CN109797342B - High-strength, high-toughness and atmospheric corrosion-resistant steel plate for manufacturing steel structure and manufacturing method thereof - Google Patents
High-strength, high-toughness and atmospheric corrosion-resistant steel plate for manufacturing steel structure and manufacturing method thereof Download PDFInfo
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Abstract
The invention relates to a high-strength, high-toughness and atmospheric corrosion-resistant steel plate for manufacturing a steel structure, which comprises the following elements in percentage by weight: c: 0.03% -0.10%, Si: 0.30-0.50%, Mn: 1.10 to 1.50 percent of Cu, less than or equal to 0.010 percent of P, less than or equal to 0.003 percent of S, 0.45 to 0.70 percent of Cr, Cu: 0.25% -0.40%, Ni: 0.30% -0.40%, Alt: not less than 0.030%, Ti: 0.006% -0.030%, V: 0.040% -0.080%, Mo: 0.02% -0.08%, Ca: 0.0010% -0.0030%, N: 0.0020% -0.0080%, B: 0.0002 to 0.0030 percent, 0.001 to 0.010 percent of Ce, an atmospheric corrosion resistance index I larger than 6.5, CEV less than or equal to 0.54, Pcm less than or equal to 0.27, and the balance of Fe and inevitable impurities. The high-performance steel plate with the bainite structure is obtained by adopting specific chemical component design and a steel plate modulation process, and can be used for manufacturing steel structures such as bridges and high-rise buildings.
Description
Technical Field
The invention relates to the production of a thick steel plate for manufacturing a steel structure, in particular to a thick steel plate with high strength, high toughness and atmospheric corrosion resistance.
Background
As bridge construction is developed in the direction of large span, heavy load, atmospheric corrosion resistance, and the like, and the construction demand for large-scale steel structures is increasing in high-rise buildings and the like, structural steel plates used for manufacturing the steel structures are also gradually developed in the direction of high strength, high toughness, large thickness, atmospheric corrosion resistance, and the like. The thick steel plate with high strength, high toughness and atmospheric corrosion resistance becomes an important research direction for steel plate product production enterprises for steel structures.
Disclosure of Invention
The invention aims to provide a method for producing a steel plate with the thickness of 60-120 mm, which can be used for steel structures of large bridges, high-rise buildings and the like, and has the advantages that the strength, the toughness and the elongation after fracture of the steel plate meet the manufacturing requirements of the steel structures, and the steel plate also has excellent atmospheric corrosion resistance.
The technical scheme adopted by the invention for solving the problems is as follows: a high-strength, high-toughness and atmospheric corrosion resistant steel plate for manufacturing a steel structure comprises the following elements in percentage by mass: c: 0.03% -0.10%, Si: 0.30-0.50%, Mn: 1.10 to 1.50 percent of Cu, less than or equal to 0.010 percent of P, less than or equal to 0.003 percent of S, 0.45 to 0.70 percent of Cr, Cu: 0.25% -0.40%, Ni: 0.30% -0.40%, Alt: not less than 0.030%, Ti: 0.006% -0.030%, V: 0.040% -0.080%, Mo: 0.02% -0.08%, Ca: 0.0010% -0.0030%, N: 0.0020% -0.0080%, B: 0.0002 to 0.0030 percent, 0.001 to 0.010 percent of Ce, an atmospheric corrosion resistance index I larger than 6.5, CEV less than or equal to 0.54, Pcm less than or equal to 0.27, and the balance of Fe and inevitable impurities.
The calculation method of the atmospheric corrosion resistance index I is as follows
The thickness of the steel plate product is 60mm-120mm, the yield strength Rp0.2 is more than or equal to 485MPa, the tensile strength Rm is more than or equal to 595MPa, the elongation A after fracture is more than or equal to 20 percent, and the impact absorption energy at 23 ℃ is more than or equal to 120J.
