JPS6235448B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a bottom-blowing nozzle installed in a molten metal refining furnace such as a top-bottom blowing converter, in which an inert gas is applied to the outer periphery of the nozzle (the nozzle and its vicinity) in order to suppress melting damage of the nozzle. This is an improved gas injection method that aims to reduce the phenomenon of bottoming out of refractories and suppress their erosion by ensuring the gas injection flow velocity is in the sonic range. Regarding the method.

It is known that bottom-blowing nozzles for molten metal refining, which are conventionally used in top-bottom blowing converters and the like, suffer from severe erosion when blowing oxidizing gas. Therefore, in the conventional double-tube nozzle shown in Fig. 1, an oxidizing gas such as O ₂ is used in the inner tube 1, and a cooling gas (hydrocarbon, etc.) or an inert gas is used in the outer tube 2. This suppressed melting loss. Also, the second
A conventional multi-hole plug (hereinafter referred to as a nozzle) as shown in Figures a and b has multiple through holes 9.
A pressure box 11 is made of a stainless steel pipe and is buried in a suitable position in the refractory 10, and a pressure box 11 is made of an iron plate and communicates with the through hole 9 at the bottom, from which one type of gas is blown. Nozzle 5 was configured. Note that 6 is a wound iron plate that covers the outer periphery of the nozzle 5 , and 7 is an outer sleeve that is further provided on the outer periphery. Further, 3 is a furnace bottom iron shell, and 4 is a furnace pit brick. However, with the conventional nozzle 5 having such a structure, when CO ₂ is injected, FeO is generated near the operating surface, leading to preliminary melting loss 8 at the joints as shown in _FIG . Acts as an oxidizing gas. This effect is particularly likely to appear at the joint between the nozzle 5 and the tuyere brick. This is because the joints are mortar or open joints, which have poor strength and oxidation resistance. In addition, since the nozzle 5 may be operated with the blown gas flow rate reduced to about 0.3 Nm ³ /hr per hole, the nozzle refractory 10 may be hit bottom as shown in FIG. 4b. There was a problem that this further accelerated the melting loss.

The present invention has been made in order to improve the above problem, and has a plurality of through holes, and the through hole in the outer peripheral part and the through hole in the central part are used as separate systems for gas injection. Gas blowing into molten metal characterized by blowing an inert gas such as Ar or N ₂ through a through hole in the outer periphery of the nozzle, and blowing an oxidizing gas such as CO ₂ through a through hole in the center of the nozzle. A method for producing molten metal, which is characterized in that the flow velocity of an inert gas such as Ar or N, which is blown through the through-holes on the outer periphery of a nozzle having a plurality of through-holes, is equal to or higher than the speed of sound (330 m/sec). This is the gas injection method.

Next, the molten metal refining nozzle of the present invention will be explained based on the embodiment shown in FIG. Reference numerals in the drawings that are common to those of the conventional nozzle in FIG. 1 indicate members of the same shape or function. That is, 9 is a plurality of through holes, and 10 is a refractory in which a plurality of the through holes 9 are arranged and embedded at appropriate positions. 6
is a wrapped iron plate that covers the outer periphery of the refractory 10. Reference numeral 12 designates a pressure box provided at the bottom of the through hole 9 so as to conduct it to the center thereof, and reference numeral 13 designates a pressure box provided at the bottom thereof so that it conducts to the object located at the outer periphery of the through hole 9. be. Gas supply sources of separate systems are connected to these pressure boxes 12 and 13, respectively, to constitute the nozzle 5 of the present invention. 14 is a sleeve portion.

Next, a method of blowing gas into the furnace using the above-mentioned nozzle 5 of the present invention will be explained. As shown in FIG. 5, in the gas blowing method of the present invention, an inert gas such as Ar or _N2 is blown into a pressure box 13 which is connected to a through hole in the outer peripheral part, and a pressure box 12 which is connected to a through hole in the center part. This method injects oxidizing gas such as CO ₂ .

FIG. 6 shows an example of a gas blowing pattern according to the gas blowing method of the present invention, and if such a blowing method is adopted, the melting damage at the joint will be reduced to the preceding melting damage portion as shown in FIG. is not generated, but is instead covered by the gas jetting 8'.

In addition, FIG. 8 shows the gas blowing pattern of FIG.
The blowing flow rate of inert gas such as Ar and _N2 is set to the sonic speed (330
This figure shows a comparison of the nozzle erosion rate when the gas flow is jetted to eliminate the bottom-striking phenomenon (m/sec) or higher, and when gas is injected using a conventional method using a conventional nozzle. .

Figure 9 shows a comparison of the nozzle erosion rate when the gas blowing method of the present invention is used as described above and the nozzle erosion rate when gas blowing is performed using a conventional nozzle and the conventional method. It is something.

As is clear from FIGS. 8 and 9, when gas blowing according to the present invention is performed, the nozzle erosion rate is slower than when gas blowing is performed using the conventional method, and its service life is significantly extended. Ta.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway perspective view of a conventional double pipe nozzle, and Fig. 2 shows a conventional multi-hole plug.
A is a vertical cross-sectional view, and b is a cross-sectional view. Fig. 3 is a vertical cross-sectional view showing the preliminary erosion of the joint part in the conventional gas blowing method, and Fig. 4 a and b are explanations showing the bottom knocking phenomenon during gas jetting and bubbling in the conventional gas blowing method. 5 is a vertical cross-sectional view of a multi-hole plug, FIG. 6 is a pattern diagram showing an example of a gas blowing pattern by the gas blowing method of the present invention, and FIG. 7 is a joint part by the gas blowing method of the present invention. FIG. 8 is a graph showing the relationship between the flow velocity during gas injection and the melting loss rate, and FIG. 9 is a graph showing the relationship between the molten steel temperature and the melting loss rate during refining. 9...Through hole, 10...Refractory, 12...Central pressure box, 13...Outer pressure box, 5 ...Nozzle, 6...Wrapped iron plate.

Claims (1)

[Claims] 1. In a nozzle that has a plurality of through holes and uses a through hole in the outer periphery and a through hole in the center as separate systems for gas injection, A method for blowing gas into molten metal, which is characterized by blowing an inert gas such as CO ₂ into the molten metal and blowing an oxidizing gas such as CO ₂ through a through hole in the center. 2. Claim 1, characterized in that the flow velocity of the inert gas such as Ar, N, etc. blown through the through-holes on the outer periphery of a nozzle having a plurality of through-holes is equal to or higher than the speed of sound (330 m/sec). The method of blowing gas into molten metal as described.