CN115491580B - Low-carbon alloy steel and preparation method and application thereof - Google Patents

Low-carbon alloy steel and preparation method and application thereof Download PDF

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CN115491580B
CN115491580B CN202110670115.1A CN202110670115A CN115491580B CN 115491580 B CN115491580 B CN 115491580B CN 202110670115 A CN202110670115 A CN 202110670115A CN 115491580 B CN115491580 B CN 115491580B
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alloy steel
low
carbon alloy
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rolling
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CN115491580A (en
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张佼
王玉杰
孙宝德
姜海涛
邢辉
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Kunshan Crystalline New Materials Research Institute Co ltd
Shanghai Jiaotong University
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Kunshan Crystalline New Materials Research Institute Co ltd
Shanghai Jiaotong University
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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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
    • B21B37/74—Temperature control, e.g. by cooling or heating the rolls or the product
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D7/00—Casting ingots, e.g. from ferrous metals
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D7/00—Casting ingots, e.g. from ferrous metals
    • B22D7/12—Appurtenances, e.g. for sintering, for preventing splashing
    • 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
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
    • 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
    • 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
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/001—Austenite
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/25—Process efficiency

Abstract

The invention discloses low-carbon alloy steel and a preparation method and application thereof, and relates to the technical field of engineering structural materials. The preparation method of the low-carbon alloy steel comprises the steps of impacting an alloy melt onto a moving cooling device placed in a vacuum cavity under the action of pressure to form a casting blank, carrying out solid solution treatment and hot rolling treatment on the casting blank, carrying out water quenching to 600-650 ℃ after the hot rolling is finished, directly carrying out heat preservation in a furnace for 1-2 hours, and then cooling along with the furnace. The application realizes fine austenite crystal grains and uniform tissue of the cast ingot through a melt impact method and a motion cooling device. The subsequent controlled rolling and controlled cooling process further refines the crystal grains, realizes the fine bainite and martensite laths and obtains larger dislocation density. The heat preservation in the furnace is helpful to remove the thermal residual stress in the rolling deformation process, and promotes the precipitation of fine carbides in the strip. Therefore, the low-carbon low-alloy steel has excellent strength and impact toughness and wide application.

Description

Low-carbon alloy steel and preparation method and application thereof
Technical Field
The invention relates to the technical field of engineering structural materials, in particular to low-carbon alloy steel and a preparation method and application thereof.
Background
The low-carbon low-alloy steel has good strength, impact toughness and excellent weldability, so that the low-carbon low-alloy steel is widely used as a bridge, a storage tank, a naval vessel, a ship, an oil and natural gas pipeline and the like, and is one of important engineering structural materials at present. The properties of low carbon low alloy steels depend on their chemical composition and the process regime of preparation, where yield strength, impact toughness and weldability are the most important performance indicators of low carbon low alloy steels, and ultimately on the microstructure of the steel, i.e. the size of the bainite or martensite laths.
The low-carbon low-alloy steel prepared by the prior art is mainly rolled after a traditional ingot is smelted, and then is quenched and tempered at high temperature. The obtained low-carbon low-alloy steel has higher impact toughness, but the strength cannot be improved, or the strength is improved by changing components, but the low-carbon low-alloy steel has poor weldability due to the increase of the content of alloy elements, namely, the crystal grains in a welding heat affected zone grow up, and the overall performance after welding is low. Such as patent publication CN 101104906A, CN 102586677A.
The prior art has the following disadvantages: the traditional smelting technology can not obtain the ingot with fine grains and uniform tissue, namely the low-carbon low-alloy steel ingot with fine austenite grains can not be obtained. Meanwhile, the subsequent quenching and tempering heat treatment process of quenching and high-temperature tempering is adopted, so that the process system is complicated, the flow is long, the efficiency is low, and the cost is increased. In addition, the strength of the low-carbon low-alloy steel cannot be ensured because the coarse austenite grains lead to subsequent rolling deformation and coarse martensite or bainite laths after heat treatment.
In view of this, the invention is particularly proposed.
