CN114990305B - Method for producing Q890D ultra-high strength steel medium plate through on-line quenching - Google Patents

Method for producing Q890D ultra-high strength steel medium plate through on-line quenching Download PDF

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CN114990305B
CN114990305B CN202210571671.8A CN202210571671A CN114990305B CN 114990305 B CN114990305 B CN 114990305B CN 202210571671 A CN202210571671 A CN 202210571671A CN 114990305 B CN114990305 B CN 114990305B
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rolling
strength steel
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ultra
high strength
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CN114990305A (en
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武卫阳
路士平
王根矶
田鹏
王志勇
魏运飞
王凯凯
韩承良
于文飞
王东柱
马国金
狄国标
霍常浩
沈开照
张光磊
冯韦
王坤
杜群超
杨子江
慕文杰
冯博
齐岩
师大兴
于海波
孙博
郑文明
辛士伟
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Shougang Jingtang United Iron and Steel Co Ltd
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Shougang Jingtang United Iron and Steel Co Ltd
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    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D8/00Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226Hot rolling
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D1/00General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18Hardening; Quenching with or without subsequent tempering
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D8/00Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0263Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/02Ferrous alloys, e.g. steel alloys containing silicon
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    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/04Ferrous alloys, e.g. steel alloys containing manganese
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/06Ferrous alloys, e.g. steel alloys containing aluminium
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/46Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/48Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/50Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/54Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D2211/00Microstructure comprising significant phases
    • C21D2211/002Bainite
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D2211/00Microstructure comprising significant phases
    • C21D2211/008Martensite

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Abstract

The application relates to the field of super-strength steel preparation, in particular to a method for producing a Q890D super-strength steel medium plate by on-line quenching; the method comprises the following steps: obtaining a casting blank after continuous casting; heating and rough rolling the casting blank before rolling to obtain an intermediate blank; performing finish rolling, online quenching cooling and heat treatment on the intermediate billet to obtain the Q890D ultra-high strength steel with medium thickness; wherein, the heat treatment comprises tempering treatment and heat preservation treatment, the end temperature of the tempering treatment is 600 ℃ to 620 ℃, the heat preservation treatment is carried out at the end temperature of the tempering treatment, and the time of the heat preservation treatment is 60min to 70min; the reduction of the last 3 passes of rough rolling is more than or equal to 36mm; the rolling is carried out through the reduction of large pass in the rough rolling stage, then the online cooling is carried out, finally the heat treatment is carried out, and the heat preservation treatment is combined, so that the structure can be effectively adjusted, the carbide is separated out, the microstructure of the steel plate is converted into a dual-phase structure containing lath martensite and granular bainite, and the effective preparation of the ultra-high strength steel with the thickness of 60-70 mm is ensured.

Description

Method for producing Q890D ultra-high strength steel medium plate through on-line quenching
Technical Field
The application relates to the field of super-strength steel preparation, in particular to a method for producing a Q890D super-strength steel medium plate by on-line quenching.
Background
The ultra-high strength steel is a product with saved resources, high technical content and high added value, and with the great development of large-scale engineering, the ultra-high strength steel with the brand of Q890D and above is widely applied to engineering machinery, mining, hoisting car, ocean platform and the like, and the ultra-high strength steel with the brand of Q890D has the characteristics that: the structure is simple, the dead weight is light, the safety is high, the large dynamic and static loads can be borne, and the service time is long; at present, regarding production of medium-thickness steel plates of Q890D ultra-high strength steel, a quenching and tempering mode including (off-line quenching and tempering) is mostly adopted, and an on-line quenching process is adopted for Q890D ultra-high strength steel with a thickness of less than 50mm, but on Q890D ultra-high strength steel with a thickness specification of more than 50mm, only the ultra-high strength steel obtained by adopting the on-line quenching mode is adopted, so that the requirements of manufacturing industries such as engineering machinery, mining machinery and the like cannot be met.
Therefore, how to provide a preparation method of Q890D ultra-high strength steel with the thickness specification of more than 50mm is a technical problem which needs to be solved at present.
Disclosure of Invention
The application provides a method for producing a Q890D ultra-high strength steel medium plate through on-line quenching, which aims to solve the technical problem that the prior art specification is difficult to effectively prepare the medium-thickness Q890D ultra-high strength steel with the specification of more than 50 mm.
