SU1565895A1 - Modifying mixture - Google Patents

Abstract

The invention relates to metallurgy, in particular to liquid iron modifiers used in the manufacture of castings from high-strength, hypoeutectic cast irons, having enhanced resistance characteristics against repeated impact and yield strength in bending. The purpose of the invention is to increase the resistance of cast iron against multiple blows. Modifying mixture contains, wt%: boric acid 15 - 25

copper oxide 10 - 17

silicobarium 15 - 23

silicon nitrides 12 - 17

Yttrium 11 - 15

zirconium carbonitrides 6–16 and lime flour 6–12. The use of the modifying mixture allows the iron to increase resistance to repeated impact by 130 to 220 cycles. 1 tab.

Description

The invention relates to metallurgy. hygiene, in particular, liquid iron modifiers used in the production of castings from high-strength .deeutectic cast irons, which have enhanced resistance characteristics against repeated impact and yield strength in bending.

The aim of the invention is to increase the resistance of cast iron against repeated impact.

The proposed modifying mixture contains boric acid, copper oxide, silicobarium, yttrium, silicon nitrides, zirconium carbonitrides and lime powder in the following ratio of components, May. %: Borna acid15 25

Oxide

medi10-17

Silicobarium15 23 Nitrides

silicon 12 - 17

Yttrium11 - 15

Zirconium carbonitrides 6 - 16 Lime flour6-12 The introduction of zirconium carbonitrides enhances the modifying and hardening effect of the mixture, provides grinding of the structure and graphite, improves the elastic-plastic properties of cast iron, contributes to stabilization and increase resistance to multi-alloy.

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multiple impact and performance properties. When the concentration of zirconium carbonitide is up to 6 wt.%, The dispersion of the structure and graphite in the cast iron, the modifying and hardening ability is low, and an increase in the content of zirconium carbonitrides of more than 16 wt.% Increases the content of non-metallic inclusions at the grain boundaries, reduces the visco-plastic properties of the iron. , the uniformity of the structure, the stability of the mechanical properties of the iron and the ability of the iron to withstand multiple impacts.

Yttrium is introduced as a strong deoxidizer and spheroidizer of graphite, which increases chilling and dispersion of the structure in the cast state, strengthens the structure and increases the resistance of cast iron against repeated impact, mechanical and operational properties. Its content is accepted from 11% by weight, from which its spheroidizing and strengthening effect begins to appear, and is limited to a concentration of 15% by weight, above which the waste and instability of cast iron resistance against repeated impact and mechanical properties increase.

Silicon nitrides grind the cast iron structure during modification, improve the compactness of the structural components, increase the crack resistance, graphitizing ability, yield strength, strength, shear modulus, and resistance of the cast iron against repeated impact. When the concentration of silicon nitrides is up to 12 wt.%, The refinement of the structure and magnitude of resistance against repeated impact and shear modulus is insufficient, and with an increase in silicon nitrides of more than 17 wt.%, The concentration of non-metallic inclusions in the pig iron increases, the waste defect increases, which leads to a decrease in the shear modulus , resistance to repeated impact, plastic and operational properties of cast iron.

Calcareous flour refines and modifies iron-carbon melt, increasing plastic properties, crack resistance, resistance to repeated impact and shear modulus. When its concentration is up to 6 wt.% Plastic properties, resistance to repeated impact and the shear modulus of cast iron are low, and at concentrations in

five

0

five

0

five

0

five

0

five

a mixture of lime flour over 12 May. 2 increases the waste of the components and decreases the shear modulus, resistance to repeated impact, yield strength and operational durability.

