US20100329923A1 - Forged beryllium-copper bulk material - Google Patents

Forged beryllium-copper bulk material Download PDF

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US20100329923A1
US20100329923A1 US12/880,429 US88042910A US2010329923A1 US 20100329923 A1 US20100329923 A1 US 20100329923A1 US 88042910 A US88042910 A US 88042910A US 2010329923 A1 US2010329923 A1 US 2010329923A1
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bulk material
copper
beryllium
forged
forged beryllium
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Naokuni Muramatsu
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NGK Insulators Ltd
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C9/00—Alloys based on copper
    • C22C9/06—Alloys based on copper with nickel or cobalt as the next major constituent
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C9/00—Alloys based on copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/08—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of copper or alloys based thereon

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  • the present invention relates to forged beryllium bulk material.
  • Beryllium copper bulk materials are used for machine structural components in which durability and reliability are demanded, such as bearings for airplanes, casings for under sea cable repeaters, rotor shafts for ships, collars of oil field drilling drills, injection molding dies, or welding electrode holders. In general, the applications require machinability and high hardness or strength of bulk materials.
  • Beryllium copper is a precipitation-hardening copper alloy similarly as many high strength copper alloys, and bulk materials thereof are manufactured through forging-homogenization annealing-hot working-solution annealing (solid solution treatment)-water quenching-age hardening, which is well-known to persons skilled in the art.
  • Patent Document 1 discloses that grains are fined to a certain degree by carefully selecting conditions of each treatment, and an increase in strength and an improvement of a fatigue life, which are important for the machine structural components, are achieved.
  • Patent Document 2 discloses that grains can be fined to a degree that has not been found in former cases by extensively examining a forging method and treatment conditions during forging.
  • Patent Document 1 Japanese Patent No. 2827102
  • Patent Document 2 Japanese Unexamined Patent Application Publication No. 2005-096442
  • the present invention provides a forged beryllium-copper bulk material, at least including Be and Cu,
  • the hardness of the central portion being 0 to 10% higher than that of the front surface
  • the Vickers hardness of the central portion being 240 or more
  • the tensile strength being 800 N/mm 2 or more
  • the bulk material having uniformity to such an extent that variation in measured values of the tensile strength in arbitrary directions being within 5%.
  • the invention provides a forged beryllium-copper bulk material that maintains uniform hardness from the front surface to the inside, has high reliability, is excellent in a fatigue life, and is hard to cause distortion during processing.
  • FIG. 1 is a perspective view showing a forged beryllium-copper bulk material according to one embodiment of the invention.
  • FIG. 2 is a flow chart showing a method for manufacturing a forged beryllium-copper bulk material according to one embodiment of the invention.
  • FIG. 3( a ) is a graph showing the relationship between the treatment time and the temperature when the solid solution treatment and the over-aging treatment of FIG. 2 are discontinuously carried out and
  • FIG. 3( b ) is a graph showing the relationship between the treatment time and the temperature when the solid solution treatment and the over-aging treatment are continuously carried out.
  • FIG. 4 is a table showing the relationship between the size reduction rate and the strain according to one embodiment of the invention.
  • FIG. 5( a ) is a view showing the appearance of a forged beryllium-copper bulk material according to one embodiment of the invention
  • FIG. 5( b ) is a graph showing the relationship between a pressure and a cumulative strain during repeated pressurization at a size reduction rate of 18%
  • FIG. 5( c ) is a table showing changes in the surface temperature immediately after the repeated pressurization.
  • FIG. 6( a ) is a view showing the appearance of a former forged beryllium-copper bulk material
  • FIG. 6( b ) is a graph showing the relationship between a pressure and a cumulative strain during repeated pressurization at a size reduction rate of 33%
  • FIG. 6( c ) is a table showing changes in the surface temperature immediately after the repeated pressurization.
