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CN113046627B - 345 MPa-grade weather-proof bridge steel and manufacturing method thereof - Google Patents

345 MPa-grade weather-proof bridge steel and manufacturing method thereof Download PDF

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CN113046627B
CN113046627B CN202110137259.0A CN202110137259A CN113046627B CN 113046627 B CN113046627 B CN 113046627B CN 202110137259 A CN202110137259 A CN 202110137259A CN 113046627 B CN113046627 B CN 113046627B
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CN113046627A (en
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翟冬雨
丁叶
张仪杰
吴俊平
洪君
郭甲男
张媛钰
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Nanjing Iron and Steel Co Ltd
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    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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    • C21—METALLURGY OF IRON
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    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
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    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
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    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
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    • 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
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    • 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
    • C21D8/0263—Modifying 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
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    • C22C33/00—Making ferrous alloys
    • C22C33/04—Making ferrous alloys by melting
    • C22C33/06—Making ferrous alloys by melting using master alloys
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    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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    • 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
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Abstract

The invention discloses 345 MPa-grade weather-proof bridge steel and a manufacturing method thereof, relating to the technical field of steel production, and comprising the following chemical components in percentage by mass: c: 0.07% -0.09%, Si: 0.10-0.30%, Mn: 1.10% -1.20%, P: 0.005-0.015 percent, less than or equal to 0.0020 percent of S, Nb: 0.010-0.020%, V is less than or equal to 0.10%, Ti: 0.006-0.020%, Cr: 0.10% -0.30%, Ni: 0.05-0.20%, Mo is less than or equal to 0.1%, Cu: 0.05-0.15%, B is less than or equal to 0.0005%, Al: 0.015% -0.030%, Mg: 0.0012 to 0.0020 percent, less than or equal to 0.0050 percent of N, more than or equal to 6.5 percent of I, no Ca, and the balance of Fe and inevitable impurities. Forming a structure which mainly comprises acicular ferrite, improving the strength and toughness of the product and improving the welding performance.

Description

345 MPa-grade weather-proof bridge steel and manufacturing method thereof
Technical Field
The invention relates to the technical field of steel production, in particular to 345 MPa-grade weather-proof bridge steel and a manufacturing method thereof.
Background
With the development of transformation of macroscopic economy, China greatly promotes the construction of traffic infrastructures such as steel structure bridges and the like, and the use amount of bridge structure products is greatly increased. The steel for bridge structure has more and more strict requirements on the quality of products, and the purity and weldability of the molten steel of the steel for bridge are the key points of whether the products can meet the key national projects.
Disclosure of Invention
Aiming at the technical problems, the invention overcomes the defects of the prior art and provides 345 MPa-grade weather-proof bridge steel which comprises the following chemical components in percentage by mass: c: 0.07% -0.09%, Si: 0.10-0.30%, Mn: 1.10% -1.20%, P: 0.005-0.015 percent, less than or equal to 0.0020 percent of S, Nb: 0.010-0.020%, V is less than or equal to 0.10%, Ti: 0.006-0.020%, Cr: 0.10% -0.30%, Ni: 0.05-0.20%, Mo is less than or equal to 0.1%, Cu: 0.05-0.15%, B is less than or equal to 0.0005%, Al: 0.015% -0.030%, Mg: 0.0012 to 0.0020 percent, less than or equal to 0.0050 percent of N, more than or equal to 6.5 percent of I, no Ca, and the balance of Fe and inevitable impurities.
The technical scheme of the invention is further defined as follows:
the 345 MPa-grade weather-proof bridge steel comprises the following chemical components in percentage by mass: c: 0.07 to 0.08 percent of Si: 0.10-0.20%, Mn: 1.10% -1.18%, P: 0.005-0.010%, S is less than or equal to 0.0015%, Nb: 0.010-0.015%, V is less than or equal to 0.10%, Ti: 0.006-0.018%, Cr: 0.10% -0.20%, Ni: 0.05-0.15%, Mo is less than or equal to 0.1%, Cu: 0.05-0.10%, B is less than or equal to 0.0005%, Al: 0.015% -0.025%, Mg: 0.0012 to 0.0018 percent, less than or equal to 0.0050 percent of N, more than or equal to 6.5 percent of I, no Ca, and the balance of Fe and inevitable impurities.
