Patent Publication Number: US-2009223271-A1

Title: Swaging method and swaging apparatus

Description:
TECHNICAL FIELD 
     The present invention relates to an upsetting method and an upsetting apparatus used in manufacturing a product, such as, e.g., an arm or a piston for vehicles (e.g., cars, railroad vehicles, etc.). 
     BACKGROUND ART 
     In general, in an upsetting process, if a bar-shaped raw material buckles during the process, the obtained upset forged product becomes defective in shape, which causes degradation in value as a product. Therefore, in order to prevent occurrence of such buckling, the following upsetting method has been conventionally proposed. 
     That is, in this method, a diameter expansion scheduled portion of a bar-shaped raw material is received and held by a receiving portion of a receiving die in a buckling prevented state with the diameter expansion scheduled portion inserted in an insertion hole penetrated in a guide in an axially slidable manner. Subsequently, the guide is moved in a direction opposite to a pressurizing direction of the diameter expansion scheduled portion of the raw material while pressurizing the diameter expansion scheduled portion of the raw material in the axial direction with a punch as a pressurizing means, to thereby radially outwardly expand the diameter expansion scheduled portion of the raw material exposed between the tip end face of the guide and the receiving portion of the receiving die (see e.g., Patent Documents 1 to 4). This upsetting method has an advantage that buckling of the diameter expansion scheduled portion of the raw material can be prevented. 
     Patent Document 1: JP H09-253782, A 
     Patent Document 2: JP H07-506768, A 
     Patent Document 3: JP 2005-59097, A 
     Patent Document 4: JP 2005-144554, A 
     DISCLOSURE OF THE INVENTION 
     Problems to be Solved 
     The aforementioned conventional upsetting method had the following defects. 
     In detail, in the aforementioned upsetting method, a friction resistance is created between the diameter expansion scheduled portion of the raw material and the peripheral surface of the insertion hole of the guide when the diameter expansion scheduled portion of the raw material is slidably moved in the insertion hole during the process. The longer the length of the diameter expansion scheduled portion of the raw material disposed in the insertion hole, the more the friction resistance is increased. In the aforementioned upsetting method, in order to overcome the friction resistance, it is required to pressurize the diameter expansion scheduled portion with a punch under a molding pressure larger than such friction resistance. Pressurizing under such a large molding pressure, however, may often cause crashing of an end portion of the diameter expansion scheduled portion of a raw material pressurized by the punch within the insertion hole. In this case, some of the material of the diameter expansion scheduled portion of the raw material will be introduced into the gap between the punch and the insertion hole, resulting in an increased molding pressure. This in turn causes immovable of the punch in the insertion hole in the pressure direction, which may result in unprocessable. 
     Furthermore, even in the case of using a pressurizing means other than a punch, when pressurized with a large molding force, a raw material will expand radially outwardly in an insertion hole of a guide, which further increases the molding pressure. This requires a driving source for the pressing means that can generates extremely large molding pressure. As a result, the driving source should grow in size, resulting in an increased mounting space of the upsetting apparatus. In addition, the purchase cost for the upsetting apparatus increases. 
     The present invention was made to solve the aforementioned drawbacks, and aims to provide an upsetting method capable of reducing the molding pressure, an upset forged product obtained by the upsetting method, and an upsetting apparatus used for the upsetting method. 
     Other objects and advantages of the present invention will be apparent from the following preferable embodiments. 
     Means to Solve the Problems 
     Problems to be Solved 
     The present invention provides the following means. 
     [1] An upsetting method using a receiving die having a receiving portion and a guide having an insertion hole for inserting and holding a diameter expansion scheduled portion of a raw material in a buckling prevented state and in an axially slidable manner and a raw material outlet portion which is one end opening of the insertion hole provided at a tip end face of the guide, 
     the upsetting method comprising: 
     a step of receiving the diameter expansion scheduled portion of the raw material by the receiving portion of the receiving die and disposing the diameter expansion scheduled portion of the raw material in the insertion hole of the guide; and 
     a step of expanding a diameter of the diameter expansion scheduled portion of the raw material exposed between the tip end face of the guide and the receiving portion of the receiving die by moving the guide in a direction opposite to a pressurizing direction of the diameter expansion scheduled portion of the raw material while pressurizing the diameter expansion scheduled portion of the raw material with a pressurizing means in an axial direction, after the step of disposing the diameter expansion scheduled portion of the raw material, 
     characterized in that, at the diameter expansion step, the diameter expansion is performed in a state in which a portion of the diameter expansion scheduled portion of the raw material corresponding to a tip end portion of the guide is locally heated by the heating means. 
     [2] The upsetting method as recited in the aforementioned Item 1, 
     wherein the heating means is an induction heating means having an induction heating coil, and 
     wherein, at the diameter expansion step, the diameter expansion is performed in a state in which the portion of the diameter expansion scheduled portion of the raw material corresponding to the tip end portion of the guide is inductively heated with the induction heating coil arranged at the tip end portion of the guide. 
     [3] The upsetting method as recited in the aforementioned Item 1, 
     wherein the heating means is an induction heating means having an induction heating coil, and 
     wherein, at the diameter expansion step, the diameter expansion is performed in a state in which the portion of the diameter expansion scheduled portion of the raw material corresponding to the tip end portion of the guide is heated by inductively heating the tip end portion of the guide with the induction heating coil arranged at the tip end portion of the guide. 
     [4] The upsetting method as recited in the aforementioned Item 2 or 3, wherein the tip end portion of the guide having the induction heating coil is connected to a main body of the guide via a heat insulating layer. 
     [5] The upsetting method as recited in any one of the aforementioned Items 1 to 4, wherein, at the diameter expansion step, the diameter expansion is performed in a state in which the portion of the diameter expansion scheduled portion of the raw material corresponding to the tip end portion of the guide is heated into a half molten state. 
     [6] The upsetting method as recited in any one of the aforementioned Items 1 to 5, wherein, at the diameter expansion step, the diameter expansion is performed in a state in which an inner surface of a portion of the insertion hole located at a basal end side of the guide relative to the tip end portion of the guide is cooled with a first cooling means 
     [7] The upsetting method as recited in the aforementioned Item 1, 
     wherein a molding portion having a cavity for molding the diameter expansion scheduled portion of the raw material into a designed shape is extended from the receiving portion of the receiving die, 
     wherein, at the step of disposing the diameter expansion scheduled portion of the raw material, the diameter expansion scheduled portion of the raw material is received by the receiving portion of the receiving die, the diameter expansion scheduled portion of the raw material is disposed in the insertion hole of the guide, and the tip end portion of the guide is disposed in the cavity of the receiving die, and 
     wherein, at the diameter expansion step, the diameter expansion scheduled portion of the raw material exposed between the tip end face of the guide and the receiving portion of the receiving die is expanded in diameter in the cavity of the receiving die. 
     [8] The upsetting method as recited in the aforementioned Item 7, wherein, at the diameter expansion step, the diameter expansion is performed in a state in which a molding surface of the cavity of the receiving die is cooled with a second cooling means. 
     [9] An upset forged article obtained by the upsetting method as recited in any one of the aforementioned Items 1 to 8. 
     [10] An upsetting method using a receiving die having receiving portions formed at both axial end portions and a holding hole communicating with both the receiving portions for holding a non-diameter-expansion scheduled portion of a raw material and two guides each having an insertion hole for inserting and holding a diameter expansion scheduled portion of the raw material located at an axial end side in a buckling prevented manner and in an axially slidable manner with respect to the non-diameter-expansion scheduled portion of the raw material and each having a raw material outlet portion constituted by one end opening of the insertion hole provided at the tip end face, 
     the upsetting method comprising: 
     a step of receiving each diameter expansion scheduled portion of the raw material by a corresponding receiving portion of the receiving die by disposing the non-diameter-expansion scheduled portion of the raw material in the holding hole of the receiving die and disposing both the diameter expansion scheduled portions of the raw material in the insertion holes of the guide respectively; and 
     a step of simultaneously expanding both the diameter expansion scheduled portions of the raw material exposed between the tip end face of each guide and the corresponding receiving portions of the receiving die by moving each guide in a direction opposite to a pressurizing direction of the corresponding diameter expansion scheduled portion of the raw material while pressurizing both the diameter expansion scheduled portions of the raw material with the pressuring means in the axial direction respectively, characterized in that, at the diameter expansion step, the diameter expansion is performed in a state in which a portion of each diameter expansion scheduled portion of the raw material corresponding to a tip end portion of the guide is locally heated with a heating means. 
     [11] The upsetting method as recited in the aforementioned Item 10, 
     wherein the heating means is an induction heating means having an induction heating coil, and 
     wherein, at the diameter expansion step, the diameter expansion is performed in a state in which the portion of each diameter expansion scheduled portion of the raw material corresponding to the tip end portion of each guide is inductively heated with the induction heating coil disposed at the tip end portion of each guide. 
     [12] The upsetting method as recited in the aforementioned Item 10, 
     wherein the heating means is an induction heating means having an induction heating coil, and 
     wherein, at the diameter expansion step, the diameter expansion is performed in a state in which the portion of each diameter expansion scheduled portion of the raw material corresponding to the tip end portion of each guide is heated by inductively heating the tip end portion of each guide with the induction heating coil disposed at the tip end portion of each guide. 
     [13] The upsetting method as recited in the aforementioned Item  11  or  12 , wherein the tip end portion of each guide having the induction heating coil is connected to a main body of the guide via a heat insulating layer. 
     [14] The upsetting method as recited in any one of the aforementioned Items 10 to 13, wherein, at the diameter expansion step, the diameter expansion is performed in a state in which the portion of each diameter expansion scheduled portion of the raw material corresponding to the tip end portion of each guide is heated into a half molten state. 
     [15] The upsetting method as recited in any one of the aforementioned Items 10 to 14, wherein, at the diameter expansion step, the diameter expansion is performed in a state in which an inner surface of a portion of the insertion hole located at a basal end side of each guide relative to the tip end portion of the guide is cooled with a first cooling means. 
     [16] The upsetting method as recited in any one of the aforementioned Items 10 to 15, 
     wherein a molding portion having a cavity for molding the diameter expansion scheduled portion of the raw material into a designed shape is extended from each receiving portion of the receiving die, 
     wherein, at the step of disposing the diameter expansion scheduled portion of the raw material, each diameter expansion scheduled portion of the raw material is received by the receiving portion of the receiving die by disposing the non-diameter-expansion scheduled portion of the raw material in the holding hole of the receiving die, both the diameter expansion scheduled portions of the raw material are disposed in the insertion hole of the guide respectively, and the tip end portions of the guides are disposed in the cavities of the receiving die respectively, and 
     wherein, at the diameter expansion step, both the diameter expansion scheduled portions of the raw material exposed between the tip end face of each guide and each receiving portion of the receiving die are simultaneously expanded in diameter in the corresponding cavity of the receiving die respectively. 
     [17] The upsetting method as recited in the aforementioned Item  16 , wherein, at the diameter expansion step, the diameter expansion is performed in a state in which a molding surface of each cavity of the receiving die is cooled with a second cooling means. 
     [18] An upset forged article obtained by the upsetting method as recited in any one of the aforementioned Items  10  to  17 . 
     [19] An upsetting apparatus, comprising: 