In a first aspect, the present application provides a method for producing a Q890D ultra-high strength steel medium plate by on-line quenching, the method comprising:
obtaining a casting blank after continuous casting;
heating and rough rolling the casting blank before rolling to obtain an intermediate blank;
performing finish rolling, online quenching cooling and heat treatment on the intermediate billet to obtain Q890D ultra-high strength steel with medium thickness;
the heat treatment comprises tempering treatment and heat preservation treatment, wherein the end temperature of the tempering treatment is 600-620 ℃, the heat preservation treatment is carried out at the end temperature of the tempering treatment, and the time of the heat preservation treatment is 60-70 min;
the reduction of the last 3 passes of rough rolling is more than or equal to 36mm;
the thickness of the Q890D ultra-high strength steel is 60-70 mm.
Optionally, the chemical components of the Q890D ultra-high strength steel comprise, in terms of mass fraction: 0.14 to 0.17 percent of C, 0.20 to 0.50 percent of Si, 1.00 to 1.50 percent of Mn, less than or equal to 0.015 percent of P, less than or equal to 0.003 percent of S, 0.30 to 0.70 percent of Cr, 0.40 to 0.70 percent of Mo, 0.30 to 0.60 percent of Ni, 0.005 to 0.025 percent of Ti, 0.015 to 0.040 percent of Nb, 0.03 to 0.06 percent of V, 0.001 to 0.0020 percent of B, 0.020 to 0.050 percent of Alt, and the balance of Fe and unavoidable impurities.
Optionally, the CEV of the Q890D ultra-high strength steel is less than or equal to 0.65, and the Pcm of the Q890D ultra-high strength steel is less than or equal to 0.35.
Optionally, the initial temperature of the online cooling is 810-830 ℃, and the redback temperature of the online cooling area is less than or equal to 200 ℃.
Optionally, the on-line cooling speed is 15 ℃/s-30 ℃/s.
Optionally, the end temperature of heating before rolling is 1150-1210 ℃, and the total time of heating before rolling is 260-450 min.
Optionally, the rough rolling comprises a first rough rolling and a second rough rolling, wherein the initial rolling temperature of the first rough rolling is 1050-1150 ℃, the initial rolling temperature of the second rough rolling is 880-900 ℃, and the final rolling temperature of the second rough rolling is 840-870 ℃.
Optionally, the reduction rate of the last 2 passes of the first rough rolling is more than or equal to 18%.
Optionally, the thickness of the intermediate blank is more than or equal to 110mm.
Compared with the prior art, the technical scheme provided by the embodiment of the application has the following advantages:
according to the method for producing the Q890D ultra-high strength steel medium plate through online quenching, rolling is carried out through the reduction of large passes in a rough rolling stage, austenite grains can be flattened, so that the area of grain boundaries is increased, recrystallization nucleation points are increased, fine and uniform austenite grains are formed, phase transformation strengthening in a finish rolled steel plate is achieved through online cooling, finally, the end temperature of tempering treatment is utilized, the microstructure after phase transformation is further changed stably, heat preservation treatment is combined, the microstructure can be effectively adjusted, carbide is separated out, and the microstructure of the steel plate can be further converted into a dual-phase structure containing lath martensite and granular bainite, so that the strength of the ultra-high strength steel with the thickness in 60-70 mm is ensured, and the effective preparation of the ultra-high strength steel with the thickness in 60-70 mm is further ensured.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description, serve to explain the principles of the invention.
In order to more clearly illustrate the embodiments of the invention or the technical solutions of the prior art, the drawings which are used in the description of the embodiments or the prior art will be briefly described, and it will be obvious to a person skilled in the art that other drawings can be obtained from these drawings without inventive effort.
FIG. 1 is a schematic flow chart of a method according to an embodiment of the present disclosure;
FIG. 2 is a schematic diagram of a metallographic structure of a 70 mm-thick Q890D high-strength steel plate 1/4 on-line quenched according to the embodiment of the application;
FIG. 3 is a schematic diagram of a metallographic structure of a 1/4-position tempering treatment of a Q890D high-strength steel plate with a thickness of 70mm provided by the embodiment of the application;
FIG. 4 is a schematic diagram of a metallographic structure of a 60mm thick Q890D high-strength steel plate 1/4 on-line quenched according to the embodiment of the application;
fig. 5 is a schematic diagram of a metallographic structure of a 60mm thick Q890D high-strength steel plate 1/4 after tempering treatment.
