SU1507842A1 - Composition for inoculating iron - Google Patents

Abstract

The invention relates to metallurgy and can be used in the production of castings from high-strength cast iron. The goal is to increase the mechanical properties of cast iron and improve its fluidity. The mixture for modifying the pig iron contains, in wt.%: Granulated magnesium 5-15

graphite 2-5

manganese slag 16-20

ferrosilicon the rest. Manganese slag from steel production 110G13L is used. The addition of manganese slag to the modifying mixture makes it possible to increase the fluidity in the iron by 1.16-1.24 times, σ by 1.06-1.12 times, δ by 1.5-1.7 times. 1 tab.

Description

l with

The invention is inclined to metallurgy, in particular to the development of mixtures for the modification of pig iron.

The purpose of the invention is to increase the mechanical properties of cast iron and improve its fluidity. The choice of the boundary limits for the content of components in the mixture of the proposed composition is due to the following.

The content of granulated magnesium in the mixture was established on the basis of the conditions for obtaining high strength properties of castings. The lower limit of magnesium content (5% by weight) corresponds to the formation of spherical and vermicular graphite with a total degree of spheroidizing graphite of at least 65%. Below this limit, the graphite of the plate- dominates in the structure: the lower form and properties of cast iron are reduced.

The upper limit of the magnesium content (15 wt%) is due to its strong carbide-stabilizing effect and the deterioration of the environmental effect of modifying

The use of graphite in the modifying mixture makes it possible to additionally create a larger number of centers of crystallization of graphite and thereby increase the number of eutectic grains. Grinding the structure in turn increases the strength of cast iron. The optimum content of graphite in the mixture is 2-5 wt. The addition of graphite less than 2 wt.% Does not give a significant increase in the positive effect, 6ojjee 5 wt.% - graphite completely: it is not absorbed by the melt, its particles coagulate and crystallize in the form of melted, reducing the strength of the cast iron and deteriorating the fluidity.

3150

The choice of ferrosilicon as a component of the modifying mixture is due to a number of factors, 75 ferrosilicon is highly soluble in liquid iron and has a high degree of assimilation by the melt. The graphitizing effect of ferrosilicon makes it possible to exclude the possibility of chill formation in thin sections of the casting and increases the ductility of cast iron. In addition, silicon improves the technological properties of the melt. The optimal amount is the content of ferrosilicon in the composition of the mixture 60-77 wt.%, Which in terms of pure silicon is 45 - 58 wt.%.

Manganese slag consists of oxides formed during the smelting reduction of high-manganese steels, for example, during the smelting of POMPL steel, which have the following chemical composition, wt%:

CaO25-40

MgO15-20

SiO j29-33

Mn15-25

FeO1.5-3.5

Up to 0.05

The choice of manganese slag as a component of the mixture for modifying Chu Gong is due to its high refining and alloying effect on the melt. Manganese, which is a part of manganese shlak, is an effective perlithizer of a metallic cast iron base. Its bleaching effect on the cast iron structure is manifested at higher amounts than chromium in chromium slag, which allows a wide variation in the composition of the modifying mixture without the danger of bleaching. The presence of CaO MgO and FeO compounds allows the desulfurization process to be actively carried out simultaneously with the modification. The limits of the content of manganese slag in the composition of the mixture (16-20%) reflect the complete perlithization of the metal matrix. A deviation upward from the boundary ones causes chipping in thin sections, and at lower manganese slag contents, partial ferritisation of the cast iron structure is observed, which also reduces its strength characteristics, although it increases fluidity and ductility.

In the manufacture of known and proposed mixtures, the following components were used: granulated magnesium MgP 1, TU 48-10-51-78; black graphite GLF-3, GOST 5420-74; ferrochrome slag from ferrochrome production; manganese slag of steel production 110G13L; ferrosilicon FS75, GOST 1415-75.,

The technology of mixture preparation consists in crushing, weighing and mixing the ingredients. The technology of using the mixture includes filling it to the bottom of a heated ladle and subsequent pouring with liquid metal.

The quantitative composition of manganese slags has a great importance on the course of the modification process. To use in the modifying mixture, it is necessary to use manganese slag with a basicity (CaO / RiO) of at least 1.6. The lowering of the Slag BASIS below 1.6 indicates an increase in the proportion of silica in the slag, which increases the surface tension of the slag and reduces the adhesion of the slag to nonmetallic inclusions in the melt, which remain in it in the form of suspensions and reduce the flowability of the pig iron. 1 does not give a significant decrease in interfacial tension at the metal-slag interface, and therefore does not affect the deeper refining of the liquid metal.

When conducting comparative tests in the proposed mixture, manganese slag of the following chemical composition, May.%, Was used for the modification:

Calcium Oxide 32.5 Magnesium Oxide 17

Silicon dioxide 29 Manganese20

Iron Oxide2

Phosphorus 0.03

The slag basicity was, 7. For carrying out comparative tests of cast iron treated with the known and proposed modifying mixtures, a high-carbon iron alloy was used, containing, in wt.%:

Carbon 3.2

Silicon 2.0

Manganese 0.6

Nickel 0.2

Chrome0.11

Sulfur0,105

Phosphorus 0.05

The mechanical properties of cast irons were studied on samples made from blanks cast in accordance with GOST 7293-85 "

The tensile test was carried out according to GOST 1497-73 on samples with a diameter of 14 mm and a calculated length of 70 mm.

Impact toughness tests were performed on three samples of 10 mm hairine according to GOST 9454-78

The table shows a comparative analysis of the properties of cast iron treated with the known and proposed modifying mixture at a mixture consumption for modification equal to 1.2% of the mass of the melt.

As follows from the table, the additional input of manganese slag into the mixture provides an increase in fluidity — 1.16–1.24 times d. 1.06- 1, 12 times, G 1, 55 - 1.77 times,

Claims (1)

Invention Formula The mixture for modifying the pig iron containing granulated magnesium, graphite and ferrosilicon, characterized in that, in order to improve the mechanical properties of the cast iron and improve its flowability, it additionally contains manganese slag, at g: ice production ratio, wt.%: Gr anul ir ev ann magnesium Graphite Manganese Slag Ferrosilicon 5-15 2-5 16-20 Else