Abstract: A solid lubricating coating film capable of imparting favorable lubricity and corrosion resistance to a connection for oil country tubular goods. Two or more solid lubricants are dispersed in a binder resin. Graphite is contained in an amount of 50% or more and 90% or less of a total weight of the solid lubricants, and the graphite has a scaly shape and an average particle diameter of 10.0 ?m or less. A solid lubricant made of one or more materials selected from BN, mica, talc, MCA, MoS2, PTFE, PFA, and FEP is further contained as other solid lubricants of the two or more types of solid lubricants. The binder resin contains a PEEK resin having an average particle diameter of 20 ?m or less as a main component, and the PEEK resin is contained in an amount of 70% or more of a total weight of the binder resin.

Abstract: A make-up/break-out evaluation method that makes it possible to evaluate the seizure resistance of a threaded joint for oil country tubular goods accurately without performing a test using a threaded joint with an actual length. When performing test with respect to the threaded joint for oil country tubular goods formed by attaching a pin lower portion to box upper portion with its axis directed vertically, a test pin formed by a pin shorter than an evaluation target pin used as test pin; a weight attached to test pin upper portion; mass of the weight is equal to or greater than a mass obtained by subtracting the test pin mass from the evaluation target pin mass; an initial set position for test pin is set where test pin five crests or ¼ of all test pin crests, whichever is greater, or more are exposed from the box upper end face.

Abstract: An agent for forming a solid lubricating coating film on a thread portion of oil country tubular goods, in which a binder resin contains a prepolymer and a curing agent, the prepolymer is formed of one or more epoxy resins, 70 parts by weight or more of the prepolymer is contained with respect to 100 parts by weight of the binder resin, the epoxy resin constituting the prepolymer has an epoxy equivalent of 100 or more and 500 or less, the solid lubricant contains boron nitride (BN) in an amount of 80% by weight or more, BN has an average particle size of 10 ?m or less, and a total weight of the solid lubricant is 0.1 times or more and two times or less a total weight of the binder resin.

Abstract: A threaded joint wherein a relationship between shoulder angle parameters and thread taper angle parameters for a coupling and a pair of pins inserted from both ends of the coupling is defined by the following expression (1), and a tightening torque with which the threaded joint is tightened is 60% or more and 85% or less of a yield torque determined by the following expression (2): - 1.5 ? ° ? ? ? ? - ? ? ? ? 2. ° , ( 1 ) T = ( T S + T D ) ? 1 12 ( 2 ) T S = f t ? P c ? E 7 2 ? ( 2 ? ? ? E 7 ) ? L 4 ? 1 2 P c = E ? ? m 2 ? ( ( W 2 ) 2 - ( E 7 2 ) 2 ) ? ( ( E 7 2 ) 2 - ( d 2 ) 2 ) 2 ? ( E 7 2 ) 3 ? ( ( W 2 ) 2 - ( d 2 ) 2 ) T D = Y m ? A S ( P 2 ? ? + R t ? f s cos ? ? + R s ? f s ) .

Abstract: Provided herein is a duplex stainless steel pipe that is high in strength and has excellent abrasion resistance and indentation resistance on inner and outer surfaces of the steel pipe. A method for manufacturing such a stainless steel pipe is also provided. A duplex stainless steel pipe of the present invention has a composition that contains, in mass %, C: 0.005 to 0.150%, Si: 1.0% or less, Mn: 10.0% or less, Cr: 11.5 to 35.0%, Ni: 0.5 to 15.0%, Mo: 0.5 to 6.0%, N: less than 0.400%, and the balance being Fe and incidental impurities, and has a microstructure with a ferritic phase and an austenitic phase, the duplex stainless steel pipe having an axial tensile yield strength of 689 MPa or more, and having an outer surface and an inner surface each having an oxide layer having an average thickness of 1.0 ?m or more.

Abstract: A solid lubricating coating film capable of imparting favorable lubricity and corrosion resistance to a connection for oil country tubular goods. Two or more solid lubricants are dispersed in a binder resin. Graphite is contained in an amount of 50% or more and 90% or less of a total weight of the solid lubricants, and the graphite has a scaly shape and an average particle diameter of 10.0 ?m or less. A solid lubricant made of one or more materials selected from BN, mica, talc, MCA, MoS2, PTFE, PFA, and FEP is further contained as other solid lubricants of the two or more types of solid lubricants. The binder resin contains a PEEK resin having an average particle diameter of 20 ?m or less as a main component, and the PEEK resin is contained in an amount of 70% or more of a total weight of the binder resin.

Abstract: An agent for forming a solid lubricating coating film on a tightening surface of a thread portion, in which a solid lubricant is dispersed in a binder resin as a matrix component, a main component of the solid lubricant is melamine cyanurate, and an average particle diameter of the melamine cyanurate is 0.1 ?m or more and 10.0 ?m or less, the binder resin contains an alkyd resin and nitrocellulose, and the alkyd resin and nitrocellulose are contained in an amount of 85 wt % or more of the total binder resin component weight, and a total weight of the solid lubricant is 10 parts by weight or more and 100 parts by weight or less based on 100 parts by weight of a total weight of the binder resin.

