JPH066730B2 - Desiliconization method in casting floor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of use> The present invention relates to a method of desiliconizing a casting bed in which a desiliconizing agent is injected into hot metal flowing in a hot metal ladle together with a carrier gas (hereinafter abbreviated as gas). .

<Prior Art> As a method of desiliconizing in a blast furnace casting, a technique has been developed in which an injection lance is immersed in hot metal flowing in a hot metal ladle and a desiliconizing agent is blown together with gas. JP 62-7809
Japanese Patent Laid-Open Publication No. 2003-242242 discloses a technique for preventing wear of a refractory material under a hot metal gutter by blowing a hot metal pretreatment agent laterally from the tip of an immersion lance. However, the present invention has a problem that the immersion portion of the lance is in contact with the gas ejected from the nozzle of the lance and has a short life. Therefore,
In order to solve this problem, the inventors of the present invention have previously filed Japanese Patent Application No. Sho 62-229743, in which a pretreatment agent injection nozzle is provided with a dipping lance in which a tip portion is projected so as to project laterally. We have proposed a hot metal pretreatment method that improves the silicon removal efficiency and extends the life of the lance. However, even when this method is used, there is a problem that it takes a long time to find a condition with good desiliconization efficiency when the operating conditions for desiliconization, for example, the particle size of the desiliconizer is changed.

<Problems to be Solved by the Invention> In the present invention, it is possible to select an immersion lance having a nozzle length and a nozzle diameter of a lance capable of quickly responding to changes in desiliconization operating conditions, and further reducing the carrier gas amount. In order to provide a desiliconizing method that can accelerate the desiliconizing agent by sufficiently accelerating the desiliconizing agent.

<Means for Solving the Problems> The present invention is a desiliconizing method in which a desiliconizing agent is blown laterally from the tip of an immersion lance into a hot metal flowing in a hot metal ladle along with a carrier gas in a desiliconizing operation condition. The relationship between the nozzle length created in advance for each particle size and density of the agent and the desiliconizing agent speed at the nozzle tip is shown for each carrier gas flow velocity at the nozzle tip, and a characteristic diagram with the desiliconizing agent entry speed limit is added. , A characteristic diagram showing the relationship between the nozzle diameter and the carrier gas flow rate for each carrier gas flow velocity at the nozzle tip, and the nozzle where the desiliconizing agent velocity at the nozzle tip exceeds the desiliconizing agent entry limit velocity This is a method of desiliconizing in a casting floor characterized by using an immersion lance satisfying the length and nozzle diameter. In the preceding paragraph, when there are multiple satisfying nozzle diameters, the carrier gas flow rate is small. It is a method of desiliconizing in a casting floor, which is characterized by using an immersion lance having a radius.

<Progress and Action of Making Invention> In the conventional desiliconization method in which the desiliconizing agent is blown into the hot metal flowing through the hot metal gutter together with the carrier gas, a considerable amount of decarburization reaction occurs in addition to the desiliconization reaction. It became clear as a result of the study by the present inventors. The relation between the decarburization efficiency and the desiliconization efficiency by the conventional method is shown in the "A" region of FIG. In the conventional method, of the effective oxygen amount (oxygen amount that can contribute to the reaction) contained in the desiliconizing agent,
25% to 35% are involved in the decarburization reaction. In order to improve the desiliconization efficiency, the reaction may proceed in the directions of (1) to (4) in FIG. However, the reaction efficiency of the desiliconizing agent (= desiliconizing efficiency +
Decarburization efficiency) is almost 80% as can be seen from the shape of area "A"
And has become constant. This is because if the reaction proceeds more than 80%, the viscosity of the desiliconization slag becomes extremely high and the reaction hardly occurs. It is impossible to move the area in the directions from) to (3).

