0001]The present invention relates to a method of manufacturing a pipe thread fittings and tube or pipe threaded joint.
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 such as Pb 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) has been proposed. For example, JP-A-2008-215473 (Patent Document 1) and JP-A 2003-074763 (Patent Document 2), wherein the pipe threaded joint for superior seizure resistance even when using a grease containing no heavy metal there is.
[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]
　In the technique disclosed in Patent Document 1, by forming a specific alloy plating layer on the contact surface, even when using the green dope, galling resistance is improved.
[0009]
　JP 2003-074763 JP by which oil well steel pipe joint is described in (Patent Document 2), 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, than even conventional using green dope sealing property is good, and it is possible to remarkably suppress the galling that occurs joints, and are described in the patent document 2.
[0010]
　WO 2016/170031 (Patent Document 3), by forming a high corrosion resistance plating layer is proposed a technique of increasing the corrosion resistance in addition to seizure resistance. WO 2016/170031 is pipe thread joint disclosed in (Patent Document 3), and a threaded portion and a first sealing surface, threaded portion and a first sealing surface, the zinc by weight (Zn) is mainly a component, characterized in that it is coated with a metallic corrosion-resistant and seizing layer.
CITATION
Patent Document
[0011]
Patent Document 1: JP 2008-215473 Patent Publication
Patent Document 2: JP 2003-074763 Patent Publication
Patent Document 3: WO 2016/170031
Summary of the Invention
Problems that the Invention is to Solve
[0012]
　Incidentally, threaded joint for pipes, after being transported to mining sites, are stored without being screwed until it is actually used. That is, the pipe threaded joint is stored a predetermined time period prior to use. Or inferior to the appearance of the appearance of the plating layer of the pipe thread joint conventional plating layer, or when or have irregularities in some cases the user concerned about deterioration of the dissimilar contamination and performance. Therefore, the Pipe threaded joint, there is a case where conventional plating equal to or more appearance is obtained.
[0013]
　By using the techniques described in Patent Documents 1 to 3 described above can improve the seizure resistance of pipe thread fittings. However, further improvement in seizure resistance of pipe thread joint has been sought. Furthermore, appearance good pipe thread joint has been sought.
[0014]
　An object of the present invention is to provide a pipe thread joint and a manufacturing method thereof having excellent seizure resistance and excellent appearance.
Means for Solving the Problems
[0015]
　Pipe thread joint of the present embodiment includes a pin and box. Each pin and box has a contact surface including a threaded portion, the metal seal portion and the shoulder portion. Pipe threaded joint, on at least one of the contact surfaces of the pin and box, comprising a Zn-Ni alloy plating layer. Zn-Ni alloy plating layer containing Cu. Cu content of the Zn-Ni alloy plating layer is 4.5 wt% or less (excluding 0).
[0016]
　Method for manufacturing a pipe thread joint of the present embodiment is a method for producing a pipe thread joint comprising a pin and box. Each pin and box has a contact surface including a threaded portion, the metal seal portion and the shoulder portion. Manufacturing method includes preparing step and Zn-Ni alloy plating layer forming step. The preparation process prepares the pin, the box and the plating solution. Plating solution contains zinc ions, nickel ions and copper ions. The concentration of copper ions in the plating solution is 1 g / L or less (excluding 0). The Zn-Ni alloy plating layer forming step, on at least one of the contact surfaces of the pin and box to form a Zn-Ni alloy plating layer by electroplating contacting the plating solution.
Effect of the invention
[0017]
　Pipe thread joint of the present embodiment has an excellent seizure resistance and excellent appearance.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018]
[1] Figure 1 is a Cu content of Zn-Ni alloy plating layer is a diagram showing the relationship between hardness.
FIG. 2 is an enlarged view of a Cu content of 0.00 to 0.10 mass% portion of FIG.
FIG. 3 is, Cu content of Zn-Ni alloy plating layer is a diagram showing the relationship between L values and hardness.
FIG. 4 is a diagram showing a configuration of a pipe thread joint according to the present embodiment.
FIG. 5 is a cross-sectional view of a pipe thread joint according to the present embodiment.
FIG. 6 is a cross-sectional view of one example of the contact surface of the pipe thread joint according to the present embodiment.
DESCRIPTION OF THE INVENTION
[0019]
　Hereinafter, with reference to the accompanying drawings, the present embodiment will be described in detail. Its description will not be repeated the same reference numerals designate like or corresponding parts in FIG.
[0020]
　The present inventors have examined the seizing resistance and appearance of the pipe thread fittings. As a result, the following findings were obtained.
