JP3769008B2 - Tungsten material for secondary processing - Google Patents

Description

  The present invention relates to a tungsten material for secondary processing, and in particular, when subjected to secondary processing steps such as coiling, there is little risk of increased brittleness, and bending, compression, torsion, tensile stress, etc. act in the secondary processing step. The present invention also relates to a tungsten material for secondary processing that has excellent durability with little disconnection or breakage and can significantly improve the yield in secondary processing.

  Conventionally, various tungsten wires and tungsten rods have been used as constituent materials such as cathode heaters for TV electron guns, automobile lamps, filament lamps for lighting lamps for home appliances, vapor deposition elements, discharge electrodes, heaters for electron tubes, and electrode rods for welding. in use.

  The above tungsten wires and the like are generally manufactured through the following manufacturing process. That is, tungsten ammonium salt is decomposed in hydrogen or air, a dopant such as Al, Si, K is added to tungsten oxide, reduced in hydrogen and then acid washed to prepare a doped tungsten raw material powder. Next, the obtained raw material powder is molded by a die press machine or the like and then sintered at a temperature of about 2700 to 3000 ° C. to form a tungsten sintered body. And when the diameter and dimension of a final product are comparatively large, or when it is plate shape, it is set as a final product directly by forging or rolling the said tungsten sintered compact.

  On the other hand, when the final product has a very fine wire diameter, such as a lamp filament, first, primary processing such as rolling and wire drawing (drawing) is performed, and processing is performed to a tungsten material with a small diameter to some extent. Is done. Thereafter, the obtained tungsten material is further processed in steps such as heat treatment such as rolling and wire drawing and recrystallization heat treatment in a stepwise manner to produce a tungsten wire having a fine diameter. Conventionally, an electropolishing method or the like has been employed to smooth the surface of the tungsten material.

  A filament is produced by carrying out a secondary processing process of winding (coiling) the tungsten wire thus obtained, and further subjected to a heat treatment (flushing) for secondary recrystallization, which is mounted on a lamp or the like.

  However, in the case where a conventional tungsten material mainly composed of tungsten as described above and subjected to primary processing is further subjected to secondary processing to produce a finer wire or coiling, In the next processing step, the brittleness of the material often becomes high, and when the stress such as bending, compression, torsion, and tension is applied, it tends to be damaged or chipped, and the production yield of the final product is greatly reduced. there were.

  In addition, in current processing facilities based on continuous processing operation, when a material disconnection accident occurs, a great labor load is placed on the operator for the replacement of the material and the restoration work of the facility, resulting in an increase in product cost and manufacturing. There was also a problem that efficiency was reduced and directly connected to a large loss.

  The present invention has been made to solve the above problems, and even when subjected to a secondary processing step such as coiling, there is little risk of increased brittleness, and bending, compression, torsion, tension in the secondary processing step is low. An object is to provide a tungsten material for secondary processing that has excellent durability with few disconnections and breakage even when stress is applied, and can significantly improve the yield in secondary processing. .

  In order to achieve the above object, the inventor of the present application has intensively studied the cause of the material becoming brittle or causing frequent fracture accidents when secondary processing is performed on a conventional tungsten material for secondary processing. As a result, it has been found that the surface properties of the tungsten material and the presence or absence of lubricants or oxides have a significant effect on embrittlement and defect generation during secondary processing.

  That is, a lubricant containing graphite (carbon), which is indispensable when the tungsten sintered body is subjected to primary processing such as rolling and drawing to prepare a tungsten material for secondary processing, is applied to the surface of the secondary processing material. This carbon component has been found to cause embrittlement of the tungsten material during high temperature wire drawing and heat treatment. At this time, if the surface roughness of the tungsten material is large, the contamination of the carbon is also increased, and the influence on embrittlement becomes more remarkable. On the other hand, when the surface roughness of the tungsten material is small, it was also found that the embrittlement is reduced because the carbon component is easily volatilized by heat treatment in a hydrogen stream.

  As means for solving the above problems, for example, it is conceivable to use a tungsten material in which the surface of the tungsten material is electropolished to remove the lubricant and the oxide layer in advance. It is also conceivable to perform a chemical treatment after the primary processing or to form a plating layer on the surface to make a tungsten material.