  • FIG. 7( a ) is a perspective view showing a test piece when measuring the hardness of a forged beryllium-copper bulk material
  • FIG. 7( b ) is a graph showing the relationship between the distance from a surface plane to the center plane and the Vickers hardness of a beryllium bulk material according to one embodiment of the invention immediately after cold forging treatment
  • FIG. 7( c ) is a graph showing the relationship between the distance from a surface plane to the center plane and the Vickers hardness of a beryllium bulk material according to one embodiment of the invention after age hardening treatment.
  • FIG. 8 is a graph showing the relationship between the distance from a surface plane to the center plane and the Vickers hardness of a former beryllium bulk material.
  • FIG. 9 is a schematic view showing distortion after processing measurement results of a forged beryllium-copper bulk material according to one embodiment of the invention and a former forged beryllium-copper bulk material.
  • FIG. 10 is a graph showing a fatigue life curve of a forged beryllium-copper bulk material according to one embodiment of the invention.
  • FIG. 11 is a graph showing an example of ultrasonic inspection test results of a forged beryllium-copper bulk material according to one embodiment of the invention and a former beryllium-copper bulk material.
  • FIG. 12 is a view showing observation results of a shear band structure crossing a plurality of grains in a beryllium-copper bulk material in a comparative example.
  • a forged beryllium-copper bulk material 1 is an alloy containing beryllium (Be) and copper (Cu) and is a rectangular parallelepiped shaped alloy having the sides of a, b, and L extending along the directions of the three axes (Z axis, X-axis, and Y-axis of FIG. 1 ) that are orthogonal to each other.
  • the size of the forged beryllium-copper bulk material 1 is not particularly limited. However, when the dimension of the sides a, b, and L becomes excessively large, it becomes difficult to control the manufacturing conditions described later due to influences of process heat generation from the forged beryllium-copper bulk material 1 during forging. Thus, with respect to the dimension of the forged beryllium-copper bulk material 1 , the a, b, and L can be adjusted in the range of about 50 to 500 mm and preferably 80 to 400 mm, for example.
  • the forged beryllium copper bulk material 1 has (1) a weight ratio of Cu 100 ⁇ (a+b) Be a Co b (0.4% ⁇ a ⁇ 2.0%, 0.15% ⁇ b ⁇ 2.8%, a+b ⁇ 3.5%) or (2) a weight ratio of Cu 100 ⁇ (a+b) Be a Co b (0.4% ⁇ a ⁇ 2.0%, 0.15% ⁇ b ⁇ 2.8%, a+b ⁇ 3.5%) and the content of Fe, S, and P as impurities is preferably limited to lower than 0.01% in terms of the weight ratio.
  • the weight ratio of Be is adjusted to 0.4% or more for increasing the strength by a precipitated phase constituted by Be and Cu and/or Be and Co.
  • the weight ratio of Be is adjusted to 2.0% or lower for increasing the strength by suppressing coarsening of a precipitated phase constituted by Be and Co.
  • the weight ratio of Co is adjusted to 0.15% or more for increasing the strength by adding Co.
  • the weight ratio of Co is adjusted to 2.8% or lower for suppressing coarsening of a precipitated phase constituted by Be and Co.
  • the combination of (2) is used for the weight ratio of the forged beryllium-copper bulk material 1 to reduce the ratio of Be for reducing the material cost by adding Ni, which is less expensive than Be.
  • the weight ratio of Be is adjusted to 0.05% or more for increasing the strength by a precipitated phase constituted by Be and Ni.
  • the weight ratio of Be is adjusted to 0.6% or lower for sufficiently obtaining the effect of reducing the cost by reducing the weight ratio of Be.
  • the weight ratio of Ni is adjusted to 1.0% or more for increasing the strength by adding Ni.
  • the weight ratio of Ni is adjusted to 2.4% or lower for suppressing a reduction in electrical conductivity or an increase in the melting point due to Ni contained in a matrix of Cu.
  • the content of Fe, S, and P as impurities is limited to be lower than 0.01% in terms of weight ratio because, the elements are likely to be segregated in the grain boundary when these elements are contained in a proportion of 0.01% or more, and thus a product is likely to break during forging treatment.
