JPH0459382B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to molybdenum materials used at high temperatures. [Prior Art] Molybdenum, which has a high melting point of about 2600°C, is a material that requires high-temperature strength, and has many uses. However, pure molybdenum recrystallizes at about 1200°C, and once heated above the recrystallization temperature, the crystals become coarse and brittle, resulting in a significant decrease in strength. To solve this problem, it is necessary to increase the recrystallization temperature of molybdenum. The present inventors used cerium oxide, which has almost the same melting point as molybdenum, to
Invented a molybdenum material with a high recrystallization temperature by adding 3.0% by weight to molybdenum (Japanese Patent Application Laid-Open No. 61-23741)
did. This molybdenum material to which cerium oxide is added has a high recrystallization temperature of 1,600°C or higher, and in particular, the material with 1.0% by weight of cerium oxide can increase the recrystallization temperature to 1,800°C. [Problems to be solved by the invention] Since then, the conditions for using molybdenum materials have become increasingly harsh, and materials that maintain high strength and toughness even after being heated to temperatures of 1800°C or higher have been developed. Materials are now in demand. Even in the molybdenum material to which 1.0% by weight of cerium oxide is added, when heated above 1800°C, the crystals become coarse and both tensile strength and elongation decrease.
There have been cases where the required high strength and high toughness cannot be fully satisfied. In view of the above-mentioned problems, an object of the present invention is to provide a molybdenum material that does not easily lose its mechanical strength even after being heated to a high temperature of 1800° C. or higher and has excellent high-temperature properties. [Means and effects for solving the problems] The present inventor solved the problems and achieved the object by changing the composition of the molybdenum material as follows. That is, a molybdenum material containing 0.1 to 3.0% by weight of cerium oxide and 0.004 to 0.03% by weight of boron, with the balance essentially consisting of molybdenum was obtained. In the molybdenum material of the present invention, cerium oxide is finely dispersed in molybdenum to prevent movement of grain boundaries and serve to increase the recrystallization temperature of molybdenum. If the amount added is less than 0.1% by weight, no improvement in the recrystallization temperature will be observed, and if it exceeds 3.0% by weight, the workability during wire drawing will deteriorate. Therefore, the amount of cerium oxide needs to be 0.1 to 3.0% by weight. Boron is presumed to have the effect of preventing grain boundary embrittlement, but the amount added is 0.004% by weight.
If it is less than 0.03% by weight, the effect of addition will not be seen, and if it exceeds 0.03% by weight, the toughness will decrease. Therefore, the amount of boron added needs to be 0.004 to 0.03% by weight. As mentioned above, when cerium oxide is added alone to molybdenum, the recrystallization temperature increases, but when heated above the recrystallization temperature, the toughness decreases, and when boron is added alone, the recrystallization temperature increases. Similarly, since the crystal temperature is low at 1200°C or less, improvement in toughness at high temperatures cannot be expected. That is, the feature of the molybdenum material of the present invention is that 0.1
~3.0 wt% cerium oxide and 0.004-0.03 wt%
According to the present invention, a molybdenum material has excellent properties not found in conventional materials, such as retaining high strength and high toughness even after being heated to a high temperature of 1800°C or higher. is obtained. The molybdenum material of the present invention can be manufactured by various methods, and for example, it can be manufactured as follows. That is, it is manufactured by mixing molybdenum powder, cerium oxide powder, and powder of a boron compound such as molybdenum boride or boron carbide, press-molding the mixture, and then sintering it in hydrogen or vacuum. In addition, the ingot obtained in this way is subjected to prescribed processing such as forging, rolling, and wire drawing.
It can be made into any desired shape. Hereinafter, the content of the present invention will be explained in detail with reference to Examples. [Example] (1) Metallic molybdenum powder with a purity of 99.9% or more, cerium oxide powder, and molybdenum boride powder are uniformly and thoroughly mixed in a predetermined ratio. Thereafter, it was pressure-molded, pre-sintered, and sintered at 90% of the melting current to form an ingot. Then,
The ingot is rolled and drawn to a diameter of φ0.8.
mm wire rod was obtained. (2) Metallic molybdenum powder with a purity of 99.9% or higher, cerium oxide powder, and boron carbide powder were mixed uniformly and well in a predetermined ratio, and then processed in the same manner as in (1) above to obtain a wire rod with a diameter of 0.8 mm. . (3) For comparison, wire rods with a diameter of 0.8 mm were made using the same processing as in (1) and (2) above for molybdenum with only cerium oxide added and pure molybdenum without any addition. did. The wire rods obtained in (1), (2), and (3) above were heated to various temperatures and then subjected to a tensile test at room temperature, and after heat treatment at 1950°C and a bending test at room temperature, the toughness was compared. . The results are shown in Table 1, Figure 1 and 2.
As shown in the figure. Table 1 shows the results of a bending test after electrically heating a molybdenum wire to 1950°C. The bending is
One time was when the wire after heat treatment was held with pliers and bent 90 degrees, and the strength was measured by the number of times the wire could be bent without breaking. As is clear from Table 1, pure molybdenum No. 90 could not be bent even once, and wire No. 10 with cerium oxide added alone also
It broke after being bent 11 times. On the other hand, Nos. 1, 2, 3, and No. 1 added cerium oxide and boron.
The molybdenum materials of the present invention Nos. 5, 6, and 7 all have improved bending properties and excellent toughness.

【table】

〔effect〕

As described above, according to the present invention, a molybdenum material having high strength and high toughness even after being heated to a high temperature can be obtained, and the present invention has great industrial utility value.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between heat treatment temperature and tensile strength. FIG. 2 is a graph showing the relationship between heat treatment temperature and elongation in a tensile test. The numbers in the figure indicate sample numbers.

Claims (1)

[Claims] 1. 0.1 to 3.0% by weight of cerium oxide, and 0.004 to 3.0% by weight of cerium oxide.
A high temperature molybdenum alloy consisting of 0.03% by weight boron and the balance essentially molybdenum. 2. A high-temperature molybdenum alloy consisting of 0.1 to 3.0% by weight of cerium oxide, 0.004 to 0.03% by weight of carbon boride as boron, and the remainder substantially molybdenum.