[0021]
　In Patent Document 3, zinc pipe threaded joint (Zn) plating or zinc alloy plating, in particular, is considering the use of Zn-Ni alloy plating. Zn-Ni alloy plating has a high hardness and high melting point. The higher the hardness of the plating layer, the plating layer is not easily damaged during the return screw tightening and screw the pipe thread fittings. Furthermore, the higher the melting point of the plating layer, during the return screw tightening and screw the pipe thread joint, even when the locally plated layer becomes high temperature, it is possible to suppress the deterioration of the hardness of the plating layer. As a result, it increases seizure of pipe thread fittings. Therefore, by forming the plating layer by Zn-Ni alloy, it is increased seizure resistance pipe thread fittings.
[0022]
　According to Patent Document 3, Zn-Ni alloy plating is further excellent in corrosion resistance. Therefore, by forming the plating layer by Zn-Ni alloy, in addition to the seizure of the pipe thread joint, it is possible to increase the corrosion resistance.
[0023]
　The present inventors have studied how to further increase the galling resistance of the Zn-Ni alloy plating layer. As a result, the following findings were obtained.
[0024]
　Previously, the Zn-Ni alloy plating layer, a zinc (Zn) and nickel (Ni) metal other than has been considered impurities. In general, in the plating art, impurities in the plating is believed can cause defective plating. Plating and bad, for example, appearance is poor and the physical properties poor. The poor appearance e.g., pits, roughness, haze, a color irregularity and non-plating. The physical properties poor example, reduction in hardness of the plating layer, a spreadable reduction, adhesion decreases and corrosion resistance such as reduction. Previously, in order to suppress the defective plating, reduction of impurities in the plating have been attempted.
[0025]
　However, we have obtained a completely different findings from the conventional. It is under certain conditions, if Cu is contained, which has been considered impurities ever Zn-Ni alloy plating layer, a finding that the hardness of the Zn-Ni alloy plating layer is increased.
[0026]
　1, Cu content of Zn-Ni alloy plating layer (hereinafter, simply referred to as Cu content) and a diagram showing the relationship between the hardness of the Zn-Ni alloy plating layer. Figure 1 was obtained by the Examples below.
[0027]
　The vertical axis of FIG. 1, in the Examples below, showing the change in hardness (Hv) of the Zn-Ni alloy plating layer. Hardness of Zn-Ni alloy plating layer is obtained by the below-mentioned test method. The higher the hardness of the Zn-Ni alloy plating layer, it is increased seizure resistance pipe thread fittings. Figure 2 is an enlarged view of a Cu content of from 0.00 to 0.10% by weight of the portion of FIG. Referring to FIG. 2, when the Cu content exceeds 0 mass%, the hardness of the Zn-Ni alloy plating layer is increased significantly. 1 and 2, if the Cu content is more than 0.01 mass%, the hardness of the Zn-Ni alloy plating layer becomes higher 470Hv, higher seizing resistance can be obtained.
[0028]
　As described above, in Patent Document 3, expect improvement of corrosion resistance, using a Zn-Ni alloy plating into Pipe threaded joint. This zinc (Zn) is because it is less noble than iron (Fe) contained much in the base of pipe thread joint, presumably because sacrificial occurs. In other words, from the viewpoint of corrosion resistance, iron (Fe) from noble metals and copper (Cu) is considered to be one element that needs to be especially reduced from Zn-Ni alloy plating layer. However, from the standpoint of galling resistance, copper (Cu) was found to be rather a preferred elements.
[0029]
　As described above, the pipe threads joint and therefore may look that good required for storage period before use. If Cu is contained in Zn-Ni alloy plating layer, the hardness of the Zn-Ni alloy plating layer is increased significantly. On the other hand, the present inventors found that when Cu is contained in the Zn-Ni alloy plating layer is often found that affects the appearance of the pipe thread fittings.
[0030]
　If Cu is less than 4.5 wt% contained in the Zn-Ni alloy plating layer, the appearance of the Zn-Ni alloy plating layer is improved. Quality of appearance is judged by the color unevenness of the Zn-Ni alloy plating layer. If color irregularity of Zn-Ni alloy plating layer is large (i.e., when the appearance of the Zn-Ni alloy plating layer is not good), L value generally Zn-Ni alloy plating layer tend to have low. Therefore, the appearance of the Zn-Ni alloy plating layer is determined by the L value. If the L value is higher, appearance is determined to be good.
