JPS61201719A - Construction of skid button for heating furnace - Google Patents

Abstract

PURPOSE:To prevent the generation of cracking, etc., by the thermal deformation of a skid button by placing the skid button body consisting of a sintered ceramic body on the inside of the annular projection of a bottom plate member, fitting a metallic retainer thereto and welding the part to be fitted to the bottom plate. CONSTITUTION:The skid button body 10 made of the sintered ceramic body is imposed on the bottom plate member 20. The cylindrical metallic retainer 30 is put thereon and the peripheral projection 32 at the bottom end edge thereof is fitted into the annular projection 21 of the member 20. A beveled groove 40 on the outside peripheral surface in the fitting part is joined by welding to assemble the skid button. The skid button body 10 consists of the sintered ceramic body and has therefore an excellent heat insulating characteristic. The uneven heating of the material to be heated which occurs in the cooling effect from a skid pipe is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a skid button for supporting a material to be heated in a walking beam heating furnace.

[Prior art]

The hearth of a walking beam heating furnace is composed of a fixed beam and a moving beam, and by vertical and horizontal reciprocating movements of the moving beam, the materials to be heated, such as slabs and billets, are alternately replaced by the fixed beam and the moving beam. Transport from

These beams have skid buttons fixed to them at regular intervals on a skid vibrator, and the material to be heated is placed on the top surface of the skid buttons.

Skid buttons made of heat-resistant alloys (e.g., 5CH12 equivalent) have been widely used in the past, but the furnace atmosphere temperature is usually set at 1300 to 1350°C, and the heated material is heated to about 1200 to 1300°C. The conditions for use are extremely harsh even for heat-resistant alloys. For this reason, cooling water is generally passed through the skid button to forcibly cool the skid button by conductive heat transfer.

[Problem to be solved] As mentioned above, the skid button is cooled by cooling water, so the heated material placed on the top surface loses heat from the contact surface with the skid button, and the temperature decreases. Unevenness occurs.

Although this temperature unevenness can be reduced by lengthening the time in which the material to be heated is in the furnace, the effect is not sufficient and, moreover, the operating efficiency is inevitably lowered.

Furthermore, cooling the skid button by passing a large amount of cooling water through the skid pipe means that the heat inside the furnace is constantly carried out of the furnace by the cooling water, resulting in a large thermoeconomic loss.

As a countermeasure against this problem, attempts have been made to use a ceramic sintered body as a skid button and fix it on the skid pipe CP with a locking tool (9o) as shown in Figure 8. However, the skid button (10') tends to crack due to distortion due to thermal expansion during use, making it difficult to maintain stable operation.

In view of the above, the present invention provides a skid button structure in which a ceramic sintered body is used as a skid button main body, and is capable of maintaining stable heating furnace operation without cracking during use.

[Technical means and effects]

The skid button structure for a heating furnace of the present invention includes a skid button body made of an axisymmetric ceramic sintered body having a truncated conical top, a bottom plate member made of a heat-resistant alloy on which the skid button body is placed, and a skid button. The main component is a heat-resistant alloy cylindrical presser fitting having a tapered portion at the top corresponding to the taper of the truncated conical top of the skid button body for holding the main body on the bottom plate member, and the cylindrical presser fitting is The bottom plate member has a circumferential protrusion formed by notching the outer circumferential edge at the lower end edge, while the bottom plate member has an annular protrusion on its upper surface for fitting the circumferential protrusion of the cylindrical presser fitting, and has a cylindrical shape. The presser metal fitting and the bottom plate are provided with a grooved part forming a substantially U-shaped groove for welding on the outer peripheral surface of the fitted part when the protrusions are fitted together,
The skid button body is placed on the bottom plate member, either directly or via the base plate member, on the inside of the annular projection, and the cylindrical presser fitting is externally fitted onto this, and the fitting part with the bottom plate is joined by welding. This is what I did.

According to the present invention, the skid button main body made of a ceramic sintered body is held on the bottom plate member by the cylindrical presser fitting externally fitted on the main body, so that cracking due to thermal deformation etc. is difficult to occur, and the skid button main body is made of a ceramic sintered body. The material to be heated placed on the button body is baked uniformly without temperature unevenness.

