JP2008144250A - Molybdenum material and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a molybdenum material of a molybdenum wire rod or provided with the three characteristics of tensile strength, elongation and bending in well-balanced, and to provide its production method. <P>SOLUTION: The molybdenum material is composed of a molybdenum wire rod or bar stock having a molybdenum purity of ≥99.9% (JIS H1404). The aspect ratio (L/W) of the cross-sectional structure parallel to the wire drawing direction in the molybdenum material is ≤8, and also, the number of the above crystal grains lies in the range of 4,200 13,000 pieces/mm<SP>2</SP>. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a molybdenum material made of any one of a molybdenum wire and a rod that are easy to plastically deform and have a good balance of three properties of tensile strength, elongation, and bending, and a method for manufacturing the same.

  Molybdenum wires and rods (hereinafter simply referred to as wire rods) have characteristics such as high melting point, high temperature strength, and low vapor pressure, and are often used for industrial furnace members and lamp parts.

  For example, typical applications for industrial furnace members include mesh heaters, bar heaters, heater support hooks, etc., as well as coil spacers for heat reflectors, C-shaped spacers, and mounting rivets.

  Examples of lamp parts include tungsten filament supports, anchors, external lead wires, and the like, and further include discharge electrodes of cold cathode fluorescent lamps (CCFLs) and lead wires connected thereto.

  Furthermore, although not directly incorporated into the lamp, it is heavily used as a mandrel material in making tungsten filaments.

  When manufacturing these, the molybdenum wire rod material used as a raw material is subjected to machining such as cutting, bending and crushing. For this reason, it is ideal that the three properties of tensile strength, elongation, and bending are provided in a well-balanced manner.

  However, molybdenum is a brittle material with small ductility, and there is a problem that cracks are likely to occur during cutting, bending, and crushing of the wire rod.

For this reason, the tensile strength of the molybdenum wire rod having a value that does not make plastic working difficult, that is, 800 MPa (N / mm ² ) or more, 15% or more elongation, and 10 or more bending characteristics. Offering is anxious.

  Here, the relationship between the tensile strength, the elongation, and the bending strength in the production of the molybdenum wire rod will be described in detail below.

  The production of the molybdenum wire rod is performed by a general powder metallurgy method. After pressing and molding the raw material powder, the ingot is obtained by sintering at high temperature. Next, this ingot is finished by rolling and drawing to a desired size.

  The wire rod material develops a structure in the length direction by performing plastic working such as rolling and wire drawing. For this reason, as the processing proceeds, the strength, elongation, and bending characteristics when pulled in the length direction are different from those in the direction perpendicular to the length direction.

  In particular, the elongation characteristics increase as the heat treatment temperature increases, but coarse crystals begin to appear above a certain treatment temperature, and the elongation decreases as the proportion of the crystal increases.

  On the other hand, the bending characteristics maintain a strength change equivalent to the tensile strength up to a certain high temperature heat treatment temperature range, and begin to be inferior at the start of recrystallization nucleation at the stage before coarse crystals appear in a temperature range higher than that.

  That is, because there is a difference between the heat treatment temperature at which the elongation becomes the maximum and the heat treatment temperature at which the bending strength can be maintained, the bending strength is small when attempting to increase the elongation, and sufficient when attempting to maintain the bending strength. There is a trade-off relationship in which a good elongation characteristic cannot be obtained.

  Therefore, for the requirements and applications that require both the elongation and bending characteristics, a wire rod material having the characteristics is selected depending on which characteristic has priority. Although there is an option to use a wire rod that has been heat-treated at an intermediate heat treatment temperature between the two, both are unavoidable choices, and the actual situation is that they do not meet the required characteristics ( Table 6 described later in this specification shows the relationship between the heat treatment temperature, elongation, and bending as a comparative example).

