JPS623206B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a bottom tuyere of a bottom blowing converter or a top and bottom blowing converter. In bottom-blowing converters and top-bottom blowing converters, oxygen gas for blowing is injected from the bottom of the furnace, but if oxygen gas alone reacts with the molten iron, the area near the tuyeres in contact with the molten iron will become hot and cause severe melting, so this is not recommended. To prevent this, it is common to use a double-pipe tuyere, with oxygen gas for blowing flowing through the inner tube and cooling gas flowing through the outer tube. The material of this tuyere is selected from the viewpoint of heat resistance.
Stainless steel, high chromium steel, etc. are often used for both the inner and outer tubes. In some cases, copper is used for the inner tube because of its good thermal conductivity. Copper tuyeres have good thermal conductivity, so the solidified iron (pine room) that forms around the tuyeres due to the cooling effect of the cooling gas has the advantage of covering a large area of the brick surface. However, since copper has a low melting point and its tensile strength decreases as the temperature rises, it has the disadvantage that it cannot fully withstand the pressure caused by the thermal expansion of the bricks, resulting in significant deformation of the tuyere. The present inventors focused on the fact that by improving the above-mentioned disadvantages of copper, it is possible to take advantage of the above-mentioned advantages and extend the life of the bottom of a bottom-blown converter, and as a result of various studies, we found that Even though it is made of pure copper, it can withstand use sufficiently due to the cooling effect of oxygen gas and the cooling gas flowing through the gap between the inner and outer tubes, and the tuyere outer tube is
We have reached the knowledge that the life of the hearth bottom can be extended by using a copper alloy with a certain strength or higher. The present invention has been completed based on the above knowledge, and by increasing the thermal conductivity of the tuyere for a bottom furnace, the solidified iron around the tuyere is generated more strongly by the cooling gas. The purpose of the present invention is to provide a tuyere that can extend its life and sufficiently enable the use of a low heat removal coolant such as CO ₂ . That is, the present invention provides a bottom-blowing converter tuyere that facilitates the formation of solidified iron and allows the use of a low heat removal coolant, and in which the inner tube is made of copper or a copper alloy. This is a tuyere for a bottom-blowing converter, characterized in that the outer tube is made of a copper alloy with a tensile strength at room temperature of 35 kg/mm ² or more. Regarding the inner tube of the present invention, the inner tube is cooled by both oxygen gas from inside the inner tube and hydrocarbon and/or carbon dioxide gas from the outside of the inner tube, and sufficient cooling is achieved. Therefore, the problem of high temperature strength could be avoided. Therefore, pure copper or copper alloy is used mainly because of its thermal conductivity. Regarding the outer tube, cooling gas passes through the inside of the outer tube, but the outside of the outer tube is in contact with the refractory, and the heat stored in the refractory is transferred to the outer tube. Steel and other steels were often used. The thermal conductivity of copper alloys is lower than that of pure copper, but it is 2 to 3 times higher than that of stainless steel or ordinary steel, and if it can withstand use as a tuyere outer tube due to its heat resistance strength, it can be replaced with an excellent tuyere. Can be configured. As a result of numerous tuyere durability experiments, the inventors have found that a combination of pure copper for both the inner and outer tubes has the highest cooling effect in laboratory-scale experiments, and the formation of solidified iron around the tuyeres is also extremely good. Moreover, the temperature indication from the thermocouple installed on the outer circumference of the outer tube also showed a low value. However, when this double-tube tuyere made of a combination of copper and copper is used in the bottom of a converter furnace on a practical scale, the outer tube deforms due to the expansion of the bricks, making the gap between the inner and outer tubes uneven, which is not desirable. The inventors investigated various materials from the viewpoint of both thermal conductivity and strength, and after repeated experiments, they found that the inner tube was made of pure copper or a copper alloy, and the outer tube had a tensile strength of 35 at room temperature.
By selecting and combining copper alloys with Kg/mm ² or more, it is possible to obtain almost the same cooling characteristics as a double-pipe tuyere made of a combination of copper and copper, while also being superior in that it does not cause deformation due to brick expansion. It was confirmed that tuyeres could be obtained. A specific example of a 5t test converter will be shown and explained below. Tuyere tubes having the following dimensions were installed in a 5t converter in the arrangement shown in the plan view of the converter in Figure 1 and tested. Outer tube: Inner diameter 14 mm Outer diameter 18 mm Inner tube: Inner diameter 10 mm Outer diameter 12 mm These materials are as shown in Tables 1 and 2.

