JP2008188610A - Method of forming cup-shaped molded body of bearing race - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a cup shape formed body of a bearing race, which method can suppress forging defects. <P>SOLUTION: In the method for manufacturing the cup shape formed body of the bearing race, (1) a round bar body 4 made of steel material is compressed in the axial direction by swaging it into a disk shape preform body 7, and (2) the preform body 7 is forged by means of a forging die set having a punch 8 and a die 9 into the cup shape formed body 1 composed of a cylindrical portion 2 and a bottom portion 3 provided at the lower end of the cylindrical portion 2. In this case, the condition of the forging is adjusted such that the diameter D of the corner circle on the end face of the preform body 7 in the swaging operation (1) is set within the range from 0.99 to 1.02 of the diameter Dm of the intermediate circle between the outside diameter and the inside diameter of the disk shape portion 10 at the upper end of the round bar shape downward projecting body 11 of the punch 8. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for forming a bearing race shape material, and more particularly to a method for forming a cup-shaped formed body of a bearing race by hot forging.

  Bearing races mainly used as automobiles and industrial machine parts are usually manufactured by forging. In this manufacturing method by forging, a cylindrical steel material is first compressed in the axial direction by an upsetting process to be formed into a disk-shaped preform. Next, the preform is put into a die of a forging die composed of a molding punch and a die by a molding process, the punch is lowered into the die, the preform is compressed, the material flows by compression, and the cylindrical portion And it is set as the cup-shaped molded object provided with the bottom part in the lower end of this cylindrical part. The molded body of the bearing race is completed by punching out the bottom from the molded body in the punching process.

  However, at the time of compression in the molding process, at the corner part between the upper part of the cylinder of the punch and the disk body, which is the last place where the material flows and fills, especially the corner part between the outer diameter of the disk body and the inner diameter of the die There is a problem that it is difficult to fill the material. For this reason, a lack of thickness may occur in the outer peripheral edge of the upper end of the cylindrical portion of the product shaped product. In order to prevent this lack of wall thickness, it is necessary to set a large forging load or adjust the clearance distance between the outermost diameter part of the upset preform in the molding process and the inner wall of the molding die. It was.

  In the hub inner ring forging method consisting of pre-forming in the conventional upsetting process, main forming in the forming process, and punching process of punching out, a cylindrical part, a bottom part, and a flange part that eliminate defects such as lack of wall and burrs are provided. In order to obtain a molded body, the diameter that is the outermost diameter of the preform is obtained from a multiple regression equation derived from the relationship between the mold shape obtained by CAE analysis and the diameter of the preform that is optimally filled in the mold. A method has been proposed in which the calculated value falls within the range of 0.95 to 1.05 times (see, for example, Patent Document 1).

  This method does not correspond to a molded body having a cylindrical portion and a bottom portion because of the difference in the target shape in that it has a flange portion. Moreover, although it is suitable for the defect suppression of the upper end outer diameter part in a cylindrical part, it does not respond to the defect suppression of the upper end inner diameter part of a cylindrical part.

JP 2003-31365 A

  On the other hand, a large forging load increases the load on the production equipment, and the material tends to flow out from a minute gap between the punch and the die during molding, which may cause a large burr. The burrs need to be removed in a subsequent process, and an increase in forging load is a factor that lowers the manufacturing cost and productivity of the bearing race. In addition, in the method of adjusting the clearance distance between the outermost diameter part of the upsetting shape and the inner diameter wall of the molding die in the molding process, the filling status of the upper end part of the inner and outer diameters must be confirmed without actually making a prototype. Can not do it. Therefore, at present, there is no effective and clear forging process design guideline regarding the problem of unfilling the upper end portions of the inner and outer diameters of the bearing race product.

  The present invention has been made in view of the above problems, and a method of forming a bearing race shape material by hot forging while suppressing molding defects at the upper end portions of the inner and outer diameters of the product. Is to provide.