[0031]
　Figure 3 is a graph showing the Cu content of the Zn-Ni alloy plating layer, the relationship between the L value of the hardness and Zn-Ni alloy plating layer of Zn-Ni alloy plating layer. Figure 3 is obtained by the Examples below. The vertical axis on the left side of FIG. 3, in the Examples below, showing the change in hardness of the Zn-Ni alloy plating layer. In Figure 3, × mark indicates the hardness of the Zn-Ni alloy plating layer. The vertical axis on the right side of FIG. 3, in the embodiment described below, shows the change in the L value of Zn-Ni alloy plating layer. In Figure 3, white circles (○) indicates the L value. In the present embodiment it was evaluated with L value good appearance if it exceeds 50.0. Referring to FIG. 3, as the Cu content is low, L value is high. That is, by controlling the Cu content below a certain level can be maintained appearance excellent condition.
[0032]
　Referring to FIG. 3, if the Cu content of 4.5 wt% or less (excluding 0), L value exceeds 50.0, good enough appearance is obtained. In this case, threaded joint for pipes, in addition to excellent seizure resistance, it has excellent appearance.
[0033]
　Been completed based on the above findings, pipe thread joint of the present embodiment includes a pin and box. Each pin and box has a contact surface including a threaded portion, the metal seal portion and the shoulder portion. Pipe threaded joint, on at least one of the contact surfaces of the pin and box, comprising a Zn-Ni alloy plating layer. Zn-Ni alloy plating layer containing Cu. Cu content of the Zn-Ni alloy plating layer is 4.5 wt% or less (excluding 0).
[0034]
　Zn-Ni alloy plating layer of pipe thread joint of the present embodiment contains Cu. Cu content of the Zn-Ni alloy plating layer is 4.5 wt% or less (excluding 0). In this case, threaded joint for pipes, it is possible to achieve both a superior seizure resistance, and excellent appearance.
[0035]
　Preferably, Cu content of Zn-Ni alloy plating layer is 0.05 to 4.5 mass%.
[0036]
　In this case, further enhanced seizure resistance pipe thread fittings.
[0037]
　The thickness of the Zn-Ni alloy plating layer may be 1 ~ 20 [mu] m.
[0038]
　Pipe thread joint of the present embodiment, on at least one contact surface of the pin and box, or may comprise a lubricant coating on Zn-Ni alloy plating layer.
[0039]
　Method for manufacturing a pipe thread joint of the present embodiment is a method for producing a pipe thread joint comprising a pin and box. Each pin and box has a contact surface including a threaded portion, the metal seal portion and the shoulder portion. Manufacturing method includes preparing step and Zn-Ni alloy plating layer forming step. The preparation process prepares the pin, the box and the plating solution. Plating solution contains zinc ions, nickel ions and copper ions. The concentration of copper ions in the plating solution is 1 g / L or less (excluding 0). The Zn-Ni alloy plating layer forming step, on at least one of the contact surfaces of the pin and box to form a Zn-Ni alloy plating layer by electroplating contacting the plating solution.
[0040]
　It described in detail below pipe thread joint and a manufacturing method thereof according to the present embodiment.
[0041]
　[Pipe thread fittings]
　pipe thread joint comprises a pin and box. Figure 4 is a diagram showing a configuration of a pipe thread joint according to the present embodiment. Referring to FIG. 4, the pipe threaded joint is provided with a steel pipe 1 and the coupling 2. At both ends of the steel tube 1, the pin 3 having the male threaded portion on an outer surface is formed. At both ends of the coupling 2, box 4 having a female screw portion on an inner surface is formed. By screwing the pin 3 and box 4, the end of the steel tube 1, it is mounted coupling 2. On the other hand, without using a coupling 2, one end of the steel tube 1 and pin 3, the other end of the steel pipe 1 was box 4, also a threaded joint for oil well pipes of the integral type. Pipe thread joint of the present embodiment can be used in the coupling method and the integral form of both pipe thread fittings.
[0042]
　Pin 3 and box 4 is provided with a contact surface having a threaded portion, the metal seal portion and the shoulder portion. Figure 5 is a cross-sectional view of a pipe thread joint according to the present embodiment. Referring to FIG. 5, the pin 3 is provided with a male thread portion 31, a metal seal part 32 and the shoulder portion 33. Box 4 includes a female threaded portion 41, a metal seal part 42 and the shoulder portion 43. A pin 3 and box 4 a portion contacting when screwing, that contact surfaces 34 and 44. Specifically, when the pin 3 and box 4 screwing, threaded portions (male thread portion 31 and the internal thread portion 41), the metal seal portions (metal seal part 32 and 42), and shoulder portions (shoulder portion 33 and 43) are in contact with each other. In other words, the contact surface 34 includes threaded portion 31, a metal seal part 32, and a shoulder portion 33. Contact surface 44 includes threaded portion 41, a metal seal part 42, and a shoulder portion 43.
