SU1177376A1 - Inoculant - Google Patents

Abstract

MODIFIER containing silicon, calcium, rare earth metals and iron, characterized in that, in order to improve the mechanical properties of cast iron and increase the absorption of silicon by iron, it additionally contains niobium in the following ratio, wt.%: Silicon 45-55 Calcium 0.5-2 , 5 Rare-earth metals 0,5-4,0 Niobium 0,1-4,0 IronErest

Description

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One invention relates to foundry production, namely, modifier compositions for high carbon iron alloys, and can be used in the mass production of engineering metal castings. The purpose of the invention is to increase the mechanical properties of cast iron and increase the absorption of silicon by cast iron. Example. The initial cast iron of the hypoeutectic composition (hard cast iron), 7.1 С 3.2-3.25; 2.2-2.6; Cr 0.1-0.12; Mp 0.5-0.55, melted in a 50 kg induction high-frequency furnace. After overheating to a temperature, the cast iron is modified with additives of the known and proposed modifiers in the amount of 0.2%. Samples for mechanical tests are cut from wedge-shaped castings 40 mm thick. The assimilation by the molten iron of the components of the modifier is estimated from the silicon absorption coefficient as the basis of the modifier. Table 1 shows the chemical compositions of the proposed and known modifiers. The silicon content in the range of 45–55% provides the minimum melting temperature of the modifier, as a consequence of the improved assimilation of its components by the iron. At the same time, a sufficient graphitic effect is ensured when processing cast iron with the proposed modifier. The calcium content (known refining element) in the range of 0.5-2 provides a sufficient degree of melt refining. The upper limit of 2.5% is the outcome of the need to ensure a sufficient degree of assimilation by the modifier. Rare-earth metals also have a significant refining effect on the molten iron, thus increasing the dispersion of the metal matrix of the alloy, which is especially important in obtaining thick-walled casting. The lower limit of 0.5% is based on the need to achieve a sufficient degree of melt refining. The upper limit of 2.5% is based on the principle of efficiency of modification. When niobium (effective modifying element) is contained in the modifier of 0.1-4.0%, it contributes to the grinding of the primary structure of cast iron. The lower limit of its content is the limit when its modifying effect is felt. The upper limit is set on the basis of adherence to the principle, cost-effective modification. With a further increase in its content in the modifier more than 4.0%, the increase in mechanical properties is not observed. In tab. 2 shows the mechanical properties of the cast irons after their treatment with the proposed and known modifier. A noticeable significant increase in the mechanical properties of cast iron in the application of the proposed modifier compared with the known. Reducing the limits of silicon content in the modifier makes it possible to improve the modifying conditions and improve the assimilation of the components of the modifier with cast iron. Table 1

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Note: Silicon uptake is estimated by increasing the silicon content in the iron after it is modified to the amount of silicon additive in the modifier.

Claims (1)

MODIFIER containing silicon, calcium, rare earth metals and iron, characterized in that, in order to increase the mechanical properties of cast iron and increase the absorption of cast iron silicon, it additionally contains niobium in the following ratio of components, wt.%: Silicon Calcium Rare Earth Metals Niobium Iron 45-55 0.5-2.5 0.5-4.0 0.1-4.0 Rest S m m 00 m Od