JPS59107970A - Heat resistant ceramic material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-resistant ceramic material used in high-temperature atmospheres such as heating furnaces, soaking furnaces, and annealing furnaces.

For example, various heat-resistant alloys have traditionally been used as materials for skid rails in heating furnaces, but the atmosphere temperature inside the furnace is set at 1300 to 1350°C, and metal pieces such as slabs are heated to 1250 to 1300°C. This is an extremely harsh operating condition for the heat-resistant alloys used in skid rails as they are exposed to high temperatures. Therefore, generally, as shown in Fig. 1, a plurality of water-cooled skid pipes (2) are installed on the lower frame +13 inside the furnace (F), and skid rails (3) are installed on the top surface of each skid pipe.
) to form the hearth (skid) and pipe (2)
A water cooling system is used to prevent the temperature of the skillet rail from rising due to the cooling water flowing inside. However, in this case, the metal piece (S) placed on the skillet rail loses heat from its contact surface with the rail and is locally cooled, resulting in temperature unevenness.

Although this temperature unevenness can be alleviated by setting the metal piece (S) to stay in the furnace for a long time, the effect is not sufficient and the efficiency of the heating furnace is significantly deteriorated.

As a countermeasure against this, a heat-resistant stand made of ceramic material is installed on the skid rail (3), and the metal piece (S) and the rail (3)
It has been proposed to prevent direct contact with zirconium oxide, (ZrOz> system,
Alumina (^12.03) system, silicon nitride (Sl)
%) system etc. are being used on a trial basis. However, these ceramic materials tend to react with the scale of the metal pieces, which are the rapidly heating materials, so it is impossible to maintain stable operation for a long time.

By the way, among ceramic materials, there is a chromium carbide ceramic material that exhibits unique properties when compared with other materials, and in particular exhibits extremely excellent corrosion resistance against molten metal. As this chromium carbide ceramic material,
Conventionally, chromium carbide bonded and sintered with metal cobalt or nickel is known as a heat-resistant and corrosion-resistant material, but these deteriorate in strength and develop scale in the high-temperature atmosphere of a heating furnace. The reaction is remarkable, for example, at 1200℃
Since the strength is drastically reduced to less than 1/3 of that at room temperature, it cannot withstand harsh environments such as the hearth of a heating furnace where dynamic stress is applied at high temperatures, and in the end, the material for skid rail heat-resistant stands was used. cannot be applied as such.

In order to solve the above-mentioned problems, the present invention aims to provide a material containing chromium carbide as a main component and having particularly improved thermal shock resistance. zirconium carbide,
One or more selected from boron carbide and silicon carbide is 0,2
It is a heat-resistant ceramic material having a composition of ~10% by weight and the balance being chromium carbide, and in this case, boron carbide and silicon carbide, if either or both of them are used in a fibrous form, the material is This is more preferable because it greatly improves the mechanical strength of the material. The material of the present invention is prepared by blending various material powders within the above-mentioned composition range and then sintering using a known sintering method, such as a cold press method, a hot press method, or a hot isostatic pressure sintering method. However, in the case of the cold press method, the sintering conditions are a vacuum degree of 10" to 10-' torr,
Temperature 1300-1500℃, Pressure force 50-350kg/car1 Temperature 1350-1550 in case of hot press method
℃, or in the case of hot isostatic pressure sintering method, the pressure is 500 kg.
It is preferable to set the temperature to /ca1 or higher and to 1500°C or lower. The various raw material powders used should be as pure as possible, preferably with a purity of 99% or higher.This is because impurities may evaporate during high-temperature firing and cause pores. This is because a low melting point phase is formed, resulting in a decrease in the high-temperature properties of the resulting product. In addition, it is desirable to use fine powder with a particle size of 10 μm or less for this raw material powder in order to improve sintering properties and obtain a high-density product.

Next, the tests that led to the development of the material of the present invention and their results will be shown. That is, 3 parts by weight of paraffin is added to 100 parts by weight of a mixture of chromium carbide powder with a purity of 99.9% and a particle size of 5 μm and various other additives in the proportions shown in Table 1 below. It was made into powder. Note that in Table 1 below, No.
32.3g, 34.40.4L 42.4L51, 5
In the case of 4.57.59, the boron carbide used there is 7
Fibrous materials with a diameter of 0 μm, and fibrous materials with a diameter of 10 μm for silicon carbide are used as raw materials (products using these fibrous materials are underlined with an underline "-" under the corresponding number), etc. Powdered materials were used for all of the above.

The raw material obtained as in Part B was molded at a molding pressure of 1.5 tons/d for 10
Illffl×301nl! Molded into ×611111,
Various test specimens were obtained from the sintered bodies obtained by preliminary sintering in vacuum at 780°C for 10 minutes and then main sintering in vacuum at 1450°C for 60 minutes.

Relative theoretical density, transverse rupture strength, and
The values for density and thermal shock resistance are shown in Table 2 below. Among these, thermal shock resistance is the ratio of the transverse rupture strength before and after dropping a specimen heated and maintained at 500°C in the atmosphere into water, that is, the value of transverse rupture strength after injection + transverse rupture force before injection X 100 (%) Indicated by

Table 1 The amount of added carbide is divided into certain ranges and summarized as shown in Table 3 below.

