JPS602129B2 - Integral molding method for straight pipe elbow - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of integrally molding an elbow with a straight pipe, and particularly to a method of integrally molding a large-diameter elbow with a straight pipe.

Conventionally, in the case of large-diameter pipes, the elbow and straight pipe were generally manufactured separately, and then welded together to form a single piece. In this case, the production cost and time increase due to the welding process required, as well as the quality assurance of the welding work, and the functionality (durability, etc.) of the welded joint during use as a product.
There is also a problem with the warranty. On the other hand, when integrally molding a large-diameter straight pipe elbow using a molding machine such as a press, there is generally a limit due to the load of the press, and even if a press with a large load can be used, it cannot be manufactured using a conventional molding die. In this method, the cross section of the center of the elbow and the boundary between the elbow and the pipe pipe becomes elliptical, and the inside of the bent part of the elbow becomes wavy. It was difficult to manufacture the elbow.

An object of the present invention is to solve the above-mentioned conventional problems, and to provide a pair of molds with a straight pipe forming part in which the molding angle of the elbow of the lower mold for elbow molding is slightly smaller than the molding angle of the elbow of the upper mold. By using the present invention, it is possible to provide a new method for integrally molding a elbow with a large diameter straight pipe.

The present invention will be explained by way of one embodiment with reference to the drawings.

FIG. 1 shows an upper mold used in the present invention, in which a is a top plan view, b is a side view, and c is a sectional view taken along the line A-A in b.

In this figure, a tube-shaped portion 1 corresponding to the half-shape of an elbow with a straight pipe is dug into the lower surface of the upper mold A. This pipe-shaped part 1 consists of a bent elbow-equivalent part 3 and two straight-pipe-equivalent parts 20, and the corner 8 formed by these two straight-pipe-equivalent parts 2 is a straight pipe part formed by this mold A. It is the same as the elbow angle. Figure 2 shows the lower mold used in the present invention,
1.a is a top plan view, b is a sectional view taken along line B-B of a, and c is a sectional view taken along line C-C of a.

In this figure, a shelf part 5 is folded into the lower mold B, and a tube-shaped part 1 is formed at the bottom of this false part 5. The pipe-shaped part 1 consists of an elbow-equivalent part 3 and two straight-pipe-equivalent parts 4,
In this lower mold, the angle 02 formed by the two straight pipe equivalent portions 4 is made slightly smaller than the angle of the straight pipe elbow formed by this mold B. That is, 8,>82.

The desirable range of this difference, ie, (8, -82), is empirically determined to be between 3 degrees and 7 degrees. Note that depending on the material, size and shape of the pipe material 10 to be molded, and other conditions,
The above (8, -a2) is selected within the above range.
Further, the upper mold A is manufactured to a size that allows it to be inserted into the recessed part 5 of the lower mold B, leaving a slight margin.

Next, the operation of forming an elbow with a straight pipe using the upper and lower molds A and B will be explained with reference to FIGS. 3a and 3b.

As shown in FIG. 3a, the tube material 10 is placed on the lower mold B and its upper surface is pressed down by the upper mold A using a press (not shown). The pipe material 10 has a straight pipe elbow 10 as shown in FIG. 3b.
It is shaped like a. As mentioned above, since the tube-shaped parts 1 are provided in the upper and lower molds A and B, the tube material 10 is prevented from spreading laterally when bent, and the corner 8 of the upper mold is connected to the corner 02 of the lower mold. Since it is 3 to 7 degrees larger than that, there is a slight margin 11 between the lower surface of the straight pipe attachment 10a and the tube shaped part of the lower mold.
Therefore, the deformation of the lower surface side of the elbow with straight pipe 10a is not restrained, thereby preventing the formation of an ellipse in the cross section at the boundary with the vessel pipe and further preventing the upper surface of the elbow from becoming wavy. Here, a supplementary explanation will be given of the reason for determining the corner 8 of the upper mold A and the corner 02 of the lower mold B in the present invention. As shown in Figure 4,
If the above-mentioned both angles are the same, that is, 0, = a2, 3 molding the straight pipe elbow 10a using the upper and lower molds,
The shape of the outer radius side of the elbow with straight pipe 10a becomes thinner at the center due to tensile strain during deformation of the pipe, and it cannot be formed according to R2 of the lower mold B, resulting in the diameter d of the straight pipe and the strangeness of the curved part. The relationship with d2 is also d,>, and the curved portion has an elliptical cross section. Therefore,
To prevent this, 03-82 is required to be at least 3 degrees. In addition, as shown in Fig. 5, normally, when the straight pipe elbow 10a is formed, a convex portion T is generated on the diameter part due to compressive strain on the inner radius side of the elbow 10a. In the present invention, the upper and lower molds are designed so that the upper and lower molds come into contact with the convex portion T of the elbow 10a) and suppress deformation from both sides as shown by arrows P and P2.

