CN112281075B - Method for improving integral rolling performance stability of niobium-titanium composite reinforced 700MPa girder steel - Google Patents
Method for improving integral rolling performance stability of niobium-titanium composite reinforced 700MPa girder steel Download PDFInfo
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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
- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/076—Use of slags or fluxes as treating agents
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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
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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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
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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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
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
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- 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
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Abstract
The invention provides a method for improving the integral rolling performance stability of niobium-titanium composite reinforced 700MPa girder steel, wherein the niobium-titanium composite reinforced 700MPa girder steel comprises the following components in percentage by weight: c: 0.06-0.09%, Mn: 1.50-1.85%, Si: 0.05-0.20%, P: less than or equal to 0.015 percent, S: less than or equal to 0.005 percent, Nb: 0.025 to 0.060%, Ti: 0.070-0.110%, Mo: less than or equal to 0.20 percent, N: 0.0040-0.0085% of AlS: 0.025 to 0.055%, the balance being Fe and unavoidable impurities. The method controls the stability of the performance of the 700MPa girder steel through linkage of a multi-process system of smelting key component control, rolling key temperature control, a post-rolling encryption type laminar cooling mode and a steel coil warehousing box type stacking slow cooling mode. The method can improve the performance initial inspection qualification rate of products, reduce the quantity of defective products and protocol materials, reduce the production cost, and greatly reduce the series of problems of flattening warping, over-tolerance of bending and rolling rebound angles, frequent adjustment of the clearance of a punching die, great reduction of the service life, unstable structural strength of the I-beam, inconsistent thermal cutting deformation degree and the like.
Description
Technical Field
The invention relates to the technical field of steel materials, in particular to a method for improving the stability of the whole rolling performance of 700MPa grade girder steel.
Background
With the development of society and economy, low carbon, energy conservation and environmental protection become new development directions of the steel industry and the transportation industry, and with the promotion of light weight of automobiles in the automobile manufacturing industry, the innovation and strength upgrade of materials used for automobile beam steel have achieved great application achievements. In GB 1589-.
The 700MPa grade automobile beam steel is mainly used for replacing materials with low strength grade such as Q345B, 510L, 550L, 600L and the like to manufacture structural parts such as automobile longitudinal beams, cross beams, bumpers and the like, and the weight reduction of the parts can be realized. However, the automotive frame is a critical part of the whole automobile and needs to bear heavier load, and the automobile is subjected to various complex stress effects such as impact, torsion and the like in the driving process, so that the automotive frame has quite strict requirements on working conditions, and not only needs to have higher strength, but also needs to have good cold forming performance, weldability, fatigue resistance and the like. When the automobile beam is used by a user, the automobile beam has to meet various processing requirements such as shearing, rolling, hot cutting, stamping, punching, bending, welding and the like.
At present, 700 MPa-level beam steel is produced in a niobium and titanium micro-composite microalloy strengthening mode basically in the market, but because 700 MPa-level steel is influenced by various factors such as smelting components, molten steel purity, rolling temperature, deformation process and the like during production, the difference of organization and performance is caused, particularly, the performance difference performance fluctuation of whole rolls and special rolls can reach 120MPa greatly, and the problems that a user has great influence in subsequent processing, such as flattening warping, bending and rolling rebound angle out of tolerance, frequent adjustment of punching die gaps, great reduction of service life, unstable structural strength of I-beams, inconsistent thermal cutting deformation degree and the like are caused.
Disclosure of Invention
The invention aims to provide a method for improving the performance stability of a niobium-titanium composite reinforced 700MPa girder steel whole coil, which controls the performance stability of the 700MPa girder steel through multi-process system linkage of smelting key component control, rolling key temperature control, a post-rolling encryption type laminar cooling mode and a steel coil warehousing box type stacking slow cooling mode. The method for improving the stability of the mechanical performance of the whole roll of niobium-titanium composite reinforced 700MPa girder steel can improve the initial pass rate of the performance of products, reduce the quantity of inferior-quality products and protocol materials, reduce the production cost, reduce the fluctuation of the inspection performance of different batches and different positions of the same roll in the length direction within 70MPa and 50MPa respectively, and greatly reduce the series of problems of flattening warping, bending and rolling springback angle out-of-tolerance, frequent adjustment of the clearance of a punching die, greatly reduced service life, unstable structural strength of an I-beam, inconsistent thermal cutting deformation degree and the like.
