Manufacturing method and application of ultralow-temperature high-manganese steel and ultralow-temperature high-manganese steel plate

Abstract

The invention discloses ultralow-temperature high manganese steel and a manufacturing method of an ultralow-temperature high manganese steel plate. The ultralow-temperature high manganese steel comprises the following components in percentage by weight: 0.35-0.55% of C, 0.01-0.10% of Si, 20.00-30.00% of Mn, 0.01-0.10% of Al, less than or equal to 0.005% of P, less than or equal to 0.003% of S, 3.0-5.0% of Cr, 0.3-1.0% of Cu, 0.2-1.20% of Ni, less than or equal to 0.008% of N, less than or equal to 0.002% of O, less than or equal to 0.0002% of H and the balance of Fe and inevitable impurity elements. The manufacturing method of the ultralow-temperature high manganese steel plate comprises the steps of molten iron pretreatment, K-OBM-S converter smelting, LF refining, continuous casting, annealing and coping, hot rolling, online solution treatment and the like. According to the method, high steel purity, low phosphorus and sulfur content, small segregation of the casting blank and the steel plate, good macrostructure of the casting blank and no crack on the surface and in the casting blank can be guaranteed, and the finished steel plate has the characteristics of low yield ratio, high tensile strength, high ultralow-temperature toughness, small thermal expansion coefficient, good fatigue resistance and the like; through the implementation of the invention, the manufacturing cost of the steel for the liquefied natural gas storage tank can be reduced to 1 / 3 of that of 9% Ni steel in the prior art.

Description

Technical Field

[0001] The invention belongs to the technical field of iron and steel metallurgy, and specifically relates to a manufacturing method and application of a high manganese steel for ultra-low temperature and a high manganese steel plate for ultra-low temperature. Background Art

[0002] At present, 9% Ni steel is used as the key metal material for large-scale liquefied natural gas storage tanks. However, since 9% of the precious metal nickel is added to the steel and my country's nickel resources mainly rely on imports, as the total demand for steel for liquefied natural gas storage tanks in my country increases significantly, there is an urgent need to develop low-cost, high-performance new nickel-free steel.

[0003] Compared with 9% Ni steel, high manganese steel has low price, small thermal expansion coefficient and good fatigue resistance. Due to the high purity requirements of high manganese steel, the difficulty of alloying, and the easy cracking of continuous casting billets, industrial smelting and continuous casting production have not yet been realized, making industrial high manganese steel for liquefied natural gas storage tanks in my country still blank.

[0004] Therefore, developing a method for manufacturing high manganese steel for ultra-low temperature and high manganese steel plate for ultra-low temperature is of great significance for meeting the demand for low-cost, high-performance steel for liquefied natural gas storage tanks. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method for manufacturing high manganese steel for ultra-low temperature and high manganese steel plate for ultra-low temperature.

[0006] The ultra-low temperature high manganese steel provided by the invention comprises, by weight percentage, C: 0.35-0.55%, Si: 0.01-0.10%, Mn: 20.00-30.00%, Al: 0.01-0.10%, P≤0.005%, S≤0.003%, Cr: 3.0-5.0%, Cu: 0.3-1.0%, Ni: 0.2-1.20%, N≤0.008%, O≤0.002%, H≤0.0002%, and the balance is Fe and unavoidable impurity elements.

[0007] The method for manufacturing a high manganese steel plate for ultra-low temperature provided by the present invention comprises the following steps:

[0008] (1) Pretreatment of molten iron to reduce the P content in the molten iron to P ≤ 0.007%;

[0009] (2) K-OBM-S converter smelting, adding molten iron into the K-OBM-S converter for smelting, after decarburization in the K-OBM-S converter to C≤0.13%, adding electrolytic manganese into the K-OBM-S converter three times, and adding aluminum pellets for deoxidation when adding electrolytic manganese for the first time and the second time, adding nickel plate and copper when adding electrolytic manganese for the third time, adding ferrosilicon after adding electrolytic manganese for the second time and the third time, and blowing oxygen to increase the temperature;