Then, as a result of conducting a test to control the reaction in the direction of (4), it was found that reducing the gas amount was effective. However, if the gas amount is reduced too much, the tip speed of the nozzle 2 of the desiliconizing agent 5 becomes slow, the desiliconizing agent is trapped in the bubbles, breaks the bubbles 7 and cannot penetrate deeply into the hot metal 8, which lowers the reaction efficiency. It turned out that it came (see Fig. 6).

Therefore, the immersion lance is designed by using the relationship between the desiliconizing agent entry limit speed at which the desiliconizing agent penetrates into the hot metal, the gas flow rate to obtain the desiliconizing agent entry limit speed, and the nozzle length, which are obtained from the balance of forces. Then, the present invention has been completed with the knowledge that the operating conditions should be determined.

In the present invention, since a dipping lance having a nozzle length and a nozzle diameter capable of obtaining the entry limit speed of the desiliconizing agent based on the desiliconizing operating condition is used, it is possible to quickly change the desiliconizing operating condition. Even if the amount of gas is reduced, the desiliconizing agent can break through the bubbles and penetrate deeply into the hot metal to improve the desiliconizing rate.

<Examples> Acceleration distance (nozzle length) l (mm) and nozzle tip speed Vr (m of desiliconizing agent when desiliconizing agent (particle size 100 μm, density 3300 kg / m ³ ) was exposed to each gas flow velocity / S) first relationship
As shown in the figure. When Vr ≧ 13 (m / s), the desiliconizing agent can penetrate into the hot metal. Vr ≧ 13 is the gas flow velocity 50,
For 60, 70, 80 (m / s), acceleration distance (nozzle length)
l is 120, 80, 65, 55 mm or more, respectively. When designing the immersion lance, it is better to add 10 to 20 mm to this length in consideration of melting loss at the nozzle tip.

If the nozzle diameter is the same, it is better to reduce the gas flow velocity (m / s) at the nozzle tip in order to reduce the gas flow rate.
As is clear from FIG. 1, if it is small, the acceleration distance (nozzle length) becomes long, the immersion lance becomes large, and it becomes difficult to handle, so an appropriate gas flow rate may be selected in consideration of the equipment.

FIG. 2 shows a nozzle diameter d (m) and a gas flow rate G (N) for obtaining a predetermined gas flow velocity in each nozzle portion in the case of a two-port lance.
m ³ / min). For example, from Figure 1, the gas flow rate is 6
Assuming that 0m / s is selected, the gas flow velocity at the nozzle is 60
When expressed as a combination of nozzle diameter and gas flow rate (d, G) to achieve m / s, (0.02 m, 2.5 Nm ³ / min), (0.
015 m, 1.4 Nm ³ / min) is obtained. In this way, the nozzle diameter and the gas flow rate may be determined.

In FIG. 5, in order to promote the reaction in the direction of (4) and increase the desiliconization rate, it is necessary to decrease the gas flow rate G, so in this example, the direction of (0.02, 2.5) → (0.015, 1.4) is used. It should be improved. That is, the immersion lance shown in Fig. 3 (a) is used in Fig. 3 (b).
It would be better to change to the immersion lance shown in.

The feature of the present invention is that when the particle size of desiliconizing agent, the gas amount, the nozzle diameter, etc., which are the operating conditions, are changed, a diagram such as those shown in FIGS. 1 and 2 is prepared according to the conditions to be changed in advance. By setting it, it is possible to quickly shift to optimum operating conditions.

Specific examples of the present invention will be described below.

Fig. 4 (b) shows the transition of desiliconization efficiency by the conventional method when changing the desiliconizing agent (particle size: 100 μm → 30 μm, density: 3300 kg / m ³ ). Conventionally, the nozzle diameter and gas amount of the immersion lance were changed and improved by trial and error after changing the desiliconizing agent, so it took about two months to obtain optimum operating conditions. Fourth
Figure (a) Reduced the gas amount when changing the desiliconizing agent (2.5 Nm ³ / min
→ 1.4 Nm ³ / min) The transition of desiliconization efficiency by the method of the present invention was shown. In this case, the diagrams of Figs. 1 and 2 were prepared in advance and the optimum operating conditions were determined, so it took only half a month to obtain the optimum conditions.