  Means of the present invention for solving the above-mentioned problems are in the following methods (1) and (2). That is, (1) a preforming method comprising an upsetting process in which a cylindrical body made of a steel material is compressed in an axial direction to form a disk-shaped preform, and (2) this preformed disk-shaped From this molding method comprising a molding step of forging a preform of the above with a forging die equipped with a molding punch and die and forming a cylindrical part and a cup-shaped molded body having a bottom at the lower end of the cylindrical part Become. The cup-shaped molded body of the bearing race formed by the means of the present invention is further provided with a punching punch for removing the bottom portion of the cylindrical portion of the cup-shaped molded body from the cylindrical portion in order to obtain a ring shaped member of the bearing race. It is made into a ring shape material.

  The above means (1) and (2) of the method of the means of the present invention will be further described. The disk-shaped preliminarily formed body is installed by the upsetting process of (1), and then the disk-shaped preliminary The molded body is inserted into a cup-shaped die, and the diameter D of the corner circle, which is a circle around the flat surface that is the upper and lower surfaces of the disk-shaped preform, is set between the disk body and the small-diameter cylinder. Method of die forging by adjusting the diameter Dm, which is intermediate between the outer diameter Do of the disk body of the punching punch made of the hanging portion and the diameter Di of the hanging portion of the small diameter cylinder, to 0.99 times to 1.02 times It is.

  By adopting the above-mentioned means, the present invention can simultaneously and satisfactorily fill and fill the upper and lower corners of the inner and outer diameters of the bearing race with the steel material. It is possible to suppress unfilling of the upper end portion of the diameter, and the bearing race formed by this forging method suppresses defects due to lack of thickness, and does not apply excessive forging pressure, so there is no concern about the occurrence of burrs. An excellent shape material can be formed, repetition of trial production can be reduced, manufacturing cost can be reduced, and productivity can be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cup-shaped molded body 1 molded by the means of the present invention, (a) is a perspective view of the cup-shaped molded body 1, and FIG. 1 (b) is a longitudinal sectional view thereof. The cup-shaped molded body 1 includes a cylindrical portion 2 and a bottom portion 3, and the inner diameter surface of the cylindrical portion 2 has a slight draft. Further, the bottom portion 3 closes the lower end of the cylindrical portion 2. A portion indicated by H in FIGS. 1B and 3 is the height of the cylindrical portion 2. In FIG. 1B and FIG. 3, the part indicated by the double-pointed arrow Di is the outer diameter of the hanging part 11 of the small-diameter column of the punch 8 having the inner diameter at the upper end of the cylindrical part 2, and is indicated by the double-pointed arrow Do. This is the outer diameter of the upper end portion of the cylindrical portion 2 and the outer diameter of the disk portion 10 of the punch 8. Further, in FIG. 1B and FIG. 3, a double arrow Dm indicates a diameter corresponding to the exact center between the inner and outer diameters of the upper end, that is, the outer diameter of the hanging portion 11 in the disk portion 10 of the punch 8. It is the diameter of the circle in the middle of the annular portion on the outer peripheral side. That is, the double arrow Do is the outer diameter Do of the disk body constituting the molding punch 8 used in the present invention, and the double arrow Di is the small diameter cylindrical hanging part 11 that also forms the molding punch 8. It corresponds to the diameter Di which is the outer diameter.

  FIG. 2 is a front view showing an upsetting process for forming the cup-shaped molded body 1 of FIG. A cylindrical body 4 made of a steel material shown in FIG. 2A is used as a material, and upsetting is performed by a press machine including an upsetting metal 5 and an upsetting metal 6. First, the cylindrical body 4 is placed on the upset lower plate 6, and then the upright upper plate 5 is lowered relative to the upset lower plate 6 by a press machine so that the cylindrical body 4 is gradually moved. Compression is finally performed to obtain an upsetting disk-shaped preform 7 as shown in FIG. In FIG. 2B, what is indicated by a double-headed arrow D is the diameter of the upper and lower flat portions of the preform 7.

  FIG. 3 is a longitudinal sectional view showing a state of the main forming process, which is a subsequent process of the upsetting process of FIG. 2. In the main forming process, a forging die having a T-shaped punch 8 and a cup-shaped die 9 is used, and the punch 8 can be moved up and down relatively with respect to the die 9. The punch 8 having a T-section has a disk part 10 and a hanging part 11 having a small-diameter cylinder. The hanging part 11 is cylindrical and hangs downward from the center of the disk part 10. The outer diameter of the hanging part 11 is smaller than the outer diameter of the disk part 10. The cup-shaped die 9 is composed of a cylindrical portion 12 and a bottom portion 13, and the inner peripheral surface of the cylindrical portion 12 is such that a clearance is formed between the punch 8 and the outer peripheral surface of the disk portion 10. It is slightly larger than the outer diameter.

