SU1407958A1 - Method of producing alloyed cast iron - Google Patents

Abstract

The invention relates to the field of smelting iron and can be used in foundry. The goal is to increase the physical and mechanical properties of cast iron. One part of the iron is smelted and overheated in electric furnaces, for example, induction, and the other in the barrel, alloying additives are introduced in both parts and both parts are mixed in the ladle, and the ratio of the said parts is in the range from 0.2 to 1.0 , their overheating is 1460-1480 C and 1260 - 1280 ° C, respectively, and the difference in the graphitization coefficients is not less than three. Carbide-forming additives, which increase the thermodynamic activity of carbon in the pig iron, are introduced into the cupola iron, and the graphitizing activity, which is increased, in the electric furnace. 1 h „p. f-ly, 1 tab. with (L

Description

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The invention relates to foundry and can be used in the smelting of iron.

The purpose of the invention is to improve the physical and mechanical properties of pig iron.

The method of producing doped cast iron includes smelting and overheating one part of the cast iron in an electric furnace, for example, induction, and the second in the cupola, putting alloying additives into both parts and mixing both parts in a ladle, the ratio of the said parts being in the range of 0.2-1 0, their overheating is, respectively, l eO-UeO C and 1260-1280 С, and the difference of the grading coefficients is 1 at least three.

Carbide-forming additives, which increase the heat-dynamic activity of carbon in cast iron, are introduced into cupola iron, and graphitizing, lowering it, in electric furnace.

The effectiveness of the proposed method, which is a liquid doping, is determined experimentally in the study of the effect of the activity of eu-carbon of mixed iron and the mechanical properties of castings. The thermodynamic activity of carbon in cast irons is estimated by the graphitization parameter K, which is determined by the formula

Cr C (Si-0.2 (Mn - 1.78-0.3) +

+ 0.1R + 0.4Ni - 1.2Cg - ORAMO +

+ 0.5 A1 - 2V),

where C, Si, 14i, S, P, Ni, Cr, Mo, Al and V - the mass fraction of the corresponding element in the iron,

When mixing cast iron, the difference of parameters, graphitization of which is less than three units, the effect of liquid doping is practically not observed. By increasing the difference in the graphitization parameters of the mixed iron, an increase in the strength and toughness of the castings is observed, as well as a decrease in the anisotropy of the mechanical properties over the cross section of the casting.

The effect of liquid doping is noticeably enhanced when carbide-forming elements are introduced predominantly into superheated (1460-1480 s) electric furnace cast iron, and graphitization is introduced into cupola iron having a temperature of 1250-1280 ° C. If this condition is not met, then even with the difference in the parameters of the graphite iron

j

0 5

0

5 o

Q

d

0

five

Newly more than three, and the mechanical properties of the samples are clearly lower than those of the castings obtained by the proposed method. The effect of liquid alloying is associated with the intensification of the processes of diffusion of alloying elements and carbon when the iron is mixed and the melt is homogenized. On the microstructure of the castings, a decrease in the length of the pre-eutectic aus-tente dendrite is observed. They become more rounded and shorter. The dispersion of perlite increases. The microstructure of the surface samples and the cores of the castings are practically the same. The description of the change in the microstructure of the specimens determines the growth of the mechanical properties and the decrease in anisotropy along the depth of the castings.

Increasing the temperature of the pig iron containing Carbide-forming elements leads to an increase in the dispersion of perlite in the structure of castings and the grinding of graphite inclusions. The best mechanical properties are observed at temperatures as low as 1460 ° C when melt homogeneity is achieved. This effect is extreme, and at temperatures above 1480 ° C, interdendritic graphite appears in the cast iron structure, the dendrites of the pre-eutectic austenite increase, resulting in a decrease in the mechanical properties of the castings.

The optimum superheat temperature of the cupola cast iron corresponding to the maximum mechanical properties of the castings is within 1250 -.

Reducing the temperature of the cupola iron below 1250 C leads to the enlargement of graphite inclusions in the iron structure, deterioration of its shape (coarse plate inclusions) and a decrease in the mechanical properties of castings. Increasing the temperature of the cupola-iron cast iron leads to an increase in the temperature of the melt after mixing, which increases the size of the dendrites of the pre-eutectic austenite and leads to the appearance of interdendritic graphite.

