CN116791009B - Large-thickness steel plate suitable for ultra-large heat input welding and production method thereof - Google Patents
Large-thickness steel plate suitable for ultra-large heat input welding and production method thereof Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 158
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- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 19
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Abstract
The application discloses a large-thickness steel plate suitable for ultra-large heat input welding and a production method thereof, wherein in the steel plate, C0.06-0.11%, si 0.15-0.35%, mn 1.4-1.8%, cr 0.1-0.5%, ni 0.3-0.8%, P < 0.015%, S < 0.015%, ti 0.02-0.05%, ti+Zr 0.025-0.15% and the balance of iron and impurities; the production method comprises the steps of molten steel smelting, continuous casting, heating, two-stage controlled rolling into a steel plate with the thickness of 80-120 mm, controlled cooling and finished product; feeding at least 800m Zr-containing cored wire at a speed of 4-5 m/s after the RH refining is broken; the final rolling temperature of the recrystallization zone rolling is 950-1050 ℃, the total rolling reduction is more than or equal to 43%, and the average rolling reduction per pass is more than or equal to 45mm; the cooling speed of the cooling procedure is controlled to be more than or equal to 15 ℃/s.
Description
Technical Field
The application belongs to the technical field of ferrous metallurgy, and relates to a production method of a large-thickness steel plate suitable for ultra-large heat input welding and the large-thickness steel plate prepared by the production method and suitable for ultra-large heat input welding.
Background
With the advent of transportation trunks and container terminal ports and the high-speed development of shipping technology, ships are continuously developed towards the direction of upsizing, container ships have been developed from generation 1 to generation 6, and the carrying capacity is increased to 7 times that of the former, with the vigorous demand for large-thickness steel plates (namely, steel plates with the thickness of more than or equal to 80 mm), but with the great increase of the thickness of steel plates for ships, the production difficulty of the large-thickness steel plates is also continuously increased, and the welding efficiency of the large-thickness steel plates is low, so that the problems of low production efficiency and high production cost of large ships are easily caused.
In order to improve the thickness of a steel plate in the steel industry, steel ingots are generally adopted for forging or rolling and cogging, and then are heated and rolled into a steel plate with large thickness, however, the metallurgical quality of the steel ingots is poor, the performance of the rolled steel plate cannot meet the high requirements of the steel plate for ships, and therefore the performance of the steel plate is generally improved through a heat treatment process after being rolled into the steel plate, so that the production flow is long and the preparation difficulty is high.
Disclosure of Invention
The application aims to provide a production method of a low yield ratio steel plate suitable for large heat input welding and the low yield ratio steel plate prepared by the production method and suitable for large heat input welding, so as to solve the problems that the preparation of a large-thickness steel plate is difficult and the welding efficiency is low.
In order to achieve the above object, an embodiment of the present application provides a method for producing a large-thickness steel sheet suitable for ultra-large heat input welding, the steel sheet comprising the chemical components by mass: 0.06-0.11% of C, 0.15-0.35% of Si, 1.4-1.8% of Mn, 0.1-0.5% of Cr, 0.3-0.8% of Ni, less than 0.015% of P, less than 0.015% of S, 0.02-0.05% of Ti, 0.025-0.15% of Ti+Zr, and the balance of iron and unavoidable impurities;
the production method comprises the following steps:
(1) Molten iron desulfurization, converter smelting, LF refining and RH vacuum refining are adopted to carry out molten steel smelting, and the finally obtained molten steel is controlled to be less than 0.015 percent by mass percent of P and less than 0.015 percent by mass percent of S, wherein in the RH refining process, vacuum degassing and inclusion removal treatment are completed, air breaking is carried out, and Zr-containing cored wires with the thickness of at least 800m are fed at the speed of 4-5 m/S;
(2) Continuously casting the molten steel obtained in the step (1) into a continuous casting blank;
(3) Heating the continuous casting blanks in a heating furnace at 1050-1150 ℃ for more than or equal to 320min;
(4) Sequentially carrying out recrystallization zone rolling and non-recrystallization zone rolling on the heated continuous casting billet, wherein the final rolling temperature of the recrystallization zone rolling is 950-1050 ℃, the total reduction is more than or equal to 43%, and the average reduction of each pass is more than or equal to 45mm; the intermediate blank obtained by rolling in the recrystallization zone is heated to below 800 ℃, and then rolling in the non-recrystallization zone is carried out to obtain a steel plate with the thickness of 80-120 mm;
(5) Conveying the rolled steel plate to accelerated cooling equipment at a speed of 1-2 m/s for cooling, wherein the cooling speed is more than or equal to 15 ℃/s, and the final cooling temperature is less than or equal to 500 ℃;
(6) Straightening, stacking, slow cooling, cutting and finishing the steel plate obtained in the step (5) to obtain a steel plate finished product.
