SU1745774A1 - Alloy for cast iron production and method of its manufacture - Google Patents

Abstract

The invention relates to alloys for the production of pig iron and methods for producing alloys. The aim of the invention is to improve the thermophysical properties of cast iron and reduce the cost of the alloy. Alloy contains. wt.%: 0.01-0.12 Cp; 0.06-0.67 MP; 0.01-0.12 V; 0.10-2.42 SI; 0,, 24 AI; 2, 4.0 С; 0.01-0.10 C; 0.01-0.10 TI; 0.05-0.38 N1; 0.007-0.12 N, iron and regulated impurities - the rest. The alloy is produced by mixing two carbon semi-products in the ladle. The first is obtained by blowing molten vanadium-containing iron in the converter with an oxidizing gas, and the second is obtained by mixing in the converter the usual intermediate product and metal-containing abrasive waste in a ratio of 1: (0.05-0.5). In this case, the weight ratio of the mixed intermediates is (0.8-1.2) :,). When processing the proposed composition of cupola iron, its thermal conductivity decreased, the heat resistance increased more than 2 times at 500 ° C, scaling resistance at 800 ° C decreased, and the coefficient of linear expansion at 500 ° C also decreased. The cost of the proposed alloy at the same time compared with the known modifier decreased to 74.5-91.5 rubles / ton. 2 sec. p. f ... 2 tabl

Description

This invention relates to ferrous metallurgy, in particular to compositions of alloys used in the production of high-quality cast iron. compositions of metals for their preparation, as well as methods for their smelting.

The aim of the invention is to improve the thermophysical properties of cast iron and reduce the cost of the alloy.

Example 1. In an industrial 22 t converter with bottom air blowing, 1.8 tons of vanadium-containing agglomerate are poured, and then 22 tons of vanadium-containing pig iron with a temperature of 1290 ° C are poured in and blown with air supplied from the bottom with an intensity of 450 m3 / min for 5 minutes. Vanadium-containing slag and carbon semi-product are obtained. The first is retained in the converter, and the second, having a temperature of 1340 ° C and containing. wt.%: C 3.8: SI 0.04; MP 0.03: V 0.03; T 0.02; P 0.07; S 0.032 (iron else), poured into a ladle. Then the slag is bagged into the bowl.

with

sl

one

four

Then, in the empty converter at the second heat, 1.2 tons of vanadium-containing iron are poured over and blown in within 4.5 minutes to a temperature of 1370 ° C. The semi-product, separated from vanadium slag, as well as at the first smelting, is again poured into the converter on the previously implanted metal-containing abrasive production waste in the amount of 2.1 tons and blown with air until the waste is completely dissolved for 3 minutes. At the same time the temperature of the intermediate increases to 1420 ° C.

The obtained intermediate product is poured into a ladle, where the intermediate product is already located after the first melting.

A mixture of intermediates after 2 minutes after mixing contains, in wt.%: C 3.2; SI 1.84; MP 0.42; V 0.05; TI 0.07; AI 0.12; N 0.022; C 0.04; NI 0.26, iron and impurities else.

According to this technology, a semi-product with a different ratio of metal-containing abrasive waste and a different ratio of mixed semi-products is smelted.

In tab. Tables 1 and 2 show the composition of the alloys obtained, the conditions of preparation and the properties of the treated irons.

PRI mme R 2. An alloy of the chemical composition specified in Example 1, poured on a casting machine, is used to smelt cupola iron for molds. The content of the alloy (a mixture of intermediates) in the metal mill of the cupola batch is 72%. After the charge has been melted, cast iron for molds has the following composition, wt%: C 3.4; Si 2.02; Mp 0.51; V 0.04; Ti 0.06; P 0.05; S 0.021; AI 0.08; N 0.018.

The resulting cast iron is tested for thermal conductivity and linear expansion coefficient. Thermal conductivity is emitted by the method of unsteady thermal floor on samples (archimedean cylinders). The calculation of the coefficient of thermal conductivity is performed by the formula

 Wed y

where I is thermal conductivity, cal / s cm;

"-Temperature, cm / s, 1

Cp - true heat capacity, cal / ° C;

y is the density, g / cm3.

The values of a, Cp, and y are determined experimentally. A decrease in the thermal conductivity of cast iron with an increase in the content of aluminum and nitrogen in the alloy was revealed.

The linear expansion coefficient () is determined from the dilatograms taken to study the eutectoid transformation interval using the formula

but

AI

I-a-DG

where D1 o U - change the length of the sample

in comparison with the standard, mm ;. I is the sample length, mm; a is an increase (taken equal to 300);

D t - temperature interval.

It has been found that the linear expansion coefficient at 350-550 ° C decreases slightly, which is very positive, i.e., the cast iron becomes less sensitive to the occurrence of stresses.

The resulting cast iron is not prone to chilling. It has good casting and rather high mechanical properties, high heat resistance and a very low modulus of elasticity. Combination of these

properties allows the use of cast iron obtained using a special alloy doped with abrasive waste containing modifiers for casting metallurgical parts.

equipment and, in particular, molds.

The carbon content in the alloy (2.4-4.0 wt.%) Is limited mainly by the technological possibilities of its production, since it is in this interval

concentrations are achieved with minimal losses during discharge and casting, the stability of obtaining other, including operational properties.

By reducing the carbon content

(less than 2.4 wt.%), as well as more than 4.0 wt.%, the performance of its technology is markedly deteriorated, and the performance properties of the alloy and the pig iron produced with its use are reduced.

