JPH0359137B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a molybdenum plate used for general structural materials, high-temperature reactors, boats for nuclear fuel sintering, materials for nuclear fusion reactors, electron tube materials, etc., and a method for manufacturing the same. [Prior Art] Generally, molybdenum plates manufactured by powder metallurgy are manufactured from pure molybdenum. The recrystallization start temperature of this molybdenum plate is 1000°C. Therefore, when a molybdenum plate made of molybdenum is used at temperatures above 1000°C, the plate becomes brittle due to the growth of recrystallized particles, and it easily deforms under load at high temperatures. There was a problem. Therefore, as a molybdenum material that compensates for the above-mentioned drawbacks, a method has conventionally been used in which molybdenum is strengthened by adding various dopants. [Problems to be Solved by the Invention] However, conventional doped molybdenum materials have manufacturing disadvantages in that they require a high processing rate in the manufacturing process and have poor processability. Furthermore, when used at high temperatures, the recrystallized structure is controlled by the arrangement of the dopant, so the recrystallized structure becomes long in the rolling direction and short in the direction perpendicular to the rolling direction. Therefore, when used in a manner that places a load on the short recrystallized structure, it has the disadvantage that it easily deforms. On the other hand, by selecting the crystal grain structure of a molybdenum plate with a purity of 99.95% or more, a method is being used to create a plate with excellent high-temperature strength without restrictions on the direction of use. However, it has the disadvantage that it easily deforms under large loads. SUMMARY OF THE INVENTION In view of the above-mentioned drawbacks, it is a technical object of the present invention to provide a molybdenum plate that is easy to use and has a small amount of deformation even when subjected to loads under high temperature conditions, and a method for manufacturing the same. [Means for solving the problem] According to the present invention, the ingot that is the starting material for producing molybdenum plates has, for example, 0.1%
A doped molybdenum layer formed from doped molybdenum powder doped with lanthanum or lanthanum oxide in an amount of 1.0% to 1.0%, and a pure molybdenum layer formed from molybdenum with a purity of 99.95% or more. Formed by combination. Next, this ingot having multiple layers is subjected to hot forging and rolling, or a combination thereof, at a total working rate of 80% or more in the thickness direction. Next, this molybdenum plate having a fibrous structure is further subjected to coarsening treatment by heat treatment at a temperature higher than the recrystallization temperature to recrystallize the crystal grains and release internal strain. At this time, the pure molybdenum layer with a purity of 99.95% or more has a disk-like structure with an average diameter of 10 mm to 150 mm because there is no grain growth inhibiting effect due to dopants or impurities. On the other hand, in the doped molybdenum layer doped with lanthanum, the dopant is arranged along the rolling direction, so grain growth in the thickness direction is suppressed.
It exhibits a so-called interlocking structure that does not become coarse in the thickness direction and extends along the rolling direction. That is, a composite molybdenum plate is obtained, which is formed by an interlocking layer that is dispersed and strengthened by lanthanum oxide grains and a layer that has a disk-like structure that does not have directionality and is unlikely to cause grain boundary sliding. It will be done. Therefore, a high-quality molybdenum plate material with very little deformation even when exposed to high temperatures can be obtained. Here, the addition amount of lanthanum oxide in the doped molybdenum layer containing lanthanum oxide was set to 1.0% or less because if the addition amount exceeds 1.0%, the amount of lanthanum oxide evaporated during sintering will increase, resulting in a purity of 99.95%. This is because it contaminates the pure molybdenum layer and prevents the formation of a disk-like structure in the pure molybdenum layer with a purity of 99.95% in the crystal grain coarsening process. The reason for setting it to 0.1% is that if it is less than 0.1%, the effect of lanthanum as a doping agent is weak, and formation of a sufficient interlocking layer cannot be expected. [Example] Next, a composite molybdenum plate material according to an example of the present invention will be described with reference to the drawings. First of all, the average particle size is 3 to 5 μm with a purity of 99.95% or more.
m pure molybdenum powder was prepared. Next, the molybdenum oxide powder doped with 0.01, 0.1, 0.5, and 1.0% by weight of lanthanum oxide, respectively, was subjected to hydrogen reduction, and the powder was prepared into doped molybdenum powder doped with lanthanum oxide and having an average particle size of 2 to 5 μm. Next, a mold for molding the powder was prepared, and first, doped molybdenum powder doped with lanthanum oxide was filled and the powder was leveled so that it was parallel to the bottom of the mold. Next, pure molybdenum powder with a purity of 99.95% or higher was filled and leveled in the same manner. Finally, fill the powder doped with lanthanum oxide again and level it out.
The work was carried out, and a pressed body was formed using a hydraulic press machine at a pressure of 2 tons/ ^cm2 , and sintered at 1900℃ for 5 hours in a hydrogen stream to obtain an ingot with a three-layer structure approximately 30 mm thick. Ta. This ingot was heated at a maximum temperature of 1300°C, hot forged, and rolled repeatedly while gradually lowering the heating temperature, followed by warm rolling and cold rolling to obtain a 2 mm thick molybdenum plate. Next, this plate was subjected to grain coarsening treatment at 2250° C. in a hydrogen stream, and then specimens of 2 mm x 20 mm x 150 mm were cut out from the final rolling direction and from the direction perpendicular to the final rolling direction. These specimens 1 to 4 according to the present invention
and other comparative specimens 5 to 8 of similar size, with a span of 100 mm and loads of 500 g and 1000 g,
A deformation test was conducted at ℃ for 10 hours, and the amount of deformation was compared. The deformation test was conducted in the manner shown in FIG. Here, the test piece used for comparison has a purity of 99.95
Plate 8 consists of molybdenum of 0.1%, 0.5% and has a disc-shaped grain structure that is effective in high temperature deformation resistance.
Molybdenum plates 5 to 7 containing lanthanum oxide at a ratio of 1.0% and 1.0%. In addition, FIG. 1 shows the concept of the structure of test pieces 1 to 4 according to the present invention and comparison test pieces 5 to 8.

