JPH09241719A - Nose hard ware - Google Patents

Abstract

PROBLEM TO BE SOLVED: To repair crack developed on a nose hardware with welding and to enable the reusing by inserting a double steel pipes for passing through cooling water in the inner part of the nose hardware made of a cast steel. SOLUTION: The nose hardware 10 fitted to the nose of a metal melting furnace is formed with the cast steel. A cooling water passage 12 is formed in the inner part of the main body 11 of the nose hardware 10. This cooling water passage 12 is formed with the double steel pipes 13. This nose hardware 10 is manufactured by arranging the double steel pipes 13 in a mold for casting and pouring the molten cast steel into the mold to cast in the double steel pipes 13. Further, the double steel pipes 13 are closely fitted between the steel pipes 13a, 13b by shrinkage-fitting with a returning heat shrinkage diameter method (RHS method). Since the cast steel generally has little carbon content, the weldability is good, and in the case of developing the crack in the nose hardware 10, this nose hardware can be repaired with the welding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a furnace metal fitting attached to a molten metal furnace such as a converter for the purpose of protecting the furnace body near the furnace mouth and fixing inner refractories.

[0002]

2. Description of the Related Art As shown in FIG. 2, a converter 1 is a molten metal furnace which holds molten iron 6 therein, and serves to convert it into molten steel containing few impurities by oxygen blowing. The upper furnace port 5 is an opening for charging materials such as hot metal and scrap, inserting a lance for oxygen blowing, and discharging slag (slag) after blowing.

The vicinity of the furnace port 5 is exposed to high-temperature exhaust gas during blowing, and the molten iron and slag ejected from the inside of the furnace are subjected to extremely high heat load. A furnace mouth metal fitting 10 having a water passage therein is attached. By covering the vicinity of the furnace port 5 with the water-cooled furnace port metal 10, the furnace body main body, that is, the iron shell 2 is protected. Further, in the case shown in the figure, the furnace mouth metal 10 also has a role of pressing the refractory brick 4 in the furnace from above and preventing it from falling off. In addition, generally, the furnace mouth metal fitting 10 of the converter 1
For ease of manufacture and convenience of replacement,
It is formed so as to cover the entire circumference of the furnace opening 5 by connecting a plurality of (about 4 to 16) divided pieces in a circumferential shape.

The main body of the furnace mouth metal fitting is conventionally manufactured from cast iron (including special cast iron such as spheroidal graphite cast iron). Cast iron is also because it can be easily formed at low cost, but also because it is easy to have a structure that does not leak cooling water. The latter point is explained as follows. That is, since a considerable heat load is applied to the furnace mouthpiece as described above, cracks may occur in a part of the main body (generally, a portion near the inner circumference where the heat load is highest). Since it is inconvenient for the cooling water to leak out of the furnace mouthpiece, even if a crack occurs in the body of the furnace mouthpiece, it is necessary to prevent the crack from reaching the cooling water passage. In order to provide the cooling water passage in the main body, it is better to encircle the pipe when casting the main body, but if the pipe is made of steel pipe and the main body is cast iron, the melting point difference between the steel pipe and cast iron (the melting point of cast iron is Based on the fact that the melting point of the steel pipe is about 1300 ° C, while the melting point of the steel pipe is about 200 ° C higher than that, without melting (melting) with the main body of the furnace mouth metal (that is, in close contact but in a discontinuous state). The pipe can be cast around. If the pipe is built in the main body so as not to be welded to the main body, even if a crack occurs in the main body, it is extremely unlikely that it will cross the wall surface of the pipe, so that the cooling water will not leak easily.

As described above, the main body is made of cast iron,
A furnace mouthpiece provided with a steel pipe without being welded therein is described in Japanese Utility Model Publication No. 3-53540.

[0006]

A cast iron furnace metal fitting, into which a steel pipe as a cooling water passage is cast, is preferable in that the steel pipe can be kept sound even if a crack occurs in the main body. It is difficult to repair the cracked body. This is because cast iron has a very poor weldability in connection with a high carbon content (2-4%). Since it is impossible to repair, it is necessary to dispose of the furnace mouth metal once cracked, so the life of the conventional furnace mouth metal is short,
It could not always be said that it was cost effective. Incidentally, such a problem is not limited only to the furnace mouth metal fittings of the converter, but the furnace mouth metal fittings of various furnaces holding molten metal-because of high heat load, cracks while including the passage of cooling water inside It is widely applied to furnace metal fittings that may cause.

An object of the present invention is to provide a furnace mouthpiece which not only does not leak cooling water when a crack occurs, but also can repair and reuse the crack, thus having a long life and cost advantages. Is to provide.

[0008]

A furnace mouthpiece according to a first aspect of the present invention is characterized in that the main body is formed of cast steel, and a double steel pipe as a cooling water passage is cast inside the main body. Is.

Cast steel has good weldability because it has a low carbon content (generally 0.5% or less). Therefore, with respect to this furnace mouthpiece whose main body is made of cast steel, even if a crack occurs, it can be repaired by welding and reused.