[0010] (3) LF refining, the molten steel obtained by K-OBM-S converter smelting is sent to LF furnace, and the temperature is raised and slag is adjusted. In the later stage of reduction, the composition is adjusted to: C: 0.35-0.55%, Si: 0.01-0.10%, Mn: 20.00-30.00%, Al: 0.01-0.10%, P≤0.005%, S≤0.003%, Cr: 3.0-5.0%, Cu: 0.3-1.0%, Ni: 0.2-1.20%, N≤0.008%, O≤0.002%, H≤0.0002%, and the balance is Fe and unavoidable impurity elements;

[0011] (4) Continuous casting: the mold taper is designed to be 1.2%, the nozzle type adopts a small hole nozzle, the nozzle insertion depth is 110-125 mm, the secondary cooling adopts peritectic steel, electromagnetic stirring is used during the continuous casting process, the tundish temperature is controlled at 1420±10℃, and the casting speed is controlled at 0.6-0.8 m / min;

[0012] (5) Annealing and grinding: the annealing temperature of the ingot is controlled at 750-770°C. After annealing, the surface of the ingot is ground, and the grinding amount is controlled at 2-3%;

[0013] (6) Hot rolling: the steel billet is heated to 1200-1230°C in a heating furnace for homogenization, and then rolled by widening longitudinal rolling. The starting rolling temperature is controlled at 1040-1060°C, and the final rolling temperature is controlled at 910-940°C;

[0014] (7) Online solution treatment: the hot rolled steel plate adopts online laminar cooling to achieve online solution treatment, and the red-return temperature of the steel plate is ≤300℃.

[0015] Further, in the above-mentioned method for manufacturing the ultra-low temperature high manganese steel plate, in the K-OBM-S converter smelting step, the total amount of electrolytic manganese added is (30% to 35%) × tons of molten iron, the first amount of electrolytic manganese added is 35% to 40% of the total amount of electrolytic manganese added, the second amount of electrolytic manganese added is 30% to 40% of the total amount of electrolytic manganese added, the third amount of electrolytic manganese added is 20% to 30% of the total amount of electrolytic manganese added, and the amount of aluminum shot added when adding electrolytic manganese for the first time is (0.3% to 0.5%). × tons of molten iron, when adding electrolytic manganese for the second time, the amount of aluminum shot added is (0.2% ~ 0.3%) × tons of molten iron, after adding electrolytic manganese for the second time, the amount of ferrosilicon added is (0.3% ~ 0.4%) × tons of molten iron, after adding electrolytic manganese for the third time, the amount of ferrosilicon added is (0.6% ~ 0.7%) × tons of molten iron, when adding electrolytic manganese for the third time, the amount of nickel plate added is (0.15% ~ 0.25%) × tons of molten iron, and the amount of copper added is (0.5% ~ 0.7%) × tons of molten iron.

[0016] Furthermore, in the above-mentioned manufacturing method of high manganese steel plate for ultra-low temperature, in the continuous casting step, a special protective slag is used, and the composition of the special protective slag is: SiO2: 37-43%, CaO: 16-22%, Al2O3: 2-5%, MgO≤2.5%, Li2O: 5-7%, Na2O: 8-12%, C-total: 5-6%, F: 5-9%, and CaO / SiO2 is 0.4-0.6. The melting point of the special protective slag is 840-900°C, and the viscosity at 1300°C is 0.18-0.28PaS.

[0017] Furthermore, in the method for manufacturing the ultra-low temperature high manganese steel plate, the yield strength R P0.2 ≥440MPa, tensile strength R m ≥830MPa, elongation A≥40%, -196℃ transverse impact energy KV2≥120J.

[0018] In addition, the present invention also provides the use of the above-mentioned ultra-low temperature high manganese steel or the ultra-low temperature high manganese steel plate produced by the above-mentioned ultra-low temperature high manganese steel plate manufacturing method in liquefied natural gas storage tanks.

[0019] The manufacturing method of the high manganese steel for ultra-low temperature and the high manganese steel plate for ultra-low temperature of the present invention can ensure high purity of steel, low phosphorus and sulfur content, small segregation of ingot and steel plate, good macrostructure of ingot, no cracks on the surface and inside of ingot, and the finished steel plate has the characteristics of low yield ratio, high tensile strength, high ultra-low temperature toughness, small thermal expansion coefficient, good fatigue resistance, etc. Moreover, through the implementation of the present invention, the manufacturing cost of steel for liquefied natural gas storage tanks can be reduced to 1 / 3 of the 9% Ni steel in the prior art, which is of great significance for meeting the demand for low-cost and high-performance steel for liquefied natural gas storage tanks. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0021] The ultra-low temperature high manganese steel of the present invention comprises, by weight percentage, C: 0.35-0.55%, Si: 0.01-0.10%, Mn: 20.00-30.00%, Al: 0.01-0.10%, P≤0.005%, S≤0.003%, Cr: 3.0-5.0%, Cu: 0.3-1.0%, Ni: 0.2-1.20%, N≤0.008%, O≤0.002%, H≤0.0002%, and the balance is Fe and unavoidable impurity elements.

