JPH021890B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a skid button for holding a material to be heated on a walking beam or a fixed beam in a heating furnace. <Prior art> This kind of skid button was previously made of heat-resistant steel, but it lacked durability because it was used in a high-temperature oxidizing atmosphere, and because it was forced to cool with water, the contact part of the heated material with the skid button In recent years, ceramic skid buttons have been considered due to drawbacks such as local cooling of the material, resulting in uneven temperature distribution of the heated material. An example of such a ceramic skid button is the technique disclosed in Japanese Patent Application Laid-Open No. 60-26615. This skid button is a product in which a ceramic sintered body is charged into a metal cylindrical body, and the cylindrical body and the ceramic sintered body are bonded together using the HIP method, or the upper end of a metal columnar body. It is similar to a ceramic sintered body inserted into a recess formed in a recess and joined using the same HIP method, and the ceramics used include silicon nitride, zirconium oxide, aluminum oxide, sialon, and silicon carbide. <Problems to be Solved by the Invention> The skid button shown in the above-mentioned Japanese Patent Application Laid-Open No. 60-26615 has problems such as insufficient strength at high temperatures because the surrounding cylindrical or columnar body is made of metal. There are problems such as oxidation, and the bonding strength between the metal cylindrical body or columnar body and the internal ceramic sintered body is low, and their coefficients of thermal expansion are greatly different, so they separate during use in high temperature ranges. There is a risk. Furthermore, the above-mentioned ceramic used in this skid button can only be stably used in a temperature range of about 1100°C at most, and has the drawback of increasing reactivity with scale at higher temperatures. The present invention attempts to solve the above-mentioned problems. <Means for solving the problems> The present invention consists of 0.5 to 48% by weight of TiC, 5 to 40% by weight of Ni, and the balance is chromium carbide.
A skid button body made of a columnar body made of chromium carbide is placed inside a cylindrical body made of cermet with a weight ratio of TiC/Ni≦1.2, and the skid button body and the skid button are joined to each other. Skid button and
TiC: 0.5 to 48% by weight, Ni: 5 to 40% by weight, the balance being chromium carbide, and the weight ratio of TiC to Ni
A skid button body made of a chromium carbide column is inserted into a recess drilled in the upper end surface of a cermet column where TiC/Ni≦1.2.
Moreover, the skid button is characterized in that the inner circumferential wall of the recess and the skid button body are joined to each other. In the present invention, the cermet cylindrical or columnar body and the chromium carbide skid button body can be joined by simply fitting them together and heating them without applying any load (gas pressure). It is. The heat treatment in this case is usually carried out at a temperature of 1250 to 1350° C. for 60 minutes in a non-oxidizing atmosphere such as vacuum, hydrogen gas or argon gas to prevent oxidation. In addition, when the skid button body and the cermet cylinder or columnar body are heat-treated for joining, both joint surfaces are
The surface shall be finished so that Rmax.3.0μm or less. As described above, in the skid button of the present invention, the cermet cylindrical or columnar body and the skid button body are joined by simply heating without any load, but if a load is applied during joining, an even stronger joint can be obtained. That's what you get. Therefore, the cermet cylindrical or columnar body and the skid button body are manufactured separately and then joined by HIP treatment, or the temporary sintered bodies of both are sintered by HIP treatment and joined at the same time. Of course, other methods may be adopted. The skid button body obtained by the method of the present invention is
Chromium _carbide such _{as Cr3C2} , _Cr7C3 , _{Cr23C6 ,}
Any one of them or a combination of two or more thereof may be used. The same applies to chromium carbide as a component of cermet materials. <Examples and Effects> The method of the present invention will be described in detail below while citing various properties of Examples and Comparative Examples of the method of the present invention. First, tests were conducted on the bonding strength and other aspects between the cermet material used for the surrounding cylindrical or columnar body and the chromium carbide used for the skid button body. The cermet materials used include chromium carbide (Cr ₃ C ₂ ) powder with a purity of 99.9% or higher and an average particle size of 5 μm, and titanium carbide (TiC) powder and Ni powder with a purity of 99.9% or higher and an average particle size of 5 μm. 3 parts by weight of paraffin was added to 100 parts by weight of the powder mixed in the ratio shown in the table, and after kneading it uniformly, it was molded into a size of 20 x 20 x 5 (mm) at a molding pressure of 1.5 tons/ ^cm2 . °C, 10
Pre-sintering in vacuum for minutes, then in vacuum
A sintered body obtained by sintering at 1350°C for 60 minutes was used. The ceramic material used for the skid button body is a raw material prepared by adding and mixing 3 parts by weight of paraffin to 100 parts by weight of chromium carbide powder with a purity of 99.9% or higher and an ^average particle size of 5 μm.
A sintered body was used which was formed into a size of x20 x 5 (mm), pre-sintered in vacuum at 780°C for 10 minutes, and then main sintered in vacuum at 1450°C for 60 minutes. The bonded surfaces of the cermet material and ceramic material obtained as described above were finished so that the Rmax.3.0 μm or less was achieved, and both were bonded under no load in a vacuum of 10 ^-2 torr. or less. Heat treatment was performed at 1250-1350°C for 60 minutes. The table below shows the bonding strength of the cermet material and ceramic material bonded in this manner and the presence or absence of cracks after bonding. The presence or absence of cracks refers to the observation of cracks entering the ceramic material side after joining. ○ indicates no cracks, and × indicates cracks. The table below also lists the thermal expansion coefficient α and the stress at the start of compressive deformation of the cermet material. About the table below
The unit for Ni, TiC, Cr ₃ C ₂ is weight %, the unit for joint strength is Kg/mm ² , and α is the coefficient of thermal expansion at 1000℃, and the unit is ℃ ^-1 ×10 ^-6 for cermet material. The stress at which compressive deformation begins is when a test piece of 10 x 20 x 20 (mm) is subjected to a crosshead speed in air at 1250°C.
A compression test is performed at 0.1 mm/min., and the stress is expressed as the stress at the start of plastic deformation, and its unit is Kg/ ^mm2 .

