SU1013488A1 - Method for modifyingcast iron - Google Patents

Description

with

four

CX) 00 1 The invention relates to foundry and can be applied in the production of castings from high-strength cast iron with lamellar or sparic graphite. To produce high-quality cast iron without an autoclave process, low-sulfur (with a sulfur content of up to 0.03 jasD, superheated up to IOO-ISOO C cast iron, which is modified with ligatures or complex modifiers containing up to 12% magnesium, is known. The method of modifying low-sulfur superheated heated iron is used; , nickel-copper-magnesium and other ligatures, in which sometimes rare-earth metals are sometimes added.1. In these ligatures, copper and the passive auxiliary role of ligature of the ligature play a role, noisbating its fragility l ease of grinding, reduction of pyroeffect, etc. Introduction of such ligatures to low-sulfur, overheated to 1COO-1500 C cast iron lowers its temperature by t (0-100 ° C. Wide use of these ligatures is restrained by a high copper deficiency. The closest in technical essence and the achieved effect of the invention is a method of modifying the cast iron with magnesium containing complex modifiers with a calcium content of 12-20%. They are introduced into the ladle before pouring the cast iron C2 3. However, when using these modifiers with a high content of m of calcium when the temperature of the iron is less than 1380 ° C, the modifier is slagged, covered with an insulating oxide film and poorly absorbed. Moreover, the introduction of the modifier in an amount up to 3.0-3.5% of the weight of the chug does not lead to a sharp decrease in metal temperature slag and, as a result, to the rapid failure of the casting bucket. Therefore, the use of magnesium-containing modifiers of this type is effective for superheated metal and in the processing of low-sulfur iron, since, despite the high content of desulfurizing agents in the modifier, the rapid drop in temperature of the liquid metal and slag during the introduction of the modifier makes slagging sulfur impossible. 8 The relatively high magnesium content of 9–12% in the modifier and large modifier additives cause prolonged pyroelectric effect and smoke emission, which are observed even after the casting bucket is emptied due to burning of the modifier inclusions and insoluble in the metal. . The purpose of the invention is to produce high-strength cast iron from gray containing up to 0.15% sulfur. The goal is achieved in that according to the method of modifying cast iron, including the processing of a liquid metal in a ladle with a calcium-calcium modifier with a calcium content of 13-20%, the modifier under the coating flux in a separate unit is pre-fused with 5-10% manganese and at 1050-1150 0 liquid modifier in the amount of 1.5-2% of the weight of the cast iron is poured into the ladle, after which iron cast iron heated to 1320-X20 C is added to the norm. The liquid modifier has the composition,%: Such modification allows for efficient ulfuratsiyu cast directly in the ladle due to the high activity of the melted components, primarily calcium and manganese, and without significantly lowering the temperature of molten iron. In addition, in the process of filling the casting ladle to the norm with liquid iron, it is intensively mixed with the molten modifier already poured into the ladle, which has a refining effect on the resulting cast iron. The role of manganese in the composition of the modifying complex is associated with its desulfurizing ability in the solidification interval of cast iron, since the microvolatile distribution of manganese corresponds to precisely those zones in which the sulfur remaining unbound in sulfides is eliminated. This also justifies the limits of its content in the modifier. at the time of the bucket treatment with the molten iron melt modifier, the main desulphurizer is calcium and to a lesser extent manganese and magnesium, and at the time of crystallization the main desulphurizer is manganese, and calcium and magnesium are spheroidizing additives. The consequence of this complete sulfur bonding process is the possibility of producing high-strength nodular cast iron from conventional cupola, containing up to 0.15% sulfur. The lower-optimal heating limit is determined by the minimum temperature of cast iron that is permissible in the manufacture of machine-building casting, and can be so low when producing high-strength cast iron only for the proposed method. In no other way of modifying at this temperature is it possible to obtain a suitable metal. The upper limit of optimal overheating of the cast iron is due to the action of two oppositely influencing factors: the metal temperature must be high for the iron to be efficiently desulfurized, the temperature of the iron must be moderate to reduce the carbon loss and calcium. Performed experiments have shown that for efficient processing of fluid. A high sulfur sulfur modifying IMG modifier is sufficient temperature. At higher temperatures, the duration of the preservation effect of the modification is shortened. The method proceeds as follows. In a separate smelting unit, 10-15% of the required amount of magnesium-containing modifier is first melted, such as LCD, and the entire addition of metallic manganese or ferromanganese is injected, and the flux under the layer of flux is introduced in separate portions of the remaining magnesium-containing modifier. As a coating flux, quartz sand mixed with fluorspar or cut slag is used, which is induced in an amount based on the weight of the liquid modifier. The resulting liquid modifier, together with the coating flux at 1050-1150 ° C, is poured into the heated “pouring ladle. which is then filled with liquid iron to normal. Slag is cleaned from the metal mirror and the mold is cast. If the obtained liquid modifier cannot be used immediately, then with prolonged exposures a metal magnesium magnesium correction additive is produced by burning a bell in one or several steps, depending on the time, which is hot. Under laboratory conditions, the main melting unit was the main induction furnace IST-016, and the melting unit of the LPZ-B7 generator was used to melt the modifier. At the pilot plant, the electric arc furnace DC-05 was used to smelt iron, and the induction furnace IST-016 was used to melt the modifier. Both series of heats were carried out to determine the degree of the modifying effect by varying all variables significant in the described method. The original cast iron to be modified was the composition of conventional machine iron and little of the composition in a series of laboratory and production heats. In the laboratory swimming trunks, cast iron had the following composition, eec.fC BftS, Si 2.3t, Mn 0.6, s 0.08, p 0.10, Cr 0.12. The original cast iron in the factory trunks had a composition, wt.%: C 3.21, Si 1.9, Mn 0.87, S 0.07, P 0.10, Cr 0.20. For the magnesium-containing liquid modifier, the degree of doping with manganese was varied (5% initial concentration and 10% final) and the total amount of modifier liquid additive introduced into the iron (.1.0% and 1.5%). For the initial cast iron in the laboratory and factory trunks, only the temperature at the time of modification was changed (1300-1320 0 and the second interval was 1ifOO-l420 ° C). The twenty-degree temperature variation within each interval corresponded to the accuracy actually achieved in the experiments. The quality of gray cast iron modification to nodular graphite high grade served