[Table] As a result, as shown in Table-1, the lanthanum was 0.1
The composite molybdenum plates (1 to 4) according to the present invention formed of a molybdenum layer containing ~1.0% and a molybdenum layer with a purity of 99.95% or more have a difference in deformation in the rolling direction and in the direction perpendicular to the rolling direction. Comparative Examples 5 to 8
It is recognized that the amount of deformation is also smaller than that of the previous one. Example 2 Using the same method as Example 1, 0.1, 0.5, and
A layer made of molybdenum with a purity of 99.95% is sandwiched between layers of molybdenum containing 1.0% by weight of lanthanum oxide, and furthermore, the respective working degrees are 65%, 80%, and 93% in the final rolling. I prepared the ingots. Next, the ingot is heated to a maximum of 1300℃,
Hot forging, hot rolling, warm rolling, and cold rolling were added so that the working ratio was 65%, 80%, and 93%, respectively, to produce a plate processed to the specified working ratio. From there, a specimen measuring 2 mm x 20 mm x 150 mm was cut out. Next, this sample was subjected to grain coarsening treatment at 2250°C in a hydrogen stream. Span this specimen 100
A deformation test was conducted at 1800°C for 10 hours under a load of 1000g in mm, and the amount of deformation was compared. The results are shown in Table-2.

〔Effect of the invention〕

As described above, according to the present invention, an ingot formed of at least one layer of each of a doped molybdenum layer containing 0.1% to 1.0% lanthanum and a pure molybdenum layer having a purity of 99.95% or more is The dopant in the doped molybdenum layer containing lanthanum oxide is aligned in the direction perpendicular to the plate thickness by hot forging or hot rolling at a processing rate of 80% or more in the transverse direction, and then by warm rolling and cold rolling. After that, by heating above the recrystallization temperature and performing a coarsening treatment, the doped molybdenum layer containing lanthanum oxide becomes an interlocking layer that is dispersed and strengthened by lanthanum oxide particles,
On the other hand, a pure molybdenum layer with a purity of 99.95% or more forms a layer having a large disk-like structure with little slippage at grain boundaries. Therefore, it is possible to provide a composite molybdenum plate with excellent usability that exhibits little deformation even under high-temperature loads, and a method for manufacturing the same.

[Brief explanation of drawings]

1 to 8 in FIG. 1 are conceptual diagrams showing the following structure. 1 is a three-layer structure according to the present invention including a molybdenum layer containing 0.01% lanthanum oxide and a molybdenum layer with a purity of 99.95%, and 2 is a three-layer structure according to the present invention including a molybdenum layer containing 0.1% lanthanum oxide and a molybdenum layer with a purity of 99.95%. Layered structure, 3 is a three-layered structure according to the present invention of a molybdenum layer containing 0.5% lanthanum oxide and a molybdenum layer with a purity of 99.95%, 4 is a book with a molybdenum layer containing 1.0% lanthanum oxide and a molybdenum layer with a purity of 99.95%. The three-layer structure according to the invention, 5 is the structure of a molybdenum plate containing 0.1% lanthanum oxide as a comparative example, 6 is the structure of a molybdenum plate containing 0.5% lanthanum oxide as a comparative example, and 7 is 1.0 as a comparative example.
% lanthanum oxide-containing molybdenum plate, 8 is the structure of a molybdenum plate with a purity of 99.95% as a comparative example. FIG. 2 is a diagram showing an aspect of a high temperature deformation test.

Claims (1)

[Claims] 1. A pure molybdenum layer with a purity of 99.95% or more, which does not contain trace additive elements, and a weight ratio of 0.1% or more to 1.0%.
A composite molybdenum plate comprising at least one layer of each of the following doped molybdenum layers containing lanthanum or lanthanum oxide and the remainder being molybdenum. 2. The composite molybdenum plate according to claim 1, wherein the pure molybdenum layer has a disk-like structure, and the doped molybdenum layer has an interlocking structure. 3 A pure molybdenum layer with a purity of 99.95% or more, which does not contain trace additive elements, and a weight ratio of 0.1% or more to 1.0%.
% or less of lanthanum or lanthanum oxide, and a doped molybdenum layer with the remainder being molybdenum. Production of a composite molybdenum plate with excellent impact resistance and high-temperature deformation resistance, which comprises a processing step in which the workpiece is processed at a processing rate and a coarsening step in which the workpiece is heated at a temperature at least at which it recrystallizes. Method.