JPS59107972A - 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, scorching 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. Since the skid rails are exposed to high temperatures, the conditions of use are extremely harsh even for the heat-resistant stands used in skid rails. Therefore, generally, as shown in Figure 1, multiple water-cooled skid pipes (2) are installed on the lower frame (1) inside the furnace (FJ), and a skid rail (3) is installed on the top of each skid pipe. A water-cooling system is adopted in which the skid is configured with a hearth (skid), and the temperature of the skillet rail is prevented from rising by cooling water flowing inside the pipe (2).However, in this case, the skillet rail The metal piece (S) placed on the rail loses heat from its contact surface with the rail and is locally cooled, resulting in temperature unevenness.

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

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
As a material, zirconium oxide (Zr07L) type,
Alumina (Al, 0.) system, silicon nitride (Si3N+
1 series is being used on a trial basis. However, these ceramic materials tend to react with the scale of the metal pieces that are the rapid heating material, making it impossible to maintain stable operation for a long period of time.

By the way, among ceramic materials, there is a chromium carbide-based ceramic material that exhibits unique properties when compared with other materials, and in particular exhibits extremely excellent corrosion resistance against molten metal. Conventionally, chromium carbide ceramic materials made by bonding and sintering chromium carbide with metallic cobalt or nickel are known as heat-resistant and corrosion-resistant materials, but these materials do not have sufficient strength in the high-temperature atmosphere of a heating furnace. For example, at 1200℃, the deterioration of the
However, the strength decreases drastically to 173 or less at room temperature, so it cannot withstand harsh environments such as the hearth of a heating furnace where dynamic stress acts at high temperatures. cannot be applied.

In order to solve the above-mentioned problems, the present invention aims to provide a material that is mainly composed of chromium carbide and does not easily react with the metal or its scale, which is the material to be heated. One or more selected from tantalum nitride, niobium nitride, zirconium nitride, aluminum nitride, vanadium nitride, silicon nitride, and boron nitride is 0
．． It is a heat-resistant ceramic material having a composition of 2 to 10% by weight, the balance being chromium carbide, and in this case, boron nitride and silicon nitride are used in the form of either or both of them in the form of fibers, as will be detailed later. This is more preferable because it greatly improves the mechanical strength of the material. The material of the present invention is obtained by blending various material powders in the composition range as described above and then sintering it by a known sintering method, such as a cold press method, a hot press method, or a hot pressure sintering method. However, as for this sintering condition, in the case of the cold press method, the degree of vacuum is 10-' to 10-'t.
orr, temperature 1300-1500℃, pressure 50-350kg/cd1 temperature 1350-1 in case of hot press method
550℃, or a pressure of 50℃ in the case of the heat equivalent isostatic pressure sintering method.
It is preferable to set the weight to 0 kg/d or more and the temperature to 1500°C or less. The various raw material powders used should be as pure as possible, preferably with a purity of 99% or higher, as 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. Further, as the raw material powder (B), it is desirable to use a fine powder with a particle size of 10 μm or less in order to improve the sinterability 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 was 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 other various additives in the proportions shown in Table 1 below. It was made into a raw material powder. In addition, in Table 1 below, No.
42.43.44.50.51. ．． 52.58°62,
In the case of 65.6B, 71.73.75.77, the silicon nitride used therein was 10 μm in diameter, and the boron nitride used was a fibrous material with a diameter of 6 μm (underlined “-” is added below the corresponding NO). ), and powders were used for all others.

The raw material obtained in this way was molded for 10 m at a pressure of 1.5 tons/
Various test specimens were obtained from the sintered bodies obtained by molding to a size of 10 mm 3 O 6 mm, pre-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 details of particle size and scale resistance are shown in the second section below.
Shown in the table. Among these, the scale resistance is determined by holding the specimen and 5C46 material at 1300℃ in the atmosphere for 5 hours under a load of 5.5kg/cj for a contact area of 5cm x 511m, and then separating them. A part of the specimen peels off from the specimen and adheres to the 5C46 material side, so the amount of peeling (volume) is shown.

Table 1 The following Table 3 summarizes each of the above Table 2 by dividing the amount of added nitride into chromium carbide into certain ranges.

As can be seen from the test results in Table 3 and above, the amount of various nitrides 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 small. In particular, the amount of flaking indicating reactivity with scale is extremely large, and on the other hand, if too much of these nitrides are added and the amount exceeds 10% by weight, the relative theoretical density and transverse rupture strength will decrease again. The amount of added nitride is 0.2 to 10% by weight.

As mentioned above, the ceramic material of the present invention has a relative theoretical density of 97.0% or more and a transverse rupture strength of 40 kg bar, and has excellent properties such as not reacting with the scale of the heated material even when exposed to high temperatures. Therefore, it is ideal for high-temperature parts such as skid rails that are subject to rapid heating and cooling without the need for special cooling equipment as conventionally used. In particular, samples using fibrous nitrides exhibit a significantly large transverse rupture strength and are 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.The heat-resistant stand +4-11 is fixed to the skid rail (3) using 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 suki-sodo being supported by . In the case of Party B,
In order to avoid direct contact between the heat-resistant stand (4-2+) and the skid pipe (2), as shown in Fig. It is also preferable to install a platform +4-21.

As stated above, the heat-resistant ceramic material of the present invention is
It has a large transverse rupture strength, has very low reactivity with scale, and has excellent heat insulation properties, so it can withstand applications such as skid rails themselves or heat-resistant stands for skid rails. Moreover, even when it comes into contact with the material to be heated, heat is not taken away from the contact area, so uniform heating can be achieved without causing temperature unevenness due to local cooling of the material to be heated. . 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 the drawing]

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 that is the material to be heated (2) Varnished skid pipe (3): Skid rail (4-1), +4-2+. (4-3): Heat-resistant stand patent applicant Kubota Tekko Co., Ltd. (and 1 other person) Agent Noriharu Ariyoshi No. 2-20-31 Shimizu, Minami-ku, Fukuoka City Written amendment (method) 1. Indication of the case 1988 Patent Application No. 2159432, Title of Invention: Heat-resistant Ceramic Material3, In relation to the case of the person making the amendment: Applicant Address: Kazuo Wakasugi, Commissioner of the Japan Patent Office1. Indication of the case 1982 Patent Application No. 215943 2 Name of the invention Heat-resistant ceramic material 4 Person making the amendment Relationship to the case Patent Applicant Address Name Kubota Iron Works Co., Ltd. Beni (1 other person) 4. Agent 6. Target of amendment The term "skilled rail" in lines 6 and 8 of page 2 of specification (1) is amended to "skid rail." (2) , ``Assistance'' on page 16, line 10 is corrected to ``assistance''. (3) , r(1)J on page 17, line 18 is changed to r(S)
Correct to J.

Claims (1)

[Claims] 1. 0.2 to 10% by weight of one or more selected from chromium nitride, titanium nitride, tantalum nitride, niobium nitride, zirconium nitride, aluminum nitride, vanadium nitride, silicon nitride, and boron nitride, the remainder A heat-resistant ceramic material whose composition consists of chromium carbide. 2. The heat-resistant ceramic material according to claim 1, wherein at least one of silicon nitride and boron nitride is in the form of fibers.