KR102315999B1 - A method for refining a high manganese steel and amanufacturing of a high manganese steel - Google Patents

Abstract

To provide a method for melting high manganese steel, which enables high manganese yield to be obtained when melting high manganese steel containing 5% by mass or more of manganese and can be smelted with high efficiency.
When smelting steel containing 5 mass% or more of manganese, decarburization is performed in the converter 1 to decarburize the molten iron (molten metal 2) to convert the molten iron into molten steel (molten metal 2) with a low carbon concentration. After the step (step S100) and the decarburization step, a reduction step (step S102) of reducing the molten steel by adding a manganese source and a silicon source to the molten steel accommodated in the converter 1 (step S102), and after the reduction step, a vacuum degassing device In (5), a degassing step (step S104) of vacuum degassing the molten steel is provided, and in the reduction step, a manganese source is added according to the target steel manganese concentration, so that the expression (1) is satisfied. Add the silicon source.

Description

High manganese steel melting method and high manganese steel manufacturing method

The present invention relates to a method for melting high manganese steel.

Manganese has an advantage of improving the strength of a steel material by adding it to steel. Moreover, manganese reacts with sulfur remaining in steel as an unavoidable impurity, and forms MnS, there exists an advantage, such as preventing the generation|generation of harmful|toxic FeS, and suppressing the influence of sulfur in a steel material. From this, most of steel materials contain manganese. In recent years, for the purpose of reducing the weight of structures, low-carbon/high-manganese steels with a low carbon content and high manganese content, which achieve both high tensile strength and high workability, have been developed, and are widely used as steel sheets for line pipes, automobile steel sheets, and the like. is being used

In the steelmaking process, as a manganese source used to adjust the manganese concentration in molten steel, manganese ore, high-carbon ferromanganese (carbon content: 7.5 mass% or less), medium-carbon ferromanganese (carbon content: 2.0 mass% or less) , low-carbon ferromanganese (carbon content: 1.0 mass% or less), silicomanganese (carbon content: 2.0 mass% or less), metallic manganese (carbon content: 0.01 mass% or less), etc. are generally used. Moreover, in these manganese sources, except for manganese ore, it becomes expensive, so that carbon content becomes low. Therefore, for the purpose of reducing manufacturing cost, a method of melting manganese-containing steel using low-cost manganese ore, manganese ore, or high-carbon ferromanganese has been proposed.

For example, in Patent Document 1, as a method of melting high manganese steel, after the blow-blending of the converter is finished, after performing a rinse treatment with a lower odor gas, when tapping with a ladle, the carbon concentration is 1.0 mass % After the above-mentioned high-carbon ferromanganese is added, aluminum is added to deoxidize, and then, a method of performing RH gas degassing treatment is proposed.

Further, in Patent Document 2, as a method for melting high manganese steel, decarburization refining of molten iron is performed while reducing manganese ore using manganese ore, and after decarburization is completed, deoxidation treatment of molten steel with aluminum is not performed. There has been proposed a melting method in which molten steel is transported to a vacuum degassing facility, and a mixed gas of oxygen gas and inert gas is sprayed to perform decarburization treatment.

Further, in Patent Document 3, as a method for melting high manganese steel, when decarburization refining of high Mn molten iron having a manganese concentration of 8 mass% or more under reduced pressure until a carbon concentration of 0.1 mass% or less is obtained, the refining gas is used as a carrier gas As such, a method of spraying a powdery decarburization refining additive containing Mn oxide to molten iron has been proposed.

Japanese Laid-Open Patent Publication No. 2013-112855 Japanese Patent Publication No. 4534734 Japanese Laid-Open Patent Publication No. 5-125428

However, in the high manganese steel melting method of Patent Documents 1 to 3, the manganese ore injected into the converter is reduced at the time of decarburization blowing of molten iron in the converter, or at the time of tapping or ladle refining from the converter or vacuum degassing. The manganese concentration of the molten steel is increased by adding a manganese source to the molten steel.

However, in such a solvent method, when a manganese source is added during decarburization blowing or steel tapping, since the yield of the added manganese source is low, it is necessary to add a large amount of manganese source, resulting in an increase in processing time and manganese The increase in cost is a problem. In addition, when a manganese source is added at the time of tapping, ladle refining, or vacuum degassing refining, heat loss occurs due to dissolution of the manganese source, so that it is necessary to raise the heat of the molten steel in the process after the converter. However, the heat raising treatment of molten steel by a ladle refining apparatus or a vacuum degassing apparatus is inferior in efficiency compared with the heat raising treatment in a converter, and an increase in the cost of treatment poses a problem. In particular, in a high manganese steel having a manganese concentration of 5 mass% or more, these problems become remarkable.

Therefore, the present invention has been made in view of the above problems, and when melting high manganese steel containing 5 mass % or more of manganese, a high manganese yield can be obtained and a method of melting high manganese steel capable of high-efficiency melting is intended to provide.

