JPS6310115B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a skid button for a walking beam, which is a member for supporting a material to be heated in a heating furnace for hot rolling or heat treatment of hot rolled steel materials, an in-furnace roll, or a covering for a walking beam. The present invention relates to a chromium carbide sintered body suitable as a heating material support surface member (balken). [Prior art and problems] A skid button for a walking beam in a heating furnace for hot rolling, which is a member for the support surface of a material to be heated in a heating furnace, a roll in the furnace for a heating furnace for heat treatment of hot rolled steel materials, or a roll in a heating furnace for heat treatment of hot rolled steel materials, The member for supporting surface of the heated material (Balken) for the walking beam of the heating furnace for steel heat treatment must be able to heat the heated material to a predetermined temperature with high thermal efficiency and without causing uneven heat. In order to maintain stable furnace operation,
It is difficult to react with the oxide scale on the surface of the heated material in the high-temperature furnace atmosphere exceeding 1300℃,
Additionally, material properties such as being able to withstand stress due to static and dynamic loads of heavy materials to be heated are required. Conventionally, the material for the support surface of the heated material in these heating furnaces is made of heat-resistant alloy, and in order to prevent softening and buckling due to the high temperature atmosphere inside the furnace, the support surface is heated by internal water cooling. This prevents the temperature of the parts used to rise excessively. However, when the support surface member is strongly cooled, the heated material placed on it loses heat from the contact surface with the support surface member, resulting in a locally low temperature, making it difficult to achieve uniform heating. I can't. Furthermore, the amount of heat carried away from the furnace by the cooling water increases, reducing the thermoeconomic efficiency of the furnace. If cooling of the support surface member is suppressed to alleviate uneven heating and uneven heating of the heated material, the support surface member itself will noticeably wear out and deteriorate due to a reaction with the melted scale on the surface of the heated material, a so-called pick-up phenomenon. In addition, static and dynamic stress concentrates on the notch portion formed by the pick-up, making it more likely that cracks and breakage will occur. Recently, attention has been focused on the heat resistance, heat insulation, chemical stability, etc. of ceramic materials, and it has been proposed to use them as materials for supporting surfaces of heated materials. As a ceramic sintered body, for example, JP-A-58-
No. 64268, JP-A-58-91066, etc. disclose improvements in the quality of sintered bodies made of silicon nitride, silicon carbide, etc. and methods for producing the same. However, in order to apply these sintered bodies as members for supporting surfaces of heated materials, there are problems with impact resistance, bending strength, etc., and pick-up resistance is not sufficient, so it is still difficult to put them into practical use. I haven't gotten around to seeing it yet. [Object of the Invention] The present invention has been made to address the above-mentioned problems, and provides a sintered chromium carbide body for the support surface of a heated material, which has excellent pick-up resistance and has required material properties such as toughness. provide. [Structure and operation of the invention] The chromium carbide sintered body for the supporting surface of a heated material of the present invention has chromium carbide, particularly Cr ₃ C ₂ chromium carbide as a main component, and Cr ₇ C ₃ and Cr ₃ C , Cr ₂₃ C ₆ , and has a component composition in which one or more of the following carbides are blended. In a narrow sense, chromium carbide includes Cr ₃ C ₂ , Cr ₇ C ₂ ,
and _Cr4C are known. Among news ceramics, these chromium carbides have unique properties compared to other oxides, nitrides, carbides, etc., and are excellent in _{pick -} up resistance. It has extremely strong corrosion resistance against scale. Each of the carbides of Cr ₇ C ₃ , Cr ₃ C and Cr ₂₃ C ₆ blended into the Cr ₃ C ₂ chromium carbide, which is the main component, functions primarily as an auxiliary agent for improving sinterability. The main component, Cr ₃ C ₂ chromium carbide powder alone, does not have good sintering properties, but by adding an appropriate amount of the above carbide, the difficulty in sintering is overcome, and it can be used under general firing conditions. A predetermined sintering can be achieved with this, and the cost required for sintering can also be reduced. Furthermore, the improvement in sinterability brings about various effects such as densification (improvement in relative density) of the obtained sintered body, high-temperature properties, especially improvement in strength, impact resistance, and pick-up resistance in the high-temperature range. The preferred combination and blending composition of Cr ₃ C ₂ chromium carbide and each carbide blended therein constituting the sintered body of the present invention are as follows. (A) _Cr3C2 75-99% by weight _{, balance Cr23C6 ,} (B) _{Cr3C2 60-99} % by weight, balance _{Cr7C3 ,} (C _{) Cr3C2 60-99} % by weight , balance _Cr3C , (D) _{Cr3C2 50-90} % by weight, _{Cr7C3 5-45} % by weight, balance _Cr23C6 , (E _{) Cr3C2 30-85} % by weight, _Cr7 C ₃ 5-40% by weight, balance Cr ₃ C, (F) Cr ₃ C ₂ 40-80% by weight, Cr ₇ C ₃ 5-45% by weight,
