SU1331896A1 - Method of microalloying steel with active elements - Google Patents

Abstract

The invention relates to ferrous metallurgy, and more specifically to methods for smelting in vacuum furnaces. The aim of the invention is to increase the stability of the assimilation of microleading active elements, to reduce the nitrogen content, to ensure the desired structure of the solid solution, to reduce the heat-resistant properties of steel, to reduce the alloying of scarce elements, such as molybdenum. The method includes the melting of the metal, its deoxidation and the introduction of micro-alloying additives at a pressure of 66.5-260 Pa. The inert gas is introduced by flat jets with a ratio of length to width of section (16-19):

Description

The invention relates to ferrous metallurgy, in particular, to methods for alloying steel in vacuum installations.

The purpose of the invention is to increase the reproducibility of the assimilation of micro-doping active elements, to reduce the nitrogen content, to ensure the desired structure of the solid solution, to increase the heat-resistant properties, to reduce the doping became scarce elements, such as molybdenum.

The essence of the invention is that the metal from the melting unit is discharged into a ladle and deoxidized with aluminum to reduce the dissolved oxygen content, and then transferred to a batch vacuum unit. When the pressure in the chamber reaches 1900-3300 Pa, the metal begins to be evacuated, i.e. move the batch vacuum chamber to the top

vanilla metal bubbles of neutral gas.

Additive of micro-alloying elements. comrades (zirconium, rare-earth metals, boron) are carried out 6–9 min after the start of the vacuum at a residual pressure of inert gas of 66.5–260 Pa, the introduction of additives at the final stage of vacuum

Q treatment is necessary for preliminary reduction of nitrogen content in the metal of less than 0.006%, as well as for laundering of non-metallic alumina-based inclusions. Reducing the content of nitrogen and non-metallic inclusions in a metal makes it possible to reduce the amount of cobalt. the amount of zirconium and rare-earth metals produced as well as hard-to-remove inclusions formed due to the recovery of aluminum from rare-earth metals 1z of non-metallic inclusions, i.e. increase the proportion of additives used to alloy the metal. The creation above the melt neutral ati lower position. The start of a stirred atmosphere with a pressure of 66.5–260 Pa, in which the vacuum chamber at the indicated RANGE with the formation of a protective gas measuring section makes it possible to provide with a metallic foam, makes it possible for practical use in the vacuum chamber about 10% to eliminate the interaction of the oxygen metal that is necessary for the effective .

yes atmosphere with squatting micro

effective degassing of the metal at a minimum of 30 alloying additives. Additive to

time In the process of vacuuming, neutral gas is introduced into the nozzles of the vacuum chamber by flat jets with a ratio of length to width of the section, of a jet at the place of its introduction into the metal in: limits (16-19): (0.3-0.5) and inert gas consumption on the tuyere (0.46 - 0.49) V 10 -e MVr. min

The introduction of argon by flat streams with the indicated lance and flow rate provides a large gas-to-metal interface due to the formation of a multitude of small bubbles. This makes it possible to efficiently remove nitrogen from an aluminum-deoxidized metal, to create a gas-metal foam on the surface of the melt, which protects the input micro-alloying elements.

a mirror of meth, alla elements in the ratio of zirconium: REM: boron (1-330): (10-70); (1: 6) leads to a change in the composition, size, shape and location of non-metallic inclusions, contributes to the doping of the solid solution, which leads to the transformation of austenite in the bainitic region, increasing the effect of the dispersion solid. In addition, this leads to a decrease in the dimensions of the hardening carbide phase — MS, block sizes, and stresses of the second kind.

Molybdenum is one of the oblique elements of heat-resistant steels that increase the heat-resistant properties of a long-lasting metal due to the fact that it enters solid (MS). Entering the microdial solution, causing significant cops from contact with oxygen to air-harden it. In addition, molybdenum, xa, continuously flowing into the vacuum in the carbide phases, contributes to the chamber, as well as additionally lower the oxygen content in the gas phase above the melt due to strong dilution with a neutral gas. The introduction of neutral gas into the metal also provides an increase in the rate of dissolution of microalloying additives due to active mixing55

their grinding (additives will reduce its content, for example, in chromium-molybdenum-vanadium steel, from 0.25-0.35 to 0.10-0.144%.