The invention also provides a key link control direction and a disposal scheme after exceeding the range in the method for improving the integral performance stability of the niobium-titanium composite reinforced 700MPa girder steel, thereby greatly reducing the risk of unstable subsequent use of a user, improving the labor efficiency and prolonging the service life of a special automobile.
The method for improving the performance stability of the niobium-titanium composite reinforced 700MPa girder steel whole roll achieves the purpose of improving the internal organization structure of the steel by stabilizing the components of the steel and changing part of the steel rolling process and the cooling process according to the structure performance determining principle, thereby obtaining the steel with consistent performance.
In order to achieve the purpose, the invention adopts the technical scheme that:
a method for improving the integral rolling performance stability of niobium-titanium composite reinforced 700MPa girder steel comprises the following components in percentage by weight: c: 0.06-0.09%, Mn: 1.50-1.85%, Si: 0.05-0.20%, P: less than or equal to 0.015 percent, S: less than or equal to 0.005 percent, Nb: 0.025 to 0.060%, Ti: 0.070-0.110%, Mo: less than or equal to 0.20 percent, N: 0.0040-0.0085% of AlS: 0.025 to 0.055%, the balance being Fe and unavoidable impurities.
Wherein, C: carbon is an important element for improving the strength of steel, the strength of steel is increased along with the increase of the carbon content, but simultaneously the toughness, the plasticity and the welding performance are reduced, and the selection of the carbon content needs to comprehensively consider the strength, the toughness and the plasticity of the steel. The emphasis in the present invention is based on log [% Ti [% ]][％C]γ-7000/T +2.75 and log [% Ti][％C]α＝-9575IT+4.40；log[％Ti][％N]α/δ-17205/T +5.56 and log [% Ti][％N]γ-15490/T + 5.19; the solid solution temperature of TiC, TiN or Ti (C, N) in austenite and ferrite is considered, i.e., the higher the carbon content, the higher the solid solution temperature.
Mn: manganese has the solid solution strengthening effect, can also reduce the gamma-alpha phase transition temperature, refine the structure and have great effect on improving the strength of steel; manganese can also improve the hardenability of steel; meanwhile, too high manganese can reduce welding performance and aggravate center segregation; in the component design process of 700MPa grade girder steel, Mn is generally distributed in 1.50-1.85 wt% in order to ensure the performance qualified rate of different specifications and the consistency of different coils and whole coils.
Mo: the addition of molybdenum can obviously increase the hardenability of steel, and the addition of molybdenum can reduce the phase transition temperature, so that the C curve pearlite transformation curve is shifted to the right, the nucleation of proeutectoid ferrite is inhibited, the formation of a low-temperature structure is promoted, the tensile strength of steel is improved, and the low-temperature toughness of steel is improved. The use of molybdenum in the present invention promotes the precipitation of niobium and titanium carbonitride, while having the property of preventing the aggregation and growth of the second particles.
Nb: niobium can delay austenite recrystallization and reduce the phase transition temperature, the strength is improved through mechanisms such as fine grain strengthening, solid solution strengthening, phase transition strengthening, precipitation strengthening and the like, and meanwhile, the fine grain strengthening effect is not only beneficial to improving the strength, but also beneficial to improving the low-temperature toughness of steel.
P and S: harmful inclusions are easily formed in the steel, the toughness and the plasticity of the steel are reduced, and the lower the content is, the better the content is.
Si: the deoxidation effect is provided, and a part of Si exists in solid solution form, so that the yield strength and the tensile strength of the alloy can be improved, but the excessive content can reduce the plasticity of the steel and increase the risk of incomplete descaling, and therefore, the content of the silicon needs to be controlled between 0.05 and 0.20 percent.
N element: the TiN can be in a high-temperature form, has the functions of refining grains and precipitation strengthening, and can also prevent the grains in a welding heat affected zone from growing, but the plasticity of the steel is reduced due to excessive content. The N content directly influences the effective Ti (the effective Ti is full Ti-3.42N) content and indirectly influences the performance fluctuation, so that the N content needs to be stably controlled.
AlS: mainly measures the quality of the deoxidation effect and reduces the quantity of other metal oxide inclusions.
