SU1723174A1 - Modifier for cast iron - Google Patents

Abstract

This invention relates to metallurgy and can be used to modify cast iron. The purpose of the invention is to increase the tensile strength of the cast iron during stretching while maintaining the level of hardness. Modifier for cast iron contains, wt%: Cu 25-35; Zn 5-15 and Te the rest. When using a modifier to treat cast iron, the tensile strength increases by 1.1-1.26 times, while maintaining the level of hardness in the range of 160-207. 3 tab.

Description

The invention relates to metallurgy / in particular to the modification of cast iron, and can be used in the modification of cast irons of various compositions.

The purpose of the invention is to increase the tensile strength of the cast iron during stretching while maintaining the level of hardness.

The modifier for cast iron contains. tellurium, copper and zinc are additionally introduced, and the cast iron modifier is an alloy in the following ratio, wt.%:

Copper25-35

Zinc5-15

Tellurium

The cast iron modifier, which is an alloy of tellurium with copper and zinc, consists mainly of refractory chemical compounds of tellurium with copper CumTemfV | (for example, Cu4Tez) and zinc - ZnTe.

The CumTem-i compounds (e.g., SshTez) have a mp. 750-800 ° C and a density of 7.3 t / cm, and the compound ZnTe has so pl. 1240 ° C and density (d) 5.6 g / cm3.

The alloy containing 25-35% Cu-15-5% Zn and the rest is tellurium and presented in the form of refractory chemical compounds - copper telluride, zinc telluride, has so pl. 850-900 ° C, which provides a high degree of assimilation of modifier components (for example, tellurium up to 70-90%), thereby increasing the reliability of modifying the cast iron, and also has a density of 7.0-7.2 g / cm, sufficient to provide immersion modifier to molten iron. Due to the fact that tellurium is introduced into liquid cast iron in the form of an alloy consisting mainly of refractory copper tellurides and zinc tellurides, the modifying process proceeds stably, and the elements that make up the proposed modifier, such as copper, zinc and tellurium, increase the reliability of modifying the cast irons of different composition, thereby contributing to the perlitization of the metal matrix and the grinding of the structure, which, respectively, causes an increase in strength.

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Depending on the chemical composition of the pig iron, the proposed modifier can be used independently or in combination with graphitizing additives, for example, ferrosilicon, silicobarme, aluminum, LCMK, REM, and the like.

The optimal amount of modifier introduced into gray cast iron is 0.005-0.015% by weight of the molten metal. As a stabilizing and bleaching additive, a modifier for cast iron in an amount of 0.005-0.30% by weight of the molten metal can be used in the production of doped cast iron, high-strength nodular and vermicular graphite cast iron, ductile iron, etc.

Example. The iron modifier is smelted in a resistance heating furnace equipped with a ventilation hood in a graphite crucible under a layer of low-melting protective flux. The flux is added in the amount of 10-20% by weight of the melted charge material and is a eutectic mixture of salts of NaCi and CS in the ratio of 1: 1.

Copper M2 (GOST 859-78), technical tellurium T1, (GOST 17614-72), bismuth Bi1 (GOST 10928-75), zinc CZ are used as charge materials for smelting the iron modifier. (GOST 3640-79).

 The smelting of the charge materials is carried out in the following sequence; heating to 350-400 ° C; extract 0.3 hours; heating to 600 ° C; extract 0.3 hours; slow heating up to 800-850 ° С at a rate of 2 deg / min; shutter speed 0.5-1.0 h; pouring the finished melt into molds.

To compensate for the loss, tellurium can be increased by 10-15% (over 100%).

The smelting of the iron modifier, represented as an alloy and consisting mainly of chemical compounds of tellurium with copper and zinc, can be carried out in the following order.

Tested compounds known and proposed modifiers for cast iron.

1. Separately for each compound.

To obtain the compound CumTem-i (e.g., CyCez), 60} wt.% Tellurium is loaded into the crucible, the rest is copper. Heating of the charge is carried out up to 800-850 ° C at a given temperature. To obtain the ZnTe compound, 66 wt.% Of tellurium is loaded, the rest is zinc. During the smelting of the ZnTe compound, the mixture is heated to 800-850 ° C randomly, then heated at a rate of no more than 2 degrees / min to 1000-1200 ° C with a holding time at this temperature for 0.5-1.0 hours.

