TMCP type F-grade marine structural steel plate and production process thereof

Abstract

The invention discloses a TMCP type F-grade marine structural steel plate and a production process thereof, and relates to the technical field of steel production, the TMCP type F-grade marine structural steel plate comprises the following chemical components by mass percentage: 0.03-0.08% of C, 0.10-0.40% of Si, 1.35-1.70% of Mn, less than or equal to 0.012% of P, less than or equal to 0.005% of S, 0.01-0.15% of Ni, 0.008-0.020% of Nb, 0.020-0.040% of Al, and the balance Fe and other inevitable impurities. According to the invention, the LF, VD, calcium treatment and soft blowing processes are adopted to reduce endogenous inclusions generated by molten steel, meanwhile, the continuous casting billet is utilized to improve the metal yield and greatly reduce the production cost, in addition, through the reasonable controlled rolling process, the steel plate has good comprehensive performance, and the production cost is greatly reduced compared with that of normalized F-level steel for the ship body structure.

Description

Technical Field

[0001] The invention relates to the technical field of steel production, in particular to a TMCP type F-grade ship structural steel plate and a production process thereof. Background Art

[0002] With the rapid development of my country's international trade, more and more large ships are needed, which has led to the rapid development of the domestic shipbuilding industry. High-strength hull structural steel has been maintained at a high consumption. At present, most of the domestic F-class hull structural steel is delivered in the normalized state, and the steel plates produced by rolling are then subjected to normalizing heat treatment. Since the steel plates delivered in the normalized state need to undergo heat treatment, an additional production process is added, so the production cost is relatively high. Summary of the invention

[0003] The technical problem to be solved by the present invention is to overcome the disadvantages of the prior art and provide a TMCP type F-class ship structural steel plate and a production process thereof.

[0004] In order to solve the above technical problems, the technical solution of the present invention is as follows: A TMCP type F-grade ship structural steel plate, the chemical composition and its mass percentage are: C: 0.03-0.08%, Si: 0.10-0.40%, Mn: 1.35-1.70%, P≤0.012%, S≤0.005%, Ni: 0.01-0.15%, Nb: 0.008-0.020%, Al: 0.020-0.040%, and the rest is Fe and other inevitable impurities.

[0005] As a preferred solution of the TMCP type F-grade ship structural steel plate of the present invention, the structure of the steel plate is ferrite and pearlite.

[0006] As a preferred solution of the TMCP type F-grade marine structural steel plate of the present invention, the yield strength of the steel plate is ≥390MPa, the tensile strength is 540-680MPa, and the V-shaped longitudinal -60°C impact energy is ≥80J.

[0007] As a preferred solution of the TMCP type F-grade ship structural steel plate of the present invention, the thickness of the steel plate is 20 to 40 mm.

[0008] The present invention also provides a production process of TMCP type F-grade ship structural steel plate, which comprises steelmaking, continuous casting and rolling steps in sequence.

[0009] As a preferred embodiment of the production process of the TMCP-type F-class marine structural steel plate of the present invention, in the steelmaking process: the molten steel smelted in the converter is fed into the LF refining furnace for refining. During the LF refining process, argon blowing is in good condition throughout, the total refining time is ≥35 min, the white slag holding time is ≥25 min, and the slag basicity at the end of refining is ≥3.5.

[0010] As a preferred embodiment of the production process of the TMCP-type F-class marine structural steel plate of the present invention, in the steelmaking process: after the LF furnace refining is completed, the molten steel is fed into the VD vacuum furnace for vacuum degassing treatment. The vacuum degree is ≤66.7 Pa, the vacuum holding time is ≥18 min, soft blowing is carried out for 10 - 12 min after vacuum breaking, and at the same time, a calcium wire of 0.8 - 1.0 kg / t of steel is fed for calcium treatment.

[0011] As a preferred embodiment of the production process of the TMCP-type F-class marine structural steel plate of the present invention, in the continuous casting process: electromagnetic stirring and soft reduction technology are used during casting, and the liquid level fluctuation range of the mold is ±3 mm, and the superheat is controlled at 15 - 35 °C.

