JP2000254751A - Die for shaft reducing and shaft reducing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a forging method with a punch stroke length, in which working is done with a die of good shaft reduction capability, capable of preventing a forming defect of jamming, etc. suitable for an arbitrary working condition and in a non-steady deformation region, so as to obtain good shaft reduction without generating jamming. SOLUTION: A die, which conducts shaft reducing as a stock 1 is drawn while reducing and has excellent shaft reduction, satisfies 1071 μ+323 n+10 θ+4R-65<0 wherein a friction coefficient μ between a die insert 3 and a stock 1, a work hardening index (n) of the stock 1, a die half angle θ (deg) and a cross section reduction R(%) of a die insert are assumed. Further, forging is done with satisfying S<2.5D0.(1-R/100), wherein a stock diameter D0 (mm), a punch 2 stroke S (mm) and a die cross section reduction R(%) are assumed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shaft drawing which is one of the basic processing methods of forging, and to a mold having excellent shaft drawability which does not cause molding defects such as a press-fitting and a press-forming method. Provided is an axial drawing method that does not cause molding failure.

[0002]

2. Description of the Related Art Conventionally, forward extrusion has been applied to stretch a material in an axial direction while reducing its diameter in a forging process. Forward extrusion can be roughly classified into closed extrusion in which the material is extruded in close contact with the punch and die, and unconstrained extrusion in which the material hardly contacts the die. When the material is stretched, unconstrained extrusion is often applied to prevent punch breakage due to excessive pressure. Unconstrained extrusion is called axial drawing, and is a process frequently performed in the forging process.However, the cross-section reduction rate of the mold and the half angle of the die, the friction coefficient between the mold and the workpiece, the work hardening coefficient of the material, Improper combination of the stroke lengths of the punches causes the material to swell on the entry side of the dies and contact the dies, resulting in a tight extrusion. There is.

[0003] The forming conditions of the axial drawing are influenced by the combination of the die shape (die half angle, area reduction, friction coefficient) and material properties, and it is difficult to quantitatively investigate the effects of these factors. Conventionally, it is common practice to repeatedly perform processing experiments using actual machines and to select empirically optimal mold shapes and materials, which has a problem in that development costs and time are greatly increased.

[0004] Further, there is no problem if the deformation behavior of the material is steady during the axial drawing, but depending on the shape of the mold, the material continues to swell and contacts with the die during the process of pushing the material in with a punch and sealing. It may be extruded.
For this reason, a method of using a range in which a clogging does not occur in an unsteady deformation region by performing rolling down with a short stroke length such as a former is also applied. Therefore,
An appropriate punch stroke length is also an important factor in the axial drawability, but the determination of the punch stroke length also required the development of trial and error.

[0005]

In the forging shaft drawing, there is no general index for designing the die while considering the influence of various factors, so that the time and cost in the forging process and the die design are increased. It was inevitable. Accordingly, an object of the present invention is to provide a mold having a good shaft drawing property, which can clarify an index of a mold having a good shaft drawing property, prevent molding defects such as press-down, and be suitable for arbitrary processing conditions. Another object of the present invention is to provide a processing method for forging with a punch stroke length that provides good axial drawability without causing clogging even when processing is performed in an unsteady deformation region in the mold.

[0006]

Means for Solving the Problems According to the present invention, CAE (computational technology support), which has undergone many technological innovations in recent years and the technical progress is remarkable, uses the deformation resistance of the material, the friction coefficient between the tool and the material, and the shape of the mold as parameters. The forming limit of the axial drawing when the material is pushed with a punch stroke length that does not cause jamming even in the region where the material undergoes unsteady deformation was studied. The molding limit was expressed by a regression equation so that the obtained results could be used under arbitrary conditions, and the mold shape at the molding limit of the axial drawing was derived. Then, by comparing the obtained result with the actual forging result, it was possible to obtain an index of a mold having excellent shaft drawability.

[0007] That is, in order to solve the above-mentioned problems of the present invention, according to the first aspect of the present invention, there is provided a mold used in an axial drawing step for extending a material in the axial direction while reducing the diameter.
When forging with a punch stroke length S (mm) specified by Equation 2, the coefficient of friction μ between the mold and the material, the work hardening index n of the material, the half angle of the die of the mold θ (deg), the reduction of the cross section of the material Rate R
A mold having excellent axial drawability, characterized by satisfying the following expression 1 between (%).

[0008]

## EQU1 ## 1071 μ + 323n + 10θ + 4R−65 <0

According to a second aspect of the present invention, when a material having a diameter D _O (mm) is machined in the axial drawing die of the first aspect,
A shaft drawing method characterized in that forging is performed such that the punch stroke length S (mm) with respect to the section reduction rate R (%) of the mold satisfies Equation 2.

[0010]

S <2.5 · D ₀ · (1-R / 100)

The operation of the present invention will be described below.
FIG. 1 is an explanatory diagram showing a model of a shaft stop. By pressing the material 1 into the die insert 3 with the punch 2, the initial value diameter D ₀ of the material is changed to the delivery side diameter D of the material. At this time, the cross-sectional reduction rate R (%) of the material is defined by Expression 3.