Abstract: A solid lubricating coating film is used to realize galling resistance equal to or higher than a method using a dope compound regarding lubrication characteristics during make-up/break-out of oil country tubular goods. A threaded joint for oil country tubular goods includes a box having a thread and a pin having a male thread. A lubricating coating film including a solid lubricating coating film forms on a tightening surface of a thread portion of at least one component of the box and pin, the solid lubricating coating film is formed by dispersing a solid lubricant in a binder resin, 90 wt % or more of the binder resin is a polyamideimide resin, an average molecular weight of the polyamideimide resin is 20,000 or more and 40,000 or less, 80 wt % or more of the solid lubricant is polytetrafluoroethylene (PTFE), and an average molecular weight of the PTFE is 30,000 or less.

Abstract: To prevent fracture of a box under a tensile load without increasing the outer diameter of the box. The presently disclosed threaded joint for pipes includes a pin provided with a male thread portion at one end of a first pipe, and a box provided with a female thread portion at one end of a second pipe, where each of a plurality of thread grooves of the female thread portion has a corner portion on a load flank side and a corner portion on a stabbing flank side on a thread bottom side, a corner portion on a load flank side of a first thread groove includes a first arc portion that has a first curvature radius, and a second arc portion that has a second curvature radius, and a ratio of the second curvature radius to the first curvature radius is 3 or more.

Abstract: A threaded joint wherein a relationship between shoulder angle parameters and thread taper angle parameters for a coupling and a pair of pins inserted from both ends of the coupling is defined by the following expression (1), and a tightening torque with which the threaded joint is tightened is 60% or more and 85% or less of a yield torque determined by the following expression (2): - 1.5 ? ° ? ? ? ? - ? ? ? ? 2. ° , ( 1 ) T = ( T S + T D ) ? 1 12 ( 2 ) T S = f t ? P c ? E 7 2 ? ( 2 ? ? ? E 7 ) ? L 4 ? 1 2 P c = E ? ? m 2 ? ( ( W 2 ) 2 - ( E 7 2 ) 2 ) ? ( ( E 7 2 ) 2 - ( d 2 ) 2 ) 2 ? ( E 7 2 ) 3 ? ( ( W 2 ) 2 - ( d 2 ) 2 ) T D = Y m ? A S ( P 2 ? ? + R t ? f s cos ? ? + R s ? f s ) .

Abstract: To prevent fracture of a box under a tensile load without increasing the outer diameter of the box. The presently disclosed threaded joint for pipes includes a pin provided with a male thread portion at one end of a first pipe, and a box provided with a female thread portion at one end of a second pipe, where each of a plurality of thread grooves of the female thread portion has a corner portion on a load flank side and a corner portion on a stabbing flank side on a thread bottom side, a corner portion on a load flank side of a first thread groove includes a first arc portion that has a first curvature radius, and a second arc portion that has a second curvature radius, and a ratio of the second curvature radius to the first curvature radius is 3 or more.

Abstract: A threaded joint with excellent tensile strength, comprising: a pin having an externally threaded part comprising a first and second externally threaded sections across a step on an outer periphery on a distal-end side of a first steel pipe or tube; and a box having an internally threaded part comprising a first and second internally threaded sections across the step on an inner periphery on a distal-end side of a second steel pipe or tube, the externally threaded part being screwed to the internally threaded part to join the pin and the box. The threaded joint has a first and second thread sequence with lengths L1 and L2, respectively, and cross-sectional areas P1, P2, B1, and B2 at end positions 4, 5, 6, and 7, respectively, satisfying Formulas (1) and (2): (P2, B2)min?P1/{L1/(L1+L2)}(1) and (P2, B2)min?B1/{L2/(L1+L2)}(2), where (P2, B2)min represents P2 or B2, whichever is smaller.

Abstract: A method of manufacturing a seamless stainless steel pipe for Oil Country Tubular Goods by heating a billet having a specified chemical composition including forming the billet into a seamless steel pipe by applying hot working to the billet, cooling the seamless steel pipe to a room temperature at a cooling rate of air cooling or more, thereafter, performing quenching by heating the seamless steel pipe to a temperature of 850° C. or above, subsequently, cooling the seamless steel pipe to a temperature of 100° C. or below at a cooling rate of air cooling or more, and subsequently, applying tempering to the seamless steel pipe at a temperature of 700° C. or below for a specific holding time.

Abstract: A threaded joint with excellent tensile strength, comprising: a pin having an externally threaded part comprising a first and second externally threaded sections across a step on an outer periphery on a distal-end side of a first steel pipe or tube; and a box having an internally threaded part comprising a first and second internally threaded sections across the step on an inner periphery on a distal-end side of a second steel pipe or tube, the externally threaded part being screwed to the internally threaded part to join the pin and the box. The threaded joint has a first and second thread sequence with lengths L1 and L2, respectively, and cross-sectional areas P1, P2, B1, and B2 at end positions 4, 5, 6, and 7, respectively, satisfying Formulas (1) and (2): (P2, B2)min?P1/{L1/(L1+L2)}(1) and (P2, B2)min?B1/{L2/(L1+L2)}(2), where (P2, B2)min represents P2 or B2, whichever is smaller.

Abstract: A method of manufacturing a seamless stainless steel pipe for Oil Country Tubular Goods by heating a billet having a specified chemical composition including forming the billet into a seamless steel pipe by applying hot working to the billet, cooling the seamless steel pipe to a room temperature at a cooling rate of air cooling or more, thereafter, performing quenching by heating the seamless steel pipe to a temperature of 850° C. or above, subsequently, cooling the seamless steel pipe to a temperature of 100° C. or below at a cooling rate of air cooling or more, and subsequently, applying tempering to the seamless steel pipe at a temperature of 700° C. or below for a specific holding time.