JP3315166B2 - High formability molybdenum plate, method for producing the same, and reflection plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly formable molybdenum sheet and a method for producing the same, and more particularly to a highly formable molybdenum sheet which is excellent in secondary workability and hardly generates cracks even when deep drawing is performed by press working. The present invention relates to a plate, a manufacturing method thereof, and a reflection plate using the molybdenum plate.

[0002]

2. Description of the Related Art In order to further increase the amount of light emitted from a halogen lamp whose luminous efficiency has been increased by increasing the filament temperature,
For example, a reflector (mirror) 1 as shown in FIGS. 4 to 6 is provided integrally with the lamp. The reflector is required to have a heat resistance so as not to be deteriorated by radiant heat from the high-temperature filament, and a high melting point metal plate such as molybdenum or tungsten is generally used as a material satisfying the requirement. ing.

Conventionally, the above-mentioned molybdenum reflection plate 1 has been manufactured through the following rolling step and press forming step. That is, the molybdenum material is hot-rolled at a rolling ratio of about 80 to 90%, and thereafter, at a temperature of 900 to 950 ° C.
In the state where the molybdenum material is softened by cold rolling at about 98% in a state where the molybdenum material is softened by appropriately performing strain relief annealing for about 20 to 60 minutes, the obtained rolled sheet is annealed at a temperature of 950 ° C. for about 20 minutes. A molybdenum plate for press forming having a thickness of about 0.1 to 0.3 mm is prepared by processing, and the molybdenum plate is deep drawn by using a press forming machine to perform deep drawing as shown in FIGS. The reflection plate 1 having the portion 2 and the overhang portion 3 was manufactured.

[0004]

However, the above-mentioned thin sheets of molybdenum and tungsten are generally difficult-to-work materials, and the depth required for press-forming into the shape of a reflector for a lamp as shown in FIGS. Molding was difficult due to insufficient drawability, overhanging properties, and the like. When the molybdenum plate is press-formed, cracks occur frequently and there is a problem that the production yield of the reflection plate is greatly reduced.

[0005] Incidentally, the processing characteristics, particularly the deep drawing characteristics, of a rolled plate for press forming are determined by the ratio of the true strain εw of the width to the true strain εw of the thickness of the rolled plate in the direction perpendicular to the tension (plasticity). (Ratio of strain ratio or Rankford value), and it has become clear from research on steel materials and the like that the r value strongly depends on the crystal orientation distribution (texture) of the metal structure of the sheet material. That is, many {111} crystal planes develop in parallel to the rolled sheet surface, and {10}
It has been confirmed that the smaller the 0 ° crystal plane, the better the deep drawing characteristics. Therefore, in the manufacturing process of a steel sheet for automobiles, measures are taken to improve the press formability of the sheet material by controlling the crystal orientation distribution by adjusting the rolling ratio, annealing conditions and the like.

However, the same body-centered cubic (bc)
c) Means for improving the deep drawability of a molybdenum plate while having a structure include adjusting the crystal grain size,
Only means for reducing the amount of impurity at the grain boundary to strengthen the grain boundary is taken, but no consideration is given to the crystal orientation distribution.

On the other hand, as a method of rolling a sheet material such as a reflector for a lamp, which is subjected to a strong working such as deep drawing, the hot rolling and the cold rolling are performed by changing the rolling direction by 90 degrees to form a plastic anisotropic material. A cross-rolling method that reduces the susceptibility is also employed. However, it is extremely difficult to apply the method in a manufacturing process for continuously processing a long coil, because the process is complicated and practical use is extremely difficult.

Further, when the molybdenum plate material is recrystallized, its low-temperature brittleness becomes remarkable because the ductile-brittle transition temperature is around room temperature, and cracks are easily generated during rolling. Conventionally, in order to prevent the occurrence of cracks, the annealing temperature after hot rolling was set to be equal to or lower than the recrystallization temperature. Warm working and even less.
As a result, the working ratio after the recrystallization heat treatment, that is, the cold working ratio, becomes excessive (substantially 95% or more), and the {100} crystal plane parallel to the plate surface excessively increases. The {111} crystal plane did not increase, and only a molybdenum plate having low moldability was obtained.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has high formability molybdenum plate which is excellent in secondary workability and hardly causes cracks even when deep drawing is performed by press working. It is an object of the present invention to provide a manufacturing method and a reflection plate using the molybdenum plate.