The 345 MPa-grade weather-proof bridge steel comprises the following chemical components in percentage by mass: c: 0.075-0.085%, Si: 0.15-0.25%, Mn: 1.11% -1.19%, P: 0.008-0.015%, S is less than or equal to 0.0015%, Nb: 0.011 percent to 0.019 percent, V is less than or equal to 0.10 percent, and Ti: 0.009% -0.019%, Cr: 0.15% -0.25%, Ni: 0.10-0.15%, Mo is less than or equal to 0.1%, Cu: 0.08-0.13%, B is less than or equal to 0.0005%, Al: 0.020% -0.030%, Mg: 0.0012 to 0.0018 percent, less than or equal to 0.0050 percent of N, more than or equal to 6.5 percent of I, no Ca, and the balance of Fe and inevitable impurities.
The 345 MPa-grade weather-proof bridge steel comprises the following chemical components in percentage by mass: c: 0.08-0.09%, Si: 0.20-0.30%, Mn: 1.11% -1.20%, P: 0.009% -0.015%, S is less than or equal to 0.0020%, Nb: 0.011 percent to 0.020 percent, V is less than or equal to 0.10 percent, Ti: 0.010-0.020%, Cr: 0.20-0.30%, Ni: 0.15-0.20%, Mo is less than or equal to 0.1%, Cu: 0.10-0.15%, B is less than or equal to 0.0005%, Al: 0.018-0.029% of Mg: 0.0012 to 0.0019 percent, less than or equal to 0.0050 percent of N, more than or equal to 6.5 percent of I, no Ca, and the balance of Fe and inevitable impurities.
The invention also aims to provide a manufacturing method of 345 MPa-grade weather-proof bridge steel, which comprises the following steps:
s1, performing desulfurization pretreatment on molten iron by a KR method, skimming slag, and blowing in a converter;
s2, blowing by adopting a top-bottom combined blowing mode, carrying out steel tapping deoxidation alloying operation on converter steel tapping, adding a high-purity graphite carbon material for deoxidation after molten steel covers the bottom of a steel ladle, then adding 2-3 kg/t of premelted refining slag, 0.6-0.9 kg/t of impurity ash, and finally adding ferromanganese, ferrosilicon and an aluminum block; adjusting the argon flow to 500-600 NL/min after tapping, ensuring that the slag surface and the alloy are completely melted, feeding a pure calcium line to the slag surface after the slag surface is melted, removing the gas content in the slag, and hoisting and conveying the molten steel to an LF furnace after treatment is finished;
s3, hoisting the molten steel to an LF furnace, then heating to ensure that the temperature of the molten steel reaches 1620-1640 ℃, then feeding an aluminum wire to the bottom of a ladle to deoxidize the molten steel, carrying out slag micro-deoxidation treatment after the oxygen content of the molten steel is less than 10ppm, not adding an aluminum deoxidizer in the slag micro-deoxidation process to ensure that the sulfur content meets the component requirement, and adding a magnesium aluminum alloy to carry out micro-alloying treatment after the treatment is finished;
s4, carrying out vacuum treatment when the molten steel reaches RH, wherein the vacuum holding time is more than or equal to 15min, and the molten steel calming time is more than or equal to 12min after the vacuum treatment is finished;
s5, lifting the molten steel after static stirring to continuous casting for casting, adopting a gas-permeable nozzle to ensure smooth casting, adopting the processes of electromagnetic stirring and dynamic soft reduction, checking the surface quality after the blank is cooled in a heap for 48 hours, and processing the blank with the problem on the surface to ensure that the blank meets the requirement;
s6, heating the qualified blank in a stepping heating furnace, wherein the austenitizing temperature is set to 1120 +/-10 ℃, the heating time is calculated according to the thickness of the blank by 9-12 min/cm, and the soaking time is more than or equal to 35 min;
s7, rolling by using a single-stand reversible rolling mill, wherein the initial rolling temperature of rough rolling is 1010-1080 ℃, the secondary rolling temperature is 850-950 ℃, the final rolling temperature is 800-900 ℃, the water inlet temperature is 750-800 ℃, and the red returning temperature is 600-700 ℃;
and S8, cooling the steel plate to 300 ℃, performing temperature straightening, shearing, surface inspection, marking and flaw detection, and delivering after passing the flaw detection.