Detailed Description
For the purposes of making the objects, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are within the scope of the present application based on the embodiments herein.
In one embodiment of the present application, as shown in fig. 1, there is provided a method of producing a Q890D ultra-high strength steel medium plate by in-line quenching, the method comprising:
s1, obtaining a casting blank after continuous casting;
s2, heating and rough rolling the casting blank before rolling to obtain an intermediate blank;
s3, performing finish rolling, online quenching cooling and heat treatment on the intermediate billet to obtain the Q890D ultra-high strength steel with medium thickness;
the heat treatment comprises tempering treatment and heat preservation treatment, wherein the end temperature of the tempering treatment is 600-620 ℃, the heat preservation treatment is carried out at the end temperature of the tempering treatment, and the time of the heat preservation treatment is 60-70 min;
the reduction of the last 3 passes of rough rolling is more than or equal to 36mm;
the thickness of the Q890D ultra-high strength steel is 60-70 mm.
In the embodiment of the application, the end temperature of tempering treatment is 600-620 ℃, and the positive effects are that in the temperature range, the finish rolled steel plate can be guaranteed to further perform phase change, the structure morphology is adjusted, and meanwhile carbide is separated out, so that the microstructure is guaranteed to be converted into a dual-phase structure containing lath martensite and granular bainite, and the final ultra-high strength steel meets the standard of Q890D ultra-high strength steel; when the temperature is smaller than the minimum value at the end of the range, the temperature is too low, and the phase change of the microstructure cannot be performed.
The heat preservation treatment time is 60-70 min, and the positive effects are that in the time range, the structure morphology can be adjusted, meanwhile, carbide is separated out, and the microstructure is ensured to be converted into a dual-phase structure containing lath martensite and granular bainite, so that the final super-strength steel meets the standard of Q890D super-strength steel; when the value of time is larger than the maximum value of the end point of the range, the heat preservation time is too long, the stability of the formed dual-phase structure is affected, and when the value of time is smaller than the minimum value of the end point of the range, the adverse effect is that the microstructure cannot be completely changed due to too short time, and the strength of the final super-strong steel is affected.
The reduction of the last 3 passes of rough rolling is more than or equal to 36mm, and the positive effects are that austenite grains can be effectively flattened within the range of the reduction, so that the grain boundary area is increased, the recrystallization nucleation points are increased, fine and uniform austenite grains are formed, and the follow-up phase change is ensured to be complete; when the reduction is smaller than the end value of the range, austenite grains cannot be effectively flattened, so that the follow-up phase change cannot be guaranteed to be completely performed, and the strength of the final ultra-high strength steel is affected.
In some alternative embodiments, the chemical composition of the Q890D ultra-high strength steel comprises, in mass fraction: 0.14 to 0.17 percent of C, 0.20 to 0.50 percent of Si, 1.00 to 1.50 percent of Mn, less than or equal to 0.015 percent of P, less than or equal to 0.003 percent of S, 0.30 to 0.70 percent of Cr, 0.40 to 0.70 percent of Mo, 0.30 to 0.60 percent of Ni, 0.005 to 0.025 percent of Ti, 0.015 to 0.040 percent of Nb, 0.03 to 0.06 percent of V, 0.001 to 0.0020 percent of B, 0.020 to 0.050 percent of Alt, and the balance of Fe and unavoidable impurities.
In the embodiment of the application, the positive effect that the mass fraction of C is 0.14% -0.17% is that the strength and the plastic toughness of a martensitic structure are adjusted, when the value of the mass fraction is larger than the maximum value of the end point of the range, the whole carbon equivalent is improved, cracks are easy to generate during welding, when the value of the mass fraction is smaller than the minimum value of the end point of the range, the tensile strength of a quenched state cannot be guaranteed to be larger than 1000MPa, the strength is further adjusted through tempering, and the toughness is improved.