_Cr23C6 5-30% by weight, balance _{Cr3C .} The blending amount of Cr ₃ C ₂ chromium carbide in the above sintered bodies (A) to (F) is determined to ensure the characteristics of Cr ₃ C ₂ chromium carbide, especially the pick-up resistance, and the blend of each added carbide. The amount is to ensure the sintering promotion effect and
This is defined as a range that does not impair the characteristics of Cr ₃ C ₂ chromium carbide. The chromium carbide and each carbide powder used in the present invention preferably have a high purity of 99% or more. This is because impurities contained in the raw material powder evaporate during high-temperature firing, causing pores, or forming a low-melting liquid phase, which deteriorates the high-temperature properties of the obtained sintered body. In addition, the larger the surface tension of the raw material powder is, the more advantageous it is when firing, and from this point of view, the particle size is 50 μm.
The following fine particles are preferably used. The chromium carbide sintered body for the support surface of a heated material of the present invention is prepared by kneading raw material powder in which an appropriate amount of the above-mentioned predetermined carbide powder is blended with Cr ₃ C ₂ chromium carbide, and adding an appropriate amount of an appropriate forming aid as necessary. After blending and, if necessary, granulating to a suitable particle size by a conventional method, the particles are manufactured through a sintering process. Sintering is preferably performed by a hot pressure sintering method such as a hot press method or a hot isostatic pressure sintering method. When using the hot press method, the pressing force is 50 to 350 kgf/cm ² and the firing temperature is 1350 to 350 kgf/cm 2
1550℃, while in the hot isostatic sintering method, the pressure is 500℃.
Good results can be obtained under conditions of Kgf/cm ² or more and a temperature of 1400 to 1500°C. The sintered body obtained in this way is extremely dense with a theoretical density of 98% or more, has almost no pores, has a fine grain size, has excellent Young's modulus, shear modulus of elasticity, fracture rate, etc., and is resistant to high temperatures. Excellent pick-up resistance against melting scale of heated materials. [Example] The production and pick-up resistance of the sintered chromium carbide body for the support surface of a heated material according to the present invention will be explained using examples. (1) Production of sintered bodies: Cr ₃ C ₂ chromium carbide and Cr ₇ C ₃ , Cr ₃ C,
3 parts by weight of parfine was added to 100 parts by weight of powder obtained by mixing Cr ₂₃ C ₆ carbides (each with a purity of 99.9% and an average particle diameter of 5 μm) in the proportions shown in Table 1, and after uniformly kneading, molding was performed. Pressure 1.5 tons/
Pressure molded into 10mm x 30mm x 6mm, pre-sintered in vacuum at 780℃ for 10 minutes, then in vacuum,
Main sintering was completed at 1450°C for 60 minutes. Trial numbers (10) to (13) are the sintered bodies (A) and (22) to
(25) is a sintered body (B), (31) to (33) are sintered bodies (C),
(47) to (53) correspond to the composition of the sintered body (D), (73) to (78) correspond to the composition of the sintered body (E), and (84) to (95) correspond to the composition of the sintered body (F). . The other sample sintered bodies are comparative examples that deviate from the composition specified in the present invention. (2) Pick-up resistance test: As a counterpart material, S45C material, which was kept at 1300℃ for 1 hour and then cooled in a furnace to form scale on the surface, was used, and each of the sintered bodies obtained above (1) was used as the counterpart material. ~(108)
is pressed with a load of 20Kgf/ ^cm2 , and
Hold at °C for 10 hours. After that, the test material (sintered body) was peeled off from the mating material, the contact surface was cut from the surface in the thickness direction at a pitch of 0.2 mm, and the presence or absence of iron on each cut surface was determined by X-ray diffraction. did. In Table 1, the circle mark in the "Presence or absence of iron content" column means that iron content is not detected (no scale reaction), and the x mark means that iron content is detected (scale reaction occurs). As shown in the table, it can be seen that the sintered bodies having the compositions (A) to (F) specified in the present invention have no scale reaction and are excellent in pick-up resistance.

