JPS6220819A - Skid button - Google Patents

Abstract

PURPOSE:To prevent the generation of skid marks to a material to be heated and to prevent high-temp. compressive creep deformation, etc., by covering the outside circumference in the corner part at the bottom end of ceramics constituting supporting aggregate with a heat resistant alloy and covering the entire surface in the remaining part of the outside circumference with an impact resistant material. CONSTITUTION:The entire outside circumferential surface in the corner part at the bottom end of the ceramics 1 constituting the supporting aggregate of a skid button is covered with the heat resistant alloy 2. The entire surface in the residual outside circumferential part of the ceramics 1 is covered with the impact resistant material 3. The parts positioned preferably in the upper and lower parts of the material 3 are covered with heat resistant alloy impregnation 3' and the remaining part is covered with the heat resistant alloy 3''. The average heat conductivity of the skid button is as low as 1/2-1/3 the average heat conductivity of the conventional skid button and the temp. in the upper part of the skid button is maintained with not much difference from the temp. of the atmosphere in a furnace.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a skid button that is provided on the upper surface of an in-furnace skid in a steel heating furnace and directly supports the steel material.

(Prior Art) Skid buttons used in heating furnaces must support the weight of the steel material to be heated in a high-temperature atmosphere, and therefore require high compressive creep strength at high temperatures.

Therefore, in the past, the materials used were ■UMCo50, H3
-21, KHR40CM, 5C) Il 3, etc., or a CO-based or Ni-Cr-based heat-resistant alloy, ■ A skid button using a single ceramic or a composite material of solid ceramic and metal has been adopted.

(Problems to be Solved by the Invention) However, in the former skid button using heat-resistant steel, creep deformation occurs on the top surface when used for a long time in a high-temperature atmosphere, no matter how heat-resistant the steel is. ■Therefore, their lifespan is short and they need to be replaced every six months. ■In order to reduce the high-temperature compression creep deformation described in ■ above, cooling water is flowed into the skid pipe for water cooling, but as a result, the temperature of the part of the skid button that comes into contact with the steel material decreases, causing skid marks on the steel material. cause it to happen. There are drawbacks such as.

In order to eliminate this former drawback, that is, to avoid skid marks (increase compressive creep strength at high temperatures), the latter skid button was proposed, but conventional ceramics alone or ceramics and metals were used. The composite type Skirad button has a structure in which the ceramic is exposed on the surface in contact with the heated steel material (Japanese Patent Publication No. 60-9566, Utility Model Publication No. 58-356).
(No. 40, Utility Model Application No. 59-449), (1) Ceramics react with oxide scale and the atmosphere in the furnace and are worn out. ■If there is a height difference in the height of the skid button due to wear and tear from use, or if the steel material is warped, an impact load will be applied to the skid button when the steel material is transferred, which will cause the ceramics to break and scatter. There are drawbacks such as.

By the way, according to the inventor's half-year in-furnace tests, with conventional composite skid buttons made of ceramic alone or with exposed ceramics, no ceramic remained on the skid pipe at the end of the test due to wear and tear caused by breakage and reactions. There wasn't.

Furthermore, since it is not possible to use welding as a means of fixing a skid button made of ceramic alone on a skid pipe, a special structure for fixing is required, resulting in high costs.

In addition to the above-mentioned skid button, there is also a so-called hot type, which has a cylindrical body filled with heat insulating material and a lid attached to the upper opening. There are drawbacks to mention.

In other words, in this skid button, the cylinder and the lid are not integrated, so the cylinder is pushed outward by the heat in the furnace and the weight of the steel material, flattening the skid button and causing skid marks. It gets bigger.

The present invention solves the above-mentioned conventional drawbacks, namely: (1) prevents the occurrence of skid marks and high-temperature compression creep deformation, especially the wear of the upper surface of the skid button, which are the drawbacks of skid buttons made of heat-resistant alloy; The disadvantages of single ceramics or conventional composite skid buttons with exposed ceramics are wear and tear of the ceramics due to reactions with oxide scale and the atmosphere in the furnace, and damage to the ceramics that occurs due to shock loads applied during the transfer of steel materials. This was done for the purpose of preventing breakage, scattering of the broken ceramics, etc., and further preventing (1) the expansion of skid marks due to flattening, which is a drawback of hot type skid buttons.

(Means for Solving the Problems) The gist of the present invention is that the entire outer periphery of the lower end corner of a ceramic supporting aggregate is coated with a heat-resistant alloy, and the entire remaining outer periphery is coated with an impact-resistant material. This is the skid button.