     a receiving die having a receiving portion for receiving a diameter expansion scheduled portion of a raw material; 
     a guide having an insertion hole for inserting and holding the diameter expansion scheduled portion of the raw material in a buckling prevented state and in an axially slidable manner and a raw material outlet portion constituted by one end opening of the insertion hole formed at a tip end face; 
     pressurizing means for pressurizing the diameter expansion scheduled portion of the raw material disposed in the insertion hole of the guide in an axial direction; and 
     guide driving means for moving the guide in a direction opposite to a pressurizing direction of the diameter expansion scheduled portion of the raw material, 
     wherein it is configured such that the diameter expansion scheduled portion of the raw material exposed between the tip end face of the guide and the receiving portion of the receiving die is expanded in diameter, and 
     characterized in that the upsetting apparatus further comprises a heating means for locally heating a portion of the diameter expansion scheduled portion of the raw material corresponding to a tip end portion of the guide. 
     [20] The upsetting apparatus as recited in the aforementioned Item  19 , 
     wherein the heating means is an induction heating means having an induction heating coil, and 
     wherein it is configured to inductively heat the portion of the diameter expansion scheduled portion of the raw material corresponding to the tip end portion of the guide by the induction heating coil disposed at the tip end portion of the guide. 
     [21] The upsetting apparatus as recited in the aforementioned Item  19 , 
     wherein the heating means is an induction heating means having an induction heating coil, and 
     wherein it is configured to heat the portion of the diameter expansion scheduled portion of the raw material corresponding to the tip end portion of the guide by inductively heating the tip end portion of the guide with the induction heating coil disposed at the tip end portion of the guide. 
     [22] The upsetting apparatus as recited in the aforementioned Item  20  or  21 , wherein the tip end portion of the guide having the induction heating coil is connected to a main body of the guide via a heat insulating layer. 
     [23] The upsetting apparatus as recited in any one of the aforementioned Items  19  to  22 , wherein the heating means is capable of heating the portion of the diameter expansion scheduled portion of the raw material corresponding to the tip end portion of the guide into a half molten state. 
     [24] The upsetting apparatus as recited in any one of the aforementioned Items  19  to  23 , further comprising a first cooling means for cooling an inner surface of a portion of the insertion hole located at a basal end side of the guide relative to the tip end portion of the guide. 
     [25] The upsetting apparatus as recited in any one of the aforementioned Items  19  to  24 , 
     wherein a molding portion having a cavity for molding the diameter expansion scheduled portion of the raw material into a designed shape is extended from the receiving portion of the receiving die, and 
     wherein it is configured to expand a diameter of the diameter expansion scheduled portion of the raw material exposed between the tip end face of the guide and the receiving portion of the receiving die within the cavity of the receiving die. 
     [26] The upsetting apparatus as recited in the aforementioned Item  25 , further comprising a second cooling means for cooling a molding surface of the cavity of the receiving die. 
     [27] An upsetting apparatus, comprising: 
     a receiving die having receiving portions formed at both axial end portions and a holding hole communicating with both the receiving portions for holding a non-diameter-expansion scheduled portion of a raw material; 
     two guides each having an insertion hole for inserting and holding a diameter expansion scheduled portion of the raw material located at an axial end side in a buckling prevented state and in an axially slidable manner with respect to the non-diameter-expansion scheduled portion of the raw material and each having a raw material outlet portion constituted by one end opening of the insertion hole formed at the tip end face; 
     two pressurizing means each for pressurizing the diameter expansion scheduled portion of the raw material disposed in the insertion hole of each guide in the axial direction; 
     two guide driving means each for moving each guide in a direction opposite to a pressurizing direction of the corresponding diameter expansion scheduled portion of the raw material, 
     wherein it is configured to simultaneously expand diameters of both the diameter expansion scheduled portions of the raw material exposed between the tip end face of each guide and the corresponding receiving portion of the receiving die, 
     characterized in that the upsetting apparatus further comprises two heating means for locally heating a portion of each diameter expansion scheduled portion of the raw material corresponding to a tip end portion of the guide. 
     [28] The upsetting apparatus as recited in the aforementioned Item  27 , 
     wherein each heating means is an induction heating means having an induction heating coil, and 
     wherein it is configured to inductively heat the portion of each diameter expansion scheduled portion of the raw material corresponding to the tip end portion of each guide by the induction heating coil disposed at a tip end portion of each guide. 
     [29] The upsetting apparatus as recited in the aforementioned Item  27 , 
     wherein each heating means is an induction heating means having an induction heating coil, and 
     wherein it is configured to heat the portion of each diameter expansion scheduled portion of the raw material corresponding to the tip end portion of each guide by inductively heating the tip end portion of each guide with the induction heating coil disposed at the tip end portion of each guide. 
     [30] The upsetting apparatus as recited in the aforementioned Item  28  or  29 , wherein the tip end portion of each guide having the induction heating coil is connected to a main body of each guide via a heat insulating layer. 
     [31] The upsetting apparatus as recited in any one of the aforementioned Items  27  to  30 , wherein each heating means is capable of heating the portion of the diameter expansion scheduled portion of the raw material corresponding to the tip end portion of each guide into a half molten state. 
     [32] The upsetting apparatus as recited in any one of the aforementioned Items  27  to  31 , further comprising a first cooling means for cooling an inner surface of a portion of the insertion hole of each guide located at a basal end side of the guide relative to the tip end portion of the guide. 
     [33] The upsetting apparatus as recited in any one of the aforementioned Items  27  to  32 , 
     wherein a molding portion having a cavity for molding the diameter expansion scheduled portion of the raw material into a designed shape is extended from each receiving portion of the receiving die, and 
     wherein it is configured to simultaneously expand diameters of both the diameter expansion scheduled portions of the raw material exposed between the tip end face of each guide and each receiving portion of the receiving die within each cavity of the receiving die. 
     [34] The upsetting apparatus as recited in the aforementioned Item  33 , further comprising a second cooling means for cooling a molding surface of each cavity of the receiving die. 
     EFFECTS OF THE INVENTION 
     According to the invention of the aforementioned Item [1], since the upsetting method includes a step of receiving the diameter expansion scheduled portion of the raw material by the receiving portion of the receiving die and disposing the diameter expansion scheduled portion of the raw material in the insertion hole of the guide, and a step of expanding a diameter of the diameter expansion scheduled portion of the raw material exposed between the tip end face of the guide and the receiving portion of the receiving die by moving the guide in a direction opposite to a pressurizing direction of the diameter expansion scheduled portion of the raw material while pressurizing the diameter expansion scheduled portion of the raw material with a pressurizing means in an axial direction, after the step of disposing the diameter expansion scheduled portion of the raw material, the buckling of the diameter expansion scheduled portion of the raw material can be prevented. 
     Furthermore, at the diameter expansion step, since only the portion of the diameter expansion scheduled portion of the raw material corresponding to the tip end portion of the guide will be locally deteriorated in deformation resistance by locally heating the portion of the diameter expansion scheduled portion of the raw material corresponding to the tip end portion of the guide with the heating means, the molding pressure can be reduced. 
     On the other hand, the portion of the diameter expansion scheduled portion of the raw material located at the basal end side of the guide relative to the tip end portion thereof does not decrease in deformation resistance. This can prevent an increase of the molding pressure caused by a radially outward expansion of the raw material within the insertion hole of the guide and an increase of the molding pressure caused by introduction of a part of the material of the diameter expansion scheduled portion of the raw material into the gap between the pressurizing member of the pressurizing means (e.g., a punch) and the insertion hole. 
     According to the present invention as recited in the aforementioned Item [2], the portion of the diameter expansion scheduled portion of the raw material corresponding to the tip end portion of the guide can be heated assuredly in an extremely efficient manner. 
     According to the present invention as recited in the aforementioned Item [3], the portion of the diameter expansion scheduled portion of the raw material corresponding to the tip end portion of the guide can be heated assuredly in an efficient manner. 
     According to the present invention as recited in the aforementioned Item [4], it can be restrained to transfer the heat of the tip end portion of the guide to the main body of the guide by the heat insulating layer. Therefore, it can be assuredly prevented that the portion of the diameter expansion scheduled portion of the raw material located at the basal side with respect to the tip end portion of the guide is heated. 
     According to the present invention as recited in the aforementioned Item [5], the molding pressure can be remarkably reduced. 
     According to the present invention as recited in the aforementioned Item [6], it can be assuredly prevented that the portion of the diameter expansion scheduled portion of the raw material located at the basal end side of the guide relative to the tip end portion of the guide is heated. 
     According to the present invention as recited in the aforementioned Item [7], the upsetting method for expanding the diameter expansion scheduled portion of the raw material in diameter within the cavity, i.e., the restriction upset forming method, has the aforementioned effects. 
     Furthermore, by heating the portion of the diameter expansion scheduled portion of the raw material corresponding to the tip end portion of the guide, the plastic flow of the material of the diameter expansion scheduled portion in the cavity will be enhanced. As a result, even in cases where the configuration of the cavity is complex, the material of the diameter expansion scheduled portion can be sequentially filled in the cavity, and a diameter expanded portion having no material-lacked portion can be formed. 
     According to the present invention as recited in the aforementioned Item [8], at the time of the diameter expansion, the crystal growth in the diameter expansion scheduled portion of the raw material within the cavity of the receiving die can be restrained. 
     According to the present invention as recited in the aforementioned Item [9], the aforementioned effects can be attained in manufacturing an upset forged article. 
     According to the present invention as recited in the aforementioned Item [10], the same effects as mentioned in the aforementioned Item [1] can be attained. Furthermore, an upset forged article having diameter expanded portions at both the axial side portions can be manufactured efficiently. 
     According to the present invention as recited in the aforementioned Item [11], the same effects as mentioned in the aforementioned Item [2] can be attained. 
     According to the present invention as recited in the aforementioned Item [12], the same effects as mentioned in the aforementioned Item [3] can be attained. 
     According to the present invention as recited in the aforementioned Item [13], the same effects as mentioned in the aforementioned Item [4] can be attained. 
     According to the present invention as recited in the aforementioned Item [14], the same effects as mentioned in the aforementioned Item [5] can be attained. 
     According to the present invention as recited in the aforementioned Item [15], the same effects as mentioned in the aforementioned Item [6] can be attained. 
     According to the present invention as recited in the aforementioned Item [16], the same effects as mentioned in the aforementioned Item [7] can be attained. 
     According to the present invention as recited in the aforementioned Item [17], the same effects as mentioned in the aforementioned Item [8] can be attained. 
     According to the present invention as recited in the aforementioned Item [18], the aforementioned effects as mentioned can be attained in manufacturing an upset forged article having diameter expanded portions at both the axial side portions. 
     According to the present inventions as recited in the aforementioned Items [19] to [26], an upsetting apparatus preferably used for the upsetting method according to any one of the inventions as recited in the aforementioned Items [1] to [8]. 
     According to the present inventions as recited in the aforementioned items [27] to [34], an upsetting apparatus preferably used for the upsetting method according to any one of the inventions as recited in the aforementioned Items [10] to [17]. 
    
