JPS6260464B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a method for producing a doped molybdenum material having excellent high-temperature strength. [Technical background of the invention and its problems] Doped molybdenum materials, which have a high recrystallization temperature and high strength after recrystallization, are generally used for molybdenum parts used at high temperatures such as furnace heaters and vapor deposition boats. There is. This material is made of molybdenum
This is a material to which one or more of Al, Si, and K are added. The method for producing a molybdenum material made of this doped molybdenum material and the secondary forming process as a product are conventionally shown in FIG. 1, that is, a molybdenum plate is obtained by subjecting a sintered ingot to hot working. After that, the as-processed plate or the plate that has been subjected to strain relief annealing at a temperature below the recrystallization temperature, usually 800°C to 1200°C, is subjected to secondary forming processing to be used as a furnace heater or vapor deposition boat. ing. However, the furnace heater and vapor deposition boat obtained by the above-mentioned conventional methods are used at high temperatures around the recrystallization temperature or higher, and are used with heating and cooling. For this reason, recrystallization grows during use, and large deformations or cracks occur due to thermal fatigue or creep phenomena, and these deformations or cracks become larger with the passage of use time.
An abnormal contact may occur in the furnace heater, resulting in a short circuit and melting, or the temperature distribution of the heating furnace may become abnormal, causing the temperature to rise locally or break, and the furnace no longer functions as a normal heating furnace. . [Object of the invention] The present invention has been made in consideration of the above points, and
An object of the present invention is to provide a method for producing a doped molybdenum material that exhibits less deformation or cracking even when used at high temperatures and has excellent high-temperature strength. [Summary of the invention] The method for manufacturing a molybdenum plate according to the present invention includes Al,
0.15 to 0.75% by weight of one or more of Si and K
% (excluding 0.15%) after surface reduction processing with a total processing rate of 85% or more, from 100℃ higher than the recrystallization temperature to 2200℃.
It is characterized by the fact that the recrystallized grains are grown long and large by heat treatment at a temperature range of up to ℃. A method for manufacturing a molybdenum plate according to the present invention will be explained with reference to FIG. The method for producing a molybdenum plate made of a doped molybdenum material according to the present invention includes one or more of Al, Si, and K in a weight percentage of 0.15 to 0.75%, preferably a total amount of 0.20 to 0.60%, and two or more of Al, Si, and K. In the case of 1/2 or 1/3 of each doped molybdenum sintered ingot, hot processing such as forging and rolling is performed to achieve a processing rate of 85% or more.
A molybdenum plate with a specified thickness is used. Afterwards, it was discovered that a molybdenum plate with less deformation or cracking could be obtained even when used at high temperatures by heat-treating the molybdenum plate in a limited temperature range to make the recrystallized grains of the molybdenum plate long and large. It is. Here, to explain the composition range of the doped molybdenum material that is the constituent material of the molybdenum plate according to the present invention, Al, Si, and K generate aligned micro dope holes by heat treatment after processing. This is the composition range necessary to cause the recrystallized grains to grow long and thin. If the amount of the added component is too small, the effect will be small, and the recrystallized grains will become hexagonal equiaxed crystal grains even after heat treatment after processing. In addition, since large amounts of recrystallized grains are produced locally, recrystallized grains become hexagonal equiaxed grains, and defective holes are generated due to aggregation of doped holes and abnormal growth. When used as a furnace heater or vapor deposition boat, it facilitates abnormal deformation due to grain boundary slippage, intergranular cracking, and intragranular cracking originating from defective holes. Therefore, this composition range is preferred. Next, to explain the limited working rate of the molybdenum material according to the present invention, a working rate of 85% or more is the working rate range necessary to grow recrystallized grains into long and large size by heat treatment after working. If this processing rate is too low, the processed fiber structure cannot be sufficiently developed, and even if heat treatment is performed within a limited temperature range after processing, the recrystallized grains will become hexagonal equiaxed crystal grains. Therefore, when used as a furnace heater or vapor deposition boat used at high temperatures, it facilitates abnormal deformation and grain boundary cracking due to grain boundary slip.
