directly carrying out water cooling, wherein the length of a water cooling roller way is 24m, the speed is 0.6m/s, and the water outlet temperature of the steel plate is 250 ℃;
(4) Tempering heat treatment is carried out on the steel plate in a heating furnace after water is discharged, the temperature of the heating furnace is 500 ℃, and the furnace time is 150min;
the steel plate of this example was subjected to structural and performance tests to obtain: the steel plate has a structure of 68% of martensite, 29% of lath bainite and 3% of granular bainite, has a yield strength of 740MPa, and has a welding heat affected zone with an impact energy A of-60 ℃ under the heat input welding condition of 200kJ/cm KV2 160J, 175J and 145J, and the content of grain boundary M/A island is 0.8%.
The detailed description set forth above is merely a detailed description of possible embodiments of the invention and is not intended to limit the scope of the invention, which is intended to include within the scope of the invention all equivalent embodiments or modifications that do not depart from the technical spirit of the invention.

Claims (11)

1. A690 MPa-grade steel plate capable of being welded at high heat input is characterized by comprising the following chemical components in percentage by mass: 0.04 to 0.07 percent of C, 0.15 to 0.20 percent of Si, 1.35 to 1.5 percent of Mn, 0.45 to 0.55 percent of Cr, 1.1 to 1.3 percent of Ni, 0.3 to 0.4 percent of Mo, 0.9 to 1.0 percent of Cu, 0.04 to 0.06 percent of Nb, 0.01 to 0.04 percent of V, 0.02 to 0.05 percent of Ti, 0.0005 to 0.0020 percent of Mg, 0.0005 to 0.0020 percent of B, 0.0015 to 0.0035 percent of O, less than or equal to 20 and less than or equal to 50 percent of Ti/Mg, and the balance of Fe and inevitable impurities, wherein part of impurities are less than or equal to 0.008 percent of P, less than or equal to 0.005 percent of S, less than or equal to 0.004 percent of Al, and less than or equal to 0.005 percent of N.
2. 690 MPa-grade steel plate capable of being welded under high heat input according to claim 1, wherein the areal density of D-shaped spherical inclusions with the diameters of 0.2 to 5 μm in the steel plate is more than or equal to 10000/mm 2 。
3. The 690MPa grade steel sheet capable of high heat input welding according to claim 1, wherein the steel sheet has a grain boundary M/A island content of 1% or less.
4. 690MPa grade steel sheet weldable with high heat input according to claim 2, wherein the D-type spherical inclusions are (Mg, al, ti) consisting of Mg, ti, al x O composite oxide particles, wherein the value of x is 0.8 to 1.5.
5. According to claim1, the 690 MPa-grade steel plate capable of being welded under high heat input is characterized in that the impact energy A of a welding heat affected zone at minus 60 ℃ is obtained under the heat input welding condition of 50 to 200kJ/cm KV2 The average value is more than or equal to 160J, and the single value is more than or equal to 140J.
6. The 690 MPa-grade steel plate capable of being welded under high heat input according to claim 1, wherein the thickness of the steel plate is 15-50mm, and the yield strength is more than or equal to 700MPa.
7. A production method of a 690 MPa-grade steel plate capable of being welded at high heat input is characterized by comprising the following steps of:
preparing a continuous casting slab of the chemical composition of the steel sheet of claim 1 in the order of molten iron pre-desulfurization, converter smelting, LF refining, RH vacuum refining, alloy wire feeding, and continuous casting;
heating the obtained continuous casting billet, and then performing two-stage rolling to prepare a steel plate; wherein the starting temperature of the first-stage rolling is 1050 +/-50 ℃, and the finishing temperature is more than or equal to 960 ℃; the starting temperature of the second stage rolling is 840 +/-20 ℃, and the finishing temperature is 780 +/-20 ℃;
straightening a steel plate at the temperature of above 720 ℃, and then directly carrying out water cooling, wherein the water outlet temperature of the steel plate is less than or equal to 300 ℃;
and (3) tempering and heat-treating the steel plate in a heating furnace after the steel plate is drained, wherein the temperature of the heating furnace is 450 to 550 ℃, the time in the furnace is (2.5t +10 to 30) min, and t is the thickness of the steel plate.
8. The production method of 690 MPa-grade steel plate capable of being welded at high heat input according to claim 7, wherein the surface density of D-type spherical inclusions with the diameters of 0.2-5 μm in the obtained continuous casting billet is more than or equal to 10000 inclusions/mm 2 (ii) a After tempering heat treatment, the content of grain boundary M/A islands of the obtained steel plate is less than or equal to 1 percent.
9. The method for producing a 690 MPa-grade steel sheet weldable with high heat input according to claim 7, wherein in the step of preparing a continuous casting slab satisfying the chemical composition of the steel sheet in the order of hot metal pre-desulfurization, converter smelting, LF refining, RH vacuum refining, alloy wire feeding and continuous casting, ni/FeMo/Cu → FeSi/SiMn alloy is added in the converter smelting process, feCr → Nb/V → FeTi alloy is added in the LF refining process, feTi → FeB is added in the RH vacuum refining process, and NiMg alloy wire is added in the alloy wire feeding process after the RH refining is finished.
10. The production method of 690 MPa-grade steel plate capable of being welded at high heat input according to claim 7, wherein the length of the water-cooling roller way is 24m and the speed is 0.6-2.0 m/s during water-cooling.
11. The production method of 690 MPa-grade steel plate capable of being welded at high heat input according to claim 7, wherein the steel plate has-60 ℃ impact energy A in a welding heat affected zone under the heat input welding condition of 50 to 200kJ/cm KV2 The single value is more than or equal to 145J; the thickness of the steel plate is 15 to 50mm, and the yield strength is 740 to 820MPa.
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