That is, the skid button of the present invention having the above-mentioned configuration can fully satisfy the various requirements that a skid button must have for the reasons explained below.

■Insulation As explained earlier, the quality of insulation has a large effect on the occurrence of steel skid marks.

Therefore, the skid button of the present invention can obtain good heat insulation properties by using ceramics, which has better heat insulation properties than metals, that is, has low thermal conductivity and excellent high-temperature compression resistance as the supporting aggregate. It is preferable that the thermal conductivity of the ceramic used be as low as possible, but according to experiments conducted by the present inventors, a high effect in reducing skid marks was found when ceramics were used that were at least A or lower than metals.

In addition, the composite ratio of ceramics as a supporting aggregate is the area occupation rate of ceramics in the cross section of the skid button (desirably 50% or more on average in the height direction. This value of 50% is This is a value obtained based on the strength and heat insulation properties of 50%, and if it is less than 50%, the required strength and heat insulation properties cannot be obtained and there is little effect in reducing skid marks.

Next, we will explain the differences between ceramics and heat insulating materials, which are generally said to be the same.

Although there is no difference between the two in terms of materials, (1) the pores generated inside are significantly different; in terms of porosity, ceramics has a porosity of less than 0.1%, while heat insulating materials have a porosity of more than 10%. This is because the particles of the raw materials are different. Therefore, (1) the compressive strength of ceramics is very high, whereas that of heat insulating materials is low. Therefore, conventional products in which a heat insulating material is interposed within a heat-resistant alloy material have good heat insulating properties, but have low compressive strength and a short lifespan.

On the other hand, the ceramics used in the skid button of the present invention are made of the same material as the heat insulating material, so they have excellent heat insulating properties, and have high compressive strength, so they can be used as supporting aggregates.

■About high-temperature compression creep strength High-temperature compression creep strength affects the service life as explained in the section (2) above regarding insulation properties.

However, in the skid button of the present invention, there is no problem because ceramics having high high-temperature compression creep strength is used as the supporting aggregate as described above.

■Impact resistance strength and prevention of wear and tear of ceramics due to reactionsAs explained above, ceramics have good effects on heat insulation and high temperature compression creep strength, but as mentioned earlier, this ceramic has ■impact resistance. It has drawbacks such as being weak and being damaged by reacting with the oxidized scale of the heated material and the atmosphere in the furnace.

Therefore, in the skid button of the present invention, the entire outer periphery of the lower end corner of the ceramic supporting aggregate is coated with a heat-resistant alloy, and the entire remaining outer periphery is coated with an impact-resistant material.

Here, the type of impact-resistant material covering the skid button is not limited in any way, but may include a heat-resistant alloy, a heat-resistant alloy containing dispersed ceramic grains, or
Ceramics impregnated with heat-resistant alloys are preferred. Further, the impact-resistant material may be made of the same material for the entire covering portion, or may be made of a different material for part of the covering portion. For example, the upper part of the skid button is particularly marked by high-temperature compression creep deformation, or
The upper and lower parts are coated with heat-resistant alloy-impregnated ceramics,
Others are coated with a heat-resistant alloy.

That is, the heat-resistant alloy-impregnated ceramic is a porous ceramic having a three-dimensional skeleton structure and continuous vent holes, for example, with a porosity of 60 to 80%. Because it is an impregnated structure, that is, a composite structure of ceramics and metal, it has better high-temperature compression creep strength than heat-resistant alloys, etc., and is also more resistant to oxidation scale and reaction with the furnace atmosphere than ceramics alone. This is because the wear and tear on the ceramics caused by this process is significantly reduced.

The ceramic foam of the heat-resistant alloy-impregnated ceramic used in the skid button of the present invention has a porosity of 6.
0 to 80% is desirable. In other words, if it is less than 60%, the impact resistance decreases, and if it is 80%, for example, ceramic grains with a grain size of φ1 to φ5 are contained inside the heat-resistant alloy, and the content of ceramic grains is also 50 to 70% by volume. %
degree is desirable. The reason why the volume ratio is preferably within this range is the same as the reason for the porosity of the ceramic foam described above.

The thickness of the impact-resistant material layer on the top surface of the skid button is 0.5~
2. It is desirable that it be within the range of 0cm.

This is because if it exceeds 2.01, the impact-resistant material layer on the top surface of the skid button will undergo high-temperature compression creep deformation, resulting in the same drawbacks as conventional skid buttons made of heat-resistant alloy. ．． This is because if the thickness is less than 5 cm, the effect of covering the ceramic with the impact-resistant material layer will not be exhibited.