To explain the skid button structure of the present invention with reference to the drawings, in Fig. 1 (10) is a skid button body having an axisymmetric shape made of ceramic sintered body, and in this example, the truncated conical part (11) at the top and the It consists of a cylindrical portion (12) that is continuous at the bottom.

(20) is a bottom plate member made of a heat-resistant alloy, and an annular protrusion (21) is provided on the periphery of the upper surface thereof.

(30) is a cylindrical presser made of a heat-resistant alloy, and has a tapered portion (31) at the top thereof corresponding to the taper of the truncated conical portion of the skid button body (10). The reason why the skid button main body (10) has a truncated cone shape and the tapered part (31) is provided at the top of the cylindrical presser fitting (30) is to make the skid button main body (10) a cylindrical presser fitting. (30) to prevent it from coming out from inside the metal fitting (30).

A bottom plate member (20
) is provided with a circumferential protrusion (32) formed by cutting out the outer periphery for fitting with the annular protrusion (21). The reason for forming the protrusions (32) and (21) on the cylindrical presser fitting (30) and the bottom plate member (20) and fitting them together is because the cylindrical presser fitting (30) is used during welding.
This is to prevent displacement and deformation.

Furthermore, the outer peripheral surface of the lower end edge of the cylindrical presser metal fitting (30) and the outer peripheral surface of the annular protrusion (21) of the bottom punching member (20) are beveled for welding, and are mutually grooved. protrusion (2
When 1) and (32) are fitted together, a substantially U-shaped opening (40) is formed on the outer peripheral surface of the fitted portion.

The skid button body (10) may have a truncated conical shape that is tapered not only from the top but also from the bottom, as shown in FIG. The cylindrical presser fitting (30) in this case may have a tapered portion (31) from the top to the bottom corresponding to the taper of the skid button body (10).

The ceramic that makes up the skid button body (10) is
For example, chromium carbide (Cr, C, Cr, Cz, etc.),
Silicon carbide thread (S i C), zirconium oxide (
ZrOz), alumina (Aj!zoz), silicon nitride thread (St, N4), etc., but especially in the case of chromium carbide ceramic, the cover placed on the top of the skid button body This is preferable because it is less likely to react with scale on the surface of the heating material, and therefore protects the material to be heated and provides excellent durability of the skid button body itself.

The above-mentioned skid button has a skid button main body (10) placed on a bottom plate member (20), and a cylindrical presser fitting (3
0) and internally fit the circumferential protrusion (32) on the lower edge into the annular protrusion (21) of the bottom plate member (20), and then weld the bevel groove (40) on the outer peripheral surface of the fitted part. (W) It is assembled by doing.

In the skid button structure of the present invention, the skid button main body (10) and the cylindrical presser fitting (30) are expressed by the following formula (1).
It is desirable that the button has a shape that satisfies the conditions shown in (II) and (II). , (If) formula is a cylindrical presser metal fitting (
The purpose of removing the skid button body (10) from the main body (10) is to ensure that it is prevented from coming out.

[In the formula, d, diameter of the varnished button body (crane) d, 1
．． Bottom diameter of Niskid button body (crane) d2: Inner diameter of cylindrical presser metal fitting (m) d, t: Top inner diameter of cylindrical presser metal fitting (n) d, lower inner diameter of two cylindrical presser metal fittings (crane) Δt: The gap between the cylindrical presser fitting and the skid button body ((
dz d+)/2) t Maximum temperature when using the Niskid button body ('C) α Coefficient of thermal expansion of the Niskid button body (approximately 4 x 10-h~
12X10-b) In addition, in order to assemble the skid button into a predetermined shape, it is necessary to prevent deformation caused by welding and joining the fitting portion of the bottom plate member (20) and the cylindrical presser fitting (30). However, local deformation tends to occur at the lower end edge of the cylindrical presser fitting (30) due to welding heat. To prevent this, approximately U
It is preferable that the wall thickness of the circumferential protrusion (32) of the cylindrical presser fitting (30) forming the bottom of the letter-shaped groove is 2.0 W or more.