  • the forged beryllium-copper bulk material 1 of FIG. 1 has a fine grain structure (average grain size ⁇ 2 ⁇ m) and has a precipitated phase at least containing Be which is precipitated from Cu.
  • the “average grain size” refers to an average grain size measured by the following measurement method.
  • structures constituted only by sub-grains having an misorientation angle ⁇ of 0° ⁇ 4° are not counted as crystal grains.
  • structures constituted only by sub-grains having an misorientation angle ⁇ of 0° ⁇ 4° are also considered to form a part of the entire structure at that moment. Therefore, structures having an misorientation angle of 15° or larger are counted as grains.
  • the forged beryllium-copper bulk material 1 is an alloy in which the hardness is uniform (or becomes gradually harder) from the near-surface portions to the center core portion, the hardness of the central portion is 0 to 10% higher than that of the front surface, the Vickers hardness (HV) of the front surface (end portion) is 218 to 450 and more preferably 273 to 450, and the Vickers hardness of the internal center is 240 to 450 and more preferably 300 to 450.
  • the “Vickers hardness” in this embodiment refers to a measurement result obtained as follows.
  • a plate 2 that is cut in parallel to the direction of the X-Z plane in such a manner as to include the center of the forged beryllium-copper bulk material 1 in the form of a rectangular parallelepiped (cube) shown in FIG. 7( a ) is used as a test piece, and then an arbitrary point on the test piece is measured according to JISZ2244 (Vickers hardness test method-Test method (Corresponding international standard; ISO/6507-1; 1995 Metallic materials-Vickers hardness test-Part 1; Test Method).
  • the forged beryllium-copper bulk material 1 is a polycrystal having no anisotropy in the orientation (random orientation) from the hardness, structure, ultrasonic inspection test, observation results of the grains by the EBSP method described later, and the tensile strength is 800 N/mm 2 or more, preferably 800 to 1500 N/mm 2 , more preferably 1100 to 1500 N/mm 2 , and still more preferably 1100 to 1300 N/mm 2 .
  • the tensile strength is made smaller than 800 N/mm 2 , the mechanical strength or the fatigue life decreases, and thus the forged beryllium-copper bulk material 1 is not accepted in the market of machine structural components in some cases.
  • the tensile strength values of the beryllium forge bulk material 1 are isotropic (uniform) in an arbitrary forging direction or in a direction making an angle of 45° within the plane including the arbitrary forging direction and the variation in the measured tensile strength values (measurement average value) was within 5%.
  • the measurement method of the tensile strength is as follows. First, plates containing the X-Y plane, the Y-Z plane, and the X-Z plane were cut out from the center of the beryllium forge bulk material 1 , and then tensile test pieces were machined so that six directions (i.e., X, Y, Z, X-Y with an angle of 45°, Y-Z with an angle of 45°, and X-Z with an angle of)45° which represent arbitrary directions correspond with the tensile axis from each plate.
  • the test pieces were produced according to JISSZ2201, but the test pieces in which the dimension was reduced to 1 ⁇ 2 due to the restriction of the size of raw materials were used.
  • the produced test pieces were measured according to JISZ2241 (Method of tensile test for metallic materials).
  • the reason for selecting the six directions as the arbitrary directions resides in the fact that, when machine structural articles are produced from the forged beryllium-copper bulk material 1 , the articles are usually produced based on the plane in which the forging direction is the normal line and the tensile stress mechanically applied in the X, Y, and Z directions are important for products.
  • the stress in the X, Y and Z directions are known to theoretically originate from the shearing strength in the direction of 45° to the X, Y and Z directions (“Zairyo Kogaku Nyumon” jointly translated by Ryo Horiuchi, Junichi Kaneko, and Masahisa Otsuka; Uchida-Rokakuho Publishing Co., 3rd edition, 1990, p 123-142 or Original: M. F. Ashby and D. R. H. Jones “Engineering Materials” PERGAMON PRESS; 1980).
  • the shearing strength in the direction of further 45° (in the X, Y, and Z directions) from the point is measured.
