JP2778339B2 - Stave cooler with thermal stress relaxation type functionally gradient material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metallurgical furnace, such as a blast furnace, having a stave cooler body made of a functionally gradient material composed of a ceramic material and a metal material and capable of effectively preventing cracks and supercooling. For stave cooler.

[0002]

2. Description of the Related Art Generally, a furnace wall provides a boundary condition of a flow and a heat flow with respect to an internal phenomenon of a reactor. However, furnace wall conditions in a metallurgical furnace such as a blast furnace change depending on the initial structure, wear of the inner surface profile after operation, and the like. Such abnormal wear of the inner surface profile disturbs the charge filling, destabilizes the gas flow and increases heat flow through the furnace wall. In particular, when the bricks on the front wall of the stave fall off in the stove blast furnace, the stave is exposed in the furnace, and the inside of the furnace is excessively cooled.
These phenomena are obstacles to stable operation, and it is considered that a case where the furnace condition is disturbed due to brick falling in the middle of the furnace life (4 to 6 years) corresponds to this.

[0003] The boundary condition of the heat flow in the furnace wall depends on the cooling structure of the furnace body before the inner surface profile changes after the operation. In recent years, from the viewpoint of maintaining the furnace body profile, prolonging the life of the blast furnace, and reducing the repair cost, furnace wall cooling has been strengthened with the aim of improving the protection and durability of the furnace body.
The basic principle of blast furnace operation is to maximize the functions of ventilation, heat exchange, and reduction while minimizing the heat load on the furnace body.However, heat loss from the furnace body is reduced by strengthening the furnace wall cooling. If the temperature increases, the temperature inside the furnace, particularly the temperature near the furnace wall, decreases, so that the so-called inactivation proceeds, and the furnace condition may fall into a poor condition.

Further, with the recent increase in the size of blast furnaces, the heat capacity in the furnace has increased dramatically, and cooling with a cooling plate has become impossible to cope with. Recently, stave coolers have been adopted in most blast furnaces. I have. Needless to say, the function required of this stave cooler is to have a high heat resistance and abrasion resistance and to maintain the furnace wall firmly for a long period of time. Efficient heat exchange, heat transfer efficiency between the cooling water pipeline inside the stave and the stave base material, and furthermore, the stave base material due to the heat load from the furnace when the stove front wall bricks fall off and the stave casting bricks fall off There is a possibility that cracks generated due to the increase of the thermal stress of the steel may spread to the cooling pipe portion and the whole damage may be propagated. However, it is necessary to satisfy such a condition that such a total damage can be prevented.

[0005] The furnace wall of the conventional blast furnace is shown in Figs.
As shown in (a) and (b), a stave 2, which is a casting in which a cooling pipe 5 is cast, is disposed and fixed inside a furnace shell 1, and a refractory lining ( Refractory brick)
7 is constructed. In such a furnace wall structure, the life of the refractory lining 7 was as short as 1 to 2 years, and the service life of the furnace shell 1 was about 6 to 7 years. Therefore, it is considered that it is necessary to extend the life of the refractory lining in order to extend the life of the blast furnace. For this reason, conventionally, the inside of the furnace was heated to a high temperature (approximately 1000
-1500 ° C.), and from the viewpoint that damage to the blast furnace lining refractory is mainly caused by abrasion due to raw materials, chemical reaction with products in the furnace, and particularly damage due to alkali erosion at high temperatures. In order to prevent an alkali reaction from occurring, a carbon-based or SiC-based refractory having excellent alkali resistance has been employed.

However, the instability of the supporting force of the refractory lining 7 which the stave cooling system basically has causes a sudden change in the profile and an imbalance in the circumferential direction in the damage process of the furnace wall after the operation, and the furnace wall A phenomenon that the stable descent of the charge in the vicinity was disturbed and the operation controllability deteriorated was inevitable.