【table】

【table】

[Table] Continuous by the tuyeres in Tables 1 and 2 above.
A durability test of 10 heats was conducted. The furnace operation conditions are as follows. Oxygen supply amount: 15Nm ³ /min, total oxygen amount: 46Nm ³ /t, cooling gas CO ₂ gas 2.25Nm ³ /min (oxygen ratio
15%) Charging hot metal temperature: Approximately 1230℃ Charging hot metal composition: C/4.4~4.5 Si/0.4~0.5
Mn／0.3～0.5 P／0.11～0.13 S／0.03～0.035 End temperature 1610℃±15℃ Stop component C／0.02～0.03 Si／tr Mn／0.1～
0.25 P/0.01 to 0.02 S/0.02 to 0.03 After each 10 heat operation, the 5 ton test converter was cooled and entered into the furnace to observe the tuyeres. In the experiments shown in Table 1, eccentricity was observed in the formation of solidified iron in No. 1 and No. 2 tuyeres, so in order to clarify the cause, the bricks around the tuyeres were removed one by one and the observations were made. As a result, deformation of the outer tube was observed, and the width of the gap in the double tube was uneven. Particularly in the No. 1 tuyere, there were places where some of the gaps were in close contact, and eccentricity was observed due to the unevenness of the cooling gas flow. It was concluded that this resulted in the formation of solidified iron. No abnormalities were observed in No. 3 and No. 4 tuyeres. Since the tensile strength of copper and copper alloys tends to decrease almost proportionally with increasing temperature,
The tensile strength at room temperature can represent the tuyere strength, and if a copper alloy with a tensile strength at room temperature of 35 kg/mm ² or more is used, solidified iron can be produced well. Next, Table 3 shows the solidified iron production, tuyere wear amount, and tuyere refractory wear amount based on the test results in Table 2, and shows comparative values between the conventional tuyere and the tuyere of the present invention. .

[Table] Tuyeres No. 1 and No. 2 in Table 3 show examples of the present invention, and tuyeres No. 3 and No. 4 show conventional tuyeres. However, the inner tubes are all made of pure copper. From Table 3, it can be seen that bottom-blown converter tuyeres whose outer tubes are made of copper alloys such as Cr-Zr copper with a room temperature tensile strength of 35 Kg/mm ^{2 or} more have good cooling of the tuyere and large growth of solidified iron.
When the average diameter (calculated by the square root of W x l shown in Table 3) becomes 2.5 times or more the outer diameter of the tuyere, the amount of wear on the tuyere and the amount of erosion of the tuyere refractory decreases significantly, and the converter It is clear that this has a great effect on extending the life of the hearth bottom.

[Brief explanation of the drawing]

Fig. 1 is a plan view of the bottom tuyere arrangement of the converter in which the embodiment of the present invention was tested, Fig. 2 is a plan view of the produced solidified iron, and Fig. 3 is a view taken along arrow A--A in Fig. 2. be. 1... Converter tuyere, 2... Converter, 3... Tuyere inner tube, 4... Tuyere outer tube, 5... Produced solidified iron, 6...
Trunnion, I... Pig iron charging side of the converter, O... Steel tapping side of the converter, No. 1 to No. 4... Test tuyere, w, l,
h...Length on the trunnion side, length on the tapping side, and height of solidified iron, respectively.

Claims (1)

[Claims] 1 In a double pipe tuyere for a bottom-blown converter, the inner pipe is made of copper or copper alloy, and the outer pipe has a tensile strength of 35 at room temperature.
A bottom blowing converter tuyere for low heat removal coolant, which is characterized by being made of a copper alloy of Kg/mm ² or more, and which facilitates the formation of solidified iron.