The Si with the mass fraction of 0.20-0.50% has the positive effect of playing a better role in deoxidization; when the mass fraction is larger than the end maximum value of the range, red iron scale is easy to generate, and the toughness of the martensitic high-strength steel is easy to be deteriorated.
The positive effect that the mass fraction of Mn is 1.00-1.50% is that the hardenability of steel can be improved; when the mass fraction is larger than the end maximum value of the range, inclusions such as segregation and MnS are liable to occur, and the toughness of the martensitic high-strength steel is deteriorated.
P, S as an impurity element affects the plasticity and toughness of steel, and the smaller the numerical value is, the better the numerical value is, and the range of the numerical value is controlled to be less than or equal to 0.015 percent of P and less than or equal to 0.003 percent of S respectively.
The positive effect of the Cr with the mass fraction of 0.30-0.70% is that the hardenability of the steel can be improved, and martensite and bainite structures can be formed during quenching; when the mass fraction is larger than the maximum value of the end point of the range, larger sparks appear during welding, and the welding quality is affected.
The mass fraction of Mo is 0.40% -0.70%, which has the positive effects of improving the hardenability of steel and being beneficial to forming martensite and bainite structures during quenching; when the mass fraction is larger than the end point maximum value of the range, the carbon equivalent is increased, the welding performance is deteriorated, and meanwhile, mo is a noble metal, and the cost is increased.
The mass fraction of Ni is 0.30% -0.60%, and the positive effects are that the steel has a refined martensitic structure and the low-temperature impact toughness of the steel is improved; when the mass fraction is larger than the end point maximum value of the range, the carbon equivalent is increased, the welding performance is deteriorated, and meanwhile, ni is a noble metal, and the cost is increased.
Nb, ti and V are microalloy elements, are added in proper amount in steel, form nano-scale precipitates with C, N and other elements, and inhibit austenite grain growth during heating; nb can raise the critical temperature of unrecrystallized and expand the production process window; fine precipitate particles of Ti can improve the welding performance; v reacts with N and C in the tempering process to separate out nanoscale V (C, N) particles, so that the strength of the steel can be improved; the content range of niobium is 0.015-0.040%, the content range of titanium is 0.005-0.025%, and the content range of vanadium is 0.03-0.06%.
The positive effect that the mass fraction of B is 0.001% -0.0020% is that the hardenability of steel can be improved, and the strength of the steel is improved; when the value of the mass fraction is larger than the end maximum value of the range, B is liable to segregate to form a carbon-boron compound, and the toughness of the steel is seriously deteriorated.
The Alt with the mass fraction of 0.020-0.050% has the positive effects of serving as a deoxidizer, refining grains and improving impact toughness. When the mass fraction is larger than the end maximum value of the range, oxide inclusion defects of Al are liable to occur.
In some alternative embodiments, the Q890D ultra-high strength steel has a CEV of 0.65 or less and the Q890D ultra-high strength steel has a Pcm of 0.35 or less.
In the embodiment of the application, the positive effect that the CEV of the Q890D ultra-high strength steel is less than or equal to 0.65 is in the range of the carbon equivalent, and the strength, the hardness and the toughness of the ultra-high strength steel can be effectively ensured to meet the standard.
The Pcm of the Q890D ultra-high strength steel is less than or equal to 0.35, and the welding cold crack sensitivity range can ensure the convenience in the use process of the ultra-high strength steel, thereby ensuring the operation convenience in the application process.
In some alternative embodiments, the initial temperature of the online cooling is 810-830 ℃, and the redback temperature of the online cooling zone is less than or equal to 200 ℃.
In the embodiment of the application, the positive effect that the initial temperature of the online cooling is 810-830 ℃ is within the temperature range, and the online cooling can ensure
In some alternative embodiments, the rate of in-line cooling is 15 ℃/s to 30 ℃/s.
In the embodiment of the application, the online cooling speed is 15 ℃/s-30 ℃/s, and the positive effect is that in the cooling speed range, the phase change of the steel plate subjected to finish rolling can be ensured, so that the subsequent microstructure is ensured to be converted into a dual-phase structure containing lath martensite and granular bainite; when the cooling rate is greater than the maximum value at the end of the range, the maximum cooling capacity of the apparatus will be exceeded, and when the cooling rate is less than the minimum value at the end of the range, insufficient or no phase change will occur, and a dual-phase structure containing lath martensite and granular bainite cannot be obtained, resulting in insufficient strength of the resulting steel sheet.