According to one aspect of the present invention, when melting steel containing 5 mass % or more of manganese, a decarburization step of converting the molten iron into molten steel having a low carbon concentration by subjecting the molten iron to a decarburization treatment in a converter, and this decarburization step; Then, a reduction process of reducing the molten steel by adding a manganese source and a silicon source to the molten steel accommodated in the converter, and after the reduction process, vacuum degassing the molten steel in a vacuum degassing device There is provided a method for melting high manganese steel comprising a degassing step, wherein in the reduction step, the silicon source is added so as to satisfy Equation (1) according to the amount of the manganese source added.

x _Mn : manganese concentration in manganese source (mass %)

x _Si : silicon concentration in silicon source (mass %)

W _Mn : the amount of manganese source added (kg/t)

W _Si : Amount of silicon source added (kg/t)

According to one aspect of the present invention, when melting high manganese steel containing 5 mass% or more of manganese, a high manganese yield can be obtained, and a method for melting high manganese steel is provided, in which the high manganese steel can be melted with high efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS It is a flowchart which shows the melting method of the high manganese steel which concerns on one aspect of this invention.
It is a schematic diagram which shows a converter.
It is a schematic diagram which shows a vacuum degassing apparatus.

In the following detailed description, numerous specific details are set forth by way of illustration of an embodiment of the invention in order to provide a thorough understanding of the invention. However, it will be apparent that one or more embodiments may be practiced without these specific details. Also, in the drawings, for the sake of brevity, well-known structures and devices are shown schematically.

<How to Solvent High Manganese Steel>

With reference to FIGS. 1-3, the melting method of the high manganese steel which concerns on one Embodiment of this invention is demonstrated. In this embodiment, high manganese steel which is molten steel containing 5 mass % or more of manganese is melted by performing the refinement process mentioned later with respect to the molten iron|metal tapped from a blast furnace.

First, as shown in FIG. 1 and FIG. 2, the decarburization process which decarburizes the molten metal 2 (it is also called "molten iron") which is molten iron accommodated in the converter 1 is implemented (S100).

The molten metal 2 is molten iron tapped from a blast furnace, and after it is tapped from a blast furnace, it is conveyed to the steelmaking plant used as a next process by the conveyance container which can accommodate molten iron, such as a molten iron|metal ladle and a topedo car. Moreover, in order to reduce the masonry agents, such as lime source used in the converter 1, before charging molten iron|metal into the converter 1, it is preferable that the dephosphorization process which reduces the phosphorus concentration of molten iron|metal is performed. In the dephosphorization treatment, with respect to the molten iron accommodated in the molten iron conveying container, an oxygen source such as iron oxide or gaseous oxygen, and a moring agent containing lime are added, and the molten iron is dephosphorized by being stirred by gaseous oxygen or gas for stirring. The reaction proceeds. In addition, in the dephosphorization treatment, in order to reduce as much as possible the solvent used in the converter 1, it is preferable to make the phosphorus concentration of molten iron|metal lower than the upper limit concentration of the final component specification of high manganese steel. In addition, since there is a concern about phosphorus pickup for molten iron from a manganese source added in the post-process or increase in phosphorus concentration due to compound phosphorus from slag, the phosphorus concentration of molten iron is 0.05 mass above the upper limit of the component specification. It is more preferable to perform a dephosphorization process until it becomes low about %, and to remove the slag which generate|occur|produced by a process after that (it is also said "removal is carried out"). Moreover, in order to make the phosphorus concentration of molten iron|metal lower than the upper limit of a component specification, it is preferable to remove the silicon which dephosphorization process is given before dephosphorization process, and inhibits an efficient dephosphorization reaction beforehand.

At a decarburization process, before implementing a decarburization process, after transferring the molten iron|metal 2 which is molten iron conveyed by a conveyance container to a molten iron|metal ladle, it charges into the converter 1 which is a primary refining furnace. In addition, before charging the molten metal 2, the scrap used as an iron source may be charged into the furnace body 10. As shown in FIG.

The converter 1 is a conventional converter installation, and, as shown in FIG. 2, the furnace body 10, the upper blow lance 11, the some lower blow nozzle 12, and the chute 13 be prepared The furnace body 10 is a barrel-shaped or pear-shaped refining furnace having a furnace inlet that is an opening at the upper portion, and a refractory material is formed therein. The upper blow lance 11 is arrange|positioned above the furnace body 10, and is comprised so that raising/lowering is possible in a perpendicular direction (the up-down direction of FIG. 2). The upper blow lance 11 has a plurality of nozzle holes formed at the lower end thereof, and from the plurality of nozzle holes, an oxidizing gas containing at least oxygen supplied from a supply facility (not shown) is accommodated in the furnace body 10 ( 2) Spray on The plurality of lower blowing nozzles 12 are formed at the bottom of the furnace body 10, and a stirring gas, which is an inert gas such as argon or nitrogen, supplied from a supply device (not shown), is placed in the molten metal 2 accommodated in the furnace body 10 . By blowing, the molten metal 2 is stirred. The chute 13 is disposed above the furnace body 10 and is connected to upper hoppers of a plurality of furnaces (not shown) for storing various auxiliary materials such as a masonry solvent containing lime and ferrous alloys, and the upper hoppers of each furnace. Additives carried out from the furnace body (10) inside.