[0010]

Means for Solving the Problems In order to achieve the above object, the present inventors carried out rolling and heat treatment under various conditions of rolling and annealing heat treatment of a molybdenum material, and obtained each molybdenum plate. The influence of the rolled surface on the crystal orientation distribution and press formability was investigated. That is, while measuring the diffraction intensity of each crystal plane parallel to the rolling plane of each molybdenum plate using an X-ray diffractometer, measuring the ratio to the diffraction intensity of each crystal plane of non-oriented molybdenum, the crystal orientation distribution and the crystal orientation The degree of plane orientation was determined, and the relationship between these measured values and press formability was analyzed.

As a result, (2) parallel to the surface of each molybdenum plate
22) When the diffraction intensity ratio of the crystal plane to the (200) crystal plane is set to 0.3 or more, or the diffraction intensity ratio of the (200) crystal plane of the molybdenum plate to the non-oriented molybdenum sample is set to 10 or less, For the first time, a finding was obtained that even when a sheet was deep-pressed, cracking hardly occurred and formability was greatly improved. The present invention has been completed based on the above findings.

That is, in the highly formable molybdenum plate according to the present invention, the X-ray diffraction intensity on the (222) crystal plane parallel to the plate surface is 0.3% on the (200) crystal plane.
It is characterized by being twice or more.

The X-ray diffraction intensity at the (200) crystal plane of the molybdenum plate is the same as that of non-oriented molybdenum.
The X-ray diffraction intensity on the crystal plane is preferably set to 10 times or less.

Further, it is preferable that the metal structure of the molybdenum plate is composed of a mixed grain structure of recrystallized grains having an area ratio of 40 to 60% and grains deformed by the remaining rolling. The method for producing a highly formable molybdenum sheet according to the present invention is characterized in that a hot-rolled molybdenum material is added to a (222) crystal plane parallel to the sheet surface.
At least heat treatment and cold rolling are performed so that the X-ray diffraction intensity is at least 0.3 times the X-ray diffraction intensity on the (200) crystal plane. In the above manufacturing method, the X-ray diffraction intensity on the (200) crystal plane is preferably 10 times or less the X-ray diffraction intensity on the (200) crystal plane of non-oriented molybdenum.

The method for producing a highly formable molybdenum sheet according to the present invention is characterized in that the hot-rolled molybdenum material is treated at a temperature of 1 ° C.
Intermediate annealing treatment at 050 to 1150 ° C, and the obtained primary rolled sheet is cold rolled at a rolling reduction of 80 to 95% after recrystallization heat treatment to prepare a secondary rolled sheet having a final target sheet thickness. The secondary rolled sheet obtained later was heated at a temperature of 980 to 1030 ° C.
By performing the final annealing treatment in (2), the X-ray diffraction intensity on the (222) crystal plane parallel to the plate surface of the secondary rolled plate is reduced by (20).
0) It is characterized by being set to 0.3 times or more the X-ray diffraction intensity on the crystal plane. In the above manufacturing method, (20
0) The X-ray diffraction intensity on the crystal plane is preferably 10 times or less the X-ray diffraction intensity on the (200) crystal plane of non-oriented molybdenum.

That is, the thickness of the primary rolled sheet after the hot rolling is set so that the working ratio after the recrystallization heat treatment, ie, the cold rolling ratio, is 80 to 95% lower than that of the conventional method. High temperature 980 to 1030 at which recrystallized grains constituting the structure of the secondary rolled sheet after rolling are not excessively grown.
A final annealing treatment is carried out at a temperature of ° C. to form a mixed grain structure in which regenerated crystal grains and deformed grains are mixed.

The intermediate annealing is a step of completely recrystallizing deformed grains remaining after hot rolling.
It is carried out by heating the primary rolled sheet for about 20 minutes to 1.5 hours at a processing temperature in the range of 1050 to 1150 ° C. which is higher than the conventional method. When the processing temperature is lower than 1050 ° C., recrystallization does not proceed, while the processing temperature is 1150 ° C.
If it exceeds, the crystal grains become excessively coarse, and cold rolling becomes difficult.

