SU1174489A1 - High-strength cast iron - Google Patents

Abstract

HIGH-STRENGTH IRON, containing carbon, silicon, manganese, magnesium, rare earth elements and iron, characterized in that, in order to increase ductility and toughness while maintaining the level of strength, it additionally contains nickel in the following ratio of components, May. %: 3.4-3.8 Carbon 1.6-2.4 Silicon 0.1-0.3 Manganese 0.04-0.07 Magnesium, 05 Up The rare earth (L 0.005-0.05 elements 0.2- 0.7 Nickel Iron Else

Description

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The invention relates to metallurgy, in particular to the development of high-strength cast iron compositions for the production of critical engineering castings.

The purpose of the invention is to increase ductility and toughness while maintaining the level of strength.

The content of elements and mechanical properties of high-strength cast iron are given in table. 1 and 2.

Carbon in the range of 3.4-3.8 provides good casting and mechanical properties of the alloy. The lower carbon limit of 3.4% is determined by the need to exclude structurally free carbide in the iron matrix. An increase in the carbon concentration above 3.8% is undesirable, since the shape of graphite worsens, its flotation is observed, etc.

The concentration of silicon 1.6-2.4% provides a favorable combination of plastic and strength properties of cast iron. The lower limit for silicon is set on the basis of the requirement to eliminate chill in the castings, the upper limit is set on the basis of the requirement for low doping of ferrite with silicon and thus an increase in the ductility of the iron lead, which also increases the strength properties. Thus, the selected combinations of carbon and silicon are optimal. The insufficiently high silicon content, which brittle the ferrite, is compensated for by a slightly higher carbon content, while the ductility and strength of the iron are high.

The limit on the manganese content (0.1-0.3%) was established on the basis of the requirement to achieve high ductility and toughness and the desirability of obtaining a ferritic matrix. The lower limit ensures the preservation of durability of the high-frequency iron class. Above the upper limit of the content. (0.3%), its negative effect on the plastic properties of cast iron is observed. Magnesium in the above concentrations (0.04- .0.06) provides nodular graphite with different sulfur contents in the initial melt. As the latter turns, the magnesium content must be increased.

Aluminum at concentrations of 0.01-0.05% contributes to an increase in the strength of cast iron, reduces the tendency to crystallization according to a metal-stable diagram. The hardening effect is manifested at concentrations of 0.01%. Increasing its content to above 0.05% can lead to the appearance of oxide deposits and a decrease in toughness values.

The content of the rare-earth metals of the cerium group in amounts of 0.005-0.05 has a positive effect on the spheroilization of graphite and the grinding of its inclusions. The lower limit of the cerium content is due to the need to obtain nodular graphite in castings. Upper - 0.03%, deterioration at large concentrations of the form of graphite (the effect of remodification) and the possibility of occurrence of carbide in castings. Experiments show that nickel is a alloying element that increases the strength of an iron-carbon alloy by dissolving significant amounts in the iron. In addition, it reduces the tendency of pig iron to crystallization by metal-stable diagram. In this case, there is no significant segregation, i.e. uniform distribution. The lower limit (0.2%) is set on the basis of achieving a sufficiently high level of strength of the high-voltage alloy. When the upper one (0.6%) is exceeded, no further increase in mechanical properties is observed.

The concentration of harmful impurities in the amount of: phosphorus up to 0.05%, sulfur up to 0.02%, chromium up to 0.05% was established based on the need to ensure the high plastic properties of the upper limit iron grades.

Example. Pure charge materials are used as the charge, - steel cutting and foundry iron, refined, ferroalloys; magnesium, REM cerium group, magnesium, technically pure aluminum and nickel. The content of impurities does not exceed the specified limit. After overheating, the cast iron is adjusted to 1420 ° C by chemical composition and then modified in a ladle with magnesium and cerium using appropriate ferroalloys.

Table 1

Claims (1)

HIGH STRENGTH IRON, containing carbon, silicon, manganese, magnesium, aluminum, rare earth elements and iron, characterized in that, in order to increase ductility and toughness while maintaining the level of strength, it additionally contains nickel in the following ratio, wt.%: 3.4-3.8 1.6-2.4 0.1-0.3 0.04-0.07 0.01-0.05 0.005-0.05 0.2-0.7 Else Carbon Silicon Manganese Magnesium Aluminum Rare Earth Nickel Iron SU „„ 1174489