JPH0320456B2 - - 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 member becomes brittle due to the growth of recrystallized particles of molybdenum, so it easily deforms under load at high temperatures. I had a problem with it. Therefore, molybdenum materials containing aluminum, potassium, silicon, etc. have been conventionally used as molybdenum materials that compensate for the above-mentioned drawback of being easily deformed at high temperatures. [Problems to be Solved by the Invention] However, conventional molybdenum materials require a high processing rate in the manufacturing process and have poor workability, so they are limited to molybdenum wire rods with small cross-sectional areas. There was a drawback. SUMMARY OF THE INVENTION In view of the above-mentioned drawbacks, an object of the present invention is to provide molybdenum rods, molybdenum wires, and other molybdenum wires that have excellent workability and yield, and are easy to use with little deformation even under high-temperature loads. That's true. [Means for Solving the Problems] According to the present invention, 0.1 to 1.0% by weight (excluding 1.0%) of lanthanum or lanthanum oxide, the balance being molybdenum, and the molybdenum crystal particles are substantially fibers. A molybdenum wire rod having a structural structure and a small amount of deformation at high temperatures can be obtained. Further, according to the present invention, there is a preparatory step of preparing an ingot consisting of 0.1 to 1.0% by weight (excluding 1.0%) of lanthanum or lanthanum oxide, the balance being molybdenum, and a step of preparing an ingot consisting of 0.1 to 1.0% by weight (excluding 1.0%) of lanthanum or lanthanum oxide, the balance being molybdenum, and 80% or more of the cross-sectional area of the ingot. A method for producing a molybdenum wire, comprising a processing step of processing at a total processing rate of (preferably 90% or more). is obtained. Further, the ingot in the preparation step has an average grain size of 0.1 to 10 mm, and the processing in the processing step is at least one selected from hot rolling, hot rolling, and warm drawing. Preferably, it is one type. That is, according to the present invention, an ingot that is a starting material for producing a molybdenum wire is obtained by hydrogen reduction of molybdenum powder doped with 0.1 to less than 1.0% by weight of lanthanum or lanthanum oxide, followed by pressing and baking. formed by joining. At this time, compared to conventional ingots having a fine grain size of about 20 to 50 μm, the ingot crystals have minute doping pores containing the doping agent due to the activation effect of lanthanum doping, and the crystal grains The average particle size becomes coarse particles of 0.1 to 10 mm. Next, the above-mentioned ingot containing the doping agent is subjected to hot rolling, hot rolling, or warm drawing at a processing rate of 80% or more with respect to its cross-sectional area, to form a wire in the longitudinal direction. The dopants are arranged in As a result, as shown in Fig. 1, the structure of the processed rod in a cross section parallel to the processing direction exhibits a fibrous structure that has grown into elongated shapes, and even when placed in a high temperature state, the structure remains the same. Alternatively, even if it is recrystallized, it becomes an interlocked structure and does not become equiaxed fine crystals. Incidentally, as shown in FIG. 2, in the case of using pure molybdenum that does not contain lanthanum, the molybdenum wire rod exhibits variations in the fiber structure. Therefore, according to the present invention, a high-quality molybdenum wire rod with very little deformation even when placed in a high temperature state can be obtained. Here, the reason for limiting the composition range of lanthanum in the molybdenum wire will be explained. In molybdenum wire rods containing less than 0.1 to 1.0% by weight of lanthanum, recrystallization is suppressed by the lanthanum grains arranged in the length direction of the wire due to processing, and even when recrystallization occurs, coarse molybdenum crystal particles remain. , grows thin and thin in the length direction of the wire, and is suppressed in the diameter direction. However, when the amount of lanthanum added is less than 0.1% by weight, the effect of lanthanum as a doping agent is weak, and it becomes difficult to sufficiently suppress the grain growth of molybdenum crystal particles. Therefore, molybdenum crystal particles become equiaxed crystal grains in a high temperature state, making it difficult to withstand deformation at high temperatures. On the other hand, if it is more than 1.0% by weight, a large amount of dopant particles will be generated, which will not only cause cracks to occur in the early stages of processing, leading to a decrease in yield and making processing impossible, but also to high temperatures. This is because, in this state, the growth of molybdenum crystal grains in the longitudinal direction of the wire is also suppressed, and the formation of equiaxed crystal grains is promoted instead. [Example] An example of the present invention will be described with reference to the drawings. First, in a preparation step, molybdenum powder doped with 0.1 to 1.0% by weight of lanthanum was subjected to hydrogen reduction, pressed, and sintered to prepare an ingot. Next, in the processing step, the ingot was subjected to rolling, rolling, and drawing processing such that the cross-sectional area had a processing rate of 65% and 80%, to form a bar having a fibrous structure. As shown in Figure 3, specimens of 3φ x 120 mm were made from the molybdenum rods obtained in this way, a load of approximately 1.0 kg was placed on these specimens, and they were placed in an electric furnace in a hydrogen atmosphere. A deformation test was conducted by heating at 1700℃ for 10 hours. The results are listed in Table 1. As a comparative example,
The results of deformation tests (a, b) of molybdenum bars manufactured using ingots made of pure molybdenum are shown in the lower part of the table. As a result, as shown in Table 1, molybdenum rods 1 to 6 according to the present invention containing less than 0.1 to 1.0% by weight of lanthanum were found to have extremely small amounts of deformation. Next, in order to investigate embrittlement at room temperature,
A molybdenum rod containing 0.5% lanthanum and a specimen (10φ x 90mm) made of pure molybdenum as a comparative example were heated at 1600°C for 10 hours, and then tested using a universal testing machine at a test speed of 1mm/min and a span of 50mm. A point bending test was conducted. As a result, as shown in Figure 4, the molybdenum bar according to the present invention was found to be able to withstand bending at an angle of 90 degrees. It was easily destroyed at 0°.

【table】

[Table] [Effect of the invention] As explained above, according to the present invention, 0.1 to
An ingot with crystal grains coarsened in advance by doping less than 1.0% by weight of lanthanum is processed at a processing rate of 80% or more of its cross-sectional area, and the dopant is arranged in the length direction of the molybdenum wire. By doing so, grain growth in the diameter direction of the wire rod is suppressed in the high temperature conditions during actual use, so the fiber structure remains unchanged or the fiber structure grows into elongated grains in the length direction even after recrystallization. Since a molybdenum wire rod having a structure can be obtained, 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 shows a rolling reduction rate of 98.7 according to an embodiment of the present invention.
% cross-sectional view (x50x) showing the interlocked metal structure of a molybdenum rod. Figure 2 shows the conventional rolling rate using pure molybdenum that does not contain lanthanum.
A cross-sectional view (×50 times) showing the structural structure of a 98.7% molybdenum bar, FIG. 3 is a schematic diagram of a deformation test, and FIG. 4 is a cross-sectional view showing the results of a three-point bending test. 1...Specimen, 2...Load.

Claims (1)

[Scope of Claims] 1 0.1 to 1.0% by weight (excluding 1.0%) of lanthanum or lanthanum oxide, the balance being molybdenum,
The molybdenum wire is characterized in that the molybdenum crystal grains have a substantially fibrous structure, and the amount of deformation at high temperatures is small. 2. Preparation step of preparing an ingot consisting of 0.1 to 1.0% by weight (excluding 1.0%) of lanthanum or lanthanum oxide, the balance being molybdenum, and processing at a total processing rate of 80% or more based on the cross-sectional area of the ingot. A method for producing a molybdenum wire, comprising a processing step. 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.