Abstract: A pipe joint comprising: a pin having a tapered male screw section formed on an outer circumferential face of an end of a pipe; a box having a tapered female screw section, which can be screwed to the tapered male screw section, formed on an inner circumferential face of an end of a pipe, wherein the tapered male screw section is screwed into the tapered female screw section, a top face of a male thread ridge of the tapered male screw section and a top face of a female thread ridge of the tapered female screw section have a predetermined width like a square screw thread, trapezoidal screw thread and buttress screw thread, and top faces of both thread ridges are inclined in a direction opposite to a tapered face of screw threads with respect to a face parallel to the pipe axis.

Abstract: This invention provides an oil well pipe threaded joint capable of preventing looping and squeezing of a soft synthetic resin ring and consequently, preventing catching of a tool during a logging operation and damage such as corrosion by a corrosive fluid, the oil well pipe threaded joint employs the construction wherein a soft synthetic resin ring is interposed between distal end surfaces of pins, each step surface of a shoulder portion on an inner peripheral side of a coupling and a step surface of each pin are brought into abuttment, and each inside thread of the coupling of the coupling and each outside thread of each pin are engaged, wherein a compressive ratio of the soft synthetic resin ring in an axial direction falls within the range expressed by an inequality 18,000/E≦compressive ratio (%)<0.038−1×1n[1−{(d1−d2)+0.36}/0.

Abstract: A packing material for refractory capable of restraining the deterioration of working environment since there is generated no smoke and foul smell even if used for setting preheated submerged nozzles or long nozzles, allowing easy visual observation of fitting operation, and maintaining the packing material deformation suppression performance. A packing material for refractory of the present invention is characterized in that a part or the whole surface of a packing base material for refractory formed from inorganic refractory powder, inorganic and/or organic fibrous raw material, and being agents and/or various types of additives is covered with a metal foil. This packing material may be used together with an inorganic paint or ceramic fiber sheet, and when so used, the metal foil is to be applied to the outermost surface thereof. In addition, a metal foil having recessed and raised portions thereof may be used.

Abstract: Quenched steel pipe is first held at a tempering temperature for a given period of time, then cooled relatively rapidly. While carrying the pipe in the direction of its length, cooling water is sprayed from outside onto its external surface at an average water flux of not lower than 0.05 m.sup.3 /min.m.sup.2 and not higher than 2 m.sup.3 /min.m.sup.2. This cooling is started when the pipe temperature is between 400.degree. C. and 700.degree. C. and ended between room temperature and 350.degree. C. Also, the cooling is effected at a mean cooling rate of not lower than 5.degree. C./sec. and not higher than 40.degree. C./sec. This cooling method improves the collapse strength of a pipe by providing an appropriate tensile residual stress to the internal surface of the pipe and reduces the cooling floor area without sacrificing the collapse strength of the pipe.