Note that, in consideration of the covering properties of the impact-resistant material layer, it is desirable that the corners of the ceramic supporting aggregate be chamfered.

In addition, in order to enable the skid button of the present invention to be welded to the skid pipe, the lower part of the skid button has the same shape as the conventional skid button made of heat-resistant alloy, and the distance between the welding part and the built-in ceramic is 15 mm at the shortest position. It is desirable to be a dragon or above.

(Function) The skid button according to the present invention uses ceramic as the supporting aggregate, and has a structure in which the entire outer periphery of the lower end corner of the ceramic is coated with a heat-resistant alloy, and the entire remaining outer periphery is coated with an impact-resistant material. Because it was adopted,
It has excellent heat insulation, high-temperature compression creep strength, and impact resistance, and there is no ceramic wear due to reaction, and it can be welded to skid pipes for easy installation.

(Example) The present invention will be described below based on an example shown in the accompanying drawings.

FIG. 1 is a front view and central vertical sectional view showing one embodiment of the skid button according to the present invention, and numeral 1 in the figure indicates ceramics forming the supporting aggregate of the skid button of the present invention. The entire outer periphery of the lower end corner of the ceramic l is coated with a heat-resistant alloy 2, and the entire remaining outer periphery is covered with an impact-resistant material 3.

In the case of this embodiment, the upper and lower portions of the impact-resistant material 3 are coated with heat-resistant alloy-impregnated ceramics 3', and the remaining portion is coated with heat-resistant alloy 3''. The heat-resistant alloy-impregnated ceramic 3' is used to hold down the ceramic 1 when manufacturing the skid button of the present invention, and to strengthen the impact-resistant material 3 on the top and bottom surfaces of the ceramic 1.In this example, The shape of the heat-resistant alloy-impregnated ceramic 3' is made to be a similar shape that is slightly smaller than the shape of the ceramic 1, so that even if the binding force of the heat-resistant alloy 3' is lost, the ceramic 1 can be held by the step difference. There is. In addition, in the figure, 9 is a pedestal, and 1o is a heat insulating material.

By the way, the shape of the ceramic 1 is not limited in any way, and the cross section may be as shown in FIG. 2 (
Any shape such as a solid circle as shown in (a), a hollow circle as shown in (b), a polygon as shown in (c) and (b), an ellipse as shown in (e), etc. In addition, the longitudinal section may also be uniform in the height direction as shown in Figure 3 (a), or the lower part where weldability is required as shown in Figure 3 (b) may be shaped like an inverted truncated cone. It may be of any shape, such as a square shape as shown in (c), a trapezoidal shape as shown in (b), or a part with a hollow bottom as shown in (e).

In addition, the structure shown in FIG. 3 (e) is designed to compensate for the decrease in strength against horizontal forces due to the increased area occupied by the ceramics 1 by the impact-resistant material 3 present in the lower hollow part 4. This may be used in conjunction with the methods shown in Figures 3 (a) to 3).

That is, according to the inventor's experiments and analysis, the thermal conductivity of ceramic 1 is 2 or less than that of metal, and the area occupation rate of ceramic 1 in the cross section of the skid button is 50% or more on average in the height direction. It has become clear that it is highly effective in reducing skid marks in some cases, and the shape is not limited in any way as long as it satisfies this.

However, the layer thickness of the upper impact-resistant material 3 in the skid button of the present invention is preferably in the range of 0.5 to 2.0 cm from the viewpoint of high-temperature compression creep strength and impact strength.

In addition, when manufacturing the skid button according to this example, it is carried out as follows.

As shown in FIG. 4, a heat-resistant alloy-impregnated ceramic 3' and a ceramic 1 are mounted inside a mold 5 made of, for example, alumina. Then, a sprue section 6 and a feeder section 7 are installed above these. Note that the sprue portion 6 and the riser portion 7 are sealed around the sprue portion 6 to prevent water leakage.

The mold 5 in the above-described state is placed in an electric furnace 8 that can be preheated to 1300° C. or higher, and heated at a temperature increase rate (200° C./hr or less) that does not cause thermal shock damage to the ceramic 1.

After holding the temperature at 1300° C. for 2 hours in this manner, for example, a Co-based heat-resistant alloy melted in a separate furnace is poured from the upper part of the electric furnace at a temperature of 1500° C.

After cooling, the mold 5 is dismantled, and the upper and lower surfaces of the skid button are slightly machined to manufacture the skid button according to this embodiment.