In the gap between the skid button body (10) and the cylindrical presser fitting (30), a ceramic fiber layer (50) may be provided as a heat insulating and/or buffer layer as shown in FIGS. 3 and 4, if desired. is loaded. Ceramic fiber layer (50)
It should not be too thick to prevent it from being pulled out due to the shape of the skid button body, and it should not be too thick when it is in a pressurized state (approximately 2
The layer thickness at 0 kgf/aJ) is preferably 0.2 mm or less. Further, in this case, the following formula [■'] is applied in place of the above-mentioned formula (13) for the gap (Δt) between the cylindrical presser metal fitting (30) and the skid button body (10).

[In the formula, t: thickness of the ceramic fiber layer (50) in a pressurized state (crane). dI+t+ α is the same as above].

The ceramic fiber layer (50) can be formed from various types of fibers such as alumina-based, silica-based, boron oxide-based, silicon carbide, and silicon nitride fibers, but especially from the three components of alumina, poron oxide, and silica. This fiber is suitable because it has a high heat resistance and retains its flexibility for a long period of time. The ceramic fiber layer (50) can be formed by winding a molded product made of ceramic fibers such as paper or felt around the circumference of the skid button body (10), or by wrapping the ceramic fiber bulk around the skid button body (10) and the cylinder. It may be formed by inserting it into the gap with the holding metal fitting (30).

By the way, the skid button main body (10) is not only placed directly on the bottom plate member (20) as described above, but also placed via a base plate member (60) as shown in FIG. The base member (60) may have a shape that is continuous with the bottom of the skid button body (10). By interposing the base plate member (60), thermal stress caused by the vertical temperature gradient generated in the skid button body (10) is alleviated. That is, the skid button main body (10) has a top part exposed to a high temperature atmosphere in the furnace, and a bottom part exposed to a skinned pipe (10).
Due to the cooling effect from the skinned pipe (P), a temperature gradient occurs in the vertical direction, and in order to protect the skinned pipe (P), fireproof and heat-insulating materials are installed on the circumferential surface of the skind pipe (P), as shown in Figure 6. Since the skid button body (1o) is coated with a material layer (the layer thickness is usually about 30 to 50n+) (R), the skid button body (1o) is fireproof and
A large temperature difference and resulting thermal stress occur between the upper and lower parts of the heat insulating material layer (R) at the outer surface level.

The generation of such thermal stress causes cracks to occur in the skid button body (10). As a countermeasure for this, if the base plate member (6o) is interposed as described above, the same effect as when the skid button body (1o) is divided into two parts, the upper and the lower part, can be obtained, and the skid button body (10) The resulting thermal stress is alleviated. Of course, in this case, it is most effective to align the mating surfaces of the skid button body (1o) and base plate member (60) with the outer surface level of the fireproof/insulating material layer (R) of the skid pipe (P). It is. The above base plate member (6o)
may be a ceramic sintered body, a refractory brick, a heat-resistant alloy, etc.

If desired, a ceramic fiber layer (70) is interposed as a heat insulating layer at the interface between the base plate member (60) and the skid button body (10), as shown in FIG. The ceramic fiber layer (70) may be made of the same type of fiber as that loaded into the gap between the cylindrical presser (30) and the skid button body (10). Although not shown, if desired, at the interface between the base plate member (60) and the bottom plate member (20),
Also, as shown in Figures 1 to 4 above, the skid button body (
10) is placed directly on the bottom plate member (20), a ceramic fiber layer similar to the above is interposed as a heat insulating layer at the interface between the bottom plate member (20) and the skid button body (lO). .

