JPS6133043B2 - - Google Patents

Description

[Detailed Description of the Invention] In recent years, in order to obtain high quality steel in the steel manufacturing process,
Additionally, hot metal dephosphorization technology is rapidly progressing to reduce refining costs.

The present invention relates to a method for dephosphorizing hot metal, and aims to enable dephosphorization of hot metal with higher efficiency.

As is well known, the dephosphorization reaction of hot metal is an oxidation reaction represented by the following equation (1): 2(P)+5(O)+4(CaO) →(4CaO・P ₂ O ₅ )...(1) A dephosphorizing agent mainly composed of lime and lime is required, and the important factors in the treatment method are how to stir the hot metal, add the dephosphorizing agent, and add oxygen to ensure the reaction is carried out efficiently. Become.

In general, methods for stirring hot metal, adding dephosphorizing agents, and adding oxygen for refining are broadly classified as follows.

(1) As a stirring method: (a) Inject gas using an immersion lance.

(b) Immerse and rotate the stirring blade.

(2) How to add dephosphorizing agent: (a) Blow into the bath through an immersion lance.

(b) Pour from above the bath surface.

(3) As a method of adding oxygen: (a) Solid iron oxide is injected through an immersion lance.

(b) Pour solid iron oxide from above the bath surface.

(c) Gaseous oxygen is sprayed from above the bath surface.

(d) Gaseous oxygen is blown into the bath through a double tube nozzle using an immersion lance.

The present invention relates to an agitation treatment method using an immersed rotary blade, and its feature is that a powdered dephosphorizing agent is blown into a bath using pure oxygen gas through nozzles provided radially on a rotary body. There is a particular thing. That is, it is possible to obtain high treatment efficiency due to the synergistic effect of the rotation of the rotary blade and the stirring by the blown gas, and the dephosphorization reaction effect due to the simultaneous injection of pure oxygen gas and the dephosphorizing agent.

FIG. 4 shows an example of an apparatus for carrying out the method of the invention. 1 is a ladle, 2 is hot metal, 3 is a rotor,
4 is a nozzle, 5 is a drive device, 6 is a rotary joint, and 7 is a dephosphorizing agent.

Conventionally, there is a method disclosed in Japanese Patent Publication No. 47-51681 as an example of blowing stirring gas and refining agent from a rotary blade. This is a molten steel processing method in which a desulfurizing agent, a dephosphorizing agent, a deoxidizing agent, and an alloy composition adjusting agent are injected using high-pressure inert gas from a rotary blade, and is different from the present invention, which is based on the injecting of pure oxygen gas. It is something to do.

In other words, conventionally, in order to inject pure oxygen gas into molten iron,
In order to avoid erosion of the blowing nozzle, it was essential to use a double pipe nozzle due to the need for cooling gas. In this case, the method of connecting multiple fluid pipes to the rotating body is complicated in terms of equipment, which has hindered its practical application. It was limited to inert gas injection.

One of the significances of the invention is that it makes it possible to inject pure oxygen gas from a particularly single tube nozzle mounted on a rotating blade. The corrosion damage of pure oxygen injection nozzles is thought to be due to the fact that the nozzle tip reaches a high temperature due to the refining reaction, and that molten iron comes into contact with and enters the nozzle, and is oxidized and burned by oxygen gas.

The present inventor conducted various basic experiments to investigate the jetting behavior of the nozzle tip when powdered material is injected, and found favorable characteristics and conditions for the powdered material to be jetted out as a high-density layer along the inner wall of the nozzle. This characteristic has a tremendous effect on cooling the nozzle tip and preventing contact and intrusion of hot metal. When blowing into hot metal from a nozzle installed on a rotor, Qo ₂ 70×A .........Equation (2) W _f 2.0×Qo ₂ It was found that melting loss could be avoided under the condition of formula (3). (Fig. 1) Here, Qo ₂ : Pure oxygen gas flow rate (Kg/Hr) A: Nozzle cross-sectional area (cm ² ) W _f : Dephosphorizing agent blowing rate (Kg/Hr) Qo ₂ <70×A, nozzle The linear gas flow velocity at the tip is low, making it easier for hot metal to contact and enter the nozzle. In addition, when W _f < _2.0 It has become clear that melting damage can be avoided by blowing under conditions that simultaneously satisfy equations ) and (3).