As a further improvement of the embodiment of the application, the thickness of the steel belt containing the Zr cored wire is 0.7-0.8 mm, and the size of the Zr alloy particles in the Zr cored wire is 0.5-2 mm.
As a further improvement of an embodiment of the present application, the surface density of the Ti-containing oxide and Zr-containing oxide in the steel sheet>800 pieces/mm 2 。
As a further improvement of an embodiment of the application, a top-bottom combined blowing process is adopted in the converter smelting process, alloy and slag materials are added into molten steel according to the sequence of ferrosilicon, manganese metal and lime, the target alkalinity of slag is 3.5, and the pressure of argon bottom blowing of a ladle during tapping is 0.5-0.6 MPa.
As a further improvement of an embodiment of the application, argon is blown in the whole process of the LF refining process; when slag and alloy are added, controlling the pressure of argon bottom-blown into the ladle to be 0.6-0.7 MPa; the pressure of argon bottom blowing of the ladle during heating is 0.5MPa.
As a further improvement of an embodiment of the application, in the RH vacuum refining process, RH circulation degassing equipment is adopted to carry out vacuum degassing and inclusion removal treatment, after Zr-containing cored wires are fed, soft stirring is carried out, the soft stirring time is controlled to be more than or equal to 8min, and carbonized rice hulls are added into a ladle before tapping for heat preservation.
As a further improvement of an embodiment of the application, in the step (2), the casting temperature is controlled to 1510-1580 ℃ during continuous casting, the pulling speed is controlled to 1.0-1.3 m/min, the continuous casting process adopts a large ladle long nozzle, an argon seal, an alkaline tundish covering agent and a submerged nozzle for full-protection casting, the immersion depth of the submerged nozzle is 120-180 mm, and the liquid level fluctuation of a crystallizer is controlled to be within +/-2 mm.
In order to achieve the above object, an embodiment of the present application further provides a large-thickness steel sheet suitable for ultra-large heat input welding, which is manufactured by the manufacturing method as described above.
As a further improvement of one embodiment of the application, the structure of the steel plate is a multiphase structure of acicular ferrite, polygonal ferrite and pearlite, wherein the content of the acicular ferrite is more than or equal to 80 percent.
As a further improvement of the embodiment of the application, the yield strength of the steel plate is more than or equal to 450MPa, the tensile strength is 560-600 MPa, and the elongation is more than or equal to 25%; the tensile strength of a welding heat affected zone formed by welding under the condition that the heat input is more than or equal to 600kJ/cm is more than or equal to 550MPa, and the impact energy at minus 40 ℃ is more than or equal to 250J.
Compared with the prior art, the application has the beneficial effects that:
(1) Through the chemical composition design scheme, the addition of Cr can effectively improve the hardenability of the steel plate, and by controlling the content of Cr, a structure taking fine acicular ferrite as a matrix can be formed, so that the welding performance of the steel plate is improved; ni is an effective element for improving strength and low-temperature toughness, and the surface quality of the steel plate can be improved and the cost can be controlled by controlling the content of Ni; ti-containing oxides which are distributed in a tiny and dispersed way can be formed in the steel plate by adding Ti, so that the low-temperature impact toughness of the steel plate is improved; zr is an important element for forming oxide inclusions, and the addition of Zr is beneficial to promoting the multidimensional nucleation of ferrite, dispersing oxide particles and reducing the size of the oxide. Therefore, the chemical composition design scheme of the application can lead the Ti-containing oxide and the Zr-containing oxide to induce and promote ferrite nucleation in the crystal during the welding thermal cycle process of the steel plate, reduce the formation of ferrite or bainite lath of the grain boundary, and further improve the low-temperature impact toughness of the welding heat affected zone of the steel plate.
