JP6448252B2 - Fastening member - Google Patents

Description

  The present invention relates to a male screw member that exhibits a screw fastening function and a fastening member that includes a female screw member.

  Applications that require corrosion resistance, such as devices that constitute industrial manufacturing processes such as semiconductors, male screw members and female screw members used in devices used in the fields of food, medicine, etc. are made of metal, In particular, it is often made of stainless steel, and the male screw member and the female screw member used for such applications are required to have no or almost no rusting.

  However, since metal, especially stainless steel, has the characteristic of being easily seized, seizure occurs when the process of fastening the male screw member and the female screw member to each other and fastening and the process of releasing (releasing) the fastening state are repeated. May occur. Once seizure occurs, the subsequent fastening process and release process cannot be performed properly and smoothly, and even if the fastening process can be performed, it is impossible or difficult to perform the release process.

  Then, the aspect which suppresses and reduces the occurrence of seizure by reducing the friction between the screw threads of the male screw member and the female screw member by using a lubricant when screwing the screw members to each other is conceivable. Reference 1).

JP 2005-299793 A

  However, although the seizure is improved by using the lubricant, the use of the lubricant is often restricted or prohibited in a use environment in which the male screw member and the female screw member are used by being fastened together. That is also true. Furthermore, the occurrence of seizure has been confirmed even in an environment where the use of a lubricant is allowed. This is because the male screw member and the female screw member are completely degreased before the fastening process. This is considered to be due to the fact that the sliding effect of the lubricant was lowered due to the application and the change over time.

  The present inventor has focused on the following mechanism that causes seizure. In other words, as shown in FIG. 13, a conventional screw, for example, a triangular screw, has a male screw member E and a female screw member I whose axes are aligned with each other so that a fastening load is not applied (standard state). The flanks E1 and E2 of the male screw member E and the flanks I1 and I2 of the female screw member I are in the form of maintaining a dimensional tolerance (hereinafter sometimes referred to as a tolerance) around the shaft core (center axis). When there is a positional relationship without geometric contact and when a load is applied during fastening, as shown in FIG. 14, the male screw member E and the female screw member I receive axial loads in opposite directions, A portion that comes into contact with the geometrical structure appears firmly. Here, of the two flanks E1 and E2 that incline in different directions that define the angle of the thread Es of the male screw member E, one flank E1 is a boundary that defines the range of the summit Et along the axial direction. Of the portions Ea and Ec, the surface connects one peak boundary portion Ea and the valley boundary portion Eb of the valley bottom Eu closest to the peak boundary portion Ea, and the other flank E1 is connected to the other peak boundary portion Ec. This is a surface connecting the valley bottom boundary portion Ed of the valley bottom Eu closest to the mountain peak boundary portion Ec. Of the two flanks I1 and I2 that incline in different directions that define the angle of the thread Is of the female screw member I, one flank I1 is a boundary portion that defines the range of the peak top It along the axial direction. Ia, Ic is a surface connecting one peak boundary part Ia and the valley boundary part Ib of the valley bottom Iu closest to the peak boundary part Ia, the other flank I1 is the other peak boundary part Ic, This is a surface connecting the valley bottom boundary Id of the valley bottom Iu closest to the mountain peak boundary Ic.

  Of the screw threads Es and Is of the male screw member E and the female screw member I, at least the flanks E1 and I1 on the side that receives a load during fastening (the peak boundary portion Ea and the valley bottom boundary portion Eb in the male screw member E in FIG. The connecting surface, the surface connecting the crest boundary portion Ia and the valley bottom boundary portion Ib of the female screw member I) is called a pressure side flank, and among the screw threads Es and Is of the male screw member I and female screw member I, The flank E2, I2 on the opposite side of the pressure side flank E1, I1 (the surface connecting the crest boundary portion Ec and the valley bottom boundary portion Ed in the male screw member E in the figure, the crest boundary portion Ic and the valley bottom boundary in the female screw member I) The surface connecting the part Id) is called a play side flank. As can be seen from FIG. 14, at the time of fastening, the pressure side flank E1, I1 of the male screw member E and the female screw member I are in contact with each other, while the play side flank E2, of the male screw member E and the female screw member I I2 is not in contact with each other. In order to make it possible to physically fasten the male screw member E and the female screw member I, a tolerance is indispensable.

  However, if the shaft centers of the male screw member E and the female screw member I are shifted during fastening, the contact of the pressure side flanks E1 and I1 of the male screw member E and the female screw member I is as shown in FIGS. Not a line contact, but a point contact in which the surface pressure (load per unit area acting on the sliding surface) is extremely increased as compared to the line contact. If the fastening process is continued in a situation where the surface pressure has increased in a manner close to that of point contact, forced sliding will occur in the circumferential direction in a situation close to point contact under high surface pressure. ) Causes local wear damage and increases the probability of seizure. 13 and 14, the alternate long and short dash line CL indicates the axial center of the male screw member E and the female screw member I, and the alternate long and short dash line CL in FIGS. 15 and 16 indicates the axial center of the male screw member E. .

  Such seizure is considered to occur easily and constantly because there is a tolerance between the threads of the male screw member and the female screw member.

  In view of the above problems, the present inventor has intensively studied to provide a male screw member and a female screw member that are unlikely to be seized, and a fastening member including the male screw member and the female screw member. By increasing the hardness of the surface layer of at least the pressure side flank of the male screw member and the female screw member to a predetermined value or higher, or by increasing the hardness of the pressure side flank of one of the screw members to a predetermined value or higher, It has been found that the occurrence of seizure can be suppressed / reduced even under use conditions (under non-lubricating conditions) that do not assume the application of the agent.

That is, a fastening member according to the present invention includes a stainless steel male screw member and a stainless steel female screw member having a thread that can be screwed and fastened to a screw thread of the male screw member. and surface hardness of the pressure flank is a side flanks given a load at least during engagement of the screw thread of the screw member, the pressure flank is a side flanks given a load at least during engagement of the threads of the female screw member varied surface layer of a hardness from each other, that only the hardness of the surface layer only of cutting and high surface pressure pressure flank only plastic deformation was made in the person relatively high hardness is a value exceeding Vickers hardness 320Hv It is characterized by. Here, when there is a variation in the hardness of the surface layer, the condition that “the hardness of the surface layer is a value exceeding the Vickers hardness of 320 Hv” in the present invention is that the highest surface layer hardness among the varying surface layer hardness is the Vickers hardness of 320 Hv. If it exceeds the value, it will be satisfied.
The present inventors have found that such a fastening member improves seizure resistance without using a lubricant.
In particular, the fastening member according to the present invention is a value in which the hardness of the surface layer of the pressure side flank of the pressure side flank of the male screw member or the pressure side flank of the female screw member that is relatively higher in hardness exceeds the Vickers hardness of 320 Hv. It is.