    
     
       BRIEF EXPLANATION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing a guide of an upsetting apparatus according to a first embodiment of the present invention. 
         FIG. 2  is a cross-sectional view of the guide showing a state in which a diameter expansion scheduled portion of a raw material is disposed in an insertion hole of the guide. 
         FIG. 3  is a cross-sectional view of the upsetting apparatus in a state before expanding the diameter expansion scheduled portion of the raw material. 
         FIG. 4  is a cross-sectional view of the upsetting apparatus in a state in which the diameter expansion scheduled portion of the raw material is being expanded in diameter. 
         FIG. 5  is a cross-sectional view of the upsetting apparatus in a state after expanding the diameter expansion scheduled portion of the raw material. 
         FIG. 6  is a perspective view of an upsetting article formed by the upsetting apparatus. 
         FIG. 7  is an explanatory view of the upsetting apparatus according to the second embodiment of the present invention and a cross-sectional view of the upsetting apparatus in a state before expanding the diameter expansion scheduled portion of the raw material. 
         FIG. 8  is a cross-sectional view of the upsetting apparatus in the middle of expanding the diameter expansion scheduled portion of the raw material. 
         FIG. 9  is a cross-sectional view of the upsetting apparatus in a state after expanding the diameter expansion scheduled portion of the raw material. 
         FIG. 10  is a perspective view of an upset forged article formed by the upsetting apparatus. 
     