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[Table] From the results shown in the table above, the following is clear. That is, the bonding strength with the ceramic material varies greatly depending on the composition of the cermet material, and it is desirable to use a cermet with the following composition for a ceramic material made of 100% chromium carbide. First of all, regarding the amount of TiC,
If the amount of Ni is the same, TiC is 0 and TiC is 10.
If the TiC content is less than 0.5% by weight, the bonding strength will hardly change, but in order to maintain the bending strength of the cermet material, it is necessary to add at least 0.5% by weight of TiC. On the other hand, TiC itself does not have good bonding properties with Cr ₃ C ₂ , and increasing TiC reduces its role as a binder.
It is also necessary to increase Ni, and in the same way TiC and Ni
If the amount of Cr 3 C ₂ is increased too much, the amount of Cr ₃ C 2 in the cermet will decrease and the compatibility with the mating material Cr ₃ C ₂ will deteriorate, and the generation of liquid phase will increase due to the increase in Ni.
There is a problem of promoting grain growth of Cr ₃ C ₂ at the interface. For these reasons, the upper limit of TiC is 48% by weight (sample
(Refer to No. 71), and Ni is at least 5% by weight in order to generate the liquid phase necessary to develop sufficient bonding strength.
On the other hand, if it exceeds 40% by weight, too much liquid phase will be generated and cracks will easily occur due to grain growth of Cr ₃ C ₂ (see sample Nos. 73 to 76 and 78), and the coefficient of thermal expansion α will decrease. Since it is too far from the 11.6×10 ^-6 °C ^-1 of the mating material Cr ₃ C ₂ , it should be 40% by weight or less. Furthermore, as mentioned above, there should be a certain relationship between the amount of TiC and the amount of Ni, and in the table above, the bonding strength is
TiC/Ni≦ as a combination of 10Kg/mm ² or more
It was set to 1.2. As shown in the table above, the stress at which compressive deformation begins for the cermet material used as the material for the cylindrical body or columnar body is:
This is significantly higher than that of cobalt-based heat-resistant steel, which is at most 0.1 Kg/mm ² at similar temperatures and conditions, indicating that the high-temperature strength is sufficient. Next, examples and comparative examples regarding specific skid buttons will be shown. Example As shown in Figure 1, the upper end diameter is 56mmφ, the lower end diameter is
The outer circumference of the truncated cone-shaped chromium carbide skid button body 1 with a diameter of 87.3 mm and a height of 54.2 mm has an inner diameter of 56 mm at the upper end.
A cermet cylindrical body 2 with an outer diameter of 85 mmφ, a lower end inner diameter of 87.3 mmφ, and an outer diameter of 119 mmφ is installed.
It was heated at 1350°C for 60 minutes in a vacuum of 10 ^-2 torr. In this case, the composition of the cermet cylinder 2 is 25% by weight of Ni, 15% by weight of TiC, and the balance is Cr ₃ C ₂ of sample No. 39 in the above table, and the cylindrical body 2 and skid button body 1 are each sintered. The conditions were the same as in the test for determining the bonding strength described above. For the skid button obtained in this way,
As shown in the figure, a washer 3 and a side pusher 4 made of heat-resistant steel
