JP2002115975A - Member for heating oven - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a member for a heating oven where no build-ups are formed. SOLUTION: In the member for the heating oven, a surface-layer section of a part in contact with at least a steel material to be heated is made of a material an oxidation speed of which calculated from the average thickness of a surface oxidation layer after an oxidation test for 100 hours under the same atmosphere and temperature as those of a heating oven that is used for the member for the heating oven is 0.1 μm/h or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating furnace member having excellent build-up resistance, such as a transport roller or a skid button for supporting and transporting a steel material to be heated in a heating furnace for heating or heat-treating a steel material. It is about.

[0002]

2. Description of the Related Art A transport roller for supporting and transporting a steel material to be heated in a heating furnace used for heating or heat treatment of steel materials of various shapes such as thick steel plates and thin steel plates, round bars and square bars and steel pipes, and the like. A so-called build-up phenomenon occurs in which metal powder or oxide scale that peels and falls off from the steel material to be heated is deposited and fixed on the surface of the heating furnace member such as a skid button or a walking beam.

[0003] This build-up not only causes indentation flaws on the surface of the steel material to be heated, significantly lowering the commercial value of the product, but also causes the steel material to be heated to be at a predetermined position on the heating furnace member. , And a transport failure occurs.

For this reason, various countermeasures have conventionally been taken. That is, the main countermeasure is to cover the surface of the heating furnace member with ceramic (for example, see JP-A-1-11-1).
39715 and 1-176020), and a heating furnace member made of a heat-resistant alloy having excellent seizure resistance (for example, JP-A-2-141522).

However, these countermeasures can only suppress the occurrence of build-up, but cannot prevent the occurrence itself, so that the build-up resistance is not sufficient.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heating furnace member having excellent build-up resistance, which can prevent the build-up itself.

[0007]

Means for Solving the Problems In order to achieve the above object, the present inventors have conducted a detailed investigation on the occurrence of build-up, and have obtained the following findings.

[0008] In the build-up phenomenon, an oxide film (hereinafter referred to as a steel scale) formed by oxidizing a steel material by heat treatment is deposited on a conveying member, and further pressed by the steel material and fixed to the surface. This is repeated until a build-up is formed.

Further, the cause of the steel scale sticking to the conveying member may be that the surface oxide of the conveying member reacts with the steel scale to contribute to the fixing, or may be fixed due to the unevenness of the surface of the conveying member.

[0010] However, when the oxidation of the surface of the conveying member exceeds the speed of build-up formation, the steel scale adhered to the surface of the conveying member can fall off, and the build-up cannot be formed.

The present invention has been completed on the basis of the above findings, and has the gist of "a heating furnace member for supporting and transporting a steel material to be heated in the heating furnace, wherein the member is in contact with at least the steel material to be heated. The surface layer of the part has the same atmosphere and temperature as the heating furnace in which the heating furnace member is used.
A heating furnace member made of a material having an oxidation rate of 0.1 μm / h or more calculated from the average thickness of the surface oxide layer after the oxidation test for 00 hours.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the rate of oxidation of a material constituting a surface layer of at least a portion of a heating furnace member (hereinafter, also simply referred to as a "member") in contact with a steel material to be heated is limited as described above. The reason for this will be described together with the operation.

When the oxidation rate of the material constituting the surface layer of at least the portion of the heating furnace member in contact with the steel material to be heated is low, the steel scale reacts with the surface oxide of the member on the surface of the member, or the surface of the member has irregularities. Starting from the above, the steel scale is fixed to the member surface, and is pressed by the steel to form a build-up.

However, the oxidation rate calculated from the average thickness of the surface oxide layer after a 100-hour oxidation test in the same atmosphere and temperature as the heating furnace in which the member is used is 0.1%.
In the case of a material of μm / h or more, even if the steel scale adheres to the surface of the member (material), the steel scale falls off together with the oxide layer on the surface of the member (material), and build-up does not occur. This is clear from the results of the examples described later.

Here, the average thickness of the surface oxidized layer after the oxidation test is defined as an oxide of a material (an oxide of a metal material or an oxide of a metal material) formed on the surface of a member (material) by microscopic observation after the oxidation test. A layer composed of an oxide of a metal material and an oxide of ceramics) is regarded as a surface oxide layer, the surface oxide layer area in the field of view is determined, and this surface oxide layer area is divided by the field width to calculate the value.

The material for obtaining the above-mentioned oxidation rate is not specified at all, and the oxidation rate obtained by the oxidation test under the above-mentioned conditions is 0.
It only needs to be 1 μm / h or more and have the strength necessary to support the steel material to be heated, and it is optional depending on the atmosphere and temperature of the heating furnace in which the member is used and the load applied to the member. You can choose.

More specifically, the material has an oxidation rate of 0.1 μm / h or more in an oxidation test under the above conditions.
Mixing of ceramics and metal materials, such as metal materials of various chemical compositions having the necessary strength to support the steel material to be heated, or spray-coated materials in which ceramic particles are dispersed in the metal material Any of the materials may be used.

As the metal material as the raw material, for example, an Fe-based alloy containing Cr, an alloy with a reduced amount of Cr, or an Fe-based alloy containing W, the iron component in the alloy or the steel scale Alloys designed to cause abnormal oxidation by reacting with iron components therein, such as SUS410 or 25% Cr-7% Ni-3% Mo-
A 3% W-residual Fe alloy can be used.

