JPS63317231A - Method for necking of forging ring - Google Patents

Abstract

PURPOSE:To improve forming accuracy by beforehand executing thinning at edge part of a forging ring or notch at peripheral direction thereof and next acting die for necking. CONSTITUTION:The notching part A in the forging ring 1 as the blank is formed by machining or gas scarfing, etc. Next, the forging ring 1 is put on a press bed 3 and ring-shaped die 4 is arranged at the upper end of the ring 1, and the necking is executed through a press anvil 6 and a plate 5. Then, the die 4 has tapered surface upward on the inner peripheral surface and the edge part of the ring 1 is uniformly pressed down with a press ram. As the notching part A is beforehand formed at the edge part of the ring 1, development of under-fill caused by deformation-dislocation of the ring 1 at the time of forming by the die 4 is prevented. By this method, the accuracy of the product ring member is improved.

Description

Detailed Description of the Invention (Field of Industrial Application) This invention relates to a method for forming a ring member for a large pressure vessel, particularly a ring member for a pressure vessel to be connected to a head plate of a chemical equipment or a pressure vessel for nuclear power. This is related to the improvement of.

(Conventional technology) Conventionally, the method of performing mouth drawing of large ring materials is as follows:
For example, Japanese Patent Publication No. 55-24378, Japanese Patent Publication No. 61-6
A technique disclosed in Japanese Patent No. 737 and a method of applying a ring-shaped die having a tapered inner diameter surface to a forged ring member after hole expansion forging are known.

(Problems to be Solved by the Invention) Among the above methods, the method in which a ring-shaped die is applied to a forged ring member to perform mouth drawing is in comparison with the above two methods in terms of the work required for tongue drawing. It is advantageous in terms of time and forming dimensional accuracy, and satisfies the required shape, for example, when drawing a relatively simple shape such as a forged ring at the top of a pressure vessel (see Figure 5 (a)). On the other hand, the forged ring at the bottom of the pressure vessel (see Figure 5 (b)) deforms slowly in the axial direction during mouth drawing. As a result, a lack of thickness occurs in the area where the mini-skirt for supporting the container is to be formed, leaving a problem in that it is difficult to finish it into the desired shape.

An object of the present invention is to solve the above-mentioned conventional problems, and to propose a method that is advantageous for improving molding accuracy by reducing deviations in the deformation position due to mouth drawing.

(Means for Solving the Problems) This invention provides a method of notching the forged ring in the circumferential direction or thinning the end region of the member before drawing the forged ring. The above object is advantageously achieved by concentrating the deformation position due to the mouth drawing in the processed portion of the forged ring material and causing local bending.

That is, the present invention provides a method for causing the die to act on the end of a forged ring when the die for mouth drawing is caused to act on the end of the forged ring and has a tapered inner surface and is arranged concentrically with the forged ring. First, the end region of the forged ring is subjected to thinning processing or notch processing is performed in the circumferential direction of the end region of the forged ring, and then the aforementioned mouth drawing die is applied. This is a molding method.

(Function) In this invention, when a forged ring is subjected to mouth drawing and finished into a predetermined shape, thinning processing or notching processing is first performed. 1 (a) and (b). In carrying out the above-mentioned processing, mechanical processing, gas solvent processing, etc. are advantageous.

Normally, when a forged ring is formed by mouth drawing, Figure 2 (a
) As shown in (b), on the placing stand 3 on the press bed,
A forged ring 1 is placed, and a ring-shaped die 4 having a tapered inner diameter surface and concentric with the ring 1 is placed at the upper end of the ring 1.

Then, a press anvil 6 located below the rolling ram is operated via a plate 5 which serves to uniformly roll down the end of the ring 1. However, when finishing a relatively complicated shape, in this type of mouth drawing, the third Especially in Figures (a) and (b) [Yes]
), underfilling (C) occurs in the forged ring 1 due to the shift in the deformation position.

In this invention, since the forged ring 1 is processed as shown in FIG. 1, the deformation position (D) due to the mouth drawing is concentrated in the processed part, and the bending is performed locally or only in that area. It is possible to give
The mini-skirt portion of the forged ring applied to the lowest part of the pressure vessel as shown in b) can be advantageously secured without occurrence of underfilling.

FIG. 4 shows another processing mode of the forged ring.

Type A in FIG. 4 is a forged ring in which a notch is formed on the circumference of the inner diameter surface. Similar to the forged ring shown in Figure 1, this kind of ring can be bent locally because stress is concentrated at the notch during mouth drawing, especially as shown in Figure 3 (b). It is advantageously adapted to such shapes.

In addition, types B and C have thinner end portions that are formed by mouth drawing, but in such rings, the thicker portions hardly deform, and only the thinner region deforms significantly. In particular, it is advantageously adapted to the shape shown in FIG. 3(a). In addition, it is also possible to use a suitable combination of types A to C for mouth drawing molding.

(Example) Using a forged ring (reduced model) with the cross-sectional shape shown in Fig. 6 (A) and (B), mouth drawing was performed, and the finished shape after forging was determined using unprocessed ring material. A field survey was conducted to compare the situation.

The results are shown in Table 1 along with the processing conditions.

The die used for drawing the molding was one with a cast surface taper angle θ of 23° (see Fig. 7).

As is clear from Table 1, it was confirmed that the finished shapes of the ring materials (A) and (B), which were subjected to mouth drawing according to the method of the present invention, were good.

FIG. 8 shows the cross-sectional shape of each ring material after molding.

(Effects of the Invention) According to the present invention, since deformation occurs in the region where the forged ring is notched or thinned, it is possible to improve the forming accuracy, and also to perform mouth drawing forming with a relatively small reduction blade. It became possible to do so.

[Brief explanation of the drawing]

FIGS. 1(a) and (b) are diagrams showing the processing mode of the forged ring, FIGS. 2(a) and (b) are diagrams showing the mouth drawing procedure, and FIGS. 3(a) and (b) are 61 is a diagram showing a forged ring in conventional mouth drawing; FIG. 4 is a diagram showing another processing mode of the forged ring; FIG. 5 is a diagram showing the basic shape of the top and bottom parts of a pressure vessel; 1(a) and (b) are diagrams showing the shape of the forged ring notched and thinned, Figure 7 is a diagram showing the shape of the die for mouth drawing, and Figure 8(a)
, (b) and (C) are diagrams showing the finished shape after forging. Patent applicant Kawasaki Steel Co., Ltd. Figure 3 (a) (b) Figure 4 Figure 5 (a) (b)

Claims (1)

[Claims] 1. When performing mouth drawing forming by applying a mouth drawing die that has a tapered inner surface and is arranged concentrically with the forged ring to the end of the forged ring, actuate the above mouth drawing die. The mouth of a forged ring characterized in that, prior to this, the end region of the forged ring is first thinned or notched in the circumferential direction of the end region, and then the mouth drawing die described above is applied. Drawing method.