(2) According to the production method, the Cr, ni, ti, zr microalloy is added, and the process means of rolling and cooling control are combined in two stages, so that a structure taking fine acicular ferrite as a matrix can be formed, the strength and the low-temperature impact toughness are improved, a large-thickness steel plate with the thickness of 80mm or more can be prepared by adopting a continuous casting blank, the maximum thickness of the steel plate can even reach 120mm, compared with a steel plate with the metallurgical quality which is inferior to that of a steel plate with the large thickness prepared by adopting a steel ingot of a continuous casting blank, the performance of the steel plate is improved by adopting heat treatment processes such as tempering, normalizing, quenching and tempering, the production process of the large-thickness steel plate with the thickness of 80-120 mm can be realized by adopting the continuous casting blank with the thickness of 320mm, the production period is saved, the production difficulty and the cost are reduced, the ultra-large linear energy with the heat input of more than or equal to 600kJ/cm can be adopted for welding, the welding joint has good welding quality and high welding efficiency, the excellent low-temperature toughness can be suitable for large ships such as container ships and the like, and the ship quality, the manufacturing efficiency and the use safety of the ship are improved. Specifically, the yield strength of the steel plate is more than or equal to 450MPa, the tensile strength is 560-600 MPa, and the elongation is more than or equal to 25%; the tensile strength of a welding heat affected zone formed by welding under the condition that the heat input is more than or equal to 600kJ/cm is more than or equal to 550MPa, and the impact energy at minus 40 ℃ is more than or equal to 250J.
Detailed Description
The technical scheme of the present application will be further described with reference to the specific embodiments, but the scope of the claims is not limited to the description.
An embodiment of the application provides a production method of a large-thickness steel plate suitable for ultra-large heat input welding and the large-thickness steel plate prepared by the production method and suitable for ultra-large heat input welding. The welding method is suitable for ultra-large heat input, namely welding by adopting ultra-large line energy with the heat input more than or equal to 600 kJ/cm. The thickness of the steel sheet is 80 to 120mm in the present embodiment. The steel plate with large thickness, namely the steel plate with the thickness of 80mm or more, is suitable for ultra-large heat input welding, and can be welded by adopting ultra-large line energy with the heat input of more than or equal to 600kJ/cm during welding, so that the steel plate has good welding quality and high welding efficiency, and the welded joint has excellent low-temperature toughness, is suitable for large ships such as container ships and the like, and is beneficial to improving the ship quality, the manufacturing efficiency and the use safety.
Specifically, in the production method, steel smelting is carried out according to a preset chemical composition design scheme, and the obtained molten steel is poured into a continuous casting blank. Thus, the chemical composition of molten steel at the steel smelting end point, the chemical composition of a continuous casting blank and the chemical composition of a finally obtained steel plate all meet the preset chemical composition design scheme. The design scheme of the predetermined chemical composition is that the chemical composition comprises the following components in percentage by mass: 0.06-0.11% of C, 0.15-0.35% of Si, 1.4-1.8% of Mn, 0.1-0.5% of Cr, 0.3-0.8% of Ni, less than 0.015% of P, less than 0.015% of S, 0.02-0.05% of Ti, 0.025-0.15% of Ti+Zr, and the balance of iron and unavoidable impurities.
Through the chemical composition design scheme, the addition of Cr can effectively improve the hardenability of the steel plate, and by controlling the content of Cr, a structure taking fine acicular ferrite as a matrix can be formed, so that the welding performance of the steel plate is improved; ni is an effective element for improving strength and low-temperature toughness, and the surface quality of the steel plate can be improved and the cost can be controlled by controlling the content of Ni; ti-containing oxides which are distributed in a tiny and dispersed way can be formed in the steel plate by adding Ti, so that the low-temperature impact toughness of the steel plate is improved; zr is an important element for forming oxide inclusions, and the addition of Zr is beneficial to promoting the multidimensional nucleation of ferrite, dispersing oxide particles and reducing the size of the oxide. Therefore, the chemical composition design scheme of the application can lead the Ti-containing oxide and the Zr-containing oxide to induce and promote ferrite nucleation in the crystal during the welding thermal cycle process of the steel plate, reduce the formation of ferrite or bainite lath of the grain boundary, and further improve the low-temperature impact toughness of the welding heat affected zone of the steel plate.
In the large-thickness steel plate suitable for ultra-large heat input welding, the surface density of the Ti-containing oxide and the Zr-containing oxide>800 pieces/mm 2 。
In terms of process flow, the production method comprises the following steps of:
(1) Molten steel smelting
Molten steel smelting is carried out by adopting a molten iron desulfurization process, a converter smelting process, an LF refining process and an RH vacuum refining process, and the content of each chemical element in molten steel is regulated and controlled according to the preset chemical composition design scheme in the whole molten steel smelting process, wherein the content of P is controlled to be less than 0.015 percent and S is controlled to be less than 0.015 percent in percentage by mass in the finally obtained molten steel.