As a mixed material of a ceramic and a metal material typified by the above-mentioned thermal spray overlay, SUS309 and Hastelloy C276 (15% Cr-16% Mo-3% W-4
% Fe-residual Ni) and a heat-resistant alloy having a low oxidation rate,
A mixture with ceramic particles made of carbide or nitride having a high oxidation rate such as NbC, TiC, NbN, VN, and WN can be given. The mixing ratio of the heat-resistant alloy having a low oxidation rate and the ceramic particles made of carbide or nitride having a high oxidation rate is not particularly limited, and the above-mentioned oxidation rate is determined under the atmosphere and temperature of the heating furnace in which the heating furnace member is used. What is necessary is just to mix suitably so that 0.1 micrometer / h or more may be obtained.

From the viewpoint of preventing the occurrence of build-up, the higher the oxidation rate, the better, and the upper limit is not particularly limited. However, if the oxidation rate is too high, the number of members is greatly reduced and the service life is shortened. Therefore, it is preferable that the rate be at most about 0.3 μm / h.

When the heating furnace member of the present invention is made of a metal material, the whole may be composed of only the material. However, the base material is made of a high-strength metal material, and the base material to be heated is made of a steel material. It is preferable that only the surface layer in contact is made of a material.

[0022]

EXAMPLES Example 1 Thirteen types of test materials shown in Table 1 were prepared and subjected to a build-up resistance test described below. The oxidation rate of each test material shown in Table 1 is a value obtained by conducting an oxidation test in which the sample is heated and held for 100 hours under the atmosphere and temperature conditions shown in Table 1.

[0023]

[Table 1] Build-up resistance test: As shown in FIG. 1, carbon steel (SS4) was placed above the prepared test material T (the upper end was a material).
1), a high-frequency heating coil H was arranged on the outer periphery of the opposite end, and the end of both materials was heated for 1 hour in the same atmosphere and temperature as shown in Table 1. Then, while rotating the rotation pressing member W at 5 rpm,
The operation of applying a load of 2.94 MPa for 6 seconds and then unloading for 100 seconds is repeated 100 times. And this operation is 3
After repetition (300 times in total), the scale thickness remaining on the upper end surface of the test material T is examined. If the scale thickness is less than 200 μm, no build-up is formed. If the scale thickness is 200 μm or more, build-up is formed. Rating as "x"
The results are shown in Table 1.

The basis for the presence / absence of build-up formation is defined as the scale thickness of 200 μm remaining on the upper end surface of the test material T. When the scale thickness is less than 200 μm, the rotary pressing member W (corresponding to a steel material to be heated) No harmful flaws requiring maintenance due to build-up were found on the rotating press member W, whereas harmful flaws due to build-up were found on the rotary pressing member W in the case of 200 μm or more.

As shown in Table 1, the oxidation rate was 0.1 μm.
Test materials (No. 1 to 6) using materials of m / h or more include:
Neither build-up was formed. On the other hand, the test materials (Nos. 7 to 13) using a material having an oxidation rate of less than 0.1 μm / h formed a build-up. << Example 2 >> Four types of transport rolls shown in Table 2 were prepared,
A test was conducted in which these were used in an actual heat treatment furnace at a set furnace temperature of 1000 ° C. in various atmospheres, and the oxidation rate of the transport roll surface after 100 hours of use at the actual furnace temperature was examined, while the presence or absence of build-up formation was performed. The evaluation was performed according to the same criteria as in Example 1. The above results are shown in Table 2 together with the materials used, the atmosphere in the furnace, and the temperature. No.
The transport roll 17 is a roll made of only Si ₃ N ₄ .

[0026]

[Table 2] As shown in Table 2, the oxidation rate of the material was 0.1 μm / h
No build-up was formed on the transport rolls (Nos. 14 and 15). On the other hand, the transport roll (No. 16, No. 16,
17) formed a build-up.

[0027]

According to the heating furnace member of the present invention, a large build-up is not formed. For this reason, since a defect due to build-up does not occur in the steel material to be heated, a product of good quality can be obtained, and a transport failure does not occur. In addition, since the build-up removal operation by lowering the furnace temperature of the heating furnace or the heat treatment furnace to about room temperature is not required, energy and cost can be reduced, and the efficiency of heating and heat treatment is improved.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a method of a build-up resistance test in an example.

[Explanation of symbols]

 T: test material, W: rotary pressing member, H: high frequency heating coil.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) F27D 3/12 F27D 3/12 Z (72) Inventor Kenji Tsubouchi 4-5 Kitahama, Chuo-ku, Osaka-shi, Osaka 33 Sumitomo Metal Industries Co., Ltd. (72) Inventor Sumio Iida 4-5-33 Kitahama, Chuo-ku, Osaka City, Osaka Prefecture F-term inside Sumitomo Metal Industries, Ltd. 4K034 AA06 AA16 BA03 BA04 BA05 BA06 CA01 DB04 EA12 EA15 EB08 EB27 EC03 EC06 4K043 AA01 AA02 CA01 CA02 EA04 GA09 4K050 AA01 BA02 CD02 CG05 CG13 CG17 4K055 AA05 AA06 HA07

Claims (1)

[Claims] 1. A heating furnace member for supporting and transporting a steel material to be heated in a heating furnace, wherein at least a surface layer of a portion in contact with the steel material to be heated has a surface layer formed by the heating furnace in which the heating furnace member is used. A heating furnace member made of a material having an oxidation rate of 0.1 μm / h or more calculated from the average thickness of the surface oxide layer after a 100-hour oxidation test under the same atmosphere and temperature.