Next, FIG. 3 (a) shows a cross section of a main part of a conventional furnace wall.
In addition, the stave 2 provided with the cast brick 4 shown in FIG. 2 is exposed in the furnace due to wear and fall of the refractory lining 7, and the stave 2 in the case where the furnace temperature becomes about 1200 ° C. FIG. 3 (b) shows the temperature distribution at. FIG.
In (b), the vertical axis indicates the temperature, the horizontal axis indicates the distance from the left side to the right side from the furnace inner surface, t ₀ is the surface temperature of the cast brick 4 at the furnace heating surface x ₀ , and t ₁ is the temperature of the cast brick 4. Bottom x ₁
, T ₂ indicates the temperature on the surface of the cast pipe 5. As apparent from FIG. 3 (b), the casting bricks 4 occurs temperature difference t ₀ -t _1, the temperature difference t ₁ -t ₂ is generated in the cast iron 3. It is generally well known that when a temperature difference occurs in an object, a thermal stress acts on the inside, and the following expression is well known as an expression representing the relationship between the temperature difference and the thermal stress.

[0008]

(Equation 1)

Σ: generated thermal stress, E: Young's modulus, α: linear expansion coefficient, μ: Poisson's ratio, ΔT: temperature difference.

[0010] When such a thermal stress acts on the refractory and the cast iron, cracks may occur due to the thermal stress. Further, in the blast furnace, a rapid temperature change due to the falling and moving of the raw material, the fluctuation of the high-temperature gas, and the like are likely to occur. For this reason, the temperature distribution in the refractory or the cast iron also changes, and a fluctuating thermal stress acts. This will be described with reference to FIG. 3A. First, the cast brick 4 is worn, cracked, and dropped. Next, cracks c enter the corners at the bottom of the cast brick 4, the ends (corners) of the staves 2 fall off, and the cast iron 3 is cracked vertically and horizontally like a grid to form small blocks. The cooling pipes 5 which are sequentially dropped and exposed are followed. After the cast brick 4 falls off, the cast iron is exposed in the furnace and excessively cools the furnace as described above, causing a temperature drop near the furnace wall stave and causing a burning. There is a possibility that a reduction and pulverization phenomenon of the condensate is induced, which impairs the air permeability of the furnace wall, that is, the furnace condition is deteriorated due to the progress of so-called inactivation.

In recent years, an improved blast furnace furnace wall protection wall has been proposed to improve the reliability of the conventional stove cooler 2 shown in FIG. 2 (Japanese Patent Application Laid-Open No. 61-37904).
FIG. 4 shows an example of the protective wall. In this protective wall, a furnace wall brick on the inner side of the furnace of the stave body 2 ′ is sandwiched by a plurality of tapered brick supporting members (ribs) 12 formed by a part of the stave body. As a specific example, a case was shown in which the wall was reduced in order to stabilize the profile and simplify and reduce the cost of the construction work without performing brickwork inside the furnace. ing. In this case, the refractory lining 7 built inside the furnace of the conventional stave cooler 2 is 2
It will wear and disappear in 3 years, but 2 more
Up to three years is expected to extend the life of the cast brick 13. However, also in this protective wall, the tip of the tapered brick support (rib 12) has a high furnace temperature (600 to 1200 °).
C) Preliminarily disappears due to gas, and the bricks 13 lose their holding power and fall off, and do not produce expected results at present.

[0012]

SUMMARY OF THE INVENTION Therefore, the present invention
In order to solve the conventional drawbacks of metallurgical furnace stave coolers such as blast furnaces, ceramic materials with durability at high temperatures, cooling heat transfer properties, mechanical strength, etc. and metal materials represented by cast iron By using a stave cooler as a furnace wall structure, which has a heat insulating property and a thermal stress relaxation function, and can suppress the heat load of the furnace body, the furnace wall has high durability and long life. The purpose is to form

[0013]

SUMMARY OF THE INVENTION The present invention has attracted attention as a heat-shielding panel in an ultra-high-temperature environment in the aerospace field such as a space shuttle and a next-generation hypersonic aircraft. The use of a thermally-insulated functionally graded material having both high mechanical properties and high mechanical properties as a material for a stave cooler for metallurgical furnaces has a novel idea.