Also, as an example of the fastening member, a male screw member made of stainless steel, and a female screw member made of stainless steel having a screw thread that can be screwed and fastened to the screw thread of the male screw member, The hardness of the surface layer of the pressure side flank, which is the flank that receives the load at the time of fastening, among the screw threads of the member, and the surface layer of the pressure side flank, the flank of the female screw member that receives the load at the time of fastening The hardness of the surface layer of the pressure-side flank of the male screw member and the hardness of the surface layer of the pressure-side flank of the female screw member are different from each other. And the second condition in which the hardness of the surface layer of the higher pressure side flank exceeds Vickers hardness of 320 Hv is satisfied. .

Further, in the fastening member, as specific processing contents satisfying the first condition that the surface layer hardness of the pressure side flank of both the male screw member and the female screw member is a value exceeding the Vickers hardness of 320 Hv, the male screw member and In addition to cutting, each pressure side flank of the female screw member can be subjected to a predetermined plastic processing or nitriding treatment. That is, when the pressure side flank is finished by cutting, the surface layer hardness of the pressure side flank is higher than the hardness of the material (stainless steel) of the screw member, and further, either plastic working or nitriding treatment or By performing both treatments, it is possible to further increase the surface layer hardness of the pressure side flank rising at the end of cutting, and to suppress seizure during fastening. In addition, a coating process that coats the surface of the thread with a film of a predetermined thickness (coating process, for the purpose of suppressing reaction, using silver that is said to be difficult to react with fluids such as food and gas to be passed Although it is conceivable to increase the hardness of the surface by silver plating, etc., it is not possible to completely eliminate the possibility that the film will peel off during use. Although it is not necessarily a good product, the above-mentioned cutting process, predetermined plastic working process, and nitriding process do not cause the phenomenon of film peeling and mixing into the product. Even when it is repeated, it is possible to prevent or suppress the situation where the surface layer hardness of the pressure side flank decreases.

  On the other hand, the hardness of the surface layer of the pressure side flank of the male screw member and the hardness of the surface layer of the pressure side flank of the female screw member are different from each other, and the hardness of the surface layer of the pressure side flank having a relatively higher hardness is Vickers. As a specific process that satisfies the second condition that is a value exceeding the hardness 320 Hv, the pressure side flank of the male screw member is subjected to at least one of predetermined plastic processing and nitriding in addition to cutting. In addition, a mode in which processing different from processing for the pressure side flank of the male screw member is performed on the pressure side flank of the female screw member can be exemplified.

  Further, as another specific process that satisfies the second condition, in addition to the cutting process, the pressure side flank of the female screw member is subjected to a predetermined plastic process or at least one process of nitriding, The aspect which performs the process of predetermined plastic processing only in addition to cutting with respect to the pressure side flank of a male screw member can be mentioned.

In addition, the fastening member may be one in which at least each pressure side flank of the male screw member and the female screw member is degreased.

  It is considered that the lower limit value of the surface layer hardness at each pressure side flank of the male screw member and the female screw member having the above-described effects is Vickers hardness of 320 Hv, and the upper limit value is Vickers hardness of 1600 Hv. The surface layer hardness at each pressure side flank of the male screw member and the female screw member can be set to about Vickers hardness 1600Hv depending on processing contents and processing conditions (nitriding temperature, etc.), but Vickers hardness 1600Hv or close to it. In some cases, the inventor has obtained a result of significant corrosion in the salt spray test. Therefore, in the present invention, it is not a particularly effective technique to set the surface layer hardness of each pressure side flank to exceed Vickers hardness of 1600 Hv. As an appropriate upper limit value, Vickers hardness of 600 Hv can be exemplified. Moreover, Vickers hardness 400Hv can be mentioned as a suitable lower limit. Of the above-described curing treatments, high surface layer hardness can be obtained by nitriding treatment. In particular, plasma nitridation can be cured at a high temperature in a short time, but the corrosion resistance of the material is reduced, so that the use and frequency of use of the fastening member are limited to some extent. On the other hand, in the case of gas nitriding, the maximum value of the surface hardness is about 400 Hv by a curing process at a temperature lower than that of plasma nitriding, but the corrosion resistance of the material is not lowered, so that it can be used in a wide range of applications. . These corrosion resistances have been confirmed through preliminary tests.

With the fastening member according to the present invention, even when the surface pressure suddenly increases at the contact point between the pressure side flank of the male screw member and the female screw member at the time of fastening, wear damage can be suppressed / reduced, and seizure occurs. Therefore, it is possible to increase the number of times that the fastening process and the opening process can be repeated, and to improve the seizure resistance. Therefore, the present invention can provide a fastening member that does not cause seizure or is extremely unlikely to occur during at least the first fastening process performed by screwing the threads of the male screw member and the female screw member. It is.

The figure which shows the state before the screwing fastening of the external thread member and internal thread member which comprise the fastening member which concerns on one Embodiment of this invention. The figure which shows the screwing fastening state of the external thread member and internal thread member which comprise the fastening member of the embodiment corresponding to FIG. The figure which shows the state which mounted | wore with the male screw member which concerns on the same embodiment. The figure which shows the state which mounted | wore the male screw member which concerns on the same embodiment with the pipe and the ring for fixing. The figure which shows typically the standard state (screwing state in which no load is applied) of the external thread member and internal thread member shown in FIG. The figure which shows the fastening state of the external thread member and internal thread member shown in FIG. 2 corresponding to FIG. The figure which shows typically the standard state of the external thread member and internal thread member which comprise the fastening member which concerns on the embodiment. The figure which shows the fastening state of the external thread member and internal thread member which comprise the fastening member which concerns on the embodiment corresponding to FIG. The figure which shows the experimental result of the fastening member regarding the test material number 6 in the same embodiment. The figure which shows the experimental result of the fastening member regarding the test material number 7 in the same embodiment. The figure which shows the modification of the fastening member which concerns on the embodiment corresponding to FIG. The figure which shows the fastening member which concerns on the modification corresponding to FIG. The figure which shows typically the standard state of the fastening member provided with the conventional male screw member and the female screw member. The figure which shows the fastening state of the fastening member corresponding to FIG. The figure which shows the mechanism in which seizure generate | occur | produces in the same fastening member corresponding to FIG. The figure which shows the mechanism in which seizure generate | occur | produces in the same fastening member corresponding to FIG.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the fastening member X according to an embodiment of the present invention includes a male screw member 1 and a female screw member 2, for example, a device that constitutes an industrial manufacturing process such as a semiconductor, food, medical It is suitably used for an apparatus used in such a field. The male screw member 1 and the female screw member 2 used for such applications are required to have corrosion resistance and are required to have no or almost no rusting. In order to satisfy such requirements, both the male screw member 1 and the female screw member 2 are made of stainless steel. There are no particular restrictions on the type of stainless steel, and any of austenite, ferrite, austenite / ferrite (two-phase), and martensite may be used. In this embodiment, the male screw is made of austenitic stainless steel. The member 1 and the female screw member 2 are applied.