  In the molding process, first, the upset preform 7 is put into the cup-shaped die 9 and placed on the bottom 13 of the cup-shaped die 9 as shown in FIG. Next, as the punch 8 having a T-shaped cross section descends, the material of the preform 7 flows, and the cylindrical portion 12 is gradually filled from the bottom 13 side. FIG. 3B shows a state where the punch 8 is lowered most. In this state, the entire cavity formed by the punch 8 and the die 9 is filled with material. Next, the punch 8 is raised, and the cup-shaped molded body 1 is taken out from the cup-shaped die 9 of the forging die. The shape of the cup-shaped molded body 1 taken out is as shown in FIG.

  Next, as shown in FIG. 4, the cup-shaped molded body 1 molded by the above-described means of the present invention is subjected to a punching process to form a poncas 15 (the cup-shaped molded body 1 of the cup-shaped molded body 1). A portion of the bottom portion 3 of the inner diameter portion is referred to as “poncas”), and is punched and removed between the die 14b by the punch 14a for punch removal, and is formed in the ring shape member 2a of the bearing race. The outer diameter Do of the cylindrical portion 2, the inner diameter Di of the cylindrical portion 2, and the height of the cylindrical portion 2 from the inner bottom surface of the cup-shaped molded body 1 to the upper end of the cylindrical portion 2. For example, when forming the hub inner ring, H is taken over to the hub inner ring as it is. In the manufacturing method according to the present invention, the inner diameter Di of the cylindrical portion 2 is 20 mm to 35 mm, the outer diameter Do of the cylindrical portion 2 is 25 mm to 45 mm, and the height H of the cylindrical portion 2 is 10 mm to 20 mm. It is formed in the bearing race formed from the cup-shaped molded object 1 which is suitable.

  5 and FIG. 6 of the cylindrical portion 2 of the cup-shaped molded body 1 are places where the filling by the flow of the material is most delayed, as shown in FIG. 5 and FIG. By filling the both almost simultaneously, the occurrence of defects in forging defects such as lacking is suppressed. The flow history of the material is affected by the diameter D which is the end diameter of the upsetting preform 7. That is, by setting the diameter D suitable for the dimensions of the cup-shaped molded body 1, simultaneous filling of the outer diameter upper edge 16 and the inner diameter upper edge 17, which is the upper edge of the cylindrical portion 2, is achieved, resulting in defective forging defects. Is suppressed.

  Assuming a forging die having various dimensions and an upsetting preform 7 having a diameter D which is various end diameters, molding is further performed from FIG. 5C and FIG. 6C. When the forming stroke rate is 99%, the filling state of the cylindrical portion 2 due to the material flow of the outer diameter upper edge 16 and the inner diameter upper edge 17, that is, the outer diameter upper edge 16 and the inner diameter upper edge 17, respectively. The void volume between the molding punch 8 and the material was determined by CAE analysis. And the void volume ratio (V / Vs) which divided each void volume (V) by the volume (Vs) of the molded object was computed.

  When D / Dm was 1.00, the void volume ratio was calculated to be 0.06% at the outer diameter upper edge 16 and 0.04% at the inner diameter upper edge 17. When D / Dm is 0.99, the void volume ratio is 0.26% at the outer diameter upper edge 16 and 0.08% at the inner diameter upper edge 17, and the void at the outer diameter upper edge 16 is greatly increased. The filling degree at the upper end of the diameter deteriorated. On the other hand, when D / Dm is 1.02, the void volume ratio is 0.07% at the outer peripheral upper edge 16 and 0.20% at the inner upper peripheral edge 17, and the void at the inner peripheral upper edge 17 is increased. It turned out that the filling degree of an upper end gets worse. Based on these analysis results, a plot of D / Dm on the horizontal axis and void volume ratio V / Vs on the vertical axis is shown as a graph in FIG.