In some optional embodiments, the end temperature of the heating before rolling is 1150-1210 ℃, and the total time of the heating before rolling is 260-450 min.
In the embodiment of the application, the heating terminal temperature before rolling is 1150-1210 ℃, and the positive effect is that in the temperature range, the metallographic structure of the steel plate can be ensured to perform phase change in an austenite region, so that the subsequent microstructure is ensured to be converted into a dual-phase structure containing lath martensite and granular bainite, and the strength of the medium-thickness steel plate is ensured to meet the requirement of Q890D ultra-high strength steel; when the temperature value is larger or smaller than the end value of the range, the metallographic structure of the steel plate cannot be effectively performed in the phase change stage, so that the subsequent microstructure cannot be ensured to be converted into a two-phase structure, and the strength of the medium-thickness steel plate cannot be ensured to meet the requirement of Q890D ultra-high strength steel.
The total heating time before rolling is 260-450 min, and the positive effects are that in the time range, the metallographic structure of the steel plate can be ensured to carry out phase change in an austenite region, so that the subsequent microstructure is ensured to be converted into a dual-phase structure containing lath martensite and granular bainite, and the strength of the medium-thickness steel plate is ensured to meet the requirement of Q890D ultra-high strength steel; when the time value is larger or smaller than the end value of the range, the metallographic structure of the steel plate cannot be effectively performed in the phase change stage, so that the subsequent microstructure cannot be ensured to be converted into a two-phase structure, and the strength of the medium-thickness steel plate cannot be ensured to meet the requirement of Q890D ultra-high strength steel.
In some alternative embodiments, the rough rolling includes a first rough rolling having a start rolling temperature of 1050 ℃ to 1150 ℃, a second rough rolling having a start rolling temperature of 880 ℃ to 900 ℃, and a finish rolling temperature of 840 ℃ to 870 ℃.
In the embodiment of the application, the initial rolling temperature of the first rough rolling is 1050-1150 ℃, and the positive effect is that in the temperature range, the initial forming of austenite grains in the rough rolling process can be ensured, and the preparation for fully extruding the austenite grains in the subsequent rolling stage is carried out; when the temperature is higher or lower than the end point of the range, the austenite grain size is not suitable for the extrusion of the stacked austenite grains in the rolling stage, and the steel plate cannot be ensured to be in a proper strength range.
The initial rolling temperature of the second rough rolling is 880-900 ℃, and the positive effects are that in the temperature range, the complete forming of austenite grains in the rough rolling process can be ensured, and the preparation for the extrusion of the austenite grains in the subsequent rolling stage is fully carried out; when the temperature is higher or lower than the end point of the range, the austenite grain size is not suitable for the extrusion of the stacked austenite grains in the rolling stage, and the steel plate cannot be ensured to be in a proper strength range.
The finish rolling temperature of the second rough rolling is 840-870 ℃, and the positive effects of the finish rolling temperature range are that the austenite grains in the metallographic structure of the steel plate after the rough rolling is finished can be ensured to exist stably after being formed, and sufficient temperature is provided for subsequent austenite grain transformation; when the temperature is higher or lower than the end value of the range, austenite in a metallographic structure is unstable, and the strength of the subsequent steel plate is affected.
In some alternative embodiments, the reduction of the last 2 passes of the first roughing is greater than or equal to 18%.
In the embodiment of the application, the reduction rate of the last 2 passes of the first rough rolling is more than or equal to 18%, and the positive effect is that austenite grains can be effectively flattened within the range of the reduction rate, so that the grain boundary area is increased, the recrystallization nucleation point is increased, fine and uniform austenite grains are formed, and the follow-up phase change is ensured to be complete; when the reduction is smaller than the end value of the range, austenite grains cannot be effectively flattened, so that the follow-up phase change cannot be guaranteed to be completely performed, and the strength of the final ultra-high strength steel is affected.
In some alternative embodiments, the thickness of the intermediate blank is greater than or equal to 110mm.