[0022] The method for manufacturing a high manganese steel plate for ultra-low temperature of the present invention comprises the following steps:

[0023] (1) Pretreatment of molten iron to reduce the P content in the molten iron to P≤0.007%.

[0024] (2) K-OBM-S converter smelting, adding molten iron into the K-OBM-S converter for smelting, after the K-OBM-S converter smelting decarburization to C ≤ 0.13%, adding electrolytic manganese into the K-OBM-S converter in three times, the total amount of electrolytic manganese added is (30% to 35%) × tons of molten iron, the first amount of electrolytic manganese added is 35% to 40% of the total amount of electrolytic manganese added, the second amount of electrolytic manganese added is 30% to 40% of the total amount of electrolytic manganese added, and the third amount of electrolytic manganese added is 20% to 30% of the total amount of electrolytic manganese added, and aluminum shots are added for deoxidation when adding electrolytic manganese for the first time and the second time, and nickel plates and copper are added when adding electrolytic manganese for the third time. After the second and third additions of electrolytic manganese, ferrosilicon is added respectively and oxygen is blown to increase the temperature. Among them, when the electrolytic manganese is added for the first time, the amount of aluminum shot added is (0.3%~0.5%)×tons of molten iron, and when the electrolytic manganese is added for the second time, the amount of aluminum shot added is (0.2%~0.3%)×tons of molten iron. After the second addition of electrolytic manganese, the amount of ferrosilicon added is (0.3%~0.4%)×tons of molten iron. After the third addition of electrolytic manganese, the amount of ferrosilicon added is (0.6%~0.7%)×tons of molten iron. When the electrolytic manganese is added for the third time, the amount of nickel plate added is (0.15%~0.25%)×tons of molten iron. When the electrolytic manganese is added for the third time, the amount of copper added is (0.5%~0.7%)×tons of molten iron.

[0025] (3) LF refining, the molten steel obtained by smelting in the K-OBM-S converter is sent to the LF furnace, and the temperature is raised and the slag is adjusted. In the later stage of reduction, the composition is adjusted to: C: 0.35-0.55%, Si: 0.01-0.10%, Mn: 20.00-30.00%, Al: 0.01-0.10%, P≤0.005%, S≤0.003%, Cr: 3.0-5.0%, Cu: 0.3-1.0%, Ni: 0.2-1.20%, N≤0.008%, O≤0.002%, H≤0.0002%, and the balance is Fe and unavoidable impurity elements.

[0026] (4) Continuous casting: the taper of the crystallizer is designed to be 1.2%. The water inlet type adopts a small hole water inlet with a water inlet insertion depth of 110 to 125 mm. The secondary cooling adopts peritectic steel. Electromagnetic stirring is used in the continuous casting process. The temperature of the tundish is controlled to be 1420±10°C. The pulling speed is controlled to be 0.6 to 0.8 m / min. A special protective slag is used in the continuous casting process. The composition of the special protective slag is: SiO2: 37 to 43%, CaO: 16 to 22%, Al2O3: 2 to 5%, MgO≤2.5%, Li2O: 5 to 7%, Na2O: 8 to 12%, C-total: 5 to 6%, F: 5 to 9%, and CaO / SiO2 is 0.4 to 0.6. The melting point of the special protective slag is 840 to 900°C and the viscosity at 1300°C is 0.18 to 0.28 PaS.

[0027] (5) Annealing and grinding: the annealing temperature of the ingot is controlled at 750-770°C. After annealing, the surface of the ingot is ground, and the grinding amount is controlled at 2-3%.

[0028] (6) Hot rolling: the steel billet is heated to 1200-1230°C in a heating furnace for homogenization, and then rolled by widening longitudinal rolling. The starting rolling temperature is controlled at 1040-1060°C, and the final rolling temperature is controlled at 910-940°C.