The steel plate adopts chemical components to design low Carbon Equivalent (CEV) and low welding crack sensitivity index (Pcm) so as to improve the welding performance of the steel plate, Cr, Cu, Si, Ni and the like improve the atmospheric corrosion resistance of the steel, and a proper amount of carbon is matched with alloy elements such as V, Ni, Cr, Cu, Mo, B and the like, so that the performance problems such as strength, toughness and the like of the steel plate are solved, Al, Ti, Ce, Ca and the like respectively refine the tissues of different working procedure stages of the steel plate production, improve the form of residual inclusions in the steel, and effectively improve the comprehensive performance of the steel plate by combining extremely low content of harmful elements such as P, S and the like.
The steel plate has the following effects that the steel plate comprises the following elements in percentage by weight:
first, carbon (C)
Carbon increases hardenability of steel, affects bainite morphology after quenching, and increases strength, but precipitates in the form of interstitial atoms or carbides and excessively grows to deteriorate low-temperature toughness and weldability of steel, so that the content of carbon (C) is controlled to 0.03% to 0.10%.
Materials, silicon (Si)
The silicon element remained in the steel can improve the atmospheric corrosion resistance of the steel, but when the content exceeds 0.5 percent, the cleanliness of the steel is reduced, the ductile-brittle transition temperature of the steel can be obviously improved, the plasticity is also deteriorated, and the scale is easily increased on the surface during heating and is not easy to remove. Therefore, the appropriate amount of Si is controlled to 0.30% to 0.50%.
-manganese (Mn)
The Mn-free austenite continuous casting strengthening and toughening agent is an important strengthening and toughening element in steel, can reduce the phase transition temperature of the steel, lower critical point (reducing critical transition temperature Ar3) of the steel, improve hardenability, increase the supercooling degree of austenite cooling, improve the low-temperature toughness of the steel, and has low cost compared with other alloys, but the Mn-free austenite continuous casting strengthening and toughening agent can increase the continuous casting segregation tendency of the steel when the Mn-free austenite continuous casting strengthening and toughening agent has over high content, so that the Mn content adopted by the invention is 1.10-1.50%.
Fourth, phosphorus (P)
The corrosion resistance of the steel can be improved, but the steel belongs to low-temperature brittle elements, is extremely harmful to low-temperature toughness, is also an element easy to segregate, remarkably enlarges a two-phase region between a liquid phase and a solid phase, segregates among crystal grains in the solidification process of the steel to form a high-phosphorus brittle layer, causes the local serious segregation of the steel, can reduce the plasticity and the toughness of the steel, and causes the steel to be easy to generate brittle cracks.
Fifthly, sulfur (S)
Is a harmful element in steel, is easy to be segregated and aggregated in the center when existing in the steel in the form of MnS, and seriously influences the toughness and plasticity of the steel. Thus minimizing the content thereof.
Sixthly, chromium (Cr)
Is one of the most main elements for improving the atmospheric corrosion resistance of the steel, simultaneously improves the hardenability of the steel, improves the toughness and the plasticity of the quenched and tempered steel, improves the tensile strength (Rm) of the steel, and slightly improves the plasticity of the steel. If the content is too high, precipitation of carbide is likely to occur, which affects the toughness of steel and deteriorates weldability, and secondary hardening may occur during tempering after quenching. Therefore, chromium (Cr) is controlled to
Barn, copper (Cu)
Is one of the most important elements for improving the atmospheric corrosion resistance of the steel. Cu is an element that expands the austenite phase region, improves the hardenability of steel, and acts as a solid solution and precipitation strengthening effect in steel, thereby improving the strength of steel. In addition, Cu is beneficial to obtaining good low-temperature toughness. However, if the content is too high, hot embrittlement is likely to occur during heating or hot rolling of the slab, and the surface properties of the slab are deteriorated. The copper (Cu) content of the invention is controlled to be 0.25-0.40%.
And, nickel (Ni)
On one hand, Ni always keeps the toughness of iron at a very high level, so that the brittle transition temperature of the iron is very low, the crystal grains of steel can be refined, and the low-temperature toughness of the steel is improved; on the other hand, the strength of the steel can be improved by forming a simple substitutional solid solution to strengthen the ferrite. In addition, Ni can effectively prevent the network fracture caused by Cu hot brittleness. The copper (Cu) of the invention is controlled to be 0.30-0.40%.
