JPS5891111A - Tuyere for bottom blown converter - Google Patents

Abstract

PURPOSE:To obtain a tuyere for a bottom blown converter having prolonged life of a furnace bottom by constituting a tuyere of an inner tube of steel or Cu alloy and an outer tube of steel alloy of a tensile strength at room temp. higher than a predetermined value in order that the iron surrounding the tuyere is strongly solidified by cooling gas due to increase of thermal conductivity. CONSTITUTION:In the double tuyere for the bottom blown converter, Cu or Cu alloy is selected for the inner tube mainly in view of thermal conductivity. The aimed double walled tuyere is constituted by combining said inner tube and the outer tube of Cu alloy satisfying requirements for both thermal conductivity and strength and having >=35kg/mm.<2> tensile strength at normal temp. Even if this inner tube of the tuyere is made of pure copper, it can be durable for use by a cooling effect of O2 gas and cooling gas flowing through a gap between the inner and outer tubes. Furthermore by using said Cu alloy as an outer tube, the tuyere is well cooled, the solidified Fe grows up, the abrasion and erosion of the tuyere and its refractory are extremely decreased and a large effect is obtained for prolonging the converter life.

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 blown 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 high temperature and cause severe melting.
To prevent this, it is common to use a double pipe structure, with oxygen gas for blowing flowing through the inner tube and cooling gas flowing through the outer tube.

From the viewpoint of heat resistance, materials such as stainless steel and high chromium steel are often used for the tuyeres for both the inner and outer tubes. In some cases, copper is used for the inner tube because of its good thermal conductivity.

Copper siding has good thermal conductivity, and has the advantage that the solidified iron (pine loom) that forms around the tuyeres due to the cooling effect of the cooling gas covers the brick surface widely.

However, since copper has a low melting point and its tensile strength drops directly as the temperature rises, it cannot withstand the pressure caused by the thermal expansion of bricks, resulting in significant deformation of the siding.

The inventors of the present invention 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. However, the cooling effect of the oxygen gas and the cooling gas flowing through the gap between the inner and outer tubes makes it durable enough to withstand use, and the tuyere outer tube is made of copper alloy with a certain strength or higher, extending the life of the furnace bottom. I have come to the conclusion that it is possible to do so.

It was completed based on the above-mentioned knowledge of Fukaisha,
By increasing the thermal conductivity of the tuyere for the bottom furnace, the cooling gas can generate more solidified iron around the siding, extending the life of the bottom furnace and making it possible to use a low heat removal coolant such as Cot. The purpose is to provide a tuyere that is fully accessible.

That is, the present invention provides a double pipe tuyere for a bottom-blown converter,
The inner tube is made of a copper alloy, and the inner tube is made of a copper alloy having a room temperature tensile strength of 35 and 4/- or more.

Regarding the inner tube of the present invention, the inner tube is cooled by both oxygen gas (K) from inside the inner tube and hydrocarbon and/or carbon dioxide gas from outside the inner tube,
Since sufficient cooling was obtained, 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,
The outside of the outer tube is in contact with a refractory, and the heat stored in the refractory is transferred to the outer tube, so stainless steel, high chromium alloy steel, or other materials for heat resistance have traditionally been used. Although the thermal conductivity of copper alloy is lower than that of pure copper, it is 2 to 3 times higher than that of stainless steel or ordinary steel, and if it can withstand use as an outer tube for tuyeres due to its heat resistance, it can be an excellent substitute for these. You can make up your mouth.

The inventors conducted numerous tuyere durability experiments and found that in laboratory-scale experiments, the combination of pure copper inner and outer tubes had the highest cooling effect, and the formation of solidified iron around the tuyere was 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, this copper-copper combination K
When this double-tube tuyere is used in the bottom of a converter furnace on a practical scale, the outer tube deforms due to the expansion of the bricks, and the gaps between the inner and outer tubes become uneven, which is undesirable.

