Technical field [0001] The present invention relates to a method of manufacturing a pipe thread fittings and pipe thread joint, more particularly to a method for producing a threaded joint and a threaded joint for oil well pipes for oil well pipes. BACKGROUND [0002] For mining oil and natural gas fields, oil well pipe is used. OCTG, depending on the depth of the well is formed by connecting a plurality of steel pipes. Coupling of the steel pipe is performed by screwing the formed pipe thread joint between the ends of the steel pipe. OCTG are lifted for inspection, are unscrewing, after being examined, is again screwing, is used again. [0003] 　Pipe thread joint comprises a pin and box. Pin includes a male screw portion formed on the outer peripheral surface and an unthreaded metal contact portion of the distal end portion of the steel pipe. Box includes a female threaded portion and an unthreaded metal contact portion formed on the inner peripheral surface of the distal end portion of the steel pipe. Each unthreaded metal contact portion, comprising a metal seal portion and the shoulder portion. When steel pipes are screwed, the male screw portion and female screw portion, the metal seal portions and the shoulder portions into contact. [0004] 　Threaded portion and the unthreaded metal contact portions of the pin and box, repeatedly subjected to strong friction at the time of the return screw tightening and screw of the steel pipe. These sites, if there is sufficient resistance to friction, galling when repeated back screw tightening and screw (with irreparable shrink) occurs. Therefore, the Pipe threaded joint, sufficient durability against the friction, i.e., is required to have excellent seizure resistance. [0005] 　Conventionally, in order to improve the seizure resistance, compound grease of heavy metal containing have been used. By applying a compound grease on the surface of the pipe thread joint, it can improve the seizure resistance of pipe thread fittings. However, heavy metals Pb, Zn and Cu or the like contained in the compound grease is likely to affect the environment. Therefore, development of a pipe thread joint not using compound grease is desired. [0006] 　Instead of the compound grease, pipe threaded joint for using the grease containing no heavy metal (referred to as green dope or yellow dope) has been proposed. For example, JP 2008-215473 (Patent Document 1), Japanese Patent Kohyo 2005-514573 (Patent Document 2) and JP 2003-074763 (Patent Document 3), using a grease containing no heavy metal there is described pipe thread joint which is excellent in seizure resistance even when. [0007] 　JP 2008-215473 discloses a screw for steel pipes described in (Patent Document 1) joint, a tubular threaded configured to contact surface and a pin and a box having respective having a threaded portion and an unthreaded metal contact portion it is a joint. The tubular threaded joint, at least one contact surface of the pin and the box, and having a first plating layer made of Cu-Zn alloy. Thus, when applying a green dope, more even undoped, exhibits sufficient leakage resistance and seizure resistance, and further have excellent corrosion resistance, there are green dope or a lubricating coating on the plating layer occurrence of crevice corrosion is prevented also be, as being described in Patent Document 1. [0008] 　Tubular members described in JP-T 2005-514573 (Patent Document 2) has at one end a metal of the internal thread, and / or the metal of the external thread. At least a portion of the threads of the internal thread and external thread are covered with copper, and tin alloy. Alloy of copper and tin, containing 80 wt% copper to 20 weight%. Thus, without the use of harmful grease environment, improved metal - metal seal coupling portion can be provided, and are described in the patent document 2. Further, Patent Document 2, the tubular members together when the screw connection is described for the use of PTFE-based lubricant, or graphite-based lubricants. [0009] 　JP 2003-074763 JP by which oil well steel pipe joint is described in (Patent Document 3), a male screw and a metal to one end of a steel pipe containing Cr 9% by weight or more - and a pin portion having a metal seal portion, the same a material, a female thread and a metal - a oil well steel pipe joint formed by the coupling provided at both ends of the box part having a metal seal portion. The oil well steel pipe fittings are female threads and the metal coupling - the surface of the metal seal part, and characterized by being further arranged to Cu-Sn alloy layer. Thus, green dope is better sealability than conventional also be used, and it is possible to remarkably suppress the galling occurring joint, and is described in Patent Document 3. [0010] 　In the above disclosed in Patent Documents 1 to 3 techniques, by forming a specific alloy plating layer on the contact surface, even when using the green dope, improves the seizure resistance. On the other hand, JP-A-2008-095019 (Patent Document 4) and WO 2009/057754 (Patent Document 5) proposes a different technique. Patent Documents 4 and 5 propose a grease which is a place of green dope. [0011] 　Patent lubricating coating composition as described in 2008-095019 (Patent Document 4), basic sulfonates, basic salicylates, basic phenates one or two or more selected from and basic carboxylate containing basic lubricant. The composition, biodegradable after 28 days in seawater (BOD) is 20% or more. Steel pipes The compositions exhibit galling resistance and anticorrosive properties comparable level to that coated with compound grease, by further high biodegradability, even in harsh country or region of environmental regulations, without applying compound grease as use threaded joint can be used without fear of environmental pollution, and is described in Patent Document 4. [0012] 　The compositions described in WO 2009/057754 (Patent Document 5) is a composition for forming a lubricating coating on a threaded joint for pipes. The composition comprises one or both of a rosin and calcium fluoride, metal soaps, waxes, and the basic metal salt of an aromatic organic acid. Thus, not contain harmful heavy metals such as lead that burden the environment, galling resistance, airtightness, and impart antirust property, a lubricating coating which can be secured even higher [Delta] T, and JP It is described in 5. [0013] 　In addition to the above disclosed in Patent Documents 1-5 technique, it is possible to improve the seizure resistance by a solid lubricating film. For example, JP-2002-327874 Patent Publication tubular threaded joint as described in (Patent Document 6), the pin and the contact surface of the box of at least one member, two or more layers of solid, each containing a lubricating powder wherein the lubricating coating layer is formed. This application of compound grease containing heavy metal powder is not required, the excellent tubular threaded joint galling resistance and airtightness is obtained, and is described in Patent Document 6. CITATION Patent Document [0014] Patent Document 1: JP 2008-215473 Patent Publication Patent Document 2: JP-T 2005-514573 Patent Publication Patent Document 3: JP 2003-074763 Patent Publication Patent Document 4: JP 2008-095019 Patent Publication Patent Document 5: International Publication the 2009/057754 Patent Patent Document 6: JP 2002-327874 Patent Publication Summary of the Invention Problems that the Invention is to Solve [0015] 　Incidentally, when screwing the steel pipes, optimum torque to terminate the screwing is predetermined. Figure 1 is a diagram showing the time of the pipe thread coupling having a shoulder portion and screwing, the relationship between the rotational speed N and the torque T of the steel pipe. Referring to FIG. 1, when screwing the pipe thread joint, initially, the torque T increases in proportion to the rotation speed N. The rate of increase in torque T at this time is low. Further if the screw tightening, the shoulder portion come into contact with each other. The torque T at this time, that shouldering torque Ts. After reaching shouldering torque Ts, further if the screw tightening, the torque T increases in proportion to the rotational speed N once again. The rate of increase in torque T at this time is high. When the torque T reaches a predetermined value (engaging torque, the To), screwing is completed. Shouldering torque Ts at the time of screw tightening is if they meet 0.05To