[0029] (7) Online solution treatment: the hot rolled steel plate adopts online laminar cooling to achieve online solution treatment, and the red-return temperature of the steel plate is ≤300℃.

[0030] The following is a detailed description of the method for manufacturing a high manganese steel plate for ultra-low temperature use of the present invention in conjunction with the embodiments. The implementation methods in the following embodiments without specifying specific conditions are carried out according to conventional methods and conditions, and the present invention does not make specific limitations on this.

[0031] Example 1

[0032] The method for manufacturing the ultra-low temperature high manganese steel plate of Example 1 specifically comprises the following steps:

[0033] (1) Pretreatment of molten iron to reduce the P content in the molten iron to 0.0061%.

[0034] (2) K-OBM-S converter smelting, using a K-OBM-S converter with a nominal capacity of 80 tons, the K-OBM-S converter is charged with 60 tons of molten iron, and after decarburization to a carbon content of 0.13% in the K-OBM-S converter, a total of 21 tons of electrolytic manganese is added to the K-OBM-S converter in three batches using a feed trough, with 8 tons, 7 tons, and 6 tons of electrolytic manganese added to the first, second, and third feed troughs, respectively. Each time the electrolytic manganese is added, stirring is performed. At the same time, 0.25 tons and 0.15 tons of aluminum shots are added to the first and second feed troughs, respectively, for deoxidation, thereby increasing the manganese recovery rate. 0.14 tons of nickel plate and 0.35 tons of copper are added to the third feed trough. After the second feed trough is charged and stirred, 0.2 tons of ferrosilicon are added and oxygen is blown at 210 Nm 3 After the third trough is charged, add 0.4 tons of ferrosilicon and blow oxygen at 230 Nm 3 The temperature is increased to ensure the process temperature requirements.

[0035] (3) LF refining. The LF arrival temperature is 1472℃. Slag samples are taken at the station, and 500kg lime, 100kg fluorite and 2 bags of aluminum powder are added for slag adjustment. During the LF process, a total of 7 bags of carbon powder, 350kg electrolytic manganese, 67kg Ni plate and 600kg low-carbon ferrochrome are added for alloying. The LF end temperature is 1473℃. The chemical composition is adjusted to: C: 0.35%, Si: 0.05%, Mn: 29.5%, Al: 0.03%, P: 0.004%, S: 0.001%, Cu: 0.35%, Cr: 4.5%, Ni: 0.80%, N: 0.008%, O: 0.0015%, H: 0.0001%, and the remainder is the target value of Fe and unavoidable impurities. Then, the steel is tapped after soft stirring for 10 minutes.

[0036] (4) Continuous casting: The mold taper is designed to be 1.2%. A special small-hole nozzle is used as the nozzle type. The nozzle insertion depth is 120±5 mm. Peritectic steel is used for the secondary cooling. Electromagnetic stirring is used during the continuous casting process. The electromagnetic stirring process parameters are 400A-5HZ-15s reversing, liquidus temperature is 1390°C, middle package temperature is 1412°C, casting speed is 0.75 m / min, and the aforementioned special protective slag is used.

[0037] (5) Annealing and grinding: the annealing temperature of the ingot is 750°C. After annealing, the surface of the ingot is ground by 3%, and the grinding amount is 3%. The ingot is tested by low-power detection. The results are: general looseness level 0.5, central looseness level 0, general skewness level 0, ingot skewness level 0, and no cracks are found.

[0038] (6) Hot rolling: The steel billet is cold loaded into the furnace, the soaking temperature is 1200℃, the heating time is 160 minutes, and the steel billet enters the 4-roll 3300mm medium plate rolling mill for rolling. High-pressure water is used to remove all iron scales. The widening longitudinal rolling is adopted. The hot rolling specifications are 6mm×2000mm×10000mm, the starting rolling temperature is 1050℃, and the final rolling temperature is 910℃. After rolling, the finished product is straightened to ensure the plate shape, and the steel plate is sheared online.

[0039] (7) Online solution treatment, the steel plate red-return temperature is 150℃.

[0040] (8) Straightening and trimming: The steel plates are cold straightened to ensure the plate shape requirements, and the edges are trimmed as required to ensure the finished product specifications of 6mm×1950mm×9000mm. The steel plates are then marked and packaged.