Disclosure of Invention
The invention aims to provide a preparation method of low-carbon alloy steel, which can obtain ingots with fine grains and uniform tissues, and can improve the strength and the impact toughness of the low-carbon alloy steel through subsequent specific rolling and heat treatment processes.
The invention aims to provide low-carbon alloy steel which has good high strength and high toughness.
The invention aims to provide application of low-carbon alloy steel as an engineering structure material in bridges, storage tanks, naval vessels, ships, oil or natural gas pipelines.
The invention is realized by the following steps:
according to the first aspect, the invention provides a preparation method of low-carbon alloy steel, which comprises the steps of impacting an alloy melt onto a moving cooling device placed in a vacuum cavity under the action of pressure to form a casting blank, carrying out solid solution treatment and hot rolling treatment on the casting blank, carrying out water quenching to 600-650 ℃ after the hot rolling is finished, directly carrying out furnace heat preservation for 1-2 hours, and then carrying out furnace cooling.
In an alternative embodiment, the solution treatment is performed at 1260-1300 ℃ for 0.3-0.7 h.
In an optional embodiment, after the solution treatment, air cooling is carried out until the initial rolling temperature is 910-1050 ℃, the hot rolling treatment is carried out, the pass is carried out for 2-4 times, and the final rolling temperature is controlled at 750-900 ℃.
In an alternative embodiment, performing the hot rolling process comprises:
carrying out first hot rolling at the initial rolling temperature of 1000-1050 ℃, and carrying out final rolling at the final rolling temperature of 850-900 ℃;
carrying out second hot rolling at the initial rolling temperature of 930-970 ℃, wherein the final rolling temperature is 780-820 ℃;
carrying out third hot rolling at the initial rolling temperature of 910-920 ℃, wherein the final rolling temperature is 750-770 ℃.
In an alternative embodiment, before subjecting the alloy melt to high pressure impact, the method further comprises the steps of smelting the low-carbon alloy steel according to the designed chemical composition to form an ingot, and melting the ingot in an induction furnace to form the alloy melt.
In an alternative embodiment, the chemical composition of the low carbon alloy steel comprises, in mass percent: c:0.05% -0.14%, si:0.5% -1.0%, mn:0.30% -0.60%, ni:2.60% -3.00%, cr:0.90% -1.20%, mo:0.20% -0.27%, V:0.04% -0.10%, cu:1.5% -2.0%, nb:0.01% -0.08%, S: less than or equal to 0.015 percent, P: less than or equal to 0.020 percent and the balance of Fe.
In an alternative embodiment, the melting temperature of the alloy melt is the carbon alloy steel melting point Tm + (150-200 ℃);
preferably, thermocouple contact temperature measurement is adopted in the process of melting the ingot casting to monitor the temperature in real time;
preferably, after the ingot is moved to the induction furnace, vacuumizing the induction furnace to-0.1 to-0.2 MPa;
preferably, the ingot is melted using an induction coil disposed within the induction furnace.
In an optional embodiment, the high-pressure impact on the alloy melt comprises introducing argon into the induction furnace and controlling the pressure difference between the pressure in the induction furnace and the outside of the motion cooling device to be 0.1-0.5MPa;
preferably, the alloy melt is formed into a melt column through a nozzle and acts on the surface of the moving cooling device;
preferably, the height difference between the nozzle and the moving cooling device is 15-35 cm;
in an alternative embodiment, circulating alcohol and dry ice are introduced into the motion cooling device.
In a second aspect, the present invention provides a low carbon alloy steel prepared by the method of preparing a low carbon alloy steel according to any one of the preceding embodiments.
In a third aspect, the present invention provides the use of the low carbon alloy steel according to the previous embodiments as an engineering structural material in bridges, storage tanks, ships, oil or gas pipelines.