The best mechanical properties and the smallest anisotropy of them in the depth of castings is achieved with a ratio of electric and cupola iron, respectively, 0.2 - 1.0

(or 1: 5 - 1: 1). If the ratio is less than 1: 5, the distribution of alloying elements becomes even, and if the ratio is more than 1: 1, transcrystallinity increases in the working layer of castings, the amount of brittle cementite increases, and the economic indicators of the process deteriorate.

The summarized test results are shown in the table.

Primer p. In an induction furnace of an industrial frequency with an acid lining, melt cast iron is used, using the rolls from the mill rolls, roll return and steel metal waste as the charge. After overheating it in the furnace, the estimated amount of ferroalloys is introduced into it, providing the following chemical composition, wt.%: C 2.5; Si 0.4; fn 0.7; Cr 1,2; Ni 0.4; P 0.08; B 0.06 (K -2.33), and then mixed with cupola iron having a temperature and the following chemical compound, wt.%: C 3.33; Si 0.9; Mp 0.5; Cr 0.4; N1 1.65; P 0.3; S 0,1 (K |. 3,7). The amount of electric furnace cast iron is 6 tons, and cupola furnace is 12 tons. After mixing, the cast iron in the ladle has a temperature before pouring into the casting molds and the next chemical mass,%,, 0; Si 0.7; Mp 0,6; Cr 0.7; Ni 1.1; P 0.2; S 0,1, and dp casting roll casting is used.

Thus, the implementation of the proposed method provides an increase in strength at a casting depth of 20 mm from the cast surface by 14%, and at a depth of 50 mm - by 20% and impact toughness at a depth of 20 mm by 36%, and at a depth of 50 mm - by 40 % In this case, the anisotropy strength decreases by 5.8 times, and the impact strength decreases by 12 times. This provides an increase in the operational durability of rolled rolls by an average of 15%.

Formula of invention

1. A method of producing doped iron, which includes smelting and overheating one part of the iron in an electric furnace, and the second in the cupola, putting in both parts of the alloying additives and mixing both parts in a ladle, which is aimed at increasing physical and mechanical the properties of cast iron, the ratio of the mentioned parts is within 0.2–1.0, their overheating is 1460–1480 ° C and 1260–1280 ° C, respectively, and the difference in the graphitization coefficients is at least three.

2. Method POP1, characterized in that the additives that increase the thermodynamic activity of carbon in the iron are introduced into cupola iron, and those lowering it in the electric furnace.

Claims (2)

Claim 1. A method of producing alloyed cast iron, including smelting and overheating of one part of cast iron in an electric furnace, and the second in a cupola, introducing both parts of alloying additives and mixing both parts in a ladle, characterized in that, in order to increase the physicomechanical properties of cast iron , the ratio of the mentioned parts is within 0.2 1.0, their overheating is 1460-1480 ° C and 1260-1280 ° C, respectively, and the difference in the graphitization coefficients is not less than three. 2. The method according to claim 1, characterized in that additives that increase the thermodynamic activity of carbon in cast iron are introduced into cupola iron, and lowering it into electric furnace. Cast iron smelting The temperature of the input ferroalloys in induction »furnace, C Tempe Difference ratrata paranet wagra- ditch gra nightly fntizatsni cast iron·" cast iron •from dk _g - - Tensile strength Power Shock elm- Power bending cast iron ^ anneotro cast iron bone anneotro * kg / m at depth pin off kg / cm on the kick kick not mm nosti in depth mm noah * izA ‘_. ioox ——— bones 20 fifty 4/ 20 'fifty -U0X Correlation of electric furnace and cupola iron <1 1460. 1250 1.86 6θ, 5 56.5 6.6 0.52 0.49 5.8 1110 2 1460 1250 4.7 72.5 71.5 1.37 0.69 0.68 1,5 115 3 J.470 1265 6.03 74.0 73.0 1.35 0.71 0.70 1.4 ' 112 4 1480 1280 9.4 77.0 76.5 0.65 0.75 0.74 1.33 111 5 . 1500 1300 9.52 68.5 56.0 3.6 0.64 0.60 6.25 1.5 "! Note. Swimming trunks 2-3 - according to the proposed method. 6, and “c,“ the mechanical characteristics of castings at a depth of 20 mi from the surface of the casting; 6 _t and a - the same, n ^ depth 50> · <.