RU2457256C2 - Modifying mixture - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: in addition, mixture contains ferrovanadium, nitrided ferromanganese, ferroaluminium and ferrosilicium at the following component ratio, wt %: copper oxide 12-20; boric acid 16-24; silicobarium 6-13; ferrovanadium 10-16; nitrided ferromanganese 9-12; ferroaluminium 12-20; ferrosilicium 12-18. Cast iron crack resistance is 3.8…5.5 mm.

EFFECT: invention allows improving antifriction properties of modified cast iron.

2 tbl

Description

The invention relates to foundry, in particular to a modifying mixture for processing antifriction cast iron of pre-eutectic composition, and can be used in the mass production of parts of the motor group of vehicles and other engineering castings.

Known modifying mixture (AS USSR No. 740837, C21C 1/00, 1980), containing, wt.%:

Silicobarium 10-30 Silikomishmetal 10-30 Silicocalcium 10-29 Lime 15-30 Magnesium 1-5 Corundum 5-10 Fluorspar 5-10

The modifying components of this mixture are not sufficiently absorbed by the melt and do not provide increased wear resistance, anticorrosion and operational properties of cast irons in castings.

Also known is a modifying mixture for cast irons (Patent PNR No. 113556, C22C 35/00, 1982) of the following composition, wt.%:

Ferrosilicon 60-80 Silicocalcium 10-30 Flux or graphite 1-20

The known mixture does not provide a significant refinement of the structure and increase the mechanical, service properties and crack resistance of cast iron in castings.

The closest analogue of the claimed invention is a modifying mixture for cast iron (SU 1232688 A1, C21C 1/10, 05/23/1986) containing a carbide-forming component, a graphitizing component and boric acid, characterized in that, in order to increase the mechanical properties of cast iron and reduce its duration annealing, it as a carbide-forming component collectively contains boric acid and copper oxide, and as graphitizing - silicobarium, in the following ratio of components, wt.%:

Copper oxide 20-30 Boric acid 50-60 Silicobarium 10-30

When using this modification of cast iron, insufficient antifriction properties and crack resistance are noted.

The objective of the invention is to increase the antifriction properties and crack resistance of modified cast iron in castings.

The problem is solved by a modifying mixture for treating antifriction cast iron, containing a carbide-forming component (silicobarium) and graphitizing, containing in total boric acid and copper oxide, while additionally containing ferrovanadium, nitrided ferromanganese, ferroaluminium and ferrosilicon in the following ratio of components, wt.%:

Copper oxide 12-20 Boric acid 16-24 Silicobarium 6-13 Ferrovanadium 10-16 Nitrogenated Ferromanganese 9-12 Ferroaluminium 12-20 Ferrosilicon 12-18

The analysis of the proposed technical solution showed that at the moment there are no technical solutions in which these differences would be reflected. In addition, these signs are necessary and sufficient to achieve the positive effect specified in the task of the invention.

An additional introduction to the composition of the modifying mixture of ferrovanadium provides an increase in the dispersion of the structure, hardness of cast iron and the stability of the isotropic structure, antifriction properties and strength of cast iron, which contributes to an increase in wear resistance, resistance to slipping and operational properties. The microalloying effect of ferrovanadium with its content up to 10 wt.% Is insufficient, it does not provide dispersed isotropic structure and increases the hardness, wear resistance and antifriction properties of cast iron, and when the concentration of ferrovanadium is more than 16 wt.%, The content of vanadium carbides along the grain boundaries increases, mechanical and antifriction decrease properties, crack resistance and wear resistance.

The content of boric acid in the modifying mixture is reduced 16-24 wt.%, Since at a higher content, the characteristics of antifriction properties and crack resistance are reduced. With its content up to 16 wt.%, The mechanical properties of cast iron are insufficient.

The additional introduction of ferrosilicon stabilizes the modification process and contributes to the grinding of the structure of cast iron, increase crack resistance, plastic and technological properties. When its concentration is up to 12 wt.%, The graphitizing ability of the mixture and the resistance of the modified cast iron to the formation of hot cracks and seizure during friction are reduced. And at a concentration of more than 13 wt.%, The characteristics of structure homogeneity, ductility, wear resistance and technological properties are reduced.

Ferroaluminium increases crack resistance, stability of the coefficient of friction and technological properties of modified cast irons. Its content in the mixture at the lower limit is 12 wt.%, Above which the uniformity of the structure improves, and below which the antifriction and plastic properties deteriorate. At a concentration of more than 20%, the characteristics of technological properties, ductility and operational properties of cast iron are reduced.