[0012] As a preferred embodiment of the production process of the TMCP-type F-class marine structural steel plate of the present invention, in the rolling process: the cast slab is heated in a continuous furnace. When the furnace temperature T ≤ 600 °C, the heating rate is ≤200 °C / h; when the furnace temperature is 600 °C < T ≤ 1200 °C, the heating rate is ≤350 °C / h; the highest heating temperature is 1270 °C, the soaking section temperature is 1230 - 1250 °C, and the total heating coefficient is ≥10 min / cm.

[0013] As a preferred embodiment of the production process of the TMCP-type F-class marine structural steel plate of the present invention, in the rolling process: the two-stage controlled rolling process is adopted. The starting rolling temperature in the first stage is 1085 - 1160 °C, the large reduction rolling process is adopted, and the air-cooled thickness is h + 70 mm, where h is the thickness of the finished steel plate. The starting rolling temperature in the second stage is 820 - 750 °C, the finishing rolling temperature is 790 - 730 °C, and the steel plate red-return temperature is 580 - 620 °C.

[0014] The beneficial effects of the present invention are: (1) The chemical composition design of the TMCP-type F-class hull structural steel plate provided by the present invention is reasonable, the internal structure of the steel plate is uniform, the amount of precious metals added is small, the cost is low, and the market competitiveness is strong.

[0015] (2) The present invention adopts the LF, VD, calcium treatment and soft blowing processes to reduce the endogenous inclusions generated in the molten steel. At the same time, the use of continuous casting billets to成材 improves the metal yield rate and greatly reduces the production cost. In addition, through a reasonable controlled rolling process, the steel plate has good comprehensive performance and greatly reduces the production cost compared with the normalized F-class hull structural steel.

[0016] (3) The steel plate produced by the present invention has a uniform and dense internal structure, which is composed of ferrite and pearlite. The strength and toughness of the steel plate produced are well matched, with a yield strength of ≥390MPa, a tensile strength of 540-680MPa, and a V-shaped longitudinal impact energy of -60°C of ≥80J. In addition, the steel plate produced is purer in quality, with a low impurity content of P≤0.012% and S≤0.005%. The thickness specification of the steel plate is 20-40mm, which meets the user's requirements for the performance of steel for hull structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.

[0018] Figure 1 Schematic diagram of the metallographic structure of the TMCP type F-grade marine structural steel plate prepared in Example 1; Figure 2 Schematic diagram of the metallographic structure of the TMCP type F-grade marine structural steel plate prepared in Example 2; Figure 3 Schematic diagram of the metallographic structure of the TMCP type F-grade marine structural steel plate prepared in Example 3 Figure 4 Schematic diagram of the metallographic structure of the TMCP type F-grade marine structural steel plate prepared in Example 4. DETAILED DESCRIPTION

[0019] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific implementation methods.

[0020] Example 1: This example provides a TMCP type F-grade marine structural steel plate, whose chemical composition and mass percentage are: C: 0.03%, Si: 0.10%, Mn: 1.35%, P: 0.010%, S: 0.004%, Ni: 0.02%, Nb: 0.008%, Al: 0.020%, and the rest is Fe and other inevitable impurities.