[0014] Namely the present invention is a stave cooler for protecting the furnace steel shell from the furnace heat load, with and Tetsugawa side becomes the furnace sides of a ceramic material is made of a metal material such as cast iron, and the ceramic material With said metal material
The stove cooler body is composed of a macro-inhomogeneous functionally gradient material whose composition ratio continuously transitions in the thickness direction of the furnace wall , and the ceramic material has a furnace size.
Arranged so that it gradually decreases from the inside toward the steel side
And and and characterized in that the cooling pipe to form a refrigerant passage iron skin side arranged integrally made by casting the metal material
I do. The intermediate layer of the stave cooler body is
Composed of a ceramic material and the metal material, and has a heat load in the furnace.
Phase with thermal stress relaxation function against temperature fluctuation due to temperature
To form, for example, the furnace inside in the thickness direction of the furnace wall
Ceramic material and metal, almost halfway between the
It is preferable that the composition ratio with the material is approximately 1: 1.
Good.

Referring to the drawings, a specific embodiment of the present invention and its operation and effect will be described.

First, a description will be given of a strobe cooler main body having a function of relieving thermal stress according to the present invention. FIG. 5 schematically shows a cross section of a main part of the stave cooler main body of the present invention.

The stave cooler body of the present invention has a macro-heterogeneous structure having a thermal stress relieving function in which different characteristics such as a heat shielding characteristic on the heating side A and a mechanical characteristic on the cooling side B are shared. Body. Moreover, this structure is of a gradient function type in which transitions from the heating side A to the cooling side B are continuously made so that the structures made of different materials having respective functions do not substantially form an interface. It is. In order to manufacture such a stave cooler body, it is necessary to simultaneously achieve both (1) optimization of the heat shielding characteristics and mechanical characteristics and (2) optimization of the thermal stress relaxation function. Here, there is difficulty in creating the panel 7 of the present invention. The part where the stave cooler body is installed is about 600 to 1200 ° during operation of the blast furnace or the like.
Since C is placed in an environment at a high temperature and in which the temperature fluctuates drastically, a great deal of thermal stress is generated. Therefore, conventional refractories and stave coolers could not cope.

Referring to FIG. 5, a ceramic material 9 is disposed on the heating side A of the stave cooler body, a metal material 10 is disposed on the cooling side B, and the ceramic material 9 is disposed from the heating side A to the cooling side B. The density is gradually lowered, and conversely, the density of the metal material is gradually increased, and the intermediate portion C has a functionally graded structure forming a composite phase of a ceramic material and a metal material. Thereby, the heating side A has excellent heat shielding properties, and performs a thermal stress relieving function of appropriately dispersing local thermal stress generated inside the stave cooler body under a temperature gradient of heating and cooling of the furnace body. Since the cooling side to which is attached is made of a high-strength metallic material, it can have necessary mechanical characteristics.

The ceramic material, when exposed to a high temperature gas stream, must have thermal barrier properties, low thermal conductivity, heat resistance, non-oxidizing properties and abrasion resistant properties to accommodate load drop. Yes, and when subjected to repeated heating, it must be able to withstand thermal fatigue fracture due to inelastic strain. Therefore, as for the ceramic material disposed on the heating side A, from the viewpoint of the characteristics or function, the heat shielding property and the heat insulating property are set so that the temperature of the heating side ceramic material surface which is the starting point of thermal stress destruction is equal to or lower than the elasto-plastic transition temperature. It is necessary to balance the thermal stress relaxation function. On the other hand, from the material side, it is necessary to apply a material having an elasto-plastic transition temperature as high as possible and a material having an appropriate coefficient of thermal expansion. From the above viewpoint, the outermost surface layer on the heating side A includes alumina Al ₂ O ₃
It is preferable to provide a system ceramic. This alumina Al
It is preferable to add silicon carbide Sic-based ceramic as a reinforcing material to ₂ O ₃ in order to improve its mechanical properties.