When the angular difference (0, -82) between the upper and lower molds is in the range of 3o to 7o, the portion corresponding to the convex portion T is held down by the upper and lower molds as shown by arrows P, , P2. If it is outside this range, the convex correction portion (arrows P, P2) will move away from the convex portion T, and a convex portion will occur. Examples will be described below.

The applicable product is an elbow with a straight pipe for cooling related to nuclear power, and its material is SA1 81 of ASTM standard and SUS316 of JIS standard, using pipe of size 26^, 9
An eruvium with a straight pipe was integrally molded by a molding machine using upper and lower molds A and B at a temperature of 25°C.

In terms of shape, there was neither an elliptical cross section nor a wavy surface, and after heat treatment, the mysterious material was removed from one end and 5 mechanical tests were conducted, and the flow rate was within the standard.

As explained above, according to the present invention, by providing a pipe-shaped part in the mold and by providing a difference in the angles formed by the straight pipe equivalent parts of the upper and lower molds, the ellipse from the bent part of the pipe to the straight part is formed. It is possible to manufacture an elbow with a straight pipe part in which the occurrence of wavy surfaces and convex parts are prevented, the inner diameter of the pipe is a perfect circle, the outer surface is flat, and the necessary angle is secured. Since the Erbo and the straight pipe are integrally molded in this way, there is no need for welding, and there are no accidents such as breakage or leakage of the weld between the Erbo and the straight pipe, which were problems in the past.
It also prevents stress corrosion, intergranular corrosion, and local stress in welds, eliminates the need for welding work and inspection of welded parts, and reduces tip processing costs, welding material costs, welding costs, and post-weld heat treatment costs. Since it is no longer necessary, manufacturing costs are greatly reduced. ，

[Brief explanation of drawings]

Figure 1 shows the upper mold used in the present invention, and a is a top plan view;
b is a side view, c is an A-A sectional view of b, FIG. 2 shows the lower mold used in the present invention, a is a top plan view, and b is a cross-sectional view of B of a
-B sectional view, c is a CC sectional view of a, and FIG. 3 is an explanatory side view of the molding method of the present invention, where a shows the state before molding and b shows the state after molding. FIG. 4 and FIG. 5 are side views for explaining the shapes of the upper and lower molds, respectively. 1... Pipe shaped part, 2... Straight pipe equivalent part, 3... Elbow equivalent part, 4... Straight pipe equivalent part, 5...
Bottling section, 10... Pipe material, 10a... Elbow with straight pipe. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1 A pipe-shaped part corresponding to the half-split shape of the pipe to be molded is formed on the lower surface, and an elbow-equivalent part equivalent to the elbow with a straight pipe into which this pipe-shaped part is molded, and two straight pipe-equivalent parts. It has an upper mold, and a recessed part into which the upper mold can be fitted, and a tube-shaped part is molded at the bottom of this recessed part, and this pipe-shaped part has an elbow-equivalent part facing the upper mold. , which consists of two straight pipe equivalent parts, and the angle formed by these two straight pipe equivalent parts is 3 to 7 degrees smaller than the angle formed by the two straight pipe equivalent parts of the upper mold. A method for integrally molding an elbow with a straight pipe, characterized in that a lower mold is used, a pipe material is placed between the upper and lower molds, and a pressing force is applied to the mold to bend and form the pipe material.