The invention has the following beneficial effects:
the preparation method of the low-carbon alloy steel realizes the perfect combination of the strength and the impact toughness of the low-carbon alloy steel according to a melt impact method and an improved heat treatment process, and can obtain a multi-phase structure of bainite, martensite and residual austenite. The melt impact method and the ultra-fast motion cooling device realize fine austenite crystal grains and uniform structure of the cast ingot. The subsequent controlled rolling and controlled cooling process further refines the crystal grains, realizes the fine bainite and martensite laths and obtains larger dislocation density. The heat preservation in the furnace is helpful to remove the thermal residual stress in the rolling deformation process, and promotes the precipitation of fine carbides in the strip. Therefore, the low-carbon low-alloy steel has excellent strength and impact toughness through fine grain strengthening, dislocation strengthening and precipitation strengthening and by combining the characteristics of a multiphase structure, and can be widely used as an engineering structure material in bridges, storage tanks, naval vessels, ships, petroleum or natural gas pipelines.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
FIG. 1 is a schematic structural diagram of a kinematic cooling device used in a method for preparing low-carbon alloy steel provided by the present application;
FIG. 2 is a schematic view of a heat treatment process of the preparation method of the low carbon alloy steel provided by the present application.
Icon: 100-a kinematic cooling device;
101-a first cylinder; 102-a second cylinder; 103-a first semi-cylindrical cavity; 104-a second semi-cylindrical cavity; 105-a receiving cavity; 106-a cooling chamber; 107-alcohol feed pipe; 108-Dry Ice feed tube.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
The invention provides a preparation method of low-carbon alloy steel, which comprises the following steps:
s1, smelting an alloy melt.
And smelting the low-carbon alloy steel according to the designed chemical components to form an ingot.
The low-carbon alloy steel comprises the following chemical components in percentage by mass: c:0.05% -0.14%, si:0.5% -1.0%, mn:0.30% -0.60%, ni:2.60% -3.00%, cr:0.90% -1.20%, mo:0.20% -0.27%, V:0.04% -0.10%, cu:1.5% -2.0%, nb:0.01% -0.08%, S: less than or equal to 0.015 percent, P: less than or equal to 0.020 percent and the balance of Fe.
And S2, melting the cast ingot in an induction furnace to form an alloy melt.
After the ingot prepared in the step S1 is moved to an induction furnace, the compactness is checked to be correct, and a mechanical pump is started to vacuumize the induction furnace to-0.1 to-0.2 MPa; the vacuum pump was turned off.
Starting an induction coil arranged in the induction furnace to rapidly melt the cast ingot, wherein the melting temperature of the alloy melt is controlled to be the melting point Tm + (150-200 ℃); and in the process of melting the ingot, thermocouple contact temperature measurement is adopted to carry out real-time temperature monitoring. The inventor researches and finds that when the melting temperature is lower than Tm + (150-200 ℃), the alloy melt has high viscosity and is not easy to impact quickly.
And S3, impacting the alloy melt to a motion cooling device 100 placed in the vacuum cavity under the action of pressure to form a casting blank.
Specifically, after the requirements of S2 are met, the argon control valve is opened, the pressure difference between the pressure in the induction furnace and the pressure outside the motion cooling device 100 is controlled to be 0.1-0.5MPa, the low alloy steel is quickly impacted under the driving action of the airflow on the melt, and the low alloy steel is deposited in the designed motion cooling device 100 to prepare the ingot with uniform tissue and fine grains.
The inventor researches and discovers that when the pressure in the induction furnace and the pressure difference outside the motion cooling device 100 are lower than 0.1-0.5MPa, the impact force is insufficient, the impact and the shearing on the growth of dendrites cannot be realized, when the pressure difference is higher than 0.1-0.5MPa, the control of the deposition speed and the formability of casting blanks are not facilitated, the splashing of melt is easily caused, and the impact speed is controlled by the pressure difference.
In the present application, the alloy melt is formed into a molten column through a nozzle and acts on the surface of the moving cooling device 100; preferably, the height difference between the nozzle and the moving cooling device 100 is 15 to 35cm; the distance is controlled by the speed of the lifting platform, and the impact of too small distance on the melt dendrites is insufficient. Too large a distance is disadvantageous for the vacuum design of the entire installation and for the shaping of the cast strand.