[0043]
　Figure 6 is a cross-sectional view of one example of the contact surfaces 34 and 44 of pipe thread joint according to the present embodiment. Pipe threaded joint, at least one of the contact surfaces 44 of the contact surface 34 and box 4 of the pin 3 provided with a Zn-Ni alloy plating layer 100. In Figure 6, the pipe threaded joint is provided with a Zn-Ni alloy plating layer 100 on the contact surface 34 of the pin 3. Pipe threaded joint may further comprise a lubricating coating 200 on Zn-Ni alloy plating layer 100. Instead of the pin 3 may be provided with a Zn-Ni alloy plating layer 100 on the contact surface 44 of the box 4. Both of the contact surfaces 44 of the contact surface 34 and box 4 of the pin 3 may be provided with a Zn-Ni alloy plating layer 100. However, it is disadvantageous in the course cost.
[0044]
　[Zn-Ni alloy plated
　layer] Zn-Ni alloy plating layer 100 is disposed on the at least one contact surface 34 or 44 of the pin 3 and box 4. Zn-Ni alloy plating layer 100, a Zn-Ni alloy, copper (Cu), consisting of impurities. Zn-Ni alloy plating layer 100, when the entire Zn-Ni alloy plating layer 100 is 100 mass%, the proportion of Ni is provided a composition of 6-20 wt%. The lower limit of the proportion of the preferred Ni is 10% by weight, more preferably from 12 mass%. The upper limit of the proportion of the preferred Ni is 16% by mass.
[0045]
　Zn-Ni alloy plating layer 100 contains Cu. Cu content of the Zn-Ni alloy plating layer 100, when the entire Zn-Ni alloy plating layer 100 is 100 mass%, is 4.5 wt% or less (excluding 0). Cu is, Zn-Ni if in the alloy plating layer 100 is also contained in trace amounts, increase the Zn-Ni alloy plating layer 100 overall hardness and melting point. That, Cu content in the Zn-Ni alloy plating layer 100 is 0 percent. On the other hand, if the Zn-Ni alloy Cu content in the plating layer 100 is 4.5 wt% or less, the appearance of the Zn-Ni alloy plating layer 100 can be maintained in good condition. Therefore, Cu content in the Zn-Ni alloy plating layer 100 is 4.5 wt% or less (excluding 0). In this case, the pipe threaded joint is able to achieve both appearance and excellent excellent seizure resistance. The preferable lower limit of the Cu content of the Zn-Ni alloy plating layer 100 is 0.01 wt%, more preferably from 0.05 mass%, more preferably 0.10 wt%, more preferably 1 a .00 wt%, more preferably from 1.10% by mass. The preferable upper limit of the Cu content of the Zn-Ni alloy plating layer 100 is 4.0 mass%.
[0046]
　The remainder of Zn-Ni alloy plating layer 100 is a zinc (Zn) and impurities. That, Zn-Ni alloy plating layer 100 contains a 6 to 20 wt% Ni, and Cu of 4.5 wt% or less (excluding 0), the balance being Zn and impurities. The impurities, for example Fe. In Zn-Ni alloy plating layer 100, the total content of impurities other than Cu is less than 0.1 wt%.
[0047]
　[Measurement method of the composition of Zn-Ni alloy plated
　layer] The composition of the Zn-Ni alloy plating layer 100, EDX; measured using a (Energy-Dispersive X-ray energy dispersive X-ray). Specifically, so as to be perpendicular to the surface of the Zn-Ni alloy plating layer 100, test piece was cut out, polished embedded in resin. Respect to the cross-section of the Zn-Ni alloy plating layer 100, using Ltd. Elionix Ltd. SEM (ERA-8900FE) / EDAX manufactured EDS device (Pegasus), to analyze the elemental composition. The entire detected elements as 100 mass%, to calculate the ratio (mass%) of each element (Ni and Cu).
[0048]
　The thickness of the Zn-Ni alloy plating layer 100 is not particularly limited. The thickness of the Zn-Ni alloy plating layer 100 is, for example, 1 ~ 20 [mu] m. When the thickness of the Zn-Ni alloy plating layer 100 is 1μm or more, it can be stably obtained sufficient seizure resistance. Be greater than a thickness of 20μm of Zn-Ni alloy plating layer 100, the effect is saturated.