Self-supporting, Aluminium (AL)
Al is a strong deoxidizing element, and is finally deoxidized after Si is deoxidized, so that the content of oxygen and oxide impurities in steel is reduced, and the comprehensive performance of the steel is improved; certain residual aluminum in the steel has the function of inhibiting austenite grains from coarsening in the heating process. Generally, the content of acid-soluble Aluminum (ALs) is controlled to be more than 0.015%, and the content of total aluminum (ALt) is controlled to be more than 0.020%.
Titanium (Ti) to make things stand alone
The steel plate is a strong carbonitride forming element, and trace Ti can form fine titanium carbide and nitride particles, effectively pin austenite grain boundaries, inhibit coarsening of austenite grains, prevent grain growth in the heating process and improve the toughness of the steel plate. In addition, the Ti compound which is highly dispersed in the steel plate can prevent crystal grains from growing in the welding process and improve the toughness of a welding heat affected zone.
Vanadium (V)
V has strong precipitation strengthening effect, the carbonitride of V can be used as an effective core position to promote the nucleation of intragranular ferrite to achieve the effect of refining grains, and the V has obvious strengthening and toughening effects in low-carbon bainite steel. The hardenability of steel is increased when a solid solution is dissolved at a high temperature, and at the same time, V increases the tempering stability of quenched steel, so that V can increase the strength and yield ratio in quenched and tempered steel. Comprehensively, the proper amount of V is controlled to be 0.040-0.080%.
Water pump, molybdenum (Mo)
The method can shift the C curve of the steel phase transformation to the right, obviously improve the hardenability and the hardenability of the steel, especially improve the tempering stability of the steel, is beneficial to obtaining a tempered sorbite with fine grains after quenching and tempering, and improves the obdurability of the steel plate.
Selection, calcium (Ca)
Firstly, Ca is an extremely strong deoxidizing element and is beneficial to deep deoxidation of molten steel; secondly, Ca can change the properties of deoxidation and desulfurization products, so that the impurities are reduced on one hand, and the harmful effects of the impurities remained in the steel are improved on the other hand; in addition, the compound of Ca remaining in the steel can also improve the weldability of the steel. Ca is controlled to be 0.0010 to 0.0030 percent.
By the generation of hydrogen and nitrogen (N)
N is combined with elements such as V, Ti to exert its effect of refining the structure. But N can act as quench aging and strain aging of the steel. The invention limits the content of N to 0.0020-0.0080%.
Quick response of boron (B)
B can remarkably improve the hardenability of the steel plate, and improve the hardenability and the hardenability so as to improve the strength and the hardness, but the B is deviated in a grain boundary and can influence the toughness of the steel plate. The content of B is controlled to be 0.0002% -0.0030%.
Cerium (Ce) in the water/oil
Can improve the form of residual inclusions in the steel. In the steel with lower carbon content, the transformation point of the steel is influenced, the transformation from austenite to bainite is slowed down, the hardenability of the steel is improved, and the structure can be refined. The carbide precipitation part can be changed from grain boundary and intragranular distribution to intragranular distribution, the carbide is refined, the aggregation and coarsening of the carbide phase are inhibited, and the strength and the toughness of the steel are improved.
The invention also aims to provide a manufacturing method of the steel plate, which comprises the following specific steps
(1) After the molten iron is pretreated by KR, firstly, carrying out primary smelting in a BOF top-bottom secondary blowing converter, controlling the [ P ] of the molten steel to be less than or equal to 0.005% and the [ C ] to be less than or equal to 0.05%, and then tapping to a ladle; then, an LF refining process is carried out, white slag is produced in the LF refining process, the total consumption of a refining agent is not less than 18kg/t steel, aluminum wires are fed for precipitation and deoxidation, the content of molten steel [ AL ] in the whole process is controlled to be more than 0.010%, and low-carbon alloy is used for fine adjustment of components, so that the components of each target element reach target values; after the temperature reaches 1600-1680 ℃, the process enters an RH vacuum treatment process, the treatment time under the condition of high vacuum degree of less than 130Pa is not less than 20min, the Ca of the molten steel is treated before and after the vacuum treatment, the final Ca content of the molten steel is ensured to reach 0.0010-0.0030 percent, and the molten steel is cast into a continuous casting slab on a continuous casting machine with the thickness of 370-450 mm after the vacuum treatment.