  • the forged beryllium-copper bulk material 1 When the forged beryllium-copper bulk material 1 is anisotropic in the direction shifted from the X, Y, and Z directions only by specific angles of ⁇ , ⁇ , and ⁇ (specific directions having a particularly low strength), abnormal values should be observed in some of the six directions insofar as the forged beryllium-copper bulk material 1 is a polycrystal. However, the variation in the tensile strength value when measured in the six directions is within 5% in this embodiment, and no abnormal values were measured. Thus, it can be said that the forged beryllium-copper bulk material 1 according to this embodiment has isotropy (uniformity) in the tensile strength in any arbitrary direction and that the values are almost the same.
  • a solid solution of Be (or a Be compound) is formed in a matrix of Cu to generate a copper alloy in which dislocation does not occur in grains.
  • a copper alloy constituted by the weight ratio of Cu 100 ⁇ (a+b) Be a Co b (0.4% ⁇ a ⁇ 2.0%, 0.15% ⁇ b ⁇ 2.8%, a+b ⁇ 3.5%) or a weight ratio of Cu 100 ⁇ (c+d) Be c Ni d (0.05% ⁇ c ⁇ 0.6%, 1.0% ⁇ d ⁇ 2.4%, c+d ⁇ 3.0%) is melted in a high frequency melting furnace to produce an ingot.
  • the content of Fe, S, and P as impurities can be limited to be lower than 0.01% in terms of the weight ratio.
  • Step S 11 the copper alloy obtained in S 10 is forged to be processed into a rectangular parallelepiped shaped copper alloy of a desired size. An oxidation film formed on the surface of a plate-like copper alloy is removed by cutting.
  • Step S 12 the copper alloy obtained in Step S 11 is held under heat for a given solid solution time (1 hour to 24 hours) in a solid solution temperature range (in the range of 700° C. to 1000° C.) to solve Be (or Be compound) in a matrix of Cu.
  • over-aging treatment of Step S 13 the copper alloy obtained in Step S 12 is held for a given period of time (2 to 6 hours) in an over-aging temperature range (in the range of 550 to 650° C.).
  • the precipitated particles of the copper alloy can be grown to such a size (e.g., average particle diameter of about 1 ⁇ m) that each manufacturing process on and after Step S 13 is not adversely affected.
  • the solution treatment of Step S 12 and the overaging treatment of Step S 13 may be independently (discontinuously) carried out or, as shown in FIG. 3( b ), the solution treatment of Step S 12 and the over-aging treatment of Step S 13 may be continuously carried out.
  • Step S 14 the copper alloy obtained in Step S 13 is cooled by water-cooling, air-cooling, or allowing to cool so that the surface temperature of the copper alloy is 20° C. or lower.
  • the cooling rate varies depending on the size of the bulk material and is preferably adjusted to ⁇ 100° C.s ⁇ 1 or higher (preferably ⁇ 200° C.s ⁇ 1 or higher).
  • Step S 15 the copper alloy after cooling is forged while cooling to remove heat.
  • the forging treatment is performed from each of the X-axis direction, the Y-axis direction, and the Z-axis direction, which are orthogonal to each other, of the rectangular parallelepiped.
  • a pressure is preferably applied in order from the axis direction corresponding to the longest side among the sides of the copper alloy.
  • Step S 151 a pressure is applied from the Z-axis direction to the copper alloy after cooling with a forging device or the like.
  • the surface temperature of the copper alloy during pressurization is preferably maintained at 120° C. or lower (more preferably in the range of 20 to 100° C.).
  • the pressure is preferably adjusted to 1200 MPa or lower. When the pressure exceeds 1200 MPa combined with the over-aging conditions or the like, a shear band structure crossing a plurality of grains is likely to generate in the copper alloy, and thus there is a possibility that cracks, fracture, or the like occurs.
  • the size reduction rate of one treatment of Step S 151 (reduction rate (%)) is in the range of 18 to 30% and the plastic strain (strain; ⁇ ) to be applied to the copper alloy is preferably in the range of 0.2 to 0.36.