The limitation of concentrations in the alloy of silicon (0.10-2.42 May.%) And manganese (0.06-0.67 wt.%) Is mainly due to the use of an alloy in the smelting of iron. A decrease in the concentration of silicon and manganese increases the thermal conductivity and reduces the heat resistance of the resulting iron, while their increase practically does not alter the indicated properties. The increase in silicon and manganese in the alloy has a positive effect on its losses upon receipt, however, with an increase in the concentration of these elements above the proposed ones, this indicator subsequently remains almost at the same level.

The concentration of vanadium (0.01-0.12 wt.%) And titanium (0.01-0.10 wt.%) In the alloy is regulated mainly from the standpoint of using the alloy to produce cast iron, in which the concentrations of these highly carbide-forming components are limited. At the same time, reducing them to less than 0.01 wt.% Is technologically difficult to achieve without increasing the cost of production.

The composition of the alloy also includes copper in an amount of 0.01-0.10 wt.%, Nickel 0.05-0.38 wt.%, Chromium 0.01-0.12 wt.%, Introduced by the materials from which the alloy is made, and not significantly affecting the achievement of the goal. However, it is advisable that the content of copper and nickel is closer to the upper limit, and that of chromium is closer to the lower one.

The concentration of aluminum in the alloy (0.005-0.24 wt.%) Is limited by the technological possibilities of the production of the alloy, however, it should be noted that its main effect in the indicated concentration range is mainly associated with heat resistance, thermal conductivity, and temperatures (350-650 ° C) - with a positive effect on the coefficient of linear expansion.

The alloy is produced by redistributing vanadium iron with vanadium extraction into commercial slag and obtaining a co-alloy — a carbonaceous intermediate. At the same time, in the first smelting, the usual operation is carried out: the agglomerate is poured into the empty converter, cast iron is poured in vanadium, it is flushed with oxidizing gas (in this solution with air, like nitrogen-containing gas), and the vanadium ice is removed. and the carbon semi-product is drained into a ladle.

At the second heat after all the above operations and removal of vanadium slag, metal-containing abrasive production waste is seated in the converter in the specified ratio and then mixed by blowing the metal with air from the bottom for 0.5-2.0 minutes, after which the resulting metal is drained into the ladle with the first intermediate product . The resulting mixture is a proposed alloy. Metal-containing waste abrasive production, for example from the smelting of normal electrocorundum, contain, wt.%: Carbon 2.5-3.2: silicon 7-15: titanium 1-4; manganese 1-3: chromium 0.5-2.0; vanadium 0.5-2.0: aluminum 1-5, calcium 0.2-2.0; magnesium 0.1-1.0; iron metal rest, and represent a by-product of smelting commodity normal electrocorundum obtained at a high temperature (1800-2400 ° C) on the furnace bottom under a layer of corundum while reducing the impurities of the aluminum-containing raw material with coke in the ore-smelting furnaces.

Due to their high density (7.7-7.8 g / cm, which is significantly higher than the density of cast iron (7.0-7.2 g / cm3), and a very low melting point (1370-1420 ° C), they dissolve well in metal including in the metal obtained at the end of vanadium pig iron blowing in the converter. Their concentration in the mixture to obtain an alloy is determined from the required silicon content in the proposed alloy, silicon concentration in the abrasive production waste and the silicon absorption rate of the waste produced by the alloy, which must not be less than 85%. When the concentration of waste in the charge is more than the recommended ratio of 1: 0.5, the degree of absorption of silicon by metal is reduced, and the silicon content in the alloy increases (2.42 wt.%), which is impractical. The reduction in the amount of waste in the mixture is less than recommended by a 1: 0 ratio , 05, is also technologically unacceptable, since it leads to a decrease in the silicon concentration in the resulting alloy less than 0.10 wt.%, Which leads to a decrease in the technical and economic indicators of its production and its quality as an alloying alloy.

The additional mixing operation, as shown by the experimental processing of the method, improves the production rates of the alloy. At the same time, the alloy becomes more homogeneous in terms of the content of impurities, cases of insufficient dissolution of abrasive production wastes are eliminated, and the waste of modifying components, calcium and magnesium, is reduced. In this case, the weight ratio of intermediates should be maintained within 1: 1. By reducing the proportion of the usual intermediate below, recommended by the ratio (0.8: 1.0) or. on the contrary, its increase above the recommended ratio (1.2: 1.0) results in either a decrease in the homogeneity of the resulting alloy (due to the low dissolution of abrasive waste) or a decrease in its quality due to a deterioration in the chemical composition of the alloy.

As follows from the data presented in table. 1 and 2, the invention makes it possible to substantially increase the thermophysical properties of cast iron and reduce the cost of the alloy.

Claims (2)

1. An alloy for the production of pig iron containing chromium, manganese, vanadium, silicon, aluminum, carbon, copper, titanium, nickel, nitrogen and iron, characterized in that, in order to improve the thermal properties of the iron and reduce the cost of the alloy, it contains components in the following ratio, May. %: 0.01-0.12 0.06-0.67 0.01-0.12 0.10-2.42 0.005-0.24 2.4-4.0 0.01-0.10 0.01-0.10 0.05-0.38 0,007-0.12 Rest 2. A method of producing an alloy for the production of pig iron, which involves purging liquid vanadium-containing pig iron in the converter with an oxidizing gas to achieve a concentration in it, wt%: carbon 3.4-4.0; silicon 0.01-0.08; manganese 0.01-0.04; vanadium 0.01-0.04; Titanium 0.01-0.04 and the subsequent discharge of the obtained intermediate into a ladle, characterized in that, in order to improve the thermophysical properties of cast iron and reduce the cost of the alloy, the intermediate melting of the second heat obtained by mixing in the converter of the initial intermediate and metal containment waste is poured into the resulting intermediate abrasive production in the ratio of 1: (0.05-0.5), while the mass ratio of mixed intermediates is (0.8-1.2): 1.0. Tables / table 2