JPS6187809A - Treatment of molten metal - Google Patents

Abstract

PURPOSE:To prevent the spilling of a molten metal occuring in the build-up of a molten metal surface by adjusting the distance from the top end edge at the aperture of an open vessel to the static molten metal surface by the specific equation in the stage of blowing a gas to the molten metal in said vessel. CONSTITUTION:A lance 2 is plunged into the molten metal M in the open vessel 1 and the gas G is blown therethrough to treat the molten metal M. The molten metal surface L builds locally up to a height H when the gas G is blown into the vessel. There is the possibility of the rise of the vertex thereof in excess of the top end line 1h at the aperture of the vessel 1 and the overflowing of the molten metal M to the outside of the vessel 1. The distance (y) from the line 1h to the molten metal surface L is thereupon adjusted by the equations I, II. In the equation II, Q: the flow rate of the gas (l/min), Tl; the temp. of the molten metal ( deg.K), Ml: the weight of the molten metal (ton), pl: the density of the molten metal (g/cm<3>), Z: the depth of gas blowing when viewed from the molten metal surface (cm), Tg: the temp. of the blowing gas ( deg.K). The spilling of the molten metal as a result of the gas blowing is thus prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for treating molten metal, and is particularly applicable to treating molten pig iron or molten steel by a gas injection method or (gas + powder) injection method. This invention relates to a gas blowing control method.

[Conventional technology]

When performing desiliconization, desulfurization, dephosphorization, etc. of hot metal, the hot metal is stirred by a gas bubbling method or In some cases, a desiliconizing agent or the like is blown into the hot metal together with a carrier gas. Also known is a method in which powdered coal and oxygen are injected into molten steel for the purpose of increasing the temperature of the molten steel after polishing treatment to facilitate subsequent handling of the molten steel. FIG. 1 is a schematic vertical cross-sectional view showing the gas blowing situation in such a case, in which a blowing lance 2 is plunged into the molten metal M in an open container (such as a ladle), and a blowing lance 2 is installed at the tip of the lance 2. Gas G is blown from the nozzle into the metal melt into f. The injected gas G rises in the molten metal M and dissipates from the surface of the metal into the atmosphere, but the upward flow of the gas G causes the surface to locally rise significantly. The height H of this protrusion varies depending on the gas blowing speed, the immersion depth of the lance 2, the density of the molten metal M, etc., but the peak of the protrusion should be above the opening top line 1h of the open container 1. If this happens, there is a risk that the molten metal λ1 will overflow into the container (1). Therefore, in the past, the surface of the molten metal was adjusted so that the top of the protrusion did not come above the opening upper line 1h. The amount of molten metal charged into the container l is adjusted so that there is a gap (free board) of a certain length or more between the opening upper end lines 1h.

[Problem that the invention seeks to solve]

By the way, as mentioned above, the height of the bulge in the scene varies considerably depending on the gas injection speed, the immersion depth of the lance, etc., but until now it has not been possible to accurately predict the bulge height, and empirical Since the free board was adjusted based on "feel", the height of the protrusion of the curve sometimes exceeded the free board, exposing the player to the risk of hot water spilling.

The present invention aims to solve these problems,
The objective is to establish a method that calculates the height of the rise of the hot water surface from various conditions during gas injection and controls the rise height so that it does not exceed the freeboard.

[Means to solve the problem]

The present invention provides a method for treating molten metal in an open container by blowing gas into it, in which the depth from the upper edge of the opening of the container to the curved surface, that is, the freeboard: y) shown below is CI) and CI
The key point is to adjust the amount of molten metal charged, the flow rate of blown gas, the blown gas temperature, and the depth of gas blown as seen from the molten metal surface so as to satisfy the relational expression D.

y≧as, 9tx; 0°692...(T'l)
Q: Gas flow rate (l!/min) T: Molten metal temperature (・K) Ml: Molten metal charging amount (tons) ρI! : Density of melted island (y/cm3) Z: Gas blowing temperature from the surface (cm) T8: Blowing gas temperature (・K) [Effect] According to the research carried out by the present inventors, The height of the molten metal surface elevation is determined by the formula [■] above, based on the blown gas flow rate, molten metal temperature, molten metal charge amount, molten metal density, gas injection depth as seen from the molten metal surface, and blown gas temperature. It has a close relationship with the stirring power value (:) that can be determined.
It has been confirmed that by adjusting the gas injection conditions and the capacity of the processing container so that this value is below a certain level, it is possible to reliably suppress the height of the rise of the hot water surface to below the above-mentioned freeboard. In other words, the second factor is that the stirring power value (
:) and the height of the scene elevation) are arranged and graphed, and there is a certain correlation between the two as shown in the figure, and the relationship is as shown in the following equation [111].

H=38.91Xε...ClIDHere, in order to prevent the molten metal from overflowing, the free board (
Since it is necessary to adjust so that 2) is equal to or higher than the scene elevation height (I), adding this requirement leads to the following formula [■], that is, the above-mentioned formula 13.

・0.692 y≧H-=-38,91Xε ...(ff') In other words, if the various conditions necessary to obtain the specified refining effect are determined in advance, formula (II) can be calculated from these conditions. Calculate the stirring power value, apply this value to the equation 19 above to calculate the scene elevation height 6), and adjust the processing vessel so that a free board (y) with the elevation height α or more is obtained. All you need to do is decide on the container or amount of molten metal to be charged.On the other hand, if the container for the processing container has already been determined, the gas injection conditions (injection gas flow rate, injection gas Adjust the temperature and the blowing depth of the lance, etc.), and set the height of the raised surface freeboard υ)
The risk of lagoon spillage can be eliminated by making the following adjustments.