Therefore, this range is preferable and the processing rate is 95%.
It is even more preferable to have the above. However, since it is impossible to have a processing rate of 100%, the processing rate of 100% is not included. Furthermore, to explain the temperature range of heat treatment after processing, the heat treatment after processing is performed to hot-work the recrystallized grains of the molybdenum plate, which has sufficiently developed a processed fiber structure, to a processing rate of 85% or more. This is the heat treatment temperature used to make the material long and thin and bonded in a large zigzag pattern, and is within the temperature range necessary to provide excellent thermal fatigue strength and creep strength at high temperatures. If the heat treatment temperature is too low, recrystallized grains will not grow sufficiently, resulting in unstable grain growth during use at high temperatures, resulting in variations in thermal fatigue strength and creep strength. On the other hand, if the temperature is too high, recrystallized grains that are long and slender and have grown in a large zigzag pattern will grow excessively, becoming similar to equiaxed crystal grains, and the aforementioned abnormal growth and aggregation of minute doped holes will occur, resulting in large defects. When used as a furnace heater or evaporation boat used at high temperatures, it may facilitate abnormal deformation and intergranular cracking due to grain boundary slip, or intragranular cracking that originates from defective holes. This may cause the furnace heater to melt due to a local increase in electrical resistance due to the formation of large defective holes. Therefore, this temperature range is preferred. Here, before the process (hereinafter referred to as the second process) of reducing the area by 85% or more and heat treating at a temperature range from 100°C higher than the recrystallization temperature to 2200°C. The reason for providing the step (hereinafter referred to as the first step) of reducing the area by 45% or more in processing rate and heat-treating at a temperature 200 to 800° C. higher than the recrystallization temperature will be explained. The purpose of the second step is to form long crystals. On the other hand, the purpose of the first step is to
The goal is to uniformly generate recrystallized grains. In other words, the 85% or more area reduction process in the second process applies different strains to the workpiece material in each part, which tends to cause long crystals of different sizes to form, and the molybdenum material has uneven high-temperature strength. were sometimes manufactured. Therefore, by providing the first step before the second step, it is possible to easily generate long recrystallized grains relatively uniformly, and to provide a doped molybdenum material with little variation. Regarding the heating temperature in the first step, if the temperature is too low, the effect will be small; if the temperature is too high, the recrystallized grains will become coarse, so the temperature range is 200℃ to 800℃ below the recrystallization temperature. is preferred. Therefore, before the second step, the first
By providing these steps, the object of the present invention can be achieved even more effectively. [Effects of the Invention] As explained above, according to the present invention, after hot working at a processing rate limited to molybdenum materials used as furnace heaters, vapor deposition boats, etc.,
By performing heat treatment within a limited heat treatment temperature range, thermal fatigue strength and creep strength can be increased. This greatly extends the destructive life of furnace heaters and evaporation boats used at high temperatures, allows them to be used in a stable state for long periods of time, and greatly improves the operating efficiency and reliability of electric furnaces, evaporation equipment, etc. effective. Furthermore, by using the molybdenum plate according to the present invention, rare metals can be effectively utilized, which is often useful in industry. [Embodiments of the Invention] The method for producing a molybdenum plate of the present invention includes Al ₂ O ₃ ,
Doped molybdenum powder with an average particle size of 4 μm containing 0.15% by weight of SiO ₂ and K ₂ O was press-molded at a pressure of 2 tons/cm ² and then heated at 1830°C in a hydrogen furnace.
It was sintered under conditions of 9 hours to produce a sintered ingot. This sintered ingot is hot-forged in a temperature range of 1100°C to 1400°C, and then hot rolled in a temperature range of 300°C to 1100°C, resulting in processing rates of 82%, 90%, and 98%.
The processing rate was adjusted so that the thickness of the plate was 2 mm. Next, four test materials were cut out from each 2 mm thick molybdenum plate with the above processing rate, and each was subjected to strain relief annealing at 1650°C, which is the recrystallization temperature of the test material, which is sufficiently lower than the recrystallization temperature. 1000