Next, in the intermediate portion C, a certain period (3 to 4)
When the outermost surface layer on the heating side A is worn out after operation, non-oxidation characteristics become important. Therefore, silicon-based non-oxide ceramics, silicon carbide Sic, and silicon nitride Si ₃ having excellent oxidation resistance are used.
It is preferable to provide a ceramic material such as N ₄ or molybdenum silicate MoSi ₄ . In the ceramic constituting the intermediate portion C, the content of the alumina-based ceramic may be increased toward the heating side A, and both types of ceramics may be used in combination.

On the other hand, as the metal material disposed on the cooling side B, gray cast iron FC150 (JIS-G550), which has abundant track record for use as a base material such as a stove cooler for a blast furnace.
1), Spheroidal graphite cast iron FCD440 (JIS-G550)
2): etc. are preferred.

FIG. 3 is a schematic view of the macro composition of the cross section of the stave cooler main body in the thickness T ′ (distance from the heating side A to the heating side surface B ′ of the cooling pipe 5) in the functionally graded stave cooler of the present invention. FIG. 6B shows a temperature distribution when the furnace temperature in the stave cooler main body becomes about 1200 ° C. in FIG. 6B. FIG. 6A is an enlarged cross-sectional view of the stave cooler 8 corresponding to FIGS. 6B and 6C.

In FIG. 6B, the horizontal axis AB 'indicates the direction of the thickness T' of the stove cooler, and the vertical axis indicates the relative component amounts of the ceramic material (dashed line) and the metal material (solid line). . Thus, the composition of the stave cooler main body of the present invention gradually decreases the content of the ceramic material from the heating side A to the cooling side B, and gradually increases the content of the metal material. The macro tissue is artificially continuously transitioned.

In FIG. 6C, the horizontal axis AB 'indicates the direction of the thickness T' of the stove cooler, and the vertical axis indicates the temperature. The solid line is the temperature distribution when the stave cooler body having the thermal stress relaxation type inclination function of the present invention is used, and the broken line is the temperature distribution when the stave cooler body is entirely made of cast iron. As is clear from FIG. 6 (c), when the stave cooler main body is entirely made of cast iron, the temperature distribution becomes substantially straight, whereas in the stave cooler main body of the present invention, the intermediate portion C is formed of the ceramic material 9. And metal material 1
Since it is in a composite phase with 0, the temperature gradient (head) is reduced. In this way, when the temperature gradient (head) is reduced, the generated thermal stress is greatly reduced and the thermal stress relaxing function is achieved even under the fluctuation of heating and cooling, as is clear from the above-mentioned relational expression. As a result, cracks in the stave cooler 8 are remarkably suppressed, and even when the stave cooler 8 is gradually worn from the inside of the furnace and the thickness T ′ is reduced, the functionally graded material structure which is continuously transitioned in the thickness direction is still obtained. Therefore, the function of relaxing the thermal stress is maintained.

Although the stave cooler body of the present invention has been described above, the shape, diameter, arrangement state, etc. of the ceramic material 9 depend on the thermal stress relaxation characteristics required for the stave cooler depending on the operating conditions of the blast furnace, and the dynamics on the cooling side. It can be appropriately selected in consideration of characteristics and the like. Therefore, FIG. 5 shows a ceramic material having a circular cross section. However, the present invention is not limited to this, and the cross section thereof is easy to manufacture such as a polygon such as a triangle, a square, a pentagon, and a hexagon, and an ellipse such as an ellipse. 5 or a shape that does not easily fall off when gradually worn from the inside of the furnace, and may be modified in consideration of the adhesion to the molten metal.
It can be arranged in a direction perpendicular or oblique to the -B section, either continuous or discontinuous.