  However, the addition of the above polishing treatment, chemical treatment, and plating treatment causes an increase in product cost and is not a possible measure. The lubricant layer and the oxide layer are always formed during the primary processing, and cause the above embrittlement and defects, but are effective in preventing rust prevention and further oxidation of the material. However, it is not necessary to remove completely completely.

  As a result of further investigation, the present inventor has obtained the following knowledge. That is, when preparing the tungsten material for secondary processing by primary processing of the tungsten sintered body, especially when the surface properties of the tungsten material are optimized by changing the conditions at the time of drawing (drawing), Even when the lubricant layer and oxide layer remain, an inexpensive tungsten material for secondary processing with less embrittlement and defects in the tungsten material can be obtained during the secondary processing, greatly increasing the production yield and efficiency of the product. The knowledge that it is improved is obtained. The present invention has been completed based on the above findings.

  That is, the tungsten material for secondary processing according to the present invention contains tungsten (W) containing 2 to 27% by weight of Re as a main component and is processed into a product through a secondary processing step such as coiling. In the tungsten material, the average interval (Sm) of the unevenness of the roughness curve when 1/3 of the diameter D of the tungsten material is the reference length is √D / 5 or more, and the peak line and valley line of the roughness curve The distance (Ry) between and is D / 50 or less.

  The tungsten material for secondary processing according to the present invention is mainly composed of tungsten (W) containing 0.5 to 5% by weight of thorium oxide and processed into a product through a secondary processing step such as coiling. In the tungsten material for next processing, the average interval (Sm) of the unevenness of the roughness curve when １ ／ of the diameter D of the tungsten material is the reference length is √D / 5 or more, and the peak line of the roughness curve And the valley bottom line (Ry) is D / 50 or less.

  Further, a lubricant layer mainly composed of graphite may be formed on the tungsten material surface. Further, an oxide layer may be formed on the surface of the tungsten material.

  The diameter D of the tungsten material is preferably in the range of 0.01 to 0.5 mm.

The tungsten material for secondary processing according to the present invention is mainly composed of tungsten (W). However, Al, Si, K, etc. are used in order to increase the recrystallization temperature and in particular to increase the non-sag property of W filament products. A small amount of the dopant may be contained. Furthermore, in order to increase the high-temperature strength of the W filament by dispersion strengthening of thorium oxide (ThO ₂ ), 0.5 to 5% by weight of ThO ₂ may be contained as a subsidiary component. Further, a predetermined amount of cobalt (Co) may be contained in order to improve non-sag and vibration resistance. Furthermore, in order to improve high temperature strength and ductility after recrystallization, 2 to 27 wt% rhenium (Re) may be contained.

The surface property of the tungsten material for secondary processing specified in the present invention is displayed in accordance with the specification of Japanese Industrial Standard (JIS B 0601-1994). That is, the average interval (Sm) of the unevenness is the diameter of the material in the direction of the average line m from the roughness curve indicating the surface properties of the secondary working tungsten material 1 having a diameter D as shown in FIG. Only the reference length L corresponding to 1/3 of D is extracted, and the sum of the lengths of the average line m corresponding to one peak and one valley adjacent to it in this extracted portion (interval of unevenness) is obtained. The arithmetic average value of the intervals (Sm1, Sm2,... Smi,... Smn) of a large number of irregularities is calculated by the following equation (1) and expressed in millimeters (mm).

  In addition, the peak line is a line parallel to the average line passing through the highest peak in the reference length L extracted from the roughness curve, and the valley line is the lowest in the reference length L extracted from the roughness curve. Ry (maximum height) is a line parallel to the average line passing through the bottom of the valley, and the distance between the peak line and the bottom line of the extracted portion expressed in micrometers (μm).

  In the tungsten material for secondary processing according to the present invention, the average interval (Sm) of the unevenness of the roughness curve when 1/3 of the diameter D of the tungsten material is the reference length L is the square root of the diameter D of the tungsten material. Is set to 1/5 or more, that is, √D / 5 or more. When the frequency of appearance of irregularities on the surface of the material increases so that the average interval (Sm) of the irregularities is less than 1/5 of the square root of the material diameter D, this material is further subjected to secondary processing, and compression, bending, and twisting When other stresses are applied, cracks are easily propagated starting from the recess, and the number of breakage accidents of the wire product increases. Or the brittleness of the raw material resulting from the graphite component (carbon) of the lubricant adhering to the surface of the raw material increases, and the material breaks before reaching the final product, or the strength characteristics of the product are greatly impaired. Therefore, the average interval (Sm) of the unevenness is set to 1/5 or more of the square root of the material diameter D, but more preferably 1/3 or more.