The rolling reduction after the recrystallization heat treatment is a factor that has a great effect on the crystal orientation distribution of the secondary rolled plate. The primary rolled plate completely recrystallized by the intermediate annealing has a high rolling reduction exceeding 95%. When cold-rolled to form a secondary rolled plate,
The processing strain increases and the {111} crystal plane does not develop on the rolled surface, while the {100} crystal plane increases, and the deep drawability of the secondary rolled sheet decreases. On the other hand, if the rolling reduction after the recrystallization heat treatment is set to less than 80%, some of the crystal grains become coarse after the final annealing described later, and a mixed grain structure having good formability cannot be obtained. Therefore, it is necessary to set the thickness of the primary rolled sheet to be small, and the rolling efficiency is reduced. Therefore, the rolling reduction after recrystallization heat treatment is 80-
It is necessary to set 95%, which is smaller than the conventional processing method. In the cold rolling step, a heat treatment operation at a temperature of 930 to 950 ° C. for about 20 to 40 minutes may be repeated a plurality of times in order to soften the work-hardened rolled sheet.

In the final annealing applied to the secondary rolled sheet after the cold rolling, the working strain is removed, the {111} crystal plane formed parallel to the rolling surface is stabilized, and the deformed grains are partially removed. In order to cause the metal structure of the secondary rolled sheet to have a mixed grain structure composed of recrystallized grains having an area ratio of 40 to 60% and deformed grains of the remaining portion, the temperature 98 is higher than that of the conventional method.
Heating is performed at 0 to 1030 ° C. for 10 to 30 minutes.

When the final annealing temperature is lower than 980 ° C., recrystallization does not proceed. On the other hand, when the annealing temperature exceeds 1030 ° C., recrystallization proceeds completely.
1) A mixed grain structure excellent in formability, consisting of recrystallized grains with developed crystal faces and deformed grains, cannot be obtained, and in any case, the deep drawability of the secondary rolled sheet is greatly reduced. Therefore, the final annealing temperature is set in the range of 980 to 1030 ° C. as described above.

According to the above-mentioned processing step, the (222) crystal plane of the molybdenum material is oriented parallel to the plate surface (rolled surface) of the secondary rolled sheet, and the X-ray diffraction intensity on the (222) crystal plane is (200). The X-ray diffraction intensity on the crystal plane is 0.3 times or more, and the {100} crystal plane, which inhibits deep drawability, is relatively reduced, and a molybdenum plate having excellent formability can be obtained.

On the other hand, as an index for evaluating the orientation of the (222) crystal plane, (200)
The ratio (I ₍₂₀₀₎ / I ₀ ) between the diffraction intensity I _{(200) on the} crystal plane and the diffraction intensity I ₀ on the non-oriented molybdenum material (random sample) was measured. According to the molybdenum plate prepared by the production method according to the present invention,
₍₂₀₀₎ / I ₀ value becomes 10 or less and relatively (222)
The crystal plane is oriented to the rolling plane. Therefore, even when deep drawing is performed using the molybdenum plate as in a reflection plate for a halogen lamp, a molybdenum plate excellent in formability can be obtained without cracking during press forming.

[0023]

According to the high formability molybdenum sheet and the method of manufacturing the same according to the above constitution, the molybdenum material is hot-rolled, then subjected to intermediate annealing at a high temperature for recrystallization, and the obtained primary rolled sheet is conventionally used. Cold rolling at a lower rolling ratio than the conventional method, and a final annealing treatment at a higher temperature than the conventional method.
22) Since a mixed grain structure of recrystallized grains whose crystal faces are oriented and deformed grains by rolling is formed, a molybdenum plate with improved formability can be obtained.

Therefore, even when the present invention is applied to a deep-drawn press-formed product such as a reflector for a halogen lamp, it is possible to mass-produce the molded product with less occurrence of cracks and a high production yield.

[0025]

Next, one embodiment of the high formability molybdenum plate according to the present invention will be described more specifically.

Examples 1 to 5 A molybdenum material (slag) having a thickness of 40 to 60 mm was prepared by compacting and sintering molybdenum powder having an average particle size of 0.5 μm. Next, as shown in Table 1, the obtained molybdenum material was hot-rolled at a rolling reduction of 94% while being heated at a temperature of 1250 ° C. to form a primary rolled sheet. Next, the obtained primary rolled sheets were each subjected to intermediate annealing at a temperature in the range of 1050 ° C. to 1150 ° C. to prepare primary rolled sheets in which the metal structure was completely recrystallized.