[0041] Through performance testing, the mechanical properties of the ultra-low temperature high manganese steel plate prepared by Example 1 are as follows: yield strength R P0.2 The tensile strength R is 480MPa. m It is 840MPa, the elongation A is 42%, and the -196℃ transverse impact energy KV2 tested with a 5*10*55mm half sample is 72J on average.

[0042] Therefore, by implementing the manufacturing method of ultra-low temperature high manganese steel plate of Example 1, the ultra-low temperature high manganese steel and ultra-low temperature high manganese steel plate prepared can be used in the construction of liquefied natural gas storage tanks.

[0043] Example 2

[0044] The manufacturing method of the ultra-low temperature high manganese steel plate of Example 2 specifically comprises the following steps:

[0045] (1) Pretreatment of molten iron to reduce the P content in the molten iron to 0.0059%.

[0046] (2) K-OBM-S converter smelting, using a K-OBM-S converter with a nominal capacity of 80 tons, the K-OBM-S converter is charged with 60 tons of molten iron, and after decarburization to a carbon content of 0.12% in the K-OBM-S converter, a total of 18 tons of electrolytic manganese is added to the K-OBM-S converter in three batches using a feed trough, with 7 tons, 7 tons, and 4 tons of electrolytic manganese added to the first, second, and third feed troughs, respectively. Each time the electrolytic manganese is added, stirring is performed. At the same time, 0.2 tons and 0.15 tons of aluminum shots are added to the first and second feed troughs, respectively, for deoxidation, thereby increasing the manganese recovery rate. 0.1 tons of nickel plates and 0.4 tons of copper are added to the third feed trough. After the addition and stirring of the second feed trough is completed, 0.2 tons of ferrosilicon are added and oxygen is blown at 220 Nm 3 After the third trough is charged, add 0.4 tons of ferrosilicon and blow oxygen at 240 Nm 3 The temperature is increased to ensure the process temperature requirements.

[0047] (3) LF refining. The LF arrival temperature is 1475℃. Slag samples are taken at the station, and 500kg lime, 100kg fluorite and 2 bags of aluminum powder are added for slag adjustment. During the LF process, a total of 9 bags of carbon powder, 400kg electrolytic manganese, 35kg Ni plate and 550kg low-carbon ferrochrome are added for alloying. The LF ending temperature is 1475℃. The chemical composition is adjusted to: C: 0.55%, Si: 0.05%, Mn: 22.5%, Al: 0.03%, P: 0.005%, S: 0.001%, Cu: 0.65%, Cr: 3.5%, Ni: 0.20%, N: 0.006%, O: 0.0015%, H: 0.0001%, and the remainder is the target value of Fe and unavoidable impurities. Then, the steel is tapped after soft stirring for 10 minutes.

[0048] (4) Continuous casting: The taper of the crystallizer is designed to be 1.2%. The water nozzle type adopts a special small-hole water nozzle with a water nozzle insertion depth of 120±5mm. The secondary cooling adopts peritectic steel. Electromagnetic stirring is used in the continuous casting process. The electromagnetic stirring process parameters are 400A-5HZ-15s reversing, liquidus temperature is 1390℃, middle package temperature is 1430℃, casting speed is 0.65m / min, and the aforementioned special protective slag is used.

[0049] (5) Annealing and grinding: the annealing temperature of the ingot is 770°C. After annealing, the surface of the ingot is ground by 2%. The ingot is tested by low-power magnification. The results are: general porosity level 0.5, central porosity level 0, general skewness level 0, ingot skewness level 0, and no cracks are found.

[0050] (6) Hot rolling: The steel billet is cold loaded into the furnace, the soaking temperature is 1200℃, the heating time is 160 minutes, and the steel billet enters the 4-roll 3300mm medium plate rolling mill for rolling. High-pressure water is used to remove all iron scales. The widening longitudinal rolling is adopted. The hot rolling specifications are 50mm×2000mm×10000mm, the starting rolling temperature is 1055℃, and the final rolling temperature is 940℃. After rolling, the finished product is straightened to ensure the plate shape, and the steel plate is sheared online.

[0051] (7) Online solution treatment, the steel plate red-return temperature is 290℃.

[0052] (8) Straightening and trimming: The steel plates are cold straightened to ensure the plate shape requirements, and the edges are trimmed as required to ensure the finished product specifications of 50mm×1950mm×9000mm. The steel plates are then marked and packaged.