In the RH refining process, vacuum degassing and inclusion removal treatment are completed, then air is broken, and Zr-containing cored wires with the thickness of at least 800m are fed at the speed of 4-5 m/s. Zr is an important element for forming oxide inclusion, the addition of Zr is favorable for promoting the multidimensional nucleation of ferrite, and Zr is added in a cored wire mode, so that oxide particles can be dispersed, oxide particles can be thinned, and the size of the oxide is reduced; in this way, in the process of the steel plate undergoing welding thermal cycle, the oxide inclusions can induce the ferrite nucleation in the promotion crystal, thereby reducing the formation of ferrite or bainite lath of the grain boundary, and further improving the low-temperature impact toughness of the welding heat affected zone.
Preferably, the thickness of the steel strip containing the Zr cored wire is 0.7-0.8 mm, the size of the Zr alloy particles in the Zr cored wire is 0.5-2 mm, the melting speed of the Zr cored wire in molten steel can be delayed by controlling the thickness of the steel strip containing the Zr cored wire and the larger Zr alloy particles, the feeding depth of the cored wire into the molten steel is increased, the residence time of the alloy in the molten steel is improved, the burning loss of the upper alloy floating to the molten steel liquid level is reduced, and the yield is improved.
Preferably, the converter smelting process is carried out in a converter, a top-bottom combined blowing process is adopted in the converter smelting process, alloy and slag materials are added into molten steel according to the sequence of ferrosilicon, manganese metal and lime, the target alkalinity of the slag is 3.5, and the pressure of argon bottom blowing of a ladle during tapping is 0.5-0.6 MPa, so that the purity of the molten steel is improved, and impurities are reduced.
Preferably, the LF refining process carries out chemical component adjustment, temperature regulation and inclusion regulation and control on molten steel smelted by a converter, and argon is blown in the whole process of the LF refining process; when slag and alloy are added, controlling the pressure of argon bottom-blown into the ladle to be 0.6-0.7 MPa; the pressure of argon bottom blowing of the ladle during heating is 0.5MPa.
Preferably, in the RH vacuum refining process, RH circulation degassing equipment is adopted for vacuum degassing and inclusion removal treatment, zr-containing cored wires are fed and then are subjected to soft stirring, the soft stirring time is controlled to be more than or equal to 8min, and carbonized rice hulls are added into a steel ladle for heat preservation before tapping, so that the production cost can be reduced, and the environmental pollution is reduced.
More preferably, in the RH vacuum refining process, the vacuum degassing time is more than 10min, and the alloying is followed by a clean cycle treatment, wherein the clean cycle treatment time is more than or equal to 5min.
(2) Continuous casting
And continuously casting the molten steel finally obtained in the molten steel smelting process into a continuous casting blank on a continuous casting machine.
Preferably, the casting temperature in continuous casting is controlled to 1510-1580 ℃, and the pulling speed is controlled to 1.0-1.3 m/min. Thus, the center segregation of the continuous casting blank can be reduced, and internal defects such as internal cracks, shrinkage cavities and the like of the continuous casting blank can be prevented.
Wherein, the thickness of the continuous casting blank is 320mm.
Preferably, the continuous casting process adopts a large ladle long nozzle, an argon seal, an alkaline tundish covering agent and a submerged nozzle for full-protection casting, the immersion depth of the submerged nozzle is 120-180 mm, and the fluctuation of the liquid level of the crystallizer is controlled within +/-2 mm.
(3) Blank heating
And (3) feeding the continuous casting blanks into a heating furnace for heating, wherein the heating temperature is 1050-1150 ℃, and the furnace time of each continuous casting blank is controlled to be more than or equal to 320min, so that the centers of the continuous casting blanks can be fully heated, the structure is optimized, and segregation and defects are reduced.
(4) Two-stage controlled rolling
And rolling the heated continuous casting billet in two stages.
The first stage is rolling in a recrystallization zone, the continuous casting blank is rough-rolled into an intermediate blank with the thickness of 160-180 mm through multiple passes, the final rolling temperature is 950-1050 ℃, the total rolling reduction is more than or equal to 43%, and the average rolling reduction of each pass is more than or equal to 45mm.