In the decarburization step, while stirring the molten metal 2 accommodated in the furnace body 10 with the stirring gas blown in from the lower blowing nozzle 12, an oxidizing gas is sprayed from the upper blowing lance 11 to the molten metal 2 (“supplying酸)") and supplying oxygen to the molten metal 2 to perform decarburization treatment (also referred to as "decarburization blow tempering") under atmospheric pressure. In decarburization blow tempering, when oxygen blown into the molten metal 2 with the top blow lance 11 and carbon in the molten metal 2 react, a decarburization reaction advances. In addition, when Cr or Ni is contained in the component specification of high manganese steel (when addition is essential), during decarburization blowing, auxiliary materials such as ferroalloy containing Cr or Ni are passed through the chute 13 to the molten metal 2 ) is added to At a decarburization process, decarburization blow tempering is performed until the carbon concentration of the molten metal 2 becomes a predetermined range, and the molten metal 2 turns into molten steel with a low carbon concentration in molten iron|metal with a high carbon concentration. At this time, it is preferable that the predetermined range of carbon concentration is 0.05 mass % or more and 0.2 mass % or less. This is because, when the carbon concentration of the molten metal 2 after the decarburization step is less than 0.05 mass%, the oxygen potential of the molten metal 2 increases and the yield of the manganese source decreases. On the other hand, when the carbon concentration of the molten metal 2 after the decarburization step is greater than 0.2 mass%, the decarburization treatment in the secondary refining step is required, and the treatment cost increases. And when the carbon concentration of the molten metal 2 becomes a predetermined range, supply of the oxidizing gas to the inside of the furnace body 10 is stopped, and a decarburization process is complete|finished.

After the decarburization step, a manganese source and a silicon source are added into the furnace body 10 in which the molten metal 2 is accommodated, and a reduction step of reducing the molten steel 2 as molten steel is performed (S102). The manganese source is an ore, alloy, or metal containing manganese. As a manganese source, manganese ore, high carbon ferromanganese, medium carbon ferromanganese, low carbon ferromanganese, silicomanganese, metallic manganese etc. can be used, for example. The silicon source is an ore, alloy, or metal containing silicon (silicon). As a silicon source, ferrosilicon, silicomanganese, etc. can be used, for example. The manganese source and silicon source may be added from the furnace inlet through the chute 13, or may be added from the furnace inlet of the furnace body 10 using a scrap chute (not shown) used for charging scrap. And when adding a manganese source and a silicon source, stirring gas is blown in from the some blow-up nozzle 12, and it is added, stirring the molten metal 2.

In the reduction step, the manganese source is added in an amount corresponding to the target manganese concentration, which is the component standard for high manganese steel. That is, the addition amount of the manganese source is determined by the manganese content of the manganese source, the carbon concentration of the molten metal 2, and the like, depending on the target manganese concentration. At this time, the performance of the yield of the manganese source may be considered. In the reduction step, it is not necessary to set the manganese concentration in the molten metal 2 to a target concentration, but to set the manganese concentration in the molten metal 2 to a concentration lower than the target concentration so as to be adjustable in the degassing step described later. You can do it. In addition, from the viewpoint of thermal efficiency, it is preferable to increase the addition amount of the manganese source in the reduction step as much as possible with respect to the addition amount of the manganese source in the degassing step. In addition, from the viewpoint of reducing the cost for treatment, it is preferable to use a manganese ore or an inexpensive manganese source having a high carbon concentration as much as possible, as long as there is no influence on the adjustment of components other than manganese such as carbon.

The silicon source is added in an amount that satisfies the following formula (1). (1) In the formula, x _Mn is the manganese concentration in the manganese source (mass %), x _Si is the silicon concentration in the silicon source (mass %), W _Mn is the addition amount of the manganese source (kg/t), W _Si is the silicon The addition amount (kg/t) of the circle is shown, respectively. In other words, the silicon source is added in an amount corresponding to the amount of the manganese source to be added.

Moreover, in a reduction process, after adding a manganese source and a silicon source, the stirring gas is blown in from the some blow-up nozzle 12, and the molten metal 2 is stirred for a predetermined time.

Here, since the molten metal 2 after the decarburization process has a high oxygen potential, when a manganese source is added to the molten metal 2, the manganese in the manganese source does not stay in the molten metal 2 but is oxidized to form manganese oxide (MnO). It becomes and is contained in the slag (3). However, in this embodiment, since a silicon source is added in addition to the manganese source, manganese in the manganese source and manganese oxide in the slag 3 generated by the decarburization step are reduced by the reaction represented by the following formula (2). , the manganese concentration of the molten metal 2 increases. Moreover, the oxygen potential of the molten metal 2 falls by preferentially oxidizing the silicon in a silicon source. Thereby, the manganese in the manganese source tends to stay in the molten metal 2, and the manganese concentration of the molten metal 2 increases.

