JPH07112580B2 - Conical end plate forming method for pressure vessel - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a conical end plate forming method for a pressure container in which a conical end plate used when forming a pressure container is formed into a predetermined shape from a blank material without requiring a welded joint. It is a thing.

[Conventional technology]

Since the pressure vessel has a wide variety of usage conditions and responds to changes in temperature, pressure, flow velocity, and the like, the end plate has a conical body, that is, a conical shape whose size (diameter) is determined.

In particular, the conical end plate according to the present invention is applied in many cases, which is regarded as important.

There are a wide range of shapes, sizes, types, etc. of pressure vessel end plates. Pressing, spinning and splitting methods are applied to the forming process of the pressure vessel end plate, and these are classified into cold working and hot working.

The conical end plate is different from other end plates in that a conical angle is specified. As shown in FIG. 5 (a), the conical end plate is formed by pressing each expanded segment to a predetermined angle with a single-acting press, temporarily assembling it, and welding it with two wires, or As shown in Figure (b), although it takes a little time for pressing, a method of press-pressing with a single plate and then welding with one wire is currently applied.

[Problems to be Solved by the Invention]

According to the method of assembling by welding, it is necessary to adjust the dimensions at the time of temporary assembly and work such as welding, which requires a large number of man-hours and makes manufacturing very complicated. When considering expansion and contraction after pressing, it is necessary to re-cut after confirming dimensions during temporary assembly.
It is a matter of course that the number of divisions increases if the diameter, height, plate thickness, etc. of the conical mirror plate change, for example, increase in size. This large conical end plate has a large number of divisions, and a large number of weldings are required for its production, which makes the production complicated.

Generally, in the case of press-molding a dish-shaped end plate, it has been put into practical use to form a conical end plate by a one-press method using a double-acting hydraulic press machine using a mold having a predetermined shape, but the same method, that is, When forming by the one-press method, there is a time lag where the conical tip and its vicinity come into contact with the mold, the tip receives a concentrated load, large strain deformation and stress are applied, and the material of that part is hardened. However, due to the increase in strength and the decrease in elongation, cracks develop near the tip of the conical end plate. FIG. 2 shows an example of this crack occurrence state. When a hole is made in the tip end first, a mold is set, and a forming process is performed using a double-acting hydraulic press, the load concentrates on that part and the hole is opened, and the phenomenon of microcracking is shown. . FIG. 3 shows this situation.

Further, when the cutting line is affirmatively installed and press-molded in order to relieve the stress concentration, the cutting line tends to widen as shown in FIG. Therefore, it takes time and effort for the other party to correct the shape, correct this portion, and perform tack welding.

In the present invention, it is possible to easily and accurately form a conical end plate into a predetermined shape from a blank material without requiring a welded joint, while preventing a crack occurrence phenomenon such as that caused by a conventional pressing method. An object of the present invention is to provide a conical end plate molding method for a pressure vessel.

[Means for Solving the Problems]

In order to achieve the above object, the method for forming a conical end plate of a pressure vessel according to the present invention is a method for forming a blank material having a plate thickness of 3 to 14 mm cut into a required size into a required conical shape using a hydraulic press machine. In the conical end plate forming method, it is possible to form a blank into a dish shape by performing a primary process on the blank material, and then form the intermediate shaped dish-shaped material into a desired conical shape using a mold having a conical shape. Use as a summary.

〔Example〕

Hereinafter, a method for forming a conical end plate of a pressure vessel according to the present invention will be described with reference to the illustrated embodiments.

The blank material 1 is formed by cutting into a required diameter using a material and a plate thickness according to the size, pressure resistance, purpose of use, etc. of the pressure vessel to be formed. Then, using a hydraulic press machine, a blank material with a plate thickness of 3 to 14 mm cut into the required size is subjected to intermediate processing by primary processing to form a dish shape, and then the intermediate shaped dish material is conical. A desired conical shape is formed using a die having a shape.

In this case, the degree of processing to be added is appropriately selected depending on the conditions such as material, plate thickness, diameter, cone angle and height.

Table 1 shows the types of conical end plates used in the test and the test contents.
Shown in.

Next, the test results of the conical end plate molded according to the present invention will be shown.

As a result of appearance inspection and PT (penetration flaw detection test), appearance inspection was performed on the entire inner and outer surfaces of all end plates, but no cracks, press scratches, body wrinkles, etc. were found. In addition, PT for the outer surface (200 mφ) of the top of all end plates
However, no defect indication was found.