[0053] Through performance testing, the mechanical properties of the ultra-low temperature high manganese steel plate prepared by Example 2 are as follows: yield strength R P0.2 The tensile strength is 440MPa and R m It is 835MPa, the elongation A is 50%, and the -196℃ transverse impact energy KV2 is 138J on average.

[0054] Therefore, by implementing the manufacturing method of ultra-low temperature high manganese steel plate of Example 2, the ultra-low temperature high manganese steel and ultra-low temperature high manganese steel plate prepared can be used in the construction of liquefied natural gas storage tanks.

[0055] Example 3

[0056] The method for manufacturing the ultra-low temperature high manganese steel plate of Example 3 specifically comprises the following steps:

[0057] (1) Pretreatment of molten iron to reduce the P content in the molten iron to 0.0055%.

[0058] (2) K-OBM-S converter smelting, using a K-OBM-S converter with a nominal capacity of 80 tons, the K-OBM-S converter is charged with 60 tons of molten iron, and after decarburization to a carbon content of 0.12% in the K-OBM-S converter, a total of 19 tons of electrolytic manganese is added to the K-OBM-S converter in three batches using a feed trough, with 7 tons, 7 tons, and 5 tons of electrolytic manganese added to the first, second, and third feed troughs, respectively. Each time the electrolytic manganese is added, stirring is performed. At the same time, 0.2 tons and 0.15 tons of aluminum shots are added to the first and second feed troughs, respectively, for deoxidation, thereby increasing the manganese recovery rate. 0.15 tons of nickel plate and 0.4 tons of copper are added to the third feed trough. After the addition and stirring of the second feed trough is completed, 0.2 tons of ferrosilicon are added and oxygen is blown at 210 Nm 3 After the third trough is charged, add 0.4 tons of ferrosilicon and blow oxygen at 230 Nm 3 The temperature is increased to ensure the process temperature requirements.

[0059] (3) LF refining, the LF arrival temperature is 1465℃, slag samples are taken at the station, 500kg lime, 100kg fluorite and 2 bags of aluminum powder are added for slag adjustment, and a total of 7 bags of carbon powder, 420kg electrolytic manganese, 50kg Ni plate and 550kg low-carbon ferrochrome are added for alloying during the LF process. The LF end temperature is 1472℃, and the chemical composition is adjusted to: C: 0.45%, Si: 0.05%, Mn: 24.5%, Al: 0.03%, P: 0.003%, S: 0.001%, Cu: 0.45%, Cr: 4.0%, Ni: 0.50%, N: 0.007%, O: 0.0014%, H: 0.0001%, and the remainder is the target value of Fe and unavoidable impurities. Then, the steel is tapped after soft stirring for 10 minutes.

[0060] (4) Continuous casting: The mold taper is designed to be 1.2%. A special small-hole nozzle is used as the nozzle type. The nozzle insertion depth is 115±5 mm. Peritectic steel is used for the secondary cooling. Electromagnetic stirring is used during the continuous casting process. The electromagnetic stirring process parameters are 400A-5HZ-15s reversing, liquidus temperature is 1390°C, middle package temperature is 1420°C, casting speed is 0.7 m / min, and the aforementioned special protective slag is used.

[0061] (5) Annealing and grinding: the annealing temperature of the ingot is 770°C. After annealing, the surface of the ingot is ground by 2%. The ingot is tested by low-power magnification. The results are: general porosity level 0.5, central porosity level 0, general skewness level 0, ingot skewness level 0, and no cracks are found.

[0062] (6) Hot rolling: The steel billet is cold loaded into the furnace, the soaking temperature is 1200℃, the heating time is 160 minutes, and the steel billet enters the 4-roll 3300mm medium plate rolling mill for rolling. High-pressure water is used to remove all iron scales. The widening longitudinal rolling is adopted. The hot rolling specifications are 20mm×2800mm×10000mm, the starting rolling temperature is 1050℃, and the final rolling temperature is 930℃. After rolling, the finished product is straightened to ensure the plate shape, and the steel plate is sheared online.

[0063] (7) Online solution treatment, the steel plate red-return temperature is 270℃.