Introduction of zirconium, rare-earth metals and boron in the ratio (1-300); (10-70): (1-6) it is necessary that with and; by using the removal of a metal with neutral gas bubbles.

The micro-alloying elements (zirconium, rare-earth metals, boron) are added 6–9 minutes after the start of the vacuum at a residual pressure of inert gas of 66.5–260 Pa.

The treatment is necessary for preliminary reduction of the nitrogen content in the metal of less than 0.006%, as well as for laundering of non-metallic alumina-based inclusions. A decrease in the content of nitrogen and non-metallic inclusions in the metal makes it possible to reduce the amount of nitrides of zirconium and rare-earth metals, as well as hard-to-remove inclusions formed due to the reduction of aluminum by rare-earth metals 1 of non-metallic inclusions, i.e. increase the proportion of additives used to alloy the metal. Creation of a neutral atmosphere of atmosphere over the melt with the micro

a mirror of meth, alla elements in the ratio of zirconium: REM: boron (1-330): (10-70); (1: 6) leads to a change in the composition, size, shape and location of non-metallic inclusions, contributes to the doping of the solid solution, which leads to the transformation of austenite in the bainitic region, increasing the effect of dispersion hardening. In addition, this leads to a decrease in the size of the hardening carbide phase — MS, block sizes, and stresses of the second kind.

Molybdenum is one of the compulsory elements of heat-resistant hoists that increase the heat-resistant properties of a long-lasting metal due to the fact that it is included in a solid (MS). Entering the microdial solution, causing significant gQ hardening. In addition, molybdenum, the entrance to the carbide phases, contributes

55

their grinding (additives will reduce its content, for example, in chromium-molybdenum-vanadium steel, from 0.25-0.35 to 0.10-0.144%.

Introduction of zirconium, rare-earth metals and boron in the ratio (1-300); (10-70): (1-6) it is necessary that with and; , help to remove the remaining oxygen and carry out desulfurization and at the same time with all three additives m} 1 to alloy the metal.

The beginning of the evacuation (swinging of the vacuum chamber) is provided at a vacuum of 1900-3300 Pa. A decrease in this limit will cause an increase in the time of vacuumization and the associated overspending of energy carriers. Increasing the pressure above 3300 Pa at the start of the evacuation will also increase the evacuation time by decreasing the rate of degassing of the metal, as well as reducing the withdrawn portion of the metal.

The introduction of a neutral gas by a flat jet with an increase in the ratio of the length to the width of the jet cross section at the site of its introduction into the metal by more than 19: 0.5 will cause a decrease in the jet velocity of the injected gas. This will reduce the length of the injected gas stream and increase the washout of the lining of the over-tuition zone. Reducing this ratio to less than 16: 0.3 will cause a significant increase in the jet velocity and thus the zone of destruction of the gas jet will dangerously approach the opposite (from the tuyere) wall of the vacuum tube and will also cause additional washout.

Increased consumption of inert ga-. for while maintaining the proposed ratio of length to width flat

The jet sections, on the one hand, will also cause additional erosion of the opposite wall of the pipe lining, and, on the other hand, will increase the residual pressure in the vacuum chamber and thereby reduce the degassing rate of the metal. The latter is explained by the fact that the stage of the steam-jet pump is created and the minimum vacuum is designed for a small amount of pumped gases and with an increase in their amount (neutral gas and air leaking) more than the calculated limit the stage creates minimal vacuum and more productive, but not providing low residual pressure in the vacuum chamber of the pump stage.

The introduction of the first REM instead of zirconium will cause the formation of a large number of oxygen inclusions of REM, which are poorly removed from the metal, as well as the deterioration of desuli 5

0 5 o

five

0 5 g

five

metal furation. The introduction of boron in the first place will also lead to the interaction of boron with oxygen dissolved in the metal, and thus its effect on the metal structure will be minimized.

