JPH0657322A - Skid button for walking beam type heating furnace - Google Patents

Abstract

PURPOSE:To provide a skid button having a structure capable of being welded to a skid pipe and to provide the desired performance relating to the whole characteristics of compressive strength, oxidizing resistance and toughness even in the heated using condition at a specific temp. or above. CONSTITUTION:This skid button is made to be a complex structure with an upper layer part 21, an intermediate layer part 22 and a lower layer part 23 and the upper layer part being in contact with a material to be heated is formed with a high Cr alloy having 80% or higher Cr content and excellent oxidizing resistance and high temp. compressive strength. The intermediate layer part is formed with an alloy having excellent toughness and the lower layer part is formed with a heat resistant alloy so as to be weldable and the intermediate layer part is finely divided into at least four or more layers and the component composition in each layer is varied from the upper layer part to the lower layer part step by step.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a skid button used in a walking beam type heating furnace for heating steel materials such as steel slabs and slabs.

[0002]

2. Description of the Related Art A walking beam type heating furnace is provided with a plurality of rows of skid beams consisting of a moving beam and a fixed beam, and the moving beam periodically moves up and down and horizontally reciprocates to heat the beam to be heated. The material is conveyed while being alternately transferred to the moving beam and the fixed beam. As shown in Fig. 1, the skid beam (1) is a hollow skid pipe (10) made of a heat-resistant alloy with a plurality of skid buttons (12) standing upright at regular intervals in the axial direction. The material to be heated (3) is supported and conveyed by the top of the skid button (12).

Cooling water is forcibly circulated in the skid pipe (10) to mitigate the heat effect on the skid button due to the high temperature oxidizing atmosphere in the furnace and prevent the temperature rise of the skid button. There is. In recent years, in order to improve the operating efficiency of the heating furnace, the operation is performed at a temperature of about 1300 ° C or higher, and the surface temperature of the skid pipe is about 200 ° C by cooling with cooling water. There is a temperature gradient of about 1100 ° C between the base and the top.

The characteristics required of the skid button are:
Considering the recent severe operating conditions, first of all, at least the vicinity of the top of the skid button must be provided with compressive strength and oxidation resistance capable of withstanding the load of the material to be heated at a high temperature of 1300 ° C. or higher.

Further, when a material to be heated is conveyed, a large dynamic load is repeatedly applied to the skid button, so the skid button must have toughness capable of withstanding impact.

Conventionally, a heat-resistant alloy or a ceramic sintered material has been used as a material for the skid button, but under such high temperature use conditions of 1300 ° C. or higher, the former material has a sufficiently high temperature compression. Since the strength cannot be obtained, the latter material has a disadvantage of poor toughness. A composite sintered alloy having a mixed structure in which fine ceramic particles are compounded with metal Co or Cr has also been proposed. However, in a high temperature use environment, the ceramic and the metal interact with each other to cause material deterioration. There was a problem.

Therefore, attention has been paid to Cr, which has excellent effects at high temperature strength and oxidation resistance.
The Cr-Fe-based high Cr alloy containing the above is used as a material for skid buttons.

By the way, in a high Cr alloy, Cr is about 80
%, The material becomes sticky when it is used at a high temperature of about 1000 ° C. or higher, but if it is used at a lower temperature, it becomes vulnerable to mechanical shock. Also, about 650-700
In a portion exposed to a temperature in the vicinity of ° C, the sigma layer precipitates and the material becomes brittle, so that at least in this region, the toughness is insufficient.

Further, since the high Cr alloy has poor weldability, the skid button made of the high Cr alloy cannot be directly attached to the skid pipe by welding.
Therefore, as shown in FIG. 2, the heat-resistant steel casing (14) was attached to the skid pipe (10) by welding (16), and the skid button (12) was fitted into the casing (14) for use. .

If the skid button can be directly attached to the skid pipe, not only the stability of the skid button is improved and the crack resistance against repeated load is improved, but also the number of parts is reduced, which is economically advantageous. Therefore, it is more desirable that the skid button has excellent weldability.