[0064] (8) Straightening and trimming: The steel plates are cold straightened to ensure the plate shape requirements, and the edges are trimmed as required to ensure the finished product specifications of 20mm×2700mm×9000mm. The steel plates are then marked and packaged.

[0065] After performance testing, the mechanical properties of the ultra-low temperature high manganese steel plate prepared by Example 3 are as follows: yield strength R P0.2 The tensile strength is 450MPa and the m It is 842MPa, the elongation A is 48%, and the -196℃ transverse impact energy KV2 is 138J on average.

[0066] Therefore, by implementing the manufacturing method of ultra-low temperature high manganese steel plate of Example 3, the ultra-low temperature high manganese steel and ultra-low temperature high manganese steel plate prepared can be used in the construction of liquefied natural gas storage tanks.

[0067] In summary, the manufacturing method of the ultra-low temperature high manganese steel and ultra-low temperature high manganese steel plate of the present invention can ensure high steel purity, low phosphorus and sulfur content, small segregation of the ingot and the steel plate, good ingot macrostructure, no cracks on the surface and inside of the ingot, and the finished steel plate has the characteristics of low yield ratio, high tensile strength, high ultra-low temperature toughness, small thermal expansion coefficient, good fatigue resistance, etc. Moreover, through the implementation of the present invention, the manufacturing cost of steel for liquefied natural gas storage tanks can be reduced to 1 / 3 of the 9% Ni steel in the prior art, which is of great significance for meeting the demand for low-cost and high-performance steel for liquefied natural gas storage tanks. Specifically, compared with the prior art, the manufacturing method of the ultra-low temperature high manganese steel and ultra-low temperature high manganese steel plate of the present invention has the following advantages and beneficial effects:

[0068] (1) The company developed the first high manganese steel K-OBM-S converter steel alloying technology in China, which shortened the smelting time by more than 50 minutes compared with the existing converter + LF alloying technology, significantly improving production efficiency;

[0069] (2) The macrostructure of the ingot is good, the general porosity is 0.5, the central porosity is 0, the general eccentricity is 0, the ingot eccentricity is 0, and there is no crack;

[0070] (4) The finished steel plate has excellent mechanical properties and yield strength RP0.2 ≥440MPa, tensile strength R m ≥830MPa, elongation A≥40%, -196℃ transverse impact energy KV2≥120J, fully meeting the construction and use requirements of liquefied natural gas storage tanks or ultra-low temperature containers;

[0071] (5) A special mold protection slag was developed to delay the reaction time between the aluminum in the steel and the SiO2 in the protection slag, reducing the surface and internal cracks caused by uneven heating and cooling, and reducing the surface and internal cracks of the ingot to zero.

[0072] It should be noted that, in addition to the explicit description herein, the process method of the present invention can be implemented by conventional methods or devices in the art, and the noun terms in this article, unless otherwise specified, have the meanings generally understood by those skilled in the art. Moreover, when a numerical range is disclosed herein, the above range is deemed to be continuous and includes the minimum and maximum values ​​of the range, and each value between such minimum and maximum values. Further, when the range refers to an integer, each integer between the minimum and maximum values ​​of the range is included. In addition, when multiple range description features are provided, the range can be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges included therein.

[0073] It should also be noted that, in this article, the term "comprise" or any other variation thereof is intended to cover non-exclusive inclusion, so that an article or device that includes a series of elements includes not only those elements, but also includes other elements that are not explicitly listed, or also includes elements that are inherent to such article or device.

[0074] In addition, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the present invention.

Claims

1. A high manganese steel for ultra-low temperature, characterized in that: The ultra-low temperature high manganese steel comprises, by weight percentage, C: 0.35-0.55%, Si: 0.01-0.10%, Mn: 20.00-30.00%, Al: 0.01-0.10%, P≤0.005%, S≤0.003%, Cr: 3.0-5.0%, Cu: 0.3-1.0%, Ni: 0.2-1.20%, N≤0.008%, O≤0.002%, H≤0.0002%, and the remainder is Fe and unavoidable impurity elements.

