16MnDR steel plate capable of guaranteeing SR high core toughness and manufacturing method thereof

Abstract

The invention relates to a 16MnDR steel plate capable of maintaining SR high core toughness and a manufacturing method of the 16MnDR steel plate. 0.30% to 0.40% of Si; mn: 1.45 to 1.55%; 0.02 to 0.03 percent of Nb; the content of V is 0.02%-0.03%, and the content of Ti is 0.008%-0.02%; 0.15 to 0.25 percent of Ni; 0.15% to 0.25% of Cu; the content of Alt is 0.025 to 0.05 percent; p: less than or equal to 0.010%; s: < = 0.003%; n: < = 0.0040%; h: < = 0.0002%; and the balance Fe, and CE is less than or equal to 0.40%. The produced steel plate has good core impact toughness, excellent simulated postweld heat treatment performance and good weldability. The production cost is relatively low, the process is simple, and the method is suitable for industrial production in batches.

Description

Technical Field

[0001] The present invention relates to the field of manufacturing pressure vessel steel plates, and particularly to a 16MnDR steel plate with high core toughness by maintaining SR and its manufacturing method. Background Art

[0002] With the rapid development of pressure vessel equipment such as large LNG storage tanks, ethylene equipment, and liquid nitrogen storage tanks, the requirements for the low-temperature toughness and welding performance of steel plates for pressure vessels in the industry have gradually increased. As a relatively common steel for low-temperature pressure vessels, 16MnDR steel plates are widely used and have a large demand. In particular, steel plates with a thickness of ≥80 mm are mainly used in important parts of pressure vessels. The processing of spherical tanks is complex, so it is required to have stable impact toughness, strong adaptability to welding processing, be safe and reliable, and have a low production cost. The existing production methods are as follows.

[0003] Existing Technology 1, Patent "16MnDR Steel Plate for High-Performance Large-Thickness Vessel Heads and Its Production Method" (Publication No. CN118497631A), adopts the composition design of "C≤0.20%, CEV≤0.45%, Ti+Nb+V: 0.02%-0.03%, and the rest are Fe and inevitable impurities". The maximum thickness of the 16MnDR steel plate produced by this invention is 150 mm. The C content is designed high, and the CEV is 0.425-0.45%, which is not conducive to subsequent welding processing. Moreover, it can only ensure the transverse impact at 1 / 4 of the thickness position, cannot meet the requirements of core impact toughness, and cannot meet the simulated post-welding performance.

[0004] Existing Technology 2, Patent "Low-Carbon High-Toughness 16MnDR Steel Plate and Its Production Method" (Publication No. CN116145031A), its chemical composition design is "C: 0.07%-0.09%, Si: 0.15%-0.30%, Mn: 1.50%-1.60%, P≤0.010%, S≤0.003%, Nb: 0.030%-0.035%". The maximum thickness of the produced steel plate is 60 mm. The steel plate produced by this invention can only meet the requirement of -50°C impact at 1 / 4 of the thickness position, cannot meet the requirements of core impact toughness and simulated post-welding. Moreover, the maximum thickness of the steel plate is 60 mm, which does not meet the demand for extra-thick head steel plates.

[0005] Prior Art 3, Patent "Normalized 16MnDR Low Temperature Pressure Vessel Steel Plate and Its Manufacturing Method" (Publication No. CN102605241A), uses a composition design of "C: 0.15 - 0.17%, Si: 0.25 - 0.40%, Mn: 1.40 - 1.55%, P: ≤0.015%, S: ≤0.005%, V: 0.05 - 0.07%, Als: 0.020 - 0.030%, O: ≤0.0040%, N ≤0.0060%". The maximum thickness of the steel plate produced by this invention is 60mm. The C content is designed to be high, and a high V design is adopted, increasing the surface crack tendency and being unfavorable for subsequent processing and use.

[0006] Prior Art 4, Patent "16MnDR Thick Plate of 120mm Low Temperature Pressure Vessel Steel and Its Production Method" (Publication No. CN102345054A), uses a composition design of "C: 0.10 - 0.17%, Si: 0.25 - 0.45%, Mn: 1.10 - 1.40%, P ≤0.015%, S ≤0.005%, Als: 0.015 - 0.055%, Nb: 0.015 - 0.045%, Ti: 0.010 - 0.020%, and the rest are Fe and residual elements. Carbon equivalent [Ceq = C + Mn / 6 + (Cr + Mo + V) / 5 + (Ni + Cu) / 15]: ≤0.40". The maximum thickness of the produced steel plate is 120mm. This invention can only meet the requirements of -30°C impact and cannot meet the requirements of core impact and simulated post-weld performance.