2 (MnO) + [Si] = (SiO ₂ ) + 2 [Mn] ... (2)

In the reduction process, the slag 3, the basicity (CaO / SiO ₂₎ of the of the slag 3, which is defined as the ratio of the concentration (mass%) of CaO for the concentration (% by mass) of SiO _2, 1.6 2.4 It is preferable to add lime in the furnace body 10 so that it may become the following. Thereby, the ash of the slag 3 and the desulfurization of the molten metal 2 represented by the following formula (3) are accelerated|stimulated.

2[S]+[Si]+2(CaO) = 2(CaS)+(SiO ₂ ) ... (3)

In addition, when the amount of the silicon source added is lower than the range of the formula (1), that is, when the amount of the silicon source added is small, the reduction reaction of manganese oxide does not proceed, so the manganese concentration of the molten metal (2) can be increased. there will be no On the other hand, when the amount of the silicon source added becomes higher than the range of the formula (1), that is, when the amount of the silicon source is large, the amount of lime added for adjusting the basicity becomes too large, so that the cost of the refining treatment increases. Moreover, when there is much addition amount of a silicon source, the silicon density|concentration of the molten metal 2 may become high, and it may exceed the upper limit of a component standard value. In such a case, since it is necessary to perform the desiliconization process which reduces the silicon concentration of the molten metal 2 in the next process, it is not preferable.

Moreover, in a reduction process, when a reduction process is complete|finished, the molten metal 2 of the furnace body 10 is transferred and poured into a ladle (it is also called "steeling"). At this time, it is preferable to preliminarily set 5 kg/t or more and 10 kg/t or less of lime in the ladle in an amount with respect to 1 t of molten metal. By placing lime in the ladle in advance, generation of white smoke at the time of steel tapping can be prevented, and a rise in the sulfur concentration of the molten metal 2 due to resulfurization from the slag 3 can be suppressed.

After the reduction step, a degassing step of vacuum degassing treatment is performed on the molten metal 2 that is molten steel in the vacuum degassing device 5 (S104). The vacuum degassing apparatus 5 is a degassing apparatus of the VOD system, and degassing by stirring the molten metal 2 accommodated in the ladle 4 under reduced pressure. The vacuum degassing apparatus 5 has a vacuum chamber 50 , an exhaust pipe 51 , a stirring gas supply path 52 , an upper blowing lance 53 , and a supply port 54 . The vacuum chamber 50 is a container which can accommodate the ladle 4 inside, and has the removable upper cover 500 so that the ladle 4 can be taken in and out of the inside. The exhaust pipe 51 is formed on the side surface of the vacuum chamber 50 and is connected to an exhaust device not shown. The stirring gas supply path 52 is disposed from the outside to the inside of the vacuum chamber 50 , and the inner tip of the vacuum chamber 50 is connected to the intake port 40 of the ladle 4 . In addition, the stirring gas supply path 52 is connected to a stirring gas supply device (not shown) at the outer end of the vacuum chamber 50, and a stirring gas such as argon gas supplied from the stirring gas supply device is ladled. 4) is supplied to the inlet 40. The upper blowing lance 53 is inserted through the center of the upper cover 500, and is comprised so that raising/lowering in a vertical direction (the up-down direction of FIG. 3) is possible. Moreover, as for the upper blow lance 53, the nozzle hole is formed in the lower end, and the oxidizing gas containing at least oxygen supplied from the supply equipment which abbreviate|omitted illustration from the nozzle hole to the molten metal 2 accommodated in the ladle 4 Spray oxidizing gas. The supply port 54 is formed in the upper cover 500 and is connected to the upper hopper of a plurality of furnaces (not shown) for storing various auxiliary materials such as a masonry agent containing lime and ferrous alloy, and the upper hopper of each furnace. It is an inlet for adding the auxiliary material discharged from the ladle 4 to the molten metal 2 accommodated in the ladle 4 .