In the manufacturing method of 345 MPa-grade weather-resistant bridge steel, in the step S3, the magnesium content of the magnesium-aluminum alloy is 20-30%.
The invention has the beneficial effects that:
(1) the invention adopts a top-bottom combined blown converter for smelting, adopts a microalloying technology to refine impurities and reduce the original austenite grain size after refining treatment, solves the problem of the cleanliness of the molten steel of bridge steel, utilizes the strong chemical activity of high vapor pressure and low melting point of magnesium element at the molten steel smelting temperature to produce fine and dispersed magnesium impurities after magnesium treatment, and the grain size of the product reaches more than 11 grades, thereby forming a multiphase homogenization tissue type which mainly comprises acicular ferrite, improving the strength and toughness of the product and improving the welding performance;
(2) according to the invention, the corrosion resistance index of the low alloy steel is improved and the weather resistance of the product is improved by setting the component ranges of Cu, Ni, Cr, Si and P;
(3) according to the invention, by desulfurization and converter smelting, the sulfur content after the converter is ensured, the deoxidation and desulfurization process in the refining process is reduced, and the magnesium microalloying process effect is ensured;
(4) according to the invention, through magnesium-aluminum alloy treatment, the high chemical activity of magnesium element at high vapor pressure and low melting point at the molten steel smelting temperature effectively modifies the form of calcium aluminate inclusion in molten steel, and nano-scale MgO-Al is formed in steel2O3Spinel, MgS and other fine inclusion form nanometer level fine inclusion as nucleation particle to strengthen performance effectively;
(5) the invention adopts low-temperature austenitization, effectively refines the structure grain size, and the steel plate structure is uniform and fine through rolling and cooling to form a multiphase structure mainly comprising acicular ferrite, thereby improving the toughness and welding performance of the steel plate.
Drawings
FIG. 1 is a metallographic structure diagram of example 1 of the present invention.
Detailed Description
Example 1
The 345 MPa-grade weather-proof bridge steel provided by the embodiment comprises the following chemical components in percentage by mass: c: 0.079%, Si: 0.13%, Mn: 1.12%, P: 0.008%, S: 0.0012%, Nb: 0.012%, V: 0.003%, Ti: 0.009%, Cr: 0.13%, Ni: 0.08%, Mo: 0.003%, Cu: 0.09%, B: 0.0003%, Al: 0.019%, Mg: 0.0017%, N: 0.0029 percent, I is more than or equal to 6.5 percent, Ca is not added, and the balance is Fe and inevitable impurities.
A method of manufacture comprising the steps of:
s1, performing desulfurization pretreatment on molten iron by a KR method, skimming slag, and blowing in a converter;
s2, blowing by adopting a top-bottom combined blowing mode, carrying out steel tapping deoxidation alloying operation on converter steel tapping, adding high-purity graphite carbon materials for deoxidation after molten steel covers the bottom of a steel ladle, then adding 2kg/t steel of premelted refining slag, 0.8kg/t steel of impurity ash, and finally adding ferromanganese, ferrosilicon and aluminum blocks; adjusting the argon flow to 550NL/min after tapping to ensure that the slag surface and the alloy are completely melted, feeding a pure calcium line to the slag surface after the slag surface is melted to remove the gas content in the slag, and hoisting and conveying the molten steel to an LF furnace after treatment is finished;
s3, hoisting the molten steel to an LF furnace, then heating to ensure that the temperature of the molten steel reaches 1633 ℃, then feeding an aluminum wire to the bottom of a ladle to deoxidize the molten steel, performing slag micro-deoxidation after the oxygen content of the molten steel is 6ppm, not adding an aluminum deoxidizer in the slag micro-deoxidation process to ensure that the sulfur content meets the component requirement, and adding a magnesium-aluminum alloy to perform micro-alloying treatment after the treatment is finished, wherein the magnesium content of the magnesium-aluminum alloy is 26%;
s4, carrying out vacuum treatment when the molten steel reaches RH, keeping the vacuum for 18min, and calming the molten steel for 16min after the vacuum treatment is finished;
s5, lifting the molten steel after static stirring to continuous casting for casting, adopting a gas-permeable nozzle to ensure smooth casting, adopting the processes of electromagnetic stirring and dynamic soft reduction, checking the surface quality after the blank is cooled in a heap for 48 hours, and processing the blank with the problem on the surface to ensure that the blank meets the requirement;
s6, heating the qualified blank in a stepping heating furnace, setting the austenitizing temperature to 1126 ℃, calculating the heating time according to the thickness of the blank by 10min/cm, and soaking the blank for 41 min;
s7, rolling by using a single-stand reversible rolling mill, wherein the rough rolling is started at 1033 ℃, the secondary starting temperature is 875 ℃, the final rolling temperature is 830 ℃, the water inlet temperature is 785 ℃, and the red returning temperature is 636 ℃;
and S8, cooling the steel plate to 300 ℃, performing temperature straightening, shearing, surface inspection, marking and flaw detection, and delivering after passing the flaw detection.