[0007] As can be seen from the prior art, there are the following deficiencies in the production of extra-thick 16MnDR steel plates in China at present: unable to meet the requirements of core impact and simulated post-weld performance; the carbon equivalent is generally on the high side, which is unfavorable for weldability. Summary of the Invention

[0008] The object of the present invention is to provide a 16MnDR steel plate with high core toughness while maintaining SR and its manufacturing method. By controlling the C content in the steel, reducing the contents of harmful elements P and S, appropriately adding alloying elements, and matching reasonable rolling processes and heat treatment process systems, a 16MnDR steel plate with high core toughness while maintaining SR is developed to solve the problems that the carbon equivalent of the existing extra-thick 16MnDR steel plates is high and unfavorable for welding, and unable to meet the requirements of core impact and simulated post-weld performance.

[0009] The present invention is realized through the following technical solutions: A 16MnDR steel plate with high core toughness and high SR retention, comprising the following components in mass percentages: C: 0.08 - 0.11%; Si: 0.30 - 0.40%; Mn: 1.45 - 1.55%; Nb: 0.02 - 0.03%; V: 0.02 - 0.03%, Ti: 0.008 - 0.02%; Ni: 0.15 - 0.25%; Cu: 0.15 - 0.25%; Alt: 0.025 - 0.05%; P: ≤0.010%; S: ≤0.003%; N: ≤0.0040%; H: ≤0.0002%; the balance being Fe and unavoidable impurities, and CEV = C + Mn / 6 + (Cr + Mo + V) / 5 + (Ni + Cu) / 15 ≤ 0.40%.

[0010] The steel plate is manufactured through the following steps: including molten steel smelting, slab casting, slab heating, steel plate rolling, ACC water cooling, and normalizing heat treatment steps, where: (1) Molten steel smelting: Add alloying elements Mn, Ni, Cu and micro-alloying elements Nb, V, Ti, and control the impurity elements P ≤ 0.010%, S ≤ 0.003%; control the gas content N ≤ 0.0040%, O ≤ 0.0030%, H ≤ 0.0002%; (2) Slab casting: Maintain a constant casting speed during the casting process, with the casting speed range of 0.55m - 0.6m / min, ensure that the central segregation of the slab is class C ≤ 1.0, and the stacking and cooling time after the casting blank is taken offline is ≥ 48h; (3) Slab heating: Use a walking beam type heating furnace to heat the slab in sections to the set soaking temperature of 1200 - 1240°C; where the temperature of the first heating section is 900 - 1020°C, the temperature of the second heating section is 1020 - 1150°C, the third heating section is 1150 - 1240°C, and the soaking temperature of the fourth heating section is 1200 - 1240°C. The slab stays in the furnace for 360 - 422min to fully austenitize the steel billet; (4) Steel plate rolling: During the rolling process, adopt a two-stage controlled rolling and controlled cooling process. The starting temperature of the first stage rolling is ≥ 1050°C, the total reduction ratio is 50 - 60%, and the single-pass reduction amount of the last 3 passes in the first stage rolling is ≥ 35mm; the thickness of the intermediate billet for waiting for temperature is 2 times the thickness of the finished steel plate; the starting rolling temperature of the second stage rolling is ≤ 850°C, and the finishing rolling temperature is 780 - 830°C; (5) ACC water cooling: Use the "ACC" cooling system, with the starting cooling temperature of 790 - 810°C, the recrystallization temperature of 620 - 670°C, and the cooling rate of 5 - 8°C / s; after the cooling is completed, quickly take it offline and stack it for slow cooling. The stacking and slow cooling temperature is 450 ± 50°C, and the stacking time is ≥ 36h; (6) Normalizing heat treatment: The normalizing temperature is 880 - 890°C. The time in the furnace for normalizing = the heating time for the steel plate to rise in temperature + the holding time; where the heating rate for temperature rise is 1.3 - 1.5 min / mm, and the holding time is 40 - 50 min.

[0011] The present invention also discloses a manufacturing method of a 16MnDR steel plate with high core toughness and preserved SR, which is characterized in that it includes steps of molten steel smelting, slab casting, slab heating, steel plate rolling, ACC water cooling, and normalizing heat treatment, where: (1) Molten steel smelting: Add alloying elements Mn, Ni, Cu and micro - alloying elements Nb, V, Ti, and control the impurity elements P ≤ 0.010%, S ≤ 0.003%; control the gas content N ≤ 0.0040%, O ≤ 0.0030%, H ≤ 0.0002%. (2) Slab casting: Maintain a constant casting speed during casting, and the casting speed range is 0.55 m - 0.6 m / min, ensure that the central segregation of the slab is class C ≤ 1.0, and the stacking and cooling time after the casting blank is taken offline is ≥ 48 h. (3) Slab heating: Use a walking - beam type heating furnace to heat the slab in sections to the set soaking temperature of 1200 - 1240°C; where the temperature of the first heating section is 900 - 1020°C, the temperature of the second heating section is 1020 - 1150°C, the third heating section is 1150 - 1240°C, the soaking temperature of the fourth heating section is 1200 - 1240°C, and the time of the slab in the furnace is 360 - 422 min to fully austenitize the steel billet. (4) Steel plate rolling: During rolling, adopt a two - stage controlled rolling and controlled cooling process. The starting temperature of the first - stage rolling is ≥ 1050°C, the total reduction ratio is 50 - 60%, and the reduction per pass in the last 3 passes of the first - stage rolling is ≥ 35 mm; the thickness of the intermediate billet for waiting for temperature is 2 times the thickness of the finished steel plate; the starting rolling temperature of the second - stage rolling is ≤ 850°C, and the finishing rolling temperature is 780 - 830°C. (5) ACC water cooling: Use the "ACC" cooling system, the starting cooling temperature is 790 - 810°C, the recrystallization temperature is 620 - 670°C, and the cooling rate is 5 - 8°C / s; after cooling ends, quickly take it offline and stack it for slow cooling, the stacking slow - cooling temperature is 450 ± 50°C, and the stacking time is ≥ 36 h. (6) Normalizing heat treatment: The normalizing temperature is 880 - 890°C. The time in the furnace for normalizing = the heating time for the steel plate to rise in temperature + the holding time; where the heating rate for temperature rise is 1.3 - 1.5 min / mm, and the holding time is 40 - 50 min.

