1. Field of the Invention
The present invention relates to a forging method and a forging die.
2. Description of the Related Art
A forging method in which a plastic strain is applied to a rectangular parallelepiped bulk body made from a copper-beryllium alloy through press-deformation from X, Y, and Z axes orthogonal to each other has been proposed previously (refer to, for example, PTL 1). According to this method, a bulk body, in which a uniform hardness is held from the surface to the inside and a working strain is not generated easily, can be provided by application of a plastic strain.
However, in this forging method described in PTL 1, a step to induce press-deformation from X, Y, and Z axes is performed repeatedly. Consequently, for example, in the case where the working speed is increased in consideration of the production efficiency, there is an issue that the rectangular parallelepiped shape of the bulk body is deformed during this repetition. As described above, more efficient execution of a forging treatment of a work has been required.
The present invention has been made in consideration of the above-described issue, and it is a main object to provide a forging method and a forging die, with which a forging treatment of a work can be executed more efficiently.
That is, a forging method according to the present invention is characterized by including:
a placement step of placing a work having a first shape which is a rectangular hexahedron in a work space of a forging die, the work space having a rectangular opening, being formed by rectangular plane wall portions, and being provided for holding the work; and
a working step of applying a plastic strain to the work by deforming the placed work into a second shape which is a rectangular hexahedron,
wherein the placement step and the working step are performed at least two times.
In addition, a forging die according to the present invention is
a forging die used in a forging method that applies a plastic strain to a work by deforming the work having a first shape which is a rectangular hexahedron into a second work having a second shape which is a rectangular hexahedron, the forging die including
an outer die which has a circular opening and which is provided with the inner peripheral surface of the circle and
an inner die which has a rectangular opening and in which a work space for holding the above-described work is formed by rectangular plane wall portions, while a plurality of die parts are combined and are fitted into the inner periphery of the above-described outer die.
According to the present invention, a forging treatment of a work can be executed more efficiently. This is because, for example, the work is press-deformed in the work space of the forging die and, thereby, the shape stability can be further ensured. Also, the forging die has a structure in which a plurality of die parts are fitted into the inner periphery of the outer die, so that, for example, the stress applied to the inner die during pressurization of the work can be dispersed to the outer peripheral side more evenly by the plurality of die parts and breakage of the die and the like can be further suppressed. Consequently, for example, die exchange and the like can be further suppressed and, by extension, the forging treatment of a work can be executed more efficiently.
Next, the embodiments according to the present invention will be described with reference to the drawings. In this regard, in the following description of the drawings, the same or similar portions are indicated by the same or similar reference numerals. Meanwhile, the embodiments described below are exemplifications of apparatuses and methods for embodying the technical idea of the present invention. The technical idea of the present invention does not limit the structures, arrangements, and the like of constituent parts to those described below. To begin with, a forging die 20 used for the forging method according to the present invention will be described.
The upper die 21 is a member which is fixed to a slide knock-out beam of a cold forging press machine, although not shown in the drawing, and which is moved in the vertical direction to press the work W placed on the lower die 30 with an upper die indenter 22. This upper die 21 is provided with the upper die indenter 22, which press-deforms the work W, on the lower surface of a disk-shaped member. This upper die indenter 22 is formed into the shape of a prism having an end with a rectangular plane.
An alignment jig 28 is a jig used for aligning the upper die indenter 22 with a work space 45. This alignment jig 28 is used by being placed on the upper portion of a die unit 40.
The lower die 30 is a disk-shaped member and is a member which is fixed to a bottom knock-out beam of the cold forging press machine, although not shown in the drawing. This lower die 30 includes a first lower die 31 serving as a pedestal, a second lower die 36 fixed above the first lower die 31, a slide pedestal 35 which constitutes the bottom of the work space 45 and which is slidable, and the die unit 40 which is provided with the work space 45 and which is fixed in the lower die 30 while being sandwiched between the first lower die 31 and the second lower die 36.