51013,886

The fracture and ratio in the structure of the series of heats were not controlled, of spherical and lamellar graphite. The data of laboratory and plant flame mechanical properties of iron in these woks are given in the table.

Note. At a cast iron modification temperature of 1520 ° C

the effect of spheroidizing graphite lasts less than two minutes.

Based on the additionally carried out tests of the method of modifying the cast iron, the following conclusions can be made: the effect of the modification is retained at any degree of superheating of the liquid cast iron studied from 1300 to, however, the optimum temperature region is l320-1ft20 C. With an increase in temperature;} s overheating the duration of the crown effect dramatically reduced, the minimum amount of additive modifier liquid; providing a stable effect of graphite spherdiaction, is 1.5%. By reducing the amount of liquid modifier, cast iron results in an unmodified stable modifying effect that differs at all three manganese concentrations, i.e. 5.0, 6.5, and U, (by calculation) in the composition of the liquid modifier. The addition of a liquid modifier in an amount of more than 2.0 was not investigated, since the positive effect was not in doubt, and the task was to determine the minimum necessary additive of the liquid modifier to obtain high-strength cast iron. The expected economic effect will be more than 120 thousand rubles. in year.

Claims (1)

METHOD OF MODIFICATION OF CAST IRON, including treatment of molten metal in a ladle with a magnesium-calcium modifier with a calcium content of 13-20%, characterized in that, in order to obtain high-strength cast iron. From gray, containing up to 0.15% sulfur, the modifier under the coating flux in a separate unit is preliminarily alloyed with 5-10% manganese and at 1050-1150 ° C the resulting liquid modifier in the amount of 1.5-2% of the weight of the treated cast iron is poured into the ladle, after which it is refilled to the norm with cast iron heated to 1320-1420 ° C.