Further, the method comprises the steps of:
(1) top and bottom combined blown converter
The content of C is controlled to be 0.04-0.06%, the content of P is less than or equal to 0.010%, and the content of S is less than or equal to 0.020% at the end point of the top-bottom combined blown converter process;
(2) LF refining
In the LF refining process, a novel environment-friendly steel ladle modifier is adopted to produce white slag, and the white slag retention time is 18 +/-1 min; in the process of making white slag, in order to reduce the nitrogen increase amount in the LF refining process, the slag must cover the liquid level of steel by using a low-nitrogen covering agent, the liquid level of the steel cannot be exposed in the smelting process, the slag is melted and made into the white slag, after the target is reached, the argon flow is immediately adjusted to a soft stirring state, the soft stirring time is more than or equal to 10min, and the soft stirring effect is based on that the liquid level of the steel cannot be exposed due to slight fluctuation of the slag surface; when producing high titanium steel, reasonably controlling the stirring strength of bottom-blown argon, and maintaining the micro-positive pressure atmosphere in the furnace to avoid the exposure of molten steel; meanwhile, in the process, the pure calcium wire feeding amount is 200 plus 230 m/furnace, the deoxidation is required to be complete before the calcium wire feeding so as to ensure the calcium content in the steel, and the sampling is carried out 2min after the wire feeding is finished; thus, the content of gas N in the steel can be stably controlled between 0.0038 and 0.0052 percent;
(3) heating of continuously cast slabs
The continuous casting slab heating adopts a control process linked with the casting slab off-line time, specifically the casting slab direct-charging (less than 12 hours), hot-charging (12 hours to 24 hours) and cold-charging (more than 24 hours) time, and different in-furnace time and soaking temperature are controlled according to different specifications and different casting slab off-line times, specifically referring to table 1;
TABLE 1 control Process of casting blank off-line time, soaking temperature and in-furnace time
(4) Rolling of
In the rolling process, the temperature of the key rolling process is adjusted according to the production specification, the furnace time of the plate blank and the content ranges of N and Ti in smelting components, and the specific reference is made to table 2;
after rolling is finished, cooling at a cooling speed of 15-30 ℃/s and a coiling temperature of 570-620 ℃ by adopting corresponding laminar cooling modes in different specifications to obtain polygonal ferrite, granular bainite, a small amount of pearlite and precipitates; the laminar flow codes 12, 28 and 16 are respectively cooled by the following modes: laminar flow code-12 is one-half sparse cooling; laminar flow code-28: sparse cooling by three fifths; laminar flow code-16: the front end is concentrated and the water outlet is limited by fine adjustment for cooling;
TABLE 2 Rolling Process parameter settings
(5) Box type slow cooling
And after the rolling is finished, the steel coil is off-line within 60 minutes, box type stacking is adopted for slow cooling for 36-72 hours, and then the steel coil is delivered for use.
Further, the novel environment-friendly ladle modifier in the step (2) comprises the following components: 20-40wt% of CaO, Al2O310-35wt％，SiO2Less than 5.0wt%, simple substance Al 20-25wt%, MgO 2-6wt%, and S less than 0.05 wt%.
Further, after the off-line time of the casting blank specified in the rolling exceeds 24 hours, the coiling target temperature corresponding to all specifications is adjusted to be 7-15 ℃.
Further, when the detection content of N element in the continuous casting tundish component is regulated to be 0.0065-0.0085% or the detection content of Ti element in the continuous casting tundish component is regulated to be 0.078-0.088% in the rolling process, the total furnace time of the casting blanks corresponding to all specifications is increased by 20 minutes at the lowest, and the coiling target temperature after the steel is rolled is adjusted to be 13 ℃.
Furthermore, the thickness of the product obtained by the method is 4.0-12.0mm, the standard yield strength of the product is more than or equal to 600MPa, the tensile strength is 700-880 MPa, and the elongation A is more than or equal to 14%.
Compared with the prior art, the invention has the beneficial effects that:
1. the 700MPa automobile beam steel produced by the invention adopts the setting of the relation among the casting blank charging time, the total in-furnace time and the soaking temperature, saves energy on the premise of not influencing the service life of the heating furnace, can ensure the solid solution of titanium and niobium microalloy elements in austenite to the maximum extent, provides a good foundation for fine dispersed 10-50nm precipitates in the subsequent rolling and cooling processes, and provides a support for ensuring the strength.