In the embodiment of the application, the thickness of the intermediate blank is more than or equal to 110mm, and the positive effect is that the thickness of the steel plate obtained later is 60-70 mm in the range, and the steel plate meets the requirement of Q890D ultra-high strength steel; when the thickness of the intermediate blank is smaller than the end value of the range, the thickness of the steel plate is reduced, and meanwhile, the steel plate cannot be ensured to meet the requirement of Q890D ultra-high strength steel.
Example 1
As shown in FIG. 1, the method for producing the Q890D ultra-high strength steel medium plate by on-line quenching comprises the following steps:
s1, obtaining a casting blank after continuous casting, wherein the size of the casting blank is 300mm multiplied by 2000mm multiplied by 3350mm;
s2, heating and rough rolling the casting blank before rolling to obtain an intermediate blank;
s3, performing finish rolling, online quenching cooling and heat treatment on the intermediate billet to obtain the Q890D ultra-high strength steel with medium thickness;
wherein, the heat treatment comprises tempering treatment and heat preservation treatment, the end temperature of the tempering treatment is 610 ℃, the heat preservation treatment is carried out at the end temperature of the tempering treatment, and the time of the heat preservation treatment is 70min;
the reduction of the last 3 passes of rough rolling are respectively as follows: 39.3mm, 39.3mm and 38.8mm;
the size of the Q890D ultra-high strength steel is 70mm multiplied by 2000mm multiplied by 14357mm;
the cooling intensity is enhanced by swinging back and forth in the cooling device at a speed of 0.5m/s in the water cooling process.
The Q890D ultra-high strength steel comprises the following chemical components in percentage by mass: 0.5% of C, 0.24% of Si, 1.22% of Mn, 0.008% of P, 0.0009% of S, 0.49% of Cr, 0.54% of Mo, 0.39% of Ni, 0.0014% of Ti, 0.022% of Nb, 0.048% of V, 0.0014% of B, 0.022% of Alt and the balance of Fe and unavoidable impurities.
Cev=0.59 for Q890D ultra-high strength steel, pcm=0.29 for Q890D ultra-high strength steel.
The initial temperature of the on-line cooling was 828℃and the redback temperature of the on-line cooling zone was 178 ℃.
The on-line cooling rate was 22 ℃/s.
The final temperature of the heating before rolling was 1194℃and the total time of the heating before rolling was 278min.
The rough rolling comprises a first rough rolling and a second rough rolling, wherein the initial rolling temperature of the first rough rolling is 1145 ℃, the initial rolling temperature of the second rough rolling is 898 ℃, and the final rolling temperature of the second rough rolling is 855 ℃.
The reduction in the last 2 passes of the first roughing was 20.2% and 25.0%, respectively.
The thickness of the intermediate blank was 110mm.
Example 2
Comparing example 2 with example 1, example 2 differs from example 1 in that:
the heat treatment comprises tempering treatment and heat preservation treatment, wherein the end temperature of the tempering treatment is 610 ℃, the heat preservation treatment is carried out at the end temperature of the tempering treatment, and the time of the heat preservation treatment is 60min;
the reduction of the last 3 passes of rough rolling are respectively as follows: 39.5mm, 39.3mm and 38.9mm;
the size of the Q890D ultra-high strength steel is 60mm multiplied by 2200mm multiplied by 15227mm;
the cooling intensity is enhanced by swinging back and forth in the cooling device at a speed of 0.5m/s in the water cooling process.
The Q890D ultra-high strength steel comprises the following chemical components in percentage by mass: 0.15% of C, 0.23% of Si, 1.21% of Mn, 0.008% of P, 0.0012% of S, 0.50% of Cr, 0.55% of Mo, 0.38% of Ni, 0.0014% of Ti, 0.022% of Nb, 0.049% of V, 0.0014% of B, 0.024% of Alt and the balance of Fe and unavoidable impurities.
Cev=0.59 for Q890D ultra-high strength steel, pcm=0.29 for Q890D ultra-high strength steel.
The initial temperature of the on-line cooling was 822℃and the redback temperature of the on-line cooling zone was 154 ℃.
The on-line cooling rate was 22 ℃/s.
The final temperature of the heating before rolling was 1197℃and the total time of the heating before rolling was 265min.