    
    
     DESCRIPTION OF REFERENCE NUMERALS 
     
         
           1  . . . material 
           2  . . . diameter expansion scheduled portion 
           3  . . . non-diameter-expansion scheduled portion 
           5 A,  5 B . . . upset forged article 
           6  . . . diameter expanded portion 
           10 A,  10 B . . . upsetting apparatus 
           11  . . . receiving die 
           12  . . . holding hole 
           13  . . . receiving portion 
           14  . . . molding portion 
           15  . . . cavity 
           20  . . . guide 
           21  . . . tip end portion of the guide 
           22  . . . guide main body 
           23  . . . insertion hole 
           23   a  . . . raw material outlet portion 
           24  . . . heat insulating layer 
           27  . . . guide driving means 
           30  . . . pressurizing means 
           31  . . . punch 
           32  . . . punch driving means 
           40  . . . heating means 
           41  . . . induction heating means 
           42  . . . induction heating coil 
           43  . . . power source portion 
           50  . . . first cooling means 
           51  . . . cooling liquid passage 
           55  . . . second cooling means 
           56  . . . cooling jacket 
         S . . . diameter expanded space 
       
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Next, some preferable embodiments of the present invention will be explained with reference to the drawings. 
       FIGS. 1 to 5  are explanatory drawings of an upsetting apparatus  10 A and an upsetting method according to a first embodiment of the present invention. In  FIG. 3 , “ 1 ” denotes a bar-shaped raw material. 
     In  FIG. 6 , “ 5 A” denotes an upset forged article obtained by an upsetting method using the upsetting apparatus  10 A of the first embodiment. This upset forged article  5 A has diameter expanded portions  6  each having an approximately spindle-shape (or approximately oval sphere-shape) and integrally formed at axial ends of a bar-shaped shaft  7 . The shaft portion  7  is straight. Each diameter expanded portion  6  is formed to have an even thickness increased in the peripheral direction thereof. 
     This upset forged article  5 A is used as a preform for manufacturing a prescribed product. Accordingly, in the present invention, the upsetting apparatus  10 A can be recognized as a preform manufacturing apparatus, and the upsetting method can be recognized as a preform manufacturing method. 
     In this embodiment, this upset forged article  5 A can be used as a preform for manufacturing, for example, a vehicle arm for use in, e.g., an automobile or a railroad vehicle. Each diameter expanded portion  6  of this upset forged article  5 A is a portion which will be subjected to after processing to form a connecting portion (e.g., bush mounting portion or york portion) to be connected to another member. In the present invention, this upset forged article  5 A can be an article to be used as, other than a preform for manufacturing a vehicle arm, a preform for manufacturing, for example, a double-headed piston for a compressor, etc. 
     The raw material  1  is a bar-shaped member as shown in  FIG. 3 , more specifically a straight solid round bar-shaped member. The raw material  1  is made of a metallic material, more specifically aluminum or aluminum alloy material. The cross-sectional shape of the raw material  1  is round, and the diameter of the raw material  1  is set to be constant in the axial direction. 
     The axial central portion of this raw material  1  is a non-diameter-expansion scheduled portion  3 . The portions of the raw material  1  located at axial both sides with respect to the non-diameter-expansion scheduled portion  3 , i.e., axial end portions of this raw material  1 , are diameter expansion scheduled portions  2 . The non-diameter-expansion scheduled portion  3  of the raw material  1  corresponds to the shaft portion  7  of the upset forged article  5 A. 
     In the present invention, material of the raw material  1  is not limited to aluminum or aluminum alloy, and can be, for example, brass, copper (including its alloy), or steel, or can be plastic. The cross-sectional shape of the raw material  1  is not limited to a round shape, and can be, for example, a polygonal shape, such as, e.g., a quadrangular shape or a hexagonal shape. Further, the raw material  1  can be made of, for example, an extruded member, or can be a continuously casted rolled member manufactured by a properch method etc., or can be a member manufactured by any other methods. 
     The length of the raw material  1  is, for example, 50 to 1,000 mm, and the diameter is, for example, 10 to 30 mm (more specifically 16 mm or the like). In the upset forged article  5 A, for example, the maximum diameter of the diameter expanded portion  6  is 30 to 100 mm (more specifically 50 mm or the like), and the length of the diameter expanded portion  6  is 10 to 100 mm, and the length of the shaft portion  7  is 20 to 300 mm (more specifically 160 mm or the like). In the invention, however, the size of the raw material  1  and the size of each portion of the upset forged article  5 A are not limited to the aforementioned sizes. For example, the size of the raw material  1  and the size of each portion of the upset forged article  5 A can be set so as to attain objects of the present invention in accordance with the production of the desired product, such as, e.g., a vehicle arm. 
     As shown in  FIG. 3 , the upsetting apparatus  10 A is equipped with a receiving die  11 , two guides  20  and  20 , two heating means  40  and  40 , two pressurizing means  30  and  30 , and two guide driving means  27  and  27 . 
     The receiving die  11  is provided with receiving portions  13  at the axial both ends. Each receiving portion  13  is configured to receive the diameter expansion scheduled portion  2  of the raw material  1 , or more specifically to receive the material of the diameter expansion scheduled portion  2  at the time of expanding the diameter of each diameter expansion scheduled portion  2  of the raw material  1 . 
     This receiving die  11  has a holding hole  12  extending in the axial direction and communicated with both the receiving portions  13  and  13 . Thus, each receiving portion  13  has an end opening of the holding hole  12 . This holding hole  12  is configured to hold the non-diameter-expansion scheduled portion  3  of the raw material  1  in a buckling prevented state and in an axial movement prevented state. This holding hole  12  can also be recognized as a raw material attaching hole for attaching the raw material  1  to the receiving portions  13 . The cross-sectional shape of the holding hole  12  corresponds to the cross-sectional shape of the non-diameter-expansion scheduled portion  3  of the raw material  1 , i.e., a round cross-sectional shape. The diameter of the holding hole  12  is set to be approximately the same as the diameter of the non-diameter-expansion scheduled portion  3  of the raw material  1 . 
     Furthermore, the receiving die  11  is divided into a plurality of members (e.g., two pieces of members) with dividing surfaces (not shown) perpendicular to the holding hole  12 . Thus, by disposing the non-diameter-expansion scheduled portion  3  of the raw material  1  between the divided grooves of the holding hole  12  of the plurality of divided members constituting the holding hole  12 , and then combining the plurality of divided members to unify them, the non-diameter-expansion scheduled portion  3  of the raw material  1  is disposed in the holding hole  12  in a slightly tightly fitted manner. With this, each diameter expansion scheduled portion  3  of the raw material  1  is received by the corresponding receiving portion  13  of the receiving die  11 , and the non-diameter-expansion scheduled portion  3  of the raw material  1  is held in the holding hole  12  in a buckling prevented state and in the axial movement prevented state. 
     Two guides  20  and  20  are the same in structure. Each guide  20  has, as shown in  FIG. 2 , an insertion hole  23  for axially inserting and holding the corresponding diameter expansion scheduled portion  2  of the raw material  1  in a buckling prevented state. This insertion hole  23  is penetrated from the basal end of the guide  20  to the tip end thereof. Therefore, as shown in  FIGS. 1 and 2 , at the tip end face  21   a  of the guide  20 , a raw material outlet portion  23   a  which is one end opening portion of the insertion hole  23  is provided. While, at the basal end face of the guide  20 , a raw material inlet portion which is the other end opening portion of the insertion hole  23  is provided. 
     This insertion hole  23  is designed for guiding the diameter expansion scheduled portion  2  of the raw material  1  inserted and disposed in the insertion hole  23  to the diameter expanding space S between the tip end face  21   a  of the guide  20  and the receiving portion  13  of the receiving die  11 . In this first embodiment, this diameter expanding space S is a space in which the diameter expansion scheduled portion  2  of the raw material  1  can be freely expanded in diameter, i.e., a free diameter expanding space. 
     The cross-sectional shape of the insertion hole  23  of the guide  20  is a shape corresponding to the cross-sectional shape of the diameter expansion scheduled portion  2  of the raw material  1 , i.e., a round cross-sectional shape. Furthermore, the diameter of the insertion hole  23  is set to be the same as or slightly larger than the diameter of the diameter expansion scheduled portion  2  of the raw material  1 . With this, the insertion hole  23  is configured such that the diameter expansion scheduled portion  2  of the raw material  1  can be inserted and disposed in the insertion hole  23  in a buckling prevented state and in an axially slidably movable manner. 
     Furthermore, as shown in  FIGS. 1 and 2 , the tip end portion  21  of the guide  20  is formed to be smaller in diameter than the basal end side portion of the guide  20 . In this embodiment, the basal end side portion of the guide  20  will be referred to as a “guide main body  22 .” 