Another significance of the present invention is that by setting the blade length and rotational speed of the rotor to appropriate conditions, it is possible to reduce the splash of hot metal that occurs due to gas injection, and to inject a large amount of gas. This makes it possible to perform dephosphorization treatment by

As is well known, refining by gas injection has the advantage that strong stirring power can be easily obtained, but there is a problem in that the hot metal flows out of the container due to the occurrence of a violent splash phenomenon. It is customary to implement this with a certain amount of free space (free board).

According to the inventor's experience, the required freeboard height is when hot metal is charged into a ladle with a diameter of 3.5 m and pure oxygen gas is blown into it using an immersion lance under the conditions of formulas (1) and (2). The results shown in Figure 2 were obtained. The height of the ladle is
When charging 3.5 m and 150 tons of hot metal, the freeboard height was 1.2 m, and pure oxygen injection of 400 Nm ³ /Hr was the limit.

The present invention is characterized by blowing pure oxygen gas through a nozzle provided on a rotary blade.By blowing while rotating, the gas is dispersed in the bath, and conditions are created to reduce the generation of splash. I found it.

The preferred conditions for dispersing gas are determined by the rotor blade length (L) and rotational speed (R), and the third
As shown in the figure, for a rotor blade with L=1.2m, R=
It was found that at 25 rpm and L = 0.6 m, the splash rapidly decreased at R = 50 rpm or higher, and the freeboard height could be reduced.

In this way, the region where the occurrence of splashes rapidly decreases depending on the blade length and rotational speed can be summarized by L×R30. In other words, this is an index representing the circumferential speed at the blade tip, and it is thought that the shearing force of the hot metal flow at the blade tip finely disperses the gas flow.
However, as L×R is increased, the vortex generated by the rotation becomes larger, the bulge of hot metal at the pot measuring wall becomes higher, and the hot metal flows out.
It is preferable to treat with ×R180. As a result, when performing dephosphorization treatment using the ladle described above, it has become possible to blow pure oxygen gas at a maximum of 1500Nm ³ /Hr.

As described above, the present invention is a treatment method in which pure oxygen gas and a dephosphorizing agent are blown into a nozzle provided on a stirring rotor, and an operation of Qo ₂ 70 × A W _f 2.0 × Qo ₂ 30 (L × R) 180 This allows pure oxygen gas and dephosphorizing agent for refining to be injected into the bath from the stirring rotor while avoiding erosion of the injection nozzle. Excellent effects such as being able to inject a large amount of gas even if the freeboard of the container is small can be obtained.

[Brief explanation of the drawing]

Figure 1 shows the relationship between pure oxygen flow rate Qo, nozzle cross-sectional area A, dephosphorizing agent blowing speed W _f , and the presence or absence of nozzle erosion (● mark: no nozzle erosion damage, × mark: nozzle erosion damage) . Figure 2 shows the required height of the ladle freeboard when pure oxygen gas is blown through the immersion lance.
FIG. 3 shows the relationship between the rotor blade length L, the rotation speed R, and the required height of the ladle freeboard, and a conceptual diagram of the rotor blade (N in the figure is a nozzle). FIG. 4 shows an overview of the entire device.

Claims (1)

[Claims] 1. A stirring body having radial blades is rotated in hot metal, and a dephosphorizing agent is blown into the hot metal using pure oxygen gas as a carrier through nozzles radially bored in the stirring body, In the dephosphorization method using blade stirring, (1) Qo ₂ 70×A (2) W _f 2.0×Qo ₂ (3) 30 (L×R) 180 Qo ₂ : Pure oxygen flow rate (Kg/Hr) A: Nozzle cross-sectional area (cm ² ) W _f : Dephosphorizing agent blowing speed (Kg/Hr) L : Rotating blade length (m) R : Rotating blade rotation speed (rpm) Dephosphorization method.