In a degassing process, after accommodating the ladle 4 in the vacuum chamber 50, while stirring the molten metal 2 by blowing in a stirring gas from the inlet 40, the exhaust pipe 51 is used using an exhaust device. A vacuum degassing process is performed by evacuating from the vacuum chamber 50 and depressurizing the inside of the vacuum chamber 50 . By performing such a vacuum degassing treatment, gas components (such as nitrogen and hydrogen) in the molten metal 2 are removed, the components of the molten metal 2 are homogenized, the inclusions in the molten metal 2 are removed, and the molten metal 2 is Adjust the temperature, etc. In addition, in the degassing step, when performing the vacuum degassing treatment, depending on the components of the molten metal 2 before or during the vacuum degassing treatment, the auxiliary material for component adjustment is supplied so that it becomes a target component range. It is added to the molten metal (2) through the sphere (54). At this time, when the manganese concentration of the molten metal 2 before the vacuum degassing treatment is lower than the target concentration, a manganese source such as metallic manganese, high-carbon ferromanganese, or low-carbon ferromanganese is added to the molten metal 2 in an amount necessary for component adjustment. ) is added to Moreover, when adjustment of components, such as Al, Ni, Cr, Cu, Nb, Ti, V, Ca, B, is required, the auxiliary material containing each component is added to the molten metal 2 . Furthermore, for the purpose of desulfurization, etc., CaO-containing material, MgO-containing material, aluminum-containing material, Al ₂ O ₃ containing material, SiO ₂ containing material, etc. used for adjusting the composition of the slag 3 or promoting desulfurization reaction An auxiliary material may be added to the molten metal 2 .

In addition, in the degassing step, it is preferable to stir the molten metal 2 under the condition that the stirring power ε (W/t) expressed by the following formula (4) is 300 W/t or more and 1300 W/t or less. do. When the stirring power ε is less than 300 W/t, the stirring power becomes small, so time is required for the denitrification treatment or dehydrogenation treatment, and the treatment time for the vacuum degassing treatment is prolonged, which is not preferable. In addition, when the stirring power ε is larger than 1300 W/t, the amount of the slag 3 added to the molten metal 2 increases, and the defect rate due to slag inclusions increases, which is not preferable. In the formula (4), Q is the flow rate of the stirring gas (Nm ³ /min), T _l is the temperature (K) _{of the molten metal 2, W m} is the weight (t) of the molten metal 2, ρ _l The density (kg/m3) of the silver molten metal 2, h is the depth of the molten metal 2 in the ladle 4, the molten metal surface height (m), P ₂ is the atmospheric pressure (Torr), η is the energy transfer efficiency (- ) and T _n represent the temperature (K) of the stirring gas, respectively. Moreover, 1 Torr is (101325/760)Pa.

Moreover, in a degassing process, when the temperature of the molten metal 2 is lower than the target temperature after completion|finish of a degassing process, you may perform the temperature raising process which raises the temperature of the molten metal 2 during a vacuum degassing process. In a temperature raising process, after adding aluminum to the molten metal 2 from the supply port 54, the oxidizing gas containing oxygen is sprayed to the molten metal 2 from the upper blow lance 53. Thereby, the temperature of the molten metal 2 can be raised by the aluminum in the molten metal 2 and oxygen of an oxidizing gas react. In addition, in a temperature increase process, the dynamic pressure P (kPa) of the jet of oxidizing gas injected from the upper blow lance 53 calculated from Formula (5) and Formula (6) is 10 kPa or more, 50 kPa It is preferable to control so that it may become the following. By controlling the dynamic pressure P within the above range, the molten metal 2 can be efficiently heated while suppressing the evaporation of manganese from the molten metal 2 to the minimum. In the formula (5), ρ _g is the density (kg/Nm ³ ) of the oxidizing gas, U is the flow velocity (m/sec) at the nozzle tip of the oxidizing gas ejected from the nozzle of the upper blow lance 53, respectively indicates. In the formula (6), F represents the flow rate (Nm ³ /h) of the oxidizing gas, and S represents the cross-sectional area (m 2 ) of the nozzle of the upper blowing lance 53 .

By passing through a degassing process, the molten steel of a target predetermined|prescribed component concentration is melt|dissolved. Further, following the degassing step, a slab of high manganese steel having a predetermined shape such as a slab is manufactured by continuously casting the molten steel.

<Modified example>

In the above, although this invention was demonstrated with reference to specific embodiment, it is not intended to limit invention by these description. Other embodiments of the present invention including various modifications along with the disclosed embodiments are also apparent to those skilled in the art by reference to the description of the present invention. Therefore, it should be construed that the embodiment of the invention described in the claims also encompasses the embodiments including these modifications described in the present specification alone or in combination.

For example, in the said embodiment, although the vacuum degassing apparatus 5 was set as the refining apparatus of a VOD system, this invention is not limited to this example. For example, the vacuum degassing apparatus 5 may be a degassing apparatus of an RH system or a degassing apparatus of a DH system. In addition, when the vacuum degassing apparatus is a degassing apparatus of the RH system, in order to suppress evaporation of manganese, the molten steel represented by the following formula (7) under the condition that the internal space pressure of the vacuum chamber is 50 Torr to 100 Torr It is preferable that the reflux amount (Q) (t/min) be 150 t/min or more and 200 t/min or less. In addition, when denitrification or dehydrogenation of molten steel is required, the treatment may be performed at a tank space pressure of less than 50 Torr. . (7) In the formula, K is an integer, G is the flow rate of reflux blown gas for reflux blown from the submerged pipe (NL/min), D is the inner diameter of the submerged pipe (m), P ₂ is the external pressure (Torr), P ₃ represents the chamber space pressure (Torr) of the vacuum chamber, respectively.