  In addition, a doped molybdenum wire having an increased recrystallization temperature and improved high-temperature strength and bending characteristics is provided. For example, there are AKS doped wires in which Al, K, and Si are slightly doped, and wires in which a transition metal such as Ti is slightly doped (see Patent Document 1). In addition, a molybdenum material obtained by adding lanthanum to a raw material molybdenum dioxide powder in the form of a lanthanum nitrate solution and reducing it to obtain a molybdenum powder, which is sintered by powder metallurgy, has been proposed (patent) Reference 2). Since these doped wires require a method for specially managing the type and amount of elements to be added, they are expensive compared to pure molybdenum wire rods. Further, when used in a vacuum, the doping element is slightly released into the vacuum, and for example, when used in the aforementioned lamp component, there is a concern about a reaction with a gas component in the lamp. For this reason, the realization expectation of the pure molybdenum wire rod which can eliminate these concerns is high.

Japanese Patent Laid-Open No. 4-214836 Japanese Patent Laid-Open No. 7-54093

  Therefore, the technical problem of the present invention is a molybdenum composed of a molybdenum wire and a rod that are substantially pure molybdenum that does not contain a doping material and that has the above-described three characteristics of tensile strength, elongation, and bending in a well-balanced manner. It is to provide a material and a manufacturing method thereof.

  As described above, the difference in elongation and bending characteristics occurs because the metal structure develops in the length direction of the wire by rolling and drawing. In order to reduce this difference, it is effective to carry out a recrystallization process once to crystallize the crystal grains coarsely, but it becomes very brittle and subsequent drawing processing becomes difficult. For this reason, conventionally, a heat treatment temperature at which the crystal grains are coarsely crystallized (referred to as a recrystallization process) at the stage where the drawing process has progressed, specifically at a high temperature of 1500 ° C. or higher, It was not performed in consideration of the difficulty of processing.

According to the knowledge of the present inventors, extremely effective results were obtained by performing post-treatment on the above-mentioned molybdenum wire rod even if it was further subjected to recrystallization heat treatment at 1500 ° C. or higher. That is, in the present invention, after performing the recrystallization heat treatment at 1500 ° C. or higher, the wire is drawn in the range of less than 58.8% and less than 81% in the area of reduction in cross section while heating in the range of 800 to 1000 ° C. It was found that the above problem can be solved by means of heat treatment in a non-oxidizing atmosphere and obtaining a structure having crystal grains having an aspect ratio (L / W) within 8 to 4200 to 13000 / mm ^2. It came to an eggplant. Here, in the present invention, the aspect ratio (L / W) of the crystal grains is the size of the material in the longitudinal direction {length in the major axis direction (L)} and the size in the radial direction of the material {minor axis Directional length (W)}.

That is, the molybdenum material comprising the molybdenum wire rod of the present invention has a purity of 99.99% or more (JIS H1404) and the aspect ratio of crystal grains having a cross-sectional structure parallel to the drawing direction of the molybdenum material. (L / W) is 8 or less, and the number of the crystal grains is in the range of 4200 to 13000 / mm ² .

  Here, in the present invention, the wire rod refers to a material having a length in a certain direction, such as a wire rod or a rod.

In addition, the molybdenum material of the present invention is the molybdenum material having a tensile strength of 800 to 1060 MPa (N / mm ² ), an elongation of 15% or more, and the number of bendings by a bending test (the JIS Z2248 winding method is applied mutatis mutandis). Has 10 or more times.

  Moreover, the manufacturing method of the molybdenum material of the present invention is a method of manufacturing the molybdenum material, and prepares a molybdenum wire rod having a purity of 99.99% or more (JIS H1404). A first heat treatment step of performing recrystallization treatment one or more times in a non-oxidizing atmosphere; a wire drawing step of subjecting the molybdenum material to an oxidation heat treatment in the air and subjecting the molybdenum material to a cross-sectional reduction process; A second heat treatment step of heat-treating the drawn molybdenum material in a non-oxidizing atmosphere.

  The method for producing a molybdenum material according to the present invention is characterized in that, in the method for producing a molybdenum material, the wire drawing step performs an adhesion baking process on the surface of the molybdenum material while performing an oxidation heat treatment.

  The method for producing a molybdenum material according to the present invention is the method for producing any one of the above molybdenum materials, wherein the heat treatment step is performed after electrolytically polishing the drawn molybdenum material and then cutting a rod, or by electrolytic polishing. It is characterized by being carried out before processing or cutting bar processing.

