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|1. (WO2018036379) LOW-COST, HIGH STRENGTH-TOUGHNESS THIN GAUGE 9NI STEEL PLATE MANUFACTURING METHOD|
|Applicants:||NANJING IRON & STEEL CO., LTD.
|Title:||LOW-COST, HIGH STRENGTH-TOUGHNESS THIN GAUGE 9NI STEEL PLATE MANUFACTURING METHOD|
Provided is a method for manufacturing a low-cost, high strength-toughness thin gauge 9Ni steel plate. Weight percentages of a molten steel composition are: C: 0.03-0.06%, Si: 0.1-0.2%, Mn: 0.5-0.8%, Ni: 8.6-9.1%, Mo: 0.02-0.05%, Als: 0.015-0.035%, S≤0.005%, P≤0.007%, N≤0.007%, and a balance being Fe and non-removable impurities. The molten steel is smelted and alloyed using a vacuum furnace with vacuum degree ≤50Pa, with heating temperature at 1160-1220℃, holding time for 90-180min, and billet thickness after cogging down of 120-150mm; adopting a two-stage controlled rolling; waiting the temperature for 10-15s after rolling; accelerate cooling to 440-550℃ at a cooling rate of 15-40℃/s, and then air-cooling to room temperature; and the steel plate is heated to 575-605℃ for tempering for 45-70min and then air cooled to room temperature. The method utilizes the properties of 9Ni steel material and the cooling characteristics of the thin gauge steel plate, combines the controlled rolling and cooling with the heat treatment process, thereby improving the performance of materials at the same time shortening the process and reducing process energy consumption, so as to achieve the purpose of reducing the production cost of high strength-toughness thin gauge 9Ni steel plate.