Since the cast steel and the steel pipe have almost the same melting point, when the double steel pipe is cast inside the cast steel, the outer surface of the double steel pipe is melted and welded (fused) to the cast steel. However, in this furnace mouthpiece, there is no inconvenience that the cooling water leaks even if a crack occurs in the cast steel body. Even if the crack generated in the main body progresses to the outer steel pipe that is welded to it, since the steel pipe is double and has a discontinuous portion on the mating surface, the crack does not reach the inner pipe. Because there is no.

Although cast steel is not as castable as cast iron, it is rarely a problem because the shape of the furnace body is generally not so complicated. Also, temporarily
Even if it has a complicated shape that is difficult to cast, since cast steel is easily welded, it is possible to separately form the part and integrate it with the main body by welding. Therefore, it can be said that there is no particular difficulty in manufacturing the body of this furnace mouthpiece.

According to a second aspect of the present invention, the inner and outer steel pipes of the double steel pipe are closely fitted by shrink fitting. When it is necessary to make a bent pipe, it is better to shrink and straighten a straight double steel pipe, and then bend it (turn it around in cast steel).

The inner and outer steel pipes have the function of stopping the development of cracks as described above even when the two are not in close contact with each other and are doubled with a gap therebetween. The cooling effect on the The thermal conductivity of the air layer, which is the gap, is extremely low (about 1/3000) compared to that of steel, so even if the gap is small, the thermal resistance will be considerably large, and the cooling water will cool the main body. It interferes. On the other hand, when the double steel pipe that is shrink-fitted and closely adhered is used as in the second aspect, the main body is effectively cooled because the thermal resistance from the main body to the cooling water is small. Therefore, the furnace mouthpiece according to the second aspect of the present invention can be used for a longer period of time.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the present invention. 1 is the same as the converter 1 shown in FIG.
Around the furnace opening 5 of the
It is attached to fix the. As shown in FIG. 1 (a), a plurality of furnace metal fittings 10 are also arranged so as to cover the periphery of the furnace metal 5, and each metal material 10 has about 45
It is a fan shape that covers the range of °. Each metal piece 10 is fixed to the upper surface of a furnace port flange 3 made of iron, which is integral with the iron shell 2, using bolts and nuts (not shown).

In order to prevent deformation and melting damage due to the heat load applied during the blowing of the converter 1 and to facilitate the removal of metal or slag even if it adheres, this furnace mouthpiece 10
However, the cooling water passage 12 is formed inside the main body 11.
As shown in FIG. 1 (b), the passage 12 extends downward from both ends of each metal fitting 10 and is connected to a cooling water feed pipe (or return pipe) 15 via a joint flange 14. There is. A feed pipe 15 at one end of the hardware 10.
From the main body 11 by sending the cooling water from the pipe to the passage 12 and discharging the cooling water from the return pipe 15 at the opposite end.
The cooling water is circulated in the (passage 12).

This furnace mouth metal 10 is characteristic in the following points. That is, the main body 11 is a cast product made of cast steel, and the cooling water passage 12 in the main body 11 is formed by a double steel pipe 13 as shown in FIGS. In other words, this hardware 10 is a double steel pipe 13 bent into the shape shown.
Is placed in a casting mold (not shown), and a molten metal of cast steel (that is, molten cast steel) is poured into the mold to cast the double steel pipe 13 around it.
Since the double steel pipe 13 becomes the cooling water passage 12 as it is, the metal piece 1 can be manufactured without using a mold for the passage 12.
0 can be cast.

The double steel pipe 13 is formed by fitting a steel pipe 13b having a slightly larger diameter to the outside of the steel pipe 13a. In the illustrated case, carbon steel pipes for pressure piping (STPG) referred to in JIS are used as the inner and outer steel pipes 13a and 13b.
For a, the inner diameter is about 50 mm and the thickness is about 5 mm,
About the steel pipe 13b, the thickness is about 5 mm and the outer diameter is about 70 m.
m. This double steel pipe 13 is made by shrink fitting by the so-called ring thermal contraction method (RHS method) because the heat transmission characteristics between the inside and outside are better when both tubes are in close contact.
3a and 13b are closely fitted.

In the ring thermal reduction method, the outer tube having the tube inserted inside is heated from one end in order by an annular heating means (not shown) such as a coil, and after cooling, The outer tube is made smaller than the original diameter, and as a result, the outer tube is clamped to the inner tube. Since only a part of the outer pipe is heated in a ring shape by the annular heating means, the heated part is restrained by the parts on both sides adjacent in the longitudinal direction (the parts on both sides adjacent to each other are sprayed with water, etc.). Thermal expansion is performed in such a manner that the diameter is hardly expanded as compared with the case of free expansion (which is effective when cooled by the above) (for example, by increasing the thickness). When the heated annular portion is subsequently cooled to room temperature, the diameter of the heated annular portion shrinks from a state in which the diameter of the heated annular portion is almost not expanded, so that the diameter becomes smaller than that before heating and the inner tube is tightened. In the double steel pipe 13 of FIG. 1 (d) fitted by the ring heat reduction method, the inner and outer steel pipes 13a and 13b are thus tightly fitted and closely attached to each other.