  In the present invention, the interval (Ry) between the peak line and the valley line of the roughness curve is 1/50 or less of the diameter D of the tungsten material. When the valley bottom of the tungsten material surface becomes deep so that the interval between the peak line and the valley line, that is, the maximum height (Ry) exceeds 1/50 of the diameter of the tungsten material, as in the case where the unevenness increases, When further secondary processing is performed on the tungsten material, cracks are likely to propagate from the bottom of the valley, and the number of breakage accidents of the wire product increases rapidly.

  In addition, the graphite component (carbon) of the lubricant adhering to the bottom of the valley reacts with tungsten, expanding the embrittlement region to a deeper part of the material, which is likely to cause frequent fracture accidents and deterioration of product characteristics. . Therefore, the maximum height (Ry) is 1/50 or less of the material diameter D, but more preferably 1/70 or less.

  Furthermore, when the diameter D of the tungsten material is in the range of 0.01 to 0.2 mm, breakage and embrittlement during the secondary processing are reduced, and the yield after the secondary processing is improved. That is, when the diameter D of the raw material is too small, less than 0.01 mm, it is difficult to finish the surface properties smoothly and it is easily affected by the lubricant. On the other hand, when the diameter D of the material is excessively large so as to exceed 0.2 mm, the secondary workability is liable to be reduced, and the material is easily broken.

  In the case of a tungsten material for secondary processing having the surface properties as described above, even if it is a so-called black wire with a graphite-based lubricant remaining, a so-called black wire may be broken or brittle during secondary processing. A product with little deterioration in characteristics can be obtained.

  That is, a lubricant layer mainly composed of graphite may be formed on the surface of the tungsten material according to the present invention. The lubricant layer is inevitably formed when a lubricant used for preparing a tungsten material for secondary processing by drawing a rolled bar is attached to the material.

  However, if the manufactured tungsten material for secondary processing has good surface properties as specified in the present invention, the carbon in the lubricant layer is volatilized even if heated to a high temperature in the secondary processing step. Since it is easy to do, there is little possibility of embrittlement of the material. From this fact, the tungsten material of the present invention does not need to be subjected to surface treatment such as electrolytic polishing treatment or chemical treatment again, and can be made as a product with a line drawn up with a lubricant (black wire). Compared with the conventional tungsten material for secondary processing that requires the surface treatment, the manufacturing cost can be greatly reduced.

  In the present invention, a lubricant layer mainly composed of graphite may be formed on the tungsten material surface. Originally, tungsten is easily oxidized, and the oxide layer formed on the surface of the material deteriorates processing characteristics such as ductility and product characteristics. This tendency is remarkable particularly in the case of a surface treatment finish line.

  However, if the thickness of the oxide layer is 2 μm or more and 5 μm or less, it is effective because a rust preventive effect for suppressing the progress of oxidation of the tungsten material is exhibited while preventing contamination by graphite (carbon).

  Specifically, the tungsten material for secondary processing having the surface property, the lubricant layer, and the oxide layer as described above is specifically 650 to 950 with a surface reduction rate of 12 to 27% until the wire diameter becomes φ0.175 mm. It is manufactured by drawing after heating at a heating temperature of 0 ° C., once electrolyzing 2 to 12% by electrolysis, oxidizing the surface again, applying a lubricant, and then drawing. Thereafter, secondary processing is performed by a normal method, and wire drawing is performed to a predetermined product size to obtain a final product.

  According to the tungsten material for secondary processing according to the above configuration, the average interval (Sm) and the maximum height (Ry) of the irregularities on the material surface are adjusted to a predetermined range, so that compression, bending, and twisting are performed during the secondary processing. Even when subjected to other stresses, there are few breaks due to the progress of cracks and the like, and the processing efficiency in the secondary processing can be greatly improved.