  • FIG. 4 shows the relationship between the size reduction rate and the strain.
  • Step S 152 the copper alloy obtained in Step S 151 is cooled.
  • the cooling method may be any method of air-cooling, water-cooling, allowing to cool, and the like, and cooling by water-cooling is preferable considering the performance and efficiency of repeated operations.
  • the cooling is preferably carried out so that the surface temperature generated from the copper alloy by pressurization is 20° C. or lower.
  • Step S 153 a pressure is applied from the Y axis direction to the copper alloy after cooling with a forging device or the like.
  • the surface temperature of the copper alloy during pressurization is preferably maintained at 120° C. or lower.
  • the size reduction rate of one treatment of Step S 153 (reduction rate (%)) is in the range of 18 to 30% and the plastic strain (strain; ⁇ ) to be applied to the copper alloy is preferably in the range of 0.2 to 0.36.
  • Step S 154 the copper alloy obtained in Step S 153 is cooled.
  • the cooling is preferably carried out so that the surface temperature of the copper alloy is 20° C. or lower.
  • Step S 155 a pressure is applied from the X axis direction to the copper alloy after cooling with a forging device or the like.
  • the surface temperature of the copper alloy during pressurization is preferably maintained at 120° C. or lower.
  • the size reduction rate of one treatment of Step S 155 (reduction rate (%)) is in the range of 18 to 30% and the plastic strain (strain; ⁇ ) to be applied to the copper alloy is preferably in the range of 0.2 to 0.36.
  • Step S 156 the copper alloy obtained in Step S 155 is cooled.
  • the cooling is preferably carried out so that the surface temperature of the copper alloy is 20° C. or lower.
  • Step S 157 an operator judges whether or not the number of times of pressurizing the copper alloy with a forging device has reached a given number of times.
  • the “number of times of pressurization” refers to the number of times that is counted up while defining the case where a pressure is applied to a copper alloy from any one of the axis (X-axis, Y-axis, and Z-axis) directions as one time.
  • the “given number of times of pressurization” refers to the number of times in which the cumulative value of the plastic strain applied to the copper alloy (cumulative strain; ⁇ total) becomes 1.8 or more, for example.
  • the treatment of each of Steps 5151 to 5156 is repeated.
  • the process progresses to Step S 16 .
  • Step S 16 age-hardening treatment
  • the Be (or Be compound) contained in the copper alloy is precipitated and hardened.
  • the forged beryllium-copper bulk material shown in FIG. 1 can be manufactured.
  • the copper alloy after cooling is forged in the cold forging process of Step S 15 while cooling to remove heat so that the surface temperature of the copper alloy after cooling is maintained at 120° C. or lower.
  • the plastic strain to be applied to the copper alloy can be increased while reducing the influences of process heat generation of the copper alloy during forging. Therefore, a forged beryllium-copper bulk material having uniform and fine grains and maintaining uniform hardness from the front surface to the inside can be manufactured.
  • the copper alloy has not been uniformly cooled at a sufficient rate from the near-surface portions to the center core portion simply by performing the cooling treatment of Step S 14 after the solid solution process of Step S 12 .
  • the copper alloy has not been rapidly cooled to the internal center simply by cooling the front surface by water cooling or the like.
  • the cold forging treatment of Step S 15 is performed in the state where the copper alloy is not sufficiently cooled to the internal center, the deformation of a product becomes non-uniform, and fracture, cracks during processing, distortion, or the like has easily occurred.
  • the treatment conditions are controlled so that the copper alloy is not rapidly cooled, which has been performed in the former technique, and the copper alloy after the solid solution treatment is inefficiently and slowly cooled in Step S 13 . More specifically, by treating the copper alloy after the solid solution treatment at an over-aging temperature (550 to 650° C.) for a given period of time (over-aging time: 2 to 6 hours) in Step S 13 , the effect is obtained that the moderately precipitated particles preferably act, and the copper alloy efficiently and uniformly deforms to the inside.
  • an over-aging temperature 550 to 650° C.