  Moreover, in the manufacturing method of the molybdenum material of this invention, in the manufacturing method of any one said molybdenum material, the heat processing temperature which performs the said recrystallization process is 1500-1700 degreeC, It is characterized by the above-mentioned.

  Further, the molybdenum material manufacturing method of the present invention is characterized in that, in the molybdenum material manufacturing method, the heat treatment temperature for performing the graphite adhesion baking and performing the cross-sectional reduction processing on the wire rod material is 800 ° C to 1000 ° C. And

  The molybdenum material manufacturing method of the present invention is the molybdenum material manufacturing method, wherein the cross-section reduction rate per drawing in the drawing process is 5 to 20%, and the total cross-section reduction rate is 58.8%. It is characterized by being applied in a range of over 81%.

  Further, the molybdenum material manufacturing method of the present invention is characterized in that, in any of the molybdenum material manufacturing methods, a heat treatment is performed at 900 ° C. to 1200 ° C. in a non-oxidizing atmosphere after the drawing process.

According to the present invention, the wire is substantially pure molybdenum wire or rod, and has a good balance of tensile strength, elongation and bending. Specifically, the tensile strength is plastic working. Provided is a molybdenum material comprising a molybdenum wire or rod having a value that does not become difficult, that is, 800 MPa (N / mm ² ) or more, an elongation of 15% or more, and a bending characteristic of 10 or more times, and a manufacturing method thereof. can do.

  For example, since the molybdenum material of the present invention has the above characteristics, a disc-shaped head having a larger area than the cross-sectional area of the wire rod material is integrated with the tip of the molybdenum wire rod material. It can be suitably used for header processing parts that are required to be formed or header processing parts that are required to have a plurality of steps.

  The present invention will be described more specifically.

The molybdenum material according to the present invention is a molybdenum material produced by powder metallurgy and having a purity of 99.99% or more (JIS H1404). And the aspect ratio (L / W) of the crystal grain of the cross-sectional structure parallel to the drawing direction which is this length direction is 8 or less. The number of crystal grains is in the range of 4200 to 13000 / mm ² per unit area.

Further, in the molybdenum material of the present invention, the tensile strength is 800 to 1060 MPa (N / mm ² ), the elongation is 15% or more, and the number of bendings by the bending test (the JIS Z2248 winding method is applied mutatis mutandis) is 10 times or more. Have

  In order to produce the molybdenum material of the present invention, a molybdenum wire rod such as a molybdenum rod or wire having a molybdenum purity of 99.99% or higher (JIS H1404) is prepared, and this is followed by a first heat treatment step. A drawing process and a second heat treatment process are sequentially performed.

  Here, in the present invention, the first heat treatment step is a step in which the molybdenum material is recrystallized at least once in a non-oxidizing atmosphere. The heat treatment temperature for performing the recrystallization treatment in the first heat treatment step is 1500 ° C. to 1700 ° C.

  The wire drawing process is a process in which the molybdenum material is oxidized and heat-treated in the atmosphere, and the molybdenum material is subjected to a cross-section reduction process. You may perform it, performing adhesion baking. Thus, the heat treatment temperature for performing graphite adhesion baking and performing cross-sectional reduction processing on the wire rod material is 800 ° C to 1000 ° C. Further, the cross-section reduction rate per drawing in the drawing process is 5 to 20%, and the total cross-section reduction rate is more than 58.8% and less than 81%.

  Further, the second heat treatment step is a step of heat-treating the drawn molybdenum material in a non-oxidizing atmosphere. The drawn molybdenum material is electropolished and then straightened and cut to a predetermined length ( However, it may be performed before the electropolishing process or before the cutting bar processing. The second heat treatment temperature is 900 ° C to 1200 ° C.

  Next, the reasons for limiting each condition of the present invention will be described.

  (A) Reason for using molybdenum wire having a molybdenum purity of 99.99% or more: When the molybdenum purity is less than 99.99%, the contained impurities serve as a dopant to promote grain growth, and the aspect ratio required in the present invention This is because the crystal grain size exceeds.

