JPS6360091B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a tuyere installed at the bottom of an electric furnace for steelmaking to blow gas into molten steel, and particularly relates to a gas discharge capillary embedded in the tuyere. This invention relates to a tuyere which is separated in the length direction and insulated.

(Prior art) Gas injection refractories (tuyeres) made of refractories have traditionally been installed at the bottom of converters, etc. to stir the molten metal for the purpose of decarburization or reaction promotion when refining molten metal. It is widely practiced to blow various gases into the tank.

Many types of tuyeres for blowing gas are known, such as porous plugs, pore-through tuyeres, thin tube porous tuyeres, tuyeres made of plate-shaped bodies pasted together to form slits, and double-tube nozzles.

(Problems with the prior art) These tuyeres are equipped with gas discharge tubes such as metal pipes on the inner periphery to increase the strength of the tuyere, or to increase the strength of the tuyeres by using gas (for example, oxygen) to ―
Since the carbon in the refractory (C+O 2 →CO 2 ) reacts with oxygen, deterioration of the refractory (C+O ₂ →CO ₂ ) may be prevented. However, if the above-mentioned tuyeres are used as they are in an electric furnace, there is a danger that conduction will occur between the molten metal and the outside of the furnace body, and the scouring arc current, etc. will short-pass as an induced current through the gas discharge capillary, which will impede the operation of the electric furnace. There is sex.

(Means for Solving the Problems) The present invention has a conductive gas discharge capillary that fits into a required number of gas discharge passages, and is fitted into an opening on the lower surface of an electric furnace to form a gas distribution chamber. In the bottom blowing tuyere of an electric furnace, which is made of a refractory layer that communicates with the inside of the furnace, the gas discharge thin tubes that fit into each gas discharge passage are separated in the length direction. be.

The gas discharge capillary in the present invention is made of a conductive material such as stainless steel or other metal and is formed into a pipe shape with a relatively small inner diameter.
- They are fitted into the required number of gas discharge passages of a tuyere having a refractory layer made of C or the like in a state in which they are separated in the length direction.

The method for fitting this separated gas discharge thin tube into the tuyere is, for example, as follows. The proximal end of the lower gas discharge capillary, which is cut into the required number of upper gas discharge capillaries and lower gas discharge capillaries at a predetermined length, is fixed to the gas distribution chamber by conventional means such as welding, screwing, or caulking. A wire whose outer diameter is the same as the inner diameter of the gas discharge tube is cut into a long length and inserted into the gas discharge tube so that the upper gas discharge tube and the lower gas discharge tube communicate with each other. A predetermined gap is provided at a position where the upper gas discharge capillary is separated from the upper gas discharge capillary, and the tip of the upper gas discharge capillary is arranged so as to match the outline of the operating surface of the tuyere. Then, the outer periphery is MgO-C, MgO, MgO-Cr ₂ O ₃
Alternatively, after forming a tuyere shape by lining it with a refractory material such as high alumina, the wire inserted into the gas discharge capillary is pulled out and passed through the gas discharge passage.

It is desirable to increase the number of gas discharge thin tubes mentioned above in order to narrow the gas discharge interval and widen the discharge range, but there is a natural limit to increasing the number from a manufacturing and construction perspective. In addition, if too many gas discharge tubes are provided, the gas discharge tubes will be in close contact with each other, and it will not be possible to sufficiently fill the spaces between the gas discharge tubes with refractory material during tuyere manufacturing, resulting in a low packing density, which will reduce the corrosion resistance of the tuyere. This will lead to a decline in sexuality. Conversely, if the number is small, the interval between the discharge ports for discharging gas into the molten steel becomes wide. In this case, the gas discharge tubes are arranged at intervals of about 10-odd mm or more between the discharge ports so that the refractory, including coarse particles, can be sufficiently filled during tuyere manufacture.

The gas discharge capillary is separated into an upper gas discharge capillary tube and a lower gas discharge capillary tube in order to prevent the generation of induced current, and the interval between the two is preferably several mm or more.
Provide an interval of approximately 50mm to ensure that induced current is prevented from occurring. The position at which the gas discharge tube is separated cannot be determined unconditionally because the shape of the tuyere, the material and quality of the refractory lining the outer periphery, the amount of gas blown, etc. differ, but it is important to replace the tuyeres to prevent the generation of induced current. In order to prevent this from occurring, it is necessary that the lower end of the refractory tuyere, which is melted into a concave shape, be located closer to the operating surface of the tuyere than the cutoff part of the gas discharge capillary. In this case, the circumstances in which the tuyere is damaged are not necessarily constant, but
According to past results, the tuyere part is 150 to 200 times smaller than the general furnace bottom.
If it becomes concave by more than a millimeter, it will affect the surroundings and shorten the life of the hearth stamp. Therefore, assuming that the damage to the hearth stamp material is almost zero due to the adhesion of slag, base metal, etc., it is necessary to replace the tuyere before the damage to the tuyere itself reaches 150 to 200 mm from the operating surface. Therefore, it is preferable that the separation position of the gas discharge capillary is at least 150 to 200 mm away from the operating surface and as close to the gas distribution chamber as possible.

In addition, if the insulation effect is insufficient by simply cutting the gas discharge tube in the length direction, or in order to insulate adjacent gas discharge tubes, the surface (for example, the outer peripheral surface or end surface) may be coated with an electrically insulating material (for example, ceramic). Thermal spray coating of fine material powder may also be used.