Moreover, in the said embodiment, although only the molten metal 2 which is molten steel manufactured by the converter 1 was used as the molten metal 2 processed by the vacuum degassing apparatus 5, this invention is not limited to this example. . For example, you may use as the molten metal 2 processed by the vacuum degassing apparatus 5 the molten steel which combined the molten steel manufactured by the converter 1 with the molten steel smelted by another refining furnace. In this case, the manganese concentration of the molten steel manufactured in the converter 1 can be made low by making the manganese concentration of the molten steel melted by the other refining furnace high.

In the above embodiment, after adding a manganese source and a silicon source to the reduction step, a stirring gas is blown in from the plurality of lower blowing nozzles 12 and the molten metal 2 is stirred for a predetermined time. The invention is not limited to these examples. In a reduction process, in addition to blowing in stirring gas, you may inject the oxidizing gas from the upper blowing lance 11. In particular, when it is necessary to raise the temperature of the molten metal 2, you may heat-up process by the oxidation reaction by an oxidizing gas.

In addition, in the said embodiment, although the dephosphorization process was performed to molten iron|metal before a decarburization process, this invention is not limited to this example. For example, before a decarburization process, in addition to a dephosphorization process, the desulfurization process which reduces the sulfur concentration in molten iron|metal may be performed. You may perform a desulfurization process before a dephosphorization process or after a dephosphorization process according to an installation structure.

In addition, in the said embodiment, although the dephosphorization process was performed with respect to the molten iron accommodated in the molten iron|metal conveyance container, this invention is not limited to this example. The method of processing by injecting an oxidizing gas from a top blow lance with respect to the molten iron accommodated in the converter type refining furnace may be sufficient as a dephosphorization process, for example.

<Effect of embodiment>

(1) In the method for melting high manganese steel according to one aspect of the present invention, when the steel containing 5 mass% or more of manganese is melted, the molten iron (molten metal 2) is subjected to decarburization treatment in the converter 1 , , a decarburization step (step S100) of converting the molten iron into molten steel having a low carbon concentration (molten metal 2), and after the decarburization step, a manganese source and a silicon source are added to the molten steel accommodated in the converter 1 to reduce the molten steel a reduction step (step S102) to perform, and a degassing step (step S104) of performing a vacuum degassing treatment on the molten steel in the vacuum degassing device 5 after the reduction step, and in the reduction step, the target steel A manganese source is added according to the manganese concentration, and a silicon source is added so as to satisfy Equation (1).

According to the configuration of (1) above, since the reduction reaction of the formula (2) can be promoted, the manganese in the added manganese source tends to stay in the molten metal (2). Moreover, since the addition of the manganese source is carried out in the converter 1 , heat loss due to the addition of the manganese source (a decrease in the temperature of the molten metal 2 ) can be suppressed. And since the molten metal 2 can be heat-raised in the converter 1 after the addition of the manganese source, the heat-raised treatment can be efficiently performed. In addition, it is possible to suppress the addition of an excessive amount of silicon source or more sufficient to promote the reduction reaction, and since there is no need for desiliconization in the degassing process, the degassing treatment can be performed efficiently in a short treatment time. can If the degassing time becomes longer, in addition to increasing the cost for the treatment, the production efficiency is lowered. In other words, according to the configuration of (1) above, when high manganese steel containing 5 mass% or more of manganese is melted, a high manganese yield can be obtained, and high manganese steel can be melted with high efficiency.

(2) In the configuration of (1) above, as the vacuum degassing device (5), a device for stirring molten steel by blowing a stirring gas from the bottom of a ladle containing molten steel is used, and in the degassing step, ( 4) Vacuum degassing treatment is performed while stirring molten steel on the condition that the stirring power (ε) represented by the formula is 300 W/t or more and 1300 W/t or less.

According to the structure of said (2), the time required for a denitrification process and a dehydrogenation process can be shortened, Furthermore, it can suppress that the slag 3 comes into the molten metal 2 . For this reason, the processing time of a vacuum degassing process can be shortened.

Example 1

Next, Example 1 implemented by the present inventors is demonstrated. In Example 1, the molten iron|metal preliminary process of a desiliconization process and a dephosphorization process was performed with respect to the molten iron|metal tapped from the blast furnace, and the phosphorus concentration was 0.010 mass %. This molten iron was subjected to a decarburization step, a reduction step, and a degassing step in the same manner as in the above embodiment, thereby smelting high manganese steel having a manganese concentration of 5 mass% or more. In addition, the components of the high manganese steel dissolved are: carbon concentration: 0.145 mass% or more and 0.155 mass% or less, manganese concentration: 24 mass% or more and 25 mass% or less, silicon concentration: 0.1 mass% or more and 0.2 mass% or less, sulfur concentration: 0.002 mass% or less, nitrogen concentration: 100 ppm or less, hydrogen concentration: 5 ppm or less.