  As shown in FIG. 2, the fastening member X according to the present embodiment is used in, for example, a connecting portion of a pipe system P for conveying a material in the manufacturing process in the above-described field. The male screw member 1 and the female screw member 2 shown in FIGS. 1 and 2 are, for example, M16 of SUS304 conforming to JIS standard, 60 ° triangular screw with a pitch of 1.

  As shown in FIGS. 1 to 3, the fastening member X according to the present embodiment employs a male screw member 1 having a hexagonal head 1 </ b> A (hexagon bolt) at the base end. This male screw member 1 is made of plastic that forms a pipe system P at the tip of the screw shaft portion 1B (the end of the screw shaft portion 1B far from the head portion 1A) having a thread 1s formed on the outer peripheral surface. A pipe mounting portion 1C to which the pipe P1 can be mounted is integrally formed. In the present embodiment, as the pipe mounting portion 1C, a small-diameter portion 1Ca that projects by a predetermined dimension in a direction away from the head 1A from the tip surface (end surface orthogonal to the axial direction) of the screw shaft portion 1B, and the small-diameter portion 1Ca. The one having a large diameter portion 1Cb formed at the distal end and a tapered portion 1Cc having a gradually decreasing diameter from the distal end of the large diameter portion 1Cb toward the distal end is applied. The shaft centers of the small diameter portion 1Ca, the large diameter portion 1Cb, and the taper portion 1Cc coincide with the shaft centers of the screw shaft portion 1B and the head portion 1A. Here, the head portion 1A of the male screw member 1 has a base end portion (a lower end portion of the head portion 1A in FIG. 1) having another pipe system (not shown) having a pipe P1 attached to the pipe device portion 1C. System P means a pipe system different from that used in the following description, or another device (a device different from a device provided with a pipe system P having a pipe P1 attached to the pipe device section 1C) May also be used synonymously in the following description), or may be connected to the other pipe system (not shown) or the other device and function as a stopper (sealing). is there. In the former case, a through-hole penetrating in the axial direction including the head portion 1A is formed inside the male screw member 1, and the base end portion of the head portion 1A (the lower end portion of the head portion 1A in FIG. 1) The other pipe system (not shown) or the other device (not shown) is connected by appropriate fixing means. On the other hand, in the latter case, no through hole is formed in the male screw member 1, and the head 1A functions as a stop.

  As shown in FIGS. 1 and 2, the female screw member 2 has a hexagonal nut shape on the outer peripheral surface and a cap nut portion 2A in which a screw thread 2s corresponding to the screw thread 1s of the male screw member 1 is formed on the inner peripheral surface. And a flange portion 2B provided at the tip end portion of the cap nut portion 2A (the upper end portion of the cap nut portion 2A in FIG. 1) and projecting inward. Moreover, the female screw member 2 of this embodiment sets the part which does not form the screw thread 2s among the inner peripheral surfaces by the side of the cap nut part 2A to the surface without an unevenness | corrugation. In the present embodiment, the height dimension (dimension along the axial direction) of the surface without unevenness is set shorter than the height dimension of the pipe mounting portion 1C of the male screw member 1 by a predetermined dimension.

  The fastening member X having the male screw member 1 and the male screw member 1 is connected to the pipe mounting portion 1C of the male screw member 1 before the male screw member 1 and the female screw member 2 are screwed together. (See FIG. 3), and then the inner diameter is set slightly larger than the outer diameter of the pipe P1, and the outer diameter is set to the screw shaft of the female screw member 2. The metal fixing ring 3 set smaller than the inner diameter of the part 1B is attached to the pipe attaching part 1C so that the pipe P1 is fitted from the outer peripheral side (see FIG. 4), and then the female screw member 2 is attached. The male screw member 1 is fastened to the male screw member 1 from the front end side (see FIG. 2). Here, when the base end portion of the head portion 1A of the male screw member 1 (the lower end portion of the head portion 1A in FIG. 1) is fixed to the other pipe system (not shown) or the other device, these male screws. In a state in which the member 1 and the female screw member 2 are screwed and fastened to each other, a through hole formed so as to penetrate the male screw member 1 including the head 1A of the male screw member 1 in the axial direction. And a pipe system having a pipe P1 attached to the pipe attaching portion 1C and the other pipe system not shown attached to the base end portion of the head 1A of the male screw member 1 (the lower end portion of the head 1A in FIG. 1). Alternatively, the fluid can be smoothly transferred to and from the other device. That is, for example, from a device in which high-tech gas or food is made into a fluid state and the pipe system P having the pipe P1 shown in FIG. 1 is connected, the base end portion of the head 1A of the male screw member 1 (in FIG. The fluid can be sent to the other pipe system or the other device connected to the lower end of the head 1A. In the case of temporarily interrupting the flow of fluid due to maintenance of the apparatus or cleaning of the flow path, the male screw member 1 in which the through hole is not formed in the head 1A is used. The male screw member 1 functions as a stop member that serves as a seal. In addition, the shape of the head of the male screw member is not limited, and the other pipe system or the method of connecting the other device to the head of the male screw member (fixing means).

  When the female screw member 2 is tightened to the male screw member 1 to some extent in the process of performing the fastening process in the fastening member X having such a configuration, the collar provided at the tip (upper end) of the female screw member 2 The portion 2B presses the fixing ring 3 in the screwing advance direction (downward) of the female screw member 2, whereby the fixing ring 3 is connected to the taper portion 1Cc of the pipe mounting portion 1C. The pipe P1 is pushed into the screw shaft portion 1B side (downward) in a state where the pipe P1 attached to the pipe is sandwiched (held) in the radial direction. At this time, since the end portion (lower end portion) of the pipe P1 is in contact with the tip end surface (upper end surface) of the screw shaft portion 1B, as shown in FIG. 4, the tapered portion 1Cc to the large diameter portion 1Cb of the pipe P1. The portion beyond the taper portion (the portion existing below the taper portion 1Cc) is compressed and deformed so as to swell in the radial direction, but the outer peripheral surface of the pipe P1 is the inner peripheral surface of the female screw member 2 in the radial direction ( In the example shown in the figure, the surface of the pipe P1 is not formed and has no irregularities), so that the deformation amount of the pipe P1 is limited, and the pressure applied to the pipe P1 increases. As a result, the pressure becomes a force that presses the female screw member 2 in a direction (upward) away from the head 1A of the male screw member 1 via the fixing ring 3, and the male screw member 1 and the female screw member 2 It will be in the fastening state which screw threads 1s and 2s contact.