The second stage is non-recrystallization zone rolling, after the recrystallization zone rolling is finished but before the recrystallization zone rolling is started, the intermediate blank obtained by the recrystallization zone rolling is heated to below 800 ℃, and then multi-pass non-recrystallization zone rolling, namely finish rolling, is carried out, so that the steel plate with the thickness of 80-120 mm is obtained.
On the basis of the chemical composition design scheme, low compression ratio rolling can be realized, a continuous casting billet with the thickness of 320mm is rolled into a steel plate with the thickness of 80-120 mm, rolling is controlled in two stages, rolling is firstly performed in a recrystallization region, and then rolling is performed in a non-recrystallization region, so that austenite grains are fully refined, mechanical property uniformity of the steel plate in the thickness direction is improved through control of rolling temperature and rolling reduction, core quality is improved, and low-temperature impact toughness and tensile strength are improved.
(5) Controlled cooling
And conveying the rolled steel plate to rapid cooling equipment at a speed of 1-2 m/s for cooling, wherein the cooling speed is more than or equal to 15 ℃/s, and the final cooling temperature is less than or equal to 500 ℃. That is, the rolled steel sheet is immediately and rapidly transported to a rapid cooling device through a roller table for rapid cooling. Thus, by combining the two-stage controlled rolling and the controlled cooling process means, the acicular ferrite nucleation rate in the phase transformation process after rolling can be improved, and the acicular ferrite proportion in the structure can be greatly improved, so that the low-temperature impact toughness and the tensile strength are improved.
In the present embodiment, the accelerated cooling equipment adopts ACC rapid cooling equipment.
(6) Finished product
Straightening, stacking, slow cooling, cutting and finishing are carried out on the cooled steel plate, and then a steel plate finished product is obtained.
In summary, the production method of the embodiment adds Cr, ni, ti, zr microalloy through reasonable chemical component design, combines two-stage controlled rolling and controlled cooling process means, can form a structure with fine acicular ferrite as a matrix, improves strength and low-temperature impact toughness, can adopt continuous casting blanks to prepare large-thickness steel plates with the thickness of 80mm or more, and even can reach the maximum thickness of 120mm. Specifically, the areal density of Ti-containing oxide and Zr-containing oxide in the steel sheet>800 pieces/mm 2 The yield strength of the steel plate is more than or equal to 450MPa, the tensile strength is 560-600 MPa, and the elongation is more than or equal to 25%; the tensile strength of a welding heat affected zone formed by welding under the condition that the heat input is more than or equal to 600kJ/cm is more than or equal to 550MPa, and the impact energy at minus 40 ℃ is more than or equal to 250J.
The application also provides a large-thickness steel plate suitable for ultra-large heat input welding, which is prepared by adopting the production method of the large-thickness steel plate suitable for ultra-large heat input welding, wherein the steel plate comprises the following chemical components in percentage by mass: 0.06-0.11% of C, 0.15-0.35% of Si, 1.4-1.8% of Mn, 0.1-0.5% of Cr, 0.3-0.8% of Ni, less than 0.015% of P, less than 0.015% of S, 0.02-0.05% of Ti, 0.025-0.15% of Ti+Zr, and the balance of iron and unavoidable impurities.
Wherein, ti+Zr is 0.025-0.15%, namely the sum of the mass percentages of Ti and Zr is 0.025-0.15%.
Further, the structure of the steel plate with large thickness suitable for ultra-large heat input welding is a multiphase structure of acicular ferrite, polygonal ferrite and pearlite, wherein the content of the acicular ferrite is more than or equal to 80 percent.
Through tests, the yield strength of the large-thickness steel plate suitable for ultra-large heat input welding is more than or equal to 450MPa, the tensile strength is 560-600 MPa, and the elongation is more than or equal to 25%; the tensile strength of a welding heat affected zone formed by welding under the condition that the heat input is more than or equal to 600kJ/cm is more than or equal to 550MPa, and the impact energy at-40 ℃ is more than or equal to 250J, so that the welding heat affected zone has excellent strength, welding performance and low-temperature impact toughness.
In order to make the objects, technical solutions and advantages of one embodiment of the present application more clear, the following further describes the embodiment in combination with examples 1 to 9 according to one embodiment of the present application. It is apparent that embodiments 1-9 described are some, but not all, embodiments of the present application. Other examples based on the foregoing embodiment do not depart from the gist of the present application.