[0049]
　The thickness of the Zn-Ni alloy plating layer 100 is measured by the following method. For four points on the contact surfaces 34 and 44 to form a Zn-Ni alloy plating layer 100, Helmut Fischer GmbH made, using the eddy current phase film thickness meter PHASCOPE PMP910, the thickness of the Zn-Ni alloy plating layer 100 It is to measure. Measurement is carried out in a way that conforms to the ISO (International Organization for Standardization) 21968 (2005). Measurement points, 4 points in the circumferential direction of the pipe of the pipe thread joint is (0 °, 90 °, 180 °, 4 positions of 270 °). The arithmetic mean of the four positions of the measurement results, the thickness of the Zn-Ni alloy plating layer 100.
[0050]
　Zn-Ni alloy plating layer 100 may be disposed on at least one part of the contact surfaces 34 and 44 may be disposed throughout. Metal seal part 32 and 42, in particular the surface pressure is increased in screwing the final stage. Accordingly, the Zn-Ni alloy plating layer 100, to partially disposed on at least one of the contact surfaces 34 and 44, is preferably disposed at least on the metal sealing portion 32 or 42. On the other hand, by arranging the entire on at least one of Zn-Ni alloy plating layer 100 to contact surfaces 34 and 44, increases the production efficiency of the pipe thread fittings.
[0051]
　Hardness and the melting point of Zn-Ni alloy plating layer 100 is conventionally higher than the hardness of the Cu plating layer has been used as a plating layer of pipe thread fittings, melting point equally high as Cu plating layer. Therefore, even after repeated back screw tightening and screw damage Zn-Ni alloy plating layer 100 is suppressed. As a result, even after repeated back screw tightening and screw, seizing resistance is maintained.
[0052]
　Furthermore, the zinc contained in the Zn-Ni alloy plating layer 100 (Zn) is a base metal compared with iron (Fe) is the main component of the steel pipe. Therefore, there is the effect of sacrificial protection increases the corrosion resistance of the pipe thread fittings.
[0053]
　Lubricating coating]
　pipe thread joint may comprise a lubricating coating 200 on Zn-Ni alloy plating layer 100. Lubricating coating 200, as shown in FIG. 6, may be disposed on the Zn-Ni alloy plating layer 100. Zn-Ni If only arranged on one of the contact surfaces 44 of the contact surface 34 or box 4 of the alloy plating layer 100 pins 3, lubricating coating 200, the contact surface 44 of the contact surface 34 or on the box 4 of the pin 3 it may be disposed directly above.
[0054]
　Lubricating coating 200 is a liquid may be either semi-solid or solid. Here, the semi-solid, receives an external load (pressure and heat, etc.), refers to a state capable of flowing while freely deformed similarly contact surface 34 and upper 44 and a liquid. The liquid or semi-solid, include a high viscosity, such as grease.
[0055]
　Lubricating coating 200 contains a well-known lubricant. Lubricants, for example, JET-LUBE Co., Ltd., is a SEAL-GUARD (trade name) ECF (trade name). Lubricating coating 200 may be, for example, well-known lubricating coating containing a lubricating particles and a binder. Lubricating coating 200, if desired, it may contain a solvent and other ingredients. Lubricating coating 200, for example, a lubricant containing rosin, metallic soaps, waxes and lubricating powder. Lubricating powder, for example, an earthy graphite. And chemical composition of the lubricating coating 200 disposed on the pin 3 may be the same as the chemical composition of the lubricating coating 200 disposed on the box 4, may be different.
[0056]
　The thickness of the lubricant film 200 is not particularly limited. The thickness of the lubricant film 200 is, for example, 30 ~ 300 [mu] m. When the thickness of the lubricant film 200 is 30μm or more, further enhanced effect of lowering the shouldering torque. Since the thickness of the lubricant film 200 be greater than 300 [mu] m, a lubricating coating 200 of excess during screwing is eliminated from the upper contact surface 34 and 44, the effect is saturated.
[0057]
　If lubricating coating 200 is a solid, the thickness of the lubricant film 200 is measured by the following method. Preparing the pins 3 or box 4 provided with a lubricating coating 200. Pins 3 or box 4 to cut perpendicularly to the axial direction of the tube. Performing microscopic observation with respect to a cross section including a lubricant film 200. Power microscope observation and 500 times. Thus, determining the thickness of the lubricating coating 200.