  • over-aging time 2 to 6 hours
  • the over-aging temperature in Step S 13 is lower than 550° C., it is difficult to grow the precipitated particles and when the over-aging temperature is higher than 650° C., a solid solution of Be is formed in Cu, and thus the temperature range above is not preferable.
  • the over-aging time is lower than 2 hours, the precipitated particles do not grow to a certain size. In contrast, even when the over-aging time is longer than 6 hours, the growth of the precipitated particles is completed to some extent, and thus it is not efficient.
  • the over-aging temperature is 550 to 650° C. and more preferably 570 to 630° C.
  • the over-aging treatment time is 2 to 6 hours and more preferably 3 to 5 hours.
  • the method for manufacturing the forged beryllium-copper bulk material 1 shown in FIG. 2 includes applying a pressure to the copper alloy from all the Z-axis, Y-axis, and X-axis directions, and then judging whether or not the number of times of pressurization has reached a given number of times of pressurization in step S 157 .
  • the invention is not limited to the above, it may be judged whether or not the number of times of pressurization has reached a given number of times of pressurization whenever a pressure is applied to the copper alloy.
  • the copper alloy after forging is cooled whenever one forging treatment in each axis direction (Steps S 151 , S 153 , and S 155 ) is completed in the cooling process shown in Steps S 152 , S 154 , and S 156 .
  • the purpose can be achieved when the copper alloy is forged while maintaining the surface temperature of the copper alloy to be processed at 120° C. or lower.
  • each cooling process shown in each of Steps S 152 , S 154 , and S 156 may be omitted as required.
  • the method for maintaining the surface temperature of the copper alloy at 120° C. or lower in Step S 15 is not limited to the case where the surface temperature of the copper alloy is sufficiently cooled to be 20° C. or lower, and then the copper alloy is forged using a usual forging device.
  • a temperature measuring mechanism such as a thermocouple
  • a temperature measuring mechanism is attached to the surface of the copper alloy under forging to control the temperature of the copper surface so that the temperature is not equal to or higher than 120° C. while always monitoring the measurement results of the temperature measuring mechanism, and when the surface temperature of the copper alloy exceeds 120° C., the operation is interrupted or the copper alloy may be water-cooled, air-cooled, allowed to cool, or the like.
  • FIG. 5( a ) is a schematic view showing the appearance of the forged beryllium-copper bulk material according to the embodiment
  • FIG. 5( b ) is a graph showing the relationship between the pressure and the cumulative strain during repeated pressurization under a fixed size reduction rate
  • FIG. 5( c ) is a table showing changes in the surface temperature immediately after repeated pressurization.
  • the rolling reduction of one pressurization during repeated pressurization was 18% and the pressure was controlled not to exceed 1000 MPa ( ⁇ 1200 MPa).
  • FIG. 5( a ) cracks or non-uniform deformation was not observed in the appearance of the obtained forged beryllium-copper bulk material 1 .
  • FIGS. 6( a ) to 6 ( c ) show an example of the result obtained when a forged beryllium-copper bulk material was manufactured according to a former method, i.e., without subjecting the copper alloy after passing through Step S 12 to the over-aging treatment (Step S 13 of FIG. 2) and the cooling treatment (Steps S 152 , S 154 , and S 156 ).
  • the size reduction rate was controlled to 33% (strain of 0.40) so that the cumulative strain was in the range of 0.3 to 0.7.
  • the pressure was about 1300 MPa (>1200 MPa) and, as shown in FIG.
  • FIGS. 7( a ) to 7 ( c ) each are views showing a method for measuring the hardness of the forged beryllium-copper bulk material according to the embodiment.
  • the forged beryllium-copper bulk material 1 having a cubic shape with one side of 100 mm was prepared, and a plate 2 was cut out in such a manner as to include the central portion and the surface portion (side end surface) of the cube to be used as a test piece.
  • the measurement was performed using the test piece according to JISZ2244 (Vickers hardness test method-Test method (Corresponding international standard; ISO/6507-1; 1995 Metallic materials-Vickers hardness test-Part 1; Test Method).