(B) Regarding the structure of the wire rod (the aspect ratio (L / W) is 8 or less and the number of crystal grains is 4200 to 13000 / mm ² ):
In order to obtain a wire material having a tensile strength of 800 to 1060 MPa (N / mm ² ), an elongation of 15% or more, and a number of bendings of 10 or more by a bending test (applying the winding method of JIS Z2248). It is necessary that the aspect ratio (L / W) of crystal grains of the structure is 8 or less and the number of crystal grains is in the range of 4200 to 13000 / mm ² .

  This is because the above tensile strength, elongation, and number of bendings cannot be obtained even if heat treatment is performed if these values are not satisfied.

(C) Regarding the first heat treatment temperature, that is, the temperature of recrystallization treatment of molybdenum (1500 ° C. to 1700 ° C.):
When the temperature is less than 1500 ° C., recrystallization of the wire rod material does not proceed uniformly, and the structure becomes uneven. Further, when the temperature is higher than 1700 ° C., the recrystallized structure becomes too coarse and the strength is lowered, and the drawing process in the next process becomes difficult.

  For the above reasons, it is desirable to set the temperature of the recrystallization treatment to 1500 ° C. to 1700 ° C.

(D) Regarding the temperature of molybdenum oxidation heat treatment (800 to 1000 ° C.):
The reason why the molybdenum oxidation heat treatment temperature is set to 800 to 1000 ° C. in the atmosphere is that the oxide film formation and the graphite baking on the surface of the wire rod material are insufficient at a temperature below 800 ° C., and the temperature exceeding 1000 ° C. is caused by the drawing stress. This is because thinning of wire diameter or disconnection failure occurs.

(E) About the cross-section reduction rate (5 to 20%) of wire drawing:
If the cross-section reduction rate is less than 5%, only the plastic deformation of the surface of the wire proceeds, and a difference in quality characteristics from the inside of the wire rod material occurs. Moreover, it is because the amount of plastic deformation will be largely disconnected at a cross-section reduction rate exceeding 20%. For the above reasons, it is desirable that the cross-sectional reduction rate of the drawing process is 5 to 20%.

(F) About the total cross-section reduction rate (exceeding 58.8% and less than 81%) of the drawing process:
If a total cross-section reduction rate of 58.8% or less or a total cross-section reduction rate of 81% or more is applied to the wire rod material, a desired number of crystal grains cannot be obtained even after heat treatment. is there.

  For the above reasons, the total cross-section reduction rate of the drawing process should be more than 58.8% and less than 81%. Preferably they are 62.8% or more and 78% or less.

  (G) Second heat treatment temperature after wire drawing (900 ° C. to 1200 ° C. under non-oxidizing atmosphere): The second heat treatment is performed by heat treatment in a non-oxidizing atmosphere after wire drawing, thereby oxidizing the surface of the wire. Remove objects. Further, if the temperature is outside the range of 900 ° C. to 1200 ° C., crystal grains having a desired aspect ratio and the number thereof, and the tensile strength, elongation, and number of bendings cannot be obtained.

  For the above reasons, it is desirable that the heat treatment is performed in a non-oxidizing atmosphere and the heat treatment temperature is 900 ° C. to 1200 ° C.

  Next, a method for producing a molybdenum wire rod used in the examples (samples 1 to 45) and comparative examples (samples 46 to 54) of the present invention will be described.

  The manufacturing method shown in the following items (i) to (iii) is a general powder metallurgy method (hereinafter referred to as “regular method”).

(I) Production of ingot:
A pure molybdenum powder having an average particle diameter of 4.2 μm is prepared, and this molybdenum powder is hydrostatically pressed at a pressure of 196 MPa (about 2.0 ton / cm ² ) to obtain a green compact, and then hydrogen reduction Sintering was performed at 1800 ° C. for 10 hours in an atmosphere to produce an ingot having a length of 300 mm and a diameter (φ) of 40 mm.

(Ii) Production of bar:
While the above ingot was heated in the range of 1100 to 1400 ° C., hole rolling was performed in which the cross-sectional reduction rate per time was set in the range of 15 to 40% in order to produce a φ5.2 mm bar.