[0058]
　If lubricating coating 200 is liquid or semi-solid, the thickness of the lubricant film 200 is measured by the following method. Any measurement point (area: 5 mm × 20 mm) of the metal seal part 32 or 42 of the pipe thread joint wiping with absorbent cotton was soaked with ethanol. From the difference between the weight before the cotton, the weight of the cotton wool after wiping to wipe calculates the application amount of the lubricant. And the coating amount of the lubricant from the area of ​​the density and the measurement point of the lubricant, and calculates an average film thickness of the lubricant film 200.
[0059]
　Lubricating coating 200 can be either a liquid-solid. On the other hand, the use of liquid or semisolid lubricating coating 200 can be lowered torque (shouldering torque) at the time of contact with the shoulder portion 33 and the shoulder 43. In this case, it becomes easy to adjust the torque during screw tightening.
[0060]
　Arrangement of Zn-Ni alloy plating layer and the lubricating coating]
　Zn-Ni alloy plating layer 100 on the pins 3 and at least one contact surface 34 or 44 of the box 4 is arranged, at least one contact pin 3 and box 4 on the surface 34 or 44, or if the lubricating coating 200 is disposed on the Zn-Ni alloy plating layer 100, the combination is not particularly limited. A case with only Zn-Ni alloy plating layer 100 and the pattern 1. A case having a lubricating coating 200 further thereon with a Zn-Ni alloy plating layer 100 and pattern 2. A case with only lubricating coating 200 and pattern 3. Zn-Ni alloy plating layer 100 is also the case not provided even lubricating coating 200 and pattern 4. Satisfies the above conditions, the contact surface 44 of contact surface 34 and box 4 of the pin 3 there may be cases of patterns 1 to 4. Specifically, the contact surface 34 of the pin 3, in the case of the pattern 1 or pattern 2, the contact surface 44 of the box 4 may be either patterns 1 to 4. The contact surface 34 of the pin 3, in the case of the pattern 3 or pattern 4, the contact surface 44 of the box 4 is either pattern 1 or pattern 2. Conversely, the contact surface 44 of the box 4, in the case of the pattern 1 or pattern 2, the contact surface 34 of the pin 3 can be either patterns 1 to 4. The contact surface 44 of the box 4, in the case of the pattern 3 or pattern 4, the contact surface 34 of the pin 3 is either pattern 1 or pattern 2.
[0061]
　[Preform pipe thread fittings]
　chemical composition of the base metal of the pipe thread joint is not particularly limited. Matrix, for example, a carbon steel, stainless steel and alloy steel. Among alloy steels, Cr, high-alloy steel such as duplex stainless steels and Ni alloy containing alloy elements such as Ni and Mo has a high corrosion resistance. Therefore, these high-alloy steel if used in the base material increases the corrosion resistance of the pipe thread fittings.
[0062]
　[Production Method]
　method of manufacturing a pipe thread joint of the present embodiment is a method for producing a pipe thread joint described above. Manufacturing method includes preparing step and Zn-Ni alloy plating layer 100 forming process.
[0063]
　[Preparation Step]
　In the preparation step, the pin 3, to prepare the box 4 and the plating solution. Plating solution contains zinc ions, nickel ions and copper ions. The plating solution, preferably, zinc ion: 1 ~ 100 g / L, nickel ions: is 1 ~ 50 g / L are contained. Plating solution further copper ions are contained. The content of copper ions in the plating solution is 1 g / L or less (excluding 0). Preferably, the lower limit of the content of copper ions in the plating solution is 10 ppm, more preferably, 50 ppm, more preferably from 100 ppm.
[0064]
　[Zn-Ni alloy plating layer forming
　step] In the Zn-Ni alloy plating layer 100 forming step, on at least one contact surface of the pin 3 and box 4, form a Zn-Ni alloy plating layer 100 made of Zn-Ni alloy to. Zn-Ni alloy plating layer 100 is formed by plating. Plating is performed zinc ions, nickel ions, and the plating solution containing copper ions, it is contacted at least one contact surface of the pin 3 and box 4 by electroplating. Conditions of the electroplating can be appropriately set. Conditions of electroplating, for example, plating solution pH: 1 ~ 10, plating solution temperature: 10 ~ 60 ° C., a current density: 1 ~ 100A / dm 2 , and the processing time: 0.1-30 minutes.
