TH2101002073A - Hot-rolled steel plates and methods of manufacture thereof - Google Patents

Abstract

DEPCT65 06/07/2021 This hot rolled steel plate has a predetermined chemical composition. and in case of thickness is shown by t. The metallurgical structure at t/4 from the surface contains annealed martensite. and benite either or both of the lower temperature ranges at a volume percentage of 90% or more, a tensile strength of 980 MPa or more. and the average Ni concentration on the surface is 7.0% or so. ---------------------------------------------------- --------- DEPCT64 This hot rolled steel plate has a predetermined chemical composition. and in case of thickness is shown by t. The metallurgical structure at t/4 from the surface contains annealed martensite. and benite either or both of the lower temperature ranges at a volume percentage of 90% or more, a tensile strength of 980 MPa or more. and the average Ni concentration on the surface is 7.0% or more. ---------------------------------------------------- ---------

Claims (14)

DEPCT65 06/07/21 1. Hot-rolled steel plate consisting of the following elements in % by mass as Chemical composition shown by average values in all sheet thickness directions C: 0.050% or more and 0.200% or less Si: 0.05% or more and 3.0.0% or less, Mn: 1.00%. or more and 4.00% or less Al: 0.001% or more and 2.000% or less N: 0.0005% or less and 0.1000% or less Ni: 0.02% or more and 2.00% or less Than Nb: 0% or more and 0.300% or less Ti: 0% or more and 0.300% or less Cu: 0% or more and 2.00% or less Mo: 0% or more That and 1.000% or less V: 0% or so and 0.300% or less Cr: 0% or so and 2.00% or less Mg: 0% or so and 0.0100% or less Ca: 0% or more and 0.0100% or less REM: 0% or more and 0.1000% or less B: 0% or more and 0.0100% or less Zr, Co, Zn and W elements One or two or more: 0% to 1.000% overall Sn: 0% to 0.050% P: 0.1% or less than that, S: 0.0300% or less, O: 0.0100% or less, and The remainder, which includes Fe and impurity Where, according to expression (1), the PCM represented by expression (2) is 0.20 or more, Ms represented by expression (3) is 400 degrees Celsius. or higher Where thickness is indicated by t, the metallurgical structure at the position t/4 from the surface will have annealed martensite and benite, either or both of the lower temperature ranges Total volume percentage equal to 90% or more. tensile strength is 980 MPa or so, and The average Ni concentration on the surface is 7.0% or more, 0.05% less than or equal to Si + Al, less than or equal to 2.50% ... Expression (1) PCM = C + Si/30 + Mn/20 + Cu/ 20 + Ni/60 + Mo/15 + Cr/20 + V/10 + 5 x B ... Expression (2) Ms = 561 - 474 x C-33 x Mn - 17 x Ni - 17 x Cr-21 x Mo ... expression (3) in which the symbol for each element shown in the expression indicates % by mass of the element present on the sheet. Hot-rolled steel 2. Hot-rolled steel sheet according to claim 1, where the hot-rolled sheet contains the following elements % by mass as a chemical element Ni: 0.02% or more, 0.05% or less. 3. Hot-rolled steel plate according to claim 1 or 2, where the average bulk density of iron-based carbide has in annealed martensite and benite at a lower temperature range of 1.0 x 10 to the 6th power carbide/mm2 or more 4. HRC based on 1 to 3 claims. any one where there is an internal oxide layer in the hot-rolled steel plate and The average depth of the internal oxide layer is 5.0 µm or more and 20.0 µm or less from the surface of the hot-rolled steel plate. where the standard deviation of the arithmetic mean roughness Ra of the surface of the plate HRC to 10.0 µm or more and 50.0 µm or less where the hot rolled steel sheet contains one or both of the following elements in % by mass as a chemical element B: 0.0001% or more and 0.0100% or less and Ti: 0.015% or more than that and 0.300% or less. 7. Hot-rolled steel sheet according to claims 1 to 6. Where hot rolled steel plate contains one or two or more of the following elements as % by mass. As a chemical element Nb: 0.005% or more and 0.300% or less Cu: 0.010% or more. and 2.00% or less Mo: 0.010% or more and 1.000% or less V:0.010% or less and 0.300% or less and Cr: 0.01% or more and 2.00% or less 8. Hot-rolled steel sheet according