     The two heating means  40  and  40  are the same in structure. As shown in  FIG. 2 , each heating means  40  is designed for locally heating the portion  2   a  of the diameter expansion scheduled portion  2  of the raw material  1  corresponding to the tip end portion  21  of the guide  20 . In this embodiment, each heating means  40  is an induction heating means  41  having an induction heating coil  42  and a power supplying portion  43  for supplying AC current (or AC voltage). Furthermore, the reference numeral “ 44 ” denotes a lead wire for connecting the induction heating coil  42  and the power supplying portion  43 . 
     The induction heating coil  42  is arranged in the tip end portion  21  of the guide  20  so as to surround the insertion hole  23 . In this embodiment, the induction heating coil  42  is embedded in the tip end portion  21  of the guide  20 . 
     The tip end portion  21  of the guide  20  is formed by, for example, a hard nonconductive material having heat resistance such as ceramics, or a hard conductive material having heat resistance (e.g., heat resistant metallic material) such as steel material. On the other hand, the portion of the guide  20  located at the basal end side thereof relative to the tip end portion  21 , i.e., the guide main body  22 , is made of metallic material such as, e.g., steel material. 
     This induction heating means  41  is configured to locally inductively heat the portion  2   a  of the diameter expansion scheduled portion  2  of the raw material  1  corresponding to the tip end portion  21  of the guide  20  by supplying current (applying voltage) having a prescribed frequency to the induction heating coil  42  by the power supplying portion  43 . Further, this induction heating means  41  is configured to heat the portion  2   a  of the diameter expansion scheduled portion  2  of the raw material  1  corresponding to the tip end portion  21  of the guide  20  in a half molten state by adjusting the current supplying amount or the like to the induction heating coil  42 . 
     Furthermore, the tip end portion  21  of the guide  20  is integrally provided with a flange portion  21   b . This flange portion  21   b  is arranged at the end portion of the guide main body  22  via a heat insulating layer  24 . With this state, the flange portion  25 , the heat insulating layer  24  and the guide main body  22  are mutually integrally connected with a plurality of connecting bolts  25  and  25 . Thus, the tip end portion  21  of the guide  20  is connected to the guide main body  22  via the heat insulating layer  24 . In this guide  20 , the heat of the tip end portion  21  of the guide  20  is restrained from being conducted to the guide main body  22  by the heat insulating layer  24 . The heat insulating layer  24  is made of, for example, an alumina plate or a zirconia plate. 
     Furthermore, this upsetting apparatus  10 A is equipped with two first cooling means  50  and  50  for cooling the periphery of the insertion hole  23  in the guide main body  22  of each guide  20 . 
     Both the first cooling means  50  and  50  are the same in structure. Each first cooling means  50  is configured to cool the peripheral surface of the insertion hole  23  in the guide main body  22  by passing a cooling liquid such as a cooling water through one or a plurality of cooling liquid passages  51  formed in the inside of the guide main body  50 . “ 52   a ” denotes a supplying pipe for supplying a cooling liquid to the cooling liquid passage  51 , and “ 52   b ” denotes a discharging pipe for discharging the cooling liquid from the cooling liquid passage  51 . Further, “ 53 ” denotes a flow direction of the cooling liquid. 
     Two pressurizing means  30  and  30  are the same in structure. Each pressurizing means  30  is designed to pressurize each diameter expansion scheduled portion  2  of the raw material  1  inserted and disposed in the insertion hole  23  of the guide  20  in the axial direction. This pressurizing means  30  has a punch  31  and a punch driving portion  32  for driving the punch  31 , and is configured to pressurize the diameter expansion scheduled portion  2  of the raw material  1  in the axial direction with the punch  31  by driving the punch  31  by the punch driving portion  32 . As the driving source of the punch driving portion  32 , for example, a fluid pressure cylinder (e.g., an oil cylinder or a gas pressure cylinder) can be used. 
     Both the guide driving means  27  and  27  are the same in structure. Each guide driving means  27  is designed to move the guide  20  in a direction opposite to the pressurizing direction of the corresponding diameter expansion scheduled portion  2  of the raw material  1 . As the driving source of this guide driving means  27 , for example, a fluid pressure cylinder (e.g., an oil cylinder or a gas pressure cylinder) can be used. 
     Next, an upsetting method using the upsetting apparatus  10 A of this first embodiment will be explained below. 
     Initially, as shown in  FIG. 3 , the non-diameter-expansion scheduled portion  3  of the raw material  1  is inserted and disposed in the holding hole  12  of the receiving die  11 . With this, each diameter expansion scheduled portion  2  of the raw material  1  is received by the corresponding receiving portion  13  of the receiving die  11 , while the non-diameter-expansion scheduled portion  3  of the raw material  1  is held in the holding hole  12  in a buckling prevented state and in the axial movement prevented manner. 
     Furthermore, both the diameter expansion scheduled portions  2  of the raw material  1  are inserted and disposed in the corresponding insertion hole  23  of the guide, respectively [Disposing step of a raw material diameter expansion scheduled portion]. With this, each diameter expansion scheduled portion  2  of the raw material  1  is inserted and held in the insertion hole  23  in a buckling prevented state and in an axially slidably movable manner. 
     In this disposing step of the diameter expansion scheduled portion  2  of the raw material  1 , as mentioned above, after receiving the diameter expansion scheduled portion  2  of the raw material  1  by inserting and disposing the non-diameter-expansion scheduled portion  3  of the raw material  1  in the holding hole  12  of the receiving die  11 , the diameter expansion scheduled portion  2  of the raw material  1  can be inserted and disposed in the insertion hole  23  of the guide  20 . Alternatively, after inserting and disposing the diameter expansion scheduled portion  2  of the raw material  1  in the insertion hole  23  of the guide  20 , the diameter expansion scheduled portion  2  of the raw material  1  can be received by the receiving portion  13  of the receiving die  11  by inserting and disposing the non-diameter-expansion scheduled portion  3  of the raw material  1  in the holding hole  12  of the receiving die  11 . 
     Furthermore, current of a prescribed frequency is supplied to the induction heating coil  42  of each induction heating means  41  by the power source portion  43  to locally inductively heat the portion  2   a  of each diameter expansion scheduled portion  2  of the raw material  1  corresponding to the tip end portion  21  of the guide to a predetermined temperature. 
     This heating temperature can be any temperature at which the deformation resistance of the portion  2   a  of the raw material  1  decreases, and not specifically limited. The preferable heating temperatures can be concretely exemplified as follows. 
     For example, in cases where the raw material  1  is made of aluminum or aluminum alloy, the preferable heating temperature range is, e.g., 200 to 580° C. (more preferably 350 to 540° C.). In the case of heating the prescribed portion  2   a  of the raw material  1  into a half-molten state, the preferable heating temperature range is, e.g., 580 to 625° C. (more preferably 600 to 615° C.). The present invention does not require that the heating temperature falls within the aforementioned ranges. 
     Further, a cooling liquid, such as a cooling water, of a normal temperature is passed through the cooling liquid passage  51  of the guide main body  22  of each guide  20  to cool the periphery of the insertion hole  23  in the guide main body  22 . Thus, the portion  2   b  of the diameter expansion scheduled portion  2  of the raw material  1  located at the basal end side of the guide  20  relative to the tip end portion  21  of the guide  20  will be locally cooled to the predetermined temperature due to the contact with the periphery of the insertion hole  23 . 
     In this case, the preferable cooling temperature range can be, for example, 30 to 85° C. (more preferably 40 to 60° C.). In the present invention, however, it is not required that the cooling temperature falls within the aforementioned ranges. 
     Subsequently, while keeping this state, each guide  20  is moved in a direction opposite to the pressurizing direction of the corresponding diameter expansion scheduled portion  2  of the raw material  1  with the guide driving means  27  while simultaneously pressurizing both the diameter expansion scheduled portions  2  of the raw material  1  with the corresponding punch  31  of the pressurizing means  30 . With this, as shown in  FIG. 4 , both the diameter expansion scheduled portions  2  of the raw material  1  exposed between the tip end face  21   a  of each guide  20  and the corresponding receiving portion  13  of the receiving die  11  are simultaneously expanded in diameter at the diameter expanding space S between the tip end face  21   a  of each guide  20  and the receiving portion  13  of the receiving die  11  [Expansion Step]. In this first embodiment, the diameter expanding space S is a free diameter expanding space as mentioned above. 
     The moving speed of the guide  20  and the pressurizing speed of the diameter expansion scheduled portion  2  of the raw material  1  by the punch  31  are set in accordance with the diameter expansion designed configuration of the diameter expansion scheduled portion  2  of the raw material  1 . These speeds can be constant or variable. 
     As shown in  FIG. 5 , when each diameter expansion scheduled portion  2  of the raw material  1  is formed into the designed shape, the movement of the guide  20  and the pressurization by the punch  31  are stopped. 