Results of Dimensional Inspection The results of dimensional inspection of each end plate are shown in Table 2, and a conical shape with a good dimension was obtained.

Results of microstructure test In the microstructure at the top, middle, and large diameter center of the molded conical mirror plate, deformation of crystal grains, harmful slip band, etc. are not observed, and it is a good microstructure. I understood it.

Hardness Test Results FIG. 6 shows the hardness test results of the top, middle and large diameter portions of the molded conical end plate.

For end plate No. 3 (material: SS41), the hardness of the apex is HV1
96 to 200, and HV162 to 168 in the middle and large diameter parts.

For end plate No. 5 (material: SUS304), the apex is HV258 ~
264, and the middle part and the large diameter part were HV197-213.

As a result, a considerable work hardening was observed at the apex of the end plate, but the hardness was almost the same as that of the flange part of general end plates (dish shape and 2: 1 semi-ellipsoidal shape) for all end plates.

Measurement Results of Plate Thickness Change and Strain As shown in FIG. 7, a blank material was marked for strain measurement, and surface strain and plate thickness change due to molding were measured.
The results are shown in the same figure.

From this, in each end plate, the strain in the circumferential direction shows an elongation of about 20% at the apex portion, and sharply decreases with distance from the apex,
There was shrinkage from the middle part to the large diameter part. on the other hand,
The radial strain is similar to the circumferential direction in the vicinity of the apex, but it does not turn into contraction from the middle part to the large diameter part, and it is several percent.
Was growing.

Looking at the change in plate thickness, it can be seen that at the top of any end plate
The plate thickness was reduced by 15 to 20%, and although the reduction rate decreased toward the middle portion, it was 0% in the middle portion. From the middle part to the large diameter part, when the plate thickness is thin, it is difficult to recognize the change in the plate thickness, but it was found that the plate thickness increases in the large diameter part as the plate thickness increases.

The following is a summary of the conical end plate molding methods examined in this test.

(1) Conical end plates with apex angles (conical angles) of 90 °, 120 ° and 140 °, and large diameter dimensions of 600 mmφ and 2000 mmφ, two types of material, SS41 and SUS304, thickness of 4.5 mm (4 mm), 6 m
As a result of performing a molding test with three types of m and 9 mm, it was found that it is possible to mold a conical end plate having good appearance and dimensions.

(2) Among conical end plates with a vertical angle of 120 ° and a large diameter of 600 mm, the material SS41, the plate thickness 9 mm and the material SUS304, the plate thickness 6 mm are 2
Regarding the type, the change in material due to molding was investigated, and it was similar to a general end plate in terms of microstructure and hardness.

(3) Conical end plate 5 with a vertical angle of 120 ° and a large diameter of 600 mm
As a result of measuring the strain and the change in plate thickness before and after molding, the strain and the decrease in plate thickness of the end plate molded by the one-press method will vary slightly depending on various conditions such as the apex angle, large diameter size, material, and plate thickness. However, it can be estimated that the strain and plate thickness decrease by around 20% at the apex, and those values decrease sharply toward the large diameter side, and the strain and plate thickness increase by several% at the large diameter part. It was

〔The invention's effect〕

According to the conical end plate forming method for a pressure vessel of the present invention, welding work is not required, and a conical end plate having a desired shape can be formed in two steps using a hydraulic press machine, which is excellent in workability. Further, since stress is not concentrated during processing of the material, the product is not cracked and the accuracy of the product can be improved. Furthermore, if the apex angles are the same, conical end plates having different sizes can be formed using a single mold, and the manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 is a process explanatory view showing a conical end plate forming method for a pressure vessel according to the present invention, FIGS. 2 to 5 show known examples, FIG. 2 is an explanatory view showing a pressing method, and FIG. 3 is a front hole. FIG. 4 is an explanatory view showing a post-production method, FIG. 4 is an explanatory view showing a partially cut manufacturing method, FIG. 5 is an explanatory view showing a welding method, FIG. 6 is a hardness distribution diagram in the plate thickness direction of each end plate, FIG. 7 is a graph showing the measurement results of strain and thickness change of the conical mirror plate. 1 is a blank material, 2 is a conical end plate molded product.

Claims (1)

[Claims] 1. In a conical end plate forming method for a pressure vessel, a blank material having a plate thickness of 3 to 14 mm cut into a required size is formed into a required conical shape by using a hydraulic press machine. A conical end plate forming method for a pressure vessel, which comprises forming a dish-shaped material by subjecting it to a dish shape, and then forming an intermediately-formed dish-shaped material into a required conical shape using a mold having a conical shape.