to one of the claims 1 to 7 Where hot rolled steel plate contains one or two or more of the following elements as % by mass. As a chemical composition Mg: 0.0005% or more and 0.0100% or less Ca: 0.0005% or more. and 0.0100% or less and REM: 0.0005% or more and 0.1000% or less Casting of molten steel with a chemical composition according to claim 1 to obtain a flat bar. Heating of flat bars in a heating furnace combined with a heat extractor burner. from the exhaust gas recovery and with at least a preheating area, heating area and immersion area. Hot rolling, the flat bar is heated so that the final rolling temperature is 850 degrees Celsius or higher that to obtain a hot-rolled steel sheet The preliminary cooling operation on hot rolled steel plates reaches a temperature range equal to or below the point temperature Ms calculated by expression (4) to give the average cooling rate from The final ironing temperature to the point temperature Ms is 50 °C/s or higher and Coiling of hot rolled steel plates at lower temperatures 350 degrees Celsius. where in heating a flat bar The ratio of air in the preheated area is 1.1 or more and 1.9 or less, Ms = 561 - 474 x C -33 x Mn - 17 x Ni - 17 x Cr - 21 x Mo ... expression (4 ) 10. Method for producing hot-rolled steel sheet according to claim 9, where the pre-cooling is stopped at a temperature below the point temperature Ms and 350 degrees Celsius. or higher and the hot-rolled steel plate after preliminary cooling is cooled. at lower temperatures 350 degrees Celsius. so that the maximum cooling rate is lower 50 °C/s 11. Method for producing hot-rolled steel sheet according to claim 9 or 10, in which the flat bar is heated. The ratio of air in the heated area is 0.9 or more and 1.3 or less. 12. The method of manufacture of hot-rolled steel sheets according to claims 9 to 11, one of them. where in heating a flat bar The ratio of air in the submerged zone is 0.9 or more and 1.9 or less. 13. Method of manufacture of hot-rolled steel sheet according to claim 11 or 12, where the ratio of air in the preheating zone is higher than the ratio of weather In the heated area 14. Any method of production of hot-rolled steel sheet according to claims 9 to 13 which combines more too Acid cleaning of HRC after HRC coiling using a solution of 1 to 10% hydrochloric acid by weight at a temperature equal to 20 degrees Celsius. up to 95 degrees Celsius Under conditions with acid cleaning times of 30 s or more and less than 60 s --------------------------- -------------------------------- DEPCT64 1. Hot-rolled steel sheet consisting of the following elements as % by mass as The chemical composition shown by the mean in the total sheet thickness direction C: 0.050% or more and 0.200% or less Si: 0.05% or more and 3.00% or less Mn: 1.00% or more. That and 4.00% or less Al: 0.001% or more and 2.000% or less N: 0.0005% or less and 0.1000% or less Ni: 0.02% or more and 2.00% or less Nb: 0% or more and 0.300% or less Ti: 0% or more and 0.300% or less Cu: 0% or more and 2.00% or less Mo: 0% or more and 1.000% or less V: 0% or more and 0.300% or less Cr: 0% or less and 2.00% or less Mg: 0% or more and 0.0100% or less Ca: 0% or more and 0.0100% or less REM: 0% or more and 0.1000% or less B: 0% or more and 0.0100% or less Zr, Co, Zn and W one element or Two or more: 0% to 1.000% overall Sn: 0% to 0.050% P: 0.1% or less that S: 0.0300% or less, O: 0.0100% or less, and the remainder, which includes Fe and adulterants. Subject to expression (1), the PCM represented by expression (2) is 0.20 or greater, Ms represented by expression (3) is 400 °C or higher. Where thickness is indicated by t, the metallurgical structure at t/4 from the surface has Tempered martensite and benite, either or both of the lower temperature ranges at the percentage. Total volume equal to 90% or more. The tensile strength is 980 MPa or so, and The average Ni concentration on the surface is 7.0% or more, 0.05% less than or equal to Si + Al, less than or equal to 2.50% ... Expression (1) PCM = C + Si/30 + Mn/20 + Cu/ 20 + Ni/60 + Mo/15 + Cr/20 + V/10 + 5 x B ... Expression (2) Ms = 561 - 474 x C-33 x Mn - 17 x Ni - 17 x Cr - 21 x Mo ... expression (3) in which the symbol for each element shown in the