JPH1180825A - Top-blown lance for converter refining and converter refining method by using this - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a top-blown lance for converter refining which can efficiently the converter refining by supplying flux for refining excellent in slag formation, and a converter refining method by using this lance. SOLUTION: The top-blown lance is provided with a main hole 2 for jetting oxygen and an auxiliary hole 3 for supplying the flux independently arranged to the supplying flow passage of the oxygen gas jetting from the main hole and can simultaneously jet fuel gas, oxygen gas and the flux for refining, and desirably, the main holes are arranged in 4-8 holes on the concentric circle centering a lance center axis and the auxiliary hole is arranged at the center of the concentric circle. Further, the center axis of the main hole is formed as 12-20 deg. angle to the center axis of the lance, and the center axis of the auxiliary hole is matched with the center axis of the lance. The converter refining method is executed by using mixed material of CaO, CaCO3 , MgO, MgCO3 , iron ore, pulverized slag, iron, dust developed in an iron-making work and manganese ore as the flux for refining.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an upper blowing lance for converter refining and a converter using the same, which can supply a refining flux having excellent slagging properties to enable efficient converter blowing with a small unit consumption. Furnace refining method.

[0002]

2. Description of the Related Art Conventionally, dephosphorization,
It is common practice to add refining agents, such as quicklime, limestone, iron ore, manganese ore, dolomite, and calcined dolomite, to the refining gas stream, as necessary, for cooling, furnace body protection, etc. I have been.

[0003] For example, Japanese Patent Application Laid-Open No. 58-19423 discloses that in a top and bottom blown composite blowing converter, the particle size and the particle size distribution of the powdery flux mixed into the top blown blowing gas are defined and the refining is performed. There is disclosed an invention which aims to avoid slopping and promote effective dephosphorization by regulating the amount of flux blown during the initial and concentrated desiliconization reactions. Japanese Patent Application Laid-Open No. 58-212213 discloses a method in which powder mixed with a slag-forming agent such as quicklime, limestone, fluorite, dolomite, etc. is mixed into a top-blown oxygen gas stream by an oxygen top-blown steelmaking method. In addition to defining the depth of penetration into the bath, an inert gas or the like is blown in for uniform mixing of the bath, thereby producing a slag having a basicity of 5 or more, thereby making it possible to melt extremely low phosphorus steel. It has been disclosed. In each of these methods, a refining agent is sprayed together with a decarburizing oxygen jet ejected from a top blowing lance, and the refining agent is applied to a surface (fire point) where the oxygen jet collides with molten steel. The slag is formed using a high temperature state.

Japanese Patent Application Laid-Open No. 58-207313 discloses that a powder mixed with a slag-making agent such as quicklime, limestone, fluorite, dolomite, etc. is mixed into an oxygen-blown oxygen stream by an oxygen-blown steelmaking method. There is disclosed an invention of a method for refining steel, which comprises adding a slag-making agent and blowing an inert gas or the like to generate slag having a basicity of 5 or more. Also,
Japanese Patent Application Laid-Open No. 58-207314 discloses that a powder mixed with quick lime, limestone, fluorite, dolomite, and other slag-making agents is used as a top-blown oxygen gas stream by using hot metal desiliconized by an oxygen top-blown steelmaking method. There is disclosed an invention of a steel refining method characterized by mixing and adding a slag-making agent and blowing an inert gas or the like. JP-A-58-207315 discloses that quick lime, limestone, fluorite,
70% or less of the total amount of slag forming agent such as dolomite is added to the molten iron in a lump, and the remainder is powdered and mixed in the top-blown oxygen gas stream and added to the molten iron. 2 degrees
As described above, there is disclosed a steelmaking method in which a slag-making agent is added in powder form at least from 2 minutes before the end of blowing to the end of blowing. In these methods, a refining agent is sprayed from a nozzle provided in the center of the lance separately from the oxygen jet for decarburization ejected from the upper blowing lance, together with the carrier gas, and the refining agent is supplied by an oxygen jet. It is intended to reach the molten steel surface without being scattered.