[0065]
　[Film forming step]
　After forming on at least one contact surface 34 or 44 of the above-described Zn-Ni alloy plating layer 100 pins 3 and box 4, it may be performed film formation step. The film-forming step, on at least one contact surface 34 or 44 of the pin 3 and box 4, or on the Zn-Ni alloy plating layer 100 to form a lubricating coating 200.
[0066]
　By applying the lubricant described above, the lubricant film 200 can be formed. Coating method is not particularly limited. Coating method, for example, spray coating, a brush coating and dip. When employing spray coating, and heating the lubricant may be sprayed in a state of increased fluidity. Lubricating coating 200 is pin 3 contact surfaces 34, contact surface 44 of the box 4, Zn-Ni alloy plating layer 100 on the contact surface 34 of the pin 3, and, Zn-Ni alloy plating on the contact surface 44 of the box 4 at least one may be partially disposed on selected from the group consisting of the layer 100. However, lubricating coating 200 on the contact surface 34 of the pin 3, on the contact surface 44 of the box 4, on Zn-Ni alloy plating layer 100 on the contact surface 34 of the pin 3, and, on the contact surface 44 of the box 4 It is disposed on at least one entire selected from the group consisting of over Zn-Ni alloy plating layer 100 is preferred. Deposition step may be carried out both pins 3 and box 4, may be performed on only one.
[0067]
　[Background process]
　manufacturing method optionally may include a surface treatment step prior to Zn-Ni alloy plating layer 100 forming process. Surface treatment step is, for example, a pickling and alkaline degreasing. The surface treatment step, cleaning the oil or the like adhering on the contact surface 34 or 44. Surface treatment step may further comprise a grinding such as sandblasting and mechanical grinding finishing. These surface treatment may be performed alone, or may be implemented by combining a plurality of substrate treatment.
Example
[0068]
　Hereinafter, the embodiment will be described. The% in the examples means mass%.
[0069]
　In the present embodiment, assuming a base material of the threaded joint, it was used a commercially available cold-rolled steel sheet. Cold-rolled steel sheet is vertical 150 mm × horizontal 100 mm (plated surface is vertical 100 mm × horizontal 100 mm) was. Steel species, was ultra-low carbon steel. The chemical composition of the steel sheet, C: 0.19%, Si: 0.25%, Mn: 0.8%, P: 0.02%, S: 0.01%, Cu: 0.04%, Ni: 0.1%, Cr: 13%, Mo: 0.04%, balanced by Fe and impurities.
[0070]
　[Zn-Ni alloy plating layer forming step]
　to form a plating layer on the cold-rolled steel sheet of each test number. Formation of Zn-Ni alloy plating layer was performed by electroplating. Details of the production conditions of the Zn-Ni alloy plating layer of each test numbers were as shown in Table 1. Plating solution, Daiwa Kasei Co., Ltd., was used trade name dyne Jin alloy N-PL. Plating solution in Cu concentration, by changing the addition amount of the plating solution of copper sulfate (pentahydrate) reagent was varied. Incidentally, if the number of "Cu concentration in the plating solution" in Table 1 is the target value, the value of "plating solution Cu concentration" is A 0 ppm, which was not added copper sulfate reagent described above in the plating solution which means that is. In Table 1, "liquid flow velocity" is the stirring rate of the plating solution, circulation amount when circulating the plating solution in the pump, a value represented by the linear velocity of the plating solution.
[0071]
[Table 1]

[0072]
　[Zn-Ni Cu content measurement test of the alloy plating
　layer] Cu content of Zn-Ni alloy plating layer is, EDX; was measured using (Energy-Dispersive X-ray energy dispersive X-ray). Specifically, so as to be perpendicular to the surface of the Zn-Ni alloy plating layer, specimens were cut and polished embedded in resin. Respect to the cross-section of the test piece, using EDX, were analyzed elemental composition. Among the compositions of each of the obtained elements, to calculate the percentage of Cu content (wt%), and the Cu content of the Zn-Ni alloy plating layer. Also calculated similarly content of other elements. In this embodiment, Ni content also calculated similarly. In the present embodiment, the amount of impurities Zn-Ni alloy plating layer is less than 0.1 wt%, the balance being Zn. The results are shown in Table 1.
[0073]
　Thickness measurement test of the Zn-Ni alloy plated layer]
　The above measuring method, to measure the thickness of the Zn-Ni alloy plating layer. The results are shown in Table 1.