Referring to fig. 1, in the present application, a motion cooling device 100 includes a first cylinder 101 and a second cylinder 102 disposed in an involutory manner, a first semi-cylindrical cavity 103 is disposed on a side surface of the first cylinder 101 opposite to the second cylinder 102, a second semi-cylindrical cavity 104 is disposed on a side surface of the second cylinder 102 opposite to the first cylinder 101, the first semi-cylindrical cavity 103 and the second semi-cylindrical cavity 104 are involutory to form an accommodating cavity 105 for accommodating an impact melt, cooling cavities 106 annularly disposed in the accommodating cavity 105 are disposed in the first cylinder 101 and the second cylinder 102, an alcohol feeding pipe 107 and a dry ice feeding pipe 108 are disposed on the first cylinder 101 and the second cylinder 102, and the alcohol feeding pipe 107 and the dry ice feeding pipe 108 are respectively communicated with the cooling cavities 106.
The alloy melt impacting to the motion cooling device 100 is rapidly cooled by respectively feeding alcohol and dry ice into an alcohol feeding pipe 107 and a dry ice feeding pipe 108 of the motion cooling device 100. Because the conventional water cooling temperature can only be 0 ℃ at least, the cooling requirement of the low-carbon alloy steel cannot be met, in the application, the alloy melt can be quickly cooled by firstly moving the cooling device 100 and introducing alcohol and dry ice, the alloy melt can be cooled to-40 ℃ at the lowest, the cooling speed is greatly increased, and the cooling temperature is reduced.
And S4, carrying out solution treatment, hot rolling and quenching on the casting blank.
Referring to fig. 2, a casting blank is placed at 1260-1300 ℃ and kept warm for 0.3-0.7h for solution treatment, then air-cooled to the initial rolling temperature of 910-1050 ℃ for hot rolling treatment, the pass is carried out for 2-4 times, the final rolling temperature is controlled at 750-900 ℃, water quenching is carried out to 600-650 ℃, the temperature is kept in the furnace for 1-2h directly, then furnace cooling is carried out, and the tempering treatment is not carried out after the water quenching.
Specifically, the 3-pass hot rolling in the present application specifically includes:
carrying out first hot rolling at the initial rolling temperature of 1000-1050 ℃, and carrying out final rolling at the final rolling temperature of 850-900 ℃;
carrying out second hot rolling at the initial rolling temperature of 930-970 ℃, wherein the final rolling temperature is 780-820 ℃;
carrying out third hot rolling at the initial rolling temperature of 910-920 ℃, wherein the final rolling temperature is 750-770 ℃.
The selection of rolling and heat treatment process parameters in the invention is mainly characterized by the selection of melt impact preparation process parameters and controlled rolling and controlled cooling parameters, and is different from the conventional method of finishing annealing, quenching and tempering after rolling deformation. The method has the advantages of short flow, accurate control and rapid realization of rolling and heat treatment of the low-carbon low-alloy steel. Firstly, the temperature is kept at 1260-1300 ℃ for 0.3-0.7h for solution treatment to realize the full solution of the alloy elements. The selection of the rolling temperature and the finishing rolling temperature is based on different passes to enable the rolling temperature and the finishing rolling temperature to be in an austenite recrystallization region and an austenite non-recrystallization region, so that an austenite and ferrite multiphase structure is formed, and the perfect combination of subsequent strength and plasticity is facilitated. The requirements on the finishing temperature are 750 ℃ to 900 ℃, and the alloy steel is required to be in austenitization. Water quenching to 600-650 ℃, directly keeping the temperature in the furnace for 1-2h, and not carrying out ordinary quenching and tempering. The heat preservation temperature range avoids the temper brittleness of the low alloy steel, the heat preservation time is beneficial to shortening the heat treatment time, the efficiency is improved, and the high strength-plasticity combination of the low alloy steel is realized.
The heat treatment of steel roughly includes four basic processes of annealing, normalizing, quenching and tempering. Annealing, normalizing, quenching and tempering are 'four-bundle fire' in the integral heat treatment, wherein quenching and tempering are closely related, and quenching and tempering are often used in a matched manner in the prior art, but the quenching and tempering are not indispensable. In the application, a special rolling and heat treatment process is adopted, the initial rolling temperature and the final rolling temperature are controlled, water quenching is carried out to 600-650 ℃, the temperature in the furnace is directly kept for 1-2h, then the furnace is cooled, and the tempering treatment is not carried out after the water quenching.