On the other hand, RH (Ruhrstahl-Her)
Aus) In vacuum secondary refining represented by a vacuum degassing apparatus, Japanese Patent Application Laid-Open No. 7-41826 discloses that a molten steel is projected or added to a molten steel bath surface under reduced pressure while heating the molten steel with a burner. An invention of a method for vacuum refining molten steel, which is a feature of the invention, is disclosed.

[0006]

However, Japanese Patent Application Laid-Open No. 58-19423 and Japanese Patent Application Laid-Open No. 58-2212 described above.
In the prior art described in Japanese Patent Publication No. 13, the refining agent stays at the high-temperature fire point only for a very short time, so that the slagging does not proceed sufficiently. Has no iron oxide, and therefore has a problem that a molten mixture of quicklime and iron oxide is not formed.

The above-mentioned Japanese Patent Application Laid-Open Nos. 58-207313, 58-207314, and 58-207314 disclose the methods described above.
In the prior art described in Japanese Patent No. 207315, since a high-temperature fire point is not used, the effect of merely supplying a fine refining agent is obtained, and there is a problem that sufficient slag cannot be obtained. The problem that a molten mixture of iron oxide is not formed cannot be solved.

The prior art described in the above-mentioned Japanese Patent Application Laid-Open No. 7-41826 does not mention converter refining using an upper blowing lance for decarburization. Since refining is performed with almost no slag, the situation is significantly different from converter refining, and it is difficult to estimate the effect when applied to a converter.

Therefore, the present invention advantageously solves the above-mentioned problems of the prior art and supplies a refining flux having excellent slagging properties, thereby enabling efficient converter blowing to be performed. It is an object of the present invention to provide a blowing lance and a converter refining method using the same.

[0010]

Means for Solving the Problems In order to promote slagging in converter refining and to increase the efficiency of metallurgical reaction represented by dephosphorization, the present inventors proceed with heat transfer to the center of powder, And passing the powder through a high-temperature range under conditions that allow the powder to be maintained in a high-temperature range, up to CaO-FeO, CaO-MgO,
-FeO-MgO, CaO-FeO-MnO, CaO-
It has been found that it is important to supply the powder as a mixture of FeO-MnO-MgO to a high temperature range. The present invention
It is constituted by the above findings, and the gist is as follows.

(1) An oxygen jetting main hole and an oxygen gas supply flow path spouted from the main hole are independent of a fuel gas,
An upper blowing lance for converter refining, comprising a flux supply sub-hole capable of simultaneously ejecting oxygen gas and refining flux. (2) Four to eight main holes for oxygen ejection are arranged on a concentric circle centered on the lance center axis on the lance heat receiving surface, and the flux supply sub-holes are arranged at the center of the concentric circle. The upper blowing lance for converter refining according to the above (1), wherein (3) The central axis of the main hole is 1 to the lance central axis.
(1) or (2) above, wherein the angle of inclination is 2 to 20 degrees, and the central axis of the sub-hole coincides with the central axis of the lance.
4. A top-blown lance for converter refining according to item 1.

(4) The jets of oxygen gas jetted from the main holes for oxygen jetting are separated from each other by using the upper blowing lance for converter refining according to any one of the above (1) to (3). A refining flux passing through the flame to promote slagging of the refining flux while maintaining a flame at the tip of the sub-hole independently of the oxygen gas jet. . (5) CaO, CaCO _{3 is} added to the refining flux.
Containing one or two of the following, and further containing iron oxide, MgO, MgC
The converter refining method according to the above (4), wherein a mixture containing one or more of O ₃ and MnO is used. (6) The refining flux contains one or more of iron ore, pulverized slag, dust from steelworks (blast furnace dust, sintered dust, converter dust), and manganese ore. Converter refining method according to 5).