As shown in FIG. 6, the skid button constructed according to the present invention is produced by bringing the bottom plate member (20) into direct contact with the peripheral surface of the skid pipe (P) and welding it to the skid pipe (Wl), or by welding (Wl) the bottom plate member (20) to the skid pipe (P). As shown in Figure 7, the skid pipe (P
), a heat-resistant alloy support member (80) having a substantially T-shaped cross section is attached by welding, and the support member (80) and bottom plate member (20) are welded together by placing it on the top surface of the support member (80). ). When the skid button is welded directly onto the skid pipe (P) as shown in Figure 6, if the peripheral edge of the bottom plate member (2o) warps upward due to welding heat, the mounting accuracy will deteriorate and the furnace During operation, an excessive load is applied to the skid button body (1o), causing cracking. To prevent this, the bottom plate member (20
), the lower surface of the skid pipe (P) has a curved shape in which the center part is upwardly convex in accordance with the curvature of the circumferential surface of the skid pipe (P), preferably the center part is convex upward by 0.5 to 3.0 m from both end edges. It is effective to process the surface into a curved surface.

〔Example〕

Assemble the skid button shown in Figure 5 using the following components, attach it to the skinned pipe of the walking beam of a heating furnace (normal temperature: 1300"C), and cover the circumferential surface of the skid pipe with a refractory layer (layer thickness approximately 50 m). The maximum temperature when using the skid button body (1o) is 1230℃.
It is.

CI) Skid button body (1o) (1) Material: chromium carbide ceramic (2) Coefficient of thermal expansion (α): 11.6X10-' (3) Dimensions 2 truncated conical part top diameter 80 MM, truncated conical part top diameter 80 MM, height 45
n+, cylindrical part diameter 110 tm, cylindrical part height 1
0B [■] Base plate member (60) (1) Material: 5CH12 (2) Shape and dimensions: 2 cylindrical body, diameter 110 mm, height 25 fins.

(III) Bottom plate member (20) (1) Material: 5CH12 (2) Dimensions: Inner diameter of annular protrusion (21) 119 mm, protrusion height 5 mm, plate thickness 15 mm.

[] Cylindrical presser metal fitting (3o) fil Material: 5CH22 (2) Dimensions 2nd part inner diameter 97.3mm, lower part inner diameter 115mm,
The height of the taber part is 25 cranes, the total height is 63 cranes, the circumferential protrusion thickness is 1 o fin.

(V) Ceramic fiber layer (5o) (], )] Material: Alumina boron oxide-silica 3
Component system (2) Layer thickness: 1.2 m (pressure force 20 kgf/crA
(thickness when pressurized).

(VI) Ceramic fiber layer (70) (11 material: same as above (2) layer thickness: 1.2 mm (pressing force 20 kg f / cd
) As a result of using the walking beam with the skid button attached above in the heating furnace, there was no damage such as cracks on the skid button body even after 24 months of continuous use, and it is in a condition that can be used continuously for an even longer period of time. This was confirmed. Note that the temperature unevenness during extraction of the material to be heated is ±20° C. or less, which significantly reduces heating unevenness.

〔Effect of the invention〕

According to the present invention, stable operation of the heating furnace can be maintained over a long period of time without causing troubles such as cracking due to thermal deformation of the skid button body.

In addition, the skid button body made of a ceramic sintered body (a) has excellent heat insulation properties, which eliminates uneven heating of the heated material caused by the cooling effect from the skid pipe. (b) Since it has excellent fire resistance and heat resistance, strong cooling as in the case of heat-resistant alloy skid buttons is not required, and therefore heat loss due to cooling inside the skid pipe can be reduced. If the skid pipe is sufficiently protected from the furnace atmosphere by a layer of refractory insulation around its circumference,
The passage of cooling water can be omitted.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a vertical sectional view showing an embodiment of the present invention, and FIGS.
The figure is a half-cut vertical cross-sectional view showing another embodiment of the present invention, and FIG. 8 is a vertical cross-sectional view showing a conventional example. 10 Niskid button body, 20: Bottom plate member, 30: Cylindrical presser metal fitting, 50: Ceramic fiber layer, 60: Base plate member.