[0012] Furthermore: It also includes a simulated post - weld heat treatment step, the furnace inlet temperature ≤ 400°C; when it is above 400°C, the heating rate is 50 - 80°C / h, hold at 600 ± 10°C for 11 - 16 h, the cooling rate is 30 - 50°C / h, the furnace outlet temperature ≤ 400°C, and then air - cool to room temperature.

[0013] Furthermore: The yield strength ReL of the steel plate is ≥ 320 MPa, the tensile strength Rm is 495 - 520 MPa, the elongation after fracture is ≥ 28%, the transverse impact energy at -40°C at the 1 / 4 position of the steel plate is ≥ 250 J, and the transverse impact energy at -40°C at the 1 / 2 position of the steel plate is ≥ 200 J.

[0014] Furthermore: For the simulated post-weld heat-treated steel plate, the yield strength ReL is ≥ 295 MPa, the tensile strength is 480 - 500 MPa, the elongation after fracture is ≥ 26%, the transverse impact energy at -40°C at the 1 / 4 position of the steel plate is ≥ 200 J, and the transverse impact energy at -40°C at the 1 / 2 position of the steel plate is ≥ 150 J.

[0015] Furthermore: The maximum thickness of the steel plate is 100 mm.

[0016] Furthermore: The flaw detection result of the steel plate meets the requirements of TI level in the NB / T 47013.3 - 2023 standard.

[0017] Furthermore: The metallographic structures of the steel plate after normalizing heat treatment and simulated post-weld heat treatment are both ferrite + pearlite, and the grain size at the 1 / 4 position and 1 / 2 position of the thickness is ≥ 8 grades.

[0018] Compared with the prior art, the advantages of the present invention are as follows: 1. The 16MnDR steel plate with high core toughness and guaranteed SR produced by the present invention not only has good strength indexes but also excellent core impact toughness. The yield strength ReL of the steel plate is ≥ 320 MPa, the tensile strength Rm is 495 - 520 MPa, the elongation after fracture is ≥ 28%, the transverse impact energy at -40°C at the 1 / 4 position of the steel plate is ≥ 250 J, and the transverse impact energy at -40°C at the 1 / 2 position of the steel plate is ≥ 200 J.

[0019] 2. The 16MnDR steel plate with high core toughness and guaranteed SR produced by the present invention still has good strength and toughness after the steel plate samples are subjected to simulated post-weld heat treatment. For the simulated post-weld heat-treated steel plate, the yield strength ReL is ≥ 295 MPa, the tensile strength is 480 - 500 MPa, the elongation after fracture is ≥ 26%, the transverse impact energy at -40°C at the 1 / 4 position of the steel plate is ≥ 200 J, and the transverse impact energy at -40°C at the 1 / 2 position of the steel plate is ≥ 150 J.

[0020] 3. For the 16MnDR steel plate with high core toughness and guaranteed SR produced by the present invention, its CEV ≤ 0.40%, which is beneficial to the welding operation during the use by downstream customers, reduces the welding crack sensitivity coefficient, and improves the service life.

[0021] 4. The 16MnDR steel plate with high core toughness and guaranteed SR produced by the present invention has excellent internal quality, and the flaw detection of the steel plate meets the requirements of TI level in the NB / T 47013.3 - 2023 standard.