2. The invention not only ensures the strength conformity, but also reduces the degradation and the judgment of the abnormal blank in the smelting process by correspondingly controlling the process under the condition of higher content of gas N, thereby greatly saving the production cost.
3. The invention greatly reduces the intensity fluctuation caused by the specification effect by controlling the different coiling temperatures of different specifications and the corresponding laminar cooling process, so that the steel coil inspection performance and the coil passing performance fluctuate within an ideal range. Meanwhile, the residual stress value of the thin gauge caused by large cooling speed is reduced, and a good original plate shape foundation is provided for subsequent processing and use.
4. According to the invention, box-type stacking slow cooling is immediately adopted within 60 minutes by coiling at a lower temperature and taking the steel coil off-line, so that the cooling stress of the steel coil is further reduced, and Ti element which is not separated out is continuously separated out in the stacking slow cooling process, so that the middle area of the steel coil in the length direction can be offset, the strength lost due to disappearance of high-temperature dislocation is eliminated, and the strength of the steel coil in the length direction is kept consistent.
5. In the process, the rolling start temperature of the finish rolling with the specification of more than 4.6mm is set to be 980-. Meanwhile, the austenite and ferrite grains can be refined, and the mixed crystal phenomenon generated by rolling in a recrystallization zone is reduced.
Detailed Description
The technical solutions and effects of the present invention will be further described with reference to specific examples, but the scope of the present invention is not limited thereto.
Example 1
In this embodiment, 700MPa automotive beam steel with a product specification of 4.0mm thick is produced by adopting a conventional hot continuous rolling 1780 production line of the company, and the method for improving the integral rolling performance stability of the niobium-titanium composite reinforced 700MPa beam steel is further explained.
The automobile girder steel of the embodiment is prepared from the following components in percentage by weight: c: 0.07%, Si: 0.12%, Mn: 1.52%, P: 0.011%, S: 0.003%, Mo: 0.02%, Nb: 0.027%, Ti: 0.088%, N: 0.0053%, Als: 0.036%, the balance being Fe and unavoidable impurities.
The production process route of the automobile beam steel comprises a top-bottom combined blown converter, a novel environment-friendly smokeless modifier participating in LF refining, rolling by a 1780mm rolling mill, a laminar flow code 12 cooling process and box type slow cooling of rolled steel coils for 36 hours.
Wherein, the continuous casting slab number: 8M07399L02, charging for 9 hours and heating for 42 minutes, wherein the soaking temperature of the heating furnace is 1259 ℃, the total furnace time is 147 minutes, and the rough rolling finishing temperature is 1088 ℃; the start rolling temperature of finish rolling is 1065 ℃, the finish rolling temperature of finish rolling is 893 ℃, and the finish rolling is carried out until the thickness is 4.0 mm; after finishing the finish rolling, adopting a code 12 cooling mode, cooling at a cooling speed of 18-22 ℃/s, wherein the coiling temperature is 627 ℃, and after rolling, adopting box-type slow cooling for 48 hours, and then testing the performance.
The steel strip produced according to the procedure of this example has the performance indexes shown in Table 3.
TABLE 3 Performance stability of 14.0 mm700MPa automotive girder steel of this example
As can be seen from Table 3, the 700MPa automobile beam steel with the thickness of 4.0mm produced by the embodiment has the extremely poor performance fluctuation of only 37MPa at different parts of the whole roll on the basis of meeting the requirements of strength, plasticity and the like.
Example 2
In this embodiment, 700MPa automotive beam steel with a product specification of 7.9mm is produced by a conventional hot continuous rolling 1780 production line of the company, and the method for improving the integral rolling performance stability of the niobium-titanium composite reinforced 700MPa beam steel of the invention is further explained.
The automobile girder steel of the embodiment is prepared from the following components in percentage by weight: c: 0.07%, Si: 0.14%, Mn: 1.61%, P: 0.012%, S: 0.002%, Mo: 0.03%, Nb: 0.032%, Ti: 0.098%, N: 0.0056%, Als: 0.034%, the balance being Fe and unavoidable impurities.
