JPS649896B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method of connecting pipes, and in particular to a method of connecting pipes suitable for reducing residual stress generated at the joints of pressure pipes used in pressure tube nuclear reactors. Regarding connection method.

[Background of the invention]

FIG. 1 shows the structure of a conventional pressure tube upper and lower rolled joint section applied to a pressure tube type nuclear reactor.

For both the upper and lower rolled joint parts A and B, parts other than the pressure pipe 1 are machined, and the lower rolled joint part of the pressure pipe 1 is flared based on the outer diameter using the rubber tube expansion method. After improving the required surface finish accuracy, each part is assembled and inserted inside, and the upper extension pipe 5 and inner ring 3 are expanded using the installed rolled joint device shown in FIG. 2, and both ends of the pressure pipe 1 are This structure mechanically connects the upper extension pipe 5 and lower extension pipe 2 of the pressure pipe 1.

Here, 4 is an outer ring which is a component for sandwiching the pressure pipe 1 at the upper roll joint.

Note that the upper rolled joint portion side of the pressure pipe 1 is only subjected to surface finishing with the necessary precision.

This mechanical joining method provides the sealing function (airtightness) and mechanical strength against tension, bending, and torsion required for a rolled joint.

However, with this structure, the residual stress generated in the pressure pipe 1, especially at the rolled joint part, may be relatively high.In order to improve the soundness and reliability of the pressure pipe 1, it is necessary to reduce this residual stress. However, it would take a lot of work time to implement measures such as carrying out local stress relief annealing after the rolled joint to reduce the residual stress to the targeted reduction target. In particular, in the case of the one disclosed in JP-A-53-139222, the position of the roller that contacts the inner ring 3 is shifted so that the non-expanded portion remains on the end of the inner ring after heat treatment, and then the tube is expanded again. It takes time and effort.

[Purpose of the invention]

The purpose of the present invention is to reduce residual stress generated in a pressure pipe at a rolled joint in a single pipe expansion operation without carrying out local stress relief annealing after rolling joint, thereby improving soundness and reliability. The aim is to improve the

[Summary of the invention]

The present invention was made based on the following study results.

The residual stress generated in the rolled joint pressure pipe is related to the radial displacement of the pressure pipe after the joint. In order to reduce the radial displacement, it is necessary to reduce the tube expansion rate by the rolled joint device shown in FIG. However, in order to guarantee the sealing performance and mechanical performance of the joint, the pipe must be expanded at a predetermined expansion rate or higher. In this way, residual stress and tube expansion rate have a contradictory relationship. Therefore, in order to reduce the residual stress generated in the pressure pipe at section C of the upper rolled joint shown in Fig. 3, the expansion ratio of the seal section at section D should be set to a predetermined value so as not to have much effect on the seal section. It is necessary to reduce the expansion rate of the E section that is not provided.

Similarly, in order to reduce the residual stress generated in the pressure pipe of the F section of the lower rolled joint shown in Fig. 4, the expansion rate of the seal section of the G section should be a predetermined value, and the expansion rate of the H section should be set to a predetermined value. Must be lowered.

However, the tube expansion operation must be performed at once, and for this purpose, the tube expansion rate must be controlled by changing the taper angle of the roller that contacts the two parts.

As shown in FIG. 2, the rolled joint device includes rollers 5 and 6 attached to a frame 8.
receives the rotational movement of the mandrel 7 and performs a relative rotational movement.

Here, by changing the taper angle of the rollers 5 and 6, residual stress can be reduced.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG.

FIG. 5 shows the basic structure of the rolled joint device according to the present invention, in which the rollers 6 are in parallel contact with the inner surface of the inner ring 3, and the rollers 5 are arranged at a taper angle α _n with the inner surface of the inner ring 3. The taper angle of the rollers has been adjusted so that they make contact with each other. By moving the mandrel 7 in the axial direction, the rollers 6 and 5 are displaced in the radial direction, but since the roller 5 contacts the inner ring obliquely, the H portion of the inner ring 3 has a smaller radial displacement than the G portion. It's summery. According to the present invention, even if the tube is expanded to a predetermined tube expansion rate or higher in the seal portion, there is no risk of residual stress increasing because the tube expansion rate at the end of the joint portion is low. The joint work can be completed in one operation, and the work time can be greatly shortened.

〔Effect of the invention〕

As described above, according to the present invention, by combining rollers with different taper angles, a joint portion with reduced residual stress can be obtained, and the joint work time can be greatly shortened.

[Brief explanation of drawings]

Fig. 1 is a sectional view of the pressure pipe rolled joint, Fig. 2 is an external view of a conventional rolled joint device, Fig. 3 is a sectional view of the upper rolled joint, and Fig. 4 is a sectional view of the upper rolled joint. FIG. 5, a sectional view of the lower roll joint portion, is a basic structural diagram of an embodiment of the present invention. 1...Pressure pipe, 2...Lower extension pipe, 3...Inner ring, 4...Outer ring, 5...Upper extension pipe, 6...
...roller, 7...mandrel, 8...frame.

Claims (1)

[Claims] 1. Insert the end of the tube between the outer ring-shaped member and the inner ring-shaped member, and set the contact angle of the portion that contacts the inner surface of the inner ring-shaped member to a point that is higher than that of the roller near the end surface of the tube. The rollers are arranged in a tube expanding device so that the rollers farther from the end surface are larger, and the rollers are pressed radially against the inner surface of the inner ring-shaped member, thereby separating the tube end and both the inner and outer rings. A rolled joint method that mechanically connects shaped members.