JPS5820389A - Structure of friction welded joint of pipe - Google Patents

Abstract

PURPOSE:To correct axial mis-alignment during friction welding automatically and to obtain a welded joint which is deburred on the inside by forming the end faces of pipes on both sides to projecting circular conical surfaces and the end faces of an intermediate material to recessing circular cones and forming a cylindrical part to the inside circumferential surface of the intermediate material in one body. CONSTITUTION:The end faces of an intermediate material 3 are formed to recessing circular conical surfaces, and the end faces of pipes 1, 2 on both sides to projecting circular conical surfaces. A cylindrical part 3a is formed to the inside circumferential surface of the material 3 in one body. If the pipes 1, 2 are pressed from both sides by rotating the material 3 in such joint construction, the end faces of the pipes 1, 2 fit to the end faces of thematerial 3, and axial mis-alignment is corrected automatically. The material 3 in a high temp. state deforms plastically and the part 3a is pressed to the inside surfaces of the pipes 1, 2, whereby th initial clearances are annihilated. Upon ending of the press welding, the outside surfaces of the material 3 go flush with the outside surfaces of the pipes 1, 2, thus assuming the state installed with a backing strip. The inside burrs produced during the welding are contained in the annular groove 3b of the inside surface in the tapered parts of the material 3.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a friction welding joint structure in which two pipes are arranged coaxially with an intermediate material sandwiched between them, and only the intermediate material is rotated to press the pipes from both sides for friction welding. Although this method has the advantage of producing joints with good performance in an extremely short period of time, conventionally a friction welding machine was installed in the factory to weld the parts that were brought in. However, with the development of the joint structure that uses the intermediate material mentioned at the beginning, it has become applicable to connection work for long pipes, curved pipes, large steel pipe structures, and on-site piping such as city gas.

However, in cases where the pipe is long and curved, or one of the parts to be welded is fixed at the site, it is not possible to align both parts coaxially even if both parts are gripped by the clamp unit of the welding machine. It was difficult and axis misalignment was unavoidable. If misalignment occurs, the joint will be incomplete. Furthermore, when pipes are friction welded, the pipes are pressed against each other at high temperatures, causing cracks to occur on the inner and outer surfaces of the pipes. The outer surface can be easily cut away, but the inner surface cannot be easily removed, and if gas is allowed to flow into the pipe, moisture may accumulate in this area and cause corrosion. There was a problem.

In view of the above-mentioned problems of conventional friction welded joints for pipes using intermediate materials, the present invention provides a friction welded joint with a simple structure that automatically corrects axis misalignment and eliminates inner surface cracks. The purpose is to

Hereinafter, the present invention will be explained in detail with reference to drawings showing embodiments thereof.

As shown in FIG. 1, when friction welding is performed by arranging the pipes 1.2 to be welded coaxially on both sides of the intermediate member 8 and rotating the intermediate member 8t and pressing the pipes 1.2 to be welded from both sides, When the groove is inclined so that it widens from the inner surface to the outer surface in the vertical cross section of the intermediate material 8, the welded pipes 1.2 on both sides
The end faces of the intermediate material 8 are convex conical faces, and both end faces of the intermediate material 8 are concave conical faces. Therefore, even if there is some axis misalignment, both sides,
By suppressing the welds, top friction welding is performed with self-alignment and axial misalignment automatically corrected. However, since the pressing force of friction welding is large and the intermediate material is red-hot,
In some cases, if the intermediate material 8 is pressed on both sides by the inclined end faces of the pipe to be welded 1.2, the diameter of the intermediate material will increase, and it will be pushed slightly outward, which may cause the inner and outer surfaces to be at different levels from the pipe to be welded. There is.

Also, as shown in Fig. 2, if both ends of the intermediate member 8 are made into convex conical surfaces and the end surfaces of the pipes 1 and 2 on both sides are made into concave conical surfaces, the axis misalignment will be automatically corrected, but in this case. By being pressed, the intermediate material 8 is pushed inward.

The present invention proposes a joint structure in which the inner and outer surfaces of the intermediate material do not have a level difference with the surfaces of the pipes on both sides when fitting conical surfaces and automatically correcting axis misalignment.