Example 2
The 345 MPa-grade weather-proof bridge steel provided by the embodiment is different from the embodiment 1 in that the weather-proof bridge steel comprises the following chemical components in percentage by mass: c: 0.088%, Si: 0.26%, Mn: 1.19%, P: 0.013%, S: 0.0016%, Nb: 0.016%, V: 0.003%, Ti: 0.019%, Cr: 0.27%, Ni: 0.16%, Mo: 0.003%, Cu: 0.13%, B: 0.0002%, Al: 0.019%, Mg: 0.0017%, N: 0.0033 percent, I is more than or equal to 6.5 percent, Ca is not added, and the balance is Fe and inevitable impurities.
The mechanical property test results of the steel sheets obtained in examples 1 and 2 are as follows:
Figure BDA0002927199590000041
in conclusion, the invention carries out unique and reasonable component design aiming at the technical requirements of high strength, high toughness, high weather resistance, high plasticity level, low yield ratio, easy welding and the like of the high weather-resistant bridge steel plate, adopts microalloying technical measures to refine the structure grain size to form a multiphase homogenization structure control route, effectively improves the cleanliness of molten steel, ensures the performance stability after welding, forms a complete set of complete process production route, improves the overall performance of the bridge steel, ensures the product quality, has good reaction after being used by users, and provides good guarantee for national key engineering construction.
In addition to the above embodiments, the present invention may have other embodiments. All technical solutions formed by adopting equivalent substitutions or equivalent transformations fall within the protection scope of the claims of the present invention.

Claims (5)

1. The 345 MPa-grade weather-resistant bridge steel is characterized in that: the chemical components and the mass percentage are as follows: c: 0.07% -0.09%, Si: 0.10-0.30%, Mn: 1.10% -1.20%, P: 0.005-0.015 percent, less than or equal to 0.0020 percent of S, Nb: 0.010-0.020%, V is less than or equal to 0.10%, Ti: 0.006-0.020%, Cr: 0.10% -0.30%, Ni: 0.05-0.20%, Mo is less than or equal to 0.1%, Cu: 0.05-0.15%, B is less than or equal to 0.0005%, Al: 0.015% -0.030%, Mg: 0.0012 to 0.0020 percent, less than or equal to 0.0050 percent of N, more than or equal to 6.5 percent of I, no Ca, and the balance of Fe and inevitable impurities;
the manufacturing method comprises the following steps:
s1, performing desulfurization pretreatment on molten iron by a KR method, skimming slag, and blowing in a converter;
s2, blowing by adopting a top-bottom combined blowing mode, carrying out steel tapping deoxidation alloying operation on converter steel tapping, adding a high-purity graphite carbon material for deoxidation after molten steel covers the bottom of a steel ladle, then adding 2-3 kg/t of premelted refining slag, 0.6-0.9 kg/t of impurity ash, and finally adding ferromanganese, ferrosilicon and an aluminum block; adjusting the argon flow to 500-600 NL/min after tapping, ensuring that the slag surface and the alloy are completely melted, feeding a pure calcium line to the slag surface after the slag surface is melted, removing the gas content in the slag, and hoisting and conveying the molten steel to an LF furnace after treatment is finished;
s3, hoisting the molten steel to an LF furnace, then heating to ensure that the temperature of the molten steel reaches 1620-1640 ℃, then feeding an aluminum wire to the bottom of a ladle to deoxidize the molten steel, carrying out slag micro-deoxidation treatment after the oxygen content of the molten steel is less than 10ppm, not adding an aluminum deoxidizer in the slag micro-deoxidation process to ensure that the sulfur content meets the component requirement, and adding a magnesium aluminum alloy to carry out micro-alloying treatment after the treatment is finished;