(Iii) Production of wire:
While the above-mentioned φ5.2 mm bar is heated in the range of 800-1000 ° C., the cross-section reduction rate is drawn in the range of 15-40%, φ0.61 mm, φ0.95, φ1.0 mm, φ1.2 mm, Molybdenum wires of φ1.3 mm and φ1.4 mm were prepared. A graphite lubricant was used for the purpose of reducing friction with the drawing die during drawing and maintaining the drawing temperature.

  By the above manufacturing method, a molybdenum wire having a molybdenum purity of 99.99% or more (JIS H1404) was prepared.

  Next, the specific manufacturing process and material of the molybdenum wire of the present invention will be described.

(I) Recrystallization heat treatment step:
Among the molybdenum wires produced by the above-mentioned regular method, the sample No. 1 to 9 and φ1.2 mm sample Nos. Shown in Table 2 below. 10-18 and a sample No. of φ1.3 mm shown in Table 3 below. 19 to 27, sample No. 28 to 36, φ1.4 mm sample Nos. Shown in Table 5 below. The molybdenum wires 37 to 45 were further subjected to recrystallization heat treatment at a temperature of 1500 ° C. or higher in a hydrogen atmosphere.

  On the other hand, as a comparative example, a φ0.6 mm sample No. 46 to 54 were prepared, but the recrystallization heat treatment (I) and the drawing process (II) were not performed.

(II) Drawing process:
Next, graphite that becomes a lubricant in the drawing process is attached and baked while performing oxidation heat treatment at 800 ° C. to 1000 ° C. in the atmosphere, and thereafter, the cross-section reduction rate is within a range of 5 to 20% and drawing with a die is performed. Processing was repeated.

  Specifically, the φ1.0 mm lines of Samples 1 to 9 shown in Table 1 below were subjected to a total cross-section reduction rate of 62.8%. In addition, the φ1.2 mm line of Samples 10 to 18 shown in Table 2 below was subjected to a total cross-section reduction rate of 74.2%. Further, the φ1.3 mm line shown in Table 3 below was subjected to a total cross-section reduction rate of 78.0%. In addition, the φ0.95 mm line shown in Table 4 below was given a total cross-section reduction rate of 58.8%. Further, the φ1.4 mm line shown in Table 5 below was subjected to a total cross-section reduction rate of 81.0%.

  After performing the above-mentioned drawing process, the sample Nos. 1 to 45 were prepared for each of 0.61 mm molybdenum wire rods.

  In addition, by arranging the furnace port of the heat treatment furnace for performing the recrystallization heat treatment at this time, the burner for forming oxides in the atmosphere, the burner for attaching and baking graphite, and the drawing dies in a straight line The problem of breakage of molybdenum wire embrittled by recrystallization heat treatment was avoided.

  In addition to the above, it is necessary to manage not only the wire heating temperature during drawing but also the drawing die heating temperature. The die heating temperature is adjusted and managed in association with the aforementioned cross-sectional reduction rate and the drawing speed described later. As wire drawing progresses and the wire diameter decreases, the wire heating temperature is lowered and controlled at 1100 ° C. to 650 ° C. When it exceeds 1100 ° C., it is likely to be thinned and disconnected. On the other hand, when the temperature is lower than 650 ° C., the deformation resistance is large, and the wire cannot be pulled and is broken. The die material is cemented carbide or diamond.

  The die heating temperature is controlled to maintain the wire temperature and to protect the die material. At this time, the upper limit is 450 ° C., and the lower limit is 300 ° C. This is because if the upper limit is exceeded, the die material will change and the function of the die will be impaired, and if the lower limit is exceeded, the wire will likely break.

  Within the above conditions, the molybdenum wire once drawn using a die does not cause any trouble such as disconnection in the subsequent drawing, and the diameter of φ0.61 mm of samples 1 to 45 in Tables 1 to 5 is not affected. Molybdenum wire was obtained.

  Furthermore, the drawing speed should be controlled faster as the wire diameter of the wire becomes thinner. In this embodiment, the speed is 3 m / min to 10 m / min. This is because, if out of these ranges, problems such as disconnection and thinning occurred.

