SU1289890A1 - Method of nitriding metal in converter - Google Patents

Abstract

This invention relates to the nitriding of a metal with nitrogen gas in the smelting of steel in a converter. The purpose of the invention is the development of nitrogen assimilation, an increase in the yield of useful and a decrease in the consumption of nitrated ferroalloys. During smelting, nitride-forming elements are introduced into the metal in the amount of 0.5-2.0 kg / ton of steel, and 20-40% of their consumption are introduced when carbon in the metal is reached 0.8-1.2% with a simultaneous increase in the nitrogen content of blowing up to 15-30%. The remaining amount is introduced at a carbon content in the metal of 0.1-0.2% and 80-95% nitrogen in the blast. Vanadium shpak is used as materials containing nitride-forming elements. Vanadium oxides, as well as the solubility of nitrogen in steel, which leads to a decrease in the consumption of ferroalloys and increase the yield of the suitable material. 1 hp f-ly, 2 tab. I O)

Description

This invention relates to ferrous metallurgy, to the nitriding of a metal in a converter, and can be used in converter shops.

The purpose of the invention is to increase the degree of nitrogen assimilation, increase the yield of yield and decrease the consumption of nitrated ferroalloys.

In addition, nitrile-forming elements in the amount of 0.5-2.0 kg / ton of steel are introduced into the metal additionally in the course of flushing in two portions, with 20-40% of the total consumption being set down when carbon in the metal is reached 0.8-1.2 % with a simultaneous increase in the nitrogen content in the blast to 15-30%, and the remaining amount is injected when carbon in the metal and thall reaches 0.1-0.2% and increases the nitrogen content in the blast to 80-95%. AT . vanadium slag is used as nitride forming agents.

The upper limit of carbon content is determined by the fact that when carbon is more than 1.2%, intensive mixing of the bath with carbon monoxide occurs in the metal, which negatively affects the kinetics of nitrogen adsorption. When the carbon content is less than 0.8%, purging with a nitrogen-oxygen mixture with 15-30% N 2 leads to a decrease in metal deposition with nitrogen, as an intensive increase in oxidation begins. slag.

The nitrogen content in the mixture is 15-30%, during this period it is determined by the need to maintain a certain oxidation of the metal and to sufficiently nitrate it due to the high decarburization rate of the metal. When the nitrogen content in the mixture is less than 15%, its amount is significantly below the solubility limit in the metal under these conditions. However, the nitrogen content in the nitric acid mixture of more than 30% is impractical due to the low decarburization rate, which causes an increase in the duration of smelting.

The lower limit of nitride consumption of 0.5 kg / t of steel is determined by the need to significantly increase the solubility limit of nitrogen in the metal. Increase

15

20

25

Nitride-forming materials are introduced in two portions during the purging with a nitrogen-oxygen mixture. Entering the first batch of less than 20% of the total flow rate 5 does not allow the maximum possible saturation of the metal with nitrogen. The consumption of nitride formers in the first portion of more than 40% causes a significant deterioration in the slag and thermal conditions of the melt and a high waste of nitride forming elements is observed ..

When the carbon content is 0.1–0.2%, the thermodynamic and kinetic conditions of nitrogen saturation of the metal change. When the carbon content is less than 0.1%, the metal is significantly over-oxidized, which causes an increased waste of nitride-forming materials and practically does not cause saturation of the metal with nitrogen. The carbon content of more than 0.2% does not provide the specified final temperature of the metal, increases the duration of melting.

The content of 80% nitrogen in the blast during this period is determined by the need to supply a sufficient amount of nitrogen, which can dissolve 30 seconds in the metal. The content of 95% nitrogen in the blast is determined by the need to supply oxygen to the blast of at least 5%, which is required to achieve an increase in the duration of smelting for a given carbon content without 35.

Entering nitride-forming materials in this period in the amount of less than 60% does not allow to bind all the nitrogen introduced into the metal, and entering 40 more than 80% of the total consumption leads to a significant change in the heat balance of the melt, while the mass of the nitrogen-oxygen mixture supplied cannot provide sufficiently complete reduction of oxides of nitride-forming elements.

Ferrovanadic slags contain a sufficient amount of vanadium oxides (10–20%), titanium 50 (8–10%) and, in addition, contain oxides such as MnO (10–12%), which have a favorable effect on slagging processes. . Vanadium recovery rate from

Consumption of more than 2.0 kg / ton of steel is not suitable; 55 of such tlak at optimal mode

accordingly, since the limit of the solubility of nitrogen remains the same, which leads to increased consumption of nitride-forming materials.

Nitride-forming materials are introduced in two portions during the purging with a nitrogen-oxygen mixture. Entering the first batch of less than 20% of the total flow rate does not allow the maximum possible saturation of the metal with nitrogen. The consumption of nitride-forming in the first portion of more than 40% causes a significant deterioration of the slag and thermal conditions of melting and there is a high waste of nitride-forming elements.

When the carbon content is 0.1–0.2%, the thermodynamic and kinetic conditions of the metal saturation with nitrogen change. When the carbon content is less than 0.1%, metald is significantly over-oxidized, which causes an increased waste of nitride-forming materials and practically does not cause saturation of the metal with nitrogen. The carbon content of more than 0.2% does not provide the specified final temperature of the metal, increases the duration of melting.