It was attached to a skid pipe 5 via a fitting 6, and used in a walking beam heating furnace maintained at 1300°C. Comparative Example A walking beam type in which a skid button body 1 made of chromium carbide having the same shape as the above example and a cylindrical body 2 made of cermet were simply fitted together and maintained at 1300°C as in the example without heat bonding treatment. Adopted in heating furnace. As a result of observing both the above example and comparative example after one year of actual operation, it was found that although the non-bonded comparative examples had sufficient impact resistance, some of the skid button bodies had cracks and chips. In addition, scale was press-fitted between the skid button body and the surrounding cermet cylindrical body, and the cermet cylindrical body was deformed. However, in the case of the present invention, no deformation, cracking, or chipping was observed in the skid button body, there was no press-fitting of scale, and there was no deformation of the cermet cylindrical body. In addition to the shape shown in FIG. 1, the skid button of the present invention has a shape in which the surrounding cermet has a columnar body 2' as shown in FIG. There is also a type of skid button body 1 that is fitted and heat-bonded. In the device shown in FIG. 2, the cermet cylindrical body 2' and the mounting bracket 6 are joined by diffusion bonding. <Effects of the Invention> As described above, according to the method of the present invention, since the skid button body is made of chromium carbide, it has very good scale resistance and also has a large transverse rupture strength in a high temperature range. It can be stably used in a high temperature range of 1300℃, and the drawback of this chromium carbide skid button body, which is its lack of toughness, is compensated for by the surrounding cermet material, which has high deformation resistance in high temperature ranges. As a result, it is highly durable. Furthermore, when the cermet material used in the present invention is bonded to the chromium carbide skid button body, there is no need to apply any load, and the bond is sufficiently strong with only heat treatment, so scale is not press-fitted, and it has excellent bondability with metal. Since the material is also of good quality, it has the advantage of being easy to join with a mounting washer or the like interposed between the skid button and the cooling pipe.

[Brief explanation of drawings]

FIG. 1 is an explanatory sectional view showing one embodiment of the skid button of the present invention, and FIG. 2 is an explanatory sectional view of another embodiment of the same. In the figure, 1: skid button body, 2: cermet cylindrical body, 2': cermet cylindrical body, 3: washer, 4: side pusher, 5: skid pipe, 6: mounting bracket.

Claims (1)

[Claims] 1. A cermet cylindrical body consisting of 0.5 to 48% by weight of TiC, 5 to 40% by weight of Ni, and the balance being chromium carbide, and in which the weight ratio of TiC to Ni is TiC/Ni≦1.2. A skid button is characterized in that a skid button body made of a columnar body made of chromium carbide is placed inside the skid button, and the skid button and the skid button are joined to each other. 2 A hole is drilled in the upper end surface of a cermet column consisting of 0.5 to 48% by weight of TiC, 5 to 40% by weight of Ni, the balance being chromium carbide, and the weight ratio of TiC to Ni is TiC/Ni≦1.2. A skid button body comprising a columnar body made of chromium carbide is inserted into a recessed part, and the inner circumferential wall of the recess and the skid button body are joined to each other.