The introduction of 10–17 wt.% Copper oxide reduces and flattens the iron hardness, increases the graphitizing ability, casting properties, dispersion and structure uniformity, which leads to an increase in toughness, yield strength, resistance to repeated impact, cast iron shear modulus. castings after heat treatment. When the concentration of copper oxide is less than 10 wt. E, there is an increase in hardness, a decrease in plastic properties and shear modulus, and with an increase in the concentration of more than 17 wt.%, Segregation, sludge, heterogeneity of the cast iron structure in castings increase, leading to a decrease in toughness, resistance to multiple impact, shear modulus and stability of mechanical properties.

Boron acid in the amount of 15–25 masD provides additional modification of cast iron with boron, an increase in the graphitizing ability of cast iron and a decrease in hardness, an increase in resistance to shocks, yield strength and shear modulus. The upper limit of boric acid concentration in the mixture is limited to 25 wt.% Above which increases the heterogeneity of the structure and the tightness of cast iron in castings, reduced resistance to repeated impact, operational properties, shear modulus and yield strength. With a decrease in boric acid concentration of less than 15 mA., Low resistance characteristics against repeated impact, mechanical properties and degree of graphitization of cast iron are noted.

Silicobarium is introduced as an effective deoxidizing, modifying and graphitizing additive. When its content is more than 23 wt.%, The waste of the mixture increases, the heterogeneity of the structure, resistance to repeated impact, the mechanical properties are reduced. When the concentration of silicobar is up to 15 wt.%, The graphitizing ability of the mixture decreases, the content of perlite in the structure increases, which reduces the shear modulus and resistance against multiple 5

th impact, plastic properties and operational properties.

Example. The melting of cast irons is carried out in open induction furnaces. For processing, eutectic cast irons of the following composition are used, May. %: carbon 2.3 - 2, silicon 1.0 - 1.1; manganese 0.3 0, chromium O, O - 0.06 $ sulfur 0.05 - 0.05 phosphorus 0.06 - 0.07; iron else. To modify the cast iron, five compositions are used of the proposed modifying mixture and the known modifying mixture in an amount of 0.12 by weight of the cast iron. Modifying mixtures are made by crushing yttri, silicobarium, zirconium carbonitrides and mixing them with powders of boric acid, copper oxide, silicon nitride and lime powder. The compositions of the modifying mixtures are presented in the table.

Technological samples and samples for mechanical tests of 10 - 16 mm are cast from modified cast iron.

Technological properties of modified cast irons are determined on standard cast samples, and mechanical properties on samples 010–16 mm after heat treatment: heating to 960–980 °, holding at this temperature for 3.5 hours, cooling to 730 ° C, holding at 720 730 ° C for k h, the final air cooling. The total heat treatment cycle is 17 hours. Resistance against repeated impact with symmetric bending of samples with a diameter of 10 mm and a length of 100 mm under a load of 30 kgf is determined on a TUI-600 machine. Mechanical and technological properties of modified cast iron are given in the table.

As can be seen from the table, cast iron, modified by the proposed mixture of compounds 2 - k, have higher mechanical properties than

658956

when modifying them with a known mixture (composition 1). A comparative analysis of the costs of modifying the chuuns, the graphitizing ability and the mechanical properties of the modified high-strength cast irons after heat treatment showed that a significant economic effect can be obtained from the use of the proposed modifying mixture. At the same time, the mechanical and technological properties of modified cast irons (crack resistance, fluidity, etc.) increase.

The application of the proposed modifying mixture will improve the resistance against repeated impact, the operational resistance and mechanical properties while reducing the duration of the graphitizing annealing of white cast iron on ferrite-pearlite ductile iron.

Claims (1)

25 claims The modifying mixture containing boric acid, copper oxide and silicon barium, characterized in that 30, in order to increase the durability of the cast iron. Against repeated impact, it additionally contains yttrium, zirconium carbonate, silicon nitride and limestone flour at the following five the ratio of components, May. Ј: 0 Boric acid Copper oxide Silicium barium Silicon nitride Yttrium zirconium carbonitrides Izvestkova flour 0 15-25 10 - 17 15-23 , 12 - 17 11-15 6-16 6 - 12