[0012]

R / 100 = 1− (D / D ₀ ) ²

Table 1 shows the limits of the axial drawability. When the friction coefficient μ, the work hardening index n, the die radius θ, and the cross-sectional reduction rate R are variously changed, the axial drawability becomes possible. Are shown by ○ or ●, and when the material expands on the entry side of the die during processing and comes into contact with the die to be closed and extruded, the case where axial drawing is impossible is indicated by ×. However, ●
Although unsteady deformation occurs in which the material continues to swell with reduction, molding is possible with a punch stroke length defined by Expression 4. In other words, ● indicates a limit condition under which the shaft drawing can be performed satisfactorily without clogging at the stroke length defined by Expression 4, and the regression equation of the forming limit is represented by Expression 5. △ in Table 1 is difficult to mold (bulging ratio> 1.05)
Is shown.

[0014]

S = 2.5 · D ₀ · (1-R / 100)

[0015]

## EQU5 ## 1071 μ + 323n + 10θ + 4R−65 = 0

[0016]

[Table 1]

Therefore, when rolling down by the stroke length defined by the inequality of the equation (2), the range of ● or な with good shaft drawability can be defined by the inequality of the equation (1).

[0018]

## EQU1 ## 1071 μ + 323n + 10θ + 4R−65 <0

[0019]

S <2.5 · D ₀ · (1-R / 100)

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIG. Axial drawing is performed by warm forging or cold forging, and steel is used as the material 1. By pressing the material 1 into the die insert 3 by the punch 2 by the punch stroke length shown in Table 2, the material initial diameter D ₀ is changed to the material discharge side diameter D. Punch 2 and die insert 3
Is a carbide tool, and lubrication is performed by applying a metal soap to a zinc phosphate film. An experiment was performed by setting the punch stroke length S, the material 1 and the shape of the tool. The n value of the work hardening index is changed by heat treatment and preliminary processing. That is, in order to make the n value close to 0, the work is sufficiently hardened by the preliminary processing. When increasing the n value, annealing is performed. If the optimum n value cannot be obtained, the chemical composition of the material is changed.

[0021]

[Table 2]

[0022]

EXAMPLE Shaft drawing was performed under the conditions shown in FIG. 1 and Table 2. Example: Test condition no. 1, test condition no. 2, test condition No. 3 and test condition No. 3 As shown in FIG. 4, under the conditions satisfying the formulas 1 and 2, in any case, the jamming was prevented and the axial drawing was completed as intended. Although the material 1 in this example is a steel SCM415 as shown in Table 2, even if the steel is SCM420, SUS304 or SUS316, the SCM415 is not used.
Similarly to the above, the axial drawing can be performed under the conditions satisfying Expressions 1 and 2.

[0023]

## EQU1 ## 1071 μ + 323n + 10θ + 4R−65 <0

[0024]

S <2.5 · D ₀ · (1-R / 100)

Comparative Example 1: Test condition No. 5 and test condition No. 5 Under the conditions shown in Equations 2 and 6, as in the case of 6, in any case, the material swells on the entry side of the dies together with the processing and comes into contact with the dies to form a closed extrusion, so that axial drawing is impossible.

[0026]

S <2.5 · D ₀ · (1-R / 100)

[0027]

[Formula 6] 1071μ + 323n + 10θ + 4R−65> 0

Comparative Example 2: Test condition no. 7 and test condition no. As shown in FIG. 8, under the conditions shown in Expressions 1 and 7, in each case, the material swelled with the reduction, and the material came into contact with the die-entering side, whereby the material was hermetically extruded and the axial drawing was impossible.

[0029]

## EQU1 ## 1071 μ + 323n + 10θ + 4R−65 <0

[0030]

S> 2.5 · D ₀ · (1-R / 100)

[0031]

As described above, the present invention shortens the machining design and the die design of the shaft drawing in providing a die and a punch stroke length which are less likely to cause molding defects such as press-fitting and the like, and which provide a punch stroke length. It can be implemented in a short time and at low cost, and has an unprecedented superior effect.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention, and shows a model of an axial stop.

[Explanation of symbols]

1 Material 2 Punch 3 Die Insert L Material Height D ₀ Material Initial Diameter D Material Outlet Diameter θ Die Half Angle H Die Height

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4E029 MB07 MB09 4E087 AA10 BA17 CA02 CA13 CA17 CA21 CA33 CB02 CB03 CB07 CB10 CB12 EC01 EC11 EC12 EC17 EC22 EC37 HA31

Claims (2)

[Claims] 1. A mold used for axial drawing in which a material is stretched in the axial direction while reducing the diameter of the material, a friction coefficient μ between the mold and the material, a work hardening coefficient n of the material, and a die radius θ (de
g), an axial drawing die, which satisfies the forming limit formula shown in Expression 1 with the die reduction ratio R (%) as a parameter. ## EQU1 ## 1071 μ + 323n + 10θ + 4R−65 <0 2. The shaft drawing die according to claim 1, wherein, when processing a material having a diameter D _O (mm), a punch stroke length S (%) with respect to a cross-sectional reduction rate R (%) of the die. mm) forging a relationship that satisfies Equation 2. S <2.5 · D ₀ · (1-R / 100)