s4, carrying out vacuum treatment when the molten steel reaches RH, wherein the vacuum holding time is more than or equal to 15min, and the molten steel calming time is more than or equal to 12min after the vacuum treatment is finished;
s5, lifting the molten steel after static stirring to continuous casting for casting, adopting a gas-permeable nozzle to ensure smooth casting, adopting the processes of electromagnetic stirring and dynamic soft reduction, checking the surface quality after the blank is cooled in a heap for 48 hours, and processing the blank with the problem on the surface to ensure that the blank meets the requirement;
s6, heating the qualified blank in a stepping heating furnace, wherein the austenitizing temperature is set to 1120 +/-10 ℃, the heating time is calculated according to the thickness of the blank by 9-12 min/cm, and the soaking time is more than or equal to 35 min;
s7, rolling by using a single-stand reversible rolling mill, wherein the initial rolling temperature of rough rolling is 1010-1080 ℃, the secondary rolling temperature is 850-950 ℃, the final rolling temperature is 800-900 ℃, the water inlet temperature is 750-800 ℃, and the red returning temperature is 600-700 ℃;
and S8, cooling the steel plate to 300 ℃, performing temperature straightening, shearing, surface inspection, marking and flaw detection, and delivering after passing the flaw detection.
2. The weather-resistant bridge steel for the 345MPa grade according to claim 1, wherein: the chemical components and the mass percentage are as follows: c: 0.07 to 0.08 percent of Si: 0.10-0.20%, Mn: 1.10% -1.18%, P: 0.005-0.010%, S is less than or equal to 0.0015%, Nb: 0.010-0.015%, V is less than or equal to 0.10%, Ti: 0.006-0.018%, Cr: 0.10% -0.20%, Ni: 0.05-0.15%, Mo is less than or equal to 0.1%, Cu: 0.05-0.10%, B is less than or equal to 0.0005%, Al: 0.015% -0.025%, Mg: 0.0012 to 0.0018 percent, less than or equal to 0.0050 percent of N, more than or equal to 6.5 percent of I, no Ca, and the balance of Fe and inevitable impurities.
3. The weather-resistant bridge steel for the 345MPa grade according to claim 1, wherein: the chemical components and the mass percentage are as follows: c: 0.075-0.085%, Si: 0.15-0.25%, Mn: 1.11% -1.19%, P: 0.008-0.015%, S is less than or equal to 0.0015%, Nb: 0.011 percent to 0.019 percent, V is less than or equal to 0.10 percent, and Ti: 0.009% -0.019%, Cr: 0.15% -0.25%, Ni: 0.10-0.15%, Mo is less than or equal to 0.1%, Cu: 0.08-0.13%, B is less than or equal to 0.0005%, Al: 0.020% -0.030%, Mg: 0.0012 to 0.0018 percent, less than or equal to 0.0050 percent of N, more than or equal to 6.5 percent of I, no Ca, and the balance of Fe and inevitable impurities.
4. The weather-resistant bridge steel for the 345MPa grade according to claim 1, wherein: the chemical components and the mass percentage are as follows: c: 0.08-0.09%, Si: 0.20-0.30%, Mn: 1.11% -1.20%, P: 0.009% -0.015%, S is less than or equal to 0.0020%, Nb: 0.011 percent to 0.020 percent, V is less than or equal to 0.10 percent, Ti: 0.010-0.020%, Cr: 0.20-0.30%, Ni: 0.15-0.20%, Mo is less than or equal to 0.1%, Cu: 0.10-0.15%, B is less than or equal to 0.0005%, Al: 0.018-0.029% of Mg: 0.0012 to 0.0019 percent, less than or equal to 0.0050 percent of N, more than or equal to 6.5 percent of I, no Ca, and the balance of Fe and inevitable impurities.
5. The weather-resistant bridge steel for the 345MPa grade according to claim 1, wherein: in the step S3, the magnesium content of the magnesium-aluminum alloy is 20-30%.
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