GB917970A - Integral lightweight drill pipe and method for making same - Google Patents

Abstract

917,970. Boring earth. PITTSBURGH STEEL CO. Aug. 22, 1960, No. 28982/60. Class 85. [Also in Groups XXII and XXVIII] A drill pipe for use with circumferentially gripping slips and having a long slip receiving portion near at least one end thereof has a thin wall portion for the major part of its length, a thick wall portion several feet long connected to the thin wall portion by a short section of intermediate thickness, the outer end of said thick wall portion being upset for several inches, the rest of the thick-wall portion which forms the slip receiving portion being of uniform thickness, and the slip receiving portion, the section of intermediate thickness and the thin wall portion having a continuous inner or outer surface of uniform inner or outer diameter. The leading end 2 (Figs. 2 and 3) of the tube 1 is pointed, passed through a die 3, and drawn cold through the die to sink the first four or five feet of the tube. A mandrel 12, the smaller diameter portion 10 of which is a little larger than the inner diameter of the reduced part of the tube is then run forward until it is gripped by the tube and drawn into the die until arrested by a stop (not shown) on the mandrel rod 8, so that the larger portion 11 is within the die. A section of the tube is compressed on the smaller part of the mandrel and as drawing continues the remainder of the tube is reduced in wall thickness by being drawn between the mandrel and the die. The resulting tube (Fig. 4) has a thick wall section 13 joined by a short section 14 to the remaining thin-walled section of the tube. The first few inches of the thick-walled section of the pipe is heated and upset and threaded to form a pipe connection, or a separate piece can be welded on. Both ends of the pipe can be provided with a thick walled section by stopping the cold-drawing of the tube before the end of the pipe is reached, retracting the mandrel until the smaller diameter portion 10 is within the die and then continuing drawing to form a short section of the same diameter as the section 14, then removing the mandrel and sinking the remainder of the tube. The tube may be made of uniform internal diameter and varying outside diameter by drawing through the tube a plug which is the same size as the internal diameter of the thin-walled section. In a modification, a three step mandrel 31 (Fig. 12) is used which has cylindrical portions 32, 33, 34 and tapered connecting portions 35 and 36. The leading end 32 of the mandrel is positioned in the die when the first four or five feet of the tube is drawn and controls the wall thickness, this part of the operation is usually used to put a finish on the inside of the thick-walled portion. The remaining two steps of the mandrel function in the same way as in the original method. In a second modification (Fig. 14), the front and rear steps 45 and 46 of the mandrel just described are joined by a uniformly tapered section 47 which produces a tube (Fig. 15) in which the thick and thin walled sections are joined by a uniformly tapered section 49.