In a decarburization process, similarly to the said embodiment, the decarburization process was performed to the molten metal 2 which is molten iron which performed the molten iron|metal preliminary process, it decarburized and blown until carbon concentration became 0.05 mass %, and it was set as molten steel.

In the reduction step, high-carbon ferromanganese and metallic manganese were added as manganese sources to the molten metal 2 which is molten steel subjected to decarburization treatment, and ferrosilicon was added as a silicon source. And while stirring the molten metal 2 with a stirring gas, the manganese source is melt|dissolved and the manganese density|concentration of the molten metal 2 is raised by carrying out the reduction process by carrying out the supply from the upper blow lance 11 continuously further. did it The amount of the silicon source added satisfies the formula (1). In the reduction step, lime was added together with the manganese source. The manganese concentration of the molten metal 2 at the end of the reduction treatment was approximately 24 mass%. In the reduction step, when the molten metal 2 is transferred from the converter 1 to the ladle 4 (to be tapped), about 0.8 kg of metallic aluminum is added per 1 ton of the molten steel to the molten metal 2 to be tapped. .

In the degassing process, the molten metal 2 which is 150 tons of molten steel which passed through the reduction process was degassed using the vacuum degassing apparatus 5 of a VOD system similarly to the said embodiment. In the degassing step, from the inlet 40 of the ladle 4, Ar gas at a flow rate of 2000 Nl/min is blown into the molten metal 2 and stirred while the internal pressure of the vacuum chamber 50 is increased to 2 Torr. and degassed. Moreover, in the degassing process, metal manganese and high carbon ferromanganese were added to the molten metal 2 during degassing process, and component adjustment was performed.

In Example 1, as a comparison, high manganese steel was smelted even under the condition that the amount of silicon source added in the reduction step did not satisfy the formula (1) (Comparative Example 1). In Comparative Example 1, conditions other than the amount of silicon source added in the reduction step were the same as in Example 1.

Table 1 shows the results of Example 1, the amount of silicon source added in the reduction step, the Mn yield, the silicon concentration in the molten metal 2 at the time of steel taping, and the time taken for the degassing treatment in the degassing step. In addition, in Table 1, 0.013 x W _Mn x x _Mn /x _Si is the lower limit of the range shown in formula (1), and 0.150 x W _Mn x x _Mn /x _Si is the upper limit of the range shown in formula (1), respectively. indicates. As shown in Table 1, in Example 1, _{6 conditions of Examples 1-1 to 1-6 in which the amount of silicon source added (W Si} ) falls within the range of the formula (1), and the amount of silicon source added (W _{Si )} ) was out of the range of formula (1), and high manganese steel was melted under a total of 10 conditions of 4 conditions of Comparative Examples 1-1 to 1-4. In addition, the Mn yield in Table 1 shows how much manganese contained in the manganese source used in the reduction process was added to the molten metal 2, that is, the manganese content contained in the manganese source before and after the reduction process. It shows how much it contributed to the increase of the manganese concentration of the molten metal (2).

As shown in Table 1, under the conditions of Comparative Examples 1-1 and 1-2, the manganese yield was 46% or less, which was lower than the other conditions. This is considered to be because the reduction reaction of the slag (3) represented by Formula (2) did not fully advance because there was little addition amount of a silicon source. In Comparative Examples 1-1 and 1-2, since the Mn yield was low, a reduction treatment was performed by adding a silicon source in the degassing step, and thereafter, it was necessary to adjust the components and the temperature, thereby degassing. The time required for the process was longer than in Examples 1-1 to 1-6.

Moreover, under the conditions of Comparative Examples 1-3 and 1-4, although the manganese yield was high, the silicon concentration at the time of steel taping exceeded 0.20 mass % which is an upper specification limit. This is considered to be because the silicon|silicone more than the amount consumed in the reduction reaction of the slag 3 represented by Formula (2) or the desulfurization reaction represented by Formula (3) was supplied to the molten metal 2 . In Comparative Examples 1-3 and 1-4, since the silicon concentration at the time of steel tapping was high, it was necessary to perform a desiliconization process in the degassing process, and the time required for the degassing process was reduced in Example 1-1. It became longer than ∼1-6. In addition, in a desiliconization process, the silicon|silicone contained in the molten metal 2 is oxidized and removed by injecting an oxidizing gas to the molten metal 2 from the upper blow lance 53.

On the other hand, under the conditions of Examples 1-1 to 1-6, a high manganese yield could be obtained in the reduction step, and furthermore, since the silicon source was not added more than necessary, the silicon concentration at the time of steel tapping could be made low. For this reason, the time required for a degassing process could be shortened.