The preparation method of the low-carbon alloy steel realizes the perfect combination of the strength and the impact toughness of the low-carbon alloy steel according to a melt impact method and an improved rolling and heat treatment process, and can obtain a multi-phase structure of bainite, martensite and residual austenite. The melt impact method and the ultra-fast motion cooling device 100 realize fine austenite grains and uniform structure of the cast ingot. The subsequent controlled rolling and controlled cooling process further refines the crystal grains, realizes the fine bainite and martensite laths and obtains larger dislocation density. The heat preservation in the furnace is beneficial to removing the thermal residual stress in the rolling deformation process, and promotes the precipitation of fine carbides in the strip. Therefore, the low-carbon low-alloy steel has excellent strength and impact toughness through fine grain strengthening, dislocation strengthening and precipitation strengthening and combined with the characteristics of a multiphase structure, and can be widely used as an engineering structure material in bridges, storage tanks, naval vessels, ships, oil or natural gas pipelines.
The features and properties of the present invention are described in further detail below with reference to examples.
Example 1
The embodiment provides a low-carbon alloy steel, which is prepared by the following preparation method:
Figure BDA0003118842910000071
s1, smelting the low-carbon alloy steel according to chemical components shown in the following table to form an ingot.
S2, after the ingot prepared in the step S1 is moved to an induction furnace, checking the compactness, and opening a mechanical pump to vacuumize the induction furnace to-0.1 MPa; the vacuum pump was turned off. Starting an induction coil arranged in the induction furnace to rapidly melt the cast ingot, wherein the melting temperature of the alloy melt is controlled at a carbon alloy steel melting point Tm + (150-200 ℃); and in the process of melting the ingot, thermocouple contact temperature measurement is adopted to carry out real-time temperature monitoring.
And S3, after the requirements of the S2 are met, opening an argon control valve, controlling the pressure difference between the pressure in the induction furnace and the pressure outside the motion cooling device 100 to be 0.1-0.5MPa, forming a melting column by the alloy melt through a nozzle under the pressure action, and impacting the melting column onto the motion cooling device 100 placed in the vacuum cavity to form a casting blank with uniform tissue and fine grains.
S4, placing the casting blank at 1280 ℃ for heat preservation for 0.5h for solid solution treatment, then air-cooling to 1050 ℃ of initial rolling temperature for first hot rolling, wherein the final rolling temperature is 900 ℃; carrying out second hot rolling at the initial rolling temperature of 950 ℃ and the final rolling temperature of 800 ℃; carrying out third hot rolling at the initial rolling temperature of 910 ℃ and the final rolling temperature of 750 ℃. Water quenching is carried out to 625 ℃, heat preservation is directly carried out in the furnace for 1h, then cooling is carried out along with the furnace, and tempering treatment is not carried out after water quenching.
Example 2
The low-carbon alloy steel provided by the embodiment 2 is prepared by the same method as that of the embodiment 1, and the difference is that the adopted post-treatment parameters are different:
in the embodiment, the casting blank obtained in the step S3 is placed at 1260 ℃, kept warm for 0.7h for solution treatment, and then air-cooled to the initial rolling temperature of 1000 ℃ for first hot rolling, wherein the final rolling temperature is 850 ℃; carrying out second hot rolling at the beginning rolling temperature of 930 ℃, wherein the finishing rolling temperature is 780 ℃; carrying out third hot rolling at the beginning rolling temperature of 920 ℃, wherein the finishing rolling temperature is 770 ℃. Water quenching to 600 ℃, directly preserving heat in the furnace for 2h, then cooling along with the furnace, and not carrying out tempering treatment after water quenching.
Example 3
The low-carbon alloy steel provided in example 3 is prepared by the same method as in example 1, except that the adopted post-treatment parameters are different:
in the embodiment, the casting blank obtained in the step S3 is placed at 1300 ℃ and kept warm for 0.3h for solution treatment, then air cooling is carried out until the initial rolling temperature is 1025 ℃ for first hot rolling, and the final rolling temperature is 870 ℃; carrying out second hot rolling at the initial rolling temperature of 970 ℃, wherein the final rolling temperature is 820 ℃; carrying out third hot rolling at the initial rolling temperature of 910 ℃ and the final rolling temperature of 750 ℃. Water quenching to 650 ℃, directly keeping the temperature in the furnace for 1h, then cooling along with the furnace, and not carrying out tempering treatment after water quenching.