By the way, the above-mentioned compressive strength and toughness are inherently antinomy properties. Therefore, as mentioned above, it is difficult to satisfy all the required properties with a single material under the operating conditions in the temperature range where the high temperature part is 1300 ° C or higher and the low temperature part is approximately 200 ° C. is there.

[0012]

DISCLOSURE OF THE INVENTION According to the present invention, there are 13
An object of the present invention is to provide a skid button having desired performance in terms of all properties such as compressive strength, oxidation resistance, toughness, and weldability even under use conditions in which the temperature is 00 ° C or higher and the low temperature part is exposed to about 200 ° C. To do.

[0013]

The skid button of the present invention has a composite structure composed of at least three layers of an upper layer portion, an intermediate layer portion and a lower layer portion, corresponding to a temperature gradient of the skid button in an actual use environment. It was done,
The upper layer is made of an alloy with a Cr content of 80% or more and is excellent in oxidation resistance and high temperature compressive strength, the intermediate layer is made of an alloy having excellent toughness, and the lower layer is made of a heat-resistant alloy that can be welded. Is formed and the intermediate layer portion is at least 4
The composition is subdivided into layers or more, and the component composition of each layer is changed stepwise between the upper layer portion and the lower layer portion.
The reason why the intermediate layer portion is subdivided into at least four layers and the component composition of each layer is changed stepwise is to reduce the difference between the components when joining the upper layer portion and the intermediate layer portion and the intermediate layer portion and the lower layer portion. This is to reduce the number. This is because if the difference in the components is too large, the amounts of thermal expansion and contraction differ, and cracks are likely to occur during joining. If the components are subdivided into at least four layers, the difference between the respective components can be small, and it is possible to prevent the occurrence of cracks during bonding.

The alloy used for the upper layer portion is an alloy having excellent compressive strength and oxidation resistance even at a high temperature of about 1300 ° C. or higher, containing 80% or more of Cr, and the balance Cr-Fe consisting essentially of Fe. The binary alloy of is preferable. In addition, Cr is 80
% Or more, and if necessary, part or all of Fe may be W, Mo, Nb, Co, Ni, Al, T.
An element such as i, V, or Ta can be substituted alone or in combination.

The heat resistant alloy used in the lower layer may be any material that can be welded to a skid pipe made of heat resistant steel. However, when the material to be heated is transported, the load may repeatedly act on the skid button, causing cracks at the base of the skid button, and the temperature at the connection with the skid pipe is about 200 to 3
Since it is 00 ° C, it is more desirable to use a heat-resistant alloy having excellent impact resistance at temperatures around this temperature.

As the heat-resistant alloy used for the lower layer portion, for example, Cr--Fe-- shown in regions (a) and (b) of FIG. 4 is used.
An example is a ternary alloy of Ni. Of course, other weldable alloys can be used.

The intermediate layer portion includes a portion exposed to a temperature range of at least about 650-700 ° C. For this reason, at least a material that does not precipitate a sigma phase must be used in the temperature region. This is because if the sigma phase precipitates, the material becomes brittle and the toughness inherent in the material cannot be exhibited.

As a heat-resistant alloy that does not precipitate a sigma phase, a Cr-Fe-Ni ternary alloy shown in the region (c) of FIG. 4 can be mentioned. Other heat-resistant alloys can be used as long as they have excellent toughness and do not precipitate a sigma phase.

[0019]

In the skid button of the present invention, the upper layer portion in contact with the material to be heated exhibits excellent oxidation resistance and high high-temperature compression strength even when used at high temperatures of 1300 ° C or higher. The intermediate layer portion exhibits excellent toughness including the portion exposed to the temperature range of about 650 to 700 ° C. Further, the lower layer portion can be directly welded to the skid pipe.

[0020]

EFFECTS OF THE INVENTION The skid button of the present invention has desired properties with respect to all properties such as compressive strength, oxidation resistance and toughness even under a high temperature operation condition of 1300 ° C. or higher. The durability can be secured. Therefore,
It can greatly contribute to the reduction of maintenance and the accompanying improvement of operating efficiency. Further, since it can be directly welded to the skid pipe, not only the crack resistance against repeated load is increased, but also the number of parts is reduced, which is economically advantageous.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 3, a skid button (12) comprises an upper layer portion (21), an intermediate layer portion (22) and a lower layer portion (23). The upper layer part is made of an alloy having a Cr content of 80% or more and excellent in oxidation resistance and high temperature compressive strength, the intermediate layer part is made of an alloy having excellent toughness, and the lower layer part is made of a weldable heat-resistant alloy. The base of (16) is, as indicated by reference numeral (16),
It is welded to the skid pipe (10).