(2) Heating the continuous casting slab to 1180-1280 ℃ in a stepping continuous heating furnace, preserving heat for 50-120 min in a soaking section to ensure that the core part of the continuous casting slab also reaches 1180-1280 ℃, taking the continuous casting slab out of the heating furnace, removing surface iron scales by high-pressure water descaling, immediately performing primary rolling on the slab to 1.6-2.4 times of the thickness of a finished product, then performing finish rolling to the thickness of the finished product, controlling the start rolling temperature of the finish rolling to be 780-880 ℃, controlling the finish rolling temperature to be below 800 ℃, cooling the rolled steel plate to 500-650 ℃ by ACC water, and then slowly cooling to the normal temperature.
(3) The bainite structure is obtained through quenching and tempering heat treatment, and the steel plate with qualified performance is produced.
Further, in order to obtain a steel sheet with acceptable properties, the quenching and tempering heat treatment in the step (3) is quenching and tempering.
When quenching, the steel plate is heated to 900-950 ℃, the heat preservation time is 0.3-1.0 min/mm, austenitization and solid solution of alloy elements are fully carried out, the steel plate is taken out of the heating furnace and immediately enters a continuous rolling type quenching machine for quenching after the heat preservation time is reached, the running speed of a roller way of the quenching machine is 0.8-3.5 m/min, and the cooling speed is enabled to reach more than 12 ℃/s.
During tempering, the steel plate is heated in a continuous tempering furnace to the tempering temperature of 590-650 ℃, the heat preservation time is 2.5-4.5 min/mm, and then the steel plate is taken out of the heating furnace and naturally cooled to the normal temperature.
Compared with the prior art, the invention has the advantages that: the steel plate has the advantages that the chemical composition design of the steel plate adopts low C, low Carbon Equivalent (CEV) and low welding crack sensitivity index (Pcm) to improve the welding performance of the steel plate; cr, Cu, Si, Ni and the like guarantee the atmospheric corrosion resistance of the steel; si and Al are jointly deoxidized in the LF refining process, so that high purity of the molten steel is realized; the content of Si and Al in the molten steel, the slag amount and the slag condition of the molten steel surface are controlled before RH vacuum treatment, the molten steel is further purified under the condition of high vacuum, the Ca treatment of the molten steel in the RH vacuum treatment process changes the form of inclusions in the molten steel, the inclusion content in the steel is extremely low, the type and the form are controllable, and the adverse effect of the inclusions on the plasticity and the toughness of the final steel plate is reduced to the maximum extent; in the solidification process of the continuous casting billet, Al, Ti and V selectivity is combined with C, N, N is fixed, combination of B is avoided, large-particle TiN inclusions are avoided, a finely dispersed C, N compound is formed, conditions are created for heating, controlled rolling and subsequent precipitation strengthening, the low C content is combined with proper Mn, V, Cr and Mo content, the segregation degree of the continuous casting billet is reduced, and a good foundation is laid for the performance uniformity of different positions of the thickness of a steel plate; in the continuous casting billet heating process before rolling, C, N compounds of V, Ti effectively pin austenite crystal boundaries, inhibit coarsening of austenite crystal grains, heat fully and avoid the growth of the austenite crystal grains, and lay a foundation for good performance of a steel plate; the rolling procedure combines the elements V, Cr and Ce with the controlled rolling process and the controlled cooling process except the forming and ensuring the good appearance, size and surface quality of the steel plate, and fully plays the role of refining the original microstructure of the steel plate; cr and Mo strongly influence a CCT curve of a steel plate, so that a bainite transformation curve and a pearlite transformation curve are separated, V, Cr, Ni, Cu, Mo, Ce and B improve the hardenability and hardenability of the steel plate in a steel plate heating process before quenching, improve the stability of austenite, and ensure that the ideal bainite tissue form is obtained by quenching; mo improves the tempering stability of the steel plate, controls carbide precipitation by combining the action of Ce, ensures that the tempered steel plate reaches an ideal microstructure, and finally obtains the steel plate with special performance, the steel plate has high strength, high toughness and atmospheric corrosion resistance, and the thickness of the steel plate reaches 60-120 mm. Can be widely used for manufacturing steel structures such as large bridges and the like.