Comparative example 1
The low carbon alloy steel provided in comparative example 1 was prepared in substantially the same manner as in example 1, except that the heat treatment was different.
After rolling, the blank is water-quenched to room temperature, then heated to 625 ℃, tempered for 1h, and cooled to room temperature.
Comparative example 2
Comparative example 2 provides a low carbon alloy steel prepared in substantially the same manner as in example 1, except that a different heat treatment was used. In comparative example 2, the cast slab obtained in step S3 was heat-treated as follows according to the heat treatment method in example 1 of the low-carbon low-alloy steel and the preparation method thereof provided in CN 201210081121.4:
heating the casting blank obtained in the step S3 to 900 ℃, preserving the temperature for 100min, and then air-cooling; then heating to 900 ℃, preserving the heat for 30min, and then cooling in the air; then heating to 200 ℃, preserving heat for 100min and tempering to obtain the low-carbon low-alloy steel.
Comparative example 3
Comparative example 3 provides a low carbon alloy steel prepared in substantially the same manner as in example 1, except that a different heat treatment was used. In comparative example 3, the cast blank obtained in step S3 is subjected to the following heat treatment according to the heat treatment method in example 1 of the low-carbon low-alloy high-strength plastic steel and the preparation method thereof provided in CN 201711285005.3:
(1) Large deformation rolling of an austenite recrystallization zone: and (4) heating the casting blank obtained in the step (S3) to 1100-1250 ℃, preserving heat for 2-10 hours, rolling by using a rolling mill, and cooling in air to 700-900 ℃ after finishing rolling. In order to fully recrystallize the material, the deformation of each pass during rolling is between 15 and 45 percent, and the cumulative deformation is more than 100 percent.
(2) Carrying out small pass rolling on an austenite non-recrystallization region: and continuously rolling the large-deformation rolling blank at 700-900 ℃ for multiple passes and small deformation, wherein the deformation of each pass is 5-15% during rolling, and the accumulated deformation is within 50%.
(3) Relaxation separation after rolling: after the small pass rolling process is completed, the billet is air cooled for 15-300 seconds and then cooled to room temperature at a rate higher than Vk (Vk being the lowest cooling rate at which the material can attain martensite or lower bainite).
(4) Critical heat treatment in a two-phase region: the material is heated to a temperature slightly higher than AC1 (AC 1+5-15 ℃) for critical tempering for 0.1-1 hour, and residual austenite stable at room temperature is obtained.
Comparative example 4
The low-carbon alloy steel provided by comparative example 4 has basically the same preparation method as that of example 1, and the difference is that the casting blank preparation process of the low-carbon alloy steel is different. In the comparative example 4, the low-carbon alloy steel provided in example 1 was directly smelted by the conventional method, the subsequent steps S2 and S3 were not performed for melt impact, and after direct smelting, a casting blank was formed by continuous casting, and the step S4 of solution treatment, rolling treatment and heat treatment was performed.