  In addition, since the surface shape of the material is appropriately adjusted, the carbon component of the lubricant is easily volatilized during the heat treatment or hydrogen furnace treatment in the secondary processing even if the lubricant adhered during the primary processing remains. In addition, contamination and embrittlement of the raw material due to carbon components and the like can be effectively prevented, breaking accidents during secondary processing can be eliminated, and deterioration of product characteristics can also be prevented.

  According to the tungsten material for secondary processing according to the present invention, the average interval (Sm) and the maximum height (Ry) of the irregularities on the surface of the material are adjusted to a predetermined range, so that compression, bending, Even when subjected to torsion, tension, and other stresses, there are few breaks due to crack propagation and the like, and the processing efficiency in the secondary processing can be greatly improved.

  In addition, since the surface shape of the material is properly adjusted, the carbon component of the lubricant is volatilized during the heat treatment or hydrogen furnace treatment in the secondary processing even if the lubricant adhered during the primary processing remains. It is easy and can effectively prevent contamination and embrittlement of the material due to the carbon component, etc., eliminate a breakage accident during secondary processing, and prevent deterioration of product characteristics.

  Next, embodiments of the present invention will be specifically described based on the following examples and comparative examples.

[Examples 1-6 and Comparative Examples 1-6]
A tungsten raw material powder containing 0.08% by weight of Al, 0.5% by weight of Si and 0.7% by weight of K as a dopant is prepared, and this tungsten raw material powder is compacted by a conventional method. The sintered compact was pre-sintered at 1200 ° C. for 30 minutes in a hydrogen furnace, and then subjected to current sintering at 2700 to 3000 ° C. for 30 minutes to obtain a tungsten sintered body.

  Further, the obtained tungsten sintered body was subjected to primary processing such as rolling, recrystallization and wire drawing. Specifically, the tungsten sintered body was forged using a rolling machine until the wire diameter became about 2 to 4 mm at a temperature of 1300 to 1500 ° C. Further, the forged W wire was drawn at a temperature of 900 ° C. with a cemented carbide / sintered diamond die until the wire diameter became about 0.18 mm, and the electrolytic polishing was further performed. Performed 2-4%. Each wire was further drawn with a diamond die. In each wire drawing (drawing) step, a lubricant mainly composed of graphite was used. By carrying out the above-mentioned treatment, tungsten materials for secondary processing according to each Example and Comparative Example having a wire diameter (diameter) D shown in Table 1 were finally prepared. In addition, about each comparative example, it set so that an area reduction rate may remove | deviate from the range in the said Example.

  A lubricant layer made of graphite adhered during the primary processing was formed on the surfaces of the tungsten materials of the examples and comparative examples prepared as described above. After taking a sample from each tungsten material and removing the lubricant layer, the surface roughness of each sample was measured with ERA-8000 manufactured by Elionix Co., Ltd., and as shown in FIG. A roughness curve indicating that regular irregularities were formed was obtained. Then, the unevenness interval (Sm) is measured from each roughness curve, the average interval (Sm) of the unevenness of the roughness curve is calculated based on the equation (1), and the peak line and valley bottom line in the roughness curve are calculated. The maximum height (Ry), which is an interval of Further, the ratio of the Sm value and the Ry value to the material diameter D was calculated, and the results shown in Table 1 were obtained.

  Further, in order to evaluate the secondary workability of the tungsten material for secondary processing according to each example and comparative example, the following impact test was performed. That is, after coiling the tungsten material according to each Example and Comparative Example in which the lubricant layer mainly composed of graphite was formed, it was heated in a hydrogen stream at a temperature of 1200 ° C. and subjected to a shaping treatment. The steel ball weight having the weight shown in Fig. 1 is allowed to freely fall from the drop height shown in Table 1 above the coil and collide with the coil, and the ratio of the coil that becomes brittle and loses its deformability and breaks into pieces is measured. The results shown in Table 1 were obtained.

  Note that the impact force applied to the coil by the impact test and the temperature conditions when it is heated and shaped in a hydrogen stream as pretreatment are added to the material when this tungsten material is further processed. It is considered to correspond to the temperature environment conditions and impact force to be applied.