Furthermore, high-grade refractories such as MgO-C are expensive, and only the parts of the tuyere that are close to the operating surface require particular fire resistance, so only the parts close to the operating surface are made of high-grade refractory However, the remaining portion may be formed of an inexpensive low-grade refractory.

(Function) In the present invention, the conductive gas discharge capillary is separated in the length direction and insulated. Therefore, even if an induced current generated by a current flowing through the molten metal in the electric furnace attempts to flow through the gas discharge capillary, the current cannot flow through the cut-off portion, so no induced current is generated at the tuyere.

(Example) The present invention will be described in more detail below based on the examples shown in FIGS. 1 to 4, but the present invention is not limited to these examples.

FIG. 1 is a longitudinal sectional side view showing a first embodiment of a bottom-blowing tuyere for an electric furnace according to the present invention, and FIG.
B, C, and D are plan views illustrating the arrangement of gas discharge passages and gas discharge capillaries in the present invention.

A tuyere 2 made of a refractory material formed into a truncated conical shape with a gently tapered surface is fitted into an opening (not shown) between the gas distribution chamber 1 for distributing gas and the inside of the furnace body on the lower surface of the furnace body. are combined. The tuyere 2 is provided with a required number of gas discharge passages 3 passing through the tuyere 2 in the longitudinal direction.
is formed to communicate the gas distribution chamber 1 with the inside of the furnace body. In each gas discharge passage 3, a long upper gas discharge capillary tube 4 and a long lower gas discharge capillary tube 4' are aligned with the upper and lower surfaces of the tuyere 2, respectively, so that a predetermined interval is created in the portion close to the gas distribution chamber 1. The upper end of the upper gas discharge capillary tube 4 has a discharge port 5.
is formed. The gas discharge capillary has a minimum pore diameter currently commercially available (for example, an inner diameter of 0.8 to 1
mmφ) stainless steel pipe can be used. Reference numeral 7 indicates a non-conductive portion in which no gas discharge tubes 4, 4' are provided.

This gas discharge passage 3 and gas discharge thin tubes 4, 4'
As shown in Fig. 2, the planar arrangement is based on three adjacent points being located at the vertices of an equilateral triangle (Fig. 2 A), in a grid pattern (Fig. 2 B), and concentrically and radially. Although the arrangement is not limited and can be arbitrary, such as arranging them (see C) or randomly positioning them on concentric circles (see D), it is preferable that they are distributed as evenly as possible.

FIG. 3 is a longitudinal sectional side view showing a second embodiment of the tuyere according to the invention, and FIG. 4 is a longitudinal sectional side view showing a third embodiment of the tuyere according to the invention. Both examples are
This relates to an improvement of the tuyere of the first embodiment, and the same members as in the first embodiment are given the same reference numerals and explanations will be omitted.

In the first embodiment described above, the gas discharge capillary tube was separated at the same position in the vertical direction to form the upper gas discharge capillary tube 4 and the lower gas discharge capillary tube 4'.
In the embodiment, the upper and lower separation positions of the gas discharge thin tubes 4, 4' are alternately shifted, thereby avoiding concentration of weak points in one place.

Further, in the third embodiment shown in FIG. 4, the gas discharge capillary 4,
In the non-conductive part 7 (refer to Figure 1 for reference numeral 7) and the refractories in the upper and lower adjacent areas of the non-conductive part 7, there are bars, plates, etc. made of stainless steel, etc. for strength correction. A long reinforcing member 6 such as a pipe is buried to prevent the tuyere refractory from peeling off or falling off even if a crack occurs in the tuyere 2 made of refractory material.

The shape and material of the tuyere, the hole diameter and number of gas discharge tubes, etc. in each of the above embodiments vary depending on the capacity of the electric furnace, the type of steel to be refined, the amount of gas blown, etc., and the shape and material of the tuyere used. It can be selected as appropriate.

(Effects of the Invention) In the present invention, each gas discharge thin tube is separated in the length direction when embedding the required number of conductive gas discharge thin tubes in the tuyere. Therefore, even if electricity used for melting steel tries to flow through the gas discharge capillary, no induced current is generated because there is a non-conductive part between the separated gas discharge capillaries, and the operation of the electric furnace is prevented. It is possible to reliably prevent situations that would cause problems.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional side view showing a first embodiment of a bottom blowing tuyere for an electric furnace according to the present invention, FIG.
B, C, and D are plan views illustrating the arrangement of gas discharge passages and gas discharge capillaries in the present invention, and FIG. 3 is a longitudinal cross-sectional side view showing a second embodiment of the bottom blowing tuyere for an electric furnace according to the present invention. , FIG. 4 is a longitudinal sectional side view showing a third embodiment of a bottom blowing tuyere for an electric furnace according to the present invention. DESCRIPTION OF SYMBOLS 1... Gas distribution chamber, 2... Tuyere, 3... Gas discharge passage, 4, 4'... Gas discharge thin tube, 5... Discharge port, 6...
Reinforcement member, 7... non-conductive part.

Claims (1)

[Scope of Claims] 1. A conductive gas discharge capillary tube that fits into a required number of gas discharge passages, and is fitted into an opening on the lower surface of the electric furnace to communicate between the gas distribution chamber and the inside of the furnace. A bottom-blowing tuyere for an electric furnace comprising a refractory layer made of a refractory layer, characterized in that a gas discharge capillary tube fitted in each gas discharge passage is separated in the length direction. 2. The bottom-blowing tuyere for an electric furnace according to claim 1, wherein the gas discharge thin tubes are alternately shifted and separated in the length direction.