Although not shown, the intermediate layer portion (22)
Must be subdivided into at least 4 layers or more, and the component composition of each layer must be changed stepwise between the upper layer portion and the lower layer portion. When the number of subdivided layers is increased, the component difference between the upper layer portion and the intermediate layer portion, each layer in the intermediate layer, and the intermediate layer portion and the lower layer portion can be minimized. Therefore, it is desirable to increase the number of layers, but the greater the number of layers, the more labor is required for manufacturing. Therefore, the number of layers may be appropriately selected within the range of 4 or more.

Before joining the upper layer portion (21) and the intermediate layer portion (22), each subdivided layer in the intermediate layer portion (22), and the intermediate layer portion (22) and the lower layer portion (23), Alternatively, it is possible to prepare alloy plate materials of predetermined components and subject them to hot pressing or HIP to integrally form them, or prepare powder of predetermined components and use HIP or self-heating combustion sintering method. It is also possible to form a dense sintered body.

An example of the skid button of the present invention will be described below. The skid button we made has 7 middle layers.
It is a rectangular parallelepiped block that is subdivided into layers and has a size of 50.
It is × 100 × 202 (height) mm. Table 1 shows the thickness and composition of each layer
Shown in. In Table 1, each of the intermediate layers is referred to as a first layer, a second layer, ..., And a seventh layer in order from the top. The block is prepared by first distributing the raw material powder into capsules according to a predetermined composition, degassing and sealing, and then HIPing for about 5 hours.
It was molded at (1200 ° C, 1000 atm).

[0025]

[Table 1]

In Table 1, the upper layer is a material which exhibits excellent oxidation resistance and high high temperature compressive strength even at a high temperature of 1300 ° C. or higher, each of the intermediate layers is a material having excellent toughness, and the lower layer is It is a material that can be directly welded to skid pipes. Further, since the alloy components of the layers to be joined are approximated to each other, the difference in the amount of thermal expansion and contraction at the time of molding was small, and a block in a good joined state could be manufactured.

[Brief description of drawings]

FIG. 1 is an explanatory view of a skid beam used in a walking beam type heating furnace.

FIG. 2 is a diagram illustrating a method of attaching a skid button made of a high Cr alloy to a skid pipe.

FIG. 3 is a sectional view of an embodiment of the skid button of the present invention.

FIG. 4 is a phase diagram of a Cr-Fe-Ni ternary alloy,
It is a figure explaining an example of the material used for a part of middle class part of a skid button of the present invention, and a lower class part.

[Explanation of symbols]

 (1) Skid beam (10) Skid pipe (12) Skid button (21) Upper part (22) Middle part (23) Lower part

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuyoshi Nishida 2-4-7 Kyomachibori, Nishi-ku, Osaka City, Osaka Prefecture Chugai Furnace Industry Co., Ltd. (72) Toru Kawai 1-1-1, Nakamiya Oike, Hirakata City, Osaka Prefecture No. 1 Inside the Kubota Hirakata Factory (72) Inventor Akira Shinozaki 1-1-1 Nakamiya Oike, Hirakata City, Osaka Prefecture Inside the Kubota Hirakata Factory

Claims (1)

[Claims] 1. A skid button used in a walking beam heating furnace for supporting a material to be heated by being attached to a skid pipe, which is joined to an upper layer portion, an intermediate layer portion and a skid pipe which are in contact with the material to be heated. The composite structure is composed of the lower layer part, and the upper layer part has a Cr content of 80
% Or more, which is excellent in oxidation resistance and high temperature compressive strength, the intermediate layer part is made of an alloy having excellent toughness, and the lower layer part is made of a heat-resistant alloy that can be welded. Is a subdivided into at least four layers, and the composition of each layer is changed stepwise between the upper layer portion and the lower layer portion, a skid button for a walking beam type heating furnace.