JP2750240B2 - Skid button for walking beam type heating furnace - Google Patents

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 billets 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 composed of a moving beam and a fixed beam. The material is conveyed while being alternately transferred to a moving beam and a fixed beam. As shown in FIG. 1, the skid beam (1) comprises a hollow skid pipe (10) made of a heat-resistant alloy and a plurality of skid buttons (12) erected at regular intervals in an axial direction. The material to be heated (3) is supported and transported by the top of the skid button (12).

[0003] In the skid pipe (10), cooling water is forcibly circulated to mitigate the thermal influence on the skid button due to the high-temperature oxidizing atmosphere in the furnace and to prevent the temperature of the skid button from rising. I have. In recent years, in order to improve the operating efficiency of the heating furnace, operation has been 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, so the skid button There is a temperature gradient of about 1100 ° C. between the base and the top.

[0004] As a characteristic required for the skid button,
Considering recent severe operating conditions, first, at least the vicinity of the top of the skid button must have compressive strength and oxidation resistance that can withstand the load of the material to be heated at a high temperature of 1300 ° C. or more.

[0005] Further, when a material to be heated is conveyed, a large dynamic load is repeatedly applied to the skid button. Therefore, the skid button must have toughness to withstand an impact.

Conventionally, a heat-resistant alloy or a ceramic sintered material has been used as a material for the skid button. However, under such a high temperature use condition of 1300 ° C. or more, the former material has a sufficient high temperature compression. The strength was not obtained, and the latter material had the disadvantage of poor toughness. In addition, a composite sintered alloy having a mixed structure in which ceramic fine particles are composited with metal Co or Cr has been proposed, but the ceramic and the metal interact with each other in a high-temperature use environment to cause material deterioration. There was a problem.

Therefore, attention has been focused on Cr which exhibits excellent effects at high temperature strength and oxidation resistance.
The Cr-Fe-based high Cr alloys described above are used as skid button materials.

In a high Cr alloy, Cr is reduced to about 80%.
If the content is more than 100 % by weight , the material becomes sticky when used at a high temperature of about 1000 ° C. or more. However, if used at a lower temperature, there is a problem that the material becomes weak against mechanical shock. Also, about 65
In a part exposed to a temperature of about 0 to 700 ° C., a sigma phase is precipitated and the material is embrittled. Therefore, at least in this region, the toughness is insufficient.

[0009] Since a high Cr alloy has poor weldability, a skid button made of a high Cr alloy cannot be directly attached to a skid pipe by welding.
Therefore, as shown in FIG. 2, the casing (14) made of heat-resistant steel 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, the stability of the skid button will be improved, the crack resistance against repeated loads will be improved, and the number of parts will be reduced, which is economically advantageous. For this reason, it is more desirable that the skid button has excellent weldability.

By the way, the above-mentioned compressive strength and toughness inherently conflict with each other. Therefore, as described above, it is difficult to satisfy all the required characteristics with a single material under a use condition in a temperature range where the high temperature part is 1300 ° C. or more and the low temperature part is about 200 ° C. is there.

[0012]

SUMMARY OF THE INVENTION In the present invention, a high-temperature part
It is an object of the present invention to provide a skid button having desired performance with respect to all properties of compressive strength, oxidation resistance, toughness, and weldability even under use conditions where the low temperature part is exposed to about 200 ° C. or more at 00 ° C. or more. I do.

[0013]

The skid button according to the present invention has a composite structure comprising at least three layers of an upper layer, an intermediate layer and a lower layer in accordance with the temperature gradient of the skid button in an actual use environment. That
The upper layer is made of an alloy that has a Cr content of 80% by weight or more and has excellent oxidation resistance and high-temperature compressive strength, the middle layer is made of a Cr alloy that does not precipitate a sigma phase, and the lower layer is weldable. It is formed from a heat-resistant alloy, and the intermediate layer portion is subdivided into at least four or more layers.
Step up the Cr content from the upper layer side to the lower layer side
It is made to change so that it may decrease as much as possible. Subdivision of the intermediate layer into at least four or more layers to gradually change the component composition of each layer is performed when joining the upper layer and the intermediate layer and the intermediate layer and the lower layer as much as possible. This is to reduce it. If the difference between the components is too large, the amounts of thermal expansion and contraction are different, and cracks are likely to occur during joining. At least 4
If the layers are subdivided, the difference between the components can be small, and the occurrence of cracks at the time of joining can be prevented.