The 80% nitrogen content in the blast during this period is determined by the need to supply a sufficient amount of nitrogen, which can be dissolved in the metal. The content of 95% nitrogen in the blast is determined by the need to supply oxygen to the blast of at least 5%, which is required to achieve a given carbon content without increasing the duration of the melt.

Entering nitride-forming materials in this period in an amount of less than 60% does not allow to bind all the nitrogen introduced into the metal, and entering more than 80% of the total consumption leads to a significant change in the heat balance of the heat, while the mass of the nitrogen-oxygen mixture cannot provide sufficiently complete reduction of oxides of nitride-forming elements.

Slags from ferrovanadium production contain a sufficient amount of vanadium oxides (10–20%), titanium (8–10%) and, in addition, contain oxides such as MnO (10–12%), which have a favorable effect on slag formation processes. Vanadium recovery rate from

melting is about 90%. Example. The method was carried out in a 10-ton experimental converter. As charge materials3

Ales used metal scrap and pig iron of the following chemical composition,%: C 4,1; Si 0.65; Mp 0.63; S 0.028; P 0.20 with a temperature of 1300 ° C. Lime and fluorspar were used as slag forming materials. In the course of blowing at different concentrations of carbon in the metal, the nitrogen content in the blast was changed and slag of ferrovanadium production in the amount of 5–15 kg / t of steel of the following chemical composition was added to the nitride-forming materials (by main elements%: 7 0510-20; AJ, 0,; 1-3; CaO 2-5; FeO 15-45; SiO 20-22;

MPO 10-12; .

2.2 tons of scrap metal was poured into the converter, 7.7 tons of pig iron were poured in and oxygen was blown into the converter at an intensity of 5.3 m / t min. Blowing was conducted from above through a 3-nozzle lance with a critical diameter of nozzles of 19 mm and an angle of 12. After more than 60% of the time of blowing, a sample was taken for chemical analysis, the first batch of slag of ferrovanadium production was fed, and at the same time the content of nitrogen in the blast was increased. the flame over the throat of the converter was attached a second portion of slag containing nitride-like

materials, and produced an additional increase in the nitrogen content in the blast. Upon reaching a carbon content in the metal of 0.05-0.06%, temperature was measured and a sample was taken. After receiving the analyzes, the metal was released from the converter and deoxidized in the ladle to the required chemical composition.

To assess the materiality of all the proposed parameters, a series of experimental heats was carried out with the output of each parameter in turn for the upper and lower limit values (while the remaining parameters were in the middle of the proposed intervals), and also melting was performed at the lower, upper, and middle aB of all parameters.

Characteristics of the technological parameters of metal nitriding in

the gaseous nitrogen converter is shown in Table 1.

For the technological evaluation of the method, melts were also carried out according to a known technology, in which the oxygen purge in the converter was carried out to a carbon concentration in the metal of 0.20%, then transferred to a nitrogen-oxygen blast with a nitrogen content of 20% before the end of the melting.

Metal quality at various values of the proposed parameters

JO f5

0

five

The nitriding of the metal in the converter in comparison with the prototype is given in Table 2.

The results of the experimental heats show that the use of the proposed technology, while respecting the parameters, allows obtaining a higher concentration of nitrogen in the metal before being released from the converter, eliminating the use of nitrated ferroalloys, and also increasing the yield of liquid steel by an average of 2%.

Claims (2)

1. A method of nitriding a metal in a converter, including loading charge materials, blowing a bath with oxygen and a nitrogen-oxygen mixture, characterized in that, in order to increase nitrogen absorption, increase yield, and reduce consumption of nitrated ferroalloys, nitride-forming elements are introduced into the metal in an amount of 0 5-2.0 kg / ton of steel, with 20-40% of the total consumption being injected when carbon reached 0.8-1.2% in the metal with a simultaneous increase in the nitrogen content in the blast to 15-30%, and the rest the amount is entered when carbon is reached in the metal 0.1-0.2% and increase the nitrogen content in the blast to 8095%. 2. A method according to claim 1, characterized in that vanadium slag is used as the nitride-forming agent. Consumption of nitride-forming elements total, kg / t at first portion% in the second portion% The nitrogen content in the blast,%: in the first period in the second period Coal content. kind in metal when it changes nitrogen content in the blast,% in the first period in the second period one of the parameters is the lower limit: 14/21 14/22 14/23 14/24 14/25 14/26 14/27 min-max Wed Table 1 1.0 0.15 0.6 0.07 1H 0.3 26 27 table 2 The output of one of the pairs for the upper-limit: 15/21 T5 / 22 15/23 15/24 15/25 15/26 15/27 rfflH.-max. All parameters are average values: 13 / 21-27 All parameters have a lower limit: 11 / 21-27 All pa, rametry have the upper limit Editor N. Kishtulints Compiled by V. Samsonov Tehred L. Oleinik Corrector. Shekmar Order 7870/25 Circulation 572Subscription VNIIPI USSR State Committee for inventions and discoveries. 113035, Moscow, Zh-35, Raushsk nab. 4/5 Production and printing company, Uzhgorod, st. Project, 4 1.8 0.9 1.9 2.7 1.0 , 0-2,7 1,2 91.3 90.5 90.6 90.3 89.7 90.1 89.4 89.4-91.3 90.3 92.7 91.8