2. A method for manufacturing a high manganese steel plate for ultra-low temperature use, characterized in that: The steps include: (1) Pretreatment of molten iron to reduce the P content in the molten iron to P ≤ 0.007%; (2) K-OBM-S converter smelting, adding molten iron into the K-OBM-S converter for smelting, after decarburization in the K-OBM-S converter to C≤0.13%, adding electrolytic manganese into the K-OBM-S converter three times, and adding aluminum pellets for deoxidation when adding electrolytic manganese for the first time and the second time, adding nickel plate and copper when adding electrolytic manganese for the third time, adding ferrosilicon after adding electrolytic manganese for the second time and the third time, and blowing oxygen to increase the temperature; (3) LF refining, the molten steel obtained by K-OBM-S converter smelting is sent to LF furnace, and the temperature is raised and slag is adjusted. In the later stage of reduction, the composition is adjusted to: C: 0.35-0.55%, Si: 0.01-0.10%, Mn: 20.00-30.00%, Al: 0.01-0.10%, P≤0.005%, S≤0.003%, Cr: 3.0-5.0%, Cu: 0.3-1.0%, Ni: 0.2-1.20%, N≤0.008%, O≤0.002%, H≤0.0002%, and the balance is Fe and unavoidable impurity elements; (4) Continuous casting: the mold taper is designed to be 1.2%, the nozzle type adopts a small hole nozzle, the nozzle insertion depth is 110-125 mm, the secondary cooling adopts peritectic steel, electromagnetic stirring is used during the continuous casting process, the tundish temperature is controlled at 1420±10℃, and the casting speed is controlled at 0.6-0.8 m / min; (5) Annealing and grinding: the annealing temperature of the ingot is controlled at 750-770°C. After annealing, the surface of the ingot is ground, and the grinding amount is controlled at 2-3%; (6) Hot rolling: the steel billet is heated to 1200-1230°C in a heating furnace for homogenization, and then rolled by widening longitudinal rolling. The starting rolling temperature is controlled at 1040-1060°C, and the final rolling temperature is controlled at 910-940°C; (7) Online solution treatment: the hot rolled steel plate adopts online laminar cooling to achieve online solution treatment, and the red-return temperature of the steel plate is ≤300℃.

3. The method for manufacturing a high manganese steel plate for ultra-low temperature use according to claim 2, characterized in that: In the K-OBM-S converter smelting step, the total amount of electrolytic manganese added is (30%-35%)×tons of molten iron, the first amount of electrolytic manganese added is 35%-40% of the total amount of electrolytic manganese added, the second amount of electrolytic manganese added is 30%-40% of the total amount of electrolytic manganese added, the third amount of electrolytic manganese added is 20%-30% of the total amount of electrolytic manganese added, the amount of aluminum shot added when adding electrolytic manganese for the first time is (0.3%-0.5%)×tons of molten iron, and the amount of aluminum shot added when adding electrolytic manganese for the second time is (0.3%-0.5%)×tons of molten iron. When electrolytic manganese is added, the amount of aluminum shot added is (0.2% ~ 0.3%) × tons of molten iron, the amount of ferrosilicon added after the second addition of electrolytic manganese is (0.3% ~ 0.4%) × tons of molten iron, the amount of ferrosilicon added after the third addition of electrolytic manganese is (0.6% ~ 0.7%) × tons of molten iron, the amount of nickel plate added when the third addition of electrolytic manganese is (0.15% ~ 0.25%) × tons of molten iron, and the amount of copper added when the third addition of electrolytic manganese is (0.5% ~ 0.7%) × tons of molten iron.

4. The method for manufacturing a high manganese steel plate for ultra-low temperature use according to claim 2, characterized in that: In the continuous casting step, a special protective slag is used, and the composition of the special protective slag is: SiO2: 37-43%, CaO: 16-22%, Al2O3: 2-5%, MgO≤2.5%, Li2O: 5-7%, Na2O: 8-12%, C-total: 5-6%, F: 5-9%, and CaO / SiO2 is 0.4-0.

6. The melting point of the special protective slag is 840-900°C, and the viscosity at 1300°C is 0.18-0.28PaS.

5. The method for manufacturing a high manganese steel plate for ultra-low temperature use according to claim 2, characterized in that: The yield strength R of the ultra-low temperature high manganese steel plate P0.2 ≥440MPa, tensile strength R m ≥830MPa, elongation A≥40%, -196℃ transverse impact energy KV2≥120J.

6. Use of the ultra-low temperature high manganese steel according to claim 1 or the ultra-low temperature high manganese steel plate produced by the manufacturing method of the ultra-low temperature high manganese steel plate according to claim 2 in liquefied natural gas storage tanks.