The relationship between the desiliconization efficiency and the decarburization efficiency at this time is shown in the area "B" in FIG. The operating conditions at this time are: nozzle diameter: 0.01
5 m, accelerating distance: 0.1 m, gas flow rate: 1.4 Nm ³ / min, desiliconizing agent blowing speed: 50 kg / min, and desiliconizing efficiency of 60 to 65% could be obtained. Before the change, the nozzle diameter was 0.02 m, the acceleration distance was 0.1 m, the gas flow rate was 2.5 Nm ³ / min, and the desiliconizing agent injection speed was 60 k.
Desiliconization efficiency was 49-55% at g / min.

As is apparent from the above, according to the present invention, it is possible to quickly shift to the optimum operating conditions when changing the desiliconizing operating conditions, and it is possible to improve the desiliconizing efficiency even when the gas flow rate is reduced.

Although the embodiment of the present invention has been described above with respect to the desiliconization operation, this is not limited to the desiliconization operation at all, and the present invention is also applied to hot metal pretreatment (decontamination, desulfurization) performed by a similar method. It is possible to

In addition, although the immersion lance has been shown as an example of a two-neck lance,
The present invention can also be applied to the case of a multiple mouth lance such as a mouth or a four mouth or a single mouth lance.

<Effects of the Invention> According to the present invention, it was possible to quickly shift the optimum operating conditions when changing the silicon removal operating conditions. Further, even when the gas flow rate was decreased, the desiliconizing agent could be sufficiently accelerated and blown in, and the desiliconizing efficiency could be improved.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing the relationship between the nozzle tip speed Vr of the desiliconizing agent and the nozzle length 1 at each gas flow velocity, which is the basis of the lance design of the present invention. FIG. 2 shows each gas flow velocity. A characteristic diagram showing the relationship between the obtained gas flow rate G and the nozzle diameter d, FIG. 3 is a schematic sectional view showing the shape of the immersion lance before and after improvement, and FIG. 4 is
A characteristic diagram showing the transition of desiliconization efficiency by the conventional method (b) and the method (a) of the present invention, FIG. 5 is a characteristic diagram showing the relationship between decarburization efficiency and desiliconization efficiency, and FIG. 6 is It is a schematic diagram showing the situation where a desiliconizing agent is blown. DESCRIPTION OF SYMBOLS 1 ... Immersion lance, 2 ... Nozzle, 3 ... Desiliconizing agent transport pipe, 4 ... Refractory material, 5 ... Desiliconizing agent, 6 ... Desiliconizing agent trapped in air bubbles, 7 ... Air bubbles, 8 ... Hot metal, 9 … Hot metal gutter.

Claims (2)

[Claims] 1. A desiliconizing method in which a desiliconizing agent is blown sideways from the tip of an immersion lance together with a carrier gas into the hot metal flowing in the hot metal launder, in a desiliconizing operating condition based on the particle size and density of the desiliconizing agent. The relationship between the nozzle length created in advance and the desiliconizing agent velocity at the nozzle tip is shown for each carrier gas flow velocity at the nozzle tip, and the characteristic diagram with the desiliconizing agent entry limit velocity is added, and the nozzle diameter and carrier gas flow rate Of the carrier gas flow velocity at the tip of the nozzle and the characteristic diagram that is shown for each nozzle, satisfy the nozzle length and nozzle diameter at which the desiliconizing agent velocity at the nozzle tip exceeds the desiliconizing agent entry limit velocity. A method of desiliconizing in a casting floor characterized by using an immersion lance. 2. The method of desiliconizing in a casting floor according to claim 1, wherein when there are a plurality of satisfying nozzle diameters, an immersion lance having a nozzle diameter with a small carrier gas flow rate is used.