  • FIG. 7( a ) the forged beryllium-copper bulk material 1 having a cubic shape with one side of 100 mm was prepared, and a plate 2 was cut out in such a manner as to include the central portion and the surface portion (side end surface) of the cube to be used as a test piece
  • FIG. 7( b ) is a graph showing the measurement results of the hardness of the copper alloy immediately after the forging treatment of Step S 15 of FIG. 2 .
  • FIG. 7( c ) is a graph showing the measurement results of the hardness of the forged beryllium-copper bulk material as the final shape immediately after the aging treatment of Step S 16 of FIG. 2 .
  • FIG. 8 is a graph showing the measurement results of the hardness of a former forged beryllium-copper bulk material obtained without performing the treatment of each of Steps S 13 and S 15 . As shown in FIG. 8 , the hardness value of the former forged beryllium-copper bulk material sharply decreased from the side end surfaces toward the central portion.
  • FIG. 9 shows an example of the distortion measurement result of the forged beryllium-copper bulk material.
  • FIG. 9 shows results obtained by placing a plate 2 a (left-side in FIG. 9 ) cut out from the former rectangular parallelepiped-shaped forged beryllium-copper bulk material and a plate 2 b (right-side in FIG. 9 ) cut out from the rectangular parallelepiped-shaped forged beryllium-copper bulk material 1 according to the embodiment on the same plane, and comparing the height of the curvature of each plate.
  • distortion of about 1 mm or more occurred but, in the plate 2 a according to the embodiment above, distortion hardly occurred.
  • FIG. 10 is a graph showing an example of the fatigue life measurement result of the forged beryllium-copper bulk material 1 according to the embodiment above and the former forged beryllium-copper bulk material.
  • the measurement was performed according to the rotating bending fatigue test of JISZ2274 using test samples No. 2 to 8 in a room temperature atmosphere. Each plot represents the point in which fatigue fracture occurred. According to the forged beryllium-copper bulk material according to the embodiment above, it was found that the fatigue life also becomes longer than that the former bulk material.
  • FIGS. 11( a ) and 11 ( b ) each show an example of the ultrasonic inspection test result of the forged beryllium-copper bulk material according to the embodiment above.
  • a surface layer of a cube-shaped forged beryllium-copper bulk material having one side of 100 mm was cut to be processed into a cube having one side of 70 mm, and then ultrasonic waves were transmitted to the processed forged beryllium-copper bulk material.
  • Tables 1 and 2 show differences in the properties between the forged beryllium-copper bulk material according to one embodiment of the invention and the forged beryllium-copper bulk material according to a comparative example (former example).
  • copper alloys constituted by the weight ratio of Cu 100 ⁇ (a+b) Be a Co b (0.4% ⁇ a ⁇ 2.0%, 0.15% ⁇ b ⁇ 2.8%, a+b ⁇ 3.5%) were prepared. Each copper alloy was melted in a high frequency melting furnace to manufacture an ingot, and then the obtained ingot was homogenized. The obtained ingot was processed by forging treatment, and the oxidation film formed on the surface was removed by cutting to be formed into a cubic shape having one side of 100 mm, thereby obtaining sample members A1 to A7, B1 to B7, A101 to A105, B101 to B105, and C101 to C103.
  • the sample members A1 to A7, B1 to B7, A101 to A105, B101 to B105, and C101 to C103 were subjected to the treatment (over-aging treatment, cooling treatment, and cold forging treatment) shown in each of Steps S 12 to S 15 of FIG. 2 under the conditions shown in Table 1.
  • the “discontinuous/continuous” of the column of the “over-aging treatment” of Table 1 indicates that the solid solution treatment of Step 12 and the over-aging treatment of Step S 13 were carried out independently and discontinuously or carried out continuously as shown in FIGS. 3( a ) and 3 ( b ).
  • the “highest temperature before pressurization” of the column of the “over-aging treatment” represents the maximum value of the surface temperature of the copper alloy measured immediately before carrying out the cold forging process of Step S 15 .