[0022] 5. The 16MnDR steel plate with high core toughness and retained SR produced by the present invention has a metallographic structure of ferrite + pearlite. The structure of the whole plate is uniform, and the grain size at the 1 / 4 thickness position and the 1 / 2 thickness position is ≥ grade 8. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is the microstructure of the steel plate after normalizing in Example 1 at 200X (1 / 4 position); Figure 2 It is the microstructure of the steel plate after normalizing in Example 1 at 200X (1 / 2 position); Figure 3 It is the microstructure of the steel plate after simulated post-weld heat treatment in Example 1 at 200X (1 / 4 position); Figure 4 It is the microstructure of the steel plate after simulated post-weld heat treatment in Example 1 at 200X (1 / 2 position). DETAILED DESCRIPTION OF THE INVENTION

[0024] The present invention discloses a 16MnDR steel plate with high core toughness and retained SR (simulated post-weld heat treatment), which comprises the following components by mass percentage: C: 0.08 - 0.11%; Si: 0.30 - 0.40%; Mn: 1.45 - 1.55%; Nb: 0.02 - 0.03%; V: 0.02 - 0.03%, Ti: 0.008 - 0.02%; Ni: 0.15 - 0.25%; Cu: 0.15 - 0.25%; Alt: 0.025 - 0.05%; P: ≤0.010%; S: ≤0.003%; N: ≤0.0040%; H: ≤0.0002%; the balance is Fe and unavoidable impurities, and CEV = C + Mn / 6 + (Cr + Mo + V) / 5 + (Ni + Cu) / 15 ≤ 0.40%.

[0025] In order to ensure that the strength indexes of the 16MnDR steel plate after normalizing heat treatment and simulated post-weld heat treatment meet the requirements, and considering that the segregation of C and Mn will affect the impact toughness of the core, the present invention comprehensively controls C within 0.08 - 0.11% and Mn within 1.45 - 1.55%.

[0026] Microalloying elements Nb, V, and Ti are added, which have the effects of refining grains and precipitation strengthening, and are beneficial to improving the impact toughness after simulated post-weld heat treatment. Therefore, both Nb and V are controlled within 0.02 - 0.03%, and Ti is controlled within 0.008 - 0.02%.

[0027] Alloying elements Cu and Ni are added mainly to ensure the strength and low-temperature impact toughness of the steel plate. Since the design contents of C and Mn are relatively low, in order to make up for the strength loss caused by normalizing heat treatment and simulated post-weld heat treatment, the addition of Cu element is used to ensure. Ni element can not only improve the impact toughness of the core, but also avoid the crack tendency caused by the addition of Cu element. Therefore, both Cu and Ni are controlled within 0.15 - 0.25%.

[0028] The present invention also discloses a manufacturing method of a 16MnDR steel plate with high core toughness and guaranteed SR, and the production steps and parameter settings of the manufacturing method are as follows: It includes steps of molten steel smelting, slab casting, slab heating, steel plate rolling, ACC water cooling, and normalizing heat treatment, wherein: (1) Molten steel smelting: Add alloying elements Mn, Ni, Cu and micro-alloying elements Nb, V, Ti, and control the impurity elements P ≤ 0.010%, S ≤ 0.003%; control the gas contents N ≤ 0.0040%, O ≤ 0.0030%, H ≤ 0.0002%; (2) Slab casting: Keep a constant casting speed during the casting process, and the casting speed range is 0.55 m - 0.6 m / min, ensure that the central segregation of the slab is class C ≤ 1.0, and the stacking and cooling time after the casting blank is taken offline is ≥ 48 h; (3) Slab heating: Use a walking beam type heating furnace to heat the slab in sections to the set soaking temperature of 1200 - 1240 °C; among them, the temperature of the first heating section is 900 - 1020 °C, the temperature of the second heating section is 1020 - 1150 °C, the third heating section is 1150 - 1240 °C, and the soaking temperature of the fourth heating section is 1200 - 1240 °C. The slab stays in the furnace for 360 - 422 min to fully austenitize the steel billet; (4) Steel plate rolling: During the rolling process, adopt a two-stage controlled rolling and controlled cooling process. The starting temperature of the first stage rolling is ≥ 1050 °C, the total reduction ratio is 50 - 60%, and the reduction per pass of the last 3 passes in the first stage rolling is ≥ 35 mm; the thickness of the intermediate billet waiting for temperature is 2 times the thickness of the finished steel plate; the starting rolling temperature of the second stage rolling is ≤ 850 °C, and the finishing rolling temperature is 780 - 830 °C; (5) ACC water cooling: Use the "ACC" cooling system, the starting cooling temperature is 790 - 810 °C, the recrystallization temperature is 620 - 670 °C, and the cooling rate is 5 - 8 °C / s; after the cooling is completed, quickly take it offline and stack it for slow cooling, the stacking slow cooling temperature is 450 ± 50 °C, and the stacking time is ≥ 36 h; (6) Normalizing heat treatment: The normalizing temperature is 880 - 890 °C, and the time of the steel plate staying in the furnace during normalizing = the heating time of the steel plate + the holding time; among them, the heating rate during heating is 1.3 - 1.5 min / mm, and the holding time is 40 - 50 min.

[0029] Preferably: Add alloying elements Mn, Ni, Cu and micro-alloying elements Nb, V, Ti, and control impurity elements P≤0.010%, S≤0.003%; control gas content N≤0.0040%, O≤0.0030%, H≤0.0002%; maintain a constant casting speed during casting, the casting speed range is 0.55 m - 0.6 m / min, ensure that the center segregation of the slab is class C≤1.0, and the stacking cooling time after the slab is taken offline is ≥48 h.