     Subsequently, by taking out the raw material  1  from the receiving die  11 , the desired upset forged article  5 A as shown in  FIG. 6  can be obtained. 
     The diameter expanded portion  6  of the obtained upset forged article  5 A as a preform is subjected to after processing according to need. 
     In this upsetting method, at the time of initiating the pressurization of the diameter expansion scheduled portion  2  of the raw material  1  by the punch  31 , i.e., at the time of initiating the diameter expansion of the diameter expansion scheduled portion  2  of the raw material  1 , the length of the diameter expansion scheduled portion  2  of the raw material  1  exposed between the tip end face  21   a  of the guide  20  and the receiving portion  13  of the receiving die  11  is set to be not longer than the buckling limit length of the diameter expansion scheduled portion  2  (preferably shorter than the buckling limit length). 
     Further, in this upsetting method, a time lag can be set between the initiation of pressurization of the diameter expansion scheduled portion  2  of the raw material  1  by the punch  31  and the initiation of movement of the guide  20 . By doing so, the cross-sectional area of the diameter expansion scheduled portion  2  is increased at the diameter expansion early stage, which can prevent buckling more assuredly. 
     Thus, the upsetting method of the first embodiment has the following effects. 
     That is, this upsetting method includes the step of receiving the diameter expansion scheduled portion  2  of the raw material  1  by the receiving portion  13  of the receiving die  11  and disposing the diameter expansion scheduled portion  2  of the raw material  1  in the insertion hole  23  of the guide  20  and the step of expanding the diameter of the diameter expansion scheduled portion  2  of the raw material  1  exposed between the tip end face  21   a  of the guide  20  and the receiving portion  13  of the receiving die  11  by moving the guide  20  in a direction opposite to the pressurizing direction of the diameter expansion scheduled portion  2  of the raw material  1  while pressurizing the diameter expansion scheduled portion  2  of the raw material  1  by the pressurizing means  30  after the disposing step. Therefore, the buckling of the diameter expansion scheduled portion  2  of the raw material  1  can be prevented. 
     In the first embodiment, since the diameter expansion scheduled portion  2  of the raw material  1  is expanded in diameter in the free diameter expanding space S between the tip end face  21   a  of the guide  20  and the receiving portion  13  of the receiving die  11 , in detail, the upsetting method and the upsetting apparatus  10 A of this first embodiment can be categorized into a free upsetting method and a free upsetting apparatus, respectively. 
     Furthermore, at the diameter expansion step, the portion  2   a  of the diameter expansion scheduled portion  2  of the raw material  1  corresponding to the tip end portion  21  of the guide  20  is locally heated by the heating means  40 . As a result, only the portion  2   a  among the diameter expansion scheduled portion  2  of the raw material  1  corresponding to the tip end portion  21  of the guide  20  is locally decreased in deformation resistance. Therefore, the molding pressure can be decreased. 
     On the other hand, the portion  2   b  located at the basal end side among the diameter expansion scheduled portion  2  of the raw material  1  will not be heated, therefore the portion  2   b  does not decrease in deformation resistance. Therefore, the end portion of the diameter expansion scheduled portion  2  of the raw material  1  is still hard and hardly deformed by the molding pressure imparted by the punch  31 . This can prevent the possible molding pressure increase caused by introduction of a part of the material of the diameter expansion scheduled portion  2  into the gap between the punch  31  and the insertion hole  23  of the guide  20 . This in turn can prevent a problem that the processing cannot be performed. Furthermore, the possible molding pressure increase caused by the radially outward expansion of the diameter expansion scheduled portion  2  of the raw material  1  in the insertion hole  23  of the guide  20  can also be prevented. Therefore, even in cases where the length of the diameter expansion scheduled portion  2  of the raw material  1  to be inserted in the insertion hole  23  of the guide  20  is long as well as short, the molding pressure can be decreased assuredly. 
     Furthermore, the heating means  40  is an induction heating means  41  having an induction heating coil  42 , and the portion  2   a  of each diameter expansion scheduled portion  2  of the raw material  1  corresponding to the tip end portion  21  of the guide  20  is inductively heated by the induction heating coil  42  disposed at the tip end portion  21  of each guide  20 . Therefore, the predetermined portion  2   a  of the diameter expansion scheduled portion  2  of the raw material  1  can be heated assuredly and very efficiently. 
     Further, in cases where the prescribed portion  2   a  of the diameter expansion scheduled portion  2  of the raw material  1  is heated into a half-molten state by increasing the heating temperature, the molding pressure can be decreased considerably. This upsetting can be categorized into a Thixo molding. 
     Further, since the tip end portion  21  of each guide  20  is connected to the guide main body  22  via the heat insulating layer  24 , the heat of the tip end portion  21  of the guide  20  can be assuredly prevented from being transferred to the guide main body  22 . Therefore, it can be assuredly prevented that the portion  2   b  of the diameter expansion scheduled portion  2  of the raw material  1  located at the basal side with respect to the tip end portion  21  of the guide  20  is heated. 
     In addition, at the diameter expansion step, the diameter expansion is performed with the periphery of the insertion hole  23  of the guide main body  22  of the guide  20  cooled by the first cooling means  50 . Therefore, the portion  2   b  of the diameter expansion scheduled portion  2  of the raw material  1  located at the basal end side of the guide  20  relative to the tip end portion  21  of the guide  20  is prevented from being heated more assuredly. 
     Further, at the diameter expansion step, both the diameter expansion scheduled portions  2  of the raw material  1  are simultaneously expanded in diameter. This enables efficient production of an upset forged article  5 A having diameter expanded portions  6  and  6  formed at both axial side portions. 
       FIGS. 7 to 9  are explanatory views showing an upsetting apparatus and an upsetting method according to a second embodiment of the present invention. 
     In  FIG. 10 , “ 5 B” denotes an upset forged article produced using an upsetting apparatus  10 B of the second embodiment. This upset forged article  5 B has a bar-shaped shaft portion  7  and approximately hexagonal plate-shaped diameter expanded portions  6  formed at both axial side portions of the shaft portion  7 . Each diameter expanded portion  6  is a portion to be subjected to after processing to produce a connecting portion (e.g., bush mounting portion) to be connected to another member. As such after processing, for example, hole forming processing for forming a bush mounting holding hole in the diameter expanded portion  6  can be exemplified. In the present invention, the shape of the diameter expanded portion  6  is not limited to a polygonal shape such as an approximately hexagonal shape, and can be, for example, a round plate shape or a columnar shape. 
     Next, the structure of the upsetting apparatus  10 B of this second embodiment will be explained while focusing structures different from those of the upsetting apparatus  10 A of the first embodiment. 
     In the upsetting apparatus  10 B of this second embodiment, as shown in  FIG. 7 , molding portions  14  each having a closed cavity  15  for forming the diameter expansion scheduled portion  2  of the raw material  1  into a designed shape are integrally extended toward the axial end sides from each receiving portion  13  of the receiving die  11 . Thus, each receiving portion  13  forms a part of a molding surface of the cavity  15 . A holding hole  12  is formed through the receiving die  11  so as to be communicated with both receiving portions  13  and  13 , i.e., communicated with both cavities  15  and  15 . 
     This upsetting apparatus  10 B is configured to simultaneously expand both the diameter expansion scheduled portions  2  and  2  of the raw material  1  exposed between the tip end face  21   a  of each guide  20  and the corresponding receiving portion  13  of the receiving die  11  within the corresponding cavities  15  of the receiving die  11 . Therefore, the upsetting method and the upsetting apparatus of this second embodiment can be categorized in a restriction upsetting method and a restriction upsetting apparatus, respectively. The cavity  15  corresponds to the diameter expanding space S in which the diameter expansion scheduled portion  2  of the raw material  1  will be expanded in diameter. 
     Further, this upsetting apparatus  10 B is provided with at least one (two in this embodiment) second cooling means  55  and  55  for cooling the molding surface of each cavity  15  of the receiving die  11 . Each second cooling means  55  has a cooling jacket  56  mounted on the right and left side portions of the die  11  so as to cover both the molding portions  14  and  14  of the receiving die  11 . And, it is configured to cool the molding surface of each cavity  15  of the receiving die  11  by supplying a cooling liquid such as a cooling water to the cooling jacket  56 . The arrow  57  denotes the flow direction of the cooling liquid. 
     Further, at the axial end portion of each molding portion  14  of this receiving die  14 , an insertion hole  16  for inserting the tip end portion  21  of the guide  20  is provided. 
     The other structure of the upsetting apparatus  10 B of this second embodiment is the same as that of the upsetting apparatus  10 A of the first embodiment. 