The production process route of the automobile beam steel comprises a top-bottom combined blown converter, participation of a novel environment-friendly smokeless modifier in LF refining, rolling of a 1780mm rolling mill, a laminar flow code 28 cooling process and box type slow cooling of rolled steel coils for 48 hours.
Wherein, the continuous casting slab number: 8K10119K03, charging for 14 hours and heating for 52 minutes, wherein the soaking temperature of the heating furnace is 1269 ℃, the total in-furnace time is 158min, and the rough rolling finishing temperature is 1034 ℃; the starting temperature of finish rolling is 1011 ℃, the finishing temperature of finish rolling is 866 ℃, and the finish rolling is carried out until the thickness is 7.9 mm; and after finishing finish rolling, adopting a code 28 cooling mode, cooling at a cooling speed of 19-25 ℃/s, wherein the coiling temperature is 607 ℃, and after rolling, adopting box-type slow cooling for 48 hours, and then testing the performance.
The steel strip produced according to the procedure of example 2 had the performance indexes shown in Table 4.
TABLE 4 stability of the 27.9 mm700MPa automotive girder steel of this example
As can be seen from Table 4, the 700MPa automobile beam steel with the thickness of 7.9mm produced by the embodiment has the extremely poor performance fluctuation of only 35MPa at different parts of the whole roll on the basis of meeting the requirements of strength, plasticity and the like.
Example 3
In this embodiment, 700MPa automotive beam steel with a product specification of 12.0mm is produced by a conventional hot continuous rolling 1780 production line of the company, and the method for improving the integral rolling performance stability of the niobium-titanium composite reinforced 700MPa beam steel of the invention is further explained.
The automobile girder steel of the embodiment is prepared from the following components in percentage by weight: c: 0.08%, Si: 0.14%, Mn: 1.73%, P: 0.014%, S: 0.002%, Mo: 0.03%, Nb: 0.042%, Ti: 0.108%, N: 0.0049%, Als: 0.035%, the balance being Fe and unavoidable impurities.
The production process route of the automobile beam steel comprises a top-bottom combined blown converter, a novel environment-friendly smokeless modifier participating in LF refining, rolling by a 1780mm rolling mill, a laminar code 16 cooling process and box type slow cooling of rolled steel coils for 72 hours.
Wherein, the continuous casting slab number: 8M03792L03, charging into a furnace, heating for 52 hours and 38 minutes, wherein the soaking temperature of the heating furnace is 1285 ℃, the total furnace time is 186 minutes, and the rough rolling finish rolling temperature is 1019 ℃; the initial rolling temperature of finish rolling is 977 ℃, the final rolling temperature of finish rolling is 838 ℃, and the finish rolling is carried out until the thickness is 12.0 mm; and after finishing finish rolling, cooling at a cooling speed of 20-30 ℃/s by adopting a code 16 cooling mode, wherein the coiling temperature is 581 ℃, and after rolling, performing box-type slow cooling for 48 hours and then testing the performance.
The performance index of the steel strip produced according to the procedure of example 3 is shown in Table 5.
TABLE 5 Performance stability of 700MPa automotive girder steel of 312.0 mm in this example
As can be seen from Table 5, the 700MPa automobile beam steel with 12.0mm thickness produced by the embodiment has the extremely poor performance fluctuation of only 38MPa at different parts of the whole roll on the basis of meeting the requirements of strength, plasticity and the like.
Example 4
In this embodiment, 700MPa automotive beam steel with a product specification of 10.0mm is produced by adopting a conventional hot continuous rolling 1780 production line of the company, and the method for improving the integral rolling performance stability of the niobium-titanium composite reinforced 700MPa beam steel is further explained.
The automobile girder steel of the embodiment is prepared from the following components in percentage by weight: c: 0.08%, Si: 0.13%, Mn: 1.66%, P: 0.013%, S: 0.003%, Mo: 0.02%, Nb: 0.035%, Ti: 0.081%, N: 0.0083%, Als: 0.038%, the balance being Fe and unavoidable impurities.
The production process route of the automobile beam steel comprises a top-bottom combined blown converter, a novel environment-friendly smokeless modifier participating in LF refining, rolling by a 1780mm rolling mill, a laminar code 16 cooling process and box type slow cooling of rolled steel coils for 60 hours.