【table】

【table】

【table】

【table】

[Table] Further, as a pick-up resistance test of the sintered bodies of the present invention in an actual furnace, sintered bodies (1) to (18) having the composition shown in Table 2 were molded and molded in the same manner as in the above test.
Each sintered body produced under sintering conditions is placed on a walking beam in the soaking zone of a heating furnace for slab hot rolling, and the slab is passed through the furnace.
A 12-month exposure test was conducted under conditions of contact with scale falling from the surface of the slab. As comparative examples, chromium carbide sintered bodies (19) to (25) having compositions that deviate from the provisions of the present invention and other ceramic sintered bodies (silicon carbide-based, silicon nitride-based, alumina-based, and zirconium oxide) were used. (26)
A similar actual furnace test was conducted for ~(29), and the presence or absence of pick-up in each sample sintered body after the test was determined by X-ray diffraction in the same manner as the above test, and the results shown in Table 2 were obtained. . In all of the comparative examples, iron penetration was observed, and in particular, in the sintered bodies of sample numbers (26) to (29), the scale reaction was so severe that it was impossible to measure the depth of iron penetration, whereas in the present invention example All of them have no scale reaction and have good pick-up resistance.

【table】

[Structure of the invention]

The skid button made of the chromium carbide sintered body of the present invention has excellent pick-up resistance, heat resistance, high temperature strength, impact resistance, etc. Compared to ceramic sintered products such as solid-based, nitride-based, and carbide-based ceramics, it can withstand extremely harsh usage conditions in high-temperature atmospheres, static and dynamic stress, and contact with high-temperature scales, and is superior to conventional materials. It exhibits an unprecedentedly long service life and stabilizes and improves furnace operation. In addition, it has excellent heat resistance and insulation properties, so there is no need for strong cooling to prevent temperature rise, as is the case with support surface members made of heat-resistant alloys.
The quality of the heated material is improved by uniform heating without localized temperature drop or uneven heating of the heated material, while the thermoeconomic efficiency of the furnace is also improved by reducing the amount of heat taken out of the furnace by cooling water. It brings about various effects such as being enhanced.

[Brief explanation of the drawing]

FIGS. 1 to 3 are sectional views of essential parts showing examples of hearth structures using the chromium carbide sintered body of the present invention as a member for supporting surfaces of heated materials. 1: Walking beam, 2: Rail, 3.
1, 3, 2: Member for supporting surface of heated material.

Claims (1)

[Claims] 1 Cr ₃ C ₂ chromium carbide 75-99% by weight, balance Cr ₂₃ C ₆
A chromium carbide sintered body made of carbide for the support surface of heated materials in heating furnaces. 2 Cr ₃ C ₂ Chromium carbide 60-99% by weight, balance Cr ₇ C ₃
A chromium carbide sintered body made of carbide for the support surface of heated materials in heating furnaces. 3 A chromium carbide sintered body for a support surface of a heated material in a heating furnace, comprising 60 to 99% by weight of Cr ₃ C ₂ chromium carbide and the remainder Cr ₃ C carbide. 4 A _chromium carbide sintered body for a support surface of _a heated material in a heating furnace, comprising 50 to 90% by weight of _Cr3C2 chromium carbide _, 5 to 45% by weight of _Cr7C3 carbide, and the balance _Cr23C6 carbide. 5 A chromium carbide sintered body for a support surface of a heated material in a heating furnace, comprising 30 to 85% by weight of _{Cr3C2 chromium} carbide _, 5 to 40% by weight of _Cr7C3 carbide, and the balance _Cr3C carbide. 6 40 to 80% by weight of Cr ₃ C ₂ chromium carbide, 5 to 45% by weight of Cr ₇ C ₃ carbide, 5 to 30% by weight of Cr ₂₃ C ₆ carbide, and the remainder Cr ₃ C carbide, supporting surface of the material to be heated in the heating furnace. Chromium carbide sintered body for use.