[0030] Preferably: Use a walking beam type reheating furnace to heat the slab in sections to the set soaking temperature of 1200 - 1240°C; among them, the temperature of the first heating section is 900 - 1020°C, the temperature of the second heating section is 1020 - 1150°C, the third heating section is 1150 - 1240°C, the soaking temperature of the fourth heating section is 1200 - 1240°C, and the slab stays in the furnace for 360 - 422 min to fully austenitize the billet; during the rolling process, adopt a two-stage controlled rolling and controlled cooling process, the starting temperature of the first stage rolling is ≥1050°C, the total reduction ratio is 50 - 60%, and the reduction per pass of the last 3 passes in the first stage rolling is ≥35 mm; the thickness of the intermediate billet for temperature holding is 2 times the thickness of the finished steel plate; the starting rolling temperature of the second stage rolling is ≤850°C, and the finishing rolling temperature is 780 - 830°C; use the "ACC" cooling system, the starting cooling temperature is 790 - 810°C, the recrystallization temperature is 620 - 670°C, and the cooling rate is 5 - 8°C / s; after cooling is completed, quickly take it offline and stack it for slow cooling, the stacking slow cooling temperature is 450±50°C, and the stacking time is ≥36 h.

[0031] In the present invention, by controlling the casting speed of the slab to ensure that the center segregation of the slab reaches a better level, making the distribution of the original columnar grains and equiaxed grains tend to be reasonable, providing the original conditions for good core impact toughness of the steel plate. In the rough rolling stage of the rolling process, a high-temperature and large reduction rolling strategy is adopted to make the austenite grains fine and the dislocation density high. Through the synergistic effect of severe plastic deformation and dynamic recrystallization, the refinement of the material structure and the improvement of performance are realized, providing ideal initial conditions for subsequent finish rolling and cooling phase transformation. In the finish rolling stage, by limiting the starting rolling temperature and the finishing rolling temperature, the entire finish rolling stage is carried out in the non-recrystallized zone. Rolling deformation will accumulate a large number of dislocations and deformation bands, providing more nucleation points for subsequent phase transformation. At the same time, the lower finishing rolling temperature can avoid the coarsening of austenite grains after rolling, ensuring the uniformity of the structure after phase transformation. In addition, water cooling after rolling is used to inhibit the coarsening of austenite grains and retain the fine grain structure formed in the rolling stage.

[0032] Preferably: The normalizing temperature is 880 - 890°C, and the time of the slab staying in the furnace during normalizing = the heating time of the steel plate for temperature rise + the holding time; among them, the heating rate for temperature rise is 1.3 - 1.5 min / mm, and the holding time is 40 - 50 min.

[0033] The finished steel plate of the present invention is normalized at 880 - 890 °C. The heating rate of the steel plate is controlled to ensure the austenitization time, and a reasonable holding time is provided to ensure sufficient austenitization of the steel plate, so that the strengthening effects of microalloying elements and alloying elements are fully manifested, obtaining refined ferrite and pearlite grains, reducing the center banded structure, and ensuring uniform structure in the thickness direction of the steel plate.

[0034] The content of the present invention will be further described below in conjunction with embodiments. Embodiment 1:

[0035] A 16MnDR steel plate with high SR and high core toughness, with a thickness-width specification of 80 * 2500 mm. The chemical composition and its mass percentage content of the steel plate are: C: 0.095%, Si: 0.336%, Mn: 1.48%, P: 0.008%, S: 0.002%, Alt: 0.036%, Nb: 0.023%, V: 0.025%, Ti: 0.016%, Ni: 0.186%, Cu: 0.179%, N: 0.0033%, H: 0.00016%, and the balance is Fe and unavoidable impurities, CEV = 0.375%.

[0036] The production steps and process parameters of the steel plate are as follows: 1. Smelting: The smelting process includes hot metal pretreatment, converter smelting, LF + RH double refining treatment, and continuous casting with a constant casting speed operation process. The casting speed is 0.55 m / min, the center segregation of the continuous casting billet is class C 1.0, and the billet is stacked and slowly cooled for 48 hours after being taken offline.

[0037] 2. Heating: Produced by a walking beam type reheating furnace. The temperature of the first heating section is 950 °C, the temperature of the second heating section is 1090 °C, the third heating section is 1220 °C, and the soaking section temperature of the fourth heating section is 1200 °C. The slab stays in the furnace for 360 min.

[0038] 3. Rolling and cooling: The rough rolling starting temperature is 1065 °C, the total reduction ratio is 55.3%, the reduction in the last 3 passes is 37, 35, 35 mm, the thickness of the intermediate billet for temperature holding is 160 mm, the finishing rolling starting temperature is 837 °C, the finishing rolling end temperature is 793 °C, the ACC starting cooling temperature is 809 °C, the recrystallization temperature is 653 °C, the cooling rate is 6.8 °C / s, the stacking temperature is 480 °C, and the stacking time is 36 h.