As can be seen from the test results in Table 3 and above, the amount of various carbides added to chromium carbide must be at least 0.2% by weight, otherwise the effect will be insufficient, and the relative theoretical density and transverse rupture strength will be low. After being heated to 500°C and put into water, the transverse rupture strength is extremely small.On the other hand, if too many of these carbides are added and the amount exceeds 10% by weight, the relative theoretical density and transverse rupture strength will decrease again. Therefore, the amount of these added carbides is set to 0.2 to 10%.

As mentioned above, the Cera E-7 material of the present invention has a relative theoretical density of 98.0% or more and a transverse rupture strength of 50 kg/am", and its strength does not decrease much even when exposed to high temperatures and rapidly cooled. In addition, it has the excellent property of not reacting with the heated metal pieces or their scales, so there is no need for the special cooling equipment used in the past, and it can be used for rapid heating such as skid rails. It is most suitable as a high-temperature member that is subjected to rapid cooling.Specifically, samples using m male carbide exhibit significantly large values in terms of transverse rupture strength and thermal shock resistance, making it even more effective.

FIG. 2 to FIG. 4 each show an example in which a skid rail heat-resistant stand is made of the ceramic material of the present invention and a skid is constructed. FIG. 2 shows a skid constructed by providing a plate-shaped heat-resistant stand (4-11) made of the ceramic material of the present invention on the top surface of a heat-resistant alloy skid rail (3) installed on a water-cooled skid pipe (2). A metal piece +S) is placed on this. To fix the heat-resistant stand +4-1) to the skid rail (3), use an appropriate locking tool (
5) with assistance. Fig. 3 shows a rail-shaped heat-resistant stand (4-21) formed from the ceramic material of the present invention, which is directly laid on the top surface of the skid pipe (2), and a locking tool (6)
This is an example of a skid supported by In this case, in order to avoid direct contact between the heat-resistant stand (4-21) and the skid pipe (2), a heat insulating material layer (7) made of ceramic fiber or the like is interposed as shown in Figure 4. It is also preferable to lay a heat-resistant stand (4-2) on top.

As described above, the heat-resistant ceramic material of the present invention is
It has a large transverse rupture strength, excellent thermal shock resistance, and excellent heat insulation properties, so it can be used, for example, as a skid rail itself.
Or, when used in applications such as heat-resistant stands for skid rails, it can withstand the heat sufficiently, and even if it comes into contact with the material to be heated, heat is not taken away from the contact area, so it is possible to prevent the localization of the material to be heated. Uniform heating can be achieved without causing temperature unevenness due to cooling. Therefore, there is no need to lengthen the furnace time as was conventionally done to alleviate temperature unevenness, and the amount of heat carried away by the cooling water system to the outside via the skid rails is also reduced, improving work efficiency and heat consumption. It is possible to reduce the amount of

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a conventional heating furnace hearth, and FIGS. 2 to 4 are cross-sectional views of essential parts showing how the heat-resistant stand made of the heat-resistant ceramic material of the present invention is used. In the figure, (1); metal piece as heated material (2) varnished skid pipe (3): skid rail (4-11, +4-2+. (4-3): heat-resistant stand patent applicant Kubota Iron Works Co., Ltd. (and 1 other person) Agent Noriharu Ariyoshi Continuing from page 1 ■Applicant Nippon Tungsten Co., Ltd., 2-20-31 Shimizu, Minami-ku, Fukuoka City April 27, 1981 Kazuo Wakasugi, Commissioner of the Patent Office 1 , Indication of the case 1982 Patent Application No. 215939 2 Title of the invention Heat-resistant ceramic material 3 Person making the amendment Relationship to the case Patent Applicant's address (2) Power of attorney will be sent as attached. Patent Agency Commissioner Kazuo Wakasugi1, Indication of the case 1982 Patent Application No. 2159392, Name of the invention Heat-resistant ceramic material4, Relationship with the case by the person making the amendment Patent Applicant Address Name Kubota Iron Works Co., Ltd. ( (1 other person) 4. Agent address: 1-10-27 Hakataeki Higashi, Hakata-ku, Fukuoka City Name (
8429) Patent attorney Noriharu Ariyoshi 5, date of amendment order 6/6/1939, subject of amendment ``Skilled rail'' in specification (1), page 2, lines 6 and 8, as ``Skilled rail'' Correct to "skid rail". (2), “Kaise-sa” on page 14, line 17 is changed to “Kaise-t”.
Correct it to "Let's do it." (3), r(1)J on page 16, line 4, r(S)j
Correct to.

Claims (1)

[Claims] 1. A composition consisting of 0.2 to 10% by weight of one or more selected from tantalum carbide, niobium carbide, tungsten carbide, vanadium carbide, zirconium carbide, boron carbide, and silicon carbide, and the balance being chromium carbide. Ceramic material for heat resistance. 2. The heat-resistant ceramic material according to claim 1, wherein at least one of boron carbide and silicon carbide is fibrous.