FIG. 8 is a diagram showing the state before welding of the embodiment of the present invention.
Ru. Both end surfaces of the intermediate material 8 have concave conical surfaces, and the end surfaces of the pipes 1.2 on both sides have convex conical surfaces.The structure is similar to that shown in FIG. 1, but the inner and outer diameters of the intermediate material 8 are Both are made slightly smaller than the inner and outer diameters of pipe 1 and 2. Further, a cylindrical portion 8a is integrally provided on the inner circumferential surface of the intermediate member 8 to which a dust abutment is applied after welding. At the intersection of the outer surface of the cylindrical portion 8a and the above-mentioned inclined groove surface, an annular groove 8b is provided with a size suitable for receiving the cracks generated by friction welding. Further, the inner surface of the cylindrical portion has an arc shape when viewed in longitudinal section.

Since this joint structure is constructed as described above, even if there is some axis misalignment between the pipes 1 and 2 on both sides during friction welding, the inner surface of the intermediate member 8 (the outer surface of the cylindrical member 8a) Since the diameter is slightly smaller than the inner diameter of the pipe, the end face of the pipe can approach the beveled surface of the intermediate material 8 without getting caught in the cylindrical part 3a, and the end face of the pipe 1.2 can be easily attached to the end face of the pipe 1.2 as shown in FIG. A slight clearance is created between the outer surface of the cylindrical portion 8a and the inner surface of the pipe 1.2. In this state, when the intermediate material 8 is rotated and one pipe 1.2 is pressed from both sides while rotating, the convex conical surface on the end surface of the pipe fits into the concave conical surface on the end surface of the intermediate material, and the axis misalignment is automatically corrected. In addition, the intermediate member which is in a high temperature state is plastically deformed during pressure welding, so that the outer surface of the cylindrical portion 8a having a large diameter is pressed against the inner surface of the pipes 1 and 2, thereby eliminating the initial clearance, and This acts as a stopper and prevents the intermediate material 8 from being pushed out any further to the outside, and when the pressure welding is completed, the outer surface of the intermediate material 8 and the pipe 1 are connected to each other as shown in FIG.
．． The outer surfaces of the cylindrical portions 8a and 8a coincide with each other, and the outer surface of the cylindrical portion 8a is the same as the pipe l.
.

It has a shape in which a backing metal is attached to the inner surface of 2 in a normal welding process. As a result, the groove surfaces of the intermediate member 8 and the pipe 1.2 are pressed into contact with each other in a completely aligned state, and friction welding is completed. The burr generated inside the welded part due to friction welding is accommodated in the annular groove 8b, thereby preventing the cylindrical portion 8a from moving toward the center line and creating a deformation gap, and by preventing the burr from being exposed inside the pipe. This also prevents adverse effects on fluid flow and pipes. Note that since the inner surface of the first cylindrical portion 8a is arcuate, an increase in fluid resistance is reduced. As described above, according to the present invention, it is possible to obtain an excellent pipe friction welded joint that has a simple structure, automatically corrects even if there is a slight axis misalignment, and eliminates burrs occurring on the inner surface.

[Brief explanation of drawings]

Figures 1 and 2 are cross-sectional views showing examples of conventional friction welded joint structures, Figure 8 is a cross-sectional view showing the welding state of the embodiment of the present invention, and Figure 4 is after the welding is completed. FIG. 1.2... Pipe to be welded 8... Intermediate material 8a...
Cylindrical part 8b... (receiving annular groove Fig. 3 Fig. 4)

Claims (2)

[Claims] (1) In a friction welding joint structure in which the ends of two pipes to be connected by sandwiching an intermediate material are arranged coaxially, only the intermediate material is rotated, and the pipes on both sides are pressed against the intermediate material and welded. The end surface of the intermediate material forms a concave conical surface; the end surfaces of the pipes on both sides form a convex conical surface, so that the bevel is inclined with respect to the axis, and a backing metal is attached to the inner circumferential surface of the intermediate material after welding. A friction welded joint structure for pipes characterized by integrally providing a cylindrical part that can be in a closed state. (2) Claim 1, characterized in that an annular groove is provided at the intersection of the groove surface of the intermediate material and the portion forming the bracing metal to receive the cracks caused by friction welding. Friction welded joint construction as described in .