[0039] 4. Heat treatment: The normalizing temperature is 880 °C, and the total in-furnace time during the normalizing process is 160 min, including a heating time of 120 min and a holding time of 40 min.

[0040] The mechanical properties of the steel plate obtained in this example are as follows: the yield strength ReL of the steel plate is 358 MPa, the tensile strength Rm is 520 MPa, the elongation rate is 31%, the transverse impact energy at -40°C at 1 / 4 position of the steel plate is 298 J, and the transverse impact energy at -40°C at 1 / 2 position of the steel plate is 231 J; after the steel plate is subjected to simulated post-weld heat treatment at 600°C * 11 h, the yield strength ReL is 319 MPa, the tensile strength Rm is 500 MPa, the elongation rate is 29.5%, the transverse impact energy at -40°C at 1 / 4 position of the steel plate is 215 J, and the transverse impact energy at -40°C at 1 / 2 position of the steel plate is 164 J; the flaw detection of the steel plate can meet the requirements of TI level in the standard NB / T 47013.3-2023; the grain size at 1 / 4 position and 1 / 2 position of the thickness is 8.5 grade.

[0041] As Figures 1-4 shown, the microstructure of the steel plate produced by the present invention using the above composition design and process parameters is observed, and it is a typical ferrite + pearlite structure. Example 2:

[0042] A 16MnDR steel plate with high toughness at the core while maintaining SR, with a thickness-width specification of 90 * 2400 mm. The chemical composition and its mass percentage content of the steel plate are as follows: C: 0.101%, Si: 0.357%, Mn: 1.47%, P: 0.007%, S: 0.0015%, Alt: 0.033%, Nb: 0.024%, V: 0.022%, Ti: 0.014%, Ni: 0.177%, Cu: 0.165%, N: 0.0037%, H: 0.0002%, and the balance is Fe and unavoidable impurities, CEV = 0.377%.

[0043] The production steps and process parameters of the steel plate are as follows: 1. Smelting: The smelting steps include hot metal pretreatment, converter smelting, LF + RH double refining treatment, and continuous casting using a constant casting speed operation process with a casting speed of 0.6 m / min. The central segregation of the cast slab is class C 1.0, and the cast slab is stacked and slowly cooled for 48 hours after being taken off the production line.

[0044] 2. Heating: It is produced by a walking beam type heating furnace. The temperature of the first heating section is 970°C, the temperature of the second heating section is 1110°C, the third heating section is 1230°C, and the soaking section temperature of the fourth heating section is 1210°C. The slab stays in the furnace for 390 min.

[0045] 3. Rolling and cooling: The rough rolling starting temperature is 1078°C, the total reduction ratio is 53%, the reduction amounts in the last 3 passes are 38, 35, and 35 mm, the thickness of the intermediate billet for temperature holding is 180 mm, the finishing rolling starting temperature is 825°C, the finishing rolling ending temperature is 787°C, the ACC starting cooling temperature is 800°C, the red return temperature is 644°C, the cooling rate is 5.9°C / s, the stacking temperature is 495°C, and the stacking time is 36 h.

[0046] 4. Heat treatment: Normalizing temperature is 880 °C, total time in the furnace during normalizing is 180 min, among which the heating-up time is 135 min and the holding time is 45 min.

[0047] The mechanical properties of the steel plate obtained in this example are as follows: The yield strength ReL of the steel plate is 335 MPa, the tensile strength Rm is 509 MPa, the elongation is 33%, the transverse impact energy at -40 °C at 1 / 4 position of the steel plate is 317 J, and the transverse impact energy at -40 °C at 1 / 2 position of the steel plate is 221 J; After the steel plate undergoes simulated post-weld heat treatment at 600 °C for 13.5 h, the yield strength ReL is 310 MPa, the tensile strength Rm is 493 MPa, the elongation is 28%, the transverse impact energy at -40 °C at 1 / 4 position of the steel plate is 233 J, and the transverse impact energy at -40 °C at 1 / 2 position of the steel plate is 171 J; The flaw detection of the steel plate can meet the requirements of Grade TI of NB / T 47013.3 - 2023 standard; The grain size at 1 / 4 position and 1 / 2 position of the thickness is 8.5 grade. Example 3:

[0048] A 16MnDR steel plate with high core toughness and high SR retention, with a thickness-width specification of 100 * 2500 mm. The chemical composition and its mass percentage content of the steel plate are as follows: C: 0.098%, Si: 0.376%, Mn: 1.52%, P: 0.007%, S: 0.0024%, Alt: 0.029%, Nb: 0.025%, V: 0.023%, Ti: 0.017%, Ni: 0.173%, Cu: 0.188%, N: 0.0031%, H: 0.00014%, and the balance is Fe and unavoidable impurities, CEV = 0.384%.

