SU1355633A1 - Mixture for alloying,deoxidation and refining steel - Google Patents

Abstract

The invention relates to ferrous metallurgy and is intended for the after-treatment of steels with carbonitride hardening. The aim of the invention is to increase the degree of reduction of vanadium and titanium to steel, increase the refining ability of the mixture and reduce the tendency of steel to brittle fracture. The mixture for alloying, deoxidizing and refining steel contains, wt% {vanadium slag 55-62; calcium cyanamide 2-5j electrothermal silicon-aluminum 8-12; Calcium carbide 6-8 and lime - the rest. The application of the proposed mixture allows increasing the degree of reduction of vanadium and titanium to steel by 10%, reducing the content of sulfur and non-metallic inclusions, respectively, by 0.008 s and 0.0040%, as well as reducing the tendency of steel to brittle fracture by 1.13 times. 1 tab. ss ate O5 SLE OO

Description

The invention relates to ferrous metallurgy and is intended for the after-treatment of steels with carbonitride hardening,

The aim of the invention is to increase the degree of reduction of vanadium and titanium to steel, increase the refining capacity of the mixture and reduce the tendency of steel to brittle fracture.

The proposed mixture for alloying the deoxidation and refining of steel contains vanadium slag, calcium cyanamide, electrothermal silicon alumina - research institutes, calcium carbide and lime in the following ratio of components,% by weight:

Vanadium slag 55-62 Calcium cyanamide 2-5 Electrothermal silicon-aluminum8-12

Calcium carbide 6-8

From the rest of the rest

In the proposed mixture, calcium cyanamide increases the refining capacity of the slag formed by increasing calcium compounds in it. Lime contributes to the cleaning of steel from sulfur and increases the degree of reduction of vanadium and titanium from their oxides.

The reduction of oxides introduced with vanadium slag using electrothermal silicon-aluminum provides the formation of dispersed alumina and high-alumina alumino-silicate inclusions easily assimilated by the slag phase. At the same time, it provides for obtaining a stable aluminum content in steel. This reduces the harmful effect of silicon and its compounds on the tendency of steel to brittle fracture. Electrothermal silicon-aluminum is a material of increased purity at low cost. Therefore, a significant decrease in the amount of non-ferrous metals in steel

Introduction to the composition of the mixture of calcium carbide contributes to the simultaneous achievement of several tasks. Due to the high melting point and the presence of more powerful reducing agents in the mixture, the dissolution of calcium carbide ends predominantly after the completion of the exothermic reduction reactions. Behind

due to this, deoxidation, refining and modification of steel with calcium are deeper than in the prototype. The presence of calcium carbide in the mixture increases its reduction potential, increases the basicity of the slag, and raises the degree of reduction of vanadium and titanium to steel,

The choice of the content of the mixture components in the above range is due to the following.

Practice has shown that direct doping of steel with vanadium using vanadium slag is advisable when the content of vanadium in steel is not higher than 0.15%. The nitrogen content of low-alloyed vanadium-containing steels with carbonitride hardening does not usually exceed 0.015%. The necessity of obtaining carbonitrides of the required composition in steel. Exceeding the limits of the contents of vanadium slag and calcium cyanamide in the mixture reduces the degree of reduction of vanadium and titanium in steel and impairs the refining capacity of the slag. The content in the mixture of these components below the proposed limits is not rational, since it does not increase the refining capacity of the mixture and the degree of reduction of vanadium and titanium and, moreover, leads to a significant decrease in the amount of dispersed vanadium carbonitrides in steel. The latter, when the aluminum content in steel is at the lower limit of its required concentrations, leads to a decrease in the modifying effect and increases the tendency of steel to brittle fracture. In addition, when the content of vanadium slag is over 62% and calcium cyanamide is less than 2%, the composition of carbonitrides changes in the direction of decreasing nitrogen content in them. This causes the occurrence of carbonitrides in steel in the upper region of the austeite along the grain boundaries, which increases the tendency of steel to brittle fracture.

The content of electrothermal silicon-aluminum in a mixture of less than 8% reduces the thermal character of the mixture and reduces the degree of reduction of vanadium and titanium to steel. Its content of more than 12% is not rational, since it does not provide any significant additional benefits.

