SU918316A1 - Method for extrafurnace treatment of molten cast iron with magnesium - Google Patents

Description

(Sk) LIQUID CHIGUNE TREATMENT METHOD

Magneem

one

The invention relates to metallurgy and foundry, in particular to the secondary treatment of pig iron with magnesium during circulating vacuuming.

The closest in technical essence and achievable goal to the invention is a method of treating liquid metals with reagents in a circulation installation, which consists in introducing powdered reagent into the gas supply pipe and flowing liquid into the lower part of the discharge pipe. iT reagent

The disadvantage of this method is the relatively low degree of absorption of the liquid reagent supplied to the lower part of the discharge pipe. In the process of introducing powdered reagent into the gas stream into the inlet pipe, an intense circulation of metal from the ladle to the vacuum chamber and back and the ladle through the discharge pipe is achieved. At the same time served as a drain

The pipe in countercurrent with the circulating metal, the liquid reagent is discharged by the melt being poured back into the ladle, and only a small part of it may float into the vacuum chamber, overcoming the hydrodynamic resistance of the column of the moving counter liquid metal. The liquid reagent thrown into the ladle melt, as a lighter one, instantly floats on

10 is a metal mirror, and the modification effect on it is terminated. Thus, the intensity of the process is reduced and the metal remains unmodified. The known method makes it possible to increase the physicomechanical properties of cast iron by one or two grades, however, to obtain high-strength nodular cast iron without using additional technological

30 liraem, this method is not possible. In addition, when magnesium is used as a liquid reactant, its release into the ladle is accompanied by a significant pyroelectric effect, which deteriorates the sanitary and hygienic working conditions. The aim of the invention is to improve the physicomechanical properties of the pig iron and to improve the sanitary and hygienic working conditions. This goal is achieved by the fact that according to the method of out-of-furnace treatment of liquid iron with magnesium in a circulating unit with the reagent injected into the gas stream, magnesium vapor is mixed into the suction inlet pipe mixed with natural gas supplied under a pressure of 1.5-2.5 atm and injected portions of the melt in the vacuum chamber until the residual magnesium content in the evacuated iron is 0,. The scheme of the method is shown in the drawing. Liquid metal 1 in a casting ladle at 1380-l4 0 C is evacuated before the casting unit by means of a circulation unit 2, submerged by suction 3 and drain 4 branch pipes under the melt mirror to a depth of 300-500 mm. The mixer with the required dose for modifying magnesium 5 is connected by hoses with a suction pipe and with a source of natural gas under a working pressure equal to or more than 1.5 atm. The vacuum in the chamber of the circulation unit is maintained at a predetermined level for a range of 12-40 mm Hg. for suction of the melt into the vacuum chamber, and the provision of intensive circulation is achieved by injecting new portions of metal with bubbles of gas mixture 6 blown into the suction nozzle. The supply of magnesium vapors with natural gas under a pressure of 1.5–2.5 atm ensures their reliable passage to the ascending branch of the vacuum chamber. At pressures below 1.5, the supply of magnesium vapors to the treated melt is difficult. With a pressure of more than 2.5 atm, the circulation rate increases sharply in a pair of magnesium and they do not have time to fully absorb the melt, which reduces the degree of magnesium absorption. The magnesium content in the final melt in the range of 0.03-0.05 is due to the production of high-strength cast iron with high physicomechanical properties. When the content of magnesium in the iron is less than 0.03%, a mixed form of graphite is obtained in the metal structure (lamellar and spherical |, which leads to a decrease in the mechanical properties of the iron, and an excess of magnesium more than 0.05 ° C leads to the formation of chill in thin-walled castings. Natural gas was chosen as a substance that facilitates the circulation of metal and the injection of magnesium vapors into it. The out-of-furnace treatment of gray cast iron of grade SCH 18-36.In an induction furnace MGP-102 melted H 50 tons of cast iron of the following composition, wt.o: carbon 3, 6; silicon 2,3; marg Ants 0.8; Sulfur 0.03, Phosphorus 0.05. Then the smelted Metal is poured into the ladle and under the metal mirror in the ladle to a depth of 400 mm immerse the suction 3 and drain 4 nozzles of the circulating vacuum chamber 2. Specified dose, magnesium 5 is heated to the evaporation temperature in the mixer and, at the same time, dried natural gas is injected into the mixer at a pressure of 1.52.5 atm. When a vacuum of 20 mm Hg is created, the melt rises through the nozzles to the bottom of the chamber. Then, at a distance of 100 mm from the surface of the bucket metal, the vacuum chambers are sucked into the ascending branch pipe of the vacuum chamber with natural gas from the evaporation chamber with magnesium of its vapor, creating a total vapor pressure of magnesium with natural gas of 1.5-2.5 atm. Gas bubbles and magnesium, raising, inject into the chamber portion of the melt from the ladle. Excess metal from the chamber through the drain pipe flows back into the bucket. In this way, continuous movement of the metal from the ladle into the vacuum chamber and the radiation chamber is created, ensuring and simultaneously modifying the melt with magnesium vapor. The magnesium consumption in the evaporator is 0.1% by weight of the metal being processed. Cast iron of the above composition is circulated under vacuum in order to compare the effect in a known manner, i.e. with the introduction of a powdery reagent with a gas stream into the tube inlet of the vacuum chamber and the supply of liquid magnesium into its discharge pipe. According to a known method, it was possible to obtain cast iron of CM 32-52 brand, and according to the proposed method, high-strength cast iron of HF 50-2 grade, the properties of which are presented in the table.

Claims (1)

Claim A method for out-of-furnace treatment of molten iron with magnesium in a circulating unit with reagent inlet in a gas stream, characterized in that, in order to increase the physicomechanical properties of cast iron and improve sanitary and hygienic working conditions, magnesium vapor is mixed into the suction pipe in a mixture with natural gas supplied under pressure 1.5 ”2.5 atm, injecting portions of the melt into the vacuum chamber to obtain a residual magnesium content in vacuum cast iron of 0.03“ 0.05%.