[0021] The production method of the TMCP type F-grade marine structural steel plate in this embodiment includes steelmaking, continuous casting, and rolling processes, and the specific process steps are as follows: (1) Steelmaking process: The molten steel smelted in the converter is sent to the LF refining furnace for refining. During the LF refining process, argon blowing is good throughout the process. The total refining time is 45 minutes, the white slag holding time is 25 minutes, and the slag basicity is 3.6 at the end of refining. After refining, the molten steel is sent to the VD furnace for vacuum degassing treatment. The vacuum degree is 60Pa and the vacuum holding time is 19 minutes. After the vacuum is broken, soft blowing is performed for 10 minutes to allow inclusions to fully float up. At the same time, 0.8kg / t of calcium wire is fed for calcium treatment to promote the spheroidization and floating of inclusions. (2) Continuous casting process: Using a large-section continuous casting machine, the mold liquid level is automatically controlled with a fluctuation range of ±3mm, the tundish superheat is 16°C, and electromagnetic stirring, light pressure reduction and strong cooling at the end of solidification are used to cast large-section high-quality continuous casting billets; (3) Rolling process: The continuous casting billet is heated in a continuous furnace with a furnace temperature of 550°C and a heating rate of 160°C / h; the maximum heating temperature is 1270°C, the soaking zone temperature is 1230°C, and the total heating coefficient is 11min / cm; A two-stage controlled rolling process is adopted, with the first-stage starting rolling temperature of 1085℃, large reduction rolling, and steel thickness of 100mm; the second-stage starting rolling temperature is 820℃, the final rolling temperature is 790℃, and the red-returning temperature is 590℃.

[0022] The steel plate obtained after cooling has a structure of ferrite and pearlite, a yield strength of 420MPa, a tensile strength of 550MPa, a V-shaped longitudinal -60°C impact energy of 156J, and a thickness of 30mm. The produced F-grade marine steel has excellent comprehensive performance, high strength, good impact toughness and high-temperature tensile properties, uniform structure and stable performance.

[0023] Example 2: This example provides a TMCP type F-grade marine structural steel plate, whose chemical composition and mass percentage are: C: 0.05%, Si: 0.25%, Mn: 1.45%, P: 0.010%, S: 0.005%, Ni: 0.12%, Nb: 0.012%, Al: 0.030%, and the rest is Fe and other unavoidable impurities.

[0024] The production method of the TMCP type F-grade marine structural steel plate in this embodiment includes steelmaking, continuous casting, and rolling processes, and the specific process steps are as follows: (1) Steelmaking process: The molten steel smelted in the primary refining furnace is sent to the LF refining furnace for refining. During the LF refining process, argon blowing is good throughout the process. The total refining time is 40 minutes, the white slag holding time is 30 minutes, and the slag basicity is 3.5 after refining. After refining, the molten steel is sent to the VD furnace for vacuum degassing treatment. The vacuum degree is 66.7Pa, the vacuum holding time is 18 minutes, and the vacuum is broken. After soft blowing for 12 minutes, the inclusions can fully float up. At the same time, 0.9kg / t of calcium wire is fed into the molten steel for calcium treatment to promote the spheroidization and floating of the inclusions. (2) Continuous casting process: Using a large-section continuous casting machine, the liquid level of the crystallizer is automatically controlled with a fluctuation range of ±3mm, the superheat of the tundish is 35°C, and electromagnetic stirring, light pressure reduction and strong cooling at the end of solidification are used to cast large-section high-quality continuous casting billets; (3) Rolling process: The continuous casting billet is heated in a continuous furnace with a furnace temperature of 600°C and a heating rate of 200°C / h; the maximum heating temperature is 1270°C, the soaking zone temperature is 1240°C, and the total heating coefficient is 10 min / cm; A two-stage controlled rolling process is adopted, with the first-stage rolling temperature at 1090°C, high reduction rolling, and a steel thickness of 110mm; the second-stage rolling temperature is 800°C, the final rolling temperature is 780°C, and the red-returning temperature is 580°C.

[0025] The steel plate obtained after cooling has a structure of ferrite and pearlite, a yield strength of 450MPa, a tensile strength of 636MPa, a V-shaped longitudinal -60°C impact energy of 207J, and a thickness of 40mm. The produced F-grade marine steel has excellent comprehensive performance, high strength, good impact toughness and high-temperature tensile properties, uniform structure and stable performance.

[0026] Example 3: This example provides a TMCP type F-grade marine structural steel plate, whose chemical composition and mass percentage are: C: 0.07%, Si: 0.38%, Mn: 1.62%, P: 0.007%, S: 0.001%, Ni: 0.15%, Nb: 0.020%, Al: 0.040%, and the rest is Fe and other inevitable impurities.