Next, each of the obtained primary rolled sheets was cold-rolled at a rolling reduction of 94% smaller than the conventional method to a final sheet thickness of 0.2 mm.
Were prepared respectively. In order to soften the work-hardened material during cold rolling, 950 ° C. × 40
And 950 ° C. for 20 minutes.

Next, as shown in Table 1, each of the obtained secondary rolled sheets was subjected to a final annealing treatment in which it was heated at a temperature higher than that of the conventional method at a temperature of 980 to 1030 ° C. for 20 minutes.
Were prepared respectively.

Next, for each of the obtained molybdenum plates, C
The crystal orientation distribution on the rolled surface was investigated using an X-ray diffractometer using u-Kα radiation. That is, the diffraction intensity I of the (200) crystal plane of the X-ray diffraction intensity I of the ₍₂₂₂ ) crystal plane
With measuring the ₍₂₀₀₎ and the ratio of (I ₍₂₂₂₎ / I _(200)), the (200) non-oriented molybdenum diffraction intensity of the crystal plane I ₍₂₀₀₎ of the (random samples) (200) crystal plane The ratio (I ₍₂₀₀₎ / I ₀ ) to the diffraction intensity I ₀ was measured. Further, the metal structure of each molybdenum plate was observed with a metallographic microscope, and the area ratio between the recrystallized grains and the deformed grains was measured. Furthermore, press forming was performed using each molybdenum plate, and FIG.
A reflector 1 for a halogen lamp having a deep drawing shape as shown in FIG. 6 was manufactured, and the rate of occurrence of defects such as cracks during molding was investigated. The results shown in Table 1 were obtained.

Comparative Example 1 On the other hand, as Comparative Example 1, the intermediate annealing temperature was set to 950 ° C. as low as the conventional method, the rolling reduction during cold rolling was increased to 98%, and the final annealing temperature was lowered to 950 ° C. A molybdenum plate according to Comparative Example 1 was manufactured in the same manner as in Examples 1 to 5, except that the eye was set. Hereinafter, similarly, the diffraction intensity ratio I
_{(222) / I (200)} , together with measuring the I ₍₂₀₀₎ / I _0, and measuring the area ratio of the mixed grain structure of recrystallized grains with the machining deformation particle further press-molded to form a reflecting plate 1 Then, the defect occurrence rate was obtained.

Comparative Example 2 As Comparative Example 2, the molybdenum material (slag) prepared in Examples 1 to 5 was rolled at a rolling reduction of 8 as shown in Table 1.
Hot rolling at 6%, without further controlling the crystal orientation distribution, that is, low temperature intermediate annealing at 850 ° C. × 20 minutes, cold rolling at a rolling reduction of 98%, and A final annealing treatment was performed at a temperature of 950 ° C. for 20 minutes to produce a molybdenum plate according to Comparative Example 2. Then, in the same manner as in Examples 1 to 5, the diffraction intensity ratio and the area ratio of the mixed grain structure were obtained, and the occurrence ratio of defects such as cracks was investigated by press molding, and the results shown in Table 1 were obtained. As the X-ray diffraction intensity, an integrated intensity was employed in order to avoid the influence of an error due to a strain of a rolled plate or the like.

[0032] Comparative Example 3 Further comparative example 3, the annealing temperature during the cold rolling process 9
A molybdenum plate was manufactured by performing the same treatment as in Comparative Example 1 except that the final annealing treatment temperature was set to 1000 ° C., while determining the diffraction intensity ratio and the area ratio of the mixed grain structure. The reflector 1 was formed by molding to determine the rate of occurrence of cracks, and the results shown in Table 1 below were obtained.

[0033]

[Table 1]

As shown in Table 1 above, the intermediate annealing temperature after the completion of hot rolling is increased, the rolling reduction during cold rolling is set lower than before, and the final annealing temperature is set higher. All of the molybdenum plates of Examples 1 to 5 which were manufactured as described above exhibited high formability, and were able to produce a reflector for a halogen lamp with high yield with little occurrence of cracks even during deep drawing press forming. .