Specifically, examples 1 to 9 each provide a large-thickness steel plate suitable for ultra-large heat input welding, the chemical compositions of which are shown in table 1, wherein P < 0.015%, S < 0.015%, and the balance of Fe and unavoidable impurities.
TABLE 1
The production methods of the respective embodiments are described in detail below.
(1) Molten steel smelting
Molten steel smelting is carried out by adopting a molten iron desulfurization process, a converter smelting process, an LF refining process and an RH vacuum refining process, and the content of each chemical element in molten steel is regulated and controlled according to the chemical composition design scheme preset in table 1 in the whole molten steel smelting process, wherein the content of P is controlled to be less than 0.015 percent and S is controlled to be less than 0.015 percent in the final molten steel.
The converter smelting process is carried out in a converter, a top-bottom combined blowing process is adopted in the converter smelting process, alloy and slag materials are added into molten steel according to the sequence of ferrosilicon, manganese metal and lime, the target alkalinity of slag is 3.5, and the pressure of argon bottom blowing into a steel ladle during tapping is 0.5-0.6 MPa.
In the RH refining process, the vacuum degassing and inclusion removal treatment are completed, then the void is broken, a Zr-containing cored wire is fed into the molten steel, and the size of Zr-containing alloy particles in the Zr-containing cored wire is 0.5-2 mm. The feeding length, feeding speed and steel belt thickness of the Zr-containing cored wire are shown in Table 2.
The LF refining process carries out chemical component adjustment, temperature regulation and inclusion regulation and control on molten steel smelted by a converter, and argon is blown in the whole process of the LF refining process; when slag and alloy are added, controlling the pressure of argon bottom-blown into the ladle to be 0.6-0.7 MPa; the pressure of argon bottom blowing of the ladle during heating is 0.5MPa.
In the RH vacuum refining process, RH circulation degassing equipment is adopted to carry out vacuum degassing and inclusion removal treatment, the vacuum degassing time is more than 10min, clean circulation treatment is carried out after alloying, the clean circulation treatment time is more than or equal to 5min, soft stirring is carried out after Zr-containing cored wires are fed, the soft stirring time is controlled to be more than or equal to 8min, and carbonized rice hulls are added into a ladle before tapping for heat preservation.
TABLE 2
(2) Continuous casting
And (3) continuously casting the molten steel finally obtained in the molten steel smelting step into a continuous casting blank with the thickness of 320mm on a continuous casting machine, wherein the casting temperature during continuous casting is controlled to 1510-1580 ℃, and the pulling speed is controlled to 1.0-1.3 m/min. And in the continuous casting process, a large ladle long nozzle, an argon seal, an alkaline tundish covering agent and a submerged nozzle are adopted for full-protection casting, the immersion depth of the submerged nozzle is 120-180 mm, and the fluctuation of the liquid level of the crystallizer is controlled within +/-2 mm.
(3) Blank heating
And (3) feeding the continuous casting blanks into a heating furnace for heating at 1050-1150 ℃ and controlling the furnace time of each continuous casting blank to be more than or equal to 320min.
(4) Two-stage controlled rolling
And rolling the heated continuous casting billet in two stages.
Wherein, the first stage is the recrystallization zone rolling, the continuous casting blank is rolled into an intermediate blank through multi-pass rough rolling, and the thickness, the finishing temperature, the total reduction ratio and the average reduction per pass of the intermediate blank are shown in table 3.
The second stage is non-recrystallization zone rolling, after the end of the recrystallization zone rolling but before the start of the recrystallization zone rolling, the intermediate billet obtained by the recrystallization zone rolling is heated to below 800 ℃, and then multi-pass non-recrystallization zone rolling, namely finish rolling is carried out, the steel plate is obtained by rolling, and the starting rolling temperature of the finish rolling and the thickness of the steel plate are shown in table 3.
(5) Controlled cooling
The rolled steel plate was conveyed to an ACC quick cooling device for cooling at a final cooling temperature of 500 ℃ or less, and the conveying speed and cooling speed of the steel plate to the ACC quick cooling device were as shown in table 3.
(6) Finished product
Straightening, stacking, slow cooling, cutting and finishing are carried out on the cooled steel plate, and then a steel plate finished product is obtained.
TABLE 3 Table 3
Sampling the steel plate finished products of examples 1-9 according to the same test method, and performing metallographic structure detection, ti-containing oxide and Zr-containing oxide density detection, mechanical property detection and welding performance test, wherein the detection results are as follows:
(1) In terms of structure, when the steel plates are observed by adopting a metallographic microscope, the structures of the steel plates in examples 1-9 are multiphase structures of acicular ferrite, polygonal ferrite and pearlite, and the content of the acicular ferrite is more than or equal to 80%.