(Experimental Results) Various types of skid buttons according to the present invention were manufactured using different components of the ceramic 1, the heat-resistant alloy 2, and the impact-resistant material 3, and were tested in an experimental heating furnace. The results are shown in Table 1. For comparison, Table 1 also shows the results when heat-resistant alloy skid buttons, single ceramic skid buttons, etc. were used.

The operating conditions for this experiment are ■ Furnace volume: effective length 31.9 m
, 9m inside the furnace, 190Ton/Hr, size of heated material: 250 cranes x 1100 m x 300011, heating temperature 1
The temperature was 150°C.

As is clear from Table 1, the superiority of the skid button of the present invention was confirmed.

(Effect of the invention) As explained above, the skid button of the present invention is listed below.
x effect.

■The average thermal conductivity of the skid button of the present invention is A - 'A in the case of the conventional skid button made of heat-resistant alloy.
The temperature above the skid button can be maintained much the same as the atmosphere inside the furnace, so skid marks do not occur on the material to be heated, and unlike conventional methods, the material to be heated is reheated at the outlet of the heating furnace to remove skid marks. There's no need to.

■1200 for conventional heat-resistant alloy skid buttons
The high temperature compression creep deformation at temperatures above .degree. C. is particularly large in the upper part, but the skid button of the present invention has almost no high temperature compression creep deformation, which is less than about A of the conventional skid button. As a result, it was confirmed that the life of the skid button of the present invention was three times longer than that of the conventional skid button.

(2) In the skid button of the present invention, the entire outer periphery of the ceramic supporting aggregate is coated with an impact-resistant material and a heat-resistant alloy, so the impact resistance, which is a disadvantage of ceramics, is greatly improved. Even if the ceramic were to break, it would not be scattered to the outside due to the coating layer, and therefore the performance under load would not change. In the actual furnace test, there was almost no damage.

(2) Furthermore, since the skid button of the present invention has ceramics integrated with a heat-resistant alloy and impact-resistant material, it can be used as fired without requiring any processing required for joining ceramics, etc., resulting in cost reduction. The cost of the product of the present invention was reduced by about 5% compared to the conventional product.

(2) For the same reason as (2) above, the skid button of the present invention can prevent wear of ceramics due to oxidized scale on the surface of the heated material and reaction with the atmosphere in the furnace. In addition, in the actual furnace test, no wear and tear due to the reaction of the ceramics was observed.

(2) The skid button of the present invention can be easily fixed to a skid pipe by welding for the same reason as (2) above.

(2) Also, due to the effect described in (2) above, the skid button of the present invention can be approximately 20% lighter than the conventional skid button using ceramics.

- In the skid button of the present invention, since the ceramic is completely isolated from the external atmosphere, it is possible to use ceramics that have poor high-temperature oxidation resistance. In addition, the strength of the coating material can depend on ceramics as long as it has sufficient heat resistance, so it is possible to remove ceramics and coating materials in any combination depending on the purpose of use, eliminating restrictions in terms of materials. Become.

Although this experiment was conducted only with alumina ceramics as the supporting aggregate, other ceramics such as silicon nitride, zirconia, silicon carbide, and alumina high-strength bricks were also used. May be used. In addition, in this experiment, the impact-resistant materials used were ceramics impregnated with a heat-resistant alloy, which is an alumina ceramic foam impregnated with a Co-based heat-resistant alloy, and ceramics using a Co-based heat-resistant alloy. Measures such as lowering the thermal conductivity by using foam may be taken, and heat-resistant alloys such as Co-based H521
, UMCo50. ．． Not limited to 5816 etc., other Co groups,
A Fe-based or Ni-based heat-resistant alloy may also be used.

[Brief explanation of the drawing]

Fig. 1 is a front view and center vertical sectional view showing one embodiment of the skid button of the present invention, Figs. 2 (A) to (E) and Figs. This is an illustrative drawing of the shape of ceramics, and FIGS.
3(e) is a cross-sectional view, FIGS. 3(a) to 3(e) are front view and center vertical sectional views, and FIG. 4 is an explanatory diagram of a manufacturing method of one embodiment of the skid button of the present invention. 1 is ceramic, 2 is heat-resistant alloy, and 3 is impact-resistant material. Patent applicant: Sumitomo Metal Industries, Ltd.
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Claims (1)

[Claims] (1) A skid button characterized in that the entire outer periphery of the lower end corner of a ceramic supporting aggregate is coated with a heat-resistant alloy, and the entire remaining outer periphery is coated with an impact-resistant material.