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic view showing a lance cross section of the present invention. 1 is the top blowing lance body, 2
Is an oxygen gas ejection hole for decarburization (main hole), 3 is a refining agent ejection hole (sub hole), 4 is a main hole oxygen gas passage, 5 is a sub hole oxygen gas and refining agent passage, and 6 is a fuel gas flow. A passage 7 indicates a cooling water passage. The central axis (X) line of the main hole is inclined at an angle θ with respect to the lance central axis (Y).

FIG. 2 illustrates an example of an upper blowing lance for converter refining and a supply system of various gases and a refining agent to the lance as an example of an apparatus configuration according to the present invention. It is a schematic diagram explaining the situation of the flame formed at the tip. The main hole oxygen gas line 8 and the sub hole oxygen gas line 9 can be controlled independently of each other. The refining agent is transported by an inert gas such as Ar gas from the supply hopper 10 and the refining agent transport line 11 Is connected to the oxygen gas line 9 for sub-holes. Fuel gas such as natural gas is supplied from the fuel gas supply line 12 and mixed with oxygen gas near the outlet of the sub-hole as shown in FIG. Reference numeral 13 denotes an inert gas line for transporting a refining agent, 14 denotes an oxygen gas jet ejected from a main hole, 15 denotes a flame formed from a sub hole, and 16 denotes a refining supplied to a molten steel surface through the flame. Shows the agent. The oxygen gas jet 14 and the flame 15 are hatched in FIGS. 2 and 4.

FIG. 3 is an explanatory view schematically showing the arrangement of main holes and sub holes on the lance heat receiving surface at the tip of the upper blowing lance.
Reference numeral 1 denotes an upper blowing lance main body, 2 denotes an oxygen gas ejection hole for decarburization (main hole), and 3 denotes a refining agent ejection hole (sub hole). The main hole is arranged on a concentric circle 17 centered on the lance central axis, and the sub hole is arranged so as to coincide with the lance central axis.

FIG. 4 shows a state (A) in which the oxygen gas ejected from the main hole is separated and a state (B) in which the oxygen gas ejected from the main hole is combined. In the case of coalescence, the flame of the sub hole and the oxygen of the main hole are united, and the flame of the sub hole is cooled by the oxygen gas from the main hole with a large flow rate and misfires, so the expected metallurgical effect is not obtained . On the other hand, in a state where the jet is separated, the refining agent passes through a high-temperature flame formed at the tip of the sub-hole, so that slagification proceeds. In other words, in this case, the refining agent stays in the flame for at least about 0.5 second because the flame formed at the tip of the sub-hole is long, so that the heat transfer sufficiently proceeds to the center of the refining agent and the molten steel is molten. Can be supplied.

The reason for limiting the numerical values in the invention described in claim 2 or claim 3 is to avoid coalescence of the jets as described above, and the specific reason is as follows.
That is, the reason why the number of the main holes is 4 to 8 is that if the number of the main holes is less than 4, the oxygen gas flow rate per one becomes large, so that the oxygen flow velocity when reaching the molten steel surface becomes large. This is because there are many splashes, which hinder the operation. When the number of the main holes is more than 8, the interval between the adjacent main holes becomes small, so that the jet flows are united, and the flame of the sub-hole is cooled and misfired as described above. This is because a sufficient metallurgical effect cannot be obtained.

The main hole is 12 to
It is necessary to incline at an angle θ of 20 degrees. If θ is smaller than 12 degrees, the main hole jets are united and the flame of the sub hole is cooled and misfired as described above, so that the desired metallurgical effect cannot be sufficiently obtained. . On the other hand, if θ is larger than 20 degrees, there is a problem that the refractory is worn because the fire point approaches the converter wall. here,
It is desirable that the sub-hole faces vertically downward. FIG. 5 shows the relationship between θ and phosphorus distribution. It can be seen that when θ is smaller than 12 degrees at which the jets merge, the phosphorus distribution is reduced. The phosphorus distribution can be determined by the following equation (1).