The rough rolling comprises a first rough rolling and a second rough rolling, wherein the initial rolling temperature of the first rough rolling is 1145 ℃, the initial rolling temperature of the second rough rolling is 899 ℃, and the final rolling temperature of the second rough rolling is 854 ℃.
The reduction in the last 2 passes of the first roughing was 20.4% and 25.2%, respectively.
The thickness of the intermediate blank is 110mm.
Comparative example 1
Comparative example 1 and example 1 are compared, and the difference between comparative example 1 and example 1 is that:
the final temperature of the tempering treatment is 580 ℃, the heat preservation treatment is carried out at the final temperature of the tempering treatment, and the time of the heat preservation treatment is 50min;
the reduction of the last 3 passes of rough rolling is less than or equal to 36mm;
the thickness of the Q890D ultra-high strength steel is 70mm.
Comparative example 2
Comparative example 1 and example 1 were compared, and comparative example 2 and example 1 differ in that:
the final temperature of tempering treatment is 630 ℃, the heat preservation treatment is carried out at the final temperature of tempering treatment, and the time of heat preservation treatment is 75min;
the thickness of the Q890D ultra-high strength steel is 60mm.
Related experiments:
the super steels obtained in examples 1-2 and comparative examples 1-2 were collected and subjected to performance test, respectively, and the results are shown in Table 1.
Test method of related experiment:
yield strength: the measurement is carried out according to the standard GB/T228;
tensile strength: the measurement is carried out according to the standard GB/T228;
elongation after break: the measurement is carried out according to the standard GB/T228;
-20 ℃ impact energy: the determination was carried out according to standard GB/T229;
TABLE 1
Specific analysis of table 1: elongation after break
The yield strength refers to the yield limit of the prepared steel plate when the yield phenomenon occurs, namely the stress resisting micro plastic deformation, and the higher the yield strength, the higher the yield limit of the steel plate.
The tensile strength refers to the maximum stress value which can be born by the prepared steel plate before the steel plate is broken, and the larger the tensile strength is, the larger the maximum stress value which can be born by the steel plate before the steel plate is broken.
The elongation after breaking refers to the percentage of the elongation of the gauge length of the steel plate after breaking to the original gauge length, and the higher the elongation after breaking, the better the toughness of the steel plate.
The impact energy at the temperature of 20 ℃ below zero means the impact force born by the steel plate under the low-temperature condition, and the larger the impact energy is, the stronger the impact resistance of the steel plate is.
From the data of examples 1-2, it can be seen that:
by adopting the method, the performance of the steel plate with the medium thickness of 60-70 mm can be effectively ensured to meet the standard, meanwhile, the mechanical property is rich, the yield margin of the steel plate in the embodiment 1 is 107MPa, the tensile margin is 98MPa, the elongation margin is 4%, and the impact property margin is more than 50J; the steel plate in the embodiment 2 has the yield allowance of 115MPa, the tensile allowance of 108MPa, the elongation allowance of 3.5 percent and the impact property allowance of more than 50J, and can meet the requirements of manufacturing industries such as engineering machinery, mining machinery and the like.
From the data of comparative examples 1-2, it can be seen that:
the tempering temperature is lower than the set temperature of the invention, the heat preservation time is shorter, and when the reduction of the last 3 passes of rough rolling is smaller, the tensile property can exceed the standard range, and the impact energy is relatively influenced; the tempering temperature is higher than the setting temperature of the invention, and the tensile property is smaller than the standard when the heat preservation time is longer.
One or more technical solutions in the embodiments of the present application at least further have the following technical effects or advantages:
(1) According to the method provided by the embodiment of the application, firstly, rolling is carried out through the reduction of large pass in the rough rolling stage, austenite grains can be flattened, then online cooling is carried out, phase transformation strengthening in the finish rolled steel plate is achieved, finally, through heat treatment and heat preservation treatment, the structure can be effectively adjusted, carbide is separated out, and further the microstructure of the steel plate can be converted into a dual-phase structure containing lath martensite and granular bainite, and further effective preparation of ultra-high strength steel with the thickness of 60-70 mm is guaranteed.
(2) The method provided by the embodiment of the application can be used for effectively preparing the 300mm blank into the steel plate with the thickness of 60-70 mm.