[0027] The production method of TMCP type F-grade marine structural steel plate in this embodiment includes steelmaking, continuous casting, and rolling processes, and the specific process steps are as follows: (1) Steelmaking process: The molten steel smelted in the converter is sent to the LF refining furnace for refining. During the LF refining process, argon blowing is good throughout the process. The total refining time is 50 minutes, the white slag holding time is 35 minutes, and the slag basicity is 4.0 at the end of refining. After refining, the molten steel is sent to the VD furnace for vacuum degassing treatment. The vacuum degree is 50Pa and the vacuum holding time is 20 minutes. After the vacuum is broken, soft blowing is performed for 11 minutes to allow inclusions to fully float up. At the same time, 1.0kg / t of calcium wire is fed for calcium treatment to promote the spheroidization and floating of inclusions. (2) Continuous casting process: Using a large-section continuous casting machine, the liquid level of the crystallizer is automatically controlled with a fluctuation range of ±3mm, the superheat of the tundish is 30°C, and electromagnetic stirring, light pressure reduction and strong cooling at the end of solidification are used to cast large-section high-quality continuous casting billets; (3) Rolling process: The continuous casting billet is heated in a continuous furnace with a furnace temperature of 1200°C and a heating rate of 300°C / h; the maximum heating temperature is 1270°C, the soaking zone temperature is 1240°C, and the total heating coefficient is 12min / cm; A two-stage controlled rolling process is adopted, with the first-stage rolling temperature of 1160℃, high reduction rolling, and steel thickness of 108mm; the second-stage rolling temperature is 780℃, the final rolling temperature is 730℃, and the red-returning temperature is 610℃.

[0028] The steel plate obtained after cooling has a structure of ferrite and pearlite, a yield strength of 470MPa, a tensile strength of 680MPa, a V-shaped longitudinal -60°C impact energy of 190J, and a thickness of 35mm. The produced F-grade marine steel has excellent comprehensive performance, high strength, good impact toughness and high-temperature tensile properties, uniform structure and stable performance.

[0029] Example 4: This example provides a TMCP type F-grade marine structural steel plate, whose chemical composition and mass percentage are: C: 0.08%, Si: 0.40%, Mn: 1.70%, P: 0.005%, S: 0.001%, Ni: 0.15%, Nb: 0.020%, Al: 0.035%, and the rest is Fe and other unavoidable impurities.

[0030] The production method of the TMCP type F-grade marine structural steel plate in this embodiment includes steelmaking, continuous casting, and rolling processes, and the specific process steps are as follows: (1) Steelmaking process: The molten steel smelted in the converter is sent to the LF refining furnace for refining. During the LF refining process, argon blowing is good throughout the process. The total refining time is 35 minutes, the white slag holding time is 31 minutes, and the slag basicity is 3.9 after refining. After refining, the molten steel is sent to the VD furnace for vacuum degassing treatment. The vacuum degree is 62Pa, the vacuum holding time is 20 minutes, and the vacuum is soft-blown for 12 minutes after the vacuum is broken, so that the inclusions can fully float up. At the same time, 1.0kg / t of calcium wire is fed into the molten steel for calcium treatment to promote the spheroidization and floating of the inclusions. (2) Continuous casting process: Using a large-section continuous casting machine, the mold liquid level is automatically controlled with a fluctuation range of ±3mm, the tundish superheat is 15°C, and electromagnetic stirring, light pressure reduction and strong cooling at the end of solidification are used to cast large-section high-quality continuous casting billets; (3) Rolling process: The continuous casting billet is heated in a continuous furnace with a furnace temperature of 900°C and a heating rate of 350°C / h; the maximum heating temperature is 1270°C, the soaking zone temperature is 1250°C, and the total heating coefficient is 12min / cm; A two-stage controlled rolling process is adopted, with the first-stage rolling temperature of 1150℃, large reduction rolling, steel thickness of 90mm, second-stage rolling temperature of 750℃, final rolling temperature of 730℃, and red-returning temperature of 620℃.