  As described above, the force that presses the female screw member 2 in the direction (upward) away from the head 1 </ b> A of the male screw member 1 through the fixing ring 3 does not act on the female screw member 2. In the state (standard state), as shown in FIG. 5, there is a clearance due to tolerance between the screw threads 2s, 2s of the male screw member 1 and the female screw member 2, and almost no torque is applied to the fastening operation. Although not hooked, when a force that presses the female screw member 2 in the direction (upward) away from the head 1A of the male screw member 1 via the fixing ring 3 starts to act on the female screw member 2, FIG. As described above, one of the flank 11 (flank 11 corresponding to the downward surface in the figure) among the flanks 11 and 12 having different inclination directions constituting the thread 1s of the male thread member 1 and the thread 2s of the female thread member 2 Flank 2 with different inclination directions (Frank 12 corresponding to the upward surface in the drawing) flank 21 of one of the 22 contacts strongly with each other. In the following description, in each of the male screw member 1 and the female screw member 2, the flank that receives a load at the time of fastening is referred to as pressure side flank 11,21. In FIG. 6, the pressure side flank 21 of the female screw member 2 is indicated by a relatively thick solid line. 5 and 6 schematically show the positional relationship between the threads 1 s and 2 s of the male screw member 1 and the female screw member 2 on the right side of the drawing in each figure, and the positional relationship according to this positional relationship. The positional relationship between the screw threads 1s and 2s of the male screw member 1 and the female screw member 2 on the left side as viewed in the drawing is omitted.

  By fastening the male screw member 1 and the female screw member 2 to each other, the pipe systems P having the pipes P1 can be connected to each other, which is required for the liquid that is a material processed by the processing apparatus and the processing apparatus. A fluid such as a gas forming an atmosphere can be sent to the processing apparatus through the pipe P1.

  By the way, the fluid sent to the processing apparatus through the pipe P1 differs for each product processed by the processing apparatus and for each processing purpose of the processing apparatus. Therefore, depending on the specifications of the final product, change of the setup (preparation work that occurs when the product type and process contents change, preparation of materials before starting the work, trial processing of machines, etc.), and the type of fluid to be sent to the apparatus through the pipe P1 Need to change. Therefore, the above-described fastening member X is applied as a member for connecting the pipe P1 attached to the processing device and the pipe P1 attached to the fluid supply device such as a tank for supplying fluid, and one or one kind of product Each time the processing is finished, the fastening state of the male screw member 1 and the female screw member 2 is released (opened), and the pipe P1 attached to the processing apparatus is internally cleaned, and then a new fluid is supplied to the pipe P1 again. By connecting through a fastening member X to a pipe P1 attached to a fluid supply device such as a tank to perform the setup change operation can be performed quickly and smoothly.

  Since the fluid flowing in the pipe P1 often dislikes corrosion and rusting at the fastening portion between the male screw member 1 and the female screw member 2 and the inward surface of the pipe P1, in this embodiment, as described above. The male screw member 1 and the female screw member 2 of the fastening member X are made of stainless steel.

  However, stainless steel has a characteristic of being easily seized, and the fastening process and the releasing process are repeated at the time of the first fastening process, the process of releasing the initial fastening state (opening process), or every replacement work. In some cases, seizure may occur. Once seizure occurs, the fastening process cannot be performed properly and smoothly, and even if it can be fastened, the opening process required for setup change work and maintenance inspection becomes difficult, which is the worst case. In this situation, the entire pipe system P of both the processing device and the fluid supply device must be completely replaced, and there is an urgent demand for avoiding such a situation even if it is not correct at the site. is there.

  Then, the aspect which reduces the friction of the screw threads of the external thread member 1 and the internal thread member 2 by using a lubricant at the time of a fastening process, and suppresses and reduces the occurrence of seizure is considered.

  However, although seizure is improved by using the lubricant, the lubricant is a foreign substance for the fluid passing through the pipe P1, and considering the risk of the lubricant entering the product, the male screw member 1 and The use of the lubricant in the scene where the female screw member 2 is fastened is restricted or prohibited in principle. Also, if it is permissible to mix the lubricant into the product up to a predetermined amount, the occurrence of seizure can be suppressed / reduced by using a lubricant that does not exceed the permissible amount. In reality, however, it is possible to completely degrease the male screw member 1, the female screw member 2, and their peripheral parts with an organic solvent before the fastening process, and the sliding effect of the lubricant is reduced due to a change over time. By doing so, it can be easily guessed that seizure occurs.

  Therefore, the present inventor conducted a fastening experiment using the above-described fastening member X including the male screw member 1 and the female screw member 2 which are 60 ° triangular screws of M16 of SUS304 and pitch 1 compliant with the J2S standard. It was. In the fastening experiment, first, the screw threads 1S and 2S of the male screw member 1 and the female screw member 2 are inclined by cutting to different directions defining the angles of the screw threads 1S and 2S as shown in FIG. 2 flanks (two flanks 11 and 12 defining the angle of one screw thread 1s shown in FIG. 7 in the case of the male screw member 1, and one screw thread shown in FIG. 7 in the case of the female screw member 2. Both of the cross-sectional shapes of the two flanks 21 and 22 that define an angle of 2s are formed into a linear shape (hereinafter sometimes referred to as a reference cross-sectional shape), and the male screw member 1 and the female screw member 2 By applying severe plastic working to the surface of each screw thread 1s, 2s, a fastening member X is produced in which the hardness of the surface layer of each screw thread 1s, 2s is set higher than the hardness inside the screw threads 1s, 2s. As shown in FIG. When the fastening process in which the pressure-side flanks 11 and 21 of the screw member 1 and the female screw member 2 are in contact with each other is performed, seizure does not occur during the initial fastening process, and the fastening process and the release process are repeated. It turned out to be possible.

  Here, as “severe plastic working”, in this embodiment, the male screw member 1 and the female screw member 2 after the cutting process are fastened while supplying a lubricant (in oil) under high surface pressure. A process that repeats the process and the release process (hereinafter referred to as pre-in-oil fastening process) was adopted. Further, by repeating such pre-fastening process in oil, the surface portions of the thread 1s and 2s of the male screw member 1 and the female screw member 2 that repeatedly receive a load are subjected to plastic deformation and are work hardened. The cross-sectional shape (cross-sectional shape including the axis) of each pressure-side flank 11 and 21 after the deformation is set within the dimensional tolerance standardized by J2S.