The inventors investigated various materials from the viewpoint of both thermal conductivity and strength, and after repeated experiments, the inner tube was made of pure copper or a copper alloy, and the outer tube was made of copper with a room temperature tensile strength of 35/- or more. By selecting and combining two alloys, an excellent nine-tuyere can be obtained that has almost the same cooling characteristics as a double-pipe tuyere made of a combination of copper and copper, and which does not cause deformation due to brick expansion. It was confirmed that

Below, 5 will be explained by showing a specific example in a test converter. A test was carried out by attaching siding pipes 5 having the following dimensions to a converter in the arrangement shown in the plan view of the converter in FIG.

Outer tube: Inner diameter 14 m Outer diameter 18 Inner tube: Inner diameter 105 m Outer vk12t+a These materials are as shown in Tables 1 and 2.

Table 1 Table 2 (Note 1) ZrO, 25%-Cr0.91G-Remaining c
u% Tensile strength at room temperature 38-/- (Note 2) N11. On-&0.15--%0.251-
! /It0.03 To-Remaining cu % Tensile strength at room temperature 59 noodles/- A durability test of 10 consecutive heats was conducted using the tuyere shown in Table 1 and Table 2, respectively.

The furnace operation conditions are as follows.

Oxygen flow volume: 15 Nn11 minutes, total oxygen amount: 46 Nj/l.

Total amount of cooling gas sent from the bottom tuyeres of the furnace C gas 2.25 Nn11 minutes (oxygen ratio 15 cm) Charging hot metal temperature 1230℃ Charging hot metal composition C/ 4.4 to 4.5 Si/Q, 4
~0.5 Mn10.3~0.5 Plo, 11~
0.13S10.03~0.035 Blowing end temperature 1610℃±15℃ Blowing component C10.02~0.03 Sl/l1MB
10.1~0.25 P2O, 01~0.02810
．． 02 to 0.03 After 10 heats of operation, the test converter was cooled and entered into the furnace, and the tuyere was observed.

In the experiment shown in Table 1, eccentricity was observed in the production of solidified iron in A1 and Mu2 tuyeres.In order to clarify the cause, we removed the bricks around the tuyere one by one and observed the outside. Due to the deformation of the pipe, the width of the gap in the double pipe became uneven, and in particular, in tuyere 41, there were places where some of the gaps were in close contact with each other.
It was concluded that non-uniform cooling gas flow caused eccentricity and the formation of nine-solidified iron. No abnormality was observed in A3.44 tuyere.

Since the tensile strength of copper and copper alloys tends to decrease almost proportionally as the temperature rises, the tensile strength at room temperature can represent the tuyere strength, and the tensile strength at room temperature is 35 hours/-
If the above copper alloys are used, solidified iron can be produced well.

Table 3 shows the solidified iron production, tuyere wear amount, and tuyere wear resistance amount based on the test results in Table 2, and compares the conventional tuyere with the present tuyere. show.

Table 3 (Note 3) The solidified iron formation status is shown in Figures 2 and 3.
The dimensions of iron are expressed as wxAxh.

FIG. 2 is a plan view of solidified iron, (I) shows the pig iron charging side of the converter, the mouth shows the tapping side, and FIG. 3 is a view taken along the line A--A in FIG.

Here, W: Length on the trunnion side L: Length on the tapping side h: Height The tuyere AI and A2 in Table 3 indicate the embodiment of the present invention, and the tuyere A3.44 indicates the conventional tuyere. be. However, the inner tubes are all made of pure copper.

Table 3 shows that the bottom-blown converter tuyeres with copper alloy outer tubes have good cooling of the tuyere, the solidified iron is large, and the amount of tuyere wear is low.
It is clear that the amount of corrosion of the wall refractories is significantly reduced, which has a great effect on extending the life of the bottom of the converter.

[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 lining, 2... Converter, 3... Tuyere inner pipe,
4... Tuyere outer tube, 5... Fiber solidified iron, 6... Trunnion, (1)... Pig iron charging side of converter, (0... Steel tapping side of converter, A1 -A4...Test tuyere, w, L, h.
・・Trunnion side length of solidified iron, tapped steel 1ill respectively
length, height. Figure 1 (0) ↑ ↓ (I) Figure 2 Figure 3

Claims (1)

[Claims] 1. A double pipe tuyere for a bottom-blown converter, characterized in that the inner pipe is made of a copper alloy, and the outer pipe is made of a copper alloy with a tensile strength at room temperature of 35 or more. Port for converter.