The production process of the steel plate comprises but is not limited to quenching and tempering, the steel plate is directly quenched on line by using the residual heat after being rolled, the related functions of the chemical elements of the steel plate are also exerted, and the basic principle of quenching of the steel plate is exerted, so the steel plate is produced by the method of directly quenching on line by using the residual heat after being rolled and then tempering, and the method is included in the application.
Drawings
FIG. 1 shows a 60mm yield strength (Rp0.2)485MPa thick steel plate metallographic structure;
FIG. 2 shows a metallographic structure of a 485MPa thick steel plate with 101mm yield strength (Rp0.2);
FIG. 3 shows the metallographic structure of a 120mm thick steel plate with yield strength (Rp0.2) of 485 MPa.
Detailed Description
The invention is described in further detail below with reference to the accompanying examples.
Example one
The steel plate of this example had a thickness of 60 mm. The alloy is prepared by smelting the following components in percentage by mass: c: 0.05%, Si: 0.38%, Mn: 1.36%, P: 0.010%, S: 0.0018%, Cr 0.59%, Cu 0.32%, Ni: 0.34%, Alt: 0.039%, Ti: 0.009%, V: 0.055%, Mo: 0.03%, Ca: 0.0010, N: 0.0031%, B: 0.0005%, Ce: 0.006%, weather resistance index I:6.8, CEV:0.46, Pcm:0.19, and the balance Fe and unavoidable impurities.
The production method of the 485 MPa-grade thick steel plate with the yield strength (Rp0.2) comprises the following steps:
firstly, after molten iron is pretreated by KR, firstly, primary smelting is carried out in a 150t BOF top-bottom combined blowing converter, and molten steel [ P ] is controlled: 0.005%, [ C ]: tapping after 0.03 percent to a ladle; the LF refining process produces white slag, the total consumption of a refining agent is 19kg/t steel, the content of molten steel [ AL ] in the whole process is 0.010-0.039%, low-carbon alloy fine adjustment components are used, after the temperature is 1650 ℃, the RH vacuum treatment process is carried out, the treatment time of high vacuum degree of less than 130Pa is 20min, the molten steel Ca treatment before and after the vacuum treatment is carried out, finally, the content of the molten steel Ca is 0.0010%, and the molten steel Ca is cast into a continuous casting slab on a continuous casting machine with the thickness of 370mm after the vacuum treatment.
And secondly, heating the continuous casting slab to 1260 ℃ in a stepping continuous heating furnace, soaking and preserving heat for 70min to ensure that the core part of the continuous casting slab also reaches 1260 ℃, taking the continuous casting slab out of the heating furnace, removing surface iron oxide scales through a high-pressure water descaling box, immediately performing primary rolling on a 4300mm thick plate rolling mill to 140mm, then performing rolling on a 4300mm finishing mill to 60mm, performing finish rolling at the initial rolling temperature of 880 ℃ and the final rolling temperature of 840 ℃, performing ACC water cooling on the rolled steel plate to 610 ℃, and then slowly cooling to normal temperature.
And thirdly, heating the steel plate to 920 ℃ in a continuous heating furnace, keeping the temperature for 0.4min/mm, heating to ensure full austenitizing and solid solution of alloy elements, taking the steel plate out of the heating furnace after reaching the temperature keeping time, immediately quenching the steel plate in a continuous rolling type quenching machine, wherein the running speed of a roller way of the quenching machine is 3.2m/min, and the cooling speed reaches 15 ℃/s. Then tempering is carried out in a continuous tempering furnace at the tempering temperature of 640 ℃ for 3.5min/mm, and then the product is taken out of the heating furnace and naturally cooled to the normal temperature.
