JPH0322460B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a molybdenum wire used for general structural materials, materials for high-temperature furnaces, materials for heaters, support rods at high temperatures, pins, bolts, etc., and a method for manufacturing the same. [Prior Art] Generally, molybdenum wires including molybdenum rods and molybdenum wires manufactured by powder metallurgy are manufactured from pure molybdenum, and the recrystallization start temperature of this molybdenum wire is about 1000°C. Therefore, when a molybdenum wire made of molybdenum is used at a high temperature of 1000°C or higher, the wire becomes brittle due to the growth of recrystallized particles of molybdenum, and it also becomes difficult to handle the load under high temperature conditions. However, there was a problem that it easily deformed. Therefore, doped molybdenum materials containing aluminum, potassium, silicon, etc. have conventionally been used as molybdenum materials that compensate for the above-mentioned drawbacks. [Problems to be solved by the invention] However, conventional doped molybdenum materials require a high processing rate in the manufacturing process.
Furthermore, there was a manufacturing drawback in that the processability was poor. SUMMARY OF THE INVENTION In view of the above-mentioned drawbacks, an object of the present invention is to provide a molybdenum wire rod that has excellent workability and yield, and has excellent high-temperature deformation resistance with little deformation even when loaded under high-temperature conditions, and a method for manufacturing the same. It is. [Means for solving the problem] According to the present invention, in terms of weight ratio, 0.01 to 1.0% by weight
lanthanum or lanthanum oxide, and the remainder is molybdenum, and has excellent workability and high-temperature deformation resistance, characterized by having molybdenum crystal grains that are substantially elongated and recrystallized in a certain direction. A molybdenum wire is obtained. Furthermore, according to the present invention, there is a preparatory step of preparing an ingot composed of lanthanum or lanthanum oxide in an amount of 0.01 to less than 1.0% by weight, and the balance being molybdenum; A molybdenum wire rod having excellent workability and high-temperature deformation resistance, comprising a processing step in which the workpiece is processed at a total processing rate, and a coarsening step in which the workpiece is heated at least at a temperature at which molybdenum recrystallizes. A manufacturing method is obtained. [Summary of the Invention] According to the present invention, first, an ingot serving as a starting material for producing a molybdenum wire rod is, for example, a doped molybdenum oxide powder doped with 0.01 to less than 1.0% by weight of lanthanum or lanthanum oxide. It is obtained by subjecting it to hydrogen reduction, pressing and sintering. At this time, compared to the conventional ingot made only of pure molybdenum with a fine particle size of about 20 to 50 μm, the ingot according to the present invention has minute doping holes containing the dopant due to the activation effect of lanthanum doping. Moreover, the average grain size of the crystal grains is coarse grains of 0.5 to 10 mm. Next, this ingot having fine doped holes and coarsened crystal grains is hot-rolled at a total processing rate of 80% or more with respect to its cross-sectional area,
One or a combination of hot rolling and warm drawing is performed. As a result, the coarsened crystal particles become elongated fibrous particles. Next, this molybdenum wire made of fibrous particles is further subjected to coarsening treatment by heat treatment at a temperature higher than the degree of recrystallization (1000°C to 2300°C) to recrystallize the crystal particles and release internal strain. At this time, as shown in Figures 1 and 2,
Molybdenum crystal particles do not become coarse in the diametrical direction of the wire because the dopant arranged along the length of the wire suppresses grain growth in the diametrical direction of the wire. extended along
Exhibits an interloking structure. Therefore, even at high temperatures, equiaxed fine crystals do not form, so a high quality molybdenum wire with very little deformation can be obtained. As a comparative example, as shown in Figure 3, a conventional pure molybdenum wire rod without any doping agent was rolled to a working degree of 98.7% and then coarsened by heating at 1700°C for 10 hours. The crystal grains exhibit an equiaxed grain shape and cannot withstand use, and no improvement in workability or high-temperature deformation resistance is observed. The reason why the amount of lanthanum added was set to be less than 1.0% is because if it is more than 1.0%, many grains of doping agent will be generated, which will not only make it impossible to process the wire, but also cause problems in the length direction of the wire. Grain growth of molybdenum crystal particles is also suppressed. On the contrary, the workability and high temperature deformation resistance deteriorate. Further, the reason why it is set at 0.01% or more is that if it is less than 0.01%, the effect of lanthanum as a doping agent is weak, and remarkable workability and high temperature deformation resistance are not observed. [Example] An example of the present invention will be described with reference to the drawings. First, in a preparation step, a doped molybdenum oxide powder doped with 0.01 to less than 1.0% by weight of lanthanum was subjected to hydrogen reduction, pressed, and sintered to prepare an ingot. Next, in the processing process, the ingot is hot-rolled to give a processing rate of 65% and 80% in cross-sectional area to give the molybdenum crystal particles a fibrous structure, and further, in the coarsening process, recrystallization is performed. The molybdenum crystal particles were coarsened by heating at a temperature higher than that temperature. Next, as shown in Fig. 4, specimens 1 of 3φ x 120 mm were made from the obtained molybdenum rods, a load of approximately 200 g was suspended in the center of these specimens, and the specimens were placed in an electric furnace in a hydrogen atmosphere. After heating at 1700°C for 10 hours, the wire was cooled and a deformation test was conducted in which the amount of warpage of the molybdenum wire was measured using a dial gauge. Table 1 shows the results of the deformation test. As a result, as shown in Table 1, the lantern
The molybdenum wire rod according to the present invention containing less than 0.01 to 1.0% by weight was found to have an extremely small amount of deformation. Next, in order to investigate embrittlement at room temperature,
A molybdenum rod containing 0.5% lanthanum and, as a comparative example, a sample made of pure molybdenum (10φ x 90mm) were heated at 1600℃ x 10 hours, and then tested using a universal testing machine at a test speed of 1mm x min and a span of 50mm. A three-point bending test was conducted. As a result, as shown in FIG. 5, it was found that the molybdenum rod according to the present invention could sufficiently withstand bending at 90 degrees. On the other hand, the specimen made from pure molybdenum as a comparative example was easily broken at a bending angle of 0°.

