SU1388454A1 - Malleable cast iron - Google Patents

Abstract

The invention relates to metallurgy and can be used in the manufacture of technological castings. go equipment. The purpose of the invention is to increase the elastoplastic properties at 400-600 C. The new cast iron contains, wt%: C 2.0-2.9; Si 0.8-1.5; Mp 0.3-0.8; V 0.06-0.57; A1 0.02-0.03; Nb 0.06-1.2; Ce 0.02-0.05 TiN 0.04-0.08 and Fe the rest. The addition of Ge, Nb, and TiN to the composition of cast iron increased the impact strength at 400 ° C by 1.9-2.2 times, and by 2.2-2.6 times, the relative elongation of 1.4-1. , 8 times at and 2-2.3 times at. 2 tab. i (L

Description

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The invention relates to metallurgy, in particular to the development of the composition of cast iron for castings of process equipment.

The purpose of the invention is to increase the elastic properties at 400 -.

The choice of boundary limits contains; . The life of the components in the composition of the proposed cast iron is due to the following.

The introduction of niobium, titanium and germanium nitrides provides a significant increase in the castings of elastoplastic properties at 400-600 C. Their optimum concentrations are, wt%: niobium 0.06-1.2; titanium nitrides 0.04-0.08; germanium 0.02-0.05.

The introduction of titanium nitrides in cast iron in specified amounts crushes the structure, increases the number of graphite x inclusions with a simultaneous decrease in their size, which provides an increase in toughness and impact resistance at 400-600 C. With a content of titanium nitrides less than 0.04 wt.% The number of centers gras - fitization is not enough and the grinding of the structure and the increase in the elastoplastic properties is not enough, and when the content of titanium nitrides is more than 0.08 wt.%, the number of nonmetallic inclusions increases and the relative dlinenie.

The introduction of niobium in the amount of 0.3-1.2 wt.% Increases the stability of the structure and properties of cast iron s castings after heat treatment, which contributes to an increase in impact resistance and plastic properties at 400-600 C. With a niobium content of up to 0.3 wt.% - impact resistance and plastic properties at 400–600 ° C are insufficient, and at a niobium concentration of more than 1.2 wt.%, the quality of annealing carbon deteriorates and the elastic – plastic properties decrease at 400–. 600 ° C.

In order to preserve the high ductility of ferritic malleable iron, the manganese content should not exceed 0.3-0.8 wt.%. - When doping cast iron with manganese to 0.3 wt.%, The stability of the cast iron deteriorates somewhat, but this increases the contamination of the cast iron with nonmetallic inclusions and increases sensitivity to thermal and mechanical shocks, while increasing

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manganese concentrations greater than 0.8 wt.% - elastoplastic properties are reduced.

Aluminum in an amount of 0.02-0.03 wt.% Modifies and grinds the matrix, increases the density and impact strength, but with an increase in its concentration of more than 0.03 wt.%, The elastic-plastic properties decrease.

The content of carbon, silicon, and vanadium is based on the experience of producing resistant malleable cast iron with enhanced plastic properties. With an increase in the content of vanadium of more than 0.57 wt.%, Its inhibitory effect on graphitization increases. The growth and elastoplastic properties increase, and with an increase in carbon and silicon concentrations above the upper limits in castings, the formation of free graphite and a decrease in plastic properties are observed. and elevated temperatures.

Germanium in the amount of 0.02 - 0.05 wt.% Has a modifying effect, stabilizes the structure, increases the dispersion of the structure and elastoplastic properties at 400-600 C. At a concentration of germanium up to 0.02 wt.%, Its modifying effect on the structure and the increase in plastic properties is insufficient, and at a concentration of more than 0.05 wt.%, the microalloying of ferrite increases, which leads to a decrease in the elastoplastic properties and operational durability under conditions of shock loads and elevated temperatures.

Example. Melting of cast iron of pre-eutectic composition was carried out by a duplex process cupola - electric arc furnace. With the release of iron from the cupola, the temperature of the metal was 1400-1420 ° C, and in the electric furnace the melt was superheated to 1480-1500 ° C. Ferromanganese and ferroniobium were introduced into an electric furnace, and briquettes of titanium nitrides, germanium and aluminum were introduced into dispensing casting buckets with a capacity of 2 tons at 1430-1450 0. Modified cast iron was poured into raw sand-clay forms to obtain process samples; 16 mm samples and castings of brackets, hubs and forks.

When smelting in casting iron, the waste of alloying and modifying elements was,%: niobium 93-95; aluminum 17-19; germanium 11-13; titanium nitride 7-9; vanadium 8-11.

In tab. 1 shows the chemical composition of ductile iron casting experienced melts

To obtain the structure of ductile iron, the samples and castings are subjected to graphitizing annealing. carrying out the 1st stage of graphitization at 960-980 C for 3-3.5 hours and the 2nd stage of graphitization at 660-680 C for 3.0-3.5 hours

A comparative analysis of the properties of the known and proposed iron is given in table. 2

As follows from the above data, the proposed ductile cast iron, in comparison with the known cast iron, possesses more high Q-elastoplastic properties at elevated temperatures (400-600 ° С) due to the additional

The introduction of niobium, germanium and titanium nitrides into the composition of cast iron.

Claims (1)

Invention Formula Malleable cast iron containing carbon, silicon, manganese, vanadium, aluminum and iron, characterized in that, in order to improve the elastic-plastic properties at 400-600 ° C, it additionally contains niobium, titanium nitrides and germanium in the following ratio of components, wt. %: five Q- Carbon Silicon Manganese Vanadium Niobium Aluminum Titanium Nitride Germanium Iron 2.0-2.9 0.8-1.5 0.3-0.8 0.06-0.57 0.06-1.2 0.02-0.03 0.04-0.08 0.02-0.05 Rest Table 1 Rest Temporary resistance, MPa Relative elongation%, C table 2 588 645 458 504