  As is clear from the results shown in Table 1 above, each embodiment in which the ratio of the average interval (Sm) and the maximum height (Ry) of the unevenness of the material surface after the primary processing to the material diameter D was adjusted within a predetermined range. It was confirmed that the tungsten material according to the example was not easily embrittled, had excellent durability against the temperature and impact force applied by the impact test, and had good secondary workability.

  This is because the surface roughness of the tungsten material according to each example is small, and as a result, the carbon component of the lubricant adhering to the surface is easily volatilized by heat treatment in a hydrogen stream. This is thought to be because there is little embrittlement due to the reaction of.

  On the other hand, in the tungsten material according to each comparative example in which the average interval (Sm) of the unevenness is small, the maximum height (Ry) is relatively high, and the surface roughness is large, the rate of breakage due to the impact test is large. It was confirmed that the next workability was lowered. This is because the surface roughness of the tungsten material of each comparative example is large, so the carbon component of the lubricant that adheres is not sufficiently volatilized, and the carbon contamination of the material advances to the deep part of the material structure and promotes embrittlement. It is thought that it is to do.

  Moreover, according to the tungsten material for secondary processing which concerns on each Example, the straight line (black line) with which the lubricant has adhered can be used as it is as the tungsten material for secondary processing. That is, in order to avoid the adverse effects of the lubricant, it is not necessary to perform an electropolishing treatment, a chemical surface treatment, or a plating treatment in advance. Therefore, it is possible to reduce the number of processes when manufacturing a final product such as a filament, and to reduce the product cost.

  Furthermore, even when the tungsten material as the black wire with the lubricant layer formed is subjected to secondary processing as it is, since the embrittlement due to the lubricant component is small and there is little disconnection, the secondary processing equipment can be used for a long time. It is possible to operate continuously, increase the production efficiency of tungsten products, and greatly reduce the labor for facility operation management.

The fragmentary sectional view explaining the prescription | regulation method of the surface property of the tungsten raw material for secondary processing manufactured with the method of this invention.

Explanation of symbols

1 Tungsten material for secondary processing

Claims (4)

Re the made 2 to 27 wt% containing tungsten (W), the secondary processing tungsten material is processed into the product via a secondary processing step such as coiling, the diameter D of the tungsten material from 0.01 to 0 in the range of .2Mm, the roughness average distance of the unevenness of the curve when the 1/3 of the diameter D of the tungsten material with the reference length (Sm) is not less √D / 5 or more, and peaks of the roughness curve A tungsten material for secondary processing, wherein a distance (Ry) between a line and a valley bottom line is D / 50 or less, and a lubricant layer mainly composed of graphite is formed on the surface of the tungsten material. Re the made 2 to 27 wt% containing tungsten (W), the secondary processing tungsten material is processed into the product via a secondary processing step such as coiling, the diameter D of the tungsten material from 0.01 to 0 in the range of .2Mm, the roughness average distance of the unevenness of the curve when the 1/3 of the diameter D of the tungsten material with the reference length (Sm) is not less √D / 5 or more, and peaks of the roughness curve A tungsten material for secondary processing, wherein a distance (Ry) between a line and a valley bottom line is D / 50 or less, and an oxide layer is formed on the surface of the tungsten material. Made of tungsten (W) with the thorium oxide contained 0.5 to 5 wt%, in secondary processing tungsten material is processed into the product via a secondary processing step such as coiling, the diameter D of the tungsten material 0. The average interval (Sm) of the unevenness of the roughness curve when it is in the range of 01 to 0.2 mm, and the reference length is 1/3 of the diameter D of this tungsten material is √D / 5 or more, and the roughness The interval (Ry) between the peak line and the valley line of the curve is not more than D / 50, and a tungsten layer for secondary processing is characterized in that a lubricant layer mainly composed of graphite is formed on the surface of the tungsten material. Material. Made of tungsten (W) with the thorium oxide contained 0.5 to 5 wt%, in secondary processing tungsten material is processed into the product via a secondary processing step such as coiling, the diameter D of the tungsten material 0. The average interval (Sm) of the unevenness of the roughness curve when it is in the range of 01 to 0.2 mm, and the reference length is 1/3 of the diameter D of this tungsten material is √D / 5 or more, and the roughness A tungsten material for secondary processing, wherein an interval (Ry) between a peak line and a valley line of the curve is D / 50 or less, and an oxide layer is formed on the surface of the tungsten material.

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