     Next, the upsetting method using this second upsetting apparatus  10 B of the second embodiment will be explained below while focusing the points different from the upsetting method of the first embodiment. 
     In this second embodiment, initially, as shown in  FIG. 7 , the non-diameter-expansion scheduled portion  3  of the raw material  1  is disposed in the holding hole  13  of the receiving die  11 . Thus, each diameter expansion scheduled portion  2  of the raw material  1  is received by the corresponding receiving portion  13  of the receiving die  11 . Further, both the diameter expansion scheduled portions  2  of the raw material  1  are disposed in the insertion holes  23  of the guides  20 , and the tip end portion  21  of each guide  20  is inserted in each cavity  15  of the receiving die  11  via the insertion hole  16  [Disposing step of disposing the raw material diameter expansion scheduled portion]. 
     Further, current of a prescribed frequency is supplied to the induction heating coil  42  of each induction heating means  41  by the power source portion  43  to inductively heat the portion  2   a  of each diameter expansion scheduled portion  2  of the raw material  1  corresponding to the tip end portion  21  of the guide  20  to a predetermined temperature. 
     Further, a cooling liquid, such as a cooling water, of a normal temperature is flowed through the cooling liquid passage  51  of the guide main body  22  of each guide  20  to cool the periphery of the insertion hole  23  of the guide main body  22 . 
     Further, a cooling liquid, such as a cooling water, of a normal temperature is flowed through the cooling jacket  56  of the second cooling means  55  to cool the molding surface of each cavity  15  of the receiving die  11  to a predetermined temperature. 
     In this case, the preferable cooling temperature range is, for example, 30 to 80° C. (more preferably 30 to 60° C.). In the present invention, however, it is not required that the cooling temperature falls within the ranges. 
     Next, while keeping this state, each guide  20  is moved in a direction opposite to the pressurizing direction of the corresponding diameter expansion scheduled portion  2  of the raw material  1  by the guide driving means  27  while simultaneously pressurizing both the diameter expansion scheduled portions  2  of the raw material  1  with the corresponding punch  31  of the pressurizing means  30 . Thus, as shown in  FIG. 8 , both the diameter expansion scheduled portions  2  of the raw material  1  exposed between the tip end surface  21   a  of each guide  20  and the corresponding receiving portion  13  are expanded in diameter in the corresponding cavity  15  of the receiving die  11  respectively. [Diameter expansion step]. 
     At this diameter expansion step, by moving the guide  20  in a direction opposite to the pressurizing direction while pressurizing each diameter expansion scheduled portion  2  of the raw material  1  in the axial direction, as shown in  FIG. 8 , the material of each diameter expansion scheduled portion  2  of the raw material  1  will be filled sequentially in the cavity  15  of the receiving die  11 . 
     Then, as shown in  FIG. 9 , when the material of each diameter expansion scheduled portion  2  of the raw material  1  is filled in the entire cavity  15  of the receiving die  11  and each diameter expansion scheduled portion  2  of the raw material  1  is formed into a designed shape, the movement of the guide  20  and the pressurization by the punch  31  are stopped. 
     Thereafter, by taking out the raw material  1  from the receiving die  11 , a desired upsetting article  5 B as shown in  FIG. 10  can be obtained. 
     The diameter expanded portion  6  of the obtained upset forged article  5 A as a preform is subjected to after processing according to need. 
     Thus, the upsetting method of this second embodiment exerts the following effects in addition to the effects by the upsetting method of the first embodiment. 
     At the diameter expansion step, the diameter expansion is performed in a state in which the molding surface of each cavity  15  of the receiving die  11  is cooled by the cooling jacket  56  of the second embodiment  55 . Therefore, the crystal growth in the diameter expansion scheduled portion  2  of the raw material  1  within each cavity  15  can be restrained. 
     Further, heating of the portion  2   a  of the diameter expansion scheduled portion  2  of the raw material  1  corresponding to the tip end portion  21  of the guide  20  enhances the plastic flow of the material of the diameter expansion scheduled portion  2 . As a result, even in cases where the configuration of the cavity  15  is complicated, the material of the diameter expansion scheduled portion  2  can be sequentially filled in the cavity  15  under a lower molding pressure, and a diameter expanded portion  6  having no material-lacked portion can be formed. 
     In the first embodiment and the second embodiment, in either case, the portion  2   a  of each diameter expansion scheduled portion  2  of the raw material  1  corresponding to the tip end portion  21  of the guide is directly inductively heated by each induction heating coil  42 . In the present invention, however, it can be configured to inductively heat the tip end portion  21  of the guide  20  by each induction heating coil  42  to heat the portion  2   a  of the diameter expansion scheduled portion  2  of the raw material  1  corresponding to the tip end portion  21  of the guide  20 . In this case, the predetermined portion  2   a  of the diameter expansion scheduled portion  2  of the raw material  1  can be heated assuredly and efficiently. Furthermore, in this case, the tip end portion  21  of the guide  20  is preferably made of a hard conductive material having heat resistance (e.g., heat resistant metallic material) such as steel material. 
     Although several embodiments of the present invention were explained above, the present invention is not limited to these embodiments and can be modified in various manner. 
     For example, in the aforementioned embodiment, the non-diameter-expansion scheduled portion  3  of the raw material  1  is disposed in the holding hole  12  of the receiving die  11  and the diameter expansion scheduled portion  2  of the raw material  1  is received by the receiving portion  13  of the receiving die  11 . In the present invention, however, in cases where a raw material  1  has no non-diameter-expansion scheduled portion  3 , or the entire raw material  1  is a diameter expansion scheduled portion  2 , without providing the holding hole  12  of the receiving die  11 , the diameter expansion scheduled portion  2  of the raw material  1  can be received by the receiving portion  13  as follows. That is, it can be configured such that the end portion of the raw material  1  is brought into contact (preferably, pressure-contact) with a receiving portion  13  so that the raw material  1  is disposed approximately perpendicular to the receiving portion  13 . 
     Furthermore, in this embodiment, the heating means  40  is an induction heating means  41  having an induction heating coil  42 . In the present invention, however, the heating means  40  is not limited to an induction heating means  41 , and can be any other means, such as, e.g., an electrical heating means for electrically heating only the tip end portion  21  of the guide  20 . In this case, the predetermined portion  2   a  of the diameter expansion scheduled portion  2  of the raw material  1  will be heated via the tip end portion  21  of the guide  20 . 
     In the aforementioned embodiments, the pressurizing means  30  has a punch  31 . In the present invention, however, the pressurizing means  30  is not limited to a member having a punch  31 , and can be a member configured to move a gripping portion for gripping the raw material  1  so as to pressurize the diameter expansion scheduled portion  2  of the raw material  1  in the axial direction with the raw material  1  gripped by the gripping portion or any other means. 
     Furthermore, in the aforementioned embodiments, the raw material  1  has two diameter expansion scheduled portions  2 . In the present invention, however, the raw material  1  can have a single diameter expansion scheduled portion  2  at the axial one side portion of the raw material  1  or at the axial central portion thereof. In this case, the number of the receiving portion  13  of the receiving die  11  or that of the cavity  15  can be one. 
     In the present invention, the diameter expansion processing can be terminated with a part of the diameter expansion scheduled portion  2  of the raw material  1  remained in the insertion hole  23  of the guide  20 . As shown in the aforementioned embodiments, the diameter expansion processing can be terminated immediately after extruding the entire diameter expansion scheduled portion  2  from the insertion hole  23  of the guide  20  into the diameter expanding space S. 
     Needless to say, the upsetting method and the upsetting apparatus according to the present invention are not limited to a method or an apparatus for manufacturing a preform for a vehicle arm and can be used to manufacture various industrial product preforms, such as, e.g., a shaft preform, a frame preform, a connecting rod preform, a conform for a single head piston or a double-headed piston, or can also be used to manufacture a round-plate shaped forging raw material. 
     EXAMPLE 
     Next, concrete examples and comparative examples of the present invention will be explained. 
     Example 1 and Comparative Example 1 and 2 
     A bar-shaped raw material  1  made of aluminum alloy (material: A6061) having a diameter of 12 mm was prepared. The diameter expansion scheduled portion  2  of the raw material  1  was expanded in diameter under the conditions shown in Table 1 in accordance with the upsetting apparatus  10 A and the upsetting method of the aforementioned first embodiment. The molding pressures required to the processing were investigated. The results are shown in Table 1. 
     In this case, as shown Table 1, the length of the diameter expansion scheduled portion  2  of the raw material  1  in Example 1 was 200 mm, and the lengths thereof were 150 mm and 200 mm in comparative Examples 1 and 2, respectively. 
     