The arrangement of the ceramic material 9 is as follows.
In addition to the staggered arrangement shown in FIG. 5, the direction A (or B
Direction), a lattice-like arrangement or a mere lamination arrangement can be taken.
May be arranged after being combined in advance in a grid or the like.

The diameter of the ceramic material 9 in the main body of the stave cooler is selected in consideration of the required thermal and mechanical characteristics in accordance with the shape, arrangement and the like.

Next, a method for manufacturing the stave cooler of the present invention will be described.

FIG. 7 shows a typical production example. Here, (a) is a cross-sectional view of the ceramic material 9 as viewed from the lateral direction, and (b) is a cross-sectional view taken along line II of (a).

As shown in FIG. 7, a rod-shaped ceramic material 9 having a different diameter is placed inside a sand mold 11 having an appropriate shape and size.
The inner lower surface of the sand mold 11 is regarded as the heating-side surface A, and the diameter is gradually reduced from the heating side in the thickness T direction of the stave cooler (in order of i → b → c → d → e → f). The ceramic material 9 is disposed while ensuring a gap where the density becomes appropriate. Here, when the molten metal 10 is injected into the sand mold 11, the ceramic material 9 moves due to the injection pressure or the like.
As shown in FIG. 7A, it is preferable to embed both ends of the rod-shaped ceramic material 9 on the inner side surface of the sand mold 11 so as not to float.

The embedding dimension L can be set arbitrarily as long as the ceramic material 9 can be fixed sufficiently. At this time, in combination with the embedding of both ends of the ceramic material 9, each ceramic material 9 may be connected and fixed near a center portion of the width dimension W thereof with a helmet rod (wire) (not shown).

Then, after disposing the ceramic material 9 in the concave portion of the sand mold 11, a required number of cooling pipes disposed in the stave cooler 8 are disposed in the concave portion of the sand mold 11 at an appropriate position on the upper surface of the ceramic material 9. I do. The number of the cooling pipes is generally four to six. As a material of the cooling pipe, a steel pipe is preferable in terms of heat conductivity, heat resistance, mechanical strength, and the like.

Thereafter, the stave cooler 8 of the present invention is manufactured by melting a metal material such as cast iron and casting it into the recess of the sand mold 11 and solidifying it.

In this case, the molten metal material is, for example, 125
Because of the high temperature of about 0 to 1280 ° C., the casting material such as a sand mold or a cooling pipe is rapidly heated at the time of casting, causing a temperature difference between the casting materials and generating thermal stress which causes cracks. Further, it is well known that a molten metal material generally shrinks when cooled and solidified, and this shrinking force can cause damage to a casting material. However, in the stave cooler of the present invention, since the density of the ceramic material 9 having low thermal conductivity and heat resistance is gradually inclined from the lower surface side of the sand mold 11, the respective materials at the time of casting the molten metal material are inclined. Since the residual stress relaxation effect is achieved, and there is no possibility of the occurrence of cracks as described above, it is also possible to manufacture a stave cooler that has high reliability and can always achieve the expected effect. It is a feature.

The size of the stave cooler of the present invention can be set by the width W, the thickness T, and an arbitrary length of the concave portion of the sand mold 11. The specific numerical value is selected in consideration of manufacturing restrictions, transportation and taking-in after manufacturing, arrangement balance on the furnace inner surface, and the like.
A thickness of about 600 mm x 1,000 mm width x 2,000 mm length is appropriate.

Next, a method for disposing the stave cooler of the present invention on the inner surface of the furnace will be described.

FIG. 8 shows a state in which the stave cooler 8 is arranged on a furnace wall of a blast furnace or the like. FIG. FIG. 6A is an enlarged view of a main part of the stave cooler main body. Generally, four to six cooling pipes 5 are cast in the stave cooler 8, and are usually fixedly installed on the furnace shell 1 by four stave fixing bolts 6 '.