The first lower die 31 is a disk-shaped member, and on the upper surface thereof, a slide groove 32 to slidably insert the tabular slide pedestal 35 is disposed from the center portion to the outer periphery of the disk. Also, a communication space 33 communicating with the work space 45 disposed in the die unit 40 is disposed at the center of the disk. That is, this lower die 30 is configured in such a way that when the slide pedestal 35 is slid, the work space 45 communicates with the communication space 33 and the work space 45 communicates with the outside. Therefore, in the lower die 30, when the slide pedestal 35 is slid, the work W can be moved from the work space 45 to this communication space 33. The slide pedestal 35 is a member which constitutes the bottom of the work space 45 and on which the work W is placed. This slide pedestal 35 has such strength that can endure the pressing force applied to the work W in the forging treatment. The second lower die 36 is a disk-shaped member having the same diameter as the diameter of the first lower die 31, and at the center thereof, a mounting space 37, which has a circular opening and in which the die unit 40 is mounted, is disposed. The first lower die 31 and the second lower die 36 are fixed firmly with bolts, although not shown in the drawing. In this regard, the first lower die 31 is provided with a through hole 34 to allow the communication space 33 to communicate with the outside (refer to
As shown in
The work W can be, for example, a copper alloy. As for the work W, besides alloys containing Be and Cu, copper alloys containing Ni, Sn, and Cu, copper alloys containing Ti, Fe, and Cu, copper alloys containing Ni, Si, and Cu, and the like, which exhibit high work hardenability and high strength as with the alloys containing Be and Cu, can be adopted. That is, examples of copper alloys include CuBeCo, CuBeNi, CuNiSn, and CuTiFe, and among them, CuBeCo, CuBeNi, and the like are more preferable. As for these alloys, the forging treatment step according to the present invention can be executed, although temperatures, times, and the like of a homogenization treatment step, a solid solution treatment step, and an age-hardening treatment step may be different depending on the selection ranges of the elements and compositions, as described later in detail. Alternatively, high purity Cu (for example, 4N—Cu) may be employed as the work W. Also, other than copper alloys, for example, magnesium alloys (AZ31; Mg—Al—Zn—Mn base alloys and the like), iron and steel materials (Fe-20Cr, SUS304, and the like), and aluminum alloys (7475Al; Al—Zn—Mg—Cu base alloys and the like) may be employed as the work W.
The thus configured forging die 20 has a structure in which the plurality of die parts are fitted into the inner periphery of the outer die 41. Therefore, for example, the stress applied to the inner die 50 during pressurization of the work W can be dispersed to the outer peripheral side more evenly by the plurality of die parts and breakage of the die and the like can be further suppressed. Also, the inner die 50 is composed of the plurality of die parts separated from each other at corner portions formed by two planes of the work space 45, so that an occurrence of cracking of the die at the corner portion 46 of the work space 45, to which the stress is applied, can be prevented. Furthermore, when the slide pedestal 35 is slid, a space communicating with the outside from the work space 45 is formed and, thereby, the work W after working is taken out of the communication space 33 easily.
Next, the forging method according to the present invention will be described. The forging method according to the present invention can be applied to, for example, a production treatment of a copper-beryllium base alloy. A method for manufacturing a copper-beryllium base alloy will be described below as a specific example. The manufacturing method according to the present invention may include (1) a homogenization treatment step, (2) a solid solution treatment step, (3) a cooling treatment step, (4) a forging treatment step which is the forging method according to the present invention, and (5) an age-hardening treatment step.