  Further, the present inventor noticed that the hardness of the surface layer of the screw threads 1s and 2s increases as the number of pre-fastening processes in oil increases, and the male screw member 1 and the female member that have been subjected to the pre-fastening process in oil 20 times. A fastening experiment was performed using the fastening member X provided with the screw member 2 and the fastening member X provided with the male screw member 1 and the female screw member 2 that had been subjected to the pre-fastening process in oil 40 times. Furthermore, the present inventor performed male nitriding treatment on the male threaded member 1 and the female threaded member 2 that have been subjected to plastic working, thereby further increasing the hardness of the surface layer of the thread 1s, 2s. On the other hand, as an example of an extreme soft material, a solution treatment was applied to the male screw member 1 and the female screw member 2 that were finished by cutting. The male screw member 1 and the female screw member 2 from which the hardening of the surfaces of the screw threads 1 s and 2 s due to the cutting process has been completely removed are prepared, and the fastening member X including the male screw member 1 and the female screw member 2 is prepared. A fastening experiment was conducted under the position of a comparative material.

  The male screw member 1 and the female screw member 2 used in the fastening experiment are obtained by degreasing (preferably completely degreasing) at least the pressure side flank 11, 21 respectively. Specifically, before performing the fastening experiment, all the components of the fastening member X including the male screw member 1 and the female screw member 2 are sufficiently washed with acetone to remove all oils and fats. In the fastening experiment, a torque wrench is used, and the fastening procedure described above, that is, the pipe P1 is fitted and attached to the pipe attachment portion 1C of the male screw member 1 (see FIG. 3), and the fixing ring 3 is attached to the pipe P1. Fastening is performed at a speed of one rotation in 10 seconds according to the procedure of fastening the female screw member 2 and the male screw member 1 (see FIG. 5) in a state where the pipe fitting portion 1C is fitted so as to be fitted (see FIG. 4). went. When the torque increased abnormally during fastening and exceeded 10 Nm, it was judged that seizure had occurred, and the fastening experiment was stopped. In this case, it is impossible to release (release) the fastening state of the male screw member 1 and the female screw member 2. When there is no sudden increase in torque and the female screw member 2 comes into contact with the end surface of the male screw member 1 (the end surface of the head 1A of the male screw member 1 described above (upper end surface in FIG. 2)), the fastening process is stopped. If there was no seizure, an opening process was performed, the fixing ring 3 and the pipe P1 were replaced with new ones, and the fastening experiment was continued.

  Here, a specimen number is assigned to each of the plurality of fastening members X for which the fastening experiment has been performed, and manufacturing histories of the male screw member 1 and the female screw member 2 that are each specimen material (processing for the thread threads 1s and 2s). Contents) and the hardness of the surface layer of the threads 1 s and 2 s are shown in Table 1, and the number of times of fastening without causing seizure (number of times of fastening) is shown in Table 2. In addition, the hardness of the surface layer in Table 1 is a Vickers hardness, for example, a hardness measured by applying a load of 10 gf to the surface layer of the thread 1s, 2s.

  The value of the surface hardness of the flank of the test material in Table 1 indicates the maximum value among the measured value range of the surface hardness at a plurality of flank locations or the measured value.

  As can be understood from Table 1, in the fastening member X (test material number 1) provided with the male screw member 1 and the female screw member 2 having the thread 1s and 2s after cutting, the number of times that the fastening can be performed is 0, that is, In the middle of the first fastening process, seizure occurred. Further, the fastening member X including the male screw member 1 and the female screw member 2 subjected to the solution treatment is cut when the processing content before the solution treatment is only cutting (sample number 4). In any case where plastic deformation processing was performed after the processing (test material number 5), the number of possible fastenings was zero.

  Further, after the cutting process, the fastening member X including the male screw member 1 and the female screw member 2 obtained by plastically deforming the surfaces of the screw threads 1s and 2s including the flank performs screw pre-fastening processing in oil 20 times. When the surfaces of the ridges 1s and 2s are plastically deformed (test material number 2), the number of possible fastenings is one (seizure occurs during the second fastening process or the first opening process. Hereinafter, fastening is possible. If the surface of the threads 1s, 2s is plastically deformed by performing the pre-fastening process in oil 40 times (test material number 3), the number of possible fastenings is 5 times. Met.

  In the fastening member X (test material number 6) in which nitriding treatment (plasma nitriding treatment in this experiment) is performed on one or both of the male screw member 1 and the female screw member 2 that have been machined, the number of times that fastening is possible is 15 to 27 times. Specifically, as shown in FIG. 9, in the fastening member X in which both the male screw member 1 and the female screw member 2 are subjected to nitriding after cutting, the number of fastenings is 15 times (circular points in the figure). In the fastening member X in which the female screw member 2 has been cut and the male screw member 1 has been subjected to nitriding after the cutting process, the number of possible fastenings is 21 ( (Refer to a scatter diagram in which data are plotted with square points in the figure.) The fastening member X is a fastening member X in which the male screw member 1 is cut up and the female screw member 2 is subjected to nitriding after cutting. The number of possible times was 27 (see the scatter diagram in which the data are plotted with triangular points in the figure).

  Further, after cutting, a fastening member X (test sample) in which one or both of the male screw member 1 and the female screw member 2 in which the surfaces of the threads 1s and 2s including flank are plastically deformed is subjected to nitriding treatment In material number 7), the number of possible fastenings was 0 to 34 times. Specifically, as shown in FIG. 10, in the fastening member X in which both the male screw member 1 and the female screw member 2 are plastically deformed after cutting and further subjected to nitriding treatment, the number of fastenings is 34 times ( (Refer to a scatter diagram in which data are plotted with circular points in the figure.) The female screw member 2 is cut up and the male screw member 1 is subjected to plastic deformation and nitriding after cutting. In X, the number of possible fastenings was 0 (see a scatter diagram in which data is plotted with square points in the figure).

  In the fastening member X in which the male screw member 1 has been cut and the female screw member 2 has been subjected to plastic deformation and nitriding after cutting, the 12th opening process is finished and the 13th fastening is performed. A trouble occurred before starting the process, and the subsequent experiments could not be continued. The size of the ring 3 for fixing the pipe P is slightly different, which is the cause of the trouble. The fixing ring 3 bites into the entrance of the female screw member 2 and falls into a state where it cannot be inserted or removed. The fastening process could not be performed. However, the number of fastenings up to that time was 12, and the tightening torque was stable so that it could be grasped from the scatter plot in which the data were plotted with triangular points in the figure, and was involved in all the above fastening experiments ( The present inventor obtained a feeling (feel) that if the experiment was continued as it was, it would exceed 30 times.

  From the above experimental results, the seizure resistance is improved by increasing the surface hardness of the thread 1s, 2s of the male screw member 1 and the female screw member 2 to be higher than the surface hardness of the thread 1s, 2s after cutting. In particular, when the surface hardness of the threads 1 s and 2 s is greater than Vickers hardness 320 Hv or exceeds 320 Hv, it has been found that multiple fastening processes are possible.

