SU1636449A1 - Inoculation mixture for ladle treatment of hot metal - Google Patents

Abstract

The invention relates to foundry, in particular, to modifying mixtures used in the production of high-strength cast iron, and can be used to obtain modified cast iron. The aim of the invention is to increase the stability of obtaining vermicular graphite, to increase the resistance of the iron against thermal shock and to reduce the pyroeffect when modifying. The modifying mixture for the pig iron pig processing contains, in wt.%: Fergclikomishite metal, S - 50; silicon magnesium. Riy alloy 20-50; an alloy with carbide & oazing elements based on ferrosilicon 20-50. The use of the mixture allows to increase the heat resistance of cast iron by 35-40%, reduce pyro-ef (Lecture during the processing of cast iron to its weakness and obtain vermicular graphite in cast iron by 90- 100%. 1 table F (L

Description

The invention relates to foundry, in particular, to modifying mixtures used in the manufacture of high-strength cast iron, and can be used to obtain modified cast iron.

The purpose of the invention is to increase the stability of obtaining vermicular graphite, to increase the resistance of cast iron against thermal shock and to reduce the pyroeffect when modifying.

The proposed modifying mixture for bucket processing of cast iron contains a ferrous silicon metal, a silicon-magnesium barium alloy with a ratio of magnesium to barium of 1: (2.0-2.5) and alloy with

carbide-converting elements based on ferrosilicon in the following ratio, wt.%:

Oerrosilikomishmet ll 10-50 Silicon magnesium barium alloy 20-50

An alloy with carbide-forming elements based on ferrosilicon 20-50. The use of a silicon-magnesium-barium alloy ensures the presence of complex compounds of magnesium with barium and silicon, having a higher interatomic bond strength than magnesium silicide. As a result of this, at the time of introduction into the melt

WITH

about

Јъ Јъ СО

In the blend mixture, the intensity of the magnesium burn-up process is sharply reduced, thereby enhancing its absorption and the intensity of the pyroeffect is reduced. The presence of Ba-Si-Mg compounds in the melt during the pre-crystallization period ensures a decrease in the activity of magnesium atoms. As shown by experimental studies, when using a silicon-magnesium alloy with a magnesium: barium ratio of 1: (2.0-2.5), the graphite iron in the structure is predominantly in the vertical form. The introduction of graphite in a vermicular form also corresponds to the introduction of iron silicides into the melt, in which some of the iron atoms are replaced by carbide-forming elements more electronegative than iron. Such a result is due to the influence on the graphitization of impurity clusters formed when alloys with silicide phases are introduced into the melt. Therefore, the replacement of an alloy based on ferrosilicon on a ferroalloy of this element results in obtaining iron with graphite of predominantly spherical irregular shape, which does not correspond to the required properties.

In the proposed modifying mixture, the content of the alloy with carbide-forming elements based on ferrosilicon and silicon-magnesium-barium alloy was chosen taking into account their joint influence on the stability of the production of vermicular graphite, as well as the preparation of predominantly ferritic alloyed metal base of the cast iron, ensuring the resistance of castings heat shock effects.

Example. For experimental verification of the proposed composition, 18 compositions of the modifying mixture were prepared (table). As a carbide-containing alloy based on ferrosilicon, ferrosilicon with FS40VD vanadium is used, containing, in wt.%: Y 6-8; Si 35-40; Mp 3-5; Fe the rest (experiments 1-13), as well as ferrosilicon with chromium, containing, wt.%: Cr 8-10; Si 65-70; Fe the rest (experiments 14 and 15), and ferrosilicon with boron, containing, wt.%:. In 5-8; Si 65-70; Fe rest (experiments 16-18). As a silicon magnesium-barium alloy, an experimental alloy is used with a content, wt.%: Mg

0

five

0

five

0

4-6; Ba 8-15; Si rest. Ferrosilicomite metal contains, in wt.%: REM 13-15; Si 55-60; A1 4-9; Fe rest.

The original cast iron with the chemical composition, wt.%: C 3,0-3,2; Si 1.0-1.3; MP 0.3-0.6; S 0.05, melted in a 50 kg induction furnace. Melt overheating temperature is 1400 + 10 ° C. A modifying mixture of each composition in an amount of 2% by weight of metal is placed on the bottom of the ladle before casting. After processing, samples of 40 mm in diameter at 132 ° to 20 ° C are poured into the iron ladle. The resistance of the cast iron to thermal shocks is determined on cylindrical specimens with a diameter of 15 mm and a height of 15 mm, thermocycled according to the scheme of heating to 900 ° C, holding for 15 minutes and cooling in water. Experiments 1-4 were carried out to analyze the effect of the ratio Ba / Mg in the silicon-magnesium alloy on the achievement of a positive effect. When Ba / Mg ratio increases by more than 2.5 (experiment 4) and decreases below 2.0% (experiment 3), there is a decrease in the stability of obtaining the vermicular form of graphite and a decrease in the resistance of the cast iron to thermal shock, which manifests itself in a decrease in the number of cycles to the appearance of thermal cracks.

five

0

five

0

five

When the content of the components of the modifying mixture is within the proposed limits (experiments 5-8), graphite is precipitated mainly in vermicular form. At the same time, the modification process is characterized by a weak appearance of the pyroelectric effect and an increased resistance of cast iron against thermal shocks, which, in particular, is indicated by an increase in the number of cycles before the appearance of thermal cracks. As can be seen from the table, the use of compositions of modifying mixtures, in which the content of the alloy with carbide-forming elements based on ferrosilicon and silicon-magnesium-barium alloy (experiments 9-12) is lower than the lower and higher than the proposed limits, does not allow to achieve a positive effect. A similar result (experiment 13) is obtained when using ferrovanadium as a carbide-containing alloy. Experiments 14-18 were carried out to show the effectiveness of using other carbide-forming elements.

The use of the proposed mixture allows to increase the productivity of the process of obtaining CVG during bucket melt processing by stabilizing the modification process, as well as reducing the cost of castings by increasing the assimilation of alloying elements, reducing the heat resistance of castings.

Claims (1)

Invention Formula A modifying mixture for bucket processing of cast iron, including ferrosilicomite, magnesium and barium-containing alloys, characterized in that, in order to increase the to obtain vermicular graphite, increase the resistance of iron against heatstroke and reduce pyrozffekta when modifying, it further contains an alloy with carbide-forming elements based on ferrosilicon and a silicon-magnesium-barium alloy with a barium-magnesium ratio of 1: (2.0-2 , 5) in the following ratio, wt.%: Ferrosilicomitemetal 10-50 Silicon-magnesium barium alloy 20-50 Alloy with carbide forming elements on ferrosilicon base 20-50 Weak  and Strong Weak Weak Strong Glory Strong Weak