WELDED DRILL PIPES IN WHICH THE INTERNAL FLASH IS REMOVED AND RELATIVE PROCEDURE OF MANUFACTURING

Abstract: Welded drill pipes for application in the civil engineering and relative procedure for the elimination of the internal flash. The pipes, manufactured by friction welding of the sections of the pipe and the tool joints, are characterized by the elimination of the internal flash (coming out from this welded joint) which fills a proper cavity. The advantages of the new product and of the process of manufacturing are the elimination of the fluid-dynamic troubles inside the pipe, caused by the inner flash, and the elimination of the crack initiations due to fatigue-stress in the welded joint.

Description: Description Welded drill pipes in which the internal flash is removed and relative procedure of manufacturing. Technical field The present invention relates to a welded drill pipe in which the internal flash is removed, and to the relative procedure for its manufacturing. Background art In the state of the technique, drill pipes for application in civil engineering are already known. Said pipes are also manufactured by means of friction welding between the pipe sections and the tool joints, both male or female. The product obtained, as schematised in fig. 1, is a modular pipe which can be adjusted to any length. As known, the process of friction welding takes place without external weld material and without smelting the joints edges. Compared to the other known welding processes (for example, the seam welding), the friction welding assures a high mechanical resistance of the joint, its compactness and a high repetitiveness of the process phases and, consequently, its quality. The drawback of the known applications is that the friction welded joints are characterized by the formation of the "flash" inside and outside the joint, as schematised in fig. 2. The external flash is easily removed with a cutting tool, whereas the elimination of the internal one is much more difficult. The inner flash disturbs the flow of the fluid inside the pipe and, due to its characteristic middle notch, can cause the crack initiations due to fatigue-stress in the welded joint. Disclosure of the invention The invention and its relative manufacturing procedure solve the technical problem above mentioned as for it is characterized by the complete elimination of the flash, which fills a cavity produced in one of the two parts to be welded, for example, in the tool joint. In this way, all the fluid-dynamic troubles inside the pipe, caused by the inner flash (pressure losses, vorticity, etc.), are avoided as well as the crack initiations due to fatigue-stress in the welded joint. These and other advantages will be pointed out in the detailed description of the invention that refers to the figures of the table 1. All of them are examplifying and not restrictive. Way of carrying out the invention With reference to the above mentioned tables: • fig. 1 shows the modular portion of a friction welded drill pipe, manufactured according to the prior art; • fig. 2 represents some shapes of the "flash", coming out from the friction welding process; • fig. 3 shows a first example of a friction welded joint with a cavity to be filled by the inner flash, according to the invention, placed between the pipe and male tool joint; • fig. 4 shows a second example of a friction welded joint with a cavity to be filled by the inner flash, according to the invention, placed between the pipe and female tool joint. With reference to figure 1 , number 1 shows a modular portion of a drill pipe for civil engineering comprising a pipe 2, a male tool joint 3 and a female tool joint 4. Said portion 1 has been manufactured by means of friction welding between pipe and tool joints, both male and female. As known, the friction welding is made by means of strong impact between the two parts to be welded; moreover, to improve the junction between them, the parts are heated to a forging temperature obtained by the rotation of one part with respect to the other. T e process produces a very compact and highly resistant joint and is characterized by a good repetitiveness of its phases and. then, by an excellent quality standard. A disadvantage of the process however lies in the formation of the flash 5 ; it is a burr which comes out just during the heating phase (produced by the friction between the two parts to be welded) and takes a shape like those schematically shown in fig. 2. In particular, it is characterized by the presence of a double burr 6 which causes vortices into the fluid flow and by a middle notch 7, possible crack initiation due to fatigue-stress in the welded joint. The removal of the inner flash can be obtained, according to the invention, manufacturing one of the two parts to be friction welded (for example, the tool joint) as the one shown in fig. 3. In said picture, the male tool joint 8 comprises an externally threaded portion 9, an internal shape 10, suitable to allow the proper motion of the fluid, a stop surface 11 , against which the section 20 to be welded is to be placed, a coupling surface 12 for said section and it is characterized by a cavity 13, whose volume and shape are such as to be completely filled with the inner flash produced by the welding process. Consequently the complete and perfect filling of the cavity avoids the formation of the middle notch. The same manufacturing, according to the invention, is depicted in fig. 4. In said picture the joint between the section 20 and the female tool joint 14 is shown. The female tool joint 14 comprises an internally threaded portion 15, an internal shape 16, suitable to allow the proper motion of the fluid, a stop surface 17, against which the section 20 to be welded is to be placed, a coupling surface 18 for said section and it is characterized by a cavity 19 with the same characteristics of the cavity 13 realized in the male tool joint.

Claims: Claims 1 ) Welded drill pipe in which the internal flash is removed, which comprises modular parts manufactured by friction welding of the sections of the pipe 20 and tool joints (8, 14) ; characterized by the fact that at least one of the two parts to be welded together contains a cavity (13, 19), whose volume and shape are such as to be completely filled with the inner flash. 2) Welded drill pipe according to the claim 1 , characterized by the fact that said cavity 13 is obtained in the male tool joint 8. 3) Welded drill pipe according to the claim 1 , characterized by the fact that said cavity 19 is obtained in the female tool joint 14. 4) Welded drill pipe according to the claim 1 , characterized by the fact that said cavities ( 13, 19) are obtained in both tool joints (8, 14). 5) Male tool joint according lo the claim 1 , characterized by a stop surface 1 1, against which the section 20 to be welded is to be placed, a coupling surface 12 for said section and said cavity 13. 6) Female tool joint according to the claim 1 , characterized by a stop surface 17, against which the section 20 to be welded is to be placed, a coupling surface 18 for said section and said cavity 19. 7) Procedure of manufacturing of drill pipes by friction welding characterized by the fact that at least one of the two parts to be welded contains (between the stop surface (11, 17) and the coupling surface (12, 18) of the other part) a cavity (13, 19), able to be filled with the inner flash coming out from the heating of the two parts to be welded during the friction welding process.

Inventors: CHIRULLI RENZO, COLLI ELIO, KIM, HEE DOO
Applicants: CHIRULLI RENZO, COLLI DRILL S R L, COLLI ELIO, CHIRULLI, RENZO, COLLI DRILL S.R.L., COLLI, ELIO
Application year: 1997
Main classification: E21B17
IPC codes: E21B17, F16L13