JPS6221066B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a molybdenum alloy with high high temperature strength and high recrystallization temperature. [Technical background of the invention and its problems] Molybdenum alloys have excellent high-temperature stability in vacuum, inert, and reducing atmospheres, so they are used as various heat-resistant materials, and recently, they are used in nuclear fusion reactors. Applications in the nuclear field, such as reactor wall materials, are expanding. However, after a molybdenum alloy is heated above its recrystallization temperature, its ductility at room temperature becomes poor, and brittle fracture easily occurs at grain boundaries, resulting in a decrease in its strength. As a solution to this problem, an alloy containing molybdenum and a small amount of vanadium is known. This improves the strength of the alloy by dissolving vanadium in molybdenum, and also cleans the grain boundaries by reacting vanadium with grain boundary impurities (such as oxygen) present in the grain boundaries. Also known is an alloy in which a small amount of carbon is added to improve the deoxidizing effect. However, in recent years, as the properties required of molybdenum alloys have become stricter, there has been a strong desire to develop molybdenum alloys that have higher recrystallization temperatures and excellent high-temperature strength. [Object of the Invention] The object of the present invention is to provide a molybdenum alloy with a novel composition that has a high recrystallization temperature and high high-temperature strength. [Summary of the Invention] The molybdenum alloy of the present invention contains 0.02 to 0.5% by weight of zirconium (Zr) and 5 to 5% by weight of boron (B).
100ppm, the balance being molybdenum (Mo). In the Mo alloy of the present invention, Zr forms a solid solution with Mo,
It also combines with oxygen, carbon, etc. in the base metal,
By dispersing it in the base metal,
It is a component that increases the mechanical strength of the alloy, especially its high-temperature strength, and also increases the recrystallization temperature and suppresses coarsening of crystal grains. The effect of Zr is 0.02% by weight
However, if the amount exceeds 0.5% by weight, the rate of increase in recrystallization temperature will decrease and the workability of the obtained alloy will deteriorate. Preferably 0.1-0.2
Weight%. B is a component that greatly contributes to cleaning grain boundaries and prevents coarsening of crystal grains after recrystallization. The effect of this B is that if it is less than 5 ppm, the grain boundary cleaning effect is not sufficient, and if it exceeds 100 ppm,
Mo ₂ B precipitates and becomes coarse, making the alloy brittle. Preferably it is 20 to 80 ppm. The Mo alloy of the present invention can be manufactured as follows. That is, Mo with a particle size of 3 to 20 μm,
Predetermined amounts of Zr and B powders are weighed, and after thoroughly mixing them in a mixer such as a porcelain pot mill, the resulting mixed powder is molded using a rubber press or the like. After sintering this molded body according to a conventional method, the obtained sintered body is arc melted in a vacuum to form an alloy. At this time, in addition to Mo, Zr, and B, a small amount of
Preferably, adding carbon in an amount of 300 ppm or less is useful because it further enhances the deoxidizing effect of carbon and the effect of B during arc melting. However, it should be noted that when the amount of residual carbon exceeds 500 ppm, the workability of the alloy deteriorates significantly. The alloy ingot thus obtained can be subjected to predetermined processing such as hot forging and hot rolling to be processed into various shapes for practical use. [Embodiments of the invention] (1) Production of alloy Mo, Zr, B, C powder (average particle size 6 μm)
were blended in a predetermined ratio, mixed using a porcelain pot roller, and then molded using a rubber press at a pressure of 3000 kg/cm ² . This molded body was fired in a hydrogen atmosphere at 1830°C for 7 hours to obtain a sintered body with a diameter of 25 mm and a length of 300 mm.
Two of these were joined together and alloyed using the consumable electrode vacuum arc melting method to form an ingot with a diameter of 50 mm and a length of 200 mm. The composition of the obtained Mo alloy is shown in the table.

〔Effect of the invention〕

The Mo alloy of the present invention has a high recrystallization temperature,
It also has high high-temperature strength, making it highly useful as a high-temperature heat-resistant material.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between annealing temperature and Witzkars hardness of the plate materials used in the examples, Figure 2 is a diagram showing the relationship between half-softening temperature and Zr content, and Figure 3 is a diagram showing the relationship between annealing temperature and recrystallized grains. FIG. 4 is a diagram showing the relationship between Zr content and recrystallized grain size, and FIG. 5 is a diagram showing the tensile strength at each temperature.

Claims (1)

[Claims] 1 Zirconium 0.02~0.5% by weight, boron 5~
A molybdenum alloy consisting of 100ppm, the balance being molybdenum, and characterized by a high recrystallization temperature and high high-temperature strength.