(2) The surface densities of the Ti-containing oxide and Zr-containing oxide inclusions obtained by counting the Ti-containing oxide and Zr-containing oxide inclusions in the steel sheet of the above example using a scanning electron microscope are shown in table 4.
(3) In terms of mechanical properties, the mechanical properties of the steel sheets of the above examples were tested with reference to the GB/T228.1-2021 standard. The method comprises the following steps:
the yield strength, tensile strength and elongation of the steel plate were tested by a tensile testing machine, and the test results are shown in table 4;
(4) Welding performance: after the steel sheets of the above examples were welded, the mechanical properties of the weld heat affected zone were tested with reference to GB/T228.1-2021 and GB/T229-2020 standards, wherein the weld heat input amounts are shown in Table 4. The method comprises the following steps:
the tensile strength of the weld heat affected zone was tested using a tensile tester, and the test results are shown in table 4;
the impact tester was used to test the impact energy at-40℃in the weld heat affected zone, and the test results are shown in Table 4.
TABLE 4 Table 4
In summary, the application can prepare a large-thickness steel plate with the thickness of 80mm or more by adopting a continuous casting blank, the maximum thickness of the steel plate can even reach 120mm, compared with the steel ingot with the metallurgical quality which is inferior to that of the continuous casting blank, the application can realize the continuous casting blank with the thickness of 320mm to produce the large-thickness steel plate with the thickness of 80-120 mm without heat treatment procedures such as tempering, normalizing, quenching, tempering and the like, thereby saving procedures, shortening production period, reducing production difficulty and cost, adopting ultra-large linear energy with the heat input of more than or equal to 600kJ/cm for welding, having good welding quality and higher welding efficiency, having excellent low-temperature toughness, being applicable to large ships such as container ships and the like, and being beneficial to improving the quality, the manufacturing efficiency and the use safety of the ships. Specifically, the yield strength of the steel plate is more than or equal to 450MPa, the tensile strength is 560-600 MPa, and the elongation is more than or equal to 25%; the tensile strength of a welding heat affected zone formed by welding under the condition that the heat input is more than or equal to 600kJ/cm is more than or equal to 550MPa, and the impact energy at minus 40 ℃ is more than or equal to 250J.
It should be understood that although the present disclosure describes embodiments, not every embodiment is provided with a separate embodiment, and that this description is for clarity only, and that the skilled artisan should recognize that the embodiments may be combined as appropriate to form other embodiments that will be understood by those skilled in the art.
The above detailed description is merely illustrative of possible embodiments of the present application, which should not be construed as limiting the scope of the application, and all equivalent embodiments or modifications that do not depart from the spirit of the application are intended to be included in the scope of the application.
Claims (8)
1. The production method of the large-thickness steel plate suitable for ultra-large heat input welding is characterized by comprising the following chemical components in percentage by mass: 0.06-0.11% of C, 0.15-0.35% of Si, 1.4-1.8% of Mn, 0.1-0.5% of Cr, 0.3-0.8% of Ni, less than 0.015% of P, less than 0.015% of S, 0.02-0.05% of Ti, 0.025-0.15% of Ti+Zr, and the balance of iron and unavoidable impurities; the yield strength of the steel plate is more than or equal to 450MPa, the tensile strength is 560-600 MPa, and the elongation is more than or equal to 25%; the tensile strength of a welding heat affected zone formed by welding under the condition that the heat input is more than or equal to 600kJ/cm is more than or equal to 550MPa, and the impact energy at minus 40 ℃ is more than or equal to 250J;
the production method comprises the following steps:
(1) Molten iron desulfurization, converter smelting, LF refining and RH vacuum refining are adopted to carry out molten steel smelting, P is controlled to be less than 0.015 percent, S is controlled to be less than 0.015 percent, wherein in the RH refining process, vacuum degassing and inclusion removal treatment are completed, air breaking is carried out, zr-containing cored wires with the thickness of 0.7-0.8 mm are fed at a speed of 4-5 m/S, and Zr-containing alloy particles in the Zr-containing cored wires are 0.5-2 mm;
(2) Continuously casting the molten steel obtained in the step (1) into a continuous casting blank with the thickness of 320 mm;
(3) Heating the continuous casting blanks in a heating furnace at 1050-1150 ℃ for more than or equal to 320min;
(4) Sequentially carrying out recrystallization zone rolling and non-recrystallization zone rolling on the heated continuous casting billet, wherein the final rolling temperature of the recrystallization zone rolling is 950-1050 ℃, the total reduction is more than or equal to 43%, and the average reduction of each pass is more than or equal to 45mm; the intermediate blank obtained by rolling in the recrystallization zone is heated to below 800 ℃, and then rolling in the non-recrystallization zone is carried out to obtain a steel plate with the thickness of 80-120 mm;
(5) Conveying the rolled steel plate to accelerated cooling equipment at a speed of 1-2 m/s for cooling, wherein the cooling speed is more than or equal to 15 ℃/s, and the final cooling temperature is less than or equal to 500 ℃;
(6) Straightening, stacking, slow cooling, cutting and finishing the steel plate obtained in the step (5) to obtain a steel plate finished product.