(III) Electropolishing process:
Next, sample No. In order to remove the graphite adhering to the surface of the molybdenum wire having a diameter of 0.61 mm provided for 1 to 45, electrolytic polishing was performed using an electrolytic solution of 30% caustic potassium (KOH). The diameter of the molybdenum wire after electrolytic polishing was φ0.60 mm. Similarly, as a comparative example, samples 46 to 54 shown in Table 6 were also subjected to electrolytic polishing.

(IV) Cutting rod material Next, the molybdenum wire shown in Tables 1 to 6 below is linearly processed and cut to an arbitrary length, φ0.60 mm × length 300 mm (however, it is an arbitrary length) ) Molybdenum cutting rod material.

(V) Heat treatment Next, in addition to the “second heat treatment temperature (none)” described in Tables 1 to 5 among the above molybdenum rods, 800 ° C. within a range of 800 to 1500 ° C. in a hydrogen atmosphere, Heat treatment was performed at eight temperatures of 900 ° C., 1000 ° C., 1100 ° C., 1200 ° C., 1300 ° C., 1400 ° C., and 1500 ° C., respectively.

  The tensile strength, elongation, bending test, and structure of each sample of the present invention example and the comparative example obtained above were measured. The results are shown in Tables 1 to 6 below.

  The tensile strength and elongation were measured according to JIS H4460. The bending was measured according to the winding method of JIS Z2248. The obtained molybdenum wire was subjected to impurity measurement by the analysis method of JIS H1404: 2001. As a result, it was confirmed that the impurity content was 0.01% or less and the molybdenum purity was 99.99% or more.

  Regarding the relationship between each characteristic and the structure morphology and the measurement of the number of crystals, first, a small piece collected from the target molybdenum material was finished to a mirror surface near the center of the wire diameter of the cross section parallel to the drawing direction (RD direction). Then, the etching process was performed and the metal microscope observation sample was obtained. Judgment of the structure is performed by observing the above samples with an optical microscope at a magnification of 400 times, obtaining the ratio of recrystallized grains in the fiber structure as an area ratio, and when the area ratio accounts for 50% or more Is defined as a recrystallized structure. Similarly, when it is less than 50%, it is defined as a fiber structure and is shown in Tables 1-6.

  Moreover, the recrystallized grain size Na was measured for the sample exhibiting the recrystallized structure. That is, the structure was observed using an optical microscope at an arbitrary magnification M (preferably 400 times and 800 times considering the counting accuracy), and a circle of φ70 mm was drawn on the obtained photograph. The number Nw of recrystallized grains completely included in the area and the number Ni of recrystallized grains partially including the area are counted, and the total number Nt (= Nw + Ni / 2) is calculated. The recrystallized grain size Na was determined. Moreover, in this specification, this recrystallized grain size Na is defined as the number of recrystallized grains, and is shown in Tables 1-6. In the formula 1, π is a circumference ratio.

  The measurement results of the number of crystals by this method are shown in Tables 1 to 6.

Actually, there are crystal grains having an aspect ratio (L / W) exceeding 8 in the structure, but the aspect ratio is 8 or less, and the number thereof is in the range of 4200 to 13000 / mm ² per unit area. It was found that a molybdenum wire having the required characteristics of the present invention, that is, the three characteristics of tensile strength, elongation, and bending, can be obtained in a balanced manner. Measurement of the number of crystal grains exceeding the aspect ratio 8 was excluded.

  1 is a metal micrograph (500 times) showing an example of the recrystallized structure of the molybdenum wire rod of the present invention. 5 shows a recrystallized structure. 2 is a metal micrograph (500 times) showing an example of the fiber structure of the molybdenum wire rod according to the comparative example. 39 fiber structures are shown. These photographs were taken with a metal microscope, and the magnification was 500 times.

  In the photograph of FIG. 1, large and small lumps that are widely scattered while leaving the fibrous structure (having a long side of one side and a pointed shape) are recrystallized grains. It can be seen that the recrystallized grains have a fine recrystallized structure.

  On the other hand, in FIG. 2, it turns out that it exists in the fiber structure state in which the recrystallized grain is not contained. In addition, all the photographs have shown the structure | tissue state of the cross section parallel to a drawing process.

