RU2602587C1 - Austenitic spheroidal graphite cast iron - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, namely, to austenitic spheroidal graphite cast irons for production of parts, intended for operation in corrosive medium at temperature from -60 to +90 °C, in particular for making of oil production submersible centrifugal pumps working members. Austenite spheroidal graphite cast iron contains, wt%: carbon 2.2-3.0; silicon 2.4-3.2, manganese 3.0-4.0, copper 6.5-7.5, nickel 9.4-11.0, magnesium 0.03-0.05, calcium 0.03-0.05, cerium 0.01-0.03, tungsten 0.1-0.3, molybdenum 0.1-0.3, iron is rest.

EFFECT: technical result is higher strength of austenitic cast iron, which is used for making articles, operating in corrosive medium at temperatures from -60 to +90°C, and cast iron castings higher machinability during surface machining.

1 cl, 2 tbl

Description

The invention relates to foundry, namely to austenitic nodular cast iron for the production of parts designed to operate in an aggressive environment at a temperature range from -60 ° to + 90 ° C, in particular for the manufacture of working bodies of submersible centrifugal pumps for oil production.

Known non-magnetic cast iron with spherical graphite containing carbon, silicon, manganese, copper, magnesium, cerium, calcium, nickel, sulfur, phosphorus and iron, in the following ratio of components, wt. %: carbon 3.0-3.5; silicon 2.5-3.5; manganese 4.5-5.0; copper 4.5-5.0; magnesium 0.015-0.03; cerium 0.03-0.05; calcium 0.03-0.06; nickel 5.0-6.0; sulfur up to 0.02; phosphorus up to 0.01 and iron the rest (SU 203916, C22C 37/10, published 09.10.1967).

However, the well-known nodular cast iron does not provide the necessary wear resistance and corrosion resistance of cast products designed to work in conditions of exposure to a corrosive environment containing abrasive materials, in the temperature range from -60 ° to + 90 °.

Known austenitic cast iron with spherical graphite containing carbon, silicon, manganese, copper, nickel, chromium, vanadium, magnesium, calcium, cerium and iron, in the following ratio, wt. %: carbon 2.2-3.0; silicon 2.4-3.2; manganese 3.0-4.0; copper 6.5-7.5; nickel 9.4-11.0; chrome 0.3-0.5; vanadium 0.01-0.03; magnesium 0.03-0.05; calcium 0.03-0.05; cerium 0.01-0.03; iron the rest (RU 2337170, C22C 37/04, published October 27, 2008).

However, the metal base of said austenitic nodular cast iron contains cementite up to 30%, which is located along the grain boundaries. Therefore, the strength of the known cast iron is negligible.

In addition, castings from said austenitic nodular cast iron are poorly machined.

The objective and technical result of the invention is to increase the strength of austenitic iron, which is used for the manufacture of products operating in an aggressive environment at temperatures from -60 ° to + 90 ° C, as well as to increase the machinability of the surface of iron castings when exposed to a machining tool.

The technical result is achieved by the fact that austenitic nodular cast iron contains carbon, silicon, manganese, copper, nickel, magnesium, calcium, cerium, tungsten, molybdenum and iron, in the following ratio of components, wt. %: carbon 2.2-3.0; silicon 2.4-3.2; manganese 3.0-4.0; copper 6.5-7.5; nickel 9.4-11.0; magnesium 0.03-0.05; calcium 0.03-0.05; cerium 0.01-0.03; tungsten 0.1-0.3; molybdenum; 0.1-0.3; iron is the rest.

Introduction to the composition of austenitic iron according to the invention of tungsten in a concentration of 0.1-0.3 wt. % allows you to optimize the amount of cementite solid inclusions, while increasing the strength of cast iron and improving the quality of its machining.

The introduction of molybdenum into the composition of austenitic iron according to the invention makes it possible to grind the structural components of the metal base of iron, thereby increasing the strength of austenitic iron.

Smelting austenitic nodular cast iron according to the invention is as follows. Iron is smelted in induction or electric arc furnaces using standard charge materials. Alloying elements — nickel, tungsten, molybdenum, and copper — are introduced into the metal plant. After the charge is melted and the cast iron is overheated to a temperature of 1450-1500 ° C, manganese in the form of 60% ferromanganese and silicon in the form of 75% ferrosilicon are introduced into the melt mirror. In order to increase fluidity, phosphorus is introduced into pig iron in an amount of 0.15-0.25% in the form of 20% ferrophosphate. Before the liquid metal is discharged from the furnace, magnesium and calcium are added to the bottom of the casting ladder as part of a spheroidizing additive, as well as cerium in the form of ferrocerium.

Table 1 shows the chemical composition of the known cast iron and cast iron according to the invention. Table 2 shows the strength values, grain size of austenite and inclusions of spherical graphite, the number of inclusions of cementite and the machining conditions.

The achievement of the technical result is illustrated by a higher strength (520-540 MPa) of cast iron according to the invention, a smaller grain size of austenite (20-40 microns) and inclusions of spherical graphite (6-10 microns), a decrease in the number of inclusions of cementite (6-12%) and better machinability of the proposed cast iron in comparison with the known.

Tensile strength was determined according to GOST 27208-87. The size of the structural components and the amount of cementite in the metal base was determined using the "Quantimeter" device.

The use of the proposed austenitic nodular cast iron for castings having a complex configuration, which is then subjected to mechanical processing by cutting, for example, the steps of submersible centrifugal pumps for oil production, allows (20-30%) increase the service life of parts in operation, while reducing the cost of their manufacture by 10-15%.

Claims (1)

Spheroidal graphite austenitic iron, containing carbon, silicon, manganese, copper, nickel, magnesium, calcium, cerium and iron, characterized in that it additionally contains tungsten and molybdenum in the following ratio of components, wt. %: carbon 2.2-3.0, silicon 2.4-3.2, manganese 3.0-4.0, copper 6.5-7.5, nickel 9.4-11.0, magnesium 0, 03-0.05, calcium 0.03-0.05, cerium 0.01-0.03, tungsten 0.1-0.3, molybdenum 0.1-0.3, iron - the rest.

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