The proposed ratios are determined by the composition of the steel and the desired properties. Introduction of zirconium less than 1, rare-earth metals less than 10, boron less than 6 leads to uneven distribution of structural components and carbide phases, which reduces the long-term strength of steel,

With zirconium more than 300, REM more than 70, non-uniform accumulations of non-metallic inclusions are formed, with more than 6 - at the grain boundaries, bordectite is observed. The accumulation of non-metallic inclusions of zirconium and rare-earth metals and the presence of boride eutectics dramatically worsens the long-term strength and technological plasticity of steel.

The optimality of the proposed parameters is proved in the table.

The proposed method is carried out in the following manner.

Steel 12X1MF is melted in a 100-ton arc furnace. After melting and oxidation of carbon and phosphorus and downloading the oxidizing slag, ferrochrome, ferrosilicon, ferromanganese, and slag-forming (lime and fluorspar) are added in the ratio (5-4) to the metal containing the molybdenum, (5-4): 1. After melting slag-forming agents are scooped with coke and aluminum powders. When the metal is released from the furnace into the ladle, a sample is taken for aluminum and nitrogen and fed to the batch vacuumizer. Begin the supply of argon before lowering the pipe of the evaporator into the metal. Gas is supplied by a flat jet with a flow rate of 0.46-10. The min through the tuyere providing the ratio of the length to the width of the jet section at the point of entry into the metal is in the range (16-19): (0.3-0.5). The tuyere is located at the bottom of the vacuum port. The pipe is lowered into the metal and turn off the pump. After the vacuum reaches 1900-3300 Pa, the displacement (swing) of the vacuum chamber begins. In the process of vacuuming. the pressure in the vacuum chamber is reduced to 66.5-260 Pa. After 3-4 minutes after the start of the evacuation (first

mixing the vacuum chamber), the gas analyzer determines the amount of oxygen in the pumped gases and, if necessary, increases the flow rate of the inert gas to 0.49 x X 10. A special treatment of 6–9 min of vacuum treatment with an inert atmosphere pressure of 66.5–260 Pa produces an additive of zirconium, rare-earth metals and boron. Metal evacuation is continued with argon purging for another 2–3 min, and then the pressure is increased to normal and argon is turned off. A sample is taken and the temperature is measured. Melting is passed to the casting.

The table shows examples of the implementation of the proposed method (1-3) in relation to steel grade 12X1MF, as well as heats carried out using the exorbitant parameters (4 and 5) and produced by the known method (6). Melting was carried out in a 100-ton arc furnace. Metal was evacuated using a batch vacuum.

As can be seen from the table, the advantage of the proposed method before iz-. It is natural to reduce the amount of nitrogen in the metal, to obtain a guaranteed bainite structure.

Editor I.Egorova

Compiled by A. Scherbakov Tehred V. Kadar

Order 3769/23 Circulation 549Subscription

VNIIPI USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5

Production and printing company, Uzhgorod, Projecto st., 4.

Claims (1)

metal, which contributes to the improvement of the heat-resistant properties of the metal. Claims The method of micro-alloying of steel with active elements, including deoxidation with aluminum, vacuuming, an additive of micro-alloying additives, for example, rare-earth metals, characterized in that. in order to increase the stability of the assimilation of microalloying active elements, to reduce the nitrogen content, to guarantee a given the structure of the solid solution and higher heat-resistant properties of steel, reduction of alloying with deficient elements, micro-alloying additives are introduced onto the metal mirror at a pressure inert gas above the melt 66.5–260 Pa, which is provided by its supply to the melt by flat jets with a ratio of the length to the width of the jet section at the point of its entry into the metal in limits (16-19): (0.3-0.5) and inert gas consumption on the lance (0.46 - 0.49) 10 m / t "min, and zirconium, rare earth metals and boron are introduced in the ratio ( 1-300): (10 70): (1-6) 6-9 minutes after reaching a pressure above the metal within 1900-3300 Pa7 Proofreader M.Sharoshi