The performance of the low carbon alloy steels obtained in the above examples 1 to 3 and comparative examples 1 to 4 was tested, and the test results were as follows:
Figure BDA0003118842910000101
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Figure BDA0003118842910000111
in summary, the preparation method of the low-carbon alloy steel provided by the application realizes the perfect combination of the strength and the impact toughness of the low-carbon alloy steel according to the melt impact method and the improved rolling and heat treatment process, and can obtain the multiphase structure of bainite, martensite and retained austenite. The melt impact method and the ultra-fast motion cooling device 100 realize fine austenite grains and uniform structure of the cast ingot. The subsequent controlled rolling and controlled cooling process further refines the crystal grains, realizes the fine bainite and martensite laths and obtains larger dislocation density. The heat preservation in the furnace is beneficial to removing the thermal residual stress in the rolling deformation process, and promotes the precipitation of fine carbides in the strip. Therefore, the low-carbon low-alloy steel has excellent strength and impact toughness through fine grain strengthening, dislocation strengthening and precipitation strengthening and by combining the characteristics of a multiphase structure, and can be widely used as an engineering structure material in bridges, storage tanks, naval vessels, ships, petroleum or natural gas pipelines.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (8)

1. A preparation method of low-carbon alloy steel is characterized by comprising the steps of impacting an alloy melt onto a motion cooling device placed in a vacuum cavity under the action of pressure to form a casting blank, carrying out solid solution treatment and hot rolling treatment on the casting blank, carrying out water quenching to 600-650 ℃ after the hot rolling is finished, directly carrying out heat preservation in a furnace for 1-2 hours, and then cooling along with the furnace;
before the impact of the alloy melt, smelting the low-carbon alloy steel according to the designed chemical components to form an ingot, and melting the ingot in an induction furnace to form the alloy melt, wherein the melting temperature of the alloy melt is carbon alloy steel melting point Tm + (150-200 ℃); after the ingot is moved to the induction furnace, vacuumizing the induction furnace to-0.1 to-0.2 MPa;
impacting the alloy melt, namely introducing argon into the induction furnace and controlling the pressure difference between the pressure in the induction furnace and the outside of the motion cooling device to be 0.1-0.5MPa; the alloy melt is formed into a melt column through a nozzle and acts on the surface of the moving cooling device; the height difference between the nozzle and the motion cooling device is 15-35cm;
after the solution treatment, air cooling to the initial rolling temperature of 910-1050 ℃ for hot rolling treatment, wherein the pass is 2-4 times, and the final rolling temperature is controlled at 750-900 ℃; performing the hot rolling process includes: carrying out first hot rolling at the initial rolling temperature of 1000-1050 ℃, and carrying out final rolling at the final rolling temperature of 850-900 ℃; carrying out second hot rolling at the initial rolling temperature of 930-970 ℃, wherein the final rolling temperature is 780-820 ℃; carrying out third hot rolling at the initial rolling temperature of 910-920 ℃, wherein the final rolling temperature is 750-770 ℃.
2. The method for preparing low carbon alloy steel according to claim 1, wherein the solution treatment is performed at 1260-1300 ℃ for 0.3-0.7 h.
3. The method for preparing the low carbon alloy steel according to claim 1, wherein the chemical composition of the low carbon alloy steel comprises the following components in percentage by mass: c:0.05% -0.14%, si:0.5% -1.0%, mn:0.30% -0.60%, ni:2.60% -3.00%, cr:0.90% -1.20%, mo:0.20% -0.27%, V:0.04% -0.10%, cu:1.5% -2.0%, nb:0.01% -0.08%, S: less than or equal to 0.015%, P: less than or equal to 0.020 percent and the balance of Fe.
4. The method for preparing the low-carbon alloy steel according to claim 1, wherein thermocouple contact temperature measurement is adopted during the process of melting the ingot so as to carry out real-time temperature monitoring; and melting the ingot by using an induction coil arranged in the induction furnace.
5. The method for preparing low carbon alloy steel according to claim 1, wherein circulating alcohol and dry ice are introduced into the motion cooling device.
6. The preparation method of low-carbon alloy steel according to claim 1, wherein the motion cooling device comprises a first cylinder and a second cylinder which are oppositely arranged, a first semi-cylindrical cavity is formed in one side face, opposite to the second cylinder, of the first cylinder, a second semi-cylindrical cavity is formed in one side face, opposite to the first cylinder, of the second cylinder, the first semi-cylindrical cavity and the second semi-cylindrical cavity are oppositely arranged to form a containing cavity used for containing impact melt, cooling cavities which are annularly arranged in the containing cavity are formed in the first cylinder and the second cylinder, an alcohol feeding pipe and a dry ice feeding pipe are formed in the first cylinder and the second cylinder, and the alcohol feeding pipe and the dry ice feeding pipe are respectively communicated with the cooling cavities.
7. A low carbon alloy steel, characterized in that it is produced by the method of producing a low carbon alloy steel according to any one of claims 1 to 6.
8. Use of the low carbon alloy steel of claim 7 as an engineering structural material in bridges, tanks, ships, oil or gas pipelines.
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