JPS5858952A - Precision closed forging method - Google Patents

Abstract

PURPOSE:To improve production efficiency in hot closed forging by fixing sizing dies concentrically to the casting knock-out exit of a forming die and thereby performing sizing work immediately when the casting is knocked out. CONSTITUTION:A material W0 heated to warm-hot temperature is placed on a lower punch 3 which is raised to upper limit position. Then, it is lowered from the lower punch to lower limit position. An upper punch 2 is lowered to compress the material W0 axially and at the same time, the material is moved radially and a casting of required shape is formed. Finally, a knock-out pinch is raised and the casting W1 is knocked out by thrusting up the casting from a forging forming die 7 through the lower punch 3. At this time, it is passed forcibly through a sizing die 8 fixed concentrically adjoining the upper part of the forging forming die 7. Accordingly, it is dimensionally corrected to a specified profile corresponding to the shape of product.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a closed forging method for manufacturing precision forged products such as gears by compression molding a heated material in a closed space formed by a mold, upper and lower punches, and the like.

Traditionally, the sealed-advanced method is applied when forging mechanical components such as gears, connecting rods, flanges, and shafts, but when cold forging is not possible depending on the material or shape of the forged product to be manufactured. In that case, closed forging is performed in a so-called warm state of 100°C or less, or in a hot state of more than 100°C.

That is, when sealingly forging a spur gear having a large tooth profile, such as the module 3.75 shown in FIG. For example, the rough material (Wo) is processed by the lower punch (3) of the hermetic forging device shown in Fig. 2.
The material Cwo) is compressed in the axial direction between the descending upper punch (2) and the lower punch (3) in a forging die (1) with a tooth profile formed on the inner periphery. At the same time as the forging die (
1) The tooth profile formed on the inner periphery is filled with meat to obtain a forged product (W/) with the tooth profile formed on the outer periphery.

However, at this time, high temperature and high pressure are applied to the inner periphery of the forging die (1), which tends to cause cracking, -1 wear, deformation, etc. over time.

After sowing, the forged product (W/) was pulled upward from the forging die (1) via the lower punch (3) by raising the knockout bin (1), and immediately cooled in a non-oxidizing atmosphere cooling φ. After that, cold sizing is performed in the next step.

The cold sizing process is for the purpose of correcting dimensional changes over time of the forged product (W/) during the closed forging, and in many cases, the forged product (W/) that has been subjected to a lubricating film treatment is The forged product (W/) is passed through the sizing die (5) of the cold sizing device shown in 4. At this time, the upper punch (6) is lowered by a hydraulic press to maintain dimensional accuracy, and the forged product (W/) is gently pushed down. It is.

The above method has the drawbacks that the number of steps increases including the lubricating coating treatment after closed forging, and that production efficiency decreases due to the use of hydraulic presses during sizing, which increases equipment costs and ultimately increases product prices. be.

In order to solve the above-mentioned drawbacks, the present invention fixes a sizing mold concentrically adjacent to the forged product knockout outlet of the 11 forging mold during warm or hot hermetic forging,
The present invention provides a precision sealed forging method characterized in that when knocking out a forged product formed in the forging mold, the forged product is immediately passed through the sizing mold to undergo sizing processing, and will be explained below based on the drawings. do.

Figures (A) to (D) are longitudinal cross-sectional views of main parts for explaining the method of the present invention step by step, and show materials that have been previously coated with graphite to prevent oxidation and heated to warm to hot temperatures. After the (Wo) is taken out of the furnace, it is placed on the lower punch (3) which has been raised to the upper limit position via the knockout bin (441) as shown in Figure μ (A) by a manipulator etc. As shown in Figure (B), the lower punch (3) descends to the lower limit position, and then the upper punch (21) descends and as shown in Figure (C), the lower punch (3) The material (W,) is compressed in the axial direction and moved in the radial direction to form a forging mold (
7) Fill the inside and form a forged product (W/) of the desired shape.

Finally, as shown in Figure (D), knockout bin (
Raise llB and lower punch the forged product (W/>) (3)
The forging mold (7) is pushed up and knocked out from the sizing mold (7) through the sizing mold (a), which is fixed concentrically adjacent to the upper part of the forging mold (7). By doing this, the dimensions are corrected to a predetermined tooth profile shape corresponding to the product shape.

For example, in the case of the gear described above, the sizing amount Δr due to the pre-sizing mold f♂j is 0. / −0,j ff, and 0. / If it is less than 0, the sizing effect will be small, and if it exceeds 0. It is.

The shape and dimensions of the sizing mold (♂1) are based on the heat shrinkage amount, scale amount, and
Sizing mold (set considering the amount of elastic deformation and thermal expansion of gJ, etc.)

By the way, during the sizing process, the sizing mold (
gl- Since the temperature and surface pressure acting on the inner circumferential surface are lower than those of castle molding molds (, 7), the mold material should be made with emphasis on wear resistance rather than heat crack resistance and high temperature strength. For example, it is desirable to select cemented carbide.

The forging mold (7) is made of a material that emphasizes heat crack resistance and high temperature strength for the tooth tips formed on the inner periphery, such as J
IS, G4! ≠03 High-speed tool steel JSKH etc. is suitable.

Furthermore, the forging mold (7) and the sizing mold IgJ
As shown in the Tsubakihiro diagram (A), the reinforcing ring (9) is tapered at the top with an inclination of about 10 mm, and is concentrically fixed by press-fitting or shrink-fitting into the hole of the reinforcing ring (9), which is tapered at the top with a slope of about 10 mm. Although provided to restrain directional movement and bending deformation, other fixed structures are possible.

Alternatively, the spur gear illustrated in Fig. 1 does not have a shaft hole, but if there is a shaft hole, a core (not shown) may be provided in the center of the lower punch (3) in Fig. 1 (A). do it.

Since the present invention is configured as described above, the sizing process is performed immediately using the knockout force after closed forging, and therefore production efficiency is improved by omitting the conventional cold sizing process and the lubricating coating treatment required therefor. It is possible to improve this, reduce tool consumption, and ultimately reduce product cost.

The method of the present invention can be applied to powder forging by powder metallurgy in addition to the above-mentioned materials such as steel, and can also be implemented by simple modification to existing closed forging equipment.

[Brief explanation of drawings]

Figure 1 is a vertical cross-sectional view showing an example of a forged product, Figures 2 and 3 are vertical cross-sectional views of the main parts of the forging process and cold sizing process, respectively, and Figure ≠ (A).
- (D) are longitudinal sectional views of main parts for explaining the method of the present invention in the order of steps. l: Forging die, 2: Upper punch, 3: Lower punch, G: Knockout bin, ! : Sizing mold, 6: Upper bunch, 7
: Forging mold, r: Sizing mold, Ri: Reinforcement ring WO: Material, Wl: Forging Applicant Sumitomo Metal Industries, Ltd. Figure 1 Figure 2 Figure 31!1

Claims (1)

[Claims] (1) A heated material is placed in a sealed space formed by a mold with a hole shaped to correspond to the external shape of the forged product to be manufactured, and an upper and lower punch that is movable in the axial direction within the hole of the mold. In warm or hot sealed forging, which is compressed and forged,
A sizing mold is fixed concentrically adjacent to the forging product knockout outlet of the forging mold, and when knocking out the forged product formed in the forging mold, the forging mold is immediately passed through the sizing mold to perform sizing processing. A precision closed forging method characterized by performing the following.