The finished modifier is crushed and added to the cast iron in the form of a mechanical mixture of compounds CumTem-i and ZnTe. in this case, the proportion of the CumTem-i compound should be 60-90% of the total weight of the modifier sample, and the ZnTe compound should be 40-10%, or as an alloy obtained by mixing CumTem-1 melts. ZnTe followed by crystallization of the finished

alloy, subject to the following ratio of elements, wt.%: copper 25-35; zinc 15-5; tellurium the rest.

2. Joint melting of all components to produce a cast iron modifier in the form of an alloy consisting mainly of the refractory chemical compounds CumTem-1 and ZnTe, the initial components are loaded into a graphite crucible in the following ratio, wt%:

Copper25-35

Zinc15-5

Tellurio

To reduce the tellurium burnout during the smelting of the alloy, the charge materials are loaded into the crucible in the following sequence: tellurium, zinc, copper, flux.

Alloy containing 25-35% of Sii 15-5% Zn, and the rest is tellurium and consisting mainly of refractory chemical compounds

tellurium with copper and zinc has a purple color, it is easily crushed, at a temperature of 850–900 ° C has a mushy state, therefore, for casting it into molds, overheating up to 950 ° C is necessary. Zinc and tellurium carbon

a layer of flux NaCI-KC is negligible.

The resulting compositions of the known and proposed modifiers of cast iron were tested when modifying the cast iron. Analysis of the experimental data shows

that alloy 1 has a low density, so it does not sink into the liquid metal, and remaining on the surface of the melt does not have the necessary modifying effect on the cast iron, and alloy 5 is not enough

refractory, the effect of boiling is observed and the modifying effect in the cast iron is again reduced. When the content is in the modifier of cast iron containing,%: copper 25, zinc 15; tellurium - the rest (alloy 2), its

density becomes sufficient for immersion in molten iron.

When the content in the modifier of cast iron, containing,%: copper 35; zinc 5 tellurium else (alloy 4), its refractoriness becomes satisfactory to provide an effective modifying effect on cast iron.

This allows us to consider the concentration range of the components in the proposed

optimal cast iron modifier (alloys 2, 3 and 4).

The known cast iron modifier showed good immersion in the liquid metal, however, a slight kick effect was observed.

In order to study the modifying effect of the proposed and known iron modifiers, the pig iron was modified to study its structure and mechanical properties. To do this, gray iron was smelted in an IST-016 induction furnace with an acid lining (Table 2). The modification was carried out in a 150-kilogram filling bucket at 1340-1400 ° C and in a runner bowl of the form.

To determine the modifying effect microstructure and strength of cast iron, cylindrical specimens with a diameter of 30 mm and a height of 340 mm were cast, from which standard specimens with a diameter of 20 mm were machined to determine the tensile strength of the cast iron.

The test results of the original and modified cast iron are presented in Table. 3

When introducing into the liquid metal the eutectic composition of the proposed cast iron modifier in an amount of 0.005-0.015% of the mass of the liquid metal, the effect of modification is most significant, for example, due to the greatest increase in mechanical properties. This makes it possible to consider for a gray cast iron a eutectic composition the given quantitative range of the proposed cast iron modifier as optimal. Studies have shown that the known modifier of cast iron has a lesser modifying effect, which is reflected in the increase in tensile strength of modified iron (Table 3). The proposed modifier of cast iron provides a higher increase in mechanical

properties with less flow modifier.

Studies have shown that for high-strength nodular and vermicular graphite iron, the optimum amount of molten metal is 0.005-0.015% (by weight of the liquid metal) of the proposed iron modifier. For ductile iron and doped iron (for example, high-chromium), the optimum is an additive in the melt of 0.005-0.30 wt.%.

The technical and economic efficiency of the proposed invention, in comparison with the known one, consists in the possibility of modifying and improving the mechanical properties of about 3 million tons of iron castings per year, produced from low-grade eutectic cast irons in small workshops and areas not adapted for high quality gray cast iron. In addition, the economic effect is obtained by applying the proposed modifier instead of scarce bismuth in the production of ductile iron.

In tab. 1 shows the content of chemical elements in cast iron modifiers of different composition ..

In tab. 2 shows the content of elements in various compositions of gray iron smelted for testing modifiers.

In tab. Figure 3 shows the effect of modifiers on the mechanical properties of gray iron.

Claims (1)

Claims of the invention. A modifier for cast iron containing tellurium. It is characterized by the fact that, in order to increase the tensile strength of cast iron upon stretching while maintaining the level of hardness, it additionally contains copper and zinc in the following ratio of components, wt.%: Copper25-35. Zinc5-15 Tellurium Table 1 table 2 Table 3 cast iron