(1) Homogenization Treatment Step
In this step, a treatment to generate a copper alloy, in which no dislocation occurs in crystal grains, is performed, wherein a solid solution of Be (or Be compound) in a Cu matrix is formed. Specifically, a copper alloy configured to have a mass ratio of Cu100−(a+b)BeaCob (0.4%≦a≦2.0%, 0.15%≦b≦2.8%, a+b≦3.5%) or a mass ratio of Cu100−(c+d)BecNid (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. At this time, preferably, Fe, S, and P serving as impurities can be limited to less than 0.01% on a mass ratio basis. The resulting ingot is heated and held in a solid solution temperature range (within the range of 700° C. to 1,000° C.) for a predetermined holding time (1 hour to 24 hours) and, thereby, is homogenized because nonuniform textures, e.g., segregation, which are generated in a non-equilibrium manner during casting and which adversely affects the downstream operations, are removed. Subsequently, the resulting ingot is worked into a rectangular parallelepiped copper alloy (bulk body) having a predetermined size. An oxide film formed on the surface of the copper alloy may be removed by cutting. The bulk body may be a rectangular parallelepiped having sides extending in directions of three axes (X, Y, and Z axes) orthogonal to each other. This bulk body is in the shape of a rectangular parallelepiped in which the ratio of lengths of the individual sides (side X, side Y, and side Z) is specified to be x:y:z (where x<y<z, 1.03x≦y≦1.49x, 1.06x≦z≦2.22x, and z=(y/x)2x are satisfied) preferably (refer to
(2) Solid Solution Treatment Step
In this step, a treatment to form a solid solution of Be (or Be compound) in a Cu matrix is performed by heating and holding the bulk body obtained in the homogenization treatment in a solid solution temperature range (within the range of 700° C. to 1,000° C.) for a predetermined solid solution holding time (1 hour to 24 hours). After the solid solution treatment step, an overaging treatment may be performed, wherein the resulting bulk body is held in an overaging temperature range (within the range of 550° C. to 650° C.) for a predetermined time (2 to 6 hours). Consequently, it is considered that precipitated grains of the copper alloy can be grown to the size (for example, an average grain size of about 1 μm) of an extent which does not adversely affect in the individual production steps thereafter. In this regard, the solid solution treatment and the overaging treatment may be performed independently (discontinuously) or be performed continuously. Grains which have been appropriately precipitated by this overaging treatment act favorably and, thereby, an effect of efficiently uniformly deforming up to the inside is obtained. According to this, generation of a shear band texture crossing a plurality of crystal grains is suppressed and cracking, breakage, and the like do not occur, so that a copper-beryllium bulk body can be obtained, where uniform hardness can be held from the surface to the inside, the fatigue life is excellent, and a working strain does not occur easily.
(3) Cooling Treatment Step
In this step, the bulk body subjected to the solid solution treatment is cooled by water cooling, air cooling, or standing to cool in such a way that the surface temperature of the copper alloy becomes, for example, 20° C. or lower. The cooling rate is different depending on the size of the bulk body and is preferably −100° C./s or more (preferably −200° C. or more).
(4) Forging Treatment Step
In this step, the bulk body after cooling is used as a work W and is subjected to a treatment in which forging is performed from the X axis, the Y axis, and the Z axis directions, which are orthogonal to each other, of the rectangular parallelepiped, while cooling and heat removal are performed. The forging treatment step includes, for example, a placement step to place the work W having a first shape, which is a rectangular hexahedron (rectangular parallelepiped), in a work space 45 of a forging die 20 and a working step to apply a plastic strain to the work W by deforming the placed work into a second shape, which is a rectangular hexahedron, wherein the placement step and the working step are performed at least two times.
In the placement step (refer to
In the working step (
In the push-out step (
In the take-out step (
In this forging treatment step, the placement step, the working step, the push-out step, and the take-out step are performed until the predetermined number of times of pressurization is reached. Here, the term “the number of times of pressurization” refers to the number of times counted up, where application of a pressure to the work W from any one of the individual axis (X axis, Y axis, and Z axis) directions is counted as once. Also, the term “the predetermined number of times of pressurization” may refers to the number of times, where a cumulative value of the amount of plastic strain added to the copper alloy (cumulative amount of strain; a total) becomes, for example, 1.8 or more, and more preferably 4.0 or more.
(5) Age-Hardening Treatment Step
In this step, a treatment is performed, wherein the work W (copper alloy) after the forging treatment is held in a precipitation temperature range (within the range of 200° C. to 550° C.) for a predetermined age-hardening time (1 hour to 24 hours) of a rectangular copper alloy and, thereby, Be (or Be compound) contained in the copper alloy is precipitation-hardened. In this manner, a copper-beryllium alloy having more improved characteristics, e.g., hardness, can be produced.