As the cast steel on which the main body 11 of the furnace mouthpiece 10 is formed, a carbon steel cast steel product (SC material) according to JIS is used. The SC material has excellent mechanical strength, and has twice the tensile strength as cast iron (FC material) that has been generally used as a furnace mouthpiece, and is a special cast iron, spheroidal graphite cast iron (FCD material). It has the same tensile strength and about twice the elongation. Above all, the SC material is easy to weld because it has a low carbon content, and can be repaired by welding, which was difficult with cast iron such as FC material and FCD material. Therefore, even if a crack or the like occurs in the main body 11 of the hardware 10 due to a high heat load including a thermal shock or a mechanical impact for removing the metal, in the case of this hardware 10 made of SC material, Can repair it and use it again. Since the SC material has excellent mechanical strength as described above, it can be said that cracks and the like tend to be less likely to occur as compared with the conventional cast iron metal piece.

The melting point of the cast steel used in this furnace mouthpiece 10 is about 1510 ° C., and the double steel pipe 13 (STPG)
Almost matches the melting point of. Since the molten cast steel poured into the mold for the above-mentioned casting has a temperature (around 1550 ° C.) in which an appropriate degree of superheat is expected at 1510 ° C., the double steel pipe 13 formed inside is a steel pipe 13 b on the outside thereof. The surface of is melted at the time of casting and is welded to the main body 11.

Although the outer steel pipe 13b is welded to the main body 11, even if a crack occurs in a part of the main body 11, the conventional furnace mouthpiece can keep the cooling water passage 12 sound. The advantage that it has is not lost even in this furnace metal fitting 10. The outer steel pipe 13b and the inner steel pipe 1 shown in FIG. 1 (d)
3a and 3a have a discontinuity, even though they are in close contact with each other, and form the cooling water passage 12 as a double pipe. That is, if the material and thickness of the steel pipes 13a and 13b are determined as described above and the main body 11 (cast steel) is cast as described above, it is possible that the inner steel pipe 13a is welded to the main body 11 and the outer steel pipe 13b. None, and therefore body 1
Even if cracks occur in No. 1, they are prevented from reaching the inner steel pipe 13a, and the leakage of cooling water is prevented.

Although one embodiment of the invention has been introduced above, the invention is not limited to this. For example, first, it is of course possible to construct a similar furnace mouthpiece by using a furnace other than the converter. Further, the main body of the furnace mouth metal is cast steel other than SC material, for example, welded structure cast steel (SCW) or high manganese cast steel (SCMn) according to JIS.
H), cast stainless steel (SCS) or the like. As the double steel pipe to be the cooling water passage, various ones such as a carbon steel pipe (SGP), a carbon steel pipe for high-pressure piping (STS), or a structural stainless steel pipe (SUS-TK) can be used. It is also possible to use different materials for the outer pipe and the outer pipe. However, when the double steel pipe is cast into the main body (cast steel), the melting point of the cast steel to be the main body is the same as that of the double steel pipe so that the inner steel pipe does not weld to the outer steel pipe and the main body (cast steel). Does not exceed the melting point (the difference between the two is 1
It is preferably set within about 00 ° C). If the former is considerably lower than the latter, generally the welding does not occur between the cast steel and the outer steel pipe, but there are two discontinuous unwelded portions between the main body and the cooling water passage. If possible, it is preferable that the former does not fall below the latter (difference between the two is within about 50 ° C.), because it lowers the cooling characteristics of the main body.

[0023]

EFFECT OF THE INVENTION Since the main body of the furnace mouthpiece according to claim 1 is formed of cast steel having good weldability, even if a crack occurs, it can be repaired by welding and reused. It has a long life and is advantageous in cost. In addition, it has an advantage that it can be easily manufactured and that cooling water does not leak even if a crack occurs in the main body.

According to the furnace mouth metal of claim 2, the inner and outer steel pipes of the double steel pipe are in close contact with each other by shrink fitting, and the thermal resistance from the main body to the cooling water is small. Withstand use for a period of time.

[Brief description of drawings]

FIG. 1 is a furnace mouthpiece 10 for a converter as an embodiment of the invention.
1A is a plan view (a view taken along the arrow I-I in FIG. 2). 1 (b) is a view taken along the line bb in FIG. 1 (a), FIG. 1 (c) is a view taken along the line cc in FIG. 1 (a), and FIG. FIG.

FIG. 2 is a vertical cross-sectional view of a converter 1 using a furnace mouthpiece 10.

[Explanation of symbols]

 1 Converter (molten metal furnace) 10 Furnace mouthpiece 11 Main body 12 Cooling water passage 13 Double steel pipe

Claims (2)

[Claims] 1. A furnace metal fitting attached to a furnace opening of a molten metal furnace, characterized in that a main body is made of cast steel, and a double steel pipe as a cooling water passage is cast inside the furnace. A clasp. 2. The furnace mouthpiece according to claim 1, wherein the double steel pipe is made by closely fitting the inner and outer steel pipes by shrink fitting.