  • the “highest pressure” of the column of the “pressurization treatment” of Table 1 represents the maximum value of the pressure to be applied to the copper alloy by a forging device.
  • the “highest temperature after-pressurization” represents the maximum value of the surface temperature of the copper alloy that gradually increases with the repetition of pressurization.
  • the “hardness after aging” represents an average value of the results of measuring 25 points after performing 2 hour age-hardening treatment at 315° C., and then cooling the temperature to room temperature.
  • the “tensile strength” of Table 2 represents the results of performing a tensile test in the 6 directions according to JISZ2241 and examining whether or not the average value and the six numerical values are within 5%.
  • test pieces used for the tensile test plates including the X-Y plane, the Y-Z plane, and the X-Z plane were cut out from the center of the forged beryllium-copper bulk material 1 of FIG. 1 , and test pieces were machined from each plate so that the six directions (i.e., X direction, Y direction, Z direction, X-Y with an angle of 45°, Y-Z with an angle of 45°, and X-Z with an angle of)45° correspond with the tensile axis. Then, the measurement was performed according to JISZ2241 (Method of Tensile Test for Metallic Materials).
  • the “presence of a shear band structure” of Table 2 represents the results of examining whether or not a shear band structure similar to that of FIG. 12 were observed when some of the plates cut as described above were observed under an optical microscope of 500 ⁇ magnification. Before observation, corrosion by a suitable chemical etching is performed subsequent to the machine polishing of the plate surface which is known to persons skilled in the art.
  • the “shear band structure” refers to a shear structure in which the phase of the arrangement position of atoms (grains) has shifted with a boundary along a certain surface, and, in particular, refers to a structure in which the phase has shifted in the form of a band in the direction in which the deformation has been applied as described above.
  • Step S 15 As shown in Table 1, it is found that, in the cold forging treatment of Step S 15 , by controlling the surface temperature of the copper alloy to be equal to or lower than 120° C., controlling the pressure to be equal to or lower than 1200 MPa, and controlling the size reduction rate in the range of 18 to 30%, a beryllium bulk material capable of maintaining almost uniform hardness from the front surface to the inside can be manufactured.
  • the hardness of the end portions (forged beryllium-copper bulk material surface) after aging is 393 to 405 and the hardness of the center is 397 to 411, which shows that, in the forged beryllium-copper bulk material according to this embodiment, the hardness is almost the same from the near-surface portions and the center core portion and the hardness of the center and the hardness of the inside are different within 10%.
  • the tensile strength in each direction was almost the same and was stable, and no shear band structures were observed in any place.
  • the present invention can be utilized for machine structural components in which durability and reliability are demanded, such as bearings for airplanes, casings for under sea cable repeaters, rotor shafts for ships, collars of oil field drilling drills, injection molding dies, or welding electrode holders.

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US9586256B2 (en) 2012-03-27 2017-03-07 Ngk Insulators, Ltd. Forging method and forging die
WO2018112325A1 (en) * 2016-12-15 2018-06-21 Materion Corporation Precipitation strengthened metal alloy article having uniform strength
CN113458303A (zh) * 2020-03-30 2021-10-01 日本碍子株式会社 铍铜合金环及其制造方法
US11529671B2 (en) 2018-03-28 2022-12-20 Ngk Insulators, Ltd. Forging tool

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WO2019099830A1 (en) * 2017-11-17 2019-05-23 Materion Corporation Metal rings formed from beryllium-copper alloys

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US9586256B2 (en) 2012-03-27 2017-03-07 Ngk Insulators, Ltd. Forging method and forging die
WO2018112325A1 (en) * 2016-12-15 2018-06-21 Materion Corporation Precipitation strengthened metal alloy article having uniform strength
US20180171455A1 (en) * 2016-12-15 2018-06-21 Materion Corporation Precipitation strengthened metal alloy article
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CN113458303A (zh) * 2020-03-30 2021-10-01 日本碍子株式会社 铍铜合金环及其制造方法
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