Method for manufacturing low-carbon and low-silicon steel

[0023] Example 1 :

[0024] A low-carbon and low-silicon steel manufacturing method. The 120t converter steelmaking plant manufactures SWRCH6A cold heading steel billets. The chemical composition control requirements of the steel are as follows: C: 0.03%~0.06%, Si: ≤0.04%, Mn: 0.20~ 0.35%, P≤0.015%, S≤0.010%, Als: 0.025~0.045%, the balance is Fe and other inevitable impurity elements; and smelted in 120t converter → RH furnace vacuum treatment → LF furnace refining → billet connection The production steps of casting are made.

[0025] The end point C of the converter is controlled within the range of 0.06%~0.10%, the end point temperature: 1650~1670℃; 300kg of high-carbon ferromanganese alloy is added during the tapping process of the converter; the free oxygen content before the vacuum treatment of the molten steel is controlled within the range of 200~480ppm, RH vacuum When the vacuum degree reaches 0.27Kpa for 7-8min, the carbon content in the steel is reduced to 0.002%~0.02% and the free oxygen content is reduced to the range of 120~200ppm. After the vacuum degree reaches 0.27Kpa, 60~80kg aluminum is added to the steel. And then vacuum cycle for 3-5 minutes, at which time the free oxygen content in the steel drops to the range of 2.0~4.0ppm. Chemical composition of molten steel after RH vacuum treatment: C: 0.002%~0.025%, Si: ≤0.005%, Als: 0.015~0.035%; the molten steel is hoisted to the LF furnace process for refining, and a certain amount of aluminum particles and aluminum calcium are added in the early stage of refining Carbon is used for slag liquid surface diffusion deoxidation, lime and fluorite are added for slagging; the medium-term aluminum feeding line increases the acid-soluble aluminum content in the steel, and the high-carbon ferromanganese is added to fine-tune the Mn composition. After the LF stops powering on, the 500m calcium iron wire is fed for calcium treatment After the calcium treatment, the molten steel is softly blown with argon for 10-12 minutes, and the molten steel after the soft argon blow is used for continuous casting of 170×170mm square billets. The typical casting speed of continuous casting is 2.2m/min, and one casting time is more than 8 furnaces. No nozzle nodules occurred in the continuous casting process. The melting composition range of steel is: C: 0.03%~0.05%, Si: 0.015% ~0.035%, Mn: 0.25%~0.30%, P≤0.015%, S≤0.008%, Als: 0.028%~0.042%, the balance is Fe and other unavoidable impurity elements.

[0026] Example 2 :

[0027] A low-carbon and low-silicon steel manufacturing method. The 120t converter steelmaking plant manufactures Q195LB low-carbon drawn steel billets. The chemical composition control requirements of the steel are as follows: C: 0.03%~0.08%, Si: 0.02~0.06%, Mn: 0.10%~0.25%, P≤0.025%, S≤0.030%, the balance is Fe and other unavoidable impurity elements; and it is produced by the production steps of converter → RH furnace vacuum treatment → billet continuous casting, and converter end point control :C: 0.06%~0.10%, bath temperature: 1680~1700℃; 100kg high-carbon ferromanganese alloying is added during the converter tapping process; free oxygen content is 250~500ppm before vacuum treatment in RH furnace, RH vacuum treatment is 7-8min vacuum When the temperature reaches 0.27KPa, the carbon and oxygen content in the steel ranges from 0.010%~0.030%, 150~250ppm respectively. After the vacuum degree reaches 0.27Kpa, add 30~40kg aluminum particles and a small amount of carbon powder to the steel, and then vacuum cycle 3 -5min, at this time the free oxygen content in the steel is 2.0~8.0ppm, the chemical composition of the molten steel after RH vacuum treatment is: C: 0.03%~0.06%, Si: ≤0.010%, Mn: 0.15%~0.20%, Als: 0.006 %~0.015%, the balance is Fe and other unavoidable impurity elements. After RH vacuum treatment, 200m calcium iron wire is fed for calcium treatment. After feeding the wire, the molten steel is softly blown for 10~12min for continuous casting of 170×170mm billet. The typical casting speed of continuous casting is 2.4m/min, and the continuous casting of 10-15 furnaces in one pouring time does not cause nozzle nodules during the continuous casting and pouring process. The melting composition range of steel is: C: 0.03%~0.05%, Si: 0.005% ~0.025%, Mn: 0.15~0.20%, P≤0.020%, S≤0.020%, Als: 0.003%~0.010%, the balance is Fe and other unavoidable impurity elements.

[0028] The invention makes full use of the principle of carbon-oxygen balance in molten steel, breaks the atmospheric carbon-oxygen balance state by changing the atmospheric state to the vacuum state, establishes the carbon-oxygen balance in the vacuum state, and promotes the generation of carbon and oxygen in the molten steel The reaction generates carbon monoxide gas, achieving the purpose of removing most of the carbon and oxygen in the molten steel, and achieving the purpose of manufacturing low-carbon steel; and because the steel-making furnace does not need to add a deoxidizer during the tapping process, and only an aluminum deoxidizer is added during the RH vacuum treatment process , No silicon-containing material is added in the whole process, which guarantees the requirement of low silicon content in steel. The present invention is precisely the vacuum decarburization and deoxidation technology of RH furnace. It produces low carbon and low silicon in steelmaking and smelting. It changes the traditional smelting method and no longer requires low C content tapping in steelmaking furnaces. At the same time, alloying uses cost-effective high Carbon alloys have created a new method for manufacturing low-carbon and low-silicon series steels with decarburization and deoxidation technology under high vacuum conditions. The present invention is convenient, simple and easy to implement, but steelmaking must have RH or VD vacuum treatment furnaces for low-carbon and low-carbon smelting. Silicon steel, steelmaking furnaces do not require low C (C≤0.05%) tapping, which reduces the oxidizing property of molten steel, thereby reducing the corrosion of molten steel with strong oxidizing properties on the furnace lining; reducing the FeO content of the steelmaking slag and improving the metal Yield rate; high-priced low-carbon iron alloys or metal elements are not added during the tapping process of the steelmaking furnace, which reduces the steelmaking cost; the use of vacuum natural decarburization and deoxidation reduces the brittle Al produced by aluminum deoxidation 2 O 3 Inclusions improve the cleanliness of steel, and the process from steel-making furnace to RH vacuum treatment can effectively control the silicon increase in molten steel, and the C and Si in the steel are easy to control and stable. Al produced by deoxidation 2 O 3 Inclusions are greatly reduced, and reasonable Ca deformation treatment has been carried out. The castability of molten steel is good, which avoids the problem of nozzle nodules during continuous casting and pouring of this type of steel.