  The evaluation result of each sample 1-54 of the said Table 1-Table 6 is demonstrated.

  As shown in Tables 1 to 3, molybdenum wire (sample 1) that was subjected to recrystallization heat treatment at 1500 ° C. as the first heat treatment, and was drawn by heating at 800 to 1000 ° C. at the above-described total cross-section reduction rate. To 27), by applying a second heat treatment temperature of 900 to 1200 ° C., all of Sample 3 to 6 in Table 1 above, Samples 12 to 15 in Table 2 above, and Samples 21 to 24 in Table 3 above can be obtained. It can be seen that both the elongation characteristics of 15% or more and the bending characteristics of 10 times or more are obtained. Note that samples 1, 2 and 7 to 9 in Table 1 above, samples 10, 11 and 16 to 18 in Table 2, samples 19 and 20 in Table 3 above, which are other samples for which the above characteristics were not obtained. 25 to 27, Samples 28 to 36 in Table 4 and Samples 37 to 45 in Table 5 were outside the scope of the present invention. As a comparative example, Table 6 shows the measurement results of each characteristic when the recrystallization treatment is not performed.

The tensile strength ranges of Samples 3 to 6 in Table 1 and Samples 12 to 15 in Table 2 and Samples 21 to 24 in Table 3 in which the elongation characteristics and the bending characteristics are obtained are 800 to 1060 MPa (N / mm ² This is almost the same as the general tensile strength subjected to heat treatment, and it is difficult to shape due to its high tensile strength even if it has 15% elongation or more and 10 or more bending characteristics. The characteristic value is such that the tensile strength is low and the strength is not insufficient.

  Further, as shown in Table 4 above, molybdenum wire rods produced by a conventional method were further subjected to a recrystallization heat treatment at 1500 ° C., and then drawn with a cross-sectional reduction rate of less than 60%, 15% or more The heat treatment temperature at which the elongation characteristic is obtained is 900 to 1100 ° C., whereas the heat treatment temperature at which the bending characteristic is obtained 10 times or more is 800 ° C. or less. For this reason, there is no heat treatment condition for obtaining both the properties of elongation of 15% or more and bending of 10 times or more, and the samples 28 to 36 in Table 4 are outside the scope of the present invention.

  Further, as shown in Table 5 above, the molybdenum wire that has been subjected to a recrystallization heat treatment at 1500 ° C. and then drawn at a cross-section reduction rate exceeding 80% has a heat treatment temperature of 1200% at which an elongation characteristic of 15% or more is obtained. While the temperature is ˜1400 ° C., the heat treatment temperature at which the bending characteristic of 10 times or more is obtained is 1100 ° C. or less. For this reason, there is no heat treatment condition for obtaining both properties of elongation of 15% or more and bending of 10 times or more, and the samples 37 to 45 in Table 5 are out of the scope of the present invention.

  Samples 46 to 54 in Table 6 of the comparative example have a heat treatment temperature of 1200 to 1400 ° C. at which an elongation characteristic of 15% or more is obtained for the molybdenum wire rod not subjected to the recrystallization heat treatment at 1500 ° C. On the other hand, the heat treatment temperature at which the bending characteristic of 10 times or more can be obtained is 1100 ° C. or less, and therefore there is no heat treatment condition for obtaining both the characteristics of elongation of 15% or more and the bending of 10 times or more. It can be seen that there is only an option to sacrifice.

  Next, the metal structure of the molybdenum wire materials in Tables 1 to 6 will be described.

  As shown in the above Tables 1 to 6, the elongation characteristics of 15% or more are all obtained in the recrystallized structure. However, the number of crystals per unit area is reduced. That is, it can be seen that if recrystallization progresses and individual crystal grains become coarse, the elongation and the bending properties are also inferior.

  This is because the grain boundary strength of the coarsened crystal becomes weaker as the recrystallization progresses, and a larger amount of stress is received due to the coarsening.

  Therefore, in order to obtain the characteristics of both elongation and bending, recrystallization has started, but coarse crystallization has not yet been achieved, and it is desirable that the crystal grains be as fine as possible.