The furnace wall structure shown in FIG. 8 is obtained by constructing a furnace body profile by lining a refractory (brick) 7 inside the furnace of a stave cooler 8. In such a furnace wall structure, even if the refractory lining 7 is damaged or dropped, the stave cooler 8 of the present invention has a functionally gradient material structure.
As in the case of the furnace wall structure as shown in FIG.
Does not follow the process of cracking, peeling, falling off, and eventually cracking at the bottom of the cast iron rib 3-1 and peeling off, falling off, and damaging the cast iron 3 body.

Further, in the present invention, the construction of the refractory lining (brick) lining the inside of the furnace is stopped on the basis of the concept of thinning the wall as a method of solving the conventional disadvantage of insufficient holding power of the cast brick inside the furnace. By increasing the thickness of the stave cooler 8 itself, the space between the inner surface on the heating side and the inner surface on the cooling side can be made of only the thermal stress relaxation type functionally gradient material.

[0040]

As described above in detail, according to the stave cooler having the stave cooler body made of the thermally stress-relaxed functionally graded material of the present invention, (1) the heat shielding characteristics on the heating side and the cooling side Because of the structure that combines the mechanical characteristics of the furnace,
The function of relieving the thermal stress can be exerted without regret, cracks can be significantly suppressed, the furnace wall can be prevented from being worn, and a stable furnace wall profile can be maintained for a long time.

(2) Even if the inner surface of the furnace is worn, the inclination function characteristics in the thickness direction do not change, the inner surface of the furnace shell is not exposed, and the furnace is not excessively cooled. Therefore, the temperature in the vicinity of the furnace wall does not decrease, the inactivation in the furnace can be prevented, and the heat loss of the furnace body can be significantly suppressed.

(3) Therefore, a metallurgical furnace such as a blast furnace provided with the stove cooler of the present invention can operate stably for a long period without any modulation of the discharge of the charge or disturbance of the gas flow. The operability such as the improvement of the operability and the reduction of the fuel ratio can be remarkably improved.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a furnace wall cross section of a conventional blast furnace.

FIG. 2 is a plan view (a) and a cross-sectional view (b) of the inside of a stave cooler of a conventional blast furnace.

FIG. 3 is a diagram showing a cross section (a) of a main part of a stave cooler of a conventional blast furnace and a temperature distribution (b) of the stave cooler.

FIG. 4 is a sectional view of a main part of a conventional thin-wall stave cooler.

FIG. 5 is a sectional view of a main part of a stave cooler body of the present invention.

6A is a sectional view of a main part of a stave cooler according to the present invention, FIG. 6B is a view showing a relative component amount, and FIG.

FIG. 7 is a diagram showing a production example of a stave cooler of the present invention.

FIG. 8 is a cross-sectional view of a main part showing a state where the stave cooler of the present invention is installed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Furnace steel shell 2 Stave 2 'stave 3 Cast iron part 3-1 Cast iron rib 4 Cast brick 4' Cast brick 5 Cooling pipe 5 'Cooling pipe 6 Stave mounting hole 6' Stave mounting bolt 7 Lining refractory 8 Stave cooler 9 Ceramic Material 10 Metallic material 11 Sand mold 12 Brick support rib 13 Cast brick 14 Castable

Claims (1)

(57) [Claims] 1. A stave cooler for protecting a furnace shell from heat load in a furnace, wherein a furnace inner surface is made of a ceramic material and a steel shell side is made of a metal material such as cast iron.
The composition ratio between the ceramic material and the metal material is
A stave cooler body composed of a macro-inhomogeneous functionally graded material that transitions continuously in the thickness direction of the
The size of the ceramic material is from the furnace inside to the steel
Towards arranged so as to gradually become smaller, and integrally arranged a cooling pipe to form a refrigerant passage iron skin side, front
A stave cooler for a metallurgical furnace such as a blast furnace , wherein the metal material is cast .