[0049] The production steps and process parameters of the steel plate are as follows: 1. Smelting: The smelting steps include hot metal pretreatment, converter smelting, LF + RH double refining treatment, and continuous casting adopts a constant casting speed operation process with a casting speed of 0.55 m / min. The central segregation of the continuous casting billet is Class C 1.0 level. After the continuous casting billet is taken offline, it is stacked and slowly cooled for 48 hours.

[0050] 2. Heating: It is produced by a walking beam type heating furnace. The temperature of the first heating section is 980 °C, the temperature of the second heating section is 1095 °C, the third heating section is 1220 °C, and the soaking section temperature of the fourth heating section is 1205 °C. The slab stays in the furnace for 422 min.

[0051] 3. Rolling and cooling: The rough rolling starting temperature is 1059 °C, the total reduction ratio is 52.5%, the reduction in the last 3 passes is 36, 35, 35 mm, the thickness of the intermediate billet for temperature holding is 200 mm, the finishing rolling starting temperature is 833 °C, the finishing rolling ending temperature is 783 °C, the ACC starting cooling temperature is 799 °C, the recalescence temperature is 638 °C, the cooling rate is 5.2 °C / s, the stacking temperature is 500 °C, and the stacking time is 36 h.

[0052] 4. Heat treatment: Normalizing temperature is 890 °C, total in-furnace time during normalizing is 200 min, among which heating-up time is 150 min and holding time is 50 min.

[0053] The mechanical properties of the steel plate obtained in this embodiment are as follows: yield strength ReL of the steel plate is 325 MPa, tensile strength Rm is 500 MPa, elongation is 29.5%, transverse impact energy at -40 °C at 1 / 4 position of the steel plate is 276 J, and transverse impact energy at -40 °C at 1 / 2 position of the steel plate is 205 J; after the steel plate undergoes simulated post-weld heat treatment at 600 °C * 16 h, yield strength ReL is 298 MPa, tensile strength Rm is 489 MPa, elongation is 27.5%, transverse impact energy at -40 °C at 1 / 4 position of the steel plate is 231 J, and transverse impact energy at -40 °C at 1 / 2 position of the steel plate is 177 J; the flaw detection of the steel plate can meet the requirements of TI level in NB / T 47013.3-2023 standard; the grain size at 1 / 4 position and 1 / 2 position of the thickness is grade 8.

[0054] In summary, for the method of the present invention, by controlling the C content in the steel, reducing the contents of harmful elements P and S, appropriately adding alloying elements Ni and Cu as well as micro-alloying elements Nb, V, and Ti, and by matching reasonable rolling process and heat treatment process system, 16MnDR steel plates with a thickness of 80 - 100 mm and high core toughness with guaranteed SR can be stably produced. The low carbon equivalent is easy to weld, the internal quality is excellent, and the flaw detection level can reach TI level in NB / T 47013.3-2023. It has good application prospects in the field of steel for containers with guaranteed SR and low-temperature impact toughness at the core.

[0055] The above is only the preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitution or change, and should be covered within the protection scope of the present invention.

Claims

1. A 16MnDR steel plate with high core toughness of SR, the steel plate comprising the following components in mass percentage: C: 0.08-0.11%; Si: 0.30-0.40%; Mn: 1.45-1.55%; Nb: 0.02-0.03%; V: 0.02-0.03%, Ti: 0.008-0.02%; Ni: 0.15-0.25%; Cu: 0.15-0.25%; Alt: 0.025-0.05%; P：≤0.010% ； S: ≤0.003%; N: ≤0.0040%; H: ≤0.0002%; the rest are Fe and unavoidable impurities, CEV=C+Mn / 6+(Cr+Mo+V) / 5+(Ni+Cu) / 15≤0.40%; The steel plate is manufactured by the following steps: including molten steel smelting, slab casting, slab heating, steel plate rolling, ACC water cooling, and normalizing heat treatment steps, wherein: (1) Molten steel smelting: add alloying elements Mn, Ni, Cu and micro-alloying elements Nb, V, Ti, and control the impurity elements P≤0.010%, S≤0.003%; control the gas content N≤0.0040%, O≤0.0030%, H≤0.0002%; (2) Slab casting: Maintain a constant pulling speed during the casting process, with a pulling speed range of 0.55m-0.6m / min, ensure that the center segregation of the slab is C ≤ 1.0, and the stacking cooling time after the slab is off the line is ≥ 48h; (3) Slab heating: The slab is heated in sections by a walking beam heating furnace to a set soaking temperature of 1200-1240°C; the temperature of the first heating section is 900-1020°C, the temperature of the second heating section is 1020-1150°C, the temperature of the third heating section is 1150-1240°C, and the temperature of the fourth heating section soaking section is 1200-1240°C. The slab is kept in the furnace for 360-422 minutes to fully austenitize the steel slab; (4) Steel plate rolling: During the rolling process, a two-stage controlled rolling and controlled cooling process is adopted. The starting temperature of the first stage rolling is ≥1050℃, the total reduction rate is 50-60%, and the single-pass reduction of the last three passes of the first stage rolling is ≥35mm; the intermediate billet waiting temperature thickness is twice the thickness of the finished steel plate; the second stage rolling start temperature is ≤850℃, and the final rolling temperature is 780-830℃; (5) ACC water cooling: Using the "ACC" cooling system, the initial cooling temperature is 790-810℃, the red-back temperature is 620-670℃, and the cooling rate is 5-8℃ / s; after the cooling is completed, the stack is quickly taken off the line for slow cooling, the stacking slow cooling temperature is 450±50℃, and the stacking time is ≥36h; (6) Normalizing heat treatment: Normalizing temperature 880-890℃, normalizing furnace time = steel plate heating time + insulation time; The heating rate is 1.3-1.5min / mm, and the insulation time is 40-50min.