The performance of a 485 MPa-grade bridge steel plate with yield strength (Rp0.2) of the first embodiment is as follows:
60mm yield strength (Rp0.2)485MPa grade thick steel plate performance
Example a microstructure referring to fig. 1, it can be seen that the steel plate has a fine and uniform grain size, matching strength and toughness.
Example two
The steel sheet of this example had a thickness of 101 mm. The alloy is prepared by smelting the following components in percentage by mass: c: 0.08%, Si: 0.47%, Mn: 1.45%, P: 0.006%, S: 0.0011%, Cr 0.66%, Cu 0.35%, Ni: 0.36%, Alt: 0.051%, Ti: 0.016%, V0.059%, Mo: 0.05%, Ca: 0.0012, N: 0.0028%, B: 0.0008 percent of Ce, 0.009 percent of Ce, 7.1 percent of weather resistance index I, 0.52 percent of CEV, 0.24 percent of Pcm, and the balance of Fe and inevitable impurities.
The production method of the 485 MPa-grade thick steel plate with the yield strength (Rp0.2) comprises the following steps:
firstly, after molten iron is pretreated by KR, firstly, primary smelting is carried out in a 150t BOF top-bottom combined blowing converter, and molten steel [ P ] is controlled: 0.004%, [ C ]: tapping after 0.03 percent to a ladle; the LF refining process produces white slag, the total consumption of the refining agent is 21kg/t steel, the content of the molten steel [ AL ] in the whole process is 0.012% -0.045%, low-carbon alloy fine adjustment components are used, after the temperature is 1660 ℃, the RH vacuum treatment process is carried out, the treatment time of the high vacuum degree of less than 130Pa is 25min, the molten steel Ca treatment before and after the vacuum treatment is carried out, finally, the content of the molten steel Ca is 0.0012%, and the molten steel Ca is cast into a continuous casting slab on a continuous casting machine with the thickness of 450mm after the vacuum treatment.
And secondly, heating the continuous casting slab to 1220 ℃ in a stepping continuous heating furnace, soaking and preserving heat for 90min to ensure that the core part of the continuous casting slab also reaches 1220 ℃, taking the continuous casting slab out of the heating furnace, removing surface iron oxide scales through a high-pressure water descaling box, immediately performing primary rolling on a 4300mm thick plate rolling mill to 200mm, then performing rolling on a 4300mm finishing mill to 101mm, performing finish rolling at the initial rolling temperature of 830 ℃ and the final rolling temperature of 800 ℃, performing ACC water cooling on the rolled steel plate to 580 ℃, and then slowly cooling to normal temperature.
And thirdly, heating the steel plate to 930 ℃ in a continuous heating furnace, keeping the temperature for 0.6min/mm, heating to ensure full austenitizing and solid solution of alloy elements, taking the steel plate out of the heating furnace after reaching the temperature keeping time, immediately quenching the steel plate in a continuous rolling type quenching machine, wherein the running speed of a roller way of the quenching machine is 1.2m/min, and the cooling speed reaches 16 ℃/s. Then tempering is carried out in a continuous tempering furnace at the tempering temperature of 610 ℃ for 4.0min/mm, and then the product is taken out of the heating furnace and naturally cooled to the normal temperature.
The performance of the 485 MPa-grade bridge steel plate with the second yield strength (Rp0.2) of the embodiment is as follows:
performance of 485MPa grade thick steel plate with 101mm yield strength (Rp0.2)
Example two microstructure referring to fig. 2, it can be seen that the grains in the steel plate structure are fine and uniform.
EXAMPLE III
The thickness of the steel sheet of this example was 120 mm. The alloy is prepared by smelting the following components in percentage by mass: c: 0.07%, Si: 0.50%, Mn: 1.46%, P: 0.005%, S: 0.0013%, Cr 0.69%, Cu 0.37%, Ni: 0.39%, Alt: 0.049%, Ti: 0.017%, V: 0.065%, Mo: 0.06%, Ca: 0.0014, N: 0.0032%, B: 0.0009 percent of Ce, 0.008 percent of atmospheric corrosion resistance index I, 7.2 percent of CEV, 0.53 percent of Pcm, 0.23 percent of Pcm, and the balance of Fe and inevitable impurities.
