SU1036783A1 - Modifier for cast iron - Google Patents

Abstract

MODIFIER FOR CAST IRON containing silicon, magnesium, barium, aluminum, calcium, copper and iron. characterized in that, in order to increase the mechanical properties of cast iron, it additionally holds titanium and rare earth metals in the following ratio of components, wt.%: Silicon 60.0-78.0 Magnesium 0.1-2.0 Barium0.1-5.0 Aluminum0.1-4.0 Calcium0.1-4.0 Copper0.1-5.0 Titanium0.1-15.0 Rare-earth 0.1-5.0 Metals about SS Iron Rest

Description

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00 The invention relates to metallurgy / in particular to research from modifiers that enhance the mechanical properties of cast iron and the elimination of free cement in the cast structure: Modifier 1J is known, containing, wt ..%: Silicon25-55 Manganese 10-30 Calcium 3-10 Aluminum1 , 5-10 Magnesium 0.6-3.0 Strontium 3-10 IronOstal The disadvantages include the low mechanical properties of cast iron, obtained as a result of processing with a known modifier, and the position of free cementite in its structure during casting in the chill mold. The closest to the proposed technical essence and the achievable result is a C2J modifier containing, in wt.%: Barium20-45 Calcium0.5-10 Iron1-15 Aluminum 0.3-4 Magnesium 0.1-2 Copper. 0.01-0.5 Silicon Rest A disadvantage of the known modifier is a weak degassing and strengthening effect, which limits its use for modifying cast iron in the production of castings that are subjected to mechanical treatment, shock loading and must have a high hydro-density. In addition, a high content of bari (1.20–45%) in the modifier leads to crystallization of cast iron with white and a decrease in the number of graphite inclusions, including a spherical shape. The structure of the iron is ledeburitna. The purpose of the invention is to improve the mechanical properties of cast iron. This goal is achieved by the fact that the modifier for cast iron, containing silicon, magnesium, barium, aluminum, calcium, copper and iron, additionally contains titanium and sharply ground metas (REM) with the following ratio of components, wt.% 60.0-78.0 Silicon 0.1-2.0 Magnesium 0.1-5.0 0.1-4.0 Aluminum 0.1-4.0 Kapi1 {0.1-5.0 0.1-15.0 0.1- 5.0 Else Iron Titanium is introduced into the modifier as the most powerful liquid metal degasser. Actively interacting with nitrogen and oxygen in the molten iron, titanium contributes to the elimination of gas defects in the castings, increasing their hydrodensity. A distinctive feature of titanium is that it favors primary crystallization and accelerates the decomposition of ledeburite. The titanium in the composition of the modifier in an amount of 0.1-15% causes the alloying of the iron matrix, helps to obtain a fine dense structure, its hardening, as well as an increase in the correct spherical and compact form in the structure of graphite inclusions, reducing the degree of chill. Entering less than 0.1% titanium into the modifier does not show its effect in this direction. The upper limit of 15% is due to the fact that, with greater titanium concentration, the mechanical properties of the pig iron deteriorate, the shape of graphite and the tendency of the pig iron to chill appear. The introduction of the REM modifier is necessary for the desulfurization, deacidification, spheroidization of graphite and the elimination of the harmful effects of the antiglobulating elements found in the molten iron. The REM in the composition of the modifier containing calcium reduces the shape, reduces the size and increases the amount of graphite inclusions with less consumption of the modifier. This is due to the fact that calcium, performing the functions of a desulphurizer and a deoxidizing agent, releases REM and magnesium from them, increasing their absorption by the liquid metal. An equally important factor is that the introduction of rare-earth metals into the composition of the modifier increases the duration of its modifying effect by about 2 times. The lower limit of the content of rare-earth metals in the composition of the modifier 0.1% is associated with the boundary concentration, below which their influence on the properties of cast iron is not obvious. The content of rare-earth metals more than 5% leads to the crystallization of cast iron through a metastable system, which worsens the shape of graphite inclusions and is not economically feasible. The joint input of magnesium and barium in the composition of the modifier in optimal quantities contributes to the crystallization of cast iron with the formation of spherical shape of graphite and without chill. Increasing the amount of barium by more than 5% and magnesium by more than 2% in the composition of the modifier leads to crystallization of the cast iron according to the metastable system and an increase in the number of graphite inclusions of spherical shape. Aluminum, the composition of the modifier, along with a deoxidizing effect, increases the effect of the absorption of magnesium by cast iron, and stabilizes the process of modification. Together with copper, aluminum favors the hardening of the iron in a stable system. Copper in the composition of the modifier causes the alloying of the matrix of cast iron, helps to obtain a dense, chalk codisperse pearlitic structure. Together with titanium, copper increases the water density of castings. The presence of calcium modifier in the composition, along with REM, magnesium and barium, promote deep deoxidation, degassing and desulfurization of cast iron.