       
         
           
               
               
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Length of diameter 
                   
                 Heating 
                 Cooling 
                   
               
               
                   
                 expansion 
                 Heating 
                 temper- 
                 or Not- 
                 Molding 
               
               
                   
                 scheduled portion 
                 manner 
                 ature 
                 cooling 
                 pressure 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Example 
                 200 mm 
                 Partial 
                 500° C. 
                 Cooling 
                 8.0 × 10 7   
               
               
                 1 
                   
                 heating 
                   
                   
                 Pa 
               
               
                 Comp. 
                 150 mm 
                 Entire 
                 400° C. 
                 Not- 
                 7.1 × 10 8   
               
               
                 Ex. 1 
                   
                 heating 
                   
                 cooling 
                 Pa 
               
               
                 Comp. 
                 200 mm 
                 Entire 
                 400° C. 
                 Not- 
                 Unable to 
               
               
                 Ex. 2 
                   
                 heating 
                   
                 cooling 
                 process 
               
               
                   
               
            
           
         
       
     
     In the column “Heating manner” in Table 1, “Partial heating” means that the portion  2   a  of the diameter expansion scheduled portion  2  of the raw material  1  corresponding to the tip end portion  21  of the guide  20  was locally inductively heated by an induction heating coil  42 . “Entire heating” means that the entire raw material  1  was heated to a predetermined temperature by a heating furnace and thereafter the raw material  1  was immediately set to the upsetting apparatus and subjected to diameter expansion processing. 
     “Cooling or Not-cooling” means whether the periphery of the insertion hole  23  of the guide main body  22  was cooled by the first cooling means  50 . In this cooling, water of a normal temperature was used as the cooling liquid. The cooling temperature was 40° C. 
     As shown in Table 1, in Comparative Example 1, the length of the diameter expansion scheduled portion  2  of the raw material  1  was 150 mm. In this case, the molding pressure was 7.1×10 8  Pa which was very high. In Comparative Example 2, the length of the diameter expansion scheduled portion  2  of the raw material  1  was 200 mm. In this case, the molding pressure exceeded the maximum driving performance of the punch driving portion  32  in the middle of the processing. As a result, the processing could not performed. The reasons are as follows. That is, by pressurizing the diameter expansion scheduled portion  2  of the raw material  1  with the punch  31 , the end portion of the diameter expansion scheduled portion  2  of the raw material  1  pressurized with the punch  31  was crushed in the insertion hole  23  of the guide  20  by the molding pressure from the punch  31 . Furthermore, since the entire raw material  1  was heated, the end portion of the diameter expansion scheduled portion  2  was deteriorated in deformation resistance. Therefore, the end portion of the diameter expansion scheduled portion  2  became to be more easily crushed. Thus, a part of the material of the diameter expansion scheduled portion  2  was considerably introduced into the gap between the punch  31  and the insertion hole  23 . As a result, the molding pressure was increased and exceeded the maximum driving performance of the punch driving portion  32 . 
     To the contrary, in Example 1, the length of the diameter expansion scheduled portion  2  of the raw material  1  was 200 mm which was the same as in Comparative Example 2. In this case, however, the molding pressure was 8.0×10 7  Pa. Therefore, it was confirmed that the molding pressure can be decreased significantly. 
     This application claims priority to Japanese Patent Application No. 2005-330528 filed on Nov. 15, 2005, the entire disclosure of which is incorporated herein by reference in its entirety. 
     It should be understood that the terms and expressions used herein are used for explanation and have no intention to be used to construe in a limited manner, do not eliminate any equivalents of features shown and mentioned herein, and allow various modifications falling within the claimed scope of the present invention. 
     While the present invention may be embodied in many different forms, a number of illustrative embodiments are described herein with the understanding that the present disclosure is to be considered as providing examples of the principles of the invention and such examples are not intended to limit the invention to preferred embodiments described herein and/or illustrated herein. 
     While illustrative embodiments of the invention have been described herein, the present invention is not limited to the various preferred embodiments described herein, but includes any and all embodiments having equivalent elements, modifications, omissions, combinations (e.g., of aspects across various embodiments), adaptations and/or alterations as would be appreciated by those in the art based on the present disclosure. The limitations in the claims are to be interpreted broadly based on the language employed in the claims and not limited to examples described in the present specification or during the prosecution of the application, which examples are to be construed as non-exclusive. For example, in the present disclosure, the term “preferably” is non-exclusive and means “preferably, but not limited to.” In this disclosure and during the prosecution of this application, means-plus-function or step-plus-function limitations will only be employed where for a specific claim limitation all of the following conditions are present in that limitation: a) “means for” or “step for” is expressly recited; b) a corresponding function is expressly recited; and c) structure, material or acts that support that structure are not recited. In this disclosure and during the prosecution of this application, the terminology “present invention” or “invention” may be used as a reference to one or more aspect within the present disclosure. The language present invention or invention should not be improperly interpreted as an identification of criticality, should not be improperly interpreted as applying across all aspects or embodiments (i.e., it should be understood that the present invention has a number of aspects and embodiments), and should not be improperly interpreted as limiting the scope of the application or claims. In this disclosure and during the prosecution of this application, the terminology “embodiment” can be used to describe any aspect, feature, process or step, any combination thereof, and/or any portion thereof, etc. In some examples, various embodiments may include overlapping features. In this disclosure and during the prosecution of this case, the following abbreviated terminology may be employed: “e.g.” which means “for example;” and “NB” which means “note well.” 
     INDUSTRIAL APPLICABILITY 
     The present invention can be applied to an upsetting method and an upsetting apparatus used in manufacturing a product, such as, e.g., an arm or a piston for vehicles (e.g., cars, or railroad vehicles).