  The fastening member X of the above-described specimen material number 2 and specimen material number 3 has a predetermined plastic deformation process for both the male screw member 1 and the female screw member 2 after the cutting process with respect to the screw threads 1s and 2s ( For the male screw member 1 and female screw member 2 of the test material number 2, pre-fastening in oil is performed 20 times, and for the male screw member 1 and female screw member 2 of the test material number 3, pre-fastening in oil is 40. When either the male screw member 1 or the female screw member 2 is cut up, or when the degree of plastic deformation is different between the male screw member 1 and the female screw member 2 The experimental results shown in Table 3 below were obtained. The numbers to the right of “male screw” and “female screw” in the table indicate the number of pre-fastening processes in oil. As can be understood from the experimental results shown in the same table, even when the surface hardness of the thread 1s of the male screw member 1 and the surface hardness of the screw thread of the female screw member 2 are different, a relatively high value is obtained. It has been found that a plurality of fastening processes can be performed if the surface hardness of the surface exceeds Vickers hardness of 320 Hv.

  In addition, for the fastening member X of the test material number 6, when both the male screw member 1 and the female screw member 2 are subjected to nitriding after cutting, the female screw member 2 is cut up, When the male screw member 1 is subjected to nitriding after cutting, the male screw member 1 is cut up, and when the female screw member 2 is subjected to nitriding after cutting, any of these Even in cases where it is proved that a plurality of fastening processes are possible, even if the surface hardness of the thread 1s of the male screw member 1 and the surface hardness of the screw thread of the female screw member 2 are different, It has been found that if the surface hardness showing a relatively high value exceeds Vickers hardness of 320 Hv, a plurality of fastening processes can be performed. In particular, with respect to the fastening member X of the specimen number 6, the male screw member 1 is different when the surface hardness of the thread 1 s of the male screw member 1 and the surface hardness of the screw thread of the female screw member 2 are different. Further, it was found that the number of times of fastening can be increased as compared with the case where the surface layer hardness of each of the screw threads 1s and 2s of the female screw member 2 is the same.

  For the fastening member X of the test material number 7, when both the male screw member 1 and the female screw member 2 are plastically deformed after cutting and further subjected to nitriding treatment, the male screw member 1 is cut. When the female screw member 2 is subjected to plastic deformation processing and nitriding after cutting, it has been proved that a plurality of fastening processes can be performed, and in particular, the latter case is the former case. It has been found that the number of possible fastenings is larger than that. On the other hand, regarding the fastening member X of the test material number 7, when the female screw member 2 is cut up and the male screw member 1 is subjected to plastic deformation processing and nitriding treatment after cutting processing, the number of possible fastenings is Focusing on the experimental result of 0 times, the surface layer hardness of the thread 1s of the male screw member 1 is more than twice as high as the surface layer hardness of the thread 2s of the female screw member 2 after cutting (see Table 1). ) Is likely to cause seizure, and the cause is considered to be that the male screw member 1 acts as a tap on the male screw member 1 and wear damage is likely to occur. As described above, when the male screw member 1 is subjected to plastic deformation processing and nitriding treatment after cutting, the female screw member 2 is not subjected to cutting and is subjected to plastic deformation processing or nitriding after cutting processing. It can be understood that it is preferable to apply one of the treatments, or one subjected to both plastic deformation and nitriding after cutting.

  Based on the experiments and experimental results detailed above, the fastening member X provided with the male screw member 1 and the female screw member 2 that can be screwed together is at least of the thread 1 s of the male screw member 1. The first condition in which at least the surface layer hardness of the pressure side flank 11 and the surface layer hardness of at least the pressure side flank 21 out of the thread 2s of the female screw member 2 exceed the Vickers hardness 320Hv, or the pressure side flank of the male screw member 1 The surface layer hardness of the pressure side flank 21 of the female screw member 2 is different from each other, and the surface layer hardness of the pressure side flank having a relatively higher hardness exceeds the Vickers hardness of 320 Hv, It has been found that if any one of the conditions is satisfied, the seizure resistance can be improved. Further, the upper limit value of the surface layer hardness of each of the pressure-side flanks 11 and 21 of the male screw member 1 and the female screw member 2 can be Vickers hardness 1600Hv, and the lower limit value can be Vickers hardness 400Hv. it can.

  In particular, as a specific configuration satisfying the first condition, the pressure side flank 11 and 12 of the male screw member 1 and the female screw member 2 may be subjected to at least one of predetermined plastic processing and nitriding in addition to cutting processing. The structure which performs either of these processes can be mentioned.

  As a specific configuration satisfying the second condition, the pressure side flank 1 of the male screw member 1 is subjected to at least one of predetermined plastic processing and nitriding in addition to the cutting processing, The pressure-side flank 21 of the female screw member 2 is subjected to processing different from the processing for the pressure-side flank 21 of the male screw member 2, and the pressure-side flank 21 of the female screw member 2 is subjected to cutting. Then, at least one of predetermined plastic processing and nitriding processing is performed, and the pressure side flank 21 of the male screw member 2 is subjected to only cutting processing or predetermined plastic processing processing in addition to the cutting processing. A configuration can be mentioned.

  The configuration of the present invention is not limited to the above-described embodiment. For example, in the above fastening experiment, the nitriding treatment is exemplified by the plasma nitriding treatment that can effectively increase the hardness in a short time and the seizure resistance is remarkably improved. There is also a concern that the corrosion resistance will deteriorate. Although it is conceivable to perform plasma nitriding at a low temperature in order to avoid the deterioration of the corrosion resistance, the low temperature nitridation makes the plasma unstable and uneven nitriding is likely to occur. Therefore, gas nitriding treatment, particularly gas nitriding treatment at a low temperature can be employed as the nitriding treatment. Of course, a nitriding treatment other than plasma nitriding or gas nitriding can be selected.

  Also, not only the pressure side flank but also the play side flank can be subjected to the same hardening treatment as the pressure side flank, so that the strength of the thread can be improved, and the deformation of the thread can be improved. The whole can prevent and suppress deformation. On the other hand, the fastening member of the present invention is not limited as long as at least the pressure side flank of the thread is subjected to a hardening treatment, and the presence or absence of the hardening treatment for other portions including the play side flank is not limited.

  Furthermore, when plastic deformation is applied to at least the pressure flank of the thread, the cross-sectional shape of the pressure flank (cross-sectional shape including the axis) is deformed from the standard shape, and this deformed cross-sectional shape is seizure-resistant. It may be possible to contribute to improvement.

