JPS61266141A - Forward extrusion forging method - Google Patents

Abstract

PURPOSE:To position a billet to the center of an extrusion molding die and to prevent the generation of a longitudinal flash by subjecting the billet to hot forging without restraining the intermediate part to form the intermediate part to the same diameter as the outside diameter of extrusion molding and chamfering both ends to the diameter smaller than the outside diameter in a stage before the extrusion molding. CONSTITUTION:The billet 4 is heated and thereafter the top and bottom ends thereof are chamfered by upper and lower dies 7, 8 until the edges over the entire circumference are eliminated while the central part thereof is not restrained. The ends are chamfered to the angle approximately equal to the angle of the guide part 2 of a cavity 3 of a forward extrusion die; at the same time the outside diameter in the non-restrained part at the center is bulged to the size approximately equal to the outside diameter of the forming part 1 of the cavity 3. The billet 4 is thus smoothly inserted into the part 1 of the cavity 3. The extrusion angle thereof and the chamfering angle are approximately equal and the outside diameter in the central part is approximately equal to the outside diameter in the forming part 1. The billet 4 is thus positioned to the center of the part 1 and the uniform clearance is maintained. The generation of the longitudinal flash at the corner on the top end face after the molding is thereby obviated.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for forward extrusion forging of metal billets.

(Prior art) As a method of this kind, for example, as shown in FIG.
1) and a guide part (2) that slopes continuously to the molded part (1).
When inserting (4) into the fillet 1 into a cavity (3) having a It is done in between or hot.

(Problems to be Solved by the Invention) However, cold forging requires complicated pretreatment processes such as spheroidization and combustion dulling of the pillets 1 to 1, and hot forging does not require pretreatment processes for the billets. However, because the billet is inserted with a gap between the mold and the mold, the billet tilts to one side in the mold, and because the billet has low deformation resistance and good fluidity, vertical cracks occur in the clearance between the punch and die. However, the burr has problems such as being caught on the upper surface of the burr during the subsequent upsetting process of the product, or gnawing on the die, resulting in severe wear of the die.

(Means for Solving the Problems) The present invention aims to solve the above problems, particularly in hot forging, and is aimed at solving the above problems, particularly in hot forging. In a forward extrusion forging method in which the billet is inserted into a cavity having an inclined guide portion and extruded with a punch, as a pre-process to the extrusion, the billet is hot forged with the intermediate portion not constrained, and the intermediate portion is formed as described above. It is characterized in that the facing is processed to have the same diameter as the outer diameter of the molded part, and both ends thereof have a smaller diameter than the outer diameter of the molded part.

(Example) Hereinafter, a cavity (
3) An embodiment of the present invention in which the billet (4) is press-formed in a chamber is explained with reference to FIGS. The upper and lower ends of the unrestrained surface are surfaced using the upper die (1) and the lower die (8) until there is no etching around the entire circumference, and the angle of the surface is set to the cavity (3) of the forward extrusion mold.
), and at the same time expand the outer diameter of the central unrestricted part to a dimension that is equal to the outer diameter of the molded part 1) of the forward extrusion mold cavity (3). . At this time, most of the center part of the billet (4) does not come into contact with the mold, so the temperature of the billet does not decrease much despite the imposition process.

Next, when the billet (4) is inserted into the capitivity (3) as shown in FIG.
) is sufficiently smaller than the outer diameter of the forming part (1), so that insertion into the forming part (1) is carried out smoothly, and the extrusion angle and imposition angle are ideally equal, and the outer diameter of the central part is smaller than that of the forming part (1).
Because the billet (4) is approximately equal to the outer diameter of the molded part <1>, it is positioned at the center of the molded part <1> without falling or shifting, and the clearance between the molded part <1) and the billets 1 to (4) is uniform over the entire circumference. Therefore, even after the molding is completed as shown in the second figure, there will be no vertical cracks at the corners of the upper end surface.

In addition, by giving the billet (4) a dimensional difference between the outside diameter at both ends and the outside diameter at the center in the imposition process, a large non-contact area is formed between the inner wall of the extrusion die and the billet (4). In order to prevent the temperature of the billet from decreasing between insertion into the mold and the start of molding, a non-contact part with the mold remains at the connection part of the molding part (1) with the guide part (2) as shown in the figure even after molding is completed. Therefore, especially when using a horizontally split type die, it absorbs the dimensional difference between the upper and lower dies and eliminates the occurrence of cracks in the split surface structure. This reduces resistance and contributes to the prevention of vertical cracks.Also, just before the start of molding, the lower end of the billet has a surface at the same angle as the die, so the corner etch does not partially hit and the surface pressure is low. Less galling and wear of the die due to lack of lubrication.

(Effects of the Invention) As described above, according to the present invention, as a pre-process of extrusion molding, the billet is hot forged without constraining the middle part to make the middle part the same diameter as the outer diameter of the molded part of the cavity, and then Since the imposition in which both ends have a diameter smaller than the outer diameter of the forming part is performed, simple imposition has the effect of preventing vertical cracking of the product by machining.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view showing the machining process, Fig. 2 is a longitudinal cross-sectional view showing the forging process, where a is the billet inserted state, b is the state after processing, and Fig. 3 is a longitudinal cross-sectional view showing the conventional forging process. In the top view, a shows the billet insertion state and the post-processing state. (1)...Molding part (2)...Guiding part (3
)...Cavity (4)...Billet (5)
···punch

Claims (1)

[Claims] In a forward extrusion forging method in which a billet is inserted into a cavity having a forming part and a guide part that is continuous with the forming part and extruded with a punch, the billet is Forward extrusion forging, characterized in that hot forging is carried out under restraint, and the middle part thereof is made to have the same diameter as the outer diameter of the forming part, and both ends thereof are subjected to surface processing with a diameter smaller than the outer diameter of the forming part. Method.