Figure 3.4 shows the gas blowing conditions that can be easily controlled: the blowing gas flow rate (Q) and the depth of the gas blowing port as seen from the hot water surface, i.e. the immersion depth of the blowing lance: Z.
) shows the influence of ) on the stirring power value.
Other gas injection conditions were as shown in Table 1 below.

Table 1, Koikuchi 1928' 7.2, 298 No. 3
．． As is clear from Figure 4, there is a certain correlation between the flow of the blown gas, the immersion depth of the lance, and the total stirring power value, so the free board is determined by the capacity of the processing vessel and the molten metal charging n. By adjusting the total stirring power value by changing the gas flow n and the lance immersion depth according to 0), the lagoon surface elevation height 6) is controlled so that it does not exceed the freeboard (y). be able to. On the other hand, if the stirring power value is determined from the requirements for processing efficiency, the free board that exceeds the lagoon height 9) according to the lagoon elevation height 6) that is inevitably determined from the power value. By adjusting the capacity of the processing container or the amount of molten metal charged so as to obtain the following, the risk of hot water spilling can be eliminated.

Since the nozzle diameter of the gas blowing lance has no relation to the stirring power value, the nozzle diameter may be determined mainly from the viewpoint of "prevention of nozzle clogging." In other words, nozzle blockage occurs when the molten metal enters the nozzle and solidifies. In order to prevent this nozzle blockage, a pressure higher than the static pressure of the molten metal applied to the nozzle surrounding surface of the immersion lance is applied. Just blow in some gas. Therefore, if the flow rate of the blown gas is determined as described above, depending on this flow rate, the density of the molten metal to be treated, the immersion depth of the lance, etc., a gas blown pressure that exceeds the static pressure of the molten metal applied to the nozzle opening surface can be obtained. By adjusting the opening surface of the nozzle in this way, it is possible to prevent the nozzle from becoming clogged due to intrusion of molten metal. In the above description, the case where the gas is blown using a lance has been described, but the same can be applied to the case where the gas is blown from a bottom blowing nozzle provided at the bottom of the container.

〔Effect of the invention〕

The present invention is constructed as described above, but the point is that the height of the lagoon surface elevation caused by gas injection can be predicted theoretically and accurately according to the injection conditions, and also by changing the injection conditions. Since the height of the raised surface can be adjusted and the processing conditions can be controlled so that it does not exceed the freeboard of the processing vessel, it is possible to eliminate spillage caused by the raised surface of the hot water.

[Brief explanation of drawings]

Figure 1 is a schematic cross-sectional view showing the gas injection treatment status of molten metal, Figure 2 is a graph showing the relationship between the stirring island force value and the height of the molten bulge, and Figure 3.4 is the gas flow rate and lance thrust. It is a graph showing the influence that depth has on the total stirring power value. l...processing container, 2...lance, SL...
Molten surface. Applicant: Hisashi Ueki, Patent Attorney, Kobe Seisaku Co., Ltd. 41, 1<Yuuhi＼ Figure 3: Gas flow rate (Nm/Hr) Figure 4: Depth of drawer plunger) (Volunteer) August 38, 1985 1. Indication of the case 1988 Patent Application No. 200797 2. Name of the invention Method for processing molten metal 3. Person making the amendment Relationship to the case Patent applicant Wakihama-cho-chome, Chuo-ku, Kobe City No. 3-18 (J19) Kobe Steel, Ltd. Representative: Fuyuhiko Maki 4, Agent: Shinko Building, 2-3-7 Dojima, Kita-ku, Osaka 530 "Claims" and "Details of the Invention" The columns of ``Brief Description of Drawings'' and ``Brief Description of Drawings'' as well as Claims (1) ``Claims'' will be corrected as shown in the attached sheet. (2) Error in page 4, line 15 of specification: X (I n (1+O, 0O09138 correct:
×(Seen (1+0.0O09BB(3) Error in the bottom line of page 4 of the same page: Molten metal charge amount is correct: Molten metal weight (4) Error in line 7 of page 5 of the same page: Molten metal charge amount is correct: Molten metal charge amount ( Weight) (5) Wrong line 15 on page 9: Lance thrust depth correct: Gas injection depth 6) In the drawings, Figures 3 and 4 are interpolated with the attached Figures 3 and 4. When treating molten metal in an open container by blowing gas into it, the distance fffl (
Processing of molten metal characterized by adjusting the molten metal charging, the blown gas flow rate, the blown gas temperature, and the gas blown depth as seen from the molten metal surface so that y) satisfies the following relational expression. Method. y≧38.91 l: Molten metal density (g/cm3) Z: Gas injection depth cm as seen from @ surface) Tg: Blowing gas temperature (0K) Oto 20 30 40 50 60
70 80 Ganu style Yu (Nm”/Hr)

Claims (1)

[Scope of Claims] When treating the molten metal in an open container by blowing gas into it, the amount of molten metal charged is determined such that the distance (y) from the upper edge of the opening of the container to the static molten metal level satisfies the following relational expression: A method for treating molten metal, characterized by adjusting the flow rate of the blown gas, the temperature of the blown gas, and the depth of the gas blown as seen from the surface of the molten metal. y≧38.91×■＾0＾. ^6^9^2 ■=(0.0062・Q・T_l)/M_l×{In(
1+0.000968・ρ_l・Z)+(1−T_g/
T_l)} Q: Gas flow rate (l/min) T_l: Molten metal temperature (°K) M_l: Molten metal charge amount (tons) ρ_l: Molten metal density (g/cm^3) Z: Depth of gas inlet seen from the molten metal surface (cm) T_g: Blowing gas temperature (°K)