When the content of calcium carbide in the mixture is less than 6%, the required effect of refining and modifying steel is not achieved, and when its content is more than 8%, the viscosity of the slag increases due to the presence of a large amount of refractory particles in it, the content of vanadium slag in the known and proposed mixture averages 58%, therefore the consumption of mixtures for doping is almost the same. At the same time, the content of reducing elements in a known mixture (aluminum, silicon, calcium, barium) is 8-27%, and in the proposed mixture (aluminum, silicon) - 5.5-8.5%. However, despite the lower content of reducing agents in the proposed mixture compared to the known, the degree of reduction of vanadium and titanium increases. This is achieved by increasing the effectiveness of reducing agents in

of the resulting slag mixture after melting.

mixtures of the proposed composition, that sv - 25 melted it in a 60-kg induction zone as with a decrease in carbon loss. The consumption of the mixture in each concrete, and with the increase in the reversible case, was determined on the basis of introducing 0.10% vanadium into the steel. The refining capacity of the mixture The reduction of the refining capacity 30 was estimated by the content of sulfur and the acid-offered mixture in comparison with imitation in steel, as well as oxide non-metallic, can be explained as follows. During the melting of the proposed mixture, the phased interaction of the components is as follows. Og first

tallic inclusions emitted by electrolytic dissolution of the metal sample.

The tendency to steel brittle fracture was evaluated by criterion K. - to the critical stress intensity factor with dynamic

The reduction of the mixture oxides is carried out by their interaction with silicon and aluminum. Due to the refractoriness of calcium carbide, its dissolution is slower than loading. To do this, the test samples with a V-shaped, ad-exothermic reaction were completed with the oscillographic recording of the load-deflection diagram. Definition

NIN oxides. This achieves deeper deoxidation and modification

fcJ

carried out by a known method.

steel The introduction of calcium carbide 45 The results obtained are shown in the form of a mixture component contributes to the table.

its even distribution throughout the volume of the metal being processed. The oxidation of the decay products of calcium carbide to lime and carbon dioxide also contributes to a deeper refining of steel. Taking into account the nature of calcium carbide degradation products, a certain amount of

analogy with steel purging powders. Due to a more efficient deoxidation and modification of steel using the proposed mixture, as well as due to a decrease in the content

in it, silicon deoxidation products show a decrease in the tendency of steel to brittle fracture.

Example. For the preparation of mixtures of the proposed and known

formulations used finely divided starting components. The mixture was introduced in Russian (p on a metal jet at the release of smelting into a pouring ladle. Studies were carried out on steel 12HGAFL,

melted it in a 60 kg induction furnace. The flow rate of the mixture in each case was determined based on the condition that 0.10% vanadium was introduced into the steel. The refining ability of the mixture was evaluated by the content of sulfur and oxygen in steel, and also oxide

tallic inclusions emitted by electrolytic dissolution of the metal sample.

melted it in a 60 kg induction furnace. The flow rate of the mixture in each case was determined based on the condition that 0.10% vanadium was introduced into the steel. The refining ability of the mixture was evaluated by the content of sulfur and oxygen in steel, and also oxide

The tendency to steel brittle fracture was evaluated by criterion K. - to the critical stress intensity factor with dynamic

TO

fcJ

carried out by a known method.

7

Thus, the use of a mixture of the proposed composition in comparison with the known one provides an increase in the degree of reduction of vanadium and titanium to steel, an increase in the degree of refining of steel and a decrease in its tendency to brittle fracture.

Claims (1)

Invention Formula A mixture for alloying, deoxidizing and refining steel, containing vanadium slag, lime, and a nitrogen-containing substance, characterized in that, in order to increase the degree of reduction of vanadium and type Composer K. Sorokin Editor 10. Sereda Tekhred L. Oliynyk Corrector I. Erdeyi 5753/25 Circulation 550Subscribe VNyIPI USSR State Committee on on inventions and open, 113035 Moscow, Zh-35, Raushsk nab., d.4 / 5 Production and printing company, Uzhgorod, Proe Ktna str., 4 In addition to the refining capacity of the mixture and reducing the tendency of steel to brittle fracture, it additionally contains electrothermal silicon aluminum and calcium carbide, and calcium cyanamide as a nitrogen-containing substance, in the following ratio of components, wt.%; th 55-62 2-5 8-12 6-8 Rest