[Table] [Effect of the invention] As explained above, according to the present invention, 0.01 to
An ingot with crystal grains that have been coarsened in advance by doping less than 1.0% by weight of lanthanum is processed at a processing rate of 65% or more of its cross-sectional area, so that the dopant is arranged in the length direction of the wire. After
Coarsening treatment is performed by heating above the recrystallization temperature. As a result, even in high-temperature conditions during actual use,
Grain growth in the diameter direction of the wire is suppressed, and a molybdenum wire made of recrystallized grains extending in the length direction of the wire can be obtained. As a result, it is possible to provide a molybdenum wire rod with excellent workability and yield, excellent usability with little deformation even under high-temperature loads, and a method for manufacturing the same.

[Brief explanation of the drawing]

Figure 1 1, 2, 3, and 4 show the roughening treatment after the processing with a processing rate of 98.7% according to the embodiment of the present invention.
FIG. 2 is a vertical cross-sectional view (×50 times) of molybdenum particles exhibiting an interlocking structure, similar to FIG. 1, after processing with a total processing rate of 98.7% according to the embodiment of the present invention
A vertical cross-sectional view (x600x) showing the arrangement direction of the dopant of a molybdenum wire rod subjected to coarsening treatment. Figure 3 shows molybdenum exhibiting an equiaxed crystal structure processed by the conventional method at a total processing rate of 98.7%. Longitudinal cross-sectional view of particles (×50 times, Figure 4 is a schematic diagram of the deformation test, and Figure 5 is a diagram showing the results of the three-point bending test. 1...Specimen, 2...Load.

Claims (1)

[Scope of Claims] 1. A product comprising 0.01 to less than 1.0% by weight of lanthanum or lanthanum oxide, the remainder being molybdenum, and having molybdenum crystal particles that are recrystallized by substantially elongating in a certain direction. , a molybdenum wire rod with excellent workability and high temperature deformation resistance. 2. A preparation step of preparing an ingot composed of 0.01 to less than 1.0% by weight of lanthanum or lanthanum oxide, the balance being molybdenum, and a processing step of processing the ingot at a total processing rate of 80% or more with respect to the cross-sectional area of the ingot. 1. A method for producing a molybdenum wire, comprising: a coarsening treatment step of heating the workpiece at least at a temperature at which molybdenum recrystallizes. 3. The method for producing a molybdenum wire according to claim 2, wherein the ingot in the preparation step has an average particle size of 0.1 to 10 mm. 4. In the method for manufacturing a molybdenum wire rod according to claim 2 or 3, the processing in the processing step is selected from hot rolling processing, hot rolling processing, and warm drawing processing. A method for producing a molybdenum wire, characterized by at least one type of molybdenum wire.