2. The method for manufacturing a 16MnDR steel plate with SR high core toughness as claimed in claim 1, characterized in that: It includes the steps of molten steel smelting, slab casting, slab heating, steel plate rolling, ACC water cooling, and normalizing heat treatment, among which: (1) Molten steel smelting: add alloying elements Mn, Ni, Cu and micro-alloying elements Nb, V, Ti, and control the impurity elements P≤0.010%, S≤0.003%; control the gas content N≤0.0040%, O≤0.0030%, H≤0.0002%; (2) Slab casting: Maintain a constant pulling speed during the casting process, with a pulling speed range of 0.55m-0.6m / min, ensure that the center segregation of the slab is C ≤ 1.0, and the stacking cooling time after the slab is off the line is ≥ 48h; (3) Slab heating: The slab is heated in sections by a walking beam heating furnace to a set soaking temperature of 1200-1240°C; the temperature of the first heating section is 900-1020°C, the temperature of the second heating section is 1020-1150°C, the temperature of the third heating section is 1150-1240°C, and the temperature of the fourth heating section soaking section is 1200-1240°C. The slab is kept in the furnace for 360-422 minutes to fully austenitize the steel slab; (4) Steel plate rolling: During the rolling process, a two-stage controlled rolling and controlled cooling process is adopted. The starting temperature of the first stage rolling is ≥1050℃, the total reduction rate is 50-60%, and the single-pass reduction of the last three passes of the first stage rolling is ≥35mm; the intermediate billet waiting temperature thickness is twice the thickness of the finished steel plate; the second stage rolling start temperature is ≤850℃, and the final rolling temperature is 780-830℃; (5) ACC water cooling: Using the "ACC" cooling system, the initial cooling temperature is 790-810℃, the red-back temperature is 620-670℃, and the cooling rate is 5-8℃ / s; after the cooling is completed, the stack is quickly taken off the line for slow cooling, the stacking slow cooling temperature is 450±50℃, and the stacking time is ≥36h; (6) Normalizing heat treatment: Normalizing temperature is 880-890℃, and the normalizing time in the furnace = steel plate heating time + holding time; the heating rate is 1.3-1.5min / mm, and the holding time is 40-50min.

3. The method for manufacturing 16MnDR steel plate with SR high core toughness according to claim 2, characterized in that: It also includes simulated post-weld heat treatment steps, with the furnace entry temperature ≤400℃; when it is above 400℃, the heating rate is 50~80℃ / h, 600±10℃ insulation for 11-16h, the cooling rate is 30~50℃ / h, the furnace exit temperature is ≤400℃, and then air-cooled to room temperature.

4. The method for manufacturing 16MnDR steel plate with SR high core toughness according to claim 2, characterized in that: The manufactured steel plate has a yield strength ReL ≥ 320MPa, a tensile strength Rm of 495-520MPa, an elongation after fracture ≥ 28%, a transverse impact energy of the steel plate at 1 / 4 position at -40°C ≥ 250J, and a transverse impact energy of the steel plate at 1 / 2 position at -40°C ≥ 200J.

5. The method for manufacturing 16MnDR steel plate with SR high core toughness according to claim 2, characterized in that: The manufactured steel plate has a simulated post-weld heat treated steel plate yield strength ReL ≥ 295MPa, a tensile strength of 480-500MPa, an elongation after fracture ≥ 26%, a transverse impact energy of the steel plate at 1 / 4 position at -40°C ≥ 200J, and a transverse impact energy of the steel plate at 1 / 2 position at -40°C ≥ 150J.

6. The method for manufacturing 16MnDR steel plate with SR high core toughness according to claim 2, characterized in that: The maximum thickness of the manufactured steel plates is 100 mm.

7. The method for manufacturing 16MnDR steel plate with SR high core toughness according to claim 2, characterized in that: The flaw detection results of the manufactured steel plates meet the TI level requirements of NB / T 47013.3-2023 standard.

8. The method for manufacturing 16MnDR steel plate with SR high core toughness according to claim 2, characterized in that: The metallographic structure of the manufactured steel plates after normalizing heat treatment and simulated post-weld heat treatment is ferrite + pearlite, and the grain size at the 1 / 4 position and the 1 / 2 position of the thickness is ≥ grade 8.

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