SU1680779A1 - Modifying mixture - Google Patents

Abstract

This invention relates to metallurgy, in particular to molten iron casting modifiers used in the manufacture of castings from high strength cast irons. The purpose of the invention is to increase the cyclic durability of cast iron. The modifying mixture contains boric acid, copper oxide, silicobarium, silicon nitride, nickel powder, lanthanum and cerium in the following ratio of components, may% boric acid 15-25; copper oxide 10-17; siliobzria 15-23; silicon nitrides 12-17; 11-15 nickel powder; lanthanum 6 16 and cerium 6-12. Additional input into the mixture of silicon nitrides, nickel powder, cerium and lanthanum provides an increase of 40-54% of the cyclic durability of iron. 1 tab.

Description

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The invention relates to metallurgists, in particular to compositions of modifying mixtures used in the manufacture of castings from high-strength cast irons.

The purpose of the invention is to increase the cyclic durability of iron

The proposed modifying mixture containing boric acid, copper oxide and silicobarium, additionally contains silicon nitrides, nickel powder, lanthanum and cerium in the following ratio of components,% in May

Borna acid15 25

Copper oxide10 17

Silicobarium15 23

Silicon nitrides 12 17

Nickel powder11 15

Lanthan6 16

Ceribab 12

Additional introduction of silicon nitrides increases the graphitizing effect of the mixture, crushes the structure, and increases the cyclic durability of the iron.

When the concentration of silicon nitrides is up to 12 mec.%, The refinement of the structure and the magnitude of the impact toughness and cyclic durability are insufficient. As the silicon nitride increases by more than 17 wt.

Langan refines and modifies iron-carbon melt, increasing the plastic properties and cyclic durability of cast iron. With lanthanum concentrations up to 6 May, the plastic properties and cyclic durability of cast iron are low,

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and when the concentration of lanthanum in the mixture is more than 16 wt.%, the content of perlite in the iron increases, and its crack resistance, yield strength, operational resistance and cyclic durability decrease.

Cerium is introduced as a strong deoxidizing and spheroidizing agent of graphite, which increases the dispersity of the structure in the cast state, strengthens the structure and increases the cyclic crack resistance, mechanical and operational properties. Its content in the mixture is based on the amount of 6 wt.%, From which its spheroidizing and strengthening effect begins to appear, and is limited to a concentration of 12 wt.%, Above which its loss and instability of the mechanical properties and cyclic durability of the iron increase.

Nickel powder stabilizes the process of modification and increases the cyclic durability of cast iron. Its effect is observed when the mixture contains more than 11 wt.%, And as the nickel powder increases to more than 15 wt.%, The modifying ability of the modifying mixture decreases, the hardness of cast iron increases, and its cyclic crack resistance decreases.

Introduction of 10-17 wt.% Of copper oxide reduces and levels the hardness of cast iron, increases the graphitizing ability of the mixture, the casting properties of cast iron, dispersion and uniformity of its structure, which leads to an increase in toughness, yield strength, cyclic durability of iron in castings heat treatment. At a concentration of less than 10 wt.%, An increase in hardness, a decrease in plastic properties and cyclic durability are noted. With increasing concentrations of more than 17 May. %, the segregation of elements and the heterogeneity of the cast iron structure in castings are increased, which leads to a decrease in the stability of the mechanical properties of the cast iron.

Boric acid in the amount of 15-25 wt.% In the mixture provides additional modification of cast iron with boron, an increase in the graphitizing ability of cast iron, a decrease in hardness, an increase in the yield strength and cyclic crack resistance. The upper limit of the boric acid concentration in the mixture is limited to 25 wt.%, Above which the heterogeneity of the structure increases and the cyclic crack resistance of cast iron in castings is reduced. With a decrease in the boric acid concentration of less than 15 wt.%, Low characteristics of the mechanical properties and degree of graphitization of cast iron are noted.

Silicobarium is introduced as an effective deoxidizing, modifying and graphitizing additive that enhances toughness and cyclic crack resistance. When its content is more than 23 wt.%, The waste of the mixture increases, the heterogeneity of the structure and the cyclic crack resistance of cast iron is reduced. When the concentration of silicobar up to 15 wt.%

0 decreases the graphitizing ability of the mixture, increases the content of perlite in the structure, which reduces the plastic and performance properties, cyclic durability.

5 Example. Melting of cast iron is carried out by a duplex process of the cupola - induction mixer. For processing, pigs of the following composition are used, wt.%: Carbon 2.8-2.85; silicon 1.6-1.7; manganese 0.5-0.6;

0 chrome 0.03-0.04; sulfur 0.03-0.04; phosphorus 0.05-0.06 and iron else.

In order to modify the cast iron, five compositions of the proposed modifying mixture and the known modifying mixture are used, added in an amount of 0.2% by weight of the melt with the release of cast iron into the ladle at a temperature of 1410-1430 ° C.

Modifying mixtures are made

0 by mechanical mixing of boric acid powders {GOST 18704-78), copper oxide, silicon nitrides (TU 6-09-03-312-77), nickel powder (GOST 9722-79), ground to a fraction of 0.5-2 mm silicoba5 SBSA (TU 14-5-116-79), lanthanum - Lat-2 (TU 48-4-218-72) and cerium SeZ (PG 48-4-227-84). The table presents the composition of the modifying mixtures and test results. From modified cast iron

0 cast technological samples, samples for mechanical tests with a diameter of 10-45 mm and tubular blanks. Technological properties of modified cast iron are determined from standard cast samples.

5 and mechanical properties - on samples with a diameter of 10 mm. Cyclic durability tests are determined on tubular billets with a diameter of 30-35 mm. Operational stability is determined by

0 when testing cylindrical specimens under shock fatigue conditions.

As can be seen from the data in the table, the cast irons modified by the proposed mixture (compounds 2, 3, and 4) have a higher cyclic durability than when modifying them with a known mixture of the optimal composition (experiment 1). Comparative analysis of the cost of modifying the cast iron, graphitizing ability and mechanical properties

Claims (1)

modified high-strength cast irons showed that the use of the proposed modifying mixture can achieve an economic effect of up to 28 rubles. for 1 ton of good to pour. This increases the mechanical and technological properties of modified cast irons (crack resistance, fluidity, etc.). The proposed modifying mixture allows to improve the operational durability and mechanical properties of cast iron. Claims Modifying mixture containing boric acid, copper oxide and silicobarium 0 characterized in that, in order to increase the cyclic durability of cast iron, it additionally contains silicon nitrides, nickel powder, lanthanum and cerium in the following ratio, wt.%: Borna acid15-25 Copper oxide 10-17 Silicobarium15-23 Silicon nitrides 12-17 Nickel powder11-15 Lanthanum6-16 Cerium6-12.