SU1420055A1 - Inoculan - Google Patents

Abstract

The invention relates to foundry, in particular, to compositions of modifiers for high-carbon iron alloys, and can be used in the preparation of engineering castings from high-strength iron. The purpose of the invention is to increase the retention time of the effect of modification and reduce the amount of chill on iron. The proposed modifier contains components in the following ratio, wt.%: Silicon 40-55; carbon 0.05-0.5; aluminum 0.1-1.5; magnesium 5-10; calcium 0.1-1.0; lithium is 0.2-0.3; cadmium 0.01-0.15; iron else. The modifier additionally contains lithium and cadmium. Cadmium in small additives as a surface-active element reduces the amount of surface tension at the graphite-melt boundary, promotes the removal of chill in castings of high-strength nodular iron with graphite (VFSHG). The modifier can be recommended for the manufacture of critical thin-walled machine-building castings from chewing gland. 1 tab. ) (L

Description

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ate

The invention relates to foundry, in particular, to modifier compositions for high carbon iron alloys, and can be used in the manufacture of machine builders: castings from high strength pig iron (VCB1G),

I The aim of the invention is to increase the retention time

diffusion and reduction of chipping.

; The modifier contains components.

i in the following ratio, wt.%:

I Silicon. 40-55

I Carbon0.05-0.5

I Aluminum 0.1-1.5

I Magnesium 5-10

i Calcium OJ-1.0

j Lithium 0.2-0.3

I cadmium. 0.01-0.15

1. Iron. Rest

The selected limits of the silicon content provide the Minimum melting point of the modifier, and therefore, good solubility when the additive is introduced into molten iron. The lower limit of 40 wt.% Provides sufficient graphitization of the modified melt. Exceeding the upper limit (55 wt.%) Impairs the solubility of the modifier.

Carbon within 0.05-0.5 glas, 7 increases the graphitizing effect of the modifier due to the formation of additional graphitization centers, which can include microinclusions of both graphite and silicon carbide, whose formation is thermodynamically likely when the carbon content in the silicon-containing modifier is above 0.05 wt.,%, - Exceeding the upper limit of the carbon content does not give a significant increase in the effect.

Aluminum is a strong deoxidizing iron-based alloy. At the same time, being fully bound by oxygen, it releases magnesium from the performance of this function, thereby reducing the amount of modifier required for the spheroidization of graphite. Exceeding the upper limit (1.5 wt.%) Can contribute to the production of oxide films in castings and reduce the mechanical properties of the upper level iron grains.

Magnesium in the selected limits (5–10 masD) provides an effective spheroidizing treatment of the melt. The lower limit (5 wt.%) Provides

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the minimum permissible vertical dissolution rate for internal processing of the melt, in addition, when the magnesium content is below the lower limit, an increased flow rate of the modifier is required for both internal and ladle modifying. Exceeding the upper limit on magnesium drastically impairs the characteristics and stability of the dissolution parameters, a pyroeffect is observed during processing, and the magnesium absorption factor decreases.

Calcium is an auxiliary element of the spheroidoidizer. In amounts of 0.1-1 „0 wt.%, It favorably affects the modification process, especially with an increased sulfur content in the initial melt. Exceeding the upper limit slows down the rate of modifier dissolution due to slagging of master alloys, to ensure satisfactory solubility, elevated temperatures (up to 1450-1500 ° C) of modifier input are required.

Lithium is a strong deoxidizer jelly. - carbon-carbon alloys. The deacidification of liquid iron favorably affects the results of spheroidizing treatment. The limits of the content of 0.2–0.3 wt.% In the modifier provide a sufficient degree of melt deoxidation a. When choosing the limits of lithium content, it was also taken into account that the process of deoxidation when entering the modifier occurs in the zones of additive dissolution, which are characterized by a higher silicon content, Li with its content in modifier O, 2-0.3 May,% is able to increase liquid cast iron in high silicon microvolumes, with the formation of additional crystallization centers of graphite in the form of lithium oxides. The surface of such non-metallic inclusions, as well as sulfons, oxides and oxysulfides of calcium, magnesium, aluminum, can be graphitized by excess carbon-containing phases (carbon and silicon carbide), which increases the graphitizing potential of the treatment,

Cadmium - surface-active element, an analog of bismuth. Magnesium cast iron melt is characterized by increased surface tension at the graphite - boundary. melt resulting in rapid deactivation of the centers

graphitization .. Therefore, the maximum graphitizing effect is achieved immediately after the modifier is introduced into the melt, with further thermal exposure, it quickly drops due to deactivation - dropping the carbon layer from non-metallic inclusion. Entering into the melt highly refined magnesium iron small additives (in terms of the content in the iron, the cadmium concentration is 0.0002-0.0035 wt.%) The surfactant element, by reducing the surface tension, can stabilize the active state of the crystallization centers and increase the time the existence of a graphitizing effect. Exceeding the upper limit of the cadmium content (0.15 wt.%) In the modifier can lead to a strong blocking of the graphitization centers and ultimately to the opposite effect - bleaching of the upper limbs.

PRI m e. The technology for the preparation of the modifier involves the fusion of ferrosilicon with magnesium-containing components. As the latter, magnesium metal can be used, as well as waste of a magnesium alloy (30% by weight of magnesium), having the composition,%: lithium 7.5-8.5; cadmium 1-5; magnesium.

For comparative testing of the known and proposed modifiers, the initial iron composition, wt.%: Carbon 3, 6; silicon 0.5-2.5, manganese 0.2; chromium 0.1; sulfur 0.02, melted in a silica oven. The technology for producing high-strength cast iron included melt processing in a crucible with known and proposed modifiers in quantities of 6 and 2, respectively.

Part of the liquid iron was poured into sand samples to determine the amount of chill, another part of the

Medium Lower Medium. Upper

70 40 52 55

1.5 1.52.0

0.050.15

0,250,87,5

0,51,510

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went to thermal analysis. As a criterion of survivability, the time of disappearance of the effect of modification was used, i.e. the melt hardening time after the introduction of the modifier, during which the temperature of the onset of the eutectic reaction (it characterizes the tendency of the pig iron to chill) of the modified melt was compared with the temperature of the eutectic reaction of the original pig iron. As the latter, cast iron of one chemical stock was used with a modified nickel-magnesium ligature, which was processed to spheroidize graphite.

The chemical composition of the tested modifiers and the results of the comparative evaluation of the known and proposed modifiers are presented in the table. The test results show a significant increase in the survivability of the effect of the modification when using the proposed modifier and a decrease in chill out of the Ч.

Claims (1)

Invention Formula The modifier is predominantly for high-strength cast iron containing silicon, carbon, aluminum, magnesium, calcium and iron, characterized in that, in order to increase the retention time of the effect of modifying and reducing, the chill cast iron value, it additionally contains lithium and cadmium in the following ratio of components, wt.%: Silicon 40-55 Carbon0.05-0.5 Aluminum 0.1-1.5 Magnesium 5-10 Calcium0,1-1,0 Li0.2-0.3; . Cadmium 0.01-0.15 Iron Else Below nicky 350.01 0.05 40.05 0.1 0.005 - -524 Viee upper 750.8 2.0 151.5 0.5 0.3. 4.5 27.5 Note, b bc, 2 mn, bn, - 33 mm. Table continuation