(3) According to the method provided by the embodiment of the application, the lath martensite and granular bainite steel with high strength and high toughness is obtained by utilizing an online quenching and tempering process, the Q890D online quenching and tempering high-strength steel plate with the thickness of 60-70 mm can be produced, the yield allowance is more than 30Mpa, the tensile allowance is more than 40Mpa, the elongation allowance is 2-4%, and the impact property allowance is more than 50J.
(4) According to the method provided by the embodiment of the application, the online quenching cooling is adopted, so that the process flow is shortened and the cost is reduced.
Explanation of the drawings:
FIG. 2 is a schematic diagram of a metallographic structure of a 70 mm-thick Q890D high-strength steel plate 1/4 on-line quenched according to the embodiment of the application;
FIG. 3 is a schematic diagram of a metallographic structure of a 1/4-position tempering treatment of a Q890D high-strength steel plate with a thickness of 70mm provided by the embodiment of the application;
FIG. 4 is a schematic diagram of a metallographic structure of a 60mm thick Q890D high-strength steel plate 1/4 on-line quenched according to the embodiment of the application;
fig. 5 is a schematic diagram of a metallographic structure of a 60mm thick Q890D high-strength steel plate 1/4 after tempering treatment.
As can be seen from fig. 2 to 5, by adopting the method of the present application, a steel sheet having a dual-phase structure including lath martensite and granular bainite can be effectively obtained, and the thickness of the Q890D super-strength steel is 60mm to 70mm.
It should be noted that in this document, relational terms such as "first" and "second" and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and are understood to encompass values approaching those ranges or values. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein.
The foregoing is only a specific embodiment of the invention to enable those skilled in the art to understand or practice the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (3)

1. A method for producing a Q890D ultra-high strength steel medium plate by on-line quenching, which is characterized by comprising the following steps:
obtaining a casting blank after continuous casting;
heating and rough rolling the casting blank before rolling to obtain an intermediate blank, wherein the thickness of the intermediate blank is more than or equal to 110mm;
performing finish rolling, online quenching cooling and heat treatment on the intermediate billet to obtain Q890D ultra-high strength steel with medium thickness;
the heat treatment comprises tempering treatment and heat preservation treatment, wherein the end temperature of the tempering treatment is 600-620 ℃, the heat preservation treatment is carried out at the end temperature of the tempering treatment, and the time of the heat preservation treatment is 60-70 min;
the rough rolling comprises a first rough rolling and a second rough rolling, wherein the initial rolling temperature of the first rough rolling is 1050-1150 ℃, the initial rolling temperature of the second rough rolling is 880-900 ℃, the final rolling temperature of the second rough rolling is 840-870 ℃, and the reduction of the last 3 passes of the rough rolling is more than or equal to 36mm; the initial temperature of the online quenching cooling is 810-830 ℃, and the redback temperature of the online quenching cooling is less than or equal to 200 ℃;
the thickness of the Q890D ultra-high strength steel is 60-70 mm, and the microstructure is a dual-phase structure containing lath martensite and granular bainite;
the speed of the online quenching cooling is 15 ℃/s-30 ℃/s, and the reduction rate of the last 2 passes of the first rough rolling is more than or equal to 18%;
the Q890D ultra-high strength steel comprises the following chemical components in percentage by mass: 0.14 to 0.17 percent of C, 0.20 to 0.50 percent of Si, 1.00 to 1.50 percent of Mn, less than or equal to 0.015 percent of P, less than or equal to 0.003 percent of S, 0.30 to 0.70 percent of Cr, 0.40 to 0.70 percent of Mo, 0.30 to 0.60 percent of Ni, 0.005 to 0.025 percent of Ti, 0.015 to 0.040 percent of Nb, 0.03 to 0.06 percent of V, 0.001 to 0.0020 percent of B, 0.020 to 0.050 percent of Alt, and the balance of Fe and unavoidable impurities.
2. The method of claim 1, wherein said Q890D ultra-high strength steel has a CEV of 0.65 or less and said Q890D ultra-high strength steel has a Pcm of 0.35 or less.
3. The method according to claim 1, wherein the end point temperature of the heating before rolling is 1150 ℃ to 1210 ℃, and the total time of the heating before rolling is 260min to 450min.
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