The production method of the 485 MPa-grade thick steel plate with the yield strength (Rp0.2) comprises the following steps:
firstly, after molten iron is pretreated by KR, firstly, primary smelting is carried out in a 150t BOF top-bottom combined blowing converter, and molten steel [ P ] is controlled: 0.003%, [ C ]: tapping after 0.03 percent to a ladle; the LF refining process produces white slag, the total consumption of a refining agent is 23kg/t steel, the content of molten steel [ AL ] in the whole process is 0.015-0.049%, low-carbon alloy fine adjustment components are used, after the temperature is 1667 ℃, the RH vacuum treatment process is carried out, the treatment time of high vacuum degree of less than 130Pa is 25min, the molten steel Ca treatment before and after the vacuum treatment is carried out, finally, the content of the molten steel Ca is 0.0014%, and after the vacuum treatment, the continuous casting slab is cast on a continuous casting machine with the thickness of 450 mm.
And secondly, heating the continuous casting slab to 1230 ℃ in a stepping continuous heating furnace, soaking and preserving heat for 106min to ensure that the core part of the continuous casting slab also reaches 1230 ℃, taking the continuous casting slab out of the heating furnace, removing surface iron oxide scales through a high-pressure water descaling box, immediately performing primary rolling on a 4300mm thick plate rolling mill to 230mm, then performing rolling on a 4300mm finishing mill to 120mm, performing finish rolling at the initial rolling temperature of 810 ℃ and the final rolling temperature of 800 ℃, performing ACC water cooling on the rolled steel plate to 590 ℃, and then slowly cooling to normal temperature.
And thirdly, heating the steel plate to 930 ℃ in a continuous heating furnace, keeping the temperature for 0.8min/mm, heating to ensure full austenitizing and solid solution of alloy elements, taking the steel plate out of the heating furnace after reaching the temperature keeping time, immediately quenching the steel plate in a continuous rolling type quenching machine, wherein the running speed of a roller way of the quenching machine is 1.0m/min, and the cooling speed reaches 18 ℃/s. Then tempering is carried out in a continuous tempering furnace at the tempering temperature of 610 ℃ for 4.0min/mm, and then the product is taken out of the heating furnace and naturally cooled to the normal temperature.
The performance of the 485 MPa-grade bridge steel plate with the yield strength (Rp0.2) in the embodiment is as follows:
120mm yield strength (Rp0.2)485MPa grade thick steel plate performance
The microstructure of the third embodiment is shown in fig. 3, and the microstructure is bainite and has fine and uniform grains, which is the same as the microstructure of the first and second embodiments.