Example 2

Next, Example 2 implemented by the present inventors is demonstrated. In Example 2, high manganese steel was melted under a plurality of conditions in which the stirring power (ε) in the degassing process was changed by the same melting method as in Example 1-4. In addition, the components of the high manganese steel dissolved are: carbon concentration: 0.145 mass% or more and 0.155 mass% or less, manganese concentration: 24 mass% or more and 25 mass% or less, silicon concentration: 0.1 mass% or more and 0.2 mass% or less, sulfur concentration: 0.002 mass% or less, nitrogen concentration: 100 ppm or less, hydrogen concentration: 5 ppm or less.

Specifically, as a decarburization step, similarly to Example 1-4, decarburization treatment is performed on the molten metal 2, which is molten iron pretreated in the converter 1, until the carbon concentration is 0.05 mass%. Blowing was performed and it was set as molten steel. Subsequently, as a reduction step, similarly to Example 1-4, a 35 kg/t silicon source was added and the molten metal 2 was subjected to reduction treatment. The manganese concentration of the molten metal 2 at the end of the reduction treatment was approximately 24 mass%. In addition, as a degassing process, the molten metal 2 was degassed by the vacuum degassing apparatus 5 similarly to Example 1-4. In the degassing process, the degassing process was performed on the several conditions which changed the stirring power (epsilon) arbitrarily by adjusting the flow volume of the Ar gas blown-in from the inlet 40 of the ladle 4 .

Table 2 shows the results of Example 2, the amount of silicon source added in the reduction step, the Mn yield, the silicon concentration in the molten metal 2 at the time of steel tapping, the stirring power in the degassing step, and degassing in the degassing step. Shows the time taken for gas processing. As shown in Table 2, in Example 2, high manganese steel was melted under 10 conditions of Examples 2-1 to 2-10 in which the stirring power in the degassing step was different. In addition, the stirring power (epsilon) in the degassing process in Example 1-4 corresponds to Example 2-1. Moreover, in Examples 2-1 to 2-10, it carried out similarly to Example 1-4 about solvent conditions other than the above.

As shown in Table 2, under the conditions of Examples 2-3 to 2-8 in which the stirring power (ε) is 300 W/t or more and 1300 W/t or less, the stirring power (ε) is less than 300 W/t Compared to Examples 2-1 and 2-2 or Examples 2-9 and 2-10 in which the stirring power (ε) exceeds 1300 W/t, it can be seen that the time required for the degassing treatment is shortened there was. This is considered to be because dehydrogenation, denitrification, and flotation of inclusions in the vacuum degassing process were promoted by applying an appropriate stirring power to the molten metal 2 and performing stirring.

On the other hand, under the conditions of Examples 2-1 and 2-2 in which the stirring power (ε) was less than 300 W/t, the stirring was weak, and it took time for dehydrogenation and denitrification, so that the degassing treatment was not performed. This resulted in a longer time required. In addition, under the conditions of Examples 2-9 and 2-10 in which the stirring power ε exceeds 1300 W/t, since the stirring was too strong, the amount of the slag 3 added to the molten metal 2 was large. and time was taken to float the slag-based inclusions in the molten metal 2, resulting in an increase in the time required for the degassing treatment.

1: converter
10: no body
11: Sangche Lance
12: lower intake nozzle
13 : suit
2: molten metal
3: slag
4: Ladle
40: intake
5: vacuum degassing device
50: vacuum chamber
51: exhaust pipe
52: stirring gas supply path
53 : Sangche Lance
54: supply port

Claims (3)

When melting steel containing 5 mass% or more of manganese,
A decarburization step of converting the molten iron into molten steel having a low carbon concentration by subjecting the molten iron to a decarburization treatment in a converter;
a reduction step of reducing the molten steel by adding a manganese source and a silicon source to the molten steel accommodated in the converter after the decarburization step;
a degassing step of performing a vacuum degassing treatment on the molten steel in a vacuum degassing device after the reduction step;
In the reduction step, the silicon source is added so as to satisfy Equation (1) according to the amount of the manganese source added.

x _Mn : manganese concentration in manganese source (mass %)
x _Si : silicon concentration in silicon source (mass %)
W _Mn : the amount of manganese source added (kg/t)
W _Si : Amount of silicon source added (kg/t) The method of claim 1,
As the vacuum degassing device, a device for stirring the molten steel by blowing a stirring gas from the bottom of a ladle accommodating the molten steel is used,
In the degassing step, vacuum degassing is performed while stirring the molten steel under the condition that the stirring power ε expressed by the formula (4) is 300 W/t or more and 1300 W/t or less A method of solvating high manganese steel.

Q: Flow rate of stirring gas (Nm ³ /min)
T _l : temperature of molten steel (K)
W _m : Weight of molten steel (t)
ρ _l : Density of molten steel (kg/㎥)
h : height of hot water surface (m)
P ₂ : Atmospheric pressure (Torr)
η: energy transfer efficiency (-)
T _n : temperature of stirring gas (K) A method for producing a high manganese steel, in which molten steel containing 5 mass% or more of manganese is melted using the method for melting high manganese steel according to claim 1 or 2, and then a cast steel is continuously cast by casting the molten steel. .

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