The alloy used for the upper layer is an alloy having excellent compressive strength and oxidation resistance even at a high temperature of about 1300 ° C. or more, and contains 80% by weight or more of Cr, and substantially Fe
A binary Cr—Fe alloy consisting of In addition, Cr
At least 80% by weight , and if necessary, F
e, W or Mo, Nb, Co, Ni, A
It can be substituted for an element such as 1, Ti, V, Ta, etc., alone or in combination.

The heat-resistant alloy used for the lower layer may be any material that can be welded to a heat-resistant steel skid pipe. However, when the material to be heated is conveyed, the load repeatedly acts on the skid button, which may cause a crack at the base of the skid button.
Since the temperature is 00 ° C., it is more desirable to use a heat-resistant alloy having excellent impact resistance at a temperature around this temperature.

As a heat-resistant alloy used for the lower layer portion, for example, Cr-Fe- shown in regions (a) and (b) of FIG.
A ternary alloy of Ni can be mentioned. 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 to 700 ° C. Therefore, a material that does not precipitate at least a sigma phase must be used in the temperature region. If the sigma phase is precipitated, the material becomes brittle, and the toughness inherent to the material cannot be exhibited.

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

[0019]

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

[0020]

As described above, the skid button of the present invention has the desired performance with respect to all the properties of compressive strength, oxidation resistance and toughness even under high-temperature operating conditions of 1300 ° C. or more. Durability can be ensured. Therefore,
This can greatly contribute to the reduction of maintenance and the improvement of operation efficiency accompanying the maintenance. Further, since it can be directly welded to the skid pipe, not only the crack resistance against the repeated load is increased, but also the number of parts is reduced, which is economically advantageous.

[0021]

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

Although not shown, the intermediate layer portion (22)
Needs to be subdivided into at least four layers, and the component composition of each layer must be changed stepwise between the upper layer part and the lower layer part. When the number of subdivided layers is increased, the component difference between the upper layer and the intermediate layer, each layer in the intermediate layer, and the intermediate layer and the lower layer can be minimized. Therefore, it is desirable to increase the number of layers. However, as the number of layers increases, a great deal of work is required. Therefore, the number of layers may be appropriately selected in a range of four or more layers.

In order to join the upper layer portion (21) and the intermediate layer portion (22), the subdivided layers in the intermediate layer portion (22), and the intermediate layer portion (22) and the lower layer portion (23), It is also possible to prepare an alloy sheet material of a predetermined component and apply hot pressing or HIP to these sheet materials to form an integrated plate. Alternatively, prepare a powder of a predetermined component and use HIP or self-heating combustion sintering. And can be formed into a dense sintered body.

An embodiment of the skid button of the present invention will be described below. The manufactured skid button has an intermediate layer portion of 7
It is a rectangular parallelepiped block divided into layers, and the size is 50
× 100 × 202 (height) mm. Table 1 shows the thickness and composition of each layer.
Shown in In Table 1, each layer of the intermediate layer is referred to as a first layer, a second layer,..., A seventh layer in order from the top. In the block, first, the raw material powder is distributed into capsules according to a predetermined composition, and after degassing and sealing, HIP processing is performed for about 5 hours.
(1200 ° C., 1000 atm).

[0025]

[Table 1]

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

[Brief description of the 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 one embodiment of the skid button of the present invention.

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

[Explanation of symbols]

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

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Kazuyoshi Nishida 2-4-7 Kyomachibori, Nishi-ku, Osaka-shi, Osaka Inside Chugai Furnace Industry Co., Ltd. (72) Inventor Toru Kawai 1-1-1, Nakamiya Oike, Hirakata-shi, Osaka No. 1 Inside Kubota Hirakata Factory (72) Inventor Bin Shinozaki 1-1-1, Nakamiya Oike, Hirakata City, Osaka Prefecture Inside Kubota Hirakata Factory (56) References JP-A-3-287716 (JP, A) 2-131543 (JP, U) JP-B 64-9378 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) C21D 1/00 116 F27D 3/02

Claims (1)

(57) [Claims] 1. A skid button for use in a walking beam type heating furnace, which is attached to a skid pipe to support a material to be heated, and which is joined to an upper layer portion, an intermediate layer portion, and a skid pipe in contact with the material to be heated. The upper layer has a Cr content of 8
0% by weight or more and formed from an alloy having excellent oxidation resistance and high-temperature compressive strength. The intermediate layer does not precipitate a sigma phase.
The lower layer is made of a heat-resistant alloy that can be welded, the middle layer is subdivided into at least four layers, and the Cr content of each subdivided layer is determined by the upper layer part.
A skid button for a walking beam heating furnace, wherein the skid button is changed so as to gradually decrease from a side toward a lower layer side .