Table 1 Reducing the solubility of carbon in iron, calcium increases the graphitizing ability of the modifier. The limits of the content of these elements in the proposed modifier are established on the basis of the studies performed and the known experimental data. Iron and silicon are the basic components and their content has been established based on the technological effectiveness of the modifier smelting. The components of the modifier are possible to be introduced into the molten iron in the form of an alloy or a mechanical mixture of components. The compositions of the modifiers are given in the table. one.

From the above data it can be seen, that the proposed composition corresponds to modifiers 2-4. In the composition of the modifier, the content of rare-earth metals and titanium is less than the lower limits; in composition 5, their concentration exceeds the upper limits.

The effectiveness of the modifier is tested in laboratory and industrial conditions on cast iron of the following composition, wt.%, Carbon 3.4-3.9, silicon 1.80-2.24, manganese 0.45-0.67, phosphorus 0 , 06-0.14, sulfur 0.051-0.086.

The cast iron is modified in a ladle. The modifier is introduced under the metal stream. The temperature of the metal during sdification is 1360-1420 ° C. The amount of modifier injected is up to 2.0% of the weight of liquid iron. In order to study the structure and mechanical properties, the trefoil samples and three types of castings with different wall thicknesses are cast. The cooling rate of the metal in such castings is 9.2, 6.1 and 3.2 s per second, respectively, and in trevidnyh samples - 1.1 C. per second. The cast castings are then subjected to metallographic examination. The number and size of nodular graphite inclusions per unit area of the thin section, the amount of cementite and ferrite are determined.

The results of metallographic studies and investigations are given in Table. 2

As can be seen from the above table.2 60figatory composition 1 and 5 and

data, cast iron, processed mod-known.

fixatives of compositions 2-4, have go- Mechanical properties (limit

less sensitivity to strength, elongation

bela, more globular inclusions f. shock viscosity A | solid graphite. in comparison with mod-sHB of modified iron

Table 2

tia specimens cut from the trefoid samples are determined. Analysis of the test results given in; Table. 3 shows that the modifiers 2-4 provide the cast iron with the highest value of ultimate strength, relative elongation and toughness, and the hardness of these cast irons is significantly lower than in the case of modifiers of known 1 and 5.

Table3

Claims (2)

MODIFIER FOR CAST IRON, containing silicon, magnesium, barium, aluminum, calcium, copper and iron, characterized in that, in order to increase the mechanical properties of cast iron he is additionally with ** ' holds titanium and rare earth tall with the following ratio com ** ponents, wt.% j Silicon 60.0-78.0 Magnesium 0.1-2.0 Barium 0.1-5.0 Aluminum 0.1-4.0 Calcium 0.1-4.0 Copper 0.1-5.0 Titanium Rare Earth 0.1-15.0 metals 0.1-5.0 Iron Rest 2 e (L from about GO ABOUT 25-55 10-30 3-10 1.5-10 0.6-3.0 3-10 The rest wt.%: 20-45 0.5-10 1-15 0.3-4 0.1-2 0.01-0.5 The rest of the known modifi-