SU1693110A1 - Modifying additive for cast iron - Google Patents

Abstract

The invention relates to cast iron modifiers. The aim of the invention is to eliminate chill in thin-walled castings and to improve the machinability of cast iron by cutting. The modifier contains, wt%: SI55-75; C 0.05-0-20; AI 0.5; 2.0; Md 0.5-1.5; Ca 0.5-2, Oj,; P3M 0.5-2.0; Mp 0.3-5.0, Fe balance,, and the ratio of calcium to magnesium is 1; (0.75-1.0). In addition, the modifier may additionally contain 0.5-2.0 wt.% BA. Modification of the C425 cast iron in the ladle with the proposed modifier in an amount of 0.3% by weight of the cast iron allows more than 2 times increase in the durability of the cutting tool, while chromic bleaching in castings with a wall thickness of 4-8 mm is not observed. 1 hp f-ly, 1 tab.

Description

The invention relates to metallurgy and can be used in the technology of modifying gray cast irons in the production of machine profile castings.

The aim of the invention is to eliminate chipping in thin-walled castings and to improve the machinability of cast iron by cutting.

Example. Modifiers 1 and form the proposed compositions obtained by fusion of appropriate ferroalloys (commercially pure magnesium ferrosilicon ferrosilikobari, ferrosilikokaltsi, ferromanganese, FSZORZMZO, antimony content in a known modifier provides input technically pure melting antimony by other constituents) into the induction furnace of 60 kg. A modifier of known composition is performed with an average content of ingredients, and the proposed composition is carried out on the bottom, middle, top,

below the lower, above the upper limits of the content of ingredients.

Modification of C245 grade cast iron is carried out in a 30 kg bucket. The consumption of modifiers is in all cases 0.30%, the temperature of the modification is 1340 ° C. The modified melt is poured into wet sandy-clay forms. Prototypes have the form of cylinders with a diameter of 60 mm and plates with a wall thickness of 4.6 and 8 mm.

The machinability tests were carried out using the method of turning cylindrical specimens. The presence of edge chill is determined visually on plate samples.

The test results of pig iron smelted using the known and proposed modifiers are presented in the table.

When mass production of castings from gray cast iron of high grades (SCH25 and above)

ON O CO

ABOUT

The main problem is the machinability on automatic lines. The reasons for the low workability, even in the case of chill elimination, are the peculiarities of the microheterogeneous structure of the metal matrix of cast iron of the specified class. Due to the low carbon equivalent and the presence of alloying elements b in the alloy, in particular chromium, there is a significant microlikonational heterogeneity. It is determined by a significant proportion of primary austenite, during solidification of which impurities are displaced to the boundaries of austenite and eutectic. This effect leads to the formation of micro-quenching zones with increased hardness and brittleness. This phenomenon leads to a deterioration in the machinability of cutting not only thin-walled, but also massive sections of castings. This phenomenon is also aggravated by phosphorus and the not optimal ratio of sulfur to manganese in the cupola iron. The main task of modifying these cast irons is the complex effect on the crystallization kinetics and morphology of primary austenite dendrites, the state of the boundaries of austenite is eutectic, and the structure of the eutectic itself. The proposed modifier sharply crushes the dendrites of the primary austenite, increases their specific surface, thereby reducing the negative effect of microlysis on the formation of zones with an increased concentration of chromium and other carbide-forming elements.

Silicon within 55-75% in the composition of the modifier provides a good solubility of the modifier and creates silicon-rich zones, in the process of dissolution of which additional crystallization centers are formed. The lower limit (55%) provides the required kinetics of zone formation. Exceeding the upper limit (75%) impairs solubility,

Carbon (0.05%) contributes to the formation of silicon carbide in the modifier. Over 0.2% is difficult to achieve in practice.

Aluminum (0.5%) and REM (0.5%) contribute to the nucleation of primary austenite dendrites and their grinding with growth. Exceeding the upper limits (2.0%) of the indicated elements does not give an increment of the specified effect.

Manganese in the range of 0.3–5.0% improves the solubility of the modifier and reduces the micro-dilution heterogeneity due to the interaction with sulfur in cuprous cast iron. The upper limit (5.0%) is limited due to the possibility of formation of cementite in the structure.

Magnesium in combination with calcium reduces segregation heterogeneity due to partial binding of sulfur until austenite crystallizes, crushes the structure of austenite and eutectic and clears the austenite-eutectic boundary from surface-active elements (impurities present in the iron). Not only absolute concentrations are important.

0 magnesium, calcium, but their ratio.

The lower limits (0.5%) are due to the need to achieve the described effects. The upper limit for magnesium (1.5%) is limited due to the pyroelectric effect and dust-gas emissions into the atmosphere during melt processing. The upper limit on calcium (2.0%) impairs the solubility of the modifier. The calcium to magnesium ratio of 1: (0.75–1.0) ensures high solubility and a complex effect on the elimination of microlactivity heterogeneity of cast irons. Above the upper limit of ratios (1: 1), modifier solubility and efficacy deteriorate.

5 processing.

For high-quality alloyed cast iron with lamellar graphite, the heterogeneity of the size and distribution of graphite in differential

0 castings. An additional input of 0.5% barium s The proposed composition contributes to the homogenization of the graphite phase in differential castings. Over 2.0% barium does not increase effect and impairs solubility.

5 Homogenization of the graphite phase in castings has a positive effect on improving the workability of cast iron.

As follows from the data presented in the table, the proposed modifier for

Cast iron 0 makes it possible to eliminate the edge edge in castings with a wall thickness of less than 8 mm and to improve the machinability by cutting cast iron more than 2 times.

Claims (2)

Invention Formula 5 1. A modifier for cast iron containing silicon, carbon, aluminum, magnesium, calcium, manganese and iron, characterized in that, in order to eliminate edge bleaching in thin-walled castings and to improve the workability of cast iron by cutting, it additionally contains rare earth metals in the following ratio, wt.%: silicon55-75 5 carbon0.05-0.20 aluminum 0.5-2.0 magnesium 0.5-1.5 calcium 0.5-2.0 rare earth metals 0.5-2.0, manganese 0.3-5.0 iron ostal the ratio of calcium to magnesium is 1: (0.75-1.0). 2. Modifier pop. 1, I differ in that it additionally contains 0.5-2.0 May. % bari. Famous Average Experience Chemical composition, May. 40 0.8 1.0 0.5 1.5 Table continuation Experience Chemical composition, mas 10 3.0 0.3 1: 0.9 113.0 3.0 1: 0.9 Note. Cutting modes: speed 100 m / min; feed 0.2 mm / rev; depth of cut 2.5 mm, tool material VK 8. Table continuation OS-80 talnoe  75