  As can be seen from FIG. 5, when Dm is larger than D and D / Dm <0.99, the void volume ratio of the outer peripheral edge 16 is rapidly increased to exceed 0.15%. That is, in the initial stage of the forming process, the corner portion, which is the end diameter of the upsetting shape, is wound in the direction of the arrow while being wound around the perforated portion corner 18 of the forming punch 8 as shown in FIG. Next, as shown in FIG. 5C, the fluid flowed upward in the direction of the arrow while being located near the diameter of the punch 8. For this reason, at the end of the molding step, the inner diameter upper end peripheral edge 17 of the cylindrical portion 2 is filled, but the outer diameter upper end peripheral edge 16 of the cylindrical portion 2 is difficult to be filled.

  Conversely, as shown in FIG. 6, when Dm was smaller than D and D / Dm> 1.02, the void volume ratio of the inner diameter upper edge 17 increased beyond 0.15%. However, the outer peripheral edge 16 is stable at a low position. That is, as shown in FIG. 6B, since the outermost diameter portion of the upset preform 7 reaches the inner diameter wall 19 of the cup-shaped die 9 at the initial stage of the molding process, As shown in FIG. 6 (c), the outer diameter portion of FIG. 6 flowed upward in the direction of the arrow while being restrained by the inner diameter wall 19 of the die 9 while being positioned from the outer diameter of the punch 8. For this reason, at the end of the molding process, the punch 8 fills the outer peripheral upper end periphery 16 of the cylindrical portion 2, but the inner peripheral upper end periphery 17 of the cylindrical portion 2 is difficult to be filled.

  From these points of view, the filling state of the outer diameter upper edge 16 and the inner diameter upper edge 17 of the cylindrical portion 2 is such that the diameter D of the end of the preform 7 is 0 of the diameter Dm of the middle circle of the disk portion 10 of the punch 8. It is preferably .99 times or more and 1.02 times or less, and closer to 1.00 times is more preferable.

A cup-shaped molded object is shown, (a) is a perspective view, (b) is a longitudinal cross-sectional view. The upsetting process of a preforming is shown, (a) is the longitudinal cross-sectional view which shows before installation and (b) shows after installation. The forging process of this shaping | molding is shown, (a) is before forging, (b) is a longitudinal cross-sectional view after forging. It is a longitudinal cross-sectional view which shows the punching process following the process of this invention. The filling behavior of the forging process of the main forming is shown, (a) is a longitudinal cross-sectional view showing a preform for D <Dm, (b) is the forging initial stage, and (c) is the forging late stage. The filling behavior of the forging step of the main forming is shown, (a) is a longitudinal cross-sectional view showing a preformed body of D> Dm, (b) an initial stage of forging, and (c) a late stage of forging. It is a figure which shows the relationship between D / Dm and void volume ratio V / Vs by CAE analysis.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cup-shaped molded object 2 Cylindrical part 2a Ring shape material 3 Bottom part 4 Cylindrical body 5 Upset metal 6 Upset metal 7 Preliminary molded object (upset shape)
8 Punch 9 Die 10 Disc part 11 Suspended part 12 Cylindrical part 13 Bottom part 14a Punch (for punching out)
14b Die (for removing poncas)
15 Ponkas 16 Upper peripheral edge of outer diameter 17 Upper peripheral edge of inner diameter 18 Corner of perforation 19 Inner diameter wall D Diameter of end face of preform Dm Diameter of circle in the middle of punch disk Do Outer diameter of disk part of punch

Claims (1)

  A cylindrical body made of a steel material is compressed in the axial direction by upsetting to form a disk-shaped preform, and the disk-shaped preform is stored in a cup-shaped die and can be inserted into the inner diameter of the die. The disc-shaped preform formed in the die is die-forged by a punch having a T-shaped cross section having a cylindrical body and a bottom portion of a cylinder having a smaller diameter projecting from the center of the lower surface of the disk body. The diameter D of the corner circle at the end of the disk of the disk-shaped preform, the diameter of the outer diameter Do of the disk of the punch and the diameter of the hanging part of the small-diameter column A method for forming a cup-shaped molded body of a bearing race, characterized in that die forging is performed by adjusting the diameter to 0.99 times to 1.02 times an intermediate diameter Dm with Di.

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