According to the forging method of the above-described embodiment, the work W is press-deformed in the work space 45 of the forging die 20 and, thereby, the shape stability can be further ensured. Also, the forging die 20 has a structure in which a plurality of die parts are fitted into the inner periphery of the outer die 50, so that, for example, the stress applied to the inner die 50 during pressurization of the work W can be dispersed to the outer peripheral side more evenly by the plurality of die parts and breakage of the die and the like can be further suppressed. Consequently, for example, exchange of the die and the like can be further suppressed and, by extension, the forging treatment of the work can be executed more efficiently. Also, the inner die 50 is composed of the plurality of die parts separated from each other at corner portions 46, so that an occurrence of cracking of the die at the corner portion 46 of the work space 45, to which the stress is applied, can be prevented and, by extension, the forging treatment of the work can be executed more efficiently. In addition, when the slide pedestal 35 is slid, a space communicating with the outside from the work space 45 is formed and, thereby, the work W after working is taken out of the communication space 33 easily. Therefore, the forging treatment of the work can be executed more efficiently. Furthermore, in the placement step, the work is employed preferably in such a way that the volume ratio of the work space 45 to the work W is specified to be within the range of (y/x)×(z/y)×z(1+α)/z; (where x<y<z, 1.10x≦y≦1.20x and 1.21x≦z≦1.44x, z=(y/x)2x, and 0<α≦0.5 are satisfied) and the amount of pressurization corresponds to press-in of the upper die indenter 22 by the amount of (z−x) from the upper surface of the work W. The amount of treatment of one batch can be automatically determined by adopting this volume ratio and the amount of pressurization and the same ratio of lengths of the individual sides as that before the treatment is reproduced after the treatment, so that the efficiency for repetition increases. The forging treatment of the work can be executed more efficiently because of this combination of the volume ratio and the amount of pressurization. Then, in this working step, the work W is deformed in such a way that the work W having the first shape and the work W having the second shape are different in the lengths of the X, Y, and Z axes but the first shape and the second shape are the same shape. Consequently, an equal plastic strain can be added to each axis. Also, in the working step, the work W is deformed at a working ratio within the range of 18% or more and less than 33%, so that the forging treatment of the work can be executed more efficiently. Furthermore, the work W is an alloy containing Be and Cu and, therefore, application of the present invention has great significance. Also, the structure in which the die unit 40 is fitted to the second lower die 36 is employed, so that the die unit 40 can be exchanged easily and the forging treatment of the works W having various types of shapes can be executed more efficiently.
In this regard, the present invention is not specifically limited to the above-described embodiment and can be executed in various aspects within the technical scope of the present invention, as a matter of course. For example, each surface of the bulk body work or the surface of each die in contact with this may be coated with a lubricant. At this time, a lubricant in the form of gel, the form of powder, the form of liquid, or the like can be selected, as necessary. At that time, more preferably, a lubricant which has high thermal conductivity and which does not inhibit heat transfer of working heat from the work W to the inner die is selected.
For example, in the above-described embodiment, the forging die 20 including the plurality of die parts provided with the convex portions 52 and the concave portions 56 are used, although not specifically limited to this. A forging die 20B shown in
In the above-described embodiment, the forging die 20 including the inner die 50 composed of the plurality of die parts is used, although not specifically limited to this.
Alternatively, a forging die 20C shown in
In the above-described embodiment, the inner die 50 in which the work space 45 is formed while the plurality of die parts are fitted into the inner periphery of the outer die 41 is included, although not specifically limited to this. The plurality of die parts may be incorporated into the inside of the outer die rather than the circumference. Also, the plurality of die parts separated from each other at the corner portions 46 are included in the above-described embodiment. However, the die parts may be separated from each other at the corner portions 46 or be separated from each other at portions other than the corner portions 46.
In the above-described embodiment, the lower die 30 is formed from the first lower die 31, the die unit 40, the slide pedestal 35, and the second lower die 36, although not specifically limited to this. Other members may be added or at least any one of them may be omitted. For example, in the above-described embodiment, the slide pedestal 35 is included, although the slide pedestal 35 may not be included.