In Samples 3 to 6 in Table 1 above, Samples 12 to 15 in Table 2 and Samples 21 to 24 in Table 3, the number of crystal grains when an elongation of 15% or more and a bending characteristic of 10 times or more were obtained, All are 4200 or more / mm ² . This is Samples 7-9 in Table 1, Samples 16-18 in Table 2, Samples 25-27 in Table 3, Samples 30-36 in Table 4, Samples 40-45 in Table 5, and Table 6 which is a comparative example. It can be seen that none of the samples 49 to 54 can be obtained at any heat treatment temperature.

  Therefore, it is clear that the number of crystal grains per unit area can be increased by the present invention.

Here, the scope of the present invention is that the tensile strength of 800 MPa (N / mm ² ) or more required for practical use in the above-mentioned industrial furnace members, lamp parts, mandrels for producing tungsten filaments, and the like, and elongation of 15 %, And a value satisfying the three characteristics of bending times of 10 or more is obtained as an invention.

  As described above, the molybdenum material according to the present invention is used for industrial furnace members, in addition to mesh heaters, bar heaters, heater support hooks, etc., coil reflectors for heat reflectors, C-shaped spacers and mounting rivets, and lamps. In addition to tungsten filament supports, anchors, external lead wires, etc., the parts for use are suitable for CCFL discharge electrodes and lead wires connected thereto.

  Furthermore, the molybdenum material of the present invention is also suitable as a mandrel material for producing a tungsten filament.

It is an optical microscope photograph which shows an example of the recrystallized structure of the molybdenum material by this invention. It is an optical microscope photograph which shows an example of the fiber structure of the molybdenum material which concerns on a comparative example.

Claims (9)

In a molybdenum material made of a molybdenum wire rod, the purity of the molybdenum material is 99.99% or more (JIS H1404), and the aspect ratio (L / W) of the crystal grains of the cross-sectional structure parallel to the drawing direction of the molybdenum material Is a molybdenum material, wherein the number of crystal grains is in the range of 4200 to 13000 / mm ² .   The molybdenum material according to claim 1, wherein the tensile strength is 800 to 1060 MPa, the elongation is 15% or more, and the number of bendings by a bending test (applying the winding method of JIS Z2248) is 10 or more. Molybdenum material to be used. A method for producing the molybdenum material according to claim 1, wherein a molybdenum wire rod having a purity of 99.99% or more (JIS H1404) is prepared,
A first heat treatment step in which the molybdenum wire rod is further subjected to one or more recrystallization treatments in a non-oxidizing atmosphere; and the molybdenum material is subjected to an oxidation heat treatment in the atmosphere; A method for producing a molybdenum material, comprising: a drawing process to be performed; and a second heat treatment process in which the drawn molybdenum material is heat-treated in a non-oxidizing atmosphere.   4. The method for manufacturing a molybdenum material according to claim 3, wherein the wire drawing process includes oxidizing and baking the surface of the molybdenum material while performing an oxidation heat treatment. 5.   5. The method for manufacturing a molybdenum material according to claim 3, wherein the heat treatment step is performed by electropolishing the cut-drawn molybdenum material, followed by cutting bar processing, or before electrolytic polishing processing or cutting bar processing. A process for producing a molybdenum material, characterized in that:   6. The method for producing a molybdenum material according to claim 3, wherein a heat treatment temperature for performing the recrystallization treatment is 1500 ° C. to 1700 ° C. 6.   4. The method for manufacturing a molybdenum material according to claim 3, wherein a heat treatment temperature for performing the graphite adhesion baking and performing a cross-sectional reduction process on the wire rod material is 800 ° C. to 1000 ° C. .   The method for manufacturing a molybdenum material according to any one of claims 3 to 7, wherein a cross-section reduction rate per drawing in the drawing process is 5 to 20%, and a total cross-section reduction rate is 58.8. A method for producing a molybdenum material, characterized by being applied in a range of more than% and less than 81%.   The method for manufacturing a molybdenum material according to any one of claims 3 to 7, wherein a heat treatment at 900 ° C to 1200 ° C is further performed in a non-oxidizing atmosphere after the drawing process. .