Claims (6)
1. A manufacturing method of a high-strength, high-toughness and atmospheric corrosion resistant steel plate for manufacturing a steel structure is characterized by comprising the following steps of: the steps are as follows
(1) The molten steel is subjected to converter primary smelting, LF refining, RH vacuum refining and slab continuous casting to produce continuous casting billets;
(2) performing controlled rolling and controlled cooling on the continuous casting billet to obtain a slab;
(3) performing quenching and tempering heat treatment to obtain a bainite structure, and producing a steel plate with qualified performance;
in the step (1), after the molten iron is pretreated by KR, firstly, primary smelting is carried out in a BOF top-bottom secondary blowing converter, and after the [ P ] of the molten steel is controlled to be less than or equal to 0.005% and the [ C ] of the molten steel is controlled to be less than or equal to 0.05%, tapping is carried out to a ladle; then, an LF refining process is carried out, white slag is produced in the LF refining process, the total consumption of a refining agent is not less than 18kg/t steel, aluminum wires are fed for precipitation and deoxidation, the content of molten steel [ AL ] in the whole process is controlled to be more than 0.010%, and the components of each target element are finely adjusted by using low-carbon alloy so as to reach target values; after the temperature reaches 1600-1680 ℃, an RH vacuum treatment process is carried out, the treatment time under the condition of high vacuum degree of less than 130Pa is not less than 20min, the Ca of the molten steel is treated before and after the vacuum treatment, the final Ca content of the molten steel is ensured to reach 0.0010-0.0030 percent, and the molten steel is cast into a continuous casting slab on a continuous casting machine with the thickness of 370-450 mm after the vacuum treatment;
in the step (2), the continuous casting slab is heated to 1180-1280 ℃, the soaking section is insulated for 50-120 min, the core part of the continuous casting slab also reaches 1180-1280 ℃, the continuous casting slab is taken out of a heating furnace, the surface iron scale is removed by high-pressure water descaling, the slab is immediately and initially rolled to 1.6-2.4 times of the thickness of the finished product, then the precision rolling is carried out to the thickness of the finished product, the precision rolling starting temperature is controlled to be 780-880 ℃, the final rolling temperature is below 800 ℃, the rolled steel plate is cooled to 500-650 ℃ by ACC water, and then the steel plate is slowly cooled to the normal temperature;
the steel comprises the following elements in percentage by mass: c: 0.03% -0.10%, Si: 0.30-0.50%, Mn: 1.10 to 1.50 percent of Cu, less than or equal to 0.010 percent of P, less than or equal to 0.003 percent of S, 0.45 to 0.70 percent of Cr, Cu: 0.25% -0.40%, Ni: 0.30% -0.40%, Alt: not less than 0.030%, Ti: 0.006% -0.030%, V: 0.040% -0.080%, Mo: 0.02% -0.08%, Ca: 0.0010% -0.0030%, N: 0.0020% -0.0080%, B: 0.0002 to 0.0030 percent of Ce, 0.001 to 0.010 percent of Ce, and meeting the requirements of the atmospheric corrosion resistance index I being more than 6.5, the carbon equivalent CEV being less than or equal to 0.54, the Pcm being less than or equal to 0.27, and the balance being Fe and inevitable impurities.
2. The method for manufacturing a high-strength, high-toughness, weather-resistant steel sheet for steel structural fabrication according to claim 1, wherein: and (3) quenching and tempering heat treatment, namely quenching and tempering.
3. The method for manufacturing a high-strength, high-toughness, weather-resistant steel sheet for steel structural fabrication according to claim 2, wherein: when quenching, the steel plate is heated to 900-950 ℃, the heat preservation time is 0.3-1.0 min/mm, austenitization and solid solution of alloy elements are fully carried out, the steel plate is taken out of the heating furnace and immediately enters a continuous rolling type quenching machine for quenching after the heat preservation time is reached, the running speed of a roller way of the quenching machine is 0.8-3.5 m/min, and the cooling speed is enabled to reach more than 12 ℃/s.
4. The method for manufacturing a high-strength, high-toughness, weather-resistant steel sheet for steel structural fabrication according to claim 2, wherein: when in tempering, the tempering temperature is set to be 590-650 ℃, the heat preservation time is 2.5-4.5 min/mm, and then the product is taken out of the heating furnace and naturally cooled to the normal temperature.
5. The method for manufacturing a high-strength, high-toughness, weather-resistant steel sheet for steel structural fabrication according to claim 1, wherein: the calculation method of the atmospheric corrosion resistance index I is as follows
I＝26.01×(％Cu)+3.88×(％Ni)+1.20×(％Cr)+1.49×(％Si)+17.28×(％P)-7.29×(％Cu)×(％Ni)-9.10×(％Ni)×(％P)-33.39×(％Cu)2。
6. The method for manufacturing a high-strength, high-toughness, weather-resistant steel sheet for steel structural fabrication according to claim 1, wherein: the thickness of the steel plate is 60mm-120mm, the yield strength Rp0.2 is more than or equal to 485MPa, the tensile strength Rm is more than or equal to 595MPa, the elongation A after fracture is more than or equal to 20 percent, and the impact absorption energy at the temperature of-23 ℃ is more than or equal to 120J.
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