expression indicates % by mass of the element present on the sheet. hot rolled steel 2. Hot-rolled steel plate according to claim 1, where the hot-rolled steel plate contains the following elements as % by mass as the chemical composition Ni: 0.02% or more, 0.05% or less. 3. Hot-rolled steel plate according to claim 1 or 2, where the average bulk density of iron-based carbides contained in Tempered martensite and benite at lower temperatures 1.0 x 10 to the 6th power carbide/mm2. or more 4. Hot-rolled steel sheet according to one of the claims 1 to 3 where there is an internal oxidizing layer in the hot-rolled steel plate and The average depth of the internal oxidizing layer is 5.0 µm or more and 20.0 µm or less from the surface of the hot-rolled steel plate. 5. Hot-rolled steel sheet according to one of the claims 1 to 4. where the standard deviation of the arithmetic mean roughness Ra of the surface of the plate Hot rolled steel is 10.0 µm or more and 50.0 µm or less. 6. Hot-rolled steel sheet according to one of the claims 1 to 5 where the hot rolled steel sheet contains one or both of the following elements in % by mass as a chemical element B: 0.0001% or more and 0.0100% or less and Ti: 0.015% or more than that and 0.300% or less 7. Hot-rolled steel sheet according to any one of the claims 1 to 6 Where hot rolled steel plate contains one or two or more of the following elements, % by mass, as a chemical element Nb: 0.005% or more and 0.300% or less, Cu: 0.010% or more. and 2.00% or less Mo: 0.010% or more and 1.000% or less V: 0.010% or less and 0.300% or less and Cr: 0.01% or more and 2.00% or less 8. Hot-rolled steel sheet according to one of the claims 1 to 7 where the hot rolled steel plate contains one or two or more of the following elements as % by mass as a chemical composition Mg: 0.0005% or more and 0.0100% or less Ca: 0.0005% or more and 0.0100% or less and REM: 0.0005% or more and 0.1000% or less 9. Method for producing hot-rolled steel sheet including Casting of molten steel with a chemical composition according to claim 1 to make a thick sheet material. Heating of thick plate materials in heating furnaces, including heat-drawn furnaces. from exhaust reuse and with preheating area, heating area and immersion area at least Hot rolling of thick sheet material that is heated to a rolling temperature range of 850 °C or higher to obtain a hot rolled steel plate. Initial cooling operations on hot-rolled steel plates to a temperature range equal to or below the point temperature Ms calculated by expression (4) to give the average cooling rate since The ironing temperature range when the final press reaches the point temperature Ms is 50 °C/s or higher and Coil rate of hot-rolled steel sheet at temperatures below 350 °C, where in the heating of thick sheets The ratio of air in the preheated area is 1.1 or more and 1.9 or less, Ms = 561 - 474 x C - 33 x Mn - 17 x Ni - 17 x Cr - 21 x Mo ... expression (4 ) 10. Method for producing hot-rolled steel plates according to claim 9, where pre-cooling is stopped at temperatures below Ms point temperature and 350 °C or higher, and hot-rolled steel plates after pre-cooling. is cooled to a temperature below 350°C to achieve a maximum cooling rate of less than 50°C/s. 11. Method for producing hot-rolled steel sheet according to claim 9 or 10, wherein the thick sheet material is heated The ratio of air in the heated area is 0.9 or more and 1.3 or less. 12. The method of producing hot-rolled steel sheet according to any of the claims 9 to 11 where in heating the thick sheet material The ratio of air in the immersion area is 0.9 or more and 1.9 or less. 13. Method for producing hot-rolled steel sheet according to claim 11 or 12, where the ratio of air in the pre-heating area is higher than the ratio of air. in the heating area 14. Method for producing hot rolled steel sheet according to any of the claims 9 to 13 which combines more too Acid cleaning of hot-rolled steel plate after coiling of hot-rolled steel plate using a 1 to 10% hydrochloric acid solution by weight at a temperature of 20°C to 95°C under conditions with an acid cleaning time of 30 s or more and less than 60 s -- ---------------------------------------------------- -------