Wherein, the continuous casting slab number: 9M09145L02, charging into a furnace, heating for 21 minutes within 126 hours, wherein the soaking temperature of the heating furnace is 1291 ℃, the total in-furnace time is 212min, and the rough rolling finishing temperature is 1022 ℃; the initial rolling temperature of finish rolling is 985 ℃, the final rolling temperature of finish rolling is 849 ℃, and the finish rolling is carried out until the thickness is 10.0 mm; and after finishing finish rolling, adopting a code 16 cooling mode, cooling at a cooling speed of 20-30 ℃/s, wherein the coiling temperature is 593 ℃, and after rolling, adopting box-type slow cooling for 48 hours, and then testing the performance.
The properties of the steel strip produced according to the procedure of example 4 are shown in Table 6.
TABLE 6 stability of the properties of the 410.0 mm700MPa automotive girder steel of this example
As can be seen from Table 6, the 700MPa automobile beam steel with 10.0mm thickness produced by the present example has the performance fluctuation of only 41MPa at different positions of the whole roll on the basis of satisfying the strength, plasticity and the like.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (1)
1. A method for improving the integral rolling performance stability of niobium-titanium composite reinforced 700MPa girder steel with the thickness of 10mm is characterized in that the niobium-titanium composite reinforced 700MPa girder steel in the method comprises the following components in percentage by weight: c: 0.08%, Si: 0.13%, Mn: 1.66%, P: 0.013%, S: 0.003%, Mo: 0.02%, Nb: 0.035%, Ti: 0.081%, N: 0.0083%, Als: 0.038%, the balance being Fe and unavoidable impurities;
the method comprises the following steps:
(1) top and bottom combined blown converter
The content of C is controlled to be 0.04-0.06%, the content of P is less than or equal to 0.010%, and the content of S is less than or equal to 0.020% at the end point of the top-bottom combined blown converter process;
(2) LF refining
In the LF refining process, a novel environment-friendly steel ladle modifier is adopted to produce white slag, and the white slag retention time is 18 +/-1 min;
(3) heating of continuously cast slabs
The continuous casting slab is heated by adopting a process of linkage control with the off-line time of the casting slab, specifically, the continuous casting slab is charged in a furnace for 126 hours and 21 minutes, the soaking temperature of the heating furnace is 1291 ℃, and the total in-furnace time is 212 min;
(4) rolling of
The rough rolling and final rolling temperature is 1022 ℃; the initial rolling temperature of finish rolling is 985 ℃, the final rolling temperature of finish rolling is 849 ℃, and the finish rolling is carried out until the thickness is 10.0 mm;
after finishing the finish rolling, adopting a laminar cooling mode, specifically a front end concentration and fine adjustment limited effluent cooling mode, cooling at a cooling speed of 20-30 ℃/s, and coiling at the temperature of 593 ℃ to obtain polygonal ferrite, granular bainite, pearlite and precipitates;
(5) box type slow cooling
After the rolling is finished, the steel coil is off-line within 60 minutes, box type stacking is adopted for slow cooling for 48 hours, and then the steel coil is delivered for use;
the novel environment-friendly ladle modifier in the step (2) comprises the following components: 20-40wt% of CaO, Al2O3 10-35wt%，SiO2Less than 5.0wt%, simple substance Al 20-25wt%, MgO 2-6wt%, S less than 0.05 wt%;
the yield strength of the product is 691MPa, the tensile strength is 742MPa, the elongation A is 19 percent, and the performance fluctuation of different parts of the whole roll is 41 MPa.
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| CN103849812A (en) * | 2014-03-31 | 2014-06-11 | 武汉钢铁(集团)公司 | Low-brittleness 700MPa-level automobile beam steel and manufacturing method thereof |
| CN109518074A (en) * | 2018-10-10 | 2019-03-26 | 安阳钢铁股份有限公司 | A kind of economical high tenacity 800MPa grades of beam steels and its production method |
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| CN103849812A (en) * | 2014-03-31 | 2014-06-11 | 武汉钢铁(集团)公司 | Low-brittleness 700MPa-level automobile beam steel and manufacturing method thereof |
| CN109518074A (en) * | 2018-10-10 | 2019-03-26 | 安阳钢铁股份有限公司 | A kind of economical high tenacity 800MPa grades of beam steels and its production method |
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