SU1296622A1 - High-strength cast iron - Google Patents

Abstract

The invention relates to metallurgy and can be used in the production of castings operating at elevated temperatures with alternating loads. The purpose of the invention is to increase the heat resistance, hardness and ultimate strength at temperatures of 20-400 C. The new cast iron contains components in a coherent ratio, wt.%: Carbon 2.8-3.8; silicon 3-3.5; manganese 0.005-0.04; molybdenum 0.1-0.4; magnesium 0.03-0.08; vanadium 0.3-1.2; cerium 0.005-0.02; - iron - the rest. Additional addition of vanadium and cerium to the cast iron increases 1.15-1.3 times the heat resistance, 1.1-1.2 times the strength and 1.2-1.4 times the hardness at TeMnepaTv-400 ° C . 1 tab. c (O (L

Description

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The invention relates to metallurgy, in particular, to the development of cast iron for castings operating at elevated temperatures.

The purpose of the invention is to increase the heat resistance, hardness and ultimate strength at temperatures of 20-400 s.

The essence of the invention consists in additionally introducing cerium and vanadium into the composition of cast iron. In the structure of the proposed cast iron, complex carbides of vanadium and molybdenum are formed. Cerium contributes to the grinding of these carbides and their uniform distribution in the structure of cast iron. Structural changes in cast iron lead to higher heat resistance, penetration and hardness of cast iron.

In order to study the structure and properties of the proposed material, cast iron containing the main components at different levels, as well as a well-known alloy with an average level of ingredients, were smelted. Heat resistance was evaluated by the number of cracks formed on the specimens.

subjected to periodic heating in a lead bath to 530 ° C overnight for 3 seconds and cooled in running water. Tests on mechanical properties (GT and HB) were carried out at 20 and 400 ° C.

A well-known alloy with an average level of ingredients and ingredients with different contents of components was subjected to research.

The chemical compositions of cast iron and the test results are presented in table 1.

As can be seen from the tables, the cast iron of the proposed composition due to the additional added magnesium, vanadium and molybdenum differs significantly in enhanced operational and mechanical properties.

The structure of the alloy consists of 70-85% perlite, ferrite and spherical graphite.

Cast iron smelting technology consists of melting in a 60 kg induction furnace with an acidic lining.

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metallized oxides, carburization, the introduction of silicon ferroalloys (75Z Si), vanadium (45% V), molybdenum (65% Mo);

The limits of the contents of the components are established on the basis of obtaining the most favorable combination of the structure and properties of cast iron.

The content of carbon and silicon is chosen from the condition of obtaining the amount of 4.3-4.7%, which ensures the formation of primary inclusions of graphite of the correct spherical shape.

Manganese with a content of more than 0.04% leads to an increase in the size of the cementite phase of the eutectoid and, in general, to its coarsening, which adversely affects the mechanical properties of cast iron.

The minimum content of vanadium 5 (0.3%) and molybdenum (0.1%) significantly increases the mechanical properties of the alloy with a minimum degree of alloying of the metal base. When the content of molybdenum in the composition of cast iron, vanadium carbides precipitate in a highly dispersed phase and crystallize in a cubic form. Molybdenum reduces the solubility of vanadium in cementite, which contributes to a more intensive formation of vanadium carbides. An increase in vanadium of more than 1.2% and molybdenum more than 0.4% does not lead to a further increase in properties and is not economically feasible.

Cerium in maximum amounts (0.02%) is introduced into cast iron with sulfur content up to 0.04% for the purpose of preliminary desulfurization, degassing, refining of the melt and in minimum quantities (at 003%) for grinding the primary structure of the cast iron.

The content of manganese is chosen experimentally and guarantees, subject to the conditions described, the production of spherical graphite. An increase in magnesium of more than 0.08% leads to the appearance of a metastable phase.

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Claims (1)

5 12966226 claims of the following ratio of components May.%: High-strength cast iron containing Carbon2.8-3.8 carbon, silicon, manganese, molybdenum, silicon 3.0-3.5 magnesium and iron, distinguishing - 5 Manganese 0.005-0.04 so that, with the aim of increasing the ter- molybdenum 0,1-0,4 hardness, hardness and magnesi0,03-0,08 la strength at temperatures of vanadium 0.3-1.2 20 - 400 ° С, it additionally contains Cerium0.005-0.02 keeps vanadium and cerium while barely