℃, 2000℃ and 2400℃ 350℃ higher than recrystallization temperature
Heat treatment was performed for 2 hours at 4 different temperatures of °C. A width of 10 mm was obtained from the test material that underwent this heat treatment.
A test piece with a length of 100 mm was cut out, this test piece was horizontally supported as shown in Figure 3, and the heating and cooling cycle of immersing it in a _H2 gas stream at 1800℃ for 10 hours and leaving it at room temperature for 1 hour was repeated 20 times. The amount of deflection (L) of the tip of piece 1 due to its own weight was measured. The results are shown in Table 1. As is clear from Table 1, the molybdenum plates of Examples 1 and 2 of the present invention obtained by the method of producing molybdenum plates made of doped molybdenum materials according to the present invention were manufactured using the conventional production method shown in Comparative Examples 1 to 10. Compared to molybdenum plates obtained by heat treatment outside the heat treatment temperature range of the present invention, the amount of deflection (L) is significantly smaller, from 1/2 to less, and has excellent heat resistance. It was confirmed that it has thermal fatigue and creep resistance. Next, the sintered ingot shown in the previous example was
After hot forging at a working rate of 70% in the temperature range of 1100°C to 1400°C, recrystallized grain homogenization treatment was performed at 2000°C for 1 hour, which is higher than the recrystallization temperature. (First step) Next, the molybdenum alloy material that has undergone recrystallization grain homogenization treatment is forged in a temperature range of 1100℃ to 1400℃, and then rolled in a temperature range of 300℃ to 1100℃ to increase the processing rate. A 98% molybdenum alloy plate with a thickness of 2.0 mm was obtained. Width 10mm, length 100mm from the above molybdenum alloy plate
A test piece was cut out. After applying heat treatment to this test piece for 2000℃ x 2 hours, it was horizontally supported using the method shown in Figure 3, and heated to 1800℃.
The heating and cooling cycle of immersing the sample in a H ₂ gas stream for 10 hours and leaving it at room temperature for 1 hour was repeated 20 times, and the amount of deflection (L) of the tip of the test piece 1 was measured. This result shows that the processing rate shown in Table 1 is 98%.
When compared with the measurement results of Example 2 of the present invention, which was heat-treated at 2000°C, the amount of deflection of the test piece was 1.0 mm.
(Example 3 of the present invention), the amount of deflection can be made smaller,
It was confirmed that the effects of the present invention can be achieved even more effectively by providing the first step in the process of working a molybdenum alloy plate. These results demonstrate that in the method for manufacturing molybdenum plates according to the present invention, after forging or rolling with a processing rate of 85% or more, heat treatment is performed in a temperature range from 100°C higher than the recrystallization temperature to 2200°C. This is because the recrystallized grains become elongated and large and bonded in a zigzag pattern.Furthermore, by performing heat treatment at a temperature sufficiently higher than the recrystallization temperature, the molybdenum plate of the present invention can be used at high temperatures. This is because the stability of the metal structure has increased.

【table】

【table】 [Brief explanation of the drawing]

FIG. 1 is a process diagram illustrating a conventional method for manufacturing a molybdenum plate. FIG. 2 is a process diagram illustrating the method for manufacturing a molybdenum plate of the present invention. FIG. 3 is a schematic diagram showing the test method of the example.

Claims (1)

[Claims] 1 One or more of Al, Si, and K in weight%
A doped molybdenum sintered body containing 0.15 to 0.75% (excluding 0.15%) is subjected to surface reduction processing with a total processing rate of 85% or more, and then heated to a temperature range from 100℃ higher than the recrystallization temperature to 2200℃. A method for producing a molybdenum material, characterized in that the recrystallized grains are grown long and large by heat treatment. 2. The method for producing a molybdenum material according to claim 1, wherein the processing rate is 95% or more. 3. Before the surface reduction processing step described in claims 1 and 2, the surface reduction processing is performed at a processing rate of 45% or more, and heat treatment is performed at a temperature 200 to 800 °C higher than the recrystallization temperature. The method for producing a molybdenum material according to claims 1 and 2, comprising a step of uniformly producing recrystallized grains. 4 Claim No. 3 in which the processing rate is 95% or more
The method for producing molybdenum material described in Section 1.