In the above-described embodiment, in the forging treatment step, the work W is cooled after being taken out, although not specifically limited to this. As shown in
Although an explanation is not specifically provided in the above-described embodiment, as shown in
Alternatively, as shown in
In the explanations of the above-described embodiments, the work W is an alloy containing Be and Cu. However, the above-described steps may be executed while the work W is specified to be a copper alloy containing Ni, Sn, and Cu, a copper alloy containing Ti, Fe, and Cu, a copper alloy containing Ni, Si, and Cu, or the like, which exhibits high work hardenability and high strength as with the alloy containing Be and Cu. In the case where this alloy is used, the above-described forging treatment steps can be executed, although temperatures and times of the homogenization treatment step, the solid solution treatment step, and the age-hardening treatment step may be different from those in the case of the alloy containing Be and Cu depending on the selection ranges of the elements and compositions. Alternatively, the above-described steps may be executed, where high purity Cu (for example, 4N—Cu) is employed as the work W. Also, in the case of application to those other than the copper alloys, when magnesium alloys (AZ31; Mg—Al—Zn—Mn base alloys and the like) and iron and steel materials (Fe-20Cr, SUS304, and the like) are used, the volume ratio of the work space 45 to the work W may be within the range of (y/x)×(z/y)×z(1+α)/z; (where x<y<z, 1.22x≦y≦1.49x, 1.49x≦z≦2.22x, z=(y/x)2x, and 0<α≦0.5 are satisfied) in the above-described forging treatment step. Furthermore, as for aluminum alloys (7475Al; Al—Zn—Mg—Cu base alloys and the like), the volume ratio of the work space 45 to the work W may be within the range of (y/x)×(z/y)×z(1+α)/z; (where x<y<z, 1.03x≦y≦1.06x, 1.06x≦z≦1.12x, z=(y/x)2x, and 0<α≦0.5 are satisfied). In this regard, in the case where these alloys are used, in the working step, the work may be deformed at the working ratio within the range of 6% or more and less than 55%.
Examples of specific studies of the forging treatment step by using the forging die 20 will be described below. In this regard, Examples 1 to 13 and 23 to 32 correspond to examples according to the present invention and Examples 14 to 22 correspond to comparative examples.
A copper alloy configured to have a mass ratio of Cu100−(a+b)BeaCob (a=1.8% and b=0.2%) and a copper alloy configured to have a mass ratio of Cu100−(c+d)BecNid (C=0.2% and d=1.8%) were prepared as bulk bodies. In the homogenization treatment step, the treatment was performed at 840° C. for 4 h and working was performed into the shape of 60 mm×66 mm×73 mm (1:1.1:1.21). In the solid solution treatment step, the treatment was performed at 800° C. for 1 h, quenching was performed at about 50° C./s, and the resulting bulk body was taken as a work W. The forging treatment step was performed under the condition in which the volume ratio of the work space 45 to the work W was (66/60)×(73/66)×{(73/66)+0.5 mm}=1.1×1.1×1.6=1.936, the working ratio was 18% (the amount of strain per batch 0.2), the Σε strain rate was about 1×100 (s−1), the total amount of strain Fe was 2.4, and the predetermined number of times of pressurization was 12. Here, initially, hardening through forging was examined. The Cu—Be—Co base copper alloy was subjected to a forging treatment with the forging die 20. The resulting work W was taken as Example 1, and the alloy which was not subjected to forging was taken as Comparative example 1. Also, the Cu—Be—Ni base copper alloy was subjected to a forging treatment with the forging die 20. The resulting work W was taken as Example 2, and the alloy which was not subjected to forging was taken as Comparative example 2. As for the lubricant, a SEALUB product produced by NOK KLÜBEL CO. LTD. was applied.
Next, the forging treatment by using the forging die 20 was studied. The shape, the volume ratio, the working ratio, and the like of the work were changed as shown in Tables 1 and 2, and the shapes before and after the forging, the linearity, the maximum dimensional difference, and the like were evaluated on the basis of the appearance thereof. A copper alloy configured to have a mass ratio of Cu100−(a+b)BeaCob (a=1.8% and b=0.2%) and a copper alloy configured to have a mass ratio of Cu100−(c+d)BecNid (c=0.2% and d=1.8%) were prepared in the same steps as those described above. In this regard, in Table 1, each of a short side x, a middle side y, and a long side z is indicated by a normalized length, where the short length x is specified to be 1.
