SU63520A1 - The method of casting iron products - Google Patents

Description

The method of casting iron products proposed by the present invention is that small graphite is placed in a liquid metal at the time of its release from the furnace and the resulting metal is poured into a chill mold.

FIG. 1, 2, 3 shows the microstructure of cast iron, chilled without the addition of Lrafit, and FIG. 4 and 5 - chilled with a graphite additive.

When casting gray iron into a metal chill mold, the metal undergoes a sharp overcooling; In connection with this, crystallization proceeds extremely rapidly, due to which graphite manages to stand out along the grain drains, as a graphite eutectic of degenerative arrangement (Fig. 1). At best, with a well-built chill, the degree of supercooling decreases slightly and, in the presence of an uncured mother liquor, the graphite eutectic can be transformed into small veinlets. In this case, about (at once (tsi nest-like location of graphite (Fig. 2). Both the first and the second type of graphite are constantly found in the chill casting. Such forms

G; raffit create conditions for local chipping, and, in connection with this, chipping products serve as an emery paste between scoop, imis surfaces, which leads to rapid wear of parts. However, the defects of the chill casting are not exhausted only by the shape and arrangement of graphite. During the formation of a eutectic nesting prafit, the presence of ferrite takes place in the metal mass (Fig. 3), which is also a negative factor for antifriction cast iron, since ferrite has negative wear-resistant properties.

Graphite, implanted in a ladle with the release of metal, makes it possible to obtain the desired shape and location of graphite for antifriction cast iron: namely, evenly spaced, without closed contours, and also provides a pure metallic mass.

As is known, carbon has three allotropic forms: diamond, graphite and amorphous carbon. A diamond with a temperature of 1000 ° is transformed into graphite. The same happens with amorphous carbon at a temperature of 800-1100 °. Thus, in the final (as a result, all allotropic forms of carbon are transformed into one — graphite. The melting temperature of graphite lies presumably at 3800 °. Therefore, graphite cannot melt in the metal when it is added to the ladle, where the temperature of the produced metal is approximately 1400 °.

There is a hypothesis of graphite inclusions, which (Pa proves that graphite crystals hardly dissolve. The maximum solubility of graphite inclusions is achieved only with high overheating and prolonged exposure of the metal. Remaining in an undissolved state of inclusion serve as nuclei. Consequently, when dredging into a ladle, due to the short time of exposure and cooling of the metal, the solubility of graphite is extremely limited, due to which it serves mainly as nuclei promoting graphitization ii.

It is known that in gray iron, carbon is emitted in the form of graphite in places where all Inclusions are homogeneous with it. Such a homogeneous in properties. The m is graphite, which sits in a ladle and is distributed in a liquid metal in a dispersed state. Due to this, subsequent discharge occurs on the same Meystach, forming a graphite plate.

A special feature of the addition of graphite to the ladle is the formation of this gases - catalysts that promote graphitization. The catalysts are CO2 and CO gases. The formation of CO2 is possible at a temperature of about 1400 ° (temperature of the metal being produced), and the reaction proceeds with the evolution of heat. C -f Og COs + 8080 cal / kg.

As a consequence, the formation of CO gas is possible according to the formula: CO2-f -f С 2СО - 3200 cal / kg.

Both; reductions can obviously go one way

places where graphite inclusions are located. Consequently, the graphite in the dispersed state at the moment of its addition to the ladle promotes the formation of micro centers of the gas mixtures of CO and CO, which serve as catalysts promoting graphitization.

Due to the above features, the addition of graphite to the ladle at the time of production of liquid iron results in the formation of evenly spaced average values of graphite plates (Fig. 4) and a purely perlite structure of the metal mass (Fig. 5).

Such a micro-structure ensures maximum durability of cast iron products cast in a metal mold.

Thus, the problem of producing antifriction products from chill castings is solved.

Of particular importance is the Ordered Method for the manufacture of piston rings designed for high-powered, high-powered aircraft engines.

Due to a sharp overcooling, a large number of crystallization centers are formed when pouring into the chill mold, which leads to the formation of relatively small crystals. In this connection, the surface contact and the cohesive force between individual crystals are much greater than between the crystals of metal casting when it is poured into the ground. This creates the conditions for better durability of the material, since the transformation of individual crystals in the course of work is less likely than in ground castings.

Casting the oil for the piston rings of an aircraft engine using a centrifugal method in a chill mold with an additive in cast iron Lra | Fita has an advantage over individual casting, since the process is extremely n (growth, while the technology of casting individual piston rings into the ground is extremely difficult and insufficiently mastered .

Thus, the addition of graffit to the ladle at the time of production of cast iron improves the technological

a die casting process, which therefore becomes the most advanced and cost-effective process that can be applied to the manufacture of any parts subject to wear

(parshnevy rings, plugs, etc. details).

Subject invention

The method of casting iron products, characterized in that, in order to impart antifriction properties to the products, fine graphite is applied to the ladle at the time of the liquid iron from the furnace and the metal is poured into the chill mold.

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FIG. one

FIG. 2

FIG. four

FIG. five