  For example, as shown in FIG. 11, as the male screw member 1 constituting the fastening member X, the one in which the cross-sectional shape of the pressure side flank 11 of the thread 1s is set to a curved convex shape is applied, and the female screw As the member 2, a member in which the cross-sectional shape of the pressure-side flank 21 of the screw thread 2s is set to a curved concave shape is applied, and the axial centers of the male screw member 1 and the female screw member 2 constituting the fastening member X are mutually connected. And a thread 1 s of the male screw member 1 including the convex pressure-side flank 11 and a female screw member 2 including the concave pressure-side flank 21 in a screwed state (standard state) in which the load is not applied. When the fastening member X satisfying the condition (standard condition clearance condition) that the screw thread 2s of each other is not in contact with each other was manufactured and the fastening process was performed, seizure did not occur during the first fastening process, and the fastening process and solution It has been found it is possible to repeat the process.

  In particular, the convex shape of the pressure side flank 11 in the thread 1 s of the male screw member 1 shown in FIG. 11 is the direction in which the cross-sectional area passing through the axis of the male screw member 1 increases (when facing the female screw member 2, it faces The concave shape of the pressure side flank 21 in the thread 2 s of the female screw member 2 passes through the axis of the female screw member 2. It is a concave shape curved in a direction to reduce the cross-sectional area (a direction away from the pressure side flank 11 of the male screw member 1 facing when screwed with the male screw member 1). In the same figure, the pressure-side flank 11 of the male screw member 1 and the pressure-side flank 21 of the male screw member 1 are linearly formed (dotted lines connecting the peak boundary part 1a and the valley boundary part 1b in the male screw member 1 in the figure). When the distance to the limit of the dimensional tolerance is assumed to be 1 in the case of the straight line shape shown by, and the straight line shape shown by the dotted line connecting the peak boundary part 2a and the valley boundary part 2b in the female screw member 2, the pressure of the male screw member 1 The protrusion height of the convex shape of the side flank 11 and the depression depth of the concave shape of the pressure side flank 21 of the female screw member 2 are set to 1 or as close to 1 as possible within the range satisfying the standard state clearance condition. In this case, the number of possible fastenings was seven. Here, the convex protrusion height of the pressure-side flank 11 of the male screw member 1 means that when the pressure-side flank 11 of the male screw member 1 is linear, the linear flank (the summit boundary portion 1a in FIG. Is the maximum protruding length from the straight flank (shown by the dotted line connecting the bottom boundary portion 1b) and the maximum value of the perpendicular of the straight flank. The concave depression depth of the pressure-side flank 21 of the female screw member 2 means that when the pressure-side flank 21 of the female screw member 2 is linear, the linear flank (the peak boundary portion 2a in FIG. The maximum depression depth from a straight flank (shown by a dotted line connecting the valley boundary portion 2b), and the maximum value of the perpendicular of the straight flank.

  Thus, by satisfying the standard state clearance conditions, by setting the convex shape of the pressure side flank 11 of the male screw member 1 and the concave shape of the pressure side flank 21 of the female screw member 2 to complementary shapes, As shown in FIG. 12, at the time of fastening, the pressure side flank 11 of the male screw member 1 and the pressure side flank 21 of the female screw member 2 are in close contact with each other, and the pressure side flank 11 and the male screw member 1 of the male screw member 1 are in close contact with each other. Compared with the configuration in which the pressure side flank 21 has a linear shape, the speed at which the contact area increases at the time of fastening is overwhelmingly fast, and the convex pressure side flank 11 of the male screw member 1 and the female screw member 2 Even if the concave pressure side flank 21 is initially point contact at the time of fastening, the area of surface contact increases rapidly as the fastening force increases, and the situation where the surface pressure rapidly increases is suppressed / reduced. Is possible It can be inferred that the seizure is less likely to occur. In FIGS. 11 and 12, the shaft cores of the male screw member 1 and the female screw member 2 are indicated by a linear one-dot chain line CL.

  And this inventor, while satisfying the standard state clearance conditions, the protruding height and the depression depth of the convex shape and concave shape of the pressure side flank 11 of the male screw member 1 and the pressure side flank 21 of the female screw member 2, A plurality of types of fastening members X set to appropriate values were prepared, and an experiment similar to the fastening experiment described above was performed in order to investigate the difficulty of seizure.

  From the experimental results, the convex shape of the pressure side flank 11 of the male screw member 1 is the pressure side flank 11 of the male screw member 1 and the pressure side flank 21 of the female screw member 2 while satisfying the above-mentioned standard state clearance condition. The maximum value of the dimensional tolerance in the case of the linear shape is 1, and the female screw member 2 while satisfying the condition that it is a convex shape having a protruding height of ½ or more and 1 or less, and satisfying the above-mentioned standard state clearance condition. The concave shape of the pressure side flank 21 is ½ or more, assuming that the maximum dimensional tolerance is 1 when the pressure side flank 11 of the male screw member 1 and the pressure side flank 21 of the female screw member 2 are each linear. The condition that it is a concave shape having a depression depth of 1 or less, and that when any of these conditions is satisfied, the number of possible fastenings is more than one, in other words, seizure hardly occurs. It has been found that say. Further, even if the convex shape of the pressure side flank 11 of the male screw member 1 and the concave shape of the pressure side flank 21 of the female screw member 2 are not complementary to each other (a shape that fits together), the seizure resistance is high. It has also become clear that there may be improvements.

  Thus, the cross-sectional shape (cross-sectional shape including the axis) of the pressure side flank 11 is a curved convex shape, the shaft core is aligned with the shaft core of the female screw member 2, and the screwing state is not applied. According to the male screw member 1 set so that the screw thread 1s including the convex pressure side flank 11 does not contact the screw thread 2s of the female screw member 2, at least the pressure side flank can be used without using a lubricant. Even if 11 is degreased, the occurrence of seizure can be suppressed and reduced as described above. The reason why seizure resistance is improved is that, as described above, the pressure-side flank 11 of the male screw member 1 and the thread 2s of the female screw member 2 (specifically, the pressure-side flank of the female screw member 2) are fastened. 21), the surface pressure at the contact point or the contact surface is reduced as compared with the embodiment in which the cross-sectional shape of the pressure side flank 11 of the male screw member 1 is linear. This is considered to be because forced sliding can be suppressed / reduced in the circumferential direction in a situation close to point contact under rolling.

  Further, in the male screw member 1, the convex shape of the pressure side flank 11 increases the cross-sectional area passing through the axis of the male screw member 1, in other words, the female screw that faces when fastened to the female screw member 2. If the convex shape is curved in the direction approaching the pressure side flank 21 of the thread 2s of the member 2, it is possible to increase seizure resistance and increase the volume that supports the torque at the time of fastening. .