Also, a copper alloy configured to have a mass ratio of Cu97.85Be0.35Ni1.8, a copper alloy configured to have a mass ratio of Cu78Ni15Sn7, a copper alloy configured to have a mass ratio of Cu96.9Ti3Fe0.1, a copper alloy configured to have a mass ratio of Cu89Ni9Si2, a magnesium alloy (AZ31), a steel configured to have a mass ratio of Fe89CR20, SUS304, an aluminum alloy (7475Al), and the like were prepared and examined.
Shape Evaluation
As for the shape evaluation, presence or absence of crack, roundness of corner, and the like were examined visually, and the alloy having a good shape was evaluated as ◯, and that includes crack or rounded corner was evaluated as x. Also, as for the linearity, whether each of six surfaces keeps flatness or not was examined by visually checking presence or absence of a gap when a ruler is placed on the surface, the case where there was no gap was evaluated as ◯, and the case where there was a gap was evaluated as x. Also, as for the maximum dimensional difference, the maximum value of difference in the dimension (length) of each side between before and after the forging was measured, the case where the maximum dimensional difference was 2% or less was evaluated as ◯, and the case where the maximum dimensional difference was more than 2% was evaluated as x. In this regard, Tables 1 and 2 show the results of the Cu—Be—Co alloy, and the same results were obtained with respect to the Cu—Be—Ni alloy.
Table 2 shows the forging treatment results of each work. As shown in Table 2, Experimental Examples 14 and 15 in which the long side z and the middle side y were relatively not so longer than the short side x and Experimental Examples 16 and 17 in which the long side z and the middle side y were relatively longer than the short side x exhibited poor shape stability. Also, Experimental Example 18 in which the number of cycles of cumulative strain was small and Experimental Example 19 in which the number of cycles was large exhibited poor shape stability. Also, Experimental Example 20 in which the top surface coefficient α indicating the gap of the top surface was large exhibited good results, although the lowering of the upper die until the start of forging took a long time and it was not easy to say that the productivity was good. Meanwhile, as for Experimental Example 21 exhibiting no top surface coefficient α, forging was not performed because a movement due to backlash in insertion of the upper die indenter was feared. Also, Experimental Example 22 subjected to flat die forging without using the forging die 20 exhibited very poor shape stability.
Also, as shown in Tables 1 and 2, the magnesium alloy (AZ31) and the iron and steel materials (Fe-20Cr and SUS304), in which the top surface coefficient α was 0.01 to 0.5, 1.22x≦y≦1.49x and 1.49x≦z≦2.22x were satisfied with respect to short side x:middle side y:long side z (x<y<z), and the volume ratio was 1.505 to 3.330, exhibited good shape retention property. Also, the aluminum alloy (7475Al), in which the top surface coefficient α was 0.01 to 0.5, 1.03x≦y≦1.06x and 1.06x≦z≦1.12x were satisfied with respect to short side x:middle side y:long side z (x<y<z), and the volume ratio was 1.07 to 1.68, exhibited good shape retention property.
In this regard, even when the die, e.g., the forging die 20C, in which the inner die was not divided was used, the forging treatment was able to be executed while the shape stability was high as with the above-described examples. However, in some cases, a stress was applied to the inner die, and cracking occurred in the corner portion of the inner die forming the work space. On the other hand, it was found that as for the forging die 20 in which the inner die 50 was composed of the plurality of die members, such cracking did not occur and a stable forging treatment was able to be executed.
The present application claims priority from Japanese Patent Application No. 2012-072259 filed on Mar. 27, 2012, the entire contents of which are incorporated herein by reference.
The present invention can be utilized for machine structural parts, e.g., aircraft bearings, casings of submarine cable repeaters, rotor shafts of ships, collars of oil field excavation drills, injection molding dies, and welding electrode holders, which are required to have the durability and the reliability.
Number | Date | Country | Kind |
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2012-072259 | Mar 2012 | JP | national |
Number | Date | Country | |
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Parent | PCT/JP2013/057246 | Mar 2013 | US |
Child | 14474645 | US |