1 General Provisions
1.0.1 This standard is formulated with a view to making the steelmaking technology design to follow out the national economic policy and technical policy, and making the steelmaking engineering construction to be of advanced technology, economy and rationality, energy conservation, environmental protection and safety and usability.
1.0.2 This standard is applicable to the technological design of steelmaking plant for which converter and electric arc furnace are mainly used.
1.0.3 The steelmaking technology design shall meet the requirements of the current relevant national standard and codes, besides this standard.
2 Terms
2.0.1 Consteel electric arc furnace
Ultrahigh-power electric furnace into which the steel scrap preheated with hot gas are added continuously
2.0.2 VD, Vacuum Degassing
A vacuum degassing device for molten steel, which can place the molten steel ladle in a closed vacuum container connected with the vacuum pump, and supply argon gas from the ladle bottom to stir molten steel and make the degassing reaction of molten steel at vacuum state
2.0.3 VOD, Vacuum Oxygen Decarburization
A vacuum oxygen decarburization refining device for refining stainless steel, which adds a oxygen core lance on the cover of the VD vacuum container to blow oxygen onto the molten steel surface in the vacuum container and to conduct the "decarbonization and chromium reserving" refining for chromium molten steel
2.0.4 CAS-OB, Composition Adjustments by Sealed argon bubbling and Blowing Oxygen
A device which uses the oxidation heat generated by metal (aluminium) burning to heat molten steel, or adds alloy in the immersion hood to adjust the composition of the molten steel
2.0.5 RH, Rheinstahl Huttenwerk Heraus
A vacuum degassing method that two refractory tubes on the vacuum container bottom are inserted into the molten steel, a refractory tube leads argon gas inside and causes density difference of two molten steel in two tubes, which results in the upward and downward circulation flow (Degassing reaction) of molten steel in ladle and vacuum container
2.0.6 RH-KTB, Rhcinstahl Huttenwerk Heraus-Kawasaki Top Blowing
A method that an oxygen core lance is inserted from the vacuum container top to blow oxygen onto the molten steel for decarbonization, which is used for refining ultra low carbon steel and stainless steel
2.0.7 LF, Ladle Furnace
A furnace in which the argon is blown from the ladle bottom at atmospheric pressure and the electric arc is used to heat the molten steel for making the composition and temperature of the molten steel accurate and uniform
2.0.8 AOD, Argon Oxygen Decarburization
A refining furnace, arranged on the side of the molten steel molten pool of a converter, which blow oxygen and argon gas at different proportion into the molten steel for smelting stainless steel
2.0.9 WF, wire feeding
A device that feeds wire or core wire to the molten steel in the casting ladle for treating the molten steel
2.0.10 Two step process
A basic technology of stainless steel manufacture that the electric furnace is used to melt solid materials like chromium, nickel and steel scrap and to complete primary decarbonization for furnace charge, and AOD or VOD refining furnace are used for "decarbonization and chromium reserving" till meeting the specified composition requirement
2.0.11 Three step process
A basic technology of stainless steel manufacture that electric furnace or converter is used to melt solid materials like chromium, nickel and steel scrap; re-blowing converter (or AOD furnace) is used for primary decarbonization; and then VOD refining furnace is used for deep decarbonization, which can produce various stainless steels including ultra low carbon steel
3 Melted iron pretreatment
3.1 Overall technological design
3.1.1 The pretreatment device for melted iron shall be arranged in new, rebuilt and extended converter steelmaking plants.
3.1.2 Blowing method or mechanical stirring method should be adopted in the desulfuration pretreatment of melted iron. The sulfur content of the melted iron after pre-desulfuration shall not be higher than 0.015% and the sulfur content of the melted iron for ultra-low sulfur steels shall be higher than 0.005%.
3.1.3 Blast furnace hot metal bottle, torpedo car and converter-pouring hot-metal bottle may be used as reaction vessel for pre-desulfuration of melted iron, and converter-pouring hot-metal bottle should be adopted. The height of the free space over the melted iron surface in hot metal bottle, for blowing method, shall not be less than 500 mm; for mechanical stirring method, it shall not be less than 700 mm.
3.1.4 The pre-dephosphoration treatment of melted iron shall meet the following requirements:
1 When the phosphorus content of the melted iron is higher than 0.12% or the ultra-low phosphoretic steel with the phosphorus content not higher than 0.005 is made, hot metal bottle blowing method or converter pre-dephosphoration technology shall be adopted;
2 In pre-dephosphoration with hot metal bottle blowing method, special hot metal bottle shall be adopted, and the height of the free space over the melted iron surface shall not be less than 1500 mm. The dephosphoration in converter should be that the converter respectively undertakes the steelmaking and dephosphoration task before and after the service period, or that special dephosphoration converter is adopted.
3 After dephosphoration pretreatment outside the furnace, the phosphorus content of the melted iron shall be higher than 0.030%, and after dephosphoration pretreatment in the furnace, the phosphorus content shall be higher than 0.010%. The phosphorus content of the melted iron after pretreatment, for ultra-low phosphoretic steel, shall be higher than 0.005%.
3.1.5 In pre-dephosphoration treatment outside of the furnace, the melted iron shall be treated with desilication pretreatment and the silicon content of the melted iron shall be higher than 0.20%.
3.1.6 The desilication, dephosphoration and desulfuration pretreatment technology for melted iron should be adopted in converter steelmaking workshop to produce ultra-low sulfur and ultra-low phosphoretic steels.
3.1.7 In pretreatment with blowing method, nitrogen gas should be adopted as carrying gas. the purity of the nitrogen shall not be lower than 99.9%; the pressure shall not be less than 1.0 MPa; the gas shall be dry and free from oil; the dew point should be -20 ℃ or -40 ℃ (for magnesium powder injecting); the gas supply flow shall be determined according to dense-phase-transport gas-powder ratio and powder supply strength.
3.1.8 In the design of melted iron pretreatment station, in addition to complete set machinery, hydraulic, valve station, electrical, and instrumental equipments for treatment device main body, the facilities related to storage and transportation of powder, media supply, slag disposal, flue gas collection and purification, making, storage and maintenance of blow gun (or stirrer), and safety protection, shall be allocated.