[0074]
　[Appearance evaluation
　test] in accordance with JIS Z8730 (2009), was carried out the appearance evaluation test. Specifically, using a Konica Minolta Co. CR-300, and calculates the average value of n number of 2 times. Measurement area was φ10mm. Values were used using the L * a * b * color system, the L value representing the luminance as an index. The results are shown in Table 1. In Table 1, L value is the case of 50.0 or more, it is determined that excellent appearance and an OK in the "quality" field of "appearance". In Table 1, if the L value is less than 50.0, the appearance is determined to bad, and the NG in the "quality" field of "appearance".
[0075]
　[Hardness measurement test of Zn-Ni alloy plating layer]
　The Vickers hardness measurement test, the hardness was measured in Zn-Ni alloy plating layer. Specifically, was cut vertically cold-rolled steel sheet of each test number was formed Zn-Ni alloy plating layer with respect to the surface of the steel sheet. For any five points of the cross section of the emerged Zn-Ni alloy plating layer was measured Vickers hardness by the method based on JIS Z2244 (2009). Was used for the measurement Co., Ltd. Fischer Instruments made of micro hardness tester Fischer scope HM2000. The test temperature room temperature (25 ° C.), test force (F) was 0.01 N. Of the obtained measurement results 5 points, the arithmetic mean of the three points excluding the maximum and minimum values, and the hardness of the Zn-Ni alloy plating layer (Vickers hardness Hv (Hv0.001)). The results are shown in Table 1.
[0076]
　[Evaluation Result]
　Referring to Table 1, cold rolled steel with test Nos. 4 to Test No. 15 and Test No. 17 was provided with a Zn-Ni alloy plating layer. Zn-Ni alloy plating layer containing Cu. Cu content of the Zn-Ni alloy plating layer was 4.5 mass% or less (excluding 0). Therefore, the hardness Hv of 470 or more, L value is 50.0 or more, had superior seizing resistance and appearance.
[0077]
　Test No. 5 to Test No. 15 and in Test No. 17 In addition, Cu content of Zn-Ni alloy plating layer was 0.05 to 4.5 mass%. Therefore, increased hardness as compared with Test No. 4 Cu content of Zn-Ni alloy plating layer was less than 0.05 wt%, seizing resistance is more excellent.
[0078]
　On the other hand, in Test Nos. 1 to Test No. 3, Cu content of Zn-Ni alloy plating layer is 0.00%, did not contain Cu. Therefore, the hardness Hv is less than 470, galling resistance was inferior.
[0079]
　In Test No. 16, Test No. 18 and Test No. 19, Cu content of Zn-Ni alloy plating layer exceeds 4.5 mass%. Therefore, L value is less than 50, the appearance was inferior.
[0080]
　It has been described an embodiment of the present invention. However, the above-described embodiment is merely an example for implementing the present invention. Accordingly, the present invention is not limited to the embodiments described above, it can be implemented by changing the above-described embodiments without departing from the scope and spirit thereof as appropriate.
DESCRIPTION OF SYMBOLS
[0081]
　3 Pin
　4 boxes
　31, 41 thread portion
　32, 42 the metal seal part
　33 and 43 the shoulder portion
　34, 44 contact the surface
　100 Zn-Ni alloy plating layer
　200 lubricating coating

WE CLAIM

Each threaded portion, a pipe thread joint comprising a pin and box has a contact surface comprising a metal seal portion and the shoulder portion,
　Zn-Ni alloy plating layer on the pin and at least one of the contact surface of the box the provided,
　the Zn-Ni alloy plating layer, containing Cu of 4.5 wt% or less (excluding 0), pipe threaded joint.
[Requested item 2]
　A pipe thread joint according to claim 1,
　wherein the Zn-Ni alloy plating layer, containing Cu 0.05 to 4.5 wt%, Pipe threaded joint.
[Requested item 3]
　A pipe thread joint according to claim 1 or claim 2,
　the thickness of the Zn-Ni alloy plating layer is 1 ~ 20 [mu] m, Pipe threaded joint.
[Requested item 4]
　A pipe thread joint according to any one of claims 1 to 3,
　comprising the pin and at least one of the contact surface of the box, or lubricant film on the Zn-Ni alloy plating layer , pipe thread fittings.
[Requested item 5]
　Each threaded portion, a manufacturing method of a pipe thread joint comprising a pin and box has a contact surface comprising a metal seal portion and the shoulder portion,
　the pin, the box, and zinc ions, nickel ions and copper ions containing the a step concentration of copper ions to prepare a plating solution is 1 g / L or less (excluding 0),
　the said pin and at least one of the contact surface of the box, it is brought into contact with the plating solution and forming a Zn-Ni alloy plating layer by electroplating Te method of pipe thread fittings.