Phosphorus distribution = log (phosphorus concentration in slag / phosphorus concentration in molten steel) (1) As a refining agent supplied from the upper blowing lance, quick lime or the like may be supplied alone. On the other hand, in the invention according to claim 5, the powder is finally CaO-FeO, CaO-Mg.
O, CaO-FeO-MgO, CaO-FeO-Mn
It is intended to be supplied to a high temperature region as a mixture of O, CaO-FeO-MnO-MgO. When supplied as such a mixture, when the powders contact each other in the flame, because the melting point is reduced, it becomes easier to melt,
Moreover, since it is supplied to molten steel as a high-temperature molten mixture, it becomes a highly reactive refining agent. CaCO ₃ , MgCO
_{When 3} is used, the decomposition endothermic reaction takes place in the flame, so the flame temperature drops, but it does not lower the molten steel temperature, so inexpensive raw materials are used without hindering the heat tolerance of the converter. be able to. FeO may be Fe ₂ O ₃ or Fe ₃ O _{4 as} long as it is iron oxide.

CaO, CaCO ₃ , MgO, MgCO ₃
Is supplied as quicklime, limestone, dolomite, lightly burned dolomite, and iron oxide is iron ore, dust, M
nO is supplied as manganese ore. Further, the use of the pulverized slag such as converter slag makes it possible to simultaneously supply the above components.

[0021]

The present invention will be described below in detail with reference to examples.

Example 1 The following test was conducted in a 300 ton scale top-bottom blow converter. The upper blowing lance had four main holes with a diameter of 60 mm, θ was 16 degrees, and the oxygen supply rate from the main holes was 70000 Nm ³ / hr. The auxiliary hole is a single hole having a diameter of 55 mm at the center of the lance, and is a hole directed vertically downward. Oxygen is 6000 Nm ³ / hr, natural gas is 1000
Nm ³ / hr. As the refining agent, calcined lime powder and converter dust powder having a particle size of 100 mesh or less are used, the supply speed is 150 kg / min, and the transfer Ar is 1300 Nm ³ /.
hr. Bottom blowing using double tube tuyere and oxygen flow rate 35
00Nm ³ / hr.

The components subjected to the desulfurization treatment are as follows:
C = 4.2%, Si = 0.35%, Mn = 0.20%,
P = 0.091%, S = 0.011%, balance iron and unavoidable impurities. After charging hot metal at a temperature of 1350 ° C into the converter, it was fed from a top blowing lance and decarbonized. Blowing conditions were as follows: C = 0.5%, temperature = 1625 ° C., and the refining agent was supplied from the upper blowing lance subhole over a period of 80% during acid supply except immediately before blowing.

As a result, P at the time of blowing is 0.015.
%, Phosphorus partitioning 2.1, analyzed slag basicity 4.1.
The slag conversion was 90%. Here, the slagging ratio is calculated based on the amount of slag calculated from the Si balance, the amount of CaO in the furnace calculated from the analytical value of the CaO concentration in the slag, and the amount of Ca actually used.
It is the ratio of the total CaO amount of the values converted from O and CaCO ₃ .

Example 2 The following tests were conducted in a 300-ton scale top-bottom blow converter. The upper blowing lance had four main holes with a diameter of 60 mm, θ was 10 degrees, and the oxygen supply rate from the main holes was 70000 Nm ³ / hr. The secondary hole is
A single hole with a diameter of 55 mm at the center of the lance and directed vertically downward, oxygen 6000 Nm ³ / hr, natural gas 10
00Nm ³ / hr. As the refining agent, quick lime powder and blast furnace dust powder having a particle size of 100 mesh or less are used, the supply speed is 150 kg / min, and the transfer Ar is 1300 Nm.
³ / hr. Bottom blowing was performed using a double tube tuyere, and the oxygen flow rate was 3500 Nm ³ / hr.

