Smelting method of 9Ni steel

Abstract

A smelting method of 9Ni steel. The method has the following characteristics: 1.a smelting process comprises steps of pretreatment on molten iron (desulfuration), converter (double dephosphorization, melting nickel plate), LF furnace (desulfuration) and RH (degassing); 2. dephosphorization is conducted in the converter and comprises two steps: step one: blending molten iron desulphurized by KR and steel scrap into a dephosphorization converter for primary smelting, using ''dephosphorization converter smelting critical control point'' to desulphurize the molten iron to a phosphorus content below 0.020%, and carrying out semi-steel tapping; and step two: blending the molten semi-steel and nickel plate into a decarburization converter for converting, desulphurizing the molten steel after converting to a phosphorus content below 0.003%, and carrying out tapping; and 3. the nickel plate is melted in the decarburization furnace. According to the present invention, the two-step dephosphorization is carried out in the converter that molten steel after converting has low phosphorus content and is stably controlled, so as to benefit improvement on the yield of 9Ni steel. Decarburization converter slag has low phosphorus content, and ladle molten steel has a low rephosphorization amount, so as to clear out molten steel in the decarburization furnace and reduce molten steel loss in a steel leaving operation.

Description

technical field [0001] The invention relates to the field of steelmaking. Specifically, the invention relates to a method for smelting low-temperature high-alloy pressure vessel steel. The method for smelting low-temperature high-alloy pressure vessel steel is a method for smelting 9Ni steel. Background technique [0002] 9Ni steel is a low-temperature high-alloy pressure vessel steel, and its low-temperature resistance can reach minus 198 degrees Celsius. It is often used to manufacture low-temperature high-alloy pressure vessels such as liquefied natural gas storage tanks. In order to be suitable for low-temperature high-alloy pressure vessels, the steel composition requirements are as follows: [C]: 0.02% to 0.04%, [Si]: 0.15% to 0.25%, [Mn]: 0.55% to 0.65%, [Ni]: 9.10%~9.50%, [P]: ≤0.006%, [S]: ≤0.003%, [N]: ≤0.0040%, [H]: ≤0.0002%, [O]: ≤0.0030%, high alloy content, The content of phosphorus, sulfur, oxygen, nitrogen and hydrogen elements must be controlled in a very lo...

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Problems solved by technology

[0006] However, the above-mentioned patent document with the patent number "ZL 200710139497.5" does not involve how to reduce the phosphorus content and nitrogen content of molten steel in the converter; at the same time, the above-mentioned patent document does not use molten iron desulfurization pretreatment equipment, converter, LF furnace, and RH furnace to smelt 9Ni steel , but using desiliconization, desulfurization, dephosphorization and three dephosphorization pretreatment process equipment, which has a large temperature drop (60-100 ℃), converter, VOD smelting 9Ni steel

[0007] Therefore, there is a problem: adopting the above-mentioned ZL 200710139497.5 smelting method requires that the tapping temperature of ironmaking should be high and stable

For enterprises that produce carbon steel, there is no pretreatment process equipment for three-deposited molten iron, and new process methods need to be explored to smelt 9Ni steel

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