  Also, the pressure-side flank 21 of the female screw member 2 is set to have a concave concave shape, and the shaft core is aligned with the shaft core of the male screw member 1 and is concave in a screwed state where no fastening load is applied. According to the female screw member 2 set so that the screw thread 2s including the pressure-side flank 21 does not contact the screw thread 1s of the male screw member 1, at least the pressure-side flank 21 is degreased without using a lubricant. Even if it is, it can suppress and reduce generation | occurrence | production of seizure as mentioned above. The reason why the seizure resistance of the female screw member 2 is improved is the same as the reason described for the male screw member 1, and the pressure side flank 21 of the female screw member 2 and the pressure of the male screw member 1 are fastened. The contact pressure with the side flank 11 or the surface pressure at the contact surface is reduced as compared with the mode in which the cross-sectional shape of the pressure side flank 21 of the female screw member 2 is linear. This is considered to be because forced sliding can be suppressed / reduced in the circumferential direction in a situation close to point contact under surface pressure.

  And, according to the fastening member X provided with such male screw member 1 and female screw member 2, the pressure side flank 11 of the male screw member 1 set to a convex shape with a curved cross-sectional shape at the time of fastening, The pressure side flank 21 set in a concave shape having a curved cross-sectional shape is in contact with each other so that the curved surfaces (arcs) are in close contact with each other, thereby increasing the contact area when a load is generated by fastening, This contact area can be expected to increase rapidly as the fastening force increases, and it is possible to suppress and reduce a sudden increase in surface pressure, and a conventional male screw member in which the flank cross-sectional shape is linear, and Compared with a fastening member provided with a female screw member, seizure is less likely to occur, the number of repetitions of the fastening treatment and the opening process can be increased, and seizure resistance can be improved.

  Here, with respect to the male screw member, the convex shape of the pressure side flank is a convex shape that does not satisfy the first condition that the maximum value of the dimensional tolerance is 1 and has a protruding height of 1/2 or more and 1 or less. It can be inferred that the seizure resistance may be improved even in the case of a shape, that is, a protruding height that does not satisfy 1/2 or a protruding height that exceeds 1, and similarly, with respect to the female screw member, Concave shape that does not satisfy the second condition that the concave shape of the flank is a concave shape having a concave depth of 1/2 or more and 1 or less, where the maximum value of the dimensional tolerance is 1, that is, a concave that does not satisfy 1/2 It can be inferred that seizure resistance may be improved even with a concave shape having a depth or a depression depth exceeding 1.

  Depending on the protruding height of the curved convex shape of the two flank (pressure side flank, play side flank) inclined in different directions that define the thread angle of the male screw member, or to the protruding height of the convex shape Without conforming, the depression depth of the curved concave shape of the two flanks (pressure-side flank and play-side flank) inclined in different directions that define the thread angle of the female screw member is set to an appropriate value. Is possible. Here, the female screw (inner screw) member is a member arranged at a position farther from the axis than the male screw (outer screw) member. Therefore, it is possible to set the thread thickness of the female screw member and the surrounding members (thickness in the radial direction) to a certain extent, and the cross-sectional area passing through the axis of the female screw member on the flank of the female screw member Even if a concave shape curved in the direction of decreasing the thickness of the screw is considered, it is considered that the strength of the screw thread is not adversely affected. It can also be inferred that the strength capable of maintaining the fastening state of the screw member with the screw thread cannot be secured. Therefore, it is important to set the recessed depth of the concave shape within a range in which the screw thread of the female screw member can secure a strength capable of maintaining an appropriate fastening state with the screw thread of the male screw member.

  The configuration in which each flank of the male screw member and the female screw member detailed above is set to a curved convex shape or concave shape is a condition that is at least one of the first condition and the second condition related to the surface layer hardness. If it satisfies the above, combined with the structure, it exhibits even better seizure resistance.

  Further, even if the male screw member or the female screw member is a screw other than a triangular screw, the technical idea forming the basis of the present invention, that is, at least one of the above-described first condition and second condition relating to surface hardness By adopting a configuration that satisfies the above, improvement in seizure resistance can be expected.

  The fastening member only needs to be provided with the male screw member and the female screw member having the above-described configuration, and actively contacts the pressure side flanks of the male screw member and the female screw member during the fastening process. There are no particular restrictions on the configuration of the repulsion part or the presence or absence of the repulsion part. It is also possible to use the fastening member according to the present invention for various uses other than the connecting portion of the pipe system.

  The male screw member and the female screw member are preferably made of stainless steel and made of the same material, but the specific material may be made of stainless steel other than SUS304, such as SUS316. .

  In FIG. 11 and the like, the male screw member 1 and the female screw member 2 set to a convex shape or a concave shape in which the cross-sectional shape of the entire pressure side flank 11, 21 is curved are illustrated, but a partial cross-sectional shape of the pressure side flank It may be a male screw member or a female screw member set to a convex shape or a concave shape that is curved only. That is, the cross-sectional shape of the predetermined portion of the pressure side flank may be a curved convex shape or a concave shape, and the cross-sectional shape of the other portion may be a linear shape. The cross-sectional shape of the play side flank can be set to a cross-sectional shape according to this.

  Further, referring to FIG. 11, the pressure side flank 11 of the male screw member 1 will be described as an example. A curved line defining a curved convex shape defines a range of the peak 1t along the axial direction of the screw thread 1s. It may be a curve that does not pass through one or both of the peak boundary portion 1a and the valley boundary portion 1b, and further, the curve that defines the convex shape or concave shape of the flank is not limited to a perfect circular arc. It may be an elliptical arc or a parabola. The same applies to the curves that define the curvature of the play side flank of the male screw member and the flank of the female screw member.

  The manufacturing method of the male screw member and the female screw member according to the present invention is not particularly limited, and may be manufactured by a cutting process, a rolling method, or other manufacturing methods.

  In addition, the winding direction, the number of lines, the diameter, the pitch, and the like of the male screw member and the female screw member are not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Male screw member 2 ... Female screw member 11 ... Pressure side flank 21 ... Pressure side flank 1s, 2s ... Screw thread X ... Fastening member

Claims (2)

A fastening member comprising a stainless steel male screw member and a stainless steel female screw member having a thread that can be screwed and fastened to the thread of the male screw member,
The hardness of the surface layer of the pressure side flank that is a flank on the side that receives a load at the time of fastening among the threads of the male screw member, and the flank on the side that receives a load at the time of fastening among the threads of the female screw member The hardness of the surface layer of a certain pressure side flank is different from each other, and the hardness of only the surface layer of the pressure side flank that has been subjected to only cutting and plastic deformation under high surface pressure is Vickers hardness of 320 Hv. Fastening member characterized by having a value exceeding. The hardness of the surface layer of the pressure side flank of only the relatively high hardness of the pressure side flank of the male screw member or the pressure side flank of the female screw member is a value exceeding Vickers hardness of 320 Hv. The fastening member as described in.

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