The components subjected to the desulfurization treatment are as follows:
C = 4.3%, Si = 0.34%, Mn = 0.22%,
P = 0.095%, S = 0.013%, balance iron and inevitable impurities. After charging hot metal having a temperature of 1354 ° C to the converter, it was fed from a top-blowing lance and decarbonized. The blow stop conditions were C = 0.51% and temperature = 1625 ° C. The refining agent was supplied from the top blowing lance sub-hole over a period of 80% of the time during the acid feeding except immediately before the blowing.

As a result, P at the time of blowing is 0.025.
%, Phosphorus distribution 1.85, slag basicity analyzed 4.
At 0, the slagging rate was 81%.

(Example 3) The following tests were conducted in a 300-ton scale top-bottom blow converter. The upper blowing lance had four main holes with a diameter of 60 mm, θ was 16 degrees, and the oxygen supply rate from the main holes was 70000 Nm ³ / hr. The secondary hole is
A single hole with a diameter of 55 mm at the center of the lance and directed vertically downward, oxygen 6000 Nm ³ / hr, natural gas 10
00Nm ³ / hr. As the refining agent, quicklime powder having a particle size of 100 mesh or less is used, and the supply speed is 70 kg.
/ Min, and Ar for transfer was 700 Nm ³ / hr. Bottom blowing uses a double tube tuyere, and oxygen flow rate is 3500 Nm ³
/ Hr.

The components subjected to the desulfurization treatment are, in weight%,
C = 4.3%, Si = 0.34%, Mn = 0.19%,
P = 0.095%, S = 0.010%, balance iron and unavoidable impurities. After charging hot metal at a temperature of 1355 ° C to the converter, it was fed from a top blowing lance and decarbonized. The blowing conditions were C = 0.5% and temperature = 1630 ° C. The refining agent was supplied from the top blowing lance sub-hole over a period of 80% of the time during the acid feeding except immediately before the blowing.

As a result, P at the time of blowing was 0.022.
%, Phosphorus partitioning 1.95, slag basicity analyzed 4.
In 1, the slag conversion was 84%.

(Comparative Example 1) The following test was carried out in a 300-ton scale top-bottom blow converter. The upper blowing lance had four main holes with a diameter of 60 mm, θ was 16 degrees, and the oxygen supply rate from the main holes was 70000 Nm ³ / hr. The secondary hole is
A single hole with a diameter of 55 mm was formed at the center of the lance and directed vertically downward, but only oxygen was set to 6000 Nm ³ / hr. As a refining agent, massive quicklime and iron ore were used. The bottom blow is 2
The oxygen flow rate was 3500 Nm ³ / hr using a heavy tube tuyere.

After the de-Si treatment and the desulfurization treatment, the components are as follows: C = 4.3%, Si = 0.13%, Mn
= 0.21%, P = 0.095%, S = 0.011%,
The balance is iron and inevitable impurities, temperature is 1355 ° C
After charging the hot metal into the converter, the hot metal was fed from the upper blowing lance and decarburized. The blow stop conditions are as follows: C = 0.51%, temperature = 1622.
° C.

As a result, P at the time of blowing is 0.040.
%, Phosphorus distribution was 1.6, slag basicity was 3.3, and slagging rate was 72%.

(Comparative Example 2) The following test was conducted in a 300-ton scale top-bottom blow converter. The upper blowing lance had four main holes with a diameter of 60 mm, θ was 16 degrees, and the oxygen supply rate from the main holes was 70000 Nm ³ / hr. The secondary hole is
A single hole having a diameter of 55 mm is formed in the center of the lance and directed vertically downward. Oxygen is supplied from the sub-hole at 6000 Nm ³ / hr, and quicklime powder having a particle size of 100 mesh or less is supplied to the lance.
It was fed at a rate of 0 kg / min. Bottom blowing was performed using a double tube tuyere, and the oxygen flow rate was 3500 Nm ³ / hr.