2. The method for producing a steel sheet of large thickness suitable for ultra-large heat input welding according to claim 1, wherein the steel sheet has an areal density of Ti-containing oxides and Zr-containing oxides>800 pieces/mm 2 。
3. The method for producing the steel plate with the large thickness suitable for the ultra-large heat input welding according to claim 1, wherein the converter smelting process adopts a top-bottom combined blowing process, alloy and slag materials are added into molten steel according to the sequence of ferrosilicon, manganese metal and lime, the target alkalinity of slag is 3.5, and the pressure of argon gas blown from the bottom of a steel ladle during tapping is 0.5-0.6 MPa.
4. The method for producing a large-thickness steel sheet suitable for ultra-large heat input welding according to claim 1, wherein the LF refining process blows argon all the way; when slag and alloy are added, controlling the pressure of argon bottom-blown into the ladle to be 0.6-0.7 MPa; the pressure of argon bottom blowing of the ladle during heating is 0.5MPa.
5. The method for producing a large-thickness steel plate suitable for ultra-large heat input welding according to claim 1, wherein in the RH vacuum refining process, RH circulation degassing equipment is adopted to carry out vacuum degassing and inclusion removal treatment, zr-containing cored wires are fed and then are subjected to soft stirring, the soft stirring time is controlled to be more than or equal to 8min, and carbonized rice hulls are added into a steel ladle before tapping for heat preservation.
6. The production method of the large-thickness steel plate suitable for ultra-large heat input welding according to claim 1, wherein in the step (2), the casting temperature is controlled to 1510-1580 ℃ during continuous casting, the drawing speed is controlled to 1.0-1.3 m/min, full-protection casting is carried out by adopting a large ladle long water gap, an argon seal, an alkaline tundish covering agent and a submerged nozzle during continuous casting, the immersion depth of the submerged nozzle is 120-180 mm, and the fluctuation of the liquid level of a crystallizer is controlled to be within +/-2 mm.
7. A large-thickness steel sheet suitable for ultra-large heat input welding, characterized in that the steel sheet is produced by the production method according to any one of claims 1 to 6.
8. The steel sheet of claim 7, wherein the structure is a multiphase structure of acicular ferrite + polygonal ferrite + pearlite, and wherein the content of acicular ferrite is not less than 80%.
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Address after: 215624 No. 1, Yongxin Road, Jinfeng Town, Zhangjiagang City, Suzhou City, Jiangsu Province Patentee after: Jiangsu Shagang Steel Co.,Ltd. Guo jiahuodiqu after: Zhong Guo Patentee after: Zhangjiagang Rongsheng Special Steel Co.,Ltd. Patentee after: INSTITUTE OF RESEARCH OF IRON & STEEL, JIANGSU PROVINCE/SHA-STEEL, Co.,Ltd. Patentee after: JIANGSU SHAGANG GROUP Co.,Ltd. Address before: 215624 No. 1, Yongxin Road, Jinfeng Town, Zhangjiagang City, Suzhou City, Jiangsu Province Patentee before: ZHANGJIAGANG HONGCHANG STEEL PLATE Co.,Ltd. Guo jiahuodiqu before: Zhong Guo Patentee before: Zhangjiagang Rongsheng Special Steel Co.,Ltd. Patentee before: INSTITUTE OF RESEARCH OF IRON & STEEL, JIANGSU PROVINCE/SHA-STEEL, Co.,Ltd. Patentee before: JIANGSU SHAGANG GROUP Co.,Ltd. |