Claims (10)

[Claims] (1) A skid button body made of an axisymmetric ceramic sintered body having a truncated conical top, a bottom plate member made of a heat-resistant alloy on which the skid button body is placed, and a skid button body held on the bottom plate member. The main component is a heat-resistant alloy cylindrical presser foot with a tapered part on the top corresponding to the taper of the truncated conical top of the skid button body, and the cylindrical presser foot has an outer peripheral edge on the lower edge. The bottom plate member has a circumferential protrusion formed by a cutout, and the bottom plate member has an annular protrusion on its upper surface for fitting the circumferential protrusion of the cylindrical presser fitting,
The cylindrical presser fitting and the bottom plate are provided with a beveled portion forming a substantially U-shaped bevel groove for welding on the outer peripheral surface of the fitted portion when the protrusions are fitted together, The skid button body is placed on the bottom plate member, either directly or via the base plate member, on the inside of the annular projection, and the cylindrical presser fitting is externally fitted onto this, and the fitting part with the bottom plate is joined by welding. The skid button structure for heating furnaces is characterized by: (2) A ceramic fiber layer is loaded in the gap between the skid button body and the cylindrical presser metal fitting.
1) Skid button structure for a heating furnace as described in item 1). (3) The skid button body and the cylindrical presser fitting are as shown below.
I] and [II]: Δt≧(d_1×t×α)/2‥[I] d_1_B≧(d_2_T+d_2_B)/2‥[II]
[In the formula, d_1: Diameter of the skid button body (mm) d
_1_B: Lower diameter of skid button body (mm) d_
2: Inner diameter of cylindrical presser metal fitting (mm) d_2_T: Top inner diameter of cylindrical presser metal fitting (mm) d_2_
B: Lower inner diameter of cylindrical presser metal fitting (mm) Δt: Gap between cylindrical presser metal fitting and skid button body [(d_2-d_1)
/2] t: Maximum temperature during use of the skid button body (°C) α: Coefficient of thermal expansion of the skid button body] The above item (1) is characterized by satisfying the following conditions.
The skid button structure for heating furnaces described in section. (4) The skid button body, cylindrical presser metal fitting, and ceramic fiber layer conform to the following formulas [I ′], [II], and [III].
: Δt≧(d_1×t×α)/2+t_f…[I′]d1
B≧(d_2_T+d_2_B)/2…[II]t_f≧
0.2...[III] [In the formula, d_1: Diameter of the skid button body (mm) d
_1_B: Lower diameter of skid button body (mm) d_
2: Inner diameter of cylindrical presser metal fitting (mm) d_2_T: Top inner diameter of cylindrical presser metal fitting (mm) d_2_
B: Lower inner diameter of cylindrical presser metal fitting (mm) Δ_t_f: Gap between cylindrical presser metal fitting and skid button body [(d_2-d
_1)/2] t: Layer thickness (mm) of the ceramic fiber layer in a pressurized state t:
Maximum temperature during use of the skid button body (°C) α: coefficient of thermal expansion of the skid button body] The above item (2) is characterized by satisfying the condition shown in
The skid button structure for heating furnaces described in section. (5) The wall thickness of the circumferential protrusion on the lower edge of the cylindrical presser metal fitting is 2 mm.
Item (3) or item ((3) above, characterized in that:
4) Skid button structure for a heating furnace as described in item 4). (6) The bottom plate member has a center portion of the lower surface that is 0.0 mm with respect to both edges.
The skid button structure for a heating furnace according to any one of the above items (3) to (5), characterized in that it is processed into an upwardly convex curved shape of 5 to 3.0 mm. . (7) Item (1) above, wherein the skid button body is made of a chromium carbide ceramic sintered body.
The skid button structure for a heating furnace according to any one of Items 1 to 6. (8) The heating furnace skid according to any one of items (1) to (7) above, characterized in that a ceramic fiber layer is interposed between the skid button body and the bottom plate member. Button structure. (9) In the case where the skid button body is placed on the bottom plate member via the base plate member, a ceramic fiber layer is interposed between the skid button body and the base plate member, Any one of item 1) or item (7)
Skid button structure for heating furnaces described in . (10) The skid button structure for a heating furnace according to item (9) above, wherein a ceramic fiber layer is interposed between the base plate member and the bottom plate member.