As shown in FIG. 1, according to the X-ray diffraction profile of the molybdenum plate according to Example 1, it was confirmed that the (222) crystal plane was developed on the rolled surface, and good deep drawability was exhibited. Was done.

On the other hand, the X-ray diffraction profiles of the molybdenum plates according to Comparative Examples 1, 3 and 2 are shown in FIGS.
As shown in FIG. As is clear from FIGS.
The molybdenum plate _No. 3 has insufficient development of the (222) crystal plane, and the value of the diffraction intensity ratio I ₍₂₂₂₎ / I ₍₂₀₀₎ is less than 0.3. The occurrence rate of cracks was extremely high, and it was confirmed that practical application was extremely difficult. The final annealing temperature is 1
When the temperature exceeds 050 ° C., the recrystallized grains occupy the majority, resulting in a sharp increase in cracks.

[0037]

As described above, according to the high formability molybdenum sheet and the method for producing the same according to the present invention, the molybdenum material is hot-rolled and then subjected to intermediate annealing at a high temperature to achieve recrystallization. The primary rolled sheet is cold-rolled at a lower rolling ratio than the conventional method, and further subjected to final annealing at a higher temperature than the conventional method.
Since a mixed grain structure of recrystallized grains whose (222) crystal faces are oriented parallel to the rolling face and grains deformed by rolling is formed, a molybdenum plate with improved formability can be obtained.

Therefore, even when the present invention is applied to a deep-drawing press-formed product such as a reflector for a halogen lamp, it is possible to mass-produce the molded product with less occurrence of cracks and a high production yield.

[Brief description of the drawings]

FIG. 1 is an X-ray diffraction profile of a molybdenum plate according to Example 1.

FIG. 2 is an X-ray diffraction profile of a molybdenum plate according to Comparative Examples 1 and 3.

FIG. 3 is an X-ray diffraction profile of a molybdenum plate according to Comparative Example 2.

FIG. 4 is a plan view showing a press-formed shape of a reflector for a halogen lamp.

FIG. 5 is a sectional view taken along the line VV in FIG. 4;

FIG. 6 is a side view of the reflector shown in FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reflector 2 Deep drawing part 3 Overhang part

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Motohisa Sakai 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Pref. Toshiba Corporation Yokohama Office (58) Field surveyed (Int. Cl. ⁷ , DB name) C22C 27 / 04 C22F 1/00-3/02

Claims (5)

(57) [Claims] 1. The X-ray diffraction intensity on a (222) crystal plane parallel to a plate surface is 0.3 times or more the X-ray diffraction intensity on a (200) crystal plane, and the X-ray diffraction on a (200) crystal plane A high-formability molybdenum plate having an intensity not more than 10 times the X-ray diffraction intensity on the (200) crystal plane of non-oriented molybdenum. 2. The metal structure of the molybdenum plate has an area ratio of 4
2. The highly formable molybdenum sheet according to claim 1, wherein the molybdenum plate has a mixed grain structure of recrystallized grains of 0 to 60% and grains deformed by the remaining rolling process. 3. The hot-rolled molybdenum material is subjected to an intermediate annealing treatment at a temperature of 1050 to 1150 ° C., and the obtained primary rolled sheet is cold-rolled at a rolling reduction of 80 to 95% after recrystallization heat treatment. Prepare a secondary rolled plate with the target plate thickness,
Thereafter, the secondary rolled sheet obtained was heated to a temperature of 980 to 1030.
C., the X-ray diffraction intensity on the (222) crystal plane parallel to the plate surface of the secondary rolled plate is reduced by (20).
0) A method for producing a highly formable molybdenum plate, wherein the X-ray diffraction intensity on a crystal plane is set to 0.3 times or more. 4. The highly formable molybdenum according to claim 3, wherein the X-ray diffraction intensity on the (200) crystal plane is 10 times or less the X-ray diffraction intensity on the (200) crystal plane of non-oriented molybdenum. Plate manufacturing method. 5. The X-ray diffraction intensity on the (222) crystal plane parallel to the plate surface is 0.3 times or more the X-ray diffraction intensity on the (200) crystal plane, and the X-ray diffraction on the (200) crystal plane A reflection plate comprising a molybdenum plate having an intensity of 10 times or less the X-ray diffraction intensity on a (200) crystal plane of non-oriented molybdenum.