After de-Si treatment and desulfurization treatment, the components were C = 4.3%, Si = 0.14%, Mn by weight%.
= 0.21%, P = 0.096%, S = 0.014%,
The balance is iron and inevitable impurities, temperature is 1365 ° C
After charging the hot metal into the converter, the hot metal was fed from the upper blowing lance and decarburized. The blow stop conditions are as follows: C = 0.51%, temperature = 1622.
° C. The refining agent was supplied from the top blowing lance sub-hole over a period of 80% of the time during the acid feeding except immediately before the blowing.

As a result, P at the time of blowing is 0.035.
%, Phosphorus distribution was 1.7, slag basicity was 3.45, and slagging rate was 76%.

[0037]

As described in detail above, according to the present invention, by supplying a refining flux having excellent slagging properties, efficient converter blowing can be performed. This is a valuable invention.

[Brief description of the drawings]

FIG. 1 is a diagram schematically illustrating a cross section of a lance according to an embodiment of the present invention.

FIG. 2 shows an example of an upper blowing lance for converter refining, a supply system of various gases and a refining agent to the lance, and a state of a flame formed at a tip of the lance during blowing, which is an embodiment of the present invention. FIG.

FIG. 3 is an explanatory view schematically showing an example of the arrangement of main holes and sub-holes on the lance heat receiving surface at the tip of the upper blowing lance of the present invention.

FIG. 4 is a diagram schematically illustrating a state in which oxygen gas ejected from a main hole is separated (A) and a state in which oxygen gas ejected from a main hole is combined (B).

FIG. 5 is a diagram showing an experimental result of a relationship between a tilt angle θ of a main hole and a distribution of phosphorus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Top blowing lance main body 2 Oxygen gas ejection hole for decarburization (main hole) 3 Refining agent ejection hole (sub hole) 4 Main hole oxygen gas channel 5 Secondary hole oxygen gas and refining agent channel 6 Fuel gas channel 7 Cooling Water flow path 8 Oxygen gas line for main hole 9 Oxygen gas line for sub hole 10 Refining agent supply hopper 11 Refining agent transport line 12 Fuel gas supply line 13 Ar supply line 14 Oxygen gas jet ejected from main hole 15 Formed from sub hole Flame 16 Refining agent supplied to molten steel surface through the flame 17 Concentric circle centered on lance center

Claims (6)

[Claims] 1. An oxygen jetting main hole and a flux supply sub-hole which is independent of a supply flow path of oxygen gas spouted from the main hole and which can simultaneously jet fuel gas, oxygen gas and refining flux. An upper-blown lance for converter refining, characterized by having: 2. Four to eight main holes for oxygen ejection are arranged on a concentric circle centered on a lance center axis on the lance heat receiving surface, and the flux supply sub-holes are arranged at the center of the concentric circle. The upper-blown lance for converter refining according to claim 1, wherein the blast is performed. 3. The central axis of the main hole is inclined at an angle of 12 to 20 degrees with respect to the central axis of the lance, and the central axis of the secondary hole coincides with the central axis of the lance. An upper blowing lance for refining a converter according to claim 2. 4. Using the upper blowing lance for converter refining according to any one of claims 1 to 3, the jets of oxygen gas jetted from the main holes for oxygen jetting are kept separated from each other. A refining flux is passed through the flame to promote slagging of the refining flux while forming a flame at the tip of the sub-hole independently of the oxygen gas jet. 5. The refining flux contains CaO, Ca
Contains one or two types of CO ₃ , and further includes iron oxide, MgO,
MgCO _3, converter refining process according to claim 4, characterized by using a mixture containing one or more of MnO. 6. The refining flux includes iron ore, pulverized slag, and dust generated at a steel mill (blast furnace dust, sintered dust,
The converter refining method according to claim 5, wherein the converter dust includes one or more of manganese ores.