SU1434000A1 - Alloying composition - Google Patents

Abstract

The invention relates to foundry, in particular to master alloys for cast iron and steel, and can be used in the manufacture of castings from high strength iron with vermicular graphite. The ligature contains, in May.%: Silicon 10.0-25.0; magnesium 4.0-6.0; barium 1.5-4.0; titanium 7.0-10.0; carbon 1.5-4.0; cerium 0.1-0.25; manganese 25.0-45.0; strontium 1.0-2.5; nitrogen 0.08-0.2; iron - the rest. The addition of magnesium into the composition of the ligature in combination with the proposed ratio of the remaining components makes it possible to obtain high-strength cast iron with vermicular graphite with high mechanical properties, the consumption of the proposed ligature in comparison with the known for modifying the cast iron is 30-50% lower. 3 tab. from the next

Description

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The invention relates to foundry, in particular to master alloys for iron and steel, and can be used in the manufacture of high-strength iron castings.

The aim of the invention is to reduce the consumption of ligatures and increase the strength of cast iron,

j The essence of the invention is that the ligature containing silicon, barium, titanium, carbon, rare-earth metals, manganese, strontium, nitrogen and iron, additionally contains magnesium in the following ratio of components, May,% Silicon 10s0-25, O

Bari5-A, 0

Titan7 0-10,0

Carbon 1.5-4.0

Cerium0,1-0,25

Manganese25.0-45.0

Strontium J, 0-2.5

Nitro0.08-0.2

Magnesium 4,0-6,0

; IronErest

Magnesium is a spheroidizer; graphite and simultaneously refines the melt from harmful impurities; sulfur, oxygen. With a magnesium content below 4%, the vermicular form of graphite is not stable, and with a content of more than 6%, the spherical form of graphite prevails in the structure of cast iron,

The introduction of manganese in quantities of less than 25% and the composition of the ligature does not allow an increase in the density of the ligature and the degree of assimilation of the components, and the introduction of manganese in an amount of more than 45% dramatically increases the hardness of the iron, which requires heat treatment. The introduction of strontium IB ligature in an amount of less than 1.0% does not provide the required tensile strength of iron with vermicular gravel, and if its content is more than 2.5%, an increased chill is observed, which leads to a high hardness of castings. The nitrogen content in the composition of ligatzfe 0.08-0.2% is optimal. At a lower content, the tensile strength of cast iron decreases due to a decrease in titanium nitrides, and at higher nitrogen content, the hardness of cast iron increases and its plastic properties decrease.

When the content of silicon in the ligature

less than 10%, there is a risk of cementite in the cast iron structure.

which leads to the bleaching of castings, with a content of more than 25%, the specific gravity of the master alloy decreases, and consequently, the degree of its absorption deteriorates.

Cerium (with an optimal content of 0.1-0.25%) contributes to the stabilization of the vermicular form of graphite in iron. When the cerium content in the ligature is less than 0.1%, the tendency to form lamellar graphite appears, and with a content of more than 0.25% - spherical shape of graphite.

A barium content in the ligature of 1.5-4.0% ensures the production of castings without chill and is optimal from the point of view of obtaining iron with vermicular graphite,

Titanium — a graphite desferoidoid — was introduced into a ligature to give a vermicular form to graphite inclusions. When the titanium content is less than 7%, the conditions for obtaining a vermicular form of graphite worsen, and the titanium content in the ligature more than 10% does not lead to further improvement of the conditions for forming graphite inclusions.

Carbon in the composition of the ligature contributes to the increased crystallization centers of the graphite phase, which favorably affects the distribution and size of graphite inclusions in the metal matrix, as well as the lowering of the melting temperature of the ligature, the carbon content in the ligate is less than 5% and has a weak effect on the nucleation of graphite crystallization centers and with a content of more than 4%, the degree of carbon assimilation in the ligature deteriorates, the number of graphite inclusions sharply increases, which has a negative effect on the strength Ystakh pig iron.

To test the proposed composition of the master alloy at the bottom of the crucible of the induction furnace EAST-0.06, the ingredients of the master alloy were filled in: ground bout of electrodes (2.55%), mixing the latter with strontium hexafluorosilicate (), ferrocerium (0.2%), metal magnesium (5 %), - ferrotitanium (8.5% ferrosilicobarium (2.55%), manganese metal and manganese nitrated (in terms of 35% manganese and 0.14% nitrogen) 5 were added ferrosilicon in an amount providing silicon content in the master alloy 17.5%. Lee

Tayn pig iron was added to obtain rbp; its iron content in the ligature was 26.66%.

As a coating flux, to prevent magnesium ignition, NaCl was used,

In order to substantiate the optimal content of the components, five compositions of the proposed ligature and one known (by prototype) for comparison were prepared in a similar way. Table 1 presents the composition data.

Comparative tests of the proposed and known (according to the prototype) of ligatures by the cast iron treatment with the following chemical composition,% are carried out: carbon 3,3; silicon 1,8; manganese 0.19; sulfur 0.021; phosphorus 0.07%.

Processing of cast iron was carried out at lASO-lSOO C in ladles at the rate of consumption of 1.3% ligature by weight of the melt being processed.

The results of the comparative tests of the SRI, the degree of assimilation of the components of the master alloy and the mechanical properties of iron with vermicular graphite are presented in Table 2,

As can be seen from Table 2, samples of iron, modified with a ligature of composition 2-4, have more favorable combinations of strength and hardness in comparison with iron treated with a known ligature.

Table 3 presents the comparative flow rates of the proposed and known ligatures, as well as the mechanical properties of the resulting cast iron.

From Table 3 it follows that when modifying liquid iron with the proposed ligature, its consumption is significantly reduced.

Thus, the proposed alloy allows to obtain high-strength cast iron with high mechanical properties without the use of special methods for introducing it into liquid iron. The specific weight of the proposed ligature is 4.8-5.6, which is 25-35% higher than the known. At the same time, the degree of assimilation of the components of ligat 1 lg is significantly higher compared to the known, which in turn allows to reduce the consumption of ligature for bucket modification by.

Claims (1)

20 claims Ligature containing silicon, barium, titanium, carbon, cerium, manganese, strontium, nitrogen and iron, characterized in that, in order to reduce its consumption and increase the tensile strength of iron, the following component ratio, wt. %: a b Yut 25 1.5-4.0 7-10 1.5-4.0 0.10-0.25 25-45 1.0-2.5 0.08-0.20 4-6 Else and c I Components Content, wt.%, In the proposed compositions of the master alloy .rDZr.Z.r. 0.05 3.55 0.1 4.0 The famous composition of the bus. 998560 2.75 12.5 4.25 5.05 0.25 6.0 0.30 6.5 Offering ma 1360 Continuation of table 1 table 2 49 74 384,187 Samples with through chill. . 1,434,000-8 Table 3