The introduction of copper oxide in an amount of 12 ... 20 wt.% Grinds the structure of cast iron, reduces the friction coefficient, increases the resistance to scoring and technological properties. When the concentration of copper oxide is up to 12 wt.%, The friction coefficient, resistance to scoring, and technological properties are insufficient. An increase in its content of more than 20 wt.% Leads to increased segregation and a decrease in the uniformity of the structure, the endurance limit in bending, and the technological and operational properties in castings.

Nitrogenated ferromanganese has an alloying effect and increases the modifying ability of the mixture, grinding grain of cast iron in castings, increases ductility and technological properties. At a concentration of less than 9 wt.%, The modifying effect of the mixture is insufficient and the technological properties of cast iron are low, and with an increase in its concentration at the upper limits, the concentration of non-metallic inclusions along the grain boundaries increases and the plasticity, fracture toughness, and performance characteristics decrease.

Silicobarium has a deoxidizing and modifying effect, increasing technological properties, crack resistance and ductility. The upper limit of its concentration of 13 wt.% Is due to an increase in fumes and porosity, a decrease in resistance to intergranular corrosion, wear resistance and elastic-plastic properties. With a decrease in its concentration of less than 6 wt.%, The deoxidizing ability deteriorates and the uniformity of the structure, technological and operational properties of cast iron in castings decrease.

The modifying mixture is obtained by mechanical mixing of copper oxide, boric acid and silicobarium with ferroalloys crushed to a fraction of 0.5 ... 5 mm. Modifying mixtures, mixed for 2 ... 3 minutes in runners, are introduced into distributing buckets before pouring molten cast iron into them in packaged form: in paper or plastic bags, or in compressed cylindrical tablets in an amount of 0.5% by weight of cast iron.

The compositions of the modifying mixtures used in the experimental cast iron melts are given in table 1. In the experiments used ferrovanadium FVd50U0.6; ferromanganese FMN78N; ferroaluminium FAL50 and ferrosilicon FS 75.

Experimental melts of cast iron containing wt.%: 2,9 ... 3,1; 1.8 ... 2.0 Si; 0.5 megapixel; 0.6 Cr; 0.06 R and 0.1 S, produced in coke cupola furnaces with a productivity of 5 t / h with a piggy bank. The release of pig iron from the piggy bank into the transfer bucket was carried out at a temperature of 1380 ... 1410 ° C.

Table 2 shows the mechanical and technological properties of cast irons obtained on standard cylindrical samples, technological samples and individual castings.

The coefficient of friction and wear resistance were evaluated on ring samples on a UMT-1M friction machine under steady-state friction conditions.

Crack resistance was determined on star-shaped technological samples with a height of 146 mm from the total total length of the cracks.

As can be seen from table 2, when modifying cast iron with the proposed modifying mixture, in comparison with the known one, an increase in crack resistance, wear resistance and antifriction properties is achieved.

Table 1 Mixture The content of components in the modifying mixture, wt.% Copper oxide Boric acid Silicobarium Ferrovanadium Ferroaluminium Nitrogenated Ferromanganese Ferrosilicon one 31 13 5 9 25 7 10 2 twenty 16 13 10 twenty 9 12 3 16 twenty 10 fourteen fifteen 10 fifteen four 12 24 6 16 12 12 eighteen 5 10 26 fourteen 17 one 13 19 6 26 54 twenty - - - - Izv

table 2 Mixture Amount of additive by weight of cast iron, Bending endurance, Contact stamina, Impact strength Average wear due to friction, Coefficient of friction Crack resistance wt.% MPa MPa J / cm ² G / m ² mm one 0.5 542 522 23 385 0.47 6.6 2 0.5 553 525 25 340 0.41 5.5 3 0.5 575 540 thirty 321 0.45 4.2 four 0.5 568 534 28 338 0.46 3.8 5 0.5 546 520 24 373 0.48 6.2 6 0.5 540 518 22 391 0.52 7.1 (wise)

Claims (1)

Modifying mixture for treating anti-friction cast iron, containing copper oxide, boric acid and silicobarium, characterized in that it additionally contains ferrovanadium, nitrided ferromanganese, ferroaluminium and ferrosilicon in the following ratio, wt.%:
Copper oxide 12-20 Boric acid 16-24 Silicobarium 6-13 Ferrovanadium 10-16 Nitrogenated Ferromanganese 9-12 Ferroaluminium 12-20 Ferrosilicon 12-18