[0031] The steel plate obtained after cooling has a structure of ferrite and pearlite, a yield strength of 440MPa, a tensile strength of 650MPa, a V-shaped longitudinal -60°C impact energy of 155J, and a thickness of 20mm. The produced F-grade marine steel has excellent comprehensive performance, high strength, good impact toughness and high-temperature tensile properties, uniform structure and stable performance.

[0032] In addition to the above embodiments, the present invention may also have other implementation modes; any technical solutions formed by equivalent replacement or equivalent transformation shall fall within the protection scope required by the present invention.

Claims

1. A TMCP type F-grade marine structural steel plate, characterized in that: Its chemical composition and mass percentages are as follows: C: 0.03 - 0.08%, Si: 0.10 - 0.40%, Mn: 1.35 - 1.70%, P ≤ 0.012%, S ≤ 0.005%, Ni: 0.01 - 0.15%, Nb: 0.008 - 0.020%, Al: 0.020 - 0.040%, and the balance is Fe and other inevitable impurities.

2. The TMCP type F-grade marine structural steel plate according to claim 1, characterized in that: The structure of the steel plate is ferrite and pearlite.

3. The TMCP type F-grade marine structural steel plate according to claim 1, characterized in that: The yield strength of the steel plate is ≥ 390 MPa, the tensile strength is 540 - 680 MPa, and the V-notch longitudinal impact energy at -60 °C is ≥ 80 J.

4. The TMCP type F-grade marine structural steel plate according to claim 1, characterized in that: The thickness of the steel plate is 20 - 40 mm.

5. A production process of the TMCP type F-grade marine structural steel plate according to any one of claims 1 to 4, characterized in that: It successively includes the processes of steelmaking, continuous casting, and rolling.

6. The production process of TMCP type F-grade ship structural steel plate according to claim 5, characterized in that: In the steelmaking process, the molten steel smelted in the converter is fed into the LF refining furnace for refining. During the LF refining process, argon blowing is good throughout, the total refining time is ≥ 35 min, the white slag holding time is ≥ 25 min, and the slag basicity at the end of refining is ≥ 3.

5.

7. The production process of TMCP type F-grade ship structural steel plate according to claim 5, characterized in that: In the steelmaking process, after the LF furnace refining is completed, the molten steel is fed into the VD vacuum furnace for vacuum degassing treatment. The vacuum degree is ≤ 66.7 Pa, the vacuum holding time is ≥ 18 min, after the vacuum is broken, soft blowing is carried out for 10 - 12 min, and at the same time, a calcium wire of 0.8 - 1.0 kg / t of steel is fed for calcium treatment.

8. The production process of TMCP type F-grade ship structural steel plate according to claim 5, characterized in that: In the continuous casting process, electromagnetic stirring and soft reduction technologies are adopted during casting, and the liquid level fluctuation range in the mold is ± 3 mm, and the superheat is controlled at 15 - 35 °C.

9. The production process of TMCP type F-grade ship structural steel plate according to claim 5, characterized in that: In the rolling process, the cast billet is heated in a continuous furnace. When the furnace temperature T ≤ 600 °C, the heating rate is ≤ 200 °C / h; when the furnace temperature is 600 °C < T ≤ 1200 °C, the heating rate is ≤ 350 °C / h; the highest heating temperature is 1270 °C, the soaking section temperature is 1230 - 1250 °C, and the total heating coefficient is ≥ 10 min / cm.

10. The production process of TMCP type F-grade ship structural steel plate according to claim 5, characterized in that: The rolling process adopts a second-order controlled rolling process. The starting rolling temperature in the first stage is 1085 - 1160 °C, and a large reduction rolling process is adopted. The air-cooled thickness is h + 70 mm, where h is the thickness of the finished steel plate. The starting rolling temperature in the